Title:

Heater, wafer heating apparatus and method for manufacturing heater

Document Type and Number:

United States Patent 7417206

Abstract:

A heater that is capable of heating an object to a desired temperature in a short period while minimizing the temperature difference the surface of the object is provided. The heater comprising a plate having a first surface and a second surface, the first surface being a mount surface whereon an object is placed and having a resistive heating member; wherein the resistive heating member is formed in a continuous band having arc bands located on one of two concentric circles of different radii, at least one arc band located on the other circle, and linkage arc band that connects the arc band located on the one circle and the arc band located on the other circle; while the distance between the adjacent linkage arc bands is smaller than the distance between the arc band located on the one circle and the arc band located on the other circle.

Inventors:

Nakamura, Tsunehiko (Kokubu, JP)

Plaque It!

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates mainly to a heater used in heating a wafer, a wafer heating apparatus and a method for manufacturing the heater.

2. Description of the Related Art

In a manufacturing process of semiconductor devices, a heater is used to heat a semiconductor wafer (hereinafter referred to simply as a wafer) during formation of thin semiconductor film, etching, baking of resist film and other steps.

For such heating purposes, for example, Patent Document 1, Patent Document 2 and Patent Document 3 disclose wafer heating apparatus as shown in FIG. 16.

A heater 771 comprises a plate-shaped ceramic member 772 and a metal casing 779 as major components, and is constituted by securing the plate-shaped ceramic member 772 made of a ceramic material of nitride or carbide on an opening of the bottomed metal casing 779 , that is made of a metal such as aluminum, via an insulating contact member 774 made of a resin by means of bolts 780 . The heater 771 uses the top surface of the plate-shaped ceramic member 772 as a heating surface 773 whereon a wafer W is to be mounted, so that the wafer W is heated by a resistive heating member 775 that is formed, for example, in concentric configuration as shown in FIG. 20, on the bottom surface of the plate-shaped ceramic member 772 .

Power terminals 777 are connected by brazing to power feeder sections of the resistive heating member 775 , with the power terminals 777 electrically connected to lead wires 778 that are passed through wiring holes 776 provided at a bottom 779 a of the metal casing 779 .

In order to form a uniform film over the entire surface of the wafer W or cause a resist film to react uniformly in heating reaction by using the heater 771 , it is important to make uniform temperature distribution over the wafer. Accordingly, various measures have been employed as described below to keep the temperature difference across the wafer surface small.

One of the measures is to divide the resistive heating member 775 and independently control the temperatures of the divided sections.

Patent Document 4 discloses a heater that has a plurality of resistive heating member blocks. The resistive heating member of this heater is radially divided into four equal sections of fan-shaped block as shown in FIG. 17. A heater such as shown in FIG. 18 is also known that comprises four blocks of resistive heating member located along the periphery and a circular block of resistive heating member located at the center.

Patent Document 5 discloses a heater comprising a resistive heating member that is divided into identical rectangular regions 711 through 718 that can be controlled either independently or in groups each consisting of a plurality of regions, as shown in FIG. 19. In this heater, as shown in FIG. 19, four regions 715 through 718 , among the regions 711 through 718 , are located at positions that correspond to the arcs formed by dividing the peripheral portion of the wafer into four equal parts, and other four regions 711 through 714 are disposed inside of the four regions 715 through 718 in parallel thereto.

As to configuration of the resistive heating member, such a heater 500 (Patent Document 6) that comprises a plurality of resistive heatin members of which one located at the outermost position is formed in a sine curve, and heater 500 having outermost resistive heating member 750 formed in rectangular shape (Patent Document 7 and Patent Document 8) is also disclosed (FIGS. 21, 22 , 23 ). In these heaters, a power feeder section 760 is disposed adjacent to the resistive heating member.

Patent Document 8 discloses a heater having a spiral-shaped resistive heating member.

Patent Document 9 discloses a heater where wafer W support pins (not shown) are provided on a mount surface 773 is provided so as to lift the wafer W from the mount surface 773 by a small distance, in order to achieve uniform temperature distribution over the wafer.

Patent Document 10 discloses a heater where a wall is provided along the periphery of the plate-shaped ceramic member 772 to surround the wafer W, so as to prevent the wafer W from moving laterally.

Patent Document 11 discloses a heater where a protrusion that engages with the wafer W is formed along the periphery of the plate-shaped ceramic member 772 , and a multitude of projections that contact with the wafer W are formed inside of the protrusion, in order to achieve uniform temperature distribution.

Patent Document 12 discloses a heater where guide pins that locate the wafer W are provided around the plate-shaped ceramic member, thereby to achieve uniform temperature distribution over the wafer W.

Patent Document 13 discloses a heater where temperature distribution over the wafer W can be controlled by adjusting the height of support pins of the wafer W. A heater having guide pins engaged with the support pins is also disclosed.

Patent Document 14, Patent Document 15 and Patent Document 16 also disclose heater 850 made of ceramics where a coil-shaped resistive heating member 853 is embedded as shown in FIG. 24. The heater 850 consists of a plate-shaped ceramic member 851 made of a nitride ceramic material such as silicon nitride or aluminum nitride in which a coil-shaped resistive heating member 853 formed in spiral configuration is embedded, while the power feeder terminals 855 are connected to both ends of the resistive heating member 853 . In order to decrease the temperature difference across the wafer surface, such measures are disclosed as increasing the density of the resistive heating member 853 in a region of 10% of the mount surface on the outside, restricting the variation in the number of windings per unit length of the coil-shaped resistive heating member 853 and 3-dimensional arrangement of the resistive heating member 853 .

Patent Document 17 and Patent Document 18 also describe attempts to decrease the temperature difference across the wafer surface by connecting and embedding a resistive heating member having different coil diameter, or by providing a swelling portion at a turn-back portion of the resistive heating member.

Moreover, in a CVD film forming process, for example, such a wafer holding member is employed that supports a ceramic heater comprising a plate-shaped ceramic member by means of a cylindrical support member made of ceramics. Such a heater 850 made of ceramics is also known as one principal surface of the plate-shaped ceramic member 851 having resistive heating members 853 , 854 embedded therein is used as mount surface 851 a and a cylindrical support member 860 made of ceramics is joined onto the other principal surface, as shown in FIG. 25. In the heater 850 , the power terminals 856 , 857 are connected by brazing to the terminals of the resistive heating members 853 , 854 , and power terminals 856 , 857 are lead through inside of the cylindrical support member 860 to the outside for connection.

In recent years, increasing number of semiconductor devices are manufactured with circuits having line width of 90 nm or 45 nm. Manufacturing such semiconductor devices requires a heater that can heat a wafer with more uniform temperature distribution.

[Patent Document 1]

Japanese Unexamined Patent Publication No. 2001-203156

[Patent Document 2]

Japanese Unexamined Patent Publication No. 2001-313249

[Patent Document 3]

Japanese Unexamined Patent Publication No. 2002-76102

[Patent Document 4]

Japanese Unexamined Patent Publication No. 11-121385

[Patent Document 5]

Japanese Unexamined Patent Publication No. 11-354528

[Patent Document 6]

Japanese Unexamined Patent Publication No. 2001-6852

[Patent Document 7 ]

Japanese Unexamined Patent Publication No. 2001-223257

[Patent Document 8]

Japanese Unexamined Patent Publication No. 2001-257200

[Patent Document 9]

Japanese Unexamined Patent Publication No. 10-223642

[Patent Document 10]

Japanese Unexamined Patent Publication No. 10-229114

[Patent Document 11]

Japanese Unexamined Patent Publication No. 2002-237375

[Patent Document 12]

Japanese Unexamined Patent Publication No. 2002-184683

[Patent Document 13]

Japanese Unexamined Patent Publication No. 2001-68407

[Patent Document 14]

Japanese Unexamined Patent Publication No. 4-101381

[Patent Document 15]

Japanese Unexamined Patent Publication No. 7-220862

[Patent Document 16]

Japanese Unexamined Patent Publication No. 7-65935

[Patent Document 17]

Japanese Unexamined Patent Publication No. 2004-6242

[Patent Document 18]

Japanese Unexamined Patent Publication No. 2004-111107

[Patent Document 19]

Japanese Unexamined Patent Publication No. 11-339939

[Patent Document 20]

Japanese Unexamined Patent Publication No. 2001-102157

[Patent Document 21]

Japanese Unexamined Patent Publication No. 2002-170655

There has been a demand for a heater that can heat a wafer with more uniform temperature distribution with a simpler structure, since it is difficult to achieve uniform temperature distribution with the conventional heater and it is necessary to carry out very complex and delicate control procedure to achieve a uniform temperature distribution.

In the case of the technology of chemically amplified resist that is being employed along with the trend toward smaller circuit line width of the semiconductor devices, emphasis is placed not only on the uniform temperature distribution over the wafer, but also on the temperature changes throughout the period from the time when the wafer is set in a heat treatment apparatus to the time when the heat treatment is completed and the wafer is taken out. Thus it is desired to stabilize the wafer temperature in uniform temperature distribution with about 60 seconds after placing the wafer on a heater, but the conventional heater cannot satisfy this requirement because it takes a long period of time to stabilize the temperature.

There has also been such a problem that a heater comprising a coil-shaped resistive heating member embedded therein has a tendency of the density of the heating member changing significantly between the outside and inside at a bending portion of the resistive heating member, which makes it difficult to decrease the radius of curvature. Accordingly, the methods described in Patent Document 17 and Patent Document 18 require it to connect the resistive heating members of different coil diameters within the plate-shaped ceramic member, or to form a swelling portion at a turn-back section of the resistive heating member. This results in a complex process that is not suitable for volume production, and it is very difficult to mass-produce products with stabilized quality and high level in the yield of production.

In addition, there has been such a problem that the heater having the cylindrical support member attached thereto allows heat to dissipate through the cylindrical support member, thus resulting in significant temperature difference across the wafer surface.

To counter this problem, Patent Document 19 discloses a heater having increased resistance density on the inside of the cylindrical support member 860 so as to keep the temperature difference across the wafer surface small even when the temperature is raised quickly and prevent the plate-shaped ceramic member 851 from breaking.

Patent Document 20 discloses a heater made of ceramics having a cylindrical support member attached thereto wherein temperature difference across the surface is decreased to prevent breakage, by increasing the resistance of a middle portion and an independent resistive heating member 854 is embedded at a position near the joint surface of the support member 860 . Furthermore, Patent Document 21 discloses a heater having a resistive heating member embedded therein so as to heat the cylindrical support member 860 .

Recently, it has been called for to decrease the time taken to raise the temperature to a very short period. However, there is a possibility that the heater made of ceramics having the coil-shaped resistive heating member breaks when heated at a high rate. Particularly, heaters made of ceramics having cylindrical support members attached thereto designed for increasing wafer size of 300 mm in diameter were often broken due to the high thermal stress generated by quick heating.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide a heater that is capable of heating a wafer or other object to a desired temperature in a shorter period of time while minimizing the temperature difference across the surface of the object, and a wafer heating apparatus that uses the heater.

Another object of the present invention is to provide a heater comprising a plate-shaped ceramic member with a coil-shaped heating member embedded therein that is capable of quickly heating an object while minimizing the temperature difference across the surface of the object with high reliability, and a method for manufacturing the same.

In order to achieve the object described above, the present invention provides a first heater comprising a plate-shaped member having a first principal surface which is a mount surface whereon an object to be heated is placed, a second principal surface and a resistive heating member provided therein or on the second principal surface; wherein the resistive heating member is formed in a continuous band having at least two arc bands located on one of two concentric circles of different radii, at least one arc band located on the other circle, and linkage arc bands each of which connects the arc band located on the one circle and the arc band located on the other circle, said linkage arc bands being located adjacent to each other;

while the distance between the adjacent linkage arc bands is smaller than the distance between the arc band located on the one circle described above and the arc band located on the other circle.

The first heater of the present invention having the constitution described above is capable of heating a wafer or other object to a desired temperature in a shorter period of time while minimizing the temperature difference across the surface of the object, and a wafer heating apparatus that uses the heater.

The present invention also provides a second heater comprising a plate-shaped member having a first principal surface which is a mount surface whereon an object to be heated is placed, a second principal surface, a resistive heating member provided therein or on the second principal surface, and a temperature measuring element; wherein

the resistive heating member is formed in a continuous band comprising arc bands that are located on at least two concentric circles of different diameters and are connected with each other, with power feeder sections provided on both ends thereof,

the temperature measuring element is provided within a ring-shaped resistive heating member zone that is defined as a region interposed between a circle inscribed to an arc band located at the innermost position among the arc bands and a circle circumscribed to an arc band located at the outermost position among the arc bands; and

the power feeder section is provided outside of the ring-shaped resistive heating member zone.

The second heater of the present invention having the constitution described above is capable of heating a wafer or other object to a desired temperature in a shorter period of time while minimizing the temperature difference across the surface of the object, and a wafer heating apparatus that uses the heater.

In the second heater of the present invention, at least two arc bands are disposed on one of the adjacent circles and the arc bands are connected by the linkage arc band that is located adjacent to the arc band disposed on the other circle, while the distance between the adjacent linkage arc bands is smaller than the distance between the arc bands that are connected by the linkage arc band.

In the first and second heaters of the present invention, the distance between the adjacent linkage arc bands is preferably set in a range from 30 to 80% of the distance between the arcs.

It is preferable that the first heater of the present invention comprises a plurality of the resistive heating members, and the resistive heating members are provided within a ring-shaped resistive heating member zone that is defined as a region interposed between a circle inscribed to an arc band located at the innermost position among the arc bands and a circle circumscribed to an arc band located at the outermost position among the arc bands.

In the first and second heaters of the present invention, it is preferable that a plurality of the ring-shaped resistive heating member zones are disposed in a concentric arrangement, with the resistive heating member disposed in each of the ring-shaped resistive heating member zones.

In the heater described above, it is also preferable that the plurality of ring-shaped resistive heating member zone comprise a first ring-shaped resistive heating member zone, a second ring-shaped resistive heating member zone and a third ring-shaped resistive heating member zone disposed in this order from the inside, while a circular or ring-shaped central resistive heating member zone is provided inside of the first ring-shaped resistive heating member zone and an additional resistive heating member is provided in the central resistive heating member zone.

Further in the heater described above, it is preferable that outer diameter D 1 of the central resistive heating member zone is in a range from 20 to 40% of the outer diameter D of the third ring-shaped resistive heating member zone, outer diameter D 2 of the first ring-shaped resistive heating member zone is in a range from 40 to 55% of the outer diameter D, outer diameter D 3 of the second ring-shaped resistive heating member zone is in a range from 55 to 85% of the outer diameter D, inner diameter D 22 of the first ring-shaped resistive heating member zone is in a range from 34 to 45% of the outer diameter D, inner diameter D 33 of the second ring-shaped resistive heating member zone is in a range from 55 to 65% of the outer diameter D, and inner diameter D 0 of the third ring-shaped resistive heating member zone is in a range from 85 to 93% of the outer diameter D.

In the heater described above, it is also preferable that the second ring-shaped resistive heating member zone and the third ring-shaped resistive heating member zone are each divided into equal sections by a plurality of boundary zones provided in the radial direction, that the boundary zones that divide the second ring-shaped resistive heating member zone and the boundary zones that divide the third ring-shaped resistive heating member zone are located at staggered positions with respect to each other so as not to overlap in the radial direction, and it is more preferable that the number of divisions of the second ring-shaped resistive heating member zone and the number of divisions of the third ring-shaped resistive heating member zone are different.

In the heater described above, the resistive heating member provided in the central resistive heating member zone and the resistive heating member provided in the first ring-shaped resistive heating member zone may be connected either in series or in parallel.

A through hole may be provided between the central resistive heating member zone and the first ring-shaped resistive heating member zone so as to penetrate the plate-shaped member.

In the first and second heaters of the present invention, it is preferable that width of the resistive heating member provided in the ring-shaped resistive heating member zone located at the outermost position is smaller than the width of the resistive heating member provided in the other resistive heating member zones.

In the first and second heaters of the present invention, it is preferable that three or more peripheral protrusions are provided along the periphery of the mount surface and inner protrusions that are lower than the peripheral protrusions in height are provided inside of the peripheral protrusions, and the peripheral protrusions are held so as to be movable at least in one of the radial direction of the plate-shaped member and a direction perpendicular thereto.

The heater described above may have power terminals for supplying electric power to the resistive heating member, a cooling nozzle for cooling the plate-shaped member and an opening, and be further provided with a casing that covers the power terminals and the other surface of the plate-shaped member and clamp bolts that clamp the peripheral protrusions onto the plate-shaped member, with the clamp bolts penetrating through the plate-shaped member from one surface described above to the other surface, so as to fasten the casing.

The plate-shaped member may also be fastened onto the casing via a clamp fixture.

A third heater of the present invention comprises a plate-shaped ceramic member having a first principal surface which is a mount surface whereon an object to be heated is placed, a second principal surface and a resistive heating member embedded therein.

The third heater is characterized in that the resistive heating member is formed in a continuous electrically conductive wire having two spiral coils of which center is one of two concentric circles of different radii, at least one spiral coil of which center is the other circle, and connecting coils that connect the spiral coils of which center is one of two concentric circles and the spiral coil of which center is the other circle, said connecting coils being located adjacent to each other;

while the distance between the adjacent connecting coils is smaller than the distance between the spiral coil of which center is the one circle and the spiral coil of which center is the other circle.

The heater of the present invention having the constitution described above comprises the plate-shaped ceramic member wherein the coil-shaped resistive heating member is embedded that is capable of heating an object in a shorter period of time with high reliability while minimizing the temperature difference across the surface of the object to be heated.

In the third heater, it is preferable that the connecting distance is in a range from 30 to 80% of the distance between the coils.

In the third heater, it is also preferable that the spiral coil located at the outermost position has a coil pitch smaller than those of other spiral coils.

Moreover, it is preferable that the third coil has a cylindrical support member joined onto the second principal surface of the plate-shaped ceramic member, while the spiral coil located inside of the support member has a coil pitch smaller than those of the spiral coils located outside of the support member.

A wafer heating apparatus according to the present invention is characterized by having one of the first through the third heaters of the present invention.

A method for manufacturing the third heater of the present invention comprises the steps of:

forming a groove in a green compact that is made of ceramic powder in a plate shape;

inserting a coil-shaped resistive heating member in the groove;

filling a gap between the groove and the resistive heating member with a ceramic powder and applying a preliminary pressure to the ceramic powder; and

firing the preliminarily pressed green compact in a heat resistant mold while applying a pressure thereto.

According to the method for processing the wafer of the present invention, at least one of formation of a semiconductor film on the wafer, etching process and formation of resist film is carried out while heating the wafer by means of the heater, with the wafer being placed on a mount surface of the wafer heating apparatus of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing the constitution of the heater according to the first embodiment of the present invention.

FIG. 2 is a plan view showing the configuration of the resistive heating member of the first embodiment.

FIG. 3A is a plan view showing a preferable example of ring-shaped resistive heating member zone according to the present invention.

FIG. 3B is a plan view showing an example of dividing the resistive heating member zone into a plurality of portions outside the ring-shaped resistive heating member zone of FIG. 3A.

FIG. 4 is a plan view showing a preferable example of configuration of the resistive heating member according to the present invention.

FIG. 5 is a plan view showing an example of constitution of the resistive heating member of the heater according to the second embodiment of the present invention.

FIG. 6 is a schematic diagram showing another example of constitution of the resistive heating member of the heater according to the second embodiment of the present invention.

FIG. 7A is a sectional view showing the constitution of the heater according to the third embodiment of the present invention.

FIG. 7B is a plan view of the heater of the third embodiment.

FIG. 8A is an enlarged sectional view of first example of the peripheral protrusion of the third embodiment.

FIG. 8B is an enlarged sectional view of second example of the peripheral protrusion of the third embodiment.

FIG. 8C is an enlarged sectional view of third example of the peripheral protrusion of the third embodiment.

FIG. 8D is an enlarged sectional view of fourth example of the peripheral protrusion of the third embodiment.

FIG. 9 is a sectional view taken along lines Y-Y of FIG. 7B.

FIG. 10A is a schematic plan view showing an example of the configuration of the resistive heating member zone of the heater according to the third embodiment.

FIG. 10B is a schematic plan view showing an example of the resistive heating member zone obtained by dividing the resistive heating member zone of FIG. 10A further.

FIG. 11A is a schematic perspective view showing the constitution of the ceramic heater according to the fourth embodiment of the present invention, b) being a schematic sectional view taken along lines X-X.

FIG. 11B is a schematic sectional view taken along lines X-X of FIG. 11A.

FIG. 12 is a schematic diagram showing the configuration of the resistive heating member of the heater according to the fourth embodiment.

FIG. 13A is a schematic perspective view showing the constitution of the ceramic heater according to the variation of the present invention.

FIG. 13B is a schematic sectional view taken along lines X-X of FIG. 13A.

FIG. 14 is a schematic diagram showing the resistive heating member of the fourth embodiment.

FIG. 15A is a schematic plan view explanatory of a preferable form of resistive heating member in the variation shown in FIG. 13A.

FIG. 15B is a schematic sectional view taken along lines X-X of FIG. 15A.

FIG. 16 is a sectional view showing an example of heater of the prior art.

FIG. 17 is a schematic diagram showing the configuration of a resistive heating member of the prior art.

FIG. 18 is a schematic diagram showing the configuration of another resistive heating member of the prior art.

FIG. 19 is a schematic diagram showing the configuration of another resistive heating member of the prior art.

FIG. 20 is a schematic diagram showing the configuration of another resistive heating member of the prior art.

FIG. 21 is a schematic diagram showing the configuration of another resistive heating member of the prior art.

FIG. 22 is a schematic diagram showing the configuration of another resistive heating member of the prior art.

FIG. 23 is a schematic diagram showing the configuration of another resistive heating member of the prior art.

FIG. 24 is a schematic diagram showing the configuration of resistive heating member of the prior art.

FIG. 25 is a schematic sectional view showing another ceramic heater of the prior art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will now be described below.

Embodiment 1

FIG. 1 is a sectional view showing the constitution of a heater 1 according to a first embodiment of the present invention. The heater 1 of the first embodiment comprises a plate-shaped ceramic member 2 , power feeder sections 6 , power terminals 11 and a metal casing 19 .

According to the first embodiment, the plate-shaped ceramic member 2 is made of a ceramic material consisting of silicon carbide or aluminum nitride as the main component, for example, and has one principal surface used as a mount surface 3 to place the wafer W thereon and a resistive heating member 5 is formed as described below on the other principal surface.

The power feeder sections 6 are electrically connected to the resistive heating member 5 that is formed on the other principal surface of the plate-shaped ceramic member 2 , while the power terminals 11 are connected to the power feeder sections 6 .

The metal casing 19 holds the power terminals 11 connected to the power feeder sections 6 and is fastened onto the periphery of the other principal surface of the plate-shaped ceramic member 2 via a contact member 17 so as to surround the power feeder sections 6 .

The plate-shaped ceramic member 2 has a through hole 26 that penetrates therethrough in the direction of thickness. Wafer lift pins 25 are provided movably in the vertical direction in the through hole 26 , so that the wafer W can be moved vertically and placed on the mount surface 3 and unloaded therefrom. With the constitution described above, electric power can be supplied from the outside through the power terminals 11 to the powder feeder sections 6 , so as to heat the wafer W while measuring the temperature of the plate-shaped ceramic member 2 by means of a temperature measuring element 27 .

The wafer W is held while being lifted by the wafer support pins 8 from the mount surface 3 , so as to prevent the wafer W from being subjected to uneven distribution of temperature due to uneven bearing.

According to the present invention, it is preferable to divide the resistive heating member 5 into a plurality of zones each provided with a separate power feeder section and connected to the power terminals 11 so that electric power can be supplied independently to each of the power feeder sections 6 . This constitution makes it possible to control the electric power supplied to the power terminals 11 so that each of the temperature measuring element 27 indicates a predetermined temperature and uniform temperature distribution over the surface of the wafer placed on the mount surface 3 . In this case, while it is preferable to provide the temperature measuring element 27 in each zone, but one temperature measuring element 27 may be provided for every two or three zones.

The power feeder sections 6 are made of gold, silver, palladium, platinum or the like, for example, and is put into contact with the power terminals 11 thereby establishing electrical continuity. There is no restriction on the method of connecting the power terminals 11 and the power feeder sections 6 , and soldering, brazing or the like may be employed as long as electrical continuity can be secured.

In the heater of the first embodiment, the band-shaped resistive heating member 5 formed inside of the plate-shaped ceramic member 2 or on the principal surface thereof comprises one continuous electrical conductor constituted from arc bands 5 i through 5 p that have substantially the same line width and formed in substantially concentric configuration and are connected by turn-back linkage arc bands 5 q through 5 v as shown in FIG. 2.

Specifically, the arc band 5 i that has the power feeder section 6 at one end thereof is formed so as to constitute a part of circle that is located at the innermost position and has center located at the center of the plate-shaped ceramic member 2 , with the other end of the arc band 5 i connected to one end of the turn-back linkage arc band 5 q . Connected to the other end of the turn-back linkage arc band 5 q is one end of the arc band 5 k that is formed so as to constitute a part of circle located at the second position from the inside (with the center located at the center of the plate-shaped ceramic member 2 ), with the other end of the arc band 5 k being connected to one end of the turn-back linkage arc band 5 t . Connected to the other end of the turn-back linkage arc band 5 t is one end of the arc band 5 n formed so as to constitute a part of circle located at the third position from the inside (with the center located at the center of the plate-shaped ceramic member 2 ), with the other end of the arc band 5 n being connected to one end of the turn-back linkage arc band 5 u . Connected to the other end of the turn-back linkage arc band 5 u is one end of the arc band 5 p that is formed so as to constitute a part of circle located at the fourth position from the inside (the outermost circle in the example shown in FIG. 2, with the center located at the center of the plate-shaped ceramic member 2 ), with the other end of the arc band 5 p being connected to one end of the turn-back linkage arc band 5 v . Connected to the other end of the turn-back linkage arc band 5 v is one end of the arc band 5 o that is formed so as to constitute a part of circle located at the third position from the inside, with the other end of the arc band 5 o being connected to one end of the turn-back linkage arc band 5 s . Connected to the other end of the turn-back linkage arc band 5 s is one end of the arc band 5 m that is formed so as to constitute a part of circle located at the second position from the inside, with the other end of the arc band 5 m being connected to one end of the turn-back linkage arc band 5 r . Connected to the other end of the turn-back linkage arc band 5 r is the arc band 5 j that is formed so as to constitute a part of the innermost circle, with the other end of the arc band 5 j being formed as the power feeder section.

As described above, the resistive heating member 5 is a long band of heat generating member constituted from the plurality of arc bands 5 i through 5 p arranged to constitute concentric circles and the turn-back linkage arc bands 5 q through 5 v that connect adjacent ones of the arc bands 5 i through 5 p , that are disposed on circles of different radii, with each other in series, and both ends (arc bands 5 i , 5 j ) form the power feeder sections 6 .

In the first embodiment, since the resistive heating member 5 is formed by disposing each of the pairs of the arc band 5 i and the arc band 5 j , the arc band 5 k and the arc band 5 m and the arc band 5 n and the arc band 5 o so as to constitute a circle, with the arc band 5 p also constituting a circle, while the circles are disposed concentrically, concentric temperature distribution patterns can be formed to repeat from the center of the mount surface 3 to the circumference by energizing the resistive heating member 5 .

The first embodiment is characterized in that distances L 1 , L 2 and L 3 of the adjacent pair of the turn-back linkage arc band 5 q and the turn-back linkage arc band 5 r , the pair of the turn-back linkage arc band 5 s and the turn-back linkage arc band 5 t and the pair of the turn-back linkage arc band 5 u and the turn-back linkage arc band 5 v , respectively, are set to be smaller than the distances L 4 , L 5 and L 6 between the arc bands 5 i through 5 p that are located adjacent to each other in the radial direction.

This constitution enables it to generate the same amount of heat per unit volume from the turn-back linkage arc bands 5 q through 5 v as well as from the arc bands 5 i through 5 p , thereby to improve the uniformity of heating the mount surface 3 (uniform temperature distribution over the mount surface 3 ). In the prior art, the distances L 1 , L 2 and L 3 of the adjacent pairs of the turn-back linkage arc band 5 q through the turn-back linkage arc band 5 v are set to be equal to the distances L 4 , L 5 and L 6 between the turn-back arc bands 5 i through 5 p that are located adjacent to each other in the radial direction. With such a constitution, since heat is generated with lower density in the turn-back linkage portion (hereinafter referred to simply as the turn-back region) P 5 that connect the arc bands 5 i through 5 p and the turn-back linkage arc band 5 q through the turn-back linkage arc band 5 v , temperature becomes lower in the outside of the turn-back region P 5 , resulting in larger temperature difference across the surface of the wafer W, thus impairing the uniform heating performance.

According to the present invention, in contrast, since the distances L 1 , L 2 and L 3 of the adjacent pair of the turn-back linkage arc bands 5 q through 5 v located on the same circle are made smaller than the distances L 4 , L 5 and L 6 between the arc bands 5 i through 5 p that are located adjacent to each other in the radial direction, shortage in heat generated from the turn-back region P 5 is compensated for by the heat generated by the turn-back linkage arc bands 5 q through 5 v , thus enabling it to avoid temperature decrease in the turn-back region P 5 . As a result, temperature difference across the surface of the wafer W that is placed on the mount surface 3 can be decreased and uniformity of heating can be improved.

Highest uniformity of heating by the mount surface 3 can be achieved by setting the distances L 1 , L 2 and L 3 of the adjacent pair of the turn-back linkage arc bands 5 q through 5 v located on the same circle in a range from 30 to 80% of the distances L 4 , L 5 and L 6 between the arc bands 5 i through 5 p that are located adjacent to each other in the radial direction, more preferably setting L 1 , L 2 and L 3 in a range from 40 to 60% of L 4 , L 5 and L 6 .

Also according to the present invention, since the resistive heating member 5 is constituted from the arc bands 5 i through 5 p and the turn-back linkage arc bands 5 q through 5 v , it is less probable that an excessive stress is generated in the edges than in the case of the rectangular turn-back resistive heating member of the prior art, and the heater 1 that has higher reliability can be provided wherein the plate-shaped ceramic member 2 and the resistive heating member 5 are less likely to break even when temperature of the heater 1 is raised or lowered at a high rate.

In the first embodiment, it is preferable for the form of the resistive heating member shown in FIG. 2 that the distance L 4 between the innermost circle whereon the arc band 5 i and the arc band 5 j are disposed and the circle located at the second position from the inside whereon the arc band 5 m and the arc band 5 k are disposed, the distance L 5 between the second circle and the circle located at the third position from the inside whereon the arc band 5 n and the arc band 5 o are disposed and the distance L 6 between the third circle and the circle located at the outermost position whereon the arc band 5 p is disposed are set substantially equal.

When the arc bands are disposed at substantially equal intervals in the radial direction as described above, it is made possible to generate the same amount of heat per unit volume from the arc bands 5 i through 5 p , thereby to suppress the unevenness of heating the mount surface 3 in the radial direction.

The effect of the constitution of the resistive heating member 5 described above is obtained, in addition to the case where the resistive heating member is embedded in the plate-shaped ceramic member, also in case the resistive heating member is provided on the other principal surface of the plate-shaped ceramic member 2 . When the band-shaped resistive heating member 5 is provided on the other principal surface of the plate-shaped ceramic member 2 , in particular, greater effect of preventing the plate-shaped ceramic member 2 and the resistive heating member 5 from breaking can be achieved by over-coating an insulation film on the resistive heating member 5 .

The resistive heating member may also be constituted from a plurality of heating members that can be heated independently in a concentric configuration. In this case, it is preferable to set the distance between the outermost band of the resistive heating member and the band located inside thereof in the concentric configuration smaller than the distance of the band located inside thereof. The resistive heating member 5 having such a constitution makes it easier to replenish heat to the periphery of the plate-shaped ceramic member 2 from which heat is dissipated at a higher rate, thereby preventing the periphery of the wafer W from becoming lower in temperature.

In the heater 1 of the first embodiment, it is preferable to divide the resistive heating member into a plurality of ring-shaped resistive heating member zones disposed in a concentric configuration with the center located at the center axis of the wafer W that is placed on the mount surface 3 . This is because, while heating of the surface of a disk-shaped wafer W is subjected to the influences of the atmosphere around the wafer W, wall surface that opposes the wafer W and the gas flow, the wall surface surrounding the wafer W, the surface that oppose the top surface of the wafer and the flow of the ambient gas are designed in centrally symmetric configuration so as to prevent the temperature from varying across the surface of the disk-shaped wafer W. Uniformly heating the wafer W requires the heater 1 to be designed to match the centrally symmetric environment with respect to the wafer W, and it is preferable to divide the mount surface 3 radially into resistive heating member zones 4 in centrally symmetric configuration.

In order to heat a wafer w of 300 mm or more in diameter with uniform temperature distribution across the surface, in particular, it is preferable to divide the mount surface 3 into three ring-shaped resistive heating member zones in concentric configuration.

FIG. 3A shows a preferable example of dividing into a plurality of resistive heating member zones 4 . In this preferable example of zone division, the mount surface is divided into resistive heating member zone 4 a of circular or ring shape located at the innermost position and three ring-shaped resistive heating member zones 4 b , 4 cd , 4 eh located concentrically on the outside thereof. In this example, the resistive heating member 5 is divided into four resistive heating member zones so as to improve the performance of uniformly heating the wafer W.

In order to minimize the temperature difference across the surface of the wafer W, it is preferable to set the outer diameter D 1 of the resistive heating member zone 4 a located at the center of the heater 1 in a range from 20 to 40% of the outer diameter D of the ring-shaped resistive heating member zone 4 eh located along the periphery, outer diameter D 2 of the resistive heating member zone 4 b located outside thereof in a range from 40 to 55% of the outer diameter D of the ring-shaped resistive heating member zone 4 eh located along the periphery, and the inner diameter D 0 of the ring-shaped resistive heating member zone 4 eh located at the outermost position in a range from 55 to 85% of the outer diameter D of the ring-shaped resistive heating member zone 4 eh located at the outermost position.

The outer diameter of the resistive heating member zone means the diameter of the circle that is circumscribed to the outermost arc band of the resistive heating member formed in the resistive heating member zone. The inner diameter of the resistive heating member zone means the diameter of the circle that is inscribed to the innermost arc band of the resistive heating member formed in the resistive heating member zone. Definition of the circumscribed circle and the inscribed circle is made by using the arc section excluding the protruding portions of the resistive heating member such as power feeder section.

When the outer diameter D 1 is less than 20% of D, temperature of the mid portion of the resistive heating member zone 4 a would not rise sufficiently even if the resistive heating member zone 4 a is caused to generate more heat, due to the small outer diameter of the central resistive heating member zone 4 a . When the outer diameter D 1 is more than 40% of D, temperature of the resistive heating member zone 4 a would become too high along the periphery thereof as the temperature of the mid portion of the resistive heating member zone 4 a is raised, due to the large outer diameter of the resistive heating member zone 4 a located at the center. The outer diameter D 1 is preferably in a range from 20% to 30% of D, and more preferably from 23% to 27%, which makes it possible to further decrease the temperature difference across the surface of the wafer W.

When the outer diameter D 2 is less than 40% of the outer diameter D, since the heater 1 tends to cool down along the periphery, an attempt to prevent temperature of the wafer W along the periphery thereof from decreasing by causing the ring-shaped resistive heating member zone 4 cd to generate more heat would result in higher temperature of the ring-shaped resistive heating member zone 4 cd in an inner portion thereof nearer to the center of the wafer W, thus increasing the temperature difference across the wafer surface. When the outer diameter D 2 is more than 55% of the outer diameter D, an attempt to prevent the temperature of the wafer W along the periphery thereof from decreasing by causing the ring-shaped resistive heating member zone 4 cd to generate more heat raises the temperature of the ring-shaped resistive heating member zone 4 cd although the effect of decreasing the temperature of the wafer W along the periphery thereof reaches the ring-shaped resistive heating member zone 4 b , thus resulting in lower temperature of the ring-shaped resistive heating member zone 4 b along the periphery thereof. The outer diameter D 2 is preferably in a range from 41% to 53% of the outer diameter D, and more preferably from 43% to 49%, which makes it possible to further decrease the temperature difference across the wafer surface.

When the outer diameter D 3 is less than 55% of the outer diameter D, since the heater 1 tends to cool down along the periphery thereof, an attempt to prevent the temperature of the wafer W along the periphery thereof from decreasing by increasing heat generation from the ring-shaped resistive heating member zone 4 eh would result in higher temperature of the ring-shaped resistive heating member zone 4 eh in the inner portion thereof nearer to the center of the wafer W, thus increasing the temperature difference across the surface of the wafer W. When the outer diameter D 3 is more than 85% of the outer diameter D, an attempt to prevent the temperature of the wafer W along the periphery thereof from decreasing by causing the ring-shaped resistive heating member zone 4 eh to generate more heat raises the temperature of the ring-shaped resistive heating member zone 4 eh although the effect of decreasing the temperature of the wafer W along the periphery thereof reaches the ring-shaped resistive heating member zone 4 cd , thus resulting in lower temperature of the ring-shaped resistive heating member zone 4 cd along the periphery thereof. The outer diameter D 3 is preferably in a range from 65% to 85% of the outer diameter D, and more preferably from 67% to 70%, which makes it possible to further decrease the temperature difference across the surface of the wafer W.

It was found that the constitution of the heater 1 comprising the plurality of the resistive heating member 5 as described above makes it possible to compensate for slight asymmetry in the lateral configuration of the environment and unevenness in the thickness of the symmetrical heating member, while further decreasing the temperature difference across the surface of the wafer W.

External dimensions of the resistive heating member zone 4 have been described in detail. According to the present invention, the resistive heating member is divided into a plurality of resistive heating member zones preferably in such a configuration as annular no-heater zones where the resistive heating member 5 does not exist between the resistive heating member zone located inside and the resistive heating member zone located outside. Forming the no-heater zones enables it to provide the support pins 8 , the through hole 26 and/or the power feeder sections 6 in the no-heater zones. This makes it possible to prevent the temperature from being unevenly distributed due to the support pins 8 , the through hole 26 and/or the power feeder section 6 that would otherwise increase the temperature difference across the wafer surface.

Inner diameter D 11 of the resistive heating member zone 4 having outer diameter of D 1 on the center side of the resistive heating member zone 4 a may be set in range from 5 to 10% of the diameter D. This allows it to provide the support pins 8 , for example, within the circle of diameter D 11 , so as to prevent the temperature of the wafer surface from decreasing due to the support pins 8 .

It is preferable that inner diameter D 22 of the resistive heating member zone that has the outer diameter D 2 is in a range from 34% to 45% of the outer diameter D, inner diameter D 33 of the resistive heating member zone that has the outer diameter D 3 is in a range from 55% to 65% of the outer diameter D and inner diameter D 0 of the resistive heating member zone that has the outer diameter D is in a range from 85% to 93% of the outer diameter D.

The reason for setting the inner diameter D 22 of the ring-shaped resistive heating member zone 4 b located at the second position from the inside preferably in a range from 34% to 45% of the outer diameter D is that this enables it to provide an annular no-heater zone measuring about 1% to 22% of the diameter between the resistive heating member zone 4 a and the ring-shaped resistive heating member zone 4 b , thus minimizing the decrease in the temperature of the wafer surface even when the lift pins 25 or the like are provided in the no-heater zone. The inner diameter D 22 is more preferably set in a range from 36% to 41% of the outer diameter D. This enables it to provide a through hole that penetrates through the plate-shaped member between the resistive heating member zone 4 a and the ring-shaped resistive heating member zone 4 b.

It is preferable that inner diameter D 33 of the ring-shaped resistive heating member zone 4 cd is in a range from 55% to 65% of the diameter D. An annular no-heater zone can be formed between the ring-shaped resistive heating member zone 4 b and the ring-shaped resistive heating member zone 4 cd . Since the power feeder sections 6 that supply electric power to the resistive heating member can be provided in this no-heater zone, cold spot or the like can be prevented from being created on the surface of the wafer W due to the disposition of the power feeder sections 6 . Inner diameter D 33 is more preferably in a range from 58% to 63% of the diameter D.

Further, inner diameter D 0 of the ring-shaped resistive heating member zone 4 eh may be in a range from 85% to 93% of the diameter D. This allows it to provide an annular no-heater zone between the ring-shaped resistive heating member zone 4 eh and the ring-shaped resistive heating member zone 4 cd . The wafer W can be heated without increasing the temperature difference across the wafer surface, by providing the support pins 8 that support the object to be heated such as wafer W, and/or the power feeder sections 6 in the annular no-heater zone. Inner diameter D 0 is more preferably in a range from 90% to 92% of the diameter D.

In the heater 1 comprising the resistive heating member 5 disposed in the configuration of a plurality of rings as described above, there has been such a possibility that thickness becomes uneven between left and right when a large-sized resistive heating member is formed by screen printing, due to slight asymmetry in the environment and/or the restriction of the manufacturing method of the band-shaped resistive heating member. It was found that division of the annular zones described above is preferable for the reason of operating environment and the restriction of the manufacturing method, resulting in smaller temperature difference across the wafer surface.

FIG. 3B shows another example of zone division of the heater 1 of the present invention, where the ring-shaped resistive heating member zones 4 cd and 4 eh are further divided. In the example shown in FIG. 3B, among the four ring-shaped resistive heating member zones 4 a , 4 b , 4 cd and 4 eh , the ring-shaped resistive heating member zones 4 a , 4 b are ring-shaped, while the ring-shaped resistive heating member zone 4 cd located outside thereof is divided into two equal parts of fan-shaped resistive heating member zone 4 c , 4 d with equal center angles (180°), and the ring-shaped resistive heating member zone 4 eh located outside thereof is divided into four equal parts of fan-shaped resistive heating member zones 4 e , 4 f , 4 g and 4 h with equal center angles (90°). Such a configuration is preferable as it achieves uniform temperature distribution over the surface of the wafer W.

In the example shown in FIG. 3B, it is preferable that the resistive heating member zones 4 a through 4 h are provided with the resistive heating members 5 a through 5 h that can independently control the heat generation, respectively.

In the examples shown in FIG. 3A and FIG. 3B, the resistive heating member zones 4 a , 4 b may be connected with each other in parallel so as to be controlled by a single control circuit, if the outside environment where the heater 1 would not be changed frequently. With this constitution, predetermined space can be provided between the resistive heating member zones 4 a , 4 b , and therefore the through hole 26 through which the lift pins that lift the wafer W pass can be provided.

When the through hole 26 that penetrates the plate-shaped member is provided between the central resistive heating member zone 4 a and the ring-shaped resistive heating member zone 4 b located outside thereof, wafer temperature can be prevented from decreasing due to the through hole 26 so as to decrease the temperature difference across the surface of the wafer W.

While the ring-shaped resistive heating member zone 4 cd is divided into two equal parts of the same center angles and the ring-shaped resistive heating member zone 4 eh is divided into four equal parts of the same center angles in the example described above, the present invention is not limited to this constitution.

While the resistive heating member zones 4 c , 4 d shown in FIG. 3B are divided by a straight border line, it needs not necessarily be a straight line but may be a wavy line. The resistive heating member zones 4 c , 4 d are preferably symmetrical with respect to the center of the concentric resistive heating member zone.

Similarly, border lines between the resistive heating member zones 4 e and 4 f , 4 f and 4 g , 4 g and 4 h and 4 h and 4 e need not necessarily be straight lines but may be wavy lines. These zones are also preferably symmetrical with respect to the center of the concentric resistive heating member zone.

It is also preferable that the border line between the resistive heating member zones 4 c , 4 d and the border lines between the resistive heating member zones 4 e , 4 f , 4 g and 4 h are not aligned with each other on a straight line, since it enables it to prevent cold spots from occurring near the border lines.

According to the present invention, the resistive heating member zones 4 e , 4 f , 4 g , 4 h and the resistive heating member zones 4 c , 4 d are divided in such a manner as the border zones of the resistive heating member zones 4 e , 4 f , 4 g , 4 h in the outermost ring-shaped resistive heating member zone 4 eh and the border zones of the resistive heating member zone 4 c , 4 d in the ring-shaped resistive heating member zone 4 cd located inside thereof are staggered with respect to each other.

The constitution will be described in more detail with reference to FIG. 3B.

First, a reference line Ls that passes the center of the plate-shaped ceramic member 2 is defined, and one of the border lines of the resistive heating member zone 4 e is defined by a straight line that is inclined by a small angle Δβ from the reference line Ls. Then the other border line of the resistive heating member zone 4 e is defined by a straight line that is inclined by an angle β 1 from the reference line Ls. These angles satisfy the relation β 1 =90°−Δβ. Further, one of the border lines of the resistive heating member zone 4 f is defined by a straight line that is inclined by an angle β 2 from the reference line Ls. These angles satisfy the relation β 2 =90°+Δβ. Thus the border zone Zef between the resistive heating member zone 4 e and the resistive heating member zone 4 f is determined. Similarly, the border zones that divide the ring-shaped resistive heating member zone 4 eh into four resistive heating member zones 4 e , 4 f , 4 g , 4 h are defined.

Then the ring-shaped resistive heating member zone 4 cd located inside of the ring-shaped resistive heating member zone 4 eh is defined by means of the reference line Ls. One of the border lines of the resistive heating member zone 4 c is defined by a straight line that is inclined by an angle α 1 from the reference line Ls. The angle satisfies the relation α 1 =α−Δα. Then one of the border lines of the resistive heating member zone 4 d is defined by a straight line that is inclined by an angle α 2 from the reference line Ls. These angles satisfy the relation α 2 =α+Δα. Thus the border zone Zcd between the resistive heating member zone 4 c and the resistive heating member zone 4 d is determined. Further, the other border line of the resistive heating member zone 4 d is defined by a straight line that is inclined by an angle (α 1 +180°) from the reference line Ls, and the other border line of the resistive heating member zone 4 c is defined by a straight line that is inclined by an angle (α 2 +180°) from the reference line Ls. Thus the border zones that divide the ring-shaped resistive heating member zone 4 cd into two resistive heating member zones 4 c , 4 d are defined.

The small angle Δβ and the small angle Δα are determined uniquely in accordance to the space L 1 which will be described later, and usually the small angle Δβ and the small angle Δα are made equal to each other.

While the ring-shaped resistive heating member zone 4 eh is divided into four resistive heating member zones 4 e , 4 f , 4 g , 4 h and the ring-shaped resistive heating member zone 4 cd is divided into two resistive heating member zones 4 c , 4 d in the example described above, the present invention is not limited to these numbers of divisions.

According to the present invention, cold spots can be prevented from being created and temperature difference across the wafer surface can be decreased, by appropriately setting the number of divisions (or the center angle of the zones created by the division) of the resistive heating member zone located at the outermost position and the resistive heating member zone located inside thereof and the angles α and β that define the border lines with respect to the reference line, so that the border zones of the resistive heating member zone located at the outermost position and the border zones of the resistive heating member zone located inside thereof are not aligned with each other on a straight line.

As described above, in the example of setting the resistive heating member zone shown in FIG. 3B according to the present invention, the border line Zcd within the ring-shaped resistive heating member zone 4 cd is located in a region encompassed by the center angle α 1 -α 2 of the plate-shaped member from the reference line that passes the center of the plate-shaped member. The border line Zef of the ring-shaped resistive heating member zone 4 eh is located in a region encompassed by the center angle β 1 -β 2 . The border zones are set in a staggered configuration so that α 1 -α 2 do not overlap with β 1 -β 2 .

In the heater 1 of the present invention, it is preferable that the interval between the plurality of resistive heating members 5 along the circumference in the same resistive heating member zone is smaller than the intervals between the bands in the radial direction in the same resistive heating member zone. With this configuration, cold spots can be prevented from being created near the borders.

In the example shown in FIG. 4, the interval Lcd between the resistive heating member 5 c and the resistive heating member 5 d along the circumference is preferably smaller than the intervals L 6 , L 7 of the arc bands in the radial direction within the same resistive heating member 5 c (or 5 d ). It is also preferable that the intervals L 1 , L 2 between the resistive heating member 5 e and the resistive heating member 5 f , between the resistive heating member 5 f and the resistive heating member 5 h , between the resistive heating member 5 h and the resistive heating member 5 g , and between the resistive heating member 5 g and the resistive heating member 5 e along the circumference is smaller than the intervals L 4 , L 5 of the arc bands in the radial direction within the same resistive heating members 5 e , 5 f , 5 g , 5 h . With this configuration, cold spots can be prevented from being created near the borders.

In the example of zone division according to the present invention shown in FIG. 3B, the resistive heating member 5 b is provided in the single resistive heating member zone that is the ring-shaped resistive heating member zone 4 b located at the innermost position which is not divided, among the three ring-shaped resistive heating member zones 4 b , 4 cd , 4 eh excluding the resistive heating member zone 4 a . The ring-shaped resistive heating member zone 4 cd located outside of the ring-shaped resistive heating member zone 4 b consists of two fan-shaped resistive heating member zones 4 c and 4 d that are equal halves of a ring, while the fan-shaped resistive heating member zones 4 c and 4 d are provided with the resistive heating members 5 c , 5 d , respectively. The ring-shaped resistive heating member zone 4 eh located outside of the ring-shaped resistive heating member zone 4 cd consists of four fan-shaped resistive heating member zones 4 e , 4 f , 4 g and 4 h that are equal quarter of a ring, while the fan-shaped resistive heating member zones 4 e , 4 f , 4 g and 4 h are provided with the resistive heating members 5 e , 5 f , 5 g and 5 h , respectively. The resistive heating member zone and the resistive heating member constituted as shown in FIG. 3B enable it to heat the wafer W with uniform temperature distribution over the surface.

In the heater 1 shown in FIG. 3B, it is preferable that the resistive heating members 5 a through 5 h that are provided in the resistive heating member zones 4 a through 4 h , respectively, can be individually controlled.

However, the zone 4 a and the zone 4 b may also be connected with each other in parallel or series so as to be controlled by a single control circuit depending on the operating conditions of the heater 1 . The space between the resistive heating member zone 4 a and 4 b may be set such that a through hole wherein the lift pin that lifts the wafer W passes can be provided therein.

While the ring-shaped resistive heating member zones 4 cd , 4 eh are divided into two parts and four parts, respectively, the present invention is not limited to this constitution.

While the resistive heating member zones 4 c , 4 d shown in FIG. 3B are divided by a straight border line, it needs not necessarily be a straight line but may be a wavy line. The resistive heating member zones 4 c , 4 d are preferably centrally symmetric with respect to the center of the concentric resistive heating member zone.

Similarly, border lines between the resistive heating member zones 4 e and 4 f , 4 f and 4 g , 4 g and 4 h and 4 h and 4 e need not necessarily be straight lines but may be wavy lines. These zones are also preferably centrally symmetrical with respect to the center of the concentric circle.

Each of the resistive heating members 5 is preferably formed by printing process or the like in the form of a band 1 to 5 mm in width and 5 to 50 μm in thickness. When a large area is printed at a time, there may arise unevenness in thickness of the printed layer due to difference in pressure between a squeegee and a screen across the printed surface. Especially when the resistive heating member 5 is large in size, thickness of the resistive heating member 5 becomes uneven across the surface, resulting in varying amount of heat generated. Varying amount of heat generated leads to larger temperature difference across the wafer surface. It was found that, in order to prevent difference in temperature from occurring due to the varying thickness of the resistive heating member, it is effective to divide the resistive heating member 5 of large diameter into five parts.

Accordingly, since the area of the resistive heating member 5 to be printed in the resistive heating member zone 4 can be made smaller when the ring-shaped resistive heating member zone 4 cd of the concentric rings except for the central portion of the wafer mount surface 3 is divided into two parts, and the ring-shaped resistive heating member zone 4 eh of the large ring is divided into four parts, thickness of the resistive heating member 5 can be made uniform. Moreover, slight difference in temperature across the surface of the wafer W can be corrected and uniform temperature distribution over the surface of the wafer W can be achieved. In order to make fine adjustment of resistance of the band of the resistive heating member 5 , a long groove may be formed along the resistive heating member by means of laser or the like, thereby adjusting the resistance.

The resistive heating members 5 a , 5 b , 5 c , 5 d , 5 e , 5 f , 5 g and 5 h shown in FIG. 4 are formed in turn-back configuration.

In the heater 1 of the present invention, diameter D of the circumscribed circle of the resistive heating member 5 is preferably in a range from 90 to 97% of the diameter DP of the plate-shaped ceramic member 2 .

When diameter D of the circumscribed circle C of the resistive heating member 5 is smaller than 90% of the diameter DP of the plate-shaped ceramic member 2 , it takes longer time to raise or lower the temperature and therefore results in unfavorable temperature characteristic of the wafer W. For the purpose of achieving uniform temperature distribution over the wafer so that temperature of the wafer W does not become lower along the periphery, diameter D is preferably about 1.02 times the diameter of the wafer W. When the diameter DP of the plate-shaped ceramic member 2 is larger than the range described above in relation to the size of the wafer W, size of the wafer W becomes too small in relation to the diameter DP of the plate-shaped ceramic member 2 , and the efficiency of heating the wafer W for the input power becomes lower. Moreover, larger size of the plate-shaped ceramic member 2 results in larger installation area of the wafer manufacturing apparatus, which is not desirable because it decreases the rate of operation of the semiconductor manufacturing apparatus.

When diameter D of the circumscribed circle C of the resistive heating member 5 is larger than 97% of the diameter DP of the plate-shaped ceramic member 2 , the space between the contact member 17 and the periphery of the resistive heating member 5 becomes too small and heat dissipates from the periphery of the resistive heating member 5 into the contact member 17 , thus resulting in uneven temperature distribution in the circumferential portion. Particularly, since heat is transferred through the contact member 17 also from the portion along the periphery that does not include arc band 51 in contact with the circumscribed circle C, and the arc band 51 located along the periphery is bended toward the center of the plate-shaped ceramic member 2 , temperature may become lower in the portion P that does not include arc band 51 along the circumscribed circle C which surrounds the resistive heating member 5 , thus resulting in larger temperature difference across the wafer surface. According to the present invention, diameter D of the circumscribed circle C of the resistive heating member 5 is set preferably in a range from 92 to 95% of the diameter DP of the plate-shaped ceramic member 2 .

In case the plate-shaped ceramic member 2 and the metal casing 19 have substantially the same outer diameters and the plate-shaped ceramic member 2 is supported by the metal casing 19 from below as shown in FIG. 1, diameter D of the circumscribed circle C of the resistive heating member 5 is preferably in a range from 91 to 95%, and more preferably in a range from 92 to 94% of the diameter DP of the plate-shaped ceramic member 2 .

In addition, in the heater 1 of the present invention, the configuration of the resistive heating member shown in FIG. 4 includes the empty portion P that does not include arc band of the resistive heating member 5 in part of the circumscribed circle C. The distance L 1 between the linkage arc bands that oppose each other in the vicinity of the empty region P is preferably smaller than the difference between the diameter DP of the plate-shaped ceramic member 2 and the diameter D of the circumscribed circle C (hereinafter denoted as LL). When the distance L 1 is larger than the difference LL, heat of the empty region P may be transferred to the periphery of the plate-shaped ceramic member, thus resulting in a lower temperature of the empty region P. When the distance L 1 is smaller than the difference LL, however, temperature of the empty region P is less likely to lower so that temperature of a part of the peripheral portion of the wafer W placed on the mount surface 3 of the plate-shaped ceramic member 2 does not lower and the temperature difference across the surface of the water W can be decreased.

In order to prevent the temperature of the empty region P from lowering, it is preferable to keep the resistance of the linkage arc band 52 that heats the empty region at the same or slightly higher level as that of the other portion so as to increase the amount of heat generation, which makes it less likely that temperature of the empty region P becomes lower and achieves uniform temperature distribution over the wafer. When the resistive heating member 5 is formed by printing process or the like, the temperature of the linkage arc band 52 can be made higher than the temperature of the arc band 51 so as to achieve uniform temperature distribution over the surface of the wafer W, by making the width Ws of the linkage arc band 52 smaller by 1 to 5% than the width Wp of the arc band 51 , thereby increasing the resistance of the linkage arc band 52 .

In the wafer heater 1 wherein one of the principal surfaces of the plate-shaped ceramic member 2 having thickness from 1 to 7 mm is used as the mount surface 3 to place the wafer W thereon and the resistive heating member 5 is formed on the bottom surface of the plate-shaped ceramic member 2 , it is preferable that thickness of the resistive heating member 5 is in a range from 5 to 50 μm and the area occupied by the resistive heating member 5 in the circumscribed circle C is in a range from 5 to 30% of the area of the circumscribed circle C that surrounds the resistive heating member 5 .

When the area occupied by the resistive heating member 5 in the circumscribed circle C is less than 5% of the area of the circumscribed circle C that surrounds the resistive heating member 5 , distances L 1 , L 2 etc. in the resistive heating member 5 become too large, and therefore temperature of a portion above a part of the mount surface 3 that does not include the resistive heating member 5 becomes lower than that of the other portions, thus making it difficult to achieve uniform temperature distribution of the mount surface 3 . When the area occupied by the resistive heating member 5 in the circumscribed circle C is larger than 30% of the area of the circumscribed circle C that surrounds the resistive heating member 5 , on the other hand, thermal stress due to difference in the thermal expansion coefficient becomes large enough to deform the plate-shaped ceramic member 2 , even when the difference in the thermal expansion coefficient between the plate-shaped ceramic member 2 and the resistive heating member 5 is made small within 2.0×10 ⁻⁶/° C. Even when the plate-shaped ceramic member 2 is made of a sintered ceramic material that is hard to deform, thickness t of the plate-shaped ceramic member 2 is as small as 1 to 7 mm. Thus the plate-shaped ceramic member 2 may warp to become concave on the mount surface 3 when the resistive heating member 5 is energized to heat. As a result, difference in temperature may become large, with the temperature of the wafer W becoming higher around the center than along the periphery.

The area occupied by the resistive heating member 5 in the circumscribed circle C is preferably in a range from 7 to 20%, more preferably from 8% to 15% of the area of the circumscribed circle C.

More specifically, distance L 1 is preferably 0.5 mm or more and not more than three times the thickness of the plate-shaped ceramic member 2 . When distance L 1 is less than 0.5 mm, whisker-like protrusion that can cause short-circuiting may be produced in a region opposing the resistive heating member 5 , when printing the resistive heating member 5 . When distance L 1 is more than three times the thickness of the plate-shaped ceramic member 2 , a cold zone may be produced on the surface of the wafer W at position corresponding to the distance L 1 , thus increasing the temperature difference across the surface of the wafer W.

In order to efficiently achieve the effect described above, thickness of the resistive heating member 5 is preferably in a range from 5 to 50 μm.

When thickness of the resistive heating member 5 is less than 5 μm, it becomes difficult to form the resistive heating member 5 with uniform thickness by the screen printing process. When thickness of the resistive heating member 5 is larger than 50 μm, the resistive heating member 5 becomes too rigid due to the relatively large thickness, even when the area occupied by the resistive heating member 5 is set to not larger than 30% of the area of the circumscribed circle C. As a result, the plate-shaped ceramic member 2 may be deformed due to expansion and shrinkage of the resistive heating member 5 caused by the temperature change of the plate-shaped ceramic member 2 . Also it becomes difficult to form the resistive heating member 5 with uniform thickness by the screen printing process, resulting in large temperature difference across the surface of the wafer W. Thickness of the resistive heating member 5 is more preferably in a range from 10 to 30 μm.

Now the constitution of the members of the heater 1 of the present invention will be described in detail.

It is understood that the present invention is not limited to the specific examples described below.

In the heater 1 shown in FIG. 1, the plate-shaped ceramic member 2 has thickness t in a range from 1 to 7 mm, and Young's modulus in a range from 200 to 450 MPa in a temperature range from 100 to 200° C.

Alumina, silicon nitride, sialon or aluminum nitride may be used as the material to form the plate-shaped ceramic member 2 having Young's modulus in a range from 200 to 450 MPa in a temperature range from 100 to 200° C. Among these, aluminum nitride is the most suitable for the material to form the plate-shaped ceramic member 2 due to high thermal conductivity of 50 W/(m·K) or even 100 W/(m·K) or higher and high resistance against fluorine or chlorine corrosive gases, and against plasma.

Thickness of the plate-shaped ceramic member 2 is more preferably from 2 to 5 mm. When thickness of the plate-shaped ceramic member 2 is less than 2 mm, strength of the plate-shaped ceramic member 2 may become too low to endure the thermal stress when cooled down with cooling air that is blown from a gas nozzle 24 after being heated by the resistive heating member 5 , thus causing cracks in the plate-shaped ceramic member 2 . When thickness of the plate-shaped ceramic member 2 is more than 5 mm, heat capacity of the plate-shaped ceramic member 2 becomes large and requires a longer period of time for the temperature to stabilize after heating or cooling.

The plate-shaped ceramic member 2 is elastically fastened by passing bolt 16 through a bottomed metal casing 19 around an opening thereof, and screwing nut 20 via an elastic material 18 placed on the bottomed metal casing 19 , while interposing the ring-shaped contact member 17 so that the plate-shaped ceramic member 2 and the bottomed metal casing 19 do not contact directly with each other. With this constitution, even when the bottomed metal casing 19 is deformed due to temperature change of the plate-shaped ceramic member 2 , the deformation is absorbed by the elastic member 18 , so that the plate-shaped ceramic member 2 is restricted from warping and the temperature of the wafer surface is prevented from varying due to the warp of the plate-shaped ceramic member 2 .

Cross section of the ring-shaped contact member 17 may be of any shape including polygon and circle. In case the plate-shaped ceramic member 2 and the contact member 17 make planar contact with each other, heat transfer from the plate-shaped ceramic member 2 through the contact member 17 to the bottomed metal casing 19 can be restricted satisfactorily small when width of contact region between the plate-shaped ceramic member 2 and the contact member 17 is in a range from 0.1 mm to 13 mm. This enables it to heat the wafer W uniformly by minimizing temperature difference across the wafer surface. The width is more preferably in a range from 0.1 to 8 mm. If width of the contact region of the contact member 17 is less than 0.1 mm, the contact region may deform when the contact member is put into contact with the plate-shaped ceramic member 2 , thus causing the contact member 17 to break. If width of the contact region of the contact member 17 is larger than 13 mm, heat of the plate-shaped ceramic member 2 is transferred to the contact member, thus resulting in lower temperature of the plate-shaped ceramic member 2 along the periphery thereof and difficulty in achieving uniform temperature distribution over the surface of the wafer W. Width of the contact region between the plate-shaped ceramic member 2 and the contact member 17 is more preferably in a range from 0.1 mm to 8 mm, and most preferably from 0.1 to 2 mm.

Heat conductivity of the contact member 17 is preferably lower than that of the plate-shaped ceramic member 2 . When heat conductivity of the contact member 17 is lower than that of the plate-shaped ceramic member 2 , it is made possible to achieve uniform temperature distribution over the surface of the wafer W that is placed on the plate-shaped ceramic member 2 , and temperature of the plate-shaped ceramic member 2 can be quickly raised and lowered without being affected by the bottomed metal casing 19 due to small heat transfer to the contact member 17 .

When heat conductivity of the contact member 17 is less than 10% of the heat conductivity of the plate-shaped ceramic member 2 , heat transfer from the plate-shaped ceramic member 2 to the bottomed metal casing 19 decreases and more heat is transferred by the ambient gas (air in this case) and radiation from the plate-shaped ceramic member to the bottomed metal casing 19 .

When heat conductivity of the contact member 17 is higher than the heat conductivity of the plate-shaped ceramic member 2 , heat is transferred from the peripheral portion of the plate-shaped ceramic member 2 through the contact member 17 to the bottomed metal casing 19 , thereby heating the bottomed metal casing 19 while the temperature of the peripheral portion of the plate-shaped ceramic member 2 decreases thus resulting in larger temperature difference across the wafer surface. Also because the bottomed metal casing 19 is heated, it takes longer time to cool down the plate-shaped ceramic member 2 due to high temperature of the metal casing 19 when it is attempted to cool down the plate-shaped ceramic member 2 by blowing air from the gas nozzle 24 , or it takes longer time to heat the plate-shaped ceramic member 2 to a predetermined temperature.

The material used to make the contact member 17 preferably has Young's modulus of 1 GPa or higher, and more preferably 10 GPa or higher, in order to be held via a small contact area. Such a level of contact area enables it to minimize the deformation of the contact member 17 even when the plate-shaped ceramic member 2 is fastened by means of the bolt 16 onto the bottomed metal casing 19 via the contact member 17 having small contact region of 0.1 mm to 8 mm in width. Thus the plate-shaped ceramic member 2 can be prevented from being displaced or deviating from parallelism so as to remain held precisely.

Use of the contact member 17 having a high Young's modulus also makes it possible to achieve a high accuracy that cannot be obtained with a contact member made of fluorocarbon resin or a resin reinforced with glass fiber as described in Japanese Unexamined Patent Publication (Kokai) No. 2001-313249.

The material used to make the contact member 17 is preferably a metal such as carbon steel or special steel that contains nickel, manganese and/or chromium due to high value of Young's modulus. The material used to make the contact member 17 also preferably has heat conductivity that is lower than that of the plate-shaped ceramic member 2 , such as stainless steel or Fe—Ni—Co alloy, the so-called Kovar.

Further, in order to hold the plate-shaped ceramic member 2 in stable condition with small contact area between the contact member 17 and the plate-shaped ceramic member 2 while reducing the possibility of the contact region being chipped into particles even with a small contact area, the cross section of the contact member 17 along the plane perpendicular to the plate-shaped ceramic member 2 preferably has circular shape rather than polygon, Use of a wire having circular section 1 mm in diameter as the contact member 17 makes it possible to achieve uniform temperature distribution over the surface of the wafer W and quickly raise and lower the temperature without causing displacement of the plate-shaped ceramic member 2 and the bottomed metal casing 19 .

The bottomed metal casing 19 has side wall 22 and bottom 21 , and the plate-shaped ceramic member 2 is placed so as to cover the opening of the bottomed metal casing 19 . The bottomed metal casing 19 also has a hole 23 for discharging the cooling gas, while the power terminals 11 connected to the power feeder section 6 for supplying electric power to the resistive heating member 5 of the plate-shaped ceramic member 2 , the gas nozzle 24 for cooling the plate-shaped ceramic member 2 and a thermocouple 27 for measuring the temperature of the plate-shaped ceramic member 2 are provided.

It is preferable that the bottomed metal casing 19 has a depth of 10 to 50 mm, with the bottom 21 disposed at a distance of 10 to 50 mm, more preferably 20 to 30 mm from the plate-shaped ceramic member 2 . This makes it easy to equalize the heating of the mount surface 3 though exchange of radiation heat between the plate-shaped ceramic member 2 and the bottomed metal casing 19 . Also as thermal insulation with the outside is provided, time required for the mount surface 3 to reach stabilized and uniform temperature distribution is reduced.

The lift pins 25 provided movably in the vertical direction in the bottomed metal casing 19 place the wafer W on the mount surface 3 and lift the wafer W from the mount surface 3 . The wafer W is held in the state of being lifted from the mount surface 3 by the wafer support pins 8 , so as to prevent the temperature from unevenly distributed due to uneven bearing or other cause.

To heat the wafer W with the heater 1 , the wafer W that has been transferred to above the mount surface 3 by a transfer arm (not shown) is held by the lift pins 25 , then the lift pins 25 are lowered thereby to place the wafer W on the mount surface 3 .

When the heater 1 is used in forming the resist film, it is preferable to use the plate-shaped ceramic member 2 that is made of silicon carbide as the main component since this material does not generate a gas through reaction with moisture that is contained in the atmosphere, thus making it possible to form fine wiring in high density without affecting the resist film structure, even when used in applying the resist film onto the wafer W. Care should be paid at this time, so that a sintering assist agent does not contain nitrogen that may react with water and form ammonia and/or amine.

Sintered body of silicon carbide that forms the plate-shaped ceramic member 2 is made by mixing silicon carbide as the main component and boron (B) or carbon (C) as the sintering aid, or adding a metal oxide such as alumina (Al ₂O ₃) or yttria (Y ₂O ₃) to be formed in plate shape after mixing well, and sintering at a temperature from 1900 to 2100° C. Silicon carbide based on either a type or B type may be used.

When the sintered body of silicon carbide is used as the plate-shaped ceramic member 2 , the insulation film that isolates the plate-shaped ceramic member 2 having semi-conductivity and the resistive heating member 5 may be made of glass or a resin. When glass is used, withstanding voltage is below 1.5 kV and sufficient insulation cannot be ensured when the thickness is less than 100 μm. When the thickness is more than 400 μm, cracks may be generated to make the layer unable to function as an insulation layer, due to large difference in thermal expansion between the insulation layer and the sintered body of silicon carbide that forms the plate-shaped ceramic member 2 or sintered aluminum nitride. Therefore, thickness of the insulation layer made of glass is preferably in a range from 100 to 400 μm, more preferably in a range from 200 to 350 μm.

The principal surface of the plate-shaped ceramic member 2 opposite to the mount surface 3 is preferably polished to achieve flatness within 20 μm and mean surface roughness (Ra) in a range from 0.1 μm to 0.5 μm, in order to improve the adhesion of the surface with the insulation layer that is made of glass or resin.

When the plate-shaped ceramic member 2 is made of a sintered material based on aluminum nitride as the main component, an oxide of rare earth element such as Y ₂O ₃or Yb ₂O ₃and, as required, an oxide of alkali earth metal such as CaO are added as the sintering assist agent to the main component of aluminum nitride and, after mixing well and forming into plate shape, sintered at a temperature from 1900 to 2100° C. in a nitrogen gas. In order to improve adhesion of the resistive heating member 5 with the plate-shaped ceramic member 2 , an insulation layer made of glass may be formed, but may be omitted in case sufficient amount of glass is in the resistive heating member 5 and sufficient bonding strength is obtained accordingly.

The glass used to form the insulation layer may be either crystalline or amorphous in nature, a material having durable temperature of 200° C. or higher and thermal expansion coefficient in a range from −5 to +5×10 ⁻⁷/° C. in a temperature range from 0 to 200° C. with respect to the thermal expansion coefficient of the ceramics that forms the plate-shaped ceramic member 2 is preferably used. Use of glass having a value of thermal expansion coefficient out of the range described above may lead to defects such as crack and peel-off when cooled down after bonding the glass due to large difference from the thermal expansion coefficient of the ceramics that forms the plate-shaped ceramic member 2 .

The insulation layer made of glass may be formed on the plate-shaped ceramic member 2 by dropping an appropriate quantity of glass paste onto the center of the plate-shaped ceramic member 2 and spreading it to form a uniform film by spin coating method, or applying the glass paste uniformly by screen printing, dipping, spray coating or the like, and firing the glass paste at a temperature of 600° C. or higher. When the insulation layer is made of glass, adhesion of the insulation layer made of glass and the plate-shaped ceramic member 2 made of sintered body of silicon carbide or sintered aluminum nitride can be improved by heating the plate-shaped ceramic member 2 at a temperature from 850 to 1300° C. thereby to oxidize the surface to be covered by the insulation layer.

The resistive heating member 5 of the present invention is preferably divided into a plurality of blocks as shown in FIG. 3 and FIG. 4 and formed in such a configuration as each block consists of arc and straight sections turning back in spiral or zigzag shape. Since it is important to achieve uniform temperature distribution over the surface of the wafer W for the heater 1 of the present invention, it is preferable that the resistive heating member 5 of band shape has uniform density. Such a configuration of the resistive heating member as shown in FIG. 20 where regions that include resistive heating member 772 disposed densely therein and regions that include resistive heating member 772 disposed sparsely therein are repeated alternately is not desirable since surface temperature of the wafer W varies between the dense region and the sparse region.

When the resistive heating member 5 is divided into a plurality of resistive heating member zones, it is preferable to control the temperature of each zone independently so as to achieve uniform temperature distribution over the surface of the wafer W placed on the mount surface 3 .

The resistive heating member 5 may be formed by printing an electrode paste containing electrically conductive metal particles, glass frit and metal oxide, onto the plate-shaped ceramic member 2 and baking it. At least one kind of metal selected from among Au, Ag, Cu, Pd, Pt and Rh is preferably used as the metal particles, and the glass frit is preferably a low-expansion glass that is made of an oxide of metal containing B, Si and Zn and has thermal expansion coefficient of 4.5×10 ⁻⁶/° C. or lower, lower than that of the plate-shaped ceramic member 2 . The metal oxide is preferably one kind selected from among silicon oxide, boron oxide, alumina and titania.

The reason for using at least one kind of metal selected from among Au, Ag, Cu, Pd, Pt and Rh as the metal particles that form the resistive heating member 5 is because of the low electrical resistance of these metals.

The glass frit that forms the resistive heating member 5 is made of an oxide of metal containing B, Si and Zn, and the metal particles that constitute the resistive heating member 5 have thermal expansion coefficient higher than that of the plate-shaped ceramic member 2 , and therefore it is preferable to use a low-expansion glass that has thermal expansion coefficient of 4.5×10 ⁻⁶/° C. or lower, lower than that of the plate-shaped ceramic member 2 , in order to make the thermal expansion coefficient of the resistive heating member 5 proximate to that of the plate-shaped ceramic member 2 .

The reason for using at least one kind selected fro

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