JP2000340343A - Disc heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a disc heater excellent in uniform heat property, suitable as a heating device for a wafer for example, and capable of suppressing generation of local hot spots or cold spots. SOLUTION: In a disc heater 1 using the top surface of a disc ceramic substrate as a heating surface and burying a heating resistor 4 inside the substrate, the heating resistor 4 is constituted with plural almost circular bodies 4a-4c having concentrically circular different radiuses from the disc center, plural high resistance regions 7 and plural low resistance regions 6 are alternately installed at equal intervals in the almost circular bodies 4a-4c, and the plural almost circular bodies 4a-4c are connected in series to form a series circuit, and preferably the electric resistance value of the high resistance region 7 is made four times or more that of the low resistance region 6, the high resistance region 7 occupies 50% or more of the circumferential length of the almost circular bodies, at least six high resistance regions 7 are arranged within each almost circular body, and a pair of power supply electrodes 9a, 9b is arranged in the central part of the disc heater 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, plasma CVD and reduced pressure CV in the manufacturing process of a semiconductor manufacturing apparatus.
The present invention relates to a disk-shaped heater used as a wafer heating device used for a film forming device such as D, photo-CVD, PVD or the like, or an etching device such as plasma etching or photo-etching.

[0002]

2. Description of the Related Art Conventionally, in a film forming apparatus such as a plasma CVD, a low pressure CVD, a photo CVD, and a PVD, and an etching apparatus such as a plasma etching and a photo etching which are used in a manufacturing process of a semiconductor element, a deposition gas or an etching A chlorine-based or fluorine-based corrosive gas has been used as a cleaning gas or a cleaning gas.

[0003] As a wafer heating device for holding a semiconductor wafer (hereinafter, referred to as a wafer) in these gas atmospheres and heating it to a processing temperature, a stainless steel heater having a built-in heating resistor or a graphite heater heated by an infrared lamp. Heaters and the like were used. However, stainless steel heaters have a problem that corrosive wear occurs due to the above-mentioned corrosive gas and particles are generated. Graphite heaters are excellent in corrosion resistance, but have inferior thermal efficiency due to indirect heating, and have a slow heating rate. There was a problem.

In order to solve such a problem, a heater for a wafer heating apparatus in which the upper surface of a disk-shaped dense ceramic base is used as a wafer W support surface and a heating resistor is embedded therein is proposed. Have been.

A heater used as a wafer heating device is required to have high uniformity. In particular, in order to process a circular wafer, it is necessary that the temperature distribution of the wafer be as close as possible to concentric circles. Eliminating spots and cold spots is an important design issue.

Therefore, in Japanese Patent Application Laid-Open No. 6-69924, a connecting portion for connecting the inner and outer arcs sequentially is provided in order to form the heating resistor partially in a concentric circle and connect the arcs in series. Heaters have been proposed. However, in this structure, since the heater pattern is spiral,
There is a problem that the starting end and the ending of the pattern are separated from the center and the outer periphery of the disk, and the routing of the power supply line restricts the surrounding structure.

In order to solve these problems, the present applicant previously formed a heating resistor 11 in an insulating substrate 10 by a screen printing method as shown in FIG. A wafer heating apparatus has been proposed in which a degree of freedom is increased, a pair of power supply electrodes 12 are arranged at the center, and a concentric section 13 and a folded straight section 14 are combined to connect a series circuit (Japanese Patent Application No. 9-360092). .

[0008]

However, it has been found that the wafer heating apparatus disclosed in Japanese Patent Application No. 9-360092 is insufficient in uniform heating of a wafer mounted on a support surface. When the temperature distribution on the wafer mounting surface was measured with an infrared radiation thermometer, the temperature distribution was non-uniform near the folded part formed in the pattern, and there were hot spots and cold spots. I understood.

As a result of studying the above-mentioned phenomenon by using a simulation based on the finite element method, the inventor has found that the cause is the non-uniformity of the current density at the concentric portion and the folded portion of the heater pattern.

This can be explained by the current distribution of the heating resistor shown in FIG. The direction of the arrow in FIG. 4 indicates the direction of the current flowing through the heating resistor 11 of FIG. 4, and the length of the arrow indicates the magnitude of the current. That is, in order to make the current flowing through the heating resistor 11 take the shortest path in the pattern, in the heater pattern composed of the concentric portion and the folded straight portion, the inner corner of the connection portion between the concentric portion and the folded straight portion is formed. a, a large amount of current flows through the outer corner b
The current flowing through is reduced.

Therefore, in such a folded portion, the heat generated by the heat generating resistor becomes non-uniform, and the inside corner a becomes a hot spot and the outside corner b becomes a cold spot. Therefore, unevenness in temperature occurs on the wafer supporting surface of the heater, which makes it difficult to uniformly heat the wafer.

In particular, when a heating resistor pattern as shown in FIG. 4 is employed, a hot spot is generated at a specific position on the circumference, and the temperature distribution does not become concentric. For this reason, a film having a uniform thickness cannot be formed on the wafer, or the processing accuracy in the etching processing has a large variation, resulting in a poor yield.

An object of the present invention is to provide a disk-shaped heater which is suitably used as a heating device for a wafer or the like and which suppresses the occurrence of local hot spots and cold spots and has excellent heat uniformity. .

[0014]

According to the present invention, there is provided a disk-shaped heater in which the upper surface of a disk-shaped ceramic substrate is used as a heating surface and a heating resistor is embedded in the substrate. A plurality of substantially circular bodies having different radii concentrically from each other, and a plurality of high resistance regions and a plurality of low resistance regions are alternately arranged at equal intervals in the substantially circular body, and the plurality of substantially circular bodies are arranged. Have been found to be achieved by connecting them all in a series circuit.

In the above configuration, the electric resistance of the high-resistance region is at least four times the electric resistance of the low-resistance region. 50% of the total length of the substantially circular body in the circumferential direction
Occupying the above, in each of the substantially circular bodies having different radii, arranging six or more high resistance regions, arranging a pair of power supply electrodes at a central portion of the disc-shaped heater, Preferably, the body is formed by co-firing with the disc-shaped ceramic substrate.

[0016]

According to the disk heater of the present invention, the heating resistor is constituted by a plurality of substantially circular bodies having different radii concentrically from the center of the disk. A plurality of low-resistance regions are provided, but the high-resistance region has a higher heat generation density than other regions, that is, a low-resistance region, and becomes a hot spot. Since the hot spots are alternately arranged at equal intervals, the hot spots are arranged at equal angular intervals on the circumference of the heating resistor ring, and such a substantially circular body is concentric from the center of the disk. Since hot spots are formed at substantially equal intervals in the radial direction of the disk as well, the distance between adjacent hot spots is made sufficiently small so that the whole is extremely uniform. It is possible to obtain the temperature distribution close to.

In addition, according to the disk-shaped heater according to the present invention, the connection portion provided for connecting a plurality of substantially circular bodies having different radii in series has only a low heat generation density. Without affecting the distribution, a temperature distribution very close to concentric circles can be realized as a result.

[0018]

1 is a schematic perspective view and (b) a schematic cross-sectional view of one embodiment of a disk-shaped heater according to the present invention. FIG. 2 is a sectional view of the disk-shaped heater of FIG. It is a top view for explaining a heating resistor pattern. The disk-shaped heater 1 shown in FIGS. 1 and 2 is made of a dense ceramic base 2, has an upper surface serving as a wafer W heating surface 3, and has a heating resistor 4 embedded therein. A pair of power supply terminals 5 for energizing the heating resistor 4 are attached to a substantially central portion of the disc-shaped heater 1, and a voltage is applied to the power supply terminal 5 to cause the heating resistor 4 to generate heat. As a result, the wafer W placed on the heating surface 3 is uniformly heated.

As the material of the ceramic substrate 2 constituting such a disk-shaped heater 1, alumina, silicon nitride, silicon carbide, sialon, aluminum nitride, which are excellent in wear resistance and heat resistance, can be used. Aluminum has a high thermal conductivity of 50 W / m · K or more, particularly 100 W / m · K or more, and further has excellent corrosion resistance and plasma resistance to fluorine-based and chlorine-based corrosive gases. 2 is suitable as the material. Specifically, it is preferable to use high-purity aluminum nitride having a purity of 99.7% or more and aluminum nitride containing a sintering aid such as Y ₂ O ₃ or Er ₂ O ₃ .

The heating resistor 4 embedded in the ceramic base 2 is made of a high-melting point metal such as tungsten, molybdenum, rhenium, platinum or the like, or an alloy thereof.
Alternatively, carbides or nitrides of Groups 4a, 5a, and 6a of the periodic table can be used, and those having a small difference in thermal expansion from the ceramic base 2 may be appropriately selected and used.

According to the present invention, in the disk-shaped heater having the above-described configuration, as shown in FIG. 2, the heating resistor 4 has a plurality of substantially circular bodies having different radii concentrically from the center of the disk. (It is referred to as a ring body.) 4a to 4c. Further, a plurality of low resistance regions 6 and a plurality of high resistance regions 7 are formed in each of the ring bodies 4a to 4c, and they are alternately arranged at equal intervals.

A plurality of ring members 4a having different radii
4c are connected as a series circuit by a low-resistance connector 8 extending in the radial direction of the disk, and terminated by a pair of power supply electrodes 9a and 9b provided at the center of the disk.

That is, the outermost ring body 4a is cut at one location, and the inner ring body 4b is cut at the cut portion.
And the connection body 8, and the inner ring body 4 b
One is connected to the outer ring 4a, and the other is connected to the connector 8 by the inner ring 4c and the connector 8. Further, the ring body 4c is also cut at two places, one of which is connected to the outer ring body 4b, and the other is connected to the pair of power supply electrodes 9a and 9b, thereby forming a series circuit as a whole. In such a configuration, the electric resistance of the high resistance region 7 is
Is preferably at least four times the resistance value of
If it is smaller than twice, the heat generated in the low resistance region affects the temperature distribution, that is, a difference in temperature occurs between the portion where the low resistance region 6 exists and the portion where the low resistance region 6 does not exist on the same circumference. Impedes the realization of

In order to adjust the resistance value as described above, the line width of the high resistance region 7 in the disk-shaped heater of FIG. 2 is set to be not more than の of the width of the low resistance region. The method of forming the high-resistance region is to reduce the line width in this way,
It can also be realized by using a material with high volume specific resistance,
Alternatively, the adjustment of the line width and the change of the material may be combined.

The power supply electrodes 9a and 9b of the heating resistor 4 are disposed substantially at the center of the disc-shaped heater 1, and through the through holes 10 provided in the ceramic base 2 as shown in FIG. It penetrates the back surface and is connected to the power supply terminal 5.

In order to make the temperature distribution in the circumferential direction uniform, it is desirable that the high resistance region 7 occupies 50% or more, particularly 70% or more, of the circumferential length of each of the ring bodies 4a to 4c. Preferably, at least six or more high resistance regions 7 are arranged at equal angular intervals in the circumferential direction.

Further, in order to make the temperature distribution in the radial direction more uniform, it is desirable to provide at least two ring bodies. Also, depending on the material of the heating resistor, the difference in radius between adjacent ring bodies is preferably 30 mm or less, particularly preferably 20 mm or less.

The side lines of the patterns forming the low-resistance region 6 and the high-resistance region 7 of the ring need not necessarily be strictly circular arcs, but may be formed by straight lines, and may be a ring made of a polygon as a whole. Good. However, in order to make the temperature distribution close to a concentric circle, it is desirable that the polygonal shape is substantially congruent with respect to the rotational movement on the same circle, that is, the formed polygon is a regular polygon.

There is no problem if the electric resistance of the connection body 8 of the ring body is lower than the electric resistance of the low resistance region 6 as long as it is below. In this case as well, the width of the connection body 8 can be set to be equal to or larger than the low-resistance region 6, or can be formed of a material having a lower resistance.

As shown in FIG. 2, it is necessary to increase the number of the high-resistance regions 7 in the outer ring body as compared with the inner ring body. It is desirable that the number of installations be in a proportional relationship.

The width, thickness, and circumferential length of the high resistance region 7 are determined by the resistivity of the resistor material, the target temperature, the applied voltage / current, and the like.

In general, the natural heat radiation from the disk-shaped heater is larger on the outer peripheral side of the disk. Therefore, in order to make the temperature distribution uniform, it is necessary to increase the calorific value of the outer ring. In that case, the high resistance region 7 of the outer ring body
May be adjusted to increase the resistance value by reducing the width of.

FIG. 3 is an enlarged view of the low resistance region 6, and as shown in FIG. 3, the boundary between the low resistance region 6 and the high resistance region 7 may be formed by an arc having a radius r1. desirable. This is because, as shown in FIG. 3, a hot spot is likely to be generated due to concentration of current at the bent portion of the heating resistor pattern, and the radius r1 should be 50% or more of the width x of the high resistance region. Is preferred.

It is desirable that the corner of the low resistance region 6 is formed by an arc of r2. As a result, the change in the current density from the low-resistance region 6 to the high-resistance region 7 becomes more gradual, and the occurrence of a hot spot at the boundary can be suppressed. It is desirable that the magnitude of r2 is equal to or greater than r1.

The disk-shaped heater of the present invention is obtained by molding a ceramic powder mainly composed of, for example, alumina, silicon nitride, silicon carbide, sialon, aluminum nitride or the like into a predetermined disk shape, and then forming the surface on the surface as described above. A conductive paste containing a conductive material such as a high-melting-point metal such as tungsten, molybdenum, rhenium, and platinum is printed and applied as shown in FIG. 2, and the formed body of the ceramic powder is laminated or slurry is applied thereon. Can be formed by simultaneous firing with a ceramic substrate. Further, as another method, a heating resistor formed into a thin plate by rolling or the like is formed into a desired pattern by pressing, chemical etching, or the like, or a heating resistor is previously formed into a heating element shape by powder metallurgy or the like. Can be produced by co-firing with a ceramic substrate.

[0036]

EXAMPLES In order to confirm the effect of the disk-shaped heater of the present invention, a disk-shaped heater having a diameter of 200 mm and a thickness of 10 mm was manufactured as follows using aluminum nitride ceramics as a ceramic substrate.

First, an aluminum nitride green sheet formed by a doctor blade method is laminated and subjected to through-hole processing, and then, on one surface, a conductor paste mainly containing tungsten is printed as a heat generating resistor. An aluminum nitride molded body layer was laminated and adhered, and processed into a disk shape. After degreased, it was simultaneously fired at 1700 ° C. by a normal pressure sintering method. After firing, the sintered body was subjected to surface grinding on both main surfaces and then a power supply electrode was brazed.

The thicknesses of the heating resistors were all 0.01 mm. Then, the number of rings having different radii, the ratio of the line width of the high-resistance region to the low-resistance region, the ratio of the circumferential length of the high-resistance region to the low-resistance region, and the number of the high-resistance regions on the ring are displayed. Various disk-shaped heaters were prototyped by designing the pattern as shown in FIG.

The produced disk-shaped heater is supplied to a heating resistor via a power supply terminal and a power supply electrode so that the maximum temperature of the upper surface of the heater is 200 ° C. in a room temperature, atmospheric pressure air and no forced convection. Was applied, and the temperature distribution on the upper surface was measured with an infrared radiation thermometer, and the difference between the maximum temperature and the minimum temperature was regarded as temperature variation. Table 1 shows the results.

As a comparative example, a disk-shaped heater on which the heating resistor pattern shown in FIG. 4 was printed was manufactured, and the same evaluation was performed.

[0041]

[Table 1]

According to this result, in the case where the number of the ring bodies is one, or as shown in FIG. 4, in the pattern having the high resistance region and the folded portion, the temperature variation is large. . In contrast, in the present invention,
The variation in temperature can be reduced. In particular, the electric resistance of the high-resistance region is at least four times the electric resistance of the low-resistance region (the line width is １ ／ or less of the low-resistance region), the number of high-resistance regions is six or more, In the case where the high resistance region occupies 50% or more of the circumferential length of the substantially circular body (sample Nos. 3 and 4), the temperature variation could be controlled to 10 ° C. or less.

[0043]

As described above in detail, according to the present invention, the occurrence of local hot spots and cold spots is suppressed, and a plurality of concentric rings having different radii are provided. The high-resistance area has a higher heat generation density than other areas and becomes a hot spot,
Since such hot spots can be arranged at equal angular intervals on the circumference of the ring body, it is possible to realize a disk-shaped heater having extremely excellent heat uniformity on concentric circles and having a small temperature variation as a whole. .

[Brief description of the drawings]

FIG. 1 shows the entire structure of a disk-shaped heater according to the present invention (a).
It is a schematic perspective view and (b) schematic sectional drawing.

FIG. 2 is a plan view for explaining a heating resistor pattern of the disc-shaped heater of FIG.

FIG. 3 is an enlarged view of a boundary between a high resistance region and a low resistance region in the heating resistor pattern of FIG. 2;

FIG. 4 is a view showing a heating resistor pattern of a conventional disk-shaped heater.

5 is a conceptual diagram showing a current distribution at a connection portion between a concentric portion and a folded linear portion of the disc-shaped heater in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Disc-shaped heater 2 Ceramic base 3 Wafer heating surface 4 Heating resistor 4a-4c Substantially circular body (ring body) 5 Power supply terminal 6 Low resistance area 7 High resistance area 8 Connection part 9a, 9b Power supply electrode

Claims (6)

[Claims] 1. A disk-shaped heater in which the upper surface of a disk-shaped ceramic substrate is used as a heating surface and a heating resistor is buried inside the substrate, wherein the heating resistor has a plurality of substantially different diameters concentrically from the center of the disk. A plurality of high-resistance regions and a plurality of low-resistance regions are alternately arranged at equal intervals in the substantially circular body, and the plurality of substantially circular bodies are all connected in a series circuit. A disc-shaped heater. 2. The disk-shaped heater according to claim 1, wherein the electric resistance of the high resistance region is at least four times the electric resistance of the low resistance region. 3. The disk-shaped heater according to claim 1, wherein in each of the substantially circular bodies having different radii, the high resistance region occupies 50% or more of the circumference of each substantially circular body. 4. The disk-shaped heater according to claim 1, wherein six or more high-resistance regions are arranged in each of said substantially circular bodies having different radii. 5. The disk-shaped heater according to claim 1, wherein a pair of power supply electrodes are provided at a central portion of said disk-shaped heater. 6. The disk-shaped heater according to claim 1, wherein said heating resistor is formed by firing simultaneously with said disk-shaped ceramic base.