JP2001297858A - Ceramic heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic heater that has good oxidization resistance, small rate of change of resistance of the resistance heating element, sufficient temperature raising and lowering speed, good corrosion resistance to reactive gas and that can increase the resistance of the resistance heating element. SOLUTION: The ceramic heater has heating element made of one or two or more circuits disposed on a ceramic substrate surface 1 and insulating coating made on the heating element. The insulating coating surface has a surface roughness of Ra 0.01 to 35 μm based on JIS B 0601.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic heater for manufacturing or testing semiconductors used mainly in the semiconductor industry.

[0002]

2. Description of the Related Art Semiconductor-applied products are extremely important products required in various industries. A typical example of a semiconductor chip is a silicon chip obtained by slicing a silicon single crystal to a predetermined thickness. After manufacturing a wafer, it is manufactured by forming various circuits and the like on this silicon wafer.

In order to form these various circuits and the like, it is necessary to apply a photosensitive resin on a silicon wafer, expose and develop the resin, and then post cure or form a conductor layer by sputtering. . For this purpose, it was necessary to heat the silicon wafer.

As a heater of this kind for mounting a semiconductor wafer such as a silicon wafer on a heater and heating the same, conventionally, a resistance heating element such as an electric resistor is provided on the back side of an aluminum substrate. Was often used,
Aluminum substrates require a thickness of about 15 mm, so that they are bulky and bulky, so that they are not always easy to handle, and are not sufficiently temperature-controllable in terms of temperature followability with respect to current flow. It was not easy to heat the wafer uniformly.

Further, in the heater used in such a semiconductor manufacturing apparatus, since the surface of the resistance heating element is easily affected by light heat or processing gas when the semiconductor manufacturing apparatus is used, the resistance of the surface of the resistance heating element to oxidation is high. Is required.

[0006]

Therefore, the present inventor has proposed:
As a result of conducting studies with the aim of forming a resistance heating element with excellent durability, the resistance heating element formed on the ceramic substrate is provided with an insulating coating to provide excellent durability such as oxidation resistance. Was found to be a ceramic heater, but since this insulating coating can also serve as a heat insulator for the resistance heating element, when the ceramic heater is heated and then cooled, it cannot be cooled quickly. was there.

In view of such problems, the present inventor has further studied and, by adjusting the surface roughness of the insulative coating, the insulative coating plays a role like a radiation fin, and is cooled. As a result, it was found that the temperature of the resistance heating element rapidly decreased, and as a result, it was possible to rapidly lower the temperature of the ceramic heater, thereby completing the present invention.

[0008]

That is, in the ceramic heater of the present invention, a resistance heating element comprising one or more circuits is disposed on the surface of a ceramic substrate, and the resistance heating element is provided with an insulating coating. Wherein the surface roughness Ra of the surface of the insulating coating according to JIS B 0601 is 0.01 to 10 μm, preferably 0.03 to 5 μm. It is.

In the above ceramic heater, the surface roughness Ra of the surface of the insulating coating according to JIS B 0601 is adjusted to 0.01 to 10 μm. , And when a refrigerant is present in the surroundings, the rough surface formed on the surface of the insulating cover serves as a radiation fin and is cooled relatively quickly. Therefore, when the temperature of the ceramic heater is increased, the temperature can be quickly increased. On the other hand, when the temperature of the ceramic heater is increased and then cooled, the temperature of the resistance heating element can be rapidly decreased. As a result, the temperature of the ceramic heater can be rapidly lowered. In addition, by setting the surface roughness Ra of the surface of the insulating coating to 0.03 to 5 μm, the variation in the rate of temperature rise can be reduced.

In addition, since an insulating coating is provided on the surface of the resistance heating element instead of forming a metal film by plating or the like, when an electric current of about 30 to 300 V is applied to the resistance heating element, mainly There is no inconvenience that current flows on the surface of the resistance heating element, and the resistance heating element can be protected by this insulating covering. Also, even when the surface temperature of the resistance heating element rises due to energization,
Because the resistance heating element is covered with an insulating coating,
Oxidation or sulfurization by oxygen or SOx in the air hardly progresses, and a change in the resistance of the resistance heating element can be prevented.

When the resistance heating element is coated by plating,
The reason why the current easily flows in the plated portion is that there is a difference between the resistance of the resistance heating element and the resistance of the plating portion. In this case, it is necessary to reduce the resistance value of the resistance heating element as much as possible. However, when the resistance heating element is coated with the insulating coating, since the coating is an insulator, no current flows through the coating portion, and the resistance value of the resistance heating element can be set high. The heating value can be increased, or the cross-sectional area of the resistance heating element can be reduced to obtain the same heating value.

When the surface roughness Ra of the surface of the insulating coating is less than 0.01 μm, the heat radiation function of the insulating coating is reduced, so that the cooling rate when cooling the ceramic heater is reduced. If the surface roughness Ra of the surface of the insulating coating exceeds 10 μm, air tends to stay in the valleys of the rough surface, and the cooling rate is reduced. In order to obtain an insulating coating having both the heat retaining effect and the heat radiation effect, the surface roughness Ra of the insulating coating is 0.03 to 0.03.
5 μm is preferred. This is because the variation in the heating rate is reduced. When Ra is less than 0.03 μm, heat reflection at the interface between the insulating coating and the air increases, and conversely, Ra
Exceeds 5 μm, the influence of heat radiation becomes large, and the temperature rise rate varies. Note that Ra is the value obtained by dividing the integral value of the absolute value of the surface roughness curve by the measured length.
x is the height difference between peaks and valleys in the surface roughness curve,
There is no correlation between the two.

In the case where the insulating cover is provided so as to integrally cover a resistance heating element including two or more circuits over an area including the portion where the circuit is formed, In addition to the effect, it is possible to prevent a short circuit or the like from occurring in the resistance heating element due to migration of a metal (for example, silver or the like) constituting the resistance heating element. In addition, even when the insulating coating is formed in the region, the coating layer can be easily formed by screen printing or the like over the entire region including the portion where the circuit is formed, so that the coating cost is reduced. And an inexpensive heater.

The ceramic substrate constituting the ceramic heater of the present invention is preferably made of a nitride ceramic or a carbide ceramic. Nitride ceramics and carbide ceramics are suitable for heater substrates because they have excellent thermal conductivity to conduct the heat generated by the resistance heating element and also have excellent corrosion resistance to processing gases in semiconductor manufacturing equipment. It is.

In the ceramic heater according to the present invention, the insulating coating can be made of oxide glass.
This is because oxide glass applicable to these uses has a high adhesion strength to a ceramic substrate and a resistance heating element, is chemically stable, and has good electric insulation.

Further, in the ceramic heater according to the present invention, the insulating coating may be made of a heat-resistant resin material. Heat-resistant resin materials applicable to these applications are also
This is because the adhesive strength to the ceramic substrate and the resistance heating element is large, the electrical insulation is good, and the film can be formed at a relatively low temperature. In addition, heat resistance means that it can be used at 150 ° C. or higher.

As the heat-resistant resin material, at least one of a polyimide resin and a silicone resin can be selected.

Further, in the ceramic heater of the present invention, the side opposite to the side on which the resistance heating element is formed is the heating surface, and it is desirable to process the semiconductor wafer on this heating surface side. This is because the heat generated by the resistance heating element is diffused while propagating through the ceramic substrate, so that a temperature distribution similar to the resistance heating element pattern is unlikely to occur, and the uniformity of the heating surface can be ensured.

The semiconductor wafer may be placed on the heating surface. Further, a through-hole is formed in the ceramic substrate, or a recess is formed in the surface of the ceramic substrate, and a support pin is provided in the through-hole or the recess with a tip slightly protruding from the surface of the ceramic substrate. , The semiconductor wafer may be held and heated at a distance of about 5 to 2000 μm from the heating surface. Japanese Patent Application Laid-Open No. Hei 6-13161 discloses a structure in which a ceramic substrate is covered with a resin. In this publication, an object to be heated is placed on a heating element. Completely different ideas.

Also, Japanese Patent No. 2724075 discloses that
Although a method is disclosed in which an alkoxide, a metal powder, and a glass powder are applied to the surface of an aluminum nitride sintered body and fired, a metal layer is applied to the surface of the aluminum nitride sintered body. This patent relates to a package substrate, in which the metal layer is a resistance heating element,
The fact that the opposite side of the resistance heating element forming surface is a heating surface, and that the resistance heating element is provided with an insulating coating,
It is not suggested, and the novelty and inventive step of the present invention are not hindered.

Further, the ceramic heater of the present invention may have a cooling mechanism. Examples of the cooling mechanism include those using a cooling medium such as an air-cooling device or a water-cooling device, and perform heat exchange by directly spraying the cooling medium on the ceramic substrate or passing a cooling pipe through the device or the ceramic substrate. You may. As the cooling medium, a gas such as air, nitrogen, argon, helium, and carbon dioxide can be used, and a liquid such as water, ammonia, and ethylene glycol can also be used. Note that the ceramic heater of the present invention has the same effect even when cooling is performed.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the ceramic heater according to the present invention will be described below with reference to the drawings.

FIG. 1 is a bottom view schematically showing one embodiment of the ceramic heater of the present invention, and FIG. 2 is a partially enlarged sectional view of the ceramic heater. The ceramic heater 10 uses a disk-shaped ceramic substrate 11 made of an insulating nitride ceramic or carbide ceramic, and a substantially linear resistance heating element 12 is provided on one main surface of the ceramic substrate 11, for example, as shown in FIG. A circuit is formed by arranging in a concentric shape as shown in FIG. It is configured to be held in a state of being separated by a distance of and heated.

As shown in FIG. 2, this ceramic substrate 1
A through hole 15 is formed in a portion near the center of 1, and a lifter pin 16 is inserted through the through hole 15 to support a silicon wafer 19. Also, the bottom 11
A bottomed hole 14 for inserting a temperature measuring element such as a thermocouple is formed in b.

In the ceramic heater 10, as shown in FIG.
With a predetermined thickness, the surface roughness Ra of the surface is 0.01 to 10 μm
By providing the insulating coating 17, the durability such as oxidation resistance and sulfidation resistance is improved. In the ceramic heater 10, an external terminal 13 is connected to an end of the resistance heating element 12, and an insulating coating 17 is formed on a part of the external terminal 13.
This is the case where the insulating terminal 17 is formed after the external terminal 13 is connected to the end of the resistance heating element 12.

When the insulating cover 17 is formed before the external terminal 13 is connected, the insulating cover 17 cannot be provided at a portion to which the external terminal 13 is connected. Therefore,
In this case, the portion to which the external terminal 13 is connected is not usually provided with the insulating covering 17. However, after connecting the external terminals 13, the coating may be performed again, and the insulating coating 17 may be formed on the portion to which the external terminals 13 are connected.

Conventionally, in a ceramic heater in which a resistance heating element is formed on the surface of a ceramic substrate, heat is radiated from the exposed surface of the resistance heating element, so that the temperature of the heating surface does not increase with respect to the applied power. However, in the present invention, since the insulating coating 17 having the surface roughness Ra of 0.01 to 10 μm is formed, the resistance heating element 1
The heat dissipation from 2 is performed appropriately.

That is, since the resistance heating element has the above-mentioned surface roughness and is covered with an insulating coating having an appropriate heat retaining effect, when the temperature of the ceramic substrate is raised, the applied electric power is reduced. Heat is generated efficiently, and a high surface temperature can be secured. Further, when a refrigerant is present in the surroundings, the rough surface formed on the surface of the insulating cover serves as a radiation fin, so that the resistance heating element is quickly cooled, and as a result,
Rapid cooling of the ceramic heater is realized.

The surface roughness Ra of the surface of the insulating coating is 0.0
When the thickness is less than 1 μm, the heat retaining effect is too high, so that when the ceramic substrate is heated, the temperature can be raised efficiently. However, when the temperature of the ceramic substrate is lowered after heating the silicon wafer or the like. In addition, the rate of temperature decrease of the resistance heating element becomes slow, and it is impossible to efficiently and repeatedly increase and decrease the temperature in a short time.

On the other hand, if the surface roughness Ra of the surface of the insulating coating exceeds 10 μm, air tends to stay in the valleys of the rough surface, and the insulating coating has a low thermal conductivity.
The effect as a heat insulating material is larger than the effect of the radiation fins, and cooling cannot be performed efficiently and in a short time.

As the insulating cover 17, an oxide-based glass material, or a heat-resistant electrically insulating synthetic resin such as a polyimide-based resin or a silicone-based resin (hereinafter referred to as a heat-resistant resin) may be used. it can. One of these materials may be used alone, or two or more thereof may be used in combination (formed as a multilayer). These materials will be described later.

In the following description, a case where an aluminum nitride sintered body substrate is used as a base material of a ceramic substrate will be described. However, the base material is not limited to aluminum nitride, of course. For example, carbide ceramics, oxide ceramics, nitride ceramics other than aluminum nitride, and the like can be given.

Examples of the carbide ceramic include metal carbide ceramics such as silicon carbide, zirconium carbide, titanium carbide, tantalum carbide, and tungsten carbide. Examples of the oxide ceramic include alumina and zirconia. , Cordierite, mullite and the like. Further, examples of the nitride ceramic include metal nitride ceramics such as aluminum nitride, silicon nitride, boron nitride, and titanium nitride.

Of these ceramic materials, nitride ceramics and carbide ceramics are generally preferable to oxide ceramics because of their higher thermal conductivity.
These sintered substrates may be used alone or in combination of two or more.

A ceramic heater using a nitride ceramic typified by aluminum nitride or another carbide ceramic has a small thermal expansion coefficient and a high rigidity in addition to a metal having a small coefficient of thermal expansion. Even if it is thin, there is no warping or distortion due to heating, and the heater substrate can be made thinner and lighter than a metal material such as aluminum. Above all,
Aluminum nitride can be suitably used as a heater because it has excellent thermal conductivity, is hardly affected by light and heat in a semiconductor manufacturing apparatus, and has excellent corrosion resistance to a processing gas or the like.

An insulating layer may be formed on the surface of the ceramic substrate made of the nitride ceramic or the carbide ceramic. If the ceramic substrate itself has high conductivity at room temperature or its resistance decreases in a high temperature region, if a resistance heating element is formed on the surface of the ceramic substrate as it is, a leak current will be generated between adjacent resistance heating elements. This is because it may occur and stop functioning as a heater. In this case, an insulating layer is formed on the surface of the ceramic substrate, a resistance heating element is formed on the insulation layer, and an insulating coating is provided on the resistance heating element.

As the insulating layer, for example, an oxide ceramic is used. Examples of such an oxide ceramic include silica, alumina, mullite, cordierite, and beryllia. These oxide ceramics may be used alone or in combination of two or more.

As a method of forming an insulating layer made of these materials, for example, a method of forming a coating layer by spin coating using a sol solution obtained by hydrolyzing an alkoxide, followed by drying and firing is used. it can. Also,
An insulating layer may be formed by CVD or sputtering, and after applying a glass powder paste, 500 to 1000
The insulating layer may be formed by baking at ℃.

The resistance heating element 12 is formed by applying a conductive paste containing particles of a metal such as a noble metal (gold, silver, platinum, palladium), lead, tungsten, molybdenum, nickel or the like to the surface of a ceramic substrate and forming a conductive paste having a predetermined pattern. After the layer is formed, it is formed by baking and sintering the metal particles. Sintering of the metal particles is sufficient if the metal particles and the metal particles and the ceramic substrate are fused. The resistance heating element 12 may be formed using conductive ceramic particles such as tungsten carbide and molybdenum carbide.

When the resistance heating element 12 is formed, the resistance value can be set to various values by controlling its shape (line width and thickness). As is well known, the resistance value can be increased as the width is reduced and the thickness is reduced. The form of the resistance heating element is a wide, substantially straight line or a curved line, but does not need to be a strictly geometrically straight line or a curved line, and may be a combination of a straight line and a curved line.

The oxide-based glass material, which is the material of the insulating coating, has a high electrical insulating property, a high adhesion strength to the ceramic substrate and the resistance heating element, and is chemically stable. A stable interface with the substrate and a stable interface with the resistance heating element can be formed.

Examples of the specific composition include, for example,
ZnO-B containing ZnO as a main component_Two O _Three -SiO_Two , P
PbO-SiO mainly composed of bO_Two , PbO-B_Two O
_Three -SiO_Two , PbO-ZnO-B_Two O_Three Etc.
Can be. These oxide-based glass materials are crystalline
Parts may be present. Glass transition of these glass materials
The point is 400-700 ° C and the coefficient of thermal expansion is 4-9p
pm / ° C.

As a method of forming such an insulating coating made of an oxide-based glass material, a paste containing the above-mentioned oxide glass powder is applied to the surface of a ceramic substrate by screen printing or the like, followed by drying and firing. To form an insulating coating. In this case, it is necessary to form a layer made of a resin or the like that is relatively easily decomposed when heated so as not to form an insulating coating on the portion where the external terminal is formed.

At this time, the surface roughness of the insulating layer can be adjusted by changing the drying conditions (drying speed), the firing conditions (the firing temperature), and the average particle size of the glass powder. Moreover, after forming the insulating coating, a rough surface may be formed by performing sandblasting or the like on the surface.

The heat-resistant resin material, which is the material of the insulating coating, also has good electrical insulation, has a high adhesion strength to the ceramic substrate and the resistance heating element, and has a stable interface with the ceramic substrate and a resistance heating element. Can form a stable interface. Also, by using this heat-resistant resin material, an insulating coating can be formed at a relatively low temperature. When forming the insulating coating, it is only necessary to apply it to the surface of the resistance heating element and dry and solidify it, so that it can be easily formed at low cost. Here, the heat resistance is 1
It means that it can be used at a temperature of 50 ° C. or higher, and at this time, deterioration of the polymer does not occur.

Specific examples thereof include, for example, polyimide resins and silicone resins.
A polyimide resin is a polymer compound obtained by reacting a carboxylic acid derivative with a diamine, has heat resistance of 200 ° C. or higher, and can be used in a wide temperature range. In addition, the silicone resin has a methyl group or an ethyl group as an alkyl group in the side chain of the polysiloxane, and has excellent heat resistance and rubber elasticity, and has good adhesion to a resistance heating element and a ceramic substrate. And 1
By drying and solidifying at a relatively low temperature of about 50 to 250 ° C., an insulating coating can be formed.

As a method of forming such an insulating coating made of a heat-resistant resin material, a paste obtained by dissolving the above-mentioned heat-resistant resin material in a solvent or the like is applied or sprayed on the surface of a ceramic substrate, and dried to dry. And a method of forming a functional coating.

At this time, the surface roughness of the insulating layer can be adjusted by changing the drying conditions (drying speed), the spray conditions, and the like. Further, after forming the insulating coating, a rough surface may be formed by performing a sand blasting treatment or a treatment with a belt sander on the surface.

In this ceramic heater 10, an insulating coating 17 is formed on the surface of the resistance heating element 12. The thickness of the insulating coating 17 is 5 to 50 μm in the case of oxide glass, 10 to 50 μm for conductive resin
It is desirable that

In the ceramic heater 10, after heating,
Cooling to return to room temperature is required, but the insulating coating 1
If it is too thick, it takes a long time to cool and the productivity will decrease. Conversely, if it is too thin, the oxidation resistance will decrease and the temperature of the heating surface will also decrease due to heat radiation from the exposed surface of the resistance heating element. Because it will go down.

As described above, when the insulating coating is provided on the surface of the resistance heating element, these materials have excellent electrical insulation properties. It is possible to protect the surface of the resistance heating element without leak current flowing through the conductive coating.

Further, since the above-mentioned ceramic substrate can be formed to have a high thermal conductivity and a small thickness, the surface temperature of the ceramic substrate quickly follows the temperature change of the resistance heating element. The ceramic heater 10
Excellent in temperature controllability and durability.

FIG. 3 is a bottom view schematically showing another embodiment of the ceramic heater of the present invention, and FIG. 4 is a partially enlarged sectional view of the ceramic heater. This ceramic heater 20 is the same as the ceramic heater 10 shown in FIG.
1, a plate-like ceramic substrate 21 is used, and substantially linear resistance heating elements 22 (22a to 22f) are arranged on one main surface of the ceramic substrate 21 in the concentric shape shown in FIG. Thus, a circuit is formed, and an object to be heated is placed or held on the other main surface and heated.

Further, in the ceramic heater 20, the area including the portion where the circuit is formed, that is, the resistance heating elements 22a, 22b, 22
In FIG. 3C, insulating coatings 27a, 27b,
27c, on the other hand, in the resistance heating elements 22d, 22e, and 22f where the distance between the circuits is small, insulation is provided in the area sandwiched by the resistance heating elements constituting the circuit, in the periphery thereof, and in the entire area between the circuits. 27d is provided.

In the ceramic heater 20 having such a configuration, the same effect as that of the ceramic heater 10 shown in FIG. 1 is obtained, and the migration of metal particles (for example, silver particles) contained in the resistance heating element 22 is performed. Accordingly, it is possible to prevent a short circuit from occurring in adjacent circuits. Also, when forming the insulating cover 27, a coating layer may be formed in a certain area by screen printing or the like, and heating or the like may be performed to form the insulating cover 27.
The heater can be formed relatively easily and efficiently, the coating cost is reduced, and the heater becomes inexpensive.

As the insulating covering 17, as in the case of the ceramic heater shown in FIG.
Alternatively, any of heat-resistant resins such as a polyimide resin and a silicone resin can be used.

As the material of the base material of the ceramic substrate, for example, a carbide ceramic, an oxide ceramic, a nitride ceramic, or the like can be used as in the case of the ceramic heater shown in FIG. The material of the resistance heating element 22 can be the same as that of the ceramic heater 10 shown in FIG.
The resistance heating element 22 can be formed by using the same method as in the above case.

In this ceramic heater 20, the thickness of the insulating covering 27 (the thickness from the surface of the resistance heating element 22) is preferably the same as that of the ceramic heater 10 shown in FIG. The thickness of the portion where the heating element 22 is not formed from the bottom surface of the ceramic substrate 21 is preferably 10 to 50 μm for oxide glass and 10 to 50 μm for heat-resistant resin.

FIG. 5 is a bottom view schematically showing still another embodiment of the ceramic heater of the present invention. This ceramic heater 30 is the same as the ceramic heater 20 described above.
The structure of the ceramic heater 20 shown in FIG. 1 is the same as that of the ceramic heater 20 except that the insulating coating 37 is formed over the entire area where the resistance heating element 22 is formed.
In addition to the same effect as in the case (1), it is possible to prevent a short circuit from occurring in an adjacent circuit due to migration of metal particles (for example, silver particles) included in the resistance heating element 22. Also, when forming the insulating cover 37,
Since the insulating coating 37 may be formed by forming a coating layer by screen printing or the like and performing heating or the like, the insulating coating 37 can be formed easily and efficiently, and the coating cost is reduced.
It becomes an inexpensive heater.

As described above, the insulating cover according to the present invention has a configuration that covers only the surface of the circuit, a configuration that covers the entire area including the portion where the circuit is formed, and an insulating cover in the diameter direction of the ceramic substrate. Various configurations such as a configuration in which two or more adjacent circuits are integrally covered, and a configuration in which the entire region where a circuit is formed is covered can be adopted.

[0061]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific example of a ceramic heater according to the present invention and a method of manufacturing the same will be described. In the following description,
The process conditions are merely examples, and can be set with appropriate changes depending on the size of the sample, the processing amount, and the like.

Example 1 100 parts by weight of aluminum nitride powder (average particle size 1.1 μm), 4 parts by weight of yttria (average particle size 0.4 μm), 12 parts by weight of an acrylic resin binder, and alcohol were mixed and kneaded. After forming the slurry, the slurry was sprayed by a spray drying method to obtain a granular powder.

Next, the granulated powder is put into a molding die and formed into a flat plate to form a formed body. The formed body is hot-pressed at about 1800 ° C. under a pressure of 200 kg / cm ^2. Then, a plate-shaped sintered body made of aluminum nitride having a thickness of 3 mm was obtained. This was cut out into a disk shape having a diameter of 210 mm to obtain a ceramic substrate 11 for a ceramic heater (see FIG. 1).

Next, a through hole 15 for inserting a lifter pin 16 for a semiconductor wafer into the ceramic substrate 11 is formed.
Then, a portion to be the bottomed hole 14 for embedding the thermocouple was drilled.

The ceramic substrate 11 after the above processing
Then, for example, a conductor paste was printed by a screen printing method so that the linear resistive heating elements 12 were formed in the pattern shown in FIG. The conductor paste used here is
Solvest PS603D (trade name) manufactured by Tokuriki Chemical Laboratory
And a metal oxide composed of a mixture of lead oxide, zinc oxide, silica, boron oxide and alumina (the weight ratio is 5/55/10/25/10 in this order) is 7.5 with respect to the amount of silver. It is a so-called silver paste containing about 10% by weight. Incidentally, the average particle size of silver was 4.5 μm, and the shape was mainly flake-like.

The ceramic substrate 11 on which the conductive paste was printed was heated and fired at 780 ° C. to sinter the silver in the conductive paste, and was baked on the ceramic substrate 11. At this time, the resistance heating element 12 formed of the silver sintered body had a thickness of about 10 μm, a width of about 2.4 mm, and a sheet resistance of 5 mΩ / □.

Thereafter, the surface of the resistance heating element 12 is coated with an oxide-based material.
An insulating coating 17 made of a glass material was formed. Ma
30% by weight of PbO, SiO_Two 50% by weight, B_Two O_Three 
15% by weight, Al_Two O _Three 3% by weight, Cr_Two O_Three 2% by weight
87 parts by weight of glass powder having a composition of
And 10 parts by weight of a solvent to prepare a paste-like mixture.
Made.

Next, using this paste-like mixture, screen printing was performed so as to cover the surface of the resistance heating element 12 to form a layer of the paste-like mixture. Thereafter, the paste-like mixture is dried and fixed at 120 ° C., and is heated at 680 ° C. for 10 minutes in an air atmosphere to be fused to the surface of the resistance heating element 12 and the ceramic substrate 11, thereby obtaining an insulating property. The coating 17 was formed. Thereafter, the surface of the insulating coating was subjected to sandblasting using SiC powder having an average particle size of 1.0 μm to adjust the surface roughness Ra of the insulating coating. At this time, the thickness of the insulating covering 17 was 10 μm. However, the insulating cover 1 is provided at the connection portions of the external terminals 13 at both ends of the circuit composed of the resistance heating element 12.
7 did not form. Therefore, the covering state near the external terminals is different from that of the ceramic heater 10 shown in FIG.
In addition, when heating and fusing, a method is also used in which a temporary shape is preliminarily formed into a shape compatible with the shape of the insulating covering 17, and the temporary formed body is placed on the resistance heating element 12 and heated. Good.

Then, a silver-containing lead solder paste (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) is printed on the portion of the resistance heating element 12 where the external terminal 13 is to be mounted by a screen printing method to form a solder layer. An external terminal 13 made of Kovar is placed on the layer and heated and reflowed at 420 ° C.
External terminals 13 were connected and fixed to both ends of the resistance heating element 12. In addition, as shown in FIG.
2 and the external terminals 13 may be connected, and thereafter, the insulating cover 17 may be formed so as to cover the portion of the resistance heating element 12 on which the external terminals 13 are formed.

Thereafter, a thermocouple (not shown) for controlling the temperature is buried in the bottomed hole 14 of the ceramic substrate.
The ceramic heater 10 shown in FIG. 2 was obtained, and the ceramic heater 10 was fitted into a support container provided with a heat insulating ring made of fluororesin for fitting the ceramic heater on the upper portion, thereby forming a hot plate unit. The resistance heating element 1
2 has a predetermined resistance value, and when energization is performed, heat is generated by Joule heat and the semiconductor wafer 19 is heated.
Heat.

For the ceramic heater 10 constituting the hot plate unit, the coefficient of thermal expansion of the insulating coating was measured and evaluated using the following method.

[0072]Evaluation method  (1) Measurement of Surface Roughness Ra of Insulating Coating Surface Roughness was measured using Surfcom 920A manufactured by Tokyo Seimitsu Co., Ltd.
Ra and Rmax were measured. (2) Measurement of surface resistance (area resistance) of insulating coating material Room temperature, D. C. It was measured under the condition of 100V. (3) Evaluation of the oxidation resistance of the resistance heating element The resistance of the heater resistance after aging at 200 ° C. for 1000 hours.
Evaluation was made by examining the change.

(4) Evaluation of Variation in Temperature Rise Time After the silicon wafer was placed on the hot plate unit, current was applied and the time required to heat the silicon wafer to 200 ° C. (temperature rise time) was measured 10 times. Then, the ratio of the earliest or the slowest temperature was calculated in% with respect to the average heating time, and the absolute value of the value obtained by subtracting from 100% was large, which was regarded as the variation of the heating. .

(5) Cooling time After raising the temperature under the condition of (4) above, supply the cooling medium (cooling air) at 25 ° C. at 0.1 m ³ / min and cool it down to 50 ° C. (Temperature drop time) was measured, and the average was taken as the temperature drop time.

(6) Sulfuration resistance An atmosphere containing 15 vol% of H ₂ S is maintained at 75 ° C.
The ceramic heater was left in this atmosphere for 10 days, the resistance change rate of the resistance heating element was measured, and the resistance was evaluated as sulfuration resistance.

(7) Presence or absence of occurrence of migration The hot plate unit was heated to 200 ° C. at 100% humidity and energized for 48 hours, and the presence or absence of metal diffusion between the resistance heating elements was checked by a fluorescent X-ray analyzer (Shimadzu Corporation) EPM-81
0S).

Example 2 A heat-resistant resin material (polyimide resin) was used in place of the oxide-based glass material, and the insulating coating 17 was formed by the following method.
Was formed, and a ceramic heater was manufactured in the same manner as in Example 1 except for performing a roughening treatment, and was evaluated in the same manner as in Example 1. The results are shown in Table 1.

That is, first, the aromatic polyimide powder 8
After preparing a solution of a paste-like or viscous mixture composed of 0% by weight and 20% by weight of polyamic acid, the solution of this mixture is selectively applied so as to cover the surface of the resistance heating element 12, A layer of the mixture formed on the surface.

Next, the formed mixture layer is heated at 350 ° C. in a continuous firing furnace to be dried and solidified.
It was fused to the surface and the ceramic substrate 11. After this,
The surface of the insulating coating was subjected to sandblasting using alumina powder having an average particle size of 1.0 μm to adjust the surface roughness Ra of the insulating coating 17. At this time, the average thickness of the formed insulating cover 17 was 10 μm.

Example 3 A heat-resistant resin material (silicone-based resin) was used in place of the oxide-based glass material, and the insulating coating 1 was obtained by the following method.
7, a ceramic heater was manufactured in the same manner as in Example 1, except that the roughening treatment was performed, and evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

That is, by a metal mask printing method or the like,
A methylphenyl-based silicone resin is selectively applied so as to cover the surface of the resistance heating element 12 and is placed in an oven at 220 ° C.
Then, it was dried and solidified by heating, and was fused to the surface of the resistance heating element 12 and the ceramic substrate 11. At this time, the thickness of the formed insulating cover 17 was 15 μm. In addition,
The surface roughness Ra of the insulating coating 17 was adjusted by sandblasting using alumina powder having an average particle size of 1.5 μm.

Embodiment 4 In this embodiment, the resistance value of the linear resistance heating element is increased.
A ceramic heater was manufactured in the same manner as in Example 1 except that the thickness of the insulating coating made of oxide glass was set to 20 μm, and evaluated in the same manner as in Example 1. The results are shown in Table 1. This is because when a voltage of 30 to 300 V is applied and the temperature is raised to 200 ° C. or higher, the resistance value must be increased. The surface roughness Ra of the insulating coating 17 was adjusted by sandblasting using SiC powder having an average particle size of 0.1 μm.

As a paste for the resistance heating element, silver: 5
6.5% by weight, palladium: 10.3% by weight, SiO
_2: 1.1 wt%, B ₂ O _3: 2.5 wt%, ZnO:
5.6% by weight, PbO: 0.6% by weight, RuO ₂ : 2.
1% by weight, resin binder: 3.4% by weight, solvent: 17.
What consisted of 9% by weight was used. The resistance heating element pattern has a thickness of 10 μm, a width of 2.4 mm, and a sheet resistance of 150 m.
Ω / □.

Example 5 A heat-resistant resin material (polyimide resin) was used in place of the oxide-based glass material, and an insulating coating 17 was formed by the method described in Example 2, and roughening was performed. A ceramic heater was manufactured in the same manner as in Example 4.
Was evaluated in the same way as The thickness of the insulating coating is 10
μm, and the adjustment of the surface roughness Ra of the insulating coating 17 is as follows:
This was performed by sandblasting using alumina powder having an average particle size of 0.1 μm. The results are shown in Table 1.

Example 6 A heat-resistant resin material (silicone resin) was used in place of the oxide-based glass material, and an insulating coating 17 was formed by the method described in Example 3, followed by roughening. Manufactured a ceramic heater in the same manner as in Example 4.
Was evaluated in the same way as The thickness of the insulating coating is 10
μm, and the adjustment of the surface roughness Ra of the insulating coating 17 is as follows:
This was performed by sandblasting using alumina powder having an average particle size of 0.03 μm. The results are shown in Table 1.

Comparative Example 1 A ceramic substrate on which a resistance heating element was formed was immersed in an electroless nickel plating bath, and the surface of the resistance heating element was about 1 μm thick.
A ceramic heater was manufactured in the same manner as in Example 1 except that a nickel metal layer was deposited.
Was evaluated in the same way as The results are shown in Table 1. The concentration of each component in the nickel plating bath was 8% nickel sulfate.
0 g / l, sodium hypophosphite 24 g / l, sodium acetate 12 g / l, boric acid 8 g / l, ammonium chloride 6
g / l.

COMPARATIVE EXAMPLE 2 A ceramic heater was manufactured in the same manner as in Example 1 except that after forming an insulating coating on the surface of the resistance heating element 12, roughening treatment by sandblasting was not performed. Was evaluated in the same way as The surface roughness Ra of the ceramic heater was 0.007 μm. The results are shown in Table 1.

Comparative Example 3 After an insulating coating was formed on the surface of the resistance heating element 12, sandblasting was performed using SiC powder having an average particle size of 15 μm to form an insulating coating having a surface roughness Ra of 11 μm. Other than that, a ceramic heater was manufactured in the same manner as in Example 4, and evaluated in the same manner as in Example 1. Table 1 shows the results.
It was shown to.

Comparative Example 4 A ceramic heater was manufactured in the same manner as in Example 1 except that an insulating coating was not formed on the surface of the resistance heating element 12, and was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0090]

[Table 1]

As is clear from the results shown in Table 1, in Examples 1 to 6, the resistance change of the resistance heating element was
While it was as small as 0.1 to 0.3%, in Comparative Example 1, it was as large as 3%. The reason for this is that the resistance fluctuated due to the oxidation of the nickel plating film itself, and it is estimated that oxygen was diffused and oxidized the silver inside because the nickel plating film was porous. are doing. Further, in Examples 1 to 6, the dispersion at the time of temperature rise was small and the temperature drop rate was relatively high, whereas in Comparative Examples 2 and 3, the surface roughness Ra of the insulating coating covering the resistance heating element was Ra. Is too small or too large, so the temperature drop rate is slow. Regarding the occurrence of migration, Ag migration occurred in the ceramic heater according to Comparative Example 4, and there was a possibility that a short circuit might occur between the resistance heating elements. FIG.
10 to 10 respectively show graphs showing the measurement results of the surface roughness of the insulating coating constituting the ceramic heaters according to Examples 1 to 5.

Further, in the ceramic heaters according to Examples 1 and 4, the thermal expansion coefficient of the oxide glass as the insulating coating was 5 ppm / ° C., and the aluminum nitride was 3.5 to 3.5 ppm.
Both are numerically close to 4 ppm / ° C., and the change in resistance caused by the separation of the metal particles constituting the resistance heating element due to expansion and contraction due to the cooling and heating cycle is relatively smaller than in the case where a heat-resistant resin is used.

In Examples 4 to 6, a resistance heating element having a sheet resistance of 150 mΩ / □ was used. In this case, the sheet resistance of the insulating coating is 10 ¹⁵ to 10 ¹⁶ Ω / □.
Since the insulator is almost completely an insulator, even if a voltage of 50 to 200 V is applied, the current propagates through the inside of the resistance heating element and the amount of generated heat increases, but the nickel plating film as in Comparative Example 1 is formed. In this case, the sheet resistance of the nickel plating film is 50
Since the current propagates through a portion having a lower resistance value, the current propagates through the nickel plating film, and the calorific value decreases.

Embodiment 7 In the same manner as in Embodiment 1, a ceramic substrate 21 for a ceramic heater is produced, a through hole 25 for inserting a lifter pin 16 for a semiconductor wafer, and a thermocouple for embedding a thermocouple. A portion to be the bottomed hole 24 was drilled.

Next, resistance heating elements 22a to 22f having the shapes shown in FIG. 3 were formed on the bottom surface of the processed ceramic substrate 21 using the same material as in the first embodiment. Thereafter, as shown in FIG. 3, the resistance heating elements 22a, 22b,
In the area 22c, insulating coatings 27a, 27b, 27c made of an oxide-based glass material are provided around the area sandwiched by the resistance heating elements constituting the circuit and the surrounding area, and in the resistance heating elements 22d, 22e, 22f. An insulating cover 27d made of the same material is provided on the region sandwiched by the resistance heating elements constituting the circuit, the periphery thereof, and the entire region between the circuits. The composition of the oxide-based glass material is the same as that of Example 1, and the method of forming the insulating coating 27 is the same as that of Example 1 except that the applied area is wide as described above. The same is true. At this time, the thickness of the insulating covering 17 was 30 μm. However, the insulating cover 27 was not formed in the portion connecting the external terminals at both ends of the circuit.
The surface roughness Ra of the insulating cover 27 was adjusted by sandblasting using SiC powder having an average particle size of 5 μm.

Thereafter, a thermocouple (not shown) for controlling the temperature is buried in the bottomed hole 24 of the ceramic substrate.
4 was obtained. After manufacturing the ceramic heater 20 using the aluminum nitride substrate 21 as described above, evaluation was performed in the same manner as in Example 1. The results are shown in Table 2.

Example 8 An insulating coating 27 was prepared by using a heat-resistant resin material (polyimide resin) instead of the oxide-based glass material in the following manner.
Was formed, and a roughening treatment was performed. A ceramic heater was manufactured in the same manner as in Example 7, and evaluated in the same manner as in Example 7. The results are shown in Table 2.

That is, first, the aromatic polyimide powder 8
After preparing a solution of a paste-like or viscous mixture consisting of 0% by weight and 20% by weight of polyamic acid, the solution of this mixture was applied to the same region as in Example 7, and was then placed in a continuous firing furnace at 350%. C. and dried and solidified to form insulating coatings 27a to 27d. The insulating coating 2
7 had a thickness of 30 μm, and the surface roughness Ra of the insulating coating 27 was adjusted by sandblasting using alumina powder having an average particle size of 4.2 μm.

Example 9 A heat-resistant resin material (silicone resin) was used in place of the oxide-based glass material, and the insulating cover 27 was formed by the following method.
Was formed, and a roughening treatment was performed. A ceramic heater was manufactured in the same manner as in Example 7, and evaluated in the same manner as in Example 7. The results are shown in Table 2.

That is, by a metal mask printing method or the like,
A methylphenyl-based silicone resin was applied to the same region as in Example 7, heated at 220 ° C. in an oven, and dried and solidified to form insulating coatings 27a to 27d.
The thickness of the insulating cover 27 was 30 μm, and the surface roughness Ra of the insulating cover 27 was adjusted by sandblasting using alumina powder having an average particle size of 2.0 μm.

[0101]

[Table 2]

As is clear from the results shown in Table 2, in Examples 7 to 9, the sheet resistance of the insulating coating was
10 ¹⁵ to 10 ¹⁶ Ω / □, which is large, and the resistance change of the resistance heating element coated with such an insulating coating is 0.2 to
It was as small as 0.3%. In addition, the variation in temperature rise was small, and the rate of temperature decrease was relatively fast. Further, after performing the oxidation resistance test in Examples 8 and 9, the insulating coating 27 was forcibly peeled off from the surface of the ceramic substrate, and migration of metal such as silver occurred from the surface of the resistance heating element. It was observed in the same manner as in Example 1 that no migration occurred.

Example 10 100 parts by weight of SiC powder (average particle size: 1.1 μm), B
_A composition comprising ₄ parts by weight of 4C, 12 parts by weight of an acrylic binder and alcohol was spray-dried to prepare a granular powder.

Next, the granulated powder is placed in a mold and molded into a flat plate to form a formed product.
Hot pressing was performed at 90 ° C. under a pressure of 20 MPa to obtain a plate-like sintered body of SiC having a thickness of about 3 mm. Further, the surface of the plate-like sintered body was polished with a # 800 diamond grindstone and polished with a diamond paste to Ra = 0.08 μm. Further, a glass paste (G-5177 manufactured by Shoei Chemical Industry Co., Ltd.) was applied to the surface,
The temperature was raised to 0 ° C. to form a 3 μm thick SiO ₂ layer.

Then, the diameter of the plate-like sintered body was 210 m.
m was cut out to obtain a ceramic substrate. Thereafter, the surface on which the SiO ₂ layer was formed was used as a surface on which a resistance heating element was formed, and as shown in FIG. 5, an insulating coating (oxide glass) having a thickness of 50 μm was formed on the resistance heating element. A ceramic heater was manufactured in the same manner as in Example 1 except that a roughened surface was formed by performing sandblasting using SiC powder having an average particle diameter of 10 μm over the entire region. After manufacturing a ceramic heater using a substrate made of SiC as described above, evaluation was performed in the same manner as in Example 1. Table 3 shows the results.

Example 11 A heat-resistant resin material (polyimide resin) was used in place of the oxide-based glass material, and the insulating cover 37 was formed by the following method.
And a ceramic heater was manufactured in the same manner as in Example 10 except that roughening was performed by sandblasting using alumina powder having an average particle size of 10 μm.
Evaluation was performed in the same manner as 0. Table 3 shows the results.

That is, first, the aromatic polyimide powder 8
After preparing a solution of a paste-like or viscous mixture composed of 0% by weight and 20% by weight of polyamic acid, the solution of this mixture is applied to the entire area where the resistance heating element is formed to form a layer of the mixture. did.

Thereafter, the formed mixture layer was heated at 350 ° C. in a continuous firing furnace to be dried and solidified, fused to the surface of the resistance heating element and the ceramic substrate, and subjected to a roughening treatment under the above conditions. At this time, the thickness of the formed insulating cover was 50 μm.

Example 12 An insulating coating (oxide glass) having an average particle size of 8 μm
A ceramic heater was manufactured in the same manner as in Example 10, except that the roughening treatment was performed by sandblasting using iC powder, and the evaluation was performed in the same manner as in Example 10. Table 3 shows the results.
It was shown to.

Example 13 An insulating coating 37 was formed in the same manner as in Example 11, except that a heat-resistant resin material (polyimide resin) was used instead of the oxide-based glass material. A ceramic heater was manufactured in the same manner as in Example 10 except that roughening was performed by sandblasting using alumina powder having a particle size of 8 μm, and the evaluation was performed in the same manner as in Example 10. Table 3 shows the results.

[0111]

[Table 3]

As is clear from the results shown in Table 3, in Examples 10 to 13, the resistance change of the resistance heating element was as small as 0.2 to 0.3%. In addition, the variation in the heating rate was slightly larger than in Examples 1 to 7 due to the large surface roughness of the insulating coating, but the cooling rate was relatively fast without changing much. Was.

As described above, the ceramic heater of the present invention has a small rate of change in resistance, a small variation in the rate of temperature rise, a fast rate of temperature drop, and excellent temperature controllability. Further, it has excellent corrosion resistance to reactive gases such as O ₂ and H ₂ S in a semiconductor manufacturing apparatus. Furthermore, since the insulating coating is an insulator, even if the resistance value of the resistance heating element is increased, current does not flow through the insulating coating, and a heater having a usage region of 150 ° C. or more can be obtained. it can.

When oxide glass is used as the insulating coating, cracks are less likely to occur because of excellent adhesion between the oxide glass and the ceramic substrate and a small coefficient of thermal expansion, and at the same time, resistance heating elements are used. Has a small resistance change rate.
Further, when a heat-resistant resin is used as the insulating covering, the insulating covering can be formed at a relatively low temperature. Thus, the present invention is most suitable as a heater for a medium temperature of 200 to 400 ° C. and a high temperature of 400 to 800 ° C.

[0115]

As described above, the ceramic heater according to the present invention has a small resistance change rate of the resistance heating element, has a sufficient temperature rising / falling rate, and has excellent temperature controllability. In addition, the resistance to the reactive gas in the semiconductor manufacturing equipment is excellent, and since the insulating coating is an insulator, the resistance value of the resistance heating element can be increased. Can be used as Further, when the insulating coating is formed over a predetermined area including the portion where the resistance heating element is formed, the above-described effect can be obtained, and migration of a metal such as silver can be prevented. Further, since the coating is easy, the cost for forming the insulating coating can be reduced.

[Brief description of the drawings]

FIG. 1 is a bottom view schematically showing one embodiment of a ceramic heater according to the present invention.

FIG. 2 is a partially enlarged sectional view showing a part of the ceramic heater shown in FIG.

FIG. 3 is a bottom view schematically showing another embodiment of the ceramic heater according to the present invention.

FIG. 4 is a partially enlarged sectional view showing a part of the ceramic heater shown in FIG. 3;

FIG. 5 is a bottom view schematically showing still another embodiment of the ceramic heater according to the present invention.

FIG. 6 is a graph showing the measurement results of the surface roughness of the insulating coating constituting the ceramic heater according to Example 1.

FIG. 7 is a graph showing the measurement results of the surface roughness of the insulating coating constituting the ceramic heater according to Example 2.

FIG. 8 is a graph showing the measurement results of the surface roughness of the insulating coating constituting the ceramic heater according to Example 3.

FIG. 9 is a graph showing the measurement results of the surface roughness of the insulating coating constituting the ceramic heater according to Example 4.

FIG. 10 is a graph showing the measurement results of the surface roughness of the insulating coating constituting the ceramic heater according to Example 5.

[Explanation of symbols]

10, 20 ceramic heater 11, 21 ceramic substrate 11a, 21a heating surface 11b, 21b bottom surface 12, 22 (22a, 22b, 22c, 22d) resistance heating element 13, 23 external terminal 14, 24 bottomed hole 15, 25 through hole 16 Lifter pin 17, 27 (27a, 27b, 27c, 27d) Insulating coating 19 Silicon wafer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) H05B 3/68 H05B 3/68 F term (Reference) 3K034 AA02 AA04 AA06 AA10 AA16 AA19 AA34 AA36 AA37 BA05 BA08 BA13 BB06 BB14 BC04 BC12 CA03 CA14 CA17 CA22 CA27 FA21 HA01 HA10 JA01 JA02 JA10 3K092 PP00 QA05 QB02 QB26 QB31 QB47 QB64 QB65 QB75 QB76 QC02 QC20 QC52 QC58 RF03 RF17 RF19 RF22 UB02 UB04 VV09 VV34

Claims (8)

[Claims] 1. A ceramic heater comprising: a resistance heating element including one or more circuits disposed on a surface of a ceramic substrate; and an insulating coating provided on the resistance heating element. The ceramic heater according to claim 1, wherein the surface roughness Ra of the surface according to JIS B0601 is 0.01 to 10 m. 2. The ceramic heater according to claim 1, wherein the insulating covering is provided over an area including a portion where the circuit is formed. 3. The ceramic heater according to claim 1, wherein the ceramic substrate is made of a nitride ceramic or a carbide ceramic. 4. The ceramic heater according to claim 1, wherein said insulating covering is made of oxide glass. 5. The ceramic heater according to claim 1, wherein the insulating covering is made of a heat-resistant resin material. 6. The ceramic heater according to claim 5, wherein the heat-resistant resin material is at least one selected from a polyimide resin and a silicone resin. 7. The ceramic heater according to claim 1, wherein a side opposite to the side on which the resistance heating element is formed is a heating surface. 8. The ceramic heater according to claim 1, wherein the insulating coating integrally covers a resistance heating element composed of two or more circuits.