JP2002231424A - Ceramic heater and method of its manufacture and wafer heating system using this ceramic heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem in a ceramic heater having an insulating layer composed of glass on at least one main surface of a plate-like body composed of ceramics, and having a heating resistance on the insulating layer wherein a large number of bubbles exist in glass of the insulating layer and desired electric insulating performance can not be obtained by the bubbles in an insulating characteristic and a withstand voltage characteristic after baking a heating element. SOLUTION: The insulating layer has the thickness of 10 to 600 μm, and a bubble nonexistent area is continued by 10 μm or more in the thickness direction of the insulating layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer heating apparatus mainly used for heating a wafer, a ceramic heater used for the same, and a method of manufacturing the same. For example, the present invention relates to a semiconductor wafer, a liquid crystal substrate or a circuit substrate. The present invention relates to a wafer heating apparatus suitable for forming a semiconductor thin film on a wafer or drying and baking a resist solution applied on the wafer to form a resist film.

[0002]

2. Description of the Related Art For example, in a process of forming a semiconductor thin film in a manufacturing process of a semiconductor manufacturing apparatus, an etching process, a baking process of a resist film, and the like, a semiconductor wafer (hereinafter, referred to as a semiconductor wafer).
A wafer heating apparatus is used to heat the wafer (abbreviated as wafer).

A conventional semiconductor manufacturing apparatus uses a batch-type apparatus for forming a plurality of wafers at a time. However, as the size of a wafer increases from 8 inches to 12 inches, the processing accuracy increases. In order to increase the quality, a technique called a single-wafer processing that processes one sheet at a time has been implemented in recent years. However, in the case of the single-wafer method, the number of processes per one process is reduced, so that the processing time of the wafer is required to be shortened. For this reason, it has been required for the wafer support member to shorten the heating time of the wafer, speed up the suction and desorption of the wafer, and improve the heating temperature accuracy.

As an example of the above-described wafer heating apparatus,
For example, Japanese Patent Application Laid-Open No. 11-40330 discloses a "heater characterized by providing a heating element formed by sintering metal particles on the surface of a plate made of nitride ceramics or carbide ceramics". ing.

[0005] This ceramic heater is a heater for drying a photosensitive resin formed on the wafer surface. This structure will be described with reference to FIG. 4. Metal particles obtained by sintering one or more metal particles selected from gold, silver, platinum, palladium, lead, tungsten, and nickel on the surface of a soaking plate 32 made of ceramics Sintered body 33 and Au, A
Heating resistor 35 composed of metal coating layer 34 composed of at least one metal selected from g, Pd, Pt, and Ni
Are formed. Further, it is disclosed that the metal particle sintered body 34 contains a metal oxide in order to make the metal particles adhere to nitride ceramics and carbide ceramics. Further, the conduction terminal 37 is fixed to the heating resistor 35 by solder 36. Further, it is shown that the wafer W is set apart from the heat equalizing plate 32 by the lift pins 39.

Aluminum nitride-based ceramics and silicon carbide-based ceramics are both suitable as a material for a heat equalizing plate 32 for a semiconductor wafer heating apparatus which requires uniform heat because both have high thermal conductivity. As a material of the heat equalizing plate 32 used in the process of forming a film made of on the wafer W and drying it, silicon carbide ceramics is more excellent. This is because in the case of aluminum nitride ceramics, the aluminum nitride reacts with moisture in the air to generate ammonia gas, which has an adverse effect on the photosensitive resin. Thus, as the heat equalizing plate 32 used in the photosensitive resin drying step, silicon carbide ceramics is more useful.

[0007] Of these, when silicon carbide-based ceramics are used as the base material of the soaking plate, the silicon carbide-based ceramics exhibit semiconductivity. Therefore, when a heating resistor is formed on the surface of the silicon carbide-based ceramics, If the heating resistor is formed directly on the surface of the silicon carbide ceramics, the electrodes will be short-circuited when the power is supplied, and in the worst case, a disconnection will occur. In addition, even when the disconnection does not occur, when the power is supplied, the wafer mounting surface is charged, so that not only cannot a uniform pattern be formed, but also the pattern of the wafer is destroyed due to electrostatic breakdown. Therefore, it is necessary to form an insulating layer between the silicon carbide ceramic and the heating resistor.

[0008]

However, when printing / baking is performed with crystallized glass using a glass paste in the formation of the insulating layer, a small grain boundary portion is formed between the crystallized portions. Many bubbles are generated,
There was a problem that desired electrical insulation could not be obtained due to these bubbles. At first glance, it seems that a transparent glass layer is formed on the amorphous glass. However, when the structure is enlarged, a large number of bubbles remain, and the desired electrical insulation is obtained by these bubbles. It turned out to be gone.

[0009] As a method for eliminating bubbles in glass, As and Sb having defoaming and defoaming effects are designated as poisonous substances, and there remain problems in the production method and in the handling of products. As for the addition of an alkali component that has the effect of increasing the viscosity of glass at high temperatures, when a heater is used with a DC power supply, the life of the heating resistor is shortened. Migration occurs, the resistance starts to rise, and in the worst case in about 200 hours, there is a problem that a disconnection occurs.

[0010]

Means for Solving the Problems The inventors of the present invention have made intensive studies on the above-mentioned problems, and as a result, have found that a ceramic heater having a plate-like body made of ceramic has an insulating layer of 10 to 6 times.
It has been found that the problem of the insulation and withstand voltage can be overcome by using a glass having a thickness of 00 μm and a region in which no bubble is present in the insulating layer in a thickness direction of 10 μm or more.

The insulating layer is made of amorphous glass containing SiO ₂ as a main component and containing at least one of B, Mg, Ca, Pb and Bi in an amount of 10% or more in terms of oxide. As a result, they have found that they are effective in solving the above problems without substantially containing an oxide of As or Sb.

Further, in the method of manufacturing a ceramic heater according to the present invention, a ceramic plate comprising an insulating layer made of glass on at least one main surface of a plate made of ceramic, and a heating resistor provided on the insulating layer. In the heater, the insulating layer is coated with a paste containing a plurality of glasses each having an average particle diameter D ₅₀ of 15 μm or more and an average particle diameter D ₅₀ of 20% or more, and the amount of residual carbon in the debinding step. Has been found to be effective in solving the above-mentioned problems by forming it at 1% by weight or less of the weight of the glass.

[0013]

Embodiments of the present invention will be described below.

FIGS. 1 and 2 are cross-sectional views showing an example of a wafer heating apparatus using a ceramic heater according to the present invention. One of the main surfaces of a heat equalizing plate made of a silicon carbide ceramic plate 2 is shown in FIG. While the mounting surface 3 on which the wafer W is mounted,
The heating resistor 5 and the overcoat layer 28 are formed on the heating resistor 5 via the insulating layer 4 made of glass on the oxide film 21 made of SiO ₂ formed on the other main surface. Is provided with a power supply section 6 to be electrically connected to form a ceramic heater.

In the wafer heating apparatus according to the present invention, when the insulating layer 4 has one
The insulating layer 4 is made of glass having a thickness of 0 to 600 μm, and a region having no bubbles in the thickness direction of the insulating layer 4 is continuous for 10 μm or more.

Regarding the air bubbles existing in the insulating layer, a position 1 where a large number of air bubbles exist is determined in advance by an ultrasonic flaw detector.
Marking was performed at 0 places, and then the insulation resistance and withstand voltage tests described in JIS were performed. After the test, embedding-polishing was performed so that the marked portions could be observed, and the state of bubbles in the thickness direction was confirmed by SEM. . At this time, as for the method of confirming the state of the bubble, the photograph taken by the SEM was observed, and the state of the bubble was determined with the value of the minimum dimension between the bubbles.

When crystallized glass is used for the conventional insulating layer 4, for example, as shown in FIG. 3B, bubbles 44 are likely to remain in a grain boundary phase 45 filling between crystal phases 43. ,
Since the distance a in the thickness direction between the bubbles 44 is less than 10 μm, flashing / short-circuiting occurs in the withstand voltage characteristics after baking of the heating resistor, and the characteristics as a heater are not satisfied.

On the other hand, the insulating layer 4 of the present invention has a structure shown in FIG.
As shown in (a), the distance a between the bubbles 44 in the thickness direction of the glass layer 42, that is, a continuous region without the bubbles 44 is 10 μm.
As described above, even after the heating resistor 5 is baked, the diffusion of metal as a component of the heating resistor 5 is suppressed, and the insulation characteristics and resistance of a circuit of 300 V or less described in JIS C 0703 Low Voltage Electrical Equipment Insulation Standard. Voltage characteristics can be satisfied.

The glass layer 42 forming the insulating layer 4 is made of SiO
_{(2) It is} composed of an amorphous glass containing at least one of B, Mg, Ca, Pb, and Bi as oxides in an amount of 10% or more in terms of oxides, and substantially contains oxides of As and Sb. Not (0.05% by weight or less in terms of oxide)
It is preferable to use glass.

By using the glass having the above composition, it is possible to reduce the viscosity of the glass at a high temperature. B, M
g, Ca, Pb, and Bi are dispersed in SiO ₂ glass to lower the apparent viscosity of the glass. In particular, PbO, B ₂ O ₃ , and Bi ₂ O ₃ do not crystallize but remain in the glass to reduce the viscosity and melting point of the glass, and are effective in suppressing the generation of bubbles in the glass.

By reducing the viscosity of the glass, the air bubbles 44 generated in the insulating layer 4 are raised on the surface of the insulating layer 4, and the number of the air bubbles 44 in the insulating layer 4 can be reduced by forming an open pore. it can. As described above, it is possible to form the glass layer 42 in which a region having no bubble is continuous for 10 μm or more in the thickness direction of the insulating layer 4. The use of amorphous glass is preferable for forming the insulating layer 4 having fewer bubbles than crystallized glass described later. As a result, the poisonous substance As with defoaming and defoaming effects
Bubbles in the insulating layer 4 can be reduced without adding Sb oxide.

On the other hand, when the added amount of B, Mg, Ca, Pb, and Bi is less than 10% by weight in terms of oxide, the viscosity of the glass at a high temperature does not sufficiently decrease, and it is difficult to reduce bubbles. It is. When crystallized glass is used, expansion and contraction occur in the process of generating crystal nuclei in the glass. In this expansion / contraction process, many small bubbles exist around the crystal nucleus. Due to the minute bubbles existing around the crystal nucleus, the insulation and withstand voltage characteristics are reduced. Therefore, it is not preferable to use crystallized glass because it is more difficult to prevent defects in the glass layer forming the insulating layer 4 than when amorphous glass is used.

It is preferable that the glass of the insulating layer 4 has an alkali content of 2% by weight or less. The alkali component is effective in lowering the viscosity of the glass by being added to the glass. However, since the migration of the glass component causes a problem in durability, the alkali content in the glass of the insulating layer 4 is reduced to 2% by weight. In the following, it was found that the durability was improved in a durability test when a DC power was applied to the heating resistor 5 and the heating resistor 5 was heated. That is, the insulating layer 4
When the alkali content in the glass is 2% by weight or less, the life in a continuous durability test at 250 ° C. is up to 1000 hours, and when the alkali content is 1% by weight or less, 50%.
It has been found that it can be extended up to 00 hours. Here, the term “alkali” refers to Li ₂ O, Na ₂ O, K
_It refers to an alkali metal oxide such as ₂ O.

The glass of the insulating layer 4 has an average particle diameter D _50.
Is 15 μm or less and the average particle size D ₅₀ is 20% or more separated paste containing a plurality of glasses blended,
In addition, it is preferable that the residual carbon amount in the debinding step is 1% by weight or less of the weight of the glass.

By blending a plurality of glass raw materials having different particle diameters as described above, packing in a powder state becomes dense and bubbles in the insulating layer can be reduced. Further, by performing the binder removal step so that the residual carbon amount in the binder removal step is 1% by weight or less of the weight of the glass, the reaction between C of the binder component and O of the glass is reduced, and By increasing the filling rate of the glass powder after the step, it is possible to more easily form a glass layer in which a region having no bubble in the thickness direction is continuous for 10 μm or more.

On the other hand, when a glass having an average particle diameter D ₅₀ larger than 15 μm or less than 20% apart from the average particle diameter D ₅₀ in the manufacturing process for forming the insulating layer 4 is mixed, Is not sufficiently dense, and it is difficult to sufficiently fill the space existing between the glass particles. Similarly, it is difficult to suppress the generation of bubbles even when the amount of residual carbon in the debinding step is more than 1% by weight of the glass.

The baking temperature of the glass is preferably set to a temperature not lower than the working point temperature (10 ⁴ poise or less in terms of the viscosity of the glass).

Referring to FIG. 1, the structure of a wafer heating apparatus 1 according to an embodiment of the present invention will be described in detail.

Silicon carbide ceramics forming the plate-like body 2;
The surface of the plate-like body 2 is treated in an oxidizing atmosphere at 1000 to 1600 ° C. for 1 to 12 hours because the glass is difficult to wet and bleed easily occurs on the surface of the aluminum nitride ceramic or silicon nitride ceramic sintered body. Oxide film 21
Is formed, it becomes easy to form the insulating layer 4 and the heating resistor 5 on the surface. In particular, when a silicon carbide ceramic is used, the above-described heat treatment is indispensable before forming the insulating layer 4 in order to prevent breakage due to current leakage since the ceramic itself shows semiconductivity.

The thickness of the insulating layer 4 made of glass is 10 to 6
The reason why the thickness is set to 00 μm is that if the thickness is less than 10 μm, the electrical insulation between the plate-like body 2 and the heating resistor 5 becomes insufficient, and if the thickness exceeds 600 μm,
This is because glass has a low heat conduction coefficient, so that heat transfer from the heating resistor 5 to the wafer W mounting surface 3 becomes slow, which is not preferable.

The flatness of the surface of the insulating layer 4 made of glass is preferably 300 μm or less. If the flatness exceeds 300 μm, the thickness variation when the heating resistor 5 and the overcoat layer 40 are formed on the surface of the insulating layer 4 becomes large, and the resistance value of the heating resistor 5 becomes large, which is not preferable. . Further, a film formation failure typified by blurring / unevenness of the overcoat layer 40 occurs, which is not preferable.

The flatness of the insulating layer 4 made of glass is 300
In order to make the thickness equal to or less than μm, the flatness of the plate-shaped body 2 on the side on which the insulating layer 4 is applied is set to 300 μm or less, and at the same time, the thermal expansion coefficient of the glass with respect to the thermal expansion coefficient of the ceramic constituting the heat equalizing plate 2 is − It is necessary to use glass in the range of 1.0 to + 1.0 × 10 ⁻⁶ / ° C. This is because the stress due to shrinkage during sintering of the glass is not sufficiently relaxed by heat treatment during baking, and warpage such that the insulating layer 4 side is concave tends to remain. As described above, by reducing the difference between the coefficient of thermal expansion of glass and the coefficient of thermal expansion of the ceramics forming the plate-like body 2 to reduce the warpage of the plate-like body 2, it is effective to improve the flatness. is there.

The insulating layer 4 made of glass is formed by forming a film having a constant thickness by printing or transferring, and performing a heat treatment at a temperature equal to or higher than the working point of the glass. The coefficient of thermal expansion of the glass is preferably set to a coefficient of thermal expansion slightly smaller than the coefficient of thermal expansion of the ceramic substrate of the soaking plate 2. This is because, when the glass is sintered and melted, the stress caused by the shrinkage is not sufficiently relaxed, and the stress caused by the shrinkage remains in the form of a warp. Then, as a result, the stress remaining in the glass becomes a compressive stress, so that cracks hardly occur due to thermal stress.

Further, a glass having a crystal phase containing SiO ₂ as a main component and containing at least one of Zn, B, and Si is used for the heating resistor 5, and the softening point of the glass is as follows.
It is preferable that the temperature is lower than the transition point of the glass contained in the insulating layer 4 in order to improve the processing accuracy of the heating resistor 5. Glass is considered to be a highly viscous fluid at temperatures above the transition point. For this reason, the softening point of the glass contained in the heating resistor 5 is set lower than the transition point of the glass contained in the insulating layer 4,
When the heating resistor 5 is baked, the insulating layer 4 serving as a base material is not affected.

Similarly, the softening point of the glass contained in the overcoat layer 28 is set to be equal to or lower than the softening point of the glass contained in the heating resistor 5, so that the overcoat layer 28 has a softening point. Processing accuracy can be improved.

Further, the flatness of the plate 2 after being fixed to the support 11 is 80 μm or less, more preferably 40 μm or less.
It is preferable that the thickness be not more than μm. The flatness of the plate 2 is set to 8
The reason why the thickness is set to 0 μm or less is that the temperature in the plane of the wafer W can be precisely controlled by controlling the distance between the wafer W and the plate-shaped body 2 when the temperature of the wafer W is rapidly increased. To do that.

It is preferable that the distance between the plate-shaped member 2 and the wafer W is smaller at the center than at the outer periphery. In order to make the temperature distribution of the plate-like body 2 constant, the heat generation distribution of the heating resistor 5 is set such that the heat generation amount is larger at the outer peripheral portion where heat is easily released to the outside than at the central portion. For this reason, when the temperature is rapidly increased, the temperature in the central portion of the wafer W tends to be easily delayed. In order to reduce this tendency, the plate 2
It is preferable that the distance between the wafer W and the center is made narrower in the central part than in the outer peripheral part, since the response to the temperature change of the plate-like body 2 becomes faster.

Further, as the ceramic forming the plate-like body 2, a ceramic mainly containing at least one of silicon carbide, boron carbide, boron nitride, silicon nitride and aluminum nitride can be used.

As the silicon carbide-based sintered body, a sintered body containing boron (B) and carbon (C) as a sintering aid, or silicon carbide as a main component is used for silicon carbide as a main component. A sintered body containing alumina (Al ₂ O ₃ ) and yttria (Y ₂ O ₃ ) and sintered at 1900 to 2200 ° C. can be used as a sintering aid, and silicon carbide is mainly α-type. thing,
Alternatively, any of those mainly composed of β-type may be used.

As the boron carbide sintered body, 3 to 10% by weight of carbon is mixed as a sintering aid with boron carbide as a main component, and the mixture is sintered by hot pressing at 2000 to 2200 ° C. You can get the body.

As the boron nitride sintered body, 30 to 45% by weight as a sintering aid is added to boron nitride as a main component.
Of aluminum nitride and 5 to 10% by weight of a rare earth element oxide, and hot-pressed at 1900 to 2100 ° C. to obtain a sintered body. As another method for obtaining a sintered body of boron nitride, there is a method in which borosilicate glass is mixed and sintered, but this method is not preferable because the thermal conductivity is significantly reduced.

As the silicon nitride sintered body, 3 to 12% by weight of a rare earth element oxide and 0.5 to 3% by weight of Al ₂ O ₃ are used as sintering aids with respect to silicon nitride as a main component. Further, the sintered body can be obtained by mixing SiO ₂ so that the amount of SiO ₂ contained in the sintered body is 1.5 to 5% by weight and performing hot press firing at 1650 to 1750 ° C. Here, the SiO ₂ amount indicated, the SiO ₂ generated from oxygen impurity contained in the silicon nitride in the raw material, and SiO ₂ as an impurity contained in other additives, are deliberately SiO ₂ in total added .

As the aluminum nitride sintered body, a rare earth element oxide such as Y ₂ O ₃ or Yb ₂ O ₃ as a sintering aid and, if necessary, CaO or the like are used for the main component aluminum nitride. After adding an alkaline earth metal oxide and mixing well and processing it into a flat plate shape,
It is obtained by firing at 0 ° C.

Further, the plate-like body 2 is composed of the plate-like body 2 and the support 11.
A bolt 17 is passed through the outer periphery of the elastic member 8 and a nut 19 is screwed from the plate-shaped body 2 side with an elastic body 8 and a washer 18 interposed therebetween, thereby being elastically fixed. Thereby, even if the temperature of the plate 2 is changed or the wafer is placed on the mounting surface 3 and the temperature of the plate 2 fluctuates, even if the support 11 is deformed, it is absorbed by the elastic body 8. In this way, it is possible to prevent the plate-like body 2 from warping and prevent a temperature distribution from occurring on the surface of the wafer W when the wafer W is heated.

The thermocouple 10 for adjusting the temperature of the plate 2
Is installed in the center of the plate-shaped member 2 and in the vicinity of the wafer mounting surface 3, and adjusts the temperature of the plate-shaped member 2 based on the temperature of the thermocouple 10. When the heating resistor 5 is divided into a plurality of blocks and the temperature is individually controlled, a thermocouple 10 for temperature measurement is installed in each block of the heating resistor 5. The thermocouple 10 has an outer diameter of 1.0 from the viewpoint of its responsiveness and workability of holding.
It is preferable to use a sheath-type thermocouple 10 of 0 mm or less. Further, the middle of the thermocouple 10 is held by the plate-like structure portion 13 of the support portion 7 so that no force is applied to the tip portion embedded in the plate-like body 2. The tip of the thermocouple 10
It is preferable to form a hole in the plate-shaped body 2 and press and fix it to the inner wall surface of the cylindrical metal body installed therein with a spring material in order to improve the reliability of temperature measurement.

The support 11 is composed of a plate-like structure 13 and side walls, and a conductive terminal 7 for supplying power to the heating resistor 5 is provided on the plate-like structure 13 via an insulating material 9. In addition, an air injection port and a thermocouple holding portion (not shown) are formed. The conductive terminal 7 is configured to be pressed against the power supply unit 6 by the elastic body 8. The plate-like structure 13 is composed of a plurality of layers.

The connection between the power supply section 6 and the conductive terminal 7 formed on the plate 2 is made contact by pressing, so that the difference in expansion between the plate 2 and the support 11 due to the temperature difference between the two. Can be alleviated by the sliding of the contact portion, so that it is possible to provide a wafer heating apparatus having good durability against a thermal cycle during use. As the elastic body 8 serving as the pressing means, a coiled spring as shown in FIG. 1 or a leaf spring or the like may be used for pressing.

As the pressing force of the elastic body 8, a load of 0.3 N or more may be applied to the conductive terminal 7. The reason why the pressing force of the elastic body 8 is set to 0.3 N or more is that the conductive terminal 7 must move in response to a dimensional change due to expansion and contraction of the plate-like body 2 and the support body 11. Since the upper conductive terminal 7 is pressed against the power supply section 6 from the lower surface of the plate-shaped body 2, the conductive terminal 7 is prevented from separating from the power supply section 6 due to friction between the conductive terminal 7 and the sliding portion. is there.

The diameter of the conductive terminal 7 on the contact surface side with the power supply section 6 is preferably 1.5 to 4 mm. Further, as the insulating material 9 holding the conductive terminal 7, at a temperature of 200 ° C. or less, a PEEK (polyethoxyethoxyketone resin) material in which glass fibers are dispersed can be used depending on the use temperature. In addition, when used at a higher temperature, a ceramic insulating material 9 made of alumina, mullite, or the like can be used.

At this time, it is preferable that at least the contact portion of the conductive terminal 7 with the power supply portion 6 is formed of a metal made of at least one of Ni, Cr, Ag, Au, stainless steel and a platinum group metal. . Specifically, the conductive terminal 7 itself is formed of the above metal, or the conductive terminal 7
May be provided with a coating layer made of the metal.

Alternatively, by inserting a metal foil made of the above-described metal between the conductive terminal 7 and the power supply portion 6, contact failure due to oxidation of the surface of the conductive terminal 7 is prevented, and the durability of the plate-like body 2 is improved. It becomes possible.

If the surface of the conductive terminal 7 is subjected to a breaking process or a sandblasting process to prevent the contact from becoming a point contact by roughening the surface, the contact reliability can be further improved. The wafer heating apparatus 1 adjusts the temperature in the plane of the plate-shaped body 2 to be uniform. However, at the time of heating, replacement of the wafer, and the like, the temperature relationship between the plate-shaped body 2 and the support 9 is structurally different. Not constant. Due to this temperature difference, the power supply unit 6 and the conductive terminal 7 often come into contact with each other in a twisted positional relationship. Therefore, when these contacts are flattened, contact failure is likely to occur due to one-sided contact.

In order to heat the wafer W by the wafer heating apparatus 1, the transfer surface (not shown)
Is supported by lift pins (not shown), and the lift pins 8 are lowered to place the wafer W on the mounting surface 3.

Next, the power supply 6 is energized to cause the heating resistor 5 to generate heat, and the wafer W on the mounting surface 3 is heated via the insulating layer 4 and the plate 2. When the plate-like body 2 is formed of a silicon carbide sintered body, deformation is small even when heat is applied, and the plate thickness can be reduced. Therefore, the heating time until heating to the predetermined processing temperature and the predetermined processing temperature to room temperature The cooling time until cooling to the vicinity can be shortened, the productivity can be improved, and the thermal conductivity of 80 W / m · K or more. And the temperature variation of the mounting surface 3 can be extremely reduced.

[0055]

EXAMPLE 1 Silicon carbide raw material was mixed with 3% by weight of B ₄ C and 2% by weight of carbon using an appropriate amount of a binder and a solvent, granulated, and then molded at a molding pressure of 100 MPa to 1900 to 2100 ° C. And the thermal conductivity is 80 W / m · K and the outer diameter is 230
A disk-shaped sintered body of silicon carbide having a thickness of 0.2 mm is obtained. Then, after both surfaces are ground, a heat treatment of 1400 ° C. × 1 hour is performed, and at least 1000 ° C. to 600 ° C. is cooled during cooling.
00 After ° C. / cooled by the time rate of forming an oxide film 21 made of SiO _2, subscriptions to those of amorphous glass powder consisting mainly of SiO ₂ to make a paste on one surface -
An insulating layer 4 was formed by performing printing at 1300 ° C. Further, on the insulating layer 4, glass and Au 20% by weight as a metal component, Pt10
Heat-generating resistor pastes each containing 70% by weight of glass containing a component to be Zn ₂ SiO ₄ as a crystal phase by weight were formed by printing and formed into a desired shape by baking at 600 ° C. to 700 ° C. . Further, an overcoat paste containing glass containing a component which becomes Zn ₂ SiO ₄ as a crystal phase is formed on the insulating layer 4 and the heating resistor 5 by printing, and the desired shape is formed by baking at 550 ° C. to 700 ° C. Formed.

Further, the sample thus produced was subjected to JIS.
C 0703 300 described in insulation standards for low-voltage electrical equipment
A general insulation resistance measurement and an AC withstand voltage test were performed based on test conditions of a circuit of V or less. Five samples were prepared for each film thickness condition, and all five samples were tested for insulation and withstand voltage. First, the insulation resistance was 10 MΩ or less. The film thickness and the state of bubbles existing in the insulating layer 4 were examined. For the film thickness of the insulating layer 4, a scanning electron microscope (SEM) is used, and for the bubbles existing in the insulating layer 4, a position 10 where many bubbles exist beforehand by an ultrasonic flaw detector.
Marks were made at the three locations, and then the above-described insulation resistance and withstand voltage tests were performed. After the test, embedding-polishing was performed so that the marked portions could be observed, and the state of bubbles in the thickness direction was confirmed by SEM. At this time, as for the method of confirming the state of the bubbles, the photograph taken by the SEM was observed, and the state of the bubbles was determined with the value of the minimum dimension between the bubbles.

The results are shown in Table 1.

[0058]

[Table 1]

As shown in Table 1, the area without bubbles in the thickness direction in the insulating layer 4 read from the result of the SEM photograph was 1
No. less than 0 μm. Nos. 1 to 5, 8 and 12 cause flashing / short circuit in the withstand voltage characteristics and do not satisfy the characteristics as a ceramic heater. In addition, it was confirmed that the thicknesses of the insulating layer 4 and the insulating layer 4 were less than 10 μm and did not satisfy the withstand voltage characteristics as described above. If the thickness exceeded 600 μm, the glass had a low heat conduction coefficient. The heat transfer from the wafer to the wafer W mounting surface 3 is undesirably slow.

On the other hand, the region without bubbles in the thickness direction in the insulating layer 4 read from the SEM photograph result is 10 μm.
In the embodiment of the present invention having the glass layer continuous as described above,
o. 6, 7, 9-11 and 13-28 are JIS C 0
703 It was confirmed that the insulation characteristics and withstand voltage characteristics of the circuit of 300 V or less described in the insulation standard of the low-voltage electrical equipment were satisfied.

Example 2 A sample was prepared in the same manner as in Example 1 except that the glass composition of the insulating layer 4 was based on SiO ₂ glass, and B, Mg, Ca was used to reduce the viscosity at high temperatures. ,
A sample in which the thickness of the insulating layer 4 was 200 μm was prepared from glass in which the addition amount of Pb, Bi, etc. was adjusted in terms of oxide, using both types of glass, crystallized glass and amorphous glass. In the same manner as in Example 1, a test of insulation characteristics and withstand voltage characteristics was performed.

The results are shown in Table 2.

[0063]

[Table 2]

As can be seen from Table 2, no. 28 to 35, it was confirmed that withstand voltage characteristics could not be obtained irrespective of the amount of the additive such as B added. The structure of the crystallized glass was enlarged and confirmed by SEM.
As shown in (b), many small bubbles 44 are generated in the grain boundary portion 45 formed between the crystallized portions 43, and the region a without bubbles in the thickness direction is not continuous for 10 μm or more. It could be confirmed.

On the other hand, the glass of the insulating layer 4 is an amorphous glass containing SiO ₂ as a main component and containing at least one of B, Mg, Ca, Pb and Bi in an amount of 10% or more in terms of oxide. . 3-6, 7-10, 12-14, 16
-18, 20-22 and 23-26, FIG.
As shown in (a), a glass layer 42 in which a region a without bubbles 44 in the thickness direction was continuous for 10 μm or more was formed, and good results were obtained in both insulating properties and withstand voltage properties.

[0066] In this way, the SiO ₂ main component, B, M
In an amorphous glass containing at least one kind of g, Ca, Pb, and Bi in an amount of 10% by weight or more in terms of oxide, the insulating property and withstand voltage property are substantially reduced without substantially containing an oxide of As and Sb. It was confirmed that it was possible to solve the problems in the production method and the handling of the product.

Example 3 A sample was prepared in the same manner as in Example 1 except that the insulating layer 4 was made of glass containing SiO ₂ as a main component.
Was prepared on the basis of a glass containing 30% by weight of an oxide as an oxide in the range of 0 to 10% by weight and a thickness of the insulating layer 4 of 200 μm.
Was prepared. For the evaluation, see Example 1
After the insulation and withstand voltage tests were performed in the same manner as described above, a continuous durability test was performed at 250 ° C. using a DC power supply, and the resistance was checked and the appearance was observed every 100 hours. Regarding the resistance change, first, the energization time of the sample whose resistance was changed by 5% was compared, and the appearance was confirmed with a 20-fold binocular microscope to check for the occurrence of cracks.

Table 3 shows the results.

[0069]

[Table 3]

As can be seen from Table 3, in a continuous endurance test at 250 ° C., N having an alkali content of 2% by weight or more was used.
o. Nos. 5 to 7, it was found that the resistance of the heating resistor 5 began to increase when the life of the heating resistor 5 was about 100 hours, and the resistance changed by 5% or more in about 500 hours.

However, in the case where the alkali content in the glass of the insulating layer 4 is 2% by weight or less, the glass of No. 3 is not used. 1-4 are 25
The life in a continuous durability test at 0 ° C. is up to 1000 hours.
Further, when the alkali content is 1% by weight or less, 500
It has been found that it can be extended to 0 hours.

It was confirmed that the insulation properties and the withstand voltage properties satisfied the desired properties irrespective of the content of the alkali component, and that the bubbles in the thickness direction were found in the thickness direction from the results of the SEM photograph in proportion to the addition amount of the alkali component. It was confirmed that no area became longer.

Example 4 Here, the relationship between the particle size composition of the glass raw material, the residual carbon content, and the region where bubbles were not continuously generated was investigated. A sample was prepared in the same manner as in Example 1, except that the insulating layer 4 was made of glass containing SiO ₂ as a main component and 30 wt% of an oxide of B added in terms of oxide. Part of the glass having an average particle diameter D ₅₀ of up to ₅₀ μm is blended, and the amount of residual carbon in the debinding step is 0.5 to 10% by weight based on the weight of the glass. A sample having a thickness of 200 μm was prepared. For evaluation, the breakdown voltage was evaluated in the same manner as in Example 1.
With respect to the breakdown voltage, the breakdown voltage was confirmed while increasing the voltage in steps of 0.1 V up to 2 kV and in steps of 0.5 kV above 2 kV.

The results are shown in Table 4.

[0075]

[Table 4]

As shown in Table 4, the particle size of the glass raw material was not mixed. 1 to 8, 21, 22, 29 to 32
Has a breakdown voltage of 2 kV or less. The average particle diameter D
No. _{50 having} a particle size ratio of less than 20%. 14-16,
In Nos. 28 to 30, the breakdown voltage was less than 3 kV. In addition, even when the proportion of the particle size is 20% or more, the residual carbon content exceeds 1% by weight. In Nos. 15 to 17, the breakdown voltage was 2 kV or less.

On the other hand, the glass having the average particle size D ₅₀ of the glass materials to be mixed of 20% or more was mixed and the amount of residual carbon in the debinding step was reduced to 1% by weight or less of the weight of the glass. 12, 13, 18-20, 26-2
In No. 8, the breakdown voltage could be set to 3 kV.

[0078]

As described above, in the ceramic heater having the insulating layer made of glass on at least one main surface of the plate-like body made of ceramics and the heating resistor provided on the insulating layer, Has a thickness of 10 to 600 μm and has no bubble in the thickness direction of the insulating layer.
By continuing 0 μm or more, the insulation and withstand voltage characteristics of a circuit of 300 V or less described in JISC 0703 low-voltage electrical equipment insulation standards can be satisfied.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a wafer heating apparatus according to the present invention.

FIG. 2 is a partially enlarged cross-sectional view of the wafer heating device of the present invention.

FIG. 3A is an enlarged sectional view of an insulating layer in a wafer heating apparatus according to the present invention, and FIG. 3B is an enlarged sectional view of a conventional insulating layer.

FIG. 4 is a sectional view of a conventional wafer heating apparatus.

[Description of Signs] 1: Wafer heating device 2: Plate-shaped body 3: Placement surface 4: Insulating layer 5: Heating resistor 6: Power supply unit 7: Conductive terminal 8: Elastic body 10: Thermocouple 11: Support body 21 : Oxide film 28: Overcoat layer W: Semiconductor wafer

Claims (5)

[Claims] 1. A ceramic heater comprising a glass plate on at least one principal surface of a ceramic body and an insulating layer made of glass and a heating resistor on the insulating layer. A ceramic heater having a thickness, and a region having no bubbles in the thickness direction of the insulating layer is continuous for 10 μm or more. 2. The insulating layer according to claim 1, wherein said insulating layer is mainly composed of SiO ₂ ,
It is composed of an amorphous glass containing at least one kind of Mg, Ca, Pb and Bi in terms of oxide in an amount of at least 10% by weight, and is substantially free of oxides of As and Sb. The ceramic heater according to claim 1, wherein 3. The insulating layer has an alkali content of 2% by weight.
The ceramic heater according to claim 1, wherein: 4. At least a plate-like body made of ceramics
An insulating layer made of glass is provided on one main surface, and on the insulating layer
Ceramic heater with heating resistor
The insulating layer has an average particle diameter D₅₀Is less than 15 μm
And average particle size D ₅₀Are separated by more than 20%
Apply paste containing glass and remove binder
The amount of residual coal in the process will be less than 1% by weight of the glass weight
2. A ceramic as claimed in claim 1, wherein
Manufacturing method of Mick heater. 5. A wafer heating apparatus according to claim 1, wherein a main surface of the ceramic heater opposite to the heating resistor is used as a wafer mounting surface.