JP2001351763A - Ceramic heater for semiconductor manufacturing- inspecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic heater, capable of heating heating objects, so that the temperature becomes uniform as a whole, when heating the heating object such as silicon wafer. SOLUTION: This ceramic heater for forming a resistance heating element on the inside or a surface of a ceramic substrate, is set with the dispersion of the thickness of the ceramic substrate being in the range of -3 to 3% of the average thickness of the ceramic substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic heater (hot plate) mainly used for manufacturing and testing semiconductors.

[0002]

2. Description of the Related Art Conventionally, in a semiconductor manufacturing / inspection apparatus including an etching apparatus and a chemical vapor deposition apparatus, a heater or a wafer prober using a metal base material such as stainless steel or an aluminum alloy is used. I have been.

[0003] However, such a metal heater has the following problems.
There were the following problems. First, because it is made of metal,
The thickness of the heater plate must be as thick as about 15 mm. This is because, in a thin metal plate, warping, distortion, and the like are generated due to thermal expansion caused by heating, and the silicon wafer placed on the metal plate is damaged or tilted. However, when the thickness of the heater plate is increased, there is a problem that the weight of the heater increases and the heater becomes bulky.

In addition, the heating temperature is controlled by changing the voltage or current applied to the heating element. However, since the metal plate is thick, the temperature of the heater plate rapidly changes with changes in the voltage or current. There is also a problem that it is difficult to control the temperature without following.

Therefore, Japanese Patent Application Laid-Open No. H11-40330 discloses that a nitride or carbide ceramic having high thermal conductivity and high strength is used as a substrate, and a plate-like body (ceramic substrate) made of these ceramics is used. There is disclosed a ceramic heater in which a heating element formed by sintering metal particles is provided on the surface.

[0006]

In such a ceramic heater, even if it expands thermally during heating, the ceramic substrate is unlikely to be warped or distorted, and has a temperature follow-up capability that changes the applied voltage and the amount of current. Was also good.

However, when an object to be heated such as a silicon wafer is heated by using the ceramic heater, a temperature variation is apt to occur on the heating surface. If such a temperature variation occurs, the silicon wafer or the like is heated. There was a problem of being damaged by impact.

Further, with the recent increase in the diameter of a heated object such as a silicon wafer or the like, a ceramic heater having a larger diameter is required. Further, in the case of a ceramic heater having a large diameter, if the thickness is the same as that of a conventional heater, the heat capacity becomes large. Therefore, a thin heater is required. However, the temperature variation of the heating surface of the ceramic substrate becomes more remarkable as the diameter of the ceramic heater increases and as the thickness of the ceramic heater decreases.

[0009]

SUMMARY OF THE INVENTION In view of the above problems, the present inventors have obtained a ceramic heater in which the temperature variation on the heating surface is small and the object to be heated such as a silicon wafer is not damaged by thermal shock. As a result of diligent research for the purpose, one of the causes of the temperature variation of the heating surface is the variation of the thickness of the ceramic substrate, and the variation of the thickness is constant with respect to the average thickness of the ceramic substrate. It has been found that the heating surface can be controlled at a uniform temperature by keeping the temperature within the range, and the present invention has been completed.

That is, the present invention relates to a ceramic heater in which a resistance heating element is formed inside or on a surface of a ceramic substrate, wherein the variation in the thickness of the ceramic substrate is -3 to 3 times the average thickness of the ceramic substrate. % Is a ceramic heater.

When a current is passed through the resistance heating element to generate heat,
Heat propagates through the ceramic substrate and reaches the heating surface.
Since the time required for heat to propagate depends on the distance, if the thickness of the ceramic substrate varies, the time required for heat to propagate from the resistance heating element to the heating surface varies. In addition, if there is a variation in the thickness, there is a difference in the volume of the ceramic substrate per fixed area depending on the location. It is considered that temperature variation occurs.

However, as described above, the ceramic heater of the present invention reduces the variation in the thickness of the ceramic substrate.
Since the average thickness of the ceramic substrate is adjusted within the range of -3 to 3%, the time required for heat to propagate from the resistance heating element to the heating surface of the ceramic substrate, the volume of the ceramic substrate per fixed area, There is almost no difference,
The temperature of the heating surface of the ceramic substrate can be made uniform, and the object to be heated such as a silicon wafer can be prevented from being damaged by thermal shock.

In the ceramic heater according to the present invention, when the resistance heating element is formed on the surface of the ceramic substrate, it is desirable that the side opposite to the surface on which the resistance heating element is formed be a heating surface. In the case where the resistance heating element is formed inside the ceramic substrate, the resistance heating element is disposed in the thickness direction from the surface opposite to the heating surface in the thickness direction.
% Is desirably formed.

Further, in the ceramic heater according to the present invention, the ceramic substrate is a disk and has a diameter of 19 mm.
It is desirable to exceed 0 mm and the thickness is 25 mm or less.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION A ceramic heater according to the present invention is a ceramic heater in which a resistance heating element is formed inside or on the surface of a ceramic substrate. Sano-3
３3%.

FIG. 1 is a bottom view schematically showing one example of the ceramic heater of the present invention, and FIG. 2 is a partially enlarged sectional view showing a part thereof. The ceramic substrate 11 is formed in a disk shape, and the resistance heating element 12 is
A single concentric pattern is formed on the bottom surface 11b of the ceramic substrate 11 in order to heat the one wafer heating surface 11a so that the entire temperature becomes uniform.

The heating elements 12 are connected such that double concentric circles close to each other form a single line, and external terminals 13 serving as input / output terminals are provided at both ends thereof with a metal coating layer. 12a. In a portion near the center, a through hole 15 for inserting a lifter pin 16 for carrying the silicon wafer 9 or the like is formed, and a bottomed hole 14 for inserting a temperature measuring element is formed. .

In the ceramic heater 10 shown in FIGS. 1 and 2, the resistance heating element 12 is provided at the bottom of the ceramic substrate 11, but may be provided inside the ceramic substrate 11. Hereinafter, members constituting the ceramic heater of the present invention will be described in detail.

In the ceramic heater 10 of the present invention,
In order to control the temperature of the heating surface 11a to be uniform, the thickness of the ceramic substrate 11 is adjusted so that the variation in the thickness is -3 to 3% of the average thickness of the ceramic substrate 11.

Here, “variation in thickness” means the difference between the average value of the thickness and the thickest portion or the thinnest portion when the thickness of the ceramic substrate varies depending on the location. In other words, this “thickness variation” occurs due to macroscopic surface undulation or the like that appears on the front surface (back surface) of the ceramic substrate. In the present invention, the minimum thickness and the maximum thickness are adjusted so as to be within a range of -3 to 3% with respect to the average thickness thereof.

Therefore, there is almost no difference between the time required for heat to propagate from the resistance heating element to the heating surface of the ceramic substrate and the volume of the ceramic substrate per fixed area, and as a result, the temperature of the heating surface of the ceramic substrate is reduced. It can be uniform.

If the variation in the thickness of the ceramic substrate 11 is out of the above range, the time required for the heat emitted from the resistance heating element 12 to reach the heating surface 11a varies depending on the location, and the heat propagates. Since the volume of the ceramic substrate 11 per fixed area varies depending on the location, a temperature variation occurs on the heating surface 11a. The range of the above-mentioned thickness variation is desirably -1 to + 1%.

When the variation in the thickness is almost zero, the heating surface is almost a perfect plane, and when the object to be heated such as the silicon wafer 9 is directly placed on the heating surface and heated, the silicon wafer 9 is heated. The object to be heated such as the silicon wafer 9 is completely separated from the object to be heated such that the object to be heated such as the silicon wafer 9 does not peel off due to the atmospheric pressure. It is desirable that the heating be performed after that.

In the ceramic heater according to the present invention, the object to be heated such as the silicon wafer 9 is placed on the heating surface 1 of the ceramic substrate 11.
In addition to mounting and heating in the state of being in contact with 1a, a through-hole 15 is provided in the ceramic substrate 11 as shown in FIG.
By inserting a lifter pin 16 into the through-hole 15 and holding the object to be heated such as the silicon wafer 9 with the lifter pin 16, the object to be heated is heated at a certain distance from the ceramic substrate 11. Is also good.

By moving the lifter pins 16 up and down, an object to be heated such as the silicon wafer 9 is received from the transfer machine, the object to be heated is placed on the ceramic substrate 11, and the object to be heated is supported. It can be heated as it is.

Further, a concave portion, a through hole or the like is formed in the ceramic substrate, and a pin having a spire or a hemispherical tip is inserted and fixed in the concave portion or the like with the tip slightly projecting from the surface of the ceramic substrate. By supporting an object to be heated such as the silicon wafer 9 with the support pins, the object to be heated may be held at a constant distance from the ceramic substrate.

FIG. 3 is a partially enlarged sectional view schematically showing the vicinity of a resistance heating element of a ceramic heater according to another embodiment of the present invention in which a resistance heating element is formed inside a ceramic substrate.

Although not shown, similarly to the ceramic heater shown in FIG. 1, the ceramic substrate 21 is formed in a disk shape, and the resistance heating element 22 is provided inside the ceramic substrate 21 as shown in FIG. Are formed in a pattern similar to the pattern shown in FIG.

Also, immediately below the end of the resistance heating element 22,
A through hole 28 is formed, and a blind hole 27 exposing the through hole 28 is formed in the bottom surface 21b.
The external terminal 23 is inserted into the blind hole 37 and joined with the brazing material 24. Although not shown in FIG. 3, for example, a socket having a conductive wire is attached to the external terminal 23, and the conductive wire is connected to a power supply or the like.

Even in such a ceramic heater having the resistance heating element 22 formed therein, the variation in the thickness of the ceramic substrate is reduced by the average thickness of the ceramic substrate 11 from -3 to -3.
By adjusting it to 3%, the time required for heat to propagate from the resistance heating element to the heating surface of the ceramic substrate and the volume of the ceramic substrate per fixed area do not differ depending on the location, and the heating surface of the ceramic substrate does not change. Can be made uniform.

In the ceramic heater according to the present invention, when a resistance heating element is provided on the surface of the ceramic substrate, it is preferable that the heating surface is on the opposite side of the resistance heating element formation surface. This is because the ceramic substrate plays a role of thermal diffusion, so that the temperature uniformity of the heating surface can be improved.

When the resistance heating element is formed inside the ceramic substrate, the resistance heating element may be formed at a position of 60% or less in the thickness direction from the surface opposite to the heating surface. desirable. If it exceeds 60%, the temperature is too close to the heating surface, so that the heat propagating in the ceramic substrate is not sufficiently diffused, and a temperature variation occurs on the heating surface.

When the resistance heating element is formed inside the ceramic substrate, a plurality of resistance heating element forming layers may be provided. In this case, it is desirable that the resistance heating element is formed in some layer so as to complement each other, and that the pattern is formed in any region when viewed from above the heating surface. As such a structure, for example, a structure in which the staggered arrangement is provided. Note that the resistance heating element may be provided inside the ceramic substrate, and the resistance heating element may be partially exposed.

The ceramic substrate in the ceramic heater of the present invention is preferably a disk, and has a diameter of 1 mm.
Those exceeding 90 mm are desirable. This is because the larger the diameter, the greater the temperature variation on the heating surface.

The thickness of the ceramic substrate of the ceramic heater of the present invention is desirably 25 mm or less. This is because if the thickness of the ceramic substrate exceeds 25 mm, the temperature followability decreases. Also, its thickness is
Desirably, it is 0.5 mm or more. When the thickness is smaller than 0.5 mm, the strength of the ceramic substrate itself is reduced, so that the ceramic substrate is easily broken. More preferably, it is more than 1.5 and 5 mm or less. When the thickness is more than 5 mm, heat is difficult to propagate, and the heating efficiency tends to decrease.
If it is less than m, the heat propagating through the ceramic substrate may not be sufficiently diffused, so that a temperature variation may occur on the heating surface, and the strength of the ceramic substrate may be reduced to cause breakage.

In the ceramic heater 10 of the present invention, ceramic is used as the material of the ceramic substrate 11. This is because ceramic has a smaller coefficient of thermal expansion than metal and is superior in mechanical strength. Therefore, even if it is thin, it does not warp or warp due to heating, and the ceramic substrate 11 can be made thin and light. Because.

Further, since the thermal conductivity of the ceramic substrate 11 is high and the ceramic substrate 11 itself is thin, the heat capacity is reduced. As a result, the surface temperature of the ceramic substrate 11 quickly follows the temperature change of the resistance heating element 12. I do. That is, by changing the temperature of the resistance heating element 12 by changing the voltage and the current amount, the surface temperature of the ceramic substrate 11 can be favorably controlled.

The ceramic is not particularly limited.
For example, nitride ceramic, carbide ceramic, oxide ceramic, and the like can be given. Among these, when a nitride ceramic is used as the material of the ceramic substrate 11, a ceramic heater is particularly excellent in the above characteristics.

As the above nitride ceramic, for example,
Examples include aluminum nitride, silicon nitride, boron nitride, and titanium nitride. Examples of the carbide ceramic include silicon carbide, titanium carbide, and boron carbide.
Further, examples of the oxide ceramic include alumina, cordierite, mullite, silica, beryllia and the like. These may be used alone or in combination of two or more. Of these, aluminum nitride is most preferred. This is because the thermal conductivity is the highest at 180 W / m · K.

The resistance heating element formed on the surface or inside of the ceramic substrate is preferably divided into at least two or more circuits. This is because, by dividing the circuit, the amount of heat generated can be changed by controlling the power supplied to each circuit, and the temperature of the heating surface of the silicon wafer can be adjusted.

As the pattern of the resistance heating element, for example,
Concentric circles, spirals, eccentric circles, bending lines, etc.
From the point that the temperature of the entire ceramic substrate can be made uniform, a concentric one as shown in FIG.
A combination of a concentric shape and a bent shape is preferable.

When the resistance heating element is formed on the surface of the ceramic substrate, a conductor paste containing metal particles is applied to the surface of the ceramic substrate to form a conductor paste layer having a predetermined pattern. The method of sintering the metal particles on the surface of is preferred. The sintering of the metal is sufficient if the metal particles and the metal particles and the ceramic are fused.

When the resistance heating element is formed on the surface of the ceramic substrate, the thickness of the resistance heating element is preferably 1 to 30 μm, more preferably 1 to 10 μm. When a resistance heating element is formed inside a ceramic substrate, its thickness is preferably 1 to 50 μm.

When the resistance heating element is formed on the surface of the ceramic substrate, the width of the resistance heating element should be 0.1 to 20.
mm is preferable, and 0.1 to 5 mm is more preferable. When the resistance heating element is formed inside the ceramic substrate, the width of the resistance heating element is preferably 5 to 20 μm.

Although the resistance value of the resistance heating element can be varied depending on its width and thickness, the above range is most practical. The resistance value increases as the resistance value decreases and the resistance value decreases. When the resistance heating element is formed inside the ceramic substrate, both the thickness and the width are larger, but when the resistance heating element is provided inside, the distance between the heating surface and the resistance heating element becomes shorter, Since the temperature uniformity is reduced, it is necessary to increase the width of the resistance heating element itself, and there is no need to consider the adhesion with nitride ceramics etc. Since high melting point metals such as molybdenum and carbides such as tungsten and molybdenum can be used, and the resistance value can be increased, the thickness itself may be increased for the purpose of preventing disconnection and the like. Therefore, it is desirable that the resistance heating element has the above-described thickness and width.

The resistance heating element may have a rectangular or elliptical cross section, but is preferably flat. This is because the flat surface is more likely to dissipate heat toward the heating surface, so that the temperature distribution on the heating surface is less likely to occur. The aspect ratio of the cross section (the width of the resistance heating element / the thickness of the resistance heating element) is 10 to 50.
00 is desirable. By adjusting to this range, the resistance value of the resistance heating element can be increased, and the uniformity of the temperature of the heating surface can be ensured.

When the thickness of the resistance heating element is constant, if the aspect ratio is smaller than the above range, the amount of heat propagation in the direction of the heating surface of the ceramic substrate becomes small, and the heat distribution approximates the pattern of the resistance heating element. If the aspect ratio is too large, on the other hand, if the aspect ratio is too large, the temperature immediately above the center of the resistance heating element becomes high, and eventually, a heat distribution similar to the pattern of the resistance heating element occurs on the heating surface. Would. Therefore, considering the temperature distribution, the aspect ratio of the cross section is 1
It is preferably from 0 to 5000.

When the resistance heating element is formed on the surface of the ceramic substrate, the aspect ratio is preferably 10 to 200. When the resistance heating element 12 is formed inside the ceramic substrate, the aspect ratio is preferably 200 to 5000. . When the resistance heating element is formed inside the ceramic substrate, the aspect ratio becomes larger, but this is because if the resistance heating element is provided inside, the distance between the heating surface and the resistance heating element becomes shorter, This is because it is necessary to make the resistance heating element itself flat because the temperature uniformity of the resistance heating element decreases.

The conductive paste is not particularly limited, but preferably contains not only metal particles or conductive ceramic for ensuring conductivity, but also resin, solvent, thickener and the like.

As the metal particles, for example, noble metals (gold, silver, platinum, palladium), lead, tungsten, molybdenum, nickel and the like are preferable. These may be used alone or in combination of two or more. This is because these metals are relatively hard to oxidize and have a resistance value sufficient to generate heat. Examples of the conductive ceramic include carbides of tungsten and molybdenum. These may be used alone or in combination of two or more.

The metal particles or conductive ceramic particles preferably have a particle size of 0.1 to 100 μm. 0.1μ
If the particle size is too small, it is easily oxidized.
If the thickness exceeds μm, sintering becomes difficult and the resistance value increases.

Although the shape of the metal particles is spherical,
It may be scaly. When these metal particles are used, they may be a mixture of the above-mentioned spheres and the above-mentioned flakes. When the metal particles are flakes or a mixture of spheres and flakes, the metal oxide between the metal particles is easily retained, and the adhesion between the resistance heating element and the nitride ceramic or the like is improved. And it is advantageous because the resistance value can be increased.

As the resin used for the conductor paste,
For example, an epoxy resin, a phenol resin, and the like can be given. Examples of the solvent include isopropyl alcohol. Examples of the thickener include cellulose and the like.

It is desirable that the conductor paste is obtained by adding a metal oxide to metal particles and sintering the resistance heating element, the metal particles and the metal oxide. In this way, by sintering the metal oxide together with the metal particles, the ceramic substrate, such as a nitride ceramic, and the metal particles can be more closely adhered.

It is not clear why the mixing with the metal oxide improves the adhesion to the nitride ceramic or the like, but the surface of the metal particles or the surface of the nitride ceramic is slightly oxidized to form an oxide film. It is considered that these oxide films are sintered and integrated via the metal oxide, and the metal particles and the nitride ceramics or the like adhere to each other. Further, when the ceramic constituting the ceramic substrate is an oxide ceramic, the surface is naturally made of an oxide, so that a conductor layer having excellent adhesion is formed.

As the metal oxide, for example, oxidized
Lead, zinc oxide, silica, boron oxide (B _Two O_Three ), Al
Selected from the group consisting of Mina, Yttria and Titania
At least one is preferred.

This is because these oxides can improve the adhesion between the metal particles and the nitride ceramic without increasing the resistance value of the resistance heating element 12.

The ratio of the above-mentioned lead oxide, zinc oxide, silica, boron oxide (B ₂ O ₃ ), alumina, yttria, and titania is as follows: 1-10, silica 1-30, boron oxide 5-50, zinc oxide 20-70, alumina 1
-10, yttria 1-50, titania 1-50, and the total is preferably adjusted within a range not exceeding 100 parts by weight. By adjusting the amounts of these oxides within these ranges, the adhesion to nitride ceramics and the like can be particularly improved.

The amount of the metal oxide added to the metal particles is preferably 0.1% by weight or more and less than 10% by weight. The area resistivity when the resistance heating element 12 is formed using the conductor paste having such a configuration is 1 to 45 mΩ / □.
Is preferred.

When the area resistivity exceeds 45 mΩ / □, the heat generation becomes too large with respect to the applied voltage, and the ceramic substrate 11 provided with the resistance heating element 12 on the surface of the ceramic substrate controls the heat generation. Because it is hard to do. If the addition amount of the metal oxide is 10% by weight or more, the sheet resistivity exceeds 50 mΩ / □, the calorific value becomes too large, the temperature control becomes difficult, and the uniformity of the temperature distribution decreases. .

When the resistance heating element is formed on the surface of the ceramic substrate, it is desirable that a metal coating layer is formed on the surface of the resistance heating element. This is to prevent the internal metal sintered body from being oxidized to change the resistance value.
The thickness of the metal coating layer to be formed is preferably 0.1 to 10 μm.

The metal used for forming the metal coating layer is not particularly limited as long as it is a non-oxidizing metal, and specific examples thereof include gold, silver, palladium, platinum and nickel. . These may be used alone or in combination of two or more. Of these, nickel is preferred.

The resistance heating element requires a terminal for connection to a power supply, and this terminal is attached to the resistance heating element via solder. Nickel prevents thermal diffusion of solder. Examples of the connection terminal include those made of Kovar.

When the resistance heating element is formed inside the ceramic substrate, the surface of the resistance heating element is not oxidized, so that the coating is unnecessary. When the resistance heating element is formed inside the ceramic substrate, a part of the resistance heating element may be exposed on the surface, and a through hole for connecting the resistance heating element is provided in the terminal portion. The terminals may be connected and fixed.

When the external terminals 13 are connected, alloys such as silver-lead, lead-tin, and bismuth-tin can be used as the solder. The thickness of the solder layer is 0.1 to
50 μm is preferred. This is because the range is sufficient to secure connection by soldering.

Next, a method for manufacturing the ceramic heater of the present invention will be described. First, a ceramic heater having a resistance heating element formed on the bottom surface of a ceramic substrate 11 (see FIGS.
4) will be described with reference to FIGS. 4 (a) to 4 (c).

(1) Manufacturing process of ceramic substrate Necessary for ceramic powder such as aluminum nitride
Yttria (Y _Two O_Three ), Sintering aids, Na,
A slurry is prepared by compounding a compound containing Ca, a binder, etc.
After making the slurry, the slurry is
Granulate, put the granules in a mold and press
Formed into a plate shape, etc. to produce a green body
You.

Next, if necessary, a portion serving as a through hole 15 for inserting a lifter pin 16 for carrying an object to be heated such as a silicon wafer 9 or a temperature measuring element such as a thermocouple is provided in the formed body. A portion serving as a bottomed hole 14 for embedding is formed.

Next, the formed body is heated, fired and sintered to produce a ceramic plate. Thereafter, the ceramic substrate 11 is manufactured by processing into a predetermined shape (see FIG. 4A), but may be a shape that can be used as it is after firing. Further, for example, by performing heating and baking while applying pressure from above and below, it becomes possible to manufacture a ceramic substrate 11 having no pores.
Heating and firing may be at least the sintering temperature, for example,
For nitride ceramics, the temperature is 1000-2500C.

Usually, after firing, a through hole 15 and a bottomed hole 14 for inserting a temperature measuring element are provided.
The through-holes 15 and the like are made of SiC particles or the like after surface polishing,
It can be formed by performing blast processing such as sandblasting.

Thereafter, the surface of the sintered body was reduced from # 100 to # 8.
By polishing using a diamond grindstone having a roughness of 00, the variation in the thickness is -3 to 3 of the average thickness.
Adjust to be%. As this polishing method, first, the outer peripheral portion of the sintered body is fixed, and the sintered body is polished only by its own weight without applying a load. Thereafter, the polished surface is used as a reference surface, the polished surface is attached to a jig using wax, and while the warpage is being corrected, polishing is performed while applying a load of 0.05 to 10 MPa. The thickness variation can be adjusted within the above range.

If the diamond grindstone is larger than # 800, the roughness is too small, so that the undulation on the surface of the sintered body cannot be completely ground. On the other hand, if the diamond grindstone is smaller than $ 100, the roughness is too large. The whetstone oscillates and this swells. Diamond whetstones are produced by electrodepositing diamond. At this time, the rotation speed of the diamond grindstone is 50 to 300 min ^-1 (50 to 300 r
pm).

(2) Step of Printing Conductor Paste on Ceramic Substrate The conductor paste is generally a high-viscosity fluid composed of metal particles, resin and solvent. The conductor paste is printed on a portion where the resistance heating element is to be provided by screen printing or the like to form a conductor paste layer.
Since the resistance heating element needs to keep the entire temperature of the ceramic substrate at a uniform temperature, it is desirable that the resistance heating element be printed in a concentric pattern as shown in FIG. The conductive paste layer is desirably formed so that the cross section of the resistance heating element 12 after firing has a rectangular and flat shape.

(3) Firing of Conductive Paste The conductive paste layer printed on the bottom surface of the ceramic substrate 11 is heated and fired to remove the resin and the solvent, and sinter the metal particles.
The resistance heating element 12 is formed (see FIG. 4B). The temperature of the heating and firing is preferably from 500 to 1000C. If the above-described metal oxide is added to the conductor paste, the metal particles, the ceramic substrate and the metal oxide are sintered and integrated, so that the adhesion between the resistance heating element and the ceramic substrate is improved.

(4) Formation of Metal Coating Layer It is desirable to provide a metal coating layer 12a on the surface of the resistance heating element 12, as shown in FIG. Metal coating layer 12a
Can be formed by electrolytic plating, electroless plating, sputtering, or the like, but in consideration of mass productivity, electroless plating is optimal. FIG. 4 shows the metal coating layer 1.
2a is not shown.

(5) Attachment of Terminals, etc. Terminals (external terminals 13) for connection to a power supply are attached to the ends of the pattern of the resistance heating element 12 via solder (see FIG. 4C). Further, a thermocouple is inserted into the bottomed hole 14 and sealed with a heat-resistant resin such as polyimide or the like, and the production of the ceramic heater is completed.

Next, a method of manufacturing a ceramic heater (see FIG. 3) in which a resistance heating element 12 is formed inside a ceramic substrate 11 will be described with reference to FIGS. 5 (a) to 5 (d). (1) Step of Producing Ceramic Substrate First, a ceramic powder such as a nitride ceramic is mixed with a binder, a solvent, and the like to prepare a paste, and a green sheet is produced using the paste.

As the above-mentioned ceramic powder, for example, aluminum nitride or the like can be used. If necessary, a sintering aid such as yttria, a compound containing Na or Ca, or the like may be added. The binder is preferably at least one selected from an acrylic binder, ethyl cellulose, butyl cellosolve, and polyvinylal.

Further, as the solvent, α-terpione,
At least one selected from glycols is desirable. A paste obtained by mixing these is formed into a sheet shape by a doctor blade method to produce a green sheet 50.
The thickness of the green sheet 50 is preferably 0.1 to 5 mm.

Next, if necessary, a portion serving as a through hole 25 for inserting a lifter pin for carrying a heated object such as a silicon wafer into the obtained green sheet 50,
A portion serving as a bottomed hole for embedding a temperature measuring element such as a thermocouple, a portion serving as a through hole 28 for connecting a resistance heating element to an external terminal pin, and the like are formed. The above processing may be performed after forming a green sheet laminate described later.

(2) Step of Printing Conductive Paste on Green Sheet A conductive paste containing a metal paste or conductive ceramic for forming a resistance heating element is printed on the green sheet 50 to form a conductive paste layer 220. Then, a conductive paste filling layer 280 for the through hole 28 is formed in the through hole. These conductive pastes contain metal particles or conductive ceramic particles.

The average particle diameter of the tungsten particles or molybdenum particles is preferably from 0.1 to 5 μm. If the average particle diameter is less than 0.1 μm or exceeds 5 μm, it is difficult to print the conductive paste. As such a conductive paste, for example, 85 to 87 parts by weight of metal particles or conductive ceramic particles; 1.5 to 10 parts by weight of at least one binder selected from acrylic, ethyl cellulose, butyl cellosolve, and polyvinylal;
A composition (paste) obtained by mixing 1.5 to 10 parts by weight of at least one solvent selected from α-terpione and glycol is exemplified.

(3) Green Sheet Laminating Step The green sheet 50 on which the conductor paste is not printed is
The green sheet 50 on which the conductive paste is printed is laminated on and under the green sheet 50 (see FIG. 5A). At this time, the green sheets 50 on which the conductive paste is printed are stacked so that they are positioned at 60% or less of the thickness of the stacked green sheets. Specifically, the number of stacked green sheets on the upper side is preferably 20 to 50, and the number of stacked green sheets on the lower side is preferably 5 to 20.

(4) Green Sheet Laminate Firing Step The green sheet laminate is heated and pressed to sinter the ceramic powder in the green sheet and the metal in the internal conductor paste (FIG. 5 (b)). reference). The heating temperature is
The temperature is preferably 1000 to 2000 ° C.
-20 MPa is preferred. Heating is performed in an inert gas atmosphere. As the inert gas, for example, argon, nitrogen, or the like can be used. Usually, after firing, a bottomed hole for inserting a temperature measuring element, a through hole 25 for inserting a lifter pin, and a blind hole 27 for exposing a through hole 28 are formed. The through-hole 25 and the bottomed hole can be formed by performing blasting of sand blast or the like after surface polishing.

Thereafter, the surface of the sintered body was reduced from # 100 to # 8.
By polishing using a diamond grindstone having a roughness of 00, the variation in the thickness is -3 to 3 of the average thickness.
Adjust to be%. As the polishing method, first, the outer peripheral portion of the sintered body is fixed, and the sintered body is polished only by its own weight without applying a load. Thereafter, the polished surface is used as a reference surface, the polished surface is attached to a jig using wax, and while the warpage is being corrected, polishing is performed while applying a load of 0.05 to 10 MPa. The thickness variation can be adjusted within the above range. At this time, the rotation speed of the diamond grindstone is 50 to 300.
min ^-1 (50 to 300 rpm). Also, if the diamond grindstone is larger than $ 800, the roughness is too small, so that the undulation on the surface of the sintered body cannot be completely ground,
On the other hand, if it is smaller than $ 100, the roughness is too large, and the grindstone vibrates, which causes undulation.
Diamond whetstones are produced by electrodepositing diamond.

(5) Attaching of terminals and the like Through holes 2 for connection with the internal resistance heating element 22
After applying the solder paste to the exposed portion of No. 8,
The external terminal 23 is inserted into the inside 7, and the external terminal 13 is connected by heating and reflowing. The temperature at the time of heating is preferably 200 to 500 ° C. Further, a thermocouple or the like as a temperature measuring element is inserted into the bottomed hole and sealed with a heat-resistant resin such as polyimide or the like, and the production of the ceramic heater is completed.

The ceramic heater of the present invention can be used as an electrostatic chuck by providing an electrostatic electrode, and by providing a chaptop conductor layer on the surface and providing a guard electrode and a ground electrode inside. It can be used as a wafer prober.

[0088]

The present invention will be described in more detail below. (Example 1) Production of a ceramic heater having a resistance heating element outside (see FIG. 4) (1) Aluminum nitride powder (average particle size: 1.1 μm) 1
A composition comprising 00 parts by weight, 4 parts by weight of yttria (average particle size: 0.4 μm), 12 parts by weight of an acrylic binder and alcohol was spray-dried to prepare a granular powder.

(2) Next, this granular powder was put into a mold and molded into a flat plate to obtain a formed green body.

(3) The processed form is processed to 1800
℃, pressure: 20MPa hot press, thickness almost 3
mm aluminum nitride plate was obtained. Next, a disk having a diameter of 210 mm was cut out from the plate to obtain a ceramic plate (ceramic substrate 11). Drilling is performed on this molded body, and lifter pins 1
6 and a portion (diameter: 1.1 mm, depth: 2 mm) serving as a through hole 15 for inserting a thermocouple and a bottomed hole 14 for embedding a thermocouple were formed (FIG. 4A).

(4) Next, the plate-shaped body obtained in (3) was polished using a rotary grinding lathe having a # 220 diamond grindstone.
1 is fixed, and one side of the plate-shaped member is applied for 100 min ^-1 (100r) only by its own weight without applying pressure.
(pm). Next, based on the polished surface, the polished surface is fixed to a jig using wax (green wax made by Mardo) to correct the warp, and a pressure of 0.1 MPa (1 kgf / cm ² ) is applied. While rotating, both surfaces were simultaneously polished after rotating at a rotation speed of 100 min ^-1 (100 rpm).

(5) A conductor paste was printed on the plate obtained in the above (4) by screen printing. The printing pattern was a concentric pattern as shown in FIG. As the conductive paste, Solvest PS6 manufactured by Tokurika Kagaku Kenkyusho used for forming through holes in printed wiring boards is used.
03D was used. This conductor paste is a silver-lead paste, and based on 100 parts by weight of silver, lead oxide (5% by weight), zinc oxide (55% by weight), silica (10% by weight), and boron oxide (25% by weight). And 7.5 parts by weight of a metal oxide comprising alumina (5% by weight). The silver particles had a mean particle size of 4.5 μm and were scaly.

(6) Next, the ceramic substrate 11 on which the conductive paste is printed is heated and fired at 780 ° C. to sinter silver and lead in the conductive paste and to form the ceramic substrate 11
To form a resistance heating element 12 (FIG. 4).
(B)). The silver-lead resistance heating element had a thickness of 5 μm, a width of 2.4 mm, and an area resistivity of 7.7 Ω / □.

(7) An electroless nickel plating bath composed of an aqueous solution having a concentration of 80 g / l nickel sulfate, 24 g / l sodium hypophosphite, 12 g / l sodium acetate, 8 g / l boric acid, and 6 g / l ammonium chloride was used. The ceramic substrate 11 prepared in (6) is immersed in the silver-lead resistance heating element 1.
2 a 1 μm thick metal coating layer (nickel layer) 12
a was precipitated.

(8) A screen is printed on the portion to which the external terminal 13 for securing the connection with the power supply is to be attached.
g-Sn solder paste (manufactured by Tanaka Kikinzoku Co., Ltd.) was printed to form a solder layer. Next, an external terminal 13 made of Kovar was placed on the solder layer, and heated and reflowed at 700 ° C. to attach the external terminal 13 to the surface of the resistance heating element 12 (FIG. 4).
(C)).

(9) A thermocouple for temperature control was sealed with polyimide to obtain a ceramic heater 10.

Next, the average thickness, the minimum thickness, the maximum thickness, and the variation of the thickness of the ceramic substrate of the obtained ceramic heater 10 were measured by the following methods. (A) Select a point at an arbitrary end of the ceramic substrate after the step (4), and accurately measure the thickness at a position of 5 mm from the end toward the center of the ceramic substrate with a micrometer. This thickness was taken as a reference thickness. The surface irregularities were measured starting from the point where the thickness was measured.

(B) Using a shape measuring instrument (manufactured by Kyocera Corporation, Nanoway), a linear portion extending from the above-mentioned reference point of the ceramic substrate to the center of the ceramic substrate to 5 mm before the other end and having a surface area of The unevenness was measured. Here, the reason why the end portions of the ceramic substrate were removed at every 5 mm is that when the silicon wafer is placed and heated, this portion does not cause a problem in temperature variation.

(C) Next, on the opposite side of the ceramic substrate, the surface irregularities were measured starting from the reference point in the same manner as in (b) above.

(D) The data obtained in the above (b) and (c)
Since the same unevenness is shown on the front and back of the ceramic substrate, the data of the thickness of the specific linear portion of the ceramic substrate can be obtained by combining the above-mentioned reference thickness and the above-mentioned data. Further, data of the average thickness T ₁ , the minimum thickness, and the maximum thickness can be obtained from the obtained data.

(E) Nine points different from the above reference points are selected,
By performing the same measurement as in the above (a) to (d), the average thickness (T ₁ to
T ₁₀₎ were measured. The intervals between the reference points were made as equal as possible.

(F) Obtained T₁ ~ T_TenAverage of
The average thickness T of the₁ ~ T _TenMinimum thickness and
And the maximum thickness of the ceramic substrate, respectively.
Maximum thickness. Also, if the thickness of this ceramic substrate
The turbulence is calculated as shown in the following equation (1).
Was. Variation in thickness of ceramic substrate (%) = [(maximum or minimum measured thickness-average thickness) x 100] / average thickness ... (1)

The average thickness of the ceramic substrate obtained above,
The minimum thickness, the maximum thickness, and the variation in the thickness are shown in Table 1 below.

Example 2 Production of Ceramic Heater Having Resistance Heating Element Inside (See FIG. 5) (1) Aluminum nitride powder (manufactured by Tokuyama Corporation)
1.1 μm) 100 parts by weight, yttria (average particle size:
0.4 μm) Using a paste obtained by mixing 4 parts by weight, 11.5 parts by weight of an acrylic binder, 0.5 parts by weight of a dispersant, and 53 parts by weight of alcohol composed of 1-butanol and ethanol, molding was performed by a doctor blade method. Thus, a green sheet having a thickness of 0.47 mm was obtained.

(2) Next, the green sheet was dried at 80 ° C. for 5 hours, and then punched with a diameter of 1.8 m.
A portion serving as a through hole for connection with a terminal pin of 3.0 mm or 5.0 mm was provided.

(3) 100 parts by weight of tungsten carbide particles having an average particle size of 1 μm, 3.0 parts by weight of an acrylic binder, 3.5 parts by weight of an α-terpineol solvent, and 0.3 part by weight of a dispersant are mixed to form a conductor. Paste A was prepared.

Tungsten particles 100 having an average particle size of 3 μm
A conductive paste B was prepared by mixing 1.9 parts by weight of an acrylic binder, 3.7 parts by weight of an α-terpineol solvent, and 0.2 parts by weight of a dispersant. This conductor paste A was printed on a green sheet by screen printing to form a conductor paste layer. The printing pattern was a concentric pattern as shown in FIG. In addition, the conductive paste B was filled in through holes for through holes for connecting terminal pins.

On the green sheet after the above treatment, 37 green sheets on which the tungsten paste is not printed are printed on the upper side (heating surface), 13 green sheets on the lower side, and 130 green sheets on the lower side.
The layers were laminated at a temperature of 8 ° C. and a pressure of 8 MPa (80 kgf / cm ² ).

(4) Next, the obtained laminate is placed in nitrogen gas.
Degreasing at 600 ° C for 5 hours, 1890 ° C, pressure 15MPa
(150 kgf / cm ² ) for 3 hours to obtain an aluminum nitride plate having a thickness of about 3 mm. This is cut out into a 215 mm disc shape and has a thickness of 6 μm inside.
A ceramic substrate having a conductor layer having a width of 10 mm was obtained. Thereafter, the through hole 25 and the bottomed hole (diameter: 1.2 mm, depth: 2.0
mm).

(5) Next, using a rotary grinding lathe having a # 220 diamond grindstone, first fix the outer peripheral portion of the ceramic substrate, and apply only the weight of the plate-shaped body without applying pressure. one side of the obtained plate-like body 100 min ^-1
Polishing was performed at a rotation speed of (100 rpm). Next, based on the polished surface, the polished surface is fixed to a jig using wax (green wax manufactured by Maltoux) to correct the warp, and a pressure of 0.1 MPa (1 kgf / cm ² ) is applied. , And the surfaces were simultaneously polished at a rotation speed of 100 min ^-1 (100 rpm). As a result, a ceramic substrate having a conductor layer having a thickness of 6 μm and a width of 10 mm inside and having a small thickness variation was obtained.

(6) Further, a part of the through-hole for the through-hole is cut out to form a concave portion, and a Ni-Au gold solder is used in the concave portion, and heated and reflowed at 700 ° C. to form a Kovar terminal pin. Connected. In addition, a plurality of thermocouples for temperature control were buried in the bottomed holes, and the manufacture of the ceramic heater having a resistance heating element as a conductor layer therein was completed.

The average thickness, minimum thickness, maximum thickness, and variation in the thickness of the ceramic substrate of this ceramic heater were measured in the same manner as in Example 1. The results are shown in Table 1 below.

Comparative Example 1 Production of Ceramic Heater Having Resistance Heating Element on Surface Using a double-sided grinding lathe having a diamond grindstone of # 220, 0.1 MPa (1 kg / cm
² ) 100min ^-1 (100rpm) while applying pressure
A ceramic heater was manufactured in the same manner as in Example 1 except that the double-side polishing was performed at a rotation speed of m). The average thickness, the minimum thickness, the maximum thickness, and the variation in the thickness of the ceramic substrate of the obtained ceramic heater are shown in Table 1 below.

Comparative Example 2 Production of Ceramic Heater Having Resistance Heating Element Inside A double-sided grinding lathe having a diamond grindstone of # 220 was used at 0.1 MPa (1 kg / cm).
² ) 100min ^-1 (100rpm) while applying pressure
A ceramic heater was manufactured in the same manner as in Example 2 except that the double-side polishing was performed at a rotation speed of m). The average thickness, the minimum thickness, the maximum thickness, and the variation in the thickness of the ceramic substrate of the obtained ceramic heater are shown in Table 1 below.

Next, the resistance heating elements of the ceramic substrates obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were energized to raise the temperature of the heating surface to 300 ° C. The temperature and the minimum temperature were measured using a thermoviewer (IR-16-2012-0012, manufactured by Nippon Datum), and the results are shown in Table 1.

[0116]

[Table 1]

In the ceramic substrates of the ceramic heaters obtained in Examples 1 and 2, the variation in the thickness with respect to the average thickness is -2.6 to 1.7% at the maximum, and Although the difference between the maximum temperature and the minimum temperature was as small as 9 ° C. or less, the silicon wafer could be heated almost uniformly. However, in the ceramic substrates of the ceramic heaters obtained in Comparative Examples 1 and 2, with respect to the average thickness. The thickness variation is as large as −6.0 to + 6.0% at the maximum, and the difference between the maximum temperature and the minimum temperature of the heated silicon wafer is as large as 17 ° C.

[0118]

As described above, according to the ceramic heater of the present invention, the variation in the thickness of the ceramic substrate is reduced.
Since the average thickness of the ceramic substrate is -3 to 3%, it is possible to suppress temperature variations on the heating surface of the ceramic substrate, and heat the silicon wafer or the like to be heated to a uniform temperature. can do.

[Brief description of the drawings]

FIG. 1 is a plan view schematically showing one example of a ceramic heater of the present invention.

FIG. 2 is an enlarged sectional view of the ceramic heater shown in FIG.

FIG. 3 is a plan view schematically showing another example of the ceramic heater of the present invention.

FIGS. 4A to 4C are cross-sectional views schematically showing a part of a manufacturing process of the ceramic heater shown in FIG.

FIGS. 5A to 5D are cross-sectional views schematically showing a part of a manufacturing process of the ceramic heater shown in FIG.

[Explanation of symbols]

 Reference Signs List 9 silicon wafer 10 ceramic heater 11 ceramic substrate 11a heating surface 11b, 21b bottom surface 12, 22 resistance heating element 13, 23 external terminal 14 bottomed hole 15, 25 through hole 16 lifter pin 24 brazing material 27 bag hole 28 through hole

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[Procedure amendment]

[Submission date] May 28, 2001 (2001.5.2)
8)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

[Title of the Invention] Ceramic heater for semiconductor manufacturing and inspection equipment

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) // C04B 35/581 C23C 16/46 C23C 16/46 C04B 35/58 104D F-term (reference) 3K034 AA02 AA08 AA21 AA22 AA28 AA34 AA37 BB06 BB14 BC12 BC16 BC17 BC29 CA03 CA14 CA22 CA26 DA04 DA08 HA01 HA10 JA01 JA02 3K092 PP09 PP20 QA05 QB02 QB17 QB18 QB33 QB37 QB44 QB45 QB61 QB75 QB76 QC02 QC07 QC18 RF37 UA18 QC32 QC18 BA09 BA36 BB36 BC42 BC52 BC73 BD03 BE32 4K030 CA04 GA02 JA10 KA23

Claims (5)

[Claims] 1. A ceramic heater in which a resistance heating element is formed inside or on a surface of a ceramic substrate, wherein a variation in the thickness of the ceramic substrate is -3 to 3% of an average thickness of the ceramic substrate. A ceramic heater, characterized in that: 2. The ceramic heater according to claim 1, wherein the resistance heating element is formed on a surface of a ceramic substrate, and a side opposite to a surface on which the resistance heating element is formed is a heating surface. 3. The resistance heating element is formed inside a ceramic substrate, and the resistance heating element is formed at a position of 60% or less in a thickness direction from a surface opposite to a heating surface. Ceramic heater. 4. The ceramic heater according to claim 1, wherein the ceramic substrate is a disk, and has a diameter exceeding 190 mm. 5. The ceramic heater according to claim 1, wherein said ceramic substrate has a thickness of 25 mm or less.