JP2003229233A - Ceramic heater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ceramic heater capable of evenly heating an object, such as a silicon wafer. <P>SOLUTION: For the ceramic heater with a heating element formed on the surface or in the interior of a ceramic plate, a blind hole is provided from a side opposite to a heating surface for heating a substance to be heated toward the heating surface, the bottom of the blind hole is formed relatively nearer the heating surface that the heating element, and a temperature sensing element is provide in the blind hole. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic heater mainly used in the semiconductor industry for drying, sputtering, etc., and particularly to a ceramic heater which is easy to control in temperature and has excellent temperature uniformity on a heating surface.

[0002]

2. Description of the Related Art Semiconductor products are manufactured through a process of forming a photosensitive resin as an etching resist on a silicon wafer and etching the silicon wafer. This photosensitive resin is in liquid form and is applied to the surface of the silicon wafer using a spin coater, etc., but it must be dried after application, and the applied silicon wafer should be placed on a heater and heated. become. Conventionally, as a metal heater used for such an application, a heater in which a heating element is arranged on the back surface of an aluminum plate has been adopted.

However, such a metal heater is
There were the following problems. First of all, because it is made of metal,
The thickness of the heater plate should be as thick as about 15 mm. This is because, in a thin metal plate, thermal expansion caused by heating causes warping and distortion, and the silicon wafer placed on the metal plate is damaged or tilted. However, if the thickness of the heater plate is increased, the weight of the heater becomes heavier and bulky.

Further, the heating temperature is controlled by changing the voltage and the amount of current applied to the heating element. However, since the metal plate is thick, the temperature of the heater plate can be quickly changed with respect to the change in the voltage and the amount of current. There was also a problem that it was difficult to control the temperature because it did not follow.

Therefore, as proposed in Japanese Examined Patent Publication No. 8-8247, there is proposed a technique for controlling the temperature by using a nitride ceramic in which a heating element is formed and measuring the temperature in the vicinity of the heating element. Has been done.

[0006]

However, when attempting to heat a silicon wafer by using such a technique, there arises a problem that the silicon wafer is damaged by thermal shock due to the temperature difference on the heater surface. .

Therefore, as a result of intensive studies on the cause of damage to the silicon wafer, the present inventors found that the silicon wafer was damaged despite the temperature control by measuring the temperature in the vicinity of the heating element. However, since this temperature does not necessarily reflect the temperature of the heated surface of the silicon wafer, the unexpected fact that the temperature difference of the silicon wafer occurs depending on the location and the silicon wafer is damaged was found. In addition, the fact that such non-uniformity of temperature is more remarkable as nitride ceramics or carbide ceramics having higher thermal conductivity is newly found.

Therefore, the present inventors have made further studies,
It was found that by measuring the temperature of the portion closer to the silicon wafer and heating it based on the result, the temperature difference on the heating surface of the silicon wafer can be reduced and damage to the ceramic plate can be prevented. The present invention has been completed, which has the following contents as its gist configuration.

[0009]

That is, the ceramic heater according to the first aspect of the present invention is a ceramic heater in which a heating element is formed on the surface or inside of a ceramic plate, the side opposite to the heating surface for heating an object to be heated. From the above, a bottomed hole is provided toward the heating surface, the bottom of the bottomed hole is formed closer to the heating surface than the heating element, and the temperature measuring element is provided in the bottomed hole. To do.

In the ceramic heater, the distance between the bottom of the bottomed hole and the heating surface is preferably 0.1 mm to 1/2 of the thickness of the ceramic plate. The ceramic constituting the ceramic heater is preferably a nitride ceramic or a carbide ceramic. The heating element of the ceramic heater is preferably divided into at least two circuits. The heating element of the ceramic heater preferably has a flat cross section.

In the ceramic heater of the second aspect of the present invention, a heating element is formed on the surface or inside of the ceramic plate, and a temperature measuring element for measuring the temperature of the ceramic plate and electric power are supplied to the heating element. A storage unit for storing temperature data measured by the temperature measuring element,
In a ceramic heater comprising a calculation unit for calculating the electric power required for the heating element from the temperature data, a bottomed hole is formed on the ceramic plate from the side opposite to the heating surface for heating an object to be heated toward the heating surface. And the bottom of the bottomed hole is formed relatively closer to the heating surface than the heating element, and the temperature measuring element is provided in the bottomed hole. In the ceramic heater, the heating element has at least 2
It is desirable that the circuit is divided into the above circuits and that different powers are supplied to the respective circuits.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION A ceramic heater according to the first aspect of the present invention is a ceramic heater having a heating element formed on the surface or inside of a ceramic plate. A bottomed hole is provided toward the bottom, the bottom of the bottomed hole is formed relatively closer to the heating surface than the heating element, and the temperature measuring element is provided in the bottomed hole.

According to the ceramic heater of the first aspect of the present invention, since the temperature measuring place is closer to the heating surface of the object to be heated (silicon wafer) than the heating element, it is possible to measure the temperature of the object to be heated more accurately. By adjusting the heat generation state of the heating element based on the measurement result of this temperature, it becomes possible to uniformly heat the object to be heated.

Further, since the coefficient of thermal expansion of nitride ceramics and carbide ceramics is smaller than that of metals and the mechanical strength thereof is significantly higher than that of metals, the thickness of ceramic plates (hereinafter referred to as heater plates) is thin. However, it does not warp or distort due to heating. Therefore, the heater plate can be thin and light. Further, since the heater plate has high thermal conductivity and the heater plate itself is thin, the surface temperature of the heater plate quickly follows the temperature change of the heating element. That is, the voltage,
By changing the current value and the temperature of the heating element,
The surface temperature of the heater plate can be controlled.

In the ceramic heater, the heating element is formed on the surface of one main surface of the heater plate, and the opposite side surface is a heating surface for heating an object to be heated such as a silicon wafer, or the inside of the heater plate. It is desirable that the heating surface be formed so as to be eccentric to the one main surface side from the center, and the surface farther from the heating element should be the heating surface.

By setting the formation position of the heating element in this way, while the heat generated from the heating element propagates, the heat is diffused over the entire heater plate and the surface to be heated (silicon wafer) is heated. The temperature distribution is made uniform, and as a result,
The temperature in each part of the object to be heated is made uniform. The heating can be performed by placing the object to be heated on the heater plate or by holding the object to be heated at a predetermined distance from the heater plate.

FIG. 1 is a bottom view schematically showing an example of the ceramic heater according to the first aspect of the present invention. The heater plate 11 is
The heating element 12 is formed in a disk shape, and the heating element 12 is a heater plate 11.
Since it is necessary to heat the heating surface of the heater plate (the side opposite to the bottom surface shown in the figure) to be uniform, the heater plate 11
Are formed in a concentric pattern on the bottom surface of the. Also,
These heating elements 12 have two concentric circles close to each other.
As a set, they are connected so as to form one line, and terminal pins 13 serving as input / output terminals are connected to both ends thereof. Further, a through hole 15 for inserting a support pin (not shown) is formed in a portion close to the center, and bottomed holes 14a to 14i for inserting a temperature measuring element are further formed.

In this ceramic heater 10, the thickness of the heater plate 11 is preferably 0.5-5 mm. 0.5
If it is thinner than 5 mm, the strength is lowered and it is easily damaged. On the other hand, if it is thicker than 5 mm, it is difficult for heat to propagate and the heating efficiency is deteriorated.

The ceramic forming the ceramic heater 10 is preferably a nitride ceramic or a carbide ceramic. Examples of the nitride ceramics include aluminum nitride, silicon nitride, boron nitride, titanium nitride and the like. These may be used alone or in combination of two or more.

Examples of carbide ceramics include silicon carbide, zirconium carbide, titanium carbide, tantalum carbide, tungsten carbide and the like. These may be used alone or in combination of two or more.

Of these, aluminum nitride is most preferred. The highest thermal conductivity of 180 W / mK,
This is because the temperature followability is excellent, but the temperature distribution is likely to be non-uniform, and the temperature measuring element forming structure as in the present invention is required.

In the ceramic heater 10 of the first present invention, the distance L between the bottoms of the bottomed holes 14a to 14i and the heating surface (see FIG. 2B) L is 0.1 mm to 1 of the thickness of the ceramic plate. It is desirable that it is / 2. Bottomed holes 14a-14i
If the distance between the bottom and the heating surface is less than 0.1 mm, heat will be dissipated and a temperature distribution will be formed on the heating surface of the silicon wafer, and if it exceeds 1/2 of the thickness of the ceramic plate, the temperature of the heating element will increase. This is because it is easily affected by, and a temperature distribution is formed on the heated surface of the silicon wafer.

As the temperature measuring element, for example, a thermocouple,
Examples include platinum resistance temperature detectors and thermistors. Further, as the thermocouple, for example, JIS-C-1602 (1
980), K type, R type, B type, S type
Examples include type, E type, J type, T type thermocouples, and of these, K type thermocouples are preferable.

The size of the joint portion of the thermocouple is preferably equal to or larger than the diameter of the wire, and is 0.5 mm or less. This is because if the joint is large, the heat capacity becomes large and the responsiveness deteriorates. It is difficult to make the diameter smaller than the diameter of the wire.

The diameter of the bottomed holes 14a-14i is 0.3-.
It is preferably 0.5 mm. This is because if it is too large, the heat dissipation becomes large, and if it is too small, the workability deteriorates and it becomes impossible to make the distance to the processed surface uniform.

The bottomed holes 14a to 14i are symmetrical with respect to the center of the heater plate 11, as shown in FIG.
It is desirable to arrange them so as to form a cross. This is because the temperature of the entire heated surface can be measured.

The temperature measuring element may be adhered to the bottoms of the bottomed holes 14a to 14i by using gold solder, silver solder or the like.
After being inserted into the bottomed holes 14a to 14i, they may be sealed with a heat resistant resin, or both may be used together. As the heat resistant resin, for example, a thermosetting resin, particularly an epoxy resin,
Examples thereof include polyimide resin, bismaleimide-triazine resin, and silicone resin. These resins may be used alone or in combination of two or more. Moreover, you may seal using ceramics, such as silica sol and an alumina sol.

As the above-mentioned brazing filler metal, 37 to 80.5 wt% Au-63 to 19.5 wt% Cu alloy, 81.5 to 8
At least one selected from 2.5 wt% Au-18.5 to 17.5 wt% Ni alloy is desirable. These are because the melting temperature is 900 ° C. or higher and it is difficult to melt even in a high temperature region. Examples of silver solder include Ag-Cu
A system can be used.

The heating element 12 is preferably divided into at least two circuits as shown in FIG.
More preferably, it is divided into 2 to 10 circuits.
This is because by dividing the circuit, the amount of heat generated can be changed by controlling the electric power supplied to each circuit, and the temperature of the heated surface of the silicon wafer can be adjusted.

As the pattern of the heating element 12, in addition to the concentric circles shown in FIG. 1, for example, a spiral, an eccentric circle, a bent line and the like can be cited.

In the present invention, the heating element 12 is replaced by the heater plate 1.
In the case of forming on the surface of No. 1, the conductive paste containing metal particles is applied to the surface of the heater plate 11 to form a conductor paste layer having a predetermined pattern, and this is baked to remove the metal particles on the surface of the heater plate 11. A method of sintering is preferred. In addition, the sintering of the metal is sufficient if the metal particles are fused to each other and the metal particles and the ceramic are fused.

As shown in FIG. 1, when the heating element 12 is formed on the surface of the heater plate 11, the thickness of the heating element 12 is preferably 1 to 30 μm, more preferably 1 to 10 μm. When a heating element is formed inside the heater plate 11, its thickness is preferably 1 to 50 μm.

When the heating element 12 is formed on the surface of the heater plate 11, the width of the heating element 12 is 0.1 to 20 m.
m is preferable, and 0.1-5 mm is more preferable. Also,
When the heating element is formed inside the heater plate 11, the width of the heating element is preferably 5 to 20 μm.

The resistance value of the heating element 12 can be changed depending on its width and thickness, but the above range is most practical. The resistance value becomes thinner and becomes thinner as it becomes thinner. When the heating element 12 is formed inside the heater plate 11, both the thickness and the width are larger. However, when the heating element 12 is provided inside, the distance between the heating surface and the heating element is shortened,
Since the uniformity of the temperature of the surface is lowered, it is necessary to widen the width of the heating element 12 itself, and it is not necessary to consider the adhesion with the nitride ceramic or the like in order to provide the heating element inside, Refractory metals such as tungsten and molybdenum and carbides such as tungsten and molybdenum can be used, and the resistance value can be increased. Therefore, the thickness itself may be increased for the purpose of preventing disconnection. Therefore, it is desirable that the heating element 12 has the above-mentioned thickness and width.

The heating element 12 may have a rectangular or elliptical cross section, but it is preferably flat. This is because the flat surface is more likely to radiate heat toward the heating surface, and thus the temperature distribution on the heating surface is less likely to occur. The aspect ratio (width of heating element / thickness of heating element) of the cross section is preferably 10 to 5,000. By adjusting to this range, the resistance value of the heating element 12 can be increased and the temperature uniformity of the heating surface can be ensured.

When the thickness of the heating element 12 is constant and the aspect ratio is smaller than the above range, the amount of heat transmitted in the direction of the wafer heating surface of the heater plate 11 becomes small, and the heating element 12
The heat distribution similar to the pattern is generated on the heating surface. On the contrary, if the aspect ratio is too large, the temperature directly above the center of the heating element 12 becomes high, and the heat close to the pattern of the heating element 12 is eventually obtained. Distribution occurs on the heated surface.
Therefore, considering the temperature distribution, the aspect ratio of the cross section is preferably 10 to 5,000.

When the heating element 12 is formed on the surface of the heater plate 11, the aspect ratio is 10 to 200, and when the heating element 12 is formed inside the heater plate 11, the aspect ratio is 200 to 5000. desirable.

The heating element 12 has a larger aspect ratio when it is formed inside the heater plate 11. This is because when the heating element 12 is provided inside, the heating surface and the heating element 12 are formed.
This is because the distance between the heating element 12 and the heating element 12 itself becomes flat because the distance between the heating element 12 and the heating element 12 becomes short and the temperature uniformity on the surface is reduced.

When the heating element 12 of the present invention is formed eccentrically inside the heater plate 11, the position is close to the side surface (bottom surface) opposite to the heating surface of the heater plate 11, and is located from the heating surface to the bottom surface. It is desirable to set the position to more than 50% and up to 99% with respect to the distance. If it is 50% or less, the temperature distribution is generated because it is too close to the heating surface. On the contrary, if it exceeds 99%, the heater plate 11 itself warps and the silicon wafer is damaged. .

When the heating element 12 is formed inside the heater plate 11, a plurality of heating element forming layers may be provided. In this case, it is desirable that the heating elements 12 be formed in some layers so that the patterns of the respective layers complement each other, and that the patterns are formed in any of the regions when viewed from above the heating surface. As such a structure, for example, a structure in which staggered arrangement is provided.

The conductive paste is not particularly limited, but it is preferable that the conductive paste contains metal particles or conductive ceramics for ensuring conductivity, and also contains 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 difficult to oxidize and have a resistance value sufficient to generate heat. Examples of the conductive ceramics include carbides of tungsten and molybdenum. These may be used alone or in combination of two or more.

The particle size of these metal particles or conductive ceramic particles is preferably 0.1 to 100 μm. 0.1μ
If it is less than m and too fine, it is easily oxidized, while 100
This is because if it exceeds μm, it becomes difficult to sinter and the resistance value increases.

Even if the shape of the metal particles is spherical,
It may be flaky. When these metal particles are used, they may be a mixture of the above-mentioned spherical material and the above-mentioned scaly material. When the metal particles are scaly particles or a mixture of spherical particles and scaly particles, it becomes easier to hold the metal oxide between the metal particles, and the adhesiveness between the heating element 12 and the nitride ceramic or the like. Is advantageous and the resistance value can be increased, which is advantageous.

The resin used for the conductor paste is
For example, an epoxy resin, a phenol resin, etc. are mentioned. Examples of the solvent include isopropyl alcohol and the like. Examples of the thickener include cellulose and the like.

As described above, the conductor paste is preferably made of metal particles to which a metal oxide is added, and the heating element 12 is formed by sintering the metal particles and the metal oxide.
As described above, by sintering the metal oxide together with the metal particles, the nitride ceramic or the carbide ceramic, which is the heater plate, can be brought into close contact with the metal particles.

Although it is not clear why the adhesion of the metal oxide to the nitride ceramic or the carbide ceramic is improved, the surface of the metal particles or the surface of the nitride ceramic or the carbide ceramic is slightly oxidized. It is considered that the oxide film is formed by sintering and the oxide film is sintered through the metal oxide to be integrated with each other, and the metal particles and the nitride ceramic or the carbide ceramic adhere to each other.

As the metal oxide, for example, oxidation
Lead, zinc oxide, silica, boron oxide (B ₂ O₃ ), Al
Selected from the group consisting of Mina, Yttria and Titania
At least one is preferable.

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

The proportions of lead oxide, zinc oxide, silica, boron oxide (B ₂ O ₃ ), alumina, yttria, and titania are, when the total amount of metal oxides is 100 parts by weight, lead oxide is a weight ratio. 1-10, silica 1-30, boron oxide 5-50, zinc oxide 20-70, alumina 1
-10, yttria is 1-50, and titania is 1-50, and it is desirable that the total is adjusted not to exceed 100 parts by weight. By adjusting the amounts of these oxides within these ranges, it is possible to improve the adhesion, particularly with the nitride ceramics.

The amount of the above metal oxide added to the metal particles is preferably 0.1% by weight or more and less than 10% by weight. Further, the heating element 1 is formed by using the conductor paste having such a configuration.
The area resistivity when forming 2 is preferably 1 to 45 mΩ / □.

If the sheet resistivity exceeds 45 mΩ / □, the amount of heat generation becomes too large with respect to the applied voltage amount, and the heater plate 11 having the heating element 12 on the surface of the heater plate controls the amount of heat generation. Because it is difficult. If the addition amount of the metal oxide is 10% by weight or more, the sheet resistivity is 50 mΩ.
/ □ is exceeded, and the amount of heat generated becomes too large, making temperature control difficult and reducing the uniformity of temperature distribution.

When the heating element 12 is formed on the surface of the heater plate 11, it is desirable that a metal coating layer (see FIG. 3) 48 is formed on the surface portion of the heating element 12. This is to prevent the internal metal sintered body from being oxidized and changing its resistance value. The thickness of the metal coating layer to be formed is 0.1
It is preferably 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 2
You may use together 1 or more types. Of these, nickel is preferred.

The heating element 12 needs a terminal for connecting to a power source, and this terminal is connected to the heating element 12 via solder.
This is because nickel prevents the heat diffusion of the solder. Examples of the connection terminal include a Kovar terminal pin 13.

When the heating element 12 is formed inside the heater plate 11, the surface of the heating element is not oxidized, so that no coating is required. When the heating element 12 is formed inside the heater plate 11, a part of the heating element may be exposed on the surface, and a through hole for connecting the heating element is provided in the terminal portion, and the terminal is provided in this through hole. It may be connected or fixed.

When connecting the connection terminals, the solder is
Alloys such as silver-lead, lead-tin, bismuth-tin can be used. The thickness of the solder layer is 0.1 to 50.
μm is preferred. This is because the range is sufficient to secure the solder connection. In the ceramic heater of the present invention, it is possible to embed an electrode inside a ceramic plate to form an electrostatic chuck, or to provide a chuck top conductor layer on the surface and form a guard electrode or a ground electrode inside to function as a wafer prober. it can.

Next, a method of manufacturing the ceramic heater according to the first aspect of the present invention will be described. First, a method of manufacturing a ceramic heater in which the heating element 12 is formed on the surface of the heater plate 11 shown in FIG. 1 will be described. (1) Manufacturing process of heater plate After preparing a slurry by adding a sintering aid such as yttria or a binder to the powder of the above-described nitride ceramic or carbide ceramic such as aluminum nitride, etc., this slurry is prepared. Granules are formed by a method such as spray drying, and the granules are put into a mold or the like and pressed to form a plate or the like to produce a green body (green).

Next, a through hole 1 for inserting a support pin for supporting the silicon wafer into the green body, if necessary.
5 and the bottomed holes 14a to 14i for embedding a temperature measuring element such as a thermocouple are formed.

Next, this green body is heated, fired and sintered to produce a ceramic plate-like body. After that, the heater plate 11 is manufactured by processing it into a predetermined shape, but it may have a shape that can be used as it is after firing. By performing heating and firing while applying pressure, it becomes possible to manufacture the heater plate 11 having no pores. The heating and firing may be performed at a sintering temperature or higher, but in the case of a nitride ceramic or a carbide ceramic, it is 1000 to 250.
It is 0 ° C.

(2) Step of printing the conductor paste on the heater plate The conductor paste is generally a highly viscous fluid consisting of metal particles, resin and solvent. The conductor paste layer is formed by printing the conductor paste on the portion where the heating element is to be provided by screen printing or the like. Since it is necessary for the heating element to have a uniform temperature over the entire heater plate, it is desirable to print the heating element in a concentric pattern as shown in FIG. The conductor paste layer is preferably formed so that the cross section of the heating element 12 after firing has a rectangular shape and a flat shape.

(3) Baking of conductor paste The conductor paste layer printed on the bottom surface of the heater plate 11 is heated and fired to remove the resin and the solvent, and the metal particles are sintered and baked on the bottom surface of the heater plate 11. The heating element 12 is formed. The heating and firing temperature is preferably 500 to 1000 ° C. When the above-mentioned metal oxide is added to the conductor paste, the metal particles, the heater plate and the metal oxide are sintered and integrated, so that the adhesion between the heating element and the heater plate is improved.

(4) Formation of metal coating layer It is desirable to provide a metal coating layer on the surface of the heating element 12. The metal coating layer can be formed by electrolytic plating, electroless plating, sputtering, etc., but in consideration of mass productivity, electroless plating is most suitable.

(5) Attachment of terminals, etc. Terminals (terminal pins 13) for connecting to a power source are attached to the ends of the pattern of the heating element 12 by soldering. Further, a thermocouple is fixed to the bottomed holes 14a to 14i with silver solder, gold solder or the like, and sealed with a heat resistant resin such as polyimide, and the manufacturing of the ceramic heater 10 is completed.

Next, a method of manufacturing a ceramic heater in which a heating element is formed inside the heater plate will be described. (1) Step of Manufacturing Heater Plate First, a powder of nitride ceramic or a carbide ceramic is mixed with a binder, a solvent, etc. to prepare a paste, and a green sheet is manufactured using the paste.

As the above-mentioned ceramic powder, aluminum nitride, silicon carbide, etc. can be used, and if necessary, a sintering aid such as yttria may be added.
Further, the binder is preferably at least one selected from acrylic binders, ethyl cellulose, butyl cellosolve, and polyvinyl alcohol.

Further, the solvent is preferably at least one selected from α-terpineol and glycol. The paste obtained by mixing these is molded into a sheet by the doctor blade method to produce a green sheet. The thickness of the green sheet is preferably 0.1 to 5 mm.

Next, in the obtained green sheet, if necessary, a portion to be a through hole into which a supporting pin for supporting a silicon wafer is inserted, and a bottomed hole for embedding a temperature measuring element such as a thermocouple. And a through hole for connecting the heating element to an external end pin.
The above-mentioned processing may be performed after forming a green sheet laminate described below.

(2) Step of printing conductor paste on the green sheet A conductive paste containing a metal paste or a conductive ceramic is printed on the green sheet. These conductive pastes contain metal particles or conductive ceramic particles.

The average particle size of the tungsten particles or molybdenum particles is preferably 0.1 to 5 μm. If the average particle size is less than 0.1 μm or exceeds 5 μm, it is difficult to print the conductor paste. Examples of such a conductor paste include, 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 polyvinyl alcohol; and Examples thereof include a composition (paste) in which 1.5 to 10 parts by weight of at least one solvent selected from α-terpineol and glycol is mixed.

(3) Laminating Step of Green Sheet The green sheet on which the conductor paste is not printed is laminated above and below the green sheet on which the conductor paste is printed.
At this time, the number of green sheets stacked on the upper side is set to be larger than the number of green sheets stacked on the lower side, and the formation position of the heating element is eccentric in the direction of the bottom surface. 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) Firing step of green sheet laminate The green sheet laminate is heated and pressed to sinter the green sheet and the conductor paste inside. The heating temperature is preferably 1000 to 2000 ° C., and the pressure applied is
100 to 200 kg / cm ² is preferable. The heating is performed in an inert gas atmosphere. As the inert gas, for example,
Argon, nitrogen and the like can be used.

After firing, a bottomed hole for inserting the temperature measuring element may be provided. The bottomed hole can be formed by performing blasting such as sandblasting after the surface is polished. Also, the terminal is connected to a through hole for connecting with an internal heating element, heated and reflowed. The heating temperature is preferably 200 to 500 ° C. Further, a thermocouple or the like as a temperature measuring element is attached with silver solder, gold solder or the like, and sealed with a heat resistant resin such as polyimide, and the manufacturing of the ceramic heater is completed.

Next, the ceramic heater of the second invention will be described. The ceramic heater of the second invention is
A heating element is formed on the surface or inside of the ceramic plate, and a temperature measuring element that measures the temperature of the ceramic plate, a control unit that supplies electric power to the heating element, and temperature data measured by the temperature measuring element. In a ceramic heater comprising a storage unit for storing the temperature and a calculation unit for calculating the electric power required for the heating element from the temperature data, the ceramic plate is heated from the side opposite to the heating surface for heating the object to be heated. The bottomed hole is provided toward the surface, the bottom of the bottomed hole is formed closer to the heating surface than the heating element, and the temperature measuring element is provided in the bottomed hole.

According to the ceramic heater of the second aspect of the present invention, since the temperature measuring place is closer to the heating surface of the silicon wafer than the heating element, it is possible to measure the temperature of the silicon wafer more accurately, and to obtain the accurate temperature. The measurement result is stored in the storage unit, and based on the temperature data stored in the storage unit, the voltage applied to the heating element for uniform heating is calculated by the calculation unit,
Since the control unit applies the control voltage to the heating element based on the calculation result, it is possible to uniformly heat the entire silicon wafer.

Further, since the coefficient of thermal expansion of nitride ceramics and carbide ceramics is smaller than that of metal and the mechanical strength thereof is significantly higher than that of metal, the heater plate can be made thin and light. Further, since the heater plate has high thermal conductivity and the heater plate itself is thin, the surface temperature of the heater plate quickly follows the temperature change of the heating element.

FIG. 2A is a block diagram showing an outline of an example of the second ceramic heater of the present invention, and FIG.
[FIG. 7] is a partially enlarged cross-sectional view showing a part thereof. As shown in FIG. 2, in the ceramic heater 20, the heater plate 21 is provided with a plurality of through holes 25 (only one in the figure), and the support pins 26 are inserted into the through holes 25 to support the heater. The silicon wafer 19 is placed on the pins 26. Further, by raising and lowering the support pins 26, the silicon wafer 19 can be delivered to a carrier (not shown) or the silicon wafer 19 can be received from the carrier. Also, the support pin 2
6, the silicon wafer 19 can be heated while holding the silicon wafer 19 at a predetermined distance from the heater plate 21.

On the other hand, the heating element 22 is provided inside the heater plate 21.
a and 22b are embedded, and the heating elements 22a and 22b are
Terminal pin 2 provided on the bottom surface through the through hole 28
Connected to 3. A socket 32 is attached to the terminal pin 23, and the socket 32 is connected to a control unit 29 having a power source.

Further, the heater plate 21 is provided with a bottomed hole 24 from the bottom face 21b side, and a thermocouple 27 is fixed to the bottom of the bottomed hole 24. The thermocouple 27 is connected to the storage unit 30 so that the temperature of each thermocouple 27 can be measured at regular intervals and the data can be stored. The storage unit 30 is connected to the control unit 29 and is also connected to the calculation unit 31 to calculate the voltage value controlled by the calculation unit 31 based on the data stored in the storage unit 30. Based on the above, a predetermined voltage can be applied from the control unit 29 to each heating element 21 to make the temperature of the heating surface 21a uniform.

The members (the heater plate 21, the heating elements 22a and 22b, the through holes 28) constituting the ceramic heater 20 and the bottomed holes 24 formed in the heater plate 21 are the same as in the case of the first ceramic heater. Since it is configured, its description is omitted here.

Next, the operation of the ceramic heater 20 of the second present invention will be described. First, when power is applied to the ceramic heater 20 by operating the controller 29, the temperature of the heater plate 21 itself begins to rise,
The surface temperature of the outer circumference becomes slightly lower.

The data measured by the thermocouple 27 is stored in the storage unit 3
It is temporarily stored in 0. Next, this temperature data is calculated by the calculation unit 3
1, the calculation unit 31 calculates the temperature difference ΔT at each measurement point, and further calculates the data ΔW necessary for equalizing the temperature of the heating surface 21a.

For example, if there is a temperature difference ΔT between the heating element 22a and the heating element 22b, and the heating element 22a is lower,
Electric power data ΔW that makes ΔT zero is calculated and transmitted to the control unit 29, and the electric power based on the calculated electric power data ΔW is generated.
It is put into 2a to raise the temperature.

Regarding the calculation algorithm of electric power, the most convenient method is to calculate the electric power required to raise the temperature from the specific heat of the heater plate 21 and the weight of the heating area, and the correction coefficient due to the heating element pattern is added to this. May be. It is also possible to perform a temperature rise test on a specific heating element pattern in advance, obtain a function of the temperature measurement position, input power, and temperature in advance, and calculate the input power from this function. Then, the control unit 2 calculates the applied voltage and the time corresponding to the power calculated by the calculation unit 31.
9, and the control unit 29 controls each heating element 2 based on the value.
2 will be powered.

FIG. 3 is a block diagram showing the outline of another example of the ceramic heater according to the second aspect of the present invention. In the ceramic heater 40 shown in FIG. 3, the bottom surface 4 of the heater plate 41 is
The heating elements 42a and 42b are formed on the heating element 42b.
A metal coating layer 48 is formed around a and 42b.
Further, the terminal pins 43 are connected and fixed to the heating elements 42 a and 42 b via the metal coating layer 48, and the sockets 52 are attached to the terminal pins 43. The socket 52 is connected to the control unit 29 having a power source, and the rest is configured similarly to the ceramic heater shown in FIG.

The operation of the ceramic heater 40 shown in FIG. 3 is similar to that of the ceramic heater 20 shown in FIG.
The temperatures of the thermocouples 42a and 42b are measured at regular intervals and stored in the storage unit 50, and the voltage value and the like controlled by the calculation unit 51 is calculated from this data. Based on this, the control unit 49 causes the heating element 42a to , 42b, a predetermined voltage can be applied to make the temperature of the entire heating surface 41a of the ceramic heater 40 uniform.

[0087]

The present invention will be described in more detail below. (Example 1) Manufacturing of ceramic heater made of aluminum nitride (see FIG. 1) (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 produce a granular powder.

(2) Next, the granular powder was put into a mold and molded into a flat plate to obtain a green molded body. This formed body is drilled to form the through holes 15 into which the support pins of the silicon wafer are inserted, and the bottomed holes 14a to 14i for embedding the thermocouple (diameter: 1.
1 mm, depth: 2 mm) was formed.

(3) 1800 the green body that has been processed
Hot pressing was performed at a temperature of 200 ° C. and a pressure of 200 kg / cm ² to obtain an aluminum nitride plate having a thickness of 3 mm. Next, a disk body having a diameter of 210 mm was cut out from this plate body to obtain a ceramic plate body (heater plate) 11.

(4) Conductor paste was printed on the heater plate 11 obtained in (3) above by screen printing. The print pattern was a concentric pattern as shown in FIG. As a conductor paste, Solbest PS manufactured by Tokuriki Kagaku Kenkyusho is used for forming through holes in printed wiring boards.
603D 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), boron oxide (25% by weight). And 7.5 parts by weight of a metal oxide composed of alumina (5% by weight). The silver particles had an average particle size of 4.5 μm and were flaky.

(5) Next, the heater plate 11 on which the conductor paste is printed is heated and baked at 780 ° C. to sinter silver and lead in the conductor paste and bake on the heater plate 11.
The heating element 12 was formed. The silver-lead heating element 12 had a thickness of 5 μm, a width of 2.4 mm, and an area resistivity of 7.7 mΩ / □.

(6) In an electroless nickel plating bath consisting of an aqueous solution having a concentration of 80 g / l of nickel sulfate, 24 g / l of sodium hypophosphite, 12 g / l of sodium acetate, 8 g / l of boric acid and 6 g / l of ammonium chloride. The heater plate 11 prepared in (5) was dipped to deposit a metal coating layer (nickel layer) having a thickness of 1 μm on the surface of the silver-lead heating element 12.

(7) A silver-lead solder paste (manufactured by Tanaka Kikinzoku Co., Ltd.) was printed by screen printing on a portion to which a terminal for securing a connection with a power source was attached to form a solder layer. Next, the Kovar-made terminal pin 13 was placed on the solder layer, and heated at 420 ° C. for tafro to attach the terminal pin 13 to the surface of the heating element 12.

(8) A thermocouple for temperature control is 81.7A.
u-18.3Ni gold brazing was used for connection (heating at 1030 ° C. for fusion) to obtain a ceramic heater 10.

Example 2 Production of Ceramic Heater Made of Silicon Carbide Silicon carbide having an average particle size of 1.0 μm was used, the sintering temperature was set to 1900 ° C., and the surface of the heater plate obtained was changed to 15 μm.
A ceramic heater made of silicon carbide was manufactured in the same manner as in Example 1 except that a SiO ₂ layer having a thickness of 1 μm was formed on the surface by firing at 00 ° C. for 2 hours.

Example 3 Production of Ceramic Heater Having Heating Element Inside (1) Aluminum Nitride Powder (Made by Tokuyama Corp. Average Particle Size:
1.1 μm) 100 parts by weight, yttria (average particle size:
0.4 μm) 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 an alcohol consisting of 1-butanol and ethanol are used to form a paste by a doctor blading method. Thus, a green sheet having a thickness of 0.47 mm was obtained.

(2) Next, this green sheet was dried at 80 ° C. for 5 hours and punched to a diameter of 1.8 m.
m, 3.0 mm, 5.0 mm, through-holes 15 for inserting silicon wafer support pins, and through-holes for connecting with terminal pins were provided.

(3) A conductor was prepared by mixing 100 parts by weight of tungsten carbide particles having an average particle diameter 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. Paste A was prepared.

Tungsten particles 10 having an average particle diameter of 3 μm
A conductor paste B was prepared by mixing 0 part by weight, 1.9 parts by weight of an acrylic binder, 3.7 parts by weight of an α-terpineol solvent and 0.2 part by weight of a dispersant. This conductive paste A was printed on the green sheet by screen printing to form a conductive paste layer. The printing pattern was a concentric circle pattern as shown in FIG. Further, the through holes for through holes for connecting the terminal pins were filled with the conductor paste B. 37 green sheets on the upper side (heating surface), 13 sheets on the lower side, 130 ° C.
Lamination was performed at a pressure of 80 kg / cm ² .

(4) Next, the obtained laminated body was placed in a nitrogen gas,
Degreasing at 600 ℃ for 5 hours, 1890 ℃, pressure 150kg
/ Cm ² was hot-pressed for 3 hours to obtain an aluminum nitride plate-shaped body having a thickness of 3 mm. This was cut into a 230 mm disk shape to obtain a ceramic heater having a heating element with a thickness of 6 μm and a width of 10 mm inside.

(5) Next, after polishing the plate-like body obtained in (4) with a diamond grindstone, a mask is placed and a bottomed hole for a thermocouple is formed on the surface by blasting with SiC or the like. (Diameter: 1.2 mm, depth: 2.0 mm).

(6) Furthermore, a part of the through hole for the through hole is cut out to form a recess, and a gold brazing material made of Ni-Au is used in the recess, and reflowing is performed at 700 ° C. by reflowing the terminal pin made of Kovar. I was connected. The connection of the terminal pins is preferably a structure in which a tungsten support body supports at three points. This is because connection reliability can be secured. (8) Next, a plurality of thermocouples for temperature control were embedded in the bottomed holes to complete the production of the ceramic heater.

(Example 4) Temperature Control of Ceramic Heater (1) A temperature controller (E5ZE made by OMRON) equipped with a control unit having a power supply, a storage unit and a calculation unit was prepared, and the ceramic produced in Example 1 was prepared. Wiring from the control unit was connected to the heater 10 (see FIG. 1) via the terminal pins 13, and the silicon wafer was placed on the ceramic heater 10.

(2) Next, a voltage is applied to the ceramic heater 10 to once raise the temperature to 200 ° C., and further to 200 to 400 ° C., and the bottomed hole 14 shown in FIG.
The temperature was measured with the thermocouple installed in a-14c.
The measurement results are shown in FIG. In addition, the heating elements 12a, 12
The profile of the electric power (expressed by a current value) applied to b and 12c is shown in FIG. In FIG. 4, the vertical axis represents temperature and the horizontal axis represents elapsed time. In FIG. 5, the vertical axis represents current and the horizontal axis represents elapsed time. The silicon wafer placed on the ceramic heater 10 was uniformly heated without being damaged during the heating process.

[0105]

As described above, according to the ceramic heaters of the first and second aspects of the present invention, the temperature of the object to be heated can be accurately measured, and the heat generated by the heating element is generated based on the temperature measurement result. By adjusting the state, the entire silicon wafer can be heated uniformly.

[Brief description of drawings]

FIG. 1 is a bottom view schematically showing an example of a ceramic heater of the first present invention.

FIG. 2A is a block diagram schematically showing an example of the ceramic heater according to the second aspect of the present invention, and FIG. 2B is a partially enlarged sectional view thereof.

FIG. 3A is a block diagram schematically showing another example of the ceramic heater according to the second aspect of the present invention.

FIG. 4 is a graph showing a temperature profile of a ceramic heater according to Example 4.

FIG. 5 is a graph showing a power profile of a ceramic heater according to a fourth embodiment.

[Explanation of symbols]

10, 20, 40 Ceramic heater 11, 21, 41 heater plate 12, 22, 42 heating element 13, 23, 43 terminal pins 14, 24, 44 bottomed holes 15, 25, 45 through holes 19 Silicon wafer 21a, 41a Heating surface 21b, 41b bottom surface 26,46 Support pin 27, 47 thermocouple 28 through holes 29, 49 Control unit 30,50 Storage 31, 51 Operation unit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H05B 3/74 H01L 21/30 566 (72) Inventor Yasuji Hiramatsu 1-1 Ibide Kitakata, Ibikawa-cho, Ibi-gun, Gifu Prefecture In-house F-term (reference) 3K034 AA02 AA04 AA10 AA16 AA21 AA34 BB06 BC03 BC04 BC12 DA04 DA05 HA04 HA10 JA10 3K058 AA22 AA86 BA19 CA12 CA23 CA51 CA61 CA69 CA92 3K092 PP09 QA05 QB02 QB30 VB22 RF17 RF22 RF17 QV22 5F046 KA04

Claims (7)

[Claims] 1. A ceramic heater having a heating element formed on the surface or inside of a ceramic plate, wherein a bottomed hole is provided from the side opposite to the heating surface for heating an object to be heated toward the heating surface, and the bottomed hole is provided. A ceramic heater characterized in that the bottom of the hole is formed relatively closer to the heating surface than the heating element, and a temperature measuring element is provided in this bottomed hole. 2. The distance between the bottom of the bottomed hole and the heating surface is
The ceramic heater according to claim 1, which has a thickness of 0.1 mm to 1/2 of the thickness of the ceramic plate. 3. The ceramic heater according to claim 1, wherein the ceramic constituting the ceramic heater is a nitride ceramic or a carbide ceramic. 4. The ceramic heater according to claim 1, wherein the heating element is divided into at least two circuits. 5. The ceramic heater according to claim 1, wherein the heating element has a flat cross section. 6. A heating element is formed on the surface or inside of the ceramic plate, and a temperature measuring element for measuring the temperature of the ceramic plate, a controller for supplying electric power to the heating element, and the temperature measuring element are used. A ceramic heater comprising: a storage unit that stores measured temperature data; and a calculation unit that calculates electric power required for the heating element from the temperature data, wherein a heating surface for heating an object to be heated is provided on the ceramic plate. A bottomed hole is provided from the opposite side to the heating surface, and the bottom of the bottomed hole is formed relatively closer to the heating surface than the heating element, and the temperature measuring element is provided in the bottomed hole. Ceramic heater characterized by. 7. The ceramic heater according to claim 6, wherein the heating element is divided into at least two or more circuits, and different powers are supplied to the respective circuits.