JP2004303736A - Ceramic heater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ceramic heater, preventing a short circuit of a resistance heater, while functioning excellently for heating a silicon wafer. <P>SOLUTION: The ceramic heater has an insulating layer on at least part of the surface of a ceramic substrate, having a volume resistivity higher than the ceramic substrate, and the resistance heater is formed on the insulation layer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a ceramic heater mainly used in the semiconductor industry, and particularly to a ceramic heater having excellent insulation between circuits of a resistance heating element.

Semiconductor products are extremely important products required in various industries, a typical product is a semiconductor chip, for example, after slicing a silicon single crystal to a predetermined thickness to produce a silicon wafer, It is manufactured by forming various integrated circuits and the like on this silicon wafer.

In order to form such an integrated circuit or the like, a process of applying a photosensitive resin on a silicon wafer, exposing and developing the same, and post-curing or forming a conductor layer by sputtering is necessary. . For this purpose, it is necessary to heat the silicon wafer.

As a heater for heating the silicon wafer or the like, a ceramic heater is used, and a heater using a carbide ceramic or a nitride ceramic is disclosed (for example, see Patent Document 1).

JP-A-11-40330

However, carbide ceramics usually contain impurities, sintering aids, and the like, and as a result, carbide ceramics often have conductivity. For this reason, even if a resistance heating element is provided on the surface of such a conductive carbide ceramic, the circuits are short-circuited and the temperature cannot be controlled.

Therefore, in order to produce a non-conductive carbide ceramic, an expensive high-purity carbide ceramic must be used, and a sintering aid must be selected. In addition, conductive ceramics often have high thermal conductivity at the same time, but even if a circuit is formed on such ceramics, they will be short-circuited and cannot be used as a ceramic substrate as it is.

Furthermore, ceramics made of insulating nitride and the like at room temperature also have defects such as solid solution oxygen, which lowers the volume resistivity at high temperatures and short-circuits between circuits, thus controlling temperature. There was a problem that it could not be done, and there was still room for improvement.

On the other hand, in particular, when the ceramic substrate and the semiconductor wafer are heated while being separated from each other, even when the temperature of the ceramic substrate surface is made uniform, the phenomenon that the temperature of the semiconductor wafer becomes non-uniform has been observed. Was expected.

The present inventors have conducted intensive studies to solve the above-described problems, and as a result, by providing an insulating layer having a higher volume resistivity than the ceramic substrate on one surface of the ceramic substrate and forming a resistance heating element thereon. It has been found that a short circuit of the resistance heating element can be prevented, and that the presence of the insulating layer also eliminates the non-uniformity of the temperature of the semiconductor wafer, thereby completing the present invention.

That is, in the ceramic heater according to the first aspect of the present invention, an insulating layer having a higher volume resistivity than the ceramic substrate is formed on at least a part of the surface of the ceramic substrate, and a resistance heating element is formed on the insulating layer. Are formed.

In the ceramic heater according to the first aspect of the present invention, since the resistance heating element is formed on the insulating layer, even if the ceramic substrate itself is conductive, the resistance heating element does not short-circuit, Works well as

In addition, even when the ceramic substrate has a low volume resistivity at a high temperature, since the volume resistivity of the insulating layer is higher than that of the ceramic substrate in the operating temperature range, it is possible to prevent a short circuit of the resistance heating element. Can be.

Further, in the present invention, it is not necessary to use particularly expensive ceramics, and even a conductive ceramic having a high thermal conductivity can be used as a heater.

In the ceramic heater according to the first aspect of the present invention, it is preferable that the ceramic substrate is made of a carbide ceramic or a nitride ceramic, and the insulating layer is made of an oxide ceramic.

Nitride ceramics have a tendency to decrease in volume resistance at high temperatures due to oxygen solid solution and the like.Carbide ceramics have conductivity unless particularly highly purified. You cannot form a body. Therefore, in the present invention, by forming an insulating layer made of an oxide ceramic on the surface of a ceramic substrate made of such a material, a short circuit between circuits can be prevented, and the circuit can function as a heater.

The opposite side of the ceramic substrate on which the resistance heating element is formed is preferably a heating surface.
In the present invention, since the opposite side of the surface on which the resistance heating element is formed can be used as the heating surface, heat propagates while diffusing from the surface on which the resistance heating element is formed to the heating surface, and the heating surface has resistance heating. Temperature distribution close to the body pattern is unlikely to occur.

The thickness of the insulating layer is desirably 0.1 to 1000 μm.
If the thickness of the insulating layer is less than 0.1 μm, insulation cannot be ensured. On the other hand, if the thickness of the insulating layer exceeds 1000 μm, heat transfer from the resistance heating element to the ceramic substrate will not be ensured. This is because it will hinder.

It is desirable that the volume resistivity of the insulating layer is 10 times or more (however, the same measurement temperature) as the volume resistivity of the ceramic substrate.
If the ratio is less than 10 times, it is not possible to prevent the short circuit of the circuit of the resistance heating element. It is desirable that the volume resistivity of the insulating layer is 10 ⁶ to 10 ¹⁸ Ω · cm at 25 ° C. If the temperature is less than 10 ⁶ Ω · cm at 25 ° C., it does not function as an insulating layer when the temperature rises, and a ceramic layer having a volume resistivity exceeding 10 ¹⁸ Ω · cm has poor thermal conductivity. .
For example, at 400 ° C., the volume resistivity of aluminum nitride is 10 ⁹ Ω · cm, and at the same temperature, the volume resistivity of alumina is 10 ¹⁰ Ω · cm. At 25 ° C., the volume resistivity of silicon carbide is 10 ³ Ω · cm, and at the same temperature, the volume resistivity of silica is 10 ¹⁴ Ω · cm.

A ceramic heater according to a second aspect of the present invention is a ceramic heater in which a resistance heating element is formed on a surface of a ceramic substrate, wherein the ceramic substrate is warped in one direction. is there.

Here, being warped in one direction means not only that the curved surface is formed in one direction without undulation, but also one that undulates in one direction while undulating within a range that does not impair the effects of the present invention. included. The amount of undulation is desirably within 50% of the amount of warpage. The measurement of warpage and undulation is performed by a shape measuring instrument (for example, Kyocera Nanoway).

FIG. 7 is a graph schematically showing the relationship between the horizontal position and the vertical position of the surface of the ceramic substrate which is warped in one direction while undulating, and the X axis indicates the horizontal position. , Y axis represent the vertical position. As shown in FIG. 7, a virtual plane is calculated from the curve of the measured data, and the difference (Y ₁ + Y ₂ ) between the maximum value Y ₁ and the minimum value Y ₂ with respect to this virtual plane is the amount of warpage. Further, from the measurement data, the maximum point of the data obtained by subtracting the warp components YW ₁ and the minimum value YW ₂ is waviness (see FIG. 8). The measurement range is the length of the outer peripheral end of the ceramic substrate (diameter for a disk) −10 mm. Within this range, in the present invention, a warpage amount of 10 to 100 μm is preferable.

In the ceramic heater according to the second aspect of the present invention, the ceramic substrate can be warped in one direction, for example, by forming an insulating layer on one surface, whereby the semiconductor wafer is heated at a predetermined distance from the ceramic substrate. In this case, the distance between the semiconductor wafer and the ceramic substrate can be easily grasped, and the surface temperature of the semiconductor wafer can be made uniform by controlling the temperature accordingly.

The ceramic substrate has undulations. If the semiconductor wafer is heated at a certain distance from the ceramic substrate and heated, the undulations change the distance between the semiconductor wafer and the ceramic substrate depending on the location and the temperature of the semiconductor wafer becomes uneven. Become.
However, according to the present invention, since the ceramic substrate is warped in one direction, irregular waviness can be eliminated, so that temperature control becomes easy and the surface temperature of the semiconductor wafer can be made uniform.

In the ceramic heater according to the second aspect of the present invention, the amount of warpage of the ceramic substrate is desirably 10 to 100 μm.

If the amount of warpage is less than 10 μm, undulation cannot be eliminated, while if the amount of warpage exceeds 100 μm, it becomes difficult to make the temperature of the semiconductor wafer uniform. This warpage is preferably convex on the side of the heating surface (the surface on which the resistance heating element is not formed). In this case, the distance between the semiconductor wafer and the ceramic substrate increases as the distance to the outer peripheral portion of the semiconductor wafer increases, but the outer peripheral portion is originally set so that the temperature tends to decrease and the amount of heat generated by the resistance heating element is increased. Therefore, the existing control algorithm can be applied as it is.

In the ceramic heater according to the first aspect of the present invention, the insulating layer is formed on the surface of the ceramic substrate, and the resistance heating element is formed on the insulation layer. It can function well as a heater.

Further, in the ceramic heater according to the second aspect of the present invention, since the ceramic substrate is warped in one direction, when the semiconductor wafer is heated with a certain distance from the ceramic substrate, the distance between the semiconductor wafer and the ceramic substrate is grasped. The surface temperature of the semiconductor wafer can be made uniform by controlling the temperature based on this.

The ceramic heater according to the first aspect of the present invention includes an insulating layer having a higher volume resistivity than the ceramic substrate is formed on at least a part of the surface of the ceramic substrate, and a resistance heating element is formed on the insulating layer. A ceramic heater characterized in that:

FIG. 1 is a bottom view schematically showing one embodiment of the ceramic heater of the first invention, and FIG. 2 is a partially enlarged sectional view of the ceramic heater shown in FIG.

As shown in FIGS. 1 and 2, the ceramic substrate 11 is formed in a disk shape, and an insulating layer 18 is formed on a bottom surface 11 b of the ceramic substrate 11. Is formed in a concentric pattern. The resistance heating elements 12 are connected such that double concentric circles close to each other form a single line as a set of circuits.

A coating layer 120 is provided on the surface of the resistance heating element 12 to prevent oxidation or the like of the resistance heating element 12, and the resistance heating element 12 on which the coating layer 120 is formed is interposed via a solder layer 17. Connected to the external terminal 13.

Further, a bottomed hole 14 is provided in the bottom surface 11b of the ceramic substrate 11 having the insulating layer 18, and a temperature measuring element (not shown) made of a thermocouple or the like is inserted into the bottomed hole 14 to provide heat resistance. It is sealed with an adhesive.

Further, a through hole 15 is provided in the ceramic substrate 11, and the silicon wafer 19 can be held by inserting a lifter pin 16 into the through hole 15 as shown in FIG. 2. By moving the lifter pins 16 up and down, the silicon wafer 19 is received from the transporter, the silicon wafer 19 is placed on the heating surface 11a of the ceramic substrate 11, and heated. It can be supported and heated in a state of being separated from the heating surface 11a by about 50 to 2000 μm.

Further, a through hole or a concave portion is provided in the ceramic substrate, and after inserting a support pin having a spire or a hemispherical tip into the through hole or the concave portion, the support pin is fixed in a state of slightly projecting from the ceramic substrate. By supporting the silicon wafer with the support pins, the silicon wafer can be supported and heated with a distance of about 50 to 2000 μm from the heating surface (see FIG. 5).

In the ceramic heater according to the first aspect of the present invention, as shown in FIG. 1, the resistance heating element 12 is preferably divided into at least two or more circuits. This is because, by dividing the circuit, the power supplied to each circuit can be changed, and the temperature of the heating surface 11a can be adjusted.

In the first aspect of the present invention, by forming an insulating layer on the bottom surface of the ceramic substrate and providing a resistance heating element on the insulating layer, the ceramic substrate itself has high conductivity at room temperature or has a high temperature. Even if the resistance decreases in the region, it can function as a heater.

FIG. 3 is a bottom view schematically showing another embodiment of the ceramic heater according to the first invention, and FIG. 4 is a partially enlarged sectional view of the ceramic heater shown in FIG.
In this ceramic heater 20, annular insulating layers 28a to 28c and a circular insulating layer 28d are provided on a bottom surface 21b of a ceramic substrate 21. A coating layer 220 is formed on the insulating layers 28a to 28d. Resistance heating elements 22a to 22f are formed, and an external terminal 23 is connected to an end thereof.
Except that the insulating layers 28a to 28d are provided on a part of the bottom surface 21b of the ceramic substrate 21, the configuration is the same as that of the ceramic heater shown in FIGS.

Also in the ceramic heater shown in FIGS. 3 and 4, short circuits between the circuits of the resistance heating element can be prevented, and the ceramic heater can function well.

Next, the ceramic substrate constituting the ceramic heater of the first aspect of the present invention will be described in more detail.
Examples of the nitride ceramic constituting the ceramic substrate include metal nitride ceramics, for example, aluminum nitride, silicon nitride, boron nitride, and the like.
Examples of the carbide ceramic include metal carbide ceramics such as silicon carbide, zirconium carbide, tantalum carbide, and tungsten carbide.

In the present invention, it is desirable that the ceramic substrate contains a sintering aid. For example, as a sintering aid for aluminum nitride, an alkali metal oxide, an alkaline earth metal oxide, a rare earth oxide, or the like can be used.

Among these sintering aids, for _{example, CaO, Y 2 O 3,} Na 2 O, Li 2 O, Rb 2 O , and the like are preferable. The content of these sintering aids is preferably 0.1 to 20% by weight.
When the ceramic substrate is made of silicon carbide, examples of the sintering aid include B, C, and AlN.

Examples of the oxide ceramic used as the insulating layer in the present invention include silica, alumina, mullite, cordierite, and beryllia.
These ceramics may be used alone or in combination of two or more.
Use of an oxide ceramic is advantageous because the resistance heating element is easily fixed.

Examples of a method for forming an insulating layer made of these materials include, for example, a method in which a sol solution obtained by hydrolyzing an alkoxide is used, a coating layer is formed on the surface of a ceramic substrate by spin coating or the like, followed by drying and firing, and a sputtering method. , CVD method and the like. As a method for forming the insulating layer on a part of the surface of the ceramic substrate, screen printing or the like can be given. Alternatively, a glass powder paste may be applied and fired at 500 to 1000 ° C.

In the present invention, it is desirable that the ceramic substrate contains 5 to 5000 ppm of carbon.
By containing carbon, the ceramic substrate can be blackened, and radiant heat can be sufficiently utilized when used as a heater.
The carbon may be amorphous or crystalline. When amorphous carbon is used, a decrease in volume resistivity at a high temperature can be prevented, and when a crystalline material is used, a decrease in thermal conductivity at a high temperature can be prevented. Because. Therefore, depending on the application, both crystalline carbon and amorphous carbon may be used in combination. Further, the content of carbon is more preferably 50 to 2000 ppm.

When carbon is contained in the ceramic substrate, it is desirable that carbon be contained so that its brightness is N4 or less as a value based on the provisions of JIS Z 8721. This is because a material having such a lightness is excellent in radiant heat and concealing property.

Here, N of lightness is 0 for ideal black lightness and 10 for ideal white lightness, and between these black lightness and white lightness, the perception of the lightness of the color is Each color is divided into 10 so as to have a uniform rate, and displayed by symbols N0 to N10.
The actual measurement of lightness is performed by comparing with color patches corresponding to N0 to N10. In this case, the first decimal place is 0 or 5.

The thickness of the ceramic substrate of the present invention is desirably 10 mm or less, and more desirably 5 mm or less.
This is because if the thickness of the ceramic substrate exceeds 10 mm, the heat capacity of the ceramic substrate increases, and the temperature followability of the ceramic substrate decreases. Note that the thickness of the ceramic substrate is desirably a value exceeding 1.5 mm.

The diameter of the ceramic substrate is preferably 200 mm or more, and more preferably 12 inches (300 mm) or more. This is because silicon wafers having a large diameter, for example, 12 inches or more, will be the mainstream of next-generation semiconductor wafers.

The ceramic heater of the present invention is desirably used at 100 ° C. or higher, and most preferably at 200 ° C. or higher.

The resistance heating element is preferably made of a metal such as a noble metal (gold, silver, platinum, palladium), lead, tungsten, molybdenum, nickel, or a conductive ceramic such as a carbide of tungsten or molybdenum. This is because the resistance value can be increased, the thickness itself can be increased for the purpose of preventing disconnection and the like, and it is hard to be oxidized and the thermal conductivity does not easily decrease. These may be used alone or in combination of two or more.

Since the resistance heating element needs to make the temperature of the entire ceramic substrate uniform, it is preferable to use a concentric pattern as shown in FIG. 1 or a combination of a concentric pattern and a bent line pattern. . The thickness of the resistance heating element is preferably 1 to 50 μm, and the width thereof is preferably 5 to 20 mm.

The resistance value can be changed by changing the thickness or width of the resistance heating element, but the above range is the most practical. The resistance value of the resistance heating element becomes thinner and becomes larger as it becomes thinner.

The cross section of the resistance heating element may be any one of a square, an ellipse, a spindle shape, and a semi-cylindrical shape. This is because the flattened surface is easier to radiate heat toward the heating surface, so that the amount of heat propagation to the heating surface can be increased, and the temperature distribution on the heating surface is difficult to achieve. The resistance heating element may have a spiral shape.

In order to form a resistance heating element on the insulating layer, it is preferable to use a conductive paste containing metal or conductive ceramic.
That is, when forming a resistance heating element on an insulating layer formed on a ceramic substrate, usually, firing is performed to produce a ceramic substrate, then an insulating layer is formed on the bottom surface, and then the conductor is formed on the surface. A resistance heating element is formed by forming a paste layer and firing the paste layer.

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

Examples of the material of the metal particles and the conductive ceramic particles include those described above. The metal particles or the conductive ceramic particles preferably have a particle size of 0.1 to 100 μm. If it is too fine, less than 0.1 μm, it is liable to be oxidized, while if it exceeds 100 μm, sintering becomes difficult and the resistance value becomes large.

The shape of the metal particles may be spherical or scaly. 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 or a mixture of spherical and scaly, it is easy to hold the metal oxide between the metal particles and ensure the adhesion between the resistance heating element and the insulating layer. And the resistance value can be increased.

Examples of the resin used for the conductor paste include an acrylic resin, an epoxy resin, and a phenol resin. Examples of the solvent include isopropyl alcohol and the like. Examples of the thickener include cellulose and the like.

When forming a conductor paste for a resistance heating element on the insulating layer, a metal oxide was added to the conductor paste in addition to the metal particles, and the metal particles and the metal oxide were sintered. It is preferable that Thus, by sintering the metal oxide together with the metal particles, the insulating layer and the metal particles can be more closely adhered.

It is not clear why mixing the above metal oxide improves the adhesion with the insulating layer, but the surface of the metal particles is slightly oxidized to form an oxide film. It is conceivable that the metal particles and the ceramic may adhere to each other via the oxide and the oxide of the insulating layer via the oxide.

As the metal oxide, for example, at least one selected from the group consisting of lead oxide, zinc oxide, silica, boron oxide (B ₂ O ₃ ), alumina, yttria, and titania is preferable.
This is because these oxides can improve the adhesion between the metal particles and the ceramic substrate without increasing the resistance value of the resistance heating element.

The ratio of the lead oxide, zinc oxide, silica, boron oxide (B ₂ O ₃ ), alumina, yttria, and titania is such that the lead oxide is 1 to 10 by weight when the total amount of the metal oxide is 100 parts by weight. , Silica is 1 to 30, boron oxide is 5 to 50, zinc oxide is 20 to 70, alumina is 1 to 10, yttria is 1 to 50, titania is 1 to 50, and the total exceeds 100 parts by weight. It is preferred that the adjustment be made within a range that does not exist.
By adjusting the amounts of these oxides in these ranges, the adhesion to the ceramic substrate 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. Further, the area resistivity when the resistance heating element is formed using the conductor paste having such a configuration is preferably 1 to 45 mΩ / □.

If the area resistivity exceeds 45 mΩ / □, the amount of heat generated is too large with respect to the applied voltage, and it is difficult to control the amount of heat generated in a ceramic substrate for a semiconductor device having a resistance heating element on the surface. . 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 insulating layer, a metal coating layer is preferably 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 from 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 include gold, silver, palladium, platinum, and nickel. These may be used alone or in combination of two or more. Of these, nickel is preferred.
When the resistance heating element is formed inside the ceramic substrate, the surface is not oxidized, and thus no coating is required.

In the present invention, as shown in FIG. 1, a bottomed hole 14 is provided on the bottom surface of the ceramic substrate, a temperature measuring element is inserted and fixed in the bottomed hole 14, and the temperature of the ceramic substrate is measured. It is desirable to control the temperature of the ceramic substrate by using the above method.

The temperature measuring element to be used is not particularly limited, and examples thereof include a thermocouple. The size of the junction between the thermocouple and the wiring is preferably equal to or larger than the wire diameter of each wiring and 0.5 mm or less. With such a configuration, the heat capacity of the junction is reduced, and the temperature is accurately and quickly converted to a current value. For this reason, the temperature controllability is improved, and the temperature distribution on the heated surface of the wafer is reduced.
Examples of the thermocouple include K-type, R-type, B-type, S-type, E-type, J-type, and T-type thermocouples as described in JIS-C-1602 (1980).

The temperature measuring element may be adhered to the bottom of the bottomed hole 14 using gold brazing, silver brazing, or the like. After the temperature measuring element is inserted into the bottomed hole 14, it is sealed with a heat-resistant resin or the like. The above two methods may be used in combination.

Examples of the heat-resistant resin include a thermosetting resin. Among the thermosetting resins, an epoxy resin, a polyimide resin, a bismaleimide-triazine resin, and the like are preferable. These heat-resistant resins may be used alone or in combination of two or more.

Examples of the gold solder include an alloy composed of 37 to 80.5% by weight of Au and 63 to 19.5% by weight of Cu, and 81.5 to 82.5% by weight of Au and 18.5 to 17%. An alloy composed of 5% by weight of Ni and the like can be mentioned. These have a melting temperature of 900 ° C. or higher and are difficult to melt even in a high temperature region.
As the silver solder, for example, an Ag-Cu-based solder can be used.

As described above, the first ceramic heater has been described. However, when the ceramic substrate itself has a relatively large volume resistivity and a short circuit of an electrode or the like provided therein is unlikely to occur, a resistance heating element is provided on the surface of the ceramic substrate. In addition, an electrostatic chuck may be provided by providing an electrostatic electrode inside the ceramic substrate.

Also, a wafer prober may be provided by providing a resistance heating element on the surface of the ceramic substrate, providing a chuck top conductor layer on the surface of the ceramic substrate, and providing a guard electrode or a ground electrode inside the ceramic substrate.

Next, an example of a method for manufacturing the ceramic heater of the present invention will be described with reference to FIG.
6A to 6D are cross-sectional views schematically showing a method for manufacturing a ceramic heater having a resistance heating element on an insulating layer formed on the bottom surface of a ceramic substrate.

(1) Step of preparing ceramic substrate A slurry is prepared by blending sintering aids such as yttria and boron and a binder as necessary with ceramic powder such as aluminum nitride and silicon carbide, and then spray drying the slurry. The granules are put into a mold or the like and pressed into a plate to form a green body. At the time of preparing the slurry, amorphous or crystalline carbon may be added.

Next, the formed body is heated, fired and sintered to produce a ceramic plate, and then processed into a predetermined shape to produce a ceramic substrate 11, which is used as it is after firing. It is good also as a shape which can be used. By performing heating and firing while applying pressure, it is possible to manufacture a ceramic substrate 11 having no pores. Heating and firing may be performed at a temperature equal to or higher than the sintering temperature.

Next, for example, a solution such as an alumina sol or a silica sol prepared by hydrolyzing an alkoxide is applied to the bottom surface 11b of the ceramic substrate 11 by spin coating, followed by drying and baking to form the insulating layer 18. The insulating layer 18 may be formed by a sputtering method or a CVD method, or the surface may be oxidized by heating the ceramic substrate in an oxidizing atmosphere to form the insulating layer 18 (FIG. 6A).

Next, a through hole 15 for inserting a lifter pin for supporting the silicon wafer and a bottomed hole 14 for embedding a temperature measuring element such as a thermocouple are formed in the ceramic substrate as necessary.

(2) Step of Printing Conductive Paste on Insulating Layer Formed on Ceramic Substrate Conductive paste is generally a high-viscosity fluid composed of metal particles, resin and solvent. This 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. In addition, since the resistance heating element needs to have a uniform temperature over the entire ceramic substrate, it is preferable that the resistance heating element be printed, for example, in a concentric shape or in a pattern combining a concentric shape and a bent line shape. .
The conductive paste layer is preferably formed such that the cross section of the resistance heating element 12 after firing has a rectangular and flat shape.

(3) Firing of the conductive paste The conductive paste layer printed on the insulating layer on the bottom surface of the ceramic substrate 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 ceramic substrate 11. The resistance heating element 12 is formed (FIG. 6B). The temperature of the heating and firing is preferably from 500 to 1000C.

If the above-mentioned 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 insulating layer is improved.

(4) Formation of Coating Layer It is desirable to provide a coating layer 120 on the surface of the resistance heating element 12.
The coating layer 120 can be formed by electrolytic plating, electroless plating, sputtering, or the like. However, considering mass productivity, electroless plating is optimal (FIG. 6C).

(5) Attachment of terminals and the like An external terminal 13 for connection to a power supply is connected to an end of the circuit of the resistance heating element 12 via a solder layer 17 made of tin-lead solder (FIG. 6D). . The connection may be made using a gold solder or a silver solder. Also, a thermocouple (not shown) is inserted into the bottomed hole 14 and sealed with a heat-resistant resin such as polyimide or ceramic, and the manufacture of the ceramic heater 10 is completed.

If the ceramic substrate constituting the ceramic heater has a relatively large volume resistivity and short-circuiting of electrodes and the like is unlikely to occur, when manufacturing the ceramic heater, an electrostatic electrode is provided inside the ceramic substrate. An electrostatic chuck can be manufactured, and a wafer prober can be manufactured by providing a chuck top conductor layer on a heating surface and providing a guard electrode and a ground electrode inside a ceramic substrate.

In the method for manufacturing a ceramic substrate, the ceramic substrate is manufactured using granules containing the ceramic powder, but a green sheet is prepared using the ceramic powder, a binder, a solvent, and the like, and the green sheet is laminated to form a ceramic substrate. May be manufactured. When an electrode or the like is provided inside, the electrode or the like can be formed relatively easily by this method.

Next, the ceramic heater according to the second aspect of the present invention will be described.
A ceramic heater according to a second aspect of the present invention is a ceramic heater in which a resistance heating element is formed on the surface of a ceramic substrate, wherein the ceramic substrate is warped in one direction.

As described above, the warpage of the ceramic substrate in one direction makes it easier to grasp the distance between the semiconductor wafer and the ceramic substrate when the semiconductor wafer is heated at a predetermined distance from the ceramic substrate, and the surface temperature of the semiconductor wafer becomes higher. Can be made uniform.

The method of warping the ceramic substrate in one direction is not particularly limited. For example, a layer (metal layer) having a different coefficient of thermal expansion from that of the ceramic substrate may be provided at a certain depth from a heating surface inside the ceramic substrate. , A ceramic layer, etc.), a method of providing an insulating layer on the bottom surface as in the above-described ceramic heater of the first invention, and the like.

In the ceramic heater of the second invention, for example, similarly to the first invention, an insulating layer is provided on the bottom surface of the ceramic substrate, and a resistance heating element is provided on the insulating layer, or A layer made of a material different from that of the ceramic substrate is provided inside the ceramic substrate. When a layer made of a material different from that of the ceramic substrate is provided inside the ceramic substrate, other portions are configured in the same manner as in the case of the ceramic heater of the first present invention.

The method of providing the insulating layer on the bottom surface has been described in the first invention, and will not be described. In addition, when forming a layer of another material inside the ceramic substrate, it is sufficient to put a metal foil or the like when the granules are put into the molding die, and when producing a molded body by laminating green sheets. May be formed by forming a paste layer containing a powder of such a material on a green sheet.
The configuration of the other parts of the ceramic substrate is the same as that of the first embodiment of the present invention, and the description thereof will be omitted here.

Also in the second invention, an electrostatic chuck can be obtained by providing an electrostatic electrode inside the ceramic substrate, a chuck top conductor layer is provided on the heating surface, and a guard electrode or ground is provided inside the ceramic substrate. By providing the electrodes, a wafer prober can be obtained.

Hereinafter, the present invention will be described in more detail.
(Example 1) Production of a ceramic heater made of silicon carbide (1) 100 parts by weight of silicon carbide powder (average particle size: 0.3 μm), B ₄ C (average particle size: 0.5 μm) as a sintering aid After mixing 4 parts by weight, 0.5 parts by weight of C (Mitsubishi Chemical Co., Mitsubishi Diamond Black), 12 parts by weight of an acrylic binder, 0.5 part by weight of a dispersant, and alcohol, the mixture was granulated using a spray drying method. A powder was made.

(2) Next, this granular powder was placed in a mold and formed into a flat plate to obtain a formed product (green).
(3) The formed body after the processing was hot-pressed at 2100 ° C. and a pressure of 17.6 (180 kg / cm ² ) MPa to obtain a silicon carbide ceramic substrate having a thickness of 3 mm.
Next, a disk-shaped body having a diameter of 210 mm was cut out from the surface of the plate-shaped body to obtain a ceramic substrate 11.

(4) Next, a mixture of 25 parts by weight of tetraethyl silicate, 37.6 parts by weight of ethanol, 0.3 part by weight of hydrochloric acid, and 23.5 parts by weight of water was added to the ceramic substrate 11 with stirring for 24 hours. The decomposed and polymerized sol solution is applied by a spin coating method, then dried at 80 ° C. for 5 hours, and baked at 1000 ° C. for 1 hour, so that the bottom surface of the ceramic substrate 11 made of silicon carbide has a thickness of 2 μm. An insulating layer 18 made of a SiO ₂ film was formed (FIG. 6A).

(5) Drilling was performed on the ceramic substrate 11 on which the insulating layer 18 was formed to form a through hole 15 for inserting a lifter pin of a silicon wafer and a bottomed hole 14 for embedding a thermocouple.

(6) After completion of the operation (5), a conductor paste was printed on the bottom surface of the ceramic substrate 11 having the insulating layer 18 by screen printing. The printing pattern was a concentric pattern as shown in FIG.
The 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 It contained 7.5 parts by weight of a metal oxide composed of alumina (5% by weight). The silver particles had a mean particle size of 4.5 μm and were scaly.

(7) Next, the ceramic substrate 11 on which the conductor paste is printed is heated and fired at 780 ° C. to sinter silver and lead in the conductor paste and to sinter the sintered body to form the resistance heating element 12 ( FIG. 6 (b)). The silver-lead resistance heating element 12 had a thickness of 5 μm, a width of 2.4 mm, and an area resistivity of 7.7 mΩ / □.
(8) Next, the above electroless nickel plating bath comprising an aqueous solution containing 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 was used. The ceramic substrate 11 prepared in 7) was immersed, and a coating layer 120 (nickel layer) having a thickness of 1 μm was deposited on the surface of the silver-lead resistance heating element (FIG. 6C).

(9) In order to secure the connection with the power supply, a silver-lead solder paste (manufactured by Tanaka Kikinzoku) was printed on the end of the resistance heating element 12 (circuit) by screen printing to form a solder paste layer.
Next, the external terminal 13 made of Kovar was placed on the solder paste layer, and heated and reflowed at 420 ° C., and the end of the resistance heating element 12 and the external terminal 13 were connected via the solder layer 17 ( FIG. 6D).

(8) Subsequently, a thermocouple for temperature control was inserted into the bottomed hole 14, and a ceramic adhesive (Aron Ceramic manufactured by Toagosei Co., Ltd.) was embedded and fixed to obtain a ceramic heater 10.

Example 2 Production of Silicon Ceramic Ceramic Heater Silicon carbide powder having an average particle size of 1.0 μm was used, the sintering temperature was 1900 ° C., and the surface of the obtained ceramic substrate was heated at 1500 ° C. for 2 hours. A silicon carbide ceramic heater was manufactured in the same manner as in Example 1 except that the surface was fired to form an insulating layer made of SiO ₂ having a thickness of 1 μm on the surface.

(Example 3) Production of a ceramic heater made of aluminum nitride (1) 100 parts by weight of aluminum nitride powder (average particle size: 0.6 μm), 4 parts by weight of yttria (Y ₂ O ₃ , average particle size: 0.4 μm), acrylic A composition comprising 12 parts by weight of a resin binder and alcohol was spray-dried to produce a granular powder.
(2) Next, this granular powder was placed in a mold and formed into a flat plate to obtain a formed product (green).
(3) The formed body after the processing was hot-pressed at a temperature of 1800 ° C. and a pressure of 200 kg / cm ² to obtain an aluminum nitride sintered body having a thickness of 3 mm.
Next, a disk having a diameter of 210 mm was cut out from the plate to obtain a ceramic substrate 11. The sol solution used in Example 1 was applied to the bottom surface of the ceramic substrate in the same manner as in Example 1, dried, and fired to form an insulating layer made of a ₂ μm thick SiO ₂ film.

Next, drilling was performed on the ceramic substrate 11 having the insulating layer to form a through hole for inserting a lifter pin and a bottomed hole (diameter: 1.1 mm, depth: 2 mm) for embedding a thermocouple.

(4) A conductor paste was printed on the bottom surface of the ceramic substrate 11 obtained in (3) by screen printing. The printing pattern was concentric as shown in FIG. As a conductive paste, Solvest PS603D manufactured by Tokuri Chemical Laboratory, which is used for forming through holes in a printed wiring board, 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.

(5) Next, the ceramic substrate 11 on which the conductor paste was printed was heated and baked at 780 ° C. to sinter silver and lead in the conductor paste and to sinter the sintered body to form the resistance heating element 12. The silver-lead resistance heating element 12 had a thickness of 5 μm, a width of 2.4 mm, and an area resistivity of 7.7 mΩ / □.
(6) Next, the above electroless nickel plating bath comprising an aqueous solution containing nickel sulfate 80 g / l, sodium hypophosphite 24 g / l, sodium acetate 12 g / l, boric acid 8 g / l, and ammonium chloride 6 g / l, The sintered body prepared in 5) was immersed to deposit a coating layer 120 (nickel layer) having a thickness of 1 μm on the surface of the silver-lead resistance heating element.

(7) In order to secure the connection with the power supply, a silver-lead solder paste (manufactured by Tanaka Kikinzoku) was printed by screen printing on the end of the resistance heating element 12 (circuit) to form a solder paste layer.
Then, an external terminal 13 made of Kovar was placed on the solder paste layer, and heated and reflowed at 420 ° C., and the end of the resistance heating element 12 and the external terminal 13 were connected via the solder layer 17.

(8) A thermocouple for temperature control was inserted into the bottomed hole 14, and a ceramic adhesive (Aron Ceramic manufactured by Toa Gosei Co., Ltd.) was embedded and fixed to obtain a ceramic heater.

(Comparative Example 1)
A ceramic heater was manufactured in the same manner as in Example 1, except that the insulating layer made of SiO ₂ was not provided on the bottom surface of the ceramic substrate.

For the ceramic heaters according to Examples 1 to 3 and Comparative Example 1 manufactured as described above, the distance (surface flatness) between the center and the outer periphery of the ceramic substrate was measured. The flatness was measured using a shape measuring instrument (Nanoway manufactured by Kyocera Corporation).

The temperature of the ceramic heaters according to Examples 1 and 2 was increased to 150 ° C., and the temperature of the ceramic heater according to Example 3 was increased to 400 ° C., and the resistance of an independent circuit was measured. The presence or absence of a short circuit was determined.

Further, for the ceramic heaters according to Examples 1 to 3 and Comparative Example 1, the temperature was raised to 400 ° C., and the difference between the maximum temperature and the minimum temperature of the silicon wafer was measured using a thermoviewer (IR-16-0012-0012, manufactured by Nippon Datum). Was measured.
After the temperature was raised to 400 ° C., the tape was cooled, and a tape test was conducted in which the tape was attached to a heating element and peeled off. Table 1 also shows the results.

As is clear from the results shown in Table 1, the maximum temperature of the ceramic substrate exists at the outer peripheral portion. The relationship between the ceramic substrate and the silicon wafer is as shown in FIG. 5, and the distance between the silicon wafer and the ceramic substrate increases toward the outer periphery. Therefore, if the temperature of the ceramic substrate in the outer peripheral portion is increased, the temperature of the entire silicon wafer can be made uniform.

It is a bottom view which shows an example of the ceramic heater of this invention typically. FIG. 2 is a partially enlarged sectional view of the ceramic heater shown in FIG. 1. It is a bottom view which shows another example of the ceramic heater of this invention typically. FIG. 4 is a partial enlarged sectional view of the ceramic heater shown in FIG. 3. It is a bottom view which shows another example of the ceramic heater of this invention typically. (A)-(d) is sectional drawing which shows typically a part of manufacturing process of a ceramic heater. 5 is a graph showing a positional relationship between a horizontal direction and a vertical direction of a surface of a ceramic substrate having waviness and warpage. 8 is a graph obtained by subtracting a warp component from measurement data in the graph shown in FIG. 7.

Explanation of reference numerals

10, 20, 30 Ceramic heaters 11, 21, 31 Ceramic substrates 11a, 21a, 31a Heating surfaces 11b, 21b, 31b Bottom surface 12 Resistance heating elements 120, 220 Coating layer 13 External terminals 14 Bottom hole 15 Through hole 16 Lifter pin 17 Solder layers 18, 28, 38 Insulating layer 19 Silicon wafer 32 Support pins

Claims (7)

A ceramic heater, wherein an insulating layer having a higher volume resistivity than the ceramic substrate is formed on at least a part of the surface of the ceramic substrate, and a resistance heating element is formed on the insulating layer. The ceramic heater according to claim 1, wherein the ceramic substrate is made of a carbide ceramic or a nitride ceramic, and the insulating layer is made of an oxide ceramic. The ceramic heater according to claim 1, wherein a side of the ceramic substrate opposite to a surface on which the resistance heating element is formed is a heating surface. The ceramic heater according to claim 1, wherein a thickness of the insulating layer is 0.1 to 1000 μm. The ceramic heater according to any one of claims 1 to 4, wherein a volume resistivity of the insulating layer is at least 10 times a volume resistivity of the ceramic substrate. What is claimed is: 1. A ceramic heater for a semiconductor manufacturing / inspection apparatus having a resistance heating element formed on a surface of a ceramic substrate, wherein the ceramic substrate is warped in one direction. The ceramic heater according to claim 6, wherein the amount of warpage of the ceramic substrate is 10 to 100 m.

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