JP2001135460A - Ceramic heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic heater which can uniformize the temperature on the heating surface of silicon wafer and can prevent the break of the silicon wafer. SOLUTION: This ceramic heater is characterized that a heater is arranged on the surface or the inside of the ceramic substrate, a temperature-measuring element which measures the temperature of this ceramic substrate, a control part which supplies power to the above heater, a memory which stores the temperature data measured by the temperature-measuring element and an operation part which computes necessary power to the heater from the above measured data are provided in the heater, and the above heater is divided into at least two or more circuits, to each of which different power is supplied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[Detailed description of the invention]

[0002]

2. Description of the Related Art Semiconductor products are manufactured through a process in which a photosensitive resin is formed on a silicon wafer as an etching resist and the silicon wafer is etched. This photosensitive resin is liquid and is applied to the silicon wafer surface using a spin coater, etc., but must be dried after application, and the applied silicon wafer must 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.

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

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

Therefore, as proposed in Japanese Patent Publication No. 8-8247 and the like, there has been proposed a technique of using a nitride ceramic having a heating element and controlling the temperature while measuring the temperature in the vicinity of the heating element. Have been.

[0006]

However, when attempting to heat a silicon wafer using such a technique, the degree of cure of the cured resin on the silicon wafer becomes non-uniform or the temperature difference on the heater surface is reduced. There has been a problem that the silicon wafer is damaged by the resulting thermal shock.

Accordingly, the present inventors have found that the degree of curing of the cured resin on the silicon wafer becomes non-uniform,
As a result of diligent research into the cause of silicon wafer breakage, despite the fact that temperature control is being performed, the reason that such a problem occurs is that even with a single temperature control, the heating surface is uniform. The inventors have found out that the temperature is not increased, and a temperature difference occurs depending on the location of the silicon wafer. The inventors have also newly found that such non-uniform temperature is more remarkable in nitride ceramics and carbide ceramics having higher thermal conductivity.

[0008]

Accordingly, the present inventors have further studied and divided the heating element into two or more circuits, and applied different electric power to each circuit based on the result of the temperature measurement to obtain the temperature. It has been found that by performing control and heating, it is possible to reduce the temperature difference between the heating surface of the silicon wafer (hereinafter, referred to as a wafer heating surface) and to prevent breakage. The present invention has been completed.

That is, a ceramic heater according to the present invention has a heating element formed on the surface or inside of a ceramic substrate, a temperature measuring element for measuring the temperature of the ceramic substrate, and a control section for supplying power to the heating element. And a storage unit for storing temperature data measured by the temperature measuring element, and a calculation unit for calculating the power required for the heating element from the temperature data, wherein the heating element is at least It is divided into two or more circuits, and each circuit is configured to be supplied with different power. In the ceramic heater, the ceramic substrate is preferably made of a nitride ceramic or a carbide ceramic.

[0010]

Next, a ceramic heater according to the present invention will be described. The ceramic heater according to the present invention has a heating element formed on the surface or inside of the ceramic substrate, a temperature measuring element for measuring the temperature of the ceramic substrate, a control unit for supplying power to the heating element, A storage unit for storing temperature data measured by the element; and a calculation unit for calculating power required for the heating element from the temperature data, wherein the heating element is divided into at least two or more circuits. Each circuit is configured to be supplied with different power.

According to the ceramic heater, the temperature can be controlled by changing the power supplied to the circuit of the heating element divided into two or more based on the temperature measurement result. It can be uniform.
Therefore, the degree of curing of the cured resin on the silicon wafer can be made uniform, and the silicon wafer can be prevented from being damaged. Japanese Patent Laid-Open Publication No. Sho 63-216283 proposes a technique for controlling a heating element circuit by dividing it. However, this technique does not have an operation unit, so that there is a sudden temperature change (disturbance). In such a case, the temperature cannot be controlled. In this regard, in the ceramic heater of the present invention, the required electric power can be accurately calculated even if there is a sudden temperature change, so that the desired heater temperature can be controlled.

FIG. 1A is a block diagram schematically showing an example of a ceramic heater according to the present invention, and FIG. 1B is a partially enlarged sectional view showing a part thereof. Also, FIG.
FIG. 2 is a plan view schematically showing a heater portion constituting the ceramic heater shown in FIG. 1.

The heater plate 11 is formed in a disk shape, and the heating elements 12 (12x, 12y) are heated so that the entire temperature of the wafer heating surface 11a of the heater plate 11 becomes uniform. It is formed in a concentric pattern inside the plate 11. The heating elements 12 are connected so that double concentric circles close to each other form a single line, and terminal pins 13 serving as input / output terminals are provided at both ends thereof through through holes 18. It is connected. A socket 20 is attached to the terminal pin 13,
The socket 20 is connected to a control unit 23 having a power supply. A lifter pin 1 is located near the center.
6 is formed, and a bottomed hole 14 for inserting a thermocouple 17 as a temperature measuring element is formed.
a to 14i are formed.

As shown in FIG. 1, in this ceramic heater 10, a lifter pin 16 is inserted into a through hole 15, and a silicon wafer 19 is placed on the lifter pin 16.
Is to be placed. By moving the lifter pins 16 up and down, it is possible to transfer the silicon wafer 19 to a carrier (not shown) or to receive the silicon wafer 19 from the carrier.

Further, a bottomed hole 14 is provided in the heater plate 11 from the bottom surface 11b side, and a thermocouple 17 as a temperature measuring element is fixed to the bottom of the bottomed hole 14. The thermocouple 17 is connected to the storage unit 21 so that the temperature of each thermocouple 17 can be measured at regular time intervals and the data can be stored. The storage unit 21 is connected to the control unit 23 and connected to the calculation unit 22, and based on the data stored in the storage unit 21,
The control section 23 applies a predetermined voltage to each heating element 12 based on the calculation of the voltage value and the like to be controlled in Step 2, and the temperature of the wafer heating surface 11a can be made uniform. ing.

Next, the operation of the ceramic heater 10 of the present invention will be described. First, when power is applied to the ceramic heater 10 by operating the control unit 23,
Although the temperature of the heater plate 11 itself starts to rise, the surface temperature of the outer peripheral portion becomes slightly lower.

The data measured by the thermocouple 17 is stored in the storage unit 2
1 is stored once. Next, this temperature data is calculated by the arithmetic unit 2
2, the arithmetic unit 22 calculates a temperature difference ΔT at each measurement point, and further calculates data ΔW necessary for uniformizing the temperature of the wafer heating surface 11a.

For example, if there is a temperature difference ΔT between the heating element 12x and the heating element 12y, and the heating element 12x is lower,
Power data ΔW that makes ΔT zero is calculated and transmitted to the control unit 23, and the power based on this is generated by the heating element 1
It is thrown into 2x and heated.

Regarding the algorithm for calculating the power, the simplest method is to calculate the power required for raising the temperature from the specific heat of the heater plate 11 and the weight of the heating area. In addition, a correction coefficient due to the heating element pattern is taken into account. You may. Alternatively, a temperature rise test may be performed on a specific heating element pattern in advance, and a function of the temperature measurement position, the input power, and the temperature may be obtained in advance, and the input power may be calculated from the function. The applied voltage and time corresponding to the power calculated by the calculating unit 22 are stored in the control unit 2.
3 and the control unit 23 controls each heating element 1 based on the value.
2 will be powered.

Next, each member constituting the ceramic heater of the present invention will be described. This ceramic heater 1
At 0, the thickness of the heater plate 11 is preferably 0.5 to 5 mm. If the thickness is less than 0.5 mm, the strength is reduced and the material is easily damaged. On the other hand, if the thickness is more than 5 mm, heat is difficult to propagate, and the heating efficiency is deteriorated.

The ceramic constituting the ceramic heater 10 is preferably a nitride ceramic or a carbide ceramic. Nitride ceramics and carbide ceramics have a smaller coefficient of thermal expansion than metals and have much higher mechanical strength than metals. Therefore, even if the thickness of the heater plate 11 is reduced, the ceramics warp or warp due to heating. do not do. Therefore, the heater plate 11 can be made thin and light. Furthermore, since the heat conductivity of the heater plate 11 is high 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 surface temperature of the heater plate can be controlled by changing the temperature of the heating element 12 by changing the voltage and the current value.

As the above-mentioned nitride ceramic, for example,
Examples include aluminum nitride, silicon nitride, boron nitride, and titanium nitride. These may be used alone or 2
More than one species may be used in combination.

Examples of the carbide ceramic 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 is 180W / m · K,
This is because, although excellent in temperature followability, the temperature distribution tends to be non-uniform, and it is necessary to adopt a structure for forming a temperature measuring element as in the present invention.

In the ceramic heater 10 of the present invention,
The heater plate 11 has a wafer heating surface 1 on which an object to be heated is placed.
1a from the opposite side to the wafer heating surface 11a.
4a to 14i (hereinafter, also simply referred to as bottomed holes 14), and the bottom of the bottomed holes 14 is formed relatively closer to the wafer heating surface 11a than the heating element 12.
It is desirable to provide a temperature measuring element in the device (see FIG. 1). Also,
The distance L between the bottom of the bottomed hole 14 and the wafer heating surface 11a is:
It is desirable that the thickness be 0.1 mm to 1/2 of the thickness of the ceramic substrate (see FIG. 1B).

As a result, the temperature measuring place is closer to the wafer heating surface 11a than the heating element 12, and the temperature of the silicon wafer can be measured more accurately. Then, the accurate temperature measurement result is stored in the storage unit 21, and based on the temperature data stored in the storage unit 21, the heating element 1 is uniformly heated.
The control unit 23 applies a control voltage to the heating element 12 based on the calculation result of the voltage to be supplied to the heating unit 12, so that the entire silicon wafer can be uniformly heated.

If the distance between the bottom of the bottomed hole 14 and the wafer heating surface 11a is less than 0.1 mm, heat is radiated, and a temperature distribution is formed on the wafer heating surface 11a. This is because the temperature of the heating element is liable to be affected and the temperature cannot be controlled, and a temperature distribution is formed on the wafer heating surface 11a.

The diameter of the bottomed hole 14 is 0.3 mm to 5 mm.
It is desirable that This is because if it is too large, the heat dissipation will be large, and if it is too small, the workability will be reduced and the distance to the wafer heating surface 11a cannot be equalized.

The bottomed holes 14a to 14i are desirably arranged symmetrically with respect to the center of the heater plate 11 so as to form a cross, as shown in FIG. This is because the temperature of the entire wafer heating surface can be measured.

Examples of the temperature measuring element include a thermocouple,
Platinum resistance thermometers, thermistors and the like can be mentioned. As the thermocouple, for example, JIS-C-1602 (1
980), K type, R type, B type, S type
Type, E-type, J-type, and T-type thermocouples, and among them, a K-type thermocouple is preferable.

The size of the junction of the above-mentioned thermocouple is preferably the same as or larger than the diameter of the strand, and 0.5 mm or less. This is because, if the junction is large, the heat capacity increases and the responsiveness decreases. It is difficult to make the diameter smaller than the diameter of the strand.

The temperature measuring element may be adhered to the bottom of the bottomed hole 14 using gold brazing, silver brazing, or the like.
And then sealed with a heat-resistant resin, or both may be used in combination. Examples of the heat-resistant resin include a thermosetting resin, particularly an epoxy resin, a polyimide resin, a bismaleimide-triazine resin, and the like. These resins may be used alone or in combination of two or more.

As the above-mentioned gold brazing filler, 37-80.5% by weight Au-63-19.5% by weight Cu alloy, 81.5-8%
2.5% by weight: Au-18.5 to 17.5% by weight: Ni
At least one selected from alloys 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. As a silver solder, for example, Ag
-A Cu-based material can be used.

The heating element 12 is preferably divided into at least two or more circuits as shown in FIG.
More preferably, the circuit is divided into two to ten circuits.
By dividing the circuit, the amount of heat generated can be changed by controlling the power supplied to each circuit.
Is adjusted.

As the pattern of the heating element 12, in addition to the concentric circles shown in FIG. 2, for example, a spiral, an eccentric circle, a bent line and the like can be mentioned.

In the present invention, the heating element may be formed on the surface (bottom surface) of the heater plate, or the heating element may be embedded inside the heater plate. When the heating element is formed on the surface of the heater plate 11, a 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. A method of sintering metal particles on the surface is preferred. The sintering of the metal is sufficient if the metal particles and the metal particles and the ceramic are fused.

When a heating element is formed on the surface of the heater plate 11, the thickness of the heating element is preferably 1 to 30 μm, more preferably 1 to 10 μm. Also, the heater plate 11
When a heating element is formed inside the
50 μm is preferred.

When a heating element is formed on the surface of the heater plate 11, the width of the heating element is preferably 0.1 to 20 mm, more preferably 0.1 to 5 mm. When a heating element is formed inside the heater plate 11, the width of the heating element is preferably 5 to 20 μm.

The resistance of the heating element can be varied depending on its width and thickness, but the above range is most practical. The resistance value increases as the resistance value decreases and the resistance value decreases. When the heating element is formed inside the heater plate 11, both the thickness and the width are larger. However, when the heating element is provided inside, the distance between the wafer heating surface and the heating element becomes shorter, and the surface temperature becomes lower. Since the uniformity is reduced, it is necessary to increase the width of the heating element itself, and there is no need 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.
Since the resistance value can be increased, the thickness itself may be increased for the purpose of preventing disconnection or the like. Therefore, it is desirable that the heating element has the above-described thickness and width.

By setting the formation position of the heating element in this manner, the heat generated from the heating element is diffused throughout the heater plate as it propagates, and the surface of the object to be heated (the 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 equalized.

The heating element may have a rectangular or elliptical cross section, but is preferably flat. This is because the flattened surface tends to radiate heat toward the heated surface of the wafer, so that the temperature distribution on the heated surface of the wafer is hardly generated. The aspect ratio of the cross section (width of heating element / thickness of heating element) is 10 to 5000
It is desirable that By adjusting to this range, the resistance value of the heating element can be increased, and the temperature uniformity of the wafer heating surface can be ensured.

When the thickness of the heating element is constant, if the aspect ratio is smaller than the above range, the amount of heat transmission in the direction of the wafer heating surface of the heater plate 11 becomes small, and the heat distribution approximates the pattern of the heating element. Is generated on the wafer heating surface,
Conversely, if the aspect ratio is too large, the temperature immediately above the center of the heating element becomes high, and eventually, a heat distribution similar to the pattern of the heating element is generated on the wafer heating surface. Therefore, considering the temperature distribution, the aspect ratio of the cross section is 1
It is preferably from 0 to 5000.

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

When the heating element is formed inside the heater plate 11, the aspect ratio becomes larger. However, when the heating element is provided inside, the distance between the wafer heating surface and the heating element becomes shorter. This is because it is necessary to flatten the heating element itself because the temperature uniformity of the surface is reduced.

When the heating element of the present invention is formed to be eccentric inside the heater plate 11, the position is close to the bottom surface 11b of the heater plate 11 facing the wafer heating surface 11a, and the bottom surface is positioned from the wafer heating surface 11a. 50% for the distance to 11b
It is desirable that the position be over 100%. 50
%, The temperature distribution is generated because the temperature is too close to the wafer heating surface. Conversely, if it exceeds 99%, the heater plate 11 warps and the silicon wafer is damaged. .

When the heating element 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 element is formed in some layer so that the patterns of each layer complement each other, and when viewed from above the wafer heating surface, the pattern is formed in any region. As such a structure, for example, a structure in which the staggered arrangement is provided.

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

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

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

The shape of the metal particles may be spherical,
It may be scaly. When these metal particles are used, they may be a mixture of the above-mentioned spheres and the above-mentioned flakes. When the metal particles are scaly, or a mixture of spherical and scaly, it is easy to hold the metal oxide between the metal particles, and the adhesion between the heating element and the nitride ceramic is improved. This is advantageous because it can be ensured and the resistance value can be increased.

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

As described above, it is desirable to add a metal oxide to metal particles in the conductor paste and to make the heating element a sintered body of the metal particles and the metal oxide. By sintering the metal oxide together with the metal particles in this manner, the nitride ceramic or carbide ceramic serving as the heater plate can be brought into close contact with the metal particles.

It is not clear why the mixing of the metal oxide with the nitride ceramic or the carbide ceramic improves the adhesion, but the surface of the metal particles and the surface of the nitride ceramic and the carbide ceramic are slightly oxidized. It is considered that an oxide film is formed by sintering and integrating the oxide films via the metal oxide, and the metal particles adhere to the nitride ceramic or the carbide ceramic.

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

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

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

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

If the area resistivity exceeds 45 mΩ / □, the amount of heat generated becomes too large with respect to the applied voltage, and it is difficult to control the amount of heat generated in the heater plate 11 having a heating element on the surface of the heater plate. Because. When the addition amount of the metal oxide is 10% by weight or more, the sheet resistivity is 50 mΩ / □.
, And the amount of heat generated becomes too large to make temperature control difficult, and the uniformity of the temperature distribution decreases.

When the heating element is formed on the surface of the heater plate 31, it is desirable that a metal coating layer (see FIG. 3) 38 be formed on the surface of the 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 38 to be formed is 0.1 to 1
0 μm is preferred.

The metal used for forming the metal coating layer 38 is not particularly limited as long as it is a non-oxidizing metal.
Specifically, for example, gold, silver, palladium, platinum, nickel and the like can be mentioned. These may be used alone or in combination of two or more. Of these, nickel is preferred.

The heating element requires a terminal for connection to a power source, and this terminal is attached to the heating element via solder. Nickel prevents heat diffusion of the solder. As the connection terminal, for example, a terminal pin 13 made of Kovar is used.

When the heating element is formed inside the heater plate 11, no coating is required since the heating element surface is not oxidized. When the heating element 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 connected to the through hole. , May be fixed.

When connecting the connection terminals, the solder
Alloys such as silver-lead, lead-tin, and 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 connection by soldering.

Next, a method of manufacturing the ceramic heater of the present invention will be described. Here, a ceramic heater 10 having a heating element formed inside a heater plate (see FIGS. 1 and 2)
A method of manufacturing the device will be described. (1) Heater plate manufacturing process First, a powder of a nitride ceramic or a carbide ceramic is mixed with a binder, a solvent, or the like to prepare a paste, and a green sheet is manufactured using the paste.

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

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

Next, if necessary, a portion serving as a through hole for inserting a lifter pin for supporting a silicon wafer and a bottomed hole for embedding a temperature measuring element such as a thermocouple in the obtained green sheet. , A portion serving as a through hole for connecting the heating element to an external end pin, and the like. The above processing may be performed after forming a green sheet laminate described later.

(2) Step of Printing Conductive Paste on Green Sheet A conductive paste containing a metal paste or a conductive ceramic is printed on the green sheet. These conductive pastes contain metal particles or conductive ceramic particles.

The average particle diameter 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 more than 5 μm, it is difficult to print the conductive paste. As such a conductive paste, for example, 85 to 87 parts by weight of metal particles or conductive ceramic particles; 1.5 to 10 parts by weight of at least one binder selected from acrylic, ethyl cellulose, butyl cellosolve, and polyvinyl alcohol; 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) Green Sheet Laminating Step Green sheets on which the conductor paste has not been printed are laminated above and below the green sheets on which the conductor paste has been printed.
At this time, the number of green sheets stacked on the upper side is made larger than the number of green sheets stacked on the lower side, and the formation position of the heating element is eccentric toward the bottom. 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) Step of firing green sheet laminate The green sheet laminate is heated and pressed to sinter the green sheet and the internal conductive paste. The heating temperature is preferably from 1000 to 2000 ° C.,
10-20 MPa is preferable. Heating is performed in an inert gas atmosphere. As the inert gas, for example, argon,
Nitrogen or the like can be used.

After firing, a bottomed hole 14 for inserting a temperature measuring element may be provided. The bottomed hole 14 is
After the surface is polished, it can be formed by performing blast treatment such as sand blasting. In addition, the terminal pins 13 are connected to through holes for connecting to the internal heating elements, and are heated and reflowed. Heating temperature is 200-50
0 ° C. is preferred. Further, a thermocouple or the like as a temperature measuring element is attached with a silver solder, a gold solder, or the like, sealed with a heat-resistant resin such as polyimide, and the wiring from the thermocouple 17 is stored in the storage unit 2.
1 and the wiring from the socket 20 is connected to the control unit 23, thereby completing the manufacture of the ceramic heater.

FIG. 3 is a block diagram schematically showing another example of the ceramic heater of the present invention. In the ceramic heater 30 shown in FIG. 3, a heating element 32 (32x, 32y) is formed on the bottom surface 31b of the heater plate 31, and the heating element 32
Is formed around the metal cover layer 38. Further, the terminal pins 33 are connected to the heating element 32 via the metal coating layer 38,
The socket 40 is fixed and the socket 40 is attached to the terminal pin 33. The socket 40 is connected to a control unit 43 having a power supply, and is otherwise configured in the same manner as the ceramic heater shown in FIG. That is, the shape of the heater plate 31 is a disk shape similar to the heater plate 11 shown in FIG. 1, and the pattern, the formation position, and the bottomed shape of the heating element 32 formed on the heater plate 11 in plan view. The shape and position of the hole 34 are the same as those of the ceramic heater 10 shown in FIG.

Next, the ceramic heater 30 shown in FIG.
The operation of will be described. The operation of the ceramic heater 30 shown in FIG.
0, the temperatures of the thermocouples 32x and 32y are measured at fixed time intervals, stored in the storage unit 41, and a voltage value and the like controlled by the calculation unit 42 are calculated from the data. By applying a predetermined voltage to the heating elements 32x and 32y from the section 43, the temperature of the entire wafer heating surface 31a of the ceramic heater 30 can be made uniform.

Next, the ceramic heater 30 shown in FIG.
A method of manufacturing the device will be described. (1) Heater plate manufacturing process After preparing a slurry by blending a sintering aid such as yttria or a binder as necessary with a powder of a nitride ceramic or a carbide ceramic such as aluminum nitride as described above, Granules are formed by a method such as spray-drying, and the granules are placed in a mold or the like and pressed to be formed into a plate shape or the like, thereby producing a green body (green).

Next, as necessary, a portion serving as a through hole 35 for inserting a lifter pin for supporting a silicon wafer and a bottomed hole 34 for embedding a temperature measuring element such as a thermocouple are formed in the formed body. Is formed.

Next, the formed body is heated, fired and sintered to produce a ceramic plate. Thereafter, the heater plate 31 is manufactured by processing into a predetermined shape, but may be a shape that can be used as it is after firing. By performing heating and baking while applying pressure, it is possible to manufacture a heater plate 31 having no pores. Heating and sintering may be performed at a sintering temperature or higher, but in the case of a nitride ceramic or a carbide ceramic, 1000 to 250
0 ° C.

(2) Step of Printing Conductor Paste on Heater Plate The conductor paste is generally a highly viscous fluid composed of metal particles, resin and solvent. The conductor paste is printed on a portion where the heating element is to be provided by screen printing or the like to form a conductor paste layer. Since the heating element needs to have a uniform temperature over the entire heater plate, it is desirable to print the pattern in a concentric pattern as shown in FIG. The conductor paste layer is desirably formed so that the cross section of the heating element 32 after firing has a rectangular and flat shape.

(3) Firing of Conductive Paste The conductive paste layer printed on the bottom surface of the heater plate 31 is heated and fired to remove the resin and the solvent, sinter the metal particles, and baked on the bottom surface of the heater plate 31. Heating element 32
(32x, 32y) are formed. The temperature of heating and firing is 5
00-1000 ° C is preferred. If 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 heating element 32
And the heater plate 31 have improved adhesion.

(4) Formation of Metal Coating Layer It is desirable to provide a metal coating layer on the surface of the heating element 32. The metal coating layer can be formed by electrolytic plating, electroless plating, sputtering, or the like, but in consideration of mass productivity, electroless plating is optimal.

(5) Attachment of Terminals and the like Terminals (terminal pins 33) for connection to a power supply are attached to the end of the pattern of the heating element 32 by soldering. Further, a thermocouple is fixed to the bottomed hole 34 with a silver solder, a gold solder, or the like, and the thermocouple is sealed with a heat-resistant resin such as polyimide. In the ceramic heater of the present invention, an electrostatic chuck may be provided by providing an electrostatic electrode, or a wafer prober may be provided by providing a chaptop conductor layer.

[0082]

The present invention will be described in more detail below. Example 1 Production of Aluminum Nitride Ceramic Heater (See FIG. 3) (1) Aluminum Nitride Powder (Average Particle Size: 1.1 μm) 1
A composition comprising 00 parts by weight, 4 parts by weight of yttria (average particle size: 0.4 μm), 12 parts by weight of an acrylic binder and alcohol was spray-dried to prepare a granular powder.

(2) Next, this granular powder was put into a mold and molded into a flat plate to obtain a formed product (green). (3) The processed form is processed at 1800 ° C., pressure: 2
Hot pressing was performed at 0 MPa to obtain an aluminum nitride plate having a thickness of 3 mm. Next, the diameter 210
mm was cut out to obtain a ceramic plate (heater plate) 31.

Drilling is performed on the formed body to form a through hole 35 for inserting a lifter pin for supporting a silicon wafer and a bottomed hole 34 for embedding a thermocouple (diameter: 1.1 mm, depth: (2 mm).

(4) A conductor paste was printed on the heater plate 31 obtained in (3) by screen printing. The printing pattern was a concentric pattern as shown in FIG. As the conductive paste, Solvest PS manufactured by Tokuriki Chemical Laboratory, which is used to form 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), 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 heater plate 31 on which the conductive paste is printed is heated and fired at 780 ° C. to sinter silver and lead in the conductive paste and to bake the heater plate 31 onto the heater plate 31.
A heating element 32 was formed. The silver-lead heating element 32 had a thickness of 5 μm, a width of 2.4 mm, and a sheet resistivity of 7.7 mΩ / □.

(6) An electroless nickel plating bath consisting of an aqueous solution having a concentration of 80 g / l nickel sulfate, 24 g / l sodium hypophosphite, 12 g / l sodium acetate, 8 g / l boric acid, and 6 g / l ammonium chloride was used. The heater plate 31 prepared in (5) was immersed to deposit a 1 μm-thick metal coating layer (nickel layer) on the surface of the silver-lead heating element 32.

(7) A silver-lead solder paste (manufactured by Tanaka Kikinzoku) was printed by screen printing on a portion to which a terminal for securing connection to a power supply was attached, to form a solder layer. Next, the terminal pins 33 made of Kovar were placed on the solder layer, and heated and reflowed at 420 ° C., and the terminal pins 33 were attached to the surface of the heating element 32.

(8) A thermocouple for controlling temperature is provided with a hole 34 having a bottom.
The ceramic heater 30 was obtained by embedding and fixing a ceramic adhesive (Aron ceramic manufactured by Toa Gosei).

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

Example 3 Production of Ceramic Heater Having Heating Element Inside (FIGS. 1-2) (1) Aluminum nitride powder (manufactured by Tokuyama Corporation, average particle size:
1.1 μm), yttria (average particle size: 0.4 μm) 4
Parts by weight, acrylic binder 11.5 parts by weight, dispersant 0.
Using a paste obtained by mixing 5 parts by weight and 53 parts by weight of alcohol composed of 1-butanol and ethanol, molding was carried out by a doctor blade method to a thickness of 0.47 mm.
Green sheet was obtained.

(2) Next, the green sheet was dried at 80 ° C. for 5 hours, and then 1.8 m in diameter by punching.
m, a portion serving as a through hole 15 for inserting a lifter pin for supporting a 3.0 mm and 5.0 mm silicon wafer, and a portion serving as a through hole for connecting to a terminal pin were provided.

(3) 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 are mixed to form a conductor. Paste A was prepared.

Tungsten particles 10 having an average particle diameter of 3 μm
A conductive paste B was prepared by mixing 0 parts by weight, 1.9 parts by weight of an acrylic binder, 3.7 parts by weight of an α-terpineol solvent, and 0.2 parts by weight of a dispersant. The conductive paste A was printed on a green sheet by screen printing to form a conductive paste layer. The printing pattern was a concentric pattern as shown in FIG. In addition, the conductive paste B was filled in through holes for through holes for connecting terminal pins. On the green sheet after the above processing, 37 green sheets on which the tungsten paste is not printed are further printed on the upper side (wafer heating surface), 13 on the lower side, and 13 on the lower side.
Lamination was performed at 0 ° C. and a pressure of 8 MPa.

(4) Next, the obtained laminate is placed in nitrogen gas.
Degreasing at 600 ° C for 5 hours, 1890 ° C, pressure 15MPa
For 3 hours to obtain an aluminum nitride plate having a thickness of 3 mm. This was cut into a disk shape of 230 mm to obtain a ceramic heater having a heating element with a thickness of 6 μm and a width of 10 mm inside.

(5) Next, the plate obtained in (4) is polished with a diamond grindstone, a mask is placed on the plate, and a bottomed hole for a thermocouple is formed on the surface by blasting with SiC or the like. 14
(Diameter: 1.2 mm, depth: 2.0 mm).

(6) Further, a part of the through-hole for the through-hole is cut out to form a concave portion, and a Ni-Au brazing filler metal is used in the concave portion, and heated and reflowed at 700 ° C. to make the Kovar terminal pin 13 Was connected. Note that the terminal pins 13
Is desirably a structure in which a tungsten support is supported at three points. This is because connection reliability can be ensured. (8) Next, a plurality of thermocouples 17 for temperature control were embedded in the bottomed holes 14 to complete the manufacture of the ceramic heater 10.

Example 4 Temperature Control of Ceramic Heater (1) A temperature controller (Omron E5ZE) equipped with a control unit having a power supply, a storage unit, and a calculation unit was prepared. Wiring from the control unit 43 is connected to the heater 30 (see FIG. 3) via the terminal pins 33, and wiring from the thermocouple 37 is connected to the storage unit 41, and the silicon wafer is placed on the ceramic heater 30. Was placed.
Note that, although not shown in FIG.
Are formed at the same positions as the bottomed holes 14a to 14c in the ceramic heater 10 shown in FIG. Further, the heating elements 32a to 32c are also the heating elements 12a to 1c in the ceramic heater 10 shown in FIG.
It is formed at the same position as 2c.

(2) Next, a voltage is applied to the ceramic heater 30 to once raise the temperature to 200 ° C., and further raise the temperature to 200 ° C. to 400 ° C.
The temperature was measured by a thermocouple installed in c. The measurement results are shown in FIG. Heating elements 32a, 32b, 32c
FIG. 5 shows the profile of the electric power (indicated by the current value) supplied to. In FIG. 4, the vertical axis indicates temperature and the horizontal axis indicates elapsed time. In FIG. 5, the vertical axis indicates current value, and the horizontal axis indicates time. As is clear from FIG. 4, the temperature of the ceramic heater becomes uniform within a short time after the current is passed through the ceramic heater 30. As a result, the silicon wafer placed on the ceramic heater 30 is heated. In the process of not being damaged,
Heated evenly. Further, a silicon wafer at 25 ° C. was placed on a ceramic heater heated to 140 ° C., and the relationship between the temperature and time at each part of the ceramic heater was measured.
The results are shown in FIG. In addition, the temperature measurement was performed for 34a to 34
The measurement was performed with a thermocouple buried in the bottomed hole of c. As is clear from the results shown in FIG. 6, even when there is a sudden temperature change, the temperature can be controlled.

[0100]

As described above, according to the ceramic heater of the present invention, the temperature of the heating surface of the silicon wafer can be made uniform, and damage to the silicon wafer can be prevented.

[Brief description of the drawings]

FIG. 1A is a block diagram schematically illustrating an example of a ceramic heater according to the present invention, and FIG. 1B is a partially enlarged cross-sectional view thereof.

FIG. 2 is a plan view schematically showing an example of a heater portion of the ceramic heater of the present invention.

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

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

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

FIG. 6 is a graph showing a relationship between a temperature change of a heater plate and a time when a normal temperature silicon wafer is placed on a ceramic heater having an increased temperature.

[Explanation of symbols]

 10, 30 Ceramic heater 11, 31 Heater plate 12, 32 Heating element 13, 33 Terminal pin 14, 34 Bottom hole 15, 35 Through hole 19 Silicon wafer 11a, 31a Heating surface 11b, 31b Bottom surface 16 Lifter pin 17, 37 Thermoelectric Pair 18 Through hole 21, 41 Storage unit 22, 42 Operation unit 23, 43 Control unit

Claims (2)

[Claims] 1. A heating element is formed on a surface or inside of a ceramic substrate, a temperature measuring element for measuring a temperature of the ceramic substrate, a control unit for supplying power to the heating element, and a temperature measuring element. A storage unit for storing the measured temperature data, and a calculation unit for calculating the power required for the heating element from the temperature data, the heating element,
A ceramic heater, which is divided into at least two or more circuits, and is configured so that different electric power is supplied to each circuit. 2. The ceramic heater according to claim 1, wherein the ceramic substrate is made of a nitride ceramic or a carbide ceramic.