JP2009009795A - Ceramic heater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To greatly simplify and reduce cost of a ceramic heater by eliminating restraint on a place where its temperature can be measured or on a device structure, and raise accuracy of temperature measurement and precision of temperature control. <P>SOLUTION: The ceramic heater is provided with a flat-plate pedestal made of ceramics with a plurality of exoergic resistive elements buried, a plurality of exoergic resistive element regions formed at burial positions of the plurality of exoergic resistive elements, and at least one temperature-measuring element buried in each exoergic resistive element region. A volume resistivity of the ceramics at use temperature is to be 10E+08 Ω cm or more. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention mainly relates to a semiconductor process, and relates to a heater that heats and holds a semiconductor substrate at a predetermined process temperature.

Ceramic heaters have been used in many processes as semiconductor process heaters. In recent years, the accuracy of wafer processing has become higher, and the requirement for temperature control when heating the wafer has become very strict. Therefore, in order to increase the temperature control accuracy of the mounting surface on which the wafer is mounted, a multi-zone heating device has been proposed in which a plurality of heating resistors are embedded in the mounting portion and each heating resistor is controlled independently. (For example, Patent Document 1). In this multi-zone heating device, independent control is possible in at least two separate heating zones, and the temperature control of the mounting surface can be performed more accurately than in the conventional single-zone heating device. There is an effect. Further, this apparatus employs a method in which a temperature sensor such as a pyrometer is arranged in a window on the outer surface of the chamber and is controlled while measuring the temperature of the mounting portion.
Japanese Patent No. 3319593

However, in such a pyrometer measurement, there are restrictions on the place where the temperature can be measured and the structure of the apparatus, and calibration of the actual temperature measurement such as setting of emissivity is very troublesome. Furthermore, especially in the case of an etching or film forming apparatus in a semiconductor process, the window material is corroded and adhered, so that the window material must be frequently replaced and cleaned, and the temperature measurement environment can be maintained. It was difficult. Therefore, in an environment such as a semiconductor process, it is very difficult to perform multi-zone control based on temperature measurement by a pyrometer. There is also a problem that the cost of the apparatus becomes high.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have made the following invention.

That is, the present invention is a plate-like mounting portion made of ceramics embedded with a plurality of heating resistors, a plurality of heating resistor regions formed at the embedded position of the plurality of heating resistors,
A ceramic heater comprising: at least one temperature measuring element embedded in each heating resistor region.

As described above, the present inventors have found that the temperature control of the ceramic heater can be precisely performed by embedding at least one temperature measuring element in one region for each of the plurality of heating resistor regions. Heading and inventing.

The temperature measuring element is a thermocouple. The thermocouple is embedded in a position separated from the heating resistor by 0.5 mm or more, more preferably 2 mm or more. Since the electromotive force of the thermocouple is smaller than the voltage applied to the heating resistor, the temperature measurement is likely to be shifted due to interference. Therefore, it is desirable to embed in the predetermined position in order to measure the temperature with high accuracy. In order to make it less susceptible to interference, it is desirable that the mounting portion is made of a ceramic material having a volume resistivity of 10E + 08 Ω · cm or more at the operating temperature. As the material for the mounting portion of the ceramic heater having such physical properties, aluminum nitride, alumina, silicon nitride, boron nitride, and yttria are suitable. The operating temperature is preferably 800 ° C. or lower. This is because if the temperature is too high, the volume resistivity is lowered even when the ceramics as described above are used, so that the temperature measurement deviation increases. “10E + 08” indicates “10 ⁸ ”.

When one thermocouple is embedded in one heat generating resistor region, the contact of the thermocouple is preferably embedded substantially at the center of the heat generating resistor region, but this is not restrictive. In addition, it is possible to adopt a configuration in which a plurality of the thermocouples are embedded in one heating resistor region and wired so that the average temperature of the heating resistor region can be measured. With such a configuration, precise temperature measurement and temperature control are possible.

Further, it is desirable that the temperature measuring element is embedded in the mounting portion without any gap. With such a structure, the temperature measurement accuracy can be further increased, and deterioration of the embedded temperature measurement element can be suppressed. Therefore, since a predetermined temperature measurement environment can be maintained over a long period of time, troublesome work such as temperature measurement with a pyrometer can be greatly reduced, and the cost of the apparatus can be reduced.

The ceramic heater of the present invention is connected to the hollow support portion that supports the mounting portion, the heating resistor embedded in the heating resistor region and the terminal connected to the temperature measuring element, and the terminal. A wiring member, wherein the terminal and the wiring member are concentrated in a hollow portion of the support portion. By supporting the mounting portion with the hollow support portion, it is possible to reduce the escape of the heat of the mounting portion through the support portion. Further, by consolidating the wiring connected to the heating resistor and the temperature measuring element in the hollow support portion, the device shape can be simplified. The terminals include a heating resistor terminal and a temperature measuring element terminal, and the wiring member includes a power supply line, a temperature measuring element lead, and a connector.

Moreover, the ceramic heater of this invention can use the manufacturing method including the process of embedding a several resistance heating element and several temperature measuring element, and integrating with sintering of ceramics. By using such a manufacturing method, it is possible to achieve a configuration in which the temperature measuring element of the ceramic heater of the present invention is embedded without a gap.

There is no restriction on the place where the temperature of the ceramic heater can be measured and the structure of the device, and the device can be greatly simplified and reduced in cost. In addition, the temperature measurement accuracy can be improved, and further the temperature control of the ceramic heater can be improved.

FIG. 1 is a representative example of the present invention. The ceramic heater 1 includes a plate-like placement portion 2 having a placement surface 2a on which a wafer is placed, a cylindrical support portion 5 and a flange 6. The vacuum chamber 13 is an airtight mechanism 11 (for example, O) provided on the flange 6. The ring is vacuum-tight. Heat generating resistors 3a and 3b and a temperature measuring element 4 are embedded in the mounting portion. A power supply line 7 connected to the heating resistor and a temperature measuring element lead 8 extending from the temperature measuring element 4 pass through a hollow portion of the cylindrical support portion 5 and through a connector 9 and a feedthrough 10 provided in the flange 6. To a temperature control device (not shown).

As shown in FIG. 2, a plurality of heating resistors 3 a and 3 b and a temperature measuring element are arranged inside the mounting portion 2. The temperature measuring element is a thermocouple. The central thermocouple contact 4a is embedded in the central heating resistor region 16a, and the outer peripheral thermocouple contact 4b is embedded in the outer peripheral heat generating region 16b. Here, the surface shown in FIG. 2A and the surface shown in FIG. 2B are separated by at least the distance between the heating resistor and the thermocouple. Therefore, the heat generating resistor region in which the thermocouple is embedded is a region including a position separated by a predetermined distance in the thickness direction from the position where the heat generating resistor is embedded in the mounting portion, and is shown in FIG. Like 16a and 16b, the heating resistor region is a region of a predetermined area surrounding one heating resistor.

When one thermocouple is embedded in one heat generating resistor region, the contact of the thermocouple is preferably embedded substantially at the center of the heat generating resistor region, but this is not restrictive. In addition, it is possible to adopt a configuration in which a plurality of the thermocouples are embedded in one heating resistor region and wired so that the average temperature of the heating resistor region can be measured. By embedding in the approximate center of the heating resistor region, temperature measurement in the region can be made more reliable. Furthermore, if the average temperature of the said area | region can be measured, temperature measurement can be ensured more.

It is desirable to embed the thermocouple simultaneously with the sintering of the ceramics constituting the mounting portion. Therefore, a material that can withstand the ceramic firing temperature is selected. For example, when aluminum nitride having excellent thermal conductivity is used as the ceramic, the firing temperature is 1600 to 2000 ° C., and as a thermocouple that can withstand this firing temperature, a JIS-regulated B thermocouple (Pt—Rh alloy, heat resistant temperature 1820) ° C or higher), R thermocouple, S thermocouple (Pt-Rh alloy / Pt, heat resistant temperature of 1760 ° C or higher) W-Re thermocouple (2400 ° C or higher), Ir-Rh thermocouple (Ir-40% Rh / Ir-50% Rh, heat resistant temperature of 2000 ° C. or higher) can be used. In particular, the B thermocouple not only has a high heat-resistant temperature, but can also measure temperature with high accuracy from 150 ° C. W-Re thermocouples have the highest heat resistance, but are oxidized in a high-temperature oxidizing atmosphere, and are therefore preferably used in a vacuum, inert, or reducing atmosphere. Specific examples of W-Re thermocouples include W / W-Re 26%, W-Re 5% / W-Re 26%, W-Re 3% / W-Re 26%, and the like.

As the heating resistor, a heat-resistant metal such as foil, plate, wire, mesh, or fibrous molybdenum or tungsten can be used.

As shown in FIG. 1, when all the terminals are arranged near the center of the mounting portion, the wiring in the hollow portion of the cylindrical support portion is connected from all the terminals to the feedthrough 10 of the flange through the hollow portion. .

When the number of independent heating resistors is large, three-dimensional internal wiring is necessary to avoid wiring interference with the heating resistors in the mounting portion. Even if a plurality of temperature measuring elements 4 are arranged on the mounting portion, the wire diameter itself is very thin and can be wired almost linearly so that it can be wired without contact. Also, by embedding a thermocouple as a temperature measuring element in the mounting portion, the contact point of the thermocouple is arranged outside the diameter of the cylindrical support portion, and the thermocouple wire is drawn into the hollow portion of the support portion. It becomes possible. The distance between the heating resistor and the thermocouple should be physically increased by 0.5 mm or more, more preferably 2 mm or more. If necessary, a low-pass filter may be installed in order to avoid interference of the electric signal input to the heating resistor with the thermocouple.

As shown in FIG. 3A, the temperature measuring element 4 is bent in the mounting portion 2 to facilitate the connection with the conductive wire on the support portion side of the mounting portion, and the three-dimensional interior. Wiring becomes possible. It is also possible to use a method in which the temperature measuring element terminal 14 is provided near the center of the mounting portion and the temperature measuring element conducting wire 8a is connected therefrom as shown in FIG. Further, as shown in FIG. 3C, a method in which the ceramic inner fine hole 18 is provided by machining after the mounting portion is fired and the sheath thermocouple 17 is inserted may be employed. In addition, wiring via via holes can be applied.

As the heating resistor terminal, foil, plate, massive molybdenum, tungsten, or the like can be used. As the temperature measuring element terminal, it is preferable to use a metal having the same composition as that of the thermocouple wire, or a metal foil, plate, or block having a similar thermoelectromotive force characteristic to that of the thermocouple. When there is no temperature difference in the part, it is possible to use a refractory metal such as molybdenum or tungsten according to the law of intermediate metal. It is desirable to use a thermocouple wire or a compensating lead wire as the temperature measuring element lead wire, but it is also possible to use other metal wires such as a nickel wire and a copper wire as long as the desired measurement accuracy and temperature control are possible. It is.

As the ceramic of the mounting portion, a ceramic having a volume resistivity of 10E + 08 Ω · cm or more at a use temperature can be used. As the material of the mounting portion having such physical properties, aluminum nitride, alumina, silicon nitride, boron nitride, and yttria are suitable. Of these, aluminum nitride is excellent in thermal conductivity, and is therefore suitable for ceramic heaters that require heat responsiveness and soaking. Further, when aluminum oxide is the main component, since the thermal conductivity is lower than that of aluminum nitride, it is easy to provide a temperature gradient in an inclined manner on the mounting surface. Further, since the sintering temperature is lower than that of aluminum nitride, the range of selection of the temperature measuring element is expanded.

The mounting portion 2 and the support portion 5 can be fixed by bonding with a bonding material such as ceramics, metal, or glass. Moreover, you may fix with the volt | bolt for fixing. The same holds for the support 5 and the flange 6. When vacuum-tightness is taken with the flange, the hollow part of the support part 5 can be made into the same atmosphere as a vacuum chamber. Therefore, it is possible to create an environment in which a W-Re alloy thermocouple that is vulnerable to oxidation can be used. On the other hand, when the mounting part 2 and the support part 5 are hermetically joined without using the flange 6 and the vacuum chamber side end face of the support part is hermetically sealed, the hollow part of the support part 5 is exposed to the atmosphere. For this reason, the heating resistor terminal 15 and the temperature measuring element terminal 14 are embedded in the mounting portion, and for example, an oxidation-resistant nickel feeding wire and a conductive wire are connected by a method such as welding or brazing. it can.

The connector 9 is provided in order to facilitate the assembly, and a socket-like one is appropriate. If there is no difficulty during assembly, the connector 9 may be omitted. The feedthrough 10 may be something like Ultra Toll (manufactured by Swagelok). In particular, it is optimal when the temperature measuring element described later is a sheath thermocouple.

Next, the present invention will be described in more detail with reference to examples.
Example 1
As the ceramic of the mounting part, aluminum nitride was added to the main raw material, yttrium oxide was added as an additive, and the raw material powder was prepared by a known manufacturing method. The heating resistor was molybdenum and the temperature measuring element was a B thermocouple. These specific embedment methods are as follows: a heating resistor is placed on the raw powder press-molded body, and then the raw material powder is placed on the pressed body and pressed, and a thermocouple element is placed on the molded body thus obtained. The raw material powder was further charged and pressed to obtain a molded body in which the heating resistor and the thermocouple were embedded in the ceramic powder. The heating resistor and the temperature measuring element are arranged as shown in FIGS. 2 (A) to 2 (C) and FIG. 3 (A), respectively, and the amount of raw material powder is adjusted so that the heating resistor and the thermocouple are arranged. The distance between the lines was 2 mm.

Firing was performed by hot pressing in a reducing atmosphere, and the firing temperature was 1800 ° C. The obtained sintered body was processed to form a circular flat plate-like mounting portion having a diameter of 210 mm × 10 mm. One surface of the mounting portion was used as a mounting surface, and a screw hole was processed to fix the support portion and the bolt to the surface opposite to the mounting surface. The element wire of the B thermocouple was taken out from the support part side of the mounting part as shown in FIG. 3A, and connected to the temperature measuring element lead with a Ni connector. The flange was provided with a current introduction terminal and connected to the temperature measuring element lead and the heater power supply line. These wiring members were collected in a hollow portion of a cylindrical support portion (inner diameter 50 mm, outer diameter 60 mm, height 200 mm). Aluminum nitride was used as the material of the support part, SUS304 was used as the material of the flange, and bolts were used for fixing the mounting part, the support part, and the flange. Thus, the ceramic heater provided with a flat mounting part and a hollow support part was obtained. In addition, when the volume resistivity of the aluminum nitride which comprises a mounting part was measured, it was 10E + 08 ohm * cm or more in the use temperature range of 100-800 degreeC of a ceramic heater.

A ceramic heater was installed in the vacuum chamber. First, heating was attempted with a set temperature at the center of 400 ° C. and a set temperature at the outer periphery of 500 ° C. The temperature was measured by thermocouples embedded in the center and the outer periphery, and the output was adjusted based on the obtained temperature to supply power from an external power source. When the temperature of the mounting surface was measured by a thermograph, the central portion was 400 ° C. and the outer peripheral portion was 500 ° C., and an inclined temperature distribution was obtained from the central portion to the outer peripheral portion. Next, when the set temperature of the center part and the outer peripheral part was both set to 500 ° C., the temperature distribution on the mounting surface had a difference from the set temperature of 1% or less.

(Example 2)
As a temperature measuring element, a wire of a W-Re thermocouple was embedded in an aluminum nitride sintered body as shown in FIG. The end of the thermocouple was used as a temperature measuring element terminal, and a bulk body (φ8 mm, thickness 0.5 mm) having the same composition as the thermocouple composition was embedded in aluminum nitride after welding with the thermocouple. After firing, a bottomed hole to the temperature measuring element terminal was processed on the surface opposite to the mounting surface for taking out the thermocouple to expose the terminal and connected to the temperature measuring element conducting wire. The connection method was performed by brazing. When heating was attempted at a set temperature similar to that in Example 1, similar results were obtained.

(Example 3)
Only the heating resistor was embedded in the aluminum nitride sintered body, and a temperature sensor thin hole was provided as shown in FIG. 3C, and a sheath thermocouple (φ2.2 mm Inconel sheath, K thermocouple) was inserted therein. The Inconel sheath is vacuum-tight with Ultra Toll (manufactured by Swagelok) provided on the flange, and the end of the sheath is located on the atmosphere side of the vacuum chamber. When heating was attempted at a set temperature similar to that in Example 1, similar results were obtained.

As shown in the above embodiment, a ceramic heater having a plurality of heating resistors embedded therein, the ceramic heater having at least one temperature measuring element in a heating resistor region in which one heating resistor is embedded By using it, it was confirmed that the temperature distribution in the mounting portion could be made uniform or inclined. In addition, the place where the temperature of the ceramic heater can be measured and the restrictions on the structure of the apparatus were eliminated, and the apparatus could be greatly simplified.

It is a schematic cross section of a ceramic heater. It is a schematic plan view which shows arrangement | positioning of the heating resistor in a mounting part, and a temperature measuring element. It is a model expanded sectional view of a temperature sensing element installation position.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1; Ceramics heater 2; Mounting part 2a; Mounting surface 3a, 3b; Heating resistor 4; Temperature measuring element (thermocouple)
4a, 4b; thermocouple contact 5; support portion 6; flange 7; feeders 8 and 8a; temperature measuring element conductor 9; connector 10; feedthrough 11; vacuum airtight mechanisms 12a, 12b and 12c; Chamber 14; temperature measuring element terminal 15; heating resistor terminals 16a and 16b; heating resistor region 17; sheath thermocouple 18;

Claims (9)

A plate-like mounting portion made of ceramics in which a plurality of heating resistors are embedded;
A plurality of heating resistor regions formed at the embedded positions of the plurality of heating resistors;
At least one temperature measuring element embedded in each heating resistor region;
A ceramic heater comprising: 2. The ceramic heater according to claim 1, wherein the ceramic has a volume resistivity of 10E + 08 Ω · cm or more at an operating temperature. The ceramic heater according to claim 1, wherein the temperature measuring element is a thermocouple. The ceramic heater according to claim 1, wherein the thermocouple is embedded at a position separated from the heat generating resistor by 0.5 mm or more. The ceramic heater according to claim 1, wherein the temperature measuring element is embedded in the mounting portion without any gap. The ceramic heater according to claim 1, wherein a contact of the thermocouple is embedded in a substantial center of the heating resistor region. The ceramic heater according to claim 1, wherein a plurality of the thermocouples are embedded in one heating resistor region, and are wired so that an average temperature of the heating resistor region can be measured. A hollow support part for supporting the mounting part,
A heating resistor embedded in the heating resistor region and a terminal connected to the temperature measuring element; a wiring member connected to the terminal;
The ceramic heater according to claim 1, wherein the terminal and the wiring member are concentrated in a hollow portion of the support portion. 9. The method for manufacturing a ceramic heater according to claim 1, further comprising a step of embedding a plurality of heating resistors and a plurality of temperature measuring elements and integrating them together with sintering of the ceramic.

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