JPH05267191A - Device for heating semiconductor wafer - Google Patents

Abstract

PURPOSE:To prevent corrosion of electrodes, terminals, thermocouples, etc., and also discharge and leakage between electrodes by providing an annular member of soft metal between a disk-shaped base body and end face of column- like body and pressing the disk-shaped base body and column-like body to the annular member. CONSTITUTION:A disk-shaped ceramic heater consists of a disk-shaped base body 2 and a resistor heating element 3 buried within the base body. An annular member 7 is provided between a flange 6a and the surface of main body 2. The cross section in the width direction of the annular member 7 is circular and made of soft metal. By tightening a bolt 22 which is a pressing member, a holding plate and a supporting member 4 are coupled together so that a load is applied between the main body 2 and the column-like body 6, and the annular member 7 is pressed against the flange 6a and a rear surface 2b, so as to obtain sealing. Since an electrode 9 and a terminal 12 are not exposed to the atmosphere of an inner space 14 within a vessel, corrosion of the electrode 9 and discharge and leakage between electrodes or between the electrode and a vessel 17 in vacuum will not take place.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention is applicable to plasma CVD, low pressure CV.
The present invention relates to a semiconductor wafer heating device used in D, plasma etching, photo-etching devices and the like.

[0002]

2. Description of the Related Art Corrosive gases such as chlorine gas and fluorine gas are used as a corrosive gas, an etching gas, and a cleaning gas in a semiconductor manufacturing apparatus requiring a super clean state. Therefore, as a heating device for heating the wafer in contact with these corrosive gases, the surface of the resistance heating element is made of stainless steel,
When a conventional heater coated with a metal such as Inconel is used, exposure to these gases produces undesired particles such as chlorides, oxides and fluorides having a particle size of several μm. Also, a so-called indirect heating type semiconductor wafer heating device has been developed. However, this type has a larger heat loss than the direct heating type, it takes time to raise the temperature, and CV to the infrared transmission window
The attachment of the D film gradually hinders the transmission of infrared rays, and there is a problem that the infrared transmission window absorbs heat and overheats the window.

[0003]

SUMMARY OF THE INVENTION In order to solve the above problems, the present inventors have developed a heating device in which a resistance heating element is embedded in a disc-shaped dense ceramic, and the ceramic heater is held by a graphite case. Was examined. As a result, it was found that this heating device was an extremely excellent device that eliminated the above-mentioned problems. However, in such a heating device, it is necessary to attach electrodes and terminals for power supply, a thermocouple, etc. on the back side of the disk-shaped ceramics heater. When these metal members are exposed to a high temperature corrosive gas, they are corroded. Also,
When the conductive film is gradually deposited on the back surface of the ceramics heater, discharge or electric leakage occurs between the pair of electrodes and between the electrode and the case. An object of the present invention is to make it possible to prevent corrosion of electrodes and terminals for power supply, thermocouples, etc., and prevent discharge and leakage between electrodes.

[0004]

DISCLOSURE OF THE INVENTION The present invention is directed to a ceramic heater in which a resistance heating element is embedded in a board-shaped substrate made of dense ceramics, and a cylindrical heater made of dense ceramics and having both ends open. A body, an annular member made of a soft metal installed between the plate-shaped base body and the end face of the cylindrical body, a support member for supporting a side peripheral surface of the ceramic heater, and the cylindrical body as the plate. A pressing member for pressing the plate-shaped base body toward the annular member, and by pressing the plate-shaped base body and the cylindrical body against the annular member, an airtight seal can be formed between the plate-shaped base body and the cylindrical body. Configured to,
The present invention relates to a semiconductor wafer heating device.

In the above semiconductor wafer heating device,
It is particularly preferable that the pressing member is a spring in a substantially constant temperature state, and the compressive load or tensile load of this spring is used to press the tubular body toward the disk-shaped substrate. Here, "substantially in a constant temperature state" means that the ambient temperature of the spring is kept substantially constant, and thus the spring constant of the spring is kept substantially constant.

[0006]

EXAMPLE FIG. 1 is a sectional view showing a state in which the heating apparatus of this example is attached to a semiconductor manufacturing apparatus. Through holes 15 and 16 are provided in the container 17, and the heating device of this embodiment is installed in the internal space 14 of the container 17. A circular through hole 20A and a water cooling jacket 18 are provided on the upper wall surface of the container 17. The cylindrical body 6 is made of dense and gastight ceramics,
It is composed of a cylindrical main body 6c and an annular flange 6a provided at the end of the main body 6c. The main body 6c is inserted and fixed in the circular through hole 20A, and the main body 6c and the container 17 are hermetically sealed by the O-ring 8.

The substantially disk-shaped ceramics heater 1 is composed of a substantially disk-shaped base 2 and a resistance heating element 3 embedded in the base 2. The base 2 is made of dense and gastight ceramics. The resistance heating element 3 is, for example, embedded in a spiral shape, and both ends of the resistance heating element 3 are connected to the terminals 12 respectively.
Is linked to. The surface of each terminal 12 is the back surface 2b of the base 2.
A round rod-shaped electrode 9 is connected to the exposed surface of each terminal 12, and a lead wire 10 is connected to the end of each electrode 9.
Further, the tip of the thermocouple 11 is fixed to the back surface 2b of the base 2.
The electrode 9 and the thermocouple 11 vertically extend in the inner space 6b of the cylindrical body 6. An annular flange is provided on the outer peripheral surface of the base body 2.
2a is formed, a flange 4a is formed on the lower inner peripheral surface of the support member 4, and the flange 2a is placed on the flange 4a. A holding plate 5 is installed on the support member 4, and the support member 4 and the holding plate 5 are fastened with bolts or the like.

The body 6c is inserted into the circular through hole 5a of the holding plate 5, and the flange 6a is in contact with the lower surface of the holding plate 5. An annular member 7 is installed between the flange 6a and the surface of the base 2. A cross section in the width direction of the annular member 7 is circular,
Made of soft metal. The holding plate and the support member 4 are fastened by tightening the bolt 22 which is a pressing member, a load is applied between the base body 2 and the cylindrical body 6, and the annular member 7 is attached to the flange 6a and the back surface 2b. Pressurize and seal hermetically. As a result, the ventilation between the gap 13A and the inner space 6b is almost shut off.

The ceramic heater 1 can be manufactured by hot press sintering or normal pressure sintering. The cylindrical body 6 can be manufactured by injection molding, extrusion molding, press molding, isostatic press molding, and normal pressure sintering.

According to the heating device of the present embodiment, the problems of contamination as in the case of the conventional metal heater and the deterioration of the thermal efficiency as in the case of the indirect heating method can be solved. Further, since the electrodes 9 and the terminals 12 are not exposed to the atmosphere of the internal space 14 of the container, the electrodes 9 and the like are corroded, the electrodes 9 are contaminated, and further, between the electrodes in vacuum or between the electrodes and the container 17. There is no risk of discharge or leakage.

Further, according to the research conducted by the applicant of the present invention, the behavior of gas molecules around the thermocouple is found to be from atmospheric pressure to
It is in the viscous flow region in the state of 1 torr, but when the degree of vacuum increases, it moves to the molecular flow region, and the mode of heat transfer in the thermocouple changes significantly with it, and it is clear that accurate temperature measurement cannot be performed. ing. It is also known that there is a temperature measurement error when the pressure fluctuation is large even in the viscous flow region. In this respect, in the present embodiment, since the thermocouple 11 is not exposed to the atmosphere in the container, the above-mentioned problem of temperature measurement error does not occur.

Further, it is important that the cylindrical body 6 and the ceramic heater 1 can be sealed with the annular member 7 made of a soft metal, which makes the sealing very easy and stable. The present inventor has also studied glass-bonding the ceramic heater 1 and the cylindrical body 6, but it is considerably difficult in manufacturing to increase the bonding strength of both and prevent cracks and breakage of the bonded portion. I understand. This is because the thermal stress concentrates on the glass bonded portion. Moreover, in order to perform such glass bonding, generally,
Although heat treatment at 1400 ° C or higher is required, there was an adverse effect such as deterioration of the tungsten wire at this time.

The use of a rubber O-ring has also been examined, but the upper limit of the operating temperature is 300 ° C. at most, and it is limited to low temperature applications. Further, it is difficult to hermetically seal ceramics with Inconel or stainless metal O-rings and metal C-rings, and cracks may occur in ceramics when a large load is applied to increase hermeticity.

Further, since the cylindrical body 6 and the ceramic heater 1 are separate bodies, if a failure such as a crack occurs in either of them, it is possible to separate the two and replace only the failed one. it can. When the cylindrical body 6 and the ceramics heater 1 are glass-bonded to each other, cracks are likely to occur in the bonded portion, and once cracked, they must be replaced all at once. Moreover, since the annular member 7 made of soft metal has a stress relaxing action, the thermal stress of each member can be absorbed. Further, by adjusting the fastening force of the bolt 22, the annular member 7
It is possible to change the pressure applied to, and thus the sealing performance of the annular member 7 can be changed appropriately.

As the soft metal forming the annular member 7, platinum having the high corrosion resistance and high melting point is most preferable. In addition, nickel, silver and gold are preferable in terms of corrosion resistance. Copper can adversely affect semiconductors.

As materials for the substrate 2 and the cylindrical body 6, silicon nitride, sialon, aluminum nitride and the like are preferable, and silicon nitride and sialon are more preferable in terms of thermal shock resistance. Aluminum nitride is most preferable from the viewpoint of corrosion resistance against halogen-based corrosive gas. The material of the resistance heating element 3 is preferably tungsten, molybdenum, platinum or the like. The seal between the container 17 and the cylindrical body 6 is, in addition to the O-ring shown in FIG. 1, diffusion bonding, friction welding, friction welding after a metal thin film is formed on the surface by sputtering, glass joining, metal backing, etc. You can

The annular member 7 can be easily manufactured, for example, as shown in FIG. First, as shown in FIG. 2 (a), a wire rod 7A made of a soft metal is prepared, and as shown in FIG. 2 (b), the wire rod 7A is processed into a circle and spot welded at both ends. In the figure, 23 is an expanded portion by welding. Then
The expanded portion is scraped off to obtain the annular member 7 shown in FIG. 2 (c).

As shown in FIG. 3, a ring-shaped groove 19 may be formed on the lower end surface of the flange 6a. The cross-sectional shape of the groove 19 in the width direction is rectangular, and the annular member 7 is formed in the groove 19.
Accommodates the upper half of the.

FIG. 4 shows a heating device according to another embodiment of the present invention.
FIG. 18 is a cross-sectional view showing a state of being attached to 17. The same members as those shown in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted. In this embodiment, the tubular body 26 having a relatively wide width is used. An annular support flange 26d is provided at the upper end of the cylindrical main body 26c and extends outward. An annular flange 26a is also projectingly provided at the lower end of the cylindrical body 26c. Container 17
A circular through hole 20B is provided on the upper wall of the
The c is inserted into the circular through hole 20b, and the support flange 26d is bridged over the upper wall surface of the container 17. Support flange 26d
An O-ring 8 hermetically seals between the container 17 and the container 17.

A holding plate 21 is fastened to the upper end of the support member 4 by bolts 22, and the holding plate 21 is supported on the flange 26a. An annular member 7B is installed between the flange 26a and the back surface 2b, and thereby the inner space 26b and the gap 13B are hermetically sealed.

In this embodiment, in addition to the above effects,
The following effects can be achieved. (1) Since the cylindrical body 26 has a large diameter and is comparable to the diameter of the substrate 2, the load is dispersed and the ceramics are less likely to be broken. (2) In the case of a thermal CVD device, it is necessary to clean the CVD film deposited other than the semiconductor wafer with plasma.
In this case, since the plasma electrode can be arranged in the inner space 26b, the plasma electrode is not exposed to the gas atmosphere in the container. (3) By installing the cooling structure in the inner space 26b,
The response during cooling can be improved. (4) By providing heat insulation and cooling means in the inner space 26b according to the temperature distribution of the chuck surface of the semiconductor wafer,
The temperature distribution on the chuck surface can be controlled.

A heating device shown in FIG. 1 was produced. The annular member 7 was made of platinum, the substrate 2, the cylindrical body 6, the support member 4, and the holding plate 5 were made of silicon nitride, and the resistance heating element 3, the terminal 12, and the electrode 9 were made of tungsten. The pressure inside the container 17 is set to 1 × 10 ^-4 mmHg and the heater surface is set to 1000
A leak test was performed by heating to ℃ and flowing helium gas into the inner space 6b. The leak amount was 6.5 × 10 ⁻⁹ atm · cc / sec or less.

In each of the above examples, the substantially disk-shaped base body 2,
The shapes of the cylindrical body 6 and the tubular body 26 can be variously changed, and accordingly, the planar shapes of the annular members 7 and 7B can be variously changed. Also, the outer shape of the cross section of the annular members 7, 7B in the width direction can be changed to a ring shape, a C shape, or the like.

FIG. 5 is a sectional view schematically showing a state in which a semiconductor wafer heating apparatus according to another embodiment of the present invention is attached to a container 17. In this embodiment, a flange 27a is provided on the inner peripheral surface of the lower end of the support member 27, and a flange 27b on the outer peripheral surface of the upper end of the support member 27 is fixed to the container 17 with bolts 22. The flange 2a of the disk-shaped substrate 2 is supported on the flange 27a via the annular heat insulating material 30A. Flange
A heat insulating material 30B is sandwiched between the outer peripheral surface of 2a and the support member 27. The heat insulating materials 30A and 30B are preferably made of alumina or the like.

A through hole 20C is provided on the wall surface of the container 17, and a cylindrical projecting portion 28 extends upward so as to surround the through hole 20C. The cylindrical body 6 is installed above the back surface 2b of the disk-shaped substrate 2, and the annular member 7 seals between the flange portion 6a and the back surface 2b. The cylindrical body 6 passes through the through hole 20C and extends above the protruding portion 28. An O-ring 8A hermetically seals between the inner periphery of the upper end of the protruding portion 28 and the outer peripheral surface of the cylindrical body 6, and a cooling jacket 29 is installed so as to surround the outer periphery of the protruding portion 28. In this embodiment, a female screw is formed on the terminal 12A, and a male screw is formed on the tip of the round rod-shaped electrode 9.
The female screw and the male screw are screwed together. Also, thermocouple 11A
Is fixed to the rear side 2b.

The shaft 31 is fixed to the upper wall surface of the container 17 preferably by a plurality of shafts 31 with screws or the like. A through hole 34a is provided at a predetermined position of the base plate 34, and each through hole 34a
Insert the shaft 31 into each. A female screw (not shown) is provided on a part of the shaft 31, a nut 32 is fitted to these, and a disc spring is provided between the nut 32 and the base plate 34.
Fix 33. A circular inner plate 35 is installed inside the base plate 34, and the electrode 9 is inserted in the through hole of the inner plate 35.
And the thermocouple 11A is inserted, and the electrode 9 and the thermocouple 11A and the inner plate 35 are sealed with an O-ring 8C.

A hemispherical seat 36a is formed on the upper end surface of the jig 36, and the seat 36a is brought into contact with the central portion of the inner plate 35. The electrode 9 and the thermocouple 11A are passed inside the jig 36, and a cylindrical recess 36b is provided in the lower half of the inner peripheral surface of the jig 36. Depression 36b
The upper end portion of the cylindrical body 6 is accommodated in the inside of the container, and a cushioning material 37 made of a soft metal is sandwiched between the upper end surface of the cylindrical body 6 and the jig 36. An O-ring 8 hermetically seals between the outer peripheral surface of the cylindrical body 6 and the inner peripheral surface of the lower end of the jig 36. A cooling jacket 29 is installed so as to surround the outer periphery of the lower half of the jig 36.

The nut 32 is fastened to apply a compressive load to the disc spring 33 to press the base plate 34 and the inner plate 35 downward, and the ball seat 36a downward. This pressing force is transmitted to the annular member 7 and the back surface 2b via the jig 36, the cushioning material 37, and the cylindrical body 6. Shaft 31 and support member 27
Are both fixed to the container 17.

According to this embodiment, the effects described in the example of FIG. 1 can be obtained. Moreover, it is important that the disc spring 33, which is a pressing member, is outside the container 17. That is, even when the ceramic heater 1 is heated to a high temperature, the elastic restoring force of the disc spring 33 does not substantially change because the disc spring 33 is outside the container. Therefore, even when the ceramics heater 1 generates heat, the pressure applied to the annular member 7 does not change so much, and thus the sealing performance can be maintained.

Further, it is important that the inner plate 35 and the jig 36 are separate bodies. That is, assuming that these are integrated, if the stress applied by the disc spring 33 is not evenly distributed in the circumferential direction in a plan view, a large eccentric load (bending force) is applied to the end surface of the ceramic cylindrical body 6. Therefore, the cylindrical body 6 may be destroyed. Even when the plates 34 and 35 and the jig 36 are separate bodies, if the two members are to be brought into solid contact with each other in a plane, contact between the planes should be made unless the contact surface is processed with extremely high precision. Unbalanced loads will be given due to the tolerance of the parts. Such high-precision machining is difficult and expensive. In this embodiment, the jig 36 is separated from the plate, and the load is once concentrated on the ball seat 36a at the center of the jig 36 to solve the above problem.

A cushioning material made of copper, gold, nickel or the like
By bringing 37 into contact with the end face of the cylindrical body 6, an eccentric load applied to this end face is relaxed, and the ceramics constituting the cylindrical body 6 are prevented from being broken or chipped. Further, in this example, the space between the cylindrical body 6 and the container 17 is sealed by a rubber O-ring 8A. The present inventor also studied metal packing, but was disadvantageous in terms of dimensional accuracy and cost during processing. However, if the ceramic heater 1 is heated to a high temperature,
A large amount of heat is generated, which may melt the O-ring 8A. Therefore, the gap between the O-ring 8A and the heater is increased by sealing at the tip of the extended portion 28, and the periphery of the O-ring 8A is cooled by the cooling jacket 29. For the same reason as above, the jig 36 and the cylindrical body 6 are sealed with an O-ring 8B, and a cooling jacket 29 is installed on the outside thereof.

The heat insulating materials 30A and 30B prevent the heat of the ceramic heater 1 from being transferred to the support member 27. Such a supporting member 27 is made of metal and thermally expands when exposed to a high temperature, and the position of the semiconductor wafer mounting surface in the container is displaced, which may reduce the productivity. Further, a part of the metal component in the support member 27 may evaporate at high temperature and become a pollution source. Therefore, the heat insulating material 30A, 3
With 0B, the temperature rise of the support member 27 was suppressed as much as possible.

Alumina is preferable as a material for the heat insulating materials 30A and 30B. The present inventor has confirmed that alumina is stable against halogen-based corrosive gases such as ClF ₃ and NF ₃ . However, although alumina has a low tensile strength, in this example, since the heat insulating material 30A is subjected to compressive stress, even if these are formed of alumina, they are not easily broken. Further, if the heat insulating material 30A made of alumina is thickened, the thermal shock resistance of alumina is low, so that there is a risk of thermal shock fracture. Therefore, for example, the heat insulating material 30A is formed of a thin plate having a thickness of 1.5 mm, and two or more heat insulating materials 30A are laminated to prevent thermal shock destruction of the heat insulating material 30A.

[0034]

According to the heating device of the present invention, it is possible to solve the problems such as the contamination as in the case of the conventional metal heater and the deterioration of the thermal efficiency as in the case of the indirect heating method. Also, the electrodes,
Since the terminals, etc. are not exposed to the atmosphere of the inner space of the container, there is no risk of corrosion of the electrodes, contamination from the electrodes, discharge between the electrodes in a vacuum or between the electrode and the container, and electric leakage. ..

Further, it is important that the tubular member and the ceramics heater can be sealed with an annular member made of a soft metal, which makes sealing very easy and stable, and facilitates manufacturing. .. In addition, since the cylindrical body and the ceramic heater are separate bodies, if a failure such as a crack occurs in either of them, the two can be separated and only the failed one can be replaced. In addition, since the annular member has a stress relieving action, the tubular body and the ceramic heater are less likely to break. In addition, a pressing member that presses the tubular body toward the disk-shaped substrate is provided, and by adjusting the pressing force by this pressing member, the pressure applied to the annular member is adjusted,
The sealing performance can be adjusted.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a state in which a heating device according to an embodiment of the present invention is attached to a container 17.

2 (a), (b) and (c) are plan views showing respective steps of producing the annular member 7. FIG.

FIG. 3 is a partially enlarged sectional view illustrating an example in which the annular member 7 is housed in a groove 19.

FIG. 4 is a cross-sectional view showing a state in which a heating device according to another embodiment is attached to a container 17.

FIG. 5 is a cross-sectional view showing a state in which a heating device according to another embodiment is attached to a container 17.

[Explanation of symbols]

 1 Ceramics heater 2 Disc-shaped substrate 2b Back surface 3 Resistance heating element 4,27 Supporting member 6 Cylindrical body 7, 7B Annular member 9 Electrode 11, 11A Thermocouple 12, 12A terminal 22 Bolt (example of pressing member) 26 Tube Shape 33 Disc spring (example of pressing member)

Claims (2)

[Claims] 1. A ceramic heater in which a resistance heating element is embedded in a board-shaped substrate made of dense ceramics, a cylindrical body made of dense ceramics and having both ends opened, and the board-shaped substrate. An annular member made of a soft metal installed between the end face of the tubular body, a support member supporting the side peripheral surface of the ceramics heater, and the tubular body being pressed toward the plate-shaped substrate. A semiconductor wafer heating device that includes a pressing member, and is configured to seal the space between the plate-shaped base body and the cylindrical body by pressing the plate-shaped base body and the cylindrical body against the annular member. apparatus. 2. The semiconductor wafer heating apparatus according to claim 1, wherein the pressing member is a spring in a substantially constant temperature state.