JPH09213775A - Wafer holder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use favorably for a long period without causing a gas leak in a connection part with a plate-like body by a method wherein a flange part of a vacuum hermetic cylinder is connected to a lower face of the plate-like body made of ceramics having a mounting face, and a stress relaxation ring is connected to a lower face of the flange part. SOLUTION: A flange part 13a of a vacuum hermetic cylinder 13 is connected to a lower face of the plate-like body 11 made of ceramics having a mounting face 11a of a wafer 30, and a stress relaxation ring 16 is connected to a lower face of the flange part 13a. For example, the mounting face 11a for mounting the wafer 30 to the plate-like body 11 made of ceramics is formed, and a heat generating resistor 12 is provided inside. Further, the flange part 13a of a hermetically sealing metallized cylinder 13 is hermetically connected with a solder material 14 on the lower face side of the plate-like body 11, and the stress relaxation ring 16 is connected to a lower face of the flange part 13a with a solder material 15. Further, a flange part 13b provided at a lower end of the cylinder 13 is hermetically connected to a bottom face of a chamber 18 via an O-ring 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer holding device used for holding and processing a semiconductor wafer or a wafer such as glass for liquid crystal in a semiconductor or liquid crystal manufacturing device.

[0002]

2. Description of the Related Art In a semiconductor manufacturing process, a PVD apparatus or a CVD apparatus for forming a film on a semiconductor wafer or a dry etching apparatus for performing a fine processing on the wafer holds the wafer in a chamber on a susceptor or an electrostatic chuck. The inside of this chamber is vacuumed and kept at a high temperature for processing.

For example, the wafer holding device shown in FIG. 3 has a mounting surface 11a on which a wafer 30 is mounted on a plate-shaped body 11 called a susceptor, and a heating resistor 12 is provided therein. Further, the flange portion 13a of the airtightly sealing cylinder 13 is airtightly joined to the lower surface side of the plate-like body 11 by the brazing material 14, and the flange portion 13b provided at the lower end of the cylinder 13 is provided with the O-ring 17 therebetween. Airtightly joined to the bottom surface of the chamber 18.

Further, on the lower surface of the plate-like body 11 inside the cylindrical body 13, a current-carrying terminal 21 to the heating resistor 12, a temperature detecting element 22 of the plate-like body 11 such as a thermocouple, or a temperature measuring optical fiber, etc. The temperature detecting element 23 of the wafer 30 and the like are provided, and these conducting wires are led out to the outside through the inside of the cylindrical body 13.

When this wafer holding device is used, the wafer 30 is placed on the plate-like body 11 and the chamber 1
The inside of 8 is evacuated, and various processing is performed while heating the wafer 30 by the heating resistor 12 and the temperature detecting elements 22 and 23 so that the wafer 30 has a constant temperature.

At this time, since the upper and lower ends of the tubular body 13 are airtightly joined to each other, the inside of the tubular body 13 can be completely cut off from the inside of the chamber 18. That is, the inside of the chamber 18 is set to a high vacuum of about 10 ⁻⁹ torr / sec or less and at a high temperature to introduce a corrosive gas.
The inside of can be an atmospheric atmosphere communicating with the outside.

Therefore, members such as the temperature detecting elements 22 and 23 and the current-carrying terminals 21 are not exposed to a corrosive atmosphere at a high temperature inside the chamber 18, so that durability can be improved and impurities inside the chamber 18 can be increased. It is possible to prevent particles and particles from mixing in.

Further, in recent years, ceramics such as alumina and aluminum nitride have been used as the material of the plate-like body 11, while the cylindrical body 13 is made of metal, and in order to reduce the difference in thermal expansion, a cylindrical body is formed. The thickness of the body 13 is 0.1-2
The thickness is reduced to about mm.

[0009]

By the way, in the semiconductor manufacturing process, the wafer 30 is often processed under a high temperature condition of 100 to 300 ° C., and further about 600 ° C., and the inside of the chamber 18 of the wafer holding device is kept at room temperature. A thermal cycle between the above processing temperatures will be added.

Therefore, repetitive stress due to this thermal cycle is concentratedly generated in the joint portion of the brazing material 14 between the cylindrical body 13 and the plate-like body 11 and, as shown in FIG.
As shown in (B), there is a disadvantage that the flange portion 13a of the tubular body 13 creep-deforms and a gap is created in the joint portion. As a result, there is a problem in that a gas leak occurs after several cycles to several tens of cycles of use, and the high vacuum state required for the semiconductor manufacturing apparatus cannot be maintained.

In order to solve this problem, the cylindrical body 1
There have been proposed measures such as 3 using a metal having a thermal expansion similar to that of the ceramic plate-like body 11 and using a brazing material 14 having a low Young's modulus capable of relaxing the difference in thermal expansion.

However, since the cylindrical body 13 and the brazing material 14 are exposed to the atmosphere in the chamber 18, they have corrosion resistance to the corrosive gas used in the processing step, and cause melting and liquefaction reactions in a high temperature vacuum atmosphere. It was required to be absent, and as a result, general low thermal expansion metals could not be used. For example, W, Mo and the like have poor oxidation resistance and high reactivity with the brazing material. In addition, Ti, Cr, Re
Cannot be used because they have poor corrosion resistance to corrosive gas and deteriorate the environment in the chamber 18.

[0013]

SUMMARY OF THE INVENTION In view of the above, the present invention joins a flange portion of a vacuum airtight cylinder to the lower surface of a ceramic plate-shaped body having a wafer mounting surface, and stresses the lower surface of the flange portion. It is characterized in that the relaxation ring is joined to form a wafer holding device.

That is, when a ceramic plate-like body and a metal cylinder are joined and the temperature changes, the flange portion of the cylinder having a low Young's modulus is likely to be deformed due to the difference in thermal expansion. In the present invention, a stress relaxation ring is joined below the flange portion to restrain the flange from both sides and prevent deformation.

Further, according to the present invention, a vacuum-tight cylinder made of ceramics having a coefficient of thermal expansion similar to that of the plate is hermetically bonded to the lower surface of the plate made of ceramic having a wafer mounting surface. A wafer holding device is configured.

That is, the cylindrical body is made of ceramics having a coefficient of thermal expansion similar to that of the plate body, so that the difference in thermal expansion is eliminated and the deformation of the cylindrical body itself is prevented.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a wafer holding device of the present invention will be described below with reference to the drawings (the same parts as those in the conventional example are represented by the same reference numerals).

The wafer holding device shown in FIG. 1 has a mounting surface 11a on which a wafer 30 is mounted on a ceramic plate-like body 11 called a susceptor, and a heating resistor 12 is provided therein. In addition, on the lower surface side of the plate-shaped body 11, the flange portion 13a of the metal cylinder 13 for hermetic sealing is provided.
4 is airtightly joined, and a stress relaxation ring 16 is joined to the lower surface of the flange portion 13a by a brazing material 15. Further, the flange portion 13b provided at the lower end of the tubular body 13
Is hermetically bonded to the bottom surface of the chamber 18 via an O-ring 17.

On the lower surface of the plate-like body 11 inside the cylindrical body 13, there are provided energization terminals 21 to the heating resistor 12, a temperature detecting element 22 of the plate-like body 11 such as a thermocouple, and the like. Of the lead wire passes through the inside of the cylindrical body 13 and is led out to the outside.

When this wafer holding device is used, the wafer 30 is placed on the plate-like body 11 and the chamber 1
The inside of 8 is evacuated, and various processing is performed while heating the wafer 30 by the heating resistor 12 and the temperature detecting elements 22 and 23 so that the wafer 30 has a constant temperature.

At this time, since the upper and lower ends of the tubular body 13 are airtightly joined to each other, the inside of the tubular body 13 can be completely cut off from the inside of the chamber 18. That is, the inside of the chamber 18 is set to a high vacuum of about 10 ⁻⁹ torr / sec or less and at a high temperature to introduce a corrosive gas.
The inside of can be an atmospheric atmosphere communicating with the outside.

Therefore, members such as the temperature detecting elements 22 and 23 and the energizing terminal 21 are not exposed to a corrosive atmosphere at a high temperature inside the chamber 18, so that durability can be improved and impurities inside the chamber 18 can be increased. It is possible to prevent particles and particles from mixing in.

Further, in the present invention, the flange portion 1 of the cylindrical body 13
By bonding the stress relaxation ring 16 to the lower surface of 3a, it is possible to make it difficult for a gap to form in this bonded portion even when a thermal cycle is applied.

That is, as shown in the enlarged view of FIG. 2 (A), a metallized layer is formed on the lower surface of the ceramic plate 11 and the brazing material 14 is used to form a metal cylinder. The flange 13a of 13 is joined. A stress relaxation ring 16 having a quadrangular cross section is joined to the lower surface on the opposite side of the flange portion via a brazing material 15.

Therefore, when a thermal cycle is applied,
Even if a difference in thermal expansion occurs, the flange portion 13a of the tubular body 13 is sandwiched and constrained by the plate-shaped body 11 and the stress relaxation ring 16, so that deformation can be prevented. As a result, a gap is less likely to occur in the brazing material 14 portion, and the occurrence of gas leakage can be prevented.

The material of the stress relaxation ring 16 is
Although metals, ceramics, etc. can be used, it is necessary to use a material having a coefficient of thermal expansion similar to that of the plate-shaped body 11 in order to achieve the above effects.
It is preferable that the difference in the coefficient of thermal expansion from that of 1 is 2 × 10 ⁻⁶ / ° C. or less. In particular, it is optimal to use ceramics having the same main component as that of the plate-shaped body 11.

The thickness t of the stress relaxation ring 16 is 1 m.
It is preferably m or more. This has a thickness t of 1 mm
This is because the effect of preventing the deformation of the flange portion 13a is insufficient when the amount is less than the above.

Further, as another embodiment, FIG.
As shown in, the flange portion 13a of the cylindrical body 13 may be formed to extend both outward and inward, and the width of the joint portion by the brazing material 14 may be increased. In this case, the stress relaxation ring 16 may be provided on either or both of the outside (vacuum side) and the inside (atmosphere side) of the cylindrical body 13.

In the above examples, the ceramics forming the plate-like body 11 are Al ₂ O ₃ , AlN, Zr.
Ceramics containing at least one of O ₂ , SiC, Si ₃ N _4, etc. as a main component is used. Among these, from the viewpoint of plasma resistance in particular, alumina ceramics containing 99% by weight or more of Al ₂ O ₃ as a main component and a sintering aid such as SiO ₂ , MgO, CaO, or AlN as a main component and the periodic rule Table 2a
0.5 to 20% by weight of Group 3 element oxide and Group 3a element oxide
Either of the aluminum nitride ceramics contained in the above range or the high-purity aluminum nitride ceramics containing 99% by weight or more of AlN as a main component is suitable.

Therefore, as the material of the stress relaxation ring 16, it is preferable to use the same ceramic as that of the plate body 11.

As the material of the cylindrical body 13, a metal having a high corrosion resistance and a difference in coefficient of thermal expansion from the plate-shaped body 11 of 6 × 10 ⁻⁶ / ° C. or less is used. This is because the difference in coefficient of thermal expansion is 6 × 10 ⁻⁶ /
This is because if the temperature exceeds ° C, cracks are likely to occur at the ceramic bonding interface immediately after brazing. In particular,
An Fe-Ni-Co alloy, an Fe-Ni alloy, or the like may be used.

Further, as the material of the brazing materials 14 and 15, a material which does not melt and liquefy at high temperature is used, and specifically, Ag—Cu based or Ti—Cu—Ag based brazing is used.

Next, another embodiment of the present invention will be described.

In the above example, the tubular body 13 is made of metal, but the tubular body 13 can also be made of ceramics.
That is, in the wafer holding device having the structure as shown in FIG. 3, the cylindrical body 13 is formed of ceramics, and the flange portion 13a and the lower surface of the ceramic plate-shaped body 11 are brazed.
It is also possible to join them by 4.

By doing so, the tubular body 13 is not deformed even when a thermal cycle is applied, and it is possible to prevent a gap from being formed in the joint portion. In order to obtain such an effect, the plate-shaped body 1 is used as the ceramic forming the cylindrical body 13.
It is preferable to use one having a coefficient of thermal expansion difference of 2 × 10 ⁻⁶ / ° C. or less from that of No. 1, and it is most preferable to use ceramics having the same main component as the plate-like body 11.

[0036]

EXAMPLES Example 1 As an example of the present invention, a wafer holding device shown in FIG. 1 was prototyped.

The plate-like body 11 has a diameter of 8 inches (about 200 m).
The disk-shaped m) was formed of high-purity aluminum nitride ceramics having an AlN content of 99.9% by weight or more. The primary raw material of AlN was mixed with methanol, and primary pulverization and mixing were performed to obtain an average particle size of 1 μm, and then 10% of an organic binder was added to obtain a secondary mixing slurry. This slurry was granulated with a spray dryer to prepare a predetermined granulated powder.
The granulated powder was CIP-molded at 0.8 ton and then further cut into a predetermined size. After this, 50
Degreased in an oxidizing atmosphere of 0 ℃, 20 in N ₂ atmosphere
Firing was performed at 00 ° C. for 5 hours. The obtained sintered body had a specific gravity of 3.26 g / cm ^3, which was a sufficient density for the theoretical density, and its coefficient of thermal expansion was 5 × 10 ⁻⁶ / ° C.

The tubular body 13 has a tubular portion with a diameter of 150 m.
m, wall thickness 0.5 mm, and its material is: Fe-Ni-Co alloy thermal expansion coefficient 8 x 10 ^-6 / ° C Fe-Ni alloy thermal expansion coefficient 11 x 10 ^-6 / ° C Stainless steel (SUS304) thermal expansion coefficient Four kinds of metals having a coefficient of thermal expansion of 13.5 × 10 ⁻⁶ / ° C. and tungsten (W) thermal expansion coefficient of 5.2 × 10 ⁻⁶ / ° C. were used.

Further, the stress relaxation ring 16 is made of the same aluminum nitride ceramics as the plate-like body 11, and four types having a width of 5 mm and a thickness t of 0.5, 1, 5, 10 mm are prepared. .

When the plate-like body 11, the cylindrical body 13 and the stress relaxation ring 16 are joined by brazing, a Cu-Ag-Ti based brazing material is preliminarily provided at predetermined positions of the plate-like body 11 and the stress relaxation ring 16. To form a metallization layer on the surface at 800 ℃,
This surface was plated with Ni. On the other hand, the flange portion 13a of the cylindrical body 13 was also plated with Ni. On the other hand, using Ag—Cu based brazing material as the brazing materials 14 and 85
Brazing was performed in a vacuum at 0 ° C.

Further, as a comparative example, one in which the stress relaxation ring 16 was not joined was also prepared.

Using these wafer holders, an experiment was conducted in an actual PVD apparatus to examine the presence or absence of leakage at the joint after a thermal cycle of from room temperature to 550 ° C. was applied.

First, the thickness t of the stress relaxation ring 16 is set to 5 m.
Table 1 shows the results when the material of the cylindrical body 13 was changed and a heat cycle of 50 cycles was applied. From these results, in the case where the stress relaxation ring 16 is not provided, a gap is generated in the joint portion to cause a leak, whereas in the case where the stress relaxation ring 16 according to the embodiment of the present invention is provided, a leak occurs. There wasn't.

However, in the case where stainless steel is used as the cylindrical body 13, the difference in coefficient of thermal expansion from the plate-shaped body 11 is 6 × 10 ⁻⁶ /
Since the temperature exceeded ℃, cracks occurred after brazing. Further, in the case where tungsten is used as the cylindrical body 13, the corrosion resistance is poor and it cannot be practically used.

[0045]

[Table 1]

Next, an experiment was carried out to find the number of thermal cycles until a leak occurred for the cylindrical body 13 using an Fe-Ni-Co alloy and the thickness t of the stress relaxation ring 16 was changed.

As shown in Table 2, it was found that when the thickness t is 1 mm or more, the durability is 50 cycles or more, and when the thickness t is 5 mm or more, the durability is 200 cycles or more.

[0048]

[Table 2]

Example 2 Next, a wafer holding device was prototyped in the same manner as in Example 1 except that the plate-like body 11 and the stress relaxation ring 16 were formed of alumina ceramics.

The plate 11 and the stress relaxation ring 16 are
l ₂ O _{3 Using} 99.9% by weight or more of alumina raw material,
The primary raw material is mixed with water and primary pulverized and blended, and the average particle size is adjusted to 0.
After adjusting the thickness to 5 μm or less, 10% of an organic binder was added to obtain a secondary blended slurry. This slurry was granulated with a spray dryer to prepare a predetermined granulated powder. This granulated powder was CIP-molded at 0.8 ton and then cut into a predetermined size. The compact was fired in an oxidizing atmosphere at about 1800 ° C. for 5 hours. The specific gravity of the obtained sintered body was 3.9 g / cm ³ , which was a sufficient density for the theoretical density, and the coefficient of thermal expansion was 7.1 × 10 ⁻⁶ /
° C.

The material of the cylindrical body 13 is as follows: Thermal expansion coefficient of Fe-Ni-Co alloy 8 x 10 ^-6 / ° C Thermal expansion coefficient of Fe-Ni alloy 11 x 10 ^-6 / ° C Stainless steel (SUS304) Thermal expansion coefficient 13 the .5 × 10 ^-6 / ℃ molybdenum (Mo) 4 kinds of metals the coefficient of thermal expansion 5.8 × 10 ^-6 / ℃ used.

Plate-like body 11, cylindrical body 13, stress relaxation ring 1
When joining 6 by brazing, a metallization layer is formed on the surface of the plate-like body 11 and the stress relaxation ring 16 at 1100 ° C. using a Mo—Mn-based brazing material in advance, and this surface is plated with Ni. Was applied. On the other hand, the flange portion 13 of the cylindrical body 13
Ni plating was also applied to a. On the other hand, brazing material 1
Brazing was performed in vacuum at 850 ° C. by using Ag—Cu based waxes as Nos. 4 and 15.

Further, as a comparative example, one in which the stress relaxation ring 16 was not joined was prepared.

Using these wafer holding devices, an experiment was conducted in an actual PVD device to examine the presence / absence of leakage at the joint after a thermal cycle from room temperature to 550 ° C. was applied.

First, the thickness t of the stress relaxation ring 16 is set to 5 m.
Table 3 shows the results when the material of the cylindrical body 13 was changed and the heat cycle of 50 cycles was applied. From these results, in the case where the stress relaxation ring 16 is not provided, a gap is generated in the joint portion to cause a leak, whereas in the case where the stress relaxation ring 16 according to the embodiment of the present invention is provided, a leak occurs. There wasn't.

However, in the case where stainless steel is used as the cylindrical body 13, the difference in coefficient of thermal expansion from the plate-shaped body 11 is 6 × 10 ⁻⁶ /
Since the temperature exceeded ℃, cracks occurred after brazing. Further, in the case where molybdenum is used as the cylindrical body 13, the corrosion resistance is poor and it cannot be practically used.

[0057]

[Table 3]

Next, an experiment was carried out to find the number of thermal cycles until a leak occurred in the case where the stress relaxation ring 16 was changed in thickness t by using a Fe-Ni-Co alloy as the cylindrical body 13.

As shown in Table 4, it was found that when the thickness t was 1 mm or more, the durability was 50 cycles or more, and when the thickness t was 5 mm or more, the durability was 200 cycles or more.

[0060]

[Table 4]

[0061]

As described above, according to the present invention, the flange portion of the vacuum hermetic cylinder is joined to the lower surface of the ceramic plate-like body having the wafer mounting surface, and the lower surface of the flange portion is joined. Since the wafer holding device is configured by joining the stress relaxation rings, the flange of the cylinder does not easily deform even when a thermal cycle is applied, so the joint with the plate does not leak gas and is good for a long time. Can be used for

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a wafer holding device of the present invention.

FIG. 2 is an enlarged cross-sectional view showing a joint portion between a plate-shaped body and a cylinder in the wafer holding device of the present invention.

FIG. 3 is a cross-sectional view showing a conventional wafer holding device.

FIG. 4 is an enlarged cross-sectional view showing a joint between a plate-shaped body and a cylinder in a conventional wafer holding device.

[Explanation of symbols]

 11: Plate 11a: Mounting Surface 12: Heating Resistor 13: Cylindrical 13a: Flange 14: Brazing 15: Brazing 16: Stress Relief Ring 17: O-ring 18: Chamber 21: Current Terminal 22: Temperature Detection element 30: Wafer

Claims (3)

[Claims] 1. A flange portion of a vacuum airtight cylinder is joined to the lower surface of a ceramic plate having a wafer mounting surface, and a stress relaxation ring is joined to the lower surface of the flange portion. Wafer holding device. 2. The wafer holding device according to claim 1, wherein the stress relaxation ring has a coefficient of thermal expansion similar to that of the plate-like body and has a thickness of 1 mm or more. 3. A ceramic vacuum-sealing cylinder having a coefficient of thermal expansion similar to that of the plate-shaped body is bonded to the lower surface of the ceramic plate-shaped body having a wafer mounting surface. Wafer holding device.