JP3469000B2 - Vertical wafer support device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for supporting a wafer when a silicon wafer or the like is processed at a high temperature, and more particularly to a vertical wafer support suitable for placing the wafer inside a vertical diffusion furnace or the like. Regarding the device.

[0002]

2. Description of the Related Art Conventionally, in a manufacturing process of a semiconductor device such as a semiconductor integrated circuit, impurities are diffused or a surface is protected to form a p-type or n-type conductivity type in a single crystal silicon wafer which is a semiconductor. An electric furnace called a horizontal diffusion furnace in which the core tube is arranged horizontally has been used for forming an oxide film. In the case of this horizontal diffusion furnace, a large number of silicon wafers are arranged side by side in a horizontal direction while standing on a support member called a wafer boat made of quartz glass, and are carried into or out of the diffusion furnace. However, in recent years, with the increasing integration of semiconductor devices, less particles are generated, oxygen entrapment can be reduced, and the floor area of a clean room can be reduced. Also in a CVD furnace for forming an insulating oxide film or the like by a growth method (CVD), a rapid shift to a vertical furnace is in progress.

In a vertical diffusion furnace, core tubes are arranged vertically. For this reason, the wafer supporting device is also of a vertical type, and is arranged so that silicon wafers are vertically stacked like a silkworm shelf. FIG. 5A shows an example of a conventional vertical wafer supporting device.

The wafer support device 10 is made of quartz glass or silicon carbide (SiC) and has a circular base 12.
A plurality of (for example, four) struts 14 (14a to 1) are provided on the periphery of
4d) is erected, and a circular top plate 16 is attached to the upper part of these columns 14. Further, as shown in FIG. 5B, each of the columns 14 is provided with a plurality of insertion grooves 18 at equal intervals in the vertical direction, and the protrusions 20 formed between the insertion grooves 18 are provided. It serves as a support portion for the silicon wafer 22, and the peripheral portion of the silicon wafer 22 is placed on the protrusion 20 to support the silicon wafer 22 at four points. Then, the silicon wafer 22 is designed to be taken in and out of the wafer supporting device 10 through the space between the columns 14a and 14d having a wider spacing than the others.

However, when the peripheral edge portion of the silicon wafer 22 is inserted into the insertion groove 18 and supported in this way, the silicon wafer 22 is supported only by the protrusion 20 of the column 14, and the other portions of the silicon wafer 22 are not supported. There is nothing to support the part, and the part is in a cantilever state, and the part adjacent to the supported part becomes the maximum stress part, and a very large stress occurs. Therefore, when the silicon wafer 22 is processed at a high temperature of 1000 ° C. or higher, a linear defect called a slip occurs in the maximum stress portion, and it becomes impossible to manufacture a semiconductor device. In particular, in recent years, the diameter of silicon wafers has been increased, and silicon wafers 22 having a diameter of 8 inches have been used. Slip is a big problem.

Therefore, as shown in FIG. 5C, the disk-shaped or ring-shaped wafer support plate 24 is supported by the projections 20 of the support columns 14, and the disk-shaped or ring-shaped wafer support plate 24 is supported. Place the silicon wafer 22 on the silicon wafer 22.
It is considered that the load is prevented from concentrating only on a part of the peripheral edge portion of the sheet to prevent plastic deformation and slippage (for example, Japanese Patent Laid-Open No. 5-114645).

[0007]

However, the above-mentioned Japanese Unexamined Patent Application Publication No.
The wafer supporting plate 24 described in Japanese Patent Publication No. 114645,
Since it is formed flat and has a large contact area with the silicon wafer 22, heat distribution is generated in the silicon wafer 22, which causes slippage. Further, the wafer support plate 24 is
Since it is formed flat, it is difficult to make the position on which the silicon wafer 22 is placed constant, and variations in the processing due to the deviation of the supporting position of the silicon wafer 22 are likely to occur. Further, when supporting the silicon wafer 22, it is optimal to support the circular silicon wafer 22 at a position of about 70% from the center in the radial direction where the weight inside the radial direction is equal to the weight outside. However, the above-mentioned ring-shaped plate 24
Supports the entire peripheral edge of the silicon wafer 22, and cannot support the optimum position.

The present invention has been made to solve the above-mentioned drawbacks of the prior art, and an object thereof is to reduce the heat distribution of the wafer to reduce the occurrence of slip. Also,
It is an object of the present invention to provide a vertical wafer support device that can keep the wafer support position constant.
The present invention has an object to support a circular wafer at an optimum supporting position. Furthermore, the present invention aims to reduce the weight and the like.

[0009]

In order to achieve the above object, a vertical wafer supporting apparatus according to the present invention is a vertical wafer supporting apparatus in which a plurality of wafer supporting columns are erected on a base. A locking part that is locked to each of the columns
The inner side of the locking part of the
A structure in which a wafer support ring having a step portion that performs an arrangement operation and a convex annular wafer support portion that is formed upward and supports a wafer is provided on an inner peripheral portion that is integrated with the step portion.
Has become. Further , it is desirable that the wafer supporting portion is formed at a position where the weights of the center side and the outer edge side of the wafer to be supported are almost equal. Then, the wafer support ring may be made of a thin film of silicon carbide. A wafer support ring made of silicon carbide is obtained by processing a ring-shaped graphite base material into a predetermined shape, and performing chemical vapor deposition (CVD) on the graphite base material.
Method) to deposit silicon carbide (SiC), and then burn and remove the graphite base material to easily obtain the same.

[0010]

According to the present invention constructed as described above, since the wafer is supported by the convex annular wafer supporting portion formed upward, the contact area with the wafer is small, so that the thermal influence on the wafer can be reduced. In addition, when the wafer is heated, the heat distribution of the wafer becomes uniform, the occurrence of thermal strain can be prevented, and the occurrence of slip can be reduced. Further, since the convex annular wafer support portion is formed lower than the outer peripheral edge portion,
By setting the inner diameter of the outer peripheral edge of the wafer support ring according to the size of the wafer, the wafer support position of the wafer can be made substantially constant. Therefore, it is possible to eliminate the variation in the heat treatment state due to the variation in the supporting position, and it is possible to make the quality of the wafer constant.

Further, when the wafer supporting portion is formed at a position where the weight of the center side of the wafer is almost equal to that of the outer edge side of the wafer, the weights of the wafer inside and outside the wafer supporting portion are balanced, and the weight of the wafer supporting portion becomes high during high temperature processing. The sagging due to the wafer is reduced, the distortion of the wafer can be reduced, and the quality of the wafer can be improved. When the wafer support ring is formed of a silicon carbide thin film, the heat capacity can be reduced, and a wafer support ring that is lightweight and has high rigidity and extremely small thermal deformation can be obtained. The influence can be reduced, and the occurrence of wafer slip can be reduced.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of a vertical wafer supporting apparatus according to the present invention will be described in detail with reference to the accompanying drawings. The parts corresponding to the parts described in the above-mentioned prior art are designated by the same reference numerals, and the description thereof will be omitted.

FIG. 1 (1) is an explanatory view of a main part of a vertical wafer supporting apparatus according to an embodiment of the present invention, and FIG. 1 (2) is
It is an expanded sectional view which follows the AA line of Drawing 1 (1). In FIG. 1, a wafer support ring 30 is arranged on each protrusion 20 of the columns 14a to 14d. The wafer support ring 30 is formed of a thin film of SiC, as will be described later, and has an outer peripheral edge portion which serves as a locking portion 32 which is inserted into the insertion groove 18 of the pillar 14 and arranged on the protrusion 20. There is. As shown in detail in FIG. 2, the wafer support ring 30 has a crank shape in which the inner peripheral side of the locking portion 32 is bent downward and has a step portion 34, and the outer peripheral surface of the step portion 34 is It is formed so as to contact the peripheral surface of the protrusion 20 (FIG. 1 (2)).
reference). Further, the inner peripheral edge of the wafer support ring 30 is bent upward so that a groove 36 is formed between the wafer supporting ring 30 and the stepped portion 34, and the bent portion of the inner peripheral edge serves to arrange the silicon wafer 22. It is a convex annular wafer support 38. The upper end of the wafer supporting portion 38 has an engaging portion 32 that is an outer peripheral edge portion.
Of the stepped portion 34 and the inner peripheral dimension of the stepped portion 34 (the diameter of the outer peripheral side wall of the groove 36) is formed to match the outer diameter of the silicon wafer 22, so that the silicon wafer 22 can be easily positioned. I am doing it.

In this embodiment, the width W of the groove 36 is formed to be 0.5 to 8 mm, and the distance h from the upper surface of the locking portion 32 to the bottom surface of the groove 36 is 0.
It is set to 5 to 15 mm. Further, the wafer support 38 is
The height may be such that the silicon wafer 22 does not contact the bottom surface of the groove 38. The base 12 and the pillars 14 that are the main body of the wafer supporting apparatus 10 are also formed of SiC.

FIG. 3 shows a manufacturing process of the wafer support ring 30. When forming the wafer support ring 30, first, as shown in the cross section of FIG. 3A, the upper surface of the ring-shaped graphite base material 40 is machined into a predetermined shape so that the wafer support ring 30 can be obtained. Next, the graphite base material 40 processed into a predetermined shape is put into a CVD furnace, and then, as shown in FIG.
As shown in FIG.
To form a thin film 42 of. The thickness of this SiC thin film 42 is
It is desirable that the thickness be 0.1 mm or more in consideration of handleability. After the SiC thin film 42 having a predetermined thickness is formed on the surface of the graphite 40, the bottom surface, the outer peripheral surface, and the inner peripheral surface of the graphite base material 40 are cut off to remove the graphite base material as shown in FIG. Material 4
The SiC thin film 42 is left only on the upper surface portion of 0. After that, FIG.
The graphite base material 40 processed as in (3) is placed in a firing furnace in an oxidizing atmosphere, and the graphite base material 40 is burned to leave only the SiC thin film 42 (see FIG. 3 (4)). Further, if necessary, the horizontal protrusions on the inner peripheral portion are cut off to finish the wafer support ring 30 having a predetermined shape as shown in FIG.

Since the wafer support ring 30 made of the SiC thin film 42 formed in this manner supports the silicon wafer 22 by the convex annular wafer support portion 38, the silicon wafer 22 and the wafer support portion 38 are separated from each other. Is relatively small, the thermal effect on the silicon wafer 22 can be reduced, the heat distribution of the silicon wafer 22 can be made uniform, and the occurrence of slip due to thermal strain can be prevented. Moreover, since the wafer supporting portion 38 is formed lower than the outer peripheral edge portion serving as the locking portion 32, the silicon wafer 22 can be easily positioned and can be supported at a substantially constant position. Variations in heat treatment due to misalignment can be eliminated.

Further, since the wafer supporting ring 30 is formed of the SiC thin film 42, the wafer supporting ring 30 is light in weight, and the weight of the wafer supporting device 10 can be reduced. Further, since the wafer support ring 30 has a thin film structure, has a small heat capacity, and is heated to the ambient temperature in a short time, the silicon wafer 2
It is possible to reduce the thermal influence on the silicon wafer 22 when heating 2. The wafer support ring 30 made of the SiC thin film 42 has high rigidity and is strong against impact, and can reduce the film thickness to reduce the cost. In addition, since the thermal stress is small, thermal deformation is extremely large. Wafer support ring 3 that is small and receives the silicon wafer 22
Since the effect of thermal deformation of 0 is small, silicon wafer 2
The occurrence of slip of 2 can be improved.

FIG. 4 shows another embodiment. In the present embodiment, the wafer support 38 and the step 3
The width of the groove 36 formed between the wafer supporting portion 38 and the wafer supporting portion 38 is increased so that the weight of the wafer supporting portion 38 on the center side of the silicon wafer 22 is substantially equal to the weight of the silicon wafer 22 on the outer peripheral edge side. The position of can be supported. That is, in the circular silicon wafer 22, the area on the inner circumference side and the area on the outer circumference side are substantially equal at a position approximately 70 to 71% of the radius r from the center. Therefore, for example, the silicon wafer 22
Supporting the position of 67 to 74% of the radius r from the center of
The difference in weight of the silicon wafer 22 between the inner peripheral side and the outer peripheral side of the wafer supporting portion 38 is relatively small, and it is possible to reduce the influence of sagging due to its own weight when the silicon wafer 22 is subjected to high temperature processing, and reduce the occurrence of slippage. can do.

[0019]

As described above, according to the present invention, since the wafer is supported by the convex annular wafer supporting portion formed upward, the contact area between the wafer and the wafer supporting portion is small. In addition, it is possible to reduce the thermal influence on the wafer when the wafer is heated, the heat distribution of the wafer becomes uniform, and the occurrence of slip can be suppressed. Further, since the convex ring-shaped wafer support portion is formed lower than the outer peripheral edge portion, the diameter of the wafer support ring inside the outer peripheral edge portion to be locked to the support pillar is set according to the size of the wafer. It is possible to make the wafer supporting position of the wafer supporting portion substantially constant, to eliminate the variation of the heat treatment state due to the variation of the supporting position, and to make the quality of the wafer constant.

Further, if the convex annular wafer support portion is formed at a position where the weights of the center side and the outer edge side of the wafer are substantially equal, the weights of the wafer inside and outside the wafer support portion are balanced, so that high temperature processing is performed. It is possible to reduce the distortion due to the sagging of the wafer due to its own weight at the time of performing, and to improve the quality of the wafer. When the wafer support ring is formed of a silicon carbide thin film, the heat capacity can be reduced, and a wafer support ring that is lightweight and has high rigidity and extremely small thermal deformation can be obtained. The influence can be reduced, and the occurrence of wafer slip can be reduced.

[Brief description of drawings]

FIG. 1 is an explanatory view of a main part of a vertical wafer supporting apparatus according to an embodiment of the present invention and an enlarged sectional view taken along the line AA of FIG. 1 (1).

FIG. 2 is a plan view of a wafer support ring according to an embodiment of the present invention and a sectional view taken along line BB.

FIG. 3 is an explanatory diagram of a manufacturing process of the wafer support ring according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram of another embodiment of the present invention.

FIG. 5 is an explanatory diagram of a conventional vertical wafer supporting device.

[Explanation of symbols]

10 Wafer support device 14a-14d prop 22 Silicon wafer 30 Wafer support ring 32 Locking part 38 Wafer support

Front page continued (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 21/22 H01L 21/205 H01L 21/68

Claims (3)

(57) [Claims] 1. A vertical wafer supporting apparatus having a plurality of wafer supporting columns standing upright on a base, wherein an outer peripheral edge portion is locked to each of the supporting columns, and a lower portion is provided on an inner peripheral side of the locking portion.
The step part that bends in one direction to position the wafer, and
2. A vertical wafer supporting device , wherein a wafer supporting ring having a convex annular wafer supporting portion that is formed upward and supports a wafer is provided on an inner peripheral portion that is integral with the step portion . 2. The vertical wafer supporting apparatus according to claim 1, wherein the wafer supporting portion is formed at a position where the weight of the center side and the outer edge side of the wafer to be supported are substantially equal. 3. The vertical wafer supporting apparatus according to claim 1 , wherein the wafer supporting ring is made of a silicon carbide thin film.