JPH09275078A - Silicon wafer retaining jig - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wafer boat where slip does not occur in the heat treatment of a large-bore silicon wafer. SOLUTION: A wafer boat 10 consists of a plurality of support bars 3a-3d and a roof plate 1 and a bottom plate to hold and fix the support bars 3a-3d roughly parallel. The wafer boat 10 is composed of the silicon carbide material consisting of 40wt.%-75wt.% silicon carbide and 60wt.%-25wt.% silicon. In this silicon carbide material, the content of the impurity elements noxious to the silicon wafer is 1ppm or under. Moreover, the surface roughness RA of the wafer boat 10 is less than 5μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a jig for holding a silicon wafer, and more particularly to a jig made of a silicon carbide material such as a silicon wafer boat used for thermal oxidation and diffusion treatment.

[0002]

2. Description of the Related Art Conventionally, quartz glass jigs have been mainly used as heat-resistant jigs for semiconductor production which require high purity. The jig made of quartz glass has an advantage that an extremely high-purity jig can be easily obtained and the inside is easy to observe because it is transparent. However, this quartz glass material is hardly used for heat treatment at 1,150 ° C or higher because it begins to be deformed by viscous flow at a temperature over 1,000 ° C, and devitrification to α-cristobalite However, it has the drawback of short life due to destruction.

As a material capable of solving such drawbacks,
A composite body has been developed in which a porous silicon carbide molded body obtained by molding silicon carbide powder is filled with metallic silicon. However, since it is difficult to obtain a high-purity silicon carbide composite material necessary for heat treatment of semiconductors, a method of forming a silicon carbide film on the surface of the composite material to reduce contamination on a silicon wafer or the like has been proposed. (Japanese Patent Laid-Open No. 63-
35452 publication).

On the other hand, with the recent progress in semiconductor processes, the diameter of silicon wafers has increased from 6 inches to 8 inches and from 8 inches to 12 inches, and the weight of the wafer has increased despite the increase in the weight of the wafer. It has been pointed out that the thickness does not increase so much and that the strength decreases. Further, along with the speeding up of the process (increasing the temperature of high temperature, the rate of temperature increase and decrease, and the rate of insertion and withdrawal), the in-plane temperature distribution of the wafer during heat treatment has become a problem. Therefore, the occurrence of wafer slip (crystal defect due to dislocation), which has not been so important in the past, has become a problem (Nikkei Microdevice, March 1995 issue, p78-79).

In the above-mentioned jig in which the surface of the silicon carbide based material is coated with silicon carbide by CVD, it has been found that slips are more likely to occur as the diameter of the wafer to be heat treated increases.

In order to suppress the occurrence of such a slip, Japanese Patent Laid-Open No. 7-273056 discloses three support rods for supporting the wafer during the heat treatment, each of which has an apex angle of 1
It is disclosed that they are arranged to form a 35 ° isosceles triangle. However, the wafer holding device disclosed in the publication is a horizontal wafer boat that holds a plurality of wafers arranged in a horizontal direction, and a vertical wafer boat has a structure for suppressing the occurrence of slips during heat treatment. It is difficult to apply.

Japanese Laid-Open Patent Publication No. 4-304652 discloses a wafer boat, in which the wafer support rod is formed of polysilicon having characteristics similar to those of a silicon wafer to reduce the occurrence of slip. However, this technique has problems that the strength of polysilicon is low, a column other than the polysilicon support rod is required for reinforcement, and the outer shape and weight of the boat become larger than necessary.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a silicon wafer holding jig having the following advantages.

(1) It does not deform under the high temperature required for heat treatment of silicon wafers. (2) It has sufficient strength to support an automatic transfer system and large-diameter wafers.

(3) Even when a large-diameter silicon wafer, for example, a silicon wafer having a diameter of 200 mm or more is oxidized and diffused, slips are not generated on the wafer.

(4) During the oxidation and diffusion process of the silicon wafer, the wafer is not contaminated with harmful elements.

(5) Even in the vertical wafer boat,
It is possible to sufficiently suppress the occurrence of slip.

[0013]

A silicon wafer holding jig according to the present invention is a jig for holding a silicon wafer during heat treatment, and has a plurality of grooves each having a plurality of grooves for holding a plurality of silicon wafers. A plurality of support rods and fixed portions that are provided at both ends of the plurality of support rods and hold the plurality of support rods substantially parallel to each other, and the support rods and the fixed portions are 40 wt% to 75 wt% carbonized. It is made of silicon and 60 wt% to 25 wt% of silicon, and is made of a silicon carbide material in which the content of an impurity element harmful to a silicon wafer is 1 ppm or less, and the surface roughness Ra of the support rod and the fixing portion is Ra. Is less than 5 μm.

The silicon wafer holding jig of the present invention can be preferably applied to a vertical wafer boat for holding a silicon wafer having a diameter of 200 mm or more.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventor has repeatedly studied the problem that slips tend to occur during heat treatment as the diameter of a silicon wafer increases. The main causes of slippage were considered to be (1) stress generated in a portion of the wafer supported by the weight of the wafer, and (2) temperature distribution generated in the wafer surface during heat treatment. It is considered that the stress acting on the supported portion of the wafer can be reduced by increasing the area of the supported portion of the wafer holding jig. Also, Nikkei Microdevice March 1995, p78-79 teaches that the support point of the wafer is moved from the wafer edge to a position closer to the center. The document also teaches increasing the spacing between the supported wafers to suppress temperature variations that increase stress. However, the present inventor considered that there is room for technical improvement in any case. If the area of the wafer supporting part is increased, the outer shape and weight of the jig will increase and the thermal effect on the wafer from the supporting part will increase. Was issued. Further, even if the wafer support point is moved from the wafer edge to a position closer to the center, the problem of temperature distribution occurring in the wafer surface cannot be sufficiently solved. Increasing the distance between the wafers means reducing the number of wafers that can be processed by the jig at one time, resulting in a decrease in the processing capacity in the batch system.

As a result of a detailed study of the factors that cause slip during heat treatment, the present inventor has found that the temperature distribution in the wafer surface that occurs during heat treatment contributes significantly to the occurrence of slip. Then, in order to solve the problem of the temperature distribution more effectively, as a result of examination, it was found that the material and physical properties of the jig as described below greatly contribute to the temperature distribution,
The present invention has been completed.

First, Table 1 shows thermophysical property values of quartz, SiC, and silicon which have been used as jig materials. From these thermophysical properties, SiC has a high emissivity,
It was found that it causes the increase of the temperature distribution in the silicon surface during temperature rise and decrease. During heat treatment of silicon wafers, the wafer boat loaded with wafers is
It is inserted into the furnace and heated by a heater from outside the reaction tube (quartz, SiC). At this time, the heat transfer to the wafer boat and the wafer is performed mainly in the form of radiant heat. Therefore,
A substance having a high emissivity has a high temperature rising rate. That is, for example, in a wafer boat made of a silicon carbide-based material coated with silicon carbide by CVD, the temperature becomes higher than that of the loaded wafer due to the high emissivity of the coated silicon carbide, and the wafer boat support rod is also in the wafer plane. It was found that the temperature increased locally in the vicinity. On the other hand, since silicon has low strength and toughness, chipping at the time of grooving when forming a wafer support rod,
There was a problem of cracking during handling, and there was a problem of lack of mechanical reliability.

[0018]

[Table 1]

Therefore, the present inventor has made various examinations by constructing a jig with a material having high mechanical reliability, which is composed of silicon carbide and metallic silicon, and which is not coated with silicon carbide. . As a result, as shown also in the following examples, the present inventor has found that the emissivity of the surface of the jig made of the silicon carbide material is less than 0.8 because slip does not occur during the heat treatment of the silicon wafer. Clarified that it is necessary. Further, the inventor has found that the emissivity of the surface of the jig is the composition of the silicon carbide material, that is, the content ratio of silicon carbide and metallic silicon, and the surface roughness of the jig, specifically, the center line average roughness (Ra). ).

First, in order to make the emissivity of the silicon carbide material constituting the jig less than 0.8, the content of silicon carbide is set to 75% by weight or less, more preferably 70% by weight or less,
The balance, that is, 25% by weight or more, more preferably 30% by weight or more, had to be silicon. When the content of silicon carbide exceeds 75% by weight, the emissivity of the jig surface is 0.8
The slip has come to occur particularly in the wafer heat treatment of large diameter. On the other hand, the content of silicon carbide is 40
If it is less than%, the emissivity can be suppressed to a low level,
Since the effect of improving the strength by silicon carbide is low, the problems of chipping during grooving and cracking during handling occurred as in the case of the jig made of silicon. From the above viewpoints, the silicon carbide material constituting the jig in the present invention is 40% by weight to 7% by weight.
5% by weight of silicon carbide and the balance, ie 60% by weight to 2
It consists of 5% by weight of silicon. A more preferable composition of the silicon carbide-based material is 50% by weight to 70% by weight of silicon carbide and the balance, that is, 50% by weight to 30% by weight of silicon. In this range of composition, in order to reduce the emissivity of the surface of the jig, the surface of the silicon carbide material may be coated with silicon. The thickness of the coated silicon can be, for example, 20 to 1000 μm, preferably 50 to 300 μm.

The jig according to the present invention comprises a plurality of support rods having a plurality of grooves for respectively holding a plurality of silicon wafers, and fixing portions provided at both ends of the support rods and holding them substantially parallel to each other. However, in order to effectively suppress the occurrence of slip during the heat treatment of the wafer, it is desirable that the support rod and the fixing portion have the above-described composition.

Further, as mentioned above, the present inventors have found that the surface roughness of the jig affects the apparent emissivity. It has been clarified that even if the material satisfying the above-mentioned composition is used, if the surface roughness exceeds a certain level, the emissivity of the jig surface becomes high, which causes the occurrence of slip. As a result of the examination, the surface roughness of the jig, specifically, the center line average roughness (R
It was necessary that a) be less than 5 μm in order to suppress the occurrence of slip. When Ra is 5 μm or more, the emissivity may exceed 0.8 due to the unevenness of the material surface. Ra less than 5 μm means that the surface is very smooth on average. In order to control the emissivity of the surface of the jig, it was necessary to control the surface roughness not by Rmax but by Ra. Since the emissivity of the support rod and the fixed portion that make up the jig both affect the occurrence of slip, it is desirable that the surface roughness of these be less than 5 μm.

The present inventor has further found that the surface roughness of the silicon carbide material composed of silicon carbide and silicon is 5 μm.
It has been found that special considerations are needed to obtain a smooth surface of less than. Usually, a silicon carbide-based material is obtained by molding silicon carbide powder, sintering it, and impregnating it with silicon, but the particle size of the silicon carbide powder used greatly affects the surface roughness of the finally obtained material. I understand. Then, it is necessary that the average particle diameter of the silicon carbide powder used is in the range of 0.5 μm to 20 μm, preferably 2 μm to 10 μm in order to obtain a silicon carbide based material having a surface roughness of Ra less than 5 μm. I found it.
When the average particle size of the silicon carbide powder is less than 0.5 μm,
The density of the compact tends to become non-uniform due to the decrease in the fluidity of the powder, and the grain growth during sintering tends to be promoted rather, so that the surface of the obtained silicon carbide material becomes rough. On the other hand, when the average particle diameter exceeds 20 μm, the bonding area between the particles is reduced, so that the bonding of the particles in the silicon carbide sintered body is weak and the material surface is likely to be roughened. The average particle diameter of the silicon carbide powder used is 0.5 to 20 μm, preferably 2 μm.
When the thickness is in the range of 10 μm, the particles are firmly bonded to each other, and a silicon carbide material having a smooth surface can be obtained. When silicon carbide powder having these particle sizes is used, the average particle size of the silicon carbide particles in the obtained silicon carbide-based material can be, for example, in the range of 2 μm to 20 μm. The silicon carbide that constitutes the silicon carbide material is α
Type, β type, or a mixture thereof.

Since the silicon wafer holding jig is a product required to have high purity, silicon carbide and silicon must also have high purity. Specifically, it is necessary that the content of the impurity element harmful to the silicon wafer is 1 ppm or less. Each harmful metal impurities content is 1p
pm or less, and the total is preferably 1 ppm or less. Impurity elements harmful to silicon wafers are vaporized into chlorides and the like during the heat treatment process of the wafers and are taken into the wafers as impurities, which lowers the insulation resistance of the silicon wafer and lowers the withstand voltage of silicon oxide. Means an element that easily causes Specifically, as harmful impurity elements, heavy metal elements such as Fe, Ni, Cu and Cr, alkali metal elements such as Li, Na and K, and alkaline earth metals such as Be, Mg, Ca, B and Ga. And elements of amphoteric metals. In the heat treatment, if the content of these impurity elements exceeds 1 ppm, the insulation resistance of the silicon wafer and the withstand voltage of the silicon oxide may be reduced.

In order to obtain such a high-purity silicon carbide material, it is desirable to use a silicon carbide powder synthesized from a higher-purity raw material. For example, a silicon carbide powder obtained by heating and firing a uniform mixture of an organic compound produced without using a metal catalyst as a carbonaceous material and a high-purity silicon compound in a non-oxidizing atmosphere is preferably used. be able to. Examples of the above-mentioned organic compound include a resol-type phenol resin synthesized by using ammonia or an organic amine as a catalyst, a novolac type phenol resin synthesized by using an acid as a catalyst, and the like. Methylsilane etc. can be mentioned.

In the jig of the present invention composed of a silicon carbide material, silicon carbide powder is molded, the obtained molded body is sintered, and then the obtained porous body is impregnated with high-purity silicon. Can be manufactured by. The silicon carbide powder used as a raw material may be either α or β type, or may be a mixture. In order to obtain a composition having a silicon carbide content of more than 60% by weight, it is necessary to mix carbon powder with silicon carbide powder. In the subsequent molten silicon impregnation step, as a result of reacting carbon and silicon to generate silicon carbide, it is possible to obtain a silicon carbide content rate of more than 60% by weight in the obtained sintered body. As the carbon source, graphite, carbon black or the like is used. The blending amount is determined from the bulk density of the molded product and the required silicon carbide content. Further, since jigs for semiconductors and the like are required to have high purity, it is needless to say that it is also necessary to use high purity carbon powder. For the relationship between the weight of carbon added and the silicon carbide content in the finally obtained sintered body, the following formula can be referred to.

[0027]

[Equation 1] Silicon carbide content (%) = [{weight of silicon carbide powder in molded body + (40 × weight of carbon in molded body) / 12}]
× 100 (%) / weight of reaction sintered body Then, a known resin as a binder is added to the silicon carbide powder or the mixture of the silicon carbide powder and the carbon powder. As the resin, phenol resin, acrylic resin or the like is used. The compound is then molded into the desired shape,
This molding may be performed by a known method such as die pressing, casting, CIP and the like. At this time, the bulk density of the molded body is adjusted according to the intended silicon carbide content, and the porosity is 40% to 60%.
%.

The silicon carbide or the silicon carbide and carbon compact is calcined to degrease the binder in the compact. Although the calcination temperature and time vary depending on the size of the molded product, the binder composition, etc., it is suitable to be 500 ° C. to 1000 ° C. and 30 minutes to 20 hours. Also, the temperature rising rate is appropriately adjusted depending on the size and thickness of the molded body.

Next, the degreased calcined body is subjected to a purification treatment, which is carried out by heat treatment in an atmosphere of HCl and Cl ₂ gas as is well known.

Next, the purified compact is made into a sintered body by reaction sintering with molten silicon, and this step may be performed by a known method. That is, silicon, for example, high-purity silicon for semiconductors may be heated to a temperature equal to or higher than the melting point and melted, and then the above-mentioned molded body may be impregnated. When carbon is present in the porous compact, when it is impregnated with molten metal silicon, it reacts with the carbon inside the porous body to cause densification while producing silicon carbide, and sintering after the reaction is completed. The pores of the body are further filled with metallic silicon to form a dense sintered body.

The silicon carbide material constituting the jig of the present invention has a gas impermeable structure in which silicon is filled in a porous body made of silicon carbide and has a surface roughness Ra of 5 μm.
The surface emissivity is less than 0.8, for example, 0.55 or more and less than 0.8.

The present invention will be specifically described below with reference to examples.

[0033]

【Example】

Example 1 A mixture of 60 parts by weight of silicon carbide powder having an average particle size of about 5 μm and having a content of each of Na, K, Ca, Fe, Ni, Cu and Cr of 1 ppm or less and 3 parts by weight of carbon powder was subjected to a conventional method. After molding, the molded body obtained was subjected to degreasing firing at a temperature of about 1000 ° C. in an Ar atmosphere, and then subjected to a purification treatment at 1200 ° C. in an HCl gas atmosphere. The obtained porous sintered body was impregnated with 37 parts by weight of metallic silicon at 1500 ° C., and then grooves (slits) for holding a wafer were formed to fabricate a vertical wafer boat. Since carbon and silicon reacted with each other in the silicon impregnation step to generate silicon carbide, the content of silicon carbide in the obtained boat was 70% by weight, and the balance was silicon. Also,
In the obtained boat, the content of each metal element described above was 1 ppm or less.

An outline of the obtained vertical wafer boat is shown in FIGS. The vertical wafer boat 10 has four support rods 3a, 3b, 3c and 3d. As shown in the enlarged view of FIG. 3, grooves 5 for inserting a wafer are formed in each of the support rods 3a to 3d at predetermined intervals. As shown in FIG. 1, the top plate 1 is joined to one end of the support rods 3a to 3d, and the bottom plate 2 is joined to the other end. These members hold and fix the four support rods 3a to 3d in parallel. In addition, openings 1a and 2a are formed in the top plate 1 and the bottom plate 2 respectively so as not to block the flow of gas during heat treatment. The wafer boat 10 is erected with the bottom plate 2 down, and the support rods 3 a to 3
The wafer is held by inserting it into the groove formed in d. FIG. 2 shows how the wafer is held from above the top plate 1. The silicon wafer 6 is held by the four support bars 3a to 3d. The plurality of wafers are inserted into the grooves formed in the support rods, respectively, and arranged and held substantially parallel to each other. The dimension D shown in FIG.
Is the height of the wafer boat, dimension A shown in FIG. 2 is the diameter of the top plate, B is the diameter of the wafer to be held, and C1 and C2 are the thickness and width of the support rods. In this embodiment, A is 2
A wafer boat having specifications of 10 mm, B 150 mm (6 inches), C1 × C2 10 mm × 15 mm, and D 750 mm was produced.

Using the obtained wafer boat, the silicon wafer was heat-treated under the conditions of the heat pattern as shown in FIG. Then, it was observed whether slips were generated on the silicon wafer. Table 2 shows the emissivity of the obtained jig surface, the silicon carbide content of the jig, and the surface roughness of the jig (R
a), the slip generation state of the silicon wafer after the heat treatment, and the presence / absence of chipping in the groove processed portion are also shown.

Example 2 A vertical silicon wafer boat was prepared in the same manner as in Example 1 except that 58 parts by weight of silicon carbide, 5 parts by weight of carbon, and 37 parts by weight of silicon were used. The same evaluation was performed. In the obtained boat, the silicon carbide content was 75% by weight, and the balance was silicon. Table 2 shows the results of the evaluation.

Example 3 A vertical wafer boat was produced in the same manner as in Example 1 except that silicon carbide was 60 parts by weight and silicon was 40 parts by weight, and the same evaluation as in Example 1 was carried out. Table 2 shows the results of the evaluation.

Example 4 A vertical wafer boat was prepared and evaluated in the same manner as in Example 1 except that 50 parts by weight of silicon carbide and 50 parts by weight of silicon were used. Table 2 shows the results of the evaluation.

Example 5 A vertical wafer boat was prepared and evaluated in the same manner as in Example 1 except that 40 parts by weight of silicon carbide and 60 parts by weight of silicon were used. Table 2 shows the results of the evaluation.

Examples 6 to 10 Dimension A shown in the figure is 255 mm, B is 200 mm (8 inches), C1 × C2 is 10 mm × 15 mm, and D is 800 m.
A vertical wafer boat having a specification of m was manufactured. Except for that, five types of wafer boats having different component compositions were prepared in the same manner as in Examples 1, 2, 3, 4 and 5, and evaluated in the same manner as in Example 1. Table 2 shows the results of the evaluation.

Examples 11 and 12 Two vertical wafer boats having different dimensions were prepared in the same manner as in Examples 1 and 6 except that the silicon carbide powder used had an average particle size of about 10 μm. Table 2 shows the results of evaluation performed in the same manner as in Example 1.

Examples 13 and 14 Two types of wafer boats having different sizes were produced in the same manner as in Examples 1 and 6 except that the silicon carbide powder used had an average particle size of about 1 μm. Table 2 shows the results of evaluation of the obtained wafer boat.

Examples 15 and 16 Two types of wafer boats having different sizes were prepared in the same manner as in Examples 1 and 6 except that the silicon carbide powder used had an average particle size of about 20 μm. Table 2 shows the results of the evaluation.

Examples 17 and 18 Two types of wafer boats having different sizes were prepared in the same manner as in Examples 1 and 6 except that the silicon carbide powder used had an average particle size of about 0.5 μm. Table 2 shows the results of the evaluation.

Examples 19 and 20 In the wafer boats obtained in Examples 1 and 6, respectively,
Silicon was vapor-deposited to a thickness of about 50 μm to prepare a vertical wafer boat coated with silicon. Table 2 shows the results of evaluation of the obtained wafer boat.

Comparative Examples 1 and 2 Two types of vertical type having different dimensions were prepared in the same manner as in Examples 1 and 6 except that the composition of the silicon carbide material was 30 parts by weight of silicon carbide and 70 parts by weight of silicon. A wafer boat was produced. Table 3 shows the results of evaluating the obtained boat in the same manner as in Example 1.

Comparative Examples 3 and 4 Two kinds of different sizes were obtained in the same manner as in Examples 1 and 6 except that 55 parts by weight of silicon carbide, 7.5 parts by weight of carbon and 37.5 parts by weight of silicon were used. A wafer boat was produced. In the obtained boat, the content of silicon carbide was 80% by weight, and the balance was silicon. Table 3 shows the results of the evaluation.

Comparative Examples 5 and 6 Two kinds of different dimensions were obtained in the same manner as in Examples 1 and 6 except that 54 parts by weight of silicon carbide, 7.8 parts by weight of carbon and 38.2 parts by weight of silicon were used. A wafer boat was produced. In the obtained boat, the silicon carbide content was 85% by weight, and the balance was silicon. Table 3 shows the results of the evaluation.

Comparative Examples 7 and 8 Two kinds of wafer boats having different sizes were prepared in the same manner as in Examples 1 and 6 except that the average particle diameter of the silicon carbide powder was set to about 25 μm. Table 3 shows the results of the evaluation.

Comparative Examples 9 and 10 Wafer boats were manufactured in the same manner as in Examples 1 and 6 except that the silicon carbide powder had an average particle size of about 35 μm.
Table 3 shows the evaluation results of the obtained wafer boat.

Comparative Examples 11 and 12 Except that the average particle size of the silicon carbide powder was about 0.2 μm,
Two types of wafer boats having different sizes were tried to be manufactured in the same manner as in Examples 4 and 9, but the desired sintered body could not be obtained because the porous body was damaged during the degreasing and purification treatments. It is considered that this is because the particle size of the silicon carbide powder was small and the molding density was lowered.

Comparative Examples 13 and 14 The surface of the wafer boats produced in Examples 1 and 6 was coated with a 100 μm thick SiC film by CVD to produce two types of wafer boats having different dimensions. Table 3 shows the results of evaluation performed on the obtained boat in the same manner as in Example 1.

Comparative Examples 15 and 16 In the production of wafer boats according to Examples 1 and 6, respectively, only the support rod portion was made of polysilicon, and the others were the same as in Examples 1 and 6 and differed in size. A variety of wafer boats were made. Table 3 shows the results of the evaluation.

As shown in Table 2, the wafer boats of the examples according to the present invention satisfy the condition that the emissivity is less than 0.8, and slip can occur even in the heat treatment of a large diameter wafer having a diameter of 200 μm. There wasn't. On the other hand, Table 3
As shown in the comparative example, the surface roughness Ra is 5 μm because the composition of the silicon carbide material is out of the range of the present invention, too fine silicon carbide powder and too coarse silicon carbide powder are used.
Those having a temperature above 1.0 and those having a SiC coating had a high emissivity, and slips were easily generated in the silicon wafer during heat treatment. FIG. 5 shows Comparative Example 1
4 shows a slip generation state of a wafer that has been heat-treated with the wafer boat obtained in FIG. As shown in the figure, the slip 7 is generated at a considerable portion of the wafer 6. On the other hand, when the support rod was made of silicon, the slit processing portion was chipped.

Although the vertical wafer boat is manufactured in the above embodiments, the present invention can be applied to the horizontal wafer boat because slips are not generated in the wafer during the heat treatment. Further, in the above embodiment, the wafer boat having four support rods has been described, but the number of support rods is not limited to this. Further, the arrangement and shape of the support rods and the shape and arrangement of the portion fixing them are not limited to those in the above-described embodiments.

[0056]

[Table 2]

[0057]

[Table 3]

[0058]

As described above, according to the present invention, it is possible to obtain a jig that does not generate a slip on a silicon wafer during heat treatment. Further, the jig according to the present invention has sufficient strength to support an automatic transfer system and a large diameter wafer. Furthermore, the jig of the present invention is excellent in the ability to process a large-diameter silicon wafer in a large-capacity batch system. Therefore, the jig of the present invention largely contributes to the improvement of the manufacturing yield and reliability of semiconductor devices.

[Brief description of drawings]

FIG. 1 is a perspective view showing a specific example of a wafer boat according to the present invention.

FIG. 2 is a plan view showing how wafers are held in the wafer boat shown in FIG.

3 is an enlarged cross-sectional view showing a groove formed in a support rod in the wafer boat shown in FIG.

FIG. 4 is a diagram showing conditions for heat-treating a silicon wafer on the boats obtained in Examples and Comparative Examples.

FIG. 5 is a schematic view showing a slip generation state of a wafer that has been heat-treated with a wafer boat according to a comparative example.

[Explanation of symbols]

 1 top plate 2 bottom plate 3a, 3b, 3c, 3d support rod

Claims (2)

[Claims] 1. A silicon wafer holding jig for holding a silicon wafer during heat treatment, comprising: a plurality of support rods having a plurality of grooves for respectively holding the plurality of silicon wafers; And a fixing portion which is provided at both ends of the supporting rod and holds the plurality of supporting rods substantially in parallel, wherein the supporting rod and the fixing portion are 40 wt% to 75 wt% silicon carbide and 60 wt% to 60 wt%. 25% by weight of silicon and a silicon carbide material having a content of an impurity element harmful to the silicon wafer of 1 ppm or less, and the surface roughness R of the support rod and the fixing portion.
A silicon wafer holding jig, wherein a is less than 5 μm. 2. The silicon wafer holding jig has a diameter of 20.
2. The silicon wafer holding jig according to claim 1, which is a vertical wafer boat for holding a silicon wafer of 0 mm or more.