JPH08268796A - Chemical vapor deposition method and susceptor therefor - Google Patents

Abstract

PURPOSE: To provide a CVD method by which a susceptor is not broken even if a semiconductor wafer is taken out after a coating film such as an epitaxially grown film is formed on the wafer surface by CVD and to obtain the susceptor used in this case. CONSTITUTION: A plurality of freely detachable isolating members 1b each coated with SiC or consisting of SiC are arranged on the edge of a spot-faced part 4 to carry the semiconductor wafer 10 of a susceptor 1 coated with SiC so that the circumference of the spot-faced part is divided into >=3 sections. A coating film such as an epitaxially grown film is formed on the wafer 10 while the side face 10a of the wafer is not in contact with the inner wall face 4a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a film such as an epitaxial growth film (epi film) on a surface of a semiconductor wafer such as silicon by a chemical vapor deposition (CVD) method, and a susceptor used at this time.

[0002]

2. Description of the Related Art When forming a film such as an epi film on a semiconductor wafer of silicon or the like by a CVD method, a susceptor having a plurality of spot facing portions for mounting the wafer is used. This susceptor has a carbon material such as graphite as a base material and has its surface coated with silicon carbide (SiC). To prevent the gas emitted from the carbon base material from contaminating the wafer, the surface of the susceptor is A susceptor having a dense SiC film formed by the CVD method is used for the above.

FIG. 3 illustrates a so-called pancake type susceptor as one kind of conventional susceptors of this type. (A) is a plan view of the susceptor 1, and (b) is an enlarged view when the wafer 10 is placed on the spot facing portion 4. The susceptor 1 is formed by coating the surface of a carbon substrate with SiC by a CVD method, and the surface of the wafer 10
A plurality of counterbore portions 4 (4 in this figure) for mounting the are provided. The diameter of the spot facing portion 4 is slightly larger than the diameter of the wafer 10 because the wafer 10 must be housed and taken out. Therefore, when accommodating the wafer 10, the wafer 10 is placed on the inner wall surface 4 a of the spot facing portion 4.
Then, the wafer side surface 10a is placed so as to come into contact (contact portion a) in a state of almost linear contact.

FIG. 4 is a part of a sectional view taken along the line YY in FIG. 3 in the case where the film is formed in such a contact state. In this figure (a), the wafer 10 is placed on the spot facing portion 4, and C
It is a figure when the film 11 is formed on the surface of the wafer 10 by the VD method, and (b) is a figure when the wafer 10 is taken out after the film forming step. Reference numeral 2 denotes a carbon base material, which is usually made of highly purified isotropic graphite. 3 is Si having a thickness of 50 to 200 μm formed on the surface of the carbon substrate 2 by the CVD method.
A C film is shown. As described above, the susceptor 1 is configured by covering the carbon substrate 2 and the surface thereof with the silicon carbide film 3. As described above, when the film 11 such as the epi film is formed on the surface of the wafer 10 by the CVD method while the inner wall surface 4a of the spot facing portion and the side surface 10a of the wafer are in contact with each other, as shown in FIG. Since the coating 11 is formed not only on the surface of the wafer 10 but also on the upper surface 7 of the susceptor,
A continuous coating 11 on the surface of the wafer 10 and the upper surface 7 of the susceptor
Is formed.

Conventionally, since the film 11 such as an epi film formed on the surface of the wafer 10 is as thin as 1 to 10 μm, the wafer 10 can be taken out smoothly without any problem after the film forming process.

[0006]

However, in recent years, since the thickness of the coating film 11 to be formed is as thick as 50 to 200 μm, the wafer 1 is attached to the susceptor 1 after the coating film forming step.
0 adheres strongly, and as shown in FIG. 4B, when the wafer 10 is to be taken out, there is a problem that the SiC film 3 coated on the susceptor 1 has a chip A. . When the chip A is generated in the susceptor 1 in this manner, the carbon base material 2 is exposed and gas is released from that portion to contaminate the wafer 10, so that the susceptor 1 can be used again. Disappear.

By the way, as proposed in Japanese Unexamined Patent Publication No. 7-74114, a barrel type susceptor having a plurality of minute projections on the lower side wall surface of a spot facing portion has a crack (crack) in the wafer itself when taking out the wafer. ) Was effective, but it was not possible to prevent the susceptor, especially the pancake type susceptor, from chipping.

Therefore, according to the present invention, C is formed on the surface of the semiconductor wafer.
An object of the present invention is to provide a CVD method in which a film such as an epi film is formed by the VD method and a chip is not generated in the susceptor even when the wafer is taken out, and a susceptor used in this case.

[0009]

In order to achieve the above object, the CVD method according to the present invention provides a susceptor coated with silicon carbide or a detachable detachable member made of silicon carbide. At the edge of the counterbore on which the semiconductor wafer is to be placed, a plurality of them are arranged so as to divide the circumference of the counterbore into three or more parts so that the side surface of the semiconductor wafer does not contact the inner wall surface of the counterbore. However, a coating film is formed on the semiconductor wafer.

Further, the CVD susceptor according to the present invention includes a detachable separating member coated with silicon carbide or made of silicon carbide, and the separating member at the edge of the counterbore for mounting a semiconductor wafer. What is claimed is: 1. A CVD susceptor comprising a silicon carbide-coated susceptor body having a holding hole, wherein a plurality of the separating members are provided so that the circumference of the spot facing portion is divided into three substantially equal parts or more. A holding hole is arranged.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings.

It has been found by the inventor's investigation that the above-mentioned chipping of the susceptor, which is a conventional defect, occurs from a corner formed by the upper surface 7 of the susceptor and the inner wall surface 4a of the counterbore.
The reason is considered to be that, when the wafer 10 is taken out, this corner portion corresponds to a portion where stress is likely to be concentrated in the susceptor 1.

FIG. 1 is a schematic view showing a structure of a susceptor according to the present invention. This figure illustrates a so-called pancake type susceptor. (A) is a top view of a susceptor, (b) is the schematic diagram which expanded the counterbore part of the cross section by the line XX. Reference numeral 1 is a disk-shaped susceptor having a hole in the center, and is composed of a susceptor body 1a in which a carbon substrate 2 is covered with a SiC film 3 and a detachable separating member 1b. The isolation member 1b has a coefficient of thermal expansion similar to that of the susceptor body 1a.
Three cylindrical members made of SiC or coated with the film are detachably inserted into holding holes 6 formed in the edge of the spot facing portion 4, respectively. This isolation member 1b
Are inserted into positions at equal intervals that divide the circumference of the spot facing portion into three parts, and even if the wafer 10 moves in the spot facing portion 4,
The side surface 10a of the wafer abuts on the side surface of the separating member 1b and is configured so as not to directly contact the inner wall surface 4a of the spot facing portion. Here, the susceptor of the present embodiment is provided with three isolation members 1b, but the present invention is not limited to three and may be three or more, for example 4 to 6. Even in this case,
It is preferable to arrange the detachable separating member 1b so as to divide the circumference of the spot facing portion as evenly as possible.

Next, the operation of the CVD susceptor of the present invention will be described with reference to FIG. This figure (a) is the CVD of FIG.
Plan view when the wafer 10 is placed on the spot facing portion 4 of the susceptor for a vehicle, (b) shows the film 1 on the surface of the wafer 10 by the CVD method.
1 is a cross-sectional view corresponding to FIG. 1B when the film 1 is formed, and FIG. 1C is a cross-sectional view when the wafer 10 is taken out after the film forming step. The same components as those in FIGS. 1, 3, and 4 are designated by the same reference numerals.

As shown in FIG. 2A, three detachable columnar separating members 1b are attached to the edge of the counterbore 4 of the susceptor body 1a, and the circumference of the counterbore is approximately three. It was placed in an equal position. The number of divisions of the circumference of the spot facing portion required in the present invention is 3 or more, and if it is more than this, it may be, for example, 4 to 6 divisions. Here, in order to prevent the wafer side surface 10a from coming into contact with the inner wall surface 4a of the spot facing portion, the size of the separating member 1b depends on the size of the wafer 10 to be placed and the spot facing portion. Although it is difficult to uniquely determine, when a wafer having a diameter of 3 to 8 inches is placed on the spot facing portion, a columnar separating member 1b having a diameter of 1 to 5 mm is used.
If a plurality of wafers are arranged so as to be equally divided into three or more on the circumference of the spot facing portion, the wafer side surface 10a will be located at the spot facing portion inner wall surface 4a.
You can avoid contact with. The reason is that if it is less than 1 mm, the strength tends to be insufficient, and it becomes difficult to keep the chip A at the time of taking out the wafer only in the separating member 1b. On the other hand, if it exceeds 5 mm, it becomes substantially difficult to maintain the state of point contact, and the temperature of the wafer becomes non-uniform, which causes a slip. The length of the separating member 1b is usually 0.5 to 3 mm, depending on the depth of the counterbore, and the inserted state is approximately the same height as the susceptor upper surface 7. Thus, it is preferable that the flow of the raw material gas is not hindered.

By disposing such a separating member 1b at a position that divides the circumference of the spot facing portion into approximately three or more parts, the wafer 1
It is possible to prevent the 0 from coming into contact with the inner wall surface 4a no matter where it moves within the spot facing portion 4.

By constructing the susceptor 1 in this way, even if a thick coating 11 is formed on the wafer 10 by the CVD method and the wafer 10 is taken out, the susceptor body 1a will not be chipped, as shown in FIG. As described above, the chip A when the wafer is taken out occurs in the isolation member 1b. Since the separating member 1b is detachably inserted into the susceptor body 1a, the separating member 1b can be removed, and the separating member 1 having the chip A can be replaced with a new one.

Here, the separating member 1b is made of a base material made of a carbon material such as graphite and having its surface coated with a SiC film, or is made of only SiC, in order to approximate the thermal expansion coefficient to that of the susceptor body 1a. Use one. Because, when forming a film on the wafer 10, 1000 ° C.
This is because the environment is to some extent, and cracks may occur in the susceptor body 1a during film formation due to the difference in thermal expansion with other materials. The shape of the separating member 1b is not particularly limited, but it is preferable to use a separating member having a circular cross section, usually a separating member 1b having a cylindrical shape. The reason is that the contact state with the wafer side surface 10a becomes a point contact, so that the film formed on that portion can be suppressed to a small amount and the temperature distribution of the wafer 10 can be made uniform. .

The place where the separating member 1b is arranged is the edge of the spot facing part 4 of the susceptor body 1a, and the separating member 1b must be arranged so as to divide the circumference of the spot facing part 4 into at least three. The reason is that the wafer 10 may move inside the spot facing portion 4 during the formation of the coating film. Therefore, at least three isolation members 1b should be provided in order to prevent the wafer 10 from contacting any wall surface of the spot facing portion inner wall surface 4a. Is necessary. At this time, if the isolating member 1b is inserted at the position where the circumference of the spot facing portion 4 is divided into substantially equal intervals, the heat uniformity of the wafer 10 is improved, so that the coating film 11 can be formed uniformly.
It becomes the best susceptor.

CV for forming a film such as an epi film on a wafer
The method D is not particularly limited, and a film may be formed as in the conventional method. For example, trichlorosilane, dichlorosilane or the like is used as a raw material gas, and if necessary, a carrier gas such as hydrogen is used to form a film at a temperature of about 1000 ° C.

<Manufacturing Example> Using a pancake type susceptor configured as shown in FIG. 1, a φ6 inch silicon wafer is placed on the counterbore part so that the side surface of the silicon wafer does not contact the inner wall surface of the counterbore part. While having a thickness of 10 μm
By repeating the formation of the epitaxially grown film of 100 times, the number of occurrences of chipping when taking out the wafer was investigated. Here, the isolation member has a carbon material as a base material, and the surface thereof is covered with a CVD-SiC film to have a diameter of 2 x a length of 1.5 m.
Use three m-shaped cylinders, which are detachably inserted into holding holes provided at positions where the circumference of the counterbore part is divided into three parts, and the side surface of the silicon wafer contacts the inner wall surface of the counterbore part. A pancake-type susceptor was constructed that would not. The raw material gas used was trichlorosilane (C
HCl ₃ ) and the carrier gas is hydrogen gas.

As a result, there are four defects when taking out the wafer.
It occurred three times, but all occurred only in the isolation member, so only the isolation member had to be replaced.

<Comparative Production Example> Using the conventional susceptor configured as shown in FIG.
The formation of the epitaxially grown film of μm was repeated 100 times, and the number of occurrences of chipping was investigated.

As a result, there are four defects when taking out the wafer.
It occurred eight times, and all of them were chipped so that the carbon base material was exposed at the corners formed by the upper surface of the susceptor and the inner wall surface of the spot facing portion. Therefore, the entire susceptor had to be replaced each time.

[0025]

As described above, according to the present invention, when the wafer is taken out, the expensive susceptor is not chipped, and only the isolation member which can be manufactured at a low cost is chipped. Therefore, when a chip is generated, only the isolation member needs to be replaced, and the chemical vapor deposition method and the susceptor are inexpensive and have high working efficiency.

[Brief description of drawings]

FIG. 1 is a plan view (a) and a cross-sectional view (b) of a counterbore part of a configuration example of a susceptor according to the present invention.

2A and 2B are a plan view (a) of a susceptor counterbore part and a partially crushed cross-sectional view (b, c) of the counterbore part for explaining the operation of the present invention.

FIG. 3 is a schematic plan view (a) of a conventional susceptor and a schematic plan view (b) of a spot facing portion.

FIG. 4 is a partially crushed sectional view (a, b) of a spot facing portion of a conventional susceptor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Susceptor 1a Susceptor body 1b Separating member 2 Carbon substrate 3 Silicon carbide (SiC) film 4 Counterbore part 4a Counterbore inner wall surface 6 Retaining hole 7 Susceptor top surface 10 Semiconductor wafer 10a Semiconductor wafer side surface A Missing contact part

Claims (2)

[Claims] 1. A detachable separating member coated with or made of silicon carbide is attached to an edge of a spot facing portion on which a semiconductor wafer of a susceptor coated with silicon carbide is mounted. The chemical vapor deposition method is characterized in that a plurality of layers are arranged so that the circumference of the semiconductor wafer is divided into three or more parts, and a side surface of the semiconductor wafer does not come into contact with the inner wall surface of the spot facing portion, and a coating film is formed on the semiconductor wafer. 2. A detachable separating member coated with or made of silicon carbide, and having a holding hole for the separating member at an edge of a counterbore for mounting a semiconductor wafer. And a susceptor for chemical vapor deposition, which comprises: a plurality of holding holes for the separating member arranged so that the circumference of the counterbore part is divided into three or more substantially evenly. The susceptor for chemical vapor deposition characterized by.