JPH06232054A - Manufacture of susceptor - Google Patents

Abstract

PURPOSE:To suppress the generation of projecting SiC without giving any obstruction to the formation of an SiC film at the part to be supported of a susceptor by supporting the susceptor in a CVD device with the bottom surface of the susceptor upward at the time of forming the SiC film by the CVD method and positioning a cover above the part to be supported of the susceptor at a prescribed distance. CONSTITUTION:At the time of forming an SiC film, a discoid susceptor substrate 15a with an opening at its central part is placed on a supporting rod 14 and a discoid cover 16 is hung from the ceiling section 12b of a furnace at a prescribed distance from the substrate 15a. The substrate 15a is supported in the CVD device 10 with the surface of the substrate 15a which becomes the lower surface of a susceptor 15 when the susceptor 15 is used on the upside and the cover 16 is positioned above the part to be supported of the susceptor 15 when the susceptor 15 is used so that a prescribed distance can be maintained between the part to be supported and the cover 16. Therefore, since no flying objects adheres to the part to be supported when the cover 16 is used, the generation of projecting SiC can be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a susceptor, and more specifically, it is used mainly as a semiconductor manufacturing process and has heat resistance and corrosion resistance and is used as a high temperature jig and a heating table of a vapor phase growth apparatus. The present invention relates to a method for manufacturing a susceptor.

[0002]

2. Description of the Related Art In a semiconductor device manufacturing process,
There is a step of forming a thin film on the substrate by supplying a reactive gas onto the semiconductor substrate which is shielded from the outside by a container. In these steps, a vapor phase growth apparatus that forms a thin film by causing a vapor phase reaction on the substrate by supplying a source gas is used.

Among them, in particular, an epitaxial growth apparatus for growing a single crystal of silicon on a silicon substrate is used in the manufacturing process of semiconductor devices such as LSI. In this apparatus, a silicon substrate is usually heated to 1000 ° C. or higher, a mixed gas of hydrogen and a raw material gas such as silicon tetrachloride and trichlorosilane is supplied into a reaction vessel, and hydrogen is reduced or thermally decomposed to obtain the silicon substrate. A single crystal silicon thin film is grown by epitaxial growth. Epitaxial growth is also used to increase the breakdown voltage of bipolar devices in the manufacturing process of semiconductor devices, and when manufacturing megabit memory for devices as well, it is a necessary technique to prevent soft errors and latch-up due to α rays. Has become.

For such epitaxial growth, for example, a vapor phase growth apparatus as shown in FIG. 4 is used.

FIG. 4 is a schematic sectional view showing a conventional vapor phase growth apparatus. In the figure, 21 indicates a vapor phase growth apparatus,
The vapor phase growth apparatus 21 is isolated from the outside by a quartz chamber 22 and a chamber base 23. Chamber 2
A cylindrical support base 24 is rotatably arranged in the central portion of the inside of the unit 2, and the support base 24 supports from below a susceptor 25 on which a plurality of semiconductor substrates 26 are mounted during use. A susceptor 25 is formed by coating a disk-shaped graphite base material having an opening 25b in the center with a SiC film having a thickness of 150 μm by a CVD method. The susceptor 25 has a diameter of about 700 mm, a thickness of about 20 mm, and a weight of about 20 mm. Is about 1
It is 0 kg.

Further, the central portion of the support base 24 serves as a source gas introducing portion 27, and the lower part of the support base 24 projects below the chamber base 23. A source gas nozzle 28 is connected to the opening 25b at the center of the susceptor 25, and a plurality of holes 28a are formed in the source gas nozzle 28 so that the source gas flows out substantially parallel to the surface of the semiconductor substrate 26. There is. Support 24 in the center of chamber base 23
A raw material gas outlet 30 is formed in the periphery. A coil 31 for induction heating the susceptor 25 from below is installed in a spiral shape.

Also, the vapor phase growth apparatus 2 as shown in FIG.
When 1 is used, the susceptor 25 of the vapor phase growth apparatus 21 is required to have heat resistance and corrosion resistance because the susceptor 25 has a high temperature of around 1000 ° C. Therefore, the susceptor 25 is mainly formed on the surface of a plate made of a graphite material. A base material on which a SiC film is formed is used.

Conventionally, when manufacturing the susceptor 25, S
For the iC film formation, a CVD method is used in which a silicon halide compound containing a carbon source such as hydrocarbon is thermally decomposed in a reducing gas flow to deposit SiC directly on the surface of a graphite substrate. It is a typical sectional view showing the CVD device used for the conventional CVD method. The CVD apparatus 20 has a furnace outer wall 11
The furnace inner wall 12 made of a heat insulating material such as graphite fiber is formed inside the furnace outer wall 11 so as to be shielded from the outside. A support base 13 is arranged in the center of the furnace inner wall 12, and an L-shaped support rod 14 is vertically provided above the support base 13. When the SiC film is formed, the susceptor base material 25 a is placed on the support rod 14. A heater 17 is installed between the support portion including the support base 13 and the support rod 14 and the furnace inner wall surface 12a, and a source gas introduction port 18 is formed in the furnace bottom portion 11b. A raw material gas outlet 19 is formed in the furnace bottom portion 11b opposite to the raw material gas inlet 18.

A method of manufacturing the conventional susceptor 25 using the above-described CVD apparatus 20 will be described. First, the susceptor base material 25 a is placed on the support rod 14. After this, heater 1
7, the susceptor base material 25a is heated at a temperature of about 1200 ° C. at a temperature rising / falling rate of 10 ° C./min. In this state, a silicon-based source gas having a composition ratio of H ₂ , SiH ₂ Cl ₂ and CH ₄ of, for example, 8: 1: 1 is supplied from the source gas introduction port 18. At this time, the gas flow rate is, for example, 6.8 cm at normal temperature and pressure.
Set to / min.

When the raw material gas reaches the vicinity of the upper surface of the susceptor base material 25a, the heat of the heated susceptor base material 25a causes the silicon-based raw material gas to decompose and react to form a SiC thin film on the surface of the susceptor base material 25a. . In this way, the SiC film of the susceptor 25 is formed.

[0011]

In the vapor phase growth apparatus 21 using the conventional susceptor 25, as shown in FIG. 6, the disk-shaped susceptor 25 has a cylindrical shape made of quartz or SiC having heat resistance and corrosion resistance. The susceptor 25 is supported directly by the support pedestal 24 by directly contacting the susceptor supported portion 29 at the central portion of the susceptor 25 and the upper surface of the support pedestal 24. Also, this support 2
Since the coil 31 does not exist in the vicinity of 4, the temperature of the support base 24 is low at the time of use, and the heat of the susceptor 25 heated by the coil 31 is conducted from the susceptor supported portion 29 to the support base 24 at the contact portion. Transfer heat. Due to this heat dissipation, a temperature gradient as shown in FIG. 6 is generated on the upper surface of the susceptor 25. As is clear from FIG. 6, the temperature of the portion not in contact with the support base 24 is about 1200 ° C., but the susceptor supported portion 29 in contact with the support base 24 is 29.
The temperature is about 800 ° C., which means that there is a considerable temperature difference.

Further, as shown in FIG. 7, the SiC film 33 on the surface of the susceptor 25 is formed on the graphite substrate 32 by the CVD method.
The protruding SiC 34 having a size of 0 μm or more is often formed. Susceptor 2 having protruding SiC 34 on the surface
In the case of using No. 5, since the surface of the support base 24 is composed of a dense flat plate, the place where the conductive heat transfer from the susceptor 25 to the support base 24 is performed is the susceptor supported portion 29.
It is limited to the protruding SiC 34. Therefore, in the vicinity of the protruding SiC 34, the heat transfer rate becomes slower than in the portion in contact with the support 24 as a whole, the temperature in the vicinity of the protruding SiC 34 becomes high, and the local temperature distribution in the vicinity of the protruding SiC 34. Occurs (see FIGS. 8A and 8B). In addition, a steep temperature gradient is generated on the upper surface of the susceptor 25 as shown in FIG. As described above, the temperature unevenness is generated in the susceptor 25 in the circumferential direction, and the epitaxial growth on the wafer surface on the susceptor 25 becomes uneven. Further, there has been a problem that the defective product occurrence rate such as occurrence of color unevenness is increased and the wafer yield is decreased.

In order to solve the above-mentioned problems, protruding SiC
It is conceivable to remove 34 by polishing or the like, but S
Since iC is extremely hard, there is a problem that polishing is not easy.

The present invention has been invented in view of the above problems, and suppresses the generation of protruding SiC without impairing the formation of the SiC film on the supported portion of the susceptor during use, thereby achieving uniform epitaxial growth. It is an object of the present invention to provide a method of manufacturing a susceptor that can be performed and that can reduce the defective product generation rate to a small value.

[0015]

In order to achieve the above object, a method for manufacturing a susceptor according to the present invention is provided with S on the surface of a graphite material.
In a method of manufacturing a susceptor in which an iC film is formed by a CVD method, when the SiC film is formed by the CVD method, the susceptor is supported in a CVD device with the lower surface of the susceptor facing upward during use, and the susceptor is used during use. The cover is installed at a predetermined distance above the supported portion of the cover.

[0016]

As a result of the study, it was found that the protruding SiC is generated by the core of fragments of the furnace inner wall material of the CVD apparatus, SiC particles, etc., having a diameter of 150 μm or more. Si
When the C film is formed, if SiC adheres to the surface of the graphite material on the inner wall of the furnace and the SiC generation layer becomes thicker,
Due to the large difference in the coefficient of thermal expansion between graphite and SiC, a crack is generated in the SiC film, and the graphite material that is the furnace inner wall material, graphite fibers, and fragments such as SiC are scattered from there. Further, some of the SiC particles having a diameter of about several μm or less, which are generated by the decomposition and reaction of the raw material gas in the gas phase, are accumulated in the furnace, and the SiC particles are also scattered. For example, in a general gas flow rate in a CVD apparatus in which the gas flow rate in the vicinity of the susceptor base material is about 2 cm / sec at 1300 ° C. under normal pressure, the fragments of the furnace inner wall material and Si
Substances such as C particles fly by the motion of gravity fall, and these fly substances 35 adhere to the surface of the SiC film being formed (see FIG. 1).
(See (a)), and a SiC film is further formed thereon (see FIG. 1 (b)), so that the protruding SiC is generated.

According to the method of manufacturing the susceptor of the present invention, the CVD apparatus as shown in FIG. 2 is used when forming the SiC film. The CVD apparatus 10 is isolated from the outside by a furnace outer wall 11, and a furnace inner wall 12 made of a heat insulating material such as graphite fiber is formed inside the furnace outer wall 11. A support base 13 is arranged in the center of the furnace inner wall 12,
Further, an L-shaped support rod 14 is vertically provided above the support base 13. At the time of forming the SiC film, a disk-shaped susceptor base material 15a having an opening at the central portion is placed on the support rod 14, and a disk-shaped cover 16 is provided at a predetermined distance from the furnace wall ceiling portion 12b with the susceptor base material 15a. It is placed and hung. In addition, a heater 17 is installed between the support portion composed of the support base 13 and the support rod 14 and the furnace inner wall surface 12a, and a source gas introduction port 18 is formed in the furnace bottom portion 11b. A raw material gas outlet 19 is formed in the furnace bottom portion 11b on the opposite side of the raw material gas inlet 18 from both sides.

In this case, the susceptor base material 15a is formed by CVD with the surface which becomes the lower surface of the susceptor 15 in use facing upward.
The cover 16 is supported inside the device 10, and the cover 16 is installed at a predetermined distance above the supported portion of the susceptor 15 during use (see FIG. 3A). Therefore, since the flying substance does not adhere to the supported portion under the cover 16 during use, the generation of the protruding SiC is suppressed, and the formation of the SiC film may be impaired by leaving a predetermined distance. Absent. Therefore, a steep temperature gradient does not occur in the supported portion even during use, and the occurrence of a local temperature distribution is suppressed. Therefore, it is possible to manufacture a susceptor that can uniformly perform epitaxial growth and can suppress the defective product generation rate to be low.

However, it is necessary to select the distance between the cover 16 and the susceptor base material 15a and the size of the cover 16 so as not to impair the formation of the SiC film on the supported portion during use. For example, in a general CVD apparatus in which the gas flow velocity in the vicinity of the susceptor base material at atmospheric pressure and 1300 ° C. is about 2 cm / sec, the cover 16 and the susceptor base material 15 are used.
The distance from a is 2 cm, and the size of the cover 16 is approximately 1.3 times the area of the supported portion when in use (see FIG. 3 (b)). These are the gas supply to the supported portion. It may be selected within a range in which the amount is not extremely impaired. Further, although graphite and SiC plates can be considered as the material of the cover 16, other materials may be used as long as they do not adversely affect the CVD reaction and do not generate flying substances.

[0020]

EXAMPLES AND COMPARATIVE EXAMPLES Examples and comparative examples of a method for manufacturing a susceptor according to the present invention will be described below with reference to the drawings. It should be noted that components having the same functions as those of the conventional example are designated by the same reference numerals. In the method of manufacturing the susceptor according to the embodiment, the CVD device 20 shown in FIG. 2 is used, and the base material of the disk-shaped susceptor base material 15a having the through hole in the center is the lower surface of the susceptor when in use. It is placed on the support rod 14 with the surface facing upward. At this time, a graphite material cover 16 having a size of about 1.5 times that of the supported portion is installed at a distance of 2 cm above the supported portion of the susceptor during use. After that, the heater 17 heats the susceptor substrate 15a to about 120 at a temperature rising / falling rate of 10 ° C./min.
Heat to a temperature of 0 ° C. In this state, the raw material gas inlet 1
8 to H ₂ , SiH ₂ Cl ₂ and CH _{4 have} a composition ratio of 8:
A 1: 1 silicon source gas is fed at room temperature and atmospheric pressure at a gas flow rate of about 6.8 cm / min. Then, when the raw material gas reaches the vicinity of the upper surface of the susceptor base material 15a, the heat of the heated susceptor base material 15a causes the silicon-based raw material gas to decompose and react, whereby a SiC thin film is formed on the surface of the susceptor base material 15a. In this way, the SiC film of the susceptor is formed.

No protrusion SiC was generated on the surface of the susceptor manufactured as described above due to flying of fine particles, and the film formation rate at the supported portion was not decreased.

[0022]

[Table 1]

Table 1 shows that a vapor phase growth apparatus using the susceptor according to the above-described embodiment and a vapor phase growth apparatus 21 using the susceptor 25 according to the comparative example according to the conventional manufacturing method are used to form a wafer. After performing epitaxial growth,
The defect occurrence rate on the wafer is investigated, and the result is shown.

The prescribed number of times of these vapor phase growth apparatuses was 800 times. As is clear from Table 1, in the comparative example, defects such as color unevenness and slip occurred in 45% of the epitaxially grown wafers, but in the example, the prescribed number of times was 800 times. Since the defective product generation rate before use was 5% or less, it was found that the defective product generation rate of the wafer could be improved to about 1/10.

[0025]

As described above in detail, in the method of manufacturing the susceptor according to the present invention, the surface of the graphite material is coated with the SiC film.
In a method of manufacturing a susceptor formed by a VD method, the susceptor is formed by CVD with the lower surface of the susceptor at the time of use during the formation of the SiC film by the CVD method.
Since the cover is supported in the apparatus and a cover is installed at a predetermined distance above the supported portion of the susceptor at the time of use, generation of protruding SiC without impairing the formation of the SiC film on the supported portion of the susceptor. It is possible to suppress the occurrence of local temperature distribution when the susceptor is used. Therefore, it is possible to provide a susceptor that can be used as a high temperature jig and a heating table of a vapor phase growth apparatus, and can significantly reduce the defective product generation rate of wafers and greatly improve the yield.

[Brief description of drawings]

FIG. 1A and FIG. 1B are schematic cross-sectional views showing a process of forming protruding SiC existing on the surface of a conventional susceptor.

FIG. 2 is a CV used in a method for manufacturing a susceptor according to the present invention.
It is a typical sectional view showing D device.

3A and 3B are a schematic cross-sectional view and a plan view showing the relationship between a susceptor and a cover when forming a SiC film in an example.

FIG. 4 is a schematic sectional view showing a vapor phase growth apparatus using a conventional susceptor.

FIG. 5 is a CVD used in a conventional susceptor manufacturing method.
It is a typical sectional view showing a device.

6A and 6B are a graph and a schematic cross-sectional view showing a temperature gradient generated on the upper surface of the susceptor.

FIG. 7 is a schematic cross-sectional view showing protruding SiC of a susceptor.

8A is a schematic cross-sectional view showing the temperature distribution generated inside the susceptor, FIG. 8B is a plan view showing the temperature distribution on the upper surface of the susceptor, and FIG. 8C is a temperature generated on the upper surface of the susceptor. It is the graph which showed the gradient.

[Explanation of symbols]

 10 CVD Equipment 15a Susceptor Base Material (Graphite Material) 16 Cover

Claims (1)

[Claims] 1. A method of manufacturing a susceptor in which a SiC film is formed on a surface of a graphite material by a CVD method, the lower surface of the susceptor being in use during the formation of the SiC film by the CVD method and the susceptor in a CVD apparatus. And a cover is installed at a predetermined distance above the supported portion of the susceptor during use.