JP2011146504A - Susceptor for vapor phase growth device, and vapor phase growth device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a susceptor preventing generation of a flaw and a contact trace in a backside of an epitaxial wafer and capable of being used semipermanently. <P>SOLUTION: In the susceptor for a vapor phase growth device, a wafer supporting member made of glassy carbon is provided to be exchangeable in at least a wafer support region of a susceptor base material. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a susceptor for a vapor phase growth apparatus and a vapor phase growth apparatus, and in particular, to prevent generation of scratches and contact marks on an epitaxial wafer during vapor phase growth, and to enable semipermanent use of the susceptor. To do.

As one type of epitaxial growth apparatus for producing an epitaxial wafer by vapor phase growth of a wafer, there is a single wafer type vapor phase growth apparatus as shown in FIG. The vapor phase growth apparatus 1 includes a susceptor 3 for placing the wafer 2 horizontally, a heating device 4 for heating the inside of the furnace, a susceptor support 5 for supporting the susceptor, a rotor 6 for rotating the susceptor, and airtightness. The furnace 1 is defined by an upper dome 9 and a low wardome 10.
Generally, in order to perform silicon epitaxial growth using a single wafer type apparatus, as shown in FIG. 1, the susceptor support 5 is lowered in the epitaxial furnace 1, and the lift pins 5a supporting the wafer 2 are lowered and installed horizontally. The wafer 2 is placed on the susceptor 3. At this time, in order to bring only the upper surface of the wafer 2 into contact with the source gas, the wafer 2 is placed in a counterbore portion 3a of the susceptor (a circular recess provided on the susceptor upper surface).
Then, while rotating the susceptor 3 by the rotor 6, the source gas is supplied in the horizontal direction along the upper surface of the susceptor 3 and heat-treated by the heating mechanism 4 to generate an epitaxial film on the wafer 2. Manufacturing.

In recent years, in particular, such epitaxial wafers are required to have high quality.
In addition, reduction of manufacturing cost is also strongly demanded, and reduction of member cost by extending the life of susceptor can be cited as one of the cost reduction means.
That is, a conventional susceptor having a structure in which graphite carbon having excellent strength is used as a base and the surface thereof is coated with SiC has been widely used because it is relatively inexpensive.
However, in this susceptor, a metal impurity floating in the epitaxial growth apparatus adheres to the surface of the susceptor, so that the SiC film is partially eroded, reaches a deep region of the susceptor, and a pinhole is generated.
When pinholes occur, the graphite carbon that is the base material of the susceptor is exposed, impurities contained in the base material rise to the surface, contaminate the epitaxial wafer, and electrical characteristics such as the lifetime characteristics of the epitaxial wafer. Therefore, it is necessary to replace the susceptor in which the pinhole is confirmed. Once the pinhole is generated, it is necessary to replace the susceptor itself, leading to an increase in cost.
In contrast, Patent Document 1 proposes a susceptor made of glassy carbon (hereinafter referred to as GC) alone. According to this, impurity contamination due to the occurrence of pinholes in the coating film can be eliminated, and since the thermal expansion coefficients of the wafer and glassy carbon are approximate, the generation of particles due to the difference in thermal expansion coefficient It is said that deformation of the susceptor can be prevented.

Japanese Patent Laid-Open No. 9-2895

However, since the susceptor made of a single GC disclosed in Patent Document 1 has a very soft surface, the support region of the susceptor that supports the wafer due to rubbing between the wafer and the susceptor that occurs when the wafer is attached or detached when repeatedly used. It has been clarified that irregularities such as dents and the like are generated in the portion, which adversely affects the generation of particles and the quality of the back surface of the epitaxial wafer.
For this reason, it is necessary to replace the susceptor at the time when the quality of the epitaxial wafer is lowered, and there is a problem that the cost of the susceptor member is increased.
Such a problem becomes more conspicuous in combination with an increase in its own weight especially in a large-diameter wafer of 300 mm or more in recent years.

  The present invention relates to a susceptor for a vapor phase growth apparatus that prevents scratches and contact marks on the back surface of a wafer and can be used semipermanently without causing deterioration of the back surface quality of an epitaxial wafer. It is intended to be provided with a growth apparatus.

Now, the inventor has intensively studied the structure of the susceptor in order to solve the above problems.
As a result, by providing a replaceable wafer support member made of GC in a part of the susceptor, that is, at least the wafer support region, and appropriately replacing the support member as replaceable, the intended purpose can be advantageously achieved. New findings were obtained.

This invention is based on said knowledge, The summary structure is as follows.
(1) A susceptor for a vapor phase growth apparatus, characterized in that a glassy carbon wafer support member is installed in at least a wafer support region of a susceptor substrate in a replaceable manner.

  (2) The susceptor base material is one of glassy carbon, SiC coated with glassy carbon on the entire surface, and graphite carbon including a first coating layer of SiC and a second coating layer of glassy carbon on the entire surface. The susceptor for a vapor phase growth apparatus according to (1) above.

  (3) The susceptor for vapor phase growth apparatus according to (1) or (2) above, wherein the glassy carbon has a Shore hardness of 100 to 1500 HS.

  (4) The wafer support surface of the wafer support member is inclined at an angle of 2 ° or less so as to become lower toward the center from the outer peripheral side of the counterbore portion of the susceptor, (1) The susceptor for a vapor phase growth apparatus according to any one of to (3).

  (5) The susceptor for a vapor phase growth apparatus according to any one of (1) to (4), wherein the wafer is a silicon wafer having a diameter of 300 mm or more.

  (6) A vapor phase growth apparatus comprising the vapor phase growth apparatus susceptor according to any one of (1) to (5).

According to this invention, the wafer support member is made of GC, so that scratches and contact marks on the back surface of the wafer can be prevented, and as a result, a high-quality epitaxial wafer can be obtained.
Further, according to the present invention, by making the wafer support member described above replaceable, the susceptor can be used semi-permanently, and the epitaxial wafer manufacturing cost can be reduced in terms of member cost.

It is sectional drawing of the conventional single wafer type vapor phase growth apparatus. It is sectional drawing of the susceptor of this invention. It is a figure which shows the relationship between the number of surface particles of a wafer, the surface roughness of a susceptor support area | region, and the number of susceptor epitaxial processes. It is a figure which shows the preparation points of GC. It is a figure which shows the connection point of the member for replacement | exchange with respect to a susceptor. It is a figure which shows the susceptor which inclined the wafer support area | region.

Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 2 is a partial cross-sectional view of a preferred susceptor of the present invention.
FIG. 2 (a) is a structural example in which a ring 12a made of GC is installed on the wafer support region 3b of the base material 11 constituting the susceptor 3. FIG.

  When performing the epitaxial growth process, the silicon wafer is placed on the ring 12a made of GC and the epitaxial growth process is performed. Since the ring 12a is made of GC, its surface is soft and the coefficient of linear thermal expansion is the same as that of silicon, preventing contact scratches and traces from occurring on the back surface of the silicon wafer in contact with the ring 12a surface. can do.

If the surface shape of the ring 12a made of GC deteriorates due to contact with the wafer as the susceptor 3 is used, the support member can be removed by removing the installed ring 12a made of GC and replacing it with a new ring. It is possible to prevent deterioration of the back surface quality of the wafer due to deterioration of the surface shape of the wafer.
In addition, since it is not necessary to replace the entire susceptor 3, it is possible to reduce the member cost.

  Further, instead of installing a GC ring on the wafer support region 3b, for example, as shown in FIG.2 (b), a circular plate-shaped replacement member 12b made of GC is removed from the wafer support region 3b to the bottom surface of the counterbore part. You may install over 3c. Further, as shown in FIG. 2 (c), a circular plate-shaped replacement member 12b made of GC may be installed on the entire upper surface of the susceptor 3 from the susceptor outer peripheral upper surface 3d to the counterbore portion bottom surface 3c. A wafer support member whose surface is coated with GC may be used.

Thus, by using GC as the support member that supports the wafer, it is possible to prevent the back surface of the wafer after the epitaxial growth process from being damaged and contact marks.
However, as described above, when repeatedly used a plurality of times, the wafer and the susceptor are rubbed when attaching and detaching the wafer. Since it adversely affects the quality of the back surface of the epitaxial wafer, it is necessary to replace the support member periodically.
For example, when the surface shape of the wafer support member 12a of the susceptor becomes rough, the number of particles on the surface of the wafer increases. Therefore, the deterioration of the surface shape of the wafer support member 12a of the susceptor is determined using the number of particles on the wafer surface as an index. can do.

  It is desirable that the susceptor substrate 11 has a configuration in which the surface of a single GC or a single SiC is coated with GC. Since graphite carbon that causes contamination is not used as a base material, impurity contamination due to the generation of pinholes can be prevented. In the case of a structure in which the surface of a single SiC is covered with GC, SiC is effective in preventing deformation of the susceptor because of its excellent strength. However, since SiC is harder than the wafer, there is a risk of contact flaws and contact marks occurring when the wafer bends greatly and comes into contact with the wafer. By covering the SiC surface with GC, the occurrence of contact flaws etc. is prevented. can do.

  Further, the susceptor base material 11 is preferably configured to have a three-layer structure in which the surface of carbon graphite is coated with SiC and the surface is coated with GC. Since graphite carbon is inexpensive and excellent in strength, it is effective for susceptor manufacturing cost and susceptor deformation prevention. However, if the carbon graphite surface is simply covered with SiC or GC, there is a problem of impurity contamination due to the generation of pinholes. Occurrence of impurities can be suppressed and impurity contamination can be avoided. In addition, when coating the SiC surface with GC, if the film thickness is thin, partial film peeling or the like occurs, and the pinhole suppressing effect is reduced. Therefore, it is desirable to coat a 2 to 40 μm GC film. .

The GC wafer support member according to the present invention can be manufactured as shown in FIG. 4, for example. In this figure, for convenience, a case where a plate-like GC member is manufactured will be described.
First, (a) a liquid resin is poured into a container, a thermosetting treatment is performed, and a thermosetting resin is molded. Next, (b) the molded thermosetting resin is subjected to roughing and heat treatment before firing. (c) High-temperature heat treatment in a furnace in an inert atmosphere and firing and carbonization. (d) Next, the product dimensions are processed. (e) Finally, heat treatment is performed in a furnace in a halogen gas atmosphere to purify the GC. Thereby, a wafer support member made of GC having a Shore hardness of 100 to 1500 HS can be manufactured. If the Shore hardness is too high, contact damage may occur on the wafer.

  In order to install a ring or plate-shaped replaceable wafer support member on the susceptor substrate, the member may simply be placed on or fitted to the susceptor. However, as shown in FIG. The material 11 may be bonded with the adhesive 13a, or may be fixed with a bolt 13b as shown in FIG. 5 (b).

Further, as shown in FIG. 6 (a), the wafer support portion 3b of the susceptor is preferably inclined with respect to the horizontal plane so as to become lower from the outer peripheral side of the counterbore portion toward the central side.
In other words, because the support member is made of GC, it has the effect of suppressing the occurrence of contact scratches on the backside of the wafer, but from the viewpoint of reducing contact scratches, the tilt angle is increased so as to make the contact area as small as possible. It is advantageous to do so. However, if the inclination angle α is too large, the wafer is supported only at the periphery of the wafer as shown in FIG. 6 (b), and no scratches are generated on the back surface as shown in FIG. 6 (c). However, since the stress concentration due to the wafer's own weight increases and the occurrence of slip at the peripheral edge of the wafer may increase, the inclination angle α is preferably 2 ° or less. Further, during the epitaxial process, the wafer placed on the susceptor due to the high-temperature heat treatment is bent, and as shown in FIG. As shown in FIG. 6 (e), there is a risk that arc-shaped scratches may occur due to the stress concentration generated at the contact portion. For this reason, the inclination angle α is preferably 0.4 ° or more, and in consideration of the use of a wafer having a diameter of 300 mm or more, the inclination angle α is preferably 1 ° or more.

  Further, the outer thickness (T in FIG. 6A) of the susceptor is preferably 3.8 mm to 7.0 mm. If the thickness is less than 3.8 mm, the epitaxial growth process, especially heating from the lower side of the susceptor at the time of temperature rise, may cause wafer quality abnormalities such as slip and backside fogging. In this case, normal temperature rise cannot be achieved and temperature control becomes difficult.

<< Experiment 1 >>
In order to verify the effect of the present invention, an epitaxial growth experiment was conducted using the single wafer type vapor phase growth apparatus shown in FIG. 1 and the susceptor shown in FIG. 6 (a).
Specifically, as a susceptor of the present invention example, a susceptor based on graphite carbon including a first coating layer of SiC having a thickness of 20 μm and a second coating layer of glassy carbon having a thickness of 5 μm is manufactured on the entire surface, A ring-shaped wafer support member made of a single GC and having an inclination angle α of 1.0 ° is placed on the wafer support region of the susceptor.
Using this susceptor of the present invention, the epitaxial growth process is repeated, and when the number of particles detected by surface observation of the epitaxial wafer is greatly increased, only the support member made of GC is replaced with a new support member, and again. The epitaxial growth process was repeated.
FIG. 3 shows changes in the number of particles on the surface of the epitaxial wafer and the roughness of the surface of the wafer support member after the experiment.
Here, the number of particles on the wafer surface is a result of counting particles having a particle size of 0.12 μm or more using a light scattering surface inspection device (manufactured by KLA-Tencor, SP-1).
The roughness of the susceptor support area is indicated by the arithmetic average roughness Ra defined in JIS B 0031 (1994), and a 200 μm × 200 μm area is measured with a 3D shape measurement microscope (manufactured by KEYENCE, VK-9500). The result calculated in this way is shown.
As is apparent from FIG. 3, as the number of epitaxial growth processes increases, the number of particles observed on the epitaxial wafer surface increases, and the roughness of the susceptor wafer support member surface also deteriorates.
It can also be seen that when the wafer support member of the susceptor is replaced, no particles are observed, and the number of particles observed on the epitaxial wafer surface increases as the number of epitaxial growth processes increases again.
In this way, the cause of the generation of particles is due to the deterioration of the surface of the wafer support member, and it is only necessary to periodically replace the wafer support member of the susceptor using the number of observed particles as a reference for continuous use. become.
The occurrence of contact scratches on the back surface of the epitaxial wafer immediately after the wafer support member of the susceptor was replaced and epitaxially grown was confirmed by visual inspection under a dark room condenser lamp, but was not observed at all.

<< Experiment 2 >>
In order to confirm the proper range of the inclination angle α of the wafer support member of the susceptor, silicon wafers having a diameter of 300 mm and a diameter of 200 mm were used, and the inclination angle α of the wafer support member of the susceptor used in Experimental Example 1 The epitaxial growth was performed under the same conditions as in Experimental Example 1 except that the conditions were changed to the standard.
Epitaxial growth conditions at this time are as follows: a crystal orientation (100), p-type silicon wafer is placed on the wafer support member of the susceptor, and after hydrogen baking, SiHCl ₃ is supplied together with a carrier gas into the furnace of the vapor phase growth apparatus. Thus, epitaxial growth was performed at a temperature of 1150 ° C., and an epitaxial film having a thickness of 4 μm was formed on the silicon wafer surface.
The epitaxial wafer manufactured as described above is confirmed by visual inspection under a dark room condenser lamp to identify the site of scratches and slips occurring on the wafer surface, and the site is identified as a surface inspection device (SP manufactured by KLA-Tencor, SP -1) was used to measure the length of arc-shaped flaws and the length of slip generated on the back surface of the epitaxial wafer.
Here, the “arc-shaped scratch length” is the total sum of the generated scratches, and the “slip length” is the total slip generated. The measurement results are shown in Table 1 below.

表1に示したように、傾斜角が2.0°を超えると、ウェーハ径サイズに関係なくスリップが発生することがわかる。また、ウェーハ裏面で観察された円弧状の傷のほとんどは、ウェーハ支持部材内側端が位置する箇所で発生していることから、ウェーハが撓み接触しているものと推定でき、このウェーハ撓みによる傷を生じない傾斜角の最小値はウェーハ径サイズに依存することがわかる。

As shown in Table 1, it can be seen that when the inclination angle exceeds 2.0 °, slip occurs regardless of the wafer diameter size. In addition, since most of the arc-shaped scratches observed on the back surface of the wafer are generated at the location where the inner edge of the wafer support member is located, it can be estimated that the wafer is in a bending contact. It can be seen that the minimum value of the tilt angle that does not cause the difference depends on the wafer diameter size.

According to this invention, it is possible to prevent generation of scratches and contact marks on the back surface of the epitaxial wafer, and the susceptor can be used semipermanently.
The present invention is particularly suitable for manufacturing a large-diameter wafer having a diameter of 300 mm or more.

1 Epitaxial furnace
2 wafers
3 Susceptor
3a Counterbore part of susceptor
3b Wafer support area of counterbore part of susceptor
3c Counterbore bottom
3d Upper surface of susceptor
4 Heating mechanism
5 Susceptor support
5a Wafer lift pin
6 Rotor
7 Upper liner
8 Lower liner
9 Upper dome
10 Lowwardome
11 Base material
12a Replacement part (GC ring)
12b Replacement parts (GC plate)
13a Adhesive
13b bolt
C Arc-shaped scratch
T susceptor outer thickness α Inclination angle of wafer support relative to horizontal plane

Claims (6)

  A susceptor for a vapor phase growth apparatus, wherein a glassy carbon wafer support member is installed in at least a wafer support region of a susceptor substrate in a replaceable manner.   The susceptor base material is one of glassy carbon, SiC coated on all surfaces with glassy carbon, and graphite carbon including a first coating layer of SiC and a second coating layer of glassy carbon on the entire surface. The susceptor for a vapor phase growth apparatus according to 1.   3. The susceptor for vapor phase growth apparatus according to claim 1, wherein the glassy carbon has a Shore hardness of 100 to 1500 HS.   The wafer support surface of the wafer support member is inclined at an angle of 2 ° or less so as to become lower toward the center from the outer peripheral side of the counterbore part of the susceptor. A susceptor for a vapor phase growth apparatus according to claim 1.   The susceptor for a vapor phase growth apparatus according to any one of claims 1 to 4, wherein the wafer is a silicon wafer having a diameter of 300 mm or more.   6. A vapor phase growth apparatus comprising the vapor phase growth apparatus susceptor according to claim 1.

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