JP5040333B2 - Vapor growth susceptor, vapor growth apparatus and vapor growth method - Google Patents

Description

  The present invention relates to a susceptor for vapor phase growth, a vapor phase growth apparatus, and a vapor phase growth method, which are mainly used for manufacturing an epitaxial wafer, and more specifically, for example, a horizontal disk for performing epitaxial growth while holding a target wafer substantially horizontal. The present invention relates to a type of susceptor for vapor phase growth, a vapor phase growth apparatus including the same, and a vapor phase growth method.

Vapor phase epitaxial growth technology is a technology for vapor phase growth of single crystal thin film layers used in the manufacture of integrated circuits such as bipolar transistors and MOSLSIs, and is aligned with the crystal orientation of the substrate on a clean semiconductor single crystal substrate (wafer). This is an extremely important technique because a uniform single crystal thin film can be grown and a steep impurity concentration gradient of a junction having a large dopant concentration difference can be formed. As the vapor phase epitaxial growth apparatus, three types are generally used: a vertical type (pancake type), a barrel type (cylinder type), and a horizontal type. The principles of these growth apparatuses are common.
Among these, the vertical type (pancake type) and the horizontal type employ a vapor phase growth susceptor that holds the substrate wafer substantially horizontally.

  FIG. 5 is a schematic sectional view showing an example of a conventional vertical vapor phase growth apparatus (see Patent Document 1). In this vertical type vapor phase growth apparatus 21, a reaction chamber 4 is formed by mounting a bell-shaped bell jar 3 on a base plate 2. In the reaction chamber 4, a horizontal disk type susceptor 16 for placing a semiconductor substrate (wafer) 5 is horizontally disposed, and a high-frequency heating coil 7 for heating the wafer 5 via the susceptor 16 is disposed on the lower surface thereof. A coil cover 8 is provided. During the vapor phase growth, the wafer 5 is placed on a counterbore 19 that is a circular recess provided on the upper surface of the susceptor 16, the source gas is supplied from the gas inlet 10, and provided on the side surface and upper surface of the nozzle 11. The gas is ejected from the ejection hole 12 introduced into the reaction chamber 4 and discharged from the gas discharge port 13. At this time, since the wafer 5 is heated by the high-frequency heating coil 7, the raw material gas ejected on the wafer reacts on the wafer surface, and a thin film epitaxial layer is vapor-phase grown on the wafer surface.

  One type of horizontal vapor phase growth apparatus is a single wafer type apparatus. In this apparatus, a wafer is placed on a horizontal disk-type susceptor disposed in a horizontal heating furnace, and the raw material gas is circulated in the horizontal direction in the furnace while rotating it around the vertical axis. An epitaxial layer is formed on the wafer surface. Such an apparatus has been widely used as the diameter of the wafer increases, and is regarded as the mainstream as an apparatus that can handle a wafer having a diameter of 300 mm.

  As described above, in these vapor phase growth apparatuses, a circular recess for accommodating a wafer is provided on the upper surface of the susceptor for the purpose of bringing the source gas into contact only with the upper surface of the wafer to be epitaxially grown. Then, the wafer is accommodated in this recess called counterbore and epitaxial growth is performed.

  By the way, a wafer having a thin film epitaxially grown on its surface is used for a power device such as an IGBT (Insulated Gate Bipolar Transistor). In such an epitaxial wafer for power devices, the epitaxial growth film may be thickened to about 100 μm or more. When forming such a thick film, the wafer on the susceptor grows across both the wafer mounting surface of the counterbore and the outer peripheral back surface of the wafer, even though the wafer is housed in the counterbore. The phenomenon of sticking (fixing) is likely to occur due to the deposited precipitates. When this sticking phenomenon occurs, when the wafer is taken out of the susceptor after epitaxial growth, the deposit on the stick portion must be peeled off, and a considerable force is applied to the stick portion of the wafer at this time. Cracks may occur and may lead to cracks. The occurrence of such cracks and cracks reduces the yield of the wafer.

Such sticking is likely to occur under reaction-limited conditions. That is, it occurs under conditions where epitaxial growth occurs even in a narrow region where the source gas does not flow around, such as between the counterbore side wall and the wafer outer peripheral side surface, or between the peripheral side of the counterbore wafer mounting surface and the wafer outer peripheral surface. . Conversely, to suppress sticking, it is effective to carry out the reaction under a transport rate-limiting condition.
Therefore, it is necessary to reduce the flow rate of the raw material gas or increase the reaction temperature in order to achieve the transport rate limiting condition. However, when the flow rate of the source gas is reduced, the growth rate of the thin film is lowered, and the productivity is also lowered. Further, when the reaction temperature is increased, slip dislocation is likely to occur, and autodoping from the substrate to the epitaxial layer becomes strong.

JP 7-45530 A

  The present invention has been made in view of such problems, and can effectively prevent the occurrence of sticking, prevent wafer cracks and cracks, and increase the productivity of epitaxial wafers. An object is to provide a susceptor, a vapor phase growth apparatus, and a vapor phase growth method.

In order to achieve the above object, the present invention provides a vapor phase growth susceptor for placing a wafer in a vapor phase growth apparatus, the vapor phase growth susceptor comprising: a wafer placement surface on which a wafer is placed; A concave counterbore composed of a side wall is formed, and the wafer mounting surface includes a center side region and a peripheral side region having a surface roughness larger than that of the center side region. that provides a vapor phase growth susceptor.

  In this way, a concave counterbore consisting of a wafer mounting surface on which a wafer is mounted and a side wall is formed, and the wafer mounting surface has a central region and a peripheral surface having a larger surface roughness than the central region. If it is a susceptor for vapor phase growth consisting of a side region, it should be used in a vapor phase growth apparatus to effectively prevent sticking, prevent wafer cracks and cracks, and increase the productivity of epitaxial wafers. It becomes a susceptor for vapor phase epitaxy. Therefore, at this time, a high quality epitaxial wafer can be efficiently produced.

In this case, the surface roughness Ra of the central region on the wafer mounting surface is 1 μm or more and less than 10 μm, and the surface roughness Ra of the peripheral region on the wafer mounting surface is 10 μm or more and 20 μm or less. It has preferred. The width from the side wall near the side region in the wafer mounting surface, have preferably not less 1mm 5mm or more or less.

  Thus, the surface roughness Ra of the central region on the wafer mounting surface is 1 μm or more and less than 10 μm, and the surface roughness Ra of the peripheral region on the wafer mounting surface is 10 μm or more and 20 μm or less. If the width from the side wall of the peripheral region on the mounting surface is 1 mm or more and 5 mm or less, the occurrence of sticking can be more effectively prevented, and slip dislocation to a semiconductor device manufactured using an epitaxial wafer as a material The influence by etc. can be reduced.

Further, the present invention is that provides a vapor phase growth apparatus characterized in that it comprises at least the vapor phase growth susceptor.

  With such a vapor phase growth apparatus provided with at least the above-mentioned vapor phase growth susceptor, it is possible to effectively prevent sticking, prevent wafer cracks and cracks, and increase the productivity of epitaxial wafers. It becomes a vapor phase growth apparatus that can.

In this case, the vapor deposition apparatus, Ru can be a vertical type vapor phase growth apparatus.
Such a vertical vapor phase growth apparatus provided with at least the above-mentioned vapor phase growth susceptor can effectively prevent sticking even in a vertical vapor phase growth apparatus in which sticking is likely to occur. A vertical vapor phase growth apparatus capable of preventing cracks and cracks and increasing the productivity of the epitaxial wafer can be obtained.

Further, the present invention includes at least placing the wafer in counterbore of the vapor phase growth susceptor, that provides a vapor phase growth method, characterized in that for thin film vapor phase growth on the surface of the wafer.

  In this way, if the wafer is placed on the counterbore of the vapor phase growth susceptor and a thin film is grown on the surface of the wafer, the occurrence of sticking can be effectively prevented, and cracking and cracking of the wafer can be prevented. In addition, the productivity of the epitaxial wafer can be increased.

  With the susceptor for vapor phase growth, the vapor phase growth apparatus, and the vapor phase growth method of the present invention, it is possible to effectively prevent the occurrence of sticking particularly on the back surface of the outer periphery of the wafer. Yield reduction can be prevented. Further, since the vapor phase growth rate does not have to be lowered, the productivity of the epitaxial wafer can be increased.

Hereinafter, the present invention will be described in more detail, but the present invention is not limited thereto.
As described above, conventionally, when the flow rate of the raw material gas is reduced for the purpose of preventing sticking, the growth rate of the thin film is lowered, and the productivity is also lowered. Further, when the reaction temperature is increased, slip dislocation is likely to occur, and autodoping from the substrate to the epitaxial layer becomes strong.

In view of this, the present inventor has intensively studied a method for suppressing such demerits and effectively preventing the occurrence of sticking on the back surface of the wafer. As a result, the roughness of the counterbore surface of the susceptor is increased to reduce the contact area between the substrate wafer and the counterbore surface in order to effectively prevent sticking between the wafer back surface and the counterbore wafer mounting surface. Found it important.
Further, it was noted that sticking between the wafer back surface and the counterbore wafer mounting surface occurs only on the outer peripheral side of the wafer. That is, sticking does not occur in the vicinity of the wafer center where the source gas does not enter. For this reason, in order to prevent sticking between the wafer back surface and the wafer mounting surface of the counterbore, it is conceived that the area where the surface roughness of the counterbore is roughened only on the peripheral side of the wafer mounting surface. The present invention has been completed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, but the present invention is not limited thereto.
FIG. 1 is a schematic sectional view showing an example of a counterbore part of a susceptor for vapor phase growth according to the present invention. The susceptor 6 is formed with a concave counterbore 9 composed of a wafer mounting surface 9a on which the wafer 5 is mounted and a side wall 9b. The wafer mounting surface 9a includes a central region 9c and a central side. It is characterized by comprising a peripheral region 9d having a surface roughness larger than that of the region 9c.

The material of the vapor phase growth susceptor 6 can be appropriately selected depending on the material of the wafer 5, the growth conditions, and the like. For example, when the wafer 5 is a silicon substrate, the vapor phase growth susceptor 6 is obtained by coating graphite with SiC. It can be.
In order to smooth the surface of the wafer mounting surface as described above, that is, to smooth the surface of the central region and roughen the peripheral region, it is realized by changing the polishing conditions of the wafer mounting surface. However, the present invention is not limited to this, and if it is a susceptor for vapor phase growth in which the above-described graphite susceptor substrate is coated with SiC, a corresponding region of the surface of the graphite susceptor substrate is polished in advance. It may be smoothed locally or, conversely, by changing the processing conditions of a processing machine such as an end mill to make it rough.

  In this way, by making the surface of the wafer mounting surface 9a rougher in the peripheral region 9d than in the central region 9c, the contact area is increased in the wafer center portion in contact with the central region 9c. While increasing the size and suppressing the occurrence of slip dislocation due to local heat concentration, the contact area with the wafer mounting surface can be reduced at the outer periphery of the wafer in contact with the peripheral region 9d. Sticking between the counterbore and the wafer mounting surface can be prevented. That is, the vapor phase growth susceptor 6 according to the present invention effectively prevents the occurrence of sticking on the outer peripheral back surface of the wafer, prevents the wafer from cracking and cracking, and does not have to reduce the growth rate. A susceptor for vapor phase growth that can increase the productivity of the wafer.

The specific numerical value of the surface roughness of each of the center side region 9c and the peripheral side region 9d is the Ra value (reference line average roughness: reference line of the wafer mounting surface (the square sum of deviations up to the waveform is minimized). It is desirable that the central region 9c is 1 μm or more and less than 10 μm and the peripheral region 9d is 10 μm or more and 20 μm or less.
Among these, the significance of the numerical value of the peripheral region 9d is that if the surface roughness Ra is 10 μm or more, the contact area between the wafer 5 and the counterbore surface can be sufficiently reduced, and sticking can be prevented more effectively. On the other hand, if the surface roughness Ra is 20 μm or less, even in the case of a vertical reactor using a susceptor as a heating source, slip due to local heat concentration in the peripheral region is possible. This is because the occurrence of dislocation can be suppressed to a certain level.
The significance of the numerical value of the center side region 9c is that the occurrence of slip dislocations in the semiconductor device fabrication region can be more reliably suppressed if the surface roughness Ra is less than 10 μm. On the other hand, in order to make the surface roughness Ra less than 1 μm, the cost required for polishing increases, which is uneconomical, and a surface roughness Ra smaller than this may be used.

Further, the width from the side wall 9b of the peripheral region 9d on the wafer mounting surface 9a is preferably 1 mm or more and 5 mm or less.
If the width from the side wall 9b of the peripheral side region 9d is 1 mm or more, sticking between the peripheral side region 9d and the portion in contact with the peripheral side region 9d of the wafer 5 (wafer outer peripheral back surface) is more reliably prevented. Because it can. On the other hand, if the width of the peripheral region 9d from the side wall 9b is 5 mm or less, even if slip dislocation occurs due to local heat concentration in the portion of the wafer 5 that contacts the peripheral region 9d (wafer outer peripheral back surface). This is because the semiconductor device to be fabricated in the wafer central portion is more surely not adversely affected. Accordingly, when the region where the semiconductor device is not formed is 5 mm or more from the outer peripheral edge of the wafer, the width of the peripheral region 9d may be wider than 5 mm.

  In addition, although the shape of the whole susceptor is a horizontal disk type | mold, for example, it is not specifically limited, Moreover, the counterbore formed can be made into one or more. The diameter and depth of the counterbore can be appropriately selected according to the size of the wafer to be placed.

FIG. 2 is a schematic sectional view showing an example of a vapor phase growth apparatus according to the present invention.
In this vertical type vapor phase growth apparatus 1, a reaction chamber 4 is formed by mounting a bell-shaped bell jar 3 on a base plate 2. In the reaction chamber 4, a horizontal disk type susceptor 6 on which a wafer 5 is placed is disposed horizontally, and a high-frequency heating coil 7 for heating the wafer 5 via the susceptor 6 is disposed in the coil cover 8 on the lower surface. Is provided.

The susceptor 6 provided in this vapor phase growth apparatus is a susceptor according to the present invention, and for example, the susceptor shown in FIG. 1 can be used. The vapor phase growth apparatus provided with the susceptor according to the present invention is a vapor phase growth apparatus that can effectively prevent sticking, prevent wafer cracks and cracks, and increase the productivity of epitaxial wafers. .
The vapor phase growth apparatus of the present invention is not limited to such a vertical type, and may be a horizontal type.

Next, a method for vapor-depositing a thin film on the wafer surface by the vapor phase growth method of the present invention will be described in the case of using the vapor phase growth apparatus of FIG.
First, the wafer 5 is placed on the counterbore 9 of the susceptor 6. Then, the source gas is supplied from the gas introduction port 10, ejected from the ejection holes 12 provided on the side surface and upper surface of the nozzle 11, introduced into the reaction chamber 4, and discharged from the gas exhaust port 13. At this time, since the wafer 5 is heated by the high-frequency heating coil 7, the ejected raw material gas reacts on the wafer surface, and a thin film epitaxial layer is vapor-phase grown on the wafer surface.

  At this time, since the wafer mounting surface of the counterbore 9 has a surface roughness distribution as described above, that is, the surface roughness of the peripheral region is larger than the surface roughness of the central region, as described above, The occurrence of sticking between the outer peripheral back surface of the wafer and the peripheral region of the counterbore wafer mounting surface is prevented, and the occurrence of slip dislocation is suppressed on the center side of the wafer. Thus, in the vapor phase growth method according to the present invention, the occurrence of sticking can be effectively prevented, cracks and cracks in the wafer can be prevented, and it is not necessary to reduce the growth rate. Productivity can be increased.

As the wafer, for example, a silicon wafer can be used, but another semiconductor wafer such as a compound semiconductor may be used, and is not particularly limited.
Further, the thin film can be, for example, a silicon thin film, but other semiconductor thin films can be formed by appropriately selecting a source gas, and is not particularly limited.

  At this time, the thickness of the thin film to be epitaxially grown can be 100 μm or more. If the thin film is thick, sticking is likely to occur because the film is also deposited on the counterbore, but the method of the present invention is beneficial because it can effectively prevent sticking from occurring on the back surface of the outer periphery of the wafer.

  Further, if the epitaxial wafer is obtained by vapor-phase growth of a thin film on the surface of the wafer by the vapor phase growth method of the present invention, it is an epitaxial wafer having a high yield in which cracking and cracking of the wafer due to sticking are prevented, and Since it is an epitaxial wafer with high productivity and a thin film grown at a high speed, it can be made inexpensive.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples of the present invention, but the present invention is not limited to these.
(Examples 1-18)
Using a vertical vapor phase growth apparatus 1 as shown in FIG. 2, a silicon wafer having a diameter of 6 inches (150 mm) was accommodated in a counterbore 9 of the susceptor 6, and an epitaxial layer of silicon was grown on the wafer 5.
At this time, as a susceptor 6 for a 6-inch wafer, as shown in a level table in Table 1 below, the width W from the side wall 9b of each peripheral region 9d of 18 counterbore 9 is 0.5 mm, A susceptor having a thickness of 0.0 mm, 5.0 mm, 30.0 mm and a surface roughness R _out (Ra) of 7 μm, 10 μm, 15 μm, 20 μm, and 25 μm arranged as shown in FIG. . In addition, the surface roughness R _in (Ra) of the center side region 9c was 3 μm in all the counterbores. Further, in FIG. 3 (b), shows a schematic diagram showing width W and the surface roughness R _out of the peripheral side _region, the surface roughness R _in the center side region.
Examples 1 to 18 correspond to levels 1 to 18, respectively.

SiHCl ₃ was used as a reaction gas, the growth rate was 1.5 μm / min, the reaction temperature was 1050 ° C., and the growth film thickness was 120 μm.
For each level, 30 vapor phase growths were repeated, one for each vapor phase growth, and 30 epitaxial wafers were obtained for each level.
Then, the sticking generation ratio between the wafer and the susceptor after the epitaxial layer was grown in this way was examined.

Figure 4 shows a graph showing the relationship between the width W (the peripheral side area width W) and the surface roughness R _out and sticking occurrence rate near side area of the side wall 9b of the peripheral side region 9d. When the width W of the peripheral region was 1.0 mm or more, the sticking rate was 3% or less when the surface roughness was 10 μm or more, and the occurrence of sticking was effectively prevented. When the surface roughness of the peripheral region was 7 μm, the sticking occurrence rate was about 20%. Further, when the peripheral region width was 0.5 mm, the sticking occurrence ratio was about 20% in any surface roughness.

  Table 2 shows the presence or absence of occurrence of slip dislocations at the outer periphery of the wafer due to local heat concentration.

When the surface roughness of the peripheral region was 25 μm, slip dislocation was observed in all cases. Generation | occurrence | production was seen in a part with the surface roughness of a peripheral area | region of 20 micrometers and 15 micrometers. Almost no surface roughness of the peripheral region was 10 μm, and no surface roughness was generated at 7 μm.
In any of Examples 1 to 18, no slip dislocation was observed near the center of the wafer, which corresponds to the center side region of the wafer mounting surface.

From these results, in Examples 1 to 18, the effects of the present invention that can suppress the occurrence of slip dislocation near the center of the wafer while preventing sticking were clearly obtained.
In particular, if the surface roughness R _out of the peripheral region is 10 μm or more and 20 μm or less and the width W of the peripheral region is 1 mm or more, sticking hardly occurs and the occurrence of slip dislocation is suppressed in the peripheral region. I was able to. In addition, by setting the width of the peripheral region to 5 mm or less, it was possible to suppress the occurrence of slip dislocation near the center of the wafer, which is the region where the semiconductor device was built.

(Comparative Examples 1-6)
The surface roughness of the wafer mounting surface is 3 μm (Comparative Example 1), 7 μm (Comparative Example 2), 10 μm (Comparative Example 3), 15 μm (Comparative Example 4), 20 μm (Comparative Example 5), and 25 μm, respectively. (Comparative Example 6) Using the same vapor phase growth apparatus as in Examples 1 to 18 except that the six types of counterbore were provided with susceptors formed in total of 18 types of counterbore, Vapor phase growth was performed 10 times under similar growth conditions, and a total of 30 epitaxial wafers were obtained for each of Comparative Examples 1-6.

As a result, in Comparative Examples 1 to 3, almost no slip dislocation was observed on the entire surface of the wafer, but the occurrence rate of sticking was 80% or more in Comparative Example 1, 20% or more in Comparative Example 2, and in Comparative Example 3 3% or less.
In Comparative Examples 4 to 6, although the sticking occurrence rate was 3% or less, slip dislocation occurred on the entire wafer surface including the vicinity of the wafer center. In particular, as the surface roughness of the wafer mounting surface increased, the amount of slip dislocations increased on the entire wafer surface.
From the above results, it has been clarified that the present invention can suppress the occurrence of slip dislocation near the center of the wafer while preventing sticking.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

It is a cross-sectional schematic explanatory drawing of the counterbore of the susceptor for vapor phase growth according to this invention. It is a cross-sectional schematic explanatory drawing which shows an example of the vapor phase growth apparatus of this invention. (A) It is a figure which shows a response | compatibility with a level table (Table 1) about the arrangement | positioning of a counterbore. (B) is a schematic diagram showing width W and the surface roughness R _out of the peripheral side _region, the surface roughness R _in the center side region in the counterbore of the wafer mounting surface. In the embodiment, it is a graph showing the relationship between the surface roughness R _out and sticking occurrence ratio of the width W and the peripheral side area of the peripheral side region. It is a cross-sectional schematic explanatory drawing which shows an example of the conventional vapor phase growth apparatus.

Explanation of symbols

1, 21 ... Vertical vapor phase growth apparatus, 2 ... Base plate, 3 ... Berja,
4 ... reaction chamber, 5 ... wafer, 6, 16 ... susceptor, 7 ... high frequency heating coil,
8 ... Coil cover, 9, 19 ... Counterbore, 9a ... Wafer mounting surface,
9b ... side wall, 9c ... center side region, 9d ... peripheral side region,
10 ... gas inlet, 11 ... nozzle,
12 ... ejection hole, 13 ... gas discharge port.

Claims (4)

A vapor phase growth susceptor for mounting a wafer in a vapor phase growth apparatus, wherein the vapor phase growth susceptor is formed with a concave counterbore comprising a wafer mounting surface on which a wafer is mounted and a side wall. are as hereinbefore, the wafer mounting surface, and a center side region, Ri Do and a peripheral side area is greater surface roughness than said center-side region, the surface roughness Ra of the center-side region in the wafer mounting surface Is 1 μm or more and less than 10 μm, the surface roughness Ra of the peripheral region on the wafer mounting surface is 10 μm or more and 20 μm or less, and the width of the peripheral region on the wafer mounting surface from the side wall is 1 mm. A susceptor for vapor phase growth characterized by being 5 mm or less . A vapor phase growth apparatus comprising at least the vapor phase growth susceptor according to claim 1 . The vapor phase growth apparatus according to claim 2 , wherein the vapor phase growth apparatus is a vertical type vapor phase growth apparatus. A vapor phase growth method comprising: mounting a wafer on at least the counterbore of the vapor phase growth susceptor according to claim 1 and vapor-depositing a thin film on the surface of the wafer.

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