JP6881283B2 - Manufacturing method of epitaxial silicon wafer and epitaxial silicon wafer - Google Patents

Description

The present invention relates to a method for manufacturing an epitaxial silicon wafer and an epitaxial silicon wafer, and more particularly to an epitaxial silicon wafer having an enhanced flatness of an epitaxial film and a method for manufacturing the same.

The epitaxial silicon wafer is a wafer in which a silicon source gas is sprayed on one side of a silicon wafer as a substrate to grow an epitaxial film, and is used in a wide range of applications such as memory devices, logic devices, and imaging devices.

Since the flatness of an epitaxial silicon wafer is one of the important factors for improving the degree of integration of a semiconductor device, an epitaxial silicon wafer having a high flatness is strongly demanded. Further, in order to make more semiconductor elements from one epitaxial silicon wafer, a flat shape is required to the entire surface of the wafer, particularly to the outer peripheral region. The edge exclusion region (Edge Exclusion) when measuring the flatness of the surface of a wafer has been 3 mm from the wafer edge in the past, but at present, it has advanced to 2 mm, and further to 1 mm. Is also required to be reduced.

However, in the outer peripheral region of the wafer, it has been found that it is difficult to make the thickness of the epitaxial film uniform because the thickness of the epitaxial film changes due to the difference in the growth rate of the epitaxial film due to the difference in crystal orientation. .. It has become clear that this change in the thickness of the epitaxial film due to the crystal orientation becomes more apparent as the thickness of the epitaxial film formed becomes thicker.

In order to reduce the change in the thickness of the epitaxial film due to the crystal orientation, for example, Patent Document 1 proposes a method of reducing the chamfer width on the front surface side of the silicon wafer to 200 μm or less. According to this method, it has been reported that the flatness in the outer peripheral region can be improved because the growth rate orientation dependence of the epitaxial film is suppressed.

Further, Patent Document 2 reports that the dependence on the growth rate of the epitaxial film can be eliminated by adjusting the gas concentration, the growth temperature, the pressure in the chamber, and the like, which are the epitaxial growth conditions.

Japanese Unexamined Patent Publication No. 2014-36153 Japanese Unexamined Patent Publication No. 2016-100483

However, although the method described in Patent Document 1 is effective in eliminating the growth rate orientation dependence of the epitaxial film, the chamfer width of the wafer must be narrowed to a width of 200 μm or less, and the chamfer width is wide. Will not have sufficient flatness. Further, if the chamfer width is too narrow, processing damage tends to remain in the chamfered portion, and slip dislocation from the chamfered portion may easily occur. On the other hand, it is not sufficient to eliminate the growth rate orientation dependence of the epitaxial film only by adjusting the pressure inside the furnace during epitaxial growth as in the method described in Patent Document 2, and sufficient flatness cannot be obtained.

Therefore, an object of the present invention is to provide an epitaxial silicon wafer in which the flatness of the epitaxial film is entirely enhanced, and a method for manufacturing the same.

In order to solve the above problems, the present invention manufactures an epitaxial silicon wafer in which a chamfered portion is formed at the outer peripheral end and an epitaxial film is formed on the main surface of the silicon wafer having a plane orientation of (100) plane or (110) plane. The method is a protective film forming step of forming a protective film on the chamfered portion of the silicon wafer, and forming the protective film so that the growth rate of the epitaxial film on the outer peripheral portion is slower than that of the central portion of the silicon wafer. It is characterized by having an epitaxial film forming step of forming the epitaxial film on the silicon wafer after the step.

According to the present invention, by forming a protective film on the chamfered portion, the influence of the growth rate orientation dependence of the epitaxial film in the outer peripheral region can be suppressed, and the thickness distribution in the circumferential direction of the epitaxial film can be made uniform. be able to. Further, by weakening the epitaxial growth in the outer peripheral region, it is possible to suppress an increase in the thickness of the epitaxial film in the outer peripheral region. Therefore, it is possible to provide an epitaxial silicon wafer in which the flatness of the epitaxial film is totally improved.

In the present invention, in the protective film forming step, it is preferable to form the protective film on the chamfered portion at least in the direction of the crystal orientation <100> of the silicon wafer, and the protective film is formed over the entire circumference of the chamfered portion of the silicon wafer. It is also preferable to form the protective film. By covering a part of the chamfered portion existing in the direction of the crystal orientation <100> with a protective film, the growth rate orientation dependence of the epitaxial film can be suppressed. Also, when the entire circumference of the outer peripheral region of silicon is covered with a protective film, the growth rate orientation dependence of the epitaxial film is eliminated, so that the amount of the raw material source gas adhering to the outer peripheral region is made uniform in the epitaxial film forming step. be able to. Therefore, it is possible to suppress the periodic change in film thickness of the epitaxial film in the outer peripheral region generated by the epitaxial growth.

In the present invention, the protective film is preferably an oxide film. In this case, in the epitaxial film forming step, it is preferable to carry out epitaxial growth using a raw material source gas to which hydrogen chloride gas is added. As a result, the growth of silicon on the oxide film can be suppressed, and the generation of granular silicon called nodules can be prevented.

The method for manufacturing an epitaxial silicon wafer according to the present invention preferably further includes a protective film removing step of removing the protective film after the epitaxial film forming step. According to this, the epitaxial defect generated in the outer peripheral region can be removed.

Further, the epitaxial silicon wafer according to the present invention is an epitaxial silicon wafer having a chamfered portion at the outer peripheral end and having an epitaxial film on a silicon wafer whose main surface is a (100) surface or a (110) surface. Is 2 μm or more in thickness, and the PV value (Peak to Valley) of the thickness of the epitaxial film in the circumferential direction and the radial direction in the outer peripheral region of 1 mm to 3 mm in the radial direction from the outer peripheral edge is 0.05 μm or less. It is characterized by that. In this case, it is preferable that no granular silicon is present on the surface of the chamfered portion. According to the present invention, it is possible to provide a high-quality epitaxial silicon wafer having high flatness, more semiconductor chips can be taken out from one epitaxial silicon wafer, and the degree of integration of semiconductor devices is improved. Can be made to.

According to the present invention, it is possible to provide an epitaxial silicon wafer in which the flatness of the epitaxial film is totally improved and a method for manufacturing the same.

1A and 1B are views for explaining the film thickness distribution of an epitaxial film in an epitaxial silicon wafer whose main surface is the (100) surface, where FIG. 1A is a top view and FIG. 1B is a circumferential direction of an outer peripheral region. It is a graph which shows the film thickness distribution. 2A and 2B are cross-sectional views of the outer peripheral region 21 of the epitaxial silicon wafer 1, where FIG. 2A shows a cross section in the <100> orientation and FIG. 2B shows a cross section in the <110> orientation. 3A and 3B are views for explaining a method for manufacturing an epitaxial silicon wafer according to the first embodiment of the present invention, in which FIG. 3A is a top view and FIG. 3B is a sectional view taken along the line AA. c) is a cross-sectional view of (a) in the BB direction. 4A and 4B are cross-sectional views showing a configuration of an epitaxial silicon wafer 1 in which an epitaxial film 3 is formed on the front surface of the silicon wafer 2 shown in FIG. 3, where FIG. 4A is an overall view and FIG. Is an end sectional view. FIG. 5 is a cross-sectional view showing the configuration of an epitaxial silicon wafer in which an epitaxial film having a thicker outer peripheral portion than the central portion is formed. 6A and 6B are views for explaining a method for manufacturing an epitaxial silicon wafer according to a second embodiment of the present invention, in which FIG. 6A is a top view and FIG. 6B is a sectional view taken along the line AA. c) is a cross-sectional view of (a) in the BB direction. FIG. 7 is a top view for explaining the surface shape of the front surface 23 of the silicon wafer 2 whose main surface is the (110) surface. FIG. 8 is a top view for explaining the surface shape of the front surface 23 of the silicon wafer 2 whose main surface is the (111) surface. FIG. 9 is a graph showing the measurement results of the epitaxial film thickness distribution in the outer peripheral region of the epitaxial silicon wafer according to Examples 1 and 2 and Comparative Examples 1 and 2.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1A and 1B are views for explaining the film thickness distribution of an epitaxial film in an epitaxial silicon wafer whose main surface is the (100) surface, where FIG. 1A is a top view and FIG. 1B is a circumferential direction of an outer peripheral region. It is a graph which shows the film thickness distribution. The outer peripheral region refers to a region of 1 to 3 mm in the radial direction from the outer peripheral edge of the wafer.

As shown in FIG. 1A, assuming that the <110> orientation of the epitaxial silicon wafer whose main surface is the (100) plane is the reference crystal orientation, the <110> orientations are 0 degrees (360 degrees), 90 degrees, and so on. It corresponds to 180 degrees and 270 degrees. On the other hand, the <100> orientation corresponds to 45 degrees, 135 degrees, 225 degrees, and 315 degrees. Then, as shown in FIG. 1B, the film thickness of the outer peripheral region of the epitaxial film is thicker in the portion corresponding to the <110> orientation and thin in the portion corresponding to the <100> orientation. That is, in the outer peripheral region of the epitaxial film, a film thickness change with a period of 90 degrees occurs in the circumferential direction.

This is because the growth rate of the epitaxial film is slow in the outer peripheral region of the <100> orientation, and the growth rate is high in the outer peripheral region of the <110> orientation. This phenomenon occurs because the growth rate of the epitaxial film differs depending on the crystal orientation of the underlying silicon wafer, and this phenomenon is called growth rate orientation dependence. The change in film thickness due to the growth rate orientation dependence does not occur in the central part of the wafer, but occurs in the outer peripheral region of about 1 to 3 mm from the outer peripheral edge of the wafer, and the effect is more remarkable as it is closer to the outer peripheral edge of the wafer. Become. The film thickness variation width of the epitaxial film varies depending on the target film thickness of the epitaxial film, but is about 100 to 200 nm. The mechanism by which the growth rate orientation dependence occurs is as follows.

2A and 2B are cross-sectional views of the outer peripheral region 21 of the epitaxial silicon wafer 1, where FIG. 2A shows a cross section in the <100> orientation and FIG. 2B shows a cross section in the <110> orientation.

As shown in FIGS. 2A and 2B, the epitaxial silicon wafer 1 according to the present embodiment is formed on one main surface (front surface 23) of the silicon wafer 2 and the silicon wafer 2. It has an epitaxial film 3. Further, the crystal plane of the front surface 23 of the silicon wafer 2 is the (100) plane. The epitaxial film 3 is not formed on the back surface 24 located on the opposite side of the front surface 23. The outer peripheral region 21 is a region near the outer peripheral edge of the wafer, and a chamfered chamfered portion 22 exists on the outer periphery thereof. The epitaxial film 3 is formed by supplying the silicon source gas 4 to the front surface 23 of the silicon wafer 2.

As shown in FIG. 2A, the epitaxial film 3 formed on the chamfered portion 22 in the <100> orientation has a (110) plane having a high growth rate, and epitaxial growth is promoted at this portion. As a result, the concentration of the silicon source gas 4 on the outer peripheral region 21 of the front surface 23 decreases, and the growth of the epitaxial film 3 is suppressed in the outer peripheral region 21. On the other hand, as shown in FIG. 2B, the epitaxial film 3 formed on the chamfered portion 22 in the <110> orientation has (311) and (111) planes having slow growth rates, and thus this portion. Epitaxial growth is suppressed. As a result, the concentration of the silicon source gas 4 on the outer peripheral region 21 of the front surface 23 is increased, and the growth of the epitaxial film 3 is promoted in the outer peripheral region 21. Due to such a mechanism, the film thickness of the epitaxial film 3 on the outer peripheral region 21 of the front surface 23 is thin in the <100> orientation and thick in the <110> orientation.

In this embodiment, a protective film is formed in advance on the chamfered portion 22 of the front surface 23 of the silicon wafer 2 in order to prevent the film thickness fluctuation of the epitaxial film 3 caused by such a growth rate orientation dependence.

3A and 3B are views for explaining a method for manufacturing an epitaxial silicon wafer according to the first embodiment of the present invention, in which FIG. 3A is a top view and FIG. 3B is a sectional view taken along the line AA. c) is a cross-sectional view of (a) in the BB direction.

As shown in FIGS. 3A to 3C, the corner portions on the front surface side and the back surface side of the outer peripheral end of the silicon wafer 2 are chamfered, and the chamfered portion 22 has a protective film 5 on the entire circumference of the wafer. It is uniformly formed over. The protective film 5 is not particularly limited as long as it is a material that can cover the surface of the chamfered portion 22, and examples thereof include a silicon oxide film, a silicon nitride film, and a polysilicon film. For example, by a CVD method or thermal oxidation. Can be formed. As a method of forming the protective film 5 on the chamfered portion 22 of the silicon wafer 2, for example, a method of superimposing a plurality of silicon wafers 2 and performing a film forming process such as a CVD method in a state where only the chamfered portion 22 is exposed. Can be adopted.

In the present embodiment, the protective film 5 not only covers the chamfered portion 22 of 45 degrees, 135 degrees, 225 degrees, and 315 degrees corresponding to the <100> orientation, but also covers the chamfered portion 22 corresponding to the <110> orientation (360 degrees). It covers the chamfered portion 22 at 90 degrees, 180 degrees, and 270 degrees. When the protective film 5 covers the chamfered portion 22, the epitaxial film 3 is not formed in the chamfered portion 22, so that the film thickness of the epitaxial film 3 does not fluctuate. Therefore, it is possible to prevent the film thickness of the epitaxial film 3 in the outer peripheral region 21 from fluctuating in the circumferential direction.

4A and 4B are cross-sectional views showing a configuration of an epitaxial silicon wafer 1 in which an epitaxial film 3 is formed on the front surface of the silicon wafer 2 shown in FIG. 3, where FIG. 4A is an overall view and FIG. Is an end sectional view.

As shown in FIGS. 4A and 4B, the epitaxial silicon wafer 1 includes a silicon wafer 2 having a main surface (100) and an epitaxial film 3 formed on the front surface of the silicon wafer 2. have. The outer peripheral edge of the silicon wafer 2 is chamfered, and the chamfered portion 22 of the silicon wafer 2 is formed with the protective film 5 described above. Therefore, the difference between the film thickness of the epitaxial film 3 in the outer peripheral region 21 corresponding to the <110> orientation and the film thickness of the epitaxial film 3 in the outer peripheral region 21 corresponding to the <100> orientation becomes small, thereby reducing the wafer. The film thickness of the epitaxial film 3 does not change at a 90-degree cycle in the outer peripheral region 21 of the

As shown in FIG. 4B, the protective film 5 is preferably separated from the outer peripheral region 21, and the distance d from the protective film 5 to the epitaxial film 3 formed in the outer peripheral region 21 is 10 to 200 μm. It is preferably present, and it is particularly desirable that the thickness is 10 to 100 μm. For example, when the protective film 5 is removed by edge polishing or the like, the outer peripheral edge of the epitaxial film 3 may also be removed, but by providing the interval d, the situation where the epitaxial film 3 is also removed is avoided. be able to. The radial outside of the outer peripheral region 21 is an edge exclusion region, and the chamfered portion 22 is formed in the edge exclusion region. For example, the width of the edge exclusion region is 1 mm, and the width of the chamfered portion is 350 to 750 μm.

As described above, in the present embodiment, since the epitaxial film 3 is not affected by the growth rate orientation dependence, it is possible to eliminate periodic irregularities in the circumferential direction of the surface of the epitaxial film 3, and the outer periphery of the epitaxial film 3 can be eliminated. The flatness in the circumferential direction of the partial region can be increased.

The protective film 5 of the epitaxial silicon wafer 1 shown in FIG. 4 may be finally removed. For example, if the protective film 5 is an oxide film, it may be removed by washing with a hydrofluoric acid solution having a weak etching action that does not deteriorate the roughness of the surface of the epitaxial film. If the protective film is a resin-based film, it may be removed by machining such as polishing. In this case, a clearance portion without an oxide film is provided on the chamfered portion as shown in FIG. 4 (b). It is desirable to keep it.

As described above, when the protective film 5 is formed on the entire circumference of the chamfered portion 22, it is possible to eliminate the dependence on the crystal orientation in the circumferential direction and make the thickness distribution of the epitaxial film 3 in the circumferential direction uniform. Then, since the epitaxial growth rate of the chamfered portion 22 on which the protective film 5 is formed becomes slow, as shown in FIG. 5, the epitaxial film 3 becomes thick over the entire circumference of the outer peripheral region 21, and the epitaxial film 3 becomes thick in the radial direction. There is a problem that the thickness distribution is not uniform.

Therefore, in the present embodiment, the thickness distribution in the radial direction is adjusted by performing epitaxial growth under the condition that the epitaxial growth rate at the outer peripheral portion is slower than the epitaxial growth rate at the central portion of the wafer. Specifically, by lowering the temperature of the outer peripheral region 21 of the wafer or reducing the flow of the raw material source gas toward the outer peripheral region 21, the epitaxial growth rate in the outer peripheral region is slower than that in the central portion of the wafer. .. In this way, by forming the protective film 5 on the chamfered portion 22, the non-uniformity of the film thickness in the circumferential direction can be eliminated, and by controlling the growth rate of the epitaxial film, the film in the radial direction (in-plane) can be eliminated. The non-uniformity of thickness can be eliminated.

In the epitaxial film forming step, if epitaxial growth is carried out with the oxide film as the protective film 5 formed on the chamfered portion 22 of the silicon wafer 2, the probability that nodules (granular silicon) are generated on the chamfered portion 22 increases. Nodules are massive polycrystalline silicon protrusions with a size that can be visually observed (0.3 μm or more), and peel off from the wafer during transportation to generate particles or cause epitaxial growth abnormalities called crowns. It causes. In the present embodiment, the generation of nodules can be prevented by mixing a small amount of hydrogen chloride gas with the raw material source gas such as trichlorosilane used for epitaxial growth.

6A and 6B are views for explaining a method for manufacturing an epitaxial silicon wafer according to a second embodiment of the present invention, in which FIG. 6A is a top view and FIG. 6B is a sectional view taken along the line AA. c) is a cross-sectional view of (a) in the BB direction.

As shown in FIG. 6A, the protective film 5 is selectively formed on the chamfered portion 22 of the silicon wafer 2. As shown in FIG. 6B, the protective film 5 does not cover the chamfered portion 22 in the <110> orientation (directions of 0 degrees, 90 degrees, 180 degrees, and 270 degrees from the center of the wafer), but is shown in FIG. 6 (c). ), It covers the chamfered portion 22 in the <100> orientation (directions of 45 degrees, 135 degrees, 225 degrees, and 315 degrees from the center of the wafer). Therefore, the growth of the epitaxial film 3 in the outer peripheral region 21 in the <100> orientation is promoted by the protective film 5, but the epitaxial film 3 in the outer peripheral region 21 in the <110> orientation is affected by the protective film 5. Grow without. The width of the region forming the protective film 5 is preferably ± 22.5 degrees or more with respect to the <100> orientation. The wider the width of the protected area, the more the film thickness fluctuation in the circumferential direction can be reduced.

Hereinafter, a method for manufacturing an epitaxial silicon wafer using the silicon wafer 2 having such a protective film 5 will be described in detail.

In the manufacture of an epitaxial silicon wafer, first, as shown in FIG. 6, a silicon wafer 2 in which a protective film 5 is formed on a chamfered portion 22 is prepared. The angle of the tapered surface with respect to the main surface of the silicon wafer 2 is preferably 20 ° or more.

Next, an epitaxial film forming step of forming the epitaxial film 3 on the front surface of the silicon wafer 2 on which the protective film 5 is formed by a well-known method is started. At this time, since the protective film 5 exists in the chamfered portion 22 in the <100> orientation, the growth of the epitaxial film 3 in the outer peripheral region 21 in the <100> orientation is promoted by the protective film 5. On the other hand, since the protective film 5 does not exist in the chamfered portion 22 in the <110> orientation, the epitaxial film 3 in the outer peripheral region 21 in the <110> orientation is affected by the <110> orientation of the chamfered portion 22 and <110>. It grows faster than the epitaxial film 3 of the 100> oriented chamfered portion 22. Therefore, the epitaxial film 3 in the outer peripheral region 21 in the <110> orientation has substantially the same thickness as the epitaxial film 3 in the outer peripheral region 21 in the <100> orientation.

As described above, in the method for manufacturing an epitaxial silicon wafer according to the present embodiment, the chamfered portion 22 of the silicon wafer 2 is protected in advance so that the film thickness of the epitaxial film 3 in the circumferential direction does not fluctuate due to the growth rate orientation dependence. Since it is covered with the film 5, the flatness of the surface of the epitaxial film 3 can be improved over the vicinity of the end portion of the wafer. As a result, the edge exclusion region is reduced, so that more semiconductor chips can be taken out from one epitaxial silicon wafer.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention, and these are also the present invention. Needless to say, it is included in the range.

For example, in the above embodiment, an example using a silicon wafer whose main surface is the (100) surface has been described, but the present invention is not limited thereto. Therefore, a silicon wafer whose main surface is the (110) surface may be used, or a silicon wafer whose main surface is the (111) surface may be used.

When the protective film 5 is selectively formed on the chamfered portion 22 of the silicon wafer 2 whose main surface is the (110) surface, as shown in FIG. 8, the film thickness distribution of the epitaxial film depends on the growth rate orientation. Since the cycle is 180 degrees, when such a silicon wafer 2 is used, a protective film 5 having a cycle of 180 degrees may be formed on the chamfered portion 22. In this case, the width of the region forming the protective film 5 is preferably 90 degrees or more, that is, ± 45 degrees or more with respect to the <100> orientation.

Further, when the protective film 5 is selectively formed on the chamfered portion 22 of the silicon wafer 2 whose main surface is the (111) surface, as shown in FIG. 9, the film thickness of the epitaxial film depends on the growth rate orientation. Since the distribution has a cycle of 60 degrees, when such a silicon wafer 2 is used, a protective film 5 having a cycle of 60 degrees may be formed on the chamfered portion 22. In this case, the width of the region forming the protective film 5 is preferably 30 degrees or more.

<Example 1>
A silicon wafer having a diameter of 300 mm, a thickness of 775 μm, a chamfer width of 300 μm, and a crystal plane (100) plane was prepared. An oxide film having a thickness of 2000 Å was formed over the entire circumferential direction of the chamfered portion of the silicon wafer by the CVD method.

Next, an epitaxial film was formed on the main surface of the silicon wafer. In the epitaxial film forming step, a silicon wafer is placed on a susceptor in a single-wafer epitaxial apparatus, hydrogen gas is supplied into the furnace, hydrogen baking is performed at a temperature of 1130 ° C. for 30 seconds, and then a carrier gas is used. _{Trichlorosilane (SiHCl 3} ) gas is supplied into the furnace as a silicon source gas together with a certain hydrogen gas, and epitaxial growth is performed at a temperature of 1130 ° C., and the thickness at the center of the silicon wafer becomes 2 μm on the main surface of the silicon wafer. The epitaxial film was formed as described above.

Further, in the epitaxial film forming step, the epitaxial growth process was performed so that the epitaxial growth rate of the outer peripheral portion of the wafer was slower than the growth rate of the central portion of the wafer. Specifically, the epitaxial growth treatment was carried out in a state where the gas flow rate toward the outer peripheral portion was reduced so that the growth rate of the central portion was 2 μm / min and the growth rate of the outer peripheral portion was 1.7 μm / min. The growth rate condition is not limited to the condition of this embodiment, and the condition may be set according to the thickness distribution in the radial direction. Generally, the growth rate of the outer peripheral portion is relative to the growth rate of the central portion. It is desirable to set it within the condition that the speed is delayed by 5% to 30%. The central portion of the wafer can be defined as a region within R / 2 (R is the radius of the wafer) from the center of the wafer. Therefore, for example, in the case of a 300 mm wafer, the central portion of the wafer is a circular region within 150 mm from the center of the wafer.

Then, the epitaxial silicon wafer was washed with hydrofluoric acid to remove the oxide film formed on the chamfered portion. In this way, the epitaxial silicon wafer according to Example 1 was obtained.

<Example 2>
In Example 2, the epitaxial growth treatment was carried out under the same conditions as in Example 1 except that hydrogen chloride (HCl) gas was mixed with _{trichlorosilane (SiHCl 3) gas.} If a large amount of HCl gas is mixed, epitaxial growth itself may become difficult. Therefore, it is desirable that the mixing ratio of HCl gas is at most 15% or less of the flow rate of the raw material gas.

<Comparative example 1>
In Comparative Example 1, the gas flow rate is uniform in the wafer surface so that the epitaxial growth rate of the outer peripheral portion of the wafer and the growth rate of the central portion are equal to each other without forming an oxide film on the chamfered portion. The epitaxial growth treatment was carried out under the same conditions as in Example 1 except that the above was adjusted.

<Comparative example 2>
In Comparative Example 2, the epitaxial growth treatment was performed under the same conditions as in Comparative Example 1 except that an oxide film was formed on the chamfered portion and the oxide film was removed after the epitaxial growth treatment.

<Measurement of epitaxial film thickness>
For each of the epitaxial silicon wafers obtained in Examples 1 and 2 and Comparative Examples 1 and 2, the epitaxial film thickness distribution in the outer peripheral region was measured using a Fourier Transform Infrared spectrometer (FTIR). It was measured. Specifically, the thickness distribution in the circumferential direction was measured at each point of 1 mm, 2 mm, and 3 mm in the radial direction from the outer peripheral edge of the wafer.

FIG. 9 is a graph showing the measurement results of the thickness distribution of the epitaxial film in the outer peripheral region.

As shown in FIG. 9, in Examples 1 and 2, since an oxide film was formed on the chamfered portion to reduce the epitaxial growth rate on the outer peripheral portion, all of them were radially from the outer peripheral end of the epitaxial silicon wafer. The PV value (Peak to Valley) of the thickness of the epitaxial film in the circumferential direction and the radial direction in the region of 1 mm to 3 mm was 0.05 μm or less, and an epitaxial silicon wafer having a uniform thickness distribution was obtained. In Example 1, a slight amount of nodules was observed in the chamfered portion, but in Example 2 in which HCl gas was mixed, no nodules were observed at all.

On the other hand, in Comparative Example 1, the PV value of the thickness of the epitaxial film in the circumferential direction and the radial direction in the region of 1 mm to 3 mm in the radial direction from the outer peripheral edge of the epitaxial silicon wafer exceeds 0.1 μm. There was a large variation in the thickness of the epitaxial film in both the radial direction. In Comparative Example 2, since the oxide film was formed on the chamfered portion, the thickness PV value in the circumferential direction was 0.5 μm or less, but the thickness of the epixial film increased toward the outer circumference, and the PV in the radial direction. The value was a result exceeding 0.1 μm. Further, in Comparative Example 2, the generation of a small amount of nodules was confirmed in the chamfered portion.

1 epitaxial silicon wafer 2 silicon wafer 3 epitaxial film 4 silicon source gas 5 protective film 21 outer peripheral region of silicon wafer 22 chamfered part of silicon wafer 23 front surface of silicon wafer 24 back surface of silicon wafer

Claims (7)

An epitaxial silicon wafer in which chamfered portions are formed at the corners of the outer peripheral ends on the front surface side and the back surface side, and an epitaxial film is formed on the front surface of the silicon wafer composed of the (100) surface or the (110) surface. It ’s a manufacturing method,
A protective film forming step of forming a protective film on at least the chamfered portion on the front surface side of the silicon wafer.
As the growth rate of the epitaxial film becomes slow at the outer peripheral portion than the central portion of the silicon wafer, and an epitaxial film forming step of forming the epitaxial layer on the front surface of the silicon wafer after the protective film forming step ,
A method for manufacturing an epitaxial silicon wafer, which comprises a protective film removing step of removing the protective film after the epitaxial film forming step. The method for manufacturing an epitaxial silicon wafer according to claim 1, wherein in the protective film forming step, the protective film is formed on the chamfered portion on the front surface side at least in the direction of the crystal orientation <100> of the silicon wafer. The method for manufacturing an epitaxial silicon wafer according to claim 1, wherein in the protective film forming step, the protective film is formed over the entire circumference of the chamfered portion on the front surface side of the silicon wafer. The method for manufacturing an epitaxial silicon wafer according to any one of claims 1 to 3, wherein the protective film is an oxide film. The method for manufacturing an epitaxial silicon wafer according to any one of claims 1 to 4, wherein in the epitaxial film forming step, epitaxial growth is performed using a raw material source gas to which hydrogen chloride gas is added. An epitaxial silicon wafer in which chamfered portions are provided at the corners of the outer peripheral ends on the front surface side and the back surface side, and an epitaxial film is provided on the front surface of the silicon wafer composed of the (100) surface or the (110) surface. ,
The epitaxial film has a thickness of 2 μm or more, and the PV value (Peak to Valley) of the thickness of each of the circumferential and radial epitaxial films in the outer peripheral region of 1 mm to 3 mm in the radial direction from the outer peripheral edge is 0.05 μm. An epitaxial silicon wafer characterized by the following. The epitaxial silicon wafer according to claim 6 , wherein no granular silicon is present on the surface of the chamfered portion.

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