JP6723416B2 - Method for manufacturing SiC epitaxial wafer - Google Patents

Description

The present invention relates to a method for manufacturing a SiC epitaxial wafer.

Silicon carbide (SiC) has characteristics such as a dielectric breakdown electric field that is one digit larger than that of silicon (Si), a band gap that is three times larger, and a thermal conductivity that is about three times higher than that of silicon (Si). Since silicon carbide has these characteristics, it is expected to be applied to power devices, high frequency devices, high temperature operating devices and the like. Therefore, in recent years, SiC epitaxial wafers have come to be used for the above semiconductor devices.

A SiC epitaxial wafer is manufactured by growing a SiC epitaxial film which becomes an active region of a SiC semiconductor device on a SiC substrate. The SiC substrate is obtained by processing a bulk SiC single crystal produced by a sublimation method or the like, and the SiC epitaxial film is formed by a chemical vapor deposition method (Chemical Vapor Deposition: CVD).

As an apparatus for manufacturing a SiC epitaxial wafer, a horizontal rotation/revolution type epitaxial growth apparatus is known in which a plurality of wafers are horizontally arranged, each wafer is revolved, and the wafer itself is rotated about the center of the wafer. (For example, patent document 1 and patent document 2).

In this epitaxial growth apparatus, a plurality of satellites are provided on a rotatable mounting plate (susceptor) so as to surround the rotation axis of the mounting plate. Since the satellite is allowed to rotate by the rotation drive mechanism, the SiC substrate mounted on the satellite is configured to be able to rotate about its axis of rotation of the mounting plate and to rotate about its axis. ..

In the epitaxial growth apparatus as described above, the source gas is supplied onto the SiC substrate by passing the source gas from the outside of the outer peripheral end of the SiC substrate mounted on the mounting plate. At this time, an epitaxial film is formed by depositing an epitaxial material on the substrate while maintaining the SiC substrate at a high temperature by the heating means.

Japanese Patent No. 2771585 Japanese Patent No. 2835338

Here, when the SiC epitaxial film is grown on the SiC substrate, there is a problem that the carrier concentration becomes low in the outer peripheral portion of the obtained SiC epitaxial film, that is, in the vicinity of the edge. This tendency is particularly noticeable when a SiC epitaxial film is grown on a large SiC substrate in order to obtain a large SiC epitaxial wafer. With the recent strong demand from the market for increasing the size of SiC epitaxial wafers, it is required to control the carrier concentration in the in-plane direction of the SiC epitaxial wafer.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for manufacturing a SiC epitaxial wafer that can control the in-plane carrier concentration of the SiC epitaxial wafer.

As a result of studies, the present inventors have found that the carrier concentration of the SiC epitaxial film can be controlled by supplying a carrier gas containing a dopant gas (referred to as a dopant carrier gas) from a predetermined position to the SiC substrate. .. Then, the inventors have found a structure of a manufacturing apparatus for a SiC epitaxial wafer capable of controlling the carrier concentration of a predetermined portion efficiently without making a great change in the existing apparatus, and completed the invention.
That is, the present invention provides the following procedures in order to solve the above problems.

(1) A method for manufacturing an SiC epitaxial wafer according to one aspect of the present invention is a SiC epitaxial that includes a mounting plate having a recessed accommodating portion and a satellite that is disposed in the recessed accommodating portion and has a SiC substrate mounted on an upper surface thereof. In the method of manufacturing a wafer, a dopant carrier gas containing a dopant gas is supplied to the outer periphery of the SiC epitaxial wafer from between the concave accommodation portion and the satellite.

(2) In the method of manufacturing an SiC epitaxial wafer according to (1) above, the dopant carrier gas is supplied from a bottom portion of the concave accommodation portion, and the satellite is rotated in the concave accommodation portion by the dopant carrier gas. Good.

(3) In the method of manufacturing an SiC epitaxial wafer according to any one of (1) and (2), the position of the upper surface of the SiC substrate may be the same as or lower than the upper surface of the mounting plate. ..

(4) The dopant gas described in any one of (1) to (3) above may be nitrogen gas.

(5) A manufacturing apparatus for a SiC epitaxial wafer according to an aspect of the present invention is a manufacturing apparatus for a SiC epitaxial wafer in which a SiC epitaxial film is grown on a main surface of a SiC substrate by a chemical vapor deposition method. A mounting plate having an accommodating portion, a satellite arranged in the concave accommodating portion and having a SiC substrate mounted on the upper surface thereof, and a raw material gas for the SiC epitaxial film on the main surface of the SiC substrate mounted on the satellite. A first gas supply pipe for supplying a gas, a second gas supply pipe having a supply port in the concave accommodating portion, a gas connected to the second gas supply pipe, and containing a dopant carrier gas in the second gas supply pipe. And a gas supply unit for supplying the gas.

According to the method and apparatus for manufacturing a SiC epitaxial wafer of the present invention, the carrier concentration in the in-plane direction of the SiC substrate can be controlled.

It is a cross-sectional schematic diagram of the manufacturing apparatus of the SiC epitaxial wafer which concerns on one aspect of this invention. It is the figure which planarly viewed the mounting plate in the manufacturing apparatus of the SiC epitaxial wafer concerning one embodiment of the present invention. FIG. 3 is an enlarged schematic sectional view of the periphery of one satellite in the SiC epitaxial wafer manufacturing apparatus according to the embodiment of the present invention. 3 is a graph showing the position dependence of carrier concentration in the in-plane direction of the SiC epitaxial films obtained in Example 1, Example 2 and Comparative Example 1. 5 is a graph showing a difference in carrier concentration between Example 1 and Example 2 and Comparative Example 1.

Hereinafter, a method and an apparatus for manufacturing a SiC epitaxial wafer to which the present invention is applied will be described in detail with reference to the drawings.
It should be noted that, in the drawings used in the following description, in order to make the features of the present invention easy to understand, there are cases where features are enlarged for the sake of convenience, and the dimensional ratios of the respective components are different from actual ones. Sometimes. Further, the materials, dimensions, and the like exemplified in the following description are examples, and the present invention is not limited to them, and can be appropriately modified and implemented without changing the gist thereof.

First, the definition of the name of gas in this specification will be described. The gas that supplies the elements that make up SiC is called the "source gas." Raw material gases include silane-based gas and hydrocarbon-based gas. As the silane-based gas, silane (SiH ₄ ), dichlorosilane (SiCl ₂ H ₂ ), trichlorosilane (SiCl ₃ ), silicon tetrachloride (SiCl ₄ ) or the like can be used. Examples of the hydrocarbon gas, propane _{(C 3 H} 8), ethane _(C 2 _{H 6)} or the like can be used. Further, in addition to these source gases, a gas containing a carrier gas described later and the like at the same time may be described as a “source gas” in a broad sense.

In addition to these main raw material gases, which are constituent elements of silicon carbide, a gas for doping is called a "dopant gas". The dopant in the SiC substrate by this dopant gas functions as a carrier in the SiC substrate. Examples of the dopant gas for silicon carbide include nitrogen for N-type doping, ammonia, and trimethylaluminum for P-type doping.

A gas that flows in a larger amount than the source gas in the CVD crystal growth and has a function of carrying the source gas and the doping gas is called a "carrier gas". Examples of the carrier gas include argon (Ar) and hydrogen (H ₂ ). That is, “carrier” of “carrier gas” does not mean the same as “carrier” of “carrier density (concentration)” in the SiC substrate.
Further, the “dopant carrier gas” means a gas containing a dopant gas, and also includes a gas in which the dopant gas and the carrier gas are mixed. For example, the dopant carrier gas may be composed of only nitrogen gas, or may be a gas in which nitrogen gas and a gas such as a rare gas are mixed.

<SiC epitaxial wafer manufacturing equipment>
To facilitate understanding of the structure, a SiC epitaxial wafer manufacturing apparatus will be described. FIG. 1 is a diagram schematically illustrating a cross section of an apparatus for manufacturing a SiC epitaxial wafer according to an embodiment of the present invention.

A SiC epitaxial wafer manufacturing apparatus 100 according to an embodiment of the present invention includes a mounting plate 10, a satellite 20, a first gas supply pipe 30, a second gas supply pipe 40, and a gas supply unit (not shown). Have. Further, the SiC epitaxial wafer manufacturing apparatus 100 has a ceiling 50 and a side wall 60 for forming the reaction space K, and a heater 70 for heating the reaction space K. In the SiC epitaxial wafer manufacturing apparatus 100, a source gas G is supplied into a chamber (deposition chamber) capable of evacuating under reduced pressure to grow a SiC epitaxial film on the surface of a heated SiC substrate W. The source gas G supplied into the chamber (film forming chamber) may be a source gas in a broad sense.

FIG. 2 is a plan view of the mounting plate in the SiC epitaxial wafer manufacturing apparatus according to the embodiment of the present invention.
The mounting plate 10 includes a rotary table 13 having a circular shape in plan view and a rotary shaft 12 connected to the center of the rotary table 13. The rotary table 13 is provided with a plurality of concave accommodating portions 11 arranged at equal intervals in the circumferential direction (rotational direction) of the rotary table 13. FIG. 2 exemplifies a case where six recessed accommodating portions 11 are provided side by side at equal intervals. For simplicity, the satellite 20 is housed in only one concave housing portion 11 of the mounting plate 10, but the configuration is not limited to this.

A rotary shaft 12 is attached to the lower center of the mounting plate 10. When the rotary shaft 12 is rotated by a drive motor (not shown), the rotary base 13 can be driven to rotate around its central axis. Hereinafter, the rotation about the rotary shaft 12 as a central axis may be referred to as “revolution”.
The mounting plate 10 only needs to have heat resistance, and a known material can be used. For example, graphite, TaC-coated graphite, SiC-coated graphite, or the like can be used.

FIG. 3 is an enlarged schematic cross-sectional view of the periphery of one satellite in the SiC epitaxial wafer manufacturing apparatus according to the embodiment of the present invention.
The satellite 20 is housed in the concave housing portion 11 of the mounting plate 10. The satellite 20 can rotate within the recessed accommodating portion 11 by rotation driving means. That is, the satellite 20 can revolve around the rotating shaft 12. The satellite 20 can be made of the same material as the mounting plate 10.

It is preferable that the outer diameter of the satellite 20 and the inner diameter of the concave accommodating portion 11 have substantially the same size, and the concave accommodating portion 11 is slightly larger. If the size of the recessed accommodating portion 11 is larger than that of the satellite 20, the satellite 20 is likely to slide sideways in the recessed accommodating portion 11 when the satellite 20 rotates. Therefore, it becomes difficult to obtain a uniform SiC epitaxial film. On the other hand, if the satellite 20 and the concave accommodation portion 11 are the same, it becomes impossible to sufficiently secure the flow path of the gas supplied from the second gas supply pipe 40 described later.

The SiC substrate W is placed on the satellite 20. As shown in FIG. 3, SiC substrate W is preferably placed in recess 21 formed in upper surface 20 a of satellite 20. Placing SiC substrate W in recess 21 can prevent SiC substrate W from sliding sideways due to rotation or the like.

The mounting surface of the SiC substrate of the satellite 20 is preferably circular. When the SiC substrate W is provided with an orientation flat (OF), the mounting surface may have a linear portion similar to the SiC substrate W and corresponding to OF. If there is a portion that is not covered with the SiC substrate W on the mounting surface of the satellite 20, crystals will also be deposited on that portion. This deposit may cause the SiC substrate W to float on the mounting surface. Therefore, by providing a linear portion on the mounting surface, it is possible to prevent unnecessary crystals from being deposited on the mounting surface outside the OF.

The upper surface of the SiC substrate W on which the SiC substrate W is mounted is preferably flush with or lower than the upper surface 13a of the turntable. When the SiC substrate W is higher than the upper surface 13a of the turntable, the disturbance of the flow of the source gas (turbulence of the laminar flow) is likely to occur at the end of the SiC substrate W. When the flow of the source gas is disturbed, the characteristics of the film formed at the end of the SiC substrate W may be different from those of the inside.

The first gas supply pipe 30 has a first end connected to a gas supply pipe (not shown) and a second end connected to a reaction space K surrounded by the ceiling 50, the side wall 60 and the mounting plate 10. There is. The source gas G can be supplied to the reaction space K by the first gas supply pipe 30. As the raw material gas G, one containing a hydrocarbon-based gas and a silane-based gas generally used as a raw material for the SiC epitaxial film can be used. As the hydrocarbon-based gas and the silane-based gas, those mentioned above can be used. The carrier gas and the dopant gas may be supplied from the first gas supply pipe 30 at the same time as the raw material gas.

As shown in FIG. 1, it is preferable that the second end (the reaction space side supply port) of the first gas supply pipe 30 is provided toward the center of the mounting plate 10. Since the supply port of the first gas supply pipe 30 is provided toward the center of the mounting plate 10, the flow of the raw material gas supplied from the first gas supply pipe 30 is directed from the center of the mounting plate 10 to the outer periphery. Can be controlled. That is, the source gas can be uniformly supplied to the satellites 20 mounted on the mounting plate 10.

The second gas supply pipe 40 has a first end connected to an external tank (not shown) or the like, and a second end connected to the recessed housing 11. Here, this external tank etc. respond|correspond to the "gas supply part" in a claim. The gas supply unit may use a tank containing a dopant carrier gas. Alternatively, a gas mixing device that mixes a carrier gas such as hydrogen and a doping gas at a controlled flow rate can be used as the gas supply unit. The gas mixing device mixes a carrier gas and a dopant gas at a fixed ratio and supplies a part or all of the mixed gas to the second gas supply pipe at a predetermined flow rate and pressure, such as a mass flow controller or a pressure controller. Can be configured by. In FIG. 1, the second gas supply pipe 40 is formed so as to penetrate through the rotary shaft 12 and the rotary base 13 of the mounting plate 10, and has a supply port 41 on the upper surface 11 a of the concave accommodation portion 11.

The second gas supply pipe 40 has a supply port 41 on the upper surface 11 a of the concave accommodation portion 11. Therefore, when the satellite 20 is stored in the recessed housing portion 11, gas is supplied between the lower surface 20b of the satellite 20 and the recessed housing portion 11. The satellite 20 slightly floats above the upper surface of the concave accommodation portion 11 by the gas supplied from the supply port 41. Therefore, the frictional force applied between the recessed accommodating portion 11 and the satellite 20 is reduced, and the satellite 20 is rotatable about its center. By rotationally driving the satellite 20 around the central axis, it is possible to uniformly form a film on the SiC substrate W mounted on the satellite 20.

The rotation of the satellite 20 may be controlled by the gas discharged from the supply port 41. The gas discharged from the supply port 41 can have a function of levitating the satellite 20 and a function of rotating the satellite 20. In order to rotate the satellite 20, for example, a spiral groove is formed on the bottom surface of the concave accommodating portion 11, and a gas is caused to flow along the groove to give a torque to the satellite 20 due to its viscosity so that the satellite 20 is rotated. There is a method. Alternatively, the same function can be provided by forming a spiral groove on the back surface side of the satellite 20 and flowing a gas flow along the groove. That is, it is not necessary to separately prepare a driving unit having an external power source or the like to rotate the satellite 20, and the structure of the SiC epitaxial manufacturing apparatus is simplified.

In this way, the gas supplied from the supply port 41 has a function of floating the satellite and a function of rotating the satellite. These functions may be provided by one kind of supply port, or the functions of levitating and rotating may be provided by gas from another supply port. When another supply port is used, the dopant carrier gas is caused to flow from either one of the function of rotating and the function of floating the satellite, and the dopant carrier gas is supplied to the outer periphery of the SiC epitaxial wafer from between the recess accommodation part and the satellite. It may be supplied.

The second gas supply pipe 40 supplies a dopant carrier gas containing a dopant gas to the reaction space K from an external tank (not shown). As shown in FIG. 3, the dopant carrier gas supplied from the second gas supply pipe 40 is supplied to the reaction space K via the space between the recessed container 11 and the satellite 20. That is, when the SiC substrate W mounted on the satellite 20 is considered as a reference, the dopant carrier gas is supplied from the outer periphery toward the center. Therefore, the carrier concentration at the outer periphery of SiC substrate W can be increased with respect to the carrier concentration at the center.

If the gas supplied from the second gas supply pipe 40 does not contain the dopant gas, the carrier concentration on the outer periphery of the SiC substrate W becomes low. In this case, the dopant element can be supplied to the SiC epitaxial film by adding the dopant gas to the source gas supplied from the first gas supply pipe 30. That is, by including the dopant gas in the gas supplied from the second gas supply pipe 40, the carrier concentration on the outer periphery of the SiC epitaxial film can be increased. As a result, by including the dopant gas in the gas supplied from the second gas supply pipe 40, it is possible to grow a uniform SiC epitaxial film.

The ceiling 50 is arranged so as to cover the mounting plate 10 and the satellite 20 from above.
Similarly to the mounting plate 10 and the satellite 20, the ceiling 50 is also a disk-shaped member formed by coating the surface of a base material made of graphite. The coating film that coats the surface of the sealing 50 can also be formed using conventionally known TaC, SiC, or the like.

A well-known thing can be used for the side wall 60. For example, as shown in FIG. 1, one having a supporting portion 61 can be used. The support portion 61 is a sealing support portion provided on the inner peripheral surface of the peripheral wall 60 over the entire circumference, and the outer peripheral portion of the sealing 50 is placed on the sealing support portion. The gas that is no longer needed in the chamber can be discharged to the outside of the chamber from the exhaust port provided between the side wall 60 and the mounting plate 10.

The heater 70 heats the reaction space K. For example, an induction coil or the like can be used. When a high frequency current is supplied to the induction coil from a high frequency power source (not shown), the mounting plate 10 and the ceiling 50 are heated by the high frequency induction heating. The SiC substrate W placed on the satellite 20 can be heated by radiation from the mounting plate 10 and the ceiling 50, heat conduction from the satellite 20, and the like. The heating means is not limited to the configuration arranged on the lower surface side of the mounting plate 10 (turntable 13) and the upper surface side of the ceiling 50, but may be arranged on only one of these sides. is there. Further, not only high frequency induction heating but also resistance heating may be used.

By using the SiC epitaxial wafer manufacturing apparatus 100 according to one aspect of the present invention, it is possible to manufacture a SiC epitaxial wafer with high in-plane carrier concentration uniformity. Further, it is possible to efficiently increase the carrier density of a predetermined portion without making a great change in the existing device. Therefore, it is possible to inexpensively and easily manufacture the SiC epitaxial wafer with high in-plane uniformity of carrier concentration.

<Manufacturing method of SiC epitaxial wafer>
A method for manufacturing a SiC epitaxial wafer according to the present invention is a method for manufacturing a SiC epitaxial wafer, comprising: a mounting plate having a concave accommodating portion; and a satellite in which the SiC substrate is mounted on the upper surface and which is arranged in the concave accommodating portion. A dopant carrier gas containing a dopant gas is supplied to the outer periphery of the SiC epitaxial wafer from between the concave accommodation portion and the satellite.
A method for manufacturing a SiC epitaxial wafer will be described based on an example using the apparatus 100 for manufacturing a SiC epitaxial wafer in FIG.

First, the SiC substrate W to be mounted on the satellite 20 is prepared. The SiC substrate W can be obtained by slicing an ingot of a SiC single crystal into a disc shape with a wire saw or the like. Further, the outer peripheral portion may be chamfered. At this time, a conventionally known method can be adopted without particular limitation as to the method for growing the SiC bulk single crystal, the method for grinding the ingot, the method for slicing, and the like.

Then, the obtained SiC substrate W is polished. As a polishing method, a conventionally known method can be adopted. It is preferable to perform rough polishing and mirror polishing, respectively. The rough polishing can be performed, for example, by using a mechanical polishing method such as lapping. By the rough polishing, it is possible to remove irregularities such as large waviness and processing strain in the SiC substrate W. The mirror polishing can be performed by, for example, the CMP method. In mirror polishing, it is possible to further improve the flatness of the SiC substrate whose roughness and parallelism are adjusted by rough polishing.

Then, a SiC epitaxial film is grown on the obtained SiC substrate W.
First, the SiC substrate W is placed on the satellite 20 of the above-described SiC epitaxial wafer manufacturing apparatus 100.

After the SiC substrate W is placed, the reaction space K is evacuated by a vacuum pump (not shown), and then a gas such as hydrogen or argon is flown from the first gas supply pipe 30 to bring it into a constant depressurized state. Further, the reaction space K is heated by the heater 70. Further, the rotary shaft 12 is rotationally driven by a drive motor (not shown), and the satellite 20 is rotated. The rotation of the satellite 20 is preferably performed by the gas supplied from the second gas supply pipe 40. By using the gas supplied from the second gas supply pipe 40, complication of the device can be avoided. The satellite 20 revolves around the rotating shaft 12.

In this state, the source gas G is further supplied from the first gas supply pipe 30. The raw material gas G supplied to the reaction space K spreads from the center of the mounting plate 10 toward the outer periphery and is discharged to the outside through the space between the mounting plate 10 and the side wall 60. At this time, in the SiC substrate W placed on the satellite 20, the silane-based gas and the hydrocarbon-based gas in the source gas react with each other to grow a SiC epitaxial film. Further, by mixing the dopant gas with the source gas, it is possible to grow a SiC epitaxial film containing a dopant element that contributes as a dopant of the semiconductor.

The gas supplied from the second gas supply pipe 40 is supplied to the reaction space K through the space between the concave housing portion 11 and the satellite 20. Therefore, considering the SiC substrate W as a reference, the gas supplied from the second gas supply pipe 40 is supplied from the outer circumference toward the center. Therefore, by including the dopant gas in the gas supplied from the second gas supply pipe 40, it is possible to increase the carrier concentration in the outer peripheral portion with respect to the central portion of the SiC epitaxial film that is epitaxially grown.

The carrier concentration on the outer periphery of the SiC substrate W may be lowered only by adding the dopant element functioning as the SiC dopant to the source gas G supplied from the first gas supply pipe 30. In such a case, the carrier gas flow rate and pressure are adjusted to adjust the carrier concentration distribution in the SiC epitaxial surface, but there is a limit when the SiC substrate has a large diameter. Further, the basic conditions such as the flow rate and pressure of the carrier gas affect characteristics other than the carrier concentration distribution, for example, characteristics such as the grown film thickness distribution, and therefore cannot be arbitrarily changed. On the other hand, in the method of supplying the dopant element as the dopant gas from the second gas supply pipe 40, the carrier concentration on the outer periphery of the SiC substrate W is adjusted without affecting the basic conditions such as the flow rate and pressure of the carrier gas of the source gas. Can be increased. Therefore, it is possible to obtain a SiC epitaxial wafer having other characteristics and a uniform carrier concentration. Regarding the in-plane distribution of the carrier concentration, the dopant element supplied from the second gas supply pipe 40 relatively increases only the carrier concentration on the outer periphery of the SiC epitaxial wafer and is uniformly doped near the center. It has almost no effect on the shape of the carrier concentration distribution near the center.

The total amount of gas supplied from the second gas supply pipe 40 to the total amount of gas supplied from the first gas supply pipe 30 is preferably 1/300 to 1/50. By making the total amount of gas supplied from the second gas supply pipe 40 smaller than the total amount of gas supplied from the first gas supply pipe, the flow of gas in the chamber is made central in the mounting plate 10. The control can be performed so that the direction from the to the outer circumference is the main direction, and the occurrence of turbulent flow can be suppressed.

The ratio of the flow rate of the dopant gas contained in the dopant carrier gas supplied from the second gas supply pipe 40 to the flow rate of the dopant gas contained in the gas supplied from the first gas supply pipe 30 is 100:1 to 0:1. Is preferred, 50:1 to 10:1 is more preferred, and 40:1 to 30:1 is more preferred. That is, the dopant gas may be entirely supplied from the second gas supply pipe. Within this range, the carrier concentration on the outer periphery of the SiC substrate W lowered by the dopant carrier gas supplied from the first gas supply pipe 30 is preferably adjusted by the dopant carrier gas supplied from the second gas supply pipe 40. Can be compensated. That is, it is possible to further improve the uniformity of carrier concentration of the SiC epitaxial wafer.

Further, the dopant gas contained in the dopant carrier gas supplied from the second gas supply pipe 40 is taken into the epitaxial wafer more efficiently than the dopant gas supplied from the first gas supply pipe 30, so that the same carrier concentration is obtained. The absolute amount of dopant introduced into the reaction space to obtain it can be reduced. This feature can reduce the memory effect due to the dopant gas. Therefore, it is more effective than the conventional method when, for example, an epitaxial layer having a high carrier concentration and a low carrier concentration are successively laminated.
The dopant carrier gas supplied from the second gas supply pipe is uniformly supplied to the wafer in all directions from the vicinity of the peripheral portion of the wafer. As a result, the dopant gas can be reliably and uniformly supplied to the outer peripheral portion of the wafer in the circumferential direction.

The mixing of the dopant gas in the gas supplied from the second gas supply pipe 40 is preferably performed at the same time as or after the supply of the raw material gas G from the first gas supply pipe 30. At the stage of supplying the raw material gas G from the first gas supply pipe 30, the satellite 20 is preferably rotating on its axis. On the other hand, it is preferable that the dopant gas is not supplied onto the SiC substrate W before the source gas G is supplied onto the SiC substrate W. This is because the SiC substrate W itself is made of a single crystal of SiC and reacts with the dopant gas.

Therefore, until the source gas G is supplied onto the SiC substrate W, the gas supplied from the second gas supply pipe 40 supplies a carrier gas (for example, a rare gas or the like) that does not contribute to the reaction, and the source gas G becomes SiC. Simultaneously with or after being supplied onto the substrate W, it is preferable that the gas supplied from the second gas supply pipe 40 contains a dopant gas to serve as a dopant carrier gas. In this way, by setting the timing of mixing the dopant gas in the gas supplied from the second gas supply pipe 40 at the same time as or after the supply of the source gas G from the first gas supply pipe 30, a more carrier concentration can be obtained. The controllability of can be improved.
When a plurality of epitaxial layers are further stacked, a growth stage in which the gas supplied from the second gas supply pipe 40 is a carrier gas containing no dopant gas and a dopant containing the dopant gas are provided for each epitaxial layer. Epitaxial growth in which growth stages using carrier gas are alternately mixed may be used.
The above description has been made on the rotation-revolution epitaxial growth apparatus, but it is limited to the rotation-revolution epitaxial growth apparatus, including the configuration in which the dopant carrier gas containing the dopant gas is supplied to the outer periphery of the SiC epitaxial wafer from between the concave accommodation portion and the satellite. It is not something that will be done. For example, it may be a device in which the wafer rotates only, or a device in which the wafer only revolves and the satellite is only levitated.

According to the method for manufacturing the SiC epitaxial wafer according to the aspect of the present invention, the controllability of the carrier concentration in the in-plane direction of the SiC epitaxial film grown on the SiC substrate can be enhanced.

Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications are possible within the scope of the gist of the present invention described in the claims. Can be modified and changed.

Hereinafter, the effects of the present invention will be specifically described using examples. The present invention is not limited to these examples.

[Example 1]
In Example 1, first, a SiC substrate (6 inch, 4H-SiC-4° off substrate) was prepared. Further, as a SiC epitaxial film manufacturing apparatus, six satellites were installed on a mounting plate having six recessed accommodating portions. Then, an SiC epitaxial film was grown to 8 to 10.5 μm while revolving the SiC wafer placed on the satellite. From the first gas supply pipe, silane and propane were supplied as raw material gases and hydrogen was supplied as a carrier gas. Further, a dopant carrier gas containing nitrogen as a dopant gas and mainly containing hydrogen was supplied from the second gas supply pipe. The ratio (B/A) of the total flow rate A of the gas supplied from the first gas supply pipe to the total flow rate B of the gas supplied from the second gas supply pipe was 0.0076 times.
The dopant gas is the amount C of nitrogen gas supplied from the first gas supply pipe, and the ratio (D/C) of the amount D of nitrogen gas supplied from the second gas supply pipe, that is, each gas. The ratio of the flow rate of nitrogen supplied from the second gas supply pipe to the flow rate of gas supplied from the supply pipe and the dopant gas flowed from the first gas supply pipe was 0.056. The film forming temperature was 1600°C.

[Example 2]
The second embodiment differs from the first embodiment only in that the total flow rate of the gas supplied from the second gas supply pipe is changed. The flow rate of nitrogen supplied from the second gas supply pipe to the flow rate of the dopant gas supplied from the first gas supply pipe was 0.028 times.

[Comparative Example 1]
Comparative Example 1 is different from Example 1 in that the dopant gas was allowed to flow only from the first gas supply pipe and the second gas supply pipe did not contain the dopant gas. Other conditions were the same as in Example 1.

FIG. 4 is a graph showing changes in carrier concentration in the in-plane direction of the SiC epitaxial films obtained in Example 1 and Comparative Example 1. The horizontal axis of the figure shows the measured value of the in-plane carrier concentration with one horizontal direction as the horizontal axis. For the measurement of the carrier concentration variation in the plane, a total of 21 points were measured at this position and the same position orthogonal thereto. The in-plane variation of carrier concentration is shown by the average value of measurement points (max-min/21 points). The in-plane variation in carrier concentration of Example 1 was 22%. The in-plane variation of Example 2 was 13%. The in-plane variation of the comparative example was 32%. In each of Examples 1 and 2, the in-plane variation in carrier concentration is improved as compared with Comparative Example 1.

As shown in FIG. 4, it can be seen that the carrier concentration in the outer peripheral portion of the SiC epitaxial films of Examples 1 and 2 is higher than the carrier concentration in the outer peripheral portion of the SiC epitaxial film of Comparative Example 1. That is, it can be seen that the carrier concentration in the outer peripheral portion of the SiC wafer is increased by the dopant carrier gas supplied from the second gas supply pipe. Further, as a result, it can be seen that the carrier concentration in the in-plane direction of the SiC wafer is homogenized.

FIG. 5 shows the difference in carrier concentration between Example 1 and Example 2 and Comparative Example 1 calculated from FIG. As shown in FIG. 5, in the method of performing doping by supplying the dopant carrier gas containing the dopant gas to the outer periphery of the SiC epitaxial wafer from between the recessed accommodating portion and the satellite, it is possible to concentrate the carrier concentration in the peripheral portion. it can. This can effectively solve the problem that the carrier concentration tends to be low in the peripheral portion of the wafer when performing epitaxial growth on a large-diameter wafer of 6 inches or more.

Further, in FIG. 5, the carrier concentration within a radius of 50 mm is extremely uniform. In this case, since a wafer having a radius of 75 mm (diameter of 6 inches) is used, it is shown that very uniform doping can be performed by using this method except for the periphery of 25 mm. From this, when a satellite having a diameter larger than that of the wafer is used, the doping gas is supplied only from between the concave accommodation portion and the satellite, or the doping gas is not supplied from between the concave accommodation portion and the satellite. By supplying so that the supply is the main, doping with a uniform in-plane distribution can be performed efficiently. At that time, by disposing a single crystal or polycrystal of SiC or a sintered body on the susceptor surface on the outer periphery of the wafer, the same growth situation as when a large wafer is placed can be achieved, which is preferable.

Since the SiC epitaxial wafer manufacturing apparatus of the present invention can manufacture a SiC epitaxial wafer having excellent electric characteristics with a simple apparatus with high productivity, for example, a SiC epitaxial wafer used for a power device, a high frequency device, a high temperature operation device, or the like. Can be manufactured.

DESCRIPTION OF SYMBOLS 10... Mounting plate, 11... Recessed accommodating part, 11a... Upper surface, 12... Rotating shaft, 13... Rotating table, 13a... Rotating table upper surface, 14... Groove, 20... Satellite, 20a... Upper surface, 20b... Lower surface, 21... Recessed portion , 30... First gas supply pipe, 40... Second gas supply pipe, 41... Supply port, 50... Ceiling, 60... Side wall, 61... Support part, 70... Heater, 100... SiC epitaxial wafer manufacturing apparatus, G... Raw material gas, K... Reaction space, W... SiC wafer

Claims (2)

A mounting plate having a concave accommodating portion, a satellite arranged in the concave accommodating portion and having a SiC substrate mounted on the upper surface thereof, and a raw material gas for a SiC epitaxial film formed on a main surface of the SiC substrate mounted on the satellite. A SiC epitaxial wafer manufacturing apparatus including a first gas supply pipe for supplying a first gas supply pipe and a second gas supply pipe for supplying a dopant carrier gas containing a dopant gas, the second gas supply pipe having a supply port in the concave accommodating portion. A method of manufacturing an epitaxial wafer, comprising:
A raw material gas is supplied to the satellite from the first gas supply pipe in a direction from the center of the mounting plate toward the outer periphery,
Using the second gas supply pipe, a dopant carrier gas containing a dopant gas is supplied to the outer periphery of the SiC epitaxial wafer from between the concave accommodation portion and the satellite,
The method for manufacturing an SiC epitaxial wafer, wherein the total amount of gas supplied from the second gas supply pipe to the total amount of gas supplied from the first gas supply pipe is 1/300 to 1/50. A mounting plate having a concave accommodating portion, a satellite arranged in the concave accommodating portion and having a SiC substrate mounted on the upper surface thereof, and a raw material gas for a SiC epitaxial film formed on a main surface of the SiC substrate mounted on the satellite. A SiC epitaxial wafer manufacturing apparatus including a first gas supply pipe for supplying a first gas supply pipe and a second gas supply pipe for supplying a dopant carrier gas containing a dopant gas, the second gas supply pipe having a supply port in the concave accommodating portion. A method of manufacturing an epitaxial wafer, comprising:
A raw material gas is supplied to the satellite from the first gas supply pipe in a direction from the center of the mounting plate toward the outer periphery,
A SiC substrate is placed on the satellite, and a single crystal, a polycrystal, or a sintered body of SiC is placed on the outer surface of the SiC substrate on the surface of the mounting plate.
A method of manufacturing a SiC epitaxial wafer, which uses the second gas supply pipe to supply a dopant carrier gas containing a dopant gas to the outer periphery of the SiC epitaxial wafer from between the concave accommodation portion and the satellite.

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