# Patent

## Title
Vapor phase growth apparatus

## Abstract

A vapor phase growth apparatus has a plurality of rotation susceptors to hold the semiconductor wafer, and a disk-like revolution susceptor on which the plurality of rotation susceptors are rotatably mounted through a bearing. The plurality of rotation susceptors each are, on its periphery, provided with a pinion gear that meshes with a common gear that allows each of the plurality of rotation susceptors to rotate on its center axis. The outermost end of rotation susceptor is substantially aligned with the outermost end of revolution susceptor and the pinion gear is located directly above the bearing.

## Background
The present application is based on Japanese patent application No. 2004-297504, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a vapor phase growth apparatus that a source gas is flown onto a semiconductor wafer held by a susceptor so as to grow a semiconductor crystal thin film (epitaxial layer) on the surface of the semiconductor wafer, and particularly to a planetarium type vapor phase growth apparatus that the susceptor rotates on its axis and revolves around an axis (in a certain orbit).
2. Description of the Related Art
A vapor phase growth method is one of methods for growing a semiconductor crystal. In the vapor phase growth method, a source gas is flown onto the surface of a heated semiconductor wafer, and thereby a semiconductor crystal thin film is grown on the surface of the semiconductor wafer. This method is characterized by that an ultra-thin film as thin as several nanometers can be grown since it uses gas as a raw material. Further, the method has a good mass productivity since it uses high-purity organic metal/hydride/carrier gas and it needs no ultrahigh vacuum required of the molecular beam epitaxy.
One of vapor phase growth apparatuses used for the vapor phase growth method is a planetarium type vapor phase growth apparatus that the susceptor rotates on its axis and revolves around an axis (in a certain orbit). The planetarium type vapor phase growth apparatus is characterized by that it has a good uniformity in the thickness of grown film.
FIG. 1 is a schematic cross sectional view showing a conventional planetarium type vapor phase growth apparatus 101.
The vapor phase growth apparatus 101 is structured such that a source gas 103 is introduced into the apparatus from the bottom through a source gas inlet 102 that opens downward. The source gas 103 is thermally decomposed in the apparatus. An exhaust gas 104 thermally decomposed is, in the horizontal direction, discharged radially from the center of the apparatus through a plurality of (e.g., six) gas exhausts 105 which are provided on the sidewall of the apparatus.
In the apparatus, there are provided rotation susceptors 107 to hold a semiconductor wafer 106, a revolution susceptor 108 (for moving the rotation susceptors 107 in orbit motion) and a heater 109 to heat the semiconductor wafer 106. The revolution susceptor 108 is connected to a shaft 111 of a motor 110 at the center thereof such that it is rotated by the driving force of the motor 110. The semiconductor wafer 106, which has a front surface and a back surface, is held by the rotation susceptor 107 while keeping the front surface downward. The rotation susceptor 107 is rotatably mounted on the revolution susceptor 108 through bearings 112.
FIG. 2 is an enlarged cross sectional view showing circled part C in FIG. 1.
The rotation susceptor 107 and the revolution susceptor 108 each are provided with a groove for placing the bearing 112 therein on the opposed surfaces. The bearing 112 is placed between the grooves. The rotation susceptor 107, which is rotatably mounted on the revolution susceptor 108 through the bearing 112, is integrally provided with a pinion gear 113 that protrudes sideward from the position of the bearing 112 and the groove for placing the bearing 112 therein. On the other hand, corresponding to the pinion gear 113, an internal gear 114 is provided on the inner wall of the vapor phase growth apparatus 101 such that the pinion gear 113 meshes with the internal gear 114. 115 is a gear mesh portion where the pinion gear 113 meshes with the internal gear 114. FIG. 4 shows the enlarged gear mesh portion 115 in top view.
FIG. 3 is a top view showing the positional relationship among the internal gear 114 on the inner wall of the vapor phase growth apparatus 101, the rotation susceptor 107 and the revolution susceptor 108. Meanwhile, since FIG. 1 is illustrated schematically, the dimensions of parts in FIG. 1 are not always identical with those in FIG. 3.
As shown in FIG. 3, the vapor phase growth apparatus 101 is provided with the twelve rotation susceptors 107 which are annually disposed on the periphery of revolution susceptor 108 which is formed like a large disk. The rotation susceptors 107 each are provided with six claws 116 by which the semiconductor 106 is held.
In operation, when the revolution susceptor 108 is rotated by the motor 110, the rotation susceptors 107 are also rotated around the center axis of the revolution susceptor 108. Simultaneously, since each of the rotation susceptors 107 also meshes with the internal gear 114, it rotates on its center axis. Thus, the semiconductor wafer 106 being held by the rotation susceptor 107 is allowed to rotate on its center axis while rotating around the center axis of the revolution susceptor 108. In this state, the source gas 103 is introduced through the source gas inlet 102 as shown in FIG. 1, and then it is thermally decomposed on the surface of the semiconductor wafer 106 being heated by the heater 109 such that a semiconductor crystal thin film is grown on the surface of the semiconductor wafer 106. Thus, since the semiconductor wafer 106 rotates on its center axis while rotating around the center axis of the revolution susceptor 108, the high uniformity semiconductor crystal thin film can be grown on the surface of the semiconductor wafer 106.
Japanese patent application laid-open No. 10-219447 discloses an example of the conventional planetarium type vapor phase growth apparatus, though this apparatus is not directly relevant to this invention.
The conventional planetarium type vapor phase growth apparatus as shown in FIGS. 1 to 4 has a problem as mentioned below.
The conventional vapor phase growth apparatus 101 is structured such that the pinion gear 113 integrated with the rotation susceptor 107 to hold the semiconductor wafer 106 is located laterally from the position of the bearing 112 and the groove for placing the bearing 112 therein. Therefore, the diameter of the rotation susceptor 107 is unnecessarily larger than that of the semiconductor wafer 106. Referring to FIG. 3, provided that the semiconductor wafer 106 with a diameter of 76 mm is held by the rotation susceptor 107, the number of the rotation susceptors 107 allocable on the periphery of the revolution susceptor 108 is limited to twelve in view of the positional relationship with the internal gear 114. However, if the number of the rotation susceptors 107 allocable on the revolution susceptor 108 increases, the number of semiconductor wafers, with a semiconductor crystal thin film formed thereon, fabricable by the one vapor phase growth apparatus 101 in one manufacture process increases. Thus, it is desired to increase the number of the rotation susceptors allocable on the periphery of the revolution susceptor to improve the productivity of the vapor phase growth apparatus.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a vapor phase growth apparatus that the number of the rotation susceptors allocable on the periphery of the revolution susceptor is increased to enhance the productivity.
(1) According to one aspect of the invention, a vapor phase growth apparatus comprises:
a source gas inlet;
a heater to heat a semiconductor wafer;
a gas exhaust;
a plurality of rotation susceptors to hold the semiconductor wafer;
a disk-like revolution susceptor on which the plurality of rotation susceptors are rotatably mounted through a bearing;
wherein the plurality of rotation susceptors are annually disposed on the periphery of the revolution susceptor,
the plurality of rotation susceptors each are, on its periphery, provided with a pinion gear that meshes with a common internal gear that is located outside of the revolution susceptor, and
the pinion gear provided on the plurality of rotation susceptors is located directly above the bearing.
(2) According to another aspect of the invention, a vapor phase growth apparatus comprises:
a source gas inlet;
a heater to heat a semiconductor wafer;
a gas exhaust;
a plurality of rotation susceptors to hold the semiconductor wafer;
a disk-like revolution susceptor on which the plurality of rotation susceptors are rotatably mounted through a bearing;
wherein the plurality of rotation susceptors are annually disposed on the periphery of the revolution susceptor,
the plurality of rotation susceptors each are, on its periphery, provided with a pinion gear that meshes with a common external gear that is located inside of the revolution susceptor, and
the pinion gear provided on the plurality of rotation susceptors is located directly above the bearing.
It is preferred that the plurality of rotation susceptors each comprise an outermost end that is substantially aligned with an outermost end of the revolution susceptor.
Further, it is preferred that the source gas inlet opens downward such that a source gas is introduced from the bottom of the apparatus toward the center of the revolution susceptor, and a plurality of the gas exhausts are disposed on the side of the apparatus such that an exhaust gas is discharged laterally and radially from the center of the revolution susceptor through the gas exhausts.
Further, it is preferred that the plurality of rotation susceptors are allowed to hold the semiconductor wafer while keeping a front surface of the semiconductor wafer downward.
(3) According to another aspect of the invention, a vapor phase growth apparatus comprises:
a source gas inlet;
a heater to heat a semiconductor wafer;
a gas exhaust;
a plurality of rotation susceptors to hold the semiconductor wafer;
a disk-like revolution susceptor on which the plurality of rotation susceptors are rotatably mounted through a bearing;
wherein the plurality of rotation susceptors are annually disposed on the periphery of the revolution susceptor,
the plurality of rotation susceptors each are, on its periphery, provided with a pinion gear that meshes with a common gear that allows each of the plurality of rotation susceptors to rotate on its center axis, and
the plurality of rotation susceptors each comprise an outermost end that is substantially aligned with an outermost end of the revolution susceptor.
It is preferred that the pinion gear provided on the plurality of rotation susceptors is located directly above the bearing.
Advantages of the Invention
In the invention, the vapor phase growth apparatus is composed such that the pinion gear provided on the rotation susceptor, which is rotatably mounted through the bearing on the revolution susceptor, is located directly above the bearing instead of protruding laterally and outward from the periphery of the rotation susceptor. Therefore, the diameter of the rotation susceptor can be reduced by that much. Thereby, the number of the rotation susceptors mounted on the revolution susceptor can be increased. As a result, the number of semiconductor wafers with a semiconductor crystal thin film grown thereon fabricable in one manufacture process can be increased. Hence, the productivity of the vapor phase growth apparatus can be significantly enhanced.



BRIEF DESCRIPTION OF THE DRAWINGS
The preferred embodiments according to the invention will be explained below referring to the drawings, wherein:
FIG. 1 is a schematic cross sectional view showing the conventional planetarium type vapor phase growth apparatus;
FIG. 2 is an enlarged cross sectional view showing circled part C in FIG. 1;
FIG. 3 is a top view showing the positional relationship among a revolution susceptor, a rotation susceptor and an internal gear in FIG. 1;
FIG. 4 is an enlarged top view showing circled part D in FIG. 3;
FIG. 5 is a schematic cross sectional view showing a vapor phase growth apparatus in a first preferred embodiment according to the invention;
FIG. 6 is an enlarged cross sectional view showing circled part A in FIG. 5;
FIG. 7 is a top view showing the positional relationship among a revolution susceptor, a rotation susceptor and an internal gear in FIG. 5;
FIG. 8 is an enlarged top view showing circled part B in FIG. 7;
FIG. 9 is a schematic cross sectional view showing a vapor phase growth apparatus in a second preferred embodiment according to the invention; and
FIG. 10 is a schematic cross sectional view showing a vapor phase growth apparatus in a third preferred embodiment according to the invention.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
First Embodiment
FIG. 5 is a schematic cross sectional view showing a vapor phase growth apparatus 1 in the first preferred embodiment according to the invention.
The vapor phase growth apparatus 1 is at its bottom provided with a source gas inlet 2 through which that a source gas 3 is introduced into the apparatus from the bottom toward the center of a disk-like revolution susceptor 8. Also, it is on its sidewall provided with a plurality of gas exhausts 5 through which an exhaust gas 4 is discharged laterally and radially from the center of the disk-like revolution susceptor 8.
Fourteen semiconductor wafers 6 with a diameter of 76 mm are held by the rotation susceptor 7 while keeping its front surface downward on the same surface as the revolution susceptor 8. The semiconductor wafer 6 on the rotation susceptor 7 is heated by a heater 9, and the source gas is thermally decomposed on the surface of the heated semiconductor wafer 6 to allow the crystal growth thereon.
The rotation susceptor 7 is rotatably mounted through bearings 12 on the revolution susceptor 8. The rotation susceptor 7 is provided with a pinion gear 13 integrally formed on the periphery thereof. A common internal gear 14 which is placed outside the pinion gear 13 is integrally formed on the inner wall of the vapor phase growth apparatus 1. The pinion gear 13 meshes with the internal gear 14 as shown in FIG. 8.
The revolution susceptor 8 is connected to a shaft 11 of a motor 10 at its center such that it is rotated by the driving force of the motor 10. As mentioned above, since the pinion gear 13 of the susceptor 7 meshes with the internal gear 14, when the revolution susceptor 8 is rotated by the motor 10, the rotation susceptor 7 rotates on its center axis and rotates around the center axis of the revolution susceptor 8.
In this embodiment, the pinion gear 13, which is integrally formed on the periphery of the rotation susceptor 7, is made to be located directly above the bearing 12 as shown in FIG. 6 instead of protruding laterally and outward from the periphery of the rotation susceptor 7. Thus, by changing the formation position of the pinion gear 13, the size (diameter) of the rotation susceptor 7 can be one size smaller than that in the conventional apparatus as shown in FIG. 3. As a result, although the twelve semiconductor wafers of 76 mm diameter are placed on the periphery of the revolution susceptor in the conventional apparatus as shown in FIG. 3, in this embodiment the fourteen semiconductor wafers can be placed thereon. In this case, due to the increase of semiconductor wafers, the productivity of the semiconductor wafer can be enhanced about 17%. Meanwhile, although the conventional rotation susceptor as shown in FIG. 3 has a diameter of 111 mm, the rotation susceptor 3 of this embodiment as shown in FIG. 7 has a diameter of 99 mm. Such an effect obtained by the reduction of diameter in the rotation susceptor can be enhanced as the diameter of the revolution susceptor increases.
Second Embodiment
FIG. 9 is a schematic cross sectional view showing a vapor phase growth apparatus in the second preferred embodiment according to the invention. In FIG. 9, like components are indicated by the same numerals as used in FIG. 5.
Although the vapor phase growth apparatus 1 in FIG. 5 is the shaft 11 of the motor 10 is connected to the center of the revolution susceptor 8 so as to rotate the revolution susceptor 8, in the second embodiment a revolution susceptor 80 is provided with an external gear 18 on its periphery. The external gear 18 meshes with a drive gear 17 that is connected to the shaft of a motor 100, and the revolution susceptor is rotated by the driving force of the motor 100.
Also in the second embodiment, the pinion gear 13, which is integrally formed on the periphery of the rotation susceptor 7, is made to be located directly above the bearing 12 as shown in FIG. 6 instead of protruding laterally and outward from the periphery of the rotation susceptor 7.
Therefore, the same effect as obtained in the first embodiment can be obtained in the second embodiment.
Third Embodiment
FIG. 10 is a schematic cross sectional view showing a vapor phase growth apparatus in the third preferred embodiment according to the invention. In FIG. 10, like components are indicated by the same numerals as used in FIG. 5 and FIG. 9.
In the third embodiment, the vapor phase growth apparatus 1 is provided with an external gear 180, which is connected to the shaft of a motor 200, to mesh with the pinion 13 of the rotation susceptor, while the internal gear 14 integrally formed on the inner wall of the apparatus 1 is removed.
In operation, the revolution susceptor 80 is rotated by the driving force of the motor 100 since the external gear 18 of the revolution susceptor 80 meshes with the drive gear 17 of the motor 100. The rotation susceptor 7 is rotated by the driving force of the motor 200 since the pinion gear 13 of the rotation susceptor 7 meshes with the external gear 180 of the motor 200.
Also in the third embodiment, the pinion gear 13, which is integrally formed on the periphery of the rotation susceptor 7, is made to be located directly above the bearing 12 as shown in FIG. 6 instead of protruding laterally and outward from the periphery of the rotation susceptor 7.
Therefore, the same effect as obtained in the first embodiment can be obtained in the third embodiment.
Although the invention has been described with respect to the specific embodiments for complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art which fairly fall within the basic teaching herein set forth.

## Claims

1. A vapor phase growth apparatus, comprising:
a plurality of rotation susceptors to hold a semiconductor wafer;
a disk-like revolution susceptor on which the plurality of rotation susceptors are rotatably mounted through a bearing; and
a common gear located at the periphery of the revolution susceptor, the common gear comprising:
a main body portion; and
a projected portion located at an upper part of said common gear, an outermost end of said projected portion of said common gear being projected from said main body portion of said common gear,

wherein the plurality of rotation susceptors are annularly disposed on the periphery of the revolution susceptor,
wherein a periphery of the plurality of rotation susceptors comprises:
a pinion gear, said pinion gear comprising a projected portion disposed at an upper portion of said periphery of the plurality of rotation susceptors; and
a bearing holding portion of the plurality of rotation susceptors, said bearing holding portion aligned with an outermost end of said projected portion of said pinion gear, said bearing holding portion meshing with said outermost end of the projected portion of said common gear at a position directly above the bearing at said projected portion of said pinion gear to form a gear mesh portion,

wherein said main body portion of said common gear is formed outside said pinion gear, and
wherein said outermost end of said projected portion of said pinion gear located at said upper portion of said periphery of the plurality of rotation susceptors is substantially aligned with said outermost end of said projected portion of said common gear located at the periphery of the revolution susceptor.

2. vapor phase growth apparatus according to claim 1, wherein:
the common gear is located outside of the revolution susceptor.

3. The vapor phase growth apparatus according to claim 2, further comprising:
a source gas inlet supplying a source gas, said source gas inlet provided such that a said source gas is introduced from a bottom of the apparatus toward a center of the revolution susceptor, and
a gas exhaust that exhausts an exhaust gas, said gas exhaust disposed on a side of the apparatus such that said exhaust gas is discharged laterally and radially from the center of the revolution susceptor through the gas exhaust.

4. The vapor phase growth apparatus according to claim 3, wherein:
the plurality of rotation susceptors are allowed to hold the semiconductor wafer while keeping a front surface of the semiconductor wafer downward.

5. The vapor phase growth apparatus according to claim 1, wherein:
the common gear is located inside of the revolution susceptor.

6. The vapor phase growth apparatus according to claim 5, further comprising:
a source gas inlet supplying a source gas, said source gas inlet provided such that a said source gas is introduced from a bottom of the apparatus toward a center of the revolution susceptor, and
a gas exhaust that exhausts an exhaust gas, said gas exhausts disposed on a side of the apparatus such that said exhaust gas is discharged laterally and radially from the center of the revolution susceptor through the gas exhaust.

7. The vapor phase growth apparatus according to claim 6, wherein:
the plurality of rotation susceptors are allowed to hold the semiconductor wafer while keeping a front surface of the semiconductor wafer downward.

8. The vapor phase growth apparatus according to claim 1, wherein:
the common gear allows the plurality of rotation susceptors to rotate on its center axis, and
the plurality of rotation susceptors comprise an outermost end that is substantially aligned with an outermost end of the revolution susceptor.

9. The vapor phase growth apparatus according to claim 1, wherein the periphery of the plurality of rotation susceptors integrally comprises said pinion gear.

10. The vapor phase growth apparatus according to claim 1, wherein an uppermost end of said projected portion of said pinion gear is located lower than an uppermost end of said periphery of said plurality of rotation susceptors.