Vapor phase growth apparatus

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.

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. 1is a schematic cross sectional view showing a conventional planetarium type vapor phase growth apparatus101.

The vapor phase growth apparatus101is structured such that a source gas103is introduced into the apparatus from the bottom through a source gas inlet102that opens downward. The source gas103is thermally decomposed in the apparatus. An exhaust gas104thermally decomposed is, in the horizontal direction, discharged radially from the center of the apparatus through a plurality of (e.g., six) gas exhausts105which are provided on the sidewall of the apparatus.

In the apparatus, there are provided rotation susceptors107to hold a semiconductor wafer106, a revolution susceptor108(for moving the rotation susceptors107in orbit motion) and a heater109to heat the semiconductor wafer106. The revolution susceptor108is connected to a shaft111of a motor110at the center thereof such that it is rotated by the driving force of the motor110. The semiconductor wafer106, which has a front surface and a back surface, is held by the rotation susceptor107while keeping the front surface downward. The rotation susceptor107is rotatably mounted on the revolution susceptor108through bearings112.

FIG. 2is an enlarged cross sectional view showing circled part C inFIG. 1.

The rotation susceptor107and the revolution susceptor108each are provided with a groove for placing the bearing112therein on the opposed surfaces. The bearing112is placed between the grooves. The rotation susceptor107, which is rotatably mounted on the revolution susceptor108through the bearing112, is integrally provided with a pinion gear113that protrudes sideward from the position of the bearing112and the groove for placing the bearing112therein. On the other hand, corresponding to the pinion gear113, an internal gear114is provided on the inner wall of the vapor phase growth apparatus101such that the pinion gear113meshes with the internal gear114.115is a gear mesh portion where the pinion gear113meshes with the internal gear114.FIG. 4shows the enlarged gear mesh portion115in top view.

FIG. 3is a top view showing the positional relationship among the internal gear114on the inner wall of the vapor phase growth apparatus101, the rotation susceptor107and the revolution susceptor108. Meanwhile, sinceFIG. 1is illustrated schematically, the dimensions of parts inFIG. 1are not always identical with those inFIG. 3.

As shown inFIG. 3, the vapor phase growth apparatus101is provided with the twelve rotation susceptors107which are annually disposed on the periphery of revolution susceptor108which is formed like a large disk. The rotation susceptors107each are provided with six claws116by which the semiconductor106is held.

In operation, when the revolution susceptor108is rotated by the motor110, the rotation susceptors107are also rotated around the center axis of the revolution susceptor108. Simultaneously, since each of the rotation susceptors107also meshes with the internal gear114, it rotates on its center axis. Thus, the semiconductor wafer106being held by the rotation susceptor107is allowed to rotate on its center axis while rotating around the center axis of the revolution susceptor108. In this state, the source gas103is introduced through the source gas inlet102as shown inFIG. 1, and then it is thermally decomposed on the surface of the semiconductor wafer106being heated by the heater109such that a semiconductor crystal thin film is grown on the surface of the semiconductor wafer106. Thus, since the semiconductor wafer106rotates on its center axis while rotating around the center axis of the revolution susceptor108, the high uniformity semiconductor crystal thin film can be grown on the surface of the semiconductor wafer106.

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 inFIGS. 1 to 4has a problem as mentioned below.

The conventional vapor phase growth apparatus101is structured such that the pinion gear113integrated with the rotation susceptor107to hold the semiconductor wafer106is located laterally from the position of the bearing112and the groove for placing the bearing112therein. Therefore, the diameter of the rotation susceptor107is unnecessarily larger than that of the semiconductor wafer106. Referring toFIG. 3, provided that the semiconductor wafer106with a diameter of 76 mm is held by the rotation susceptor107, the number of the rotation susceptors107allocable on the periphery of the revolution susceptor108is limited to twelve in view of the positional relationship with the internal gear114. However, if the number of the rotation susceptors107allocable on the revolution susceptor108increases, the number of semiconductor wafers, with a semiconductor crystal thin film formed thereon, fabricable by the one vapor phase growth apparatus101in 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.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

FIG. 5is a schematic cross sectional view showing a vapor phase growth apparatus1in the first preferred embodiment according to the invention.

The vapor phase growth apparatus1is at its bottom provided with a source gas inlet2through which that a source gas3is introduced into the apparatus from the bottom toward the center of a disk-like revolution susceptor8. Also, it is on its sidewall provided with a plurality of gas exhausts5through which an exhaust gas4is discharged laterally and radially from the center of the disk-like revolution susceptor8.

Fourteen semiconductor wafers6with a diameter of 76 mm are held by the rotation susceptor7while keeping its front surface downward on the same surface as the revolution susceptor8. The semiconductor wafer6on the rotation susceptor7is heated by a heater9, and the source gas is thermally decomposed on the surface of the heated semiconductor wafer6to allow the crystal growth thereon.

The rotation susceptor7is rotatably mounted through bearings12on the revolution susceptor8. The rotation susceptor7is provided with a pinion gear13integrally formed on the periphery thereof. A common internal gear14which is placed outside the pinion gear13is integrally formed on the inner wall of the vapor phase growth apparatus1. The pinion gear13meshes with the internal gear14as shown inFIG. 8.

The revolution susceptor8is connected to a shaft11of a motor10at its center such that it is rotated by the driving force of the motor10. As mentioned above, since the pinion gear13of the susceptor7meshes with the internal gear14, when the revolution susceptor8is rotated by the motor10, the rotation susceptor7rotates on its center axis and rotates around the center axis of the revolution susceptor8.

In this embodiment, the pinion gear13, which is integrally formed on the periphery of the rotation susceptor7, is made to be located directly above the bearing12as shown inFIG. 6instead of protruding laterally and outward from the periphery of the rotation susceptor7. Thus, by changing the formation position of the pinion gear13, the size (diameter) of the rotation susceptor7can be one size smaller than that in the conventional apparatus as shown inFIG. 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 inFIG. 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 inFIG. 3has a diameter of 111 mm, the rotation susceptor3of this embodiment as shown inFIG. 7has 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. 9is a schematic cross sectional view showing a vapor phase growth apparatus in the second preferred embodiment according to the invention. InFIG. 9, like components are indicated by the same numerals as used inFIG. 5.

Although the vapor phase growth apparatus1inFIG. 5is the shaft11of the motor10is connected to the center of the revolution susceptor8so as to rotate the revolution susceptor8, in the second embodiment a revolution susceptor80is provided with an external gear18on its periphery. The external gear18meshes with a drive gear17that is connected to the shaft of a motor100, and the revolution susceptor is rotated by the driving force of the motor100.

Also in the second embodiment, the pinion gear13, which is integrally formed on the periphery of the rotation susceptor7, is made to be located directly above the bearing12as shown inFIG. 6instead of protruding laterally and outward from the periphery of the rotation susceptor7.

Therefore, the same effect as obtained in the first embodiment can be obtained in the second embodiment.

Third Embodiment

FIG. 10is a schematic cross sectional view showing a vapor phase growth apparatus in the third preferred embodiment according to the invention. InFIG. 10, like components are indicated by the same numerals as used inFIG. 5andFIG. 9.

In the third embodiment, the vapor phase growth apparatus1is provided with an external gear180, which is connected to the shaft of a motor200, to mesh with the pinion13of the rotation susceptor, while the internal gear14integrally formed on the inner wall of the apparatus1is removed.

In operation, the revolution susceptor80is rotated by the driving force of the motor100since the external gear18of the revolution susceptor80meshes with the drive gear17of the motor100. The rotation susceptor7is rotated by the driving force of the motor200since the pinion gear13of the rotation susceptor7meshes with the external gear180of the motor200.

Also in the third embodiment, the pinion gear13, which is integrally formed on the periphery of the rotation susceptor7, is made to be located directly above the bearing12as shown inFIG. 6instead of protruding laterally and outward from the periphery of the rotation susceptor7.

Therefore, the same effect as obtained in the first embodiment can be obtained in the third embodiment.