JPH02295112A - Vapor growth apparatus - Google Patents

Abstract

PURPOSE:To improve the utilization efficiency of raw material and obtain an epitaxial substrate having a uniform film thickness by a method wherein a susceptor provided in the reaction tube of a vapor growth apparatus has a specific shape. CONSTITUTION:Raw gas for vapor growth is introduced into a reaction tube 1 through a raw material introducing inlet 2. A multi-sided pyramid-shaped susceptor 3 supported by a rotary shaft 6 is provided in the reaction tube 1. The susceptor 3 is roughly composed of an upper commutating part 4 and a lower substrate holding part 5 and its rate of diameter increase is larger in the substrate holding part 5 than in the commutating part 4. The susceptor can be subjected to radio frequency heating or the like by an external RF coil 8. As the main flow of the introduced raw gas flows nearly in the form of streamline flow between the commutating part 4 of the susceptor 3 and the wall of the reaction tube 1, especially near the surface of the commutating part 4, the utilization efficiency of the raw material and the uniformity of the built-up film thickness can be improved.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a semiconductor thin film vapor phase growth apparatus, and in particular suppresses turbulence of raw material gas introduced from the introduction path of a reaction tube, improves raw material efficiency and improves growth on a substrate. The present invention relates to a vapor phase growth apparatus that can improve the uniformity of the film thickness distribution of a semiconductor thin film.

<Conventional technology> Conventionally, a raw material gas is introduced from the upper part of a reaction tube, and the gas is reacted or decomposed on a substrate held on a heated susceptor, thereby forming a group of 1-2 compounds such as silicon and gallium arsenide on the substrate. Various semiconductor thin film vapor phase growth apparatuses for vapor phase growth of semiconductor films such as compounds are known.

For example, a vapor phase growth apparatus as shown in FIG. 2 is used. That is, there is a feed gas introduction path 2 at the upper part of the reaction tube 1.
A so-called barrel-shaped susceptor 3 in the shape of a circle or polygonal pyramid whose diameter gradually increases facing the gas introduction path 2 is provided downstream thereof.
is supported and installed on a rotatable shaft 6. This susceptor 3 is roughly divided into an upper rectifying section 4 and a lower substrate holding section 5.
Thus, the substrate 7 is placed on the slope of the holding part 5. Further, the susceptor 3 is heated to a predetermined temperature by high frequency induction heating by a high frequency (RF) coil 8 provided outside the reaction tube 1. On the other hand, the raw material gas is introduced together with a carrier gas from the gas introduction path 2 provided at the upper part of the reaction tube, and a thermal decomposition reaction occurs near the surface of the heated susceptor, thereby growing a semiconductor thin film on the substrate 7-. The unreacted raw material gas is discharged from the exhaust port 9.

Problems to be Solved by the Invention> However, the present inventors have found that the diameter expansion ratio of the susceptor used in the conventional Halul type vapor phase growth apparatus is gradually decreasing, so that It was found that the main stream of gas flowing through the space is biased toward the space closer to the reaction tube due to inertial force, and most of the raw material is discharged from the exhaust port unreacted, resulting in a lower raw material usage efficiency. moreover,
Since the kinematic viscosity increases as the temperature increases, the spread of the flow is larger on the susceptor side and smaller on the reaction tube side, which aggravates the above-mentioned imbalance of the main stream, and the above-mentioned decline in the efficiency of raw material usage becomes even more significant. It has been found that upward flow along the susceptor surface in the space, in other words, natural convection in the space, tends to occur, making the grown film non-uniform and making it extremely difficult to obtain a steep profile at the interface.

SUMMARY OF THE INVENTION An object of the present invention is to provide a vapor phase growth apparatus in which the above-mentioned drawbacks are improved.

<Means for Solving the Problems> That is, the present invention provides a gas phase reactor equipped with a raw material gas inlet in the upper part of the reaction tube and a susceptor in the downstream part of the reaction tube, in which the susceptor has a substantially circular to polygonal pyramid shape. A vapor phase growth apparatus characterized in that the circular or polygonal pyramidal body is composed of an upper rectifying part and a lower substrate holding part, and the diameter expansion rate in the lower part is larger than the diameter expansion rate in the upper part. I will provide a.

In view of the above-mentioned circumstances, the present invention has been made as a result of intensive studies and has found that the above-mentioned drawbacks can be overcome by making the susceptor installed in the reactor of the vapor phase growth apparatus into a specific shape.

<Example> Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram of an embodiment of the vapor phase growth apparatus of the present invention. A raw material gas for vapor phase growth is introduced into the reaction tube 1 through a raw material introduction path 2. A polygonal pyramidal susceptor 3 supported by a rotatable shaft 6 is installed inside the reaction tube 1 . The susceptor 3 is roughly divided into an upper rectifying section 4 and a lower substrate holding section 5, and the substrate holding section 5 has a larger diameter expansion ratio. The susceptor is capable of high frequency heating by an external RF coil 8. The main flow of the introduced raw material gas flows between the rectifying section 4 of the susceptor 3 and the reaction tube wall, particularly near the surface of the rectifying section 4, in a substantially laminar flow state,
A thermal decomposition reaction occurs near the surface of the substrate 7 placed on the substrate holder 5, and a thin film of semiconductor crystal grows on the substrate 7. Note that the substrate 7 is normally placed on the slope of the substrate holder 5 in a concentric circle when viewed from directly above the susceptor 3. Unreacted gas and gas generated by the reaction are exhausted from an exhaust port 9 provided at the bottom of the reaction tube 1.

In the present invention, the diameter expansion ratio means the slope a measured from the susceptor rotation axis at a certain point on the susceptor surface, as shown in FIG.

Further, the angle of the substrate holding portion 5 of the susceptor in the apparatus of the present invention is not particularly limited, but is preferably 15 to 80 degrees, more preferably 20 to 75 degrees, and most preferably 35 to 70' with respect to the rotation axis.

In the vapor phase growth apparatus of the present invention, the turbulence of the raw material gas flow near the susceptor 3 is suppressed, thereby improving the efficiency of raw material use and the uniformity of the grown thin film.

FIG. 3 is a schematic diagram of an apparatus showing another embodiment of the present invention, and is an example in which a rectifier tube section 10 is provided in which the diameter of the reaction tube 1 near the susceptor 3 increases as it goes downward. FIG. 4 shows an example in which a rectifier tube section 10 is provided inside the reaction tube 1, the diameter of which increases as it goes downwards, which allows the raw material gas to flow more along the susceptor surface than the device shown in FIG. This is preferable since it is possible to further improve the usage efficiency of raw material gas. As shown in the figure, in the rectifier tube section 10, the gas passage cross-sectional area between the tube wall and the susceptor remains unchanged or gradually decreases from the susceptor tip to the rear end, and finally the gas passage cross-sectional area at the susceptor tip changes after the susceptor. By designing the cross-sectional area ratio at the end to be preferably 1.0 to 0.5, more preferably 1.0 to 0.75, the substrate placed on the susceptor can be more uniformly distributed. crystal growth is possible. In addition, at this time, the distance between the center of the substrate and the tube wall is desirably 5 to 5 times the diameter of the susceptor at the center of the substrate.
By setting it at 45%, more preferably between 10 and 25%, disturbances in the flow of the raw material gas can be further suppressed.

5 and 6 show other embodiments of the susceptor 3. In FIG. 5, the rectifying section 4 is conical and the substrate holding section 5 is polygonal, and in FIG. 6, both are circular. It is something. Note that even if the diameter expansion rate of the susceptor is increased continuously or sequentially as it goes downward, or the diameter expansion rate of the holding part 5 is
If the diameter expansion rate is larger than the diameter expansion rate of can do.

Figure 7 shows trimethyl gallium (TMG), a group II raw material, and arsine (arsine, a group V raw material) using the vapor phase growth apparatus shown in Figure 3.
A raw material gas (A s H 3) diluted with high purity hydrogen (
TMG mole fraction 1. A s H 3 /T M G molar ratio of 30) was introduced into the reaction tube through the introduction channel 2 at a concentration of IX 10-5 mol/l, and the diameter was reduced to 5C by heating with the susceptor 3.
The temperature of the ITl CraAs substrate 7 is maintained at 650°C,
This figure shows the results of examining the uniformity of the film growth rate when a thin film of GaAs, which is a compound semiconductor, is grown on top of the film. The rectifying section 4 of the susceptor used had a height of 120 mm and a maximum diameter of 84 mm, and the holding section 5 had a height of 120 mm and a maximum diameter of 200 mm. Further, the distance between the rectifying pipe portion and the susceptor was 45 mm at the tip of the susceptor and 15 mm at the rear end of the susceptor.

In addition, as a comparative example, the above-mentioned growth method was performed using the conventional growth apparatus shown in FIG. Figure 7 also shows the results of examining the uniformity of the film growth rate when vapor phase growth was performed under the same conditions as above. In FIG. 7, the horizontal axis represents the distance from the upstream side on a line connecting the most upstream and downstream points on the substrate, and the vertical axis represents the film thickness growth rate at each point at each distance. When using a conventional barrel-type semiconductor thin film vapor phase growth apparatus, the uniformity of the grown film is determined by the large difference in film growth rate between the upstream and downstream sides of the substrate, and the variation rate (standard deviation ÷ average value XIOO). was about 10.0%, whereas the difference was small when the vapor phase growth apparatus of the present invention was used, and the variation rate was about 2.3%.
This is an improvement of about 5 times. Furthermore, the average value of the film growth rate is approximately 0.8 μm/hr in the conventional device (L'), whereas in the device of the present invention it is approximately 1.0 μm/hr, which is an increase of about 25%, so the use of raw materials is It can be seen that efficiency has also improved.

<Effects of the Invention> As explained above, the vapor phase growth apparatus of the present invention can improve the usage efficiency of raw materials and can manufacture an epitaxial substrate with a uniform film thickness.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a vapor phase growth apparatus of the present invention, FIG. 2 is a schematic diagram of a conventional vapor phase growth apparatus, FIGS. 3 and 4 are schematic diagrams of a vapor phase growth apparatus of the present invention, and FIGS. 6 is a schematic diagram of the susceptor in the vapor phase growth apparatus of the present invention, and FIG. It is a figure showing the relationship with growth rate (vertical axis). l-...1 raw material gas introduction path, 2...1 reaction tube, 3 susceptor, 7-1111 board diagram (mm)

Claims (1)

[Claims] In a vapor phase growth apparatus equipped with a raw material gas introduction passage in the upper part of the reaction tube and a susceptor in the reaction tube, the susceptor is approximately circular or polygonal pyramid-shaped, and the circular or polygonal pyramid-shaped body is connected to the upper rectifying part and the lower part. What is claimed is: 1. A vapor phase growth apparatus comprising a substrate holding part, the diameter expansion rate of the lower part being larger than the diameter expansion rate of the upper part.