JPH01294598A - Vapor phase growth equipment - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is directed to the production of epitaxial crystals of compound semiconductors such as GaAs and lnP by thermal decomposition reactions and chemical reactions.
iOt,S+! Insulator thin film such as <, and 11Six, T
The present invention relates to an apparatus for vapor phase growth of conductive polycrystalline thin films such as iSix.

(Prior art) Conventionally, some vapor phase growth apparatuses have a barrel-shaped susceptor built into a vertical reaction chamber, while others have a pancake-shaped susceptor built into a horizontal reaction chamber. In addition to this, there are also resistance heating and infrared heating. As a vapor phase growth method for thin films, there is a method in which a gaseous substance carried by a source gas or a carrier gas is introduced into a reaction chamber, and a thin film is formed on a substrate by a thermal decomposition reaction or a chemical reaction.

A description will be given below using the barrel type vapor phase growth apparatus shown in FIG. 2 as an example. A barrel-shaped susceptor 2 carrying a substrate 1 is supported at the center of a reaction chamber 4 by a rotating shaft 3, a pressure control valve 6 of an exhaust pipe 5 is opened, and a rotary pump 7 is used to draw the reaction chamber to a high vacuum.

Next, the high-frequency coil 8 is energized to heat the substrate I to the growth temperature, and then raw material gas is introduced from the introduction pipe 9 to heat the substrate 1.
deposit a thin film on top of the The gas flow accompanied by unreacted substances and reaction products flows down around the barrel-type susceptor 2, passes through an exhaust pipe 5, a pressure control valve 6, and a rotary pump 7, and is further discharged to the outside of the system via a dust filter, etc. Ru.

This pressure control valve 6 is for adjusting the pressure in the reaction chamber 4, and a slot valve, a conductance control valve, or the like is used. Note that IO is a cooling jacket through which cooling water flows.

(Problem to be Solved by the Invention) In this type of vapor phase growth apparatus, dust from unreacted substances and reaction products is carried by the gas flow and sent to the exhaust pipe, pressure control valve, and even the rotary pump, where it becomes attached. As a result, the exhaust conductance of the exhaust system decreases, the exhaust pipe tends to become clogged, and the pressure in the reaction chamber increases. If the pressure in the reaction chamber fluctuates during one thin film growth process, for example, the doping level of the thin film crystal will not be constant, resulting in non-uniform electrical and optical properties.

Furthermore, if similar vapor phase growth is repeated, there is a problem that the pressure control valve is blocked, making it impossible to control the pressure in the reaction chamber, and sometimes causing the rotary pump to stop. This kind of problem is not unique to barrel-type vapor phase growth apparatuses, but is common to the above-mentioned vapor phase growth apparatuses.

The present invention solves the above problems, prevents dust from scattering into the exhaust system, makes it possible to maintain a constant pressure in the reaction chamber, and makes it possible to easily form a thin film with stable quality. The aim is to provide a vapor phase growth apparatus that can achieve this goal.

(Means for Solving the Problems) The present invention provides a vapor phase growth apparatus in which a reaction chamber in which a substrate is installed, a raw material gas introduction pipe, and an exhaust pipe connected to a vacuum exhaust system is provided. This is a vapor phase growth apparatus characterized by a baffle plate installed near the exhaust pipe.

(Function) FIG. 1 is a conceptual diagram of a barrel type vapor phase growth apparatus which is a specific example of the present invention. In this apparatus, the exhaust pipe 5 of the apparatus shown in FIG. 2 was moved from the side wall of the reaction chamber 4 to the bottom, and a bar-soffl plate II was installed near the exhaust pipe 5. Specifically, by extending the exhaust pipe 5 into the reaction chamber 4 and covering the exhaust pipe 5 with a cylindrical partition wall 12 with a closed upper end, an annular flow path directed upward is formed between the partition wall 12 and the exhaust pipe 5, A baffle plate +1 is installed in the flow path. Note that the rotating shaft 3 supporting the barrel-shaped susceptor 2 is supported by a bearing 13 provided at the center of the partition wall I2, and is connected to a drive shaft 14 via a bevel gear.

In this device, the dust of unreacted substances and reaction products flowing down around the two barrel-shaped susceptors collides with the baffle plate 11 while rising in the annular flow path, falls to the bottom of the reaction chamber 4, and is captured. Ru.

Then, the clean exhaust gas excluding dust flows through the exhaust pipe 5 to the pressure control valve 6 and the rotary pump 7.
Since there is no dust adhesion or accumulation, the exhaust system equipment always operates accurately and the reaction chamber pressure can be controlled reliably. As a result, it becomes possible to vapor phase grow a thin film with stable quality under a constant pressure atmosphere. In addition, as in the apparatus shown in Fig. 1, a baffle plate is provided in the annular flow path below the reaction chamber.
By connecting an exhaust pipe to the flow path, one-sided flow within the reaction chamber can be suppressed, and the quality of the thin film can be made more uniform.

(Example) A crystal in Si-doped GaAs was epitaxially grown on a GaAs wafer having a diameter of 3 inches by metal organic vapor phase epitaxy using the apparatus shown in FIG.

After mounting the GaA3 wafer on a barrel-shaped susceptor, the reaction chamber was evacuated, and the high-frequency coil was energized to heat the wafer to the growth temperature of 700'C. Next, trimethyl gallium was added at a rate of 20 seconds (flow rate at 0'C, standard state of fats: cm3/5 inches), and arsine was added at a rate of 1.2 seconds.
231. M (flow In at standard conditions at 0℃iatm
1 /win), 5scc of silane and hydrogen as carrier gas, maintaining the total flow rate at 8S I,H, IQT
Epitaxial growth was performed for 1 hour under a growth pressure of orr.

During one crystal growth, the pressure fluctuation in the reaction chamber is 0 with respect to the set value.
．． It was extremely stable within 5%. Further, even after 200 crystal growths were completed, no clogging was observed in the exhaust pipe or pressure control valve, and no disassembly and cleaning or maintenance of the growth chamber was required.

A GaAs epitaxial layer of about 2.0 .mu.I was formed on the wafer, and according to SIMS analysis, the Si concentration distribution in this layer was constant in the depth direction, as shown by the solid line in FIG. Note that the Si concentration at a depth of about 2.0 atl and above is at the background level.

For comparison, epitaxial growth of a Si-doped GaAs single crystal was performed using the apparatus shown in Figure 2 under the same conditions as in the example described above, and the pressure fluctuation in the reaction chamber was reduced to the set value after one crystal growth. 15-20% or more, 20-20%
After 30 crystal growths, the exhaust pipe and pressure control valve became noticeably clogged, so the growth chamber was disassembled for maintenance and cleaning.

The GaAs epitaxial layer had a thickness of about 2.0 .mu.m, and the results of SIMS analysis showed that a Si'e 5 degree gradient was formed in the depth direction of the layer, as shown by the dotted line in FIG.

(Effects of the Invention) By adopting the above-mentioned configuration 4, the present invention can prevent pressure fluctuations in the reaction chamber during the vapor phase growth process, making it possible to easily form a thin film with stable quality. Ta. Additionally, the operability of the pressure control valve has been improved, making it possible to significantly reduce maintenance of the entire device.

[Brief explanation of the drawing]

Fig. 1 is a conceptual diagram of a barrel-type vapor phase growth apparatus which is a specific example of the present invention, Fig. 2 is a conceptual diagram of a conventional barrel-type vapor phase growth apparatus, and Fig. 3 is a conceptual diagram of a barrel-type vapor phase growth apparatus that is a specific example of the present invention. It is a graph showing sif:5 degree distribution in an epitaxial layer.

Claims (2)

[Claims] (1) In a vapor phase growth apparatus that has a reaction chamber in which the substrate is installed, a raw material gas introduction pipe, and an exhaust pipe connected to the vacuum exhaust system, a baffle plate is installed near the exhaust pipe of the reaction chamber. Characteristic vapor phase growth equipment. (2) A barrel-shaped susceptor is used as a substrate support, a raw material gas introduction pipe is connected to the top of the reaction chamber, an annular flow path is formed upward in the lower part of the reaction chamber, and a baffle plate is installed in the flow path. The vapor phase growth apparatus according to claim (1), further comprising an exhaust pipe connected to the outlet of the flow path.