JPH06188194A - Vapor growth device - Google Patents

Abstract

PURPOSE:To reduce servicing frequency by keeping an inside wall, the upstream of a susceptor and near there, to which gas contacts always clean and configuring so that the part where sublimation-deposition takes place is always situated downstream of a substrate through the entire processes. CONSTITUTION:A spray tube 4, that extends from a material gas introduction part 3 to above a susceptor 2 and gas a divergent open end part, extends as far as a downstream end of the susceptor 2. Further, the diameter of the upstream end of an inside tube 5 is larger than that of the downstream end of the spray tube 4, and the diameter of the downstream end of the spray tube 4 is larger than that of the downstream end of the susceptor 2. In addition, the upstream end of the inside tube 5 is situated upstream of gas than the downstream end of the spray tube 4 is. At least one kind of gas, among hydrogen, nitrogen and argon, is introduced from a gas introduction part 9 that is the tap part of a reaction tube 6, into the inside tube through the gap between the upstream end of the inside tube and the downstream end of the spray tube. With this, effect from reaction-deposition material is suppressed, and substrates of high quality are produced for a long period.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vapor phase growth apparatus used for manufacturing a thin film such as a semiconductor.

[0002]

2. Description of the Related Art A vapor phase growth apparatus for producing a compound semiconductor thin film that can be used in various electronic devices by vapor phase growth on a crystal substrate is constructed as shown in FIG. 1 in the case of a vertical furnace, for example. As shown in this figure, in the conventional vapor phase growth apparatus, the source gas (for example, AsH ₃ , PH ₃ , Ga (C
H ₃ ) ₃ etc.) is a suitable carrier gas (eg H ₂ ,
N ₂ etc.) together with the source gas introduction part 3 to the susceptor 2
It is supplied to the substrate 1 placed on. The substrate on the susceptor is heated to a predetermined temperature by, for example, induction heating from the outside or a resistance heater or an infrared heater inside the susceptor. Vapor growth occurs on the surface of the substrate, and the reaction residual gas is discharged from the gas downstream side of the susceptor. After completion of the growth reaction, the temperature is lowered, the inside of the reaction tube is purged, the susceptor is taken out of the reaction tube as shown in FIG. 2, the substrate is exchanged, and then the next thin film growth is started.

During the reaction at this time, generally, the same thermal decomposition reaction as on the substrate surface occurs even on the surface of the susceptor other than the substrate and a part of the inner wall of the reaction tube near the susceptor heated by radiation or heat transfer from the susceptor. Occurs and a polycrystalline deposit is generated. Moreover, a part of the raw material gas component thermally decomposed in the vicinity of the susceptor becomes a substance having a lower vapor pressure than the raw material gas,
Sublimation adheres to the low temperature part on the downstream side of the reaction tube. The deposits formed on the inside of the reaction tube other than the substrate are generally brittle and peel off, which causes dust generation in the reaction tube. The generated dust adheres to the substrate and deteriorates the quality of the substrate. In particular, since the amount of sublimation deposits in the downstream portion of the reaction tube is large and has an indefinite shape, it easily peels off due to subtle vibrations and fluctuations in the air flow when the substrate is taken in and out, and easily adheres to the substrate surface. Therefore, in producing a semiconductor thin film using such an apparatus, it was necessary to periodically disassemble and clean the reaction tube to remove such deposits. However, such regular maintenance usually causes a decrease in the running time of the device, which is a major factor in reducing productivity.

On the other hand, in a vertical organometallic compound vapor phase growth apparatus equipped with a source gas inlet in the upper part of the reaction vessel,
The reaction gas is surrounded by a carrier gas as a gas inlet structure in which the wall of the reaction vessel between the source gas inlet and the substrate crystal is forcibly cooled and the periphery of the reaction gas inlet is surrounded by the carrier gas inlet. A method has been reported in which the decomposition reaction product is prevented from adhering to the reaction tube wall by forming a gas flow and bringing it into contact with the substrate crystal (Japanese Patent Application Laid-Open No. Sho 6-62).
2-20160). However, in this method, the temperature gradient in the upper part of the reaction tube becomes extremely large, and flow instability due to thermal convection tends to occur, so an extremely large amount of carrier gas is required to form a stable and uniform gas layer. There is. In addition, since the formation of sublimation deposits from the vicinity of the susceptor to the downstream portion is the same as the conventional one, there is no effect on the surface defects caused by the deposits.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to suppress the influence of deposits on a substrate, significantly reduce the maintenance frequency, and significantly improve the running time of the device. Is.

[0006]

The present inventors have arrived at the present invention as a result of intensive investigations in view of such problems. That is, the present invention relates to a thin film vapor phase growth apparatus having a source gas introduction section, a susceptor for mounting a substrate, a reaction tube and an exhaust tube, and (1) has a blowing tube for introducing the source gas onto the substrate. However, the downstream end of the blowing pipe extends to the downstream end of the susceptor, the diameter of the downstream end of the blowing pipe is larger than the diameter of the downstream end of the susceptor, and (2) has an inner pipe surrounding the susceptor holding shaft. The inner pipe and the exhaust pipe are connected in the lower part, the diameter of the upstream end of the inner pipe is larger than the diameter of the downstream end of the blowing pipe, and the upstream end of the inner pipe is located on the gas upstream side of the downstream end of the blowing pipe. And (3) at least one gas selected from the group consisting of hydrogen, nitrogen and argon is provided in the upper part of the reaction tube so that the gas flows between the reaction tube and the blowing tube, (4) The susceptor moves up and down together with the inner tube It relates vapor deposition apparatus characterized by having a mechanism for.

The present invention will be described in more detail with reference to the drawings. FIG. 3 shows an outline of the vapor phase growth apparatus of the present invention. The apparatus is composed of a raw material gas introduction unit 3, a susceptor 2 on which the substrate 1 is placed, a blowing pipe 4, an inner pipe 5, a reaction pipe 6, and an exhaust pipe 10. Susceptor 2 is
It is held by the susceptor holding shaft 7, and the susceptor holding shaft 7 can be rotated if necessary. The raw material gas 8 is introduced into the spray pipe 4 through the raw material gas introduction part 3 together with the carrier gas.

The blowing tube 4 extends from the raw material gas introduction portion onto the susceptor and has an opening end portion that widens toward the end. The open end, that is, the downstream end of the spray tube 4 extends to the downstream end of the susceptor 2. Further, the diameter of the upstream end of the inner pipe 5 is larger than the diameter of the downstream end of the blowing pipe 4. Also, the blowing tube 4
The diameter of the downstream end of the susceptor is larger than the diameter of the downstream end of the susceptor.
Further, the upstream end of the inner pipe 5 is located upstream of the gas from the downstream end of the blowing pipe 4. At least one gas selected from the group consisting of hydrogen, nitrogen and argon (hereinafter,
(It may be called an inert gas) is introduced from the inert gas introducing portion 9 at the upper part of the reaction tube 6, flows along the outer wall of the blowing tube, and then from the gap between the inner tube upstream end and the blowing tube downstream end. It flows into the inner pipe. The inert gas and the reaction residual gas are merged, then passed through the inside of the inner pipe, and are discharged to the exhaust system from the exhaust pipe 10 installed in the gas downstream portion.

The vapor phase growth apparatus of the present invention has a mechanism in which the susceptor moves up and down together with the inner tube. In particular, when the substrate is replaced, the susceptor has a mechanism that moves up and down together with the inner tube to a position where the substrate can be replaced. When exchanging the substrate, the susceptor can be moved by moving the susceptor together with the inner tube as shown in FIG. Therefore, in particular, the susceptor can be moved together with the inner pipe to a position where the substrate can be exchanged while maintaining the positional relationship so that the susceptor is located on the upstream side of the gas from the upstream end of the inner pipe. Further, in order to avoid atmosphere pollution due to substrate exchange, it can be implemented in combination with a load lock mechanism composed of the sub chamber 11 and the gate valve 12.

According to the present invention, the raw material gas is blown from the blowing pipe onto the surface of the substrate on the susceptor to grow a predetermined thin film, and the reaction residual gas passes through the inner pipe from the exhaust pipe provided therebelow. Is discharged. At this time, the flow rate of at least one gas selected from the group consisting of hydrogen, nitrogen and argon, which flows between the outside of the blowing tube and the reaction tube, by appropriately selecting the distance of the blowing tube from the susceptor. It is possible to control the radiation and heat transfer from the heated susceptor by appropriately selecting Therefore, the temperature of the blowing tube can be set so as to minimize the decomposition of the raw material gas in contact with the temperature gradient between the blowing tube and the susceptor to the extent that thermal convection does not occur. As a result, first, it is possible to reduce the adhesion of the reaction product to the susceptor near the substrate and the wall of the spray tube other than the substrate surface.

Next, a part of the reaction gas component decomposed on the heating substrate and the susceptor surface is transported to the downstream portion together with the carrier gas, and sublimates and adheres to the wall of the inner tube having a low temperature. At this time, the inert gas flowing between the blowing pipe and the reaction pipe forms an inert gas layer between the inner pipe wall and the reaction residual gas when flowing into the inner pipe, and the inner pipe wall Plays a role of protecting the upper part of the above from the sublimation adhesion of the above reaction product, and the site where the sublimation adhesion occurs can be moved further downstream of the gas from the susceptor. Further, when the substrate is exchanged, by moving the susceptor together with the inner tube, the sublimation product adhesion site generated as described above can be always located downstream of the susceptor through the growth of the thin film and the substrate exchange operation. It will be possible.

As a result of the above, from the upstream to the vicinity of the susceptor, the inner wall with which the gas comes into contact is always kept in a clean state, and the site where sublimation adheres occurs through all steps such as thin film growth and substrate exchange. Always located downstream of the substrate. Therefore, even if peeling occurs due to the deposition of the product, the substrate surface is not adversely affected, and high-quality products can be produced for a long period of time.

The positional relationship between the downstream end of the blowing pipe, the downstream end of the susceptor and the upstream end of the inner pipe at this time will be described in more detail. The reaction product is not sublimated and adhered to the spray tube, and the reaction residual gas can be prevented from leaking out from the gap between the spray tube and the inner tube to attach unnecessary deposits to the inner wall of the reaction tube and the outer wall of the spray tube. As described above, the downstream end of the blowing tube is preferably located within ± 50 mm from the downstream end of the susceptor. In addition, the upstream end of the inner pipe is preferably located 0 mm or more upstream from the downstream end of the blowing pipe.

However, if the upstream end of the inner pipe is located upstream of the upstream end of the susceptor, it will hinder the substrate replacement. Therefore, the upstream end of the inner pipe is located downstream of the upstream end of the susceptor, or the substrate replacement is performed. In this case, it is necessary to install a mechanism that moves the susceptor upstream with respect to the inner pipe. Also,
The gap between the upstream end of the inner pipe and the downstream end of the blowing pipe can be selected according to the flow rate of the inert gas flowing therethrough, but is preferably in the range of 2 to 50 mm. The form of the vapor phase growth apparatus of the present invention is not limited to the vertical furnace used in the above description, and it goes without saying that it can be applied to a horizontal furnace, a barrel furnace, a pancake furnace, etc. .

[0015]

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited thereto. Example 1 The outline of the apparatus used in this example is similar to that shown in FIG. A quartz member was used for each of the spray tube, the upper part of the inner tube, and the upper part of the reaction tube. As a carrier gas, 9 standardl / min (hereinafter, abbreviated as slm) hydrogen gas was used, and it was performed under a reduced pressure condition of 0.1 atm. After cleaning a single crystal GaAs wafer as a substrate, the sub chamber 1
1 was placed under reduced pressure with hydrogen, the gate valve 12 was opened, and placed on the graphite susceptor 2 under a hydrogen stream. After moving the susceptor to a predetermined position, the inside of the reaction tube was adjusted to 0.1 atm, and induction heating was performed by the external high frequency heating coil 13. The pressure in the reaction tube was detected by the pressure sensor 14 attached to the reaction tube, and the output was adjusted by feeding it back to the control valve provided in the exhaust section.

The substrate temperature was controlled by detecting it with a thermocouple inserted inside the susceptor and feeding back the output to a high frequency heating coil. In order to suppress the decomposition of GaAs when the temperature reached 550 ° C. in the process of increasing the temperature, 5.2 × 10 ⁻⁵ mol / min of arsine (As
H ₃₎ was started supply. At this time, the gap between the downstream end of the blowing pipe and the upstream end of the inner pipe was 5 mm, and 6 slm of hydrogen was flown from the inert gas introducing portion 9 to the outside of the blowing pipe. The inner pipe upstream end is 5 mm from the susceptor downstream end.
The structure is located on the downstream side.

When the temperature became stable at 650 ° C., the flow rate of arsine (AsH ₃ ) was changed to 2.6 × 10 ^-3 mol / min.
When the temperature, the pressure and the flow rates of the respective gases were stabilized, 5.2 × 10 ⁻⁵ mol / min of trimethylgallium (TMG) was supplied to start crystal growth. After growing for 2 hours, stop the supply of raw materials and immediately stop heating,
When the temperature was lowered to near room temperature, the susceptor was moved as shown in FIG. 4, the gate valve was opened to move the substrate to the sub chamber, the gate valve was closed, the sub chamber was replaced with nitrogen, and the substrate was taken out to the atmosphere. At this time, the grown film thickness was 6 microns and the number of surface defects was about 15 / cm ² . As a result of Hall measurement, this crystal was n-type and had an electron mobility of 9 at 77K.
At 8000 cm ² / Vsec, it was found that the product had practically sufficient quality. After the reaction at this time, almost no reaction products were adhering to the spray tube in the reaction tube and the upper part of the inner tube.

After that, the same crystal growth was repeated 30 times, and the surface defect density was measured again. As a result, 12 defects / cm.
Turned out to be ² . After repeating the same growth as above 30 times, the surface defect density of the same crystal was measured again, and the result was 13 defects / cm ² .
After that, when the equipment was disassembled, reaction products were found to have adhered to the lower part of the inner pipe, and most of them fell off and accumulated on a collection filter (not shown) installed downstream of the exhaust pipe. I found out. As a result, it was found that the vapor phase growth apparatus according to the present invention is suitable for stable production of high quality crystals.

Comparative Example 1 Crystal growth was carried out in the same manner as in Example except that the apparatus shown in FIG. 1 was used as the vapor phase growth apparatus.
After the initial crystal growth, a large amount of deposits were found on the downstream side of the susceptor. The surface state of the grown crystal at this time was good with a defect density of 21 defects / cm ² , but during the subsequent growth, a part of the deposits fell off on the substrate surface, and the crystal defect density was 5000 defects. / Cm ² or more. Then, the reaction tube was once disassembled and washed, and growth was again carried out under the same conditions to obtain a crystal having a surface defect density of 100 / cm ² . However, in the next growth, the surface defect density became 10,000 or more / cm ² due to the influence of the exfoliated material as in the previous time.

[0020]

According to the present invention, the influence of reaction deposits can be suppressed and high quality substrates can be produced for a long period of time, which is extremely significant in industrial production.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a reaction device used in a comparative example, which is an example of a conventionally used reaction device.

FIG. 2 is an explanatory view of a situation when a substrate is placed in a conventionally used apparatus.

FIG. 3 is a sectional view of an example of a vapor phase growth apparatus of the present invention.

FIG. 4 is an explanatory view of a situation when a substrate is placed in the vapor phase growth apparatus of the present invention.

[Explanation of symbols]

 1 Substrate 2 Susceptor 3 Raw Material Gas Introducing Section 4 Spraying Tube 5 Inner Tube 6 Reaction Tube 7 Susceptor Holding Shaft 8 Raw Material Gas 9 Inert Gas Introducing Section 10 Exhaust Pipe 11 Sub Chamber 12 Gate Valve 13 High Frequency Heating Coil 14 Pressure Sensor

Claims (1)

[Claims] 1. A thin film vapor phase growth apparatus having a source gas introduction part, a susceptor for mounting a substrate, a reaction tube and an exhaust tube, comprising: (1) a blowing tube for introducing the source gas onto the substrate. , The downstream end of the blowing pipe extends to the downstream end of the susceptor, the diameter of the downstream end of the blowing pipe is larger than the diameter of the downstream end of the susceptor, and (2) has an inner pipe surrounding the susceptor holding shaft and has a lower portion of the inner pipe. The inner pipe and exhaust pipe are connected with each other, the diameter of the upstream end of the inner pipe is larger than the diameter of the downstream end of the blowing pipe, and the upstream end of the inner pipe is located upstream of the gas from the downstream end of the blowing pipe. (3) The reaction tube has an inlet for at least one gas selected from the group consisting of hydrogen, nitrogen, and argon,
(4) A vapor phase growth apparatus having a mechanism in which the susceptor moves up and down together with the inner tube so that the gas flows between the reaction tube and the blowing tube.