JP2709182B2 - Vapor phase growth apparatus and vapor phase growth control method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a vapor phase growth apparatus for growing a thin film and a vapor phase growth control method.

[Conventional technology]

A compound semiconductor vapor phase growth apparatus (MOCVD apparatus) is an apparatus for growing a thin film crystal by reacting and decomposing a mixed gas of an induced metal and a hydrogen compound on a crystal substrate heated to a predetermined temperature. This apparatus is excellent in controllability of crystal growth rate, simplicity of operation and mass productivity.

An example of such a vapor phase growth apparatus is shown in FIG. A susceptor 3 for holding a crystal substrate 2 is provided in a reactor 1. The susceptor 3 is rotatably supported.
The reactor 1 has a reaction gas supply port 4 at an upper part, a reaction gas discharge port 5 at a lower part, and an induction heating device 8 for heating the crystal substrate 2 at an outer peripheral part of the reactor 1. Have been.

A reaction gas containing a raw material gas to be crystal-grown is introduced into the reactor 1 from the supply port 4 and reacts and decomposes on the surface of the crystal substrate 2 to grow a crystal.

In order to manufacture a semiconductor device such as a laser or a light-emitting diode, it is necessary to stack and grow a plurality of crystals having different compositions. In this case, a semiconductor having good characteristics can be manufactured unless a mixed layer of different materials is formed at an interface between crystals having different compositions.
That is, it is necessary to switch and supply different reaction gases supplied to the crystal substrate to the crystal substrate so as not to mix.

However, in the conventional device, a vortex is generated in the gas introduction portion,
The gas in the reactor becomes unrectified. Because of this unrectification,
Even if the type of the introduced gas is changed, the gas supplied on the crystal substrate cannot be switched sharply.

In order to solve this problem, Japanese Patent Application Laid-Open No. 63-318734 discloses a method of switching the gas introduction section and separately providing a gas supply port to prevent mixing of two gases. However, it is not yet complete.

Japanese Patent Application Laid-Open No. 28316/1990 discloses a technique of discharging a raw material gas toward the wall of the reaction tube in a direction opposite to the direction in which the crystal substrate is located. Has reached the substrate in a turbulent state, and it cannot be said that it has been sufficiently improved.

Japanese Patent Application Laid-Open No. 2-28928 discloses that a concentric gas inlet pipe for introducing two or more kinds of process gases is inserted into a process tube in a diffusion furnace for performing pyrogenic steam oxidation, and an outer end is provided at a tip portion thereof. It shows a structure that radiates radially at an angle of 10 to 30 ° to the center line in the direction opposite to the direction of introduction of the tube. This apparatus is superior to the conventional apparatus in terms of temperature uniformity in the process tube, but the flow is turbulent, and the turbulence has not been eliminated. Therefore, the film forming quality of these apparatuses is not sufficient.

[Problems to be solved by the invention]

An object of the present invention is to provide a vapor phase growth apparatus and a method for appropriately controlling vapor phase growth that solve the following problems.

(A) The source gas applied to the crystal substrate can be switched quickly and completely, and a good semiconductor crystal can be grown without forming a mixed layer at the crystal interface.

(B) To suppress the turbulence of the gas flow inside the reaction furnace and improve the film formation quality.

[Means for solving the problem]

According to the present invention, in a thin film vapor phase growth apparatus, a small diameter end of a reducer is connected to an upper reaction gas inlet of the apparatus, and a large circle of a hemispherical shell is directly or directly connected to a short diameter straight pipe at a large diameter end of the reducer. And a gas inlet pipe for forming an airflow toward the reducer along the inner surface of the hemispherical shell.
The gas inlet pipe is provided with, for example, a supply pipe that penetrates the center of the hemispherical shell from the outside to the inside, and reflects the gas at its tip to eject the gas toward the inner surface of the hemispherical shell.

In this device, it is more preferable that a straight pipe having the same diameter as the small diameter portion of the reducer is suspended from the small diameter portion of the reducer.

In addition, when a straight pipe for introducing the raw material gas is inserted from above into the axis of the reducer, and this pipe is hung down, it is possible to obtain a gas flow in which turbulence is suppressed at the time of gas supply, which should be turbulent. Can be. Further, when the straight pipe is extended below the reducer through the reducer, the gas flow can be further stabilized.

Using any one of the above apparatuses, a carrier gas and a reaction gas are supplied to grow a crystal on a crystal substrate, and a crystal growth reaction state on the crystal substrate is measured by, for example, a laser or the like. By controlling the amount of air supply accordingly, a thin film of any accurate thickness can be obtained.

[Action]

When a fluid flow in the axial flow direction having an annular minimum flow velocity portion concentric with the flow passage is formed in the axially symmetric enlarged or reduced flow passage, a swirling speed component is generated in the fluid flow. Applying this principle, the hemispherical shell 20 is connected to the pipe 15 as shown in FIG. 1 via the reducer 14 and closed, and when the fluid is sent from the air supply pipe 11 toward the closed end, the droop occurs. A swirling flow is generated in the pipe 15. The flow in the hanging pipe 15 becomes a spiral flow or a linear flow (laminar flow). By adjusting the inflow rate of the fluid, the promotion and suppression of the growth of the crystal on the crystal substrate can be freely controlled. In addition, the air flow introduced in this way is rectified without generating spatially and temporally unstable eddies, and a good film formation can be ensured even in the pyrogenic oxidation apparatus. When forming a film by switching, when switching the gas, the gas before and after is not mixed.

The present inventors have previously provided the following invention in Japanese Patent Application No. 1-050125. In other words, when a reducer is provided in the conduit, and a fluid having a different length from the fluid flowing through the conduit is fixed concentrically to the reducer inner axial position and / or the reducer exit side axial position, the Reynolds number is 2300 or more. The fluid in the pipeline can be made into a laminar flow also in the region.

The present invention measures the growth state of the crystal on the crystal substrate of the vapor phase growth apparatus by applying such a technology, and can control the crystal growth to any desired thickness, film formation rate, component, and the like. .

〔Example〕

FIG. 1 (a) shows a longitudinal section of an embodiment of the apparatus of the present invention. The main body of the vapor phase growth apparatus 1 includes a susceptor 3 that rotates with the crystal substrate 2 placed thereon, and gas is introduced from an upper gas supply pipe 11 and discharged from a lower outlet 5. The hemispherical shell 20 is attached to the large diameter side of the reducer 14. The shorter diameter side of the reducer 14 was connected to the gas inlet side of the vapor phase growth apparatus 1. Also, reducer
A hanging tube 15 having the same diameter as the short diameter of 14 was attached.

The gas inlet pipe 11 was attached to the end of the hemispherical shell 20. Air pipe
The other end of 11 was connected to gas mixer 16. The gas mixer 16 mixes the source gas 17 and the carrier gas 18 and sends the mixed gas to the air supply pipe 11.

The gas supply device can arbitrarily change the amount and flow of the supplied gas. Further, another gas can be fed after one gas in a turbulence-suppressed state without mixing gases.

Therefore, the adjustment of the film thickness on the crystal substrate 2 and the switching without causing the mixture of different gases can be easily performed.

FIG. 1B shows an embodiment in which the shape of the end of the air supply pipe 11 is changed.

Next, FIG. 2 shows another embodiment of the present invention, in which a reducer 14, a short straight tube 13, and a hemispherical shell 20 are connected to the upper part of the crystal growth apparatus 1, and a drooping tube at the lower end of the reducer is omitted. The air supply pipe 11 is attached to the short straight pipe 13 to supply gas toward the inner surface of the hemispherical shell 20. Also in this case, similarly to the example of FIG. 1, the gas reaching the crystal substrate can be freely adjusted.

FIG. 3 shows an example in which a thin raw gas introduction straight pipe 21 is inserted into or through the reducer 14 and below the reducer 14 at the axis thereof. As described above, even in the pipe system in which the elongated insert is inserted into the axis of the reducer, turbulence is suppressed even at a high Reynolds number. Raw gas introduction straight pipe 21
Gas flows from the center of the flow and has little turbulence. By making this central flow reach the crystal substrate, the thin film can be easily adjusted, and no mixed layer is formed at the boundary between different kinds of films.

Using the vapor phase growth apparatus shown in FIGS. 1 to 3, air was introduced into the apparatus, and the generation of vortices in the airflow reaching the crystal substrate was investigated. As a result, the generation of vortices was significantly reduced.

〔The invention's effect〕

ADVANTAGE OF THE INVENTION According to this invention, the turbulence of the gas flow in a reaction furnace is suppressed, and even if the source gas is switched, since different gases reaching the crystal substrate are not mixed, a good semiconductor crystal which does not form a mixed layer at the crystal interface is obtained. And its usefulness is enormous.

[Brief description of the drawings]

1 (a) and 1 (b) are longitudinal sectional views of an embodiment of the present invention, FIG. 2 is a longitudinal sectional view of another embodiment, and FIGS. 3 (a) and 3 (b) are those of another embodiment. FIG. 4 is a longitudinal sectional view of a conventional device. DESCRIPTION OF SYMBOLS 1 ... Vapor phase growth apparatus, 2 ... Crystal substrate 3 ... Susceptor 4, ... Reactant gas supply port 5 ... Reactant gas outlet, 8 ... Heating apparatus 11 ... Gas inlet pipe, 13 ... Short Straight pipe 14 ... Reducer, 15 ... Dropping pipe 16 ... Mixing chamber, 17 ... Raw material gas 18 ... Carrier gas, 20 ... Hemispherical shell 21 ... Introduction straight pipe

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-60-27690 (JP, A) JP-A-60-72223 (JP, A) JP-A-63-185017 (JP, A)

Claims (5)

(57) [Claims] In a thin film vapor phase growth apparatus, a small diameter end of a reducer is connected to an upper reaction gas inlet of the apparatus, and a large circle of a hemispherical shell is connected directly or a short straight pipe to a large diameter end of the reducer. A gas feed pipe connected to the gas flow tube through the inner surface of the hemispherical shell to form an air flow along the inner surface of the shell. 2. The vapor phase growth apparatus according to claim 1, wherein a straight pipe having the same shape as the small diameter end is suspended from the small diameter end of the reducer. 3. The vapor phase growth apparatus according to claim 1, wherein a straight pipe for introducing a raw material gas having a diameter smaller than the diameter of the small diameter end of the reducer is inserted and hung down on the axis of the reducer. 4. The vapor phase growth apparatus according to claim 3, wherein the introduction straight pipe extends through the reducer to a position below the reducer. 5. A crystal growth reaction state on a crystal substrate is measured when a carrier gas and a reaction gas are supplied and a crystal is grown on the crystal substrate by using the apparatus according to claim 1. And controlling a gas supply amount according to the measured value.