JPH0516170B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a closed tube epitaxial growth method for forming an epitaxial layer on a substrate.

(b) Background of the technology Chemical vapor deposition is generally known as a method for epitaxial growth in the manufacture of semiconductor devices, but liquid layer growth is also often used when the epitaxial layer to be grown is a compound semiconductor. has been done.

In the case of epitaxial growth of mercury cadmium telluride (Hg _{1-X Cd} A closed tube epitaxial growth method is used in which a solution to be grown is sealed in a closed tube, and the substrate is brought into contact with the solution to grow an epitaxial layer on the substrate.

(c) Prior art and problems Figure 1 is a front sectional view (a) and side sectional view (b) of a closed tube body showing an example of a conventional closed tube liquid phase epitaxial growth method. 1 is an outer tube, 2 is an inner tube, 3 is a displacement gas, 4 is a rod, 5 is a carbon membrane, indicates the substrate, B indicates the raw material, and B1 indicates the solution.

The method illustrated in FIG. 1 is as follows.

First, an epitaxial layer, such as Hg _1-
When a substrate A for forming a _Cd After inserting the inner tube 2 made of the same material as the outer tube 1 into the outer tube 1 and replacing the inside of the outer tube 1 with a replacement gas 3 such as an inert gas such as nitrogen or a reducing gas such as hydrogen, the outer tube 1 and the inner tube 2 are The opening is sealed, and a rod-shaped rod 4 made of the same material as the outer tube 1 is fused thereto to form a closed tube body.

Next, the closed tube is heated by placing it in a horizontal heating furnace with the substrate A facing upward (position A indicated by the broken line in the figure), and when the raw material B becomes the solution B1 and reaches a predetermined temperature, the rod 4 is operated to close the tube. The body is rotated, and the substrate A is moved downward (position A indicated by the solid line in the figure), brought into contact with the solution B1, and growth is started. When the growth progresses and the epitaxial layer reaches a predetermined thickness, the closed tube is rotated again, and the substrate A is moved upward to fill the solution B1.
Separate it from the plant and stop its growth. Thereafter, the temperature is returned to room temperature, the outer tube 1 of the closed tube body taken out from the heating furnace is broken, and the substrate A on which the epitaxial layer has been grown is taken out to complete the entire operation.

In epitaxial growth using this method, if the replacement gas 3 is an inert gas, the oxygen is removed by the presence of oxygen remaining during gas replacement, or if it is a reducing gas, the oxygen is removed by the reducing gas. The presence of oxygen that remains even after the removal of oxygen increases the carrier concentration of the grown layer, making it difficult to obtain an epitaxial layer of high purity, which is desirable for the manufacture of semiconductor devices.

The method shown in FIG. 2 is a method tried by the inventor of the present application.
The carbon film 5 is previously deposited on the inner surface of the carbon film 5, but other aspects are the same as those shown in FIG.

Epitaxial growth using this method is performed using raw material B.
It was found that because the solution B1 touches the carbon film 5 and moves, the fine powder of the carbon film 5 mixes into the solution B1, and during growth, the fine powder adheres to the substrate A and causes pinhole-like defects in the grown layer. However, it has drawbacks that prevent it from being used in the manufacture of semiconductor devices.

However, in the method shown in FIG.
We have found that if we use a reducing gas, the removal of oxygen, which was a problem in the case shown in Figure 1, can be achieved by combining the reducing gas with carbon. .

(d) Object of the Invention In view of the above-mentioned conventional drawbacks, the object of the present invention is to provide a method for performing liquid phase epitaxial growth by placing a substrate on which an epitaxial layer is to be formed and a solution in which the epitaxial layer is to be grown in a closed tube. It is an object of the present invention to provide a method for manufacturing a semiconductor device in which a reducing gas and carbon are used together to remove oxygen in the closed tube, and in which generation of defects in the epitaxial layer due to the carbon is suppressed.

(e) Structure of the Invention The above object is to place a substrate for forming an epitaxial layer and a solution for growing the epitaxial layer in a tube having a ventilation window, and to place the tube in a closed tube whose inner surface is coated with carbon. A reducing gas is introduced into the closed tube, the tube is rotated or tilted within a range where the carbon does not come into contact with the substrate and the solution, and the surface of the substrate is coated with the solution. This is achieved by a method of manufacturing a semiconductor device that includes a step of performing growth.

(f) Embodiments of the invention Examples of the invention will be described below with reference to the drawings. The same reference numeral indicates one object throughout the figures.

FIG. 3 is a front sectional view (a) and a side sectional view (b) of a closed tube body showing an embodiment of the closed tube liquid phase epitaxial growth method according to the present invention, in which 1a is an outer tube, 3a is a replacement gas,
6 indicates a growth tube, and 61 indicates a window.

The illustrated method according to the invention is as follows.

First, a ventilation window 6 which is made of the same material and has the same dimensions as the outer tube 1 shown in FIG.
1 is opened at the back side of the growth tube 6, and the substrate A is held at an angle of about 90 degrees from the window 61, and the raw material B is placed inside the growth tube 6. Inner tube 2 is inserted, and the inner tube 2 is inserted so that the diameter thereof is larger than that of the growth tube 6. The outer tube 1a is a cylinder with a bottom made of the same material as the growth tube 6, and the inner surface is covered with a carbon film 5. After replacing the inside of the outer tube 1a with a reducing gas such as hydrogen, which is the replacement gas 3a, the outer tube 1a, the openings of the growth tube 6 and the inner tube 2 are sealed, and the rod 4 is fused thereto to form a closed tube body.

The following operations are the same as those described with reference to FIG. 1, except that caution is required regarding the direction of rotation of the closed tube body. That is, the closed tube body is placed in a horizontal heating furnace and heated with the substrate A facing upward (position A indicated by the broken line in the figure).
When the raw material B becomes the solution B1 and reaches a predetermined temperature, the rod 4 is operated to open the window 61 which is turned sideways.
rotates the closed tube body approximately 180 degrees in an upward direction,
The substrate A is moved downward (position A indicated by the solid line in the figure) and brought into contact with the solution B1 to start growth. When the growth progresses and the epitaxial layer reaches a predetermined thickness,
The window 61 facing sideways on the opposite side of the tip rotates approximately 180 degrees in the upward direction (opposite direction of rotation).
The closed tube is rotated once, and the substrate A is moved upward and separated from the solution B1 to stop the growth. Thereafter, the outer tube 1 of the closed tube body was returned to room temperature and taken out from the heating furnace.
A and the growth tube 6 are destroyed, and the substrate A on which the epitaxial layer has been grown is taken out to complete the entire operation.

In epitaxial growth using this method, the substrate A and the raw material B or solution B1 are always inside the growth tube 6 and do not come into contact with the carbon film 5 deposited on the inner surface of the outer tube 1a. There is no adhesion of fine powder of the carbon film 5 to the substrate A as in the illustrated method, and the occurrence of pinhole-like defects caused by this can be prevented. However, since the removal of oxygen in the growth tube 6 by the carbon film 5 functions through the window 61, the removal is extremely excellent when a reducing gas and carbon are used in combination, which is desirable for the manufacture of semiconductor devices. It becomes possible to obtain an epitaxial layer with high purity and few defects.

According to the present method, the inventor of the present application uses a growth tube 6 with an inner diameter of about 25 mmφ and an outer tube 1a with an outer diameter of about 35 mmφ coated with a carbon film 5 with a thickness of about 1 μm, and uses a replacement gas 3a.
An epitaxial layer of Hg _{1-X Cd} The carrier concentration was reduced by about one order of magnitude compared to when hydrogen was used as 3, and an epitaxial layer without defects could be obtained.

(g) Effects of the Invention As explained above, according to the structure of the present invention, a substrate on which an epitaxial layer is to be formed and a solution for growing the epitaxial layer are put into a closed tube to perform liquid phase epitaxial growth. It is possible to provide a method for manufacturing a semiconductor device in which a reducing gas and carbon are used together to remove oxygen in the closed tube, and in which generation of defects in the epitaxial layer due to the carbon is suppressed. This has the effect of making it possible to manufacture a semiconductor device using an epitaxial layer with high purity and few defects.

[Brief explanation of the drawing]

FIG. 1 is a front sectional view a of a closed tube body showing an example of a conventional closed tube liquid phase epitaxial growth method, and FIG. 2 is a front sectional view a of a closed tube body showing another embodiment. 3 is a front cross-sectional view (a) and a side cross-sectional view (b) of a closed tube body showing an embodiment of the closed tube liquid phase epitaxial growth method according to the present invention. In the drawings, 1 and 1a are outer tubes, 2 is inner tubes,
3 and 3a are replacement gases, 4 is a rod, 5 is a carbon film, 6 is a growth tube, 61 is a window, A is a substrate, B is a raw material, and B1 is a solution, respectively.

Claims (1)

[Claims] 1. A substrate for forming an epitaxial layer and a solution for growing the epitaxial layer are placed in a tube having a ventilation window, the tube is placed in a closed tube whose inner surface is coated with carbon, and a reducing agent is placed inside the closed tube. The method includes a step of introducing a gas, rotating or tilting the tube within a range where the carbon does not come into contact with the substrate and the solution, coating the surface of the substrate with the solution, and performing liquid phase epitaxial growth. A method for manufacturing a semiconductor device.