JPH01242483A - Liquid phase epitaxy method - Google Patents

Abstract

PURPOSE:To stabilize and improve the compsn. ratio over the entire surface of a grown crystal film by housing a raw material melt into a hollow cylinder which is mounted with a substrate at one longitudinal end of a rectangular box body vessel having a specific structure and is glidably installed with a bottom end face and inclining and oscillating the vessel to stir the melt then to bring the melt into contact with the substrate. CONSTITUTION:The growth vessel 1 which is the rectangular box body consisting of high-purity carbon is constituted by forming a recess 2 to the part near one longitudinal end of the flat inside base thereof, installing the substrate 3 consisting of, for example, CdTe, thereto and installing the cylinder which has the outside diameter smaller than the min. spacing between the inside walls of said vessel and is formed glidably with the aperture bottom end face to the base. In addition, the vessel is so constituted that the vessel can incline around the longitudinal axis and can oscillate around the axis orthogonal with said direction. This vessel is then installed in an electric furnace and a raw material 5 for crystal growth such as, for example, HgCdTe, is housed into the cylinder 4. After the raw material is melted by heating, the vessel 1 is inclined and oscillated to glide the cylinder 4 back and forth within the range where the cylinder does not touch the the substrate 3 from one end on the side where there is no substrate 3 in the longitudinal direction to stir the raw material melt 5: thereafter, the cylinder is moved to above the substrate 3 to bring the melt 5 into contact with the substrate. The crystal film is thus formed by liquid epitaxy.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a liquid phase epitaxial growth method in which a growth substrate is brought into contact with a supersaturated raw material melt to precipitate crystals to grow a single crystal thin film on the substrate. In particular, the present invention relates to a liquid phase epitaxial growth method in which crystal growth is performed by a tilting method.

[Prior Art] To apply semiconductors to devices, a thin film-like single crystal with a large area is required. One of the methods used to form such a semiconductor single crystal film is a liquid phase epitaxial growth method. The desired single crystal is Hg1-
In the case of xcdx Te, cadmium telluride (C
dTe ) formed on a substrate.

In this case, since the vapor pressure of Hg is high, most of the growth occurs in the sealed tube.

FIG. 4 is a longitudinal sectional view showing a conventional liquid phase epitaxial growth apparatus using a tilting method. In the figure, the device is a growth tank (hereinafter referred to as a carbon boat) made from a high-purity carbon block.

The inclined part 42 of the carbon boat 41 is provided with a recess 43 for installing a substrate, and cadmium telluride (
A growth substrate 44 for CdTe) is installed, and a raw material 46 is accommodated in the horizontal portion 45. The carbon boat 41 is vacuum sealed in a sealed tube (not shown) made of quartz. This quartz sealed tube is installed in a heating electric furnace (not shown),
The heating electric furnace is made rotatable in advance about an axis perpendicular to the longitudinal direction, so that the sealed tube together with the electric furnace can be swung as shown by the arrow in the figure. After the quartz sealed tube is thus installed in the furnace, the raw material 46 is completely melted by heating it. At this time, the carbon boat 41 is fixed horizontally or so that the inclined portion 42 side is higher so that the raw material 46 does not come into contact with the substrate 44. After the raw material 46 is sufficiently melted, the entire electric furnace is rotated so that the inclined part 42 is in a horizontal state so that the raw material 46 sufficiently covers and contacts the substrate 44 as shown by the dotted line in the figure. . Then, the temperature is gradually lowered, and the substrate 4
A crystal of Hg1-x CdxTe is grown on 4. After the required film thickness (q) is achieved by moderately lowering the temperature, the electric furnace is rotated again to return to the initial state, and the raw material melt 46 and the substrate 4 are heated.
4 and stop the growth.

[Problems to be Solved by the Invention] However, the above conventional method has the following problems. That is, although stirring cannot be performed when melting the raw materials for crystal growth, the raw materials HCI, Cd, T
Since there is a difference in specific gravity between the two materials e, if stirring is not performed, a gradient in the composition ratio, so-called compositional unevenness, will occur in the melt, and this will result in compositional unevenness in the growing crystal. Is it possible to consider a method of moving the entire electric furnace within a small angle range in order to stir it? In that case, there is a risk that the raw materials will touch the substrate and partially melt it, or that it will overflow outside the carbon boat. There is.

Also, due to the small angle, sufficient stirring cannot be expected.

The present invention was devised in view of these problems, and it is possible to solve the inclination and non-uniformity of the composition ratio in the raw material melt, which has conventionally been an obstacle to obtaining a good quality and uniform epitaxially grown film. The object of the present invention is to provide a liquid phase epitaxial growth method in which a high quality and uniform epitaxially grown film is obtained by homogenizing the melt by removing and actively stirring and mixing.

[Means for Solving the Problems] The present invention relates to a liquid phase epitaxial growth method in which a raw material melt is brought into contact with a substrate and crystals are precipitated on the substrate to grow a single crystal thin film. As shown in the figure, which also serves as an example and shows the basic configuration, a rectangular box-like container is arranged in an electric furnace so that it can be tilted around a longitudinal axis and can be rocked around an axis perpendicular to the longitudinal axis. 1, a substrate 3 attached to a bottom recess 2 at one end in the longitudinal direction of the container 1, and a hollow cylinder 4 installed on the bottom surface of the container 1 so as to be able to slide on the opened bottom end surface. The raw material melt 5 is stored in a cylinder, and the raw material melt is first slid back and forth from one end of the longitudinal direction of the container 1 on the side without the substrate by tilting and swinging motions without touching the substrate 3. This is a liquid phase epitaxial growth method characterized by stirring the liquid 5 and then moving the cylinder 4 to a range where it touches the substrate, thereby bringing the raw material melt 5 into contact with the substrate 3 to perform crystal growth.

[Function] The present invention is configured to sufficiently stir and mix the raw materials for growth, which was incomplete in the prior art, and then perform crystal growth. Below, regarding the effects of the present invention,
This will be explained using FIG.

Each figure in FIG. 3 shows the method of the present invention viewed from above, in which a cylinder 4 with an open bottom is installed in a growth container 1;
A growth material 5 is housed in this cylinder 4, and the growth container 1 is installed in an electric furnace (not shown) that can swing around a short axis perpendicular to the longitudinal direction. During this installation, rotate the growth container 1 by 10° to 2° around the long sleeve in the longitudinal direction of the container.
Install it at a 0° angle. Initially, as shown in Figure 3(a),
The cylinder 4 is located at the end of the side without the growth substrate 3, or
This is achieved by rotating the electric furnace about 30 degrees around the short axis so that the substrate 3 side is raised.

Next, when the temperature of the electric furnace is increased and the growth raw material 5 is melted,
The electric furnace is rocked so that the growth container 1 seesaws around the short axis. The angle limit of this swing is shown in Figure 3 (b).
The range indicated by the arrow, that is, the range where the cylinder 4 does not touch the substrate 3 is defined as the range in which the cylinder 4 can reciprocate. Growth container 1
Since the cylinder 4 is installed tilted around its long axis, the cylinder 4 always rolls without slipping due to friction with the inner wall of the container. Therefore, by repeating this swinging motion, the raw material 5 in the cylinder is forcibly stirred and mixed.

After sufficient mixing has been performed, the cylinder 4, ie, the growth material 5, is finally placed on the substrate 3 as shown in FIG. 3(C). When this state is reached, slow cooling for crystal growth is started, and crystal growth is performed for a predetermined period of time.

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

FIG. 1 is a vertical cross-sectional view showing an embodiment of a liquid phase epitaxial growth apparatus which also serves as the basic structure of the present invention, and FIG.
FIG.

In FIG. 1, 1 is a growth container made of high-purity carbon. The internal bottom surface is flat, and a recess 2 in which a substrate 3 is placed is formed near one end in the longitudinal direction. Inside the growth container 1, there is a cylinder 4 having an outer diameter smaller than the minimum distance between its inner walls.
can be installed. This cylinder 4 accommodates an HgCdTe raw material 5 for crystal growth.

Next, the procedure of the epitaxial crystal growth method using the above apparatus will be explained.

First, a substrate 3 made of CdTe is placed in a recess 2 of a growth container 1, and a HqCdTe raw material 5 for crystal growth is placed in a cylinder 4. This is placed in a quartz sealed tube (not shown), sealed under vacuum, and this sealed tube is placed in a horizontal electric furnace that can swing like a seesaw around the swing shaft 6 shown in FIG. . At this time, as shown in FIG.
Install it so that it is tilted 20'. Thereby, when the cylinder 4 slides inside the container 1, it can be reliably rotated by friction with the inner wall of the cylinder 4.

Initially, in order to position the cylinder 4 at the end of the container in the longitudinal direction on the side where the substrate 3 is not present, the cylinder 4 is rotated about 30' around the swing axis 6 so that the substrate 3 side is higher.

Next, the temperature of the electric furnace is raised, and when the raw material 5 is melted, the electric furnace is swung around the oscillation shaft 6 as shown by the arrow in the figure.
The cylinder 4 is moved reciprocally within the container 1 within the range where the melt 5 and the substrate 3 do not come in contact with each other, by shifting against the side wall surface and sliding against the bottom surface. This allows the melt to be stirred and mixed to be homogenized.

After that, the melt temperature is lowered to the set temperature for starting growth,
The electric furnace is tilted so that one end of the substrate 3 is lowered, and thereby the cylinder 4 is rolled and slid to a position where the substrate 3 is located, and the raw material melt 5 and the substrate 3 are brought into contact. Then, by lowering the temperature, Hg1-x is formed on the substrate 3.
A CdxTe epitaxial film was grown.

After growing to a predetermined thickness, the electric furnace is rotated again to tilt it back to its original state, and the cylinder 4 is rotated and slid to separate the substrate 3 and the melt 5. At this time, the lower end surface of the cylinder 4 acts as a wiper, and all excess melt is removed without remaining on the substrate, resulting in a good surface condition of the grown 1-x CdxTe film. .

When the uniformity of the composition of the grown (g1-x Cdx) film surface was examined using a Fourier transform infrared spectrometer, it was found that uniformity superior to that of the conventional method could be obtained with good reproducibility.

[Effect of the invention] As described above, according to the present invention, stirring and
It is an object of the present invention to provide a liquid phase epitaxial growth method in which sufficient mixing is performed, the unevenness of the composition ratio is extremely reduced, the composition ratio is stable over the entire surface of the grown crystal film, and an epitaxially grown film having a good surface condition can be obtained. can.

[Brief explanation of the drawing]

1 and 2 are vertical cross-sectional views showing an example of a liquid phase epitaxial growth apparatus used in the method of the present invention which also serves as the basic structure of the present invention, FIG. 3 is a detailed explanatory diagram of the present invention, and FIG. 4 is a FIG. 2 is a longitudinal sectional view of a conventional liquid phase epitaxial device. 1... Container 2, 43... Recessed portion 3.4
4... Substrate 4... Cylinder 5, 46... Raw material 6... Swing shaft 41... Carbon boat 42... Inclined part 45... Horizontal part

Claims (1)

[Claims] (1) In the liquid phase epitaxial growth method, in which a raw material melt is brought into contact with a substrate and crystals are precipitated on the substrate to grow a single crystal thin film, it is possible to tilt around a longitudinal axis and to rotate around an axis perpendicular to the longitudinal axis. A rectangular box-like container is swingably disposed in an electric furnace, a substrate is attached to a bottom concave portion at one longitudinal end of the container, and a bottom surface of the container is slidably mounted on an open bottom end surface. and a hollow cylinder installed in the cylinder, the raw material melt is accommodated in the cylinder, and the tilting movement and the swinging movement
First, the raw material melt is stirred by sliding the cylinder back and forth from one end of the longitudinal direction of the container without the substrate within a range that does not touch the substrate, and then the raw material melt is stirred by moving the cylinder to the range where it touches the substrate. A liquid phase epitaxial growth method characterized in that crystal growth is performed in contact with the substrate.