JPH01242484A - Crystal growth method by liquid epitaxy - Google Patents

Abstract

PURPOSE:To stabilize and improve the compsn. ratio over the entire surface of a grown crystal film by mounting a substrate to the prescribed position of a rectangular box body vessel having a specific constructure, housing a raw material melt into a hollow cylinder installed glidably 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 substrate 2 consisting of, for example, CdTe, etc., is installed in a recess 3 provided at one end of the growth vessel 1 which consists of high-purity carbon and has zigzag inside walls and a flat base. The hollow cylinder 4 formed glidably with the aperture bottom end face is imposed on the base of the vessel. In addition, the vessel is so constituted that the vessel can incline around the longitudinal axis 1 and oscillate around the axis orthogonal with the direction thereof. This vessel 1 is then installed in an electric furnace and the raw material 5 for crystal growth such as, for example, HgCdTe, is housed into the cylinder 4. After the material is melted by heating, the vessel 1 is inclined and oscillated to glide the cylinder 4 back and forth in the range (A-B) of a detaining part 6 from one end in the inside wall in the longitudinal direction of the vessel 1 to stir the raw material melt 5; thereafter, the vessel is further inclined and oscillated so as to be moved (B C D), by which the melt 5 is brought into contact with the substrate 3 to grow the crystal film by liquid epitaxy on the substrate.

Description

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

[Prior Art] To apply a semiconductor as a device, a thin film-like single crystal with a large area is required. A liquid phase epitaxial method is used as one of the methods for forming such a semiconductor single crystal film. The desired single crystal is Hg1
-x When the component is a material with high vapor pressure such as CdxTe, the growth is often in a sealed tube.

FIG. 2 is a longitudinal sectional view showing a conventional liquid phase epitaxial growth apparatus using a tilting method. In the figure, the device is a growing container or main component made from high-purity carbon blocks. A recess 23 for installing a substrate is dug in the inclined part 22 of this growth container 21, and a substrate (for example, CdTe) 24 is installed here, and a growth raw material 26 is accommodated in the horizontal part 25. .

The container 21 is vacuum sealed in a sealed tube (not shown) made of quartz.

This quartz sealed tube is installed in a horizontal electric furnace (not shown),
The electric furnace is necessarily rotatable around an axis perpendicular to the longitudinal direction of the caulking, that is, around a short axis, and the sealed tube together with the electric furnace can be swung as shown by the arrow in the figure. ing. After the quartz sealed tube is installed in the furnace in this way, the growth raw material 26 is completely melted by heating it. At this time, in order to prevent the raw material 26 from coming into contact with the substrate 24, the electric furnace is fixed so that the container 21 is horizontal or the inclined part 22 side is higher. After melting the raw material 26, the electric furnace is rotated around its short axis to melt the inclined part 2.
2 is held horizontally so that the raw material 26 sufficiently covers and contacts the substrate 24 as shown by the dotted line in the figure. Then, the temperature of the electric furnace is gradually lowered, and H! A crystal of 111-xCdxTe is grown. When the required film thickness is obtained by appropriately lowering the temperature, the electric furnace is rotated again to return to the initial state, the raw material melt 26 and the substrate 24 are separated, and the growth is stopped.

[Problems to be Solved by the Invention] However, the above conventional method has the following problems.

In other words, stirring cannot be performed when melting the raw material for crystal growth, but since the raw materials H(], Cd, and Te have different specific gravities, there will be variations in the composition ratio in the melt, so-called composition. This causes unevenness in the composition of the grown crystals.In order to perform stirring, it is possible to oscillate the entire electric furnace within a certain angle, but a sufficient stirring effect cannot be obtained.

The present invention was devised in view of these problems, and aims to eliminate variations in the composition ratio and non-uniformity in the raw material melt, which have traditionally been an obstacle to obtaining a high quality and uniform epitaxial crystal film. The object of the present invention is to provide a liquid phase epitaxial crystal growth method that can homogenize the melt by active stirring and mixing to obtain a high quality and uniform epitaxial crystal film.

[Means for Solving the Problems] The present invention provides a liquid phase epitaxial crystal growth method in which a raw material melt is brought into contact with a substrate and crystals are deposited on the substrate to grow a single crystal thin film. A rectangular box-like container arranged in an electric furnace so as to be tiltable and swingable around an axis perpendicular to the direction thereof, and one end of the container in the longitudinal direction and one end in the direction perpendicular to the longitudinal direction. a substrate attached to the bottom recess, a hollow cylinder installed on the bottom of the container so as to be able to slide on the opened bottom surface, and a hollow cylinder on the side without the substrate in the direction perpendicular to the longitudinal direction of the container. The cylinder is provided with a locking part that prevents contact between the substrate and the cylinder, and the raw material melt is stored in the cylinder, and the substrate is first moved in the longitudinal direction of the container and in the direction perpendicular thereto by tilting and swinging movements. The raw material melt is stirred by sliding the cylinder back and forth from one end of the free side within the range of the locking part, and then the raw material melt is stirred by further tilting and swinging movements to move the cylinder to the range where it touches the substrate. This is a liquid phase epitaxy crystal growth method characterized in that crystal growth is performed by bringing a substrate into contact with the substrate.

[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. 1 shows an example of the method of the present invention viewed from above. Inside the growth container 1, there is a bottom recess 3 at one end in the longitudinal direction of the container and at one end in a direction perpendicular to the longitudinal direction. A substrate 2 is provided. A cylinder 4 with an open bottom is first installed at the end facing the substrate, as shown in FIG. The growth container 1 is installed in an electric furnace (not shown) that can swing in an angular range around a short axis perpendicular to the longitudinal direction. This electric furnace is also rotatable around the long axis in the longitudinal direction of the container, and is installed tilted at a predetermined angle. However, the slope is such that the side where the substrate 2 is placed is higher and the side where the cylinder 4 is placed is lower. 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 container 1 seesaws around the short axis. As a result, the cylinder 4 reciprocates between point A and point B, where the movement is stopped by the locking portion 6, as shown in FIG. 1(b). Since the container 1 is installed tilted around the 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. Furthermore, since the locking portion 6 prevents the cylinder 4 from moving, it does not come into contact with the substrate during this time.

When sufficient mixing has been achieved, the cylinder 4 is finally rotated around the long axis in the opposite direction as shown in Figure 1 (C).
is moved from point B to point 0, and the cylinder 4 is moved from point 0 to point D, that is, above the substrate 2, by roughly rotating around the short axis so that the substrate 2 is lowered. When this state is reached, slow cooling for crystal growth is started, and crystal growth is continued for a predetermined period of time.

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

Figure 1 shows the apparatus and operating procedure for realizing the liquid phase epitaxial growth method according to the present invention, in which (a) is the initial state, (b) is the rocking process, and (C) is the epitaxial crystal growth process. It represents the process. In FIG. 1, reference numeral 1 denotes a growth container made of high-purity carbon and has a meandering inner wall and a flat bottom.

A recess 3 in which the substrate 2 is installed is formed at one end, and a cylinder 4 having an outer diameter smaller than the minimum interval between inner walls can be installed therein. This cylinder 4 accommodates a raw material 5 for crystal growth.

Next, the procedure of the epitaxial crystal growth method using the above apparatus will be explained. First, as shown in FIG. 1(a), a substrate 2 made of CdTe was placed in the recess 3 of a growth container 1, and a crystal growth H (lcdTe raw material 5) was placed in a cylinder 4. (not shown), vacuum-sealed the sealed tube, and installed this sealed tube in a horizontal electric furnace that can swing like a seesaw around the short axis indicated by the dotted line in the figure. It can be rotated within a certain angle range around the long sleeve shown by the chain line, so after installing the sealed tube, rotate it 20 degrees in the direction of the arrow.
I left it at an angle. 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. Next, when the temperature of the electric furnace is raised and the raw material 5 is melted, the cylinder 4 is moved around the short axis of the container 1 as shown by the arrow in FIG. 1(b). It rolls and slides like a seesaw from one end A to a point B where it comes into contact with a locking part 6 formed on the inner wall of the container. The angle range was approximately ±30', and the cycle was 15 times per minute, which continued for 15 minutes. Finally, the cylinder 4 was stopped at position B, and the electric furnace was placed in a horizontal state. As a result, the cylinder 4 is reciprocated in the double circle indicated by the dotted line, between A and B, by repeatedly moving against the side wall surface and sliding against the bottom surface. Through the above operations, the raw material melt was stirred and mixed and was able to be homogenized.

After that, the temperature of the melt was lowered to the growth starting temperature, as shown in Figure 1 (
As shown in C), the electric furnace was rotated around the sleeve in the direction of the arrow and tilted about 20' in the opposite direction from the beginning. This moved the cylinder 4 from position B to position C. Further, the cylinder 4 was rotated about the short axis by about 30 degrees in the direction of the arrow, and the cylinder 4 was moved from the position C to the position D, that is, above the substrate 2. Since the raw material 5 and the substrate 2 came into contact at this stage, the temperature was then lowered to grow a Hg1-x CdxTe epitaxial film. After growing to a predetermined thickness, the electric furnace was rotated in the opposite direction to return the cylinder 4 from position D to position C, and the melt 5 and the substrate 2 were separated. At this time, since the lower end surface of the cylinder 4 acts as a wiper, all excess raw material melt is removed without remaining on the substrate, so that the grown H
(] The surface condition of the 1-xCdxTe film has become better.As a result of examining the uniformity of the composition of this crystal film using a Fourier transform infrared spectrometer, it was found that better uniformity than before can be obtained with good reproducibility. Do you get it.

[Effect of the invention] As explained above, according to the present invention, stirring and
It is possible to provide a liquid phase epitaxial crystal growth method in which mixing is carried out sufficiently, compositional unevenness is extremely reduced, the composition ratio is stable over the entire surface of the crystalline film, and an epitaxial crystalline film having a good surface condition can be obtained.

[Brief explanation of the drawing]

FIG. 1 is an explanatory view showing one embodiment of the method of the present invention, and FIG. 2 is a longitudinal sectional view of a conventional liquid phase epitaxial device.

Claims (1)

[Claims] (1) In the liquid phase epitaxial crystal growth method in which a raw material melt is brought into contact with a substrate and crystals are deposited on the substrate to grow a single crystal thin film, an axis that can be tilted around a longitudinal axis and is perpendicular to that direction. a rectangular box-like container arranged in an electric furnace so as to be able to swing around; a substrate mounted in a bottom recess at one end in the longitudinal direction of the container and in a direction orthogonal to the longitudinal direction; a hollow cylinder installed on the bottom surface of the container so as to be able to slide on the bottom end surface of the container; and a member provided on the side without the substrate in a direction perpendicular to the longitudinal direction of the container to prevent contact between the substrate and the cylinder. The raw material melt is accommodated in the cylinder, and by tilting and swinging movements, the area of the locking part is first moved from one end of the side without the substrate in the longitudinal direction of the container and the direction perpendicular thereto. The raw material melt is stirred by sliding the cylinder back and forth, and then the cylinder is moved to a range where it touches the substrate by further tilting and rocking motions, thereby bringing the raw material melt into contact with the substrate to grow crystals. A liquid phase epitaxial crystal growth method characterized by the following.