JPH0476204B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a method and apparatus for liquid phase epitaxial growth of compound semiconductor mixed crystals.

(b) Technical background Compound semiconductor crystals containing mercury (Hg), such as mercury-cadmium-tellurium (Hg _1-x Cd _x Te), have a narrow energy gap and are suitable for photoelectric conversion elements such as infrared detection elements. It is used as a forming material.

Liquid phase epitaxial growth is a method for forming such Hg _1-x Cd _x Te crystals in a large area and in a thin layer for convenient device formation.

Epitaxial crystals of Hg _1-x Cd _x Te are usually grown using a liquid phase epitaxial method such as the Tipping method in which epitaxial growth is performed by tilting a quartz ampoule, or the so-called boat slide method using a carbon slide boat. By the growth method,
For example, it is formed as a crystal layer on a crystal substrate of cadmium foruride (CdTe).

Crystals obtained by these methods govern the characteristics and reliability of semiconductor light emitting and light receiving devices, and are therefore required to have a stable composition and a reduction in defects.

(c) Conventional technology and problems Figure 1 shows the boat slide method, which is widely used as an LPE method for compound semiconductors.

In the figure, 1 is a fixed part and 2 is a sliding part, both of which are made of carbon. The fixed part is provided with recesses 3 and 4, and the sliding part is provided with a hole 5. A substrate crystal 6 is housed in the cavity 3, and a source wafer (solute source crystal) 7 is housed in the cavity 4.
Epitaxial crystal growth is performed on the substrate crystal 6.

First, in FIG. 1a, crystal components are put into the holes 5 of the slide part at a predetermined ratio and left at a predetermined temperature for a predetermined time to obtain a melt (solution) 8 in which a certain component is unsaturated.

Next, in FIG. 1b, the slide section is moved to guide the unsaturated melt 8 onto the source wafer 7 and bring it into contact with it, and hold it at a predetermined temperature for a predetermined time. During this time, the unsaturated components are dissolved from the source wafer 7 into the unsaturated melt 8 to become a saturated melt 8A. Conversely, when the melt is supersaturated, the supersaturated components are
The melt is deposited on the wafer 7 and becomes saturated to become an equilibrium solution.

Next, in FIG. 1c, the slide portion is further moved to bring the saturated melt 8A into contact with the substrate crystal 6 and hold it at a predetermined temperature for a predetermined time.

In this way, an epitaxial crystal having a desired composition and thickness can be grown on the substrate crystal 6 by controlling the melt components, holding temperature, and time.

Figure 2 shows a conventional example of the taping type LPE method.
A cross section perpendicular to the quartz tube of the crystal growth apparatus is shown. In the figure, the same numbers as in FIG. 1 indicate the same objects, 21 indicates a quartz tube, and 22 indicates a holding plate for a substrate crystal made of quartz.

In FIG. 2a, a substrate crystal 6 and a source wafer 7 are held on both sides of a holding plate 22, the holding plate is held horizontally, and an unsaturated melt 8 is placed on the underside of the holding plate at a predetermined temperature. Hold for a predetermined time.

Next, in FIG. 2b, when the quartz tube 21 is rotated to the right from the state shown in FIG. Hold for a specified period of time. During this time, the unsaturated melt 8 reaches an equilibrium state as explained in FIG. 1, and a saturated melt 8A is obtained.

Next, in FIG. 2c, the quartz tube 21 is rotated to the left from the state shown in FIG. conduct. The epitaxial crystal layer is maintained at a predetermined temperature for a predetermined time and cooled at a predetermined cooling rate to obtain an epitaxial crystal layer having a predetermined composition and thickness.

In the conventional method described above, even when the substrate crystal 6 and the source wafer 7 are the same crystal, two crystals must be prepared. During growth, a quartz tube 2 was used to prevent evaporation of crystal components.
Consideration must be given to reducing the free space within the quartz tube, and it is better to make the configuration within the quartz tube as simple as possible.

(d) Purpose of the Invention The purpose of the present invention is to eliminate the above drawbacks of the prior art, and to maintain the melt in an equilibrium state by using the back side of the substrate crystal as a source wafer without preparing a separate source wafer. An object of the present invention is to provide a liquid phase epitaxial crystal growth method and apparatus that allow stable growth.

(e) Structure of the Invention According to the present invention, the above object is achieved by: 1. When growing a crystal on a substrate crystal by a liquid phase epitaxial method, the back surface of the substrate crystal is brought into contact with an unsaturated melt in advance, and the unsaturated melt is grown on the substrate crystal. 1. A liquid phase epitaxial crystal growth method comprising the steps of: saturating a saturated melt; and then bringing the saturated melt into contact with the substrate surface to lower the temperature and grow crystals on the substrate surface.

2. In a liquid phase epitaxial crystal growth apparatus that deposits crystals on a substrate crystal from a saturated melt,
A substrate holding plate that separates a melt holding container having a horizontal rotational axis into two chambers parallel to the rotational axis; and a substrate holding plate having a hole formed in the substrate holding plate and having a front and a back surface of the substrate crystal respectively separated into two chambers; A through hole is provided in the substrate crystal holding plate to hold the substrate plate crystal so as to be exposed to the melt, and when the melt holding container rotates about the rotation axis, the melt is transferred between the two chambers. What is claimed is: 1. A liquid phase epitaxial crystal growth apparatus, characterized in that it has an opening so that the liquid phase epitaxial crystal growth apparatus can be moved.

This is achieved by providing

The present invention combines a substrate crystal on which an epitaxial crystal is to be grown and a source material used to saturate the melt and reach an equilibrium state.
This method can be applied when the wafers are of the same crystal, and aims to achieve stable growth by saving the number of crystal substrates used and by simplifying the internal structure of the crystal growth apparatus.

(f) Embodiment of the Invention Fig. 3 is an actual diagram of a holding plate showing an embodiment of the present invention, and Fig. 4 shows an example in which this holding plate is applied to a closed-tube tapering liquid phase epitaxial crystal growth method. . In the figure, the same numbers as in the previous figure indicate the same objects.

In FIG. 3, 31 is a substrate crystal holding plate according to the present invention, 32 is a recess for accommodating the substrate crystal, and 33
indicates a through hole through which the back surface of the substrate crystal 6 housed is exposed.

In Fig. 4a, CdTe6 as a substrate crystal is held on the lower surface by a holding plate 32, keeping the holding plate horizontal, and unsaturated melt (Hg _1-y Cd _y ) ₁ is separated from the holding plate and placed below it. _-z Te _z (y=0.8, z=0.1)8
Hold at 500℃ for 60 minutes.

Next, in FIG. 4b, when the quartz tube 21 is rotated to the right from the state shown in FIG. 4a so that the holding plate 32 stands vertically from the bottom, the melt 8 contacts the back surface of the CdTe substrate crystal 6 Hold at 500℃ for 60 minutes. During this time, the unsaturated melt 8 reaches an equilibrium state as explained in FIG. 1, and a saturated melt 8A is obtained.

Next, in FIG. 4c, the quartz tube 21 is rotated to the left from the state shown in FIG. 4b to make the holding plate 32 horizontal, and the substrate crystal 6 is brought into contact with the melt 8A to cause epitaxial growth on the substrate crystal 6. conduct. 60 at 500℃
Cool for 100 minutes at a cooling rate of 0.05°C/min. A 10 μm thick epitaxial crystal layer having the desired composition Hg _1-x Cd _x Te (x=0.3) is obtained.

(g) Effects of the Invention As explained in detail above, according to the present invention, by using the back side of the substrate crystal as a source wafer, the melt can be kept in an equilibrium state and stabilized without preparing a separate source wafer. It is possible to provide a liquid phase epitaxial crystal growth method and apparatus that can perform growth.

[Brief explanation of the drawing]

1 and 2 are conventional liquid phase epitaxial crystal growth methods, FIG. 3 is an actual diagram of a substrate crystal holding plate according to the present invention, and FIG. 4 is a liquid phase epitaxial crystal growth method according to the present invention. shows. In the figure, 1 is a fixed part, 2 is a sliding part, 3,
4 is a depression, 5 is a hole, 6 is a substrate crystal, 7 is a source wafer, 8 is an unsaturated melt, 8A is a saturated melt, 21 is a quartz tube, 22 and 31 are substrate crystal holding plates, 32 is a depression, 33 is a A through hole is shown.

Claims (1)

[Scope of Claims] 1. When growing a crystal on a substrate crystal by liquid phase epitaxial method, a step of bringing the back surface of the substrate crystal into contact with an unsaturated melt in advance to saturate the unsaturated melt; 1. A liquid phase epitaxial crystal growth method comprising the step of bringing a saturated melt into contact with the substrate surface to lower the temperature and growing a crystal on the substrate surface. 2. In a liquid phase epitaxial crystal growth apparatus for depositing crystals on a substrate crystal from a saturated melt, a melt holding container having a horizontal rotational axis is separated into two chambers by a substrate holding plate that separates the sample container into two chambers parallel to the rotational axis. , a through hole formed in the substrate holding plate and holding the substrate crystal so that the front and back surfaces of the substrate crystal are exposed to the two chambers, respectively; and a through hole provided in the substrate crystal holding plate and holding the melt holding container. A liquid phase epitaxial crystal growth apparatus characterized in that the liquid phase epitaxial crystal growth apparatus has an opening so that the melt can be moved between the two chambers by rotating around the rotation axis.