JPS621358B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of performing liquid phase epitaxial growth using an atmosphere separating material between a growth melt and its atmosphere.

The liquid phase epitaxial growth method is particularly often applied to the crystal growth of compound semiconductors, and the characteristics of devices made using crystals obtained using this method are generally similar to those of devices made using so-called bulk crystals made by the melting method. Better. Regarding conventional liquid phase epitaxial growth methods, the tilting method among them will first be explained in detail. For convenience of explanation, a GaAs epitaxial growth method will be explained as an example.

FIGS. 1a and 1b are schematic cross-sectional views of a conventional epitaxial growth apparatus. In FIG. 1, 1 is a growth melt, 2 is a GaAs substrate, 3 is a port, 4 is a transparent quartz tube, and 5 is an electric furnace. In FIG. 1, the electric furnace control system, gas piping system, electric furnace tilting mechanism, etc. are omitted. Liquid phase epitaxial growth of GaAs is performed by the method described below. A mirror-finished GaAs substrate 2 from which the processing layer has been removed by pretreatment is used, and a predetermined amount of Ga is added to the substrate so that it becomes a saturated melt at the growth starting temperature.
A growth melt 1 made of GaAs is placed in a boat 3 made of high-purity glassy carbon that has been treated in advance and set as shown in FIG. 1a. High purity hydrogen gas is already flowing through the quartz tube 4, and the electric furnace 5 is also heated to a predetermined temperature. Therefore, the boat 3 containing the growth melt 1 and the GaAs substrate 2 is heated in high purity hydrogen to reach a predetermined temperature. At this time As
A saturated Ga melt is formed and the GaAs substrate 2 is formed.
Arsenic evaporates from the surface and is carried away to the cooler parts. When the predetermined temperature is reached, the electric furnace 5 is tilted so that its slope is opposite to that shown in FIG. 1a, as shown in FIG. 1b. By this operation, the growth melt 1 comes into contact with the GaAs substrate 2, as shown in FIG. 1b. Thereafter, the temperature is raised from several degrees to about 10 degrees, and the surface of the GaAs substrate 2 is etched with the growth melt 1. After etching the GaAs substrate surface by a desired amount, the temperature of the electric furnace 5 is lowered. At this time
GaAs is epitaxially grown on the crystal of GaAs substrate 2. When the desired growth layer thickness is obtained, the electric furnace 5 is tilted again to its original state, that is, the state shown in FIG.
The GaAs epitaxial wafer is separated. After the boat 3 is cooled in a low-temperature part, it is taken out of the quartz tube 4. The method described above is useful for growing only a single epitaxial growth layer on a substrate.

In order to obtain two or more epitaxially grown layers, a slide boat 3' as shown in FIG. 2 is used. In this case, there is no need to tilt the electric furnace 5 as explained in FIG. A case in which two epitaxially grown layers are formed on the GaAs substrate 2, for example, as shown in the cross section of FIG. 3, will be briefly described. In Figure 3, 2 is a GaAs substrate, 6 is a p-type GaAs
The epitaxial growth layer 7 is an n-type GaAs epitaxial growth layer.

When growing an epitaxial wafer having the cross-sectional structure shown in FIG. 3, a pretreated GaAs substrate 2 and a growth melt 1, 1' are first set in a slide boat 3' as shown in FIG. At this time, the growth melt 1 has Ga added with a predetermined amount of GaAs and a p-type impurity, and the growth melt 1' has Ga added with a desired amount of GaAs and an n-type impurity. A slide board 3' on which a GaAs substrate 2 and a growth melt 1 are set is heated in high-purity hydrogen gas. When heated to a predetermined temperature, the growth melt 1 is brought into contact with the GaAs substrate 2. When the temperature is lowered, the p-type is formed on the GaAs substrate 2.
GaAs grows. When the desired growth layer is obtained, the growth melt 1 in contact with the GaAs substrate 2 is removed, and the growth melt 1' is brought into contact with the GaAs substrate 2. this is
This is carried out by relatively moving the GaAs substrate 2 and the growth melt 1'. After this, by continuing to lower the temperature, the n-type GaAs is grown from the growth melt 1'.
precipitates and grows epitaxially. When the desired growth layer thickness is obtained, the growth melt 1' is separated, cooled to room temperature, and then the grown crystal is taken out.

The above-mentioned GaAs growth temperature is carried out at a high temperature of 500°C to 1000°C. Further, liquid phase epitaxial growth of compound semiconductor crystals is generally performed in a high purity hydrogen gas atmosphere as described above. For this reason, elements that easily evaporate in the compound semiconductor crystal, such as As in GaAs, P in GaP, and P in InP, evaporate while the temperature rises to a predetermined temperature, and the substrate crystal is thermally corroded. Since the surface of the substrate is subject to thermal corrosion, methods are used to reduce this by placing a cover on the substrate or introducing an element that easily evaporates into the atmosphere. Furthermore, before crystal growth, a melt is provided to etch away the substrate crystal surface.

The present invention provides a method for performing liquid phase epitaxial growth without using such a method and without using a high-purity hydrogen gas atmosphere. This invention will be explained below.

An embodiment of this invention will be explained using FIGS. 4, 5, and 6. The crystal growth of InSb among compound semiconductor crystals will be explained below as an example. 4th, 5th, 6th
The figure is a schematic cross-sectional view of an epitaxial growth apparatus according to an embodiment of the present invention, in which liquid phase epitaxial growth is carried out in the order shown in FIGS. 4-6.

In Figure 4, 10 is a boat, 11, 12, 13,
14 is a slide member; 15, 16, 17 are through holes formed in the slide members 11, 12, 13, respectively; 18, 19, 20, 21, 22 are containers, with through holes 23, 24, 25, 26, respectively. ,2
It has 7. 28, 29, 30, 31, and 32 are growth material chambers, 33, 34, and 35 are atmosphere separation materials whose specific gravity is lighter than that of the growth melt, and 36, 37.
38 is a growth melt, 38 is a substrate crystal, and 39 is an atmosphere separation material preliminary chamber. The same reference numerals in Figures 5 and 6 are number 4.
Shows the same or equivalent parts as in the figure.

Next, the process of actually performing liquid phase epitaxial growth will be explained with reference to these figures.

First, as shown in FIG. 4, the growth material chamber 29
An InSb substrate crystal 38 from which processing strain has been removed is placed in a container 19, and then an atmosphere separation material 34 is placed therein. Next, a growth melt 36 in which a predetermined amount of InSb and a p-type impurity are added to In is put into the container 18 of the growth material chamber 28, and then an atmosphere separating material 33 is put therein.
Similarly, a growth melt 37 in which a predetermined amount of InSb and n-type impurities are added to In is placed in the container 2 of the growth material chamber 31.
After that, the atmosphere separating material 35 is added. The boat set up in this way is heated to 250℃.
When the temperature reaches 250°C, InSb and impurities dissolve and become an In melt, the slide member 13 is moved to align the conduction hole 16 of the slide member 13 with the conduction hole 24 of the container 19, thereby reducing the atmosphere inside the container 19. The separation material 34 is transferred to the growth material chamber 30. Then slide member 1
Return 3 to its original position. Next, move the slide member 11 and move the slide member 11 in the same manner as described above.
The through hole 15 of No. 1 is aligned with the through hole 23 of the container 18, the growth melt 36 and the atmosphere separation material 33 in the container are transferred to the container 19, and the slide member 11 is returned to its original position. A schematic cross-sectional view at this time is shown in FIG.

At this time, the substrate crystal 38 comes into contact with the In melt for growth. Immediately gradually cool the temperature from 250℃. During slow cooling, p-type InSb grows epitaxially on the InSb substrate crystal. When the desired growth layer thickness is obtained, the slow cooling is stopped and the temperature is maintained at a constant temperature, and the slide member 14
5 to move the container 19 to the right end in FIG. Thereafter, the conduction hole 16 of the slide member 13 is aligned with the conduction hole 24 of the moved container 19, and the growth melt 36 and atmosphere separation material 33 in the container are moved to the lower container 22 in the figure. Next, the slide member 13 is returned to its original position. Immediately, the conduction hole 17 of another slide member 12 is aligned with the conduction hole 26 of the container 21 containing the In melt for growth, and the growth melt 37 is brought into contact with the InSb substrate crystal. An atmosphere separation material 35 is placed on top of the growth melt 37. After that, the slide member 12 is returned to its original position. A schematic cross-sectional view at this time is shown in FIG.

When the layer is slowly cooled in the state shown in FIG. 6, n-type InSb is epitaxially grown on the p-type InSb growth layer. When the desired growth layer thickness is obtained, slide member 1 is moved again.
3 to open the conduction hole 1 of the slide member 13.
6 is the through hole 2 of the container 19 containing the growth melt.
Separate the growth melt and the growth crystal in accordance with step 4. The growth melt and atmosphere separation material exceeding the volume of the container 22 accumulate in the preliminary chamber 39. The entire process of liquid phase epitaxial growth is completed by cooling to room temperature and taking out the grown crystal.

As described in detail above, according to the present invention, both the growth melt and the substrate are covered with an atmosphere separating material before epitaxial growth. Therefore, even after the growth melt and the growing crystal are separated and while they are being cooled to room temperature, the surface of the growing crystal is covered with the atmosphere separation material, and the growing crystal is protected. As an atmosphere separating material according to this invention, the temperature
If the temperature is lower than about 350°C, stearic acid or the like is used. Boats can also be made from high-purity glassy carbon. Therefore, if a boat is made of high-purity carbon that is not airtight with the atmosphere, the influence of the atmosphere can be easily avoided by adding a container that can be completely surrounded by an atmosphere separating material. As described above, according to the present invention, a high-quality thin film growth layer can be easily obtained without using high-purity gas, while preventing thermal corrosion of the substrate crystal. Further, according to the present invention, it is possible to apply it to other materials by selecting the atmosphere separating material, and it is also easy to sequentially grow a desired number of growth layers on a large number of substrates by changing the boat structure. This provides advantages such as the ability to perform

[Brief explanation of the drawing]

Fig. 1 is a schematic cross-sectional view of a liquid phase epitaxial growth apparatus using a conventional tilt method, and Fig. 2 is a schematic cross-sectional view of a conventional liquid phase epitaxial growth apparatus using a slide boat.
FIG. 3 is a schematic cross-sectional view of two layers grown on a substrate, and FIGS. 4, 5, and 6 are schematic cross-sectional views of a liquid phase epitaxial growth apparatus used in an embodiment of the present invention. In the figure, 10 is a boat, 11, 12, 13, 14
1 is a slide member, 15, 16, 17 are conduction holes, 1
8, 19, 20, 21, 22 are containers, 23, 2
4, 25, 26, 27 are conduction holes, 28, 29, 3
0, 31, 32 are growth material chambers, 33, 34, 3
5 is an atmosphere separation material, 36 and 37 are growth melts, 3
Reference numeral 8 indicates a substrate crystal, and reference numeral 39 indicates an atmosphere separation material preliminary chamber.

Claims (1)

[Claims] 1. In liquid phase epitaxial growth, a desired growth melt is covered with an atmosphere separation material having a lighter specific gravity than the growth melt, which separates the growth melt from the atmosphere, and the substrate is immersed in the atmosphere separation material. a step of bringing the growth melt into contact with a substrate to grow a desired crystal on the substrate; and a step of making the growth melt and the substrate on which the crystal has grown subsequent to this step; A method for liquid phase epitaxial growth, comprising the step of separating.