JPH0558563B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a liquid phase epitaxial growth apparatus, and particularly to a multilayer epitaxial wafer in which single crystal layers with different conductivity types and compositions are grown on the same substrate. It is related to mass production.

[Prior Art] Generally, epitaxial wafers for compound semiconductor devices such as light emitting diodes (LEDs) and laser diodes (LDs) have a multilayer structure.
In order to obtain this multilayer structure, because it is possible to grow a high quality epitaxial layer,
Liquid phase epitaxial growth is widely used instead of vapor phase epitaxial growth. Among liquid phase growth methods, the slide boat method is particularly used for multilayer growth.

This slide boat method, as shown in Figure 3,
This is one of the typical horizontal furnace methods in which different single crystals are grown on the same substrate by sliding the substrate 2 horizontally under several kinds of solutions 1 together with the holder 3 one after another and bringing them into contact with the solutions. .

However, since this slide boat method is a method in which crystals are grown while keeping the substrate 2 horizontal and sliding the bottom side of each solution reservoir 4, the boat 5 that supports the holder 3 naturally becomes long. However, there is a limit depending on the length of the reactor. Therefore, in this method, at most one crystal growth
Even on a small substrate, only about two sheets could be grown.

By the way, among the liquid phase epitaxial methods, an apparatus has been announced that allows crystal growth on multiple substrates at once by pushing up the solution, although it is a single layer growth method (Japanese Patent Laid-Open No. 196528/1983). Public bulletin). As shown in FIG. 4, this apparatus slides an L-shaped slider 6 in the direction of the arrow in order to perform epitaxial growth, and the slider 6 holds a substrate holding device 7.
While blocking the solution outlet 8 provided on the bottom of the
The saturated solution 10 moving in the direction of the arrow and filling the volume of the chamber 9 is taken into the substrate holding device 7 through the solution introduction port 11 provided on the side surface of the substrate holding device 7. Then, in order to stop the epitaxial growth on the substrate 12 installed vertically in the substrate holding device 7, the L-shaped slider 6 is slid in the direction opposite to the arrow in FIG. The solution outlet 8 at the bottom is opened and the saturated solution 10 is stored in the chamber 9 again. As a result, many large substrates can be grown at once, and since the distance that the slider 6 moves is short, the apparatus can be made shorter and smaller.

[Problems to be Solved by the Invention] However, the technique described in Japanese Patent Application Laid-Open No. 196528/1983 is limited to single layer growth;
When trying to apply this method to multilayer growth by increasing the number of chambers, the following problems occurred.

(1) The slider has an L-shape that enters the room from above the box, so the slide operation part that passes under the previous room can be bent upward, and the slider can be inserted into the next room after securing the sliding distance. Since the tip of the slide must be inserted, it is necessary to provide a large distance between the chambers to ensure the slide distance. As a result, the overall length of the device increases.

Additionally, as the number of rooms increases, the number of sliders must also increase. In that case, the sliders would be required to be arranged in multiple stages in the vertical direction and extended to each chamber with varying lengths, but since most of the operating parts of the sliders are in a free state, these should be arranged in multiple stages to avoid mutual interference. Complicated support means are required to restrain and ensure stable sliding operation.

(2) Since two ports, the solution inlet 11 and the solution outlet 8, must be provided separately in the substrate holding device 7, the structure of the substrate holding device 7 is complicated.

In addition, a front high wall 13 is required as a guide to the box 13 that constitutes the chamber 9 in order to introduce the solution 10 into the solution inlet 11 provided on the side surface of the substrate holding device 7.
a becomes an obstacle when sliding the substrate holding device 7 to come into contact with each solution.

(3) Furthermore, since the number of parts including the main body 14 increases, the device as a whole is complicated.

[Object of the Invention] An object of the present invention is to provide a liquid phase epitaxial growth apparatus that is capable of multilayer epitaxial growth and has a simple structure while employing a method of pushing a solution toward a substrate.

[Summary of the Invention] The liquid phase epitaxial growth apparatus of the present invention, which achieves the above object, has a plurality of elongated main bodies 20 containing a raw material solution 21, as shown in FIGS. 1 and 2 corresponding to the embodiments. The solution reservoirs 24 are formed so as to become deeper in the longitudinal direction, and the pistons 26, which raise and lower the liquid level of the solution 21 by moving heads into and out of each solution reservoir 24, are aligned with each other in accordance with the depth of the solution reservoirs 24. Arrange in multiple stages without interference.

Further, on the main body 20, there are a plurality of substrates 22 inside.
A substrate holder part 23 is slidably provided to hold the substrate upright and have a common solution inlet/outlet 28 at the bottom.
The liquid level on each solution reservoir 24 is sequentially raised and lowered by a piston 26 through the inlet/outlet 28.

As a result, a crystal layer of a predetermined thickness is grown on the substrate by raising the liquid level and bringing it into contact with the substrate, then lowering the liquid level and cutting off contact with the substrate, and then sliding the substrate holder part. By doing this, different crystal layers are grown in multiple layers on a plurality of substrates.

By the way, in the present invention, since the piston is inserted straight into the main body according to the depth of the solution reservoir, there is no need to complicately bend the piston and install it in each solution reservoir. There is no need to increase the distance between the reservoirs. Furthermore, since the piston is inserted into the main body, no complicated support means are required to ensure stable sliding operation. Furthermore, since it has a common solution inlet and outlet,
The substrate holder part is not complicated, and there is no need for a high front wall on the main body side that would impede the sliding of the substrate holder part.

The liquid phase growth of the present invention can be applied to - group compound semiconductors including GaAs, mixed crystal compound semiconductors such as GaAl As, and further to - group compound semiconductors and mixed crystals thereof.

[Example] Hereinafter, the apparatus and working method of the present invention will be explained according to the examples shown in FIGS. 1 and 2.

1 and 2 are a longitudinal sectional view and a transverse sectional view showing a preferred embodiment of the apparatus of the present invention.

Solution storage part 20 as a main body having a diameter and length that can be inserted into a horizontal reactor type reactor (not shown)
In the longitudinal direction, a plurality of solution reservoirs 24 (two in the illustrated example) containing various raw material solutions 21 are formed so as to become deeper one after another. The solution storage section 20 is provided with multiple pistons 26 that move the stored solutions 21 up and down in a manner that corresponds to the solution reservoirs 24 that become deeper in sequence. This piston 26 is the solution reservoir 2
4, and a piston rod 30 that is inserted into a straight insertion passage formed along the longitudinal direction inside the housing part 20 and protrudes from the end of the housing part to independently operate each piston head 25. It is composed of.

A substrate holder section 23 for holding a plurality of substrates 22 upright is provided above the solution storage section 20 through which the piston 26 is inserted, that is, on the solution reservoir opening side. This substrate holder section 23 has four closed sides and an open top and bottom surface, the lower surface of which serves as a common solution inlet/outlet 28, the depth is approximately the same size as the solution reservoir opening, and the width is approximately the same as that of the solution storage section 20. The lower surface of the holder is engaged with an engaging part formed on the upper surface of the accommodating section, so that the holder is slidably and watertightly attached in the longitudinal direction of the accommodating section 20. Therefore, the board holder part 2 is provided on the upper surface of the accommodating part.
There are no obstacles that could impair the slide of 3.

In the illustrated example, the engaging means includes a dovetail structure 4.
0 is adopted, and it comes off at the end of the accommodating part, but it does not come off during the slide, but it is not limited to this example. The substrates 22 held upright in the space within the holder section 23 are set facing each other in order to increase the number of substrates to be processed.

Now, a detailed explanation will be given of the work order when epitaxially growing GaAs for a Schottky barrier diode (SBD) using the liquid phase epitaxial growth apparatus as described above.

In advance, ten 2-inch GaAs wafers were set in the substrate holder part 23, and the first solution reservoir 24 of the storage part 20 contained 500 g of Ga, 50 g of GaAs, and 200 g of Sn, and the second solution reservoir 24 contained 500 g of Ga, 35 g of GaAs, and 10 g of Sn.
Each of the raw materials consisting of
0 and the substrate holder part 23 is engaged. and,
The apparatus with the substrate and raw materials set and engaged in this way is inserted and fixed into a reactor, and the inside of the reactor is replaced with hydrogen gas.

After this replacement, first slide the substrate holder part 23 onto the first solution reservoir 24 to establish communication between the two, and then raise the temperature inside the furnace to the growth temperature of 800°C.
Start slow cooling at a cooling rate of 0.5°C/min. When the temperature drops by 2° C., the first piston 26 provided in the first solution reservoir 24 is pushed out to push the growth solution in the solution reservoir into the substrate holder section 23 through the solution inlet/outlet 28 . This pushing up causes the solution to come into contact with the substrate 22, and single crystal growth on the substrate begins.
This contact state is maintained and growth is continued for 4 minutes.

Next, when the time is up, the first piston is pulled to return the growth solution 21 that had been pushed up into the holder part 23 from the solution inlet/outlet 28 into the first solution reservoir 24, cutting off contact with the substrate 22. Finish growing the first layer.

Subsequently, the substrate holder section 23 is slid and moved onto the second solution reservoir 24 using an operation rod (not shown). Immediately after the movement, the second piston 26 is pushed to push up the growth solution 21 into the substrate holder part 23, and the growth of the second layer is started.

The contact time between the second layer substrate 22 and the growth solution 21 is 5 seconds, and as soon as the time is up, subtract 26.
The growth solution 21 is separated from the substrate 22 .

After completing the above epitaxial growth process, the apparatus is taken out from the reactor. Remove the epitaxial wafer from the substrate holder section 23, set a new substrate that has been previously cleaned in the holder section 23,
This is attached to the solution storage part 20, and all the above steps are repeated again.

Therefore, simply by replacing the wafer on which growth has been completed in the substrate holder section 23 with a new substrate, the next growth can be performed without touching the growth solution. can be reused, keeping raw material costs low.
In addition, if wafers with a large size of 2 inches are grown in two layers, the depth of the substrate holder section 23 can be increased, so it is possible to grow up to about 50 wafers at a time.
Even with multilayer epitaxial wafers of 4 to 5 layers, it is possible to grow up to about 10 wafers by increasing the number of solution reservoirs and pistons within the allowable range of the reactor length.

By this method, it was possible to simultaneously obtain a large number of mirror-finished epitaxial wafers with good reproducibility. In addition, the first layer carrier concentration required for SBD
It was possible to grow an epitaxial wafer having a density of 1.0×10 ¹⁸ cm ⁻³ and a thickness of 2.0 to 2.5 μm, a second layer carrier concentration of 1.5×10 ¹⁷ cm ⁻³ , and a thickness of 0.4 to 0.6 μm. especially,
Since the present invention employs a method of pushing up the solution, it is possible to precisely control the contact time with the substrate, making it possible to grow from an extremely thin layer of about 0.3 to 0.5 μm to a thick layer of about 50 μm. .

In addition, using the above equipment, the mixed crystal ratio was 0.2 and 0.3.
I tried growing GaAl As layers of 2 μm each, and was able to grow them with a mirror surface and a uniform thickness. That is, since a large number of substrates can be grown without taking them out of the reactor, it is also possible to grow multiple layers of easily oxidized mixed crystals such as GaAl As.

Although the above-mentioned embodiment shows the case of two-layer growth, single-layer growth is also possible, and multi-layer growth of three or more layers is also possible by increasing the number of solution reservoirs.

[Effects of the Invention] In summary, the present invention exhibits the following excellent effects.

(1) By forming multiple solution reservoirs so that they become deeper one after the other and by providing pistons in multiple stages according to the depth of the solution reservoirs, the interval between each solution reservoir can be increased by increasing the interval between each solution reservoir. Since a sufficient stroke amount of each piston can be secured without increasing the size, the length of the device can be made as short as possible even though it is a multilayer growth device. Furthermore, since the pistons are inserted into the main body, they can be supported without interfering with each other, allowing stable piston operation.

(2) By providing a common solution inlet/outlet in the substrate holder, unlike the conventional solution in which the inlet and outlet are provided separately, it not only eliminates the trouble of sliding the substrate holder, but also The structure of the part can be simplified, and by forming a large solution inlet and outlet, a large amount of solution can be taken in and out.This, together with item (1) above, dramatically increases the production volume of epitaxial wafers with a multilayer structure. Can be increased.

(3) Since the number of parts in the entire device is reduced, the structure can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing one embodiment of the device of the present invention, FIG. 2 is a sectional view taken along the - line in FIG. 1, and FIG.
Figures 1 to 4 are vertical sectional views showing examples of conventional devices. In the figure, 20 is a solution storage part as a main body, 21 is a raw material solution, 22 is a substrate, 23 is a substrate holder part, 2
4 is a solution reservoir, 25 is a head, 26 is a piston,
28 is a solution inlet/outlet.

Claims (1)

[Claims] 1. A plurality of solution reservoirs containing the raw material solution are formed in a long main body so as to become deeper in sequence along the longitudinal direction, and a piston that raises and lowers the liquid level of the solution by making a head appear in each solution reservoir. The substrates are inserted in multiple stages according to the depth of the reservoir, and a plurality of substrates are held upright inside the main body. A liquid phase epitaxial growth apparatus characterized in that it is slidably provided so that raising and lowering is performed sequentially through the entrance and exit.