JPH05886A - Growing method for liquid phase epitaxy - Google Patents

Abstract

PURPOSE:To improve the uniformity of a thickness by growing a raw material soln. on a substrate by sliding in one direction, then executing the next growth by sliding in an inverse direction, thereby laminating the respective grown layers. CONSTITUTION:A slide boat obtd. by disposing a substrate 2, a soln. holder 3 and the raw material soln. 4 on a substrate holder 1 is heated up in a reaction tube kept in a high-purity H2 atmosphere to obtain the purified soln. 4 (Stage 1). After the soln. 4 is heated up to a desired temp., the holder 3 is slide toward the left by an operating rod 5 until the holder exists on the substrate 2 and, thereafter, the temp. is lowered to allow the epitaxial layer to grow (stage 2). The holder 3 is then further slid to the left side to separate the substrate 2 and the soln. 4 (stage 3) (1st growth). The holder 3 is slid to the right side to bring the substrate 2 and the soln. 4 into contact with each other (stage 4) to grow the epitaxial layer in superposition on the above-mentioned epitaxial layer. The holder 3 is slid to the left side to separate the substrate 2 and the soln. 4 (stage 5) to end the growth (2nd growth).

Description

Detailed Description of the Invention

[0001]

The present invention relates to GaAs, AlGaA
The present invention relates to a liquid phase epitaxial growth method for a compound thin film such as s or InP.

[0002]

2. Description of the Related Art A method called a slide boat method is known as one of epitaxy technologies for compound semiconductors. As a general example of this, a substrate 2 as shown in FIG.
The substrate holder 21 in which 2 is set and a solution holder 23 that can slide on the holder and stores the raw material solution 24
When the raw material solution 24 is not in contact with the substrate 22 (step 1), the temperature of the entire apparatus is raised, and then the temperature is lowered at a predetermined rate to reach a constant temperature. The holder 23 is slid, the raw material solution 24 is placed on the substrate (step 2) to grow an epitaxial layer, and then the substrate 22 and the raw material solution 23 are separated (step 3) and cooled.

[0003]

However, in the above-mentioned conventional example, the thickness of the epitaxial layer formed tends to be nonuniform in the sliding direction of the raw material solution. This is because the solute concentration in the raw material solution is non-uniformly distributed with the start of growth of the epitaxial layer. Therefore, the side where the raw material solution slides and comes into contact with the substrate first (on the right side of the substrate in FIG. 3) is better. Thick,
When the raw material solution is separated from the substrate, the side in contact with the raw material solution until the end (left side of the substrate in FIG. 3) is likely to be thin. Therefore, the formed epitaxial layer has a non-uniform thickness with a gradient distribution as shown in FIG. In addition, this characteristic is more remarkable as the supersaturation degree of the raw material solution is higher.

[0004]

The present invention has been made in view of the above circumstances, and in the liquid phase epitaxial growth method by the slide boat method, the solution holder is slid in one direction to position the raw material solution on the substrate. After growing the epitaxial layer, slide the solution holder in the same direction to temporarily separate the raw material solution and the substrate, then slide the solution holder in the other direction and position the raw material solution on the substrate again to grow the epitaxial layer. It is characterized by that.

The present invention will be described more specifically with reference to FIG. The figure shows a slide boat used in the method of the present invention. Reference numeral 1 denotes a substrate holder on which a substrate 2 can be set. A solution holder 3 which can slide horizontally via an operating rod 5 is provided on the upper part thereof, and a raw material solution 4 is stored therein. Such a slide boat is inserted into a reaction tube (not shown) in a state where the substrate 2 and the raw material solution 4 are not in contact with each other (step 1), and is heated to a predetermined temperature while flowing high-purity hydrogen. It After maintaining such a state for several hours to purify the raw material solution 4, the raw material solution 4 is cooled at a constant rate, and when the temperature reaches a predetermined temperature, the raw material solution 4 is positioned on the substrate via the operating rod 5. So that the solution holder 3 is
To the left, and the temperature is lowered to grow an epitaxial layer (step 2). After the above growth,
The solution holder 3 is further slid to the left, and the substrate 2 and the raw material solution 4 are once separated (step 3) (first growth).

Next, this time, the solution holder 3 is slid to the right, and the substrate 2 and the raw material solution 4 are again kept in contact with each other (step 4), and an epitaxial layer is grown on the epitaxial layer grown previously. Let And finally,
Further, the solution holder 3 is slid to the right, the substrate 2 and the raw material solution 4 are separated (step 5), and the growth is completed (second growth).

[0007]

[Function] As described above, after the first growth is performed by the one-direction slide, the second growth is performed by the opposite-direction slide,
By stacking each growth layer, the gradient distribution of the thickness of the epitaxial layer in the first growth is almost canceled by the epitaxial layer in the second growth, and an epitaxial layer having a uniform thickness as a whole can be obtained. After the first growth in Figure 2,
The state of each epitaxial layer after the second growth is shown in comparison with the state before the growth.

In the examples described above, the apparatus of the type in which the substrate holder is fixed and the solution holder is slid is described, but conversely, the method of the present invention is applied to the apparatus of the type in which the substrate holder is slid and the solution holder is fixed. Needless to say, it can be used as long as the raw material solution reciprocates on the substrate in relative terms and the first growth and the second growth can be performed.

[0009]

EXAMPLE An epitaxial growth was actually conducted by the method of the present invention using the apparatus shown in FIG.

Using a GaAs substrate, 100 g of Ga and 8.7 g of GaAs raw material crystal were put into the solution holder, the entire slide boat was put into the reaction tube, and the raw material solution was kept at 900 ° C. for 6 hours in a hydrogen stream. Purified.

Then, after gradually cooling to 860 ° C.
The temperature was lowered at a rate of 1 ° C./min, and when the temperature reached 850 ° C., the solution holder was slid in one direction to bring the raw material solution into contact with the substrate. This state was maintained for 10 seconds for epitaxial growth (first growth), and then the substrate and the raw material solution were separated.

After another 2 minutes, this time, the solution holder was slid in the other direction, and the raw material solution was brought into contact with the substrate again to start growth (second growth). After 10 seconds, the raw material solution and the substrate were separated and grown. Finished.

As a comparative example, an epitaxial layer having the same thickness as the growth layer of this example was grown by the conventional method shown in FIG. 3 and the thickness distributions were compared.

As a result, the thickness distribution of the growth layer according to the conventional example was 1 ± 0.31 μm, whereas the thickness distribution of the growth layer according to the method of the present invention was 1 ± 0.12 μm, and the epitaxial layer with high uniformity was obtained. It was confirmed that a layer could be formed.

By the way, as already described, the solute concentration distribution becomes non-uniform with the start of growth, but when the film thickness to be grown is large, the growth time in the state of step 2 in FIG. The solute diffuses into the solution and the solute concentration becomes uniform. Therefore, the unevenness of the thickness distribution of the epitaxial layer will be improved.

On the other hand, when the grown film thickness is thin, the growth time is not so long as to make the solute concentration uniform,
The non-uniformity of the thickness distribution of the film thickness is larger. Therefore, it can be said that, when the film is grown by the method of the present invention, the effect of making the thickness uniform becomes more remarkable as the film thickness to be grown becomes thinner.

[0017]

As described above, according to the method of the present invention, the thickness distributions of the growth layers of the first growth and the second growth cancel each other out, so that an epitaxial layer having a highly uniform thickness can be formed. Can be formed. In particular, the effect of making the thickness uniform becomes more remarkable as the epitaxial layer becomes thinner.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a method of the present invention.

FIG. 2 is an explanatory view showing a growth state of an epitaxial layer by the method of the present invention.

FIG. 3 is an explanatory diagram showing a conventional method.

FIG. 4 is a sectional view of an epitaxial layer formed by a conventional method.

[Explanation of symbols]

 1, 21 Substrate holder 2, 12, 22, 32 Substrate 3, 23 Solution holder 4, 24 Raw material solution 5, 25 Operation rod 6, 16 Epitaxial layer

Claims (1)

Claim: What is claimed is: 1. In a liquid phase epitaxial growth method using a slide boat method, a solution holder is slid in one direction to position a raw material solution on a substrate to grow an epitaxial layer, and then in the same direction. A liquid phase epitaxial growth method comprising: sliding a solution holder to temporarily separate a raw material solution and a substrate, and then sliding the solution holder in the other direction to position the raw material solution again on the substrate to grow an epitaxial layer.