JPS622453B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid phase epitaxial growth method that is generally used in semiconductor device manufacturing, and particularly to a liquid phase epitaxial growth method that forms a plurality of different types of growth layers. The present invention relates to the structure of a crystal growth apparatus that allows easy and economical production of high-quality crystals with high reliability in controlling the thickness and composition of each layer.

In the conventional crystal growth method for semiconductor laser diodes, as a measure to obtain high-quality crystals, the growth atmosphere is kept highly clean, the oxidation of the solution is prevented,
A crystal with few crystal defects was obtained. In addition, in order to obtain reproducibility in the growth layer thickness and composition, precise weighing was performed for each growth cycle, and new solutions were used to suppress compositional fluctuations. Furthermore, in order to facilitate layer thickness control, a plate-shaped seed crystal is placed in the growth solution (using a dummy crystal) before the growth onto the substrate crystal.
This prevented unstable rapid growth at the start of growth, which would occur due to supersaturation of the solution.

In addition, with regard to improving economic productivity, this goal has been achieved by repeatedly using a growth solution, growing multiple sheets in the same growth process, etc. However, in the crystal growth of semiconductor laser diodes, AlGaAs, which is a compound that is easily oxidized, is used, and a compound different from AlGaAs is used in multiple layers under strict composition control, e.g. 0.1 to 0.2
An active layer of [μ·m] must be grown as a crystal with good reproducibility.

When the same solution is used repeatedly to improve productivity, in a growth apparatus with a conventional structure, the solution composition changes as the solution is brought in, increasing the variation in the composition of the growth layer from growth to growth. do. A solution with a precisely controlled composition ratio could not be obtained unless the solution whose composition changed once was replaced. Furthermore, since the conventional growth apparatus grows an epitaxial layer by sealing the core tube, it is almost impossible to install a new substrate crystal in the same core tube.

As mentioned above, in the crystal growth of semiconductor laser diodes, the quality of layer thickness control and productivity largely depends on the structure of the growth equipment, and both good quality and high productivity can be achieved with high reliability. It was extremely difficult to obtain both at the same time.

As mentioned above, as long as conventional growth apparatuses are used, measures to obtain high-quality crystals and measures to obtain high productivity thereof are contradictory. The present invention eliminates the unproductivity caused by these contradictory measures, controls the growth layer thickness and composition with good reproducibility, and ensures the cleanliness of the growth atmosphere to produce high-quality crystals with stable and high productivity. The purpose of the present invention is to provide a growth apparatus that can replace the conventional liquid phase epitaxial growth apparatus that can be supplied under the conditions of the present invention.

The configuration of the present invention will be described below.

In a liquid phase epitaxial growth apparatus, a plurality of growth solutions equal to the number of growth apparatuses are prepared. A plurality of these growth solutions can be arranged in parallel so that epitaxial growth can be performed on a plurality of substrates simultaneously in the same apparatus. The growth solution is made to have a thin and uniform thickness of about 3 mm on the substrate crystal. A plate-shaped seed crystal of the same type as the substrate crystal is placed at the bottom, and is used as a solute supply source and a seed crystal for adjusting the saturation level. Further, the substrate crystal is cut out to be larger than the contact area of the solution, and the part that does not come in contact with the crystal is used for holding or moving.
In this case, a substrate crystal holder is prepared that can be stacked or arranged hierarchically so that it has the same number of growth surfaces as the number of substrate crystals used.
The holding part is placed outside each growth solution, and is introduced into the center of each thin layer solution by moving the movable holding part. In this way, a structure is created in which only the substrate crystal can come into contact with each growth solution.

Furthermore, according to the present invention, in the liquid phase epitaxial growth apparatus described above, a solvent bath is disposed above the upper plate-shaped seed crystal holding part that constitutes a part of each growth bath, and the plate-shaped seed crystal and Keep the solvent separate. A connection hole is formed in the upper plate-shaped seed crystal holding part, through which each solvent can be introduced into each growth bath by moving the holding part relative to the bath. Furthermore, a movable impurity input plate is placed above each solvent bath to separate and hold added impurities. Then, each added impurity placed on the top of each solvent bath can be added to each solvent by moving the input plate. In this way, it is possible to reproduce the composition of each growth solution within the growth reactor core tube.

Furthermore, according to the present invention, a plurality of substrate crystal holders on which substrate crystals are placed are arranged in a substrate crystal storage section installed in one of the low-temperature parts of the growth reactor tube. During growth, the substrate crystals placed on the holding section are individually moved over a substrate crystal supply plate connected to the storage section, introduced into each growth solution, and crystal growth is performed. At the end of the growth, the grown crystal is stored in a growing crystal storage section installed in the other low temperature section by moving it on a growing crystal carrying-out plate connected to the storage section. The above operations can be repeated in a sealed growth reactor core tube, and a plurality of substrate crystals can be processed continuously, resulting in high productivity.

Next, the effects of the present invention will be explained in more detail.

The structure of the present invention in which a growth solution is brought into contact with a substrate crystal has the following advantages.

By forming each growth solution to have a thin and uniform thickness on the substrate crystal, the distribution of solute concentration within the solution becomes more uniform, and as a result, the growth layer thickness can be easily controlled.

As a result of placing plate-shaped seed crystals above and below the solution,
At the holding temperature for homogenizing the solution before growth, it becomes a solute supply source, and the saturated amount of solute is uniquely determined, making it unnecessary to weigh the sample for each growth cycle. Furthermore, during growth, the seed crystal plays a role in adjusting the saturation level to bring nucleation to a steady state.
The amount of precipitation on the substrate crystal is stable.

As a result of using multiple substrate crystals, the yield of crystal growth increases.

By fixing each solution and moving only the substrate crystal, fluctuations in the temperature distribution of the growth system are minimized. As a result, the uniformity of the layer thickness increases.

The advantage of passing the substrate crystal through the center of the solution is that a clean area, where the solution is not in contact with the side walls of the solution bath, can be used for crystal growth. This is very effective in obtaining high quality crystals.

According to other configurations of the present invention, there are further advantages as follows.

Since the substrate crystal, solute, solvent, and added impurities can be separated and retained in a sealed growth furnace, the effect of hydrogen reduction of the solvent metal is increased, making it possible to obtain high-quality crystals. .

By keeping the substrate crystal sealed inside the growth furnace and placing it in the low-temperature part of the growth furnace, it becomes possible to perform multiple crystal growths in succession.
As a result, operations and procedures such as installing an atmospheric gas and a growth apparatus in a growth furnace during the crystal growth process can be omitted. Therefore, operations for preparing for growth and processing solutions after growth can be significantly reduced. This means that economical production is possible.

As is clear from the above points, by employing the present invention, it is possible to obtain high quality semiconductor laser diode wafers with easy operations and a high yield.

An embodiment in which the apparatus of the present invention is applied to crystal growth of an AlGaAs semiconductor laser diode will be described below with reference to the drawings. For example, consider the growth of an AlGaAs semiconductor laser diode. FIG. 1 shows a cross section of the vapor phase growth section before epitaxial growth, FIG. 2 shows a cross section during the growth process, and FIG. 3 shows the entire growth apparatus. GaAs substrate crystals 101 and 102, which have been surface-treated with a sulfuric acid-based etching solution, are arranged in a substrate holding section 100 with their back sides stacked one on top of the other, and are placed in the substrate crystal storage section 330 of FIG. 3. GaAs plate-shaped seed crystal 111~
114 and 121 to 124 are each processed to have the same area as the growth area of the substrate crystal. Its mass is determined by the saturation amount determined by the growth temperature and the mass of the solvent Ga, but in order to prevent the entire seed crystal from melting and make it act as a plate-shaped seed crystal, the mass is set to about 1.5 to 2 times the saturation amount. After performing the same surface treatment as the substrate crystal, they are placed in the upper and lower plate-shaped seed crystal holding parts 110 and 120 as shown in FIG.
The mass of the solvent Ga-131 to Ga-134 is determined so that the volume is about 2 to 3 times the volume of the growth solution bath, and each is placed in the solvent holding bath 130. The impurities 141 to 144 are placed in the upper part of the solvent holding bath 130, as shown in FIG. 1, in the amount generally used, for example, Sn as the P type and Gen type. Thereafter, the growth apparatus shown in FIG. 1 is installed in a growth furnace, and after the growth atmosphere is made clean, the temperature is raised. Hydrogen reduction of the solvent Ga131-134 is carried out at about 800°C. After releasing gas such as moisture adsorbed in the device and reducing the solvents Ga131 to 134 with hydrogen for several hours, the impurity injection plate 140 is moved in the direction of the arrow in FIG.
Impurities 141 to 144 are added to 134. After the impurities are uniformly melted, the upper plate-shaped seed crystal holder 110 is moved in the direction of the arrow in FIG. Through the above operations, GaAs plate-shaped seed crystals -111-114, 121-124, and the solvent Ga
The three impurities 131 to 134 and impurities 141 to 144 easily combine, and the growth solution dissolves the solute from the upper and lower seed crystals and reaches an equilibrium state at a saturation amount determined by the holding temperature.

The solution is held for a time necessary to obtain a uniform equilibrium state, and then the temperature is lowered to the growth temperature of the first layer-n-AlGaAs. During the cooling process, the plate-shaped seed crystal literally plays the role of a seed crystal in each solution, and crystals are precipitated on the surface of the plate-shaped seed crystal below.
A stable growth solution is realized by the above operations. While the growth starting temperature of the first layer n-AlGaAs is reached, open the substrate crystal storage opening/closing valve 320 from the substrate crystal storage 310 in FIG. The substrate crystal supply plate 340 is moved over the solution holding bath 11.
A substrate crystal 10 is placed at the position shown in FIG.
1,102 is placed. Due to temperature drop, the first layer -n
- When the growth start temperature of AlGaAs is reached, the substrate crystal holder 100 is moved into the first layer growth solution 251 by moving the holder movable piece 390.
1,102 is placed. In that case, the substrate crystal 10
1 and 102 cut the center of the first layer growth solution 251 and are arranged as shown in FIG.

FIG. 2 is a cross-sectional view showing the arrangement of the growth apparatus during growth of the first layer of n-type AlGaAs.

Upper surface of substrate crystal 101 and substrate crystal 10
Crystal growth is performed on the lower surface of 2 at a constant growth rate under stable nucleation of the first layer growth solution 521. The first layer n-AlGaAs is coated with a predetermined layer thickness (~
2 [μ・m]) After the growth, the substrate crystal is sequentially moved to form the second layer - GaAs and the third layer P -.
AlGaAs and fourth layer GaAs are each −0.2 [μ・
Crystals are grown with layer thicknesses of 1.0 [μ.m], 2.0 [μ・m], and 1.0 [μ・m]. The grown crystal 301 that has finished growing is placed on the grown crystal carrying out piece 360 shown in FIG.
50 is carried out, the growing crystal storage section opening/closing valve 380 is opened, and the growing crystal storage section 370 is stored. The first crystal growth is completed through the above growth apparatus operation process. After that, when the temperature is raised again to the pre-growth holding temperature (800°C), each growth solution 251~
In 254, each plate-shaped seed crystal 111 to 11
4,121-124, the grown layer is redissolved into a reusable saturated solution. The second crystal growth can be performed by repeating the above-described operation of taking out the substrate crystal from the substrate crystal storage section 330 and supplying it to the growth solution.

According to this example, the growth layer thickness can be easily controlled, and the uniformity of the growth layer thickness is such that the thickness change at both ends is about 5% with respect to the center of the growth crystal, and There is also a variation in the thickness of 5 to 10%.
It became a degree. The variation in Al concentration between growth cycles was negligible after 3 to 4 repetitions. In addition, as a result of maintaining the cleanliness of the growth atmosphere, crystal defects etc. were reduced and wetting of the solution was improved, so the effective growth area was increased and the production yield of high quality crystals was increased. Furthermore, due to the use of multiple substrates, repeated use of solutions, repeated growth in a sealed furnace, etc., productivity has dramatically increased from the conventional 5 to 8 sheets/month to 20 to 40 sheets/month.

As described above, by carrying out the present invention, the growth layer thickness becomes uniform and uniform, and it becomes possible to produce high-quality crystals with few crystal defects at a high yield, thereby greatly improving the productivity of semiconductor laser diodes.

The above implementation is one example, and it goes without saying that the present invention is not limited to this.

Furthermore, the present invention can also be applied to liquid phase epitaxial growth of compound semiconductors such as InGaAs.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a growth process of a growth section of a liquid phase epitaxial growth apparatus according to an embodiment of the present invention. FIG. 2 is a sectional view showing the growth process of the first layer in the growth section of FIG. 1. 100...Substrate crystal holding part, 101, 102...
...Top and bottom GaAs substrate crystals, 110, 12
0... Upper and lower plate-shaped seed crystal holding parts (solution holding baths), 111 to 114, 121 to 124...
GaAs plate-shaped seed crystal for upper first to fourth layers and lower first to fourth layers, 130...solvent holding bath;
131-134...For 1st layer to 4th layer, solvent
Ga, 140... Impurity injection plate, 141-144
...Additional impurities for the first to fourth layers. FIG. 3 is a diagram showing the entire liquid phase epitaxial growth apparatus according to an embodiment of the present invention. 300...Substrate crystal before growth, 301...Substrate crystal placed in a bathtub, 302...Substrate crystal after growth (grown crystal), 310...Substrate crystal storage section, 320...Substrate crystal storage section opening/closing Valve, 330...
...Substrate crystal insertion rod, 340...Substrate crystal supply plate,
350... Growing crystal carrying out plate, 360... Growing crystal carrying out side, 370... Growing crystal storing section, 380...
Growth crystal storage section opening/closing valve, 390...Substrate crystal holding section movable side.

Claims (1)

[Claims] 1. An apparatus bottom plate having a plurality of recesses arranged in a row constituting a lower part of the growth bath, an apparatus upper plate having a plurality of through holes constituting a holding bath at positions corresponding to the recesses of the apparatus bottom plate, and recesses of the apparatus bottom plate. The apparatus bottom plate has a plurality of recesses constituting the upper part of the growth bath at positions respectively corresponding to the apparatus bottom plate and a plurality of holes penetrating vertically between the recesses, and between the apparatus bottom plate and the apparatus top plate. using a growth apparatus having a movable plate attached to be movable in the same direction as the row of recesses, and a means for moving two overlapping growth plates between the apparatus bottom plate and the movable plate, attaching first and second plate-shaped seed crystals to the bottom surface of the depression and the top surface of the depression, respectively, and introducing a growth solution into the holding bath, and then moving the movable plate to pour the growth solution through the hole. a step of placing the movable plate into the recess, a step of further moving the movable plate to form the growth bath with the recess and the recess, and then a step of placing the two
Crystal growth is performed on each of the two growth substrates while passing a growth plate through the growth bath and bringing the growth solution into contact with the first and second plate-shaped seed crystals. A liquid phase epitaxial growth method.