JPS5941959B2 - Liquid phase epitaxial growth equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a liquid phase epitaxial growth apparatus particularly suitable for manufacturing compound semiconductor light emitting devices.

A conventional liquid phase epitaxial growth apparatus is constructed as shown in FIG.

That is, the growth apparatus shown in FIG. 1 is comprised of a substrate support 2 made of carbon that supports a semiconductor substrate 1, and a solution container 3 made of carbon that accommodates a liquid phase epitaxial solution 4. The substrate 1 supported by the substrate support 2 is provided in a recess as shown in FIG. 2, and is arranged at a certain distance d from the surface of the substrate support 2. Usually, this interval d is about 50 to 80 tLm. In the growth apparatus configured in this manner, the solution container 3 and the substrate support 2 are moved relatively to bring the solution 4 into contact with the substrate 1 to perform liquid phase epitaxial growth. Next, the case of manufacturing a double eterojunction GaAlAs light emitting device using the growth apparatus shown in FIG. 1 will be described.

First, the solution container 3 is provided with two solution reservoirs as shown in the figure, one solution reservoir contains a solution 4a into which Ga, Al, and p-type impurities are introduced, and the other solution reservoir contains Ga, Al, and p-type impurities. Al
and a solution 4b into which n-type impurities are introduced. 5 is a polycrystalline plate of GaAs, and A is inserted into solutions 4a and 4b.
Its role is to supply s atoms.

Reference numeral 6 denotes a carbon lid, which acts as a weight so that the solutions 4a and 4b are flat when they come into contact with the substrate 1.

This crystal growth apparatus is sealed in a reaction tube, and the temperature is raised to 850°C in a hydrogen atmosphere. The temperature is then maintained at 850°C for 1 hour. -cQ After cooling slowly, the substrate support 2 is slid and brought into contact with solution 4a and then with solution 4b as shown in FIG. The layer thickness grown on the substrate 1 is
Depends on contact time. FIG. 3 shows a cross-sectional view of a state in which a grown layer 7 has been obtained on the substrate 1. As is clear from FIG. 3, the thickness of the grown layer 7 grows abnormally 7a at the edge of the substrate. The reason for this is that even though the surface of the substrate 1 is a low index crystal of (100), its edges are high index planes. Generally, the crystal growth speed is (100) < (110) < (11
1) There is a plane relationship, and crystal growth is faster on high index planes than on low index planes. Therefore, crystal growth at the edges becomes faster. Another reason is that heat is dissipated from the edges of the substrate, creating a temperature difference between the center and edges of the substrate. The temperature is higher in the center and lower at the edges. Therefore, the As atom is (G
The a atoms (excessive a) are diffused more toward the lower temperature, resulting in thicker growth at the edges. Such a crystal substrate not only obstructs the relative movement of the solution container 3 and the substrate support plate 2, but also causes scratches on the sliding surface of the solution container 3 and the substrate support plate 1, causing damage to the substrate 1. The abnormal growth layer 7a on the surface makes it difficult to remove the solution from the substrate 1.

For this reason, the desired composition of each grown layer of the multi-layer grown layer could not be obtained. Further, the abnormally grown layer 7a mixed into the solution by rubbing carbon, inhibiting crystal growth and resulting in an unsatisfactory growth surface. Furthermore, when these substrates are fabricated into devices, this abnormally grown layer complicates the process. The present invention has been made in view of the above points, and provides a liquid phase epitaxial growth apparatus in which no abnormally grown layer is obtained.

That is, in the present invention, a member such as quartz glass having a lower thermal conductivity than carbon constituting the substrate support and the solution container is disposed only on the side wall of the recess in which the substrate is accommodated, and the edge of the substrate is This is a growth device that eliminates abnormal growth at the edges of the substrate by slowing down the growth rate at the edges of the substrate.

Next, the present invention will be explained based on an embodiment shown in FIG.

In FIG. 4, the same reference numerals as in FIG. 1 indicate the same things, so the explanation will be omitted. The difference in FIG. 4 from FIG. 1 showing the conventional example is that a member 9 having a thermal conductivity lower than that of carbon constituting the substrate support 2 and the solution collector 3 is, for example, 10 to 100% lower than that of carbon. The quartz glass having a double thermal conductivity is provided around the recessed portion of the substrate support 2 which is the substrate accommodating portion. When crystal growth is performed using the liquid phase epitaxial growth apparatus configured in this manner in the same manner as conventional methods, unlike conventional growth apparatuses, the edges of the substrate 1 are surrounded by quartz glass 9 with low thermal conductivity. Therefore, as the growth apparatus is slowly cooled, the temperature at the center of the substrate 1 decreases quickly and the growth occurs quickly, but the temperature at the ends of the substrate 1 decreases more slowly than the center and the growth occurs more slowly.

Therefore, as a result, a crystal layer 7 without an abnormal growth layer, that is, a thick growth layer, is obtained at the edge of the single-layer substrate 1 shown in FIG. The external dimensions and thickness of the quartz glass 9 must be determined depending on the heat capacities of the solutions 4a, 4b, the substrate 1, and carbon. Furthermore, as shown in FIGS. 5A and 5B, the effect will be greater if the contact area with the substrate is increased to further slow down the temperature drop at the edge of the substrate. Also, whether the sliding surface between the solution reservoir and the quartz glass 9 of the substrate support is a mirror surface or a frosted surface does not affect this effect, but if the quartz glass 9 is frosted, the solution and This makes it difficult for Si, etc. in the quartz glass 9 to enter, and as a result, a high-quality growth layer can be obtained. Further, in the growth apparatus shown in FIGS. 4 and 5, even when the growth layer 7 is relatively thin and has a thickness of 5 μm or less, there is an effect even if the vertical and horizontal dimensions of the substrate are slightly larger than the dimensions of the bottom of the solution reservoir. However, when the growth layer 7 becomes thicker than 5 μm, the influence of the crystal orientation of the crystal edges cannot be ignored. That is, the vertical and horizontal dimensions of the solution reservoir are made smaller than the vertical and horizontal dimensions of the bottom of the recess of the substrate support, and of course the dimensions of the solution reservoir are made smaller than the dimensions of the substrate. In this way, the influence of the crystal orientation at the edge of the substrate can be removed. The growth layer obtained with this growth apparatus was thinner from the edge to about 200 μm than the center, and was extremely uniform except for the peripheral area. Furthermore, as explained above, with the growth apparatus of the present invention, a grown layer with a desired composition can be obtained with less solution contamination than with conventional growth apparatuses. Although .5 mm was cut out and subjected to the element formation process, there was no need to do so if the apparatus of the present invention was used.

In the above embodiment, the peripheral part of the substrate accommodating part of the substrate support may be made of quartz glass, such as quartz glass, which has a lower thermal conductivity than carbon.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a conventional liquid phase epitaxial device.
FIG. 2 is a sectional view showing only the substrate support of the liquid phase epitaxial apparatus shown in FIG. , 4th
The figure is a sectional view showing a liquid phase epitaxial growth apparatus according to one embodiment of the present invention, FIG. 5 is a schematic diagram of a substrate support of a liquid phase epitaxial growth apparatus according to another embodiment of the present invention, and a is a sectional view ,
6b is a plan view, and FIG. 6 is a sectional view showing a state in which a growth layer is formed on a substrate using the growth apparatus of FIG. 4. In the figure, 1 is a semiconductor substrate, 2 is a carbon substrate support, 3 is a solution container, 4a and 4b are solutions, and 5 is a GaSa
6 is a carbon lid, 7 is a growth layer, 7a is an abnormal growth layer, and 9 is a quartz glass plate.

Claims (1)

[Claims] 1. A liquid-phase epitaxial solution container made of carbon that accommodates a liquid-phase epitaxial solution, and a carbon-made substrate support having a concave portion in which a substrate is disposed so as to constitute the bottom of the solution container. A liquid phase epitaxial growth apparatus comprising: relatively sliding the solution container and the substrate support to bring the liquid phase epitaxial solution and the substrate into contact with each other to form a liquid phase epitaxial growth layer on the substrate; A liquid phase epitaxial growth apparatus characterized in that the side wall of the recess in which the substrate of the carbon substrate support is accommodated is made of a material having a lower thermal conductivity than carbon, and the bottom of the recess is made of carbon.