JPH02192487A - Method for liquid-phase epitaxial growth - Google Patents

Abstract

PURPOSE:To obtain homogeneous epitaxial growth over the whole surface of a disklike substrate by providing a conical surface having a slope extending upward in the upper part of each ring for holding the substrate and holding the disklike substrate on the conical surface in linear contact therewith. CONSTITUTION:A material for carrying out epitaxial growth is charged into a crucible 5 and heated to provide a melt 4 for growth and many chambers are provided with partition plates 8 having a slit 6 in part of the periphery thereof to assemble a cassette 3 containing many sets of a ring 1 made of carbon and a substrate 2. In this case, the substrate 2 is brought into linear contact with the conical surface of the ring 1. If the cassette 3 is lowered into the crucible 5, the solution in the bottom of the crucible 5 is pushed, passed through a clearance between the crucible 5 and the cassette 3 and raised. The raised solution is passed from the slit 6 through openings 7 of the ring 1 made of the carbon and admitted into the respective chambers of the cassette 3 to fill the interiors of the chambers. The substrate is then pushed up to provide a floated state separated from the rings 1. The flow of the melt is completely distributed to the whole surface without interference by the rings 1 and brought into contact with the surfaces of the substrates 2.

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Application Field" The present invention relates to a method for performing liquid phase epitaxial growth on the surface of a semiconductor substrate (wafer), particularly a compound semiconductor substrate.

``Prior art'' It is common practice to manufacture various semiconductor devices by heating and melting a material to be grown, bringing the surface of a semiconductor substrate into contact with the melt, cooling it, and epitaxially growing the material on the surface of the semiconductor substrate. Are known. This epitaxial growth method uses a vertical dip method as a technique for simultaneously performing epitaxial growth on a large number of substrates.

In the vertical dipping method, as shown in FIG. 4(a), a material to be epitaxially grown is put into a crucible 5 and heated and melted to form a growth solution 4. A cassette 3 having a slit 6 in a part of its periphery and a large number of chambers formed by a partition plate 8 and storing a large number of carbon rings 10 and 20 sets of substrates in each chamber is assembled. Carbon is often used as the wafer holding ring, but any material that does not contaminate the solution and is Wr# thermal may be used. When the cassette 3 is lowered into the crucible 5, as shown in FIG. From there, it flows into each chamber of the cassette 3 through the open lower part of the carbon ring 10, fills the chamber, and comes into contact with the surface of the substrate 2. When the temperature of the crucible 5 is gradually lowered, the solution grows crystals on the surface of the substrate, and epitaxial growth is performed.

For example, AlGaAs is deposited on a GaAs compound semiconductor wafer.
In some cases, LEDs are manufactured by epitaxially growing. In this way, GaAs compound semiconductor wafers are
When growing a compound semiconductor crystal containing Ga and As as a solvent, the As concentration tends to be high in the upper part of the growth solution and lower in the lower part because As has a smaller specific gravity than Ga. By holding the substrate on top of the growth solution in each chamber, thick epitaxial layers can be grown in a short time. Furthermore, as shown in FIG. 6, since the GaAs compound semiconductor wafer has a lower specific gravity than the growth solution, it floats up in the solution indoors until it touches the bottom surface of the partition plate 8, so that epitaxial growth eventually occurs on the bottom surface of the wafer. It is something.

``Problem to be Solved by the Invention'' Conventionally, a substrate holding carbon ring 1G for holding a substrate above a growth solution using a dip method has a rectangular cut seat 11 at the top as shown in FIG. A ring 10 with .

If the carbon ring 10 having this notch seat 11 is used, even if the part of the substrate 2 that is in contact with the notch seat 11 or the substrate 2 floats as shown in FIG.
Since the gap between the growth solution 4 and the growth solution 4 is very narrow, the growth solution 4 cannot make sufficient contact with the growth solution 4. Therefore, epitaxial growth is not performed on the seven sides around the substrate 20, requiring a post-process to remove that portion of the substrate, and there is also the problem that the area of the epitaxial wafer obtained is smaller than the area of the substrate used. Ta.

"Means for Solving the Problems" The present invention is characterized by using a carbon ring having a conical surface on the upper part of the inner surface that is inclined so as to spread upward in the dip method. That is, as shown in FIGS. 1(a) and 1(b), a crucible 5 and a cassette 3 having the same structure as the conventional dipping method are used.
The names of each part are shown in Figure 1(a).

Although they are indicated by the same numbers as ('b) and have the same functions, the carbon ring 1 to be stored in the cassette 30 chamber has an open lower ring as shown in FIGS. 2(a) and (b). The ring is characterized by having an upwardly sloping conical surface 12 on the upper part of the inner surface of the ring.

"Operation" That is, as shown in FIG. 1(a), a material to be epitaxially grown is put into a crucible 5, heated and melted to form a growth solution 4, and a slit 6 is provided in a part of the periphery to form a partition. A cassette 3 which has a large number of chambers formed by a plate 8 and stores a large number of pairs of carbon rings (1) and substrates (2) in each chamber.
Assemble. In that case, the substrate 2 is the carbon ring 1
It is in line contact with the 0 conical surface. When the cassette 3 is lowered into the crucible 5, as shown in FIG. From there, the solution flows into each chamber of the cassette 3 through the open lower part of the carbon ring 1, filling the chambers, pushing up the substrate, separating it from the carbon ring, and leaving it in a floating state, so that the flow of the solution is not hindered by the carbon ring. It contacts the surface of the substrate 20 completely over the entire surface. Even if the wafer does not lift up, epitaxial growth occurs on the entire surface because the holding ring and the wafer are in line contact. By slowly cooling in this state, epitaxial growth can be performed on the entire surface of the substrate 2. Therefore, the area of the substrate is not wasted, and when the obtained epitaxial wafer is used, it is not necessary to remove the portion without the epitaxial growth layer, so that the substrate and working time can be saved.

"Example" AlxGa1-xAs was epitaxially grown by the method shown in FIG. 1 using a carbon ring according to the present invention. GaAs for Ga100 as growth solution
A compound containing 4.75 flAl and 505 mf was used. For comparison, the same epitaxial growth was performed using a conventional carbon ring using the method shown in FIG.

Observing the peripheral area of the obtained epitaxially grown wafer, it was found that in the method of the present invention, an epitaxially grown layer 9 was obtained up to the end of the peripheral area of the substrate 2 as shown in FIG. When a ring was used, the epitaxial growth layer 9 was extremely thin at the periphery of the wafer 2, as shown in FIG. The manufactured epitaxial growth wafer has an epitaxial growth layer on the bottom surface, but it is shown upside down in the drawing.

"Effects of the Invention" As explained in detail above, according to the method of the present invention, a uniform epitaxial growth layer can be obtained over the entire surface of the substrate. The area of the original substrate is reduced, and the yield for the substrate is improved. Furthermore, when performing the next process using the obtained epitaxial wafer, there is no need to remove the portion where no epitaxial growth layer is present, which has the effect of shortening the process and saving time and cost.

[Brief explanation of the drawing]

FIG. 1(a) is a front cross-sectional view showing the epitaxial growth apparatus of the present invention during preparation, FIG. 1(b) is a front cross-sectional view during the growth operation, and FIGS. 2(a) and (b) are the main FIG. 2 is a plan view and a sectional view taken along line A-A of a substrate holding ring used in the invention. FIG. 5 is a cross-sectional view of the periphery of a wafer having an epitaxially grown layer manufactured according to the present invention. Figure 4 (a
) and (b) are front sectional views showing the state of a conventional epitaxial growth apparatus during preparation and operation. Figure 5 is a cross-sectional view of a substrate holding ring used in the conventional method;
The figure is a cross-sectional view of the substrate and substrate holding ring immersed in a solution. FIG. 7 is a cross-sectional view of the peripheral portion of a substrate having an epitaxially grown layer manufactured by a conventional method. 1.10: Substrate holding ring 2: Substrate (wafer) 3
: Cassette 4: Epitaxial growth solution 5 Nylpot 6: Slit 7: Opening 8: Partition plate 9: First section of epitaxial growth layer

Claims (1)

[Claims] 1. A crucible containing a growth solution containing melted material to be epitaxially grown has a number of chambers separated by partition plates, and a cassette containing a number of pairs of substrate holding rings and substrates is immersed in each chamber. In a dip method liquid phase epitaxial growth method in which an epitaxial growth layer is simultaneously formed on a substrate, a conical surface having an upwardly expanding slope is provided at the upper part of the inner surface of the ring, and a disk-shaped substrate is held in line contact with the conical surface. A liquid phase epitaxial growth method 2 characterized in that a ring for holding a substrate is used, and a compound semiconductor crystal containing Ga and As is grown on a GaAs compound semiconductor substrate by liquid phase epitaxial growth using Ga as a solvent. Liquid phase epitaxial growth method