JPS63252996A - Hot-wall epitaxial growth apparatus - Google Patents

Abstract

PURPOSE:To obtain the titled growth apparatus capable of forming an epitaxial layer having large area and uniform thickness on a substrate held above a crucible containing a source for forming epitaxial crystal layer, by forming the opening part of the crucible in elliptic shape and the side part of the crucible in flat shape. CONSTITUTION:The cross-section of the top opening part 32 of a crucible 31 has flat elliptic shape and the bottom of the crucible 31 is furnished with a bottom-closed inner tube 33 protruded downward. A source material (PbTe or PbSnTe) for epitaxial layer to be formed on a substrate 35 (e.g. PbTe) is placed in the crucible 31 and the inner tube 33 contains Te for the control of the composition of the epitaxial layer. Accordingly, the molecules evaporated from the bottom of the crucible 31 are moved along the dotted lines and reach the positions A, B and C at the opening part 32. Since the opening part 32 has flat shape and the dimension l in the direction of the short side is short, all parts of the opening part 32 have equal distance from the hot wall 34 of the crucible 31. Consequently, the ratio of molecules slantly incident upon the substrate 35 after collision to the hot wall 34 is decreased to equalize the amount of evaporated molecules of the source material.

Description

[Detailed Description of the Invention] [Summary] A hot wall epitaxial growth apparatus that houses a source of a compound semiconductor crystal to be formed on a substrate in a vacuum chamber evacuated to a high vacuum, and is provided with a crucible whose side walls are heated. , the opening of the source crucible containing the source is processed into an elliptical flat shape, and the amount of evaporated molecules of the source that adheres to the substrate without colliding with the real wall of the crucible,
The proportion of molecules that collide with the hot wall and adhere to the substrate is increased, so that the amount of evaporated source molecules is uniform between the center of the crucible and the periphery of the crucible, thereby creating a uniform thickness on the substrate. A hot wall epitaxial growth device that enables the formation of large-area epitaxial layers.

[Industrial application field]

The present invention relates to a hot wall epitaxial growth apparatus, and more particularly to a hot wall epitaxial growth apparatus capable of obtaining epitaxial crystals of uniform thickness over a large area.

Lead telluride (PbT) is used as a board for forming semiconductor laser elements.
e) on a compound semiconductor substrate such as lead, tin, tellurium (P).
As a method for forming compound semiconductor crystals such as (SnTe) in multiple layers with different compositions, a plurality of crucibles containing sources for forming these compound semiconductor crystals and having heated side walls are used. A hot wall epitaxial growth method is used, in which a disk-shaped substrate support with a substrate placed on the crucible is moved horizontally in a chamber evacuated to a high vacuum, and source components are vapor-phase epitaxially grown on the substrate. ing.

This hot wall epitaxial growth method uses simple equipment and is similar to closed-tube vapor phase growth, and the evaporated components of the source reach the substrate while colliding with the side walls of the hot wall, resulting in a state close to thermal equilibrium. A thin layer crystal having a uniform composition and chiaria concentration without segregation in the formed crystal layer can be obtained.

[Prior Art] An explanatory diagram of such a conventional hot wall epitaxial growth apparatus is shown in FIG.

As shown in the figure, a vacuum chamber 1 evacuated to a high vacuum of about 10-'torr has a heater 3 on a side wall 2, and a tellurium (Te) is used to control the composition of the epitaxial layer formed inside. ) 3 is accommodated, and a protruding inner tube 6 protrudes from the bottom of the outer tube 5, which will be described later, and lead-tellurium (PbTe) or lead-tin-tellurium (PbSnTe) 7 as a source material for forming an epitaxial layer. A crucible 8 consisting of an outer tube 5 housed therein is installed.

A disk-shaped substrate mounting table 11 is installed above the opening 9 at the top of the crucible 8 and is movable in the horizontal direction, with a substrate 10 provided thereon.

Although not shown in the drawings, in an actual apparatus, a plurality of such crucibles 8 are installed with different compositions of the source materials contained therein.

After the inside of the vacuum chamber 1 of such a hot wall epitaxial growth apparatus is evacuated to a degree of vacuum of about 10 to 10 torr, the component of the PbTe source 7 is epitaxially grown on the substrate 10, and then the substrate mounting table 11 is further removed. It is moved in the horizontal direction onto a crucible containing another source, and a plurality of epitaxial crystal layers are formed on the substrate 10.

[Problem that the invention seeks to solve]

Incidentally, in such a conventional hot wall epitaxial growth apparatus, the cross-sectional shape of the opening 9 of the source crucible 8 is circular, and the source material 7 heated by the heater 3 on the side wall 2 of the source crucible 8 The components collide with the side wall 2 (generally referred to as a hot wall) of the crucible 8, reach a thermal equilibrium state, evaporate, and adhere to the substrate 10. These evaporated source material molecules collide with the hot wall 2 as shown by the dotted line 12 and rise toward the substrate 10, so that at the center of the opening 9 of the crucible 8,
Molecules that collided with the hot wall 2 and were reflected will be added to the molecules that evaporated without colliding with the hot wall 2, compared to the periphery of the opening 9 of the crucible. Therefore, there is a problem that evaporated components increase in the central part of the opening 9.

Therefore, as shown by curve 21 in FIG. 6, the thickness of the epitaxial layer at the center of the substrate is thicker than the thickness of the epitaxial layer at the periphery of the substrate. The variation in thickness is as much as 20%.

In FIG. 6, the horizontal axis indicates the radial dimension of the substrate, 0 indicates the position of the center of the substrate, and the vertical axis indicates the thickness of the epitaxial layer.

Therefore, in order to maintain a uniform thickness of the epitaxial layer formed on the substrate, a baffle 13 made of a quartz plate is installed in the crucible 8 as shown in FIG. The amount of evaporation at the center of the crucible 8 was kept uniform, but in this way, the thickness of the epitaxial layer at the periphery of the substrate was smaller than that at the center of the substrate, as shown by curve 22 in FIG. The thickness of the epitaxial layer is greater than that of the epitaxial layer.

It is an object of the present invention to provide a hot wall epitaxial growth apparatus which eliminates the above-mentioned problems and allows an epitaxial layer of uniform thickness to be obtained over a large area on a substrate.

[Means for solving problems]

The hot wall epitaxial growth apparatus of the present invention that achieves the above object includes a vacuum chamber, a crucible installed in the vacuum chamber, containing a source for forming an epitaxial crystal layer, and having a heated side wall, and a crucible placed on the crucible. In the apparatus, the opening of the crucible in which the source is accommodated is elliptical, and the side portions of the crucible are processed into flat shapes.

[Effect]

The hot wall epitaxial growth apparatus of the present invention maintains the cross-sectional shape of the opening of the source crucible in an elliptical flat shape, so that the distances of the evaporated molecules at the opening to the hot wall are equidistant. This reduces the influence of molecules that collide with the crucible, ensuring that the amount of evaporation of the source in the crucible is constant whether at the center or the periphery of the crucible opening, and creating an epitaxial layer of uniform thickness on the substrate. Try to get the following.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

Figure 1 (al is a perspective view of the first embodiment of the crucible used in the device of the present invention, Figure 1 (b) is a side view of Figure 1, Figure 1 T
O) is a front view of FIG. 1 (al).

As shown in FIG. 1 ia) to FIG. 1(C), the cross section of the upper opening 32 of the crucible 31 used in the apparatus of the present invention has a flat elliptical shape, and the crucible 31 A protruding inner tube 33 with a bottom is provided at the bottom of the tube.

Inside the crucible 31 is PbTe, which is the source material for the epitaxial layer to be formed on the PbTe substrate, or pb
SnTe is contained in the inner tube 33, and Te for controlling the composition of this epitaxial layer is contained in the inner tube 33.

In this way, the molecules that have evaporated from the bottom of the crucible 31 as shown by the dotted line will be transferred to A, B, and C at the opening 32.
Since the opening 32 is flat and the dimension β in the lateral direction of the opening is short, both of them are equidistant from the hot wall 34 of the crucible 31. Therefore, the proportion of molecules evaporated from the source material at the bottom of the crucible 31 that collide with the hot wall 34 and enter the substrate from an oblique direction is small compared to conventional crucibles, and and the evaporated molecules of the source material at the periphery of the opening 32 are equal.

In addition, in this crucible structure, when the dimension l of the opening is narrowed and the substrate is fixed on the crucible and epitaxial growth is performed, a linear epitaxial layer corresponding to the line segment is formed on the substrate. Therefore, as shown in FIG.
It is preferable to determine the moving direction of the substrate mounting table so that the substrate 35 moves in a direction perpendicular to the long axis.

In this way, a high-quality epitaxial layer can be obtained in which the variation in the thickness of the epitaxial layer formed at the center and the periphery of the substrate is within 3%, as shown by the straight line 36 in FIG.

In FIG. 3, the vertical axis represents the thickness of the epitaxial layer formed on the substrate, and the horizontal axis represents the radial dimension of the substrate.
The 0 position on the horizontal axis indicates the position of the center of the substrate.

A second embodiment of the crucible in the apparatus of the present invention is shown in FIG.

As shown in the figure, the crucible 41 of this embodiment has a bottomed inner tube 42 at the bottom, a bottomed cylindrical outer tube 44 having a circular opening 43 at the top, and an elliptical flattened upper opening 45. It is also possible to adopt a structure in which a guide tube 46 having a similar shape and an open bottom is fitted into the guide tube 46. With this structure, the source material can be easily filled into the crucible 41 by removing the guide tube 46 compared to the first embodiment.

As described above, according to the apparatus of the present invention, molecules evaporated from the source material in the crucible collide with the real wall of the crucible, and then the influence of the components reflected and attached to the substrate is reduced.
Epitaxial crystals with uniform thickness can be obtained.

〔Effect of the invention〕

As described above, according to the hot wall epitaxial growth apparatus of the present invention, an epitaxial crystal having a uniform thickness can be obtained over a large area on a substrate.

[Brief explanation of drawings]

Figure 1+a) is a perspective view of the crucible of the device of the present invention;
bl is a side view of the crucible of the apparatus of the present invention, FIG. 1(C) is a front view of the crucible of the apparatus of the present invention, FIG. FIG. 4 is a perspective view of the second embodiment of the crucible of the present invention, FIG. 5 is a schematic diagram of the hot wall epitaxial growth device, and FIGS. 6 and 7 are A distribution diagram of the thickness of an epitaxial layer formed using a conventional device is shown. In the figure, 31.41 is a cooking pot, 32.43.45 is an opening, and 33.
42 is an inner tube, 34 is a hot wall, 35 is a substrate, 36
is the epitaxial layer thickness distribution curve, 44 is the outer tube, 4
6 is the guide tube, ^, B, C are the positions occupied by the evaporated molecules, l is the dimension of the opening, is the line segment, 0 is the long axis, 0 is the substrate 4
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Claims (2)

[Claims] (1) In an apparatus consisting of a vacuum chamber, a crucible installed in the vacuum chamber, which houses a source for forming an epitaxial crystal layer and has a heated side wall, and a substrate installation stand on which a substrate is placed on the crucible. an opening (32) of the crucible (31) in which the source is accommodated;
1. A hot wall epitaxial growth device characterized by having an elliptical shape and a side surface having a flattened shape. (2) The crucible includes a cylindrical outer tube (44) with a circular opening (43) and a bottom, and an upper opening (44) installed inside the outer tube.
Hot wall epitaxial growth according to claim 1, characterized in that the guide tube (45) has an elliptical shape, the side portions are processed into a flat shape, and the bottom portion is composed of a cylindrical guide tube (46). Device.