JPH0720912Y2 - Rotating susceptor for semiconductor substrate - Google Patents

Description

[Detailed Description of the Invention] [Outline] The present invention relates to a rotary semiconductor substrate susceptor for a vapor phase epitaxial growth apparatus, and suppresses the generation of defects on the epitaxial growth surface caused by fine foreign particles generated as the substrate support rotates. For the purpose, the width of the annular gap between the rotation support of the substrate and the fixed support around it is set to be larger than 0.5 mm, or the shape of the rotation support is conical, and the part where they rub is the crystal growth surface. It will be configured to be kept away from.

[Industrial application field]

In vapor phase epitaxial growth of semiconductors, especially compound semiconductors, the wafer size has been increased to 3 inches φ, so that the distribution of the grown film thickness is made uniform,
It is usual to advance crystal growth while rotating the substrate wafer.

As the structure of the substrate support base, as can be easily understood from FIG. 1 or 3, the rotation driving rod 4 is extended in the axial direction of the reaction tube, and the rotation of the rod is bitten by the racks 7 and 7 '. In many cases, the structure is such that it is transmitted to the support base 2 by matching and the support base is rotated. When the gas flow velocity in the tube is several tens of cm / s, the rotation speed is
It is about several to ten and several rpm.

Further, graphite is often used as a material for forming this kind of semiconductor substrate susceptor. This is a selection made by evaluating that high-purity materials are easily available, and that it has a large thermal conductivity and is advantageous for making the temperature distribution of the wafer uniform, but it has a small friction coefficient. Also, it is advantageous to smoothly perform the rotation operation with the above structure.

[Conventional technology]

FIG. 3 shows the structure of a known rotary substrate susceptor. The figure (a) is a top view and the figure (b) is the XX 'sectional view. Reference numeral 1 is a fixed base that is a susceptor body, and 2 is a rotary base that is a substrate support base. There is a dowel hole in the center of the fixed base and a protrusion in the center of the rotary base, and the rotary base rotates around the part where the two are fitted together.

The power of rotation is transmitted from the outside by the drive rod 4,
Racks 7 and 7'are formed on the tip of the rod 4 and on the bottom of the turntable, and the rotational force is transmitted by the biting of both.

Further, the upper surface of the rotary table on which the substrate is placed and the upper surface of the fixed table are substantially flush with each other. This is to smooth the gas flow in the reaction tube.

[Problems to be solved by the device]

When epitaxial growth is performed using the substrate susceptor having such a structure, fine depressions or projections may occur on the growth surface. This surface defect does not always occur, but it causes a defective chip when an integrated circuit is formed, and in order to improve the manufacturing yield, it is required to prevent the occurrence of this kind of defect as much as possible. .

[Means for Solving the Problems]

In order to meet this demand, the substrate susceptor of the present invention has a width of the annular gap between the substrate rotation support base and the surrounding fixed base of more than 0.5 mm, or the rotation support base has a conical shape. .

[Operation] The present inventor has found that the cause of the above-mentioned depressions or protrusions is that fine foreign matter is discharged into the airflow due to the friction between the rotary table and the fixed table and drops onto the substrate. Hereinafter, in the present specification, these depressions and protrusions are collectively referred to as surface defects.

In the conventional rotary susceptor, as shown in FIG.
The structure is such that the gap 5 between the fitting of the fixing base 1 and the fixing base 1 is as small as possible. This is because the reaction gas remains in the space below the turntable when it is desired to change the composition of the growth layer, and it is difficult to obtain a sharp change in the crystal composition. It is a thing.

Since the material forming the susceptor is graphite as described above, it rotates smoothly with little friction before the crystal growth proceeds. However, as the crystal growth progresses, the reaction product is also deposited on the upper surface of the susceptor, and the reaction product is scraped off with the rotation and scattered in the air flow.

When the fine particles thus scattered fall on the surface of the substrate, crystal growth in that portion is hindered or abnormal growth occurs, resulting in the formation of depressions or protrusions.

Therefore, if the annular gap 6 between the rotary table and the fixed table is made sufficiently large as in the present invention of FIG. 1, even if the deposition progresses in each of these parts, it is scraped off and the air flow is reduced. It doesn't scatter inside. Therefore, the fall of the foreign matter that causes the surface defect is significantly suppressed, and the occurrence of the surface defect is significantly reduced.

Further, as shown in FIG. 2, if the portion where friction is mainly generated is moved to the back surface of the rotary table, the accumulation and scattering of foreign matter can be reduced, and the occurrence of surface defects can be reduced.

〔Example〕

FIG. 1 shows a first embodiment of the present invention. In the figure, 1 is a fixed base that is a susceptor main body, and 2 is a substrate support that is a rotary base. The substrate is centered around a portion where a center hole of the fixed base and a protrusion of the central part of the rotary base fit together The point that the support base rotates is the same as the conventional device. Furthermore, the rotary drive rod 4
The point that the rotational force of the drive rod 4 is transmitted by the biting of the rack 7 at the tip of the rack 7 and the rack 7'on the back of the turntable remains unchanged. The size of the substrate supporting surface is such that a 3-inch wafer can be mounted.

In this embodiment, the annular space 6 is intentionally provided between the rotary table and the fixed table, which is different from the conventional device. Here, the width of the gap is set to 0.5 mm,
This is a target value, and even if it expands to about 1 mm due to an error in graphite processing, it does not mean that there is a particular obstacle.

It has been found that when the voids of this degree are provided, the problem of retention of the reaction gas, which has been a concern in the past, does not cause the inconvenience expected in the past, judging from the results of actual use.

FIG. 2 is a schematic sectional view showing a second embodiment of the present invention. Also in the drawing, the parts having the same numbers as in FIG. 1 and FIG. 3 indicate that they have the same function. The apex angle of the cone on the back surface of the substrate support is 170 degrees here (tilt angle 5
Every time).

In this embodiment, the rotating support base is supported by the conical portion on the back surface and has a structure in which the support base rubs against the fixed base. Since the friction part is on the back side of the substrate support, it is far from the substrate surface and the deposition of the friction part is small, it is less likely that fine foreign particles will scatter in the air flow, and the epitaxial growth surface will be fine. The occurrence of various surface defects is also reduced.

[Effect of device]

As described above, by using the rotary substrate susceptor of the present invention, it is possible to suppress the generation of fine depressions or protrusions on the crystal growth surface and obtain a low defect epitaxial crystal.

According to the conventional apparatus, the defect density of this type 60 to 1,000 / cm ²
However, when the susceptor of the present invention was used, this was 50 to 100 / cm ² . That is, in the conventional apparatus, the lot-to-lot variation was large and the lots were distributed on the high density side, whereas the apparatus of the present invention shows a stable value in the lower side.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing the structure of the susceptor of the first embodiment, FIG. 2 is a schematic sectional view showing the structure of the susceptor of the second embodiment, and FIG. 3 is a sectional view showing the structure of a conventional susceptor. In the drawing, 1 is a fixed base, 2 is a substrate support, 3 is a GaAs wafer, 4 is a rotary drive rod, 5 and 6 are voids, and 7 and 7'are racks.

Claims (2)

[Scope of utility model registration request] 1. A circular substrate support table (2) disposed in a reaction tube and having a substrate support surface substantially parallel to a gas flow, and rotating in the surface, and a substrate support surface surrounding the support table. A fixed base (1) having a substantially flat surface as a surface, and a rotary drive rod (4) having a rotary shaft substantially orthogonal to the rotary shaft of the support base and rotating the rotary base by its own rotation. A rotary susceptor for a semiconductor substrate, characterized in that an annular gap having a width of 0.5 mm or more is provided between the substrate support base and the fixed base. 2. A circular substrate supporting base (2) disposed in a reaction tube, having a substrate supporting surface substantially parallel to a gas flow, and rotating in the surface, and the substrate supporting surface surrounding the supporting base. A fixed base (1) having a substantially flat surface as a surface, and a rotary drive rod (4) having a rotary shaft substantially orthogonal to the rotary shaft of the support base and rotating the rotary base by its own rotation. Is a semiconductor substrate susceptor for vapor phase epitaxy, which has a conical shape having a maximum thickness at a rotation axis portion on a back surface side of the substrate support surface of the substrate support base. Rotating susceptor.