JPH0773099B2 - Semiconductor vapor deposition equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a semiconductor vapor phase epitaxy apparatus, and more particularly, to a method for growing a semiconductor substrate on a semiconductor substrate by reducing the turbulence of the flow of a source gas and a carrier gas in a lower portion of a susceptor. The present invention relates to a semiconductor vapor phase epitaxy apparatus that improves the uniformity of a thin film.

(Prior Art) Conventionally, a semiconductor vapor phase epitaxy apparatus of this type is shown in FIG.
1 on the carbon susceptor (21) in the vertical cylindrical reaction tube (20) as shown in (b) and FIGS. 3 (a) and (b).
While mounting one or more semiconductor substrates (22) and performing high-frequency heating with an external RF coil (23), the cooling jacket (24) is supplied with a coolant, such as cooling water, to control the temperature of the peripheral wall of the reaction tube (20). Are doing
In this apparatus, the mixed gas consisting of the raw material gas and the carrier gas introduced from the gas introduction port (25) in the upper part of the circular tubular reaction tube (20) reacts near the surface of the carbon susceptor (21), A semiconductor thin film grows on the semiconductor substrate (22). In this case, the influence of the geometrical symmetry deviation between the susceptor (21) and the reaction tube (20) and the asymmetry of the flow due to the discharge port (26) is reduced to make the thickness of the growing semiconductor thin film uniform. Therefore, growth is usually performed while rotating the susceptor (21) at a constant rotation speed. Sign (2
7) is a front chamber for replacing the substrate (22) on which the semiconductor thin film is grown, (28) is a gate valve, (29) is a purge gas inlet of the front chamber, and (30) is an opening / closing door. Further, (31) is a susceptor holder, (32) is a rotating shaft, and (33) is a thermocouple. In addition, in FIG. 2 and FIG. 3, the same parts are designated by the same reference numerals.

(Problems to be Solved by the Invention) By the way, the susceptor holder (31) in the conventional semiconductor vapor phase epitaxy apparatus as shown in FIG. 2 has a top surface end portion at best as shown in FIG. 2 (b). The flow of the reaction gas introduced from the gas introduction port (25) of the reaction tube (20) is partly separated, and the flow is greatly disturbed from the downstream part of the upper end, and the effect is upstream. It was not possible to say that the uniformity of the film thickness distribution deposited up to the edges and on the semiconductor substrate (22) was 10 mm inward from the edge of the substrate. Moreover, the susceptor (2
In 1), the corners are only chamfered as shown in Fig. 2 (b), so the gas flow separates in the downstream part of the susceptor, and small vortices are generated, and the rotation axis (32) An upward flow is generated along with it, and a large vortex is generated. The influence of such disturbance of the flow is transmitted to the upstream, so that the uniformity of the film thickness on the surface of the semiconductor substrate (22) is deteriorated.

As described above, in the conventional semiconductor vapor phase growth apparatus shown in FIGS. 2 and 3, the flow of the reaction gas is separated at the downstream end of the susceptor (21), and various vortices are generated. Since the vortices are periodically generated, the pressure fluctuation affects upstream and changes the thickness of the boundary layer on the substrate. The fluctuation of the thickness of the boundary changes the deposition rate. Further, since this effect becomes larger nearer to the downstream side, it causes a larger variation in the deposition rate at the edge portion of the wafer. Under normal growth conditions, the Mach number M is much smaller than 1 (M = v / a
<< 1.0, where v: gas velocity, a: speed of sound) Therefore, it is difficult to obtain a film having a uniform film thickness. Especially when a large number of wafers are grown at the same time, the semiconductor substrate (22) near the downstream part of the susceptor (21).
The film thickness uniformity is worse than that of the semiconductor substrate (22) on the upstream side. However, it is difficult to reduce the variation between the substrates. In addition, the reaction product of the raw material is apt to adhere to the rotary shaft (32) near the downstream portion of the susceptor (21), and when the adhered product drives the rotary shaft (32), it may scrape off, and may cause the shaft of an O-ring or the like. The sealing material is often damaged, resulting in a large number of maintenances.

The present invention has been made in view of the above circumstances, and in particular, reduces the turbulence of the flow in the vicinity of the downstream portion of the susceptor with a simple structure to create a flow with little pressure fluctuation, and to improve the uniformity of the film thickness. It is an object of the present invention to provide a semiconductor vapor phase growth apparatus that can be further improved.

(Means for Solving the Problems) The above object of the present invention is to mount a semiconductor substrate on a susceptor rotating in a reaction tube and introduce a source gas and a carrier gas into the reaction tube to heat the semiconductor substrate. In a device for causing a reaction such as thermal decomposition to grow a semiconductor thin film on a semiconductor substrate, a gas rectifying tube is formed below the susceptor, and a rectifying gas supply tube is provided downward from the inside of the gas rectifying tube. This has been achieved by a semiconductor vapor phase growth apparatus characterized in that a rectifying gas is blown out through it.

(Example) Hereinafter, an example of an embodiment of a semiconductor vapor phase growth apparatus according to the present invention will be described with reference to the drawings.

In FIGS. 1 (a) and 1 (b), reference numeral (A) indicates a susceptor portion in the semiconductor vapor phase epitaxy apparatus, and in this example, parts other than the susceptor portion (A) are shown in FIGS. 2 and 3. Since it is similar to the conventional semiconductor vapor phase epitaxy apparatus shown in FIG. 1, its illustration and description are omitted.

First, the susceptor part (A) in the semiconductor vapor phase epitaxy apparatus shown in FIG. 1A has a gas flow straightening tube (7) having a taper part (7a) from the upper part to the substantially central part on the side surface part of the susceptor holder (2). A cover member (9) provided with a flat plate (8) having a rectified gas blowing hole (8a) ... The tip of a rectifying gas supply pipe (9a) for introducing the rectifying gas is arranged inside the covering member (9), and the rectifying gas supply pipe (9a) is provided with a carbon susceptor (1). It is formed to rotate with a rotating shaft (5) for rotating. (6) shows a wafer provided on the carbon susceptor (1), and (3) shows a capillary tube interposed between the carbon susceptor (1) and the sheath thermocouple (4).

Since the susceptor part (A) is configured as described above,
In using it, first, the rectifying gas supply pipe (9)
By letting the rectifying gas pass through the inside, the rectifying gas is introduced into the cover member (9) provided at the bottom of the susceptor holder (2) and the flat plate (8) provided below the cover member (9). The rectified gas is blown into the reaction tube (not shown) of the semiconductor vapor phase growth apparatus through the rectifying gas blowing holes (8a), (8a). As a result, the turbulence of the flow due to the separation of the reaction gas in the lower portion of the gas rectifying cylinder (7) can be significantly reduced, and a uniform film thickness can be grown on the semiconductor substrate. In this case, the film thickness uniformity was good from the edge of the substrate to within 5 mm (the variation was within ± 5%), and the gas blown out was much higher than the reaction gas in the reaction tube (not shown). Since the temperature is extremely low, the adhesion of reaction products to the rectifying gas supply pipe (9) and the like is reduced, and the adhered material is peeled off when the susceptor (1) is rotated or moved up and down to take out the substrate, and an O-ring for sealing is used. Less likely to deteriorate,
We were able to reduce the number of maintenances and improve safety. Further, it can be seen that in the case of the wafer, the effect of increasing the uniformity is represented by the surface ratio, and in the case of the 2 ″ wafer, the effect is 78%, which is a remarkable effect.

Next, in the susceptor part (A) in the semiconductor vapor phase epitaxy apparatus shown in FIG. 2B, a heat insulating gas rectifying cylinder (11) is attached to the lower part of the carbon susceptor (10) to attach a reaction tube (not shown). The position where the turbulence of the flow of the reaction gas is generated in the downstream part of (1) is set as far as possible from the susceptor (10). Further, at the bottom of the carbon susceptor (10), the rectifying gas blowing holes (12a), (1
A cover member (13) provided with a flat plate (12) perforated with 2a) is attached, and inside the cover member (13), a rectified gas supply pipe (for introducing rectified gas) ( The tip of 14) is arranged. The rectifying gas supply pipe (14) is formed so as to rotate together with the rotation shaft (15) for rotating the carbon susceptor (10).
(16) is a wafer provided on the outer surface of the carbon susceptor (10), (17) is a susceptor holder, (18) is a capillary tube,
(19) indicates a thermocouple.

Since the susceptor part (A) is configured as described above,
In growing a semiconductor thin film, first, a rectifying gas is passed through a rectifying gas supply pipe (14), so that the rectifying gas is covered with a cover member (13) provided at the bottom of the susceptor (10).
The rectified gas blowing holes (12a) and (12a) of the flat plate (12) that is guided inside and is provided below the cover member (13).
Is blown into a reaction tube (not shown) of the semiconductor vapor phase growth apparatus. As a result, an ascending flow of the reaction gas along the rotating shaft (15) for rotating the carbon susceptor (10) in the reaction tube is hardly seen. When an epitaxial film of GaAs was actually grown, in the conventional device shown in FIGS. 2 and 3, the uniformity was extremely poor at 5 mm from the edge of the semiconductor substrate (variation was ± 5.
%), But when the device of the present invention is used, it is 3 mm from the edge of the substrate.
At this point, the uniformity deteriorated. In the case of a 2 ″ wafer, this increase in uniformity was 27% in terms of area ratio, which shows that a remarkable effect was obtained.

(Operation and Effect of the Invention) According to the semiconductor vapor phase growth apparatus of the present invention, as described above, the gas rectifying cylinder is provided in the lower portion of the susceptor, and the rectifying gas is directed downward from the inside of the gas rectifying cylinder. It is formed so that the rectified gas is blown out through the supply pipe. Therefore, since the turbulence of the reaction gas in the downstream portion of the susceptor in the reaction tube can be significantly reduced, the uniformity of the thin film grown on the semiconductor substrate can be remarkably enhanced, and the rotation axis of the reaction product and the like can be improved. Can be prevented, the frequency of maintenance is reduced, and further safety can be obtained.

[Brief description of drawings]

1 (a) and 1 (b) are explanatory views of a susceptor portion in a pancake and barrel type semiconductor vapor phase growth apparatus according to the present invention, FIGS. 2 (a), 2 (b) and 3 (a), FIG. 2B is an overall view of a conventional pancake and barrel type vapor phase growth apparatus and an explanatory view of a susceptor section. Explanation of code A …… Susceptor part (1) …… Carbon susceptor (2) …… Susceptor holder (7) …… Gas flow straightening cylinder (8) …… Flat plate (9) …… Cover member (9a) …… Rectifying gas Supply pipe

Claims (1)

[Claims] 1. A semiconductor substrate is mounted on a susceptor that rotates in a reaction tube, and a raw material gas and a carrier gas are introduced into the reaction tube to heat the semiconductor substrate, thereby causing a reaction such as thermal decomposition to cause a reaction on the semiconductor substrate. In a device for growing a semiconductor thin film, a gas rectifying cylinder is provided in the lower part of the susceptor, and rectified gas is blown out downward from inside the gas rectifying cylinder through a rectifying gas supply pipe. Semiconductor vapor phase growth equipment.