JPS6327426B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a vapor phase growth apparatus, and in particular, the present invention relates to a vapor phase growth apparatus, and in particular, at least the upper part of a reaction chamber has a double wall structure with an inner bell gear and an outer bell gear, and there is a gap between the double walls. The present invention relates to effective cooling of an inner bell gear in a vapor phase growth apparatus in which the inner bell gear is cooled by flowing cooling gas.

[Prior art]

For example, in a vertical vapor phase growth apparatus, as shown in FIG. 2, a reaction chamber 3 is formed by a base plate 1 made of stainless steel and an inner bell gear 2 made of quartz.
The outside of the inner bell gear 2 is covered with an outer bell gear 4 made of stainless steel, and the outer bell gear 4 is cooled by flowing cooling water into a jacket (not shown), and is also cooled through a cooling gas supply port 5 provided at the top of the outer bell gear 4. In addition to supplying cooling gas such as _N2 gas and air, the outer bell gear 4
The inner bell gear 2 is cooled by causing cooling gas to flow into the gap 7 between the two bell gears 2 and 4 by exhausting air from a plurality of exhaust ports 6 provided at the lower side of the inner bell gear.

In addition, in FIG. 2, 8 is a susceptor, 9 is a work coil, 10 is a wafer, 11 is a hollow rotating shaft,
12 is a nozzle, 13 is an exhaust port, 14 is an observation window, 1
Reference numeral 5 denotes a photosensor for controlling the temperature of the susceptor 8, which heats the susceptor 8 and the wafer 10 with a work coil 9, and blows out semiconductor material gas from the nozzle 12 to grow semiconductor crystals on the surface of the wafer 10.

The inner bell gear 2 is cooled by the cooling gas from the cooling gas supply port 5.
This is done to prevent the semiconductor material gas supplied from the nozzle 12 into the reaction chamber 3 from thermally decomposing and adhering to the inner surface of the inner bell gear 2 when the temperature becomes high.

By the way, since the gap 7 is relatively narrow, conventionally the cooling gas supply port 5 has been formed as a simple hole opening to the gap 7, as shown in FIG.
By supplying cooling gas at a predetermined flow rate such as /mm, a flow of cooling gas is generated within the gap 7, thereby cooling the inner bell gear 2.

[Problem that the invention seeks to solve]

However, if the cooling gas supply port 5 is a simple hole, even if N ₂ gas is passed at 60/mm and silicon tetrachloride (SiCl ₄ ), which is a semiconductor material gas with a relatively high decomposition temperature, is used, If the vapor phase growth time is set to a long time, such as one hour, silicon will adhere to the inner surface of the top of the inner bell gear 2. The attached silicon absorbs infrared rays emitted from the susceptor 8, so its temperature rises and polysilicon is produced. This polysilicon is generated quickly and spreads over the entire top of the inner bell gear 2, making it impossible to measure the temperature with the photo sensor 15, or falling onto the wafer 10 during vapor phase growth and causing crystal defects. This will cause problems. The polysilicon is removed by gas etching with hydrogen chloride or cleaning with a mixture of boiling acid and nitric acid, but productivity decreases due to this removal, and cleaning with the mixture requires proper concentration control. If this is not done properly, problems such as devitrification of the quartz will occur, so it is necessary to suppress the adhesion of the semiconductor material to the inner bell gear 2 as much as possible. For this purpose, the flow rate of cooling gas supplied to the gap 7 may be increased to keep the inner bell gear 2 at a lower temperature, but this increases running costs and also causes the gap 7 to communicate with the reaction chamber 3. In the vapor phase growth apparatus of this structure, there is a problem that there is a limit to the increase in the supply flow rate because it adversely affects the flow of the semiconductor material gas in the reaction chamber 3.

[Means for solving problems]

The present invention provides a vapor phase growth apparatus in which at least a part of the reaction chamber has a double-walled structure consisting of the above-mentioned inner bell gear and outer bell gear, and the inner bell gear is cooled by flowing cooling gas between the double walls. A cooling gas nozzle provided at the top, and a plurality of nozzle holes provided radially in the cooling gas nozzle and oriented at an acute angle with respect to the upper outer surface of the inner bell gear, and the total cross-sectional area of the nozzle holes is This is set smaller than the cross-sectional area of the flow path on the base side of the cooling gas nozzle.

[Effect]

In the present invention, the cooling gas is injected between the double walls from the cooling gas nozzle provided at the top of the outer bell gear and having the nozzle hole as described above, so that the flow rate of the cooling gas does not have to be increased. Also, the cooling gas flows over a wider area at a relatively high speed, and the upper part of the inner bell gear, where semiconductor material is particularly likely to adhere, is effectively cooled.

〔Example〕

FIG. 1 showing one embodiment of the present invention will be described below. Reference numeral 2 is an inner bell gear made of quartz, which is the same as the inner bell gear 2 shown in FIG. 2, and reference numeral 4 is the same as the outer bell gear 4 shown in FIG. 2, except that the mounting portion of a cooling gas nozzle 20, which will be described later, is different. A flange 22 having a hole 21 is provided at the top of the outer bell gear 4. Flange 22
A cooling gas nozzle 20 is attached to the holding plate 23 and bolts 24. Cooling gas nozzle 2
0 and the flange 22 are sealed by an O-ring 25. The cooling gas nozzle 20 has a flow path 26, and a cooling gas supply source (not shown) is connected to the base end of the flow path 26 through a hose 27. The tip of the cooling gas nozzle 20 is formed into a conical shape, and a nozzle hole 28 opens from the flow path 26 to the conical surface of the tip.
There are multiple radial openings. These nozzle holes 28 are set so that the total cross-sectional area of the flow paths is smaller than the flow path cross-sectional area of the flow path 26, and by applying pressure to the cooling gas supply source, the nozzle holes 28 are
8, the cooling gas is injected at a relatively high speed.

Said nozzle holes 28 are oriented at a relatively small acute angle α with respect to the outer surface of the inner bell gear 2 to bring the cooling gas into positive contact with and flow along the outer surface of the inner bell gear 2. There is.

Since the present device is configured as described above, the cooling gas is vigorously injected from the nozzle hole 28 as shown by the symbol F, flows further within the gap 7 at high speed, and the degree of contact with the inner bell gear 2 increases.
Heat exchange efficiency increases. Furthermore, since the range in which the cooling gas flows at high speed is expanded, the range in which heat exchange can be performed effectively is expanded. The number of nozzle holes 28 is preferably determined in consideration of the injection opening angle in order to prevent the cooling gas from each nozzle hole 28 from coming into too strong contact with each other. Even when flowing from the top to the entire circumference, about 4 pieces are sufficient.

Next, in order to clarify the effects of the present invention, experimental results regarding the flow of cooling gas conducted using a conventional device and a device according to the present invention will be shown.

In the conventional device, the cooling gas supply port 5 shown in Fig. 2 has a diameter of 10 mm and simply opens toward the outer surface of the inner bell gear 2, and the cooling gas
_N2 gas was used at a flow rate of 60/mm.

On the other hand, in the device of the present invention, four nozzle holes 28 having a diameter of 4 mm are provided at equal intervals, and the angle α is approximately 4 mm.
The angle was 37°, and the same N ₂ gas was used as the cooling gas, with a flow rate of 50/mm. Note that both conditions are exactly the same except for the above conditions.

As shown in FIG. 3, a large number of tufts 30 that are blown by the wind are attached to the outer surface of the inner bell gear 2 at appropriate intervals around the apex of the inner bell gear 2, and cooling within the gap 7 is determined based on the behavior of these tufts 30. When the gas flow condition was investigated, it was found that in the conventional device, the range where the tuft 30 was observed to fall was in the range A shown in Fig. 4, whereas in the device of the present invention, it was found that the range B was wide. It was confirmed that the area was expanded to cover almost the entire area above the inner bell gear 2.

In addition, the semiconductor material gas was silicon tetrachloride, the vapor phase growth rate was 0.8 μm/mm, and the time for one vapor phase growth was 60 μm/mm.
mm, and with the above conventional device and the device of the present invention,
When vapor phase growth was actually performed, polysilicon was deposited on the inner surface of the top of the inner bell gear 2 in the conventional equipment, and the usability limit was reached after about 20 charges, whereas the equipment of the present invention failed even after 40 charges. There was almost no occurrence of polysilicon, which is a cause of leakage.

〔Effect of the invention〕

As described above, according to the present invention, the upper part of the inner bell gear can be effectively cooled over a wide range with a relatively small flow rate of cooling gas, thereby greatly reducing the adhesion of semiconductor material to the surface of the reaction chamber. This makes it possible to achieve higher quality vapor phase growth, improve productivity, and facilitate the use of semiconductor material gases such as monosilane (SiH ₄ ), which have a low decomposition temperature. Effects can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a partially enlarged sectional view showing the main parts of an embodiment of the present invention, Fig. 2 is a schematic sectional view showing an example of a conventional device, and Fig. 3 shows a tuft used for observing the flow of cooling gas. FIG. 4 is a partially enlarged sectional view showing the strength of the cooling gas flow in the conventional device and the device of the present invention. 2...Inner bell gear, 3...Reaction chamber, 4...
Outer bell gear, 20...Cooling gas nozzle, 28
... Nozzle hole, 30 ... Tuft.

Claims (1)

[Claims] 1. In a vapor phase growth apparatus in which at least the upper part of the reaction chamber has a double wall structure with an inner bell gear and an outer bell gear, and the inner bell gear is cooled by flowing cooling gas between the double walls, a vapor phase growth apparatus is provided at the top of the outer bell gear. and a plurality of nozzle holes provided radially in the cooling gas nozzle and oriented at an acute angle with respect to the upper outer surface of the inner bell gear, and the total cross-sectional area of the nozzle holes is A vapor phase growth apparatus characterized in that the cross-sectional area of the cooling gas nozzle is smaller than that of the flow path on the base side.