JPH07142398A - Vertical type low pressure cvd apparatus - Google Patents

Abstract

PURPOSE:To form a film of a uniform thickness on a wafer, without contamination by homogeneously mixing reactive gases, without causing an early reaction thereof. CONSTITUTION:Fans 12a and 12b having blades facing at jet holes of gas injectors 6a and 6b for respectively jetting reactive gases into an inner tube 2 are disposed at a lower part of the tube 2, i.e., low temp. part, and a ring gear 15 and pinion 16 forming a rotary structure of the fan are disposed outside a reaction tube. The fans 12a and 12b are rotated in a narrow and low-temp. closed space of a manifold 4a to stir the reactive gases.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical low pressure CVD grassland for forming a thin film on a wafer which is a semiconductor substrate.

[0002]

2. Description of the Related Art Conventionally, a vertical low pressure CVD apparatus of this type is
Polycrystalline silicon film, silicon dioxide film,
It has been used for forming various films such as a silicon nitride film.

FIG. 4 is a sectional view showing an example of a conventional vertical low pressure CVD apparatus. As shown in FIG. 4, this vertical depressurization CVD apparatus includes a boat 3 on which a plurality of wafers 10 are vertically arranged and stacked, a heat retaining cylinder 8 on which the boat 3 is mounted, a heat retaining cylinder 8 and the boat 3. Inner pipe 2 surrounding the circumference and this inner pipe 2
An outer tube 1 for wrapping the outer tube 1 and mounting a heater 9 on the outer periphery,
First and second gas injectors 6a for mounting the inner pipe 2 and the outer pipe 1 and introducing a reaction gas into the inner pipe 2,
The manifold 4 is provided with a gas exhaust port 5 for discharging unreacted gas after the reaction from the outer pipe 1 and a hatch 7 for closing the opening of the manifold 4 and attaching the heat insulation tube 8. A motor 11 for rotating the boat 3 is attached to the hatch 7 via a magnetic seal.

Next, the operation of the apparatus will be described by taking an example of forming a silicon oxide film on the wafer 10 using this apparatus. First, the wafer 10 is mounted on the boat 3, and the boat 3
The boat 3 is housed in the inner pipe 2 together with the heat insulation cylinder 8 on which Next, the heater 9 heats the closed space of the inner tube 2 to a predetermined temperature and supplies silane gas and nitrous oxide gas from the gas injectors 6a and 6b. Silane gas and nitrous oxide gas are mixed and heated to cause a thermal decomposition reaction on the surface of the wafer 10 to be deposited on the wafer 10 to form a silicon oxide film. The reacted gas or unreacted gas is discharged to the outside from the exhaust port 5 through the outer tube 1.

Further, in order to make the film thickness within the surface of the wafer 10 more uniform, the vapor phase growth was performed while the boat 3 was rotated by the motor 11 as needed.

[0006]

However, in the conventional vertical depressurization CVD apparatus described above, since the two gas injectors are arranged offset to a part along the peripheral edge of the inner tube, the supplied reaction gas is a wafer. It does not flow uniformly into the plane, and it becomes difficult to mix and supply the two kinds of gas at a constant mixing ratio. As a result, there is a problem that the film thickness to be formed varies within the wafer surface. For example,
The variation in film thickness is such that the peripheral portion of the wafer is thick and the central portion is thin. There is also a method of rotating the boat as a countermeasure against this, although the variation in the film thickness is reduced, but it cannot be suppressed within the desired variation, and rather the wafer and the holder surface of the boat are rotated because the boat is rotated. The rubbing causes dust and causes a new problem of contaminating the wafer surface.

On the other hand, in a horizontal CVD apparatus, a solution to such a problem is disclosed in, for example, Japanese Patent Laid-Open No. 4116819. This method is a method in which a fan is provided in a closed space of a substrate holder on which a single substrate is mounted and a furnace core tube for storing raw materials, and the reaction gas is agitated by the rotation of the fan to flow onto the substrate surface. However, even when this method is applied to this vertical low pressure CVD apparatus, there is a structural problem that the inner tube which is the furnace core tube is occupied by the boat and there is no space for installing the fan. Even if the boat is shortened to secure a space and a fan is provided above the inner pipe, the stirring effect cannot be expected even if the fan is rotated in a closed space in a molecular flow region state under reduced pressure. Further, since it is provided in a high temperature portion, there is a concern that the reaction gas reacts early and foreign matters may fall on the wafer surface and contaminate due to the mechanism of rotating the fan and the rotation of the fan.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a vertical decompression CVD apparatus which makes the film thickness uniform in the wafer surface and does not generate dust that contaminates the wafer surface.

[0009]

A feature of the present invention is that a boat in which a plurality of wafers are vertically arranged and stacked, a heat retaining cylinder on which the boat is mounted, an inner pipe surrounding the heat retaining cylinder and the boat. An outer tube for enclosing the inner tube and mounting a heater on the outer circumference; first and second gas injectors for mounting the inner tube and the outer tube and introducing a reaction gas into the inner tube; A vertical depressurization CVD apparatus comprising: a manifold having a gas exhaust port for exhausting a subsequent gas from the outer pipe; and a hatch for closing the opening of the manifold and attaching the heat retaining cylinder.
Is a vertical depressurization CVD apparatus having first and second fans which are positioned with their blades facing the respective gas ejection ports of the gas injector and which rotate around the center of the boat.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of the vertical decompression CVD apparatus of the present invention. This vertical low pressure CVD apparatus is
As shown in FIG. 1, the rotation mechanism of the boat 3 that induces the generation of dust is abolished, and a fan that is located with the blades facing each of the gas injection ports of the gas injectors 6a and 6b and that rotates as the center of the boat. 12a and 12b are provided, and the reaction gas is stirred in a narrow and low-temperature space region so that the mixing ratio becomes uniform. Otherwise, it is the same as the conventional example.

Here, the vanes of the fan 12a and the fan 12b have the same inclination so that the reaction gas can easily flow upstream, but it is desirable to change the pitch of the vanes in order to enhance the stirring action. The fans 12a and 12b are formed outside the sleeve-shaped rotating shaft 18. Further, the sleeve-shaped rotary shaft 18 is exposed to the outside of the hatch 8a via the magnetic seal 14 in order to prevent dust from being generated, and the rotary shaft 18 protruding from the hatch 8a.
Attach the ring gear 15 to the end of the
Engages with the pinion 17 of the motor 17. In addition,
In order to enhance the stirring action by this fan, it is possible to think of a method in which the rotation directions are different from each other, but there is a danger that dust will be generated due to one additional rotation mechanism, so it is not a good idea. .

2 (a) and 2 (b) are a graph showing the film thickness in the wafer surface and a plan view of the wafer. A syrincon oxide film was formed on a 6-inch wafer by trial, and evaluation was performed in the sense of comparing the device of this example with the conventional device. As a result, as shown in FIG. 2, the variation in the wafer surface was reduced as compared with the case where the boat was rotated by the conventional device.

FIG. 3 is a view showing a modification of the fan shown in FIG. In order to reduce the generation of dust and further improve the stirring function, the fan of this vertical low-pressure CVD apparatus staggers the positions of the blades 19a of the fan 12a and the blades 19b of the fan 12b as shown in FIG. It is arranged. By shifting the pitches of the fan blades from each other, the probability of collision with the molecules of the reaction gas increases and the stirring effect can be expected even in the reduced molecular flow region. In particular, this device is effective when the difference in the molecular weight of the reaction gas is large.

[0015]

As described above, according to the present invention, the fan having the blades facing the ejection ports of the gas injectors for ejecting the respective reaction gases reacts with the lower part of the inner tube which is the low temperature part and the rotation mechanism of the fan. The reaction gas is agitated by rotating the fan inside a closed space with a narrow and low temperature outside the tube, so that the reaction gas is uniformly mixed without causing an early reaction and then uniformly on the wafer surface in the high temperature region. Since it can be flowed, there is an effect that a film having a uniform film thickness can be grown in the surface without being contaminated.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a vertical low pressure CVD apparatus of the present invention.

FIG. 2 is a graph showing a film thickness within a wafer surface and a plan view of the wafer.

FIG. 3 is a diagram showing a modified example of the fan of FIG.

FIG. 4 is a cross-sectional view showing an example of a conventional vertical low pressure CVD apparatus.

[Explanation of symbols]

 1 Outer Pipe 2 Inner Pipe 3 Boat 4, 4a Manifold 5 Gas Exhaust Port 6a, 6b Gas Injector 7, 7a Hatch 8, 8a Heat Insulation Tube 9 Heater 10 Wafer 11, 17 Motor 12a, 12b Fan 14 Magnetic Seal 15 Ring Gear 16 Pinion 18 Rotating shafts 19a, 19b wings

Claims (2)

[Claims] 1. A boat in which a plurality of wafers are vertically arranged and stacked, a heat retaining cylinder on which the boat is mounted, an inner tube surrounding the heat retaining cylinder and the boat, and an outer periphery surrounding the inner tube. An outer tube to which a heater is attached, and first and second gas injectors for mounting the inner tube and the outer tube and introducing a reaction gas into the inner tube are provided, and the gas after the reaction is discharged from the outer tube. In a vertical decompression CVD apparatus equipped with a manifold having a gas exhaust port and a hatch for closing the opening of the manifold and mounting the heat retaining tube, a wing portion is provided at each of the gas ejection ports of the first and second gas injectors. A vertical depressurization CVD apparatus comprising first and second fans that face each other and rotate around the center of the boat. 2. The vertical low pressure CVD apparatus according to claim 1, wherein the blades of the first fan and the blades of the second fan are arranged in a staggered manner.