JPH0689863A - Formation of thin film - Google Patents

Abstract

PURPOSE:To pile up reaction gas on a substrate by thermal decomposition while arranging a plurality of base bodies in a tubular reactor in the vertical direction and using an exhaust system. CONSTITUTION:During thermal decomposition of reactive gas by using a vertical CVD device, inert gas is simultabeously introduced so as to suppress particles generated from an L-shaped tube without oxidizing the base body surfaces. Thereby, reliability and yield of a semiconductor device can be improved by in every way preventing adhesion of particles to the base body surfaces.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for forming a thin film on a plurality of substrates.

[0002]

2. Description of the Related Art In recent years, a vertical CVD apparatus has been replaced with a horizontal CVD apparatus in which a plurality of substrates are horizontally arranged in a tubular reactor.
So-called low-pressure CVD in which a thin film is thermally reacted under reduced pressure
Has become the mainstream of law.

A conventional technique will be described below with reference to the process chart of FIG. 2 and the schematic sectional view of the vertical CVD apparatus of FIG.

In FIG. 3, the manifold 1 is provided with a plurality of gas introduction ports 2 and 3, through which reaction gas is introduced into the reactor. The inside of the reactor is formed by a quartz inner tube 4 and a quartz outer tube 5, a plurality of substrates are fixed by a boat 6, and a thin film is formed on the surfaces of these substrates by thermal reaction. The remaining reaction gas then passes between the quartz inner tube 4 and the quartz outer tube 5 and is exhausted from the exhaust port 7 to the exhaust system. Further, an L-shaped tube 8 is connected from the manifold 1 between the quartz inner tube 4 and the quartz outer tube 5, and when the quartz boat 6 is taken in and out of the reactor, nitrogen is passed through the L-shaped tube 8. By flowing a large amount, the surface of the substrate is prevented from being oxidized.

FIG. 2 shows a process of forming a thin film by a conventional technique. When the quartz boat 6 is taken in and out of the reaction tube, nitrogen is flown from the L-shaped tube 8 and the gas introduction ports 2 and 3, and when the thermal decomposition is caused, only the reaction gas is flown from the gas introduction ports 2 and 3. ing. Also, in reactive gas exhaust, L
No gas is flowing through the character tube 8 and the gas inlets 2 and 3.

[0006]

However, in the above-mentioned conventional method, the reactive gas also flows into the inside of the L-shaped tube 8 at the time of thermal decomposition and exhaust of the reactive gas, and a thin film is formed to form the quartz boat 6. L tube 8 when putting in and out of the reactor
When a larger amount of nitrogen gas is flowed, there is a problem in that mainly exfoliated material of the thin film material, so-called particles, which adheres to the inner surface of the L-shaped tube 8 adheres to the surface of the substrate. Further, if nitrogen gas was not flown, the particles would not adhere, but there was a problem that the surface of the substrate was oxidized.

The present invention solves the above problems by providing a method for forming a thin film that does not oxidize the surface of a substrate, suppresses particles generated from an L-shaped tube 8 and prevents the particles from adhering to the surface of the substrate as much as possible. The purpose is to improve the reliability and yield of the device.

[0008]

In order to achieve the above object, according to the present invention, a small amount of an inert gas is fed from the L-shaped tube into the reactor during reactive gas exhaust during or after thermal decomposition in a thin film forming process. I tried to flush it.

[0009]

By the above-mentioned means, even if the reactive gas flows into the reactor, the inert gas is caused to flow from the L-shaped tube so that the reactive gas does not flow into the L-shaped tube and a thin film is not formed. Particles do not adhere to the substrate even when nitrogen is flowed from the L-shaped tube during the loading and unloading.

[0010]

EXAMPLE An example of the present invention will be described below with reference to FIGS. 1 and 3 for forming a silicon nitride film.

In the wafer transfer process, a silicon wafer having a diameter of about 150 cm that has been cleaned in advance is placed on the quartz boat 6. Next, in the boat loading process, the quartz boat 6 was charged with nitrogen into the quartz inner tube 4 in the reactor from the L-shaped tube 8 at about 10 liters / minute, and from the gas introduction tubes 2 and 3 at about 1 liter / minute, respectively. It was introduced into the reactor while flowing at a speed. A temperature of about 780 ° C. is set in the reactor by using the heater 9. Then, in the process of vacuum evacuation I
The reactor was evacuated to less than or equal to millitorr, and the inside of the reactor was left at a pressure of 300 millitorr for about 30 minutes while flowing nitrogen through the gas introduction pipes 2 and 3, and this was made a temperature stabilization process, and the temperature stabilization was waited. Then, again in the process of evacuation II, the nitrogen in the reactor was evacuated and the pressure was lowered to 10 mTorr or less. During the film formation (pyrolysis) process, ammonia was introduced through the inlet 2 at 750 cc / min, and dichlorosilane was introduced at 75 cc through the inlet 3.
Introduced at a rate of / min. During this period, nitrogen was simultaneously introduced from the L-shaped tube 8 at a rate of about 50 cc / min, the pressure inside the reactor was set to about 300 mTorr, and after about 50 minutes, while nitrogen was flowing from the L-shaped tube, ammonia and dichlorosilane were removed. The flow stopped. Further, in the process of evacuation III, after the remaining reaction gas was exhausted for about 15 minutes, nitrogen gas was stopped and the inside of the reactor was further exhausted to 10 mTorr or less. Then, the vacuum exhaust valve was closed, and the process was returned to atmospheric pressure. The inside of the reactor was back-filled with nitrogen from the gas inlets 2 and 3, and the atmospheric pressure (about 7
60 torr). Next, in the boat unloading process, the quartz boat 6 is charged with nitrogen in the quartz inner tube 4 in the reactor.
Approximately 10 liters / minute from the character tube 8, gas introduction tubes 2 and 3
Each of them was taken out while flowing at a rate of about 1 liter / minute. Then, the wafer was taken out from the quartz boat 6 during the wafer transfer process and evaluated. About 1 for these wafers
It was confirmed that a 600 Å silicon nitride film was deposited and the number of particles of about 0.3 μm or more was 10 or less.

In this embodiment, nitrogen is used as the gas introduced from the L-shaped tube 8. However, the gas is not limited to this, and an inert gas such as helium or argon may be used.

[0013]

As described above, according to the thin film forming method of the present invention, it is possible to reduce the mixing of particles in the process of forming the thin film without oxidizing the surface of the substrate, thereby improving the reliability and yield of the semiconductor device. be able to.

[Brief description of drawings]

FIG. 1 is a schematic view of a thin film forming process according to the present invention.

FIG. 2 is a schematic view of a thin film forming process according to a conventional technique.

FIG. 3 is a schematic sectional view of a vertical CVD apparatus.

[Explanation of symbols]

 1 Manihold 2 Gas inlet 3 Gas inlet 4 Quartz inner tube 5 Quartz outer tube 6 Quartz boat 7 Exhaust port 8 L-shaped tube 9 Heater

Claims (1)

[Claims] 1. A plurality of substrates are vertically arranged in a tubular reactor, and an exhaust system is used to pyrolyze and deposit the reactive gas on the substrate during the pyrolysis or thin film formation of the reactive gas. A method for forming a thin film, which comprises introducing an inert gas into the tubular reactor during the exhaust after the introduction of the reactive gas in the forming process.