JPS6294942A - Manufacture of thin film - Google Patents

Abstract

PURPOSE:To reduce the oxygen concentration in a silicon nitride film also reducing the interfacial level of silicon nitride film/III-V compound by a method wherein, when the silicon nitride film is formed by plasma chemical vapor growing process on a III-V compound semiconductor substrate, the substrate is impressed with bias voltage. CONSTITUTION:A GaAs wafer e.g. loaded on a carbon susceptor 3 to be heated by a heater 11 is arranged in a quartz reaction tube 1. The inside of quartz tube 1 is pressure-reduced to be exhausted by a rotary pump 4. To deposit a silicon nitride film, silane gas and ammonium gas are led into the quartz tube 1 at the flow ratio of 15:1 through a stainless pipe 5 to be plasma-excited by a high-frequency power supply 6 and a high-frequency coil 8. At this time, the wafer 2 is impressed with bias voltage of -100--200V to form the silicon nitride film.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a silicon nitride film with extremely low impurities in the film.

[Conventional technology]

Conventionally, attempts have been made to form a silicon nitride film by plasma chemical vapor deposition as a stabilizing film on the surface of a ■-■ group compound semiconductor.

[Problem that the invention seeks to solve]

However, silicon nitride films manufactured by plasma chemical vapor deposition contain several atomic percent of oxygen as an impurity in the film, and this makes it difficult to form silicon nitride films on, for example, gallium arsenide substrates. MIS (Metal-Insulator-8 m1c) obtained by
In a transistor with a conductor structure, this increases the interface state density, which is one of the factors that deteriorates the characteristics (IEEE, Trans, ED-26°185
4, 1979)).

An object of the present invention is to provide a method for manufacturing a silicon nitride film that solves this problem.

[Means for solving problems]

The gist of the present invention is to apply /(ias) to the substrate when a silicon nitride film is formed on the substrate of a -V group compound semiconductor by plasma chemical vapor deposition.

[For production]

Some of the ions in the plasma flow into the bias-applied substrate surface, and during the film formation process, the substrate surface is bombarded with ions, knocking out impurity gases adsorbed on the formed film surface and purifying the film. will be held. (Basics of thin film creation, P2
S5.1981, Nikkan Kogyo Shimbunsha).

〔Example〕

Hereinafter, this invention will be explained based on examples.

FIG. 1 shows a state in which a ■-v group compound semiconductor, such as a GaAg wafer 2, is placed on a carpin susceptor 3 in a quartz reaction tube 1. In FIG. The susceptor 3 is heated by the heater 1. Inside the quartz tube 1 is a rotary pump f for depressurizing exhaust.
To deposit a silicon nitride film, evacuate under reduced pressure in step 4, silane gas and ammonia gas are introduced through a stainless steel tube 5 at a flow rate ratio of 15:1, and plasma is generated using a high frequency power source 6 and a high frequency coil 8. At this time, the wafer 2 is excited by the DC power supply 9.
A bias voltage of -100 to -200v is applied to. Note that the substrate temperature during film formation was 300°C. The film growth rate is 200X/min at a reaction gas pressure of 1 torr.

Through the above steps, a silicon nitride film was formed on the arsenic lithium substrate. The following table shows the results of evaluating the oxygen concentration contained in the silicon nitride film formed by this method and the interface state density at the interface between the silicon nitride film and gallium arsenide. For comparison, the case of a silicon nitride film produced by a conventional method is also shown.

Film manufacturing method Oxygen concentration in film (at%) Interface state density (α
-2) Conventional method 5.6 ~ 1012 Current method 0.60 ~ 1011 The oxygen concentration in the film was determined by secondary ion mass spectrometry, and the interface state density was determined by C
This is the result of measurement using the v method. In the silicon nitride film produced by this method, the oxygen concentration in the film was reduced by a C order compared to the conventional method, and the interface state density was also reduced by a C order.

Therefore, it can be seen that the oxygen concentration in the film and the interface state density of the obtained silicon nitride film are significantly reduced compared to films made by the conventional method.

〔Effect of the invention〕

The present invention has the effect of reducing the oxygen concentration in the silicon nitride film formed on the m-v group compound substrate and reducing the interface state density of the silicon nitride film/m-v group compound. It is something.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an apparatus for forming a silicon nitride film by the plasma CVD method used in the example. 1 is a quartz reaction tube, 2 is a G1As wafer, 3 is a carbine susceptor, 4 is a rotary pump, 5 is a stainless steel tube for introducing raw material gas, 6 is a high frequency power supply, 7 is a cooling water, 8 is a high frequency coil, 9 is a substrate bias voltage DC power supply for town use, 10
1 is an electrode for applying a substrate bias, and 11 is a heater for heating the substrate.

Claims (1)

[Claims] (1) A method for manufacturing a silicon nitride film, which comprises applying a bias to the substrate when forming the silicon nitride film on a III-V compound semiconductor substrate by plasma chemical vapor deposition.