JPH0740605B2 - Method for manufacturing semiconductor device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device including a step of forming an insulating film on the surface of a GaAs compound semiconductor.

2. Description of the Related Art Conventionally, as a method for forming an insulating film by directly processing a GaAs substrate, a heat treatment at a high temperature in a gas atmosphere has been a main method.

Problems to be Solved by the Invention In the conventional method, since the GaAs substrate is heat-treated at a high temperature of 600 ° C. or higher, As evaporates and the surface level increases, which causes an increase in the leakage current of the substrate. It is unsuitable as a film forming method.

Means for Solving the Problems The present invention aims to solve the above problems, and after cleaning the surface of a GaAs substrate, the temperature is preferably 500 ° C. in ammonia plasma.
By treating at the following low temperature, the GaAs substrate is directly nitrided to form an insulating film.

By the method of manufacturing a semiconductor device of the present invention,
The evaporation of As can be suppressed, the surface depletion layer between the GaAs surface and the insulating film can be reduced, and the yield in the semiconductor device manufacturing process can be improved.

Example An example of the method for manufacturing a semiconductor device of the present invention will be described below. Fig. 1 shows the result of XPS analysis of the insulating film on the GaAs surface by the ammonia plasma treatment. Ammonia plasma conditions are: ammonia flow rate 15cc / min, reaction chamber pressure 0.3torr, R
F frequency is 13.56MHz and power is 100W.

In FIG. 1, the ammonia plasma-treated substrate (line a in FIG. 1 and untreated substrate (line b in FIG. 1) are compared. As a result, an As ₂ O ₃ film which is a natural oxide film when untreated is compared. However, when ammonia plasma treatment is performed, GaN
Appears, and the GaAs surface is nitrided to form GaN which is a chemically stable film.

FIG. 2 is a graph showing changes in the concentrations of Ga, As, O, and N in the insulating film on the GaAs surface by the ammonia plasma treatment when the GaAs substrate temperature is changed.

Figure 3 shows the insulating films Ga, As, O, N on the GaAs surface when the reaction time of ammonia plasma treatment on the GaAs substrate was changed.
5 is a graph showing the change in the concentration of.

In FIG. 2, a GaN nitride film is formed on the GaAs substrate surface at a substrate temperature of 500 ° C. or lower.

In addition, since the As concentration and N concentration are saturated when the GaAs substrate temperature is around 300 ° C, a stable insulating film that suppresses As vaporization in which GaAs and GaN coexist is obtained by ammonia plasma treatment at 250 ° C or less. GaAs / GaAs by continuous ammonia plasma treatment at 250 ° C or higher.
-GaN As vaporization of GaN is suppressed and a chemically stable nitride film, GaAs / insulating film, is obtained.

In FIG. 3, the concentrations of As and N are saturated when the reaction time of the ammonia plasma treatment is 3 hours or more.

In addition, nitride is formed on the surface of the GaAs substrate in a short reaction time of 1 hour or less. This shows that a chemically stable nitride film can be formed on the GaAs substrate surface in a short time.

From Fig. 2 and Fig. 3, when forming an insulating film of 1000 Å on the surface of GaAs substrate, GaAs was treated by ammonia plasma treatment for a short time at a substrate temperature of 250 ° C to suppress As evaporation.
A chemically stable insulating film can be formed on the surface.

Figure 4 shows GaAs nitride and Ga by ammonia plasma treatment.
This is a sample preparation process for measuring the surface level density of the As substrate surface by the Turman method.

In FIG. 4 (a), n-type (n2 × 10 ¹⁷ cm ⁻³ ) GaAs
A plasma CVD silicon nitride film 2 is deposited on the substrate 1 for 3000 liters, and a window 3 is opened by selective etching. As shown in FIG. 4 (b), it was installed in a parallel plate type plasma CVD apparatus, and was subjected to ammonia plasma treatment for 3 hours at a substrate temperature of 250 ° C., RF power of 100 W, and NH ₃ flow rate of 15 cc / min, and the GaAs surface of the opening 3
GaAs nitride 4 is produced. After that, the plasma CVD silicon nitride film 2 is removed by etching. In FIG. 4C, the AuGe / Ni / Au of the ohmic electrode 7 is formed by forming the ohmic electrode window 6 by the photo-etching technique using the resist 5.
(1500/500 / 1500Å) is formed by lift-off method.
In FIG. 4D, the gate electrode window 9 is formed by the photo-etching technique using the resist 8 and the gate electrode 10 is formed.
Ti / Au (1000 / 1500Å) is formed by lift-off method.
In FIG. 4e, the Turman method sample is completed.

In FIG. 4 (e), the ohmic electrode 7 and the gate electrode 10
Biased to GaAs1 / GaAs nitride 4 by the Turman method
The surface state density between at to the 8 × ¹⁰ 10 cm ^-2 measurement, in the conventional manner with 1.5 × 10 ¹² cm ^-2 1 digit order of low, reducing such leakage current due to surface states is improved.

According to the method of manufacturing the semiconductor device of the present invention,
The evaporation of As was suppressed, the surface depletion layer of the GaAs surface and the insulating film was reduced, and the yield in the semiconductor device manufacturing process was improved.

[Brief description of drawings]

Fig. 1 is a characteristic diagram showing the result of XPS analysis of the insulating film on the GaAs surface by the ammonia plasma treatment, and Fig. 2 is the Ga by the ammonia plasma treatment when the GaAs substrate temperature is changed.
Fig. 3 is a characteristic diagram showing changes in the concentrations of Ga, As, O, and N in the insulating film on the As surface. Fig. 3 shows Ga of the insulating film on the GaAs surface when the reaction time due to ammonia plasma treatment of the GaAs substrate was changed. As,
FIG. 4 is a characteristic diagram showing changes in O and N concentrations, and FIG. 4 is a process diagram showing a sample preparation process for measuring the surface state densities of GaAs nitride and GaAs substrate surfaces by the ammonia plasma treatment of the present invention by the Tarman method. Is. 1 '... XPS line when treated with ammonia plasma,
2 '... XPS line when untreated, 1 ... n-type GaAs substrate,
2 ... Plasma CVD silicon nitride film, 3 ... Opening, 4
...... GaAs nitride, 5,8 ...... resist, 6,9 ...... electrode window,
7 ... Ohmic electrode, 10 ... Gate electrode.

Claims (4)

[Claims] 1. When forming an insulating film on one surface of a GaAs substrate, the insulating film is formed by directly nitriding one surface of the GaAs substrate only by treatment in ammonia plasma. Of manufacturing a semiconductor device according to claim 1. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the GaAs substrate temperature is 500 ° C. or lower in the ammonia plasma treatment. 3. The method of manufacturing a semiconductor device according to claim 1, wherein in the ammonia plasma treatment, the GaAs substrate temperature is continuously changed from a low temperature to a high temperature to perform the plasma treatment. 4. The method of manufacturing a semiconductor device according to claim 1, wherein the temperature of the GaAs substrate is 250 ° C. or less when the thickness of the insulating film formed on the GaAs substrate by the ammonia plasma treatment is 1000 Å or less.