JPS60254621A - Thin film forming method - Google Patents

Abstract

PURPOSE:To form a thin film with a small interfacial level density over a compound semiconductor substrate, by a method in which, after the compound semiconductor substrate is treated by heating at a temperature of 200-450 deg.C in hydrogen plasma, a thin film is formed over the semiconductor substrate surface. CONSTITUTION:An N type GaAs substrate 2 being a sample is put in the plasma apparatus 1. After vacuum-evacuated, the plasma apparatus 1 is supplied with H2 gas to produce H2 plasma by applying high frequency electric power while heating the substrate 2 at a temperature of 200-450 deg.C by a heater 3. After the substrate 2 is left at this state for a predetermined time, SiH4 and NH3 gas is introduced to deposite an Si3N4 film over the substrate 2. By forming the Si3H4 film in this way, the interfacial level density can be decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application - The present invention relates to a method of forming a thin film on a compound semiconductor substrate.

The structure of the conventional example and its problems The interface characteristics between the compound semiconductor and the insulating film are Si and Si02
The interface state density is higher than that of the interface of G a A
With s, it was difficult to form an inversion layer. This high density of interface states is due to dangling bonds due to loss of constituent elements.

OBJECTS OF THE INVENTION In view of these conventional problems, the present invention provides a method for forming a thin film with a low density of interface states on a compound semiconductor substrate.

Structure of the Invention The present invention provides a method for heating a compound semiconductor substrate in a hydrogen plasma for 200 minutes.
By forming a thin film after processing at a temperature of .degree. C. to 460.degree. C., a method of forming a thin film with a low density of interface states can be achieved.

DESCRIPTION OF EMBODIMENTS A method for forming a Si3N4 film on an n-type GaAa substrate will be described below as an example.

As shown in FIG. 1, an n-type GaAs substrate 2 as a sample is placed in a plasma CVD apparatus 1, and after evacuation, H2 gas is introduced (approximately 0.05 Torr), and the substrate 2 is heated to approx. While heating with heater 3 at 350℃, high frequency (
13,56 h) Apply power supply 4 (power 60W) to H
2 Plasma is generated, left for about 2 hours, and then S
A Si3N4 film is deposited on the substrate 2 by introducing iH and NH3 gases. Reference numerals 5 and 6 are a gas introduction section and an exhaust section.

Figure 2 shows the Si3N4 film obtained in this way and the n-type Ga
Figure 9 compares the interface state density with As between a sample subjected to H2 plasma treatment and a sample not treated with H2 plasma.

It can be seen that the interface state density has decreased by two orders of magnitude.

This is because the number of dangling bonds decreased due to the diffusion of H atoms.

The substrate heating temperature during H2 plasma processing is 20
0°C to 460°C is good. Figure 3 shows n-type G a A g
This figure shows the relationship between the minimum interface state density of the Si3N4 film and the substrate heating temperature. Note that H2 plasma is 0.05
Torr power 50W, 2 hours.

The minimum interface state density is in the temperature range lower than 200℃ and 460℃
It becomes larger in the higher temperature range. The cause of this is
In the low temperature range, this is because damage from the H2 plasma remains, and in the high temperature range, this is due to the dissociation of As in GaAs.

A similar tendency was observed for the interface between 1nP and Si3N4 films.As for the substrate heating temperature, 200°C to 450°C is good.0 Figure 4 shows the interface between n-type InP and plasma CVD'S.
Regarding the interface characteristics with the L3N4 film, the plasma H2 treatment of the present invention (substrate heating temperature 300°C, 0.05 Torr
, power 50W, 2 hours) and without. It can be seen that in this case as well, the interface state density decreases by two factors. Note that the above effect was not observed for the sample that was left in an H2 gas atmosphere instead of in horse plasma.

As described above, if the method of the present invention is used, compared to the conventional method,
It is possible to significantly reduce the interface state density. In the above description, the formation of an insulating film has been described, but it goes without saying that the invention can also be used for forming a metal film.

Effects of the Invention As described above, the present invention processes a compound semiconductor substrate in H2 plasma at a temperature of 200°C to 450°C, and then forms a thin film, thereby producing a compound semiconductor substrate with a lower density of interface states than before. This method realizes a method for forming a thin film with interfacial properties.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a plasma CVD apparatus, and FIG. 2 is a schematic diagram of a plasma CVD apparatus. Figure 4 shows n-GaAa and n-I nP, respectively.
FIG. 3 is a diagram showing the relationship between the minimum interface state density and substrate heating temperature of n-GaAs and Si3N4 films. 1...CVD equipment, 2...n-type Ga
A s board. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2

Claims (1)

[Claims] Compound semiconductor substrate in hydrogen plasma at 200°C to 450°C
A method for forming a thin film, comprising forming a thin film on the surface of the semiconductor substrate after heating and processing at a temperature of °C.