JPS59194451A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To reduce the characteristic change of an active region as large as possible by forming an interlayer insulating film in 2-layer structure having the first insulating film made of a thin deposited insulating film due to resistance heating and the second insulating film which is sufficiently thick due to a plasma CVD method. CONSTITUTION:Electrodes 1, 2, 4 are formed on a semi-insulating GaAs substrate, the first insulating film 5a made of thin silicon oxidized film due to resistance heating deposition is accumulated, and the second insulating film 5b made of sufficiently thick silicon nitrided film is accumulated by plasma CVD method on the entire surface. Further, a photoresist layer 7 is covered and a window 8 is patterned thereon by the normal photolithography the film 5 of 2-layer structure is selectively etched, opened at a hole 9, and wiring metal 6 is formed on the second insulating film 5b.

Description

Detailed Description of the Invention - [Technical Field of the Invention] The present invention relates to a method for manufacturing a semiconductor device, and particularly to a method for forming an interlayer insulating film that reduces changes in characteristics of an active region.

[Prior art]

Taking a gallium arsenide (hereinafter abbreviated as GaAs) integrated circuit as an example, FIG. 1 shows the structure of a semiconductor device after wiring is formed using a conventional interlayer insulating film. That is, in FIG. 1, on the semi-insulating Gaps substrate, there are a source electrode (1), a drain electrode (2), and a gate electrode (4) on a channel region (3) sandwiched between these. After forming a silicon nitride film (SiaN+), a silicon nitride film (SiaN+),
Alternatively, an interlayer insulating film (5) made of a silicon oxide film (8iσ0, etc.) is deposited, and holes are selectively opened in the interlayer insulating film (5) on the drain/electrode (2) by ordinary photolithography. A wiring metal (6) connected to the electrode (2) is formed.

However, in the case of such a conventional configuration, since the glabellar insulating film (5) is deposited by plasma CVD or sputter deposition, it is difficult to deposit the glabellar insulating film (5) compared to, for example, a vapor-deposited insulating film by resistance heating. The film quality is dense and has high in-plane uniformity,
On the other hand, it has excellent reliability.

Because the mechanism uses a plasma reaction phenomenon, it causes a lot of damage to the substrate surface during deposition.
For example, these sources result in a significant reduction in the surface impurity concentration of the channel region (3).

A GaAs field effect transistor consisting of drain and gate electrodes (1), (21, and (4)) has the disadvantage that the saturated drain current Idss is significantly reduced after the interlayer insulating film is deposited. .

[Summary of the invention]

In view of these conventional drawbacks, the present invention has developed an interlayer insulating film by forming a first insulating film consisting of a thin insulating film deposited by resistance heating, followed by a sufficiently thick second insulating film by plasma CVD or sputter deposition. By forming the active region into a two-layer structure with an insulating film, changes in the characteristics of the active region are minimized.

[Embodiments of the invention]

Hereinafter, one embodiment of the method of this invention will be described in detail with reference to FIGS. 2(a) to 2d).

FIGS. 2(a) to 2d) show this embodiment method in the order of manufacturing steps. That is, similarly to the conventional example,
After forming source, drain, and gate electrodes (1), (21, and (4)) on a semi-insulating GaAs substrate, silicon oxide 1 ( A first insulating film (5a) made of a thin film of SiQ2) is deposited (see figure (a)), and then the first insulating film is deposited on the entire surface by the conventional plasma CVD method or sputter deposition method. (5a) A second insulating film (5a) made of a sufficiently thick silicon nitride film (SiaN4) or silicon oxide film (Sing).
b) is deposited (FIG. 2(b)), and then a photoresist layer (7) is deposited on top of it by ordinary photolithography, and a window opening (8) corresponding to the drain electrode (2) is formed. The glabella insulation 7! (51) of the two-layer structure is selectively etched to form an opening ( 9), and a wiring metal (6) connected to the drain electrode (2) through this opening (9) is formed on the second insulating film (5b) (FIG. 9(d)).

Therefore, in the case of this embodiment method, the glabella insulating film has a two-layer structure, and the first insulating film (5a) is directly deposited on the substrate.
As a silicon oxide thin film formed by resistance heating vapor deposition is used, crystal damage induced on the substrate surface layer during the formation of the film is extremely small, and the second insulating film (5a) on the first insulating film (5a) is 5b), even if a thick film is formed by plasma CVD or sputter evaporation, there is no risk of this damaging the surface layer because there is the first insulating film (5a) in the lower layer) As a result, the glabella insulating film (5
) The characteristics of the active layer before and after the formation of the active layer hardly change, and moreover, it is possible to obtain a dense and highly reliable layer interlayer 1# film (5) that could not be satisfied by the first insulating film (5a) alone. It is. [Effects of the Invention] As described above in detail, according to the method of the present invention, a thin film formed by resistance heating vapor deposition is used as the first insulating film directly deposited on the substrate crystal layer, and a thin film is continuously and uniformly deposited on the first insulating film. Since the second insulating film is thickly deposited using a highly precise, highly reliable plasma CVD method or sputter evaporation method to form an interlayer insulating film, changes in the electrical characteristics of the active layer before and after the formation of this insulating film can be avoided. It has the advantage of being able to reduce the size and improve uniformity and reliability.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a semiconductor device using a conventional interlayer insulating film, and FIGS. 2(a) to 2d) show manufacturing steps for obtaining an interlayer insulating film structure according to an embodiment of the method of the present invention. FIG. (1)...Φ source electrode, (2)...drain electrode, (4)...gate electrode, (5)...interlayer insulating film, (5a), (5b) 11 @ * @1st. Second insulating film, (6)...wiring metal. Agent Masuo Oiwa

Claims (1)

[Claims] In a semiconductor device in which source, drain, and gate electrodes are formed on the surface of a semiconductor substrate, and each of these electrodes is covered with an interlayer insulating I# film, in order to make the interlayer insulating film have a two-layer structure, A step of forming a first insulating film made of a thin film by resistance heating vapor deposition, and a second insulating film made of a thick film is formed on this first insulating film by a plasma CVD method, a sputter deposition method, etc. A method for manufacturing a semiconductor device, comprising the steps of: