JP3019446B2 - High frequency semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency semiconductor device, and more particularly to a high-frequency semiconductor device such as an FET having a reduced parasitic capacitance between electrodes.

[0002]

2. Description of the Related Art In the process of manufacturing a high-frequency semiconductor device, for example, a bipolar transistor, a collector, a base,
After each electrode of an emitter (field effect transistor: source, gate, drain in the case of FET) is formed on a semiconductor substrate, the operation region of the transistor is usually covered with an insulating film, and the space between the electrodes is buried. .

As an insulating film used in the process of manufacturing such a transistor, an interlayer insulating film in the process of forming a metal wiring layer, an insulating film for overcoating, and the like can be given.

[0004]

These insulating films completely fill the gaps between the electrodes, so that the base electrode to the emitter electrode (gate electrode to source electrode in the case of FET) and the base electrode to collector electrode (gate electrode to gate electrode in the case of FET). The parasitic capacitance increases between the respective electrodes (drain electrode), and the high-frequency characteristics deteriorate.

In particular, a base electrode to a collector electrode (FET)
In the case (2), when the parasitic capacitance between the gate electrode and the drain electrode) increases, the feedback capacitance increases, resulting in a decrease in gain.

SUMMARY OF THE INVENTION An object of the present invention is to provide a high-frequency semiconductor device in which a parasitic capacitance that deteriorates high-frequency characteristics is reduced.

[0007]

According to the present invention, a space for preventing parasitic capacitance is provided in an opposing gap between electrodes formed on the surface of a semiconductor substrate, and an opposing interlayer insulation formed above the electrodes. The problem is solved by a high-frequency semiconductor device having a space communicating with the space between the films and between the opposing covering insulating films formed on the interlayer insulating film.

[0008]

According to the present invention, since the opposing gap between the electrodes is a space (air is interposed), the parasitic capacitance can be reduced as compared with the conventional case where the electrode is covered with an insulating film.
In addition, since there is a space above the electrode that communicates with the space, the operation portion of the transistor is not buried in the insulating film, and the above operation can be further promoted.

The high-frequency semiconductor device used in the present invention includes a bipolar transistor, an FET and the like.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of a high-frequency semiconductor device according to the present invention.

In FIG. 1, 1 is a semiconductor substrate made of, for example, GaAs, 2 is a source electrode, 3 is a gate electrode, 4 is a drain electrode, 5 is a protective film made of, for example, silicon nitride SiN, and 7a and 7b are, for example, SiO or SiN. Is an upper layer wiring made of, for example, Ti / Au, and 9a and 9b are coating insulating films made of, for example, SiN or SiO. In FIG. 1, a space A is formed in the gap between the source electrode 2 and the gate electrode 3 formed on the surface of the semiconductor substrate 1, and a space B is formed in the gap between the gate electrode 3 and the drain electrode 4 formed above the electrodes. Between the opposing interlayer insulating films 7a and 7b and the opposing covering insulating films 9a and 9
The space C between the points b and b forms a space continuous with the above-mentioned spaces A and B.

FIG. 2, FIG. 3, and FIG. 4 are a series of process charts for explaining one embodiment of a manufacturing method for obtaining the high-frequency semiconductor device according to the present invention shown in FIG. The same reference numerals indicate the same parts.

First, as shown in FIG.
A 3000 .ANG. Thick source electrode 2 of, for example, Al on a semiconductor substrate 1 of
3,000 angstroms gate electrode 3, thickness 3000
An Å drain electrode 4 is formed, and then a protective film 5 made of thin silicon nitride (SiN) having a thickness of 500 Å is formed on the entire exposed surface as shown in FIG. 2B by CVD (chemical vapor deposition). It is formed by a method.

Next, as shown in FIG. 2C, a resist 6 is applied to the entire surface by a spin coating method, and a resist pattern 6a constituting an operating portion protective film except for a predetermined region shown in FIG. 2D. To form In FIG. 2C, instead of the resist 6, SiO or polyimide may be used.

After forming the resist pattern 6a, FIG.
As shown in FIG. 3A, an interlayer insulating film 7 made of SiO having a thickness of about 2,000 Å is formed on the entire surface by the CVD method, and then, as shown in FIG. The ends of the protective film 5 and the interlayer insulating film 7 are removed by etching.

Next, as shown in FIG. 3C, a wiring layer 8 made of Ti / Au (thickness: 500 Å / 1 μm) having a thickness of 1.5 μm is formed by a sputtering method. As shown in (d), the central part of the wiring layer 8 is removed by dry etching to form the upper wiring 8a.

Next, as shown in FIG. 4A, a coating insulating film 9 made of SiN having a thickness of about 2000 Å is deposited on the entire surface by the CVD method.

Next, as shown in FIG. 4 (b) and FIG. 4 (c), first, the groove 1 is formed in the coating insulating film 9 by lithography.
0 to form opposed covering insulating films 9a and 9b,
Subsequently, the interlayer insulating film 7 at the center is removed using the coating insulating films 9a and 9b as masks to form interlayer insulating films 7a and 7b, and the resist pattern 6a is further removed, thereby obtaining the high-frequency semiconductor device shown in FIG. . This semiconductor device has a source electrode 2
Between the gate electrode 3 and between the gate electrode 3 and the drain electrode 4
Between them, only a thin protective film 5 is formed, and all the others are removed to form a space, and the parasitic capacitance is reduced as compared with the conventional case. The protective film 5 functions as an etching stopper when removing the resist or the operating portion protective film 6a made of polyimide SiO or the like, and protects the semiconductor substrate 1.

[0020]

As described above, according to the present invention,
Since the parasitic capacitance between the electrodes is reduced, for example, the gain (G
ain) can be prevented from deteriorating.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a high-frequency semiconductor device according to the present invention.

FIG. 2 is a first-half process cross-sectional view illustrating a method for manufacturing a semiconductor device according to the present invention.

FIG. 3 is an intermediate step sectional view following the step shown in FIG. 2;

4 is a sectional view of the latter half of the step that follows the step of FIG.

[Explanation of symbols]

 Reference Signs List 1 semiconductor substrate 2 source electrode 3 gate electrode 4 drain electrode 5 protective film 6 resist 6a resist pattern 7, 7a, 7b interlayer insulating film 8 wiring layer 8a upper wiring 9, 9a, 9b covering insulating film 10 groove

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/338 H01L 21/331 H01L 29/73 H01L 29/812

Claims (1)

(57) [Claims] 1. A parasitic capacitance preventing space in an opposing gap between electrodes formed on a surface of a semiconductor substrate, and a space formed between opposing interlayer insulating films formed above the electrodes and on the interlayer insulating film. A high-frequency semiconductor device comprising: a space communicating with the space between opposing covering insulating films.