JPS63138729A - Formation of insulating film sidewall in manufacture of schottky gate type field effect transistor - Google Patents

Abstract

PURPOSE:To enable insulating film sidewalls to be formed without damaging a substrate by preforming on the substrate surface an insulating film A which has different etching characteristics from an insulating film B and has excellent etching resistance characteristics, and after an anisotropical dry etching, performing a second etching different from this. CONSTITUTION:An insulating film 3 is performed on a substrate having a projecting part 2 (a). An insulating film 4 is formed on the whole substrate, and an anisotropical dry etching is performed (b). As a result, the insulating film 4 formed on the part other than the sidewalls 2a of the projecting part 2 is removed. However, the insulating film 3 is not removed since it is excellent in the etching resistance characteristics against the anisotropical dry etching, protecting the substrate 1 from the anisotropical dry etching (c). Thereafter, by means of a second dry etching method different from the anisotropical dry etching, with the insulating film 4 as a mask the insulating film except the sidewalls 2a of the projecting part 2 is removed so as to expose the substrate surface (d). With this, no damage is provided to the substrate surface adjoining the insulating film side walls.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for forming an insulating film sidewall in the manufacture of a Schottky gate field effect transistor.

Conventional technology In recent years, with the increase in the density of semiconductor integrated circuits,
Ultra-fine processing technology is also required in the manufacturing process of chips such as SI. In the manufacturing process of semiconductor integrated circuit chips, etching technology is essential for forming patterns of electrodes and insulating films on substrates such as semiconductors. Conventionally, such etching has mainly been carried out by a method called wet etching, but subsequently, dry etching using active radicals generated during plasma discharge has come to be used. In particular, reactive ion etching, which is one type of dry etching, is currently becoming mainstream as an etching technique suitable for materials that require microfabrication on the submicron order, since it allows anisotropic dry etching.

Such reactive ion etching (hereinafter abbreviated as RIE) is effectively used when forming an insulating film on the side wall of an electrode or the like. FIG. 5 illustrates one typical example of a conventional method for forming an insulating film on the sidewalls when manufacturing a gate electrode of a Schottky gate field effect transistor.

In FIG. 5(a), a low-GaAs conductive layer is formed by a vapor phase growth method such as OMVPE (organic metal vapor phase epitaxy) on an active layer 5 which has been formed in advance on the surface of a substrate 1 by an ion implantation method or the like. A state in which layered convex portions 2 are selectively formed is shown. Fifth
In Figure (a), the valley formed by the semiconductor conductive layer 2 serves as an opening (hereinafter referred to as gate opening) 9 in which a gate electrode is provided.

An insulating film 4 is formed on such a substrate 1 by a CVD method or the like as shown in FIG. 5(b).

Next, the insulating film 4 is anisotropically dry etched by reactive ion etching from above the substrate 1, as shown in FIG.
A gate opening 9 as shown in C) is obtained in which an insulating film 4 is formed only on the side surface of the protrusion 2 which is a semiconductor conductive layer.

Problems to be Solved by the Invention In manufacturing Schottky gate field effect transistors, the conventional method of forming an insulating film on the sidewalls of the gate opening as described above involves performing RIE to form an insulating film on the surface of the substrate inside the gate. During etching, there is a drawback that the surface of the substrate begins to be exposed at the end of etching and is easily exposed to plasma and damaged.

In a Schottky gate field effect transistor, the gate electrode is provided directly on the substrate, but if the substrate is damaged by plasma as described above, the characteristics of the channel region formed in the surface area of the substrate directly under the gate electrode will deteriorate. do. As a result, there was a problem in that the electrical characteristics as a semiconductor element deteriorated. Also, if the ratio of etching speed between the insulating film to be processed and its underlying layer is not appropriate, R
It was almost impossible to use IE.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for forming an insulating film sidewall using anisotropic dry etching without damaging the substrate in manufacturing a Schottky gate field effect transistor. An object of the present invention is to provide a method for forming a sidewall.

Means for Solving the Problems As a result of intensive study and research in order to solve the above-mentioned drawbacks in the manufacturing method of Schottky gate field effect transistors, the present inventors discovered that two types of insulating films with different etching characteristics were used as a mask on the substrate. It has been discovered that by stacking the insulating films one above the other and using the lower insulating film as a protective film against anisotropic dry etching, the side walls of the insulating film can be formed without damaging the substrate.

That is, according to the present invention, when manufacturing a Schottky gate field effect transistor, an insulating film B is formed on a substrate having a convex portion, and is formed on a portion other than the side wall of the convex portion by anisotropic dry etching. In the method of forming an insulating film sidewall on the convex portion by removing the insulating film B,
Before forming the insulating film B, an insulating film A having different etching properties from the insulating film B and having excellent etching resistance against anisotropic dry etching is previously formed on the substrate surface. After the anisotropic dry etching, a second etching method different from the anisotropic dry etching is used to remove the insulating film A other than the side walls of the convex portions to expose the substrate surface.

That is, in the method for forming an insulating film sidewall according to the present invention, an insulating film A is formed in advance on a substrate 1 having a convex portion 2, as shown in FIG. 1(a).

Then, as shown in FIG. 1 et al., an insulating film B is formed over the entire surface of the substrate. After that, anisotropic dry etching is performed. As a result, as shown in FIG. 1C, the insulating film B formed on the portions of the convex portion 2 other than the side wall 2a is removed. but,
Insulating film A has excellent etching resistance against anisotropic dry etching, so even if insulating film B thereon is removed by anisotropic dry etching, it will not be removed, and substrate 1 will not be removed by anisotropic dry etching. protect from after that,
By a second etching method different from anisotropic dry etching, as shown in FIG. 1(d), using the insulating film B as a mask, the insulating film A other than the side wall 2a of the convex portion 2 is removed to expose the substrate surface. do. In other words, since the insulating film A and the insulating film B have different etching characteristics, as a second etching method,
By employing an etching method that preferentially removes the insulating film A, the insulating film A on the substrate 1 can be removed except for the insulating film A on the side wall protected by the insulating film B.

In such a method of forming an insulating film sidewall according to the present invention, a substrate is protected by a two-layer insulating film having an insulating film A having excellent resistance to anisotropic dry etching as the lower layer. Therefore, by anisotropic dry etching, the substrate is protected by the insulating film A while the insulating film sidewalls are formed by the insulating film. Therefore, the substrate is not damaged by anisotropic dry etching, and there is no deterioration in electrical effectiveness caused by damage to the substrate, which has conventionally been a problem in Schottky gate field effect transistors.

In the method for forming an insulating film sidewall of the present invention described above, the convex portion 2 may be any of a semiconductor conductive layer, a gate electrode, a drain electrode, a source electrode, etc. In particular, if it is used to form sidewalls for a gate electrode portion, a Schottky gate field effect transistor with a gate width on the order of submicrons can be realized.

Further, in the method for forming an insulating film sidewall according to the present invention described above, it is preferable that the anisotropic dry etching be performed by any one of reactive ion etching, reactive ion beam etching, and electron cyclotron resonance plasma etching. Furthermore, wet etching can be used as the second etching method.

Furthermore, in the method for forming an insulating film sidewall according to the present invention, the insulating film A and the insulating film B are made of materials having different etching rates, and the etching rates of the insulating film A and the insulating film B are set to (4), Assuming Va, it is preferable that VA<VB for anisotropic dry etching and VA>V for wet etching.

As two types of insulating films A and B that satisfy this etching rate relationship, CF is used in anisotropic dry etching.
, and when hydrofluoric acid is used for wet etching, insulating film A is a SiC2 film and insulating film B is an SI3 film.
Preferably, it is an N4 film.

According to this preferred embodiment, when 5102 is used for the insulating film A and 513N4 is used for the insulating film B, the etching rate ratio when CF4 is used as the reaction gas for anisotropic dry etching is VA: VB = 1: 5. The etching process can be easily controlled to stop on the interface between the insulating film A and the insulating film B. In addition, in wet etching, if a slow etching solution (hydrogen fluoride) is used, the etching rate ratio becomes A:8 = 5:1, and the 513N4 film, which is the insulating film B formed on the sidewall, is not damaged. The 5102 film, which is the insulating film A, can be easily removed by etching.

EXAMPLES Next, the present invention will be explained in detail with reference to Examples, but the present invention is not limited thereto.

Example 1 A Schottky gate field effect transistor was manufactured using the method of forming an insulating film sidewall according to the present invention in accordance with the process sequence shown in FIG.

First, a resist film is applied on a GaAs substrate 1, exposed and developed in a predetermined pattern to form a resist pattern 6 as shown in FIG. has been established.

Next, after removing the resist pattern 6 with acetone solvent, a SiC2 film is formed as an insulating film A on the substrate 1 by CVD to a film thickness of approximately 1000 nm, and a resist film is further applied over the entire surface. The resist pattern was exposed and developed using another pattern different from the above pattern, and the resulting resist pattern was used as a mask and through-etched to form patterns 3 and 3' of the insulating film A as shown in FIG. 2(b). Second
In Figure (b), the width of the 5102 film pattern 3 formed at the center of the substrate is about 1.5 μm.

Next, Figure 2 (C) 1. : As shown, OMVPE (
A convex portion 2 consisting of an n = -GaAs layer was selectively grown on the substrate 1 in a portion where the 5102 film was not formed, that is, between patterns 3 and 3° of the 5102 film by metalorganic vapor phase epitaxy (organic metal vapor phase epitaxy).

Thereafter, a Si3N4 film 4 was formed as an insulating film B over the entire surface of the substrate by CVD to a thickness of about 1008 as shown in FIG. 2(d).

Next, in order to provide an ohmic electrode on the n=-GaAs, a resist pattern 8 was formed by removing a predetermined portion of the 5i3N4 film as shown in FIG. 2(e), and after removing the 513N4 film by plasma etching. Then, Au/Ge/Ni was deposited as an electrode material, and the surface was washed with acetone as a solvent to obtain an ohmic electrode 7 as shown in FIG. 2(f).

Next, perform RTE and n as shown in the second EU(g).
”-Si3 of the portion other than the side wall of the convex portion 2 made of GaAs layer
The N4 film was removed. At this time, the gate opening is made of Si3N,
It was shortened by the film thickness of , and became 0.9 μm.

Further, the central opening was wet-etched using buffered hydrofluoric acid, and the 8102 film at the bottom of the opening was removed as shown in FIG. 2(h).

Finally, Mo/Au is formed on the substrate as a gate electrode material by vacuum evaporation, and lift-off is performed as shown in Figure 2 (1).
A Schottky gate field effect transistor was obtained by forming a gate electrode as shown in ).

The embodiment described above is an example in which the method for forming an insulating film sidewall according to the present invention is applied to the case where an insulating film is formed on the sidewall of a gate opening. The present invention can also be applied to the formation of the sidewall insulating film 12 of the gate electrode 11 having an LDD structure such as this or a short tube-pole structure as shown in FIG. In these structures, the sidewalls of the insulating film are n
”-provided on the gate electrode itself rather than on the GaAs conductive layer.

Effects of the Invention According to the method for forming an insulating film of the present invention, no damage is caused to the substrate surface adjacent to the side wall of the insulating film.

Therefore, the present invention is an extremely effective and essential method for manufacturing Schottky gate field effect transistors, and has extremely high value in the industry.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating the steps of a method of forming an insulating film sidewall according to the present invention. FIG. 2 is a diagram illustrating a method of manufacturing a Schottky gate field effect transistor using the method of forming an insulating film sidewall according to the present invention. FIGS. 3 and 4 are diagrams illustrating structures to which the method of forming an insulating film sidewall according to the present invention can be applied. FIG. 5 is a diagram showing a method of forming an insulating film on the sidewall of a gate electrode in a conventional method of manufacturing a Schottky gate field effect transistor. (Main reference numbers) 1. Substrate, 2. Convex portion, 3. Insulating film A, 4. Insulating film B15.. Ion implantation layer, 6. Resist pattern, 7. Ohmic electrode, 8. Resist pattern, 9...Gate opening, 10...Gate electrode 11...Gate electrode 12
... Insulating film side wall Fig. 1 1 ... Substrate 2゛° convex part 2a ... Convex part A regular wall 3 ... Insulating film A4
...Insulating film B 1--Substrate 2,..., n''-GaA
s W part 3.3'・Insulating film A 4 Insulating film B5
Ion implantation layer 6-resist pattern 7 Ohmic electrode 8...-resist pattern 9
Gate opening 10 ・Gate electrode Figure 3 Figure 4 11...Gate electrode

Claims (6)

[Claims] (1) When manufacturing a Schottky gate field effect transistor, an insulating film B is formed on a substrate having a convex portion, and the insulating film B is formed on a portion other than the side wall of the convex portion by anisotropic dry etching. In the method of forming an insulating film sidewall on the convex portion by removing the insulating film B, before forming the insulating film B, a An insulating film A is formed on the substrate surface in advance, and after the anisotropic dry etching, the insulating film A is removed except for the side walls of the convex portion by a second etching method different from the anisotropic dry etching. A method for forming an insulating film sidewall, the method comprising: exposing the surface of the substrate. (2) The method for forming an insulating film sidewall according to claim 1, wherein the convex portion is one of a gate electrode, a source electrode, a drain electrode, or a semiconductor conductive layer. (3) The anisotropic dry etching is performed by any one of reactive ion etching, reactive ion beam etching, and electron cyclotron resonance plasma etching. 2. The method for forming an insulating film sidewall according to item 2. (4) The method for forming an insulating film sidewall according to any one of claims 1 to 3, wherein the second etching method is wet etching. (5) A patent claim characterized in that the insulating film A is formed so that the etching rate for anisotropic dry etching is sufficiently lower than that of the insulating film B, and the etching rate for wet etching is sufficiently higher than that of the insulating film B. The method for forming an insulating film sidewall according to item 4. (6) The insulating film A is formed of SiO_2, the insulating film B is formed of Si_3N_4, the anisotropic dry etching is performed by reactive ion etching with CF_4, and the wet etching is performed with hydrofluoric acid. A method for forming an insulating film sidewall according to claim 4 or 5, characterized in that: