JPH0883782A - Method for manufacturing compound semiconductor device - Google Patents

Abstract

(57) [Summary] [Object] To provide a method for manufacturing a compound semiconductor device capable of obtaining a clean compound semiconductor substrate surface without using a dry process for removing resist residues and surface stains. A surface oxide film 2 containing gallium oxide and arsenic oxide is formed by oxidizing the surface of a gallium arsenide compound semiconductor substrate 1, and a desired resist pattern 3 is formed on the surface oxide film 2. Then, the exposed portion of the surface oxide film 2 which is not covered with the resist pattern 3 is removed by wet etching with hydrofluoric acid. At this time, the resist residue and surface stains are simultaneously removed, and the clean compound semiconductor substrate surface is exposed. Then, etching and electrode formation are performed on the surface of the clean compound semiconductor substrate 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a compound semiconductor device, and more specifically, it removes resist residues and surface stains, which are problems during processing such as etching and electrode formation, and is a clean compound. The present invention relates to a method for obtaining a semiconductor substrate surface.

[0002]

2. Description of the Related Art A compound semiconductor device is required to have a fine recess shape in order to operate at a high frequency and also to have a low contact resistance of electrodes. On the other hand, in manufacturing a compound semiconductor device, it is desirable not to use a dry process in order to avoid deterioration of electrical characteristics. However, if only the organic cleaning is used without using the dry process after removing the resist, the resist residues and stains, which are resist-altered, are easily attached to the surface of the compound semiconductor substrate. When a compound semiconductor substrate surface having resist residues or stains on such a surface is subjected to extremely fine recess processing by wet etching, there arises a problem that variations in etching depth and side etching become large. In addition, when the electrodes are formed, problems such as an increase in contact resistance and peeling of the electrodes may occur due to resist residues and stains.

On the other hand, dry processes such as plasma ashing and plasma etching have been used in the manufacture of silicon semiconductor devices. A method for removing the resist residue at this time is proposed in Japanese Patent Laid-Open No. 4-82221. This method removes the resist residue generated when the aluminum alloy wiring pattern is formed by the etching process using the chlorine-based gas plasma reaction by the fluorine-based gas plasma reaction at the same time as the previously formed underlying sacrificial film. That is.

[0004]

However, when this technique is applied to recess processing and electrode formation in the production of the compound semiconductor device as described above, the surface of the compound semiconductor substrate exposed to the plasma reaction is used as it is, The produced compound semiconductor device has a problem that electrical characteristics such as Schottky characteristics are low.

Therefore, an object of the present invention is to provide a method for manufacturing a compound semiconductor device which can obtain a clean compound semiconductor substrate surface without using a dry process for removing resist residues and surface stains.

[0006]

According to a first aspect of the present invention, there is provided a first step of forming a surface oxide film by oxidizing a surface of a compound semiconductor substrate containing at least gallium or arsenic, and the surface oxide film. A second step of forming a desired resist pattern on the upper surface, and a wet compound for removing exposed portions of the surface oxide film that are not covered with the resist pattern by wet etching to simultaneously remove resist residues and surface stains, and to obtain a clean compound. The gist is a method of manufacturing a compound semiconductor device including a third step of exposing the surface of a semiconductor substrate and a fourth step of etching or forming electrodes on the surface of the clean compound semiconductor substrate.

According to a second aspect of the present invention, in the method for manufacturing a compound semiconductor device according to the first aspect, the second to fourth steps are repeated using different resist patterns as the resist pattern in the second step. The gist of the invention is a method of manufacturing a compound semiconductor device.

The invention according to claim 3 is the method for manufacturing a compound semiconductor device according to claim 1, wherein the wet etching solution in the third step is hydrofluoric acid. And

[0009]

According to the invention of claim 1, in the first step, the surface of the compound semiconductor substrate containing at least gallium or arsenic is oxidized to form a surface oxide film.
By the second step, a desired resist pattern is formed on the surface oxide film. Then, in the third step, the exposed portion of the surface oxide film which is not covered with the resist pattern is removed by wet etching, whereby the resist residue and the surface dirt are removed at the same time to expose the clean compound semiconductor substrate surface. In other words, in the third step, the oxide film of the compound semiconductor substrate containing at least gallium or arsenic is easily dissolved in the etching solution, and the resist residue and surface stains are removed as the oxide film of the compound semiconductor substrate is dissolved by etching. A compound semiconductor substrate surface is obtained.

Further, in the fourth step, etching and electrode formation are performed on the surface of the clean compound semiconductor substrate. According to the second aspect of the invention, in addition to the effect of the first aspect of the invention, the second to fourth steps are repeated using different resist patterns as the resist pattern in the second step. That is, after forming the surface oxide film, the step of removing the surface oxide film by using a different resist pattern and the step of etching and forming electrodes are sequentially repeated. As a result, a clean compound semiconductor substrate surface is exposed when necessary without being affected by the resist residue and surface contamination generated in the previous resist pattern forming step.

According to the invention of claim 3, claim 1
In addition to the effect of the invention described in (1), the surface oxide film is wet-etched with hydrofluoric acid in the third step.

[0012]

【Example】

(First Embodiment) A first embodiment of the present invention will be described below with reference to the drawings.

In this embodiment, a gallium arsenide compound semiconductor substrate is recess-etched, and the manufacturing process is shown in FIGS. Further, FIG. 6 shows the results of summarizing the peak areas of oxygen and carbon on the surface of the compound semiconductor substrate using XPS in each step.

First, as shown in FIG. 1, a gallium arsenide compound semiconductor substrate 1 to be subjected to recess etching is prepared. Then, as shown in FIG. 2, the surface of the gallium arsenide compound semiconductor substrate 1 is oxidized to form a surface oxide film 2 containing gallium oxide and arsenic oxide. This surface oxide film treatment is carried out by treating the gallium arsenide compound semiconductor substrate 1 with 5% in 200 ml of 18% hydrogen peroxide solution at 80 ° C.
Soak for a minute. When the surface oxide film 2 formed at this time was analyzed by Auger electron spectroscopy, the thickness of the surface oxide film 2 was about 35Å.

Next, as shown in FIG. 3, a positive resist is applied on the surface oxide film 2 to a thickness of 1.4 μm, and a bribake is carried out at 100 ° C. for 120 seconds. The film is exposed using a mask and then developed. Then, a desired resist pattern 3 is formed.
At this time, in the developed portion, that is, in the exposed portion of the surface oxide film 2 which is not covered with the resist pattern 3 (opening 4 of the resist pattern 3), a resist residue which is a development residue and a surface stain 5 are generated. It

The change in the surface of the gallium arsenide compound semiconductor substrate described above is apparent from the surface analysis by XPS shown in FIG. That is, as shown in FIG. 2 from the state of FIG. 1, the oxygen peak area was greatly increased from the initial stage of the substrate by performing the oxidation treatment, and it was shown that an oxide film was formed on the surface of the gallium arsenide compound semiconductor substrate. ing.
Further, as shown in FIG. 3, the peak area of carbon increases after the step of forming the resist pattern 3, which indicates that resist residues and surface stains 5 have occurred.

Subsequently, the gallium arsenide compound semiconductor substrate 1 having the resist pattern 3 formed thereon is immersed in 5% hydrofluoric acid for 5 minutes. As a result, as shown in FIG. 4, the surface oxide film 2 in the opening 4 (exposed portion of the surface oxide film 2) of the resist pattern 3 is removed. XPS after this process
As shown in FIG. 6, the analysis result shows that both the oxygen peak area and the carbon peak area decrease, and the surface oxide film 2 is dissolved while the compound semiconductor substrate 1 is immersed in hydrofluoric acid. This indicates that the resist residue and the surface stain 5 are also removed.

In this way, a clean compound semiconductor substrate surface is obtained. As shown in FIG. 5, recess etching is performed on the clean surface of the compound semiconductor substrate to obtain a desired etching shape. In this way, the etching shape can be stably produced using a clean compound semiconductor substrate surface.

As described above, in this embodiment, the surface of the gallium arsenide compound semiconductor substrate 1 is oxidized to form the surface oxide film 2 (first step), and the desired resist pattern 3 is formed on the surface oxide film 2. After forming (second step), the exposed portion of the surface oxide film 2 which is not covered with the resist pattern 3 is removed by wet etching to simultaneously remove the resist residue and surface stains 5, thereby forming a clean compound semiconductor substrate surface. It was exposed (third step) and the clean compound semiconductor substrate surface was etched (fourth step).

As described above, a clean compound semiconductor substrate surface can be obtained without using a dry process in the etching step, variations in etching depth and side etching can be reduced, and a stable compound semiconductor device can be manufactured.

Since the surface oxide film 2 is wet-etched with hydrofluoric acid, the surface oxide film 2 can be surely wet-etched. In the above embodiment,
The case of using a gallium arsenide compound semiconductor substrate has been described, but it can be applied to a binary, ternary or quaternary compound semiconductor substrate containing at least gallium or arsenic such as indium gallium arsenide, indium aluminum arsenide and aluminum gallium arsenide. Is. However, the compound semiconductor substrate referred to here is not limited to a single substrate as shown in FIG. 1, but a plurality of films having different compositions including gallium or arsenic, which have been subjected to processing such as electrode formation or etching on the surface. Also includes those in which are laminated. Further, in the above example, the oxidation treatment of the surface of the compound semiconductor substrate was carried out by immersion in heated hydrogen peroxide water, but in addition, immersion in room temperature hydrogen peroxide water or room temperature and heated water was carried out. Immersion, and since the surface oxide film is removed later, plasma oxidation method or thermal oxidation method,
Various methods are conceivable, such as utilizing the anodizing method.

Further, in the above embodiment, the case where the clean compound semiconductor substrate surface is etched as the fourth step has been described, but it may be applied when the electrode is formed on the clean compound semiconductor substrate surface. At this time, a clean compound semiconductor substrate surface can be obtained without using a dry process in the electrode formation step, contact failure of the electrodes can be reduced, and a stable compound semiconductor device can be manufactured. (Second Embodiment) Next, the second embodiment will be described focusing on the differences from the first embodiment.

In this embodiment, a case including a step of forming an ohmic electrode on the surface of a gallium arsenide compound semiconductor substrate and a step of performing recess etching (and forming a Schottky electrode) will be described with reference to FIGS. 7 to 14. .

First, as shown in FIG. 7, the surface oxide film 2 containing gallium oxide and arsenic oxide is formed on the surface of the gallium arsenide compound semiconductor substrate 1 under the same surface oxidation treatment conditions as in the first embodiment.

Next, as shown in FIG. 8, a resist pattern 3 for an ohmic electrode is formed as in the first embodiment. At this time, in the opening 4 of the resist pattern 3,
Resist residues that are undeveloped and surface stains 5a are generated. Then, as shown in FIG. 9, the compound semiconductor substrate 1
Is immersed in hydrofluoric acid to remove the surface oxide film 2 in the opening 4 of the resist pattern 3. At this time, the resist residue that is the undeveloped residue and the surface stain 5a are also removed at the same time, and the clean gallium arsenide compound semiconductor substrate surface is exposed. Then, as shown in FIG. 10, gold-germanium / nickel /
After vapor deposition of gold and lift-off, alloying treatment is performed to form the ohmic electrode 6.

Further, as shown in FIG. 11, a resist pattern 7 for recess etching is formed similarly to the first embodiment. At this time, the opening 8 of the resist pattern 7
On the other hand, a resist residue which is a development residue and a surface stain 5b are generated. Then, as shown in FIG. 12, the compound semiconductor substrate 1 is immersed in hydrofluoric acid to form a resist pattern 7.
The surface oxide film 2 in the opening 8 is removed. At this time, the resist residue that is the undeveloped residue and the surface contamination 5b are also removed at the same time, and the clean gallium arsenide compound semiconductor substrate surface is exposed.

Subsequently, as shown in FIG. 13, the surface of the compound semiconductor substrate 1 is subjected to etching treatment to obtain a recess shape, and then titanium / platinum / gold is vapor-deposited and lift-off is applied to the Schottky as shown in FIG. The electrode 9 is formed.

As described above, in this embodiment, the second to fourth steps are repeated by using different resist patterns 3 and 7 as the resist patterns. That is, the step of forming the surface oxide film 2 and forming a different resist pattern prior to all the steps, the step of removing the surface oxide film 2, and the step of etching or forming electrodes were sequentially repeated. Therefore, it is possible to always obtain a clean compound semiconductor substrate surface without being affected by the resist residue and surface stains generated in the previous resist pattern forming step. In this way, by simply forming the surface oxide film 2 first, a clean compound semiconductor substrate surface can be obtained by performing acid treatment at a necessary position when necessary.

The present invention is not limited to the above-mentioned embodiments. For example, instead of hydrofluoric acid as an etching solution for removing the surface oxide film 2, dilute sulfuric acid, acetic acid, citric acid, or ammonia is used. May be used.

[0030]

As described in detail above, according to the invention described in claim 1, it is possible to obtain a clean compound semiconductor substrate surface without using a dry process for removing resist residues and surface stains. Be effective.

According to the invention described in claim 2, claim 1
In addition to the effect of the invention described in (1), a clean compound semiconductor substrate surface can be exposed when necessary without being affected by the resist residue and surface stains generated in the previous resist pattern forming step.

According to the invention of claim 3, claim 1
In addition to the effect of the invention described in (1), the surface oxide film can be surely wet-etched.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a manufacturing process of a compound semiconductor device of a first embodiment.

FIG. 2 is a cross-sectional view showing a manufacturing process of the compound semiconductor device of the first embodiment.

FIG. 3 is a cross-sectional view showing a manufacturing process of the compound semiconductor device of the first example.

FIG. 4 is a cross-sectional view showing a manufacturing process of the compound semiconductor device of the first example.

FIG. 5 is a cross-sectional view showing the manufacturing process of the compound semiconductor device of the first example.

FIG. 6 is a diagram showing a result obtained by performing surface analysis by XPS for each step in the first example and summarizing peak areas of oxygen and carbon.

FIG. 7 is a cross-sectional view showing a manufacturing process of the compound semiconductor device of the second embodiment.

FIG. 8 is a cross-sectional view showing the manufacturing process of the compound semiconductor device of the second embodiment.

FIG. 9 is a cross-sectional view showing the manufacturing process of the compound semiconductor device of the second example.

FIG. 10 is a cross-sectional view showing a manufacturing process of the compound semiconductor device of the second embodiment.

FIG. 11 is a cross-sectional view showing the manufacturing process of the compound semiconductor device of the second example.

FIG. 12 is a cross-sectional view showing the manufacturing process of the compound semiconductor device of the second example.

FIG. 13 is a cross-sectional view showing the manufacturing process of the compound semiconductor device of the second embodiment.

FIG. 14 is a cross-sectional view showing the manufacturing process of the compound semiconductor device of the second example.

[Explanation of reference numerals] 1 ... Gallium arsenide compound semiconductor substrate, 2 ... Surface oxide film,
3 ... Resist pattern, 4 ... Aperture, 5 ... Resist residue and surface stain, 6 ... Ohmic electrode, 7 ... Resist pattern, 8 ... Aperture, 9 ... Schottky electrode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Michiyo Mizutani, 1-1, Showa-cho, Kariya, Aichi Prefecture, Nihon Denso Co., Ltd. (72) Inventor, Tetsuo Toyama 1-1, Showa-cho, Kariya, Aichi, Nidec Within the corporation

Claims (3)

[Claims] 1. A first step of oxidizing a surface of a compound semiconductor substrate containing at least gallium or arsenic to form a surface oxide film, and a second step of forming a desired resist pattern on the surface oxide film. A third step of removing a resist residue and surface stains at the same time by removing an exposed portion of the surface oxide film which is not covered with a resist pattern by wet etching to expose a clean compound semiconductor substrate surface; And a fourth step of etching or forming electrodes on the surface of the compound semiconductor substrate. 2. The method of manufacturing a compound semiconductor device according to claim 1, wherein different resist patterns are used as resist patterns in the second step, and the second to fourth steps are repeated. 3. The method for manufacturing a compound semiconductor device according to claim 1, wherein the wet etching solution in the third step is hydrofluoric acid.