JPH05291245A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent disconnection of a metallic thin film formed on a semiconductor substrate. CONSTITUTION:The manufacturing process of a semiconductor devide includes the following: a process which performs one out of a process wherein a film which is errosion-resistant in a wet etching operation is formed on a semiconductor substrate 1 on which a silicon dioxide insulating film 2 has been formed and a process wherein an electrode is formed selectively; a process wherein the other of said processes is performed; a process wherein a PSG film 4 is formed on the whole surface and a photoresist pattern 5 is formed on its surface; a process wherein a metal thin film 6 is formed on the whole surface; and a process wherein the metal thin film 6 on the photoresist is removed by a lift-off method.

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 semiconductor device in which a desired metal thin film pattern is formed on a semiconductor substrate.

[0002]

2. Description of the Related Art Conventionally, as a manufacturing method for forming various thin film patterns such as electrodes and wirings on a semiconductor substrate, for example, a method disclosed in JP-A-59-124780 is known. . Hereinafter, a conventional method for manufacturing a semiconductor device will be described with reference to FIG.

In FIG. 3A, a gallium arsenide substrate 1
A silicon dioxide insulating film 2 for protecting the semiconductor element formed on the gallium arsenide substrate 1 is formed thereon, and an aluminum electrode 3 is selectively formed on the silicon dioxide insulating film 2. Next, in FIG. 3B, a phosphorus-doped silicon dioxide insulating film 4 (hereinafter referred to as a PSG film) is formed on the entire surface. Subsequently, a photoresist film 5 that serves as an etching mask when the PSG film 4 is wet-etched is applied on the PSG film 4, and a pattern of the photoresist film 5 is formed by selective exposure. In FIG. 3C, the PSG film 4 is selectively wet-etched using the photoresist film 5 as a mask. In FIG. 3D, a nickel-cobalt metal thin film 6 is formed on the entire surface by vapor deposition, and in FIG. 3D, the photoresist film 5 and the PSG film 4 are dissolved in a solution containing acetone to form the photoresist film 5. The nickel-cobalt metal thin film 6 is removed, and a metal thin film pattern is formed on the gallium arsenide substrate 1.

Conventionally, when performing lift-off, an insulating film is generally provided as a lower layer of the photoresist film 5. This is because a metal thin film left on the gallium arsenide substrate 1 at the time of forming the metal thin film 6 and a metal thin film to be removed by forming an overhang structure at the pattern end portion of the photoresist film 5 by erosion by the etching solution at the time of etching the insulating film. This is because and can be easily separated by cutting the step. Further, since the metal thin film to be left on the gallium arsenide substrate 1 does not rise or turn up, the solvent for lift-off does not soak into the lower layer of the end of the metal thin film, and good patterning is possible, which is an effective method. In order to facilitate the separation of the metal thin film left on the gallium arsenide substrate 1 and the metal thin film to be removed due to step breakage, the insulating film under the photoresist film 5 is preferably thick. The PSG film 4 is used as this insulating film because a silicon oxide film containing phosphorus (that is, a PSG film) can relax the stress of the film and cracks are less likely to occur even if formed thick, so that the film does not contain phosphorus. This is because the film can be formed thicker than

[0005]

By the way, in the case of an ordinary semiconductor device, an insulating film of a silicon oxide film is formed on a semiconductor substrate in order to mechanically or chemically protect a semiconductor element. The protective film formed on the semiconductor substrate needs to have a large film thickness for the purpose of protecting the semiconductor element. The silicon oxide film is suitable as a protective film because it does not crack due to stress and does not adversely affect the semiconductor element even if the film thickness is increased. However, when a step of forming a conductive portion such as the electrode 3 is performed on the silicon oxide film and there is a step on the upper surface, the lower portion of the electrode (I in FIG. 3C) is subjected to wet etching of the PSG film.
Part) also has an overhang structure. This is because the insulating PSG film and the silicon dioxide insulating film are almost eroded by the etching solution for the silicon oxide film at the substantially same rate, so that the silicon dioxide insulating film is easily eroded during the etching of the PSG film. . When the metal thin film is formed after the pattern of the PSG film 4 and the photoresist film 5 is formed by performing the step of forming the electrode 3 as described above, the electrode end portion, that is, the step portion between the electrode 3 and the silicon dioxide insulating film 2 ( There is a problem that the probability that the metal thin film will be broken becomes high in the part II of FIG. 3D.

In view of the above problems, the present invention has an object to cut off the silicon oxide film in the lower layer of the conductive portion which is not desired to form an overhang structure from the etching solution to overhang the lower layer of the conductive portion. It is to prevent the structure from occurring.

[0007]

In order to achieve the above object, a method of manufacturing a semiconductor device according to the present invention comprises forming a first silicon oxide film on a semiconductor substrate and forming a first silicon oxide film on the first silicon oxide film. A protective film having erosion resistance against an etching solution for a silicon oxide film is formed, then a conductive portion is selectively formed on the protective film, and a second silicon oxide film is formed on the entire surface. A photoresist film is selectively formed on the second silicon oxide film, the second silicon oxide film is wet-etched using the photoresist film as an etching mask, and then a metal thin film is formed on the entire surface. The metal thin film pattern is formed by removing the resist film and then removing the metal thin film on the photoresist film. Alternatively, a first silicon oxide film is formed on a semiconductor substrate, a conductive portion is selectively formed on the first silicon oxide film, and then silicon oxide is formed on the first silicon oxide film and the conductive portion. The metal on the photoresist film is removed by removing the photoresist film from the step of forming a protective film having erosion resistance against the etching solution for the film and then forming the second silicon oxide film on the entire surface as described above. It is characterized in that a metal thin film pattern is formed by removing the thin film.

[0008]

[Operation] By the above means, the first silicon oxide film under the conductive portion is covered with the protective film having corrosion resistance to the etching solution for the silicon oxide film, and the second silicon oxide film is wet-etched. At this time, the first silicon oxide film under the conductive portion does not come into contact with the etching solution for the silicon oxide film and is not corroded, so that the overhang structure does not occur in the lower layer at the end of the conductive portion.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a series of manufacturing steps for forming electrodes and metal wiring patterns on a semiconductor substrate according to an embodiment of the present invention. The same parts as those in FIG. 3 are designated by the same reference numerals.

In FIG. 1A, a gallium arsenide substrate 1
Silicon dioxide insulation for protecting the semiconductor element formed on the gallium arsenide substrate 1 and for insulating the underlying circuit formed on the gallium arsenide substrate 1 by the atmospheric pressure CVD method (chemical vapor deposition method). The film 2 is formed with a thickness of about 1450 nm. Next, a metal aluminum layer is formed to a thickness of 800 nm on the entire surface of the silicon dioxide insulating film 2 by a sputtering method or the like, and a photoresist pattern corresponding to the electrode wiring pattern is formed on the surface of the metal aluminum layer. Then, the aluminum metal layer in the photoresist pattern opening is selectively removed by isotropic etching to form an aluminum electrode 3. In the present embodiment, the example in which the aluminum electrode is formed as the conductive portion is shown, but this is not limited to the metal electrode, and may be polycrystalline silicon or diffusion resistance. In FIG. 1B, silicon nitride for protecting the silicon dioxide insulating film 2 from the etching solution when the PSG film 4 described later is wet-etched by the atmospheric pressure CVD method (chemical vapor deposition method) or the sputtering method. The film 7 is formed on the entire surface by about 50 to 100 nm.
Then, a contact hole 24 is formed on the upper surface of the aluminum electrode 3 by dry etching. Here, the contact hole 24 is formed to electrically connect the nickel-cobalt metal thin film 6 described later and the aluminum electrode 3 to each other. In FIG. 1C, a phosphorus-doped silicon dioxide insulating film 4 (hereinafter referred to as a PSG film) is formed on the entire surface by atmospheric pressure CVD to a thickness of about 400 nm.
A photoresist film as an etching mask at the time of wet etching of the PSG film 4 is applied thereon, and a resist film pattern 5 is formed by selective exposure. As the photoresist film, a film that can withstand the later wet etching of the PSG film is used. In FIG. 3D, the PSG film 4 is wet-etched using the photoresist film 5 as an etching mask. At this time, the pattern end portion of the PSG film 4 is degenerated from the resist end portion to form an overhang structure (see part III in FIG. 1D). By doing so, when the metal thin film 6 is formed on the gallium arsenide substrate 1 described later,
The metal thin film left on the gallium arsenide substrate 1 and the metal thin film to be removed on the photoresist film 5 can be separated at the end of the photoresist film 5, and the metal thin film on the photoresist film 5 can be easily lifted off. . However, since the silicon dioxide insulating film 2 is covered with the silicon nitride film 7 at the end of the aluminum electrode 3, the silicon dioxide insulating film 2
Is not corroded even when the PSG film 4 is wet-etched because it does not come into contact with the etching solution for the PSG film, so that this portion does not form an overhang structure. The erosion resistance of the silicon nitride film is that the silicon nitride film has a dense structure,
The reason is that the chemical bonding force of Si and N is strong, the invasion of H ⁺ and OH ^{− in} the etching solution for the PSG film is prevented, and the chemical reaction rate is very slow.
In FIG. 1E, a nickel-cobalt metal thin film 6 is formed to a thickness of 100 nm by vapor deposition. Finally, in FIG. 1F, the gallium arsenide substrate 1 is dipped in a solution containing acetone to dissolve the photoresist film 5 in the solution to remove the unnecessary nickel-cobalt metal thin film 6 on the photoresist film 5. By the lift-off method described above, a semiconductor device having a desired metal wiring pattern is obtained. Further, the PSG film 4 remaining on the gallium arsenide substrate 1 can be removed by using a hydrofluoric acid-based (HF-based) solution in a later step when the existence thereof is inconvenient.

As another embodiment of the present invention, as shown in FIG. 2, after the step of forming the silicon dioxide insulating film 2 on the gallium arsenide substrate 1, the step of forming the silicon nitride film 3 on the entire surface is performed. (FIG. 2 (a)), and even if the step of forming the aluminum electrode 3 (FIG. 2 (b)) is performed (the subsequent steps are the same as those described above), a silicon dioxide insulating film for the PSG is formed under the aluminum electrode 3 There is a silicon nitride film 3 for protecting it from the etching solution, and since the silicon dioxide insulating film 2 is not eroded during the wet etching of the PSG film 4, an overhang structure does not occur under the aluminum electrode. As a result, disconnection of the metal thin film at the time of forming the metal thin film pattern can be prevented.

Further, as the film formed on the silicon dioxide insulating film, other than the silicon nitride film, a film having corrosion resistance to an etching solution for a silicon oxide film such as a silicon carbide film or a carbon film may be used. Even if these materials are used, it is possible to prevent an overhang structure from being formed in the lower part of the electrode, and it is possible to obtain an effect of preventing disconnection of the metal thin film.

According to the present invention, the effect of improving the heat resistance and the moisture resistance of the gallium arsenide substrate 1 can be expected by covering almost the entire surface of the gallium arsenide substrate 1 with the silicon nitride film 7.

[0015]

As described above, according to the present invention,
Since the method of manufacturing a semiconductor device has a step of forming a protective film having erosion resistance against an etching solution for a silicon oxide film on the first silicon oxide film, During the wet etching, the first silicon oxide film does not come into contact with the etching solution for the silicon oxide film and is not corroded. Therefore, an overhang structure does not occur in the lower layer at the end of the conductive portion. Therefore, the metal thin film is formed when the metal thin film pattern is formed. It is possible to manufacture a semiconductor device having a good metal thin film pattern without disconnection.

[Brief description of drawings]

FIG. 1 is a process drawing in a method of manufacturing a semiconductor device showing an embodiment of the present invention.

FIG. 2 is a process drawing in the method of manufacturing a semiconductor device showing another embodiment of the present invention.

FIG. 3 is a process diagram of a conventional semiconductor device manufacturing method.

[Explanation of symbols]

 1 ... Gallium arsenide substrate 2 ... Silicon dioxide insulating film 3 ... Aluminum electrode 4 ... PSG film 5 ... Photoresist film 6 ... Nickel-cobalt metal thin film 7 ... Silicon nitride film

Front Page Continuation (72) Inventor Yuji Suzuki 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Automobile Co., Ltd.

Claims (2)

[Claims] 1. A first step of forming a first silicon oxide film on a semiconductor substrate, and a protective film having erosion resistance against an etching solution for a silicon oxide film on the first silicon oxide film. A second step of forming, a third step of selectively forming a conductive portion on the protective film, a fourth step of forming a second silicon oxide film on the entire surface, and further on the second silicon oxide film. A fifth step of selectively forming a photoresist film on the substrate, a sixth step of wet etching the second silicon oxide film using the photoresist film as an etching mask, and a seventh step of forming a metal thin film on the entire surface, A method for manufacturing a semiconductor device, comprising: an eighth step of forming a metal thin film pattern by removing the photoresist film and removing the metal thin film on the photoresist film. 2. A first step of forming a first silicon oxide film on a semiconductor substrate, a second step of selectively forming a conductive portion on the first silicon oxide film, and the first silicon. A third step of forming a protective film having corrosion resistance against an etching solution for a silicon oxide film on the oxide film and the conductive portion, a fourth step of forming a second silicon oxide film on the entire surface, and further A fifth step of selectively forming a photoresist film on the second silicon oxide film, a sixth step of wet etching the second silicon oxide film using the photoresist film as an etching mask, and a metal thin film on the entire surface. And a seventh step of forming and a eighth step of forming a metal thin film pattern by removing the photoresist film and removing the metal thin film on the photoresist film. Method of manufacturing a body apparatus.