JPS5823929B2 - Manufacturing method of semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor device in which an electrode layer is formed on a film.

A conventional example is shown in FIG. 1 and FIG. 2.

In FIG. 1, when an electrode layer 12 made of polycrystalline silicon, molybdenum, etc. is formed on the upper surface of a first film 11 such as a 5102 film formed on a semiconductor substrate such as silicon, the electrode layer 12 is formed at room temperature (approximately 400° C.). A polycrystalline Sl film 12 is formed by vacuum evaporation while maintaining the structure.

This sample is subjected to impurity diffusion and thermal oxidation processes that will be performed later.
．． When heat-treated in an electric furnace at 100°C, the polycrystalline Si film 12 peels off when taken out from the electric furnace, resulting in poor adhesion.

A case in which the conventional method is applied to a semiconductor device such as a CCD will be explained with reference to FIGS. 2a" to 2e.

A first film 2 such as a 5i02 film formed on a silicon substrate
A first polycrystalline silicon film 2 is deposited on the upper surface of 1 by CVD method.
2, and a second film 23 of phosphorus, glass, etc. is formed (FIG. 1A).

A two-layer film consisting of the second film 23 and the polycrystalline silicon film 22 is formed into an island shape by ordinary photo-etching (Fig.
).

Thereafter, the exposed side surfaces of the polycrystalline silicon film 22 are selectively oxidized by a thermal oxidation method to form a 5i02 film 24.

In this case, since the polycrystalline silicon film 22 is formed by the CVD method, it has excellent adhesion to the first film 21 and does not peel off even during heat oxidation treatment at high temperatures (for example, 1.100°C). Figure C).

Next, a second polycrystalline silicon film 25 is formed by vacuum evaporation while heating the substrate 21.

At this time, a polycrystalline silicon film 25 is formed on the side surface of the second film 23.
(d) in the same figure.

After that, when the second film 23 is selectively removed (using an HF aqueous solution when phosphorus glass is used), the second polycrystalline silicon film 25 formed thereon is also removed at the same time ( lift-off etch method) (Figure e).

Through the above steps, the polycrystalline silicon film 22°25 becomes S
It is arranged so as to be insulated by an iO□ film 24.

These structures are useful as high density gate electrodes in charge coupled devices.

In the structure shown in FIG. 2e obtained by the conventional method,
By performing a high-temperature heat treatment process (for example, a subsequent thermal oxidation process or thermal diffusion process), peeling of the second polycrystalline silicon film 25 occurs, making it impossible to put it to practical use.

The present invention was made in order to eliminate the above-mentioned peeling phenomenon of the electrode layer, and provides a method for manufacturing a semiconductor device that can reliably form the electrode layer.

The present invention will be explained below based on examples together with the drawings.

FIG. 3 is an explanatory diagram showing the basics of the present invention.

In the figure, first, a polycrystalline silicon film 31 (first electrode layer) of 100 to 1,000 layers is formed on the upper surface of a first film 11 on a semiconductor substrate by the CVD method, and then the substrate is
A polycrystalline silicon film 12 having a desired thickness is formed by vacuum evaporation while heating to 00°C to 400°C.

In this sample, the polycrystalline silicon film 31.degree. 12 does not peel off at all even when heat treatment is performed by rapid heating and cooling in an electric furnace at 1.100.degree.

An embodiment of the present invention using this basic principle is shown in FIGS. 4a''-e.

FIG. 4a is formed in exactly the same way as the conventional example up to FIG. 2.

Next, a polycrystalline silicon film 41 having a thickness of 100λ to 1,000 is formed over the entire surface by CVD.

At this time, since it is formed by the CVD method, the 5IO2 film 24
It is evenly deposited on the entire surface including the side surfaces (Figure b)
Here, since the second film 23 is used for lift-off, it is not preferable for the polycrystalline silicon film 41 to be formed thickly on the side surface of the second film 23.

Therefore, the polycrystalline silicon film 41 is formed to have a thickness that allows for good adhesion to the semiconductor substrate 217.

Thereafter, as in the conventional example, the substrate 21 is heated to 100 DEG C. to 400 DEG C., and a polycrystalline silicon film 25, which will become the second electrode layer, is formed by vacuum evaporation.

At this time, the polycrystalline silicon film 25 is prevented from being deposited on the polycrystalline silicon film 41 on the side surface of the second film 23 (
Figure C).

Therefore, only the thin polycrystalline silicon film 41 is formed on the side surface of the second film 23.

In this way, the polycrystalline silicon film 25 is deposited by CVD using the vapor deposition method.
By forming the film after the polycrystalline silicon film 41 by the method, it is possible to improve the adhesion to the semiconductor substrate 21 and the second film 2 to be described later.
This has the advantage that the lift-off of step 3 becomes easier.

Next, when the entire surface is etched away by an amount equal to the thickness of the polycrystalline silicon film 41, only the portion 41 formed on the side surface of the second film 23 of the polycrystalline silicon film 41 is removed, and the second film 23 is removed. The side of the is exposed (d in the same figure).

In this state, if the second film 23 is selectively removed, a structure similar to that shown in FIG. 2e can be obtained (FIG. 2e).

That is, in the present invention, the polycrystalline silicon film 25 formed by the vapor deposition method is in contact with 24 of the SiO2 films 24 through the polycrystalline silicon film 41 formed by the CVD method, and the adhesion is extremely high. It's expensive.

1. Even after performing rapid heating and cooling treatment at 100°C, peeling of the vapor-deposited polycrystalline Si film 25 as seen in conventional examples was not observed.
Adhesion was significantly improved.

Incidentally, although the polycrystalline silicon film 25 formed by the vapor deposition method has been described in this 5, the same adhesion improvement effect can be obtained with a Mo film, a W film, or the like.

As explained above, by using the present invention, it is possible to form electrode layers such as polycrystalline silicon films by vapor deposition methods, which have been difficult to introduce into conventional semiconductor device manufacturing, and can be combined with lift-off etching methods. Accordingly, an electrode layer can be formed reliably without peeling even in a high-temperature treatment process.

[Brief explanation of the drawing]

1 and 2 a''-e are structural cross-sectional views showing a conventional example, and FIGS. 3 and 4 a''-e are structural cross-sectional views showing each embodiment of the present invention. 11.21.24...S 102 film (first film), 22.31.41...CVD polycrystalline silicon film, 23...second film, 12, 25...
...Polycrystalline silicon film by vapor deposition.

Claims (1)

[Claims] 1. A step of forming a film for lift-off on a semiconductor substrate, a step of forming a pattern of the film, a step of forming a first electrode layer on the pattern and the semiconductor substrate by a CVD method, and a subsequent vapor deposition method. forming a second electrode layer made of the same material as the first electrode layer on the first electrode layer; and etching the first conductive layer so that the side surface of the coating is exposed. By removing the coating, the first and second layers formed on the coating are removed.
1. A method of manufacturing a semiconductor device, comprising the step of lifting off a conductive layer.