JPS5826659B2 - Electrode formation method for semiconductor devices - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor device, and particularly to a method for forming electrodes in a semiconductor device using two types of insulating films.

Generally, in order to protect the surface of various semiconductor devices,
A silicon oxide film is formed on the surface of a semiconductor substrate, and a different type of protective insulating film, such as a silicon nitride film, is further formed on the film.

On the other hand, even in a semiconductor device having such a two-layer protective film structure, a contact hole passing through both protective films is required to take out an electrode.

However, in order to form a contact hole penetrating both protective insulating films, since the materials are different, it is impossible to form the contact hole in one etching process using one type of etching solution.

Therefore, usually a photoresist film corresponding to the contact hole is provided on the upper protective film, such as a silicon nitride film, the silicon nitride film is etched with phosphoric acid, and then the lower layer is etched with hydrofluoric acid using this silicon nitride film as a mask. The silicon oxide film of the protective film is etched to obtain a contact hole penetrating both the nitride and oxide silicon films.

The contact hole thus obtained is shown in FIG.

In the figure, 1 is a silicon substrate, 2 is a silicon oxide film, and 3 is a silicon substrate.
4 is a silicon nitride film, 4 is a metal wiring pattern provided on this silicon nitride film 3, and 5 is a contact hole.

As is clear from this figure, eaves-like bodies 6, 6 are formed on the side of the contact hole 5 of the silicon nitride 3, which served as a mask during the etching of the silicon oxide 2, due to the side etching phenomenon. Due to the presence of the bodies 6, 6, there is a risk that an undesirable contact failure such as foil breakage may occur during electrode formation which is subsequently performed to connect the substrate 1 and the metal wiring pattern 4 via the contact hole 5. be.

The present invention has been made for the purpose of preventing the occurrence of poor contact accidents caused by such eaves-like bodies 6, 6, and will be described in detail with reference to FIG. 2 and subsequent figures.

The first step of the present invention is to form a relatively thin first insulating film, for example, a silicon oxide film 11 of about 5,000 layers, on the surface of the semiconductor substrate 10 (FIG. 2).

This silicon oxide film 11 may be formed by thermal oxidation of the silicon substrate 10, or may be formed by other methods, and is not a matter of choice.

In the second step, as shown in FIG.
A second insulating film, for example, a silicon nitride film 12 of about 1,000 layers, is formed on top of the silicon oxide film 12. It's fine as long as it's something you can get.

In the third step, a silicon oxide film 1 is applied to a silicon nitride film 12.
The first step is to form an etching hole 13 corresponding to the position where the first contact hole is to be provided (FIG. 4).

This step is carried out by a photoresist method using hot phosphoric acid or the like.

Next, as shown in FIG. 5, the silicon oxide film 1 is etched using hydrofluoric acid using the etching hole 13 of the silicon nitride film 12 as a mask.
The fourth step is to form a contact hole 14 in 1.

At this time, as is clear from FIG. 5, the silicon oxide film 1
Eaves-like bodies 15.degree. 15 are formed on the silicon nitride film 12 by the side etching of step 1.

The fifth step consists in depositing a molybdenum film 16, which can be used later as a wiring pattern, on the entire surface of the silicon substrate 10 that has gone through each of the above steps using the C, V, D method, etc. (FIG. 6).

The thickness of this molybdenum film 16 is approximately 300 OA.

Next, in the sixth step, a photoresist film 17 having a metal wiring pattern having holes the same as or slightly larger than the contact holes 14 is formed on this molybdenum film 16.
This is the process (Figure 7).

In the seventh step, as shown in FIG. 8, Freon gas (CF) is applied using the photoresist film 17 obtained in the sixth step as a mask.
The molybdenum film 16 is left in the form of a metal wiring pattern by the plasma etching in step 4), and at the same time, the contact holes 14 are formed by the Freon gas plasma etching.
The eaves 15.15 of the silicon nitride film 12 formed at the upper end of the silicon nitride film 12 are also removed by etching.

The Freon gas plasma etching used here is about 30MH under a Freon gas pressure of 0.3 Torr.
By applying a high frequency wave of z, a discharge occurs, and during the discharge, the exposed molybdenum film 16 on the surface of the silicon substrate 10 and the eaves-like body 15.1 of the silicon nitride film 12 are exposed.
5 is etched and is carried out at room temperature, but it has been confirmed that when plasma discharge occurs, the temperature of the surface of the substrate 10 rises to 200 to 300 degrees Celsius.
Plasma etching is performed for 1 minute.

The final step of the present invention, as shown in FIG. 9, is to connect the substrate 10 and the molybdenum film 16 patterned with metal wiring through the contact hole 14 using an aluminum electrode material 18.

This electrode formation is performed by aluminum vapor deposition of about 1.2 μm and a photoresist method.

As is clear from the above description, in the present invention, the eaves-like body formed around the periphery of the contact hole is removed at the same time when the molybdenum film is patterned into a metal wiring pattern by plasma etching with Freon gas. There is no contact failure due to foil breakage when forming electrodes for connection, and the reliability of the semiconductor device can be made extremely high.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the main part showing the current state of a semiconductor device, and FIGS. 2 to 9 are cross-sectional views of the main part showing the method of the present invention in order of process, in which 10 is a substrate, 11 is a silicon oxide 12 is a silicon nitride film, 14 is a contact hole, 15 is an eave-shaped body,
Reference numeral 16 indicates a molybdenum film, and reference numeral 18 indicates an electrode material.

Claims (1)

[Scope of Claims] 1. A method for forming electrodes of a semiconductor device, which comprises sequentially carrying out the following steps: (a) forming a relatively thick first insulating film on the surface of a semiconductor substrate; and (b) the insulating film. a step of forming a second insulating film on top of the insulating film that can serve as a mask during selective etching of the insulating film; ＼) etching the second insulating film at a location corresponding to a position where a contact hole is to be provided in the first insulating film; 2) forming a contact hole by selectively etching the first insulating film using the etched hole; e) forming a contact hole on the entire surface of the substrate that has gone through each of the above steps, which will later be used as a wiring pattern. a step of attaching a molybdenum film, f) forming a metal wiring pattern on the molybdenum film with a photoresist film having a hole the same as or slightly larger than the contact hole, g) masking the photoresist film pattern as CF4
The molybdenum film is left in accordance with the metal wiring pattern by gas plasma etching, and at the same time, the eaves-like body of the second insulating film existing at the upper end of the contact hole is also removed by this CF4 gas plasma etching. Step h) Connecting the substrate and the molybdenum metal wiring pattern through the contact hole using a metal electrode material. 2 The first insulating film is made of a silicon oxide film, and the second insulating film is made of a silicon oxide film.
2. The method of forming an electrode for a semiconductor device according to claim 1, wherein the insulating film is made of a silicon nitride film.