JPS6225425A - Etching method for surface protective film - Google Patents

Abstract

PURPOSE:To improve the step coverage of a metal electrode by plasma etching a nitride film with a resist as a mark and chemically etching an oxide film when forming a hole after laminating the oxide film and the nitride film on a semiconductor element, thereby forming a step in the hole. CONSTITUTION:An oxide film 2 and a nitride film 3 are laminated to become a surface protective film on an Si substrate 1, a resist 4 of the prescribed shape is formed on the film 3 to be exposed with CF4+O2 plasma gas 5, and the exposed portion of the film 3 is first removed. After a tapered part is formed at the edge of the film 3 in this manner, the resist 4 is removed, and a resist 6 is again coated from the remaining part of the film 3 to the edge of the exposed film 2. Thereafter, the exposed part of the film 2 is removed by etching with fluoric acid solution, a tapered part is formed at the edge of the film 2 which similarly remains, and an aluminum electrode film 7 is coated from the remaining film having the step to the exposed surface of the substrate 1.

Description

[Detailed description of the invention] [Technical field to which the invention pertains]

The present invention relates to a method of etching a semiconductor surface protection film in order to provide an opening for electrode contact after a nitride film is deposited on an oxide film formed on the surface of a semiconductor body.

[Prior art and its problems]

Since the oxide film formed on the surface during the process is not sufficient to protect the exposed portion of the junction formed in the semiconductor element, a nitride film is further deposited thereon. In order to provide a metal pole on a semiconductor body in this way, it is necessary to remove the stacked oxide film and nitride film, which are vA-related, to expose the semiconductor body. Prior to deposition, the oxide film was selectively etched, a nitride film was then deposited on the entire surface, and the nitride film was selectively plasma etched. However, in this case, since the etched portion of the oxide film does not have a taper, the aluminum electric bridge that is subsequently formed does not come into close contact with the edge of the oxide film, resulting in the problem of so-called step coverage.

[Purpose of the invention]

In contrast, the present invention improves the step coverage of the four metal poles at the edge of the opening of the surface protective film formed by depositing a nitride film on the oxide film formed on the surface of the semiconductor element. The purpose of the present invention is to provide an etching method that can be used for etching.

[Key points of the invention]

The present invention achieves the above object by plasma etching the nitride film through a mask, bringing the exposed oxide film into contact with the plasma, and chemically etching the oxide film through the mask.

[Embodiments of the invention]

FIGS. 1(8) to 1(el) show the steps of an embodiment of the present invention, in which the silicon plate 1 has a surface protection film with a two-layer structure of an oxide film 2 and a nitride film 3, FIG. 1 shows a state in which a mask is formed on this surface protective film using a resist 4 and exposed to (CF4+O2) plasma gas 5 for etching. As a result, the edges of the nitride film 3 are etched into a tapered shape as shown in Figure Cb1. (c) As shown in Figure 1, the resist 4 is removed and a mask is formed again using the resist 6. Figure (d) shows the state of chemical etching with a hydrofluoric acid aqueous solution, and the oxide film 2 also has a tapered edge. This seems to be because the oxide film 2 exposed during plasma etching shown in Figure +81 is also affected by the plasma 5, and the parts near the surface of the oxide film are more likely to be etched. Also, when the aluminum electrode film 7 is deposited as shown in Figure 61, the electrode film exhibits good step coverage at the step portion having the two-step taper.

【Effect of the invention】

In the present invention, when forming an opening in a 2N surface protective film consisting of an oxide film and a nitride film thereon, the oxide film is exposed to plasma gas at the same time as the nitride film is plasma etched. This allows the formation of a tapered surface during etching, and the Q4m film that contacts the semiconductor surface in the opening adheres well to the stepped portion at the edge of the surface protective film, greatly improving the reliability of the semiconductor element. can be improved.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part sequentially showing the steps of an embodiment of the present invention. 1: Silicon plate, 2 Dioxide film, 3: Nitride film, 4.6:
l/cyst, 5: (CF4 + O plasma, 7
:AI electrode film.

Claims (1)

[Claims] 1) After depositing a nitride film on the oxide film formed on the surface of the semiconductor element, when forming an opening, the nitride film is plasma etched through a mask, and the exposed oxide film is brought into contact with plasma gas; A surface protective film etching method characterized in that the oxide film is then chemically etched through a mask.