JPH05251443A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To improve a step coverage of an upper layer film on a step generated at an edge of a lower layer film. CONSTITUTION:A surface of a lower layer film 2 slightly inside from a part to become an edge of the film 2 is roughed. Thus, since adhesive strength of a mask is low outside from the roughed surface 6, side etching at the time of patterning the lower layer film is advanced, a tapered surface 7 is generated at the edge of the lower layer film, thereby improving a step coverage of an upper layer film 3.

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 an upper layer film is formed over a step formed at an edge of a film partially formed on a semiconductor substrate.

[0002]

2. Description of the Related Art In a semiconductor device, a film deposited on a substrate includes an insulating film, a conductor film such as a metal forming an electrode or a wiring, a passivation film, etc., and it is often the case that these structures are laminated. Are known. At that time, there is a problem of so-called step coverage when the upper layer film is formed straddling a step portion generated at the edge portion of the lower layer film. In order to improve the step coverage, a method such as increasing the film thickness of the upper layer film is used.

[0003]

However, increasing the film thickness of the upper layer film requires a long film forming time, and further has a bad influence on the step coverage when the film is formed thereon. Further, for example, as shown in FIG. 2, even if the Al wiring film 3 extending over the edge portion of the oxide film 2 formed on the silicon substrate 1 is thickened, the constrictions 31 and 32 are basically generated. However, there was a problem such as crack generation.

An object of the present invention is to solve such problems and to provide a highly reliable method for manufacturing a semiconductor device which can obtain good step coverage without increasing the thickness of the upper layer film. .

[0005]

In order to achieve the above object, the present invention provides a method for manufacturing a semiconductor device in which an upper layer film is provided over a step formed at an edge of the lower layer film. The inner portion of the surface of the lower layer film covered with the mask, which is separated from the portion to be the edge of the mask by a predetermined distance, is roughened in advance, and then a mask pattern is formed to selectively etch the upper layer film. The taper surface is formed at the edge of the lower layer film that is provided over. Then, it is effective that the mask is made of a photomask film, the lower layer film is an oxide film, and the surface thereof is heat-treated in nitrogen gas or roughened by plasma etching.

[0006]

[Function] The surface to which the etching mask is applied when patterning the lower layer film provided over the upper layer film is
If the mask is roughened slightly inside the part that should be the edge of the mask, the mask adheres well to the rough surface but not to the outside, so that the etching solution penetrates into the interface where adhesion is poor. A tapered surface occurs at the edge of the lower layer film. Therefore, the step coverage of the upper layer film formed over the edge portion is good.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 (a) to 1 (i) in which the same parts as those in FIG. First, 1 to 1 on the silicon substrate 1 by a thermal oxidation method or the like.
A silicon oxide film 2 having a thickness of 1.5 μm is formed (the same figure)
(a)). Next, a silicon nitride film 4 is formed thereon by a CVD method or the like (FIG. 2B). A pattern of the photoresist film 5 is formed on the nitride film 4 by photolithography.
((C) of the same figure), the exposed nitride film 4 is removed by etching
(Figure (d)). The pattern of the nitride film 4 generated at this time reaches a position where the pattern of the oxide film 2 to be formed thereafter is located within 1 to 1.5 μm from the outside of the edge to the inside of the edge. Next, after the resist film 5 is ashed, the exposed portion 6 on the surface of the oxide film 2 is roughened by annealing in a nitrogen atmosphere (FIG. 7E). After that, the remaining nitride film 4 is removed (FIG. 3F), and a pattern of the photoresist film 5 is formed so as to be deposited to the outside of 1 to 1.5 μm of the rough surface 6 (FIG. 2G). When the oxide film 2 is etched in this state, the adhesion strength of the resist film 5 is weaker outside the rough surface 6, so that the etching solution penetrates into the interface and side etching proceeds, and the edge of the oxide film 2 is exposed to about 40%. A tapered surface 7 having an angle θ of ℃ is generated (Fig.
(h)). Therefore, the step coverage of the wiring Al film 3 formed across the step having the tapered surface 7 becomes good, and the constricted shape does not occur ((i) in the same figure). The oxide film 6 may be roughened by plasma etching.

[0008]

According to the present invention, before the patterning of the lower layer film, the surface of the lower layer film is roughened at a portion inside the edge portion thereof to improve the adhesion of the film serving as a mask. Since side etching proceeds in a portion having poor adhesion, a step having a tapered surface is generated at the edge of the lower layer film. As a result, the step coverage of the upper layer film is improved and the upper layer film thickness can be reduced, so that the operating rate of the film forming equipment is improved and a highly reliable semiconductor device can be manufactured.

[Brief description of drawings]

FIG. 1 is a sectional view showing the steps of forming a wiring film on an oxide film according to an embodiment of the present invention in the order of (a) to (i).

FIG. 2 is a cross-sectional view showing a wiring film on a conventional oxide film step portion.

[Explanation of symbols]

 1 Silicon substrate 2 Oxide film 3 Al film 4 Nitride film 5 Photoresist film 6 Rough surface 7 Tapered surface

Claims (4)

[Claims] 1. A method of manufacturing a semiconductor device, wherein an upper layer film is provided so as to extend over a step generated at an edge portion of a lower layer film, and a portion to be an edge portion of a surface of the lower layer film covered with a mask for selective etching. It is possible to roughen the inner part that is separated by a predetermined distance in advance, then form a mask pattern and perform selective etching to form a tapered surface at the edge of the lower layer film over which the upper layer film is provided. A method of manufacturing a semiconductor device having a feature. 2. The method for manufacturing a semiconductor device according to claim 1, wherein the mask is made of a photoresist film. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the lower layer film is an oxide film, and the surface thereof is roughened by heat treatment in nitrogen gas. 4. The method for manufacturing a semiconductor device according to claim 1, wherein the lower layer film is an oxide film and the surface thereof is roughened by plasma etching.