JPH07245286A - Method for manufacturing semiconductor device - Google Patents

Abstract

(57) [Abstract] [Purpose] Solves the problem that an overhang is formed at the edge of the wiring when an Al alloy wiring is patterned, and a crack occurs in the nitride film covering the overhang, thereby improving the moisture resistance of the semiconductor element. Improve. [Structure] The patterning is divided into two etchings, the interface between the resist and the wiring metal layer is etched by the first etching with a hydrofluoric acid-based etching solution, and then the second etching with a phosphoric acid-based etching solution is performed. If the metal layer exposed in the mask window is removed, the wiring edge is gently sloped and no overhang occurs.

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 which requires high humidity resistance.

[0002]

2. Description of the Related Art Regarding semiconductor elements, particularly power elements, since a new item related to moisture resistance has been added to the standards established by the Japan Electronic Machinery Manufacturers Association, customers are required to have high moisture resistance elements. It has become so.

[0003]

There are various causes of deterioration of the moisture resistance, and one of the biggest causes is corrosion of the wiring material mainly composed of Al. This is because when the wiring material is etched to form a wiring pattern, an overhang state occurs in which the upper edge projects from the lower layer on the etched side surface, and the protective film coated on the overhang state is formed by resin sealing. This is because a stress is generated from the resin at the time of assembly, or a thermal stress due to a thermal cycle during a test or operation causes cracks on the edge portion thereof, and moisture penetrating therethrough corrodes the wiring material.

2 (a) and 2 (b) show a conventional wiring patterning process in which such an overhang occurs. In FIG. 2 (a), A containing 1% Si on the silicon substrate 1 is used.
1-Si alloy 2 is vapor-deposited and a photosensitive polymer resin is deposited on it.
(Hereinafter, a resist will be described.) 3 is applied and then patterned by photoetching. In the figure (b), phosphoric acid
Al-Si using mixed acid of nitric acid and acetic acid and its aqueous solution
The alloy 2 is etched to form voids 4 that expose the substrate at one time. At this time, the portion A becomes an overhang that projects.

Moisture resistance deteriorates due to cracking of the protective film due to such overhangs. It is expected that the power semiconductor devices will become thinner and thinner in the future, and the protective film will become thinner and more likely to crack, so improvement of the etching shape is essential. SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for manufacturing a semiconductor device, which solves the above-mentioned problems, improves etching shapes, and does not cause cracks in the coating on wiring.

[0006]

In order to achieve the above object, a method of manufacturing a semiconductor device according to the present invention is a method of patterning a wiring metal layer made of a material mainly containing Al by using a mask of a resist film. First, the interface between the resist film and the wiring metal layer is first etched through the window of the resist mask, and then the wiring metal layer is etched.
It is a good method to use a hydrofluoric acid-based etching solution for the etching of the interface between the resist film and the wiring metal layer and a phosphoric acid-based etching solution for the etching of the wiring metal layer. A mixed solution of acid or phosphoric acid and nitric acid or acetic acid is preferable.

[0007]

When the interface between the resist and the wiring metal layer is etched first, and then the wiring metal layer is etched, the edges of the wiring are gently sloping and no overhang occurs.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The wiring patterning process of one embodiment of the present invention will be described below with reference to FIGS. As shown in FIG. 1 (a), a pattern having a window of 20 μm width of the resist 2 is formed on the Al—Si alloy 2 containing 1% of Si as in the case of FIG. 2 (a). It is dipped in an etching solution using an aqueous solution of a mixed solution for 2 minutes, and the interface between the resist 2 and the Al—Si alloy 3 is etched to form a void 5 as shown in FIG. 1 (b). At the same time, the surface layer of the Al—Si alloy 3 is also etched, but the etching amount is set to 1/3 or less of the thickness of the wiring layer 2 of 3 to 5 μm. It was found that the composition ratio of hydrofluoric acid in the etching solution should be adjusted in the range of 0.5 to 2 depending on the angle of the void 5 formed, and the composition ratio of water should be adjusted in the range of 20 to 40.

Next, using an aqueous solution of a mixed acid of phosphoric acid / nitric acid / acetic acid which is usually used, as shown in FIG.
-Si alloy 2 was etched to form voids 4. The etching end point may be determined using a sensor of the reflectance of the etching surface, but it is appropriate to set the etching time to the usual etching time of about 80%. This is Al-Si alloy 2
Is a result of taking into account that the thickness of the film is halved and the remaining film thickness variation. As a result, the overhang unlike the portion A in FIG. 2 did not occur, and the edge portion of the wiring 2 had a smooth shape as shown in the figure. As a result, even if the thickness of the protective film such as a nitride film covering the wiring is thinned, the protective film is not cracked during assembly, testing, or operation, and the moisture resistance is improved.

[0010]

According to the present invention, the patterning of the wiring metal layer mainly composed of Al is divided into two etchings, and the first etching solution is made to enter between the wiring metal and the resist to separate them. By removing the wiring metal up to the substrate surface by the second etching, a gentle slope is formed without causing an overhang at the wiring edge. This makes it possible to prevent cracking of the protective film that covers the wiring, manufacture a highly moisture-resistant semiconductor element, and is particularly effective in promoting thinning of the power semiconductor element.

[Brief description of drawings]

FIG. 1 shows a wiring patterning process according to an embodiment of the present invention.
Sectional drawing which shows in order of (a), (b), (c)

FIG. 2 shows a conventional wiring patterning process (a), (b)
Sectional view in order of

[Explanation of symbols]

 1 Silicon substrate 2 Al-Si alloy 3 Resist 4, 5 Void

Claims (3)

[Claims] 1. When patterning a wiring metal layer made of a material mainly composed of aluminum using a mask of a photosensitive polymer resin film, first, a photosensitive polymer resin film is formed through a window of the photosensitive polymer resin mask. A method of manufacturing a semiconductor device, comprising etching an interface portion with a wiring metal layer and then etching the wiring metal layer. 2. The semiconductor device according to claim 1, wherein a hydrofluoric acid-based etching solution is used for etching the interface between the photosensitive polymer resin film and the wiring metal layer, and a phosphoric acid-based etching solution is used for etching the wiring metal layer. Production method. 3. The method for manufacturing a semiconductor device according to claim 2, wherein the etching solution is a mixed solution of hydrofluoric acid or phosphoric acid and nitric acid and acetic acid.