JPS62115832A - Forming method for mesa groove of semiconductor device - Google Patents

Abstract

PURPOSE:To effectively cover a portion exposed in a mesa groove with a coating material by simultaneously etching parts of a semiconductor wafer and a protecting film to prevent the film from extending in an overhanging state. CONSTITUTION:A protecting film 2 made of silicon oxide is formed on one side surface of a semiconductor wafer 1, and processed in a photoetching step to form a protecting film removed portion 3. Then, the film 2 is coated with a photoresist 5, and a photoresist removed portion 4 is formed on a region having a width wider than that of the portion 3. The photoresist removed portion of the film 2 and a part of a semiconductor wafer 1 are simultaneously etched with a mixture of nitric acid and fluoric acid from the photoresist removed portion 4 to obtain a mesa groove 6. The groove 6 with the film 2 not extending an an overhanging state can be obtained at the film 2 by setting the thickness of the film 2 and the width of the removed portion 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming a mesa groove in a semiconductor device by etching a mesa groove in a semiconductor device.

[Prior art]

Mesa-type semiconductor devices, which generally require high breakdown voltage, are made by regularly arranging a large number of semiconductor devices on a single semiconductor wafer through processes such as diffusion and photoetching, and then selecting between each semiconductor device. A mesa groove is formed by etching the part from which the protective film has been removed, and the PN junction exposed in the mesa groove is covered with a coating material such as glass or silicone rubber to stabilize it and then divided into individual pieces. It explodes.

As shown in FIG. 2, a conventional method for forming a mesa groove in a semiconductor device involves forming a protective film 12 made of silicon oxide or the like on at least one surface of a semiconductor wafer 11, and selectively removing the protective film 12 by etching. forming a protective film removed portion 13,
Further, the mesa groove 14 is obtained by etching the protective film removed portion 13.

However, since the etching progresses in a hemispherical manner inside the semiconductor wafer 11, a mesa groove 14 is formed in which the etching extends directly under the protective film 12 in the vicinity of the protective film removed portion I3. For this reason, the protective film 12 has a shape that protrudes like an eave, and when covering the PN junction portion exposed in the mesa groove with a covering material, there is a drawback that it is difficult to cover the area directly under the protective film 12 that protrudes like an eave. had.

[Purpose of the invention]

The present invention has been made in consideration of the above-mentioned conventional problems, and it prevents the protective film from protruding like an eave when forming a mesa groove, and the exposed part of the mesa groove is covered with a covering material. It is an object of the present invention to provide a method for forming a mesa groove in a semiconductor device that can be reliably covered.

[Structure of the invention]

A method for forming a mesa groove in a semiconductor device according to the present invention includes forming a protective film on at least one surface of a semiconductor wafer, etching the protective film to selectively form a protective film removed portion, and further forming a protective film and a protective film. A resist layer is formed on the protective film removed part, a resist removed part is formed in the resist layer on the protective film removed part in a region wider than the width of the protective film removed part, and the resist is removed from the resist removed part. By simultaneously etching the underlying protective film and the semiconductor wafer, it became possible to obtain a mesa groove in which the protective film did not protrude like an eave, and ensured that the exposed parts of the mesa groove were covered. It is characterized by this.

〔Example〕

An embodiment of the present invention will be described below based on FIG. On one side of the semiconductor wafer 1 there is a protection H'J! made of silicon oxide. 2 is formed, and through a photo-etching process, a protective film removed portion 3 is selectively formed as shown in FIG. 1(a). Next, a photoresist 5 is applied onto the protective film 2 and subjected to an exposure process and a development process, thereby forming a photoresist removed area in an area wider than the width of the protective film removed area 30, as shown in FIG. form 4. Thereafter, the mesa groove 6 is obtained by simultaneously etching the portion of the protective film 2 from which the photoresist has been removed and a portion of the semiconductor wafer 1 using a mixed solution of nitric acid and hydrofluoric acid from the photoresist removal section 4. At this time, assuming that the etching rate of the mixed solution of nitric acid and hydrofluoric acid is 1 for the protective film 2, the etching rate for the semiconductor wafer 1 is 10. Therefore, the protective film 2 is etched so that the entire portion of the protective film 2 from which the photoresist has been removed is etched while the etching of the semiconductor wafer 1 is completed.
By setting the thickness of the photoresist removed portion 4 and the width of the photoresist removed portion 4, it is possible to obtain a mesa groove 6 in which the protective film 2 does not protrude like an eaves.

〔Effect of the invention〕

As described above, the method for forming a mesa groove in a semiconductor device according to the present invention prevents the protective film from protruding like an eaves by etching a part of the semiconductor wafer and a part of the protective film at the same time. The exposed portion can be reliably covered with a covering material such as glass or silicone rubber.

This has the effect of improving the reliability of the semiconductor device.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, and FIG.
) is a cross-sectional view showing a state in which a protective film is selectively formed on one side of a semiconductor wafer, and FIG. FIG. 2C is a cross-sectional view showing a state in which the photoresist is peeled off after forming a mesa groove, and FIG. 2 is a cross-sectional view showing a conventional example. 1 is a semiconductor wafer, 2 is a protective film, 3 is a protective film removal part,
4 is a photoresist removal part, 5 is a photoresist, and 6 is a mesa groove. Patent applicant Sharp Corporation Figure 1 (a) Figure 1 (b) '$1 Figure (C) Figure 2

Claims (1)

[Claims] 1. Forming a protective film on at least one surface of the semiconductor wafer, etching the protective film to selectively form a protective film removed part, and further forming a resist layer on the protective film and the protective film removed part. , a resist removed portion is formed in a region wider than the width of the protective film removed portion in the resist layer above the protective film removed portion, and the protective film under the resist removed portion and the semiconductor wafer are simultaneously etched from the resist removed portion. A method for forming a mesa groove in a semiconductor device, the method comprising forming a mesa groove by: