JPH0546972B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for manufacturing a semiconductor device.

[Conventional technology]

Generally, in order to improve the light emitting characteristics of optical semiconductor devices such as LEDs, the mesa is selectively formed so that the shape of the mesa flat part of the selectively mesa-etched semiconductor device matches the shape of the ohmic electrode thereon. There is a need.

3a to 3c are cross-sectional views of a semiconductor chip shown in the order of steps for explaining a conventional method of manufacturing a semiconductor device.

As shown in FIG. 3a, a photoresist layer 3d is formed covering the surface of the InP substrate 1. As shown in FIG.

Next, a ring-shaped opening 4c is selectively formed in the photoresist layer 3d by photolithography.

Next, InP is etched by isotropic wet etching.
The substrate 1 is etched to form a mesa flat part 6 and a mesa etch part 5 so as to create an undercut near the opening in the photoresist layer 3d.

Next, as shown in FIG. 3b, a photoresist layer 3 is applied.
After peeling off the InP substrate 1, an automic contact CrAu layer 1 consisting of a double layer of Cr and Au is placed on the front surface of the InP substrate 1.
2.

Next, as shown in FIG. 3c, a photoresist layer 3
After forming the photoresist layer 3e on the CrAu layer 12, the photoresist layer 3e is left only in the part corresponding to the mesa flat part 6 where the automic electrode is to be formed, and then the CrAu layer 12 in other parts is etched by wet etching. Finally, the photoresist layer 3e is removed to form an ohmic electrode 12a on the surface of the mesa flat portion 6.

FIG. 4 is a perspective view of the semiconductor chip corresponding to FIG. 3c.

FIG. 3c corresponds to the sectional view taken along line A-A' in FIG.

The mesa flat portion 6 is covered with an ohmic electrode 12a, leaving an exposed portion 6a.

In order to avoid exposing the surfaces 6a on both sides of the mesa flat portion 6 in this method, it is necessary to match the mask butter shape of the photoresist layer 3e to the planar shape of the mesa flat portion 6.

For this reason, since the degree of wet etching varies depending on the production lot of semiconductor wafers, many types of exposure masks for forming the photoresist layer 3e are prepared.

[Problem that the invention seeks to solve]

In the conventional semiconductor device manufacturing method described above, the shape of the mesa flat portion varies depending on the degree of etching and the production lot of wafers, so it is necessary to prepare a large number of exposure masks to form the photoresist layer, and it is necessary to prepare many exposure masks before exposure. There were problems such as the need to measure the shape and dimensions of the mesa flat part and the need for high accuracy in aligning the exposure mask.

The present invention relates to a method of manufacturing a semiconductor device having a mesa flat portion completely covered with an automic electrode.

[Means for solving problems]

The method for manufacturing a semiconductor device of the present invention includes the following steps: A. Forming a conductive layer to serve as an ohmic electrode on the entire surface of one principal surface of a semiconductor substrate; (B) Forming a material layer to serve as an etching mask on the surface of the conductive layer. (C) isotropically etching the material layer excluding the openings using the material layer as a mask to make the material layer covered with the conductive layer; (D) forming a mesa flat part and a mesa etched part that causes an undercut in the vicinity of the opening part in the semiconductor substrate; (E) removing the material layer, leaving only the material layer, removing the other material layer, and etching the conductive layer using the remaining material layer as a mask; .

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

1A to 1D are cross-sectional views of a semiconductor chip shown in the order of steps for explaining a first embodiment of the present invention.

As shown in Figure 1a, approximately
A 200 nm thick CrAu layer 2 is formed by vacuum evaporation, and a photoresist layer 3a is formed on its surface.

Next, the photoresist layer 2 is coated with a centerline diameter of approximately
After forming the annular opening 4a of 30 μm, the portion of the CrAu layer 2 exposed in the opening 4a is removed by etching.

Next, as shown in FIG.
The substrate 1 is isotropically etched to form a mesa etch portion 5 with a depth of about 5 μm and a mesa flat portion 6 with a flat portion diameter of about 20 μm below the opening 4a.

Each mesa flat portion 6 is covered more widely with the CrAu layer 2 and the photoresist layer 3a, including the mesa flat portion 6.

Next, as shown in FIG. 1c, from the opening 4a
Using a wet etching solution corresponding to each layer of Cr and Au, the portion of the CrAu layer 2 facing the mesa etching portion 5 is removed using the InP substrate 1 and the photoresist layer 3a as an etching mask to flatten the mesa in a self-aligned manner. An ohmic electrode 2a having the same planar shape as the portion 6 is formed.

Finally, as shown in FIG. 1d, the photoresist layer 3a is peeled off.

Here, since the ohmic electrode 2a completely covers the mesa flat portion 6, there is no exposed portion that was conventionally present.

2A to 2E are cross-sectional views of a semiconductor chip shown in order of steps for explaining a second embodiment of the present invention.

As shown in FIG. 2a, in the step shown in FIG. 1a, the surface of the InP substrate 1 is covered with a CrAu layer with a thickness of about 200 nm, and a silicon oxide film 7a is formed on the surface.

Next, a photoresist layer 3b having a diameter of about 25 μm is selectively formed using a photoresist technique.

Next, as shown in FIG. 2b, using the photoresist layer 3b as a mask, the silicon oxide film 7a is selectively etched to form a silicon oxide film 7b having a diameter of about 25 μm, and then the photoresist layer 3b is peeled off. .

Next, after forming a photoresist layer 3c on the entire surface, an opening 4b is selectively provided in the photoresist layer 3c along a circumference of 30 μm in diameter concentric with the silicon oxide film 7b, and the exposed CrAu layer 2 is Remove by etching.

Next, as shown in FIG. 2c, using the CrAu layer 2 as a mask, the In substrate 1 is isotropically etched using a bromine-based etching solution to form a mesa etch portion 5 with a depth of 5 μm and a mesa flat portion 6 with a diameter of about 20 μm. form.

Next, as shown in FIG. 2d, using the In substrate 1 and the silicon oxide film 7b as an etching mask,
Wet etching is performed using an etching solution suitable for the CrAu layer 2 to form an ohmic electrode 2a having a diameter of about 20 μm.

Here, since the diameter of the silicon oxide film 7b is 25 μm, which is longer than the diameter of the mesa flat portion 6, which is 20 μm, the automic electrode 2a is formed in self-alignment with the InP substrate 1, and has the same circular shape as the mesa flat portion 6. Become.

This embodiment has the advantage that the ohmic electrode 6 can be provided on any mesa flat portion 6.

〔Effect of the invention〕

As explained above, in the present invention, by forming an automic electrode using a selectively mesa-etched semiconductor device as an etching mask,
This has the effect of providing a method of manufacturing a semiconductor device having an ohmic electrode shaped to completely cover the flat part of the mesa.

[Brief explanation of drawings]

1A to 1D are cross-sectional views of a semiconductor chip shown in the order of steps for explaining the first embodiment of the present invention;
2A to 2E are cross-sectional views of a semiconductor chip shown in the order of steps for explaining a second embodiment of the present invention, and FIGS. 3A to 3C are steps for explaining a conventional method for manufacturing a semiconductor device. 4 is a perspective view of the semiconductor chip corresponding to FIG. 3c. 1...InP substrate, 2...CrAu layer, 3a, 3b,
3c... Photoresist layer, 4a, 4b... Opening part, 5... Mesa etched part, 6... Mesa flat part, 6
...Exposed portion, 7a, 7b...Silicon oxide film.

Claims (1)

[Claims] 1. (A) A step of forming a conductive layer to serve as an ohmic electrode over the entire surface of one principal surface of a semiconductor substrate; (B) After forming a material layer to serve as an etching mask on the surface of the conductive layer; , selectively forming openings in the material layer by photolithography; (C) isotropically etching the material layer excluding the openings as a mask to remove the material covered with the conductive layer; (D) forming a mesa flat part and a mesa etched part that causes an undercut in the vicinity of the opening part in the semiconductor substrate; a step of etching the conductive layer using the remaining material layer as a mask; (E) a step of removing the material layer; and (E) removing the material layer. Method of manufacturing the device.