JPH0621431A - Mesa-type semiconductor element and its manufacture - Google Patents

Abstract

PURPOSE:To provide a mesa-type semiconductor element which can screen out a pellet easily by varying the shapes of the electrode parts on both surface of a substrate. CONSTITUTION:Local electrodes 5a and 5b are formed on the front and rear surfaces of a substrate 1 with a resist pattern 4 as a mask. Then, after the resist pattern 4 is released, a brazing material 6a is formed on a local electrode 5a of the surface of the substrate 1. Then, after an etching-prevention layer 9 covering the local electrode 5b and the brazing material 6b is formed on the rear surface of the substrate 1, the substrate 1 is etched isotropically on the substrate 1 with a first electrode part 7 on the substrate surface as a mask. Then, after the etching-prevention layer 9 is eliminated, the brazing material 6a out of the first electrode part 7 is dissolved again and the lower end face is formed in the same shape as a lower local electrode 5, thus differing the shape of the first electrode part 7 on the substrate surface from that of a second electrode part 8 on the substrate surface and then dicing the substrate 1 along an etched line for obtaining a pellet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a mesa type semiconductor device used in an SR composite circuit device (STACK).

[0002]

2. Description of the Related Art Conventionally, in the manufacture of a mesa type semiconductor device (pellet), for example, donor and acceptor impurities are entirely diffused on both sides of an N type wafer, and a local electrode is formed thereon by plating or vapor deposition. A brazing material is formed thereon by a dipping method or the like for connection with an external electrode, and is further pelletized by etching while masking the electrode including the brazing material.

By the way, the pellets thus obtained are generally discriminated by visual observation or electrical characteristics, but the discrimination method based on the electrical characteristic characteristics is not mass-produced, and therefore the visual discrimination is performed. Mainstream.

[0004]

However, in the conventional semiconductor device, since the shapes of the local electrodes formed on the front and back surfaces of the substrate are the same, a method such as selective etching from one side is used in the subsequent etching process. Also has the same shape when viewed from above, making it difficult to sort the front and back. Therefore, when making a composite circuit semiconductor device such as a rectifying bridge, it may take a long time to arrange the pellets according to the circuit, or defects may frequently occur.

The present invention has been made in view of the above circumstances, and by making the shapes of the first electrode portion and the second electrode portion on both surfaces of the substrate different, it is possible to easily perform pellet selection and improve workability. An object of the present invention is to provide a mesa type semiconductor device that can be improved and a method for manufacturing the same.

[0006]

SUMMARY OF THE INVENTION A first invention of the present application is a semiconductor substrate of a first conductivity type in which a high concentration region of a first conductivity type and a high concentration region of a second conductivity type are formed on both surfaces, respectively, and this semiconductor. A mesa-type semiconductor device, comprising: first and second electrode portions having different shapes formed on both surfaces of a substrate, respectively.

A second invention of the present application is the step of forming a high-concentration region of the first conductivity type and a high-concentration region of the second conductivity type on both surfaces of the semiconductor substrate of the first conductivity type, and on both surfaces of the substrate, respectively. A step of selectively forming the local electrodes, a step of melting and forming a brazing material on these local electrodes to form the first electrode portion and the second electrode portion, and a step of forming the local electrodes and the brazing material on the back surface side of the substrate. A step of forming an etching preventive layer for covering, a step of performing isotropic etching of the substrate just before the high concentration region on the back surface of the substrate, a step of remelting the brazing material on the exposed substrate surface, and the etching preventive layer And a step of pelletizing after removing the above. A method of manufacturing a mesa-type semiconductor device, comprising:

[0008]

According to the first invention of the present application, since the shapes of the electrode portions on both surfaces of the substrate are different, pellet selection can be performed easily and workability can be improved.

According to the second invention of the present application, the brazing material formed on the substrate via the local electrode is gradually melted to have a shape different from that of the brazing material on the back surface side of the substrate. Since the second electrode portion has a different shape, pellet selection can be easily performed and workability can be improved, as in the first invention of the present application.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a mesa type semiconductor device according to an embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

First, for example, an n-type impurity is diffused on the surface of an N-type silicon substrate 1 to form a high concentration region (N ⁺ type region) 2, and then a p-type impurity is diffused on the back surface of the substrate 1. A high concentration region (P ⁺ type region) 3 was formed. Next, after electrode materials were formed on both surfaces of the substrate 1 by plating or vapor deposition, a resist pattern 4 was formed on these electrode materials by a photo-etching method. Subsequently, the electrode material was selectively removed by etching using the resist pattern 4 as a mask to form local electrodes 5a and 5b on the front surface and the back surface of the substrate 1 (shown in FIG. 1A).

Next, after removing the resist pattern 4, the brazing material 6a is placed on the local electrode 5a on the front surface of the substrate 1 and the brazing material 6b is placed on the local electrode 5b on the back surface of the substrate 1 by, for example, a dipping method. Formed (shown in FIG. 1B). In FIG. 2B, the local electrode 5a and the brazing material 6a are collectively referred to as the first electrode portion 7, and the local electrode 5b and the brazing material 6b are collectively referred to as the second electrode portion 8. Subsequently, an etching prevention layer 9 was formed on the back surface of the substrate 1 so as to cover the local electrodes 5b and the brazing material 6b. Then, the substrate 1 was isotropically etched using the first electrode portion 7 on the front surface side of the substrate as a mask. However, this etching was stopped immediately before reaching the P ⁺ type region 3 on the back surface of the substrate 1. At this time, the exposed local electrode 5a and the brazing material 6a were also slightly etched (see FIG. 1).
(C) Illustration).

Next, after the etching prevention layer 9 is removed, the brazing material 6a of the first electrode portion 7 is melted again so that the lower end surface thereof has the same shape as the lower local electrode 5a (FIG. 1).
(D) Illustration). As a result, the shape of the first electrode portion 7 on the front surface of the substrate was different from the shape of the second electrode portion 8 on the back surface of the substrate. Then, the substrate 1 was diced along the etched line to obtain pellets shown in FIGS. 2 (A) and 2 (B). However, FIG. 7A is a plan view of FIG.

According to the method of the present invention, however,
As shown in FIG. 1B, after the first electrode portion 7 and the second electrode portion 8 are formed on the front and back surfaces of the substrate 1 by melting the brazing material, respectively, and then the substrate front surface side is masked with the etching prevention layer 9 Only the isotropic etching is performed, and the brazing material 6a of the first electrode portion 7 is melted again. Therefore, as shown in FIG. Small pellets could be obtained. Therefore, the first electrode portion 7
Side and the second electrode portion side can be easily distinguished visually,
Pellet selection can be performed more easily than before.
As a result, a desired polarity can be arranged at a desired position by applying it to a vibrator or the like, and workability can be significantly improved.

Further, in the mesa type semiconductor device according to the above-mentioned embodiment, since the shapes of the first electrode portion 7 and the second electrode portion 8 on the front and back surfaces of the substrate are different, as described above, It is easy to sort, and workability can be improved.

The semiconductor element according to the present invention is not limited to the one having the structure shown in FIG.
A planar semiconductor element having a quadrangular planar shape as shown in FIG. 4B, a semiconductor element having a hexagonal planar shape as shown in FIGS. 4A and 4B, or a brazing material for connection with an external electrode. May not be soaked. However,
3B is a plan view of FIG. 3A, and FIG. 4B is FIG.
It is a top view of (A).

[0017]

As described in detail above, according to the present invention, pellets can be easily selected by changing the shapes of the first electrode portion and the second electrode portion on both surfaces of the substrate, and the workability is improved. An improved mesa-type semiconductor device and a method for manufacturing the same can be provided.

[Brief description of drawings]

FIG. 1 is a sectional view showing a method of manufacturing a mesa type semiconductor device according to the present invention in the order of steps.

FIG. 2 is an explanatory view of a mesa type semiconductor device according to the present invention.

FIG. 3 is an explanatory diagram of a semiconductor device according to another embodiment of the present invention.

FIG. 4 is an explanatory diagram of a semiconductor device according to another embodiment of the present invention.

[Explanation of symbols]

1 ... N type silicon substrate, 2 ... N ⁺ type region, 3 ... P ⁺ type region, 4 ... Resist, 5a, 5b ... Polarizing electrode, 6a, 6b ... Brazing material, 7 ... First electrode portion, 8 ... 2 electrode parts, 9 ... Etching prevention layer.

Claims (2)

[Claims] 1. A first-conductivity-type semiconductor substrate having a first-conductivity-type high-concentration region and a second-conductivity-type high-concentration region formed on both sides, and a mutually-shaped semiconductor substrate formed on both sides of the semiconductor substrate. A mesa-type semiconductor device comprising different first and second electrode portions. 2. A step of forming a high-concentration region of a first conductivity type and a high-concentration region of a second conductivity type on both surfaces of a semiconductor substrate of the first conductivity type, and a local electrode selectively on both surfaces of the substrate. And the process of forming and melting the brazing material on these local electrodes,
Forming a first electrode portion and a second electrode portion, a step of forming an etching prevention layer covering the local electrode and the brazing material on the back surface side of the substrate, and isotropic etching of the substrate on the back surface side of the substrate. A mesa-type semiconductor device characterized by comprising: a step of performing until just before the high-concentration region, a step of remelting the exposed brazing material on the substrate surface, and a step of pelletizing after removing the etching prevention layer. Production method.