JP2858866B2 - Method of manufacturing mesa-type semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a mesa-type semiconductor device used especially for an SR composite circuit device (STACK).

[Prior art and problems] Conventionally, in the manufacture of a mesa-type semiconductor element (pellet), for example, donor and acceptor impurities are entirely diffused on both surfaces of an N-type wafer, and a local electrode is formed thereon by plating or vapor deposition. Then, a brazing material is formed thereon by an immersion method or the like for connection with an external electrode, and further formed by etching into a pellet using the electrode including the brazing material as a mask.

By the way, the determination of the pellet thus obtained is generally performed visually or by electrical characteristics, but the determination method based on the electrical characteristics is not mass-produced, so that the visual determination is the mainstream.

However, in the conventional semiconductor device, since the shape of the local electrodes formed on the front and back surfaces of the substrate is the same, the shape becomes the same when viewed from above even if a device such as selective etching from one side is used in a subsequent etching process. It is difficult to sort the front and back. Therefore, when a composite circuit semiconductor device such as a rectifier bridge is manufactured, it may take time to arrange the pellets according to the circuit or the defect may occur frequently.

The present invention has been made in view of the above circumstances, and by making the shapes or sizes of local electrodes on both surfaces of a substrate different from each other, a pellet sorting can be easily performed, and a mesa semiconductor that can improve workability. An object is to provide an element and a method for manufacturing the element.

[Means and Actions for Solving the Problems] The present invention provides a semiconductor device of the first conductivity type on both surfaces thereof.
A step of forming a high-concentration region of the conductivity type and a high-concentration region of the second conductivity type; a step of selectively forming local electrodes on both surfaces of the substrate; and melting and forming a brazing material on these local electrodes Performing a step of forming an etching prevention layer covering the local electrode and the brazing material on the back side of the substrate; a step of isotropically etching the substrate from one side and stopping immediately before the back side; and removing the etching prevention layer. And a step of pelletizing by isotropically etching from both surfaces, and a step of melting the brazing material on the exposed pellet surface again to vary the shape or size of the local electrode. This is a method for manufacturing a mesa semiconductor device.

According to the present invention, by changing the shape or size of the electrodes on both surfaces of the substrate from each other, it is possible to easily perform pellet sorting and obtain a mesa-type semiconductor element capable of improving workability.

Example A method of manufacturing a mesa-type semiconductor device according to an example of the present invention will be described below with reference to FIGS. 1 and 2.

First, a high-concentration region (N ⁺ -type region) 2 is formed by diffusing an n-type impurity on the surface of an N-type silicon substrate 1,
A high concentration region (P ⁺ type region) 3 was formed by diffusing a p-type impurity on the back surface of the substrate 1. Next, after electrode materials are formed on both surfaces of the substrate 1 by plating or vapor deposition, a resist pattern 4 is formed on these electrode materials by photolithography.
Was formed. Subsequently, using the resist pattern 4 as a mask, the electrode material was selectively etched away to form local electrodes 5a and 5b on the front and back surfaces of the substrate 1, respectively (see FIG. 1 (A)).

Next, after the resist pattern 4 is peeled off, a brazing material 6a is formed on the local electrode 5a on the surface of the substrate 1 and a brazing material 6b is formed on the local electrode 5b on the back surface of the substrate 1 by, for example, an immersion method or the like ( FIG. 1 (B) is shown. Subsequently, an etching prevention layer 7 was formed on the back surface of the substrate 1 so as to cover the local electrode 5b and the brazing material 6b. Next, the brazing material 6a on the substrate surface side
Using the mask as a mask, the substrate 1 was isotropically etched (shown in FIG. 1 (B)). However, this etching was stopped immediately before reaching the P ⁺ type region 3 on the back surface of the substrate 1.

Next, after removing the etching prevention layer 7, the substrate 1
Was isotropically etched from both sides to separate into pellets (FIG. 1 (C) and FIG. 2). Here, FIG. 2 is a plan view of FIG. 1 (C).

Next, the brazing filler metal of each electrode part of the individually separated pellet
6a and 6b were melted again, and the shape of the brazing material 6a and 6b of each electrode portion was made the same diameter as that of the local electrodes 5a and 5b (FIG. 1 (D) and FIG.
Illustration). Here, FIG. 3 is a plan view of FIG. 1 (D).

According to the method of the present invention, as shown in FIG. 1 (A), after the local electrodes 5a and 5b are respectively formed on the front and back of the substrate 1 by melting the brazing material, the back surface of the substrate is masked with the etching preventing layer 7. In this state, only the surface side of the substrate is isotropically etched, and then, with the etching prevention layer 7 removed, isotropically etching is performed from both sides of the substrate.
In order to re-melt b, finally, as shown in FIGS. 1 (D) and 3, a local electrode 5a on the substrate front side may be obtained as a pellet smaller than the shape of the local electrode 5b on the substrate rear side. did it. Therefore, since the front and back of the pellet can be easily distinguished visually, the pellet can be easily sorted as compared with the related art. As a result, the desired polarity can be arranged at a desired position by applying to a vibrator or the like, and workability can be significantly improved.

Further, according to the mesa semiconductor device according to the above embodiment,
Since the local electrode 5a on the front surface side of the substrate and the local electrode 5b on the rear surface side of the substrate have different shapes, the selection of the pellets is easy as described above, and the workability can be improved.

The semiconductor device according to the present invention is not limited to the structure as shown in FIG. 2, but may be, for example, FIGS. 4 (A) and 4 (B).
The semiconductor element may have a hexagonal planar shape as shown in FIG. 3 or may not be immersed in a brazing material for connection to an external electrode. FIG. 4 (B) is a plan view of FIG. 4 (A).

[Effects of the Invention] As described in detail above, according to the present invention, a mesa-type semiconductor that can easily perform pellet sorting and improve workability due to different shapes or sizes of front and rear electrodes. An element and a method for manufacturing the same can be provided.

[Brief description of the drawings]

1 (A) to 1 (D) are cross-sectional views showing a method of manufacturing a mesa semiconductor device according to an embodiment of the present invention in the order of steps, FIG. 2 is a plan view of FIG. 1 (C), and FIG. 1 is a plan view of FIG. 1 (D), and FIG. 4 is an explanatory view of a semiconductor device according to another embodiment of the present invention. 1 ... N-type silicon substrate, 2 ... N ⁺ type region, 3 ... P ⁺
Mold region, 4 ... resist, 4a, 4b ... polarization electrode, 6a, 6b ...
... brazing material, 7 ... etching prevention layer.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yoshiyuki Iijima 647 Mobara, Mobara City, Chiba Prefecture Inside the Mobara Plant of Toshiba Components Corporation (56) References 38650 (JP, B1) JP 46-14410 (JP, B1) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01L 29/861-29/885

Claims (1)

(57) [Claims] A first conductive type semiconductor substrate provided on both sides thereof;
A step of forming a high-concentration region of the conductivity type and a high-concentration region of the second conductivity type; a step of selectively forming local electrodes on both surfaces of the substrate; and melting and forming a brazing material on these local electrodes Performing a step of forming an etching prevention layer covering the local electrode and the brazing material on the back side of the substrate; a step of isotropically etching the substrate from one side and stopping immediately before the back side; and removing the etching prevention layer. And a step of pelletizing by isotropically etching from both surfaces, and a step of melting the brazing material on the exposed pellet surface again to vary the shape or size of the local electrode. A method for manufacturing a mesa semiconductor device.