JPS595631A - Mesa type semiconductor device and manufacture thereof - Google Patents

Abstract

PURPOSE:To eliminate an adverse effect such as an application unevenness on processes by forming the side wall section of a groove in two-stage structure and forming a porjecting coating section, around which glass fines round, into the lower groove from the surface of a substrate. CONSTITUTION:A window l2 for etching in relationship narrower than the width l1 of an opening window is formed to a groove section 4 in a corrosion-resisting film 7 on a novel oxide film 3' coating the semiconductor substrate 1 through heat treatment. A second groove 4' penetrating a P-N junction in depth deeper than the groove section 4 is formed in two-stage structure through etching through window l2. A glass coating 5 is applied and formed to the groove section 4' through an electrophoresis method. A projecting section 6 is formed at the top section of the end of the groove section of the glass coating 5 through baking treatment, but there is the projecting section in the surface of a surface region low by one stage, the section can be formed so that it is not projected to the flat surface of the semiconductor substrate 1, and it does not hinder a mask process.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mesa-type semiconductor device having a two-tiered mesa sidewall structure and a method for manufacturing the same.

As is well known, in a mesa type semiconductor device, a PN junction is exposed on the sidewall of a groove formed by mesa etching, and a surface stabilizing film is usually formed on the groove including this sidewall.
This stabilizes the characteristics of the mesa semiconductor device. In a method for forming such a surface stabilizing film, fine glass powder is suspended in an organic solvent such as alcohol, and a small amount of hydrofluoric acid or aqueous ammonia is added as an electrolyte. An electrophoresis method is used in which the material is electrophoresed and deposited on the groove portion of the semiconductor substrate.

FIG. 1 is a sectional view of a conventional semiconductor substrate having a mesa structure in which a glass film is deposited in a groove by such electrophoresis.

In the figure, 1 is a silicon substrate part, 2 is a surface region forming a PN junction with the substrate part 1, 3 is an oxide film (5iO2) covering the semiconductor substrate, 4 is a groove formed by mesa etching, and 6 is a glass coating formed on the groove portion.

By the way, in the electrophoresis method, if the edge of the oxide film 3, which serves as a mask for the deposition of fine glass powder, is in contact with the exposed semiconductor substrate surface, a wrapping phenomenon of the deposition of fine glass powder occurs, causing the deposition of fine glass powder onto the oxide film 3 as well. A protrusion 6 is formed. These protrusions 6 not only cause uneven coating of the photoresist film that will serve as a mask during electrode formation, but also impair the ability to maintain the mutual distance between the mask used for electrode pattern formation and the semiconductor substrate. There were many problems such as.

The present invention provides a mesa that can eliminate any adverse effects such as uneven coating on subsequent processes caused by protrusions caused by the wrapping phenomenon of fine glass powder when depositing a glass film on a groove by electrophoresis. The present invention provides a type semiconductor device and a method for manufacturing the same. That is, in the present invention, the groove side wall portion has a two-stage structure, and the part where the fine glass powder wraps around and adheres to the protrusion is formed inside the groove below the substrate surface.

Hereinafter, the method for manufacturing a mesa-type semiconductor device of the present invention will be explained in detail with reference to FIG.

2, (a) to (C) are process diagrams showing the main processing steps for depositing and forming a glass film in a groove by the method of the present invention. First, the surface area 2 where a PN junction is formed with the semiconductor substrate 1
Then, an oxide film 3 is formed, a mesa etching window 4 is opened in the oxide film 3, and an etching process is performed to form a relatively shallow first trench in the surface region 2 to the extent that it does not penetrate the PN junction. 4 (Fig. 2(a)). After that, oxide film 3
Then, a new oxide film 3' is formed to cover the semiconductor substrate 1 by well-known heat treatment, and a corrosion-resistant coating 7 such as photoresist is applied on the oxide film 3' to form an etching film narrower than the width of the opening window. A window 12 is formed in the groove 4 (Fig. 2 (1)) o Etching is performed through this window 12 to form a second groove 4' deeper than the groove 4 (a second groove 4' passing through the PN junction part). It has a shallow depth.It is formed to have a so-called two-stage structure.Then, the glass coating 6 is deposited on this groove 4' by the electrophoresis method described above (FIG. 2 (0)). When the baking process is performed after the adhesion is formed, a protrusion 6 is formed at the top of the groove end of the glass coating 5 as in the conventional case. It is possible that the surface does not protrude, so that this does not interfere with the subsequent masking process.

An embodiment of the present invention shown in FIG. 2 will be described below. After applying a photoresist film 7 to a thickness of about 10 pm on the surface region 2 of the silicon substrate 1 whose surface is covered with an oxide film 3, an etching window having a window width (11) of 260 μm is formed on this photoresist film 7. At the same time, the oxide film inside this window was removed, and then hydrofluoric acid, nitric acid, and acetic acid were added in a volume ratio of 1. rs
By immersing the semiconductor substrate in an etching solution mixed at a ratio of: 7: 1.5, a groove 4 whose depth does not penetrate the PN junction is formed.

After performing such etching treatment, the photoresist film is removed, and then the oxide film 3 is removed, and then heat treatment is performed to cover the semiconductor substrate again with a new oxide film 3, and the photoresist is further removed by 16//m. An etching window with a window width (42) of 180//m was formed in the groove, and the oxide film within the window was removed. Grooves 4' passing through the PM joint are treated with an etching solution mixed at a ratio of 6:2.
, and the groove shape has a two-stage structure. The semiconductor substrate subjected to such treatment is treated with a treatment solution made by suspending fine glass powder mainly composed of lead oxide in alcohol and adding aluminum chloride as an electrolyte.

By applying a voltage of 20 V for 30 seconds, electrophoresis is caused in the glass fine powder to form a glass coating 6 with a thickness of about 16 μm. The glass film 6 is formed with protrusions 6 in shallow grooves, but the oxide film 3' on the surface of the flat conductor substrate
It had not reached the point where it was protruding from the surface.

As is clear from the above description, the mesa semiconductor device having the two-stage groove structure according to the present invention substantially eliminates the wrap-around phenomenon of fine glass powder adhering, which is a problem when forming a glass film by electrophoresis. Since it can be eliminated, it has the effect of eliminating problems such as uneven resist coating and mask defects.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a semiconductor substrate in which a glass film has been deposited in the groove of a conventional structure by electrophoresis, and Figure 2 (
a) to (C) are processing process diagrams for explaining the method of forming a glass coating in a two-stage groove of the present invention.01...Semiconductor substrate,2...・Surface area,
3.3'...Oxide film, 4.4'...Etched groove, 6...Glass coating, 6...Protrusion, 7... ...Photoresist. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
figure

Claims (2)

[Claims] (1) A semiconductor substrate having a PN junction surface, a first groove shallower than the PN junction surface on the surface of the semiconductor substrate, and a second groove formed in the first groove and penetrating the PM junction surface; and a glass coating formed from the first groove to the second groove. (2) forming a first opening in a first insulating film covering a semiconductor substrate having a PN junction surface, and using the first opening as a mask to form a first groove shallower than the PN junction surface; , forming a second insulating film, forming a second opening in the second insulating film within the first trench, and forming a second trench deeper than the PN junction surface through the second opening; A method for manufacturing a mesa-type semiconductor device, comprising the steps of: forming a glass film on the first and second groove portions by electrophoresis.