JPH02163938A - Manufacture of semiconductor element - Google Patents

Abstract

PURPOSE:To form a glass passivating film which is not thick on the bottom of a mesa groove and which is thick on an inside face of the mesa groove where a P-N junction is exposed by a method wherein, before the glass passivating film is formed on the inside face of the mesa groove by an electrophoretic method, an oxide film is deposited on the bottom of the mesa groove from a direction perpendicular to a face of a semiconductor substrate. CONSTITUTION:A P-N junction parallel to a face of a semiconductor substrate is formed on the semiconductor substrate 3; an etching operation is executed from one surface; a mesa groove 1 is formed; after that, before a glass passivating film 2 is formed on an inside face of the mesa groove 1 by an electrophoretic method, an oxide film 5 is deposited on the bottom 11 of the mesa groove from a direction perpendicular to the face of the semiconductor substrate. For example, a P-layer 4 is formed by diffusion from the surface of an N-type silicon substrate 3; after that, a mesa groove 1 is formed by an etching operation. Then, an oxide film 5 is deposited by a CVD method; then, the oxide film 5 whose thickness is the same as that on the surface of the substrate is deposited on the bottom 11 of the mesa groove 1; the oxide film 5 deposited on an inside face 12 of the mesa groove 1 is made thin. Then, a part excluding a part used to from a glass passivating film is covered with a resist film 6; after that, a glass film 2 is made to adhere to the inside face of the mesa groove 1 by an electrophoretic method.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention provides a PN junction parallel to the substrate surface on a semiconductor M plate, and forms a mesa groove with a depth exceeding the PN junction by etching from one surface. The present invention also relates to a method of manufacturing a semiconductor device, in which a glass powder is deposited on the inner surface of the mesa groove by electrophoresis and fired, thereby forming a glass bathobasin film that protects the exposed portion of the PN junction on the inner surface of the mesa groove.

[Conventional technology]

When using glass as the base material, conventionally a method has been adopted in which fine glass powder is attached to the surface of the semiconductor element by electrophoresis because a uniform glass film can be formed by subsequent firing.

This electrophoresis method uses glass powder as an organic solvent for semiconductor substrates immediately after mesa groove formation or after pretreatment such as acid treatment! ! !
This was carried out by making the solution cloudy and supporting it on the cathode plate of an electrodeposition tank containing a solution containing annimore, and applying a DC voltage between it and the opposing anode plate.

(Problem to be Solved by the Invention) In the case of forming a glass pansibasicon film by the conventional electrophoresis method, the direction of the macroscopic electric field in the glass powder suspension, that is, the direction of the mesaic acid perpendicular to the migration direction of the glass powder, is Glass powder tends to adhere to the vicinity of the bottom of the groove, and conversely, it becomes difficult for glass powder to adhere to the inner surface of the mesa groove, which is parallel to the macroscopic migration direction of the glass powder.For this reason, the mesa groove where the PN junction end is exposed The thickness of the banshibasin glass on the inside surface becomes thinner, and the glass at the bottom of the mesa groove, which does not require a banshibasin, becomes thicker.If you try to increase the thickness of the glass on the inside surface of the mesa groove to the thickness required for the banshibasin, as shown in Figure 2. As shown, the glass I!lI2 on the bottom 11 of the mesa groove 1 is significantly thicker, 1.5 to 3 times as thick as the glass film on the inner surface 12 of the mesa groove, and the coefficient of thermal expansion with the semiconductor material is Due to the difference, the semiconductor substrate warps.

There is a problem in that cracks in the glass or cracks in the glass occur, resulting in a decrease in the yield rate and reliability of the device.

The invention! ! The object of the present invention is to provide a method for manufacturing a semiconductor device that solves the above-mentioned problems and forms a glass badge-based film that is not thick on the bottom of the mesa trench and is thick on the inner surface of the mesa trench where the PN junction is exposed. It is in.

[Means to solve the problem]

In the present invention, a PN junction is provided in a semiconductor substrate parallel to the substrate surface, a mesa groove is formed by etching from one surface, and then a glass badge basic film is formed on the inner surface of the mesa groove by electrophoresis. An oxide film is deposited on the bottom of the mesa groove in a direction perpendicular to the substrate surface.

[Effect]

If an oxide film is deposited on the bottom of the mesa trench from a direction perpendicular to the semiconductor substrate surface using the CVD method, the bottom of the mesa trench is covered with an oxide film that is an insulating film, making it difficult for glass powder to adhere to the mesa trench by electrophoresis. When depositing an oxide film on the bottom, some oxide film may adhere to the inner surface of the mesa trench, but the oxide film is thin and the oxide has a rough texture, especially in CVD oxide films, resulting in low insulation. Glass powder is deposited thereon by electrophoresis, and by firing a glass badge-based film sufficient to protect the PN junction exposed on the inner surface of the mesa groove is formed.

〔Example〕

Figure 1 shows a state in which a mesa groove (dl indicates an embodiment of the present invention, after forming a two-layer 4 from the surface of an N-type silicon substrate 3 by diffusion) is formed by etching.
Then, this substrate is placed horizontally in a CVD apparatus and oxidized Il! Figure 1 f shows the state in which J5 was deposited using the CVD method.
bl, an oxide film 5 with the same thickness as the substrate surface is deposited on the bottom 11 of the mesa trench 1, but the oxide film 5 deposited on the inner surface 12 of the mesa trench is thin and Figure 1 (C1 shows that the glass padding was covered with resist 1lI6 except for the part where the film was to be formed. After this, the electrophoresis method was performed using the apparatus shown in Figure 3. A solution 22 in which fine glass powder is suspended in an organic solvent such as isopropyl alcohol or ethyl acetate is contained in a deposition tank 21, and a cathode plate 24 supports a semiconductor substrate 23 in this solution.
and the anode plate 25 facing parallel to it, and add ammonia water to the suspension in advance (or if not, connect the power between the two electrodes while blowing out ammonia gas from the inlet tube 26 as shown). 27, apply a DC voltage of 50 to 500 V with positive polarity of the electrode 25. As a result, the first
As shown in Figure fdl, the glass film 2 is attached to the inner surface of the mesa groove. On the mesa groove bottom 11 and the silicon substrate surface, a thick oxide II with high m-edge properties is formed! 5 exists, only a thin glass film 2 is deposited, but a thin oxide film 1! with low insulation is deposited on the inner surface 12 of the mesa groove. Since only I5 is present, a thick glass [II2] is attached. The thickness of M5 at the bottom of the mesa groove is 0.5 to 3. Otm, the thickness of the bottom glass 1112 is 1 of the thickness of the glass film on the inner surface.
．． It becomes 0 to 0.5 times. By the subsequent firing, Nl&
The exposed part of the PN junction between plate 3 and PIL 14 will be covered with a thick glass bassine membrane.

In the above example, oxidation 1[! 5 Thin mesa groove inner surface 1
2, but a glass film may be directly attached to the inner surface of the mesa groove by electrophoresis without forming an oxide film at all.Alternatively, the oxide film 5 on the mesa groove bottom ll should be sufficiently thick. Although it is possible to increase the insulation properties by using electrophoresis to prevent the glass film from adhering, there is a risk of cracks occurring due to the thicker oxide film and a decrease in adhesion strength due to discontinuity of the glass basin basin film. Therefore, care must be taken in implementation.

〔Effect of the invention〕

According to the present invention, an oxide film is deposited on the bottom of a mesa groove before forming a glass badge basin film of a semiconductor element, and by reducing the thickness of the glass film deposited during electrophoresis, unnecessary mesa without thickening the glass film on the bottom of the groove.
The glass film on the inner surface of the mesa groove, which is the exposed portion of the PN junction parallel to the substrate surface, can be made thicker, and a stable bungee base four film can be obtained. As a result, it is possible to significantly reduce warping of the semiconductor substrate, cracking of the semiconductor substrate due to the glass film at the bottom of the mesa groove becoming too thick, and cracks in the vanosy basis film, thereby improving the yield rate and reliability of semiconductor devices. It can greatly contribute to improvement.

[Brief explanation of the drawing]

Figures 1 ial to fd+ are cross-sectional views of mesa grooves sequentially showing the glass film deposition process of an embodiment of the present invention, Figure 2 is a cross-sectional view of mesa grooves after conventional glass film deposition, and Figure 3 is a glass film attachment process. 1 is a cross-sectional view of an example of an electrophoresis device used for. 1: Mesa groove, 2 glass film, 5: oxide film, 11: Fig. 1 Fig. 2

Claims (1)

[Claims] 1) After providing a PN junction parallel to the substrate surface on a semiconductor substrate and forming a mesa groove by etching from one surface, a PN junction perpendicular to the semiconductor substrate surface is formed before forming a glass passivation film on the inner surface of the mesa groove by electrophoresis. 1. A method of manufacturing a semiconductor device, comprising: depositing an oxide film on the bottom of a mesa groove from a direction.