JPS60170933A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To carry out photo etching without warpage and obtain highly accurate electrode pattern by previously executing selective processing for semiconductor substrate or electrode film provided at the surface by the photo etching, placing a brazing material between the substrate and supporting member and integrating them by dissolution and coagulation. CONSTITUTION:An electrode pattern is formed previously by the photo etching before coupling of the supporting member which has been carried out usually in the preceding stage in order to reinforce a semiconductor substrate. Thereby, a good pattern accuracy can be obtained. Namely, the substrate of gate turn-off thyristor is formed with 4-layer structure of P-N-P-N and a recessed surface 14 which enters the lower P type layer is formed to the upper most N type layer when the supporting member 4 is not yet bonded. Thereafter, an Al electrode film 7 is deposited on the entire part including such recessed surface, a cathode electrode 3 is formed at the upper most layer by the photo etching and a gate electrode is formed in separation to the next layer in the same way. Next, the supporting member 4 is fixed to the rear surface of substrate using an Al material 5.

Description

[Detailed Description of the Invention] [Technical field to which the invention pertains] The present invention relates to a turn-off thyristor (hereinafter referred to as O
The present invention relates to a method of manufacturing a semiconductor device having a complex-shaped electrode on its surface, such as a TO Nyristor.

Prior Art and Its Problems] In order to facilitate current interruption, the GTO Zyristor has a narrow cathode electrode and gate electrode that are intertwined with each other. FIG. 1 shows a cross section of a GTO'-filister, in which a p base layer 11 of a silicon substrate 1 consisting of four pn pn layers is provided with gate electrodes 2. A cathode electrode 3 is provided on the n-emitter layer 12, and the gate electrode 3 is formed on a concave surface dug into the n-emitter layer 12 so as not to be short-circuited by an unillustrated electrode plate that contacts the cathode electrode 4. On the other hand, on the side of the p emitter layer 13 is a support plate 4 made of molybdenum or tungsten, which has a thermal expansion coefficient similar to that of silicon.
This fixing is usually done by brazing using aluminum', which is a p-type impurity, as the brazing material 5.

FIGS. 2(a) and 2(b) show the conventional manufacturing process of such a GTO Zyristor, and parts common to those in FIG. 1 are given the same reference numerals. First, one layer 11 and one layer 1 in which p-type impurities are diffused from both sides of an n-type silicon substrate 1 shown in FIG.
3 (Figure b), and further diffuse n-type impurities from one side to form a four-layer structure (Figure C).

Next, in order to form a concave surface for installing a gate electrode, a pattern is made on the oxide film 6 using photoetching technology (Fig. d). A concave surface 14 is formed by etching (Fig. e). For this purpose, an aluminum layer 5 made of aluminum foil or a vapor-deposited aluminum layer is sandwiched between the support plate 4 and the aluminum is melted and alloyed.
The substrate 1 is bonded to a support plate 4 made of molybdenum or tungsten (Fig. f). Next, the entire surface is covered with an electrode film 7 by vapor deposition of aluminum (Fig. g), and strong sintering is applied to reduce the photoetching contact resistance. conduct. However, in such a process, the thermal expansion coefficients of silicon and molybdenum or tungsten do not completely match, so
During alloying as shown in FIG. 2 (tf), a bend occurs in the silicon substrate 1 due to the bimetallic effect. The degree of this bending increases as the diameter of the silicon substrate becomes larger. For example, the thickness of the silicon substrate 1 is 0.91i1J4, the diameter is 64mm,
When the thickness of the molybdenum support plate 4 is 3 Inn, the warpage at the peripheral portion reaches o, t am compared to the central portion.

In order to form a pattern by photolithography on the electrode film on the surface of the semiconductor substrate 1 having such a groove, a photosensitive material 8 is coated on the aluminum A film 7 as shown in FIG. 3, and then a mask 9 is applied. When the photosensitive material 8 is selectively exposed by placing the mask 9 and exposing it to light 1O, a gap 11 is created between the mask 9 and the substrate 1, which becomes larger in the peripheral portion IT. The accuracy of the photosensitive pattern is good in the central area where there is little plowing, but in the peripheral area where there is a large gap, light interference occurs and the accuracy decreases. Therefore, in a semiconductor device such as a GTO Zyristor that requires divided electrodes that are uniform over the entire surface, the larger the diameter, the more difficult it becomes to form the electrodes.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a semiconductor device that can eliminate the above-mentioned drawbacks and form an electrode butter 7 with high precision on the surface of a large-diameter semiconductor substrate by photolithography. .

[Key points of the invention]

The present invention includes a step of selectively processing an electrode film on a semiconductor substrate or an optical surface using a photoetching method from the surface side of a semiconductor substrate, and interposing a wax film between a semiconductor substrate and a support plate.
In a manufacturing method that includes a step of melting and solidifying a brazing material to bond a semiconductor substrate and a support plate, the above objective is achieved by bonding the semiconductor substrate and the support plate after performing a selective processing step. do.

[Embodiments of the invention]

FIG. 4(b) shows the manufacturing process of a GTO thyristor according to the present invention, and parts common to those in FIG. 2 are given the same reference numerals. In Fig. 4 ta+~(C), the second
A four-layer structure is formed on the silicon substrate 1 through the same steps as shown in FIGS.
Figure (d).

A concave surface 14 is formed in the same process as in (e). An aluminum electrode film 7 is deposited on a silicon substrate 1 having such a concave surface 14 (as shown in FIG. I can ask you how to change it (Fig. h)
).

By performing manufacturing using such a process, the photoetching method is performed on a silicon substrate with good flatness, so that the accuracy of electrode pattern formation by original etching can be improved. Further, when the silicon substrate 1 and the support plate 4 are brazed, the contact resistance between the aluminum electrode 7 and the p base layer 12 can be reduced, so that a strong 7/ter for reducing the contact is not necessary.

[Effect of the Invention J] The present invention postpones the process of bonding the substrate and support plate by alloying, which was conventionally performed at an early stage to strengthen the semiconductor substrate, to the later stage, and performs the processing process by photoetching first.
Since it is possible to perform exposure using the photoetching method on a semiconductor substrate without warping, it is possible to form a pattern with the same accuracy in the center and on the same side, so it can be used especially for GTO thyristors with complex electrode shapes, etc. It can be applied extremely effectively to the production of. It is also effective in streamlining the manufacturing process, such as eliminating the need for a step of sintering electrodes patterned by photoetching, and the effects obtained by the present invention are extremely large.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the (jTo thyristor; FIG. 2 is a cross-sectional view sequentially showing the manufacturing process of a conventional GTO thyristor; FIG. 3 is a cross-sectional view showing the state of exposure by photolithography in the conventional manufacturing process; Fig. fs4 is a cross-sectional view sequentially showing an embodiment of the manufacturing process of the G'l'O thyristor according to the present invention. l...Silicon substrate, 2... Gate electrode, 3... Cathode electrode, 4... Support plate. , 5... Aluminum coating, 7.
,・Mineral electrode film. Figure 1 Figure 2

Claims (1)

[Claims] ■) A process of selectively processing the electrode film on the surface of the semiconductor substrate using photoetching from the surface side of the semiconductor substrate, and a process of sandwiching a brazing material between the semiconductor substrate and the support. A manufacturing method including a step of melting and solidifying the semiconductor substrate and the support plate to bond the semiconductor substrate and the support plate, characterized in that after performing the selective processing step, a MiJ bonding step of the semiconductor substrate and the support plate is performed. A method for manufacturing a semiconductor device.