JP2643001B2 - Method for manufacturing semiconductor device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a semiconductor device having a passivation film for protecting a surface.

2. Description of the Related Art Conventionally, a semiconductor device having a high breakdown voltage is divided into individual semiconductor elements by a chemical corrosion method, and then a junction coating range is applied to protect a pn junction. (So-called can) was sealed. Recently, SiO ₂ formed by CVD method
With the progress of passivation technology using films, ZnO-based or PbO-based films, or polycrystalline silicon films, resin-sealed products have been put to practical use.

INVENTION Problems however to be Solved, Pashiibeshon using glass coating, i.e. in the SiO ₂ film formed by a CVD method, SiO ₂ film of the +
If ions are to be avoided, and if the film thickness is 2 μm or more and glass cracks are to be avoided, the withstand voltage is limited to about 1000 V. In addition, a method of forming by using a ZnO-based or PbO-based glass powder and an electrophoresis method or a grade method is relatively easy to achieve a high withstand voltage, but is not suitable for fine processing, and is not suitable for forming over a desired region. Glass powder is also adhered to the electrode, which makes it difficult to form an electrode. In an extreme case, performance degradation and reliability are reduced. On the other hand, a semiconductor device using a polycrystalline silicon film as a passivation film has a high reverse current and lacks the performance and reliability of the semiconductor device.
For this reason, a film obtained by adding oxygen to a polycrystalline silicon film has been put to practical use and has a low reverse current, but it is still insufficient.

As described above, the passivation method of the conventional high breakdown voltage apparatus has problems such as limitation of breakdown voltage by + ions, delay of fine processing technology, and increase of reverse current.

The present invention is to solve such a problem of the prior art, and by using glass powder having a small amount of + ions in the passivation film, it is possible to prevent a decrease in withstand voltage generated near the surface and to reduce the reverse direction. By realizing a current, easily realizing a high withstand voltage, and by mixing a photosensitive host resist and the above-mentioned glass powder, it is possible to perform precision processing, and trouble in electrode formation, that is, performance of a forward voltage. It is an object of the present invention to provide a method for manufacturing a semiconductor device capable of preventing a reduction and a reduction in reliability.

Means for Solving the Problems The present invention comprises a first step of thinly applying a photosensitive liquid obtained by mixing a glass powder for passivation to a photoresist to a semiconductor substrate, and a step of photoetching the photosensitive thin film applied to the semiconductor substrate. A second step of partially removing the semiconductor substrate by a technique; and a third step of heat-treating the photosensitive thin film of the semiconductor substrate at a temperature of 750 ° C. to 900 ° C. in an oxidizing atmosphere. .

The present invention provides a coating having a uniform thickness by spin-coating a suspension obtained by mixing a photosensitive photoresist and a glass powder as described above, for example, on a semiconductor substrate on which the pn junction is exposed. Thereafter, the film in the region where the electrode is to be formed is selectively removed by photoetching. Thereafter, the semiconductor substrate on which the glass film is present is baked in an oxidizing atmosphere to burn the resist contained in the film and remove it as a gas from the film. Is added. Thereafter, the oxide film formed during firing is dissolved and removed with an aqueous solution containing HF, and then an Al film is formed by, for example, vacuum evaporation. The silicon film and the Al film can be brought into ohmic contact by photoetching again, leaving the Al film so as to form a desired electrode, and performing heat treatment at about 500 ° C. in an inert gas atmosphere.

Examples Hereinafter, examples of the present invention will be described with reference to the drawings.

FIG. 1 shows a method of manufacturing a planar npn transistor according to the present invention.

On a silicon substrate 1 (having a high resistance region of specific resistance 40 Ωcm) of a triple diffusion type npn type planar transistor in which all diffusion has already been completed (a), a commercially available viscosity 40 cp photoresist 2 (for example, manufactured by Tokyo Ohka Co., Ltd. Product name: OMR-87-
To 40 g) of 10 g, commercially available glass powder 3 (for example, product name: IP820, manufactured by Inotech Co., Ltd., USA) was added to form a suspension.
A coating 4 of μm was formed and applied (b). The thickness of the obtained coating 4 is 60 μm. After the coating 4 was heated at 130 ° C. for 30 minutes (c), the glass coating was removed by photoetching in an area to be used as the respective electrode portions of the base 5 and the emitter 6 (d). Then, after heating for 30 minutes in a firing section in an oxidizing atmosphere heated to 800 ° C., thereafter, hydrofluoric acid: water =
After immersion in an aqueous solution of 1:30 for 10 seconds to remove the oxide film on the silicon substrate formed by firing (e), a thickness of 3 μm was obtained.
m Al film was obtained by a vacuum evaporation method (f). Then, after the Al film was left only on the base and emitter electrodes by photoetching (g), heat treatment was performed at 500 ° C. for 30 minutes in a nitrogen atmosphere ((h) is a partially enlarged view of (g)). ). Thereafter, an electrode in the collector region was formed, the chip was divided into individual chips by a dicing saw, the chip was bonded to a lead frame, and external leads were connected with a 200 μφ Al wire, followed by resin sealing.

In the embodiment, the photoresist 2 is described as a negative type, but a photoresist type (for example, a product name: OFPR manufactured by Tokyo Ohkasha Co., Ltd.)
−800-30 cp). Further, as the glass powder 3 suspended with the photoresist 2, a Pb-based glass has been described in the embodiment, but a Zn-based glass (for example, Nippon Electric Glass Co., Ltd., trade name: OP-030) may be used. Further, the thickness of the predetermined passivation glass coating 4 can be changed by changing the spin rotation speed.

Further, it is important that the temperature at which the glass film 4 is fired is changed depending on the type and amount of the resist contained in the film 4 and the type of the glass, so that the firing time is lengthened, the firing temperature is increased, Further, a resist baking step (relatively low temperature of 500 to 600 ° C.) and a glass baking step (relatively high temperature of 750 ° C.)
(To 900 ° C.) is also necessary to obtain a uniform passivation glass coating 7.

The mixing ratio of the resist 2 to the glass powder 3 was good when the glass powder was 0.1 to 11 with respect to the photoresist. If the glass powder is 0.1 or less, many bubbles are generated in the passivation glass coating 7 after firing, and the reverse breakdown voltage of the semiconductor device becomes unstable. Conversely, if the glass powder is 11 or more, The coating 4 after the spin coating is brittle, and the glass is lost in the photoetching step, thereby increasing the reverse current of the semiconductor device. Further, the thickness of the passivation glass coating 7 on the semiconductor substrate is preferably 0.3 to 40 μm, and if it is 0.3 μm or less, the reverse breakdown voltage of the semiconductor device becomes unstable, and if it is 40 μm or more. In addition, cracks are likely to occur in the glass coating 7, which lowers the reverse breakdown voltage of the semiconductor device and increases the reverse current. Further, the present invention can be applied to passivation of a mesa semiconductor device.

As described above, the present invention is suitable for the manufacturing direction of a semiconductor having a high breakdown voltage, and includes, for example, the conventional method 1 (passivation using a thermal oxide film), the conventional method 2 (passivation using an oxygen-added polycrystalline silicon film), and Compared with the conventional method 3 (a passivation film obtained by electrophoresis of glass powder), it has the following features.

 High withstand voltage is easily obtained as compared with the conventional method 1.

 The reverse current is lower than that of the conventional method 2.

Compared with the conventional methods 2 and 3, a special device and complicated process control are not required.

That is, the present invention is a passivation method that solves the disadvantages of the conventional method 1, the conventional method 2, and the conventional method 3 and realizes only the advantages.

FIG. 2 is a graph showing an example of the effect of the present invention.
FIG. 3 is a graph comparing the withstand voltage between the collector and the base when a silicon substrate of Ωcm (effective thickness 60 μm) is used, and FIG. As is clear from the graph, the present invention is superior in both the withstand pressure and the reverse current.

Effect of the Invention As described above, the method of manufacturing a semiconductor device according to the present invention has an effect of enabling fine processing with a high withstand voltage and a low reverse current, since glass powder is mixed with the photoresist.

[Brief description of the drawings]

FIG. 1 is a process chart showing one embodiment of the present invention, and FIGS. 2 and 3 are graphs showing the reverse breakdown voltage and the reverse current of one embodiment of the present invention in comparison with the conventional example. It is. Reference Signs List 1 silicon substrate already diffused 2 photoresist photoresist 3 glass powder 4 glass coating formed by spin coating method 5 base electrode window 6 emitter electrode window 7 ...... Glass film for passivation obtained by combustion, 8 ... Al film, 9 ... Al film for base electrode, 10
..... Al film for emitter electrode.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-50-104572 (JP, A) JP-A-1-187932 (JP, A) JP-A-56-27936 (JP, A)

Claims (2)

(57) [Claims] 1. A first step of thinly applying a photosensitive liquid in which a glass powder for passivation is mixed to a photoresist to a semiconductor substrate, and partially removing the photosensitive thin film applied to the semiconductor substrate by a photoetching technique. And a third step of performing a heat treatment on the photosensitive thin film of the semiconductor substrate at a temperature of 750 ° C. to 900 ° C. in an oxidizing atmosphere. 2. In the first step, the passivation glass is contained in a composition ratio of 0.1 to 11 with respect to the photoresist.
2. The method of manufacturing a semiconductor device according to claim 1, wherein the passivation glass thin film on the semiconductor substrate has a thickness of 0.3 to 40 [mu] m.