JPH03229418A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To realize a low backward current and realize a high breakdown strength easily by a method wherein glass powder whose + ion content is very low is employed in a passivation film. CONSTITUTION:A glass film 4 is formed by applying suspension which is obtained by adding glass powder 3 to photoresist 2 to the silicon substrate 1 of a three-layer diffusion type p-n-p planar transistor in which all diffusions are finished. After the film 4 is heated, the glass film 4 is selectively removed by photoetching on regions which are to be the respective electrode parts of a base 5 and an emitter 6. After the substrate 1 is heated in a baking part having a heated oxidation atmosphere, the substrate 1 is dipped in solution of fluoric acid/water whose content ratio is 1/30 to remove an oxide film formed on the silicon substrate 1 by baking. Then an Al film is formed by a vacuum deposition method. After, that, the Al film is selectively removed by photoetching except on the electrode parts of the base and the emitter and the substrate is subjected to a thermal treatment in a nitrogen atmosphere. Then an electrode is formed on a collector region and, after the substrate 1 is divided into individual chips by a dicing saw, the chips are bonded to a lead frame and connected with external leads through Al wires and then the chips and the lead frame are sealed with resin.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of manufacturing a semiconductor device having a surface-protecting vacillation film.

Conventional technology Semiconductor devices with high withstand voltage are conventionally divided into individual semiconductor elements using a chemical corrosion method, then a junction coating resin is applied to protect the pn junction, and hermetic coating is performed in an active gas atmosphere. (so-called can) was sealed. Recently, Si formed by CVD method
Due to advances in vacillation technology using O2 films, ZnO-based or PbO-based films, or polycrystalline silicon films, resin-sealed products have been put into practical use.

Problems to be Solved by the Invention However, passivation using a glass coating,
In other words, in the 5i02 film formed by the CVD method, if + ions in the SiO2 film are avoided and the film thickness is 211 m or more to avoid glass cracks, the withstand voltage is approximately 100 m.
0V is the limit. In addition, methods of forming using ZnO-based or PbO-based glass powder, electrophoresis method, or grate method are relatively easy to achieve high voltage resistance, but are not suitable for Wi fine processing, and the desired area to be formed is Glass powder is deposited on the top and outside, making it difficult to form electrodes and, in extreme cases, leading to performance deterioration and reduced reliability. on the other hand,
A semiconductor device using a polycrystalline silicon film as a passivation film has a high reverse current, and the semiconductor device lacks performance and reliability. For this reason, a film in which oxygen is added to a polycrystalline silicon film has been put into practical use and has a low reverse current, but even this is not sufficient.

As explained above, the conventional passivation method for high voltage devices has three problems: voltage resistance limitation due to positive ions, delay in microfabrication technology, and increase in reverse current.

The present invention solves the problems of the prior art, and by using glass powder with fewer + ions in the vanyon film, it prevents a drop in breakdown voltage that occurs near the surface and reduces the It is possible to realize reverse current, easily realize high breakdown voltage, and by mixing the photosensitive photoresist with the glass powder, it is possible to perform precision processing. It is an object of the present invention to provide a method for manufacturing a semiconductor device that can prevent performance deterioration and reliability deterioration.

Means for Solving the Problems The present invention includes a first step of thinly applying a photosensitive liquid, which is a mixture of photoresist and glass powder for passivation, onto a semiconductor substrate, and a photoetching technique for the photosensitive thin film applied to the semiconductor substrate. A second step of partially removing the
The present invention is characterized by comprising 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.

As mentioned above, Seraki Ki is able to spin-coat a suspension of a mixture of photosensitive photoresist and glass powder onto a semiconductor substrate with an exposed pn junction, for example, to form a film with a uniform thickness. After that, the film in the region where the -C electrode is to be formed is selectively removed by photoetching. After that, the semiconductor substrate on which the glass film is present is fired in an oxidizing atmosphere to burn the resist contained in the film and remove it from the film as a gas. Add. Thereafter, the oxide film formed during firing is dissolved and removed with an aqueous solution containing HF, and then the A1 film is formed, for example, by vacuum evaporation. By photo-etching again, make the desired electrode.
By performing heat treatment in an inert gas atmosphere at a temperature of about 500° C. while leaving the A1 film, the silicon substrate and the A1 film can be brought into ohmic contact.

Examples Examples of the present invention will be described below with reference to the drawings.

FIG. 1 shows a method for manufacturing a Brainer type pn transistor according to the method of the present invention.

The silicon substrate of the triple diffusion type +1p n-type planar transistor (specific resistance 40Ωc) has already been completely diffused.
(a) A commercially available viscosity 40cp photoresist 2 (for example, manufactured by Tokyo Ohka Co., Ltd., trade name: OMR-87-40cp) (having a high resistance region of m), a glass powder also available commercially. 3 (for example, manufactured by Inochik, USA, trade name: 1P820) was added thereto, and the mixture was thoroughly multiplied to form a suspension, and a coating 4 of 30 g and 60 μm thick was formed and applied at a rotation speed of 300 rpm (b). The thickness of the obtained coating 4 is 60 μm. After heating this film 4 at 130° C. for 30 minutes (C), the glass film was removed by photoetching in areas to be used as electrode portions of each of the hese 5 and the emitter 6 (d). After that, the silicon substrate was heated for 30 minutes in a baking section heated to 800°C in an oxidizing atmosphere, and then immersed in an aqueous solution of hydrofluoric acid:water = 1:30 for 10 seconds to remove the oxide film formed on the silicon substrate by baking. After removal (e)
, an A1 film with a thickness of 3 It tn was obtained by vacuum evaporation (f
). Thereafter, after photoetching to leave only the A1 film on the electrode part of the base and emitter (g), heat treatment was performed at 500°C for 30 minutes in a nitrogen atmosphere ((ll) is (
Partially enlarged view of g). Thereafter, electrodes for the collector region were formed, and the chips were separated into individual chips using a buoy sink saw. The chips were bonded to a lead frame, and the chips were connected to an external lead using a 200 μΦ A1 wire, followed by resin sealing.

In the examples, photoresist 2 was explained as a negative type, but a positive type (for example, manufactured by Tokyo Ohka Co., Ltd., product name: 0F)
PR-800-30cp) may also be used.

Further, as the glass powder 3 suspended with the photoresist 2, although Ph-based glass was used in the embodiment, Zn-based glass (for example, manufactured by Nippon Electric Glass Co., Ltd., product name: C; P-0
30) is also acceptable. Furthermore, the thickness of the predetermined passivation glass film 4 can be changed by changing the spin rotation speed.

In addition, it is important to change the temperature at which the glass coating 4 is fired depending on the type and amount of resist contained in the coating 4 and the type of glass, such as increasing the firing time or increasing the firing temperature. Historically, a resist burning stage (relatively low temperature of 500 to 600°C) and a glass firing stage (relatively high temperature of 750 to 900°C') have been used in two stages. Necessary to get -7.

The mixing ratio of the resist 2 and the glass powder 3 was good in the range of 0.1 to 11 of the glass powder to the photoresist.

If the glass powder is O01 or less, many bubbles will be generated in the passivation glass film 7 after firing, and the reverse withstand voltage of the semiconductor device will become unstable.
If it is 1 or more, the film 4 after spin coating will be brittle, and the glass will be missing in the photoetching process, increasing the reverse current of the semiconductor device. Further, the thickness of the glass coating 7 for opacity on the semiconductor substrate is 0.3~
40 μm is good; if it is 0.3 μm or less, the reverse breakdown voltage of the semiconductor device becomes unstable; on the other hand, if it is 40 μm or more, cracks tend to occur in the glass coating 7, reducing the reverse breakdown voltage of the semiconductor device. or increase the reverse current. Furthermore, the present invention can be applied to passivation of mesa type semiconductor devices.

As described above, the present invention is suitable for manufacturing high-voltage semiconductors,
For example, comparisons are made with Conventional Method 1 (passivation using a thermal oxide film), Conventional Method 2 (passivation using a polycrystalline silicon film doped with # elements), and Conventional Method 3 (vacillation film obtained by electrophoresis of glass powder). and has the following characteristics.

Compared to conventional method 1, it is easier to obtain a high withstand voltage.

Compared to conventional method 2, the reverse current is lower.

Compared to conventional methods 2 and 3, special equipment and complicated process control are not required.

That is, the present invention is a perfusion method that solves the disadvantages of Conventional Method 1, Conventional Method 2, and Conventional Method 3, and embodies only their advantages.

FIG. 2 shows a specific resistance of 40% as an example of the effect of the present invention.
FIG. 3 is a graph comparing the breakdown voltage between collector heses when using a silicon substrate of Ωcm (effective thickness 6011 m), and reverse current for conventional methods 1 to 3. As is clear from the graph, the present invention is superior in both pressure resistance and reverse current.

As described in detail, the method for manufacturing a semiconductor device according to the present invention mixes glass powder with photoresist, and therefore has the advantage of being able to perform fine processing with high withstand voltage and low reverse current.

[Brief explanation of drawings]

FIG. 1 is a process diagram showing an embodiment of the present invention, and FIGS. 2 and 3 are graphs showing reverse breakdown voltage and reverse current of an embodiment of the present invention in comparison with a conventional example. It is. DESCRIPTION OF SYMBOLS 1... Silicon substrate which has already been diffused, 2... Photoresist, 3... Glass powder, 4... Glass film formed by spin coating method, 5... Window for base electrode, 6...
... Window for emitter electrode, 7... Glass coating for vacillation obtained by combustion, 8... AI [, 9...
A1 film for heath electrode, 10... A1 film for emitter electrode.

Claims (2)

[Claims] (1) The first step is to apply a thin layer of photosensitive liquid, which is a mixture of photoresist and glass powder for passivation, onto the semiconductor substrate.
a second step of partially removing the photosensitive thin film applied to the semiconductor substrate by photoetching; and heat-treating the photosensitive thin film of the semiconductor substrate in an oxidizing atmosphere at a temperature of 750°C to 900°C. A method for manufacturing a semiconductor device, comprising a third step. (2) In the first step, the passivation glass has a composition ratio of 0.1 to 11 with respect to the photoresist, and the passivation glass thin film on the semiconductor substrate has a thickness of 0.3 to 40 μm. 2. The method of manufacturing a semiconductor device according to claim 1.