JPS58177B2 - Manufacturing method for semiconductor devices - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor device, and particularly to a method for forming a lift-off electrode using a photosensitive resin.

Conventionally, methods for selectively forming electrodes in semiconductor devices include a method using a metal mask and a method using a photosensitive resin as a mask.

The method of selectively forming electrodes using a photosensitive resin as a mask is frequently used in semiconductor device manufacturing technology because it allows formation of electrodes with highly accurate patterns.

Methods for forming electrodes using photosensitive resin include a method in which the electrode metal is selectively formed by etching the photosensitive resin as a mask, and a lift-off method in which the photosensitive resin is decomposed and carbonized to selectively form the electrode. be.

The former method has disadvantages such as a more complicated process than the latter method.

In particular, the lift-off method is effective for semiconductor devices in which the PN junction of the semiconductor device is passivated with glass.

FIG. 1 shows a conventional lift-off method.

a shows a silicon wafer 1 having a pn junction.

An oxide film 2 is provided on both sides of the wafer.

b shows a state in which the photosensitive resin 3 is applied to the entire surface of the silicon wafer 1.

3C shows a state in which a contact window hole 4 is formed using a normal semiconductor device manufacturing technique.

d shows a state in which a metal vapor deposited film 5 is formed on the entire surface of the silicon wafer 1 by vacuum vapor deposition.

e, the photosensitive resin 3 is decomposed and carbonized by heating in an inert gas at a temperature below the alloy temperature of the metal vapor deposited film 5 and silicon, the metal vapor deposited film 5 thereon is removed, and the metal electrode 6 is placed on the silicon wafer 1. Shows selective formation.

In this case, the pn junction is passivated with an oxide film 2.

However, according to this method, the photosensitive resin 3 is sealed with the metal vapor deposited film 5, and it becomes difficult for the photosensitive resin 3 to decompose and scatter when heated. The decomposition products of No. 3 remain.

These decomposed products are difficult to remove in the cleaning process of normal semiconductor manufacturing technology, and the decomposed products of the photosensitive resin 3 have an adverse effect on the electrical characteristics of semiconductor devices, leading to problems such as decreased yield and reliability. Ta.

An object of the present invention is to provide a method for manufacturing a highly reliable semiconductor device by removing the decomposition products of the photosensitive resin described above.

The present invention is characterized in that after an electrode is formed by a lift-off method using a photosensitive resin, heat treatment is performed in a non-oxidizing gas to remove decomposition products of the photosensitive resin.

Hereinafter, the present invention will be explained based on examples and with reference to FIG.

1A shows a silicon wafer 10 used in an example of the present invention, after impurity diffusion of a planar thyristor has been completed.

Diffusion is formed so that a large number of semiconductor devices can be obtained from one silicon wafer.

Oxide films 11 are formed on both sides of the silicon wafer 10.

b is a photosensitive resin 12, for example 0MR, on the upper surface of the oxide film 11.
83 (trade name: manufactured by Tokyo Ohka Co., Ltd.) is formed, a portion is exposed to light through a predetermined pattern, developed, unnecessary portions are dissolved, and holes 13 of photosensitive resin are formed.

C shows a state in which the oxide film 11 is etched using a hydrofluoric acid-based etching solution to form a window hole 14 in a required portion.

d shows a state in which the silicon wafer 10 is placed in a vacuum deposition apparatus and aluminum 15 is deposited on the upper surface of the silicon wafer 10.

e shows a state in which the photosensitive resin 12 is decomposed by heating in an inert gas, and the aluminum 15 on the oxide film 11 is removed using adhesive tape or the like to form an aluminum electrode 16 in the window hole 14. .

The heating temperature at this time is such that the photosensitive resin 12 is decomposed and carbonized.
The temperature is selected within a range where unnecessary electrode material can be removed using adhesive tape or the like and where electrical ohmic contact can be obtained between silicon and the electrode material.

Usually, when forming an aluminum electrode on a silicon wafer, a temperature lower than the alloy temperature (577° C.) is used.

Further, 0MR83 is decomposed and carbonized at around 400°C.

In the present invention, the photosensitive resin 12 was decomposed and carbonized by heating at 450° C. to form the aluminum electrode 16.

However, in this case, since the entire surface of the photosensitive resin 12 is covered with aluminum 15, decomposition occurs in a sealed state.

For this reason, the photosensitive resin 12 is not sufficiently decomposed and carbonized,
The decomposed product 17 remains on the oxide film 11, which serves as passivation for the junction.

f shows the state in which the decomposed product 17 was scattered and removed by heating at 450° C. for 10 minutes in nitrogen gas.

g shows an assembled semiconductor element in which an electrode 16 is formed on the lower surface of a silicon wafer 10 and cut and separated.

That is, the pellet semiconductor element 18 is mounted on the stem 19, the gate and cathode are tangentially connected with a gold wire 20 by thermocompression bonding, molded with a resin 21, and assembled.

FIG. 3 shows the heating temperature in nitrogen and the breakdown voltage yield of the semiconductor element after forming the aluminum electrode of the present invention.

The yield increases from a heating temperature of 400°C, and when the heating temperature reaches 500°C or higher, almost no deteriorated products are observed.

As a result of examining the decomposition temperature of photosensitive resin using a thermobalance, it was found that 4
It was found that it decomposes at temperatures above 00°C.

Figure 4 shows a planar thyristor (4
00V class) high temperature application test.

It shows stable characteristics after 1000 hours.

In addition, there were no problems at all in all reliability tests, including thermal cycle tests.

The heating temperature in the present invention is effective to be higher than the temperature at which the photosensitive resin decomposes, and optimally to be lower than the temperature at which electrical ohmic contact can be obtained, that is, the alloy temperature of silicon and electrode metal.

FIG. 5 is a sectional view of a moat type gracivation thyristor to which the present invention is applied.

A lift-off method using a photosensitive resin is particularly effective for forming electrodes of semiconductor elements passivated with glass.

Diffusion is performed using normal semiconductor device manufacturing techniques to form a pn junction.

Mort etching is performed to expose the pn junction, glass passivation 20 is applied, and electrodes 21 and 22 are formed by applying the above-described present invention.

Thereafter, electrodes 23 are formed, separated into individual pellets, and assembled.

A high temperature application test regarding this element showed stable characteristics for 1000 hours, and no problems were found in all reliability tests.

As described above, by heating above the decomposition temperature of the photosensitive resin, decomposition products that affect the characteristics of semiconductor elements, especially decomposition products on passivation that have a large effect, can be removed.
A highly reliable semiconductor device was obtained.

In the present invention, the electrode material is aluminum and the photosensitive resin is 0M.
Although R83 was used, the same effect can be obtained with other electrode materials and photosensitive resins.

As described above, according to the present invention, after electrode formation, the decomposition products of the photosensitive resin can be removed by heating in a non-oxidizing gas.
Highly reliable semiconductor devices can be obtained at a high yield.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a conventional electrode forming method, FIG. 2 is a manufacturing process of a silicon semiconductor device explaining the present invention, FIG. 3 is a diagram showing the relationship between breakdown voltage yield and heating temperature of the present invention, and FIG. The figure shows the results of a high-temperature application test of the silicon semiconductor device of the present invention, and FIG. 5 is a cross-sectional view of a moat type gracivation thyristor to which the present invention is applied. 1.10...Silicon wafer, 3,12...
... Photosensitive resin, 16,21-23 ... Electrode, 17 ... Decomposition product, 20 ... Glass passivation.

Claims (1)

[Claims] 1. Partially forming a photosensitive resin on a silicon wafer,
A desired part on the silicon wafer is exposed, an electrode material is deposited using the photosensitive resin as a mask, and the photosensitive resin is decomposed and carbonized by heating. After that, the electrode material on the photosensitive resin is removed and the silicon wafer is removed. A method for manufacturing a semiconductor device, which comprises further heating the silicon wafer in a non-oxidizing gas after forming the electrodes in the above method. 2. A method for manufacturing a silicon semiconductor device according to claim 1, characterized in that the heating temperature in the non-oxidizing gas is below the alloy temperature of silicon and electrode material and above the decomposition temperature of the photosensitive resin. 3. A method for manufacturing a semiconductor device according to claim 1, characterized in that a pn junction of silicon is passivated with glass or an oxide film.