JPS6229909B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a semiconductor device, and particularly to a method of forming a protective film that protects a semiconductor element from radiation.

In recent years, malfunctions of the semiconductor devices due to α particles emitted by resin and ceramic sealing materials have become a problem in resin-sealed semiconductor devices and ceramic-sealed semiconductor devices.

A cross-sectional view of a conventional resin-sealed semiconductor device is shown in FIG. 1a, and a cross-sectional view of a ceramic-sealed semiconductor device is shown in FIG. 1b, respectively. That is, in the resin-sealed semiconductor device, a semiconductor element 1 is fixed to a lead frame 6, and electrodes 2,
3, metal wires 4, 5 such as aluminum are attached to lead frames 7, 8 different from the lead frame 6.
connected by. These are covered with resin 9 and the whole is fixed. In the ceramic type semiconductor device shown in FIG. 1B, a semiconductor element 1 is fixed on a thin metal plate 12 in a cavity of a ceramic container 10, and electrodes 13 and 14 of the semiconductor element are connected to leads 13 and 15, respectively, by metal wires 4, 5 to connect and seal with a lid plate 11 made of ceramic or metal.

In such conventional encapsulation methods, alpha particles released from container materials such as resin and ceramics are
The light enters the semiconductor device and generates charges within the device. In particular, in semiconductor integrated circuit devices such as random access memories (RAMs) that store information by accumulating charges, the information is destroyed by charges generated by the incidence of alpha particles.

As a countermeasure against these problems, a common method is to apply a resin having an ability to block α particles to the surface of the semiconductor element to protect it. For example, in a resin-sealed semiconductor device, a polyimide resin film 17 is formed over the entire surface of a semiconductor substrate as shown in FIG. 2a. However, in this case, although the blocking ability against α particles is sufficient, the metal wires 4 connecting the semiconductor element electrodes 2, 3 and the lead frames 7, 8,
5 was easily disconnected, making it difficult to obtain a highly reliable semiconductor integrated circuit. On the other hand, conventionally, as shown in FIG. 2b, polyimide resin 17' is sometimes formed excluding the electrodes, but the thickness of resin 17' is
Since the polyimide resin film is coated to a thickness of 30 to 100 μm and shaped using photoresist technology, the pattern accuracy is very poor and is not practical.

An object of the present invention is to provide a method for manufacturing a resin-sealed semiconductor device and a ceramic-sealed semiconductor device that eliminates the above-mentioned drawbacks of conventional semiconductor devices.

In order to achieve the above object, the present invention selectively applies a resin film such as polyimide or silicon to the surface of a portion of a semiconductor device that is highly sensitive to α particles.
It is characterized by being formed in more than one layer.

The present invention will be explained below with reference to Examples.

3 and 4 show the case where the present invention is applied to a MOS type RAM. On the entire surface of the semiconductor element 1,
After applying polyimide resin to a thickness of approximately several μm, a polyimide resin film 15 is formed using photoresist only on areas susceptible to the influence of α particles, such as memory cells and sense amplifiers (third step).
Diagram a). Thereafter, the polyimide resin film 16 formed by the dropping method does not flow out to the outside of the polyimide resin film 15 due to the difference in surface tension and adhesion between the surface of the polyimide resin film 15 and the surface of the semiconductor element 1. Thereafter, the polyimide is cured by heat treatment. At this time, the first layer resin 15 and the second layer resin 16 may be different types of resin. If this is fixed as a whole using epoxy resin 9, a resin-sealed semiconductor device shown in FIG. 4 is formed. 5 is a plan view of FIG. 3a. Also, Figures 3 to 5
In the figure, the same functions as in FIG. 1a are indicated by the same reference numerals.

Further, in the present invention, by using different types of resins for the first layer resin and the second layer resin, the difference in etching characteristics of the resins can be utilized. That is, the second layer of resin can be etched using the photo resist as a mask, and then the first layer of resin can be etched using the second layer of resin as a mask. By doing so, it becomes possible to form a highly accurate pattern.

FIG. 6 shows another embodiment of the present invention, in which a first layer of resin 15 and a second layer of resin 16 are partially provided on the surface of a semiconductor element 1 of a ceramic sealed semiconductor device. It is something. In FIG. 6, the same functions as in FIG. 1b are indicated by the same reference numerals.

According to the present invention, the second layer of resin film is formed only on the surfaces of the parts that are easily affected by alpha particles, such as memory cells and sense amplifiers in the device, making manufacturing easy and achieving a sufficiently high A highly reliable semiconductor integrated circuit can be realized.

[Brief explanation of the drawing]

FIGS. 1a and 1b are cross-sectional views of a conventional resin-sealed semiconductor device and a conventional ceramic-sealed semiconductor device, respectively. FIGS. 2a and 2b are cross-sectional views showing a structure in which the semiconductor device of FIG. 1a is protected from radiation using a conventional technique. 3a and 3b are cross-sectional views showing each step of an embodiment of the present invention, and FIG. 4 is a cross-sectional view of an embodiment,
FIG. 5 is a plan view of FIG. 3a. FIG. 6 is a sectional view showing another embodiment of the present invention. In the figure, 1...semiconductor element, 2, 3... bonding pad of the semiconductor element, 4, 5... metal wire,
6, 7, 8... Lead frame, 9... Sealing resin, 10... Ceramic container, 11... Lid plate, 1
2... Metal thin plate, 13, 14... Lead, 15...
...First layer resin, 16... Second layer resin, 17,
17'...Resin.

Claims (1)

[Claims] 1. Partially covering the surface of a semiconductor element with a first resin having radiation blocking ability, dropping a second resin onto the first resin, and then thermosetting the dropped second resin. Alternatively, the first resin is coated with a second resin having different etching characteristics from the first resin.