JPS61140155A - Semiconductor device - Google Patents

Abstract

PURPOSE:To contrive to improve erasure characteristic while keeping the moisture resistance and mechanical strength as the whole chip by a method wherein only the EPROM memory cell part is covered with an oxide nitride film excellent in ultraviolet permeability, whereas the other part with a plasma nitride film excellent in moisture resistance and mechanical strength. CONSTITUTION:The part 3 except the EPROM memory cell part 2 on a semiconductor substrate 1 is covered with a plasma nitride film 4 excellent in moisture resistance and mechanical strength, and the memory cell part with an oxide nitride film 5 excellent in ultraviolet permeability. Though the oxide nitride film 5 covering the part 2 is some faulty in mechanical strength, most part of the surface of the semiconductor substrate 1 is covered with the plasma nitride film 4 much excellent in moisture resistance and mechanical strength. This construction makes the hole chip excellent in moisture resistance and mechanical strength and eliminates the problem point of erasure characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a technique that is effective when applied to a semiconductor device in which an EPROM occupies a small area on one chip.

[Background Art] Generally, the surface of a semiconductor substrate (so-called semiconductor chip) is covered with a surface protective film having excellent moisture resistance and mechanical strength. This surface protection film is called a final passivation film, and together with the plastic or ceramic package, it has an important function of protecting the semiconductor chip from the external environment. From the viewpoint of moisture resistance and mechanical strength, a silicon nitride film produced by plasma CVD (hereinafter referred to as a plasma nitride film) is most suitable as a surface protective film.

However, since the plasma nitride film has poor transmittance to ultraviolet rays, there is a problem in the ultraviolet erasable EPROM in that the erasing characteristics for erasing the stored contents are deteriorated.

Therefore, as a surface protection film for UV-erasable EPROMs, an oxynitride film (OX
Attempts have been made to use ynitrids.

However, the oxynitride film has a drawback in terms of mechanical strength, and it seems that it is necessary to take measures such as making the protective film a two-layer structure (as described above).

Nikkei Electronics, May 7, 1984 issue, ρ16
(see 1).

[Objective of the Invention] The object of the present invention is to maintain moisture resistance and mechanical strength, and to erase data in a semiconductor device such as a microcomputer with built-in EPROM, which has an ultraviolet erasable EPROM along with a CPU, input/output device, etc. on a single chip. The object of the present invention is to provide a chip surface protection technology that has no problems in terms of characteristics.

The above and other objects and novel features of the present invention are accomplished by the present invention J! It will become clear from the description in the book and the attached drawings.

[Summary of the Invention] Among the inventions disclosed in this application, a brief outline of typical inventions is as follows.

In other words, only the memory cell portion of the EPROM on the semiconductor chip is covered with an oxynitride film that has good UV transparency, while the other parts are covered with a plasma nitride film that has extremely good moisture resistance and mechanical strength. In this way, the erase characteristics are improved while maintaining the moisture resistance and mechanical strength of the chip as a whole.

Embodiment 1 is a chip plan view of an embodiment of the semiconductor device according to the present invention, and FIG. 2 is a sectional view taken along line nn in FIG. 1.

Although not shown in the figure, a semiconductor substrate 1 made of a silicon substrate has an EPROM, a CPU, etc. formed thereon, and has an EPROM memory cell, which itself has the function of a one-chip microcomputer. The portion 3 other than the portion 2 is covered with a plasma nitride film 4 having good moisture resistance and mechanical strength, and the memory cell portion 2 is covered with an oxynitride film 5 having good ultraviolet transmittance. In the example shown in FIGS. 1 and 2, the oxynitride film 5 is formed after patterning the plasma nitride film 4, but as shown in FIG. 3, the oxynitride film 5 is formed. After that, a plasma nitride film 4 is formed, or as shown in FIG. 4, an oxynitride film 5 is formed.
In this case, it is also possible to cover the entire surface of the semiconductor substrate 1.

In a microcomputer with built-in EPROM, the area occupied by the EPROM memory cell portion 2 is very small.

Therefore, although the oxynitride film 5 covering the memory cell portion 2 has some drawbacks in terms of mechanical strength, most of the surface of the semiconductor substrate 1 is made of plasma nitride, which has extremely good moisture resistance and mechanical strength. Since it is covered with membrane 4,
Looking at the whole chip.

It has excellent moisture resistance and mechanical strength, and also solves the problem of erasing properties.

[Effects] On the chip, only the memory cell portion of the EPROM is selectively covered with a film that has good ultraviolet transparency, and the other parts are covered with a film that has good moisture resistance and mechanical strength, so that the overall chip Erasing characteristics can be improved while maintaining the surface protection function.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the above Examples and can be modified in various ways without departing from the gist thereof. 1゜[Field of Application] The present invention can be widely applied to semiconductor devices that partially include ultraviolet erasable EPROM, but is particularly applicable to EPR
The lower the OM memory cell area occupation rate, the greater the effect can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing one embodiment of the present invention, and Fig. 2 is a plan view showing an embodiment of the present invention.
A cross-sectional view taken along the line ■--■ in the figure, and FIGS. 3 and 4 are cross-sectional views showing other embodiments, respectively.

Claims (1)

[Claims] 1. In a semiconductor device having an ultraviolet-erasable EPROM together with other functional elements on one semiconductor substrate, the surface protective film covering the memory cell portion of the EPROM is more suitable than the surface protective film covering other parts. A semiconductor device characterized by using a film that is highly transparent to ultraviolet rays.