JPS6052041A - Semiconductor memory device - Google Patents

Abstract

PURPOSE:To magnify the margin of the accuracy of the position of projection of laser beams against a link, and to blow a laser positively by forming a film inclined-section capable of refracting laser beams on the link. CONSTITUTION:Sections 2a in this thickness are formed to a field oxide film 2 positioned at both sides of a link 3. Consequently, inclined sections 4a are shaped on both sides of the upper sections of the link 3 in a PSG film 4 on the section 2a. Accordingly, since projected laser beams are refracted to the link 3 side by the inclined sections 4a of the PSG film 4, laser beams are projected positively to the link 3 even when the position of projection of laser beams is displaced from the link 3.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD OF THE INVENTION The present invention relates to a structure of a laser plow link in a semiconductor memory device, and in particular a redundancy memory.

[Prior art]

Generally, in a semiconductor memory device equipped with this type of redundant circuit, that is, a semiconductor memory device having spare memory cells, a redundant circuit is used to deactivate a defective memory cell or to write an address to be replaced in a spare decoder. A link is provided on the device, and this link is blocked by a laser.

FIG. 1 shows a schematic configuration of a laser plow link in such a conventional semiconductor memory device. That is, in the conventional device shown in FIG. 1, reference numeral (1) indicates a semiconductor substrate, (2) indicates a field oxide film formed on this substrate (1), and (3) indicates a field oxide film formed on this oxide film (2). (4) is a PEG film covering the laser plow links formed of polysilicon, silicide, or polycide. In this case, the PSG film (4)
In some cases, the structure may be such that it is not covered.

And this semiconductor memory device, for example, 256 K(D)
Currently, the width of RAM and 64K(S) RAM is 2.
A link of about μm is used, and YAG with a wavelength of 1.06 μm is used as a laser light source.
Since the beam diameter of this laser is about 6 μm, in the link (3) of the conventional device in FIG.
Since the refraction caused by The same applies to the case without (4).

However, on the other hand, the beam irradiation accuracy of the laser device itself is at most about ±1.5 μm, and various other factors come into play for accurate beam irradiation.
The value of the deviation from the link of about 2 μm or less was too small as a margin for reliable laser plowing.

[Summary of the invention]

In view of these conventional drawbacks, the present invention utilizes the refraction of the laser beam by the film covering the link to expand the margin regarding the accuracy of the laser beam irradiation position, thereby ensuring reliable laser beam irradiation. This is what I did.

[Embodiments of the invention]

Embodiments of this invention device will be described below with reference to FIGS. 2 to 4.
This will be explained in detail with reference to the drawings.

2 to 4 show different embodiments, and in each of these figures, the same reference numerals as in the conventional device shown in FIG. 1 indicate the same or corresponding parts.

In this case, the laser beam is irradiated perpendicularly to the substrate surface, so in order to refract the laser beam, it is necessary to provide a sloped part with a large angle on the surface of the PSG film (4) as a coating near the link. There is.

In the embodiment shown in FIG. 2, a thin portion (21) is formed in the field oxide film (2) located on both sides of the link (3), and this causes the PSG film (4) thereon to be formed on the link (3).
3), sloped portions (4M) are formed on both sides of the upper part.

Therefore, in the case of the embodiment shown in FIG. 2, since the irradiated laser beam is refracted toward the link (3) by the inclined portion (4a'7) of the PSG film (4), the irradiation position of this laser beam is Even if the laser beam deviates slightly from the link (3), the link (3) can be reliably irradiated and the margin of accuracy of the irradiation position of the laser beam can be expanded.

The PSG film in the embodiment shown in FIG. 2 can be replaced with a silicon nitride film having a higher refractive index to further expand the margin of irradiation position accuracy. It is also possible to form a double structure by forming a silicon nitride film thereon.

In addition, as in the embodiment shown in FIG.
The sloped portion (4m) may be similarly formed by selectively removing saM (4) by etching, and specifically, etching may be performed simultaneously with the opening of the contact hole. Also in the case of the embodiment of FIG. 3, the PSG film is replaced with a silicon nitride film as described above.

A double structure of a PSG film and a silicon nitride film can be applied, and as shown in the embodiment of FIG. 4, a silicon nitride film (5) can be further formed on the structure of FIG. 3. can also have some effect.

[Effects of the Invention] As detailed above, according to the present invention, since a sloped portion of the coating that can refract the laser beam is formed on the link, the margin of accuracy of the irradiation position of the laser beam with respect to this link is expanded. This method not only enables accurate laser plowing at all times, but also has the advantage of being simple in structure.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the general structure of a laser plow link according to a conventional device, and FIGS. 2 to 4 are cross-sectional views showing the general structure of laser plow links according to different embodiments of the device of the present invention. be. (1)...Semiconductor substrate, (2)...Field oxide film, (3)...Laser blow link, (4)...
... PSG film, (4a) ... Slanted portion of PSG film, (5) ... Silicon nitride film. Agent Masuo Oiwa 221- 4th figure procedural amendment (voluntary) Commissioner of the Japan Patent Office 1. Indication of the case: Japanese Patent Application No. 161369/1982. 2. Title of the invention: Semiconductor memory device 3. Relationship with the person making the amendment. Patent. Applicant address 2-2-3 Marunouchi, Chiyoda-ku, Tokyo Name
(601) Mitsubishi Electric Corporation Representative Hitoshi Katayama 4, Agent Address 2-2-3 Marunouchi, Chiyoguchi 1-ku, Tokyo Column 6 of the brief explanation of the drawings in the specification, Contents of the amendment

Claims (1)

[Scope of Claims] (1) In a semiconductor memory device having a laser plow link, a coating capable of refracting a laser beam is provided on the link, and sloped portions are formed in the coating on both sides of the link. Features of semiconductor memory device. (→ The semiconductor memory device according to claim 1, characterized in that the film on both sides of the link is selectively etched to form sloped parts on both sides. (3) The film is a PSG film. (4) A semiconductor memory device according to claim 1 or 2, characterized in that: (4) a semiconductor memory device according to claim 1 or 2, characterized in that the film is a silicon nitride film; (5) The semiconductor memory device according to claim 1, wherein the coating has a double structure of a PSG film and a silicon nitride film. (6) Further silicon nitride on the coating. 3. The semiconductor memory device according to claim 2, wherein a film is formed.