JPH0256815B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a semiconductor device using a thermally easily cuttable fuse as a storage medium.

(b) Background of the Technology Fuses are often used as means for writing information into read-only memory (PROM) that allows users to program information, and as means for switching redundant circuits in IC memories. (The above PROM is especially
(referred to as ROM) (c) Prior Art and Problems Conventionally, self-heating type fuses made of polysilicon patterns provided with a desired resistance value have been mainly used in the above-mentioned semiconductor devices.

Figure 1 shows a schematic cross section of a conventional structure in which a step is provided in the insulating film at the bottom of the fuse to allow molten polysilicon to flow down and improve the reliability of fusing. ,
2 is an insulating film, 3 is a stepped portion, and 4 is a polysilicon film.
Fuse pattern, 8 is surface protective film, E and
E′ represents a current-carrying terminal.

Figure 2 is a schematic cross section of a conventional structure in which a p-n junction is provided at the bottom of the fuse, and the p-n junction is also energized at the same time to generate heat, making it easy to blow the fuse. In the figure, 1 is a p-type semiconductor substrate, 4 is a polysilicon fuse pattern, 5 is an n ⁺ type region, 6 is a p-n junction, 7 is a thin insulating film, and 8 is a surface protection film. ,
E and E' represent current-carrying terminals.

The above two types are typical conventional structures, but in both structures, the fuse pattern is formed of a high-resistance polysilicon layer that can self-heat when energized. This polysilicon is
It has a high melting point of 1400 [℃] or higher. Therefore, in the conventional structure, the amount of heat generated during fusing is extremely large.
At the time of fusing, as shown in FIGS. 1 and 2, holes 9 as shown by dotted lines are formed in the surface protection film 8, such as phosphosilicate glass (PSG), covering the fuse part, and the surface protection There is a problem in that the protective effect of the film 8 on the substrate surface is impaired.

Therefore, in order to ensure the reliability of the semiconductor device, it has become necessary to form an additional surface protective film.

A device having a fuse that does not require the formation of an additional surface protective film is already known as a conventional improved semiconductor device, and will be described below.

Figure 4 shows this conventional improved fuse
This figure shows a cross-sectional view in the direction A and a cross-sectional view in the Y direction, showing an example of a structure in which the conductor pattern to be melted and cut is heated and melted by heat generated by a resistor pair layer formed mainly of polysilicon. In this Figure 4,
11 is a semiconductor substrate, 12 is a first insulating film made of a field oxide film, etc., 13 is a heating element pattern made of a polysilicon layer 16 having a resistivity of about 100 [Ω-cm], and 14 is made of Si ₃ N ₄ . 15 is a conductor pattern to be fused made of Al (aluminum) or Al (aluminum) alloy, etc., 17 is an interlayer insulating film made of phosphosilicate glass (PSG), etc., and 18a, 18b are electrode contact windows. , 19a and 19b are fusing current supply wiring made of Al or Al alloy, and 20 is a surface protection film made of PSG or the like.

According to the improved conventional technique shown in FIG. 4, a heat generating resistive layer serving as a preheating means is disposed below the fuse layer to be blown, so that the fuse layer can be blown without passing current through the fuse layer itself. . In the conventional technology shown in FIGS. 1 and 2 before the improvement, the fuse layer was blown by its own heat generation, so the entire fuse layer was heated, and the insulation covering the fuse layer was heated. However, with this improved technology, the fuse layer itself is melted by generating heat from another source, so there is no need to heat the entire fuse layer, and there is no chance of damaging the cover insulation film. This means that there is less.

Although this configuration eliminates the problem of damaging the insulating film covering the upper part of the fuse layer, it still requires a sufficient amount of heat to blow out the fuse to damage surrounding elements. In addition, since this preheating means is made of a resistor made of polysilicon, for example, in the example shown in FIGS. This consumes relatively little power compared to blowing fuses, but it has become necessary to be able to blow fuses with less power consumption.

As mentioned above, even with conventional improved methods, the problems that cannot be solved are that the heat generated when a fuse blows spreads over a wide area, which tends to damage surrounding elements, and that power consumption The point is that it is unnecessarily large.

(d) Purpose of the Invention The present invention provides a semiconductor device that has a configuration that can generate heat only in an extremely narrow range, thereby making it possible to blow out a fuse with less power consumption without causing thermal damage to other peripheral elements. With the goal.

(e) Structure of the invention In other words, the present invention was made in view of the thermal problems that could not be solved even with the above-mentioned semiconductor device which is an improvement on the conventional fuse, and the following structure has been developed. It is meant as a means.

That is, in the semiconductor device of the present invention, a heating element is formed as a convex step on a substrate surface and includes a semiconductor region of one conductivity type and a semiconductor region of an opposite conductivity type, and at least the opposite conductivity type of the heating element. an insulating layer deposited on the surface of the semiconductor region; and an insulating layer formed on the surface of the insulating layer directly above the semiconductor region of the opposite conductivity type, and formed to be easily fused by the heat generated by the heating element. It is characterized by having a pattern.

(f) Embodiments of the Invention The present invention will be described in detail below with reference to the drawings.

FIG. 3 is a schematic perspective view showing a fuse structure of a semiconductor device of the present invention, and FIG. 5 is a cross-sectional view in the X direction (A) and a cross-sectional view in the Y direction (B) of another embodiment of the present invention.

The indirect heating type fuse of the present invention is, for example, as shown in FIG. 1 [μm], width 2-3 [μm]
m], a band-shaped heating element pattern 13 having a step between itself and the surface of the first insulating film 12 is provided.
A thin second layer of about 500 Å thick made of silicon nitride (Si ₃ N ₄ ), for example, is formed on the surface of the
The heating element pattern 13 is straddled, for example, at right angles through an insulating film 14 of 1 [μm] in thickness and 2 to 3 in width.
It has a structure in which a belt-shaped conductor pattern 15 to be melted and made of a wiring material with a low melting point such as aluminum (Al) or an Al alloy with a diameter of approximately [μm] is disposed.

The heating element pattern 13 is formed as a resistor layer made of a semiconductor material such as polysilicon, and is formed with a p-n junction so that the local part where heat generation is particularly desired is of the opposite conductivity type. It is something that Figure 5 shows a p-type conductor pattern formed mainly within the heating element pattern.
They are an X-direction cross-sectional view (a) and a Y-direction cross-sectional view (b) of an embodiment having a structure that is thermally fused due to heat generated by the n-junction.

In the figure, 11 is a semiconductor substrate, 12 is a first insulating film, 13 is a semiconductor pattern, 14 is a thin second insulating film made of Si ₃ N ₄ , 15 is a low melting point conductor pattern to be fused, and 16a and 16c is an n-type polysilicon layer, 16b is a p-type polysilicon layer, and 17
1 is an interlayer insulating film, 18a and 18b are electrode contact windows, 19a and 19b are wirings for supplying fusing current, and 2
0 indicates a surface protective film.

In this structure, for example, a p-type region 19 of a conductivity type opposite to that normally imparted to the polysilicon wiring.
B is formed using an ion implantation method to have a width narrower than the width of the conductor pattern 15 at the lower part of the conductor pattern 15 to be fused, as shown in FIG. 5A.

In the indirectly heated fuse having the structure of the present invention, the temperature of the heating element pattern 13 is raised to a temperature higher than the melting point of the conductor pattern 15 to be fused by passing a fusing current through the heating element pattern 13. The melting conductor pattern 15 is melted.
In the structure of the first embodiment, that is, in the case where the heating element pattern 13 is a high-resistance layer, the fusing current may be either alternating current or direct current, and in the case of the present invention where the heat generation is mainly due to a pn junction, as shown in FIG. As shown, for example, p-type polysilicon layers 16b are formed on both sides.
When using the heat generated from the -n junction, the fusing effect will be the same no matter which direction the current flows. In addition, in order to further increase the amount of heat generated, a p-type polysilicon layer 1
It is better to lower the impurity concentration of 6b. Furthermore, if the direction of the fusing current is taken into account, a single pn junction may be sufficient.

In the structure of the present invention, current can also be applied to the conductor pattern 15 to be fused at the same time to further ensure selective fusion. In this case, in order to facilitate the heat generation of the conductor pattern 15 itself to be fused, it is desirable to form the pattern cross-sectional area of the fused portion to be small.

In the above embodiment, a Si ₃ N ₄ film was used as the insulating film between the heating element pattern and the conductor pattern to be fused.
This insulating film may be a silicon dioxide (SiO ₂ ) film. However, the SiO ₂ film has the problem of reacting with aluminum at high temperatures and reducing its insulation properties, so when using the SiO ₂ film, its thickness must be
It needs to be thicker than the Si ₃ N ₄ film.

(g) Effects of the Invention As shown in the above embodiments, according to the structure of the present invention, the heated part can be limited to only the lower part of the fuse, and when trying to blow it out, it is possible to heat parts other than the lower part of the fuse. There is no risk of thermal damage to other elements near the fuse blowout. Furthermore, the area to be heated can be limited to a very narrow area, and the fuse can be blown by passing a small amount of current.

[Brief explanation of drawings]

Figures 1 and 2 are schematic sectional views of a conventional fuse, Figure 3 is a schematic perspective view showing the fuse structure of the present invention, and Figure 4 is a sectional view of a conventional improved fuse in the X and Y directions. 5 is a sectional view B in the X direction and a sectional view B in the Y direction in another embodiment of the present invention. In the figure, 12 is a first insulating film, 13 is a heating element pattern, 14 is a second insulating film, 15 is a conductor pattern to be fused, 16 is a polysilicon layer, 16a,
16c is an n-type polysilicon layer, 16b is a p-type polysilicon layer, 17 is an interlayer insulating film, 18a, 1
Reference numeral 8b indicates an electrode contact window, 19a and 19b indicate wiring for supplying fusing current, and 20 indicates a surface protection film.

Claims (1)

[Scope of Claims] 1. A heating element formed as a convex step on a base surface and having a semiconductor region of one conductivity type and a semiconductor region of the opposite conductivity type, and at least a semiconductor of the opposite conductivity type of the heating element. an insulating layer deposited and formed on the surface of the region; and a fusing conductive layer formed on the surface of the insulating layer directly above the semiconductor region of the opposite conductivity type and formed to be easily fused by the heat generated by the heating element. A semiconductor device having a pattern.