JPS628539A - Semiconductor device - Google Patents

Abstract

PURPOSE:To make it possible to cut a fuse with low electric power, by forming a contact hole for connection to the fuse element comprising poly Si so that the positions of the holes are located at an equal distance from the cutting part of the fuse element. CONSTITUTION:On an SiO2 layer 2 on an Si substrate 1, a fuse element comprising a cutting part 3a and a connecting part 3b is formed with a poly Si layer 3. The connecting part 3b is connected to a metal wiring layer 6 through contact holes 5, which are formed in an interlayer insulating film 4. At this time, the contact holes 5 are formed in a circular-arc shaped hole 5A or in a plurality of holes 5B, which are arranged in an arc shape, so that each part of the hole is separated by an equal distance from the cutting part 3a. Then, the resistance at the connecting part of the fuse element is decreased, and the fuse is cut with low electric power and at a short time. This device is suitable for the trimming circuit of an analog semiconductor integrated circuit.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a semiconductor device, and in particular to a semiconductor device equipped with a fuse element suitable for use in a redundant circuit of a semiconductor memory device and a trimming circuit of an analog semiconductor integrated circuit device. The present invention relates to a semiconductor device.

[Conventional technology]

In recent years, semiconductor devices, typified by semiconductor integrated circuit devices, have a fuse element formed within the device, and the fuse element has been trimmed (cut) to provide circuit redundancy, or circuit-specific adjustments have been made. There are suggestions for what to do. As this fuse element, there are those that utilize wiring metal such as aluminum, or those that are constructed of a PN junction diode or polycrystalline silicon. Further, as a trimming method, there are a method of irradiating a laser beam and utilizing the light energy, and a method of utilizing Joule heat by applying a voltage or current. Among these trimming methods, the method using laser light irradiation has the problem that it is difficult to align the laser light and the fuse element. has been adopted.

For example, FIGS. 3(A) and 3(B) show a longitudinal cross-sectional view and a cross-sectional view of a semiconductor fuse element previously proposed by the present inventor in Japanese Patent Application No. 160456/1983. That is, a silicon dioxide layer 2 is formed on a single crystal silicon substrate 1 with a thickness of 900 to 10
Formed by oxidation treatment in H2-0□ atmosphere at about 00℃,
A polycrystalline silicon layer 3 is formed thereon by low pressure vapor phase epitaxy, and a portion of this layer is configured as a fuse element. This fuse element is formed by introducing impurities such as phosphorus, poron, arsenic, etc. during or after the growth of the polycrystalline silicon layer 3 so as to have a predetermined specific resistance, and also by forming the polycrystalline silicon layer 3 into a narrow width. It is composed of a cut portion 3a formed and wide connecting portions 3b, 3b disposed at both ends of the cut portion 3a. Then, on this polycrystalline silicon layer 3, a glabellar insulating film 4 made of silicon dioxide doped with phosphorus or boron is formed, and the connecting portion 3b is formed therein.

A contact hole 5.5 is opened to expose the contact hole 5.3b, and a metal wiring layer 6.6 provided thereon is formed in the contact hole 5.5.
5, it is electrically connected to the connecting portions 3b, 3b. Further, a protective insulating film 7 is formed on the metal wiring layer 6.6.

According to this fuse element, when a predetermined voltage or current is applied between the metal wiring layers 6, 6, the current flows to the cut portion 3a through the connection portions 3b, 3b of the polycrystalline silicon layer 3. The cutting portion 3a is melted and cut by the Joule heat generated in the cutting portion 3a, and trimming is performed.

[Problem that the invention seeks to solve]

When trimming the conventional fuse element mentioned above,
In order to easily cut the fuse element, the cutting part 3a
It is necessary to reduce the voltage applied to other parts and increase the proportion of the voltage applied to the cutting part 3a. That is, the contact resistance between the wiring metal layer 6 and the connection portion 3b and the contact hole 5
It is necessary to reduce the layer resistance of the connecting portion 3b from the connecting portion 3b to the connecting point 3C between the connecting portion 3b and the cutting portion 3a.

The inventor studied this point and found that the resistance value of the fuse element was determined to be 1.
It has been found that cutting occurs after passing through a critical value R3 and a second critical value R2.

The first critical value R8 is the specific resistance ρ3 of the polycrystalline silicon layer 3.
and the width wb and length b of the connecting portion 3b, the width Wa and length La of the cutting portion 3a, and the contact resistance Re between the wiring metal layer 6 and the connecting portion 3b, proximally by the following formula % formula %. K is a coefficient for the current distribution depending on the structure of the connection portion 3b.

The second critical value R2 is determined by the voltage application, which causes the cut portion 3b to self-heat and the polycrystalline silicon to undergo a phase change.
This is thought to be caused by a decrease in the specific resistance of a. Therefore, the second critical value R2 is given by the following equation, assuming that the resistivity of the polycrystalline silicon layer 3 after phase change is ρ6°.

R2= 2 (Rc+K XLb/Wb x ρs+)
+La/Wa c.
rm, Wb =24. crm.

For a fuse element with dimensions La = l 5pm, Wa = 3pm, Rc = 1Ω, the first critical value R,
showed 125Ω. This is because the resistance values were 35Ω at the connecting portion 3b and 90Ω at the cutting portion 3a, while the second critical value R2 immediately before cutting was 50Ω. Assuming that there is no change in the resistance value at the connection part 3b,
This means that the resistance value of the cut portion 3a changes from 90Ω to 15Ω before and after the phase change.゛From this result, although approximately 70% of the total applied voltage is applied to the cutting section 3a when the first critical value R1 is exhibited, when the second critical value R2 is exhibited, approximately 70% of the total applied voltage is applied to the cutting section 3a.
It can be seen that only % has been added.

For this reason, conventional fuse elements require relatively large voltages and currents for cutting, and the time required for cutting takes a long time.

[Means for solving problems]

The semiconductor device of the present invention has a voltage that cuts the fuse element,
In order to reduce the current and shorten the disconnection time, the contact area with the metal wiring layer that is connected to the connection part of the fuse element through the interlayer insulating film is connected to the disconnection part of the fuse element at any point. The configuration is such that the positions are set so as to be substantially equidistant from the connection point with the section.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a cross-sectional view for explaining one embodiment of the present invention, and its vertical cross-sectional structure is the same as that of FIG. 3(A), and this will be used in conjunction with the explanation.

That is, in the semiconductor fuse element, a silicon dioxide layer 2 is formed on a single crystal silicon substrate 1, and a polycrystalline silicon layer 3 as a fuse element is formed thereon. The polycrystalline silicon layer 3 is set to a predetermined resistivity by introducing impurities such as phosphorus, boron, arsenic, etc., and its planar shape has a wide connecting portion 3b at each end of a narrow cut portion 3a. , 3b are continuously formed. Further, an interlayer insulating film 4 is formed on the polycrystalline silicon layer 3, and contact holes 5A, 5A are formed in this glabellar insulating film 4.

Then, a wiring metal layer 6 having a desired pattern is formed on the interlayer insulating film 4, and the wiring metal layer 6 is electrically connected to the connecting portion 3b through the contact holes 5A, 5A.

Here, the contact holes 5A, 5A are formed in a planar shape such that the planar shape is an arc centered on the connection point 3C between the cut portion 3a and the connection portion 3b.

In other words, the contact holes 5A, 5A are formed at the same distance from the connection portion 3C at the connection portion with the connection portion 3b.

Note that a protective insulating film 7 is formed on the wiring metal layer 6.

According to this configuration, in the connecting portion of any contact hole 5A, the connecting portion 3 between the cutting portion 3a and the connecting portion 3b
Since the distances to C are equal, the distribution of the current flowing through the fuse element through the wiring metal layer 6 and the contact hole 5A is uniform, and therefore the resistance value at the connection portion 3b can be reduced. In other words, in the case of FIG. 3(B), the current from the contact hole 5 closest to the connection point 3c becomes dominant, and the contribution of the contact hole located further away is small, so the current is actually the most Only the holes near the center are utilized, and even if the width wb of the connecting portion 3b is increased, it is not effective in reducing the resistance at the connecting portion 3b. In this respect, in this example, all of the connecting portions 3b can be utilized, and as a result, the resistance value of the connecting portions 3b can be reduced.

FIG. 2 shows another embodiment of the present invention, in which the same parts as in the previous embodiment are denoted by the same reference numerals, and detailed explanation thereof will be omitted.

In this embodiment, instead of forming the contact hole 5B in an arc shape, a plurality of contact holes 5B are arranged at equal distances from the connection point 3C of the fuse element. That is, each contact hole 5B is arranged so as to be located on the circumference with the connection point 3C as the center. In this embodiment as well, since current is passed through all the contact holes 5B, the entire width of the connecting portion 3b can be effectively utilized, and the resistance at the connecting portion 3b can be reduced.

According to experiments conducted by the present inventor, even if a fuse element of the same standard as the conventional one was constructed, the resistance value of the connecting portion 3b could be improved to 15Ω, which is about half of the conventional one.

Here, the smaller the distance between the contact holes 5A, 5B and the connection part 3c, the more effective it is in reducing the resistance of the connection part 3b.
When the current determined by the total resistance value of the fuse element is at its maximum, the metal component of the wiring metal layer 6 may migrate into the fuse element and make it impossible to cut the fuse. That's difficult. Further, in each of the embodiments described above, the contact holes 5A and 5B are arranged at an arc angle of 180 degrees or less with respect to the connection point 3c, but it is of course possible to arrange them at an angle greater than this.

〔Effect of the invention〕

As explained above, in the present invention, the position of the contact hole in the connection part of the fuse element is arranged so that the distance from the connection part of the fuse element is the same at any part of the contact part. It is possible to conduct current to the fuse element by effectively utilizing the entire width, thereby reducing the resistance at the connection part and increasing the power ratio at the cutting part, making it possible to cut the fuse element with low power, and Trimming can be easily performed, such as cutting in a short time.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of one embodiment of the present invention, FIG. 2 is a cross-sectional view of another embodiment, and FIG. 3 is a diagram showing a conventional structure.
A) is a longitudinal cross-sectional view, (B) is a cross-sectional view along the AA line,
FIG. 4 is a diagram showing the change in resistance over time of the fuse element during cutting. DESCRIPTION OF SYMBOLS 1... Single crystal silicon substrate, 2... Silicon dioxide layer, 3... Polycrystalline silicon layer, 3a... Cutting part, 3
b... Connection portion, 3c... Connection location, 4... Interlayer insulating film, 5°5A, 5B... Contact hole, 6... Wiring metal layer, 7... Protective insulating film. Figure 1

Claims (1)

[Claims] 1. Made of polycrystalline silicon set to a predetermined resistivity,
It has a fuse element composed of a narrow cutting part and wide connecting parts at both ends thereof, and a wiring layer is connected to the connecting part through a contact hole formed in an insulating film provided on the fuse element, In a semiconductor device in which the fuse element is disconnected by applying current through the contact hole, the contact hole connects the disconnection area of the fuse element and the connection area wherever the connection area is connected to the connection area. A semiconductor device characterized in that the semiconductor device is positioned so as to be substantially equidistant from a location. 2. The semiconductor device according to claim 1, wherein the contact hole has an arcuate planar shape centered on the connection location. 3. The semiconductor device according to claim 1, wherein the contact hole is a plurality of holes arranged at positions on a circumference centered on the connection point.