JPH0363819B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a semiconductor fuse element, and more particularly to a semiconductor fuse element suitable for a redundant circuit of a semiconductor memory device and a trimming circuit of an analog semiconductor integrated circuit device.

(Prior Art) In recent years, there has been remarkable progress in increasing the density and integration of semiconductor integrated circuit devices. This densification,
Although higher integration has become possible due to advances in circuit configuration technology and manufacturing technology, the chip area has gradually increased, aided by reductions in the size of the devices used. As is well known, in the manufacture of semiconductor integrated circuit devices, an increase in chip area is accompanied by a decrease in product yield, and it is becoming an important issue to compensate for this decrease in yield. For example, in a semiconductor memory circuit device, one or two of the memory cells may be one of the causes of failure.
In this case, the
By replacing the defective memory cell with a good memory cell, it is possible to turn a defective chip into a good chip. That is, a concept of a redundant circuit has been proposed in which spare memory cells are prepared in addition to necessary memory cells, and a pair of memory cells in a row or column containing the defective memory cell is replaced with a pair of spare good memory cells. There is. This replacement is performed by inserting a fuse element into the address decoder circuit and changing the logic by blowing or not blowing the fuse element.

Furthermore, in analog semiconductor integrated circuit devices, it may be necessary to correct changes in characteristics due to variations in the manufacturing process after the device has been manufactured. The correction is, for example, gain adjustment or offset adjustment of the amplifier, and this correction uses a trimming circuit consisting of a parallel-connected pair of a resistor and a fuse element as a feedback circuit of the operational amplifier,
This is done by blowing out some of the fuse elements. The fuse element used in the redundant circuit and trimming circuit is usually formed of a polycrystalline silicon layer or an aluminum layer, and is blown by laser beam irradiation energy or by applying a voltage across the fuse element. This is done by the Joule heat generated by

Next, the structure of a conventional fuse element will be described with reference to the drawings, taking as an example a semiconductor fuse element in which a polycrystalline silicon layer is used as the material for the blowing part and blowing is performed by applying a voltage. FIGS. 4a and 4b are a plan view and a sectional view for explaining a conventional semiconductor fuse element. Hereinafter, the same parts will be described using the same numbers. Figure 4a,
As shown in FIG. 1B, a silicon dioxide layer 2 is formed on a single crystal silicon substrate 1, and a polycrystalline silicon layer 3, which will become a semiconductor fuse element, is formed thereon.
The polycrystalline silicon fuse 3 is composed of a fusing part 3a and connecting parts 3b at both ends thereof. An interlayer insulating film 4 is formed on the polycrystalline silicon fuse 3.
Further, the interlayer insulating film 4 is provided with a connection hole 5 for electrical connection to the polycrystalline silicon fuse 3 leading to the connection part 3b, and a first opening 6 leading to the fusing part 3a. provided. Further, on the interlayer insulating film 4, a wiring metal layer 7 made of aluminum or the like is formed.
is provided, and the polycrystalline silicon fuse 3 is connected to the wiring metal layer 7 via the connection hole 5 . A protective insulating film 8 is formed on the wiring metal layer 7 to protect the semiconductor integrated circuit device including the semiconductor fuse element from moisture or contamination.

In the semiconductor fuse element having the above structure, the silicon dioxide layer 2 is usually formed by a thermal oxidation process in an H ₂ -O ₂ atmosphere at about 900 to 1000°C. It is used for separating device regions of a device (not shown). Further, the polycrystalline silicon layer 3 which becomes the semiconductor fuse element is formed by a known low pressure vapor phase growth method, but in the growth process,
Alternatively, after growth, impurities such as phosphorus, boron, or arsenic are introduced into the layer, and the layer resistance is set to about 20 to 200 Ω/□. The interlayer insulating film 4 and the protective insulating film 8 are made of phosphorus-doped silicon dioxide or the like, and are formed by a well-known atmospheric vapor phase growth method. Further, the polycrystalline silicon fuse 3, connection hole 5, first opening 6, wiring metal layer 7, etc. are patterned by a known photolithography method. It goes without saying that most of these manufacturing steps are performed simultaneously with the formation of other circuit elements in the semiconductor integrated circuit device.

The first opening 6 is formed at the same time as the formation of the connecting hole 5 or in a separate process.
This is for removing a silicon dioxide film (not shown) formed when the surface of the polycrystalline silicon fuse 3 is oxidized by heat treatment during the manufacturing process of a semiconductor integrated circuit device. This is effective in reducing the applied voltage and current when the fuse element is blown.

In the semiconductor fuse element having the above structure, in order to facilitate fusing, the fusing portion 3a must be
It is necessary to reduce the voltage applied to other parts. That is,
The resistance of the wiring metal layer 7 from the voltage application point to the connection hole 5, the contact resistance in the connection hole 5, and the resistance of the connection part 3b from the connection hole 5 to the fusing part 3a are compared with the resistance of the fusing part 3a, and are determined to be sufficiently small. Must. Considering that the layer resistance of the wiring metal layer 7 is about 1/200 to 1/2000 of the layer resistance of the polycrystalline silicon fuse 3, in order to satisfy the above conditions, the opening area of the connection hole 5 must be In addition to reducing the contact resistance by appropriately increasing , the width l ₁ of the connection part 3b extending from the connection hole 5 to the fusing part 3a is made wider, and the length l ₂ is made shorter to reduce the resistance value at the connection part 3b. There is a need to.

However, the length l ₂ of the connecting portion 3b is
Since this is a margin for making a reliable electrical connection on
The solution was to widen l ₁ , and in the end,
This increases the size of the semiconductor fuse element.

Furthermore, when the semiconductor fuse element is blown, the energy of the fusion may cause cracks in the protective insulating film 8 located on the blown portion 3a. It is known that when a crack occurs, moisture, contaminants, etc. enter the semiconductor integrated circuit device through the crack and corrode the wiring metal layer 7, etc., leading to deterioration and damage to the device.

As a means to prevent the occurrence of this crack, as shown in FIG. 5, it has been proposed that a second opening 9 is provided in the protective insulating film 8 leading to the fusing part 3a, so that excess energy at the time of fusing is released to the outside. However, this case also has the following drawbacks. Needless to say, since the second opening 9 is formed regardless of whether the polycrystalline silicon fuse 3 is blown or not, development similar to the deterioration and damage caused by cracks described above occurs. That is, moisture, contaminants, etc. enter the semiconductor integrated circuit device through the second opening 9, and in this case, the electrical connection at the connection hole 5 closest to the second opening is deteriorated. . As a result of this deterioration, the unblown semiconductor fuse element behaves as if it were a blown semiconductor fuse element.

As mentioned above, regardless of the presence or absence of the second opening 9, a semiconductor integrated circuit device including the semiconductor fuse element 3 requires measures against moisture and contaminants. In this case, it is necessary to take measures not to place circuit elements in areas where cracks may occur, and when forming the second opening 9, the second opening 9 should be This results in an increase in unnecessary steps such as burying the opening 9 with an insulator or the like.

(Object of the invention) The object of the present invention is to eliminate the above-mentioned conventional drawbacks,
An object of the present invention is to provide a semiconductor fuse element that is highly reliable and easy to blow.

(Structure of the Invention) The semiconductor fuse element of the present invention includes a polycrystalline silicon fuse made of polycrystalline silicon containing phosphorus, boron, arsenic, etc., and composed of a fusing part and connecting parts located at both ends of the fusing part, and an interlayer insulating film extending over the crystalline silicon fuse; a connection hole provided in the interlayer insulating film reaching the connection portion; a first opening provided in the interlayer insulating film reaching the fusing portion; It consists of a wiring metal layer extending on an interlayer insulating film and connected to the polycrystalline silicon fuse via the connection hole, and a protective insulating film extending on the wiring metal layer, and the connection hole is connected to the polycrystalline silicon fuse through the connection hole. At least two connecting holes, a first connecting hole provided close to the first opening and extending from the connecting part to the fusing part, and a second connecting hole provided apart from the first opening. It is made up of several connection holes.

(Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIGS. 1a and 1b are a plan view and a sectional view, respectively, for explaining the structure of a semiconductor fuse element according to a first embodiment of the present invention.

As shown in FIGS. 1a and 1b, a silicon dioxide film 2 is formed on a single-crystal silicon substrate 1 by the same method as that shown in the conventional example, and a polycrystalline silicon layer 3, which will become a fuse element, is formed on the silicon dioxide film 2. Then, an interlayer insulating film 4 is formed on the polycrystalline silicon fuse 3. The polycrystalline silicon fuse has a fusing part 3a.
and connecting portions 3b located at both ends thereof. Next, a first connection hole 15a is formed in the interlayer insulating film 4 leading to the connection part 3b of the polycrystalline silicon fuse 3.
and a second connection hole 15b are formed, and a first opening 6 reaching the fusing portion 3a of the polycrystalline silicon fuse 3 is formed. Next, a wiring metal layer 7 is provided on the interlayer insulating film 4 by means similar to the method shown in the conventional example, and the polycrystalline silicon fuse 3 is connected through the first connection hole 15a and the second connection hole 15b. It is connected to an external circuit by a wiring metal layer 7. Next, a protective insulating film 8 is formed on the wiring metal layer 7.

A part of the first connection hole 15a is formed on the connection part 3b of the polycrystalline silicon fuse 3, the remaining part is formed on the fusion part 3a of the polycrystalline silicon fuse 3, and the second connection hole 15a is formed on the connection part 3b of the polycrystalline silicon fuse 3. The hole 15b is provided on the connecting portion 3b of the polycrystalline silicon fuse 3, spaced apart from the first opening 6 by 15 μm.
Further, the first opening 6 may be formed simultaneously with the first connection hole 15a and the second connection hole 15b, as shown in the conventional example, or may be formed in separate steps.

In the first embodiment of the present invention configured as described above, since the first connection hole 15a is provided over the fused portion 3a of the polycrystalline silicon fuse 3, the connection shown in the conventional example is There is no resistance in the connecting hole 3b leading from the hole 5 to the fusing part 3a, and substantially only the contact resistance in the connecting hole 15a is a concomitant that requires reduction with respect to the resistance of the fusing part 3a of the polycrystalline silicon fuse 3. becomes the resistance. This is clearly effective in reducing the voltage and current required to blow the polycrystalline silicon fuse 3, and is also effective in reducing the frequency of cracks by reducing the energy generated when blowing. be. Further, the second connection hole 15b is designed to compensate for the fact that the first connection hole 15a has a structure that does not have a margin for reliable electrical connection, as described in the conventional example. with the purpose of
This is provided to ensure reliable connection, and is provided at a distance of about 15 μm from the first opening 6.

FIG. 2 shows a second connecting hole 15
FIG. 3 is a diagram showing the results of an experiment conducted to determine the position of b. In the experiment, a semiconductor integrated circuit device sealed in a package made of resin such as epoxy was left for 300 hours at a temperature of 125° C., a humidity of 100%, and a pressure of 3 atmospheres. FIG. 2 shows the correlation between the defective rate at that time and the distance between the first opening 6 and the second connection hole 15b. 15b by 10 μm or more, the defective rate decreases dramatically, and it becomes 0 when the distance is about 12 μm or more.

FIG. 3 is a sectional view for explaining the structure of a semiconductor fuse element according to a second embodiment of the present invention. The second embodiment of the present invention is a semiconductor fuse element according to the first embodiment of the present invention, in which a second opening is formed in the protective insulating film 8 to reach above the fused portion 3a of the polycrystalline silicon fuse 3. A hole 9 is added, and the semiconductor fuse element other than this second hole 9 is the same as the semiconductor fuse element of the first embodiment of the present invention. The second opening 9 is formed in the protective insulating film 8 on the fused portion 3a of the polycrystalline silicon fuse 3, as shown in the conventional example.
This is to prevent cracks from occurring in the semiconductor fuse element, and as shown in the first embodiment of the present invention, it does not reduce the reliability of the semiconductor fuse element.

(Effects of the Invention) As described above in detail, the semiconductor fuse element of the present invention facilitates fusing by the first connecting hole extending over the blowing part of the polycrystalline silicon fuse, and by the second connecting hole. It becomes possible to improve reliability.

[Brief explanation of drawings]

Figures 1a and b are a plan view and a sectional view of the first embodiment of the present invention, and Figure 2 shows the relationship between the distance between the first opening and the second connecting hole and the defective rate in the embodiment of the present invention. The figure shown,
FIG. 3 is a sectional view of a second embodiment of the present invention, FIGS. 4a and 4b are a plan view and a sectional view of a conventional semiconductor fuse element, and FIG. 5 is a sectional view of another example of a conventional semiconductor fuse element. It is a diagram. DESCRIPTION OF SYMBOLS 1...Single crystal silicon substrate, 2...Silicon dioxide layer, 3...Polycrystalline silicon fuse, 3a...
... Fusing part, 3b... Connection part, 4... Interlayer insulating film,
5... Connection hole, 15a... First connection hole, 15b
...Second connection hole, 6...First opening, 7... Wiring metal layer, 8... Protective insulating film, 9... Second opening.

Claims (1)

[Claims] 1. A polycrystalline silicon fuse made of polycrystalline silicon containing phosphorus, boron, arsenic, etc., and consisting of a fusing part and connecting parts located at both ends of the fuse, and a polycrystalline silicon fuse on the polycrystalline silicon fuse. an interlayer insulating film extending on the interlayer insulating film, a connection hole provided in the interlayer insulating film and reaching the connection portion, a first opening provided in the interlayer insulating film and reaching the fusing portion, and a first opening provided on the interlayer insulating film reaching the melting portion; In a semiconductor fuse element comprising a wiring metal layer extending and connected to the polycrystalline silicon fuse via the connection hole, and a protective insulating film extending over the wiring metal layer, the connection hole is connected to the first polycrystalline silicon fuse. at least two connecting holes, a first connecting hole provided close to the opening and extending from the connecting part to the fusing part, and a second connecting hole provided apart from the first opening. A semiconductor fuse element characterized by comprising a connection hole. 2. The semiconductor fuse element according to claim 1, wherein the surface protection insulating film is provided with a second opening that reaches the fused portion of the polycrystalline silicon fuse.