JPH04300081A - Cutting method for fuse - Google Patents

Abstract

PURPOSE:To surely melt the fuse and to improve the yield of a repair by immersing a semiconductor memory cell into an electrolyte, connecting a fuse cut by a laser light to a positive electrode of a power source and electrolyzing it. CONSTITUTION:A fuse conductor 2 consists of Al, an Al alloy or titanium, etc., and it is covered with an insulating film, for instance, PSG. A semiconductor memory cell containing this fuse conductor 2 is immersed into a 2% oxalic acid of 20 deg.C temperature, an electrode pad of the fuse conductor 2 is connected to a positive electrode of a DC power source of 12V, a platinum electrode is connected to the electrode, and anodic oxidation is executed for five minutes. In such a way, the Al surface and slag 4 exposed in the opening part are oxidized, and an insulating oxide film 5 is formed. Accordingly, a failure memory cell can be insulated completely.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to semiconductor memory repair technology.

0002

2. Description of the Related Art Conventionally, as a repair technique for semiconductor memory, a defective memory cell is replaced with a spare memory cell. A redundant data line is provided in advance in parallel to the normal data line. When the normal data line becomes a defective data line, the circuit is switched from the defective data line to the redundant data line. This switching method is performed by irradiating a laser beam onto a conductor fuse connected in series to the defective data line to blow the fuse. FIG. 4(A) shows a cross-sectional view of the fuse. As is clear from the figure, the fuse connects the conductor wiring 2 provided on the substrate 1 and the wiring 2.
It consists of an insulating film 3 covering the top. When blowing the fuse, laser light is selectively irradiated from above the fuse to blow the insulating film and wiring.

0003

[Problem to be Solved by the Invention] In order to cut fuses connected in series with defective data lines, a conductive metal fuse such as aluminum is cut with a laser beam. Fuse metal that cannot be blown or melts and scatters from the cut surface fuses with the glassy insulating layer that covers it.
A slag is formed, and as shown in FIG. 4(B), this slag may be interposed between the cut wiring lines, resulting in defective cutting, and this is a cause of lowering the repair yield. SUMMARY OF THE INVENTION In view of these problems, it is an object of the present invention to ensure that the fuse blows out, thereby improving the repair yield.

0004

[Means for Solving the Problems] The above object is a method for cutting a fuse consisting of metal wiring provided on a substrate and an insulating film covering the metal wiring, in which energy rays are selectively applied to the fuse. irradiation to melt the metal wiring and insulating film and cutting the wiring, and then anodizing the metal wiring exposed in the opening made in the insulating film by the melting. The problem can be solved by a method for cutting a fuse, which is characterized by having the following characteristics.

[0005]

[Function] Even if, as in the conventional case, there is a defect in cutting the metal wiring of the fuse or the slag is present between the cut metal wiring, according to the present invention, such a defective cutting part and the slag are removed by anodic oxidation. Since it is insulated, the metal wiring can be cut reliably, which contributes to improving the repair yield.

[0006] By immersing the semiconductor memory cell in an electrolytic solution,
When a fuse cut by a laser beam is connected to the positive electrode of a power source and electrolyzed, the cut surface and the slag partially in contact with the cut surface are anodized to form an insulating oxide film. This makes it possible to completely insulate defective memory cells.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 shows a top view of a fuse. The fuse conductor 2 is made of, for example, aluminum, an aluminum-copper alloy, or titanium, and is connected to the electrode pad 7 through a wiring 6. The fuse conductor 2 is connected to an insulating film 3 such as PSG.
covered with. Note that the electrode pad 7 is not covered with the insulating film 1 because it is used for energization during anodic oxidation according to the present invention after cutting the fuse. FIG. 2 shows the portion 8 of the fuse conductor 2 to be cut.

FIG. 1 shows a process diagram of the fuse insulation method of the present invention. FIG. 1A corresponds to a cross-sectional view taken along line A-A' of the fuse in FIG. A fuse conducting wire 2 is provided on an insulating film 1, and an insulating film 3 is provided thereon. For example, the thickness of each layer is approximately 7000 Å for the fuse conductor 2, and approximately 1 μm for the insulating film 3.
It is m. In a conventional manner, using a 1.2 μJ YAG laser, the portion 8 of the fuse conductor 2 to be cut is approximately 5
When irradiated with a μm spot, as shown in FIG. 1B, first the upper PSG film is locally dissolved, and then the aluminum conductive wire 2 underneath is also dissolved, and the aluminum conductive wire 2 is cut. However, at this time, as shown in FIG. 1C, a slag 4 containing a mixture of aluminum and PSG may adhere between the cut aluminum and the conductive wire.

Note that FIG. 3 shows an enlarged partial plan view of the cut portion corresponding to FIG. 1(C). The fuse conductor 2 melts into a crater shape and is cut, but it mixes with the glassy substance of the insulating film 3 melted around the crater to form a slag 4. If this slug 4 is not connected to the left and right metal films, no cutting failure will occur, but if it protrudes from the recess and is connected to the left and right conductive films as shown in FIG. 1(B), a cutting failure will occur.

Next, according to the present invention, the semiconductor memory cell containing this fuse is immersed in a 2% oxalic acid solution at a temperature of 20° C., the electrode pad 7 of the conductive fuse 2 is connected to the positive terminal of a 12 V DC power supply, and the platinum Connect the cathode to the negative pole of the electrode,
Anodic oxidation was performed for 5 minutes. The fuse after anodizing is shown in the figure (
As shown in C), the aluminum surface and slag exposed in the opening were oxidized. This oxidized portion 5 is non-conductive, and circuit tests have shown that it is completely insulated.

[0011]

According to the present invention, a fuse cut using laser light can be completely insulated.

[Brief explanation of drawings]

FIG. 1 is a process diagram of a method for cutting a fuse according to the present invention.

FIG. 2 is a plan view of the fuse.

FIG. 3 is an enlarged partial plan view of a blown fuse.

FIG. 4 is a sectional view taken along line A-A' of the fuse in FIG.
A) shows the cross section before cutting, and (B) shows the cross section after cutting.

[Explanation of symbols]

1, 3...Insulating film 2...Fuse conductor wire 4...Slag 5...Anodized part 6...Wiring 7...Electrode pad 8... Part to be cut

Claims (1)

[Claims] 1. A method for cutting a fuse consisting of a metal wiring provided on a substrate and an insulating film covering the metal wiring, the method comprising: selectively irradiating the fuse with an energy beam; and a step of melting the insulating film and cutting the wiring, and then anodizing the metal wiring exposed in the opening made in the insulating film by the melting. Cutting method.