JPS6216544A - Fuse for redundant circuit - Google Patents

Abstract

PURPOSE:To enable the decision of the length of the cuttable region without relying on the radius of the laser beam and on the irradiation error thereof by a method wherein the device is provided with the fuse formed of the same material as that of the metal wiring and with the film member having a reflectance smaller than that of the fuse and formed on part of the fuse. CONSTITUTION:A field oxide film 2 is formed on an Si substrate 1, and after that, the desired first-layer poly Si gate wiring is formed. Then a PSG film 4 used as the second insulating film is formed on the field oxide film 2 by a CVD method and a fuse 3 for redundancy circuit Si formed thereon along with an Al wiring used as the second-layer wiring. Then a resist mask 9 is formed on the fuse 3, is removed over the length of l2. The exposing part of the fuse 3 is sputter etched and whole the is left to stand in warm water or in an atmosphere of steam and is oxidized, thus forming an Al oxide film 8 of the desired thickness; and moreover, the resist mask 9 is removed. In addition, the length l2 of the Al oxide film 8 shall be nearly equal to the length obtained with a laser beam 7A of radius r0.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuse for a redundant circuit, and more particularly to a fuse for a redundant circuit for a laser trimming method.

[Conventional technology]

FIG. 4 is a schematic diagram of a conventional redundant circuit fuse,
Figure 4(a) is a plan view, Figure 4(b) is Figure 4(a)
・A cross-sectional view taken along the line A-A is shown. In Figure 4, (1) is a silicon substrate, (2) is a field oxide film, (3) is a fuse for a redundant circuit formed by a polycrystalline silicon gate, (4) is a PSG film, (5A)
A method of manufacturing a conventional fuse for a redundant circuit using (5B) and (6) an initial contact hole, and (6) an aluminum film will be described. ``First, a field oxide film (2) is formed on a silicon substrate (1), and then a fuse (3) is formed on the field oxide film (2). Next, a PSG film (4) is grown on the fuse (3) by the CVD method, and the PSG film is selectively removed using a photoresist mask (not shown) to partially expose the fuse (3). Contact holes (5A) and (5Bl) are formed.Furthermore, contact holes (5A) and (5B1) are formed with wiring (6) in the part.

Next, the disconnection of the conventional redundant circuit fuse manufactured by the above manufacturing method will be explained with reference to FIG.

Fuse (3) has length l. The constricted portion (hereinafter referred to as a cuttable region) is irradiated with a laser beam through the PSG film (4) to cut it. A laser beam (7A) with an irradiation center C1 and a beam radius r0 is transmitted through a fuse (
When the fuse (3) is irradiated to the cuttable region of (3) (see Fig. 5(a)), the fuse (3) is lengthened and cut (
(See Figure 5(b)). Here, the cutting length of the fuse (3) is L+=2ro (1).If the irradiation error of the laser beam (7A) is ±do, then the laser beam (7A) is
The irradiation center of A) shifts within the range of C1 to C3. That is, the fuse (3) is irradiated with the laser light (7B) at the irradiation center C1 or the laser light (7C) at the irradiation center C1 (see FIG. 5<c>). Therefore, the cutting length L1 of the fuse (3) is x, s = 2 rO + 2 do (2). Since the cutting length must be shorter than the length of the cuttable area, 10, 10≧L1 = 2 (ro+do 1) (3) must hold true.Currently, the most accurate laser system Then, the beam radius r 6 =2 um s W
'A radiation error of 1.5 μm is guaranteed, so the minimum dimension of the length 10 of the cuttable area is In = 2 (2 + 1.5) = 7 μm (4), and the size cannot be reduced further than this. It turns out to be impossible.

[Problem that the invention seeks to solve]

In this way, in the conventional redundant circuit fuse, the length 10 of the cuttable area is determined by the irradiation accuracy of the laser system as shown in equation 6.

Furthermore, since aluminum as the material of the fuse (3) has a very high reflectance, even if it is directly irradiated with a laser beam, it will not absorb the energy of the laser beam (7A) and will not be cut. For this reason, as described above, the laser beam (7A) is irradiated through the PSG film (4). However, this may have an adverse effect on the reliability of the device, and the energy absorbed by the fuse (3) will not be uniform depending on the thickness of the PSG film (4).

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fuse for a redundant circuit that is not affected by the beam diameter and irradiation error of laser light and can be cut by direct irradiation with laser light. .

[Failure to solve the problem]

Therefore, in the present invention, a fuse formed of the same material as the metal wiring has a reflectance smaller than that of the fuse,
A redundant circuit fuse is constituted by a membrane member formed on a portion of the fuse.

[For production]

In the fuse for redundant circuits having the above configuration, when the membrane member is irradiated with laser light, only the membrane member is cut due to the difference in reflectance between the membrane member and the fuse even if the fuse is irradiated with the laser beam.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic diagram of a fuse for a redundant circuit according to the present invention, in which FIG. 1 (1) is a plan view and FIG.
A sectional view along line BB of a) is shown.

In FIG. 1, (1) is a silicon substrate, (2) is a field oxide film, (4) is a PSG film, (3) is used for a redundant circuit, and (8) is an aluminum oxide layer.

Next, a method for manufacturing a redundant circuit fuse according to the present invention will be explained with reference to FIG. First, the silicon substrate (
1) After forming a field oxide film (2) thereon, a desired first layer polycrystalline silicon gate wiring is formed. Then,
PSG% (4) as a second insulating film is formed on the field oxide film (2) by CVD method, and a fuse (
3) (see FIG. 2(a)). Next, a resist mask (9) is formed on the fuse (3), and the resist mask (9) is removed over a length l, as shown in FIG. 2(b).
), the exposed portion of the fuse (3) is sputter-etched, left in hot water or a steam atmosphere to oxidize to form an aluminum oxide film (8) of the desired thickness, and then coated with resist. Mask (9)
is removed to complete a redundant circuit fuse as shown in FIG.

Note that the length of the aluminum oxide film (8) is approximately equal to the length cut by the laser beam (7A) with a beam radius r0. Also, aluminum oxide film (8)
is 0 ion implantation method or 0. It may also be formed by a plasma processing method.

Next, the operation of the redundant circuit fuse according to the present invention will be explained with reference to FIG. The redundant circuit fuse according to the present invention manufactured by the above manufacturing method has a reflectance of 80 to 90 for laser light, whereas the fuse (3) whose constricted portion has a length of 1 mm has a reflectance of 80 to 90. , the reflectance of the aluminum oxide film (8) to laser light is 50~
I am 60 years old. Therefore, if the energy key of the laser beam is set to a size that cuts the aluminum oxide film (8) but does not cut the fuse (3), the cutting length of the fuse (3) LI B can be adjusted to the beam radius of the laser beam and the irradiation error. There is no influence, and the length of the aluminum oxide film (8) will not exceed 13. For example, if a laser beam (7A) with a beam radius r0 is irradiated so that the irradiation center C1 is approximately at the center of the aluminum oxide film (8) (Fig. 6 (1)
), and the portion where the aluminum oxide film (8) is formed is cut (see FIG. 6(b)). Furthermore, even if the irradiation center CI shifts to the left side of the aluminum oxide film (8) and the laser beam (7B) at the irradiation center C1 is irradiated (see No. 31ii4(e)), the formed portion of the aluminum oxide film (8) will be severed.

The length lx of the nine constricted portions of the fuse (6), that is, the length 11 of the cuttable area, is the length of the aluminum oxide film (8)! , and the mask alignment margin Δj between the resist mask (9) for forming the aluminum oxide film (8) and the fuse (6), 11=1. +2Δ1(5). Current photolithography technology uses aluminum oxide film (
8) Length Jt = 1.5 μm and mask alignment margin Δ! =
Since 0.5 μm is guaranteed, the length l of the cuttable area is It = 1.5 + 2X0.5 = 2.5 μm
(6), which is 4.5 μm smaller than the conventional 7 μm.

〔Effect of the invention〕

As explained above, according to the present invention, only the film member formed on the fuse is cut by irradiating the film member with a lower reflectance than the fuse with a laser beam.
The length of the cuttable area can be determined without depending on the beam radius of the laser beam or the irradiation error. Further, since the laser beam is directly irradiated onto the film member, the energy of the laser light absorbed by the film member does not change, and the reliability of the device is not adversely affected.

[Brief explanation of drawings]

Figure wJ1 is a schematic diagram of a redundant circuit fuse according to the present invention,
FIG. 2 is an explanatory diagram showing a method of manufacturing a fuse for a redundant circuit according to the present invention, FIG. 6 is an explanatory diagram showing the action of the fuse for a redundant circuit according to the present invention, and FIG. 4 is an explanatory diagram showing a method of manufacturing a fuse for a redundant circuit according to the present invention. The schematic diagram, FIG. 5, is an explanatory diagram showing disconnection of a conventional redundant circuit. In each figure, 1 is a silicon substrate, 2 is a field oxide film, and 6 is a silicon substrate.
4 is a fuse, 4 is a P2O film, and 8 is an aluminum oxide film. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (5)

[Claims] (1) In a fuse for a redundant circuit in which a fuse formed of the same material as the metal wiring is irradiated with a laser beam to cut the fuse, the fuse has a reflectance smaller than that of the fuse, and A fuse for a redundant circuit, characterized by comprising a membrane member formed in a portion. (2) The fuse for a redundant circuit according to claim 1, wherein the fuse is an aluminum film. (3) A fuse for a redundant circuit according to claim 1, wherein the film member is an aluminum oxide film. (4) The fuse for a redundant circuit according to claim 1, wherein the film member is an aluminum oxide film formed by O^+ ion implantation method. (5) The redundant circuit fuse according to claim 1, wherein the film member is an aluminum oxide film formed by O_2 plasma treatment.