JP3299627B2 - Method for cutting fuse structure and apparatus for cutting fuse structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for cutting a fuse structure, and more particularly to a method for cutting a fuse using metal wiring as a fuse.

[0002]

2. Description of the Related Art Japanese Patent Laying-Open No. 58-60560 discloses a semiconductor memory in which when a defective portion is found in a test of a semiconductor device, the defective portion can be separated by a fuse structure. In this semiconductor memory, a plurality of redundant (Re
Dundancy) circuits are connected via a fuse structure, and defective portions are cut off and removed by the fuse structure. The fuse structure has a laminated film structure in which a polysilicon film is covered with a molybdenum film. The cutting of the fuse is performed as follows.

First, a laser beam whose energy has been adjusted to an appropriate level is irradiated. As a result, in the portion irradiated with the laser beam, the polysilicon film and the molybdenum film are heated and melted, react, and are turned into molybdenum silicide.
Since molybdenum silicide has a lower oxidation rate than molybdenum, thermal oxidation of the surface forms an oxide film thicker than molybdenum silicide on the surface of molybdenum.

Next, molybdenum oxide and silicon oxide are selectively etched by molybdenum silicide by using an etching method having a low etching rate (for example, chemical dry etching).
Blow the fuse.

As described above, by cutting a fuse, a defective portion can be deleted, and a decrease in yield accompanying high integration of a semiconductor device can be compensated.

Particularly, in this method, the fuse is cut not by a laser beam but by melting, so that the output of the laser beam can be suppressed. As a result, the thermal effect on the peripheral elements of the fuse can be reduced.

[0007]

However, in the above-described fuse structure, there is a problem that the step of cutting the fuse becomes complicated because it is necessary to use the etching together.

Further, in this method, in order to form a fuse structure, it is necessary to wire a polysilicon film having excellent cutting characteristics by a laser beam. Therefore, in a semiconductor device that does not use a polysilicon film as a structure, it is necessary to form a polysilicon film only to form the fuse structure.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and an apparatus for cutting a fuse structure, which can solve the above-described problems and can surely cut the fuse structure without complicating the manufacturing process.

[0010]

A method for cutting a fuse structure according to claim 1 is a method for cutting a fuse structure having the following a1) to a3), wherein a1) a substrate, and a2) a portion to be cut. A3) a coating film that covers the metal wiring; B) a first irradiation step of irradiating a laser beam to a portion of the metal wiring to be cut; C) the first metal wiring A second irradiation step of irradiating a laser beam having a beam size larger than that of the first irradiation step so as to include a region irradiated with the laser beam in the irradiation step.

According to a second aspect of the present invention, there is provided an apparatus for cutting a fuse structure according to the first aspect of the present invention.
A first optical unit that irradiates a laser beam having a first beam size to perform the first irradiation step, and a second optical unit that irradiates a laser beam having a beam size larger than the first beam size to perform the second irradiation step. Optical means.

[0012]

In the method for cutting a fuse structure according to the first aspect, a laser beam is applied to a portion of the metal wiring to be cut in the first irradiation step. Here, the coating film covers the metal wiring. Therefore, when the energy of the laser beam is applied to the metal wiring, the metal wiring sublimes in the coating film, thereby causing volume expansion, and the metal wiring ruptures and scatters together with the coating film. As a result, the metal wiring is almost disconnected.

In the second irradiation step, a laser beam having a beam size larger than that of the first irradiation step is irradiated so as to include the region irradiated with the laser beam in the first irradiation step. Thereby, even if there is a metal piece remaining in the first irradiation step, this metal piece sublimes. In this way, the metal wiring can be completely cut by a total of two laser irradiations.

According to a second aspect of the present invention, the first optical means performs the first irradiation step by irradiating a laser beam having the first beam size. The second optical unit performs the second irradiation step by irradiating a laser beam having a beam size larger than the first beam size. As described above, since two optical units are provided, the time for changing the beam size is not required, and the fuse structure can be quickly cut.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for cutting a fuse structure according to an embodiment of the present invention will be described with reference to the drawings. 3 and 4
FIG. 3 is a diagram showing a method of manufacturing a fuse structure to be cut using the present invention. This fuse structure is manufactured together with a bipolar transistor during an LSI manufacturing process. That is, a fuse structure is formed in the fuse structure formation region H1, and a bipolar transistor is formed in the transistor formation region T1.

First, as shown in FIG. 3, arsenic is diffused on a p-type silicon substrate 2 as a substrate using an oxide film (not shown) as a mask to form an n ^{+ -type} diffusion layer 4. .
Further, an n-type silicon layer 6 is formed on the upper surface of the p-type silicon substrate 2 by epitaxial growth.

Next, after forming a thermal oxide film (not shown) on the wafer surface to form an opening, n-type and p-type impurities are sequentially diffused to form an n ^{+ -type} diffusion layer 8 and a p ^{+ -type} impurity. The diffusion layer 10 is formed. The p ^{+ type} diffusion layer 10 is an isolation diffusion layer for electrically isolating the transistors on the LSI chip.

After the thermal oxide film on the wafer surface is removed by etching, the wafer surface is thermally oxidized again to form an oxide insulating film 12. Boron is ion-implanted into a base portion of the transistor. By diffusing this boron ion, the p ⁺ -type external base 14 and the p ^--type active base
Form 16. p ^- the oxide insulating film 12 on the oxide insulating film 12 and the n ⁺ type diffusion layer 8 on the form the active base 16 is provided an opening to diffuse the phosphorus. Thus, p ^- forms the active base 16
An n ⁺ -type emitter 18 is formed therein.

Thereafter, aluminum wiring is provided between the elements. First, as shown in FIG. 4, the entire surface of the wafer including the fuse structure formation region H1 is covered with the insulating film 20 by the CVD method. next,
Using a resist, the insulating film 20 is selectively etched,
A contact hole for taking out wiring is provided.

Further, aluminum is sputtered on the entire surface of the structure including the fuse structure formation region H1 to form a wiring pattern of the aluminum wiring 22 having a thickness of 0.5 μm. In order to protect the aluminum wiring 22, a silicon nitride film is deposited to a thickness of 1 μm by a CVD method to form a passivation film 24.

Through the above steps, a bipolar transistor is formed in the transistor forming region T1. At the same time, a fuse structure having an aluminum wiring 22 as a metal wiring and a passivation film 24 as a coating film is formed in the fuse structure forming region H1.

When the manufacturing process of the semiconductor device approaches the end, the function and performance of the semiconductor device are tested. As a result of the test, if the numerical value of the target electrical characteristic item is out of the range of the target specification value, the fuse structure is cut and the numerical value of the electrical characteristic item is adjusted. For example, in a circuit as shown in FIG.
By cutting the fuses F1 to F4 connected in parallel with, the fv distribution (frequency-potential distribution) is adjusted so as to be within the range of the target specification value.

Next, a method of cutting the fuse structure will be described with reference to FIGS. FIG. 1A is a top view showing a laser beam irradiation site in the fuse structure. FIG. 1B is a cross-sectional view (n-type silicon layer 6, oxide insulating film 12, interlayer insulating film 2) of the fuse structure taken along the direction of line AA in FIG. 1A (hereinafter referred to as "fuse width direction").
0, aluminum wiring 22, and passivation film 24). FIG. 4 is a sectional view of the fuse structure taken along line BB in FIG. 1A.

First, a first irradiation, which is a first irradiation step, is performed to cut the aluminum wiring 22 in the fuse width direction. The coordinates of the irradiation are set at the center P1 in the fuse width direction. Regarding the energy, beam size and beam pulse of the laser beam, the aluminum wiring 22 is damaged over substantially the entire width (width L1) around the coordinate P1, and the n-type silicon layer 6 and the oxide insulating film 12 are damaged by the laser beam. The irradiation area S1, the intensity, and the like are adjusted so as not to reach.

In the present embodiment, LR2F manufactured by NIKON is used as a laser repair device, and in the first irradiation step, the laser is Nd-
YLF semiconductor laser, wavelength 1047 nm, energy intensity 4-8 μJ, beam spot 6-12 μm
φ. The width of the fuse used was 4 μm or less, and the thickness was 0.5 μm to 1.5 μm.

Here, the passivation film 24 covers the aluminum wiring 22. Accordingly, when the energy of the laser beam is applied to the aluminum wiring 22 and the aluminum sublimates in the passivation film 24, the sublimated aluminum expands in volume, and the aluminum wiring 22 ruptures and scatters together with the passivation film 24. Thus, in the laser beam irradiation area S1, the fuse is almost disconnected as shown in FIG. 2B. On the other hand, when the passivation film 24 is not provided, by irradiating the fuse structure of FIG. 2A with a laser beam from above, the energy of the laser beam is given to the aluminum wiring 22 and aluminum is instantaneously sublimated. However, the sublimated aluminum liquefies in the vicinity of the cut portion by being cooled, and then solidifies. As a result, the fuse is not blown.

Although the theoretical support of the passivation film 24 is not always clear, the inventors have considered as described above.

By the way, in the laser beam irradiation area, a part of the aluminum ruptured and scattered together with the passivation film 24 may be cooled and solidified in the vicinity of the cut portion to form an aluminum piece 26 (see FIG. 2). 2B). With such an aluminum piece 26, the fuse may not be completely disconnected depending on the state of adhesion. In this embodiment, assuming such a situation, the second laser irradiation is continuously performed. In the present embodiment, the second laser irradiation corresponds to a second irradiation step.

FIGS. 1A and 2C show the second laser irradiation.
As shown in (2), a laser beam having a larger beam size than the first irradiation step is irradiated so as to include the irradiation area S1 (irradiation area S2). Thereby, even if there is a metal piece remaining in the first irradiation step, the metal piece can be sublimated. In this way, the metal wiring can be completely cut by a total of two laser irradiations.

Although it is possible to perform the second irradiation step by shifting the irradiation point of the irradiation area, a moving time for the second irradiation step is required. On the other hand, by irradiating a laser beam having a beam size larger than that of the first irradiation step in the second irradiation step, the moving time becomes unnecessary.

It is necessary to change the beam size in each of the first irradiation step and the second irradiation step. Normally, the beam size is changed using an aperture. But,
Changing the beam size using the aperture requires time, and thus the cutting process takes time. In order to solve such a problem, a cutting device 50 as shown in FIG. 6 may be used.

The cutting device 50 has two types of optical systems. The first optical system 30, which is the first optical means, includes a laser 3
2, mirrors 33 and 35, aperture 34, optics 36, dichroic mirror 37, and objective lens 38. The second optical system 40 as the second optical means includes a laser 42, mirrors 43 and 45, an aperture 44, an optics 46, and a dichroic mirror 47.
And an objective lens 48. The table 53 is an XYZ table, and a semiconductor device 55 having a fuse structure to be cut is placed on the table 53.

The first optical system 30 and the second optical system 40 have different beam sizes, and in this embodiment, the second optical system 4
The beam size at 0 is adjusted in advance to be larger than the beam size at the first optical system 30, and after the first irradiation step is performed by the first optical system 30,
The second irradiation step is performed by the second optical system 30.

By providing two independent optical systems in this way, it is not necessary to adjust the beam size by means of the aperture, so that the interval between the first irradiation step and the second irradiation step can be shortened. Thereby, the cutting time can be shortened.

In this embodiment, a bipolar transistor is formed as a semiconductor device connected to the fuse structure. However, another semiconductor device may be formed. Also, by connecting circuit elements such as capacitors and resistors with the fuse structure,
The present invention may be used when making adjustments to electrical standards.

In this embodiment, aluminum wiring is used as the metal wiring. Alternatively, tungsten may be used.
AlSiCu, AlCu or the like may be used as the wiring.

Further, in this embodiment, a silicon nitride film is used as a coating film for coating the metal wiring, but a silicon oxide film or the like may be used.

The thicknesses of the metal wiring and the coating film and the shapes of the areas S1 and S2 formed by the laser beam are not limited to the above embodiment.

Although the laser beam is irradiated twice, the number of times of irradiation may be three or more.

In this embodiment, in the first irradiation, the cutting is performed over the entire width (width L1) of the aluminum wiring 22, but a part of the entire width of the aluminum wiring 22 is cut at the first time. Alternatively, it may be removed together with the residue in the second and subsequent irradiations.

In the fuse structure according to the present invention, the metal wiring is formed of aluminum, an aluminum alloy or tungsten. For this reason, the fuse structure can be formed of a metal material used in a manufacturing process of a semiconductor device such as a semiconductor memory and a circuit element such as a capacitor and a resistor. Therefore, it is not necessary to prepare another material only for forming the fuse structure, and the metal wiring can be easily formed.

In the fuse structure according to the present invention, since a silicon oxide film or a silicon nitride film is used for the coating film,
A covering film can be formed using a passivation film or a silicon oxide film used in a manufacturing process of a semiconductor device such as a semiconductor memory. Therefore, a coating film can be easily formed.

[0043]

According to the first aspect of the present invention, the method for cutting a fuse structure includes a first irradiation step of irradiating a cut portion of the metal wiring with a laser beam, and a region irradiated with the laser beam in the first irradiation step. As described above, the method includes the second irradiation step of irradiating a laser beam having a larger beam size than the first irradiation step. By the second irradiation step ST, even if there is a metal piece remaining in the first irradiation step, the metal piece can be sublimated and the metal wiring can be completely cut. Thus, it is possible to provide a method for cutting the fuse structure that can be reliably cut without complicating the manufacturing process.

According to a second aspect of the present invention, there is provided a fuse structure cutting apparatus comprising:
A first optical unit that irradiates a laser beam having a beam size to perform the first irradiation step, and a second optical unit that irradiates a laser beam having a beam size larger than the first beam size to perform the second irradiation step Means. As described above, since two optical units are provided, the time for changing the beam size is not required, and the fuse structure can be rapidly cut. This makes it possible to provide a cutting device having a fuse structure that can surely be cut without complicating the manufacturing process.

[Brief description of the drawings]

FIG. 1 is a view for explaining a portion irradiated with a laser beam in a method for cutting a fuse structure according to the present invention.

FIG. 2 is a diagram for explaining a method of cutting a fuse structure by a laser beam.

FIG. 3 is a view illustrating a method of manufacturing a fuse structure according to an embodiment of the present invention.

FIG. 4 is a view illustrating a method of manufacturing a fuse structure according to an embodiment of the present invention.

FIG. 5 is a circuit diagram illustrating an example of a semiconductor device having a fuse structure.

FIG. 6 is a schematic view of a configuration of a cutting device 50 used in a method for cutting a fuse structure according to the present invention.

[Explanation of symbols]

 6, a semiconductor substrate 22, an aluminum wiring 24, a passivation film 30, a first optical system 40, a second optical system

Claims (2)

(57) [Claims] 1. A method for cutting a fuse structure having the following a1) to a3): a1) a substrate, a2) a metal wiring having a portion to be cut and formed above the substrate, a3) A coating film for coating the metal wiring; B) a first irradiation step of irradiating a laser beam to a portion to be cut of the metal wiring; and C) the first irradiation step so as to include a region irradiated with the laser beam in the first irradiation step. A second irradiation step of irradiating a laser beam having a larger beam size than the first irradiation step. 2. An apparatus for use in the method for cutting a fuse structure according to claim 1, wherein said first optical means executes a first irradiation step by irradiating a laser beam having a first beam size; A second optical unit that irradiates a laser beam having a larger beam size to execute the second irradiation step.