JPH0936239A - Wiring cutting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wiring cutting method which can be applied to the cutting of various kinds of wiring composed of different materials and having different thicknesses and by which redundant wiring, etc., provided in an integrated circuit, such as the memory, etc., can be surely cut without giving any damage to an insulating film. SOLUTION: In a first laser beam irradiating process, a wiring material 6 is melted by irradiating the part to be cut of wiring with a first laser beam having a low peak value and a wide pulse width. In a second laser beam irradiating process, the molten wiring material 6 is vaporized by irradiating the molten material 6 with a second laser beam 10 having a high peak value and a narrow pulse width.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring cutting method for cutting a redundant wiring provided in an integrated circuit such as a memory with a laser beam.

[0002]

2. Description of the Related Art In an integrated circuit such as a RAM (Random Access Memory), a redundant circuit is generally provided, and when a defect is detected in a part of the circuit by chip inspection, the circuit of the defective part is detected. By switching to the redundant circuit, the reduction in product yield (acquisition rate) is suppressed. In the manufacturing process of an integrated circuit equipped with this kind of redundant circuit,
After the inspection of the chip, it is necessary to disconnect the wiring connected to the defective circuit or the wiring connected to the redundant circuit.

FIGS. 4A to 4C are sectional views showing a conventional wiring cutting method in the order of steps. In the figure, reference numeral 1 is an insulating film under the wiring, reference numeral 2 is a wiring made of polysilicon, and reference numeral 3 is an insulating film on the wiring. First, as shown in FIG. 4A, the laser beam 8 is applied to the portion of the wiring 2 to be cut. The laser light 8 passes through the insulating film 3 and reaches the wiring 2 to heat the wiring 2. As a result, FIG.
As shown in FIG. 4B, the wiring 2 in this portion is melted to become liquid molten polysilicon 4, and further, as shown in FIG. 4C, the molten polysilicon 4 is vaporized and the upper insulating film is formed. Three
Blow away. In this way, the cutting of the wiring is completed.

FIG. 5 is a diagram showing a pulse waveform of a laser beam used for cutting a wiring, in which the horizontal axis represents time and the vertical axis represents power (energy) of laser light.
In the figure, Pm is the peak value 1 maximum value, and Ph is Ph = (1 /
2) ・ Pm, t1 is the time to reach Ph at the time of rising, t2
Indicates the time to reach Ph at the fall. As shown in FIG. 10, the pulse waveform of the laser light shows a roughly normal distribution. The pulse width is represented by t2-t1.

Conventionally, when the thickness of the wiring is different, the Pm and pulse width of the laser light are adjusted to deal with this.

[0006]

By the way, in recent years, metal wiring such as Al or Al alloy (hereinafter simply referred to as "aluminum") has been used as a wiring material.
In the case of aluminum wiring, about 90% of the laser light is reflected, so the energy of the laser light is not sufficiently absorbed by the wiring. Therefore, in the case of the aluminum wiring, the power of the laser light is insufficient under the same laser light irradiation condition as in the case of the wiring made of polysilicon, and a cutting failure occurs.

For example, when the power of the laser light is small, about 90% of the laser light 8 is used as shown in FIG. 6 (a).
Is reflected on the surface of the aluminum wiring 5, and FIG.
As shown in (b), the upper portion of the wiring 5 melts to become molten aluminum 6, but the molten aluminum 6 in the upper portion vaporizes before the lower portion melts. At this time,
As shown in FIG. 6C, molten aluminum is scattered around and solidifies between the surrounding wirings, and a short circuit occurs due to the aluminum solidified material 7a, or the lower portion 7b of the wiring remains uncut. It will remain.

On the other hand, when the power of the laser light is large, about 90% of the laser light 8 is used as shown in FIG.
Is reflected on the surface of the aluminum wiring 5, but FIG.
As shown in (b), the laser light 8 melts to the lower side of the wiring to form molten aluminum 6 and heats the insulating films 1 and 3 to a high temperature. Then, as shown in FIG. 7C, when the molten aluminum 6 is vaporized, the upper insulating film 3 and the lower insulating film 1 are greatly damaged (cracks or the like).
give. The surrounding wiring may be cut due to the cracks in the insulating films 1 and 3.

In the conventional method, in the case of a wiring made of a material having a high reflectance such as an aluminum wiring, the lower and upper insulating films are damaged even if the crest value (Pm) of the laser light and the pulse width are adjusted. It is difficult to obtain an irradiation condition that can surely cut the wiring without giving a wire, and it is extremely difficult especially when the wiring has a large thickness. The present invention has been made in view of the above problems, and can be applied to the cutting of various wirings having different materials and thicknesses, and reliably cuts the wirings without damaging the insulating film. It is an object of the present invention to provide a wiring cutting method that can achieve

[0010]

[Means for Solving the Problems] The first object is to irradiate the portion of the wiring to be cut with the first laser light to heat the wiring material, and the first laser light irradiation step. A second laser beam irradiation step of vaporizing the wiring member by irradiating the portion heated in the irradiation step with a second laser beam having a power higher than that of the first laser beam. Achieved by the wiring cutting method,
Secondly, it is achieved by a wiring cutting method characterized by irradiating the second laser light within a few nanoseconds to a few tens of nanoseconds after irradiating the first laser light. In the first invention, the entire wiring is melted in the first laser light irradiation step, and the second laser light is irradiated before the portion melted in the second laser light irradiation step is not solidified. Thirdly, the pulse waveform of the second laser light is higher in crest value and shorter in pulse width than the pulse waveform of the first laser light. It is achieved by the wiring cutting method according to the first or second invention.

[0011]

In the present invention, the wiring to be cut is sequentially irradiated with the first and second laser beams. In this case,
Depending on the wiring to be cut, the peak value and pulse width of the first laser light, the peak value and pulse width of the second laser light, and the timing of irradiating the second laser light after the irradiation of the first laser light Etc., the optimum irradiation conditions can be obtained for the wirings of different materials and thicknesses, and the wirings are surely cut without damaging the insulating film below the wiring and the insulating film above the wiring. be able to.

For example, in the first laser light irradiation step, the wiring material is heated to leave most of the wiring material in the molten state, and the second laser light is applied within a few nanoseconds to a few tens of nanoseconds. By irradiating, the molten wiring material can be vaporized in a short time. This makes it possible to more reliably cut the wiring while avoiding damage to the insulating film. In order to do so, the first laser light having a low crest value and a long pulse width is used, and the second laser light having a high crest value and a short pulse width is used. Is preferred.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 (a) to 1 (c), FIG.
(A), (b) is sectional drawing which shows the wiring cutting method which concerns on the Example of this invention in process order. Further, FIG. 3 is a diagram showing a pulse waveform of laser light in the present embodiment.

As shown in FIG. 1A, the wiring 5 to be cut is, for example, an Al alloy (Au / Cu / T) formed on the insulating film 1.
i: thickness 900 nm), and the insulating film 3 is formed on the wiring 5. This insulating film 3 is
For example, an oxide film with a thickness of 1000 nm and a thickness of 500 n
It has a two-layer structure with a nitride film of m. In this embodiment, first, as shown in FIG. 1A, as the first laser beam irradiation step, the first laser beam 9 is irradiated to the portion of the wiring 5 to be cut. The pulse waveform of the laser light 9 at this time has a peak value of 0.3 μm as shown in FIG. 3, for example.
J and pulse width is 15 ns.

By irradiating this laser beam 9,
As shown in (b), the wiring material in the upper portion of the wiring 5 is melted to become molten aluminum 6, and as shown in FIG. 1 (c), the wiring material in the lower portion is also melted. In this case,
Since the peak value of the laser beam 9 is relatively low and the irradiation time is relatively long, the wiring material in the lower portion can be melted before the molten aluminum 6 in the upper portion of the wiring is vaporized.

Next, as shown in FIG. 2A, in the second laser beam irradiation step, the second laser beam 10 is irradiated. The pulse waveform of this laser light 10 is, for example, as shown in FIG.
As shown in, the peak value is 2.0 μJ and the pulse width is 3 nsec (which means nanosecond). In this case, since the power of the laser light 10 is relatively large and the irradiation time is short, the molten aluminum 6 can be vaporized while avoiding damage to the insulating films 1 and 3. When the molten aluminum 6 is vaporized, as shown in FIG.
As shown in (b), the upper insulating film 3 is blown off, and the cutting of the wiring is completed.

In this embodiment, the peak value and pulse width of the first laser light, the peak value and pulse width of the second laser light, the timing of irradiating the second laser light after the irradiation of the first laser light, etc. By appropriately setting the value according to the material and thickness of the wiring material, it is possible to avoid damaging the insulating films 1 and 3 and to reliably cut the wiring. In addition, the wiring material does not scatter around in a molten state, and short-circuiting of surrounding wiring can be prevented.
For example, after irradiating the first laser light 9, it is preferable to irradiate the second laser light at a timing within several nanoseconds to several tens of nanoseconds.

Furthermore, since the disconnection failure of the wiring can be prevented,
The effect of increasing the redundancy efficiency of the integrated circuit such as RAM and improving the product yield (acquisition rate) can be obtained. In addition, although the case of aluminum wiring has been described in the above-mentioned embodiments, the present invention is configured by laminating wirings made of various metals, alloys and polysilicon, and layers made of these materials in addition to aluminum wirings. It can be applied to cut wiring, etc.

[0019]

As described above, according to the present invention, since the wiring is cut by sequentially irradiating the first and second laser beams, the wiring material is made of a metal such as aluminum or an alloy. However, the insulating film can be reliably cut without damaging it. As a result, there is an effect that the product yield (acquisition rate) of integrated circuits such as RAM is improved.

[Brief description of drawings]

FIG. 1 is a sectional view (1) showing one step of a wiring cutting method according to an embodiment of the present invention.

FIG. 2 is a sectional view (No. 2) showing one step of the wiring cutting method according to the embodiment of the present invention.

FIG. 3 is a diagram showing a pulse waveform of a laser beam used in the wiring cutting method according to the example of the present invention.

FIG. 4 is a cross-sectional view showing one step of a wiring cutting method according to a conventional example.

FIG. 5 is a diagram showing a pulse waveform of a laser beam used in a wiring cutting method according to a conventional example.

FIG. 6 is a cross-sectional view for explaining a problem of a conventional example, which shows the occurrence of wiring disconnection failure when the power of laser light is small.

FIG. 7 is a cross-sectional view for explaining a problem in a conventional example, which shows the occurrence of wiring disconnection failure when the power of laser light is large.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Insulating film under wiring 2, 5 ... Wiring 3 ... Insulating film over wiring 4 ... Molten polysilicon 6 ... Molten aluminum 7a ... Aluminum coagulation 7b ... Lower part of the remaining wiring 8, 9, 10 ... Laser light

Claims (3)

[Claims] 1. A first laser light irradiation step of irradiating a portion of a wiring to be cut with a first laser light to heat a wiring material, and a portion heated in the first laser light irradiation step 1
And a second laser beam irradiation step of vaporizing the wiring member by irradiating a second laser beam having a power higher than that of the laser beam. 2. The wiring cutting method according to claim 1, wherein the second laser light is irradiated within a few nanoseconds to a few tens of nanoseconds after the irradiation with the first laser light. 3. The pulse waveform of the second laser light is:
The wiring cutting method according to claim 1 or 2, wherein a crest value is higher and a pulse width is shorter than a pulse waveform of the first laser light.