JPS59209499A - Method and device for cutting metallic wiring or the like by laser beam - Google Patents

Abstract

PURPOSE:To cut quickly and exactly the wiring of an integrated circuit by subjecting said circuit to preliminary working in the range narrower than the cutting region of said wiring then removing the wiring in the remaining cutting region by a laser beam having the beam intensity at which no damages are given to the region under the wiring. CONSTITUTION:The cutting position of a sample 19 on an X-Y table 20 is determined by the inputs of memories 24- and control devices 23 and the laser having a specified intensity is generated by a power source 12 and an oscillator 11. The size and shape of the beam are controlled by the X-Y slit 14 of an optical processing means 16 and the laser light is irradiated by an objective lens 17. The beam 4 is irradiated in the range narrower than the cutting region of the Al wiring 3 on the silicon oxide film 2 of a substrate 1 to evaporate and scatter a part of the wiring 3. The wiring 3' for which the min. energy for working is decreased is cut by the laser having the smaller beam intensity. The metallic wiring is thus quickly and cleanly cut without deteriorating the circuit characteristics.

Description

[Detailed Description of the Invention] [Technical field to which the invention pertains] The present invention relates to a method and apparatus for cutting metal wiring, etc., using a laser beam, and particularly to an improved method and apparatus for cutting metal wiring, etc., such as integrated circuits, using a laser beam. Regarding the device.

[Prior art]

BACKGROUND OF THE INVENTION In integrated circuits (ICs), especially large-scale integrated circuits (LSIs), there are many situations in which it is necessary to check the characteristics of each part after completion, and especially to immediately investigate the cause of a failure when it occurs. In this case, a rough check of the circuit block can be made using an external terminal, and a rough estimate can be made, but it is necessary to disconnect the wiring to confirm the location of the failure within the block and its contents.

Usually, at least a few cuts are required, but sometimes as many as ten or more cuts are required. The location of this cut is determined by comparing the drawing with the pellet wiring under the enlarged sharpener, but determining the location is difficult and takes a lot of time.

In particular, the difficulty is increasing as the density of integrated circuits increases and the pattern becomes finer.

On the other hand, in order to quickly find out the cause of the failure, it is an emergency M that does not allow any delay from the viewpoint of production or user measures.In the past, various methods have been used to disconnect integrated circuit wiring. The simplest method is the needle cutting method, which uses a metal needle to mechanically destroy the wiring and the insulating film covering it. On the other hand, it has the advantage of being easy to use, but when it comes to fine patterns such as those used in recent ICs, there are problems in that the cutting of the fine pattern part is similar to that of 9, and it is difficult to cut cleanly, and furthermore, this method requires skill.

In addition to this, there is also the condenser method, in which needles are placed at both ends of the cut point, and the electricity charged in a capacitor is applied to the needles to discharge the entire wire, the PR method is used to etch the cut point using photoresist, and the spot exposure method uses positive type photoresist. There are laws, etc., but what about the process? J! Both have their advantages and disadvantages, such as being rough or difficult to cut fine patterns.
There are many problems in cutting without damaging the IC characteristics.

Cutting wiring with laser beams has recently been considered, and cutting with laser beams is easy.

It has many advantages, such as being able to cut fine patterns, making clean cuts, requiring no skill, being able to easily cut a large number of cuts, and being easy to automate.

However, when cutting aluminum interconnects, polysilicon resistors, platinum silicide interconnects, etc. using conventional laser beam equipment, for example, as shown in Figure 1, the iron surface of an integrated circuit is A silicon oxide film 2 is formed on the surface of the silicon oxide film 1, and an aluminum wiring 375 is formed on the silicon oxide film 2.

A silicon oxide film 2' is covered thereon.

In order to reliably cut this wiring, it was necessary to apply a laser beam with a higher energy than the minimum processing energy for aluminum to the outside of the aluminum wiring, as shown in the figure.

However, when irradiating the beam in this way, the outside of the aluminum warehouse will be directly irradiated with the laser beam,
Moreover, since the silicon oxide film is easily permeable, the semiconductor substrate under the circle is damaged.

And the Thevis formed there will be damaged.

In addition, if the intensity of the beam is strong, the aluminum will evaporate and the wiring will be easily cut, but the effect will be downward and damage the devices below.

This may deteriorate the characteristics or cause limited IThk breakdown, causing the aluminum wiring to short-circuit with the underlying silicon. On the other hand, if the beam intensity was weak, the aluminum would not evaporate at all, or it would melt and then return to metal aluminum.

Therefore, in actual cutting work, it was common to gradually increase the beam strength starting from a weak beam and cut while checking.

As mentioned above, the method of cutting aluminum wiring using a laser beam has the potential to cut fine patterns more quickly and cleanly than other methods, but it has the problems mentioned above. Solving the problem has become a priority issue, and there is a desire to develop a device for cutting metal wiring and the like using a laser beam that is suitable for this cutting method.

[Purpose of the invention]

The present invention has been made to address the above-mentioned problems, and its purpose is to quickly conduct wiring for integrated circuits, especially fine pattern wiring, without degrading or damaging the characteristics of the integrated circuit. Another object of the present invention is to provide a method for cutting metal wiring, etc. using a laser beam that cuts cleanly, and an apparatus for the same.

[Structure of the invention]

The first invention includes a step 41 in which preliminary processing is performed in an area narrower than the cut area of the wiring, such as metal wiring of an integrated circuit, and a process in which the wiring in the cut area remaining in the il step is not damaged in the area under the wiring. A method for cutting metal wiring, etc. using a laser beam, characterized in that it includes a second step of removing with a laser beam of a predetermined beam intensity of 5.

In addition, the second invention provides a laser emitter equipped with a power source that adjusts the intensity of the laser beam, an expander, and a slit driver to freely control the shape and size of the beam.
An optical adjustment means including an X-Y slit, a dichroic mirror, etc. that can be used for 111 hours, an objective lens system means that can change the depth of focus, an X-Y table on which the sample is placed and fixed,
A device for cutting metal wiring, etc. using a laser beam is characterized in that it includes a control means for controlling a laser power source, a slit driver, and an XY table, and a microcomputer including these control means.

[Principle and operation of the invention]

The principle of the present invention is that materials that are easily processed by laser beams are those that easily absorb laser beams.

The fact is that materials that are difficult to process are materials that are difficult to absorb laser radiation. Second, even if the material is the same, the minimum energy required for processing will vary depending on the surface condition. FIG. 2 is a characteristic diagram showing a situation in which the minimum energy required for processing differs depending on the surface state of the material to be processed. In the figure, the horizontal axis indicates the laser power, and the vertical axis does not indicate the degree of machining, that is, the depth of machining, the size of machining, etc. A song 1i
it4 indicates the relationship between the two. In other words, even if the interest rate is the same, if the surface state is different, for example, a1+ a2+ "3+
34 and the minimum energy required for processing changes. In other words, the ease of laser absorption is a 1) a 2) a s>
a 4 and the laser power at that time is ”
1+E2+" 3+E4. By creating a surface condition that facilitates laser absorption, the minimum processing energy can be lowered. If the minimum energy required for processing is reduced, there will be no damage to the wiring cutting area. Fig. 3 is a principle explanatory diagram showing the basic configuration of the present invention. In the figure, the horizontal axis and the vertical axis indicate the laser power and processing degree, respectively. Eight curves are used for wiring. material.

The relationship between the minimum energy required for processing a semiconductor substrate material and the zero curve layer is shown. In other words, if the wiring material is pre-processed to make it easier to absorb the laser beam, the initial minimum processing energy for the wiring in the normal state was Eill, which corresponds to curve b2, but by performing the first preliminary processing, the minimum processing energy is reduced. indicates that it has moved to Ell, which corresponds to bl. It also shows that the semiconductor substrate material has a minimum processing energy of E1□, which corresponds to C1 of the C curve.

Therefore, the first preliminary processing requires an energy of E13 or more, so if processing is performed with an energy equivalent to t2, the wiring material will evaporate or melt and the film thickness will become thinner, but the laser absorption will improve, and as a result, the first After the preliminary machining in step 1, the minimum machining energy is E1□, so in the second machining step E1
Thicker than □ and smaller than F'l□ For example, if processed with a laser beam with an energy corresponding to tl, the interconnected material can be easily broken, and this energy is smaller than the minimum processing energy EI2 of the semiconductor substrate material. Note that in the first preliminary processing, the processing energy is greater than the minimum processing energy on the semiconductor substrate 1, so that no damage is caused to the semiconductor substrate 1. Therefore, the wiring pattern in the area irradiated with the laser beam remains. It is preferable to cancel it. In addition, it is desirable to process the wiring material in a state where the minimum processing energy is lower than that of the underlying material, but
It goes without saying that even if the situation shown in the figure does not occur, it is possible to break the wiring with less damage to the underlying material.

It is clear that the preliminary processing may be carried out by any method that makes it easier to absorb laser light without using laser light.

〔Example〕

The present invention will be described in detail below based on Examples. FIGS. 4(a) to 4(c) are process sectional views showing a method for cutting an integrated circuit arrangement according to a first embodiment of the first invention.

In FIG. 4(a), a semiconductor element is formed on a semiconductor substrate 1 (the semiconductor element is not shown), an aluminum wiring 3 is formed on a silicon oxide film 2 formed on the surface of the semiconductor element, and an aluminum wiring 3 is formed on the silicon oxide film 2 formed on the surface of the semiconductor element. A silicon oxide film 2' is formed. In order to cut the wiring of this integrated circuit, first, as a first preliminary processing, a laser power higher than the minimum processing energy of aluminum is used, and aluminum Be4'J
The laser beam 4 is applied to an area shorter than the width and cutting length, that is, narrower than the cutting area. If this happens, please refer to Figure 4 (b)
), when the laser power is high in the area irradiated with the laser beam, part of it evaporates and part of it scatters, and the surface of the aluminum wiring becomes discolored or uneven, making it easier to absorb the laser beam. becomes. 3' indicates the thinned part, and 3" indicates the remaining peripheral aluminum wiring. Also, when the laser power is a little low, Fig. 4 (C
), it partially melts, and as shown in 3'', it changes color or changes in quality, making it easier to absorb the laser power.

Therefore, the minimum machining energy at the cutting location is smaller than before machining. In the second removal step, even if the laser beam intensity is lower than that in the first preliminary processing, the aluminum in the remaining disconnection region can be easily removed if the laser beam intensity is greater than the minimum energy for processing the remaining aluminum wiring.
In this first embodiment, since the relationship shown in FIG. 3 described in the explanation of the principle holds true, the wiring can be quickly and precisely cut off without damaging the integrated circuit.

Note that the shape and size of the laser beam used in the second step is such that the aluminum pH in the cut area can be easily removed if it is irradiated with a laser beam of a size that covers the cut area of the aluminum wiring and does not extend beyond the wiring area. Alternatively, a small beam may be moved instead of the large beam to remove the aluminum in the area of the break.

In addition, in processing by laser beam irradiation, the processing depth is related to the focal depth of the beam, and a beam with a shallow focal depth is better for shallow processing. Therefore, if a beam with a shallow focal depth is used in the first preliminary processing, it will damage the substrate area. You can achieve your goals without giving away.

Furthermore, aluminum wiring and the like have a high beam reflectance and a high thermal conductivity, whereas a dielectric material has a low beam reflectance and a low thermal conductivity. Therefore, since adult organisms are easily damaged by the beam, to prevent this, it is recommended to use a beam with a short pulse width, which is especially effective when applied to the second removal step.

FIGS. 5(a) and 5(b) are process explanatory diagrams showing a method for cutting metal wiring, etc. using a laser beam according to a second embodiment of the invention of the present invention. In the figure, the symbols of each part are as shown in Figure 4 (a
) to (C), although the aluminum wiring 3 formed on the silicon oxide film 2 is covered with the silicon oxide film 2', in this embodiment, a tungsten needle is applied to a part of the cutting location to determine the cutting width. The wiring is rubbed within a narrower range without damaging the underlying silicon oxide film 2, thereby mechanically scratching the aluminum wiring as the first preliminary processing. Fifth
Figure (b) is a cross-sectional view seen from a direction perpendicular to the direction in which the tungsten needle 5 is moved, and a in the figure is the cutting area. Since the minimum processing energy for the region subjected to such first processing is reduced, processing can be performed using a weak beam intensity that does not damage the base material after the preliminary processing. Therefore, the wiring in area a can be easily removed by irradiating the aluminum in the remaining processing area with a beam of low beam intensity all at once or by moving a small beam.

Figure 6 (al) and (b) are the third fruit M1 of the invention of this Eki 1.
FIG. 3 is a process explanatory diagram showing a method of cutting metal wiring and the like using a laser beam according to an example. In FIG. 6(a), a hole 6 is made inside the cutting area of the metal placement line 3 using a tungsten needle. By performing such pre-processing, the same effects as in the second embodiment shown in FIGS. If you use 1M, you can easily cut the desired forest.

7 is the size of the beam at the time of batch cutting. The ease of cutting by making scratches in this way is considered to be a result of increasing heat absorption and decreasing heat dissipation in the cutting area. Note that unlike the conventional method using a tungsten needle, the method of making mechanical scratches does not require cutting all the parts, so it is easy to operate and relatively easy to apply to fine patterns.

In the above embodiments, as the first preliminary processing, a method is used in which laser beam irradiation is used to reduce the film thickness, deterioration, and discoloration of the aluminum coating in an area narrower than the cutting area to reduce the minimum processing energy, and to reduce the minimum processing energy. Although we have explained the method of reducing the minimum machining energy by giving do not have.

Next, the apparatus for cutting metal wiring using a laser beam, which is suitable for carrying out the method for cutting metal wiring using a laser beam, will be described with reference to page 1 of the first page of this publication. 7th
The figure is a block diagram of a cutting device according to an embodiment of the invention of this publication. In the figure, 11 is a laser oscillator and 12 is a laser 1 source. The intensity of the laser beam can be easily adjusted by changing the pressure applied to the flash lamp of the laser oscillator. The roll of this ridge pressure (+11 is 1llll94+) by a controller 23 connected to the laser power source 12, and this control can be automated using the memory 24. The light generated by the laser oscillator is An expander 131 is adjusted according to the X-Y slit 14, dichroic mirror 15, etc. that determine the size and shape of the laser beam, which are important for implementing the present invention, and the laser beam 18 is projected onto the processed wiring sample 19 by the objective lens system 17. The sample 19 is fixed on an X-Y table 2°0,
The cutting point of the wiring Iβ is set to X,
The Y table will move and be displayed.

Further, the X-Y slit that determines the shape and size of the laser beam can be controlled by a slit driver 21 controlled by a memory 24' and a controller 23'.

Next, a method of carrying out the cutting method shown in FIGS. 4 (fan, (b), fc) using the cutting device shown in FIG. 6fj7 will be explained.

First, the sample shown in FIG. 4(a) is placed on the XY table 2o. The location and order of the Caloes are stored in memory 2 in advance.
4". Based on this input result, the X-Y table 2o is controlled and the first cutting position of the sample 19 appears. Next, the laser beam intensity condition determined by the wiring (・1・The controller 23 is driven by the input memory 24, adjusts the laser 1 source 12, and generates a laser beam of a specified intensity from the oscillator 11.This laser beam is adjusted by the optical processing means 16. In particular, X/Y By passing through the slit, a beam 4 is formed which is smaller than the area determined by the wiring width and cutting length as shown in Fig. 4(a).The sample is irradiated with this laser beam whose intensity and shape are adjusted through the objective lens system. Since this laser beam has an intensity higher than the minimum machining energy determined in advance by experiment, it easily scatters aluminum, and by thinning the film or melting it, light absorption can be increased. If the beam is irradiated in this state, there is a possibility that the underlying material will be damaged, but since the aluminum is not completely removed, the underlying material will not be affected by this.

The situation is shown in FIG. 4(b). Here, 3' is aluminum wiring that has become thinner due to some scattering. 6 In addition, Figure 4 (C) shows a portion 3'' that has not been scattered but has been altered by the beam. +41 Wiring after preliminary processing It shows.

In this way, the first pre-processed wiring has a significantly reduced minimum processing energy ("), and then the laser beam is changed to a weaker beam, especially when the beam intensity is reduced to less than the minimum processing energy of the underlying material. It is most preferable that the first preliminary machining can ensure the minimum energy for machining the cut portion of the aluminum.It is best to input the second machining beam intensity conditions determined by the first preliminary machining conditions into the memory 24. Immediately, the controller 23 adjusts the laser direct shot to obtain an unusual beam intensity.Next, use the same x-y slit to apply a weak laser beam to the size of the relationship shown in FIG. Since this beam has a higher energy than the minimum processing energy for the aluminum film after processing, it can easily remove the aluminum film in the area 7 in Figure 6 (bl). ) line is 1↓ in Figure 3 above.
゛Since the first preliminary processing, which is Section 4, can be easily carried out by laser beam machining, the wiring is cut into pieces using a cutting device such as the metal wiring section 7 using a laser beam shown in Figure 7.]
You can make a loaf.

In order to perform the first preliminary processing mechanically, a mechanical / JO using a metal needle or the like that can be controlled by a controller is added to the above device.
If the processing means is made more advanced, the device can be used in a wider range of applications.

〔Effect of the invention〕

As explained above, according to the invention of Headquarters 1, the arrangement of integrated circuits, etc. *S! , especially for wiring fine patterns quickly according to the purpose without deteriorating the circuit characteristics.

Can be cut cleanly. Furthermore, since the device of the invention of Headquarters 2 has the ability to carry out the invention of Headquarters 1, the first invention can be easily carried out, and its effects are excellent.

[Brief explanation of the drawing]

Figure 1 is a new diagram for explaining the conventional cutting method for cutting wires, etc. using a laser beam, and Figure 1] f2 is a characteristic diagram showing the situation in which the minimum energy for machining the laser beam differs depending on the surface condition of the machining material. , Figure 3 is a diagram explaining the principle of the present invention, ・21
4(a) to (C1 are partial process cross-sectional views for explaining the method of the embodiment of Bell 1 of the invention of Headquarters 1, and FIGS. 5(a) to 5(b)
) is a partial process sectional view 1. for explaining the method of the invention of Headquarters 1, 1. Mulberry 2. Figure A46 (a), (bl is z;% of the invention of Headquarters 1; Part 3 is a top view of a partial process for explaining the method of the field example, and Figure g7 is a laser according to an embodiment of the invention of Headquarters 2. A block diagram of a beam-based cutting device for metal wiring, etc. is shown. 1...Silicon semi-circular substrate, courtesy 2'...
...Silicon oxide film, 3,3ζ3r3°゛...Aluminum wiring, 4...Laser beam, 5...
...Metal needle (tungsten). 6... Machining hole, 7... Beam irradiation area, 11... Laser oscillator, 12... Laser kick source, 13... Expander , 14...
...X-Y slot, 15... Dichroic mirror, 16... Optical processing means, 17
... Objective lens, 18 ... Laser beam, 19 ... Sample, 21 ... Slit driver, 22 ... Microcomputer,
23. 23', 23"...controller, 24. 24', 24"...memory. Filled, b go-shi-length°°higher three ``rr erz cts -5-7'' tl
Twa-de7~φ half-4n

Claims (9)

[Claims] (1) The first step of performing preliminary processing in an area narrower than the wiring cutting area, such as the diamond wiring of an integrated circuit, and the wiring f in the cutting area remaining in the first step: causing damage to the area under the wiring. A method for cutting metal wiring, etc. using a laser beam, characterized in that it includes a second step of removing with a laser beam of a weak beam intensity that does not have a small amount of damage. (2) Patent search 1, characterized in that the first step of performing preliminary processing is performed with a laser beam having energy greater than the minimum processing energy of the wiring, and the wiring in the preliminary processing area remains in the first step 1. A method for cutting metal wiring, etc. using a laser beam as described in the range ( ). (3) The first step of performing preliminary processing is performed using a laser beam with a shallow focal depth.
A method for cutting metal wiring, etc. using a laser beam as described in item 1) or item (2). (4) The first step of pre-processing is performed using a laser beam with energy greater than the minimum processing energy of the interconnect, and the second step of removing the interconnect is the minimum processing of the underlying material that must not cause damage. A method for cutting metal wiring, etc. using a laser beam as described in item (1), item (2), or item (3) of the range of % leaf scanning, characterized in that the cutting is performed with a laser beam having an energy smaller than that of the laser beam. . (5) Clause (1), clause (2), or clause (4) of claim No. 1, characterized in that the second step of removing the wiring is performed using a large beam including the cutting area. A method for cutting metal wiring, etc. using a laser beam as described in Section 1. (6) The second step of removing the wiring is carried out by moving a laser beam having a smaller beam area than the laser beam used in step 41 of the preliminary processing. (2) or (3) or (
4) A method for cutting metal wiring, etc. using a laser beam as described in section 4). (7) Patent ml characterized in that at least the second step of removing the wiring is performed using a laser beam with a short pulse width.
A method for cutting metal wiring, etc. using a laser beam according to item (1), item (5), or item (6). (8) Paragraph (1) or (5) or (6) of the patent claim, characterized in that the first step of performing preliminary processing is a step of damaging the trim with a needle or the like. A method for cutting metal wiring, etc. using a laser beam as described in Section 1. (9) A laser oscillator that is fully equipped to adjust the intensity of the laser beam, an optical adjustment means that includes an expander, an X-Y slit controlled by a slit driver, a dichroic mirror, etc., and the depth of focus can be changed. An objective lens system, an X-Y table on which a sample is placed, and a laser source. 1. An apparatus for cutting metal wiring, etc., using a laser beam, characterized in that it includes a control means for controlling a slit driver and an X-Y table, and a microcomputer including the control means.