JPH07106465B2 - Laser processing method and apparatus for metal thin film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a processing technique for removing a metal thin film formed on an organic film by a laser beam.

2. Description of the Related Art Conventionally, as a method for linearly processing a metal thin film on an organic film using a laser, as disclosed in, for example, Japanese Patent Laid-Open Nos. 56-500155 and 57-118622. , Q
Processing is generally performed using a pulsed laser beam with a switch. The reason why the Q-switched pulsed laser beam is used is that the organic film is less damaged by heat.

An example of the conventional laser processing method described above will be described below with reference to the drawings.

FIG. 6 and FIG. 7 show a conventional processing method in which a metal thin film on an organic film is linearly removed and processed by using a pulsed laser beam with a Q switch. In FIG.
1b is a pulsed laser beam, 2 is a metal thin film formed on an organic film, and 3 is a processing line obtained by removing the metal thin film.

When a metal thin film is removed by a pulsed laser beam, the metal thin film must be melted → evaporated or sublimated, so the heat from the metal thin film is transferred to the organic film,
Organic films suffer heat damage. Of course, if the organic film itself absorbs the laser beam relatively strongly,
Even if there is no heat transfer from the metal thin film, the heat damage to the organic film is large. However, YA often used for laser processing
Since a laser having a relatively short wavelength, such as a G laser, almost penetrates a transparent film such as polystyrene or polyvinyl chloride, heat damage to the organic film by the laser itself can be almost eliminated. Therefore, in order to minimize the heat damage to the organic film, it is important to minimize the heat transfer from the metal thin film described above. This can be realized by a processing method using a pulse laser beam with a Q switch.

Problems to be Solved by the Invention However, the above-mentioned processing method using the pulsed laser beam has a drawback that the processing speed is low. That is, when using a pulsed laser beam to perform linear processing at the highest possible speed, the overlap ratio of the pulsed laser beams should be 50% or more, but the frequency of the Q switch should be stable. At most 30
It is KHz. High processing speed even if the beam diameter is 100 μm
It is 90m / min. Further, the smaller the overlap ratio, the more extreme the waviness of the processed line becomes, as shown by 3 in FIG.

A continuous wave laser beam may be used in order to make the waviness of the processing line extremely small, but in the usual method, the film is damaged by heat and cannot be practically used. As described above, the reason why the film is hardly damaged by the pulsed laser beam by the Q switch and the damage is large by the continuous wave laser beam has not been conventionally explained. Although both the pulsed laser beam and the continuous wave laser beam have the same phenomenon of melting → evaporation or sublimation of a metal thin film, an experimental study was conducted to investigate the cause of a very large difference in film damage. It came to such a conclusion.

FIG. 7 is a diagram for explaining that the processing by the conventional Q-switch pulse laser beam does not damage the film.

In FIG. 7, t ₁ is the pulse width of the laser beam, t ₂ is the pause time of the laser beam, and 17 is the shaded area is the energy of one pulse laser beam. The intensity of the laser used for processing the Q switch 4 is very large on the KW order, and the pulse width t ₁ is usually 100 to 300 nsec, which is a short time. Therefore, the metal thin film is removed in the order of 10 ^-7 sec, the heat transfer from the metal thin film becomes very small, and the heat damage to the organic film can be almost eliminated. The rest time t ₂ is 1 to 0.01
Since it is msec, in the pulse laser beam processing of the Q switch, only 0.01 to 3% of the processing time is irradiated with the laser beam, which is also advantageous from the viewpoint of cooling the part irradiated with the laser.

On the other hand, in the case of a continuous wave laser beam, the metal thin film can be removed and processed with a small intensity, but since the laser is continuously irradiated, heat transfer from the metal thin film becomes large, and thus the film is greatly damaged.

As described above, the present invention obtained by pursuing the problems of the conventional processing method provides a laser processing method in which the waviness of the processing line is small, the processing speed is large, and the damage to the organic film is small. is there.

Means for Solving the Problems A laser processing method for a metal thin film of the present invention for solving the above problems is as follows. By irradiating a metal thin film with a thickness of 2000 Å or less formed on an organic film with a thickness of 10 μm or less with a continuous wave beam of a solid-state laser with a wavelength of 0.5 to 1.2 μm by high-speed scanning of 300 m / min or more. The metal thin film is removed. Further, for those in which a metal thin film is formed on both sides of the organic film, under the condition that the continuous wave laser beam is irradiated, and the processing width of the metal thin film on the opposite side is smaller than the processing width of the metal thin film on the irradiation side, The metal thin film is removed.

Various processing optical systems are conceivable for that purpose, but a laser beam expanding optical system, two galvanometers having rotation axes that are not parallel to each other, two galvanometer mirrors that rotate by being attached to the respective rotation axes, and A configuration having a reflecting mirror located between two galvanometers and a condensing optical system is desirable.

Action The present invention, by using the method and apparatus configuration described above, by irradiating a minute spot of a continuous wave laser beam to a metal thin film at a high speed, the metal thin film is instantaneously removed and processed, and thereby the damage to the film is very small, In addition, a stable working width can be obtained.

Example A laser processing method and apparatus according to an example of the present invention will be described below with reference to the drawings.

FIG. 1 shows a laser processing method for a metal thin film according to a first embodiment of the present invention. 1a is a continuous wave laser beam after passing through a condenser lens, 2 is a thin metal film formed on the film, and 3 is a processing line. 2 and 3 show transverse modes of the laser beam on the metal thin film for explaining the operation of this embodiment. In FIG. 2, the vertical axis represents the intensity and the horizontal axis represents the distance from the center of the laser beam. When the intensity at the center of the laser beam is 1, the beam diameter d _{1 at} which the intensity is 1 / e ² is called the spot diameter.

Pt represents a threshold value at which the metal film is processed with higher strength. Therefore, the diameter indicated by w ₁ becomes equal to the processing width for processing the metal thin film. The metal thin film is not processed at the strength of Pt or less, and therefore the diagonal line of 6a indicates energy enough to heat the metal thin film. Since the film is damaged by the energy in the shaded area of 6a, the smaller the energy in this area, the more desirable. Since the threshold value Pt is constant depending on the metal, the smaller the spot diameter d ₁ , the smaller the energy of the shaded portion 6a and the smaller the film damage. FIG. 3 illustrates this state. Even if the energy per unit time of the laser beam is the same, when the spot diameter is small, both the processing width w ₂ and the perspective portion 6b are small, and when the spot diameter is large, both the processing width w ₃ and the shaded portion 6c are large. Therefore, the smaller the spot diameter, the larger the energy required to heat the metal thin film, and the more the film is damaged. According to the results of experiments, when the film thickness is 10 μm or less, the spot diameter is 350 μm or less, the processing width is 200 μm or less, and the laser beam scanning speed is 300 m / min or more. There was found.

As described above, according to this example, a continuous wave beam of a solid-state laser is irradiated at a high speed of 300 m / min or more on a metal thin film having a thickness of 2000 Å or less formed on an organic film having a thickness of 10 μm or less. By instantaneously removing and processing the metal thin film so that the processing width becomes 200 μm or less, damage to the film is extremely small, and a stable processing width can be obtained.

The second embodiment of the present invention will be described below. FIG. 4 is a cross-sectional view showing a laser processing method for irradiating the continuous film 1a of the solid-state laser on the metal thin film 2 formed on both surfaces of the organic film 7. Reference numeral 8a is a removal processing portion on the laser beam irradiation side, and 8b is a removal processing portion on the opposite side. Also in this case, the processing width is 200 μm or less, and the laser beam scanning speed is 300 m /
The minimum requirement is min. However, in the case of this embodiment,
Since the metal thin film 2 is present on both sides of the film, heat transfer from the metal thin film to the film is larger than that in the first embodiment, and the film is easily damaged. In order to reduce this damage to a practical level, it is necessary to set a laser condition such that the processing width of the opposite side processing portion 8b is smaller than the processing width of the laser aiming side processing portion 8a. When the laser intensity is such that both processing widths are equal, it is higher than the intensity required for removing and processing the metal thin film, so the temperature at which the metal thin film is heated also rises and the damage to the film also increases. If the processing portion of the removal processing portion 8b is not necessary, it is possible to form only the removal processing portion 8a by setting the laser intensity to be appropriately small.

In the case where the metal thin films are formed on both sides of the organic film as described above, the processing width on the opposite side of the processing width on the laser irradiation side is the condition that the laser beam irradiation speed is 300 m / min or more and the processing width is 200 μm or less. By removing and processing the metal thin film so as to reduce the amount of damage, damage to the film is extremely small, and stable laser processing becomes possible.

The third embodiment of the present invention will be described below. FIG. 5 is a perspective view showing a laser processing apparatus according to the third embodiment of the present invention. In the figure, 9 is a solid-state laser oscillator, 10 is a beam expanding optical system, 11a and 11b are galvanometers, and 12a and 12b.
Is a galvanometer mirror, 13 is a reflection mirror, and 14 is a condensing optical system. The laser beam emitted from the oscillator 9 is 6
Enlarged to 12 times, galvano mirror 12a, reflection mirror 1
3, the galvano mirror 12b and the condensing optical system 14 are irradiated to the metal thin film 2 to form the processed line 3. Galvano mirror
The rotation axes of 11a and 11b are arranged so as to be orthogonal to each other.

As described in Examples 1 and 2, a processing width of 200 μm or less and a beam scanning speed of 300 m / min or more are required to prevent damage to the organic film. The spot diameter of the laser beam is f · θ, where θ is the beam divergence angle and f is the focal length of the focusing optical system. Further, since θ is reduced by the magnification of the magnifying optical system, it is advantageous that the magnification of the magnifying optical system is large in order to reduce the spot diameter. On the other hand, in order to perform high-speed scanning, the galvanometer mirror must be made small to reduce the inertial force and air resistance of the mirror. Due to these restrictions, it is useful that the galvanomirror has as large an effective area as possible within a range where a predetermined response characteristic can be obtained. Also, the beam incident on the carbano mirror is usually incident at an angle of about 45 °. Therefore, if the diameter of the incident beam is D, the length of the galvano mirror is The above is necessary. Therefore, the present invention aims to increase the angle of the incident beam with respect to the carbano mirror, and to minimize the length of the galvano mirror.
Specifically, by placing a reflecting mirror between the orthogonal galvano mirrors, the angle between the incident beam and the galvano mirrors is increased by 10 to 25 °, and the length of the galvano mirrors is reduced to about 1.1 to 1.2D. We were able to. Accurately aligning the center of the laser beam with the center of rotation of the galvanometer mirror is also important for stable processing of the metal thin film. By finely adjusting the angle of the reflection mirror of the present invention, it becomes possible to easily set the center of the laser beam to the center of the galvano mirror.

EFFECTS OF THE INVENTION As described above, according to the first aspect of the present invention, by appropriately selecting the processing conditions such as the feed rate of the continuous wave beam of the solid-state laser, the metal can be processed at high speed without causing thermal damage to the film. A thin film can be removed.

Further, according to the second aspect of the present invention, the angle-adjustable reflection mirror is provided between the two carbano mirrors attached to the respective rotation axes of the two galvanometers having the rotation axes orthogonal to each other. The miniaturization of the galvanometer mirror and the high speed scanning of the laser for realizing the method of the first aspect of the present invention are possible, and stable processing of the metal thin film can be performed.

[Brief description of drawings]

FIG. 1 is a perspective view showing a laser processing method of a first embodiment of the present invention, FIGS. 2 and 3 are views for explaining the operation of the present invention,
4 is a sectional view showing a laser processing method according to a second embodiment of the present invention, FIG. 5 is a perspective view showing a laser processing apparatus according to a third embodiment of the present invention, and FIG. 6 is a conventional laser processing. FIG. 7 is a perspective view of the method, and FIG. 7 is a diagram for explaining pulses in the laser processing method of FIG. 1a ... laser beam, 2 ... metal thin film, 3 ... processing line,
7 ... Organic film, 8a, 8b ... Removal processing part, 9 ... Solid-state laser oscillator, 10 ... Enlarging optical system, 11 ... Galvanometer, 12a, 12b ... Galvanometer mirror, 13 ... Reflection mirror, 14 ... … Condensing optics.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kunio Oshima 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP-A-57-118622 (JP, A)

Claims (3)

[Claims] 1. A metal thin film having a thickness of 2000 Å or less formed on an organic film having a thickness of 10 μm or less has a wavelength of 0.5 to
A laser processing method for a metal thin film, in which a continuous wave beam of a 1.2 μm solid laser is irradiated by high-speed scanning at 300 m / min or more, and the metal thin film is removed so that the processing width is 200 μm or less. 2. A metal thin film formed on both sides of an organic film is irradiated with a continuous wave laser beam so that the processed width of the metal thin film on the opposite side is smaller than the processed width of the metal thin film on the irradiation side. The laser processing method for a metal thin film according to claim 1, wherein the removal processing is performed. 3. A laser oscillator, two galvanometers having rotation axes that are not parallel to each other, two galvanometer mirrors attached to each rotation axis of the galvanometer and rotating, and between the two galvanometer mirrors. Laser processing device for metal thin film consisting of a reflective mirror located at the position and adjustable in angle.