JPH03264184A - Method for removing decomposition with pulse laser beam - Google Patents

Abstract

PURPOSE:To easily improve machining speed by making optical path of beam on one side of the pulse laser beam longer than that on the other side to delay the arrival of the one side pulse laser beam. CONSTITUTION:The pulse laser beam outputted from a laser beam generator 1 is decomposed into two by using a first half mirror 2, first mirror 3, second half mirror 4 and second mirror 5. Then, the optical path of beam on the one side of pulse laser beam is made to longer than the optical path of beam on the other side pulse laser beam. By this method, the arrival of the one side pulse laser beam is delayed and radiated on a material 73 to be machined as the following pulse. By this method, it is unnecessary to reconstruct the generator itself.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a decomposition and removal method using a pulsed laser that has excellent processing speed.

[Conventional technology]

As a pulsed laser decomposition and removal device using a short pulse laser, there has been one shown in, for example, Precision Engineering Journal, 5 s/s/1989. In such devices, there has conventionally been a method of increasing the energy density of the irradiated beam in order to improve the processing speed. However, with this method, the machining periphery may be damaged due to an increase in energy density, and as shown in FIG. 2, even if the irradiation energy density is increased, the removal depth per pulse does not increase significantly. Therefore, methods such as increasing the pulse repetition frequency of the laser oscillator have been used.

That is, as shown in FIG. 3, since the removal depth increases in proportion to the increase in the number of shots, the pulse repetition frequency has been increased to improve the machining speed.

[Problem to be solved by the invention]

The conventional decomposition and removal method using a pulsed laser was carried out as described above, but in order to increase the pulse repetition frequency, it was necessary to modify the laser oscillator itself. For example, in an excimer laser, which is a type of gas laser, in order to increase the pulse repetition frequency, it is necessary to increase the flow rate and discharge period of the laser gas, which makes the oscillator larger and more complex, making it an expensive and unreliable device. In some cases, it was necessary to redesign the laser mirror itself.

The present invention has been made to solve these problems, and provides a decomposition and removal method using a pulsed laser that can easily increase processing speed without modifying the oscillator itself.

[Means to solve the problem]

The decomposition removal method using a pulsed laser according to the present invention splits a pulsed laser beam into two and makes the optical path length of one beam longer than the other, thereby delaying the arrival of the beam and transferring it onto the workpiece as the next pulse. It is something that irradiates.

[Effect]

In the method according to the present invention, the beam is divided without touching the laser oscillator body, and the optical path length of each beam is changed to increase the pulse repetition frequency and improve the processing speed.

〔Example〕

In this invention, the pulse laser is an excimer laser,
A YAG laser with a Q switch is used.

The target workpieces include polymer materials, metal materials, ceramic materials, and compound semiconductors.

Particularly, the present invention is highly effective when applied to fine processing of polymeric materials that are unsuitable for thermal processing using pulsed lasers on the order of nanoseconds.

As mentioned above, it is not clear why the removal depth per pulse does not increase much even if the irradiation energy density is increased, but the irradiation energy density and the laser penetration depth into the material are not proportional to each other. This is presumed to be because the logarithm of energy density and the penetration depth of the laser into the material are approximately proportional.

Furthermore, the reason why the removal depth per pulse increases in proportion to the increase in the number of shots mentioned above is not clear, but it is presumed that the decomposition and removal mechanism by each pulse is always the same.

This invention will be explained in detail below. 4 In an embodiment of the present invention, decomposition and removal are carried out using optical parts for a pulsed laser as shown in FIG.

The above-mentioned optical parts for a pulsed laser include an excimer laser oscillator (1), a first half mirror (1) for dividing the pulsed laser beam emitted from the excimer laser oscillator (1), and the excimer laser oscillator (0) into two. 2) and the t i
The second half mirror (4) is used to further divide the pulsed laser beam heated through the first half mirror (2) and the second half mirror (4) into two, and the pulsed laser beam reflected from the first half mirror (3). ) and the second mirror (5).

When performing decomposition removal using a pulsed laser using these optical components, first the pulsed laser beam emitted from the excimer laser oscillator (1) is
The pulsed laser beam that has passed through the first half mirror (2) of the two pulsed laser beams is further divided at the second half mirror (0). The pulsed laser beam is directly guided to the first processing optical system (6).The pulsed laser beam reflected by the second half mirror (4) is reflected once by the second mirror (5), and is then guided to the 2270th processing optical system. The pulsed laser beam reflected from the 17th mirror (2) is guided to the optical system (7).
You will be guided by the half mirror 0). However, after the pulsed laser beam reflected by the first half mirror (2), the pulsed laser beam transmitted by the first half mirror (2), and the pulsed laser beam transmitted or reflected by the second half mirror (4), the second half mirror I4 ), the optical path length passing through the first mirror (3) is lengthened so that the light reaches

Next, a specific example in which fine removal processing of a polymeric material is performed using the pulsed laser optical component described above will be described.

In this example, a 125 μm thick polyimide film was used as the polymer material. Laser maximum output 24W
1 pulse repetition frequency 80H, maximum pulse energy 300mJ, pulse width 2fJ seconds, beam shape 1cwx
In this example, the rectangular ArF excimer laser has a pulse repetition frequency of 20 Hz and a pulse energy of 2.
It was used as 30mJ. Also, the optical path length passing through the first half mirror (2) and heading toward the second half mirror (0) is 1Oc1.
1. The optical path length reflected by the first half mirror (2), further reflected by the first mirror (3), and directed toward the second half mirror (4) was set to 100cIII, and the difference in optical path length was set to 90α. Therefore, the pulsed laser beam
The time difference until arriving at (4) is 37'noseconds, so 2
The beam divided into two pulses has a pulse repetition frequency twice that of the other pulses.

Here, the energy of one pulse emitted from the optical components for pulsed laser shown in FIG. 1 is divided into losses due to transmission and fouling, and 1. Since the pulse was extracted into two pulses from two locations, a total of four pulses, the energy of the original pulse was approximately 22
．． 5%, but by changing the processing optical system, the energy density of the pulses irradiated to the processing sample can be made to the same value. When the laser beam emitted from the excimer laser oscillator is directly introduced into the processing optical system, φt
Mask φ2ooItrn to make a hole of OOμm
Projection exposure was carried out using a lens with a light transmittance of 90% and a reduction ratio of 1/2. The irradiation energy density at this time is approximately o
, 4J/W. Therefore, when using the optical components for pulsed laser shown in Fig. 1, the irradiation energy density is reduced to approximately 0.
．． In order to process it as 4J7'd, it is necessary to make the energy passing through the mask machine and n the same value. Therefore, the area of masks (2) and (2) is
/225 times, so the diameter of the mask and 0 is 2.1
Need to double it. Therefore, when using the optical parts for pulsed laser shown in Fig. 1, the mask desk and the same
0 μm, using a lens with a light transmittance of 90%,
By projection exposure with a reduction ratio of 1/4.2, the energy density is approximately 0.
A 100 μm hole was drilled in the processed sample and the fourth sample at 4J/W.

As is known from the above results, it can be seen that according to the present invention, it is possible to obtain twice the machining speed as when the pulsed laser beam emitted from the excimer laser oscillator is directly introduced into the machining optical system.

Further, as shown in FIG. 1, by using two optical systems for processing and performing processing in parallel, the production speed can be further increased by a factor of two.

In the above processing, the second mirror (5) was used for processing with the processing optical systems arranged in parallel, but the processing may be performed without using the second mirror (5).

Further, in the above processing, only one of the pulse laser optical parts shown in FIG. 1 was used, but if a plurality of them are used in combination, the production speed can be further increased.

Furthermore, in the above processing, one of the two divided beams was used as another pulse, but by shifting the two divided beams by about half the pulse width and making them into one pulse. The pulse width can be increased without modifying the laser oscillator by gradually removing each discharge bridge of the laser oscillator, which has been done in the past.

〔Effect of the invention〕

As described above, according to the present invention, a pulsed laser beam is divided into two, the optical path length of one beam is made longer than the other, the arrival of the beam on the workpiece is delayed, and the beam is used as the next pulse. By using irradiation, the processing speed can be easily increased without modifying the oscillator itself.

[Brief explanation of drawings]

FIG. 1 is an optical path diagram showing the optical path of a pulsed laser beam according to an embodiment of the present invention, and FIGS. 2 and 3 are diagrams showing the optical path when drilling a polyimide film using an A r F excimer laser, respectively. FIG. 3 is a characteristic diagram showing the relationship between irradiation energy density and ablation depth per pulse, and the relationship between the number of shots and ablation depth. (1)...-Laser oscillator, (2)...Second half mirror 1 (3-n...First mirror, 0)...Second half mirror-1 (5)...Second mirror, (6)...12th
1Li engineering optical system, toughness...mask, eyes...lens,
Groan...Tobi Esample (7)...Second processing optical system (2)...Pa? Screw σ force...Lens -...
processing sample

Claims (1)

[Claims] By splitting the pulsed laser beam into two and making the optical path length of one of the pulsed laser beams longer than the optical path length of the other pulsed laser beam, the arrival of one of the pulsed laser beams is delayed and the next pulse is A decomposition removal method using a pulsed laser that irradiates the workpiece.