JP2002028799A - Method of fine machining by laser beam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of a laser beam machining, by which method a fine machining is performed at high speed, at a low cost, with a high quality and a high precision for a material which is hardly machined with a conventional low output laser beam. SOLUTION: In a method of machining for a work of a transparent material, by which method a light absorbing material is adhered on the surface of a work to be machined and the surface of the work to be machined on which the light absorbing material is adhered is irradiated with a laser beam, the machining is performed by making a plasma generated by the machining absorb the laser beam.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for finely processing a workpiece using a laser beam.

[0002]

2. Description of the Related Art In recent years, needs for fine processing of glass have been increasing, but a fine processing method having low cost, high quality and high speed has not yet been established. As a technique for this, attention has been paid to fine processing of glass by laser. Transparent materials such as glass can absorb an excimer laser, which is ultraviolet light, and a CO ₂ laser, which is far infrared light, to a certain extent. YAG lasers in the range of infrared light have almost no absorptivity, and processing with lasers in the range of visible light to near infrared light has been considered impossible. In addition, there is a research report that processing with visible light or near-infrared light is possible by using a laser having a high peak output called a giant pulse.

On the other hand, according to a paper by Junichi Ikeno et al. Concerning YAG laser, "YAG laser processing of quartz glass using solution" (Journal of the Japan Society of Precision Engineering, 55/2/1989, pp. 93-98), When the ion-containing solution is dropped on a surface of a transparent quartz glass plate having a thickness of 1.5 mm or is irradiated with a pulsed YAG laser while being in contact with the surface, the solution absorbs the laser and generates high heat, and the quartz glass is heated. Is reported to be able to form through-holes by fusing. The same paper also describes that, in the case of general glass containing impurities, the through-hole can be similarly laser-processed without the above-mentioned solution only by applying Magic Ink (registered trademark) to the surface. .

Also, Ikeno et al. Applied a pigment to a glass surface, irradiated it with a pulsed YAG laser to form a molten portion on the glass surface, and scattered out to remove cracks. It was also reported that a through-hole can be formed in crystallized glass with a thickness of 4 mm (19)
Proc. Of the 1997 Japan Society for Precision Engineering Fall Meeting, No. 232
page). Mr. Ikeno explains that the processing mechanism is that the deteriorated layer is formed by the absorption of the YAG laser by the pigment and the melting of the glass, because the deteriorated layer is observed in the processing hole. Analyzes that the processing proceeds by absorbing the following laser (Paper "Three-dimensional drilling of glass using YAG laser" (Report of the Laser Society of Japan, No. RTM-98-4, Laser Society of Japan, January 30, 1998
Published on pages 23-27).

[0005]

However, as described above,
Conventional laser processing methods for transparent materials are as follows.
There is a problem. First, excimer lasers can be fine-processed
However, the equipment is expensive, running cost is high, and
There are problems such as poor maintainability of the device. Also,
CO_TwoBecause laser is thermal processing,
Cracks easily occur due to thermal strain over a wide range
There is a risk that the quality will be impaired.
And is not suitable for fine processing. Also Giant
In the case of a pulsed laser, the laser device is relatively expensive.
And the pulse energy is large,
There is a problem that the hit is large and a crack is easily generated.
In addition, light absorbing substances such as the above-mentioned magic inks and pigments
Both methods use a YAG laser to remove the affected layer
In order to obtain, the transparent material to be processed has Al _TwoO_ThreeSuch
High purity stones must be properly contained
It is still impossible to process English glass or quartz
Had become.

The present invention has been made in view of the above-described conventional problems, and has as its object to use a laser which is relatively inexpensive and easy to handle, and which is conventionally made of a material which has been considered difficult to laser-process. In particular, it is an object of the present invention to provide a laser processing method capable of forming fine holes such as deep holes at high speed and at low cost, and with high quality and high precision, on transparent materials such as quartz glass and quartz.

[0007]

According to a method of the present invention, a light-absorbing substance is adhered to the surface of a workpiece, and a laser is irradiated toward the surface of the workpiece to which the light-absorbing substance is adhered, whereby the workpiece is irradiated. Is characterized in that the processing is performed while a laser is absorbed by the plasma generated by the processing. One means for that is to make the laser irradiation interval shorter than the interval from generation to extinction of plasma generated by processing.

According to this, the energy of the laser is absorbed by the plasma generated in the processing portion and is held as heat in the processing portion, and the workpiece heated by the heat transfer from the plasma is further processed. This makes it possible to form a deep hole such as a through hole in a transparent material or the like, which has been conventionally difficult to process. In addition, by making the laser irradiation interval shorter than the interval from generation to extinction of the plasma generated by the processing, the plasma can always be maintained during the processing.

When the laser beam is of a single mode, the laser beam can be narrowed down to the diffraction limit of the light.
In the following, the power density can be increased, and fine holes and the like can be easily and accurately processed.

Further, any one of a fundamental wave, a second harmonic, a third harmonic, a fourth harmonic and a fifth harmonic of the laser is used for the laser. For example, high-purity quartz glass is
Since the fundamental wave, the second harmonic, the third harmonic, the fourth harmonic or the fifth harmonic of the YAG laser is hardly absorbed, the present invention works effectively on these lasers.

When the laser beam is linearly polarized, cracks tend to occur particularly near the incident portion. Experiments have shown that cracks occur in the direction perpendicular to the polarization direction. Further, since the machined hole has a property of being easily bent in the direction of the vibration plane of the magnetic field, there is a possibility that the machined hole is bent in any direction and the hole is bent or the hole diameter is increased. Therefore, when the workpiece is irradiated with a circularly or randomly polarized laser beam, the generation of cracks near the incident portion, the bending of the processing hole and the expansion of the hole diameter are suppressed, and the processing accuracy and quality are improved.

Further, when the laser beam is branched by the phase grating and irradiated on the workpiece, a plurality of holes can be processed at the same time, so that the productivity can be improved.

Further, the light-absorbing substance is a pigment or a paint. The light-absorbing substance only needs to adhere to the periphery of the processed part of the workpiece, which not only saves the amount of light-absorbing substance used and the amount of cleaning solution used to remove the light-absorbing substance, but also minimizes the necessary light-absorbing substance. For application,
It is conceivable that all of them will be lost during laser processing, and there is a possibility that the cleaning itself may become unnecessary.

When forming a through hole in a workpiece, drilling is performed on the workpiece in a state where a dummy area is provided on a surface of the workpiece opposite to a laser incidence surface, and the workpiece is processed. After the through hole is formed in the through hole forming area, the hole processing is continuously performed on the dummy area. According to the experiment, if the through hole is processed without the dummy region, the hole diameter on the laser emission side becomes smaller than the hole diameter on the incident side.
This is considered to be because the plasma was emitted from the hole on the laser beam emission side near the end of the processing, and the amount of heat required for the processing was not sufficiently supplied. However, by performing the above, the plasma is held in the processing part also in the vicinity of the laser emission side of the workpiece, and the processing is performed under the same conditions as the previous processing part, and the hole diameter is reduced. It becomes almost the same throughout the entire length of the through hole. In this specific method, the thickness of the processed portion of the workpiece is made extra thick than the thickness that is to be finally obtained, and the extra thickness portion is processed as a dummy region, and after processing, the extra thickness is processed. There are a method in which a portion is polished or the like to a predetermined thickness, a method in which a dummy member is brought into close contact with the surface of a workpiece, processing is performed, and the dummy member is removed after processing. It is preferable that the workpiece and the dummy region have the same processing conditions. Therefore, it is desirable that the dummy region be made of the same material as the workpiece.

When a hole is formed in the workpiece and the periphery of the opening of the hole is polished, light-absorbing substances sticking to the surface of the workpiece and melted substances scattered from the processed hole and adhered to the surface are removed. Can be removed.

Further, in this processing, a YAG laser, a YLF
Lasers such as a laser and a YVO laser can be used. These lasers are characterized by being capable of fine processing, being relatively inexpensive, having good operability, and being easy to handle. Further, when the Q-switch pulse oscillation type of these lasers is used, the stored energy of the laser is temporarily stored and output at once, so that even a lower output of about several W, a high peak output of about several hundred kW can be obtained. There is an advantage. The workpiece in the present invention can be used irrespective of the type of material, but is particularly effective for transparent materials such as quartz glass and quartz, which were conventionally difficult to process.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings using preferred embodiments. Figure 1
1 schematically illustrates an example of a laser processing apparatus suitable for forming micro holes in glass using the laser processing method of the present invention. This laser processing apparatus includes a laser oscillator 1 having a built-in Q switch unit for generating a Q-switch pulse oscillation YAG laser, a mirror 2, a condenser lens 3, and a laser beam between the laser oscillator 1 and the mirror 2. Mechanical shutter means 4 disposed in the optical path. Further, the laser oscillator 1 and the shutter means 4 are electrically connected to a computer 5 for controlling these operations.

Note that the Q switch pulse oscillation YAG
Instead of the laser, a Q-switch pulse oscillation YLF laser and a YVO laser, and a YAG laser, a YLF laser, and a YVO laser that do not use the Q switch can be used.

Laser light B oscillated from laser oscillator 1
Is reflected by the mirror 2 after passing through the shutter means 4, is condensed by the condenser lens 3, and is irradiated on the workpiece 6. The workpiece 6 includes hard glass such as quartz glass, soda glass, and Pyrex (trademark), lead or crystal glass, crystallized glass, alkali-free glass, crystal, and the like, which were conventionally difficult to laser process. It covers almost all transparent materials regardless of their purity.

According to the present invention, the laser oscillator 1 outputs a single-mode beam. The single mode beam is excellent in condensing property, the beam spot diameter can be narrowed to 10μm or less, the beam shape is circular, and the power density is concentrated at the center, so a large power density can be obtained with low output, and fine processing Suitable for.

As the laser beam B of the YAG laser, the fundamental wave (1064 nm) can be used, and a nonlinear crystal 7 (for example, LBO) can be placed in the optical path between the laser oscillator 1 and the shutter means 4 or inside the laser oscillator. , The second harmonic (532 nm), the third harmonic (355 nm),
The fourth harmonic (266 nm) or the fifth harmonic (21 nm)
3 nm) can be taken out and used respectively, and in these cases, a high power density can be obtained with a relatively low output. In each of the embodiments described below, the second harmonic (532 nm) is used. In addition,
Quartz glass shows a light transmittance of 90% or more for each of the above wavelengths. Therefore, for quartz glass, the method of this embodiment is used regardless of which laser of any of the above wavelengths is used. Otherwise, it is presumed that fine processing by laser is difficult.

The computer 5 outputs a laser oscillation signal having a predetermined pulse interval to the laser oscillator 1, and the laser oscillator 1 oscillates a laser beam having a pulse interval corresponding to the laser oscillation signal. At this time, if the waiting time until the oscillation is restarted becomes longer than the pulse interval of the subsequent pulse train, the peak output of the first pulse of the pulse train tends to be excessive. Then, the computer 5 synchronizes the timing with the first pulse of the pulse train of the laser light in synchronization with the laser oscillation signal, and outputs the shutter signal to the shutter means 4.
The laser beam B is selectively cut off or passed by the on / off operation, the first pulse of the pulse train of the laser beam is cut, and the laser beam controlled to a constant peak output is continuously output to the workpiece 6. Irradiation is performed.

The computer 5 generates a pulse (oscillation) shorter than an interval from generation to extinction of plasma generated by processing the workpiece 6 by irradiating a laser beam.
The laser oscillator 1 is controlled so that the workpiece 6 is continuously irradiated with laser light at intervals.

Next, an example in which a through hole is formed in a quartz glass substrate having a thickness of 1 mm will be described. Here, the pulse width (irradiation time) of the laser light oscillated from the laser oscillator 1 is 0.06 μs, and the pulse (oscillation) interval is 100 μs.
(Repetition frequency 10 kHz) The laser oscillator 1 was controlled by the computer 5. That is, as shown in FIG. 2, since the light emission time (interval from generation to extinction) of the plasma generated by the irradiation of the laser beam having the pulse width (irradiation time) of 0.06 μs was about 100 μs, it was generated by processing. The pulse (oscillation) interval of the laser light is set within 100 μs, which is smaller than the interval from generation to extinction of the plasma, so that the plasma is always retained in the processing portion and the laser light is absorbed therein.

By the way, instead of using one laser and setting the laser oscillation frequency relatively high to shorten the laser irradiation interval to the workpiece, a plurality of lasers are used alternately. By oscillating, the laser irradiation interval to the workpiece can be made shorter than the interval from generation to extinction of plasma generated by processing. For example, by using two lasers having an oscillation frequency of 5 kHz and oscillating them alternately, the workpiece can be irradiated with the laser beam at an oscillation frequency of 10 kHz in the same manner as described above. The pulse energy (or peak power) of the laser becomes extremely small as the oscillation frequency increases, and the work efficiency decreases. In this regard, if a plurality of lasers are used, even a laser with a small output of one class can be used for this processing, and if the laser has the same power, the number of branches that can be branched by the phase grating increases, so that the processing efficiency can be increased. become.

FIGS. 3A to 3D show a process of forming fine holes in the quartz glass substrate 16 under the above-described conditions using the laser processing apparatus of FIG. First, FIG.
As shown in FIG. 1A, a pigment 8 such as a synthetic resin ink used as a magic ink or the like as a light absorbing material is uniformly applied to the surface of a quartz glass substrate 16 to a thickness that absorbs a heat amount exceeding a processing threshold value. (Here, the thickness is 70-
80 μm). By making the thickness of the pigment 8 uniform, when a plurality of holes are formed in the quartz glass substrate 16, variations in the processing can be suppressed. Therefore, it is preferable that the pigment 8 is a more homogeneous and high-purity material.

The pigment 8 may be applied to the entire surface of the quartz glass substrate 16 or may be applied only around the processed portion.
When applying only around the processing portion, for example, the processing hole diameter is 30
If it is 50 μm, it may be applied to a range of about 100 μm in diameter. In particular, by applying and processing the pigment 8 only around the processing portion, there is an advantage that the amount of the pigment used and the amount of the cleaning liquid used for removing the pigment later can be reduced. As a method for applying the pigment 8, a method using a dispenser, a screen printing method, an inkjet printing method, or the like can be used. In addition, as a light-absorbing substance other than the pigment,
It is possible to use a paint or the like that easily absorbs the laser light to be irradiated, and further heat the toner used in a copying machine or a laser printer to fix it on a workpiece (a glass substrate or the like).

Next, as shown in FIG. 3B, the surface of the quartz glass substrate 16 is irradiated with the laser beam B while being focused. The first pulse of the pulse train oscillated from the laser oscillator 1 is Since the peak becomes excessive, as described above, the shutter means 4 is turned on and off by the shutter signal from the computer 5 to cut off the laser light having an excessive peak, and the peak output of each pulse is made constant to convert them into a quartz glass substrate. Irradiate 16. When the first pulse or the first plurality of pulses are irradiated, the pigment 8 in that portion is irradiated.
Absorbs the laser energy and generates a high-temperature, high-pressure plasma state on the surface of the glass substrate. As shown in FIG. 3C, the surface layer of the quartz glass substrate 16 is partially melted by the plasma, and the recess 9 is formed by evaporation or scattering.

In this case, the irradiation energy of the first part is made smaller than the irradiation energy of the subsequent part, so that the thermal stress acting on the surface of the workpiece at the start of processing is reduced, thereby suppressing the occurrence of cracks. Can also. However, even in that case, it is necessary to irradiate the next laser before the plasma generated by the processing is extinguished. Before the laser light irradiation, the quartz glass substrate 1
For example, if 6 is previously heated to a temperature of, for example, about 200 to 300 ° C., a rapid rise in temperature inside the glass substrate during laser light irradiation can be avoided, so that the occurrence of cracks can be effectively suppressed. .

Further, by continuously irradiating the laser at the previously set pulse interval, the laser is absorbed by the plasma generated by each laser irradiation, and the workpiece is continuously heated by the heat transfer from the plasma. Finally, a through hole as shown in FIG. 3D is formed. Since the laser irradiation interval is shorter than the interval between the generation and extinction of the plasma generated by the processing, the plasma is always generated during the processing, so that the processing heat is supplied to the processing section and the processing is interrupted. Absent.

As described above, a through hole was formed in the quartz glass substrate 16 by laser processing, and the diameter of the hole was such that the laser light incident surface side was larger than the laser light emission surface side as shown in FIG. It becomes a large shape. This is presumably because when processing progressed and a hole was formed on the laser light emitting surface side of the quartz glass substrate 16, plasma escaped from the hole and sufficient processing heat was not supplied to the processing portion.

However, the above-mentioned problem that the processing hole diameters are different can be solved by using the following processing method. That is, as shown in FIG. 4, a dummy member 6 a made of the same material as the workpiece 6 is adhered to the laser light emitting surface side of the workpiece 6 so as to be in close contact therewith, and a through hole is formed in the workpiece 6. After that, processing is continued on the dummy member 6a,
Thereafter, the dummy member 6a is removed from the workpiece 6. As a result, it has been found that the diameter of the through-hole of the workpiece 6 can be made substantially equal throughout the whole. This is because even after the through-hole is formed in the workpiece 6, the plasma is prevented from escaping by the dummy member 6a and the processing proceeds, and the processing is performed on the laser light emitting surface side under substantially the same conditions as the laser light incident surface side. It is considered that The processing depth of the hole processing to be performed on the dummy member 6a is a depth corresponding to the through hole of the workpiece 6 until the through hole has substantially the same diameter throughout the entire length thereof, and is appropriately determined. .

By the way, most of the pigment remaining on the surface of the workpiece after the formation of the through hole can be washed with a suitable solvent. However, some pigments burn on the substrate surface due to the high heat of the irradiation laser and cannot be easily removed with a solvent. In addition, a part of the melt scattered from the processing hole is re-attached to the vicinity of the entrance side and the exit side opening of the processing hole to become dross. Such burn-in and dross of the pigment can be removed by polishing both surfaces of the workpiece by a known method after forming the processing hole. At the same time, the affected layer formed on the surface of the workpiece can be removed by this polishing.

In the above-described laser processing for a glass material, the laser beam may be converted to random polarized light or circularly polarized light instead of linearly polarized light before irradiation. In the case of linearly polarized light, when the p-polarized light and the s-polarized light are incident on the inner wall of the processing hole, the processing characteristics are different if the absorption characteristics are different from each other. In addition, there is a possibility that the processing hole is bent without being formed immediately. On the other hand, in the case of random polarized light and circularly polarized light, s-polarized light and p-polarized light are randomly irradiated,
5 (a) and 5 (b) since there is no deviation between s-polarized light and p-polarized light.
As shown in (1), the machined hole is formed straight, and the occurrence of cracks near the incident part is suppressed.

Further, in the laser processing apparatus of FIG. 1, as shown in FIG. 6, a known phase grating 12 is added in the optical path before the condenser lens 3, and after the laser beam B passes through the phase grating, The light can be incident on the condenser lens 3. When the laser beam B passes through the phase grating 12, one original beam is split into a plurality of beams, and each split beam is condensed by the condensing lens 3 and irradiated on the surface of the workpiece 6. Therefore, micro holes can be simultaneously formed at a plurality of converging positions corresponding to the branched beams on the surface of the workpiece 6, and
The processing time is shortened and the productivity is improved.

[0036]

EXAMPLES The results of drilling holes in various transparent materials using the method of the present invention will be presented together with photographs. (Example 1) FIG. 7 is a photograph showing a result of drilling a 1 mm-thick quartz glass under the following conditions.
(A) is a photograph (a) of the processed surface, and (b) is a photograph of the cross section of the hole. Laser conditions • Type of laser: SHG-YAG laser • Laser wavelength: 532 nm • Oscillation frequency: 10 kHz • Irradiation power: 3.8 W (380 μJ) • Number of shots: 400

Example 2 FIGS. 8A and 8B are photographs showing the results of drilling a 1 mm-thick LBO (LiB ₃ O ₅ ) under the following conditions. FIG. Photo (a),
(B) is a photograph of the cross section of the hole. Laser conditions • Laser type: SHG-YAG laser • Laser wavelength: 532 nm • Oscillation frequency: 10 kHz • Irradiation power: 3.8 W (380 μJ) • Number of shots: 800

Example 3 FIGS. 9A and 9B are photographs showing the results of hole drilling performed on a quartz (SiO ₂ crystal) having a thickness of 400 μm under the following conditions. FIG. (A) and (b) are photographs of the hole cross section. Laser conditions • Laser type: SHG-YAG laser • Laser wavelength: 532 nm • Oscillation frequency: 10 kHz • Irradiation power: 3.8 W (380 μJ) • Number of shots: 800

(Embodiment 4) FIG.
It is a photograph of a hole cross section showing a result of a hole processing performed on two pieces of soda glass having a plate thickness of 300 μm adhered together to form a single body. Laser conditions-Type of laser: SHG-YAG laser-Laser wavelength: 532 nm-Oscillation frequency: 1 kHz-Irradiation power: 400 mW (400 µJ)-Number of shots: 400

It can be seen that in any of the above Examples 1 to 3, straight fine holes could be formed in the workpiece. In addition, the processed hole on the laser light incident surface of the workpiece, which was cleaned after the processing, was substantially circular, and almost no cracks were observed around the hole. Further, in the fourth embodiment, the diameter of the through hole of the upper side (laser light incident side) of the soda glass is
You can see that their lengths are almost equal. From these results, it can be seen that the laser processing method of the present invention can process high-quality fine holes in a transparent material regardless of the type of the workpiece.

In the above embodiment, all the workpieces are made of a transparent material. However, the present invention is not limited to this, and can be applied to an opaque material.

[0042]

According to the laser processing method of the present invention, the processing is performed while absorbing the laser beam into the plasma generated by the processing, so that high-purity quartz glass, quartz, and other materials that were conventionally difficult to process can be obtained. On the other hand, it is possible to form fine holes such as deep holes at high speed, at low cost, and with high quality and high precision. In addition, the use of Q-switched pulse oscillation lasers such as YAG laser, YLF laser, and YVO laser enables laser processing with a low laser output of about several watts and high-purity quartz glass and quartz, which were conventionally difficult to process. In addition, it is possible to form fine holes and deep holes at high speed and with high accuracy, and to reduce the laser device and the processing cost.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an example of a laser processing apparatus suitable for implementing the present invention.

FIG. 2 is a timing chart of a pulse width (irradiation time), an oscillation pulse interval, and a plasma generated during the processing of a laser beam used for processing a fine hole in quartz glass.

FIG. 3 is a cross-sectional view schematically illustrating a process of forming fine holes in a quartz glass substrate according to an embodiment of the present invention.

FIG. 4 is an exemplary view showing a case where a hole is formed in a workpiece in a state where a dummy member is attached.

FIG. 5 is a sectional view showing a state of a processing hole when laser light is converted into circularly polarized light (a) and random polarized light (b).

FIG. 6 is a schematic view showing a fine drilling process by an optical system using a phase grating.

FIG. 7 is a photograph showing a processed surface and a processed cross section in a hole processing performed on quartz glass.

FIG. 8 is a photograph showing a processed surface and a processed cross section in a hole processing performed on an LBO (optical crystal).

FIG. 9 is a photograph showing a processed surface and a processed cross section in the hole processing performed on the quartz crystal.

FIG. 10 is a photograph showing a processing cross section when two soda glasses are stacked and drilled.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser oscillator 2 Mirror 3 Condensing lens 4 Shutter means 5 Computer 6 Workpiece 6a Dummy member 7 Nonlinear crystal 8 Pigment 9 Concave part 11 Processing hole (through hole) 12 Phase grating 16 Quartz glass substrate

Claims (17)

[Claims] Claims: 1. A light absorbing substance is attached to a surface of a workpiece,
A method of processing the workpiece by irradiating a laser toward the surface of the workpiece to which the light-absorbing substance is attached, wherein the processing is performed while absorbing a laser beam into plasma generated by the processing. Processing method using laser. 2. The method according to claim 1, wherein the laser irradiation interval is shorter than the interval from generation to extinction of the plasma generated by the processing. 3. The method according to claim 1, wherein a plurality of lasers are alternately oscillated so that a laser irradiation interval on the workpiece is shorter than an interval from generation to extinction of plasma generated by the processing. 3. A micromachining method using the laser according to 2. 4. The method according to claim 1, wherein a beam of the laser is a single mode. 5. The laser according to claim 1, wherein the laser is one of a fundamental wave, a second harmonic, a third harmonic, a fourth harmonic and a fifth harmonic of the laser. A micromachining method using a laser according to any of the above. 6. A micromachining method using a laser according to claim 1, wherein the laser beam is irradiated on the workpiece after being circularly polarized. 7. The micromachining method using a laser according to claim 1, wherein the laser is randomly polarized and irradiated onto the workpiece. 8. The micromachining method using a laser according to claim 1, wherein the laser beam is branched by a phase grating and irradiated onto the workpiece. 9. The method according to claim 1, wherein the light absorbing material is a pigment or a paint. 10. The micromachining method using a laser according to claim 1, wherein the light-absorbing substance is attached only to the periphery of a processed portion of the workpiece. 11. When forming a through hole in a workpiece, a hole is formed in the workpiece in a state where a dummy member is brought into close contact with the surface of the workpiece opposite to the surface on which the light absorbing substance is attached. The method according to any one of claims 1 to 10, wherein the processing of the dummy member is continued even after a through hole is formed in the workpiece. 12. The method according to claim 11, wherein the dummy member is made of the same material as the workpiece. 13. The micromachining method according to claim 1, further comprising, after forming a hole in the workpiece, polishing a portion around an opening of the hole. 14. The micromachining method according to claim 1, wherein the laser is any one of a YAG laser, a YLF laser, and a YVO laser of Q-switch pulse oscillation. 15. A processing method for irradiating a laser beam from one surface of a workpiece to form a through hole in the workpiece, wherein a dummy area is provided on a surface of the workpiece facing a laser incidence surface. Laser processing in a state where a hole is formed in the workpiece, and after forming a through hole in the workpiece, the hole processing is continuously performed in the dummy area. 16. The method according to claim 15, wherein the dummy region is made of the same material as the workpiece. 17. The method according to claim 1, wherein the workpiece is a transparent material.