JP2010158686A - Optical device for laser processing, laser processing device and laser processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently form a modified layer or a laser processed groove with a depth required for dividing a workpiece with fewer number of times of irradiation of laser beam while reducing processing time. <P>SOLUTION: An optical device for laser processing includes a light source for emitting light and a condenser for condensing light toward the workpiece 1 being an object for processing and processes the workpiece 1. Light is made to be multiwavelength coherent light 113. The condenser irradiates the multiwavelength coherent light 113 to form condensing points at different positions per multiwavelength along the optical length, so that a plurality of the condensing points are made to be present per wavelength contained in the multiwavelength coherent light 113 in a range L inside the workpiece 1 on the optical axis. A long modified layer is formed over the range L in a depth direction inside the workpiece 1 by irradiating pulse laser once. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a laser processing optical apparatus for processing a workpiece such as a semiconductor wafer, a laser processing apparatus including the laser processing optical apparatus, and a laser processing method.

  As a method of dividing along the streets of semiconductor wafers, optical device wafers, etc., a pulsed laser beam having transparency to the wafer is used, and the focused laser beam is irradiated within the region to be divided and the pulsed laser beam is irradiated. Laser processing methods have also been attempted. The dividing method using this laser processing method is to irradiate the inside of the wafer along the street by irradiating a pulse laser beam having a wavelength that is transparent to the wafer by aligning the condensing point from one side of the wafer to the inside. Thus, the workpiece is divided by continuously forming a deteriorated layer and applying an external force along a street whose strength is reduced by forming the deteriorated layer (see, for example, Patent Document 1).

  There is also a proposal example in which light is condensed near the surface of the wafer and laser processing grooves are formed by ablation (see, for example, Patent Document 2), which has been put into practical use.

Japanese Patent No. 3408805 JP-A-10-305420

  However, in the conventional method, in order to properly divide the workpiece, the process of irradiating a pulsed laser beam a plurality of times along the street is repeated to form an altered layer or a laser processing groove having a predetermined depth. There is a need. As a result, there is a problem that it takes a long processing time.

  The present invention has been made in view of the above, and it is possible to shorten the processing time of a modified layer and a laser processing groove having a depth necessary for dividing a work by irradiating a laser beam with a smaller number of times. It is an object of the present invention to provide a laser processing optical device, a laser processing device, and a laser processing method that can be efficiently formed.

  In order to solve the above-described problems and achieve the object, an optical apparatus for laser processing according to the present invention includes a light source that emits light and a condenser that condenses the light onto a workpiece to be processed. An optical apparatus for laser processing for processing the workpiece, wherein the light is multi-wavelength and coherent multi-wavelength coherent light, and the condenser uses the multi-wavelength coherent light as its optical axis. A condensing point is formed at a different position for each wavelength along.

  In the optical apparatus for laser processing according to the present invention as set forth in the invention described above, the light source includes a photonic crystal fiber.

  In the laser processing optical apparatus according to the present invention as set forth in the invention described above, the light source includes a wavelength-dependent delay mechanism that delays the multi-wavelength coherent light for each wavelength.

  The optical device for laser processing according to the present invention is the above-described invention, wherein the processing is a modified layer forming processing by condensing the multi-wavelength coherent light inside the workpiece, and the wavelength-dependent delay mechanism. Is characterized in that the multi-wavelength coherent light is delayed for each wavelength so as to reach the work sequentially from light having a wavelength collected at a position far from the condenser.

  Further, in the optical apparatus for laser processing according to the present invention, in the above invention, the processing is ablation removal processing by condensing the multi-wavelength coherent light near the surface of the workpiece, and the wavelength-dependent delay mechanism is The multi-wavelength coherent light is delayed for each wavelength so as to reach the workpiece sequentially from light having a wavelength condensed at a position close to the condenser.

  In the optical apparatus for laser processing according to the present invention as set forth in the invention described above, the wavelength dependent delay mechanism is a chirped optical fiber Bragg grating.

  The optical apparatus for laser processing according to the present invention is characterized in that, in the above invention, the light source has an optical circulator.

  The optical apparatus for laser processing according to the present invention is characterized in that, in the above-mentioned invention, the optical apparatus has a light cutting means for cutting an arbitrary wavelength among wavelengths included in the multi-wavelength coherent light.

  In addition, the laser processing apparatus according to the present invention is described in any one of the above-described inventions for processing the holding unit having a holding surface for holding the workpiece and the workpiece held on the holding surface of the holding unit. And an optical device for laser processing.

  In the laser processing method according to the present invention, the multi-wavelength and coherent multi-wavelength coherent light emitted from the light source is applied to the optical axis of the light collector by the light collector. Irradiation is performed so as to form a condensing point at a different position for each wavelength along the workpiece, and the workpiece is processed.

  According to the present invention, a laser capable of efficiently forming an altered layer and a laser processing groove having a depth necessary for dividing a workpiece by reducing the processing time by irradiating a laser beam a smaller number of times. A processing optical device, a laser processing device, and a laser processing method can be provided.

  Hereinafter, a laser processing apparatus and a laser processing method including an optical apparatus for laser processing, which is the best mode for carrying out the present invention, will be described with reference to the drawings. The present invention is not limited to each embodiment, and various modifications can be made without departing from the spirit of the present invention.

(Embodiment 1)
FIG. 1 is an external perspective view showing the main part of the laser processing apparatus of the first embodiment. The laser processing apparatus 20 according to the first embodiment schematically irradiates light onto the holding means 21 having the holding surface 21a for holding the work 1 and the work 1 held on the holding surface 21a of the holding means 21. And an optical device for laser processing 100A for processing.

  The holding means 21 sucks and holds the workpiece 1 and is rotatably connected to a motor (not shown) in the cylindrical portion 22. The holding means 21 is provided so as to be movable in the X-axis direction, which is the horizontal direction, by a processing feed means 23 having a known configuration using a ball screw or the like, and the mounted work 1 is irradiated by the laser processing optical device 100A. Processed relative to the light beam. Similarly, the holding means 21 is provided so as to be movable in the Y-axis direction, which is the horizontal direction, by an index feed means 24 having a well-known configuration using a ball screw or the like, and the mounted work 1 is irradiated by the laser processing optical device 100A. Index and send relative to the light beam.

  Here, as shown in FIG. 1, the workpiece 1 to be processed is attached to a dicing tape 3 made of a synthetic resin sheet such as polyolefin attached to an annular frame 2 with the surface facing down. Prepared at. The workpiece 1 is not particularly limited. For example, an adhesive member such as a wafer such as a semiconductor wafer, a DAF (Die Attach Film) provided on the back surface of the wafer for chip mounting, or a package of semiconductor products, ceramic, glass, etc. Examples thereof include various types of processing materials that require accuracy of the order of μm. The workpiece 1 of the present embodiment is based on a semiconductor wafer or the like, and a plurality of rectangular areas partitioned by streets 4 arranged in a lattice pattern are formed on the surface, and devices are formed in the plurality of rectangular areas. . At the time of processing, such a workpiece 1 is placed on the holding surface 21a of the holding means 21 and sucked and held. The frame 2 is fixed by a clamp member 21b.

  The laser processing optical device 100A includes a casing 101 arranged substantially horizontally, and is movable in the Z-axis direction by a Z-axis moving means (not shown) via the casing 101 with respect to the support block 25. Is provided. FIG. 2 is a schematic view schematically showing an internal optical system configuration of the laser processing optical apparatus 100A. The laser processing optical device 100A according to the first embodiment schematically includes a light source 110 that emits light and a condenser 120 that condenses the light onto the work 1 held on the holding surface 21a. Here, the light source 110 includes a pico-fetom second oscillator 111. Therefore, as shown in FIG. 2, the light source 110 including the pico-fetom second oscillator 111 emits multi-wavelength and coherent multi-wavelength coherent light 113 including wavelengths λ1, λ2,. The shaded pulses indicate that multi-wavelength components are included). That is, the pico-fetom oscillator 111 that oscillates a picosecond or femtosecond pulse laser beam functions as a wavelength conversion unit by itself, and can emit, for example, multi-wavelength coherent light 113 having a wavelength distribution range of several tens of nm. it can.

  The concentrator 120 includes, for example, a chromatic aberration lens 121, and multi-wavelength coherent light 113 emitted from the light source 110 is placed at different positions along the optical axis (Z axis) for each of the wavelengths λ1, λ2,. A condensing point is formed. In the first embodiment, laser processing is applied to the modified layer forming processing, and the concentrator 120 is set to condense the multi-wavelength coherent light 113 along the street 4 inside the workpiece 1. ing. As the multi-wavelength coherent light 113, a wavelength range extracted from about 150 to 1200 nm is used.

  Here, the state of light collection into the work 1 for forming the modified layer will be described. FIG. 3 is an explanatory diagram showing the state of light condensing inside the workpiece 1 according to the method of the first embodiment shown in comparison with the conventional method.

  First, in the conventional method, since coherent light 113a having a single wavelength λ0 is used, when the light is condensed by a condenser (condensing lens), as shown in FIG. Condensed to one point. Therefore, only a short modified layer in the depth direction can be formed by one pulse irradiation. Therefore, in order to form a modified layer for a predetermined length in the depth direction, the focal point position is shifted in the vertical direction. However, the step of irradiating the pulse laser a plurality of times must be repeated.

  On the other hand, in the system according to the first embodiment, the chromatic aberration lens 121 has the focal length that the multi-wavelength coherent light 113 that has passed through varies depending on the wavelengths λ1, λ2,. That is, the chromatic aberration lens 121 forms a plurality of condensing points on the optical axis inside the work 1 for each of the wavelengths λ1, λ2,... Λn included in the multi-wavelength coherent light 113. Therefore, as shown in FIG. 3A, the range L inside the work 1 on the optical axis of the chromatic aberration lens 121 is plural for each of the wavelengths λ1, λ2,... Λn included in the multiwavelength coherent light 113. There will be a condensing point. Therefore, a long modified layer over the range L in the depth direction can be formed inside the workpiece 1 by one-time pulse laser irradiation with the multi-wavelength coherent light 113. Therefore, it is possible to efficiently form the modified layer by shortening the processing time by irradiating the pulse laser a smaller number of times.

  In the first embodiment, the example of application to modified layer formation processing has been described as laser processing, but the present invention is similarly applied to the case of ablation removal processing in which a laser processing groove is formed on the surface of the workpiece 1. it can. That is, in the case of ablation removal processing, the multi-wavelength coherent light 113 may be condensed near the surface along the street 4 of the workpiece 1 (the same applies to each embodiment described later). In this case, as the multi-wavelength coherent light 113, a wavelength range extracted from about 300 to 550 nm is used. Therefore, a long laser processing groove can be formed over the range L in the depth direction with respect to the surface of the workpiece 1 by one-time irradiation of the pulse laser with the multiwavelength coherent light 113. Therefore, it is possible to efficiently form the laser processing groove by shortening the processing time by irradiating the pulse laser a smaller number of times.

(Embodiment 2)
FIG. 4 is a schematic diagram schematically showing an internal optical system configuration of the laser processing optical apparatus 100B according to the second embodiment of the present invention. Portions that are the same as or correspond to those described in Embodiment 1 are denoted by the same reference numerals, and description thereof is omitted (the same applies to the following embodiments).

  The laser processing apparatus 20 according to the second embodiment includes a laser processing optical apparatus 100B instead of the laser processing optical apparatus 100A. This laser processing optical device 100B includes a light source 130 and a condenser 120. The light source 130 includes a nanosecond oscillator 131, a photonic crystal fiber 132, a condenser lens 133, and a collimator lens 134.

  As shown in FIG. 4, the nanosecond oscillator 131 emits coherent light 135 having a single wavelength as a nanosecond pulse laser. The photonic crystal fiber 132 is a multi-wavelength coherent light 136 having wavelengths λ1, λ2,..., Λn, in which the coherent light 135 having a single wavelength emitted from the nanosecond oscillator 131 is spread over a range of several thousand nm. Wavelength converting means. The shaded pulses for the multi-wavelength coherent light 136 in FIG. 4 indicate that multi-wavelength components are included.

  The condensing lens 133 is a lens that condenses the coherent light 135 emitted from the nanosecond oscillator 131 and efficiently enters the incident end of the photonic crystal fiber 132, and a lens without chromatic aberration is used. It has been. The collimating lens 134 is a lens without chromatic aberration for converting the multi-wavelength coherent light 136 emitted from the photonic crystal fiber 132 into a parallel beam and guiding it to the chromatic aberration lens 121.

  In the case of the second embodiment as well, as in the case of the first embodiment, a single pulse laser irradiation with the multi-wavelength coherent light 113 causes a long modification over the range L in the depth direction inside the work 1. A quality layer can be formed. Therefore, it is possible to efficiently form the modified layer by shortening the processing time by irradiating the pulse laser beam a smaller number of times. In particular, the wavelength distribution in the case of the above-described pico-femtosecond pulse laser is in the range of several tens of nanometers, and it is difficult to disperse the focal point over a sufficiently wide range. When the photonic crystal fiber 132 is used, the wavelength distribution can be expanded to a range of several thousand nm, and the condensing points can be easily dispersed in a sufficiently wide range. Further, as the oscillator, a nanosecond oscillator 131 that is less expensive than the pico-fetom second oscillator 111 can be used.

(Embodiment 3)
FIG. 5 is a schematic diagram schematically showing an internal optical system configuration of the laser processing optical device 100C according to Embodiment 3 of the present invention. The laser processing apparatus 20 according to the third embodiment includes a laser processing optical apparatus 100C instead of the laser processing optical apparatus 100A. This laser processing optical device 100 </ b> C includes a light source 140 and a condenser 120. The light source 140 includes an optical fiber 141 a, a condenser lens 142, and a collimator lens 143 that constitute the wavelength-dependent delay mechanism 141 in addition to the pico-fetom second oscillator 111.

  The wavelength dependent delay mechanism 141 is for delaying the multi-wavelength coherent light 113 emitted from the pico-fetom second oscillator 111 for each of the wavelengths λ1, λ2,. In the third embodiment, the wavelength-dependent delay mechanism 141 includes a normal optical fiber 141 a having a length of several meters disposed between the pico-fetom second oscillator 111 and the chromatic aberration lens 121. Even in the case of a normal optical fiber 141a having a length of several meters, a delay of about several hundred picoseconds occurs. Therefore, if the pulse of the multiwavelength coherent light 113 is pico-fetomsecond, the multiwavelength coherent light 113 is In terms of time, it can be decomposed into wavelengths λ1, λ2,. Therefore, after passing through the optical fiber 141a, as shown in FIG. 5, the wavelengths λ1, λ2,..., Λn are temporally decomposed and the wavelengths λ1, λ2,. The time difference multiwavelength coherent light 144 having a time difference for each λn can be obtained. The shaded portions of the time difference multiwavelength coherent light 144 in FIG. 5 represent different wavelength components λ1, λ2,.

  The condensing lens 142 is a lens that condenses the multi-wavelength coherent light 113 emitted from the pico-fetom second oscillator 111 and efficiently enters the incident end of the optical fiber 141a, and has no chromatic aberration. Is used. The collimator lens 143 is a lens having no chromatic aberration for converting the time-difference multi-wavelength coherent light 144 emitted from the optical fiber 141 a into a parallel beam and guiding it to the chromatic aberration lens 121.

(Embodiment 4)
FIG. 6 is a schematic diagram schematically showing an internal optical system configuration of the laser processing optical apparatus 100D according to Embodiment 4 of the present invention. The laser processing apparatus 20 according to the fourth embodiment includes a laser processing optical apparatus 100D instead of the laser processing optical apparatus 100B. This laser processing optical device 100 </ b> D includes a light source 150 and a condenser 120. In addition to the nanosecond oscillator 131, the photonic crystal fiber 132, the condensing lens 133, and the collimating lens 134, the light source 150 includes an optical circulator 151 and a chirped optical fiber Bragg grating 152a that constitutes the wavelength-dependent delay mechanism 152.

  The wavelength dependent delay mechanism 152 is for delaying the multi-wavelength coherent light 136 emitted from the photonic crystal fiber 132 for each of the wavelengths λ1, λ2,. In the fourth embodiment, the wavelength dependent delay mechanism 152 includes a chirped optical fiber Bragg grating 152a. The chirped optical fiber Bragg grating 152a is a device having an optical filter function by forming gratings at appropriate positions in the core using, for example, ultraviolet rays, and reflects only light of a specific wavelength by each grating. It is something to be made. Since the optical path length of the reflected light changes for each of the wavelengths λ1, λ2,..., Λn, delays having different time differences occur for each wavelength. Specifically, in the case of the chirped optical fiber Bragg grating 152a, a delay of about 100 to 200 nm occurs with a length of about 20 meters, so even a nanosecond pulse laser can be decomposed for each wavelength. Therefore, after reciprocating the chirped optical fiber Bragg grating 152a, the multi-wavelength coherent light 136 is temporally decomposed into wavelengths λ1, λ2,..., Λn within one pulse as shown in FIG. A time-difference multi-wavelength coherent light 153 having a time difference for each of the wavelengths λ1, λ2,. The shaded portions of the time difference multiwavelength coherent light 153 in FIG. 6 represent different wavelength components λ1, λ2,.

  The optical circulator 151 is an optical device for coupling the time-difference multi-wavelength coherent light 153 incident from the photonic crystal fiber 132 side and reciprocating in the chirped optical fiber Bragg grating 152a to the chromatic aberration lens 121 side. Coupling or the like can be used, but by using the optical circulator 151, it is possible to suppress the loss of light emitted from the nanosecond oscillator 131 side and propagate it, and to perform stable laser processing. Can do.

  There are various laser absorption processes depending on the type of workpiece 1 and the type of laser used. Therefore, in the third and fourth embodiments, the multi-wavelength coherent light 113, 136 is delayed for each of the wavelengths λ1, λ2,. Therefore, it is possible to cause the workpiece 1 to reach the workpiece 1 for each of the wavelengths λ1, λ2,..., Λn in any order according to each absorption process, and to improve the processing efficiency. . As an example of the laser absorption process, multi-photon absorption may occur in light in a short wavelength region, and absorption may occur in the long wavelength region triggered by an electron / hole pair. In such a case, it is expected that efficient processing can be performed by using the time-difference multi-wavelength coherent lights 144 and 153 that are delayed so as to reach the workpiece 1 sequentially from the short wavelength side. Note that the order of the wavelengths λ1, λ2,..., Λn to be irradiated may be from the short wavelength side or from the long wavelength side.

  In the case of the modified layer forming processing by condensing the multi-wavelength coherent lights 113 and 136 including the wavelengths λ1, λ2,..., Λn inside the work 1, as the wavelength-dependent delay mechanisms 141, 152, It is possible to use time-difference multi-wavelength coherent lights 144 and 153 obtained by delaying the multi-wavelength coherent lights 113 and 136 for each wavelength so as to reach the workpiece 1 sequentially from light having a wavelength condensed at a position far from the condenser 120. desirable. That is, when the modified layer is formed inside the work 1, the upper side of the modified layer that is subsequently formed by condensing from the lower side (deeper side) becomes less affected by the preceding laser irradiation, and is stable. Can be processed. In addition, since the expansion of the modified layer on the upper side is suppressed and the modified layer is formed in a sharp shape, it is possible to improve the division characteristics in the subsequent process.

  On the other hand, in the case of ablation removal processing by condensing multi-wavelength coherent light including wavelengths λ1, λ2,..., Λn near the surface of the work 1, the wavelength-dependent delay mechanism is as follows: It is desirable to use time-difference multi-wavelength coherent light obtained by delaying multi-wavelength coherent light for each wavelength so as to sequentially reach the work 1 from light having a wavelength collected at a close position. That is, in the case of forming a laser processing groove by ablation, ablation removal can be sequentially performed from the surface side by condensing light from the upper side, and the laser processing groove can be formed efficiently.

(Embodiment 5)
FIG. 7 is a schematic diagram schematically showing a part of the optical system configuration inside the laser processing optical apparatus 100E according to the fifth embodiment of the present invention. The laser processing apparatus 20 according to the fifth embodiment includes a laser processing optical apparatus 100E instead of the laser processing optical apparatuses 100A to 100D. This laser processing optical device 100E includes a light cutting means 160 on the emission side of the light sources 110, 130, 140, and 150 (not shown in FIG. 7). The light cut means 160 is for cutting an arbitrary wavelength among the wavelengths λ1, λ2,... Λn included in the multiwavelength coherent light (or time difference multiwavelength coherent light). As the light cut means 160, for example, a band pass filter, a sharp cut filter or the like is used.

  According to this, by adding the light cutting means 160 to the completed laser processing optical devices 100A to 100D to configure the laser processing optical device 100E, the depth depends on the target workpiece 1 or the like. The modified layer and the laser processed groove can be formed so as to have a desired length. Therefore, after completion of the laser processing optical devices 100A to 100D, an undesired wavelength may be removed by inserting the light cutting means 160 in accordance with the target workpiece 1 or the like. The versatility of 100D can be expanded.

  In the first to fourth embodiments described above, the concentrator 120 has been described by using the chromatic aberration lens 121 as a representative. However, the chromatic aberration lens 121 is not necessarily required as the concentrator, and various configurations can be employed. . For example, FIG. 7 shows an example of a condenser 170 composed of a chromatic aberration combination lens that is a combination of a condenser lens 171 having no chromatic aberration characteristics and an optical component 172 having chromatic aberration characteristics. In short, an optical component having a chromatic aberration function for forming a condensing point at different positions for each wavelength along the optical axis of multi-wavelength coherent light may be provided at any position on the optical axis.

It is an external appearance perspective view which shows the principal part of the laser processing apparatus of Embodiment 1 of this invention. 2 is a schematic diagram schematically showing an internal optical system configuration of the laser processing optical apparatus according to Embodiment 1. FIG. It is explanatory drawing which shows the mode of the condensing of the light inside the workpiece | work by the system of Embodiment 1 shown in contrast with the conventional system. It is the schematic which shows typically the optical system structure inside the optical apparatus for laser processing of Embodiment 2 of this invention. It is the schematic which shows typically the optical system structure inside the optical apparatus for laser processing of Embodiment 3 of this invention. It is the schematic which shows typically the optical system structure inside the optical apparatus for laser processing of Embodiment 4 of this invention. It is the schematic which shows typically the one part optical system structure inside the optical apparatus for laser processing of Embodiment 5 of this invention.

DESCRIPTION OF SYMBOLS 1 Work | work 100A-100E Optical apparatus for laser processing 110 Light source 113 Multi-wavelength coherent light 120 Condenser 130 Light source 132 Photonic crystal fiber 136 Multi-wavelength coherent light 140 Light source 141 Wavelength-dependent delay mechanism 144 Time difference multi-wavelength coherent light 150 Light source 151 Light Circulator 152 Wavelength-dependent delay mechanism 152a Chirped optical fiber Bragg grating 153 Time difference multiwavelength coherent light 160 Optical cut means 170 Condenser

Claims (10)

A laser processing optical device for processing the workpiece, comprising: a light source that emits light; and a condenser that collects the light on the workpiece to be processed;
The light is multiwavelength and coherent multiwavelength coherent light,
The optical apparatus for laser processing, wherein the concentrator forms a condensing point at different positions for each wavelength along the optical axis of the multi-wavelength coherent light.   The optical device for laser processing according to claim 1, wherein the light source includes a photonic crystal fiber.   The optical device for laser processing according to claim 1, wherein the light source includes a wavelength-dependent delay mechanism that delays the multi-wavelength coherent light for each wavelength. The processing is a modified layer forming processing by condensing the multi-wavelength coherent light inside the workpiece,
4. The wavelength-dependent delay mechanism delays the multi-wavelength coherent light for each wavelength so as to reach the workpiece sequentially from light having a wavelength condensed at a position far from the condenser. An optical device for laser processing as described in 1. The processing is ablation removal processing by condensing the multi-wavelength coherent light near the surface of the workpiece,
4. The wavelength-dependent delay mechanism delays the multi-wavelength coherent light for each wavelength so as to reach the workpiece sequentially from light having a wavelength condensed at a position close to the condenser. An optical device for laser processing as described in 1.   6. The laser processing optical apparatus according to claim 3, wherein the wavelength dependent delay mechanism is a chirped optical fiber Bragg grating.   The optical apparatus for laser processing according to claim 6, wherein the light source includes an optical circulator.   The optical apparatus for laser processing according to any one of claims 1 to 7, further comprising light cutting means for cutting an arbitrary wavelength among wavelengths included in the multi-wavelength coherent light. Holding means having a holding surface for holding the workpiece;
An optical device for laser processing according to any one of claims 1 to 8, for processing the workpiece held on the holding surface of the holding means,
A laser processing apparatus comprising:   The multi-wavelength and coherent multi-wavelength coherent light emitted from the light source is focused on the workpiece held by the holding means at different positions for each wavelength along the optical axis of the light collector. The laser processing method is characterized in that the workpiece is processed by irradiation so as to form.

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