JP2006320938A - Apparatus and method for laser beam machining - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser beam machining method and a laser beam machining apparatus capable of easily performing the laser beam machining of a work having a complicated surface shape with inexpensive equipment. <P>SOLUTION: In the laser beam machining method for performing the laser beam machining of a surface of a work or a part in the vicinity thereof by using laser beams, the laser beam machining of the work 2 along the surface shape is performed by controlling the beam intensity distribution 4 in the vicinity of a laser beam condensing position 3 by controlling the laser pulse energy or the numerical aperture of a condensing lens. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a laser processing method and apparatus for performing laser processing on the surface of a workpiece or in the vicinity thereof using, for example, a laser beam of an ultrashort pulse laser.

  For example, when laser processing is performed on the surface of a workpiece or in the vicinity thereof using a laser beam of an ultrashort pulse laser, the processing is conventionally performed only in the vicinity of the condensing point of the laser beam. Therefore, as shown in the principle diagram of FIG. 8, even when the surface of the workpiece 2 has a complicated shape such as a spherical surface or a free-form surface, the condensing position 3 of the laser beam condensed by the condensing lens 1. And the relative distance between the workpiece 2 and the surface of the workpiece 2 must be kept constant.

  Therefore, conventionally, the processing optical system and the measurement optical system are configured coaxially, and the laser beam is controlled by controlling the focusing position of the processing optical system based on the surface shape displacement amount of the workpiece 2 measured by the measurement optical system. A laser processing technique for keeping the relative distance between the condensing position 3 and the surface of the workpiece 2 constant has been known (for example, see Patent Document 1).

As a laser processing technique using an ultrashort pulse laser, there is a technique for performing laser processing by collectively irradiating the surface of a workpiece with a plurality of branched laser beams (see, for example, Patent Document 2).
JP 2004-188422 A JP 2001-236002 A

  However, in the conventional laser processing technique in which the relative distance between the converging position 3 of the laser beam and the surface of the workpiece 2 is kept constant, the workpiece 2 is kept in order to keep this relative distance constant. Alternatively, high positioning accuracy and high resolution of the condensing lens 1 are required. In particular, when using the condensing lens 1 having a high numerical aperture (NA), resolution and positioning accuracy of several tens of nm are necessary. In addition, there is a problem that complicated control is required and expensive equipment is required.

  In addition, although laser processing technology that collectively irradiates the surface of a workpiece with a plurality of branched laser beams has the advantage of shortening the processing time compared to single point processing, an interference pattern can be obtained only at the same focal position. For this reason, laser processing can only be performed on a flat surface, which is not suitable for laser processing of the workpiece 2 having a complicated surface shape.

  The present invention has been made based on such circumstances, and an object of the present invention is to provide a laser capable of easily and inexpensively processing a workpiece having a complicated surface shape with inexpensive equipment. It is an object of the present invention to provide a processing method and apparatus.

  In order to achieve the above object, the present invention controls the light intensity distribution near the condensing position of the laser beam along the surface shape of the workpiece.

  Further, the laser beam is branched into multiple points to form a laser beam having a large number of condensing positions, and the light intensity distribution near the condensing position of the laser beam having a large number of condensing positions follows the surface shape of the workpiece. May be controlled.

  In this case, it is desirable to perform a simulation for obtaining a light intensity distribution along the surface shape of the workpiece, and to control the light intensity distribution near the condensing position of the laser beam based on this simulation.

  The laser beam is, for example, a laser beam of an ultra-short pulse laser, and it is conceivable to control the light intensity distribution in the vicinity of the focal position along the surface shape of the workpiece by controlling the pulse width of the laser beam. .

  It is also conceivable to control the light intensity distribution near the condensing position along the surface shape of the workpiece by controlling the pulse energy distribution of the laser beam.

  Furthermore, it is conceivable to control the light intensity distribution near the condensing position along the surface shape of the workpiece by controlling the numerical aperture of the laser beam.

  The present invention also relates to a light intensity distribution for measuring light intensity distribution data in the vicinity of a condensing position of a laser beam in a laser processing apparatus that performs laser processing on or near the surface of a workpiece using a laser beam from a laser oscillator. Measuring means, shape measuring means for measuring the surface shape of the workpiece, simulation means for simulating the light intensity distribution necessary for laser processing of the surface shape measured by the shape measuring means, and light intensity distribution measurement And control means for controlling the laser beam so that the light intensity distribution data measured by the means coincides with the light intensity distribution simulated by the simulation means.

  For example, when laser processing is performed on the surface of a workpiece or in the vicinity thereof using a laser beam of an ultrashort pulse laser, conventionally, processing was performed only near the condensing point of the laser beam. It was noticed that the processing position in the optical axis direction is determined by the processing threshold value of the light intensity in the light intensity distribution of the laser beam. FIG. 1 shows the principle thereof. As shown in the figure, even if the relative distance in the optical axis direction between the condenser lens 1 and the workpiece 2, that is, the relative distance in the optical axis direction between the focal position 3 and the workpiece 2 is constant, the laser beam focal position. By controlling the light intensity distribution 4 in the vicinity, the processing threshold of light intensity (indicated by the solid line at the outermost periphery of the light intensity distribution 4) changes in the optical axis direction. Therefore, by controlling the light intensity distribution 4 so that the processing threshold value of the light intensity changes along the surface shape of the workpiece 2, the surface of the workpiece 2 having a complicated shape can be easily obtained. Laser processing can be performed.

  In addition, even when the laser beam is branched into multiple points to form a laser beam having a large number of condensing positions, each laser beam is processed so that the processing threshold value of the light intensity of each laser beam follows the surface shape of the workpiece 2. By controlling the light intensity distribution 4 in the vicinity of the beam condensing position, the surface of the workpiece 2 having a complicated shape can be laser-processed by batch surface irradiation, and high throughput can be obtained.

  In addition, a simulation of the light intensity distribution is performed so that the processing threshold of the light intensity follows the surface shape of the workpiece, and the light intensity distribution near the laser beam condensing position is controlled based on this simulation. Thus, laser processing can be easily performed on a workpiece having various complicated shapes.

ADVANTAGE OF THE INVENTION According to this invention, the laser processing method which can perform a laser processing easily and cheaply with respect to the workpiece which has a complicated surface shape can be provided.
Further, it is possible to provide an inexpensive laser processing apparatus that can easily perform laser processing on a workpiece having a complicated surface shape.

[First Embodiment]
First, a first embodiment corresponding to a laser processing method for controlling the light intensity distribution near the laser beam condensing position along the surface shape of the workpiece will be described with reference to FIGS.

  FIG. 2 is a configuration diagram of the laser processing apparatus according to the present embodiment. In the figure, reference numeral 5 denotes a laser oscillator, which outputs an ultrashort pulse laser having a pulse repetition frequency of 1 KHz, a laser wavelength of 800 nm, and a pulse width of 150 fs. The ultrashort pulse laser desirably has a pulse width of about 10 fs to 100 ps and a repetition frequency of about 1 Hz to 10 MHz. The wavelength of the ultrashort pulse laser does not depend on the absorption wavelength of the material and is not limited, but it is desirable to use a wavelength of about 100 nm to 2000 nm in view of the energy required for absorption.

  In this laser processing apparatus, an ultrashort pulse laser oscillated and output from a laser oscillator 5 passes through a pulse width control function unit 6, a beam diameter control function unit 7, and a pulse energy control function unit 8, and is processed by a condenser lens 1. It is focused on the object 2.

  Incidentally, the pulse width control function unit 6 includes a dispersion mirror, a diffraction grating pair, a prism pair, and the like. Examples of the beam diameter control function unit 7 include a collimator. Examples of the pulse energy control function unit 8 include an ND filter, an oxide multilayer filter, a phase plate, a DOE, and a deformable mirror.

  The workpiece 2 is a metal, a wafer, glass, a crystal material, a biomaterial, a resin material, or the like, and is placed on the processing stage 9. The processing stage 9 is controlled by a personal computer (hereinafter simply referred to as a personal computer) 10 as a control unit. During laser processing, scanning of the laser beam is performed by driving the processing stage 9. The rough relative distance in the optical axis direction between the condenser lens 1 and the workpiece 2 is also adjusted by the processing stage 9.

  Further, in this laser processing apparatus, the light intensity distribution of the ultrashort pulse laser that has passed through the pulse energy control function unit 8 is measured by the light intensity distribution measuring device 11. Examples of the light intensity distribution measuring device 11 include a knife edge and a beam profiler using a CCD. The data of the light intensity distribution measured by the light intensity distribution measuring device 11 is monitored by the personal computer 10 and fed back to the control function units 6, 7, and 8, so that the light intensity distribution near the laser beam condensing position is obtained. It is controlled along the surface shape of the workpiece 2.

  That is, as a method for controlling the light intensity distribution near the laser beam condensing position, a method for controlling the pulse width by the pulse width control function unit 6, a method for controlling the pulse energy distribution by the pulse energy control function unit 8, and a beam There is a method of controlling the numerical aperture (NA) of the laser beam by the diameter control function unit 7 and the condenser lens 1. In the present embodiment, as shown in FIG. 3, light is emitted by any one method or a combination of a plurality of methods regardless of the relative distance in the optical axis direction between the surface of the workpiece 2 and the condensing position 3. The light intensity distribution 13 in the radial direction is controlled so that the processing threshold 11 of the intensity follows the surface shape of the workpiece 2 or exceeds the surface.

  As described above, in this embodiment, laser processing is performed depending on the light intensity distribution near the condensing position of the laser beam by the ultrashort pulse laser. That is, by controlling the light intensity in the optical axis direction of the laser beam to an intensity exceeding the processing threshold 11, the workpiece 2 is subjected to laser processing even in a region away from the condensing position 3. Can do.

  FIG. 5 is a graph showing the relationship between the relative distance μm (horizontal axis) between the workpiece 2 and the converging position 3 for obtaining the same ablation trace and the increase amount μJ (vertical axis) of the pulse energy. It is. The numerical aperture (NA) of the condenser lens 1 was 0.46. As can be seen from the figure, even if the relative distance between the workpiece 2 and the light condensing position 3 is increased, the light intensity distribution 4 is controlled by increasing the pulse energy, thereby processing the same processing trace. Can do.

  As described above, according to the present embodiment, the surface shape of the workpiece 2 can be obtained by controlling the light intensity distribution near the laser beam condensing position even for the workpiece 2 having a complicated surface shape. Laser processing can be performed along. Therefore, since high positioning accuracy and high resolution of the workpiece 2 or the condenser lens 1 are not required, laser processing can be easily performed with inexpensive equipment.

  Note that the laser processing method of this embodiment is used not only for ablation of the material surface but also for laser processing using an ultrashort pulse laser such as surface modification and internal modification in the vicinity of the surface.

[Second Embodiment]
Next, the laser beam is branched into multiple points to obtain a laser beam having a plurality of condensing positions, and the light intensity distribution in the vicinity of each condensing position of the laser beam having the many condensing positions is determined as the surface shape of the workpiece. A second embodiment corresponding to the laser processing method controlled along the lines will be described with reference to FIGS.

  FIG. 5 is a configuration diagram of the laser processing apparatus according to the present embodiment. In addition, the same code | symbol is attached | subjected to the part which is common in FIG. 2 which shows 1st Embodiment, and detailed description is abbreviate | omitted.

  In the second embodiment, the laser oscillator 5 oscillates and outputs the light intensity distribution of the workpiece 2 through the pulse width control function unit 6, the beam diameter control function unit 7, and the pulse energy control function unit 8. A laser beam controlled along the surface shape is split into a large number of beams by the multipoint splitting function unit 12 and then irradiated onto the workpiece 2 through the condenser lens 1. Examples of the multipoint division function unit 12 include a mask, a diffraction grating, a microlens array, a phase plate, a DOE, and a homogenizer. Further, a multi-point condensing position may be created using a beam pattern by interference exposure or the like.

  FIG. 6A is a principle diagram in the case of processing the surface of the workpiece 2 having a concave shape with a laser beam divided into a large number, and FIG. 6B is an enlarged view of the S portion. Incidentally, the pulse energy control function unit 8 is used for light intensity distribution control, and a mask is used for the multipoint division function unit 12.

  As shown in the drawing, the light intensity processing threshold 11 of the plurality of laser beams divided by the multipoint dividing function unit 12 is set to the surface of the workpiece 2 by the radial light intensity distribution 13 controlled to a Gaussian distribution. The laser processing is performed by irradiating along the concave surface shape.

  As described above, according to the present embodiment, it is possible to perform laser processing by surface collective irradiation even on the surface of the workpiece 2 having a complicated shape such as a concave shape, so that processing time is longer than single point processing. And a high throughput can be obtained.

  In addition, when the surface shape of the workpiece 2 has a convex shape, laser processing by multi-point batch irradiation is possible by controlling the laser beam before division into a distribution opposite to the Gaussian distribution. become. In the case of the workpiece 2 having a free shape, it may be controlled to a desired light intensity distribution using a deformable mirror or the like.

  In this embodiment, the light intensity distribution is controlled and then the multiple division is performed. However, the light intensity distribution may be controlled for each beam after the multiple division.

  Further, the laser processing method of the present embodiment is used not only for ablation of the material surface but also for laser processing using an ultrashort pulse laser such as surface modification and internal modification near the surface.

[Third Embodiment]
Next, a simulation for obtaining a light intensity distribution along the surface shape of the workpiece is performed, and a laser processing method corresponding to a laser processing method for controlling the light intensity distribution near the condensing position of the laser beam based on the simulation is performed. The third embodiment will be described with reference to FIG.

  FIG. 7 is a configuration diagram of a laser processing apparatus according to the present embodiment. In addition, the same code | symbol is attached | subjected to the part which is common in FIG.2 and FIG.5 which shows 1st and 2nd embodiment, and detailed description is abbreviate | omitted.

  In the third embodiment, the surface shape measuring instrument 14 is provided as a shape measuring means for measuring the surface shape of the workpiece 2. Examples of the surface shape measuring instrument 14 include an interferometer and an atomic force microscope in addition to a contact-type surface shape measuring instrument. The surface shape data measured by the surface shape measuring instrument 14 is given to the personal computer 10. The personal computer 10 is also provided with data of light intensity distribution measured by a light intensity distribution measuring device 11 as light intensity distribution measuring means.

  In the personal computer 10, the light intensity distribution required for laser processing of the surface shape is simulated by the surface shape data measured by the surface shape measuring instrument 14 (simulating means). Then, the pulse width control function unit 6, the beam diameter control function unit 7 or the pulse energy control function is used so that the data of the light intensity distribution measured by the light intensity distribution measuring device 11 matches the simulated light intensity distribution. Any one or more of the units 8 are controlled (control means).

  In the laser processing apparatus having such means, the relative distance in the optical axis direction between the condensing lens 1 and the workpiece 2 is obtained from the displacement amount of the surface shape measured by the surface shape measuring instrument 14. Then, the light intensity distribution 4 corresponding to this relative distance is controlled.

  The light intensity distribution 4 is obtained by simulation. For example, when the light intensity distribution 13 in the radial direction is a Gaussian distribution and the light intensity distribution 4 is controlled by controlling the numerical aperture (MA), the light intensity distribution in the optical axis direction when the Gaussian distribution is condensed is It is calculated as follows.

  First, when the numerical aperture (MA) of the condensing lens 1 is Q and the laser wavelength is λ, the spot diameter W0 is expressed by equation (1).

W0 = 2λ / π · Q (1)
Next, when the Rayleigh length ^{Zr k · W0 2/2 (} k is wavevector), Gaussian beam radius W on the optical axis z (z) is expressed by equation (2).

W ² (z) = W 0 ² (1 + Z ² / Zr ² ) (2)
Therefore, the light intensity distribution of the focused beam is expressed by equation (3).

I = {1 / (1 + Z ² / Zr ² )} · exp [{− 2 (X ² + Y ² )} / W ² (z)] (3)
Therefore, by simulating the light intensity distribution 4 according to the equation (3), the relative distance in the optical axis direction between the condenser lens 1 and the workpiece 2 and the equal light intensity line are obtained. By controlling the numerical aperture (MA) of the condensing lens 1 so that the position of the equal light intensity line indicating the value is equal to or exceeds the relative distance in the optical axis direction between the condensing lens 1 and the workpiece 2 Laser processing along or near the surface of the workpiece 2 having a shape is possible.

  As described above, according to the present embodiment, by combining the surface shape measurement function and the simulation function, it is possible to perform laser processing on the workpiece 2 having any surface shape with high accuracy.

  In each of the above embodiments, the case where laser processing is performed with a laser beam of an ultrashort pulse laser has been shown, but the light source of the laser beam is not limited to the ultrashort pulse laser.

The schematic diagram used for the principle description of the laser processing method of this invention. The schematic diagram which shows the principal part structure of the laser processing apparatus in the 1st Embodiment of this invention. The schematic diagram used for the principle description of the laser processing method in the said 1st Embodiment. The graph which showed the relationship between the relative distance of the workpiece and the condensing position for obtaining the same ablation process trace, and the increase amount of pulse energy in the said 1st Embodiment. The schematic diagram which shows the principal part structure of the laser processing apparatus in the 2nd Embodiment of this invention. The schematic diagram used for description of the principle of the laser processing method in the second embodiment. The schematic diagram which shows the principal part structure of the laser processing apparatus in the 3rd Embodiment of this invention. The schematic diagram used for the principle description of a prior art example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Condensing lens, 2 ... Workpiece, 3 ... Condensing position, 4 ... Light intensity distribution, 5 ... Laser oscillator, 6 ... Pulse width control function part, 7 ... Beam diameter control function part, 8 ... Pulse energy control Functional part, 9 ... processing stage, 10 ... personal computer, 11 ... light intensity distribution measuring instrument, 12 ... multipoint division functional part, 13 ... radial light intensity distribution, 14 ... surface shape measuring instrument.

Claims (10)

In a laser processing method for performing laser processing on or near the surface of a workpiece using a laser beam,
A laser processing method, wherein a light intensity distribution in the vicinity of a condensing position of the laser beam is controlled along a surface shape of the workpiece. In a laser processing method for performing laser processing on or near the surface of a workpiece using a laser beam,
The laser beam is branched into multiple points to form a laser beam having a large number of condensing positions, and the light intensity distribution in the vicinity of the condensing position of the laser beam having the many condensing positions follows the surface shape of the workpiece. A laser processing method characterized by being controlled. The laser processing method according to claim 1 or 2,
A laser processing method characterized by performing a simulation for obtaining a light intensity distribution along the surface shape of the workpiece, and controlling the light intensity distribution near the condensing position of the laser beam based on the simulation. In the laser processing method according to any one of claims 1 to 3,
The laser beam is a laser beam of an ultrashort pulse laser, and the light intensity distribution in the vicinity of the focusing position is controlled along the surface shape of the workpiece by controlling the pulse width of the laser beam. A laser processing method characterized by the above. In the laser processing method according to any one of claims 1 to 3,
The laser beam is a laser beam of an ultrashort pulse laser. By controlling the pulse energy distribution of the laser beam, the light intensity distribution near the focusing position is controlled along the surface shape of the workpiece. The laser processing method characterized by the above-mentioned. In the laser processing method according to any one of claims 1 to 3,
The laser beam is a laser beam of an ultrashort pulse laser, and the light intensity distribution near the condensing position is controlled along the surface shape of the workpiece by controlling the numerical aperture of the laser beam. A laser processing method characterized by the above. In a laser processing apparatus that performs laser processing on or near the surface of a workpiece using a laser beam from a laser oscillator,
A light intensity distribution measuring means for measuring light intensity distribution data in the vicinity of the condensing position of the laser beam;
Shape measuring means for measuring the surface shape of the workpiece;
Simulating means for simulating the light intensity distribution necessary for laser processing of the surface shape measured by the shape measuring means;
Control means for controlling the laser beam so that the light intensity distribution data measured by the light intensity distribution measuring means matches the light intensity distribution simulated by the simulating means;
A laser processing apparatus comprising: The laser processing apparatus according to claim 7, wherein
The laser beam is a laser beam of an ultrashort pulse laser,
The control means controls the pulse width of the laser beam so that the light intensity distribution data measured by the light intensity distribution measuring means matches the light intensity distribution simulated by the simulating means. Laser processing equipment. The laser processing apparatus according to claim 7, wherein
The laser beam is a laser beam of an ultrashort pulse laser,
The control means controls the pulse energy distribution of the laser beam so that the light intensity distribution data measured by the light intensity distribution measuring means matches the light intensity distribution simulated by the simulating means. Laser processing equipment. The laser processing apparatus according to claim 7, wherein
The laser beam is a laser beam of an ultrashort pulse laser,
The control means controls the numerical aperture of the laser beam so that the light intensity distribution data measured by the light intensity distribution measuring means matches the light intensity distribution simulated by the simulating means. Laser processing equipment.

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