JP5865671B2 - Pulse laser processing equipment - Google Patents

Description

  The present invention relates to a pulse laser processing apparatus and a pulse laser processing method for processing a workpiece surface with a pulse laser beam.

  In recent years, flat panel displays (FPDs) such as liquid crystal panels, for example, have been required to have a member that has been subjected to high-precision microfabrication on a large area, for example, on the order of μm or less, with an increase in size. . Various studies have been made on microfabrication of large roll molds for sheet creation, molds having fine shapes for blind grooves and deep microlenses, difficult-to-cut materials, etc., which are difficult to produce by conventional machining.

  On the other hand, it is known that, for example, a fine pattern of 1 μm or less can be easily formed on a metal surface by ablation processing using an ultrashort pulse laser beam having a pulse width of the order of picoseconds (ps) or less. And so far, various methods have been proposed for techniques for processing the surface of a workpiece made of a polymer material containing a resin, a semiconductor material, a glass material, a metal material, etc. by this ultrashort pulse laser processing ( For example, see Patent Document 1).

  In ultra-short pulse laser processing, it is desired to shorten the processing time in order to increase productivity. In order to shorten the processing time, it is common to increase the repetition frequency and at the same time increase the laser output energy.

For this reason, for example, a ps laser or fs laser using Nd: YVO ₄ is used. Furthermore, the second harmonic (2ω), the third harmonic, etc. are obtained from the fundamental wave (ω) by using BBO (β-BaB ₂ O ₄ ), LBO (LiB ₃ O ₅ ), etc., which are nonlinear crystals. Is being processed. However, in order to obtain high output energy at a high repetition frequency, it is necessary to make the beam diameter very small.

  In this case, for example, problems such as deterioration of the beam profile, shortening of the lifetime of the nonlinear crystal, and deterioration of the stability of the laser beam output from the nonlinear crystal occur.

Japanese Patent No. 4612733

  In view of the above circumstances, the present invention improves the positioning accuracy of an irradiation spot of a pulse laser beam, and enables stable fine processing of a large workpiece surface and its speed increase, and a pulse laser processing method. The purpose is to provide.

A pulse laser processing apparatus of one embodiment of the present invention includes a reference clock oscillation circuit that generates a clock signal, a first laser oscillator that emits a first pulse laser beam that is synchronized with the clock signal, and a clock signal that is synchronized with the clock signal. A second laser oscillator that emits the second pulsed laser beam, a first pulse picker that switches between passing and blocking the first pulsed laser beam in synchronization with the clock signal, and in synchronization with the clock signal. A first pulse picker control that controls the first pulse picker based on the number of optical pulses of the first pulse laser beam, and a second pulse picker that switches between passing and blocking of the second pulse laser beam And a second pulse picker for controlling the second pulse picker based on the number of light pulses of the second pulse laser beam. A car controller, a first attenuator that adjusts the output of the first pulse laser beam, and a second stage that is provided after the second pulse picker; A second attenuator for adjusting the output of the first pulse laser beam, and the first attenuator and the second attenuator after the second attenuator, and combining the first pulse laser beam and the second pulse laser beam. A combiner that generates a combined pulse laser beam, a laser beam scanner that scans the combined pulse laser beam only in a one-dimensional direction in synchronization with the clock signal, and a workpiece that can be placed thereon. a stage that moves in a direction perpendicular to the one-dimensional direction, an input unit for inputting the processed data of the workpiece, machining path for converting the processed data to the processing pattern And over plane generator, a processing pattern division unit that divides the processing pattern to the first sub-processing pattern and the second sub-processing pattern, wherein the first pulse picker control unit, the first sub based on the processing pattern, the first control pulse pickers, the second pulse picker control unit, based on the second sub-processing patterns, characterized that you control the second pulse picker .

  In the apparatus of the above aspect, it is preferable that the stage moves in a direction orthogonal to the one-dimensional direction based on a scanning angle signal from the laser beam scanner.

  In the apparatus of the above aspect, the first and second sub-machining patterns are preferably machining tables described by the number of light pulses of a pulse laser beam.

  In the apparatus of the above aspect, it is preferable that the laser beam scanner is constituted by a galvanometer scanner, and the pulse picker is constituted by an acousto-optic element (AOM) or an electro-optic element (EOM).

  According to the present invention, there are provided a pulse laser processing apparatus and a pulse laser processing method that improve the positioning accuracy of an irradiation spot of a pulse laser beam and enable stable fine processing of the surface of a large workpiece and its speed increase. It becomes possible.

It is a block diagram of the pulse laser processing apparatus of 1st Embodiment. It is explanatory drawing of the laser beam scanner using the galvanometer scanner of 1st Embodiment. It is explanatory drawing of the scanning of the laser beam scanner of the pulse laser processing apparatus of 1st Embodiment. It is a figure which shows the specific example of the process table which is an example of the definition format of the process pattern of 1st Embodiment. It is a signal waveform diagram explaining timing control of the pulse laser processing apparatus of the first embodiment. It is a signal waveform diagram explaining timing control of the pulse laser processing apparatus of the first embodiment. It is a signal waveform diagram explaining timing control of the pulse picker operation of the pulse laser processing apparatus according to the first embodiment. It is a schematic diagram explaining the process of the to-be-processed object by 1st Embodiment. It is a figure which shows the example of 1 process by the pulse laser processing apparatus of 1st Embodiment. It is a figure which shows the scanning of the specific one-dimensional direction in the process of FIG. It is a figure which shows the two-dimensional process about the specific layer in the process of FIG. It is a processing example of the metal mold | die formed by the manufacturing method of 2nd Embodiment.

  Hereinafter, a pulse laser processing apparatus and a pulse laser processing method according to embodiments of the present invention will be described with reference to the drawings.

  In this specification, “in the front stage” and “in the rear stage” of a certain member is a concept based on the traveling direction of the laser beam. Therefore, a member on the side of the laser beam traveling direction with respect to a certain member is a “rear stage” member.

(First embodiment)
The pulse laser processing apparatus of the present embodiment includes a reference clock oscillation circuit that generates a clock signal, a first laser oscillator that emits a first pulse laser beam that is synchronized with the clock signal, and a second that is synchronized with the clock signal. A second laser oscillator that emits a pulsed laser beam of the first pulse, a first pulse picker that switches between passing and blocking the first pulsed laser beam in synchronization with the clock signal, and a second pulsed laser in synchronization with the clock signal A second pulse picker that switches between passing and blocking of the beam, a first pulse picker control unit that controls the first pulse picker based on the number of light pulses of the first pulse laser beam, and a second pulse laser beam A second pulse picker control unit for controlling the second pulse picker based on the number of optical pulses of the first pulse picker, and a subsequent stage of the first pulse picker A first attenuator provided for adjusting the output of the first pulse laser beam, a second attenuator provided after the second pulse picker for adjusting the output of the second pulse laser beam, And a multiplexer for combining the first pulse laser beam and the second pulse laser beam to generate a combined pulse laser beam, in synchronization with the clock signal. A laser beam scanner that scans the combined pulse laser beam only in a one-dimensional direction; and a stage that can place a workpiece and moves in a direction orthogonal to the one-dimensional direction.

  The pulse laser processing apparatus according to the present embodiment includes a plurality of laser oscillators synchronized with the same clock signal, and can irradiate a workpiece by combining pulse laser beams emitted from these laser oscillators. That is, a plurality of laser systems are provided, and pulse laser beams obtained from the plurality of laser systems are multiplexed. With the combined pulsed laser beam, it is possible to increase the output and the repetition frequency of the laser beam during processing.

  The pulse laser processing apparatus of the present embodiment directly or indirectly synchronizes the pulse of the laser oscillator, the passage and blocking of the pulse laser beam, and the scanning of the laser beam scanner with the same reference clock signal. In this way, the positioning accuracy of the irradiation spot of the pulse laser beam is improved by maintaining the synchronization between the laser system and the beam scanning system.

  Further, it is possible to control the passage and blocking of the pulse laser beam based on the number of light pulses of the pulse laser beam. As a result, it becomes easy to maintain the synchronization of the pulse of the laser oscillator, the passage and block of the pulse laser beam, and the scanning of the laser beam scanner. Further, the configuration of the control circuit can be simplified. The pulse laser processing apparatus according to the present embodiment further improves the positioning accuracy of the irradiation spot of the pulse laser beam, and easily realizes stable fine processing of the surface of a large workpiece and its speed increase.

  FIG. 1 is a configuration diagram of a pulse laser processing apparatus according to the present embodiment. The pulse laser processing apparatus 10 includes, as main components, a processing data input unit 11, a first laser oscillator 12a, a second laser oscillator 12b, a first pulse picker 14a, a second pulse picker 14b, and a first pulse oscillator. Beam shaper 16a, second beam shaper 16b, first attenuator 17a, second attenuator 17b, multiplexer 40, laser beam scanner 18, XY stage unit 20, first pulse picker controller 22a, second 2 pulse picker control unit 22b, processing pattern dividing unit 50, and processing control unit 24. The processing control unit 24 includes a reference clock oscillation circuit 26 that generates a desired clock signal S1, a frequency divider 52, and a processing pattern generation unit 54.

  In the reference clock oscillation circuit 26, a reference clock signal S1 is generated. The reference clock signal S1 is divided by the frequency divider 52 into a first clock signal S1a and a second clock signal S1b. The first clock signal S1a and the second clock signal S1b are, for example, clock signals whose phases are shifted by 180 degrees. Further, for example, each frequency is half of the reference clock signal S1.

  The first laser oscillator 12a is configured to emit a pulsed laser beam PL1a synchronized with the first clock signal S1a. That is, the pulse laser beam PL1a synchronized with the reference clock signal S1 is emitted. The laser oscillator 12a desirably oscillates a ps (picosecond) laser beam or an fs (femtosecond) laser beam which is an ultrashort pulse.

  Here, the wavelength of the laser emitted from the first laser oscillator 12a is selected in consideration of the light absorption rate, light reflection rate, etc. of the workpiece. For example, in the case of a workpiece made of a metal material including Cu, Ni, difficult-to-cut material SKD11, or diamond-like carbon (DLC), use the second harmonic (wavelength: 532 nm) of an Nd: YAG laser. Is desirable.

  The first pulse picker 14 a is provided in the optical path after the first laser oscillator 12 a and before the laser beam scanner 18. Then, in synchronization with the first clock signal S1a, that is, in synchronization with the reference clock signal S1, the passage of the first pulse laser beam PL1a is switched between on and off (on / off) so that the workpiece (workpiece W) is switched. It is configured to switch between processing and non-processing. In this way, the first pulse laser beam PL1a becomes the first modulated pulse laser beam PL2a which is controlled to be turned on / off for the processing of the workpiece by the operation of the first pulse picker 14a.

  The first pulse picker 14a is preferably composed of an acousto-optic element (AOM), for example. Further, for example, a Raman diffraction type electro-optic element (EOM) may be used.

  The first beam shaper 16a turns the incident first pulse laser beam PL2a into a first pulse laser beam PL3a shaped into a desired shape. For example, a beam expander that expands the beam diameter at a constant magnification. Further, for example, an optical element such as a homogenizer for making the light intensity distribution in the beam cross section uniform may be provided. Further, for example, an element that makes the beam cross section circular or an optical element that makes the beam circularly polarized light may be provided.

  The first attenuator 17a is provided after the first pulse picker 14a, adjusts the output of the first pulse laser beam PL3a, and emits it as the first pulse laser beam PL4a. For example, the first attenuator 17a monitors the output of the first pulse laser beam PL4a with a beam sampler, and adjusts the first pulse laser beam PL3a to a desired output with a controller based on the monitoring result of the beam sampler. 1 pulse laser beam PL4a.

  The second laser oscillator 12b is configured to emit a pulsed laser beam PL1b synchronized with the second clock signal S1b. That is, the pulse laser beam PL1b synchronized with the reference clock signal S1 is emitted. The laser oscillator 12b desirably oscillates a ps (picosecond) laser beam or an fs (femtosecond) laser beam which is an ultrashort pulse.

  Here, the wavelength of the laser emitted from the second laser oscillator 12b is selected in consideration of the light absorption rate, light reflection rate, etc. of the workpiece. For example, in the case of a workpiece made of a metal material including Cu, Ni, difficult-to-cut material SKD11, or diamond-like carbon (DLC), use the second harmonic (wavelength: 532 nm) of an Nd: YAG laser. Is desirable.

  The second pulse picker 14 b is provided in the optical path after the first laser oscillator 12 b and before the laser beam scanner 18. Then, in synchronization with the second clock signal S1b, that is, in synchronization with the reference clock signal S1, the second pulse laser beam PL1b is switched between passing and blocking (on / off) of the workpiece (work W). It is configured to switch between processing and non-processing. As described above, the second pulse laser beam PL1b is changed to the second modulated pulse laser beam PL2b, which is controlled to be turned on / off for processing the workpiece by the operation of the second pulse picker 14b.

  The second pulse picker 14b is preferably composed of an acousto-optic element (AOM), for example. Further, for example, a Raman diffraction type electro-optic element (EOM) may be used.

  The second beam shaper 16b turns the incident first pulse laser beam PL2a into a second pulse laser beam PL3a shaped into a desired shape. For example, a beam expander that expands the beam diameter at a constant magnification. Further, for example, an optical element such as a homogenizer for making the light intensity distribution in the beam cross section uniform may be provided. Further, for example, an element that makes the beam cross section circular or an optical element that makes the beam circularly polarized light may be provided.

  The second attenuator 17b is provided after the second pulse picker 14b, adjusts the output of the second pulse laser beam PL3b, and emits the second pulse laser beam PL4b. For example, the second attenuator 17b monitors the output of the second pulse laser beam PL4b with a beam sampler, and adjusts the second pulse laser beam PL3b to a desired output with a controller based on the monitoring result of the beam sampler. 2 pulse laser beam PL4b.

  The multiplexer 40 includes, for example, a first mirror 40a and a second mirror 40b. The first mirror 40a is, for example, a folding mirror, and the second mirror 40b is, for example, a half mirror. The first mirror 40a is held by, for example, a holder having a drive system using a piezo element, and enables fine position adjustment. The multiplexer 40 combines the first pulse laser beam PL4a and the second pulse laser beam PL4b whose phases are shifted by 180 degrees, for example, to generate a combined pulse laser beam PL5.

  In this way, by combining two series of pulse laser beams generated by separate laser oscillators to generate a combined pulse laser beam, high output energy is ensured at a high repetition frequency, and the reliability of the laser oscillator is ensured. And can be realized.

  The laser beam scanner 18 is configured to scan the combined pulsed laser beam PL5 only in the one-dimensional direction in synchronization with the clock signal S1. As described above, by scanning the combined pulse laser beam PL5 in synchronization with the clock signal S1, the positioning accuracy of the irradiation spot of the pulse laser beam is improved.

  In addition, it is possible to improve the positioning accuracy of the irradiation spot of the pulse laser beam by performing scanning only in the one-dimensional direction. This is because a laser beam scanner that scans in a two-dimensional direction is structurally deteriorated with respect to a laser beam scanner that scans only in a one-dimensional direction.

  As the laser beam scanner 18, for example, a galvanometer scanner provided with a uniaxial scan mirror can be cited.

  FIG. 2 is an explanatory diagram of a laser beam scanner using a galvanometer scanner.

  The galvanometer scanner has a uniaxial scan mirror 28, a galvanometer 30, and a laser beam scanner controller 32. Here, the galvanometer 30 is provided with a scanning mirror rotation drive mechanism such as servo control by feedback from the scanning angle sensor 36, for example.

  A scanning command signal S2 synchronized with the clock signal S1 is sent from the processing control unit 24. The galvanometer 30 is configured to be driven and controlled by a driving signal S3 from the laser beam scanner control unit 32 based on the scanning command signal S2. The galvanometer scanner scans the combined pulsed laser beam PL5 totally reflected by the uniaxial scanning mirror 28 according to the rotational movement (swinging) of the scanning mirror as indicated by the arrow in FIG.

  The laser beam scanner 18 is provided with a scanning angle sensor 36. In the case of a galvanometer scanner, the rotation position of the single-axis scan mirror 28 is detected by a rotary encoder or the like. Then, the scanning angle sensor 36 sends the detected scanning angle detection signal S4 to the laser beam scanner control unit 32 and is used for driving control of the galvanometer 30. Further, the laser beam scanner control unit 32 transmits a scanning angle signal S5 to the processing control unit 24 based on the scanning angle detection signal S4.

  Then, the combined pulsed laser beam PL5 reflected by the uniaxial scanning mirror 28 passes through the fθ lens 34 and is scanned in a one-dimensional direction in parallel at a constant speed V, for example, at an image height H = fθ. The pulse laser beam PL6 is obtained. Then, the combined pulse laser beam PL6 is projected onto the workpiece W as irradiation pulse light that finely processes the surface of the workpiece W held on the XY stage unit 20.

  In addition to the galvanometer scanner, for example, a polygon scanner, a piezo scanner, a resonant scanner, or the like can be applied to the laser beam scanner 18.

  In any of the above laser beam scanners, it is important from the viewpoint of improving the processing accuracy that the laser beam scanner is configured to be controlled so as to ensure a constant scanning speed V within a processing range.

  FIG. 3 is a diagram for explaining scanning of the laser beam scanner of the pulse laser processing apparatus according to the present embodiment. As shown in FIG. 3, the position range corresponding to the scan end position from the scan start position in the scan angle range of the scan mirror includes an acceleration period, a stable region, and a deceleration period. In order to increase the processing accuracy, it is important that the apparatus is configured to control the scanning speed V to be constant within a stable range including the actual processing range.

  The XY stage unit 20 can place the workpiece W and can freely move in the XY direction including the direction orthogonal to the one-dimensional direction in which the pulse laser beam is scanned, its drive mechanism unit, and the XY stage. For example, a position sensor having a laser interferometer for measuring the position is provided. Here, the XY stage can be moved continuously or stepped in a two-dimensional wide range, for example, a distance range in the X direction and Y direction of about 1 m. And it is comprised so that the positioning accuracy and movement error may become the high precision of the range of a submicron.

  In the machining data input unit 11, machining data of a workpiece is input. The machining data includes, for example, designation of a three-dimensional shape, dimensions, number of shapes, arrangement, workpiece material name, workpiece dimensions, and the like. The designation of the three-dimensional shape is performed by, for example, bitmap format data in which the processed shape of the workpiece is included as color data. The processed data input unit 11 is, for example, a storage medium for storing processed data, for example, a storage medium reading device such as a semiconductor memory or a DVD (Digital Video Disk).

  The processing control unit 24 integrates and controls the processing by the pulse laser processing apparatus based on the processing data input from the processing data input unit 11. The processing control unit 24 includes a reference clock oscillation circuit 26 that generates a reference clock signal S1, and a frequency divider 52 that divides the reference clock signal S1 into a first clock signal S1a and a second clock signal S1b.

  Further, the machining control unit 24 includes a machining pattern generation unit 54 that converts the machining data input from the machining data input unit 11 into a machining pattern of parameter data in accordance with actual machining. The machining data is analyzed by the machining data analysis unit of the machining pattern generation unit 54. The processing amount of the unit light pulse can be obtained empirically from conditions such as the operation of the laser oscillator used for processing, the irradiation pulse energy, which is the beam scanning condition, the beam spot diameter, the repetition frequency, the scanning speed, and the stage feed amount. .

  Based on the above conditions, the three-dimensional shape is further decomposed into a two-dimensional layer and converted into two-dimensional data based on bitmap data for each layer. This two-dimensional data is converted into pulse picker operation data (number of machining pulses, number of non-machining pulses, number of standby length pulses).

  The machining pattern generated by the machining pattern generation unit 54 is, for example, a machining table in which a standby length, a machining length, and a non-machining length for each scan of the laser beam are described in units of pulses. For example, the processing data generation unit generates a processing table described in units of the number of pulses of the combined pulse laser beam after being combined.

  FIG. 4 is a diagram illustrating a specific example of a processing table which is an example of a processing pattern definition format. A certain one-layer processing table is shown. As shown in FIG. 4, the processing table describes, for example, the standby length, processing length, and non-processing length of the processing pattern based on the number of light pulses of the pulse laser beam. In FIG. 4, the stage feed (μm) is a movement distance moved in the Y direction orthogonal to the X direction by the XY stage unit after the scanning in the X direction by the laser beam scanner 18 is completed.

  The processing pattern division unit 50 has a function of dividing the processing pattern generated by the processing pattern generation unit 54 into a first sub processing pattern and a second sub processing pattern. The first sub-machining pattern is used to generate the first pulse laser beam PL2a from the first pulse laser beam PL1a. Further, the second sub-machining pattern is used to generate the second pulse laser beam PL2b from the second pulse laser beam PL1b.

  The first sub machining pattern is, for example, a machining table in which the standby length, machining length, and non-machining length for each scan of the laser beam are described in units of the number of pulses of the first pulse laser beam PL1a. The second sub machining pattern is, for example, a machining table in which the standby length, machining length, and non-machining length for each scan of the laser beam are described in units of the number of pulses of the second pulse laser beam PL1b. For example, the data of each line (each scan) of the processing table shown in FIG. 4 is divided into two for two laser series.

  The first sub machining pattern is transferred to the first pulse picker control unit 22a and used for controlling the first pulse picker 14a. Further, the second sub machining pattern is transferred to the second pulse picker control unit 22b and used for controlling the second pulse picker 14b.

  The processing control unit 24 and the processing pattern division unit 50 are hardware such as a microcomputer (MCU), a microprocessor (MPU), a digital signal processor (DSP), a semiconductor memory, a circuit board, or the like made of a semiconductor integrated circuit. And a combination of software.

  Next, a pulse laser processing method using the pulse laser processing apparatus 10 will be described. In this pulse laser processing method, a workpiece (work) is placed on a stage, a clock signal is generated, a first pulse laser beam synchronized with the clock signal is emitted, and an optical pulse of the first pulse laser beam is emitted. Based on the number, the irradiation with the first pulse laser beam is switched between irradiation and non-irradiation in synchronization with the clock signal, the second pulse laser beam synchronized with the clock signal is emitted, and the number of optical pulses of the second pulse laser beam is set. Based on this, switching between irradiation and non-irradiation of the second pulse laser beam in synchronization with the clock signal, and combining the first pulse laser beam and the second pulse laser beam to generate a combined pulse laser beam, The surface of the workpiece is scanned with the combined pulsed laser beam in a one-dimensional direction in synchronization with the clock signal, and the combined pulsed laser beam is scanned in the one-dimensional direction, followed by the primary And moving the stage in a direction orthogonal to the direction, further scanning in synchronization with a clock signal multiplexed pulsed laser beam in the one-dimensional direction.

  5 and 6 are signal waveform diagrams illustrating timing control of the pulse laser processing apparatus according to the present embodiment. When processing the workpiece W placed on the stage, the first and second laser oscillators 12a and 12b operate autonomously with most of the laser oscillation controlled by a built-in control unit. Of course, as shown in FIG. 5, the timing of pulse oscillation is controlled by the first clock signal S1a and the second clock signal S1b which are divided from the reference clock signal S1 having the period Tp generated by the reference clock oscillation circuit. Done.

  In this way, the first pulse laser beam PL1a and the second pulse laser beam PL1b synchronized with the reference clock signal S1 are emitted. Since the first clock signal S1a and the second clock signal S1b are divided so that the phases are different by 180 degrees, the first pulse laser beam PL1a and the second pulse laser beam PL1b are also different in phase by 180 degrees. .

  The first pulse laser beam PL1a and the second pulse laser beam PL1b are combined by the combiner 40, thereby generating a combined pulse laser beam PL5.

  The laser beam scanner 18 starts scanning at the scanning start position (scanning origin) shown in FIG. 3 based on the scanning start signal S11. At this time, as shown in FIG. 5, the laser beam scanner 18 receives an instruction from a scanning command signal S2 having a cycle Ts generated by the processing control unit 24 in synchronization with the rising (or falling) of the reference clock signal S1. . The laser beam scanner control unit 32 controls driving of the galvanometer 30 based on the scanning command signal S2.

  As described above, the laser beam scanner 18 scans the pulse laser beam in a one-dimensional direction in synchronization with the reference clock signal S1. At this time, a pattern is processed on the surface of the workpiece W by switching between irradiation and non-irradiation of the pulse laser beam. Note that the scan command signal S2 conforms to the XY2-100 protocol, and follows an absolute scan angle command based on the position of the scan angle “0 degree” of the galvanometer 30 at, for example, 100 kHz (Ts = 10 μsec).

  After scanning the combined pulsed laser beam PL6 in the one-dimensional direction, the stage is moved in a direction orthogonal to the one-dimensional direction, and the combined pulsed laser beam S6 is moved in the one-dimensional direction in synchronization with the reference clock signal S1. Scan in the direction. In this way, the scanning of the pulse laser beam in the one-dimensional direction and the movement of the stage are alternately performed in the direction orthogonal to the one-dimensional direction.

  Here, the scanning angle signal S5 from the laser beam scanner 18 instructs the movement timing of the XY stage unit. Assuming that the one-dimensional scanning direction of the laser beam scanner 18 is the X-axis direction, step movement or continuous movement of a predetermined width in the Y-axis direction is performed according to the movement timing. Thereafter, the pulse laser beam is scanned in the X direction.

  Here, in the acceleration period of FIG. 3, the laser beam scanner 18 is controlled by the scanning command signal S2 so that the scanning speed becomes a stable scanning speed V at an early stage. It is empirically clear that the reproducibility of the scanning angle of the uniaxial scanning mirror 28 under the optimum condition is about 10 μrad / pp in the stable region. This value becomes a scanning position reproducibility of 1 μm / pp when an fθ lens having a focal length of 100 mm is used.

  However, the repeated stability of the scanning speed V during the acceleration period deteriorates to about 10 times in the long-term scanning. For this reason, the position of the processing origin in FIG. 3 may vary from scan to scan. Therefore, a synchronization angle (θsy) for synchronizing the oscillation of the pulse laser beam PL1 and the beam scanning is set in a sufficiently stable region after the end of the acceleration period. The scanning angle range until reaching a sufficiently stable region is, for example, about 2.3 degrees to 3.4 degrees when an fθ lens having an acceleration period of 1 msec to 1.5 msec and a focal length of 100 mm is used.

Then, as shown in FIG. 6, the scanning angle sensor 36 detects this synchronization angle as a synchronization angle detection signal S12. Then, a phase difference θi between the scan command signal S2 corresponding to the scanning angle theta ₀ from the scanning start position in detecting the synchronization angle. Then, based on this phase difference θ _i , the distance to the processing origin with respect to the scanning command signal S2 is corrected.

As the correction value of the distance to the processing origin, the first scanning (i = 1) at the time of processing is stored as a reference correction value. Then, each time scanning from the n-th scanning start position where i = n thereafter, the difference between the phase difference θ _n and the phase difference θ ₁ is processed for the scanning command signal S2 for the first scanning of the n-th scanning. The distance correction value to the origin is used. The determined distance correction value, the scanning command signal to the scanning angle theta ₀ from the scanning start position: By giving the (S2 absolute scanning angle command) after the scanning command signal (S2), machining origin position is corrected. In this way, even if the scanning speed varies during the acceleration period of the laser beam scanner 18, it is possible to match the processing origin positions during the first scan and the n-th scan.

  As described above, after scanning the combined pulse laser beam PL6 in the one-dimensional direction, the stage is moved in a direction orthogonal to the one-dimensional direction, and further, the combined pulse laser beam is synchronized with the reference clock signal S1. In the case where the PL 6 is scanned in the one-dimensional direction, the machining origin position for each scan coincides and the machining accuracy is improved.

  When the combined pulse laser beam PL6 is scanned in the one-dimensional direction, irradiation of the combined pulse laser beam PL6 in synchronization with the reference clock signal S1 based on the number of optical pulses of the combined pulse laser beam PL6. And non-irradiation. Irradiation and non-irradiation of the pulse laser beam are performed using the first and second pulse pickers 14a and 14b.

  FIG. 7 is a signal waveform diagram illustrating timing control of the pulse picker operation of the pulse laser processing apparatus according to the present embodiment. A machining pattern signal S7 generated from the machining data and managed by the number of light pulses, for example, is output from the machining pattern generation unit 54.

As shown in FIG. 7, the first pulse laser beam PL1a delayed by t ₁ from the first clock signal S1a generated from the reference clock signal S1 having the period Tp is blocked / generated based on the first pulse picker driving signal S6a. Passage is controlled. The scanning of the laser beam scanner 18 is synchronized with the blocking / passing of the first pulse laser beam by synchronizing the generation timing of the scanning angle command signal S2 with the reference clock signal S1.

For example, the first pulse picker driving signal S6a samples the first machining pattern signal S7a generated by the machining pattern dividing unit 54 from the machining pattern signal S7 at the rising edge of the first clock signal S1a. The rises in t ₂ hours delay from the rise of one clock of the first clock signal S1a. After the number of clocks corresponding to the number of desired pulses, the state in which the first processing pattern signal S7a becomes inactive sampled at the rising edge of the first clock signal S1a, falls with a delay t ₃ hours.

Then, by the first pulse picker drive signal S6a, the operation of the first pulse picker 14a occurs after a delay time _{t 4} and _{t 5} elapses. By the operation of the first pulse picker 14a, the first pulse laser beam PL1a is extracted as the first modulated pulse laser beam PL2a.

Similarly, the second pulse laser beam PL1b from the second clock signal S1b generated from the reference clock signal S1 periods Tp and t ₁ delay shutoff / passage is controlled based on the second pulse picker drive signal S6b The The scanning of the laser beam scanner 18 and the interruption / passage of the second pulse laser beam are performed by synchronizing the generation timing of the scanning angle command signal S2 with the reference clock signal S1.

For example, the second pulse picker driving signal S6b samples the second machining pattern signal S7b generated by the machining pattern dividing unit 54 from the machining pattern signal S7 at the rising edge of the second clock signal S1b. Then, it rises from the rising one clock of the second clock signal S1b is delayed t ₂ hours. After the number of clocks corresponding to the number of required pulses, a state where the second processing pattern signal S7b becomes inactive sampled at the rising edge of the second clock signal S 1 b, it falls with a delay t ₃ hours.

Then, by the second pulse picker drive signal S6b, the operation of the second pulse picker 14b occurs after a delay time _{t 4} and _{t 5} elapses. By the operation of the second pulse picker 14b, the second pulse laser beam PL1b is extracted as the second modulated pulse laser beam PL2b.

  The first modulated pulse laser beam PL2a and the second modulated pulse laser beam PL2b are combined by the combiner 40 (FIG. 1), thereby generating a combined pulse laser beam PL5 synchronized with the reference clock signal S1. By the scanning of the laser beam scanner 18 synchronized with the reference clock signal S1, the workpiece is irradiated as a combined pulse laser beam PL6.

  FIG. 8 is a schematic diagram for explaining processing of a workpiece according to the present embodiment. As shown in FIG. 8, each of the first and second modulated pulse laser beams PL2a and PL2b generated by the first and second pulse picker operations is obtained by the first and second beam shapers. Shaped into shape. Further, the two outputs are adjusted by the first and second attenuators so as to be equal to each other and are combined by the multiplexer 40.

  The combined pulsed laser beam PL5 generated in this way has an output twice as long as a unit length as compared with a case where only one laser system is used. The combined pulse laser beam PL5 is irradiated to a predetermined position of the workpiece W by scanning in the X-axis direction by the laser beam scanner and movement of the workpiece W position by the XY stage unit 20 in the Y-axis direction. Fine processing of the W surface with high output and high accuracy is possible. Note that the time width of the pulse picker operation and the time interval of each operation in FIG. 8 may be different from each other.

  Next, pulse picker operation data for each layer, that is, the number of machining pulses, the number of non-machining pulses, and the number of standby length pulses will be described. FIG. 9 is a diagram showing an example of processing by the pulse laser processing apparatus of the present embodiment. FIG. 10 is a diagram showing scanning in a specific one-dimensional direction in the processing of FIG. FIG. 11 is a diagram showing two-dimensional processing for a specific layer in the processing of FIG.

As shown in FIG. 9, for example, LX ₁ (horizontal) × LY ₁ (vertical) × Dp (depth), specifically, for example, a pocket of 52.5 μm × 37.5 μm × 0.1 Rn μm It is formed at the top nine locations. In this machining example, the machining direction of LX ₁ and the non-machining length of LX ₂ are performed in the X direction that is the beam scanning direction, and the machining length of LY ₁ is performed in the Y direction that is the stage moving direction. _2. Processing of non-processed length of LY ₃ is performed.

  Here, Rn is the number of layers decomposed in the depth direction of the workpiece.

FIG. 10 shows one-dimensional scanning of one line in the region corresponding to LY ₁ in the Y direction. S _L + W ₁ from the sync angle detection position, the number of light pulses is (S _L + W ₁ ) / (D / n) Lw based on the processing origin (SYNC) that is a distance away, and the number of light pulses is L _W / (D / The workpiece is irradiated with a pulsed laser beam with a waiting length of n). The irradiation with the number of light pulses _{(LX 1 / (D / n} )) - 1. Thereafter, the number of light pulses is not irradiated for (LX ₂ / (D / n)) + 1, and irradiation and non-irradiation controlled by the number of light pulses are repeated in the same scan.

  Here, D is a beam spot diameter, and n is a beam irradiation movement ratio. The beam irradiation movement ratio is a value of n when the movement amount between beam spots is D / n.

  When the line scan in the specific X direction is completed by the laser beam scanner 18 scanned only in the one-dimensional direction, the stage is moved in the Y direction orthogonal to the X direction, and further the X direction scan is performed by the laser beam scanner 18. I do. That is, the workpiece is processed by alternately repeating the scanning in the one-dimensional direction of the combined pulse laser beam by the laser beam scanner 18 and the movement of the stage in the direction orthogonal to the one-dimensional direction following this scanning.

  In this way, two-dimensional processing for a specific layer as shown in FIG. 11 is performed. Further, two-dimensional processing is performed on another layer generated by layer decomposition by the same method as shown in FIG. Such processing for each layer is repeated to finally complete the three-dimensional pocket processing as shown in FIG.

For example, as one laser system is used, the processing scanning condition is
Scanning speed: 30.0m / sec
Beam spot diameter: 15.0μm
Then,
Beam spot unit travel: 7.5μm
In order to achieve this, a repetition frequency of 4 MHz is required.

  Here, when two laser systems are used for the above conditions as in the present embodiment, each series of laser oscillators can satisfy the machining scanning condition at a repetition frequency of 2 MHz. This is because when a picosecond laser oscillator having a repetition frequency of “2 MHz” and a SHG (Second Harmonic Generation) output of “3 W” is used, processing at a repetition frequency of 4 MHz is equivalent to energy of 1.5 μJ. "It can be processed to the extent."

  For example, if one laser oscillator is used at a high repetition rate such as “4 MHz”, the beam profile is deteriorated, the damage rate of the nonlinear crystal is increased, the lifetime of the nonlinear crystal is shortened, the energy per pulse is reduced, the laser There is concern about unstable output. According to the present embodiment, in order to perform the same level of processing, the repetition frequency of one laser oscillator is half, for example, “2 MHz”. For this reason, deterioration of the beam profile, increase of the damage rate of the nonlinear crystal, shortening of the lifetime of the nonlinear crystal, reduction of energy per pulse, destabilization of the laser output, and the like are suppressed.

  For example, when one laser oscillator is used at a repetition frequency of “4 MHz”, it is necessary to consider the influence of prepulses and postpulses. According to the present embodiment, in order to perform the same level of processing, the repetition frequency of one laser oscillator is half, for example, “2 MHz”. This reduces the burden of considering the effects of prepulses and postpulses.

  Here, in order to improve the processing quality of the workpiece, generally the beam spot unit moving amount is reduced. For example, when the beam spot unit moving amount is 5 μm and 3 μm, the scanning speed is 20.0 m / sec and 12.0 m / sec, respectively.

When the laser beam scanner is a galvanometer, if the processing range is 100 mm and the repetition frequency of each oscillator is 2 MHz, the actual processing scan time is
Beam spot unit moving amount = 5 μm: 10 msec for laser 1 series
: 5msec when laser 2 series
Beam spot unit moving amount = 3 μm: Laser 1 series 16.6 msec
: 8.3 msec when laser 2 series
Beam spot unit movement amount = 7.5 μm: Laser 1 series 6.6 msec
: Laser 2 series 3.3msec
In the case of two series, since it is possible to irradiate twice as many beam spots as one series per unit time, the scanning time is shortened.

(Second Embodiment)
The present embodiment is a microlens mold manufacturing method using the pulse laser processing apparatus and pulse laser processing method of the first embodiment, a microlens mold manufactured using the same, and this This is a method of manufacturing a microlens using a microlens mold.

  For example, a microlens used for a flat panel display is required to have a large area and high processing accuracy. Therefore, when manufacturing this microlens using a metal mold, the metal mold inevitably requires a large area and high processing accuracy. FIG. 12 shows an example of processing a mold formed by the manufacturing method of the present embodiment.

  As shown in FIG. 12, for example, dimples having a diameter R and a depth Dp are formed at nine locations with a spacing I on a Cu workpiece. Laser processing is performed in the same manner as in the first embodiment. By using a table conforming to the three-dimensional shape of FIG. 12 as the processing table, the processing of FIG. 12 can be realized. According to the present embodiment, it is possible to manufacture a microlens mold having a large area and high accuracy.

  The microlens mold is useful for manufacturing a large-area and high-precision microlens. According to the microlens manufacturing method using this microlens mold, it is possible to manufacture a large-area and high-precision microlens.

  The embodiments of the present invention have been described above with reference to specific examples. However, the present invention is not limited to these specific examples. In the pulse laser processing apparatus, the pulse laser processing method, etc., the description of the parts that are not directly necessary for the explanation of the present invention is omitted, but the required pulse laser processing apparatus and the pulse laser processing method should be appropriately selected and used. Can do. In addition, all pulse laser processing apparatuses and pulse laser processing methods that include the elements of the present invention and that can be appropriately modified by those skilled in the art are included in the scope of the present invention.

  For example, in the embodiment, the case where the laser system is two series has been described as an example. However, it is also possible to apply three or more series.

  Further, for example, in the embodiment, the case of processing pockets and dimples has been described as an example. However, the present invention is not limited to these shapes. For example, a conical shape or a triangular pyramid for manufacturing a rib for electronic paper is used. Further, a pulse laser processing apparatus or a pulse laser processing method for processing an arbitrary shape such as a square pyramid, a V groove, a concave groove, an R groove, or a combination thereof may be used.

  Moreover, although Cu material was mainly demonstrated to the example as a to-be-processed object, even if it is other materials, such as metal materials, such as Ni material and SKD11, DLC material, a polymer material, a semiconductor material, a glass material, for example, I do not care.

Further, the laser oscillator is not limited to the YAG laser, but is a single wavelength band laser such as a second harmonic (wavelength: 532 nm) of other Nd: YVO ₄ laser suitable for processing a workpiece. Or you may output a multiple wavelength band laser.

DESCRIPTION OF SYMBOLS 10 Pulse laser processing apparatus 11 Processing data input part 12a 1st laser oscillator 12b 2nd laser oscillator 14a 1st pulse picker 14b 2nd pulse picker 17a 1st attenuator 17b 2nd attenuator 18 Laser beam scanner 20 XY Stage unit 22a First pulse picker control unit 22b Second pulse picker control unit 26 Reference clock oscillation circuit 50 Processing pattern division unit 52 Frequency divider 54 Processing pattern generation unit

Claims (4)

A reference clock oscillation circuit for generating a clock signal;
A first laser oscillator that emits a first pulsed laser beam synchronized with the clock signal;
A second laser oscillator that emits a second pulse laser beam synchronized with the clock signal;
A first pulse picker that switches between passing and blocking of the first pulsed laser beam in synchronization with the clock signal;
A second pulse picker that switches between passing and blocking of the second pulse laser beam in synchronization with the clock signal;
A first pulse picker controller that controls the first pulse picker based on the number of light pulses of the first pulse laser beam;
A second pulse picker controller that controls the second pulse picker based on the number of light pulses of the second pulse laser beam;
A first attenuator provided at a subsequent stage of the first pulse picker and for adjusting an output of the first pulse laser beam;
A second attenuator provided at a subsequent stage of the second pulse picker and for adjusting an output of the second pulse laser beam;
A multiplexer provided at a stage subsequent to the first attenuator and the second attenuator, for combining the first pulse laser beam and the second pulse laser beam to generate a combined pulse laser beam;
A laser beam scanner that scans the combined pulsed laser beam only in a one-dimensional direction in synchronization with the clock signal;
A stage on which a workpiece can be placed and moves in a direction perpendicular to the one-dimensional direction;
An input unit for inputting machining data of the workpiece;
A machining pattern generator for converting the machining data into a machining pattern;
A processing pattern dividing unit for dividing the processing pattern into a first sub-processing pattern and a second sub-processing pattern ;
Equipped with a,
The first pulse picker control unit controls the first pulse picker based on the first sub-machining pattern;
The second pulse picker control unit, based on the second sub-processing pattern, pulse laser processing apparatus characterized that you control the second pulse picker.   The pulse laser processing apparatus according to claim 1, wherein the stage moves in a direction orthogonal to the one-dimensional direction based on a scanning angle signal from the laser beam scanner. 3. The pulse laser machining apparatus according to claim 1, wherein the first and second sub machining patterns are machining tables described by the number of light pulses of a pulse laser beam. The laser beam scanner is constituted by a galvanometer scanner, the pulse picker acoustooptic element (AOM) or claims 1 to 3 any one, characterized in that it is constituted by an electro-optical element (EOM) The pulse laser processing apparatus described in 1.

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