Laser device, laser processing system, and laser processing method

Abstract

A laser device according to one aspect of the present disclosure is used in a laser processing system for performing laser processing by irradiating a workpiece with laser light in a gas including oxygen, the laser device comprising: a solid-state oscillator including a solid-state laser device that outputs laser light having a pulse width within the range of 100 ps to 1 ns and a center wavelength obtained by removing an oxygen absorption line in the oscillation wavelength range of an ArF excimer laser device; an ArF excimer amplifier that amplifies the laser light output from the solid-state oscillator; and a first optical pulse stretcher that outputs burst-pulsed laser light by dividing the laser light amplified by the ArF excimer amplifier into a plurality of pulses by causing the laser light to circulate through a delay optical path.

Description

[Technical Field]

[0001] This disclosure relates to a laser device, a laser processing system, and a laser processing method. [Background technology]

[0002] In recent years, semiconductor lithography equipment has been required to improve resolution as semiconductor integrated circuits become smaller and more integrated. Therefore, efforts are being made to shorten the wavelength of light emitted from lithography light sources. For example, KrF excimer laser equipment that outputs laser light with a wavelength of approximately 248.0 nm, and ArF excimer laser equipment that outputs laser light with a wavelength of approximately 193.4 nm are used as gas laser equipment for lithography.

[0003] The spectral linewidth of the spontaneously emitted light from KrF and ArF excimer laser systems is broad, ranging from 350 pm to 400 pm. Therefore, when a projection lens is constructed using a material that transmits ultraviolet light, such as KrF and ArF laser light, chromatic aberration may occur. As a result, the resolution may decrease. Therefore, it is necessary to narrow the spectral linewidth of the laser light output from a gas laser system until chromatic aberration is negligible. For this reason, a line narrowing module (LNM) containing narrowing elements (such as etalons or gratings) may be provided inside the laser resonator of a gas laser system to narrow the spectral linewidth. In the following, a gas laser system with a narrowed spectral linewidth will be referred to as a narrow-band gas laser system. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] U.S. Patent Application Publication No. 2018 / 0057390 [Patent Document 2] U.S. Patent Application Publication No. 2019 / 0245321 [Patent Document 3] International Publication No. 2021 / 024436 [Patent Document 4] Japanese Patent Application Publication No. 3-157917 [Patent Document 5] Japanese Patent Publication No. 2010-145038 [Patent Document 6] Summary of International Publication No. 2018 / 100638

[0005] A laser device relating to one aspect of this disclosure is a laser device used in a laser processing system that performs laser processing by irradiating a workpiece with laser light in an oxygen-containing gas, and comprises a solid oscillator including a solid laser device that outputs laser light having a pulse width in the range of 100 ps to 1 ns and a center wavelength that is outside the oxygen absorption line in the oscillation wavelength range of an ArF excimer laser device; an ArF excimer amplifier that amplifies the laser light output from the solid oscillator; and a first optical pulse stretcher that outputs laser light that is divided into multiple pulses by making the laser light amplified by the ArF excimer amplifier circulate through a delayed optical path and is converted into burst pulses.

[0006] A laser processing system according to one aspect of the present disclosure is a laser processing system that performs laser processing by irradiating a workpiece with laser light in an oxygen-containing gas, and comprises a solid oscillator including a solid laser device that outputs laser light having a pulse width in the range of 100 ps to 1 ns and a center wavelength that is outside the oxygen absorption line in the oscillation wavelength range of an ArF excimer laser device; an ArF excimer amplifier that amplifies the laser light output from the solid oscillator; a first optical pulse stretcher that outputs laser light that is divided into a plurality of pulses by making the laser light amplified by the ArF excimer amplifier circulate through a delayed optical path and is thus burst-pulsed; and an optical device that irradiates the workpiece with the burst-pulsed laser light output from the laser device.

[0007] A laser processing method relating to one aspect of this disclosure is a laser processing method that performs laser processing by irradiating a workpiece with laser light in an oxygen-containing gas, and includes a solid oscillator including a solid laser device that outputs laser light having a pulse width in the range of 100 ps to 1 ns and a center wavelength that is outside the oxygen absorption line in the oscillation wavelength range of an ArF excimer laser device; an ArF excimer amplifier that amplifies the laser light output from the solid oscillator; and a first optical pulse stretcher that outputs laser light that is divided into a plurality of pulses by making the laser light amplified by the ArF excimer amplifier circulate through a delayed optical path and is thus burst-pulsed laser light, and the burst-pulsed laser light generated by the laser device is irradiated onto a workpiece to perform laser processing. [Brief explanation of the drawing]

[0008] Some embodiments of this disclosure are described below, merely as examples, with reference to the accompanying drawings. [Figure 1] Figure 1 is a schematic diagram showing the configuration of a laser processing system related to a comparative example. [Figure 2] Figure 2 is a schematic diagram showing the configuration of a laser apparatus related to a comparative example. [Figure 3] Figure 3 is a graph showing an example of a pulse waveform of laser light output from a laser device. [Figure 4] Figure 4 is a graph showing the spectral waveform of ArF excimer laser light. [Figure 5] Figure 5 is a graph showing the relationship between the repetition frequency of the laser light output by the laser device in the comparative example and the power of the laser light at the irradiated surface. [Figure 6] Figure 6 is a schematic diagram showing the configuration of the laser apparatus according to the first embodiment. [Figure 7] Figure 7 illustrates the burst pulse generation by the third OPS. [Figure 8] Figure 8 is a graph showing an example of the waveform of burst-pulsed laser light output from the laser device according to the first embodiment. [Figure 9] FIG. 9 is a graph showing the relationship between the repetition frequency of the laser light output from the laser device according to the first embodiment and the power of the laser light on the irradiated surface. [Figure 10] FIG. 10 is a graph showing the absorption spectra of ozone and oxygen. [Figure 11] FIG. 11 is a diagram schematically showing the light intensity of a single pulse. [Figure 12] FIG. 12 is a diagram schematically showing a burst pulse generated by dividing the single pulse shown in FIG. 11. [Figure 13] FIG. 13 is a cross-sectional photograph showing the result of drilling with the laser processing system according to the first embodiment. [Figure 14] FIG. 14 is a graph showing the relationship between the number of pulses and the processing depth shown in FIG. 13. [Figure 15] FIG. 15 is a graph showing the relationship between fluence and ablation rate. [Figure 16] FIG. 16 is a block diagram schematically showing the configuration of the solid-state laser device according to the first embodiment. [Figure 17] FIG. 17 is a block diagram schematically showing the configuration of the solid-state laser device according to a modification of the first embodiment. [Figure 18] FIG. 18 is a block diagram schematically showing the configuration of the laser device according to the second embodiment. [Figure 19] [[ID=3I]]FIG. 19 is a graph showing an example of the waveform of the burst-pulsed laser light output from the laser device according to the second embodiment. [Figure 20] [[ID=A]]FIG. 20 is a cross - sectional photograph showing the result of drilling with the laser processing system according to the second embodiment. [Figure 21] FIG. 21 shows the result of drilling with the laser processing system according to the first embodiment. [Figure 22] FIG. 22 is a graph showing an example of the waveform of the single - pulse laser light output from the laser device according to the comparative example. [Figure 23] It should be noted that there seems to be a mislabeling in the original text where "図31" is likely a misspelling and should be "図3I" in the context. The translation is adjusted accordingly.Figure 23 is a cross-sectional photograph showing the results of drilling using the laser processing system in the comparative example. [Figure 24] Figure 24 is a cross-sectional photograph showing the results of drilling using the laser processing system according to the second embodiment. [Figure 25] Figure 25 is a schematic block diagram showing the configuration of the laser device according to the third embodiment. [Figure 26] Figure 26 is a schematic block diagram showing the configuration of the laser apparatus according to the fourth embodiment. [Figure 27] Figure 27 is a graph showing an example of the waveform of burst-pulsed laser light output from the laser device according to the fourth embodiment. [Figure 28] Figure 28 is a block diagram schematically showing the configuration of a solid-state laser device according to the first modified example. [Figure 29] Figure 29 is a block diagram schematically showing the configuration of a solid-state laser device according to the second modified example. Embodiment

[0009] <Contents> 1. Comparative Example 1.1 Laser Processing System 1.1.1 Configuration 1.1.2 Operation 1.2 Laser equipment 1.2.1 Configuration 1.2.2 Operation 1.3 Challenges 2. First Embodiment 2.1 Configuration 2.2 Operation 2.3 Effects 2.4 Solid-state laser devices 2.4.1 Configuration and Operation 2.5 Variations of Solid State Laser Devices 2.5.1 Configuration and Operation 3. Second Embodiment 3.1 Configuration and Operation 3.2 Effects 4. Third Embodiment 4.1 Configuration and Operation 5. Fourth Embodiment 5.1 Configuration and Operation 5.2 Effects 6. Modified Solid-State Laser Devices 6.1 First Variation 6.1.1 Configuration and Operation 6.1.2 Effects 6.2 Second Variation 6.2.1 Configuration and Operation 6.2.2 Effects

[0010] The embodiments of this disclosure will be described in detail below with reference to the drawings. The embodiments described below are examples of the disclosure and are not intended to limit the scope of this disclosure. Furthermore, not all configurations and operations described in each embodiment are necessarily essential to the configurations and operations of this disclosure. The same reference numerals are used for identical components, and redundant descriptions are omitted.

[0011] 1. Comparative Example 1.1 Laser Processing System 1.1.1 Configuration Figure 1 schematically shows the configuration of the laser processing system 1 according to the comparative example. Note that the comparative example is a form that the applicant recognizes as being known only to the applicant, and is not a prior art example that the applicant acknowledges.

[0012] The laser processing system 1 mainly consists of a laser device 2 and a laser processing device body 4. The laser device 2 and the laser processing device body 4 are connected by an optical path tube 5. The laser processing system 1 is used, for example, to drill holes in glass substrates for interposers.

[0013] The laser processing apparatus body 4 includes a laser processing processor 40, an optical device 41, a frame 42, a moving stage 43, and a table 44. The optical device 41 and the moving stage 43 are fixed to the frame 42.

[0014] The table 44 supports the workpiece 45. The workpiece 45 is the object to be processed by irradiating it with laser light L. The workpiece 45 is a substrate that is transparent to ultraviolet laser light L, for example, an Eagle glass substrate or a quartz glass substrate.

[0015] The moving stage 43 supports the table 44. The moving stage 43 is movable in the X, Y, and Z directions, and the position of the workpiece 45 can be adjusted by adjusting the position of the table 44. Under the control of the laser processing processor 40, the moving stage 43 adjusts the position of the workpiece 45 so that the laser beam L output from the optical device 41 is irradiated to the desired processing position.

[0016] The optical device 41 comprises a housing 41a, high-reflection mirrors 47a, 47b, and 47c, an attenuator 49, a focusing optical system 48, and a window 46, and transfers an image corresponding to the processing shape onto the surface of the workpiece 45. The high-reflection mirrors 47a, 47b, and 47c, and the focusing optical system 48 are each fixed to holders and are arranged in predetermined positions within the housing 41a.

[0017] During operation of the laser processing system 1, nitrogen (N2) gas, an inert gas, constantly flows inside the housing 41a. The housing 41a is provided with an intake port 41b for drawing nitrogen gas into the housing 41a and an exhaust port 41c for discharging nitrogen gas from the housing 41a to the outside. Intake pipes, exhaust pipes, etc. (not shown) can be connected to the intake port 41b and the exhaust port 41c. A nitrogen gas supply source 41d is connected to the intake port 41b.

[0018] The high-reflection mirrors 47a, 47b, and 47c reflect the laser light L output from the laser device 2 with high reflectivity. High-reflection mirror 47a reflects the laser light L output from the laser device 2 toward high-reflection mirror 47b. High-reflection mirror 47b reflects the laser light L toward high-reflection mirror 47c. High-reflection mirror 47c reflects the laser light L toward the focusing optical system 48. The high-reflection mirrors 47a, 47b, and 47c are, for example, transparent substrates made of synthetic quartz or calcium fluoride, and their surfaces are coated with a reflective film that highly reflects the laser light L.

[0019] The focusing optical system 48 focuses the incident laser beam L and outputs it towards the workpiece 45 through the window 46. Specifically, the focusing optical system 48 is positioned so that the beam waist position of the focused laser beam L is within the workpiece 45 and the beam can be focused to a predetermined depth ΔZsfw from the incident side surface of the workpiece 45. The focusing optical system 48 may be a single lens or a set of lenses with aberration correction.

[0020] The window 46 is positioned in the optical path between the focusing optical system 48 and the workpiece 45, and is fixed in an opening formed in the housing 41a, sealed by an O-ring (not shown). There is air between the window 46 and the workpiece 45.

[0021] The attenuator 49 is located within the housing 41a on the optical path between the high-reflection mirror 47a and the high-reflection mirror 47b. The attenuator 49 includes, for example, two partial-reflection mirrors 49a and 49b, and rotation stages 49c and 49d for these partial-reflection mirrors. The partial-reflection mirrors 49a and 49b are optical elements whose transmittance changes depending on the incident angle of the laser beam L. The tilt angles of the partial-reflection mirrors 49a and 49b are adjusted by the rotation stages 49c and 49d so that the incident angles of the laser beam L coincide with each other and the transmittance is desired.

[0022] 1.1.2 Operation Next, the operation of the laser processing system 1 will be described. When laser processing is performed, the workpiece 45 is set on the table 44 of the moving stage 43. The laser processing processor 40 sets the initial processing position data on the moving stage 43.

[0023] On the moving stage 43, the workpiece 45 is moved to the initial laser processing position. Specifically, the workpiece 45 is positioned in the YZ plane and in the X direction. For the position in the X direction, the laser processing processor 40 moves the workpiece 45 so that the beam waist position of the laser beam L output from the focusing optical system 48 is at a position ΔZsfw from the surface of the workpiece 45. At the beam waist position, the laser beam L is focused with a predetermined irradiation diameter Dw.

[0024] Next, the laser processing processor 40 transmits a target pulse energy Et to the laser device 2 and controls the transmittance T of the attenuator 49 so that the laser light L irradiated onto the workpiece 45 has a target fluence Fm. Specifically, the laser processing processor 40 controls the energy incident on the workpiece 45 by controlling the target pulse energy Et and the transmittance T of the attenuator 49.

[0025] Here, the target fluence Fm is the fluence required for laser processing, and is the irradiation energy density of the laser light L at the beam waist position. If the optical loss of optical elements other than the attenuator 49 of the optical device 41 is negligible, the target fluence Fm is defined by the following equation (1).

[0026]

number

[0027] In this case, the transmittance T of the attenuator 49 is determined by equation (2) below, which is obtained by rearranging equation (1) above.

[0028]

number

[0029] After setting the transmittance T of the attenuator 49, the laser processing processor 40 transmits a light emission trigger signal Tr0, defined by the repetition frequency and the number of pulses, to the laser device 2. As a result, laser light L is output from the laser device 2 to the laser processing device body 4 in synchronization with the light emission trigger signal Tr0.

[0030] The laser beam L incident on the laser processing apparatus body 4 passes through the high-reflection mirror 47a and is incident on the attenuator 49, where it is attenuated. The laser beam L that has passed through the attenuator 49 is reflected by the high-reflection mirror 47b and incident on the high-reflection mirror 47c. The laser beam L reflected by the high-reflection mirror 47c is incident on the focusing optical system 48.

[0031] The laser beam L that has passed through the focusing optical system 48 is focused through the window 46 to a predetermined depth ΔZsfw within the workpiece 45, from the incident side surface of the workpiece 45. As a result, the laser beam L is irradiated into the workpiece 45 at a predetermined depth ΔZsfw with a predetermined fluence, repetition frequency, and pulse count, and the workpiece 45 is drilled using the laser beam L.

[0032] In this disclosure, the reflectance or transmittance of the high-reflectance mirrors 47a, 47b, 47c, the focusing optical system 48, and the window 46 are assumed to be 100%, but these reflectances or transmittances are not limited to 100%. For example, the transmittance T0 of the entire optical element may be determined in advance, and the transmittance T of the attenuator 49 may be determined based on the following equation (3).

[0033]

number

[0034] 1.2 Laser equipment 1.2.1 Configuration Figure 2 schematically shows the configuration of the laser device 2 according to the comparative example. The laser device 2 includes a solid oscillator 10, an ArF excimer amplifier 20, a monitor module 30, and a laser processor 50.

[0035] The solid oscillator 10 includes a solid laser device 11 that outputs pulsed laser light L having a central wavelength within the oscillation wavelength range of a typical ArF excimer laser device. The oscillation wavelength range of an ArF excimer laser device is, for example, a wavelength range of 193.0 nm to 193.9 nm.

[0036] The ArF excimer amplifier 20 is an excimer laser device that uses a mixed gas containing argon (Ar), fluorine (F2), and neon (Ne) as the laser medium.

[0037] The ArF excimer amplifier 20 includes a laser chamber 21, a pulse power module (PPM) 22, a charger 23, a convex mirror 25a, and a concave mirror 25b. The laser chamber 21 is provided with windows 21a and 21b. Laser gas is sealed inside the laser chamber 21 as the laser medium.

[0038] Furthermore, an opening is formed in the laser chamber 21, and an electrical insulating plate 26 with multiple feedthroughs 26a embedded in it is provided to close this opening. A PPM 22 is placed on the electrical insulating plate 26. Inside the laser chamber 21 are a pair of discharge electrodes 27a and 27b as the main electrodes, and a ground plate 28.

[0039] The discharge electrodes 27a and 27b are arranged so that their discharge surfaces face each other in order to excite the laser medium by discharge. The space between the discharge surface of discharge electrode 27a and the discharge surface of discharge electrode 27b is called the discharge space. The side of discharge electrode 27a opposite to the discharge surface is supported by the electrical insulating plate 26. Discharge electrode 27a is connected to the feedthrough 26a. The side of discharge electrode 27b opposite to the discharge surface is supported by the ground plate 28.

[0040] The PPM22 includes a switch 22a, a charging capacitor (not shown), a pulse transformer, a magnetic compression circuit, and a peaking capacitor. The peaking capacitor is connected to a feedthrough 26a via a connector (not shown). The charger 23 charges the charging capacitor. Specifically, the charger 23 charges the charging capacitor based on a set value of the charging voltage V input from the laser processor 50.

[0041] Switch 22a is controlled to be on or off by the first internal trigger signal Tr1, which will be described later. When switch 22a is turned on, current flows from the charging capacitor to the primary side of the pulse transformer, and a reverse current flows to the secondary side of the pulse transformer due to electromagnetic induction. The magnetic compression circuit is connected to the secondary side of the pulse transformer and compresses the pulse width of the current pulse. The peaking capacitor is charged by this current pulse. When the voltage of the peaking capacitor reaches the breakdown voltage of the laser gas, dielectric breakdown occurs in the laser gas between the discharge electrodes 27a and 27b, causing a discharge.

[0042] The convex mirror 25a and the concave mirror 25b are positioned such that the laser beam L output from the solid oscillator 10 passes through the discharge space between the discharge electrodes 27a and 27b three times, thereby expanding the beam width. In other words, the ArF excimer amplifier 20 is a multipath amplifier.

[0043] The laser beam L output from the solid oscillator 10 passes through window 21a and through the discharge space, passes through window 21b and is reflected by the convex mirror 25a. The laser beam L reflected by the convex mirror 25a passes through window 21b and through the discharge space, passes through window 21a and is reflected by the concave mirror 25b. The laser beam L reflected by the concave mirror 25b passes through window 21a and through the discharge space, passes through window 21b and is output to the outside from the ArF excimer amplifier 20. When the laser beam L is reflected by the convex mirror 25a, the beam width is expanded in the X direction.

[0044] The laser processor 50 generates a first internal trigger signal Tr1 and a second internal trigger signal Tr2. The laser processor 50 inputs the first internal trigger signal Tr1 to the ArF excimer amplifier 20 and the second internal trigger signal Tr2 to the solid oscillator 10. The first internal trigger signal Tr1 and the second internal trigger signal Tr2 have a predetermined time difference so that a discharge occurs when the laser light L output from the solid oscillator 10 is incident on the discharge space of the ArF excimer amplifier 20.

[0045] The laser beam L incident on the discharge space of the ArF excimer amplifier 20 is amplified by the discharge that occurs in the discharge space and output from the ArF excimer amplifier 20. The monitor module 30 is positioned on the optical path of the laser beam L output from the ArF excimer amplifier 20. In the laser device 2, the optical paths of the laser beam L other than the laser chamber 21 are sealed by a housing and optical path tube (not shown) and purged with N2 gas.

[0046] The monitor module 30 includes a first beam splitter 31, a second beam splitter 32, an energy sensor 33, and a wavelength monitor 34. The first beam splitter 31 is positioned on the optical path of the laser beam L and reflects a portion of the laser beam L. The second beam splitter 32 is positioned on the optical path of the reflected light reflected by the first beam splitter 31 and reflects a portion of the reflected light.

[0047] The energy sensor 33 is incident on transmitted light that has passed through the second beam splitter 32. The energy sensor 33 includes, for example, a photodiode sensitive to ultraviolet light, and detects the energy of the incident light. That is, the energy sensor 33 measures the pulse energy E of the laser light L. The energy sensor 33 transmits the measured value of the pulse energy E to the laser processor 50.

[0048] The wavelength monitor 34 is incident on reflected light reflected by the second beam splitter 32. The wavelength monitor 34 includes an etalon spectrometer and is composed of a diffuser plate (not shown), an air gap etalon, a focusing lens, and a line sensor. The wavelength λ of the laser light L is measured by detecting the radius of the interference fringes generated by the diffuser plate, air gap etalon, and focusing lens with the line sensor. The wavelength monitor 34 transmits the measured value of wavelength λ to the laser processor 50.

[0049] 1.2.2 Operation Next, the operation of the laser device 2 will be described. When the laser processor 50 receives the light emission trigger signal Tr0 from the laser processing processor 40, it generates a first internal trigger signal Tr1, and after the first internal trigger signal Tr1 has been generated and the trigger delay time has elapsed, it generates a second internal trigger signal Tr2. The laser processor 50 inputs the first internal trigger signal Tr1 to the ArF excimer amplifier 20 and the second internal trigger signal Tr2 to the solid oscillator 10.

[0050] When the second internal trigger signal Tr2 is input to the solid oscillator 10, the solid laser device 11 outputs laser light L.

[0051] When the first internal trigger signal Tr1 is input to the ArF excimer amplifier 20, the charging voltage V output from the charger 23 is converted into a high-voltage pulse in the PPM 22 and applied to the discharge electrodes 27a and 27b. When a discharge occurs in the discharge space, the laser gas is excited. At this timing, laser light L is incident from the solid oscillator 10 into the laser chamber 21. The laser light L is amplified by the discharge, and its beam width is expanded by reflection between the convex mirror 25a and the concave mirror 25b. The laser light L, which has been amplified in the discharge space and whose beam width has been expanded, is output from the ArF excimer amplifier 20.

[0052] The laser beam L output from the ArF excimer amplifier 20 is incident on the monitor module 30. A portion of the laser beam L incident on the monitor module 30 is sampled by the first beam splitter 31, and the pulse energy E and wavelength λ are measured. The measured values ​​of pulse energy E and wavelength λ are output to the laser processor 50.

[0053] The laser processor 50 compares the measured wavelength λ with the target wavelength λt and controls the solid oscillator 10 so that the measured value approaches the target wavelength λt. The laser processor 50 also compares the measured pulse energy E with the target pulse energy Et and controls the ArF excimer amplifier 20 so that the measured value approaches the target pulse energy Et.

[0054] The laser beam L that has passed through the monitor module 30 is output to the laser processing device main unit 4. The laser processing device main unit 4 uses the laser beam L output from the laser device 2 to perform laser processing on the workpiece 45.

[0055] Figure 3 shows an example of the pulse waveform of the laser light L output from the laser device 2. The pulse width of the laser light L is in the range of 100 ps to 1 ns. In the example shown in Figure 3, the pulse width of the laser light L pulse waveform is approximately 0.46 ns. Here, pulse width refers to the full width at half maximum, which represents the time duration at which the light intensity is 50% of the peak value. In the comparative example, the pulse waveform of the laser light L output from the solid-state laser device 11 is the same as the pulse waveform of the laser light L output from the laser device 2, except that the light intensity is different.

[0056] 1.3 Challenges Figure 4 shows the spectral waveform of the ArF excimer laser light output when the ArF excimer laser device is allowed to oscillate spontaneously (free running) without narrowband processing. air This shows the spectral waveform of ArF excimer laser light in an oxygen-containing gas, for example, air. FR N2 This is the spectral waveform of ArF excimer laser light in nitrogen gas that does not contain oxygen.

[0057] Spectral waveform FR N2 The central wavelength is approximately 193.4 nm, and the spectral linewidth is approximately 500 pm at full width at half maximum. Oxygen is known to have multiple absorption lines, which are absorption bands that absorb laser light. The wavelength range of ArF excimer laser light overlaps with multiple oxygen absorption lines, resulting in a spectral waveform FR air Multiple absorption lines are generated. Here, the vertical axis in Figure 4 shows the relative intensity normalized from the light intensity.

[0058] The oxygen absorption shown in Figure 4 is due to absorption transitions in the Schumann-Runge band. Oxygen has an vibrational band around 193 nm and has absorption characteristics represented by branches R(17), P(15), R(19), P(17), R(21), P(19), R(23), and P(21) for each rotational level. Spectral waveform FR air The spectral waveform FR N2 In comparison, a drop in light intensity occurs in the absorption lines corresponding to each of the above branches.

[0059] The waveform W shown in Figure 4 is an example of the spectral waveform of the laser light L output from the solid-state laser device 11. To reduce absorption of the laser light L by oxygen, the solid-state laser device 11 should be made to oscillate at a wavelength outside the oxygen absorption line within the oscillation wavelength range of the ArF excimer laser device. For example, the solid-state laser device 11 can be made to oscillate in the wavelength range between P(15) and R(19), between P(17) and R(21), or between P(19) and R(23).

[0060] Specifically, the central wavelength of the laser light L is set to a wavelength within the range of 193.113 nm to 193.273 nm, 193.292 nm to 193.472 nm, or 193.493 nm to 193.697 nm. Preferably, the central wavelength of the laser light L is set to a wavelength within the range of 193.12 nm to 193.26 nm, 193.30 nm to 193.46 nm, or 193.50 nm to 193.68 nm. More preferably, the central wavelength of the laser light L is set to 193.4 nm.

[0061] However, even when using a wavelength that avoids the oxygen absorption line as described above, there are the following problems when laser processing the workpiece 45 with a laser beam L having a short pulse width.

[0062] Figure 5 shows the relationship between the repetition frequency of the laser light L output by the comparative example laser device 2 and the power of the laser light L at the irradiated surface. Here, the repetition frequency corresponds to the number of pulses of the laser light L output by the solid-state laser device 11 per unit time. The power corresponds to the sum of the pulse energy per unit time at the irradiated surface.

[0063] When performing drilling or other operations on a workpiece 45 using a laser beam L, it is necessary to increase the power of the laser beam L. Simply put, the power of the laser beam L should increase in proportion to the repetition frequency. This is because the number of laser beam pulses L irradiated onto the surface per unit time increases in proportion to the repetition frequency.

[0064] However, in the comparative example laser device 2, it was confirmed that when the repetition frequency exceeds 2 kHz, the power of the laser light L does not increase proportionally with the repetition frequency, but rather the rate of increase decreases. This means that as the repetition frequency increases, the pulse energy of the laser light L decreases at the irradiated surface. Therefore, in order to increase the power of the laser light L, it is necessary to suppress the decrease in pulse energy at the irradiated surface that occurs with increasing repetition frequency.

[0065] 2. First Embodiment Next, a laser processing system according to the first embodiment of this disclosure will be described. Components similar to those described above will be denoted by the same reference numerals, and redundant descriptions will be omitted unless specifically stated.

[0066] 2.1 Configuration The laser processing system according to the first embodiment mainly comprises a laser device 2a and a laser processing device body 4. The configuration of the laser processing device body 4 is the same as in the comparative example.

[0067] Figure 6 schematically shows the configuration of the laser apparatus 2a according to the first embodiment. In addition to the configuration of the laser apparatus 2 according to the comparative example, the laser apparatus 2a includes a first optical pulse stretcher (OPS) 61, a second OPS 62, and a third OPS 63.

[0068] The first OPS61 and the second OPS62 are positioned between the ArF excimer amplifier 20 and the monitor module 30. The configuration of the ArF excimer amplifier 20 is the same as in the comparative example. The third OPS63 is positioned inside the solid oscillator 10a, downstream of the solid-state laser device 11. The solid oscillator 10a according to this embodiment differs from the solid oscillator 10 in that it includes the third OPS63 in addition to the solid-state laser device 11.

[0069] The configuration of the solid-state laser device 11 is the same as that of the comparative example. The solid-state laser device 11 outputs laser light L having a pulse width in the range of 100 ps to 1 ns and a central wavelength that is outside the oxygen absorption line in the oscillation wavelength range of the ArF excimer laser device.

[0070] The first OPS61, second OPS62, and third OPS63 are delay optical systems that split a single pulse into multiple pulses by transmitting a portion of the incident laser light L and outputting the remaining portion after it has passed through a delay optical path one or more times. The delay optical path is composed of multiple concave mirrors. The delay time due to the delay optical path is longer than the pulse width of the single incident pulsed laser light L.

[0071] The third OPS63 is configured such that a portion of the laser light L output from the solid-state laser device 11 circulates through a delayed optical path within the third OPS63, and the laser light L output from the third OPS63 is incident on the ArF excimer amplifier 20. The third OPS63 includes a beam splitter 66, a first concave mirror 63a, a second concave mirror 63b, a third concave mirror 63c, and a fourth concave mirror 63d. For example, the reflectivity of the beam splitter 66 is in the range of 40% to 70%. For example, the optical path length DL3 of the delayed optical path of the third OPS63 is in the range of 0.6m to 1.4m.

[0072] The first OPS61 is arranged such that a part of the laser beam L output from the ArF excimer amplifier 20 circulates in the delay optical path within the first OPS61, and the laser beam L output from the first OPS61 is incident on the second OPS62. The first OPS61 includes a beam splitter 64, a first concave mirror 61a, a second concave mirror 61b, a third concave mirror 61c, and a fourth concave mirror 61d. For example, the reflectivity of the beam splitter 64 is within the range of 40% or more and 70% or less. For example, the optical path length DL1 of the delay optical path of the first OPS61 is within the range of 2 m or more and 14 m or less. Specifically, it is preferable that the delay time due to the delay optical path of the first OPS61 is within the range of 2 times or more and 500 times or less of the pulse width of the laser beam L output from the solid-state laser device 11.

[0073] The second OPS62 is arranged such that a part of the laser beam L output from the first OPS61 circulates in the delay optical path within the second OPS62, and the laser beam L output from the second OPS62 is incident on the monitor module 30. For example, the reflectivity of the beam splitter 65 is within the range of 40% or more and 70% or less. For example, the optical path length DL2 of the delay optical path of the second OPS62 is within the range of 1.5 times or more and 3 times or less of the optical path length DL1.

[0074] In the present embodiment, the optical path lengths of the delay optical paths of the first OPS61, the second OPS62, and the third OPS63 are determined so as to satisfy the relationship of DL3 < DL1 < DL2.

[0075] 2.2 Operation Next, the operation of the laser device 2a will be described. Hereinafter, only the points different from the operation of the laser device 2 according to the comparative example will be described.

[0076] The laser light L output from the solid-state laser device 11 is incident on the third OPS 63. As shown in Figure 7, the laser light L incident on the third OPS 63 is divided into multiple pulses, with a portion being output directly and another portion circulating in the delayed optical path one or more times before being output. For example, if the optical path length DL3 is 0.6 m, the pulse of the laser light L is delayed by approximately 1.8 ns each time it circulates. Since the pulse width of the laser light L output from the solid-state laser device 11 is 1 ns or less, pulses with different numbers of circulations in the delayed optical path do not overlap in time. This generation of multiple pulses that do not overlap in time from a single pulse is called burst pulsing.

[0077] The laser beam L, which has been burst-pulsed by the third OPS63, is amplified by the ArF excimer amplifier 20. The laser beam L output from the ArF excimer amplifier 20 is further divided by circulating through the delayed optical path of the first OPS61 and the delayed optical path of the second OPS62.

[0078] The laser light L output from the laser device 2a is converted into burst pulses, as shown in Figure 8, and output to the laser processing device body 4. In Figure 8, the tails of adjacent pulses appear to overlap, but this is because the time resolution of the measuring device is insufficient.

[0079] 2.3 Effects Figure 9 shows the relationship between the repetition frequency of the laser beam L output by the laser device 2a according to the first embodiment and the power of the laser beam L at the irradiated surface. As shown in Figure 9, when a burst-pulsed laser beam L was used, the power of the laser beam L increased proportionally to the repetition frequency up to 6 kHz. That is, the decrease in pulse energy at the irradiated surface was suppressed up to a repetition frequency of 6 kHz. This effect is presumed to have been obtained for the following reasons.

[0080] Even with a laser beam L having a central wavelength that avoids the oxygen absorption line, a single-pulse laser beam L like the one in the comparative example has a high peak intensity, so in an oxygen-containing gas, ozone (O3) is generated by two-photon absorption.

[0081] If the ozone decomposition reaction rate is slower than the period, which is the reciprocal of the repetition frequency of the laser light L output from the laser device 2, the generated ozone will remain in the optical path. The ozone generation reaction is represented by equations (4) and (5) below. The ozone decomposition reaction is represented by equation (6) below. Note that the ozone remaining in the optical path will also decrease due to diffusion.

[0082]

number

number

number

[0083] Figure 10 shows the absorption spectra of ozone and oxygen. According to Figure 10, at a wavelength of 193 nm, ozone has an absorption cross-section that is more than an order of magnitude higher than that of oxygen. Therefore, it is presumed that at high repetition frequencies, a large amount of ozone remains in the optical path, and the pulse energy decreases as the remaining ozone absorbs the laser light L.

[0084] Figure 11 schematically shows the light intensity of a single pulse. Let the light intensity of the single pulse shown in Figure 11 be Is. Figure 12 schematically shows a burst pulse generated by dividing the single pulse shown in Figure 11 into Nb pulses. It is assumed that each pulse in the burst pulse has the same light intensity, and let the light intensity of each pulse be Ib. In this case, the ratio of light intensities Ib / Is is expressed by the following equation (7).

[0085]

number

[0086] Generally, the transition probability in two-photon absorption is proportional to the square of the light intensity. Therefore, the ratio R of the amount of ozone generated in the burst pulse case shown in Figure 12 to the amount of ozone generated in the single pulse case shown in Figure 11 can be approximately expressed by the following equation (8).

[0087]

number

[0088] According to equation (8) above, it can be seen that the amount of ozone generated decreases by dividing a single pulse into burst pulses. Specifically, it can be seen that the amount of ozone generated decreases inversely proportional to the number of pulses Nb contained in the burst pulse.

[0089] In the laser apparatus 2a according to the first embodiment, the laser light L output from the solid-state laser apparatus 11 is pulsed in bursts using the first OPS61, the second OPS62, and the third OPS63, thereby reducing the amount of ozone generated. As a result, it is presumed that the above effect was obtained by reducing the amount of laser light L absorbed by ozone.

[0090] Figure 13 shows the results of drilling using the laser processing system according to the first embodiment. In this experiment, an Eagle glass substrate was used as the workpiece 45, and the target fluence Fm was set to 11 J / cm². 2 Furthermore, the number of pulses of the laser light L output from the solid-state laser device 11 was changed within the range of 10 to 2000, and the processing depth, which is the depth of the processed hole, was measured.

[0091] Figure 14 shows the relationship between the number of pulses and the machining depth, as shown in Figure 13. According to Figure 14, in the initial stages of machining, the workpiece 45 is machined at a machining speed of 1350 nm / pulse. The machining speed corresponds to the ablation rate, which will be discussed later.

[0092] FIG. 15 shows the relationship between fluence and ablation rate. In FIG. 15, the result of drilling a hole with a depth of 20 μm using the burst-pulsed laser beam L according to the present embodiment and the result of drilling a hole with a depth of 20 μm using the single-pulse laser beam L according to the comparative example are shown. The workpiece 45 is an Eagle glass substrate. The repetition frequency in the case of burst pulses is 1 kHz, and the repetition frequency in the case of single pulses is 100 Hz.

[0093] According to FIG. 15, it can be seen that the ablation rate (1350 nm / pulse) in burst pulses when the fluence is 11 J / cm 2 is about 8 times the ablation rate in single pulses. Also, even when the fluence is 5 J / cm 2 , the ablation rate in burst pulses is about 6 times the ablation rate in single pulses.

[0094] When performing processing with single pulses, after the product generated by the irradiation of the pulse re-adheres, the re-adhered material is processed with the next pulse. In contrast, when performing processing using burst pulses, the next pulse is irradiated before the product generated by the irradiation of the pulse re-adheres. Therefore, it is considered that the ablation rate becomes large in burst pulses. Note that the same effect is expected even when a quartz glass substrate is used as the workpiece 45.

[0095] By performing drilling using the burst-pulsed laser beam L in this way, the ablation rate increases, so the threshold value at which damage such as cracks occurs increases, and the processing quality improves.

[0096] 2.4 Solid Laser Device 2.4.1 Configuration and Operation Figure 16 schematically shows the configuration of a solid-state laser device 11 according to the first embodiment. The solid-state laser device 11 includes a semiconductor laser 12, a semiconductor optical amplifier (SOA) 13, a titanium-sapphire amplifier 14, a wavelength conversion system 15, and a solid-state laser processor 16.

[0097] When the solid-state laser processor 16 receives a second internal trigger signal Tr2 from the laser processor 50, it outputs a trigger signal to the semiconductor laser 12. When the semiconductor laser 12 receives a trigger signal from the solid-state laser processor 16, it outputs a continuous-oscillation laser beam with a wavelength of approximately 773.6 nm.

[0098] When SOA13 receives a control signal from the solid-state laser processor 16, it amplifies the laser light output from the semiconductor laser 12 for a predetermined time, thereby outputting laser light with a predetermined pulse width. The pulse width of the laser light output from SOA13 is in the range of 100 ps to 1 ns.

[0099] The titanium-sapphire amplifier 14 amplifies and outputs the laser light output from the SOA 13 based on a control signal from the solid-state laser processor 16. The titanium-sapphire amplifier 14 is composed of, for example, a titanium-sapphire crystal and a pulsed laser for the pump.

[0100] The wavelength conversion system 15 converts the wavelength of the laser light output from the titanium-sapphire amplifier 14. Specifically, the wavelength conversion system 15 converts the laser light with a wavelength of 773.6 nm output from the titanium-sapphire amplifier 14 into laser light with a wavelength of 193.4 nm, which is the fourth harmonic. The wavelength conversion system 15 is composed of, for example, an LBO crystal and a KBBF crystal. The laser light whose wavelength has been converted by the wavelength conversion system 15 is output as laser light L from the solid-state laser device 11.

[0101] 2.5 Variations of Solid State Laser Devices 2.5.1 Configuration and Operation Figure 17 schematically shows the configuration of a solid-state laser apparatus 11a according to a modified example of the first embodiment. The solid-state laser apparatus 11a includes a semiconductor laser 12a, an SOA 13a, a fiber amplifier 17a, a solid-state amplifier 18, a semiconductor laser 12b, an SOA 13b, a fiber amplifier 17b, a wavelength conversion system 15a, and a solid-state laser processor 16.

[0102] When the solid-state laser processor 16 receives a second internal trigger signal Tr2 from the laser processor 50, it outputs a trigger signal to the semiconductor laser 12a and the semiconductor laser 12b. When the semiconductor laser 12a receives a trigger signal from the solid-state laser processor 16, it outputs a continuous-oscillation laser beam with a wavelength of approximately 1030 nm. When the semiconductor laser 12b receives a trigger signal from the solid-state laser processor 16, it outputs a continuous-oscillation laser beam with a wavelength of approximately 1553 nm.

[0103] When SOA13a receives a control signal from the solid-state laser processor 16, it amplifies the laser light output from the semiconductor laser 12a for a predetermined time, thereby outputting laser light with a predetermined pulse width. When SOA13b receives a control signal from the solid-state laser processor 16, it amplifies the laser light output from the semiconductor laser 12b for a predetermined time, thereby outputting laser light with a predetermined pulse width. The pulse widths of the laser light output from SOA13a and SOA13b are in the range of 100 ps to 1 ns, respectively.

[0104] Fiber amplifier 17a amplifies and outputs the laser light output from SOA13a. Fiber amplifier 17b amplifies and outputs the laser light output from SOA13b. Multiple fiber amplifiers 17a may be placed after SOA13a. Similarly, multiple fiber amplifiers 17b may be placed after SOA13b.

[0105] The solid-state amplifier 18 amplifies the laser light output from the fiber amplifier 17a. The solid-state amplifier 18 is composed of a Yb-doped crystal or ceramic. For example, the solid-state amplifier 18 is a Yb:YAG solid-state amplifier. Note that there is not limited to one solid-state amplifier 18, and multiple solid-state amplifiers 18 may be placed after the fiber amplifier 17a.

[0106] The wavelength conversion system 15a includes an LBO crystal and three CLBO crystals (CLBO1, CLBO2, CLBO3). The LBO crystal converts the 1030 nm wavelength laser light output from the solid-state amplifier 18 into a 515 nm wavelength laser light, which is the second harmonic. CLBO1 converts the 515 nm wavelength laser light output from the LBO crystal into a 257.5 nm wavelength laser light, which is the second harmonic. CLBO2 generates a 220.9 nm wavelength laser light, which is the sum frequency of the 257.5 nm wavelength laser light output from CLBO1 and the 1553 nm wavelength laser light output from the fiber amplifier 17b. CLBO3 generates a 193.4 nm wavelength laser light, which is the sum frequency of the 220.9 nm wavelength laser light output from CLBO2 and the 1553 nm wavelength laser light that has passed through CLBO2. The laser light whose wavelength has been converted by the wavelength conversion system 15a is output as laser light L from the solid-state laser device 11.

[0107] 3. Second Embodiment Next, a laser processing system according to the second embodiment will be described. Components similar to those described above will be denoted by the same reference numerals, and redundant explanations will be omitted unless otherwise specified.

[0108] 3.1 Configuration and Operation The laser processing system according to the second embodiment differs from the laser processing system according to the first embodiment only in the configuration of the laser device. The differences from the configuration of the laser device 2a according to the first embodiment will be explained below.

[0109] Figure 18 schematically shows the configuration of the laser apparatus 2b according to the second embodiment. The laser apparatus 2b differs from the laser apparatus 2a according to the first embodiment only in that the solid oscillator 10 does not have a third OPS63, as in the comparative example. That is, in this embodiment, the laser light L is burst-pulsed by the first OPS61 and the second OPS62, which are located downstream of the ArF excimer amplifier 20.

[0110] Figure 19 shows an example of the waveform of the burst-pulsed laser light L output from the laser device 2b according to the second embodiment. Figure 20 shows the results of drilling using the laser processing system according to the second embodiment. Figure 21 shows the results of drilling using the laser processing system according to the first embodiment. In both experiments, the same focusing optical system 48 was used and drilling was performed with the same input energy.

[0111] As shown in Figure 19, in the second embodiment, the number of burst pulses is reduced compared to the first embodiment shown in Figure 8. However, as can be seen from Figures 20 and 21, although the number of burst pulses is reduced in the second embodiment, drilling can be performed at almost the same processing speed as in the first embodiment.

[0112] Next, the results of drilling using the comparative example laser processing system 1 are shown. Figure 22 shows an example of the waveform of a single-pulse laser beam L output from the laser device 2 of the comparative example. Figure 23 shows the results of drilling in the comparative example, where the input energy of the laser beam L was 0.2 mJ, the repetition frequency was 1 kHz, and the number of pulses was 1000, while shifting the beam waist position. As shown in Figure 23, cracks occurred in the comparative example even when the beam waist position was adjusted, indicating low processing quality.

[0113] Figure 24 shows the results of drilling in the second embodiment, with an input energy of 1.1 mJ for the laser beam L, a repetition frequency of 1 kHz, and a pulse count of 1000. As shown in Figure 24, in the second embodiment, cracks did not occur even with an input energy more than five times higher than in the comparative example shown in Figure 23, indicating an improvement in processing quality. This is thought to be due to the fact that the next pulse is irradiated before the product generated by the pulse irradiation can re-set, thereby suppressing stress on the workpiece 45 due to re-settlement.

[0114] 3.2 Effects The laser apparatus 2b according to the second embodiment does not include the third OPS63, thus simplifying the configuration compared to the first embodiment. In the second embodiment as well, processing can be performed at the same processing speed as in the first embodiment. Furthermore, in the second embodiment, by performing processing with burst pulses, the threshold at which damage such as cracks occurs is raised, similar to the first embodiment, thereby improving processing quality.

[0115] 4. Third Embodiment Next, a laser processing system according to the third embodiment will be described. Components similar to those described above will be denoted by the same reference numerals, and redundant explanations will be omitted unless otherwise specified.

[0116] 4.1 Configuration and Operation The laser processing system according to the third embodiment differs from the laser processing system according to the first embodiment only in the configuration of the laser device. The differences from the configuration of the laser device 2a according to the first embodiment will be explained below.

[0117] Figure 25 schematically shows the configuration of the laser device 2c according to the third embodiment. The laser device 2c differs from the laser device 2a according to the first embodiment in that the solid oscillator 10 does not have a third OPS63 and also does not have a second OPS62. That is, in this embodiment, the laser light L is burst pulsed by the first OPS61, which is located after the ArF excimer amplifier 20.

[0118] 4.2 Effects The laser apparatus 2c according to the third embodiment does not include the second OPS62 and the third OPS63, thus simplifying its configuration compared to the second embodiment. Furthermore, the same effects as the first embodiment can be obtained in the third embodiment.

[0119] 5. Fourth Embodiment Next, a laser processing system according to the fourth embodiment will be described. Components similar to those described above will be denoted by the same reference numerals, and redundant explanations will be omitted unless otherwise specified.

[0120] 5.1 Configuration and Operation The laser processing system according to the fourth embodiment differs from the laser processing system according to the first embodiment only in the configuration of the laser device. The differences from the configuration of the laser device 2a according to the first embodiment will be explained below.

[0121] Figure 26 schematically shows the configuration of the laser apparatus 2d according to the fourth embodiment. The laser apparatus 2d differs from the laser apparatus 2a according to the first embodiment in that it is equipped with an ArF excimer amplifier 20a having an optical resonator as a power oscillator, rather than a multipath amplifier. Specifically, the ArF excimer amplifier 20a has a Fabry-Perot type optical resonator composed of a rear mirror 29a and an output coupling mirror 29b, instead of a convex mirror 25a and a concave mirror 25b. The rear mirror 29a is, for example, a partial reflection mirror with a reflectivity in the range of 50% to 90%. The output coupling mirror 29b is, for example, a partial reflection mirror with a reflectivity in the range of 10% to 30%.

[0122] Furthermore, the laser device 2d differs from the laser device 2a according to the first embodiment in that it includes a beam expander 70 between the solid oscillator 10a and the ArF excimer amplifier 20a. The beam expander 70 expands the beam size of the laser light L output from the solid oscillator 10a so that the beam size matches the size of the discharge space of the ArF excimer amplifier 20a.

[0123] The laser beam L, expanded by the beam expander 70, passes through the rear mirror 29a and is amplified by the optical resonator. The laser beam L amplified by the optical resonator is output from the output coupling mirror 29b.

[0124] Figure 27 shows an example of the waveform of the burst-pulsed laser light L output from the laser device 2d according to the fourth embodiment. Because the ArF excimer amplifier 20a has an optical resonator, the burst pulse output from the laser device 2d has a larger number of pulses compared to the first embodiment.

[0125] 5.2 Effects The laser device 2d according to the fourth embodiment can produce more burst pulses than the first embodiment, thus further suppressing ozone generation. The same effects as the first embodiment can be obtained in the fourth embodiment as well.

[0126] Furthermore, the optical resonator in the ArF excimer amplifier 20a is not limited to a Fabry-Perot type optical resonator, but may also be a ring resonator. Alternatively, instead of placing the beam expander 70, a slit having a size 0.7 to 2 times the beam size of the laser light L output from the solid oscillator 10a may be placed inside the ArF excimer amplifier 20a.

[0127] 6. Modified Solid-State Laser Devices In the first embodiment, the laser beam L is pulsed in bursts by providing a third OPS63 downstream of the solid-state laser device 11. Below, we will illustrate a solid-state laser device that can output pulsed laser beam L without providing a third OPS63.

[0128] 6.1 First Variation 6.1.1 Configuration and Operation Figure 28 schematically shows the configuration of a solid-state laser device 11b according to the first modified example. The solid-state laser device 11b includes a semiconductor laser 12, a beam splitter 80, a plurality of SOAs 13, a beam coupler 81, a titanium-sapphire amplifier 14, a wavelength conversion system 15, a burst pulse generation processor 82, and a solid-state laser processor 16.

[0129] Multiple SOA13s are connected in parallel between the beam divider 80 and the beam coupler 81. In this modified example, four SOA13s are provided. The beam divider 80 and the beam coupler 81 are each composed of fiber couplers or the like.

[0130] When the solid-state laser processor 16 receives a second internal trigger signal Tr2 from the laser processor 50, it outputs a trigger signal to the semiconductor laser 12. When the semiconductor laser 12 receives a trigger signal from the solid-state laser processor 16, it outputs a continuous-oscillation laser beam with a wavelength of approximately 773.6 nm.

[0131] The beam splitter 80 splits the laser light output from the semiconductor laser 12 into multiple laser beams. The multiple laser beams split by the beam splitter 80 are incident on each of the multiple SOA 13. When each SOA 13 receives a control signal from the burst pulse generation processor 82, it amplifies the laser light incident from the beam splitter 80 for a predetermined time, thereby outputting a laser beam with a predetermined pulse width.

[0132] The burst pulse generation processor 82 generates burst pulses from the laser light output from the beam coupler 81 by staggering the timing of pulse generation in each of the multiple SOA 13s. The timing difference in pulse generation is, for example, within the range of 2 ns to 4 ns. That is, the interval between the multiple pulses included in the burst pulse is between 2 ns and 4 ns.

[0133] The beam coupler 81 combines multiple laser beams output from multiple SOA13s at different timings and outputs a burst-pulsed laser beam.

[0134] The titanium-sapphire amplifier 14 amplifies and outputs the laser light output from the beam coupler 81. The wavelength conversion system 15 converts the wavelength of the laser light output from the titanium-sapphire amplifier 14. Specifically, the wavelength conversion system 15 converts the laser light with a wavelength of 773.6 nm output from the titanium-sapphire amplifier 14 to laser light with a wavelength of 193.4 nm, which is the fourth harmonic. The laser light converted by the wavelength conversion system 15 is output from the solid-state laser device 11b as burst-pulsed laser light L.

[0135] 6.1.2 Effects The solid-state laser apparatus 11b according to this modified example allows for arbitrary setting of the number and intensity of burst pulses. Therefore, in this modified example, the number of burst pulses can be increased compared to when burst pulses are generated using the third OPS63 as in the first embodiment, and the amount of ozone generated can be further suppressed.

[0136] 6.2 Second Variation 6.2.1 Configuration and Operation Figure 29 schematically shows the configuration of a solid-state laser apparatus 11c according to a second modified example. The solid-state laser apparatus 11c includes a semiconductor laser 12a, an SOA 13a, a fiber amplifier 17a, a solid-state amplifier 18, a semiconductor laser 12b, a beam splitter 80, a plurality of SOAs 13b, a beam coupler 81, a fiber amplifier 17b, a wavelength conversion system 15a, a burst pulse generation processor 82, and a solid-state laser processor 16.

[0137] Semiconductor laser 12a corresponds to the "first semiconductor laser" in the technology of this disclosure. Semiconductor laser 12b corresponds to the "second semiconductor laser" in the technology of this disclosure. SOA 13a corresponds to the "first semiconductor optical amplifier" in the technology of this disclosure. SOA 13b corresponds to the "second semiconductor optical amplifier" in the technology of this disclosure. Fiber amplifier 17a corresponds to the "first fiber amplifier" in the technology of this disclosure. Fiber amplifier 17b corresponds to the "second fiber amplifier" in the technology of this disclosure.

[0138] When the solid-state laser processor 16 receives a second internal trigger signal Tr2 from the laser processor 50, it outputs a trigger signal to the semiconductor laser 12a and the semiconductor laser 12b. When the semiconductor laser 12a receives a trigger signal from the solid-state laser processor 16, it outputs a continuous-oscillation laser beam with a wavelength of approximately 1030 nm. When the semiconductor laser 12b receives a trigger signal from the solid-state laser processor 16, it outputs a continuous-oscillation laser beam with a wavelength of approximately 1553 nm.

[0139] Multiple SOA13b units are connected in parallel between the beam divider 80 and the beam coupler 81. In this modified example, the number of SOA13b units is set to four.

[0140] The SOA13a, fiber amplifier 17a, and solid-state amplifier 18 have the same configuration as those included in the solid-state laser device 11a shown in Figure 17. The amplified single-pulse laser beam is output from the solid-state amplifier 18.

[0141] The beam splitter 80, multiple SOA13b, and beam coupler 81 have the same configuration as the beam splitter 80, multiple SOA13, and beam coupler 81 included in the solid-state laser apparatus 11b shown in Figure 28. Burst-pulsed laser light is output from the beam splitter 80. The fiber amplifier 17b amplifies and outputs the laser light output from the beam coupler 81.

[0142] The wavelength conversion system 15a has the same configuration as the wavelength conversion system 15a shown in Figure 17. The wavelength conversion system 15a generates laser light with a wavelength of 193.4 nm by wavelength conversion between the single-pulse laser light output from the solid-state amplifier 18 and the burst-pulsed laser light output from the fiber amplifier 17b. The laser light wavelength-converted by the wavelength conversion system 15a is output as burst-pulsed laser light L from the solid-state laser device 11c.

[0143] The burst pulse generation processor 82 staggers the timing of pulse generation for each of the multiple SOA13b units. The timing difference in pulse generation is, for example, within the range of 2ns to 4ns. That is, the interval between the multiple pulses included in the burst pulse is between 2ns and 4ns.

[0144] The solid-state laser processor 16 controls the SOA 13a in the wavelength conversion system 15a so that the single pulse and the burst pulse overlap in time, making the pulse width of the single pulse longer than the time width that includes all the pulses of the burst pulse.

[0145] 6.2.2 Effects The solid-state laser apparatus 11c according to this modified example allows for arbitrary setting of the number and intensity of burst pulses. Therefore, in this modified example, the number of burst pulses can be increased compared to when burst pulses are generated using the third OPS63 as in the first embodiment, and the amount of ozone generated can be further suppressed.

[0146] The above description is intended to be illustrative and not restrictive. It will therefore be apparent to those skilled in the art that modifications can be made to each embodiment of this disclosure without departing from the scope of the attached claims.

[0147] Terms used throughout this specification and the accompanying claims should be interpreted as “non-limiting” terms. For example, the terms “includes” or “contains” should be interpreted as “not limited to what is described as included.” The term “has” should be interpreted as “not limited to what is described as having.” Furthermore, the modifying phrase “one” as used throughout this specification and the accompanying claims should be interpreted as “at least one” or “one or more.” Also, the term “at least one of A, B, and C” should be interpreted as “A,” “B,” “C,” “A+B,” “A+C,” “B+C,” or “A+B+C,” and further, should be interpreted as including combinations of these with anything other than “A,” “B,” and “C.”

Claims

1. A laser device used in a laser processing system that performs laser processing by irradiating a workpiece with laser light in an oxygen-containing gas, A solid-state oscillator including a solid-state laser device that outputs laser light having a pulse width in the range of 100 ps to 1 ns and a central wavelength that is outside the oxygen absorption line in the oscillation wavelength range of an ArF excimer laser device, An ArF excimer amplifier that amplifies the laser light output from the solid oscillator, A first optical pulse stretcher outputs a burst pulsed laser beam by dividing the laser light amplified by the ArF excimer amplifier into multiple pulses by passing it through a delayed optical path, A laser device equipped with the following features.

2. A laser apparatus according to claim 1, The oscillation wavelength range of the ArF excimer laser apparatus is between 193.0 nm and 193.9 nm.

3. A laser apparatus according to claim 1, The aforementioned central wavelength is a wavelength included in the wavelength range of 193.113 nm to 193.273 nm, the wavelength range of 193.292 nm to 193.472 nm, or the wavelength range of 193.493 nm to 193.697 nm.

4. A laser apparatus according to claim 1, The aforementioned central wavelength is a wavelength included in the wavelength range of 193.12 nm to 193.26 nm, the wavelength range of 193.30 nm to 193.46 nm, or the wavelength range of 193.50 nm to 193.68 nm.

5. A laser apparatus according to claim 1, The delay time of the laser light due to the delay optical path of the first optical pulse stretcher is within the range of 2 times or more and 500 times or less the pulse width.

6. A laser apparatus according to claim 1, The optical path length of the delay optical path of the first optical pulse stretcher is in the range of 2 m to 14 m.

7. A laser apparatus according to claim 1, The system further includes a second optical pulse stretcher that outputs a burst pulse of laser light by dividing the laser light output from the first optical pulse stretcher into multiple pulses by making it circulate through a delayed optical path.

8. A laser apparatus according to claim 7, The optical path length of the delay optical path of the second optical pulse stretcher is longer than the optical path length of the delay optical path of the first optical pulse stretcher.

9. A laser apparatus according to claim 8, The optical path length of the delay optical path of the second optical pulse stretcher is within the range of 1.5 times or more and 3 times or less the optical path length of the delay optical path of the first optical pulse stretcher.

10. A laser apparatus according to claim 7, The solid oscillator further includes a third optical pulse stretcher that outputs laser light that has been split into multiple pulses by passing the laser light output from the solid laser device through a delayed optical path, thereby creating a burst pulse of laser light.

11. A laser apparatus according to claim 10, The optical path length of the delay optical path of the third optical pulse stretcher is shorter than the optical path length of the delay optical path of the first optical pulse stretcher.

12. A laser apparatus according to claim 10, The optical path length of the delay optical path of the third optical pulse stretcher is in the range of 0.6 m to 1.4 m.

13. A laser apparatus according to claim 10, The ArF excimer amplifier has an optical resonator.

14. A laser apparatus according to claim 1, The ArF excimer amplifier is a multipath amplifier.

15. A laser apparatus according to claim 1, The solid-state laser device is A semiconductor laser that outputs a continuous-oscillation laser beam, A beam splitter that splits the laser light output from the semiconductor laser into multiple laser beams, Multiple semiconductor optical amplifiers that pulse multiple laser beams output from the beam splitter, A beam coupler that combines multiple laser beams output from multiple semiconductor optical amplifiers, A burst pulse generation processor that converts the laser light output from the beam coupler into burst pulses by shifting the timing of pulse conversion of the laser light in each of the multiple semiconductor optical amplifiers, A titanium-sapphire amplifier that amplifies the laser light output from the beam coupler, A wavelength conversion system that outputs burst-pulsed laser light in the oscillation wavelength range of the ArF excimer laser device by wavelength conversion of the laser light output from the titanium-sapphire amplifier, Includes.

16. A laser apparatus according to claim 15, The interval between the multiple pulses contained in the burst-pulsed laser light output from the beam coupler is between 2 ns and 4 ns.

17. A laser apparatus according to claim 1, The solid-state laser device is A first semiconductor laser that outputs a continuous-oscillation laser beam, A first semiconductor optical amplifier that pulses the laser light output from the first semiconductor laser, A first fiber amplifier that amplifies the laser light output from the first semiconductor optical amplifier, A solid-state amplifier that amplifies the laser light output from the first fiber amplifier, A second semiconductor laser that outputs a continuously oscillating laser beam, A beam splitter that splits the laser light output from the second semiconductor laser into multiple laser beams, Multiple second semiconductor optical amplifiers that pulse multiple laser beams output from the beam splitter, A beam coupler that combines multiple laser beams output from multiple second semiconductor optical amplifiers, A burst pulse generation processor that generates a burst pulse from the laser light output from the beam coupler by shifting the timing of pulse generation of the laser light in each of the multiple second semiconductor optical amplifiers, A second fiber amplifier that amplifies the laser light output from the beam coupler, A wavelength conversion system that outputs burst-pulsed laser light in the oscillation wavelength range of the ArF excimer laser device by wavelength conversion of the laser light output from the solid-state amplifier and the laser light output from the second fiber amplifier, Includes.

18. A laser apparatus according to claim 17, The interval between the multiple pulses contained in the burst-pulsed laser light output from the beam coupler is between 2 ns and 4 ns.

19. A laser processing system that performs laser processing by irradiating a workpiece with laser light in an oxygen-containing gas, A solid-state oscillator including a solid-state laser device that outputs laser light having a pulse width in the range of 100 ps to 1 ns and a central wavelength that is outside the oxygen absorption line in the oscillation wavelength range of an ArF excimer laser device, An ArF excimer amplifier that amplifies the laser light output from the solid oscillator, A first optical pulse stretcher outputs a burst pulsed laser beam by dividing the laser light amplified by the ArF excimer amplifier into multiple pulses by passing it through a delayed optical path, A laser device including, An optical device that irradiates the workpiece with the burst-pulsed laser light output from the laser device, A laser processing system equipped with [the following features].

20. A laser processing method that performs laser processing by irradiating a workpiece with laser light in an oxygen-containing gas, A solid-state oscillator including a solid-state laser device that outputs laser light having a pulse width in the range of 100 ps to 1 ns and a central wavelength that is outside the oxygen absorption line in the oscillation wavelength range of an ArF excimer laser device, An ArF excimer amplifier that amplifies the laser light output from the solid oscillator, A first optical pulse stretcher outputs a burst pulsed laser beam by dividing the laser light amplified by the ArF excimer amplifier into multiple pulses by passing it through a delayed optical path, Laser processing is performed by irradiating the workpiece with burst pulsed laser light generated by a laser device equipped with the above, A laser processing method including [specific type of laser processing].

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