Laser machining apparatus, microscope apparatus, laser machining method, and observation method

Abstract

To provide a laser machining apparatus, a microscope apparatus, a laser machining method, and an observation method capable of suppressing quality deterioration of a machined cross section.SOLUTION: A laser machining apparatus 20 includes: a laser outputting unit 30 for outputting a laser beam L having pulse width equal to or less than 1ps; a half-wave plate 54 and a spatial light modulating unit 41 for branching the laser beam L into a plurality of branched laser beams and outputting the branched laser beams; a lens 42 for focusing the branched laser beams toward a sample A; and a galvanometer mirror 43 for scanning the sample A with the condensed branched laser beams. A first irradiated region R1 of a first branched laser beam L1 having a first polarizing direction P1 is formed, and a second irradiated region R2 of a second branched laser beam having a second polarizing direction P2 orthogonal to the first polarizing direction P1 is formed so as to be aligned with the first irradiated region R1 along the first direction D1 crossing an optical axis of the branched laser beam.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a laser processing apparatus, a microscope apparatus, a laser processing method, and an observation method. [Background technology]

[0002] Patent Document 1 describes a laser processing method. In this method, a groove processing step is carried out in which a groove of a predetermined depth is formed by irradiating a workpiece with a groove processing laser beam. The groove processing step is composed of a pre-processing step and a main processing step. In the pre-processing step, a first groove processing laser beam is irradiated onto a groove processing area of ​​the workpiece to form a preliminary groove. In the main processing step, a second groove processing laser beam is irradiated onto a groove bottom surface constituting the preliminary groove so that the groove depth of the preliminary groove becomes a predetermined depth, and the groove bottom surface is processed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-174103 Summary of the Invention [Problem to be solved by the invention]

[0004] In the laser processing method described in Patent Document 1, the bottom surface of the groove is the processing surface irradiated with the laser light, and the inner surface of the groove along the scanning direction of the laser light is the processing cross section. In the above technical field, there is a demand for improving the quality of this processing cross section. That is, if the pulse width of the laser light is increased, the properties of the processing cross section may change due to the influence of heat generated during processing, and as a result, the quality of the processing cross section may deteriorate.

[0005] In response to this, by using an ultrashort pulse laser with a pulse width of 1 ps or less during the processing, it is possible to suppress changes in the properties of the processed cross section due to heat. However, when processing is performed using an ultrashort pulse laser, a new fine periodic structure (for example, a laser induced periodic surface structure (LIPSS)) is formed on the processed cross section, which may cause a problem of degraded quality of the processed cross section.

[0006] Therefore, an object of the present invention is to provide a laser processing apparatus, a microscope apparatus, a laser processing method, and an observation method that can suppress deterioration in the quality of the processed cross section. [Means for solving the problem]

[0007] The laser processing device according to the present invention is [1] "a laser processing device for forming a processing cross section by irradiating a target object with laser light, comprising: a laser output unit for outputting laser light having a pulse width of 1 ps or less; a branching unit for branching the laser light output from the laser output unit into a plurality of branched laser light beams and outputting the branched laser light beams; a focusing unit for focusing the plurality of branched laser light beams output from the branching unit toward the target object; and a scanning unit for scanning the plurality of branched laser light beams focused by the focusing unit over the target object, wherein the branching unit divides the laser light into a first branched laser light beam having a first polarization direction and a second branched laser light beam having a second polarization direction orthogonal to the first polarization direction, the focusing unit focuses the first branched laser beam toward the object to form a first irradiation region of the first branched laser beam on the object, and focuses the second branched laser beam toward the object to form a second irradiation region of the second branched laser beam on the object so as to be aligned with the first irradiation region along a first direction intersecting an optical axis of the branched laser beam; and the scanning unit scans the first irradiation region and the second irradiation region on the object along a second direction intersecting the optical axis of the branched laser beam and the first direction, thereby forming the processed cross section on the object that intersects the first direction and is along the second direction.

[0008] In this laser processing device, a processed cross section is formed on the object along the scanning direction (second direction) of the laser light by irradiating the object with laser light. The laser light is an ultrashort pulse laser with a pulse width of 1 ps or less. Therefore, it is possible to suppress deterioration in the quality of the processed cross section caused by changes in the properties of the processed cross section due to the influence of heat. In addition, by having the following configuration, this laser processing device is also able to suppress deterioration in the quality of the processed cross section caused by the formation of a fine periodic structure on the processed cross section by using an ultrashort pulse laser.

[0009] That is, in this laser processing apparatus, a laser beam is branched into a plurality of branched laser beams, including a first branched laser beam having a first polarization direction and a second branched laser beam having a second polarization direction orthogonal to the first polarization direction. The first branched laser beam is focused toward an object to form a first irradiation region of the first branched laser beam on the object, and the second branched laser beam is focused toward the object to form a second irradiation region of the second branched laser beam on the object so as to be aligned with the first irradiation region along a first direction intersecting the optical axis of the branched laser beam. The first irradiation region and the second irradiation region are then scanned on the object along a second direction (the scanning direction) intersecting the optical axis of the branched laser beam and the first direction, thereby forming a processed cross section on the object that intersects the first direction and is aligned with the second direction. By scanning the first irradiation region of the first branched laser beam and the second irradiation region of the second branched laser beam, which are unlikely to interfere with each other, while arranging them as described above, formation of a fine periodic structure on the processed cross section is suppressed. As described above, this laser processing device can suppress deterioration in the quality of the processed cross section.

[0010] The laser processing apparatus according to the present invention may be [2] "the laser processing apparatus according to the above [1], wherein the focusing unit forms a third irradiation area of ​​the branched laser beam on the object so as to be aligned with the second irradiation area on the opposite side to the first irradiation area along the first direction, and the scanning unit forms the processed cross section by scanning the first irradiation area, the second irradiation area, and the third irradiation area along the second direction." In this way, by performing scanning while further forming the third irradiation area, it is possible to improve the processing speed while suppressing deterioration in the quality of the processed cross section.

[0011] The laser processing apparatus according to the present invention may be [3] "the laser processing apparatus according to the above [2], wherein the branched laser beam has the first polarization direction in the third irradiation region." In this case, interference of the branched laser beam can be suppressed between the second irradiation region and the third irradiation region arranged adjacent to the second irradiation region.

[0012] The laser processing apparatus according to the present invention may be [4] "the laser processing apparatus according to the above [3], wherein the branching unit branches the laser beam into a plurality of branched laser beams further including a third branched laser beam having the first polarization direction, and the focusing unit focuses the third branched laser beam toward the object to form the third irradiation region on the object." In this way, the third irradiation region may be formed based on a third branched laser beam separate from the first and second branched laser beams. In this case, the conditions for suppressing the generation of a fine periodic structure are less dependent on the intensity of the laser beam and the focusing density of the laser beam than when the third irradiation region is not formed, and therefore the fine periodic structure can be suppressed under a wider range of conditions.

[0013] The laser processing apparatus according to the present invention may be [5] "the laser processing apparatus according to the above [3], wherein the focusing unit focuses the first branched laser beam toward the object, thereby forming the first irradiation region and the third irradiation region on the object so as to be continuous in an annular shape." In this way, the first irradiation region and the third irradiation region may be formed based on the first branched laser beam. In this case, the dependence on the intensity of the laser beam and the focusing density of the laser beam is lower than in the case where the third irradiation region is not formed, and therefore the fine periodic structure can be suppressed under a wider range of conditions.

[0014] The laser processing device according to the present invention may be [6] "the laser processing device according to any one of the above [1] to [5], wherein the focusing unit forms the first irradiation region and the second irradiation region on the object so that the distance between the peak position of intensity in the first irradiation region and the peak position of intensity in the second irradiation region is 1.2 times or less the diameter of the second irradiation region." In this case, flatness of the processed cross section can be ensured.

[0015] The laser processing device according to the present invention may be [7] "the laser processing device according to any one of the above [1] to [6], wherein the branching section branches the laser light so that the peak intensity value in the first irradiation region is lower than the peak intensity value in the second irradiation region." In this way, even if the peak intensity value of the laser light is lower in the first irradiation region than in the second irradiation region, it is possible to suppress the formation of a fine periodic structure on the processed cross section.

[0016] The laser processing device according to the present invention may be [8] "the laser processing device according to any one of the above [1] to [6], wherein the branching section branches the laser light so that the peak intensity value in the first irradiation region is higher than the peak intensity value in the second irradiation region." In this way, even if the peak intensity value of the laser light is higher in the first irradiation region than in the second irradiation region, it is possible to suppress the formation of a fine periodic structure on the processed cross section.

[0017] The laser processing device according to the present invention may be [9] "the laser processing device according to any one of the above [1] to [8], wherein the branching section and the focusing section do not form an irradiation area that interferes with the first irradiation area or the second irradiation area in a range from the peak position of the intensity in the first irradiation area to 1.5 times the diameter of the first irradiation area, and in a range from the peak position of the intensity in the second irradiation area to 1.5 times the diameter of the second irradiation area." In this case, it is possible to more reliably suppress the formation of a fine periodic structure on the processed cross section.

[0018] The laser processing device according to the present invention may be

[10] "the laser processing device according to any one of the above [1] to [9], wherein the scanning unit scans the first irradiation region on the object so that the distance between the peak position of the intensity of the first irradiation region corresponding to one pulse of the laser light and the peak position of the intensity of the first irradiation region corresponding to another pulse subsequent to the one pulse is equal to or less than half the diameter of the first irradiation region." In this case, it is possible to form a processed cross section with fewer irregularities along the scanning direction of the laser light.

[0019] The microscope device according to the present invention may be

[11] "a microscope device including the laser processing device according to any one of [1] to

[10] above and a microscope unit for observing the processed cross section." In this case, deterioration in the quality of the processed cross section is suppressed, so that highly accurate observation results of the processed cross section can be obtained.

[0020] The laser processing method according to the present invention is

[12] "a laser processing method for forming a processing cross section by irradiating a target with laser light, the method comprising: a branching step of branching laser light having a pulse width of 1 ps or less to generate a plurality of branched laser beams; a focusing step of focusing the plurality of branched laser beams generated in the branching step toward the target; and a scanning step of scanning the target with the plurality of branched laser beams focused in the focusing step, wherein in the branching step, the laser light is branched into a plurality of branched laser beams including a first branched laser beam having a first polarization direction and a second branched laser beam having a second polarization direction orthogonal to the first polarization direction; the focusing step focuses the first branched laser beam toward the object to form a first irradiation region of the first branched laser beam on the object, and the second branched laser beam focuses the second irradiation region of the second branched laser beam toward the object to be aligned with the first irradiation region along a first direction intersecting the optical axis of the branched laser beam; and the scanning step scans the object with the first irradiation region and the second irradiation region along a second direction intersecting the optical axis of the branched laser beam and the first direction, thereby forming the processed cross section on the object that intersects the first direction and is along the second direction.

[0021] In this laser processing method, a processed cross section is formed on the object along the scanning direction (second direction) of the laser light by irradiating the object with laser light. The laser light is an ultrashort pulse laser with a pulse width of 1 ps or less. Therefore, it is possible to suppress deterioration in the quality of the processed cross section caused by changes in the properties of the processed cross section due to the influence of heat. Furthermore, by having the following configuration, this laser processing method is also able to suppress deterioration in the quality of the processed cross section caused by the formation of a fine periodic structure on the processed cross section by using an ultrashort pulse laser.

[0022] That is, in this laser processing method, a laser beam is branched into a plurality of branched laser beams, including a first branched laser beam having a first polarization direction and a second branched laser beam having a second polarization direction orthogonal to the first polarization direction. Furthermore, the first branched laser beam is focused toward an object to form a first irradiation region of the first branched laser beam on the object, and the second branched laser beam is focused toward the object to form a second irradiation region of the second branched laser beam on the object so as to be aligned with the first irradiation region along a first direction intersecting the optical axis of the branched laser beam. The first irradiation region and the second irradiation region are then scanned along a second direction (the scanning direction) intersecting the optical axis of the branched laser beam and the first direction, thereby forming a processed cross section on the object that intersects the first direction and is aligned with the second direction. By scanning the first irradiation region of the first branched laser beam and the second irradiation region of the second branched laser beam, which do not interfere with each other, while arranging them as described above, formation of a fine periodic structure on the processed cross section is suppressed. As described above, this laser processing method can suppress deterioration in the quality of the processed cross section.

[0023] The laser processing method according to the present invention may be

[13] "the laser processing method according to the above

[12] , wherein in the focusing step, a third irradiation area of ​​the branched laser beam is formed on the object so as to be aligned with the second irradiation area on the opposite side to the first irradiation area along the first direction, and in the scanning step, the first irradiation area, the second irradiation area, and the third irradiation area are scanned along the second direction to form the processed cross section." In this way, by performing scanning while further forming a third irradiation area, it is possible to improve the processing speed while suppressing deterioration in the quality of the processed cross section.

[0024] The laser processing method according to the present invention may be

[14] "the laser processing method according to the above

[13] , wherein the branched laser beam has the first polarization direction in the third irradiation region." In this case, interference of the branched laser beam can be suppressed between the second irradiation region and the third irradiation region arranged adjacent to the second irradiation region.

[0025] The laser processing method according to the present invention may be

[15] "the laser processing method according to the above

[14] , wherein in the branching step, the laser beam is branched into a plurality of branched laser beams further including a third branched laser beam having the first polarization direction, and in the focusing step, the third branched laser beam is focused toward the object, thereby forming the third irradiation region on the object." In this way, the third irradiation region may be formed based on a third branched laser beam separate from the first branched laser beam and the second branched laser beam. In this case, the conditions for suppressing the generation of a fine periodic structure are less dependent on the intensity of the laser beam and the focusing density of the laser beam than in the case where the third irradiation region is not formed, and therefore the fine periodic structure can be suppressed under a wider range of conditions.

[0026] The laser processing method according to the present invention may be

[16] "the laser processing method according to the above

[14] , wherein in the focusing step, the first irradiation region and the third irradiation region are formed on the object so as to be continuous in an annular shape by focusing the first branched laser beam toward the object." In this way, the first irradiation region and the third irradiation region may be formed based on the first branched laser beam. In this case, the dependency on the intensity of the laser beam and the focusing density of the laser beam is lower than in the case where the third irradiation region is not formed, and therefore the fine periodic structure can be suppressed under a wider range of conditions.

[0027] The laser processing method according to the present invention may be

[17] "the laser processing method according to any one of the above

[12] to

[16] , wherein in the focusing step, the first irradiation region and the second irradiation region are formed on the object so that the distance between the peak position of intensity in the first irradiation region and the peak position of intensity in the second irradiation region is 1.2 times or less the diameter of the second irradiation region." In this case, it is possible to more reliably suppress the formation of a fine periodic structure on the processed cross section.

[0028] The laser processing method according to the present invention may be

[18] "the laser processing method according to any one of the above

[12] to

[17] , wherein in the branching step, the laser beam is branched so that the peak intensity value in the first irradiation region is lower than the peak intensity value in the second irradiation region." In this way, even if the peak intensity value of the laser beam is lower in the first irradiation region than in the second irradiation region, it is possible to suppress the formation of a fine periodic structure on the processed cross section.

[0029] The laser processing method according to the present invention may be

[19] "the laser processing method according to any one of the above

[12] to

[17] , wherein in the branching step, the laser beam is branched so that the peak intensity value in the first irradiation region is higher than the peak intensity value in the second irradiation region." In this way, even if the peak intensity value of the laser beam is higher in the first irradiation region than in the second irradiation region, it is possible to suppress the formation of a fine periodic structure on the processed cross section.

[0030] The laser processing method according to the present invention may be

[20] "the laser processing method according to any one of the above

[12] to

[19] , wherein in the splitting step and the focusing step, no irradiation area interfering with the first irradiation area or the second irradiation area is formed in a range from the peak position of the intensity in the first irradiation area to 1.5 times the diameter of the first irradiation area, and in a range from the peak position of the intensity in the second irradiation area to 1.5 times the diameter of the second irradiation area." In this case, it is possible to more reliably suppress the formation of a fine periodic structure on the processed cross section.

[0031] The laser processing method according to the present invention may be

[21] "the laser processing method according to any one of the above

[12] to

[20] , wherein in the scanning step, the first irradiation region is scanned over the object so that the distance between the peak position of the intensity of the first irradiation region corresponding to one pulse of the laser light and the peak position of the intensity of the first irradiation region corresponding to another pulse subsequent to the one pulse is equal to or less than half the diameter of the first irradiation region." In this case, it is possible to form a processed cross section with fewer irregularities along the scanning direction of the laser light.

[0032] The observation method according to the present invention may be

[22] "an observation method comprising the branching step, the focusing step, and the scanning step provided in the laser processing method according to any one of the above

[12] to

[21] , and an observation step of observing the processed cross section formed in the scanning step after the scanning step." In this case, deterioration in the quality of the processed cross section is suppressed, so that highly accurate observation results of the processed cross section can be obtained. [Effects of the Invention]

[0033] According to the present invention, it is possible to provide a laser processing apparatus, a microscope apparatus, a laser processing method, and an observation method that can suppress deterioration in the quality of the processed cross section. [Brief explanation of the drawings]

[0034] [Figure 1]FIG. 1 is a schematic diagram showing a part of a microscope apparatus according to this embodiment. [Figure 2] FIG. 2 is a schematic diagram showing the remainder of the microscope apparatus shown in FIG. [Figure 3] FIG. 3 is a schematic diagram showing how a sample is processed by laser light, and an SEM photograph showing the processed cross section of the sample. [Figure 4] FIG. 4 is a schematic diagram for explaining how the laser light is split by the control unit, the half-wave plate, and the spatial light modulator shown in FIG. [Figure 5] FIG. 5 is a diagram showing the polarization directions of the laser beam and the branched laser beam shown in FIG. [Figure 6] FIG. 6 is a diagram showing a branching pattern, which is a diffraction grating pattern displayed on the spatial light modulator shown in FIGS. [Figure 7] FIG. 7 is a schematic diagram showing an irradiation area formed on a sample. [Figure 8] FIG. 8 is a diagram showing the intensity of the irradiated area formed on the sample. [Figure 9] FIG. 9 is a graph showing how branched laser beams overlap. [Figure 10] FIG. 10 is a diagram showing the relationship between the branch pitch of the irradiation areas and the separation state of each irradiation area. [Figure 11] FIG. 11 is an SEM photograph showing the results of observing the processed cross section. [Figure 12] FIG. 12 is an SEM photograph showing the processing result according to the comparative example. [Figure 13] FIG. 13 is a schematic diagram showing the polarization direction of branched laser light according to a modified example, and an SEM photograph showing the processing result. [Figure 14] FIG. 14 is a schematic diagram showing the polarization direction of branched laser light according to a modified example, and an SEM photograph showing the processing result. [Figure 15] FIG. 15 is a schematic diagram showing the arrangement of irradiation regions according to a comparative example, and an SEM photograph showing the processing result. [Figure 16] FIG. 16 is a schematic diagram showing the arrangement of irradiation regions according to a comparative example, and an SEM photograph showing the processing result. [Figure 17] FIG. 17 is a schematic diagram showing the arrangement of irradiation regions according to a comparative example, and an SEM photograph showing the processing result. [Figure 18] FIG. 18 is a schematic diagram showing the arrangement of irradiation regions according to a modified example, and an SEM photograph showing the processing result. [Figure 19] FIG. 19 is a schematic diagram showing the arrangement of irradiation regions according to a comparative example, and an SEM photograph showing the processing result. [Figure 20] FIG. 20 is a diagram showing the intensity distribution of the irradiation area and the processing result according to the modified example. [Figure 21] FIG. 21 is a diagram showing the intensity distribution of the irradiation area and the processing result according to the modified example. [Figure 22] FIG. 22 is a schematic diagram showing the arrangement of irradiation areas according to a modified example. [Figure 23] FIG. 23 is a SEM photograph showing the processing result and a diagram showing an example of a branching pattern. [Figure 24] FIG. 24 is a diagram showing the arrangement of irradiation areas according to a modified example and SEM photographs showing the processing results in the irradiation areas. [Figure 25] FIG. 25 is a diagram showing an example of a branching pattern according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0035] Hereinafter, a laser processing apparatus, a microscope apparatus, a laser processing method, and an observation method according to an embodiment will be described with reference to the drawings. In the description of the drawings, the same or corresponding elements are designated by the same reference numerals, and duplicated descriptions may be omitted.

[0036] Fig. 1 is a schematic diagram showing a part of a microscope apparatus according to this embodiment. Fig. 2 is a schematic diagram showing the remaining part of the microscope apparatus shown in Fig. 1. As will be described later, the microscope apparatus 1 shown in Fig. 1 and Fig. 2 includes a focused ion beam (FIB) apparatus that irradiates a sample with focused ions (e.g., Ga ions) to etch the sample, a scanning electron microscope (SEM) apparatus that irradiates the sample with an electron beam to observe the sample, and a laser processing apparatus that irradiates the sample with laser light to perform laser processing (e.g., ablation processing) of the sample, and is an apparatus that allows the SEM apparatus to observe the processed cross section of the sample formed by processing using the FIB apparatus and / or the laser processing apparatus.

[0037] The microscope device 1 includes a sample holder (placement unit) 2, a beam irradiation unit 3, a first microscope unit (microscope unit) 4, a second microscope unit (microscope unit) 5, a cover 7, a chamber 10, and a laser processing device 20. A sample A is placed on the sample holder 2. The sample A is also the object to be processed by the FIB device and the laser processing device 20. The object to be processed by the FIB device and the laser processing device 20 (i.e., the material of the sample A) is, for example, copper, iron, an alloy, a semiconductor material, etc. The sample holder 2 may support the sample A without fixing it, as in the case where the sample A is simply placed on it, or may fix and hold the sample A by, for example, gluing it on something. In this example, the sample holder 2 holds the sample A. The beam irradiation unit 3 is for irradiating the sample A held (placed (the same applies below)) on the sample holder 2 with a focused ion beam. Therefore, the beam irradiation unit 3 may include at least the focused ion beam emission unit of the FIB device.

[0038] The first microscope unit 4 is for observing the sample A held in the sample holder 2. More specifically, the first microscope unit 4 is configured to be able to obtain an image of the sample A (observe the sample A) by irradiating the sample A held in the sample holder 2 with an electron beam and detecting secondary electrons and the like generated in the sample A. Therefore, the first microscope unit 4 can be at least a part of the SEM device that includes an electron beam emission unit and detection unit.

[0039] Like the first microscope unit 4, the second microscope unit 5 is used to observe the sample A held in the sample holder 2. More specifically, the second microscope unit 5 is capable of irradiating the sample A held in the sample holder 2 with an electron beam and detecting the electron beam scattered by the sample A, thereby acquiring information about the crystalline structure of the sample A (observing the sample A). That is, an example of the second microscope unit 5 may be a part of an SEM device that uses the electron backscatter diffraction (EBSD) method, including at least an electron beam emission unit and a detection unit. Note that the microscope device 1 may be equipped with a transmission electron microscope (TEM) device instead of (or in addition to) the SEM device. In this case, the first microscope unit 4 and the second microscope unit 5 may be at least a part of the TEM device.

[0040] The cover 7 is made of a material that transmits the laser light L described below, and is provided so as to cover the sample A held in the sample holder 2. As a result, the cover 7 can be placed at a reference position that is between the sample holder 2 and the beam irradiation unit 3, the first microscope unit 4, and the second microscope unit 5, and that is interposed in the optical path of the laser light L. The cover 7 is configured to be movable from the reference position so as not to be interposed between the sample holder 2 and the beam irradiation unit 3, the first microscope unit 4, and the second microscope unit 5.

[0041] The chamber 10 houses the sample holder 2, the beam irradiation unit 3, the first microscope unit 4, the second microscope unit 5, and the cover 7. The chamber 10 is formed with an entrance unit 11 for the laser light L, which is configured in the shape of a window and made of a material that transmits the laser light L. The chamber 10 also has an exhaust unit 12 for exhausting the inside of the chamber 10 to reduce the pressure (to create a vacuum). Furthermore, the chamber 10 may be provided with another unit 6 for processing or observing the sample A held in the sample holder 2.

[0042] The laser processing apparatus 20 includes a laser output unit 30 and a laser optical system 40. The laser output unit 30 outputs low-fluence, ultrashort-pulse laser light L. The pulse width of the laser light L output from the laser output unit 30 is, for example, 1 ps or less. The low fluence of the laser light L may mean, for example, that the energy density of the laser light L is near the processing threshold of the sample A, which is determined so that ablation processing occurs during laser processing of the sample A. The laser optical system 40 is a laser irradiation unit that irradiates the laser light L output from the laser output unit 30 onto the sample A held in the sample holder 2. The laser light L output from the laser output unit 30 is guided by the laser optical system 40 and incident into the chamber 10 from the incident unit 11.

[0043] The laser optical system 40 has a spatial light modulator (branching unit) 41, a lens (condensing unit) 42, and a galvanometer mirror (scanning unit) 43. The spatial light modulator 41 modulates the laser light L output from the laser output unit 30 according to a modulation pattern and emits the modulated laser light. More specifically, the spatial light modulator 41 is, for example, an LCOS-SLM (Liquid Crystal On Silicon - Spatial Light Modulator), and displays a modulation pattern on a liquid crystal layer, thereby modulating the laser light L that enters and exits the liquid crystal layer according to the modulation pattern.

[0044] The lens 42 focuses the laser light L (a first branched laser light L1, a second branched laser light L2, and a third branched laser light L3, which are a plurality of branched laser lights described later) output from the spatial light modulator 41 toward the sample A. The lens 42 is, for example, an fθ lens.

[0045] The galvanometer mirror 43 includes mirrors 43a and 43b, and is interposed on the optical path of the laser light L between the spatial light modulator 41 and the lens 42. By driving the mirrors 43a and 43b, the galvanometer mirror 43 irradiates the laser light L emitted from the spatial light modulator 41 via the lens 42 onto the sample A held by the sample holder 2 while scanning the laser light L.

[0046] As a result, the galvanometer mirror 43 functions as a scanning unit, which is an optical element that emits the laser light L (a first branched laser light L1, a second branched laser light L2, and a third branched laser light L3, which are a plurality of branched laser light described later) emitted from the spatial light modulator 41 and collected by the lens 42, so as to scan and irradiate the sample A held in the sample holder 2. Note that, instead of (or in addition to) the galvanometer mirror 43, the laser processing apparatus 20 may include, as a scanning unit, a configuration that mechanically moves the sample holder 2 (i.e., the sample A) so as to scan and irradiate the laser light L emitted from the spatial light modulator 41 and collected by the lens 42 to the sample A. Furthermore, when the galvanometer mirror 43 is a three-dimensional galvanometer scanner, for example, the function of the light collecting unit and the function of the scanning unit may be integrated.

[0047] The laser optical system 40 further includes a relay optical system 44. The relay optical system 44 is disposed between the spatial light modulator 41 and the galvanometer mirror 43. The relay optical system 44 includes a pair of lenses 44a and 44b, and is configured to transfer an image of the laser light L modulated by the spatial light modulator 41 onto the lens 42. The laser light L emitted from the spatial light modulator 41 and passed through the relay optical system 44 has its optical path adjusted by predetermined mirrors 56 and 57 and is then supplied to the galvanometer mirror 43.

[0048] The laser optical system 40 further includes a collimating lens 51, an output control unit 52, a beam diameter control unit 53, and a half-wave plate 54, which are arranged in this order on the optical path of the laser light L traveling from the laser output unit 30 to the spatial light modulator 41. The collimating lens 51 collimates the laser light L output from the laser output unit 30 and emits it. Therefore, the collimated laser light L is incident on the spatial light modulator 41. The collimating lens 51 may be omitted.

[0049] The output control unit 52 is, for example, an attenuator, and adjusts the output of the laser light L output from the laser output unit 30. The beam diameter control unit 53 is, for example, a beam expander, and adjusts the beam diameter of the laser light L output from the laser output unit 30. In this way, the output control unit 52 and the beam diameter control unit 53 are disposed between the spatial light modulator 41 and the laser output unit 30, and function as adjustment units that adjust the output and beam diameter of the laser light L.

[0050] The half-wave plate 54 changes the polarization direction of the laser light L output from the laser output unit 30. That is, the laser light L whose polarization direction has been changed by the half-wave plate 54 is made incident on the spatial light modulator 41. As described above, the laser light L incident on the spatial light modulator 41 is modulated according to a predetermined modulation pattern, and then passes through the galvanometer mirror 43 and the lens 42 to be incident on the chamber 10 and used to scan the sample A.

[0051] The microscope device 1 described above can process the sample A using the focused ion beam from the beam irradiation unit 3 and the laser light L from the laser processing device 20. When the focused ion beam is used, the sample A can be processed with high precision. On the other hand, when the laser light L is used, a large area of ​​the sample A can be processed with high throughput.

[0052] Here, as shown in FIG. 3 , when processing sample A using ultrashort pulsed laser light L with a low fluence near the processing threshold of sample A, a fine periodic structure such as a laser induced periodic surface structure (LIPSS) may be formed on the processed cross section As of sample A. Since flatness of the processed cross section As is required for observation with an SEM device, the formation of a fine periodic structure on the processed cross section As is undesirable. Furthermore, not only for observation with an SEM device but also from the viewpoint of ensuring the flexural strength of sample A, the formation of a fine periodic structure on the processed cross section As is undesirable. The processed cross section As is a surface that intersects with the processed surface Ar of sample A, which intersects with the optical axis of the laser light L (i.e., is aligned with the optical axis of the laser light L). The phrase "the processed cross section As is aligned with the optical axis of the laser light L" includes cases where the processed cross section As is parallel to the laser light L and cases where the processed cross section As is slightly inclined with respect to the optical axis of the laser light L.

[0053] One hypothesis for the formation of LIPSS is that it is due to the interaction between plasma and laser light. This hypothesis is summarized as follows: When an ultrashort pulse of laser light is irradiated onto a sample, atoms and ions are removed from the sample surface. Once the atoms and ions are removed, plasma with a shielding effect is generated directly above the point of irradiation with the laser light. As a result, the atoms and ions removed from the sample surface are deposited on the processed cross section without diffusing due to the shielding effect of the plasma. As a result, LIPSS is formed on the processed cross section due to the deposits.

[0054] In contrast to this, the laser processing apparatus 20 according to this embodiment has a configuration that can suppress the occurrence of a fine periodic structure on the processed cross section As of the sample A. Next, this point will be described.

[0055] The laser processing apparatus 20 further includes a control unit 60 that controls the spatial light modulator 41 and the half-wave plate 54. The control unit 60 controls the half-wave plate 54, which is disposed upstream of the spatial light modulator 41 (e.g., adjusts the angle of the laser light L about the optical axis), to convert the polarization direction of the laser light L emitted from the half-wave plate 54 into a polarization direction P0 including a first polarization direction P1 along the X-axis direction and a second polarization direction P2 along the Y-axis direction, as shown in FIG. 5(a). The example in FIG. 5 illustrates a case where the first polarization direction P1 and the second polarization direction P2 are linearly polarized light orthogonal to each other. Note that "linearly polarized light is orthogonal to each other" means that the polarization directions of the two light beams are in the range of 90°±10°. Similarly, "linearly polarized light is the same" means that the polarization directions of the two light beams are in the range of 0°±10°.

[0056] On the other hand, the control unit 60 causes the spatial light modulator 41 to display a modulation pattern (hereinafter sometimes referred to as a "branching pattern") for branching the laser light L from the half wavelength plate 54 into branched laser light including at least a first branched laser light L1 having a first polarization direction P1 and a second branched laser light L2 having a second polarization direction P2. In the examples of Figures 4 and 5, the control unit 60 causes the spatial light modulator 41 to display a modulation pattern for branching the laser light L into branched laser light including the first branched laser light L1 having the first polarization direction P1, the second branched laser light L2 having the second polarization direction P2, and a third branched laser light L3 having the first polarization direction P1.

[0057] An example of the branching pattern is a diffraction grating pattern. When a diffraction grating pattern is displayed on the spatial light modulator 41, for example, a component of the laser light L from the half-wave plate 54 in the second polarization direction P2 is not modulated (diffracted) by the spatial light modulator 41 and is emitted from the spatial light modulator 41 as a second branched laser light L2, which is zero-order light. On the other hand, a component of the laser light L from the half-wave plate 54 in the first polarization direction P1 is modulated (diffracted) by the spatial light modulator 41 and is emitted from the spatial light modulator 41 as a first branched laser light L1 and a third branched laser light L3, which are ±1st-order light. As a result, the laser light L is branched into a plurality of branched laser light. FIG. 6 shows a branching pattern M1, which is a diffraction grating pattern displayed on the spatial light modulator 41. In FIG. 6, differences in modulation amount (brightness of the image signal) are indicated by gray shades.

[0058] In this way, in the laser processing apparatus 20, the half-wave plate 54 and the spatial light modulator 41 function as a branching unit for branching the laser light L output from the laser output unit 30 into a plurality of branched laser light beams and outputting the branched laser light beams. Therefore, the lens 42 focuses the plurality of branched laser light beams output from the spatial light modulator 41 toward the sample A, and the galvanometer mirror 43 scans the plurality of branched laser light beams focused by the lens 42 over the sample A.

[0059] 7 and 8, the lens 42 focuses the first branched laser beam L1 toward the sample A to form a first irradiation region R1 of the first branched laser beam L1 on the sample A, focuses the second branched laser beam L2 toward the sample A to form a second irradiation region R2 of the second branched laser beam L2 on the sample A, and focuses the third branched laser beam L3 toward the sample A to form a third irradiation region R3 of the third branched laser beam L3 on the sample A. The first irradiation region R1, the second irradiation region R2, and the third irradiation region R3 are not limited to the focusing positions of the first branched laser beam L1, the second branched laser beam L2, and the third branched laser beam L3, respectively, and may be formed at positions shifted from the focusing positions in the optical axis direction (i.e., may be defocused). Furthermore, focusing the branched laser beams toward the sample A by the lens 42 means that the diameter of the branched laser beam is smaller at a second position on the sample A side than at a first position on the exit surface side of the lens 42.

[0060] The lens 42 forms a second irradiation region R2 on the sample A so as to be aligned with the first irradiation region R1 along a first direction D1 intersecting with the optical axis (third direction D3) of the branched laser beam (first branched laser beam L1 or second branched laser beam L2) according to the emission directions of the first branched laser beam L1, the second branched laser beam L2, and the third branched laser beam L3 from the spatial light modulator 41, and forms a third irradiation region R3 on the sample A so as to be aligned with the second irradiation region R2 on the opposite side to the first irradiation region R1 along the first direction D1. As a result, on the processing surface Ar of the sample A, the second branched laser beam L2 having the second polarization direction P2 orthogonal to the first polarization direction P1 is disposed between the first branched laser beam L1 and the third branched laser beam L3 having the first polarization direction P1 along the first direction D1. In addition, Figure 7 shows an example in which the first direction D1 in which the first irradiation area R1, the second irradiation area R2, and the third irradiation area R3 are aligned is perpendicular to the processing cross section As, but the first direction D1 does not have to be perpendicular to the processing cross section As, and may be inclined with respect to the normal to the processing cross section As.

[0061] 9, the first branched laser beam L1, the second branched laser beam L2, and the third branched laser beam L3 may overlap in a low-intensity region. In the example of FIG. 9, when the peak intensity values ​​of the first branched laser beam L1 and the third branched laser beam L3, which have relatively low peak intensities, are set to 100%, an overlapping portion R12 between the first branched laser beam L1 and the second branched laser beam L2 occurs in a region where the peak intensity is less than 80%, and an overlapping portion R23 between the second branched laser beam L2 and the third branched laser beam L3 occurs. Therefore, the first irradiation region R1, the second irradiation region R2, and the third irradiation region R3 shown in FIG. 7 can be defined so that the contours of each irradiation region are contiguous by being set to regions where the intensity in FIG. 9 is 80% or more.

[0062] Fig. 10 is a diagram showing the relationship between the branching pitch of irradiation regions and the separation state of each irradiation region. Fig. 10(a) shows three irradiation regions Q1, Q2, and Q3 according to a comparative example formed by three laser beams having the same polarization direction, and Fig. 10(b) shows the first irradiation region R1, second irradiation region R2, and third irradiation region R3 according to this embodiment. The diameters of irradiation regions Q1 to Q3, first irradiation region R1, second irradiation region R2, and third irradiation region R3 according to the comparative example are all, for example, approximately 11.5 μm.

[0063] 10, the irradiation regions Q1 to Q3 according to the comparative example maintain a separated state when the distance (branching pitch K) between the peak intensity position of irradiation region Q1 and the peak intensity position of irradiation region Q3 is in the range of approximately 54 μm to 32 μm, but when the branching pitch K is approximately 19 μm, the separated state is no longer maintained due to mutual interference. On the other hand, it can be seen that the first irradiation region R1, second irradiation region R2, and third irradiation region R3 according to this embodiment maintain a separated state when the branching pitch K is from 59 μm to approximately 19 μm. Furthermore, it has been confirmed that the first irradiation region R1, second irradiation region R2, and third irradiation region R3 according to this embodiment can maintain a separated state when the branching pitch K is up to 9.5 μm (approximately 82% of the diameter).

[0064] The galvanometer mirror 43 scans the first irradiation region R1, second irradiation region R2, and third irradiation region R3 formed as described above on the sample A along the optical axis (third direction D3) of the branched laser light and the second direction D2 intersecting the first direction D1, thereby forming a processed cross section As on the sample A that intersects the first direction D1 and extends along the second direction D2 (and further along the third direction D3). Therefore, with the illustrated processed cross section As as a reference, the irradiation region closest to the processed cross section As is the first irradiation region R1, the irradiation region second closest to the processed cross section As is the second irradiation region R2, and the irradiation region farthest from the processed cross section As is the third irradiation region R3. In other words, the illustrated processed cross section As is the surface of the sample A facing the first irradiation region R1.

[0065] The wavelength of the laser light L is, for example, about 515 nm, the repetition frequency of the laser light L is, for example, 500 kHz, and the intensity of the laser light L is, for example, 1000 mW. The intensity ratio of the peak intensity of the first irradiation region R1 to the peak intensity of the second irradiation region R2 to the peak intensity of the third irradiation region R3 is, for example, 20:60:20 (although not limited to this as will be described later).

[0066] As shown in Fig. 11, in this case, it is possible to form the processed cross section As while suppressing the formation of the fine periodic structure. On the other hand, as shown in Fig. 12, when the irradiation areas Q1 to Q3 according to the comparative example are scanned, it is understood that the fine periodic structure is formed on the processed cross section As.

[0067] The laser processing performed by the above-described laser processing apparatus 20 is also one aspect of the laser processing method according to the present embodiment. That is, the laser processing method according to the present embodiment is a laser processing method for forming a processing cross section As by irradiating a sample A with laser light. The laser processing method includes a step S101 (branching step, see FIGS. 4 and 5) of branching laser light L having a pulse width of 1 ps or less to generate a plurality of branched laser beams, a step S102 (focusing step, see FIGS. 4 and 7) of focusing the plurality of branched laser beams generated in step S101 toward the sample A, and a step S103 (scanning step, see FIG. 7) of scanning the plurality of branched laser beams focused in step S102 over the sample A.

[0068] In step S101, the laser light L is branched into a plurality of branched laser lights including a first branched laser light L1 having a first polarization direction P1, a second branched laser light L2 having a second polarization direction P2 perpendicular to the first polarization direction P1, and a third branched laser light L3 having the first polarization direction P1.

[0069] In step S102, the first branched laser light L1 is focused toward the sample A to form a first irradiation region R1 of the first branched laser light L1 on the sample A, the second branched laser light L2 is focused toward the sample A to form a second irradiation region R2 of the second branched laser light L2 on the sample A, and the third branched laser light L3 is focused toward the sample A to form a third irradiation region R3 of the third branched laser light L3 on the sample A.

[0070] Furthermore, in step S102, a second irradiation region R2 is formed on the sample A so as to be aligned with the first irradiation region R1 along a first direction D1 intersecting the optical axis (third direction D3) of the branched laser beam, and a third irradiation region R3 is formed on the sample A so as to be aligned with the second irradiation region R2 on the opposite side of the first irradiation region R1 along the first direction D1. As a result, on the processing surface Ar of the sample A, the second branched laser beam L2 having the second polarization direction P2 orthogonal to the first polarization direction P1 is disposed along the first direction D1 between the first branched laser beam L1 having the first polarization direction P1 and the third branched laser beam L3.

[0071] In step S103, the first irradiation region R1, the second irradiation region R2, and the third irradiation region R3 are scanned on the sample A along the optical axis (third direction D3) of the branched laser light and a second direction D2 intersecting the first direction D1, thereby forming a processed cross section As that intersects the first direction D1 and is along the second direction D2 (and further along the third direction D3) on the sample A. Note that the processed cross section As being along the third direction D3 includes the case where the processed cross section As is parallel to the third direction D3 and the case where the processed cross section As is slightly inclined with respect to the third direction D3.

[0072] As described above, in the laser processing apparatus 20 and laser processing method according to this embodiment, a processed cross section As along the scanning direction (second direction D2) of the laser light L is formed on the sample A by irradiating the sample A with laser light. The laser light L is an ultrashort pulse laser having a pulse width of 1 ps or less. Therefore, it is possible to suppress deterioration in the quality of the processed cross section As caused by changes in the properties of the processed cross section As due to the influence of heat. Furthermore, the laser processing apparatus 20 and laser processing method according to this embodiment have the following configuration, and therefore it is also possible to suppress deterioration in the quality of the processed cross section As caused by the formation of a fine periodic structure on the processed cross section As by using an ultrashort pulse laser.

[0073] That is, in the laser processing apparatus 20 and the laser processing method according to this embodiment, the laser beam L is branched into a plurality of branched laser beams including a first branched laser beam L1 having a first polarization direction P1 and a second branched laser beam L2 having a second polarization direction P2 orthogonal to the first polarization direction P1. The first branched laser beam L1 is focused toward the sample A to form a first irradiation region R1 of the first branched laser beam L1 on the sample A, and the second branched laser beam L2 is focused toward the sample A to form a second irradiation region R2 of the second branched laser beam L2 on the sample A so as to be aligned with the first irradiation region R1 along the first direction D1 intersecting the optical axis (third direction D3) of the branched laser beam.

[0074] Then, the first irradiation region R1 and the second irradiation region R2 are scanned on the sample A along the optical axis (third direction D3) of the branched laser light and the second direction D2 (the above-mentioned scanning direction) intersecting the first direction D1, thereby forming a processed cross section As on the sample A that intersects the first direction D1 and is along the second direction D2. In this way, by scanning the first irradiation region R1 of the first branched laser light L1 and the second irradiation region R2 of the second branched laser light L2, which are unlikely to interfere with each other, while arranging them as described above, formation of a fine periodic structure on the processed cross section As is suppressed. As described above, the laser processing apparatus 20 and laser processing method according to this embodiment can suppress deterioration in the quality of the processed cross section.

[0075] Furthermore, in the laser processing apparatus 20 according to this embodiment, the lens 42 forms a third irradiation area R3 of the branched laser light on the sample A so as to be aligned with the second irradiation area R2 on the opposite side to the first irradiation area R1 along the first direction D1. The galvanometer mirror 43 scans the first irradiation area R1, the second irradiation area R2, and the third irradiation area R3 along the second direction D2 to form a processed cross section As.

[0076] Similarly, in the laser processing method according to this embodiment, in step S102, a third irradiation region R3 of the branched laser beam is formed on the sample A so as to be aligned with the second irradiation region R2 on the opposite side to the first irradiation region R1 along the first direction D1. Then, in step S103, the first irradiation region R, the second irradiation region R2, and the third irradiation region R3 are scanned along the second direction D2 to form a processed cross section As. In this way, by performing scanning while further forming the third irradiation region R3, it is possible to improve the processing speed while suppressing deterioration in the quality of the processed cross section As.

[0077] In the laser processing apparatus 20 and the laser processing method according to this embodiment, the branched laser beam has the first polarization direction P1 in the third irradiation region R3, which makes it possible to suppress interference of the branched laser beam between the second irradiation region R2 and the third irradiation region R3 arranged adjacent to the second irradiation region R2.

[0078] In the laser processing apparatus 20 according to this embodiment, the half-wave plate 54 and the spatial light modulator 41 branch the laser light L into a plurality of branched laser beams further including a third branched laser beam L3 having a first polarization direction P1. The lens 42 focuses the third branched laser beam L3 toward the sample A, thereby forming a third irradiation region R3 on the sample A.

[0079] Similarly, in the laser processing method according to this embodiment, in step S101, the laser light L is branched into a plurality of branched laser light beams further including a third branched laser light L3 having a first polarization direction P1. Then, the lens 42 focuses the third branched laser light L3 toward the sample A to form a third irradiation region R3 on the sample A. In this manner, the third irradiation region R3 may be formed based on the third branched laser light L3, which is separate from the first branched laser light L1 and the second branched laser light L2. In this case, the conditions for suppressing the generation of a fine periodic structure are less dependent on the intensity of the laser light L and the focusing density of the laser light L than in the case where the third irradiation region R3 is not formed, and therefore the fine periodic structure can be suppressed under a wider range of conditions.

[0080] Furthermore, the microscope apparatus 1 according to this embodiment includes the laser processing apparatus 20 according to this embodiment, and a first microscope unit 4 and a second microscope unit 5 for observing the processed cross section As. Therefore, deterioration in the quality of the processed cross section As is suppressed, and highly accurate observation results of the processed cross section As can be obtained. Furthermore, the observation method according to this embodiment includes steps S101 to S103 of the laser processing method according to this embodiment, and, after step S103, step S104 (observation step, see FIG. 11 ) of observing the processed cross section As formed in step S103. In step S104, the processed cross section As can be observed, for example, by an SEM device provided in the microscope apparatus 1. According to this observation method, deterioration in the quality of the processed cross section As is suppressed, and highly accurate observation results of the processed cross section As can be obtained.

[0081] The above embodiment has described one aspect of the laser processing apparatus, microscope apparatus, laser processing method, and observation method according to the present invention. Therefore, the laser processing apparatus, microscope apparatus, and laser processing method according to the present invention may be modified in any manner. Next, modifications will be described. [First Modification]

[0082] For example, as shown in FIG. 13(a), in the laser processing apparatus 20 (or the laser processing method), the half-wave plate 54 and the spatial light modulator 41 (i.e., the branching unit) (or in step S101) may branch the laser beam L into a plurality of branched laser beams including a first branched laser beam L1 having a first polarization direction P3, a second branched laser beam L2 having a second polarization direction P4, and a third branched laser beam L3 having the first polarization direction P3. The first polarization direction P3 is a polarization direction orthogonal to the first polarization direction P1 and corresponds to the second polarization direction P2. The second polarization direction P4 is a polarization direction orthogonal to the first polarization direction P3 and corresponds to the first polarization direction P1. Even in this case, as shown in FIG. 13(b), formation of a fine periodic structure on the processed cross section As is suppressed.

[0083] 14(a), in the laser processing apparatus 20 (or the laser processing method), the half-wave plate 54 and the spatial light modulator 41 (i.e., the branching unit) (or in step S101) may branch the laser beam L into a plurality of branched laser beams including a first branched laser beam L1 having a first polarization direction P5, a second branched laser beam L2 having a second polarization direction P6, and a third branched laser beam L3 having the first polarization direction P5. The first polarization direction P5 and the second polarization direction P6 are circularly polarized beams that are orthogonal to each other (have opposite rotation directions). Even in this case, as shown in FIG. 14(b), the formation of a fine periodic structure on the processed cross section As is suppressed.

[0084] As described above, the polarization direction of the branched laser light in the first irradiation region R1 (and the third irradiation region R3) and the polarization direction of the branched laser light in the second irradiation region R2 only need to be orthogonal to each other, and there is no dependency on the specific polarization direction. [Second Modification]

[0085] 15(a) is a schematic diagram showing the arrangement of irradiation regions according to a comparative example. In the example shown in FIG. 15(a), a pair of fourth irradiation regions R4 are formed near the first irradiation region R1 and the second irradiation region R2. In this example, the fourth irradiation regions R4 have a first polarization direction P1, which is linearly polarized light similar to the first branched laser beam L1, and are arranged on both sides of the second irradiation region R2 along the second direction D2 (scanning direction) so as to sandwich the second irradiation region R2 therebetween.

[0086] The fourth irradiation region R4 is formed, for example, by concentrating a branched laser beam different from the first branched laser beam L1, and may interfere with the first irradiation region R1. When the first irradiation region R1, the second irradiation region R2, and the fourth irradiation region R4 are irradiated onto the sample A while scanning them, a fine periodic structure may be formed on the processed cross section As, as shown in (b) of FIG.

[0087] Similarly, as shown in (a) of Figure 16, even if the first branched laser light L1 has a first polarization direction P3 that is linearly polarized in the first irradiation region R1 and the second branched laser light L2 has a second polarization direction P4 that is linearly polarized in the second irradiation region R2, if a fourth irradiation region R4 is formed that has the same first polarization direction P3 as the first branched laser light L1, there is a risk that a fine periodic structure will be formed on the processed cross section As, as shown in (b) of Figure 16.

[0088] Furthermore, as shown in (a) of Figure 17, even if the first branched laser light L1 has a first polarization direction P5 that is circularly polarized in the first irradiation region R1 and the second branched laser light L2 has a second polarization direction P6 that is circularly polarized in the second irradiation region R2, if a fourth irradiation region R4 is formed that has the same first polarization direction P5 as the first branched laser light L1, there is a risk that a fine periodic structure will be formed on the processed cross section As, as shown in (b) of Figure 17.

[0089] However, if the fourth irradiation region R4 is not near the first irradiation region R1 and the second irradiation region R2, specifically, if it is outside the range of 1.5 times the diameter of the first irradiation region R1 from the peak position of the intensity in the first irradiation region R1, and outside the range of 1.5 times the diameter of the second irradiation region R2 from the peak position of the intensity in the second irradiation region R2, the formation of a fine periodic structure on the processed cross section As can be suppressed.

[0090] Therefore, in the laser processing apparatus 20 (or the laser processing method), the half-wave plate 54, the spatial light modulator 41, and the lens 42 (i.e., the branching section and the focusing section) (or in steps S101 and S102) can prevent the formation of an irradiation area (for example, an irradiation area formed by focusing a branched laser beam having the same polarization direction as the first branched laser beam L1 and different from the first branched laser beam L1) that interferes with the first irradiation area R1 or the second irradiation area R2 in a range from the peak position of the intensity in the first irradiation area R1 to 1.5 times the diameter of the first irradiation area R1 and in a range from the peak position of the intensity in the second irradiation area R2 to 1.5 times the diameter of the second irradiation area R2. In this case, it is possible to more reliably prevent the formation of a fine periodic structure on the processed cross section As. Note that the diameters of the first irradiation area R1 and the second irradiation area R2 are defined as 1 / e of the diameters at which the light intensities of the first branched laser beam L1 and the second branched laser beam L2 are at their peaks. 2 The size range falls below: [Third Modification]

[0091] In the above embodiment and modified example, the first irradiation region R1, the second irradiation region R2, and the third irradiation region R3 are formed so that their contours are in contact with each other. Specifically, in the example shown in Fig. 13, the diameter J of the first irradiation region R1, the second irradiation region R2, and the third irradiation region R3 is approximately 11.5 µm, and the branch pitch K, which is the distance between the peak position C1 of the intensity of the first irradiation region R1 and the peak position C3 of the intensity of the third irradiation region R3, is approximately 23 µm. In this case, as described above, the formation of a fine periodic structure on the processed cross section As is suppressed, and the flatness of the processed cross section As is ensured.

[0092] 18(a), the branching pitch K may be enlarged so that the contours of the first irradiation region R1, the second irradiation region R2, and the third irradiation region R3 do not contact each other. In the example of FIG. 18(a), the branching pitch K is about 27 μm. Even in this case, as shown in FIG. 18(b), the formation of a fine periodic structure on the processed cross section As is suppressed, and the flatness of the processed cross section As is ensured.

[0093] In contrast, if the branch pitch K is further increased to, for example, about 32 μm as shown in (a) of Fig. 19, the flatness of the processed cross section As may be reduced as shown in (b) of Fig. 19. If the branch pitch K is, for example, up to about 2.4 times the diameter J of the second irradiation region R2, the flatness of the processed cross section As may be ensured.

[0094] Therefore, in the laser processing apparatus 20 (or the laser processing method), the lens 42 (i.e., the focusing unit) (or in step S102) can form the first irradiation region R1 and the second irradiation region R2 on the sample A so that the distance between the intensity peak position C1 in the first irradiation region R1 and the intensity peak position in the second irradiation region R2 (which is half the value of the branching pitch K, or the branching pitch in the case of two branches) is 1.2 times or less the diameter J of the second irradiation region R2. In this case, the flatness of the processed cross section As can be ensured as described above. [Fourth Modification]

[0095] In the above embodiment, as shown in Fig. 8, an example was shown in which the laser light L is branched so that the peak intensity values ​​in the first irradiation region R1 and the third irradiation region R3 are lower than the peak intensity value in the second irradiation region R2. However, the intensity ratio of each irradiation region is not limited to this case. For example, in the example shown in Fig. 20(a) and (b), the laser light L is branched so that the peak intensity values ​​in the first irradiation region R1 and the third irradiation region R3 are higher than the peak intensity value in the second irradiation region R2. Even in these cases, the formation of a fine periodic structure on the processed cross section As is suppressed.

[0096] 21(a) and 21(b), the peak intensity values ​​of the first irradiation region R1 and the third irradiation region R3 may be lower than the peak intensity value of the second irradiation region R2 at an intensity ratio different from that shown in FIG. 8. In this case, too, the formation of a fine periodic structure on the processed cross section As is similarly suppressed. In this way, it can be understood that the effect of suppressing the formation of a fine periodic structure on the processed cross section As does not depend on the intensity ratio of each irradiation region.

[0097] Therefore, in the laser processing apparatus 20 (or the laser processing method), the half-wave plate 54 and the spatial light modulator 41 (i.e., the branching section) (or in step S101) may branch the laser light L so that the peak intensity value in the first irradiation region R1 (and the third irradiation region R3) is lower than the peak intensity value in the second irradiation region R2, or may branch the laser light L so that the peak intensity value in the first irradiation region R1 (and the third irradiation region R3) is higher than the peak intensity value in the second irradiation region R2. In either case, it is possible to suppress the formation of a fine periodic structure on the processed cross section As. [Fifth Modification]

[0098] In the above embodiment, the laser light L is branched into a plurality of branched laser beams including the first branched laser beam L1, the second branched laser beam L2, and the third branched laser beam L3, and three irradiation regions, the first irradiation region R1, the second irradiation region R2, and the third irradiation region R3, are formed. However, as shown in Fig. 22, two irradiation regions, the first irradiation region R1 and the second irradiation region R2, may be formed without forming the third irradiation region R3. In the example of Fig. 22, the laser light L is branched into the first branched laser beam L1 and the second branched laser beam L2, and each of the branched laser beams is condensed to form the first irradiation region R1 and the second irradiation region R2.

[0099] At this time, as shown in Fig. 22(a), the first irradiation area R1 on the side of the processed cross section As to be evaluated may be larger than the second irradiation area R2, or vice versa as shown in Fig. 22(b). That is, the size relationship between the first irradiation area R1 and the second irradiation area R2 is arbitrary, and in either case, it is possible to suppress the formation of a fine periodic structure on the processed cross section As, as shown in Fig. 23(a) as an example. Note that Fig. 23(b) shows a branching pattern M2 displayed on the spatial light modulator 41 to branch the laser beam L into the first branched laser beam L1 and the second irradiation area R2. [Sixth Modification]

[0100] In addition, in an example in which three irradiation regions, the first irradiation region R1, the second irradiation region R2, and the third irradiation region R3, are formed, the first irradiation region R1 and the third irradiation region R3 may be formed so as to be continuous with each other in an annular shape, as shown in (a) of Fig. 24. In this case, for example, by using a branching pattern M3 shown in Fig. 25 to branch the laser light L into a first branched laser light L1 and a second branched laser light L2, and by converging the first branched laser light L1 toward the sample A, the first irradiation region R1 and the third irradiation region R3 that are continuous with each other in an annular shape can be formed.

[0101] That is, the lens 42 (i.e., the focusing unit) (or in step S102) may focus the first branched laser beam L1 toward the sample A, thereby forming the first irradiation region R1 and the third irradiation region R3 in a continuous ring shape on the sample A. Even in this case, as shown in FIG. 24(b), the formation of a fine periodic structure on the processed cross section As is suppressed. [Other variations]

[0102] Furthermore, by adjusting the repetition frequency of the laser light L, which is an ultrashort pulse laser, and the scanning speed of the irradiation area, it is possible to control the interval between the irradiation area corresponding to one pulse of the laser light L and the irradiation area corresponding to another pulse subsequent to the one pulse (i.e., the pulse next to or before the one pulse).

[0103] In particular, in the laser processing apparatus 20 (or the laser processing method), the galvanometer mirror 43 (i.e., the scanning unit) (or in step S103) can scan the first irradiation region R1 relative to the sample A so that the distance (in the second direction D2) between the peak position of the intensity of the first irradiation region R1 corresponding to one pulse of the laser light L and the peak position of the intensity of the first irradiation region R1 corresponding to another pulse subsequent to the one pulse is equal to or less than half the diameter of the first irradiation region R1. In this case, it is possible to form a processed cross section As with few irregularities along the scanning direction of the laser light L (second direction D2).

[0104] Furthermore, the laser processing apparatus 20 may use, instead of the spatial light modulator 41, an optical member having a function corresponding to the branching pattern to be displayed on the spatial light modulator 41. For example, in the laser processing apparatus 20, instead of displaying the branching pattern M1, which is a diffraction grating pattern, on the spatial light modulator 41, a diffraction grating may be disposed after the half-wave plate 54.

[0105] Although the embodiments and several modified examples have been described above, some of the configurations of these embodiments and modified examples may be replaced (or added) and adopted. As an example, when three irradiation areas are formed as in the above embodiment, the size relationship between the first irradiation area R1 (or the third irradiation area R3) and the second irradiation area R2 may be changed, as shown in the fifth modified example.

[0106] Furthermore, when forming two irradiation regions, the first irradiation region R1 and the second irradiation region R2, as shown in the fifth modified example, or when forming the first irradiation region R1 and the third irradiation region R3 that are continuous with each other in a ring shape, as shown in the sixth modified example, the intensity ratio between the first irradiation region R1 (and the third irradiation region R3) and the second irradiation region R2 may be appropriately adjusted as shown in the fourth modified example. Furthermore, when forming two irradiation regions, the first irradiation region R1 and the second irradiation region R2, as shown in the fifth modified example, the first branched laser beam L1 and the second branched laser beam L2 may have circular polarization as shown in the first modified example. Furthermore, the laser processing device 20 does not have to be incorporated into the microscope device 1. [Explanation of symbols]

[0107] 1...microscope device, 20...laser processing device, 30...laser output section, 41...spatial light modulator (branching section), 42...lens (focusing section), 43...galvanometer mirror (scanning section), 54...half wavelength plate (branching section), L...laser light, L1...first branched laser light, L2...second branched laser light, L3...third branched laser light, R1...first irradiation area, R2...second irradiation area, R3...third irradiation area, P1, P3, P5...first polarization direction, P2, P4, P6...second polarization direction.

Claims

1. A laser processing device for forming a processed cross section by irradiating a target with laser light, a laser output unit for outputting laser light having a pulse width of 1 ps or less; a branching unit for branching the laser beam output from the laser output unit into a plurality of branched laser beams and outputting the branched laser beams; a focusing unit for focusing the plurality of branched laser beams output from the branching unit toward the target; a scanning unit for scanning the target object with the plurality of branched laser beams collected by the light collecting unit; Equipped with the branching unit branches the laser beam into a plurality of branched laser beams including a first branched laser beam having a first polarization direction and a second branched laser beam having a second polarization direction orthogonal to the first polarization direction, the focusing unit focuses the first branched laser beam toward the object to form a first irradiation region of the first branched laser beam on the object, and focuses the second branched laser beam toward the object to form a second irradiation region of the second branched laser beam on the object so as to be aligned with the first irradiation region along a first direction intersecting an optical axis of the branched laser beam, the scanning unit scans the first irradiation region and the second irradiation region on the object along a second direction intersecting the optical axis of the branched laser light and the first direction, thereby forming the processed cross section on the object intersecting the first direction and along the second direction. Laser processing equipment.

2. the light collecting unit forms a third irradiation area of ​​the branched laser beam on the object so as to be aligned with the second irradiation area on an opposite side to the first irradiation area along the first direction, the scanning unit forms the processed cross section by scanning the first irradiation area, the second irradiation area, and the third irradiation area along the second direction. The laser processing device according to claim 1 .

3. the branched laser beam has the first polarization direction in the third irradiation region; The laser processing device according to claim 2.

4. the branching unit branches the laser beam into a plurality of branched laser beams further including a third branched laser beam having the first polarization direction, the focusing unit focuses the third branched laser light toward the object to form the third irradiation region on the object. The laser processing device according to claim 3.

5. the focusing unit focuses the first branched laser light toward the object, thereby forming the first irradiation region and the third irradiation region on the object so as to be continuous in an annular shape. The laser processing device according to claim 3.

6. the light collecting unit forms the first irradiation region and the second irradiation region on the object so that a distance between a peak position of intensity in the first irradiation region and a peak position of intensity in the second irradiation region is 1.2 times or less a diameter of the second irradiation region; The laser processing device according to claim 1 .

7. the branching unit branches the laser light so that a peak value of intensity in the first irradiation region is lower than a peak value of intensity in the second irradiation region. The laser processing device according to claim 1 .

8. the branching unit branches the laser light so that a peak value of intensity in the first irradiation region is higher than a peak value of intensity in the second irradiation region. The laser processing device according to claim 1 .

9. the branching portion and the focusing portion do not form an irradiation region that interferes with the first irradiation region or the second irradiation region in a range from a peak position of intensity in the first irradiation region to a diameter 1.5 times the diameter of the first irradiation region, and in a range from a peak position of intensity in the second irradiation region to a diameter 1.5 times the diameter of the second irradiation region, The laser processing device according to claim 1 .

10. the scanning unit scans the first irradiation region with respect to the object so that a distance between a peak position of intensity of the first irradiation region corresponding to one pulse of the laser light and a peak position of intensity of the first irradiation region corresponding to another pulse subsequent to the one pulse is equal to or less than ½ of a diameter of the first irradiation region. The laser processing device according to claim 1 .

11. The laser processing device according to any one of claims 1 to 10, a microscope unit for observing the processed cross section; A microscope apparatus comprising:

12. A laser processing method for forming a processed cross section by irradiating a target with laser light, comprising: a branching step of branching a laser beam having a pulse width of 1 ps or less to generate a plurality of branched laser beams; a focusing step of focusing the plurality of branched laser beams generated in the branching step toward the target; a scanning step of scanning the target object with the plurality of branched laser beams focused in the focusing step; Equipped with In the branching step, the laser beam is branched into a plurality of branched laser beams including a first branched laser beam having a first polarization direction and a second branched laser beam having a second polarization direction orthogonal to the first polarization direction, In the focusing step, the first branched laser beam is focused toward the object to form a first irradiation region of the first branched laser beam on the object, and the second branched laser beam is focused toward the object to form a second irradiation region of the second branched laser beam on the object so as to be aligned with the first irradiation region along a first direction intersecting an optical axis of the branched laser beam, In the scanning step, the first irradiation region and the second irradiation region are scanned on the object along a second direction intersecting the optical axis of the branched laser light and the first direction, thereby forming the processed cross section on the object intersecting the first direction and along the second direction. Laser processing method.

13. In the focusing step, a third irradiation area of ​​the branched laser beam is formed on the object so as to be aligned with the second irradiation area on an opposite side to the first irradiation area along the first direction, In the scanning step, the first irradiation region, the second irradiation region, and the third irradiation region are scanned along the second direction to form the processed cross section. The laser processing method according to claim 12.

14. the branched laser beam has the first polarization direction in the third irradiation region; The laser processing method according to claim 13.

15. In the branching step, the laser beam is branched into a plurality of branched laser beams further including a third branched laser beam having the first polarization direction, In the focusing step, the third branched laser beam is focused toward the object to form the third irradiation region on the object. The laser processing method according to claim 14.

16. In the focusing step, the first branched laser light is focused toward the object, thereby forming the first irradiation region and the third irradiation region on the object so as to be continuous in an annular shape. The laser processing method according to claim 14.

17. In the focusing step, the first irradiation region and the second irradiation region are formed on the object so that a distance between a peak position of intensity in the first irradiation region and a peak position of intensity in the second irradiation region is 1.2 times or less a diameter of the second irradiation region. The laser processing method according to claim 12.

18. In the splitting step, the laser beam is split so that a peak value of intensity in the first irradiation region is lower than a peak value of intensity in the second irradiation region. The laser processing method according to claim 12.

19. In the splitting step, the laser beam is split so that a peak value of intensity in the first irradiation region is higher than a peak value of intensity in the second irradiation region. The laser processing method according to claim 12.

20. In the branching step and the focusing step, an irradiation area interfering with the first irradiation area or the second irradiation area is not formed in a range from a peak position of intensity in the first irradiation area to a diameter of 1.5 times the first irradiation area, and in a range from a peak position of intensity in the second irradiation area to a diameter of 1.5 times the second irradiation area. The laser processing method according to claim 12.

21. In the scanning step, the first irradiation region is scanned over the object so that a distance between a peak position of intensity of the first irradiation region corresponding to one pulse of the laser light and a peak position of intensity of the first irradiation region corresponding to another pulse subsequent to the one pulse is equal to or less than ½ of a diameter of the first irradiation region. The laser processing method according to claim 12.

22. The laser processing method according to any one of claims 12 to 21, comprising the branching step, the focusing step, and the scanning step; an observation step of observing the processed cross section formed in the scanning step after the scanning step; An observation method comprising:

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