Laser processing device and laser processing method

Abstract

To provide a laser processing device and a laser processing method which can easily and accurately check whether or not a center position of an image of a laser beam transferred to an entrance pupil surface of a light-focusing part coincides with a center position of an entrance pupil surface of the light-focusing part.SOLUTION: A 4f lens unit 420 transfers an image of a laser beam L in a spatial light modulator 410 to an entrance pupil surface 430a of a condensing lens unit 430. An observation camera 488 detects reflection light RL of the laser beam L incident on an object 1. A control unit 500 acquires a reference position P1 based on a point image of reflection light RL and a reference position P2 based on a processing result of the object 1 as a reference position being a reference of a display position of a phase pattern in the spatial light modulator 410, causes the spatial light modulator 410 to display a phase pattern with the reference position P2 as a reference in the time of processing of the object 1, and acquires a reference position P3 based on a point image of the reflection light RL in the time of confirmation of the reference position.SELECTED DRAWING: Figure 10

Description

[Technical Field]

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

[0002] A laser processing device is known that includes a support section that supports an object, a light source that emits laser light, a spatial light modulator that modulates the laser light emitted from the light source, a focusing section that focuses the laser light modulated by the spatial light modulator on the object, and an image transfer section that transfers an image of the laser light in the spatial light modulator onto an entrance pupil plane of the focusing section (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-51011 Summary of the Invention [Problem to be solved by the invention]

[0004] In the laser light irradiation device as described above, if the center position of the image of the laser light transferred onto the entrance pupil plane of the focusing unit does not coincide with the center position of the entrance pupil plane of the focusing unit, it may not be possible to obtain the desired processing quality.

[0005] The present invention aims to provide a laser processing device and a laser processing method that can easily and accurately confirm whether the center position of an image of laser light transferred onto the entrance pupil plane of the focusing unit coincides with the center position of the entrance pupil plane of the focusing unit. [Means for solving the problem]

[0006] The laser processing apparatus of the present invention includes a support section for supporting an object having opposing first and second surfaces, a light source for emitting laser light, a spatial light modulator for modulating the laser light emitted from the light source, a focusing section for focusing the laser light modulated by the spatial light modulator onto the object from the first surface side, an image conversion section for converting an image of the laser light in the spatial light modulator onto an entrance pupil plane of the focusing section, a photodetector for detecting reflected light of the laser light reflected by the object, and a control section for controlling at least the spatial light modulator, wherein the control section is configured to determine whether the center position of the image of the laser light converted onto the entrance pupil plane is the same as that of the incident light. A setting process is executed to set a reference position, which is the reference for the display position of the phase pattern on the spatial light modulator, so that it coincides with the center position of the pupil plane. The setting process includes a process of acquiring a first reference position as the reference position based on the detection result of reflected light, and acquiring a second reference position as the reference position based on the processing result of the object, a process of displaying the phase pattern on the spatial light modulator based on the second reference position when processing the object, and a process of acquiring a third reference position as the reference position based on the detection result of reflected light when confirming the reference position after processing the object.

[0007] In this laser processing device, a first reference position is acquired based on the detection results of reflected light as a reference position for the display position of the phase pattern on the spatial light modulator, and a second reference position is acquired based on the processing results of the object. With the first and second reference positions acquired, when processing the object, the spatial light modulator displays the phase pattern based on the second reference position acquired based on the processing results of the object. This allows the object to be processed with the center position of the image of the laser light transferred onto the entrance pupil plane of the focusing unit coinciding with the center position of the entrance pupil plane of the focusing unit. Then, when checking the reference position, a third reference position is acquired based on the detection results of reflected light. By comparing this third reference position with the first reference position acquired in advance based on the detection results of reflected light, it is possible to easily and accurately confirm whether the center position of the image of the laser light transferred onto the entrance pupil plane of the focusing unit coincides with the center position of the entrance pupil plane of the focusing unit.

[0008] In the laser processing apparatus of the present invention, the setting process may further include a process of calculating a fourth reference position as a reference position based on the first, second, and third reference positions and storing the fourth reference position when the third reference position is deviated from the first reference position, and a process of displaying a phase pattern on the spatial light modulator based on the fourth reference position when processing the object. A constant positional relationship tends to be maintained between the reference position acquired based on the detection result of the reflected light and the reference position acquired based on the processing result of the object. Therefore, when the third reference position is deviated from the first reference position, the spatial light modulator displays a phase pattern based on the fourth reference position calculated based on the first, second, and third reference positions when processing the object. This allows the object to be processed with the center position of the image of the laser light transferred onto the entrance pupil plane of the focusing unit aligned with the center position of the entrance pupil plane of the focusing unit.

[0009] In the laser processing apparatus of the present invention, the setting process may further include a process of acquiring a fourth reference position as a reference position based on the processing result of the object when the third reference position is deviated from the first reference position, and a process of displaying a phase pattern on the spatial light modulator based on the fourth reference position when processing the object. There is a tendency for a constant positional relationship to be maintained between the reference position acquired based on the detection result of the reflected light and the reference position acquired based on the processing result of the object. Therefore, when the third reference position is deviated from the first reference position, the spatial light modulator displays a phase pattern based on the fourth reference position acquired again based on the processing result of the object when processing the object. This allows the object to be processed with the center position of the image of the laser light transferred onto the entrance pupil plane of the focusing unit coincident with the center position of the entrance pupil plane of the focusing unit.

[0010] In the laser processing apparatus of the present invention, the setting process may further include a process of comparing a first difference between the first reference position and the second reference position with a second difference between the third reference position and the fourth reference position, and a process of storing the third reference position and the fourth reference position instead of the first reference position and the second reference position if the first difference and the second difference are different. If a constant positional relationship is maintained between the reference position acquired based on the detection result of the reflected light and the reference position acquired based on the processing result of the object, the first difference and the second difference should be the same. Therefore, by comparing the first difference and the second difference, it is possible to confirm whether a constant positional relationship is maintained between the reference position acquired based on the detection result of the reflected light and the reference position acquired based on the processing result of the object. Furthermore, if the first difference and the second difference are different, the control unit stores the third reference position and the fourth reference position instead of the first reference position and the second reference position, thereby updating the positional relationship between the reference position acquired based on the detection result of the reflected light and the reference position acquired based on the processing result of the object.

[0011] The laser processing device of the present invention may further include a display unit that displays the detection result of the reflected light when the reference position is confirmed. This makes it possible to notify the operator of the detection result of the reflected light.

[0012] The laser processing method of the present invention is carried out in a laser processing apparatus comprising: a support section for supporting an object having opposing first and second surfaces; a light source for emitting laser light; a spatial light modulator for modulating the laser light emitted from the light source; a focusing section for focusing the laser light modulated by the spatial light modulator on the object from the first surface side; an image transfer section for transferring an image of the laser light in the spatial light modulator onto an entrance pupil plane of the focusing section; and a photodetector for detecting reflected light of the laser light reflected by the object. The laser processing method sets a reference position that is a basis for the display position of a phase pattern in the spatial light modulator so that the center position of the image of the laser light transferred on the entrance pupil plane coincides with the center position of the entrance pupil plane, and comprises the steps of acquiring a first reference position as the reference position based on the detection results of the reflected light, and acquiring a second reference position as the reference position based on the processing results of the object; displaying the phase pattern on the spatial light modulator based on the second reference position when processing the object; and acquiring a third reference position as the reference position based on the detection results of the reflected light when confirming the reference position after processing the object.

[0013] According to this laser processing method, as described above, after the first and second reference positions have been acquired, when processing the object, the spatial light modulator displays a phase pattern based on the second reference position acquired based on the processing results of the object. This allows the object to be processed with the center position of the image of the laser light transferred onto the entrance pupil plane of the focusing unit coinciding with the center position of the entrance pupil plane of the focusing unit. Then, when checking the reference positions, a third reference position is acquired based on the detection results of the reflected light. By comparing this third reference position with the first reference position acquired in advance based on the detection results of the reflected light, it is possible to easily and accurately check whether the center position of the image of the laser light transferred onto the entrance pupil plane of the focusing unit coincides with the center position of the entrance pupil plane of the focusing unit. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a laser processing apparatus and a laser processing method that can easily and accurately confirm whether the center position of the image of laser light transferred onto the entrance pupil plane of the focusing unit coincides with the center position of the entrance pupil plane of the focusing unit. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a perspective view of a laser processing apparatus according to an embodiment; [Figure 2] 2 is a perspective view of an object attached to the support base shown in FIG. 1. FIG. [Figure 3] FIG. 2 is a plan view of the laser output section shown in FIG. [Figure 4] FIG. 2 is a perspective view of a laser output unit and a laser focusing unit shown in FIG. [Figure 5] FIG. 2 is a cross-sectional view of the laser focusing unit shown in FIG. [Figure 6] 6 is a cross-sectional view of the laser focusing portion taken along line VI-VI shown in FIG. 5. [Figure 7] 7 is a cross-sectional view of the laser focusing portion taken along line VII-VII shown in FIG. 6. FIG. [Figure 8] FIG. 6 is a cross-sectional view of the spatial light modulator shown in FIG. [Figure 9] 6 is a diagram showing the optical arrangement relationship between the spatial light modulator, the 4f lens unit, and the condenser lens unit shown in FIG. 5. FIG. [Figure 10] FIG. 2 is a configuration diagram of a main part of the laser processing device shown in FIG. [Figure 11] FIG. 2 is a diagram illustrating a state in which laser light is focused on an object. [Figure 12] FIG. 10 is a diagram showing a point image. [Figure 13] FIG. 10 is a diagram showing a state in which no image transfer position deviation occurs. [Figure 14] FIG. 10 is a diagram showing a state in which a transfer position deviation occurs. [Figure 15] 10A and 10B are diagrams showing point images at respective display positions of the phase pattern. [Figure 16] 10A and 10B are diagrams showing point images at respective display positions of the phase pattern. [Figure 17] 10A and 10B are diagrams showing point images at respective display positions of the phase pattern. [Figure 18] 10A and 10B are diagrams showing point images at respective display positions of the phase pattern. [Figure 19] 10 is a flowchart showing a method for setting a reference position based on a point image. [Figure 20] 10 is a flowchart showing a method for setting a reference position based on a point image. [Figure 21] 10 is a flowchart showing a method for setting a reference position based on a point image and a processing result. [Figure 22] 10A to 10C are diagrams showing processing results for each display position of the phase pattern. [Figure 23] 10A to 10C are diagrams showing processing results for each display position of the phase pattern. [Figure 24] 10A to 10C are diagrams showing processing results for each display position of the phase pattern. [Figure 25] 10 is a flowchart showing a method for setting a reference position based on a point image and a processing result. [Figure 26] 10 is a flowchart showing a method for setting a reference position based on a point image and a processing result. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are designated by the same reference numerals, and duplicated explanations will be omitted. [Overall configuration of laser processing equipment]

[0017] 1, the laser processing apparatus 200 includes an apparatus frame 210, a first moving mechanism 220, a support table (support unit) 230, and a second moving mechanism 240. The laser processing apparatus 200 further includes a laser output unit 300, a laser focusing unit 400, and a control unit 500. In the following description, directions that are orthogonal to each other in a horizontal plane are defined as the X direction and the Y direction, and the vertical direction is defined as the Z direction.

[0018] The first movement mechanism 220 is attached to the device frame 210. The first movement mechanism 220 has a first rail unit 221, a second rail unit 222, and a movable base 223. The first rail unit 221 is attached to the device frame 210. The first rail unit 221 is provided with a pair of rails 221a, 221b extending along the Y direction. The second rail unit 222 is attached to the pair of rails 221a, 221b of the first rail unit 221 so as to be movable along the Y direction. The second rail unit 222 is provided with a pair of rails 222a, 222b extending along the X direction. The movable base 223 is attached to the pair of rails 222a, 222b of the second rail unit 222 so as to be movable along the X direction. The movable base 223 is rotatable about an axis parallel to the Z direction.

[0019] The support table 230 is attached to the movable base 223. The support table 230 supports the target object 1. The target object 1 is, for example, a wafer on which a plurality of functional elements (light-receiving elements such as photodiodes, light-emitting elements such as laser diodes, or circuit elements formed as circuits) are formed in a matrix on the surface side of a substrate made of a semiconductor material such as silicon. When the target object 1 is supported on the support table 230, for example, the surface 10a of the target object 1 (the surface on which the plurality of functional elements are located) is attached to a film 12 attached to an annular frame 11, as shown in FIG. 2. The support table 230 supports the target object 1 by holding the frame 11 with a clamp and adsorbing the film 12 with a vacuum chuck table. On the support table 230, a plurality of parallel lines 5a and a plurality of parallel lines 5b are set on the target object 1 in a grid pattern so as to pass between adjacent functional elements. The plurality of lines 5a and the plurality of lines 5b are lines for cutting the target object 1 into individual functional elements.

[0020] 1, the support base 230 is moved along the Y direction by operation of the second rail unit 222 in the first movement mechanism 220. The support base 230 is moved along the X direction by operation of the movable base 223 in the first movement mechanism 220. The support base 230 is further rotated about an axis parallel to the Z direction by operation of the movable base 223 in the first movement mechanism 220. In this way, the support base 230 is attached to the apparatus frame 210 so as to be movable along the X and Y directions and rotatable about an axis parallel to the Z direction.

[0021] The laser output unit 300 is attached to the device frame 210. The laser focusing unit 400 is attached to the device frame 210 via a second movement mechanism 240. The laser focusing unit 400 is moved along the Z direction by operation of the second movement mechanism 240. In this way, the laser focusing unit 400 is attached to the device frame 210 so as to be movable along the Z direction relative to the laser output unit 300.

[0022] The control unit 500 is configured by a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc. The control unit 500 controls each part of the laser processing apparatus 200.

[0023] As an example, in the laser processing device 200, modified regions are formed inside the object 1 along the lines 5a and 5b (see FIG. 2) as follows.

[0024] First, the object 1 is supported on the support table 230 so that the back surface 10b (see FIG. 2) of the object 1 is the laser light incident surface, and each line 5a of the object 1 is aligned parallel to the X direction. Next, the second moving mechanism 240 moves the laser focusing unit 400 so that the focal point of the laser light L is located at a position inside the object 1 a predetermined distance away from the laser light incident surface of the object 1. Next, while maintaining a constant distance between the laser light incident surface of the object 1 and the focal point of the laser light L, the focal point of the laser light L is relatively moved along each line 5a. As a result, a modified region is formed inside the object 1 along each line 5a.

[0025] When the formation of the modified region along each line 5a is completed, the first moving mechanism 220 rotates the support table 230, and each line 5b of the object 1 is aligned parallel to the X direction. Next, the second moving mechanism 240 moves the laser focusing unit 400 so that the focal point of the laser light L is positioned inside the object 1 at a position a predetermined distance away from the laser light incident surface of the object 1. Next, while maintaining a constant distance between the laser light incident surface of the object 1 and the focal point of the laser light L, the focal point of the laser light L is relatively moved along each line 5b. As a result, a modified region is formed inside the object 1 along each line 5b.

[0026] As described above, in the laser processing apparatus 200, the direction parallel to the X direction is the processing direction (the scanning direction of the laser light L). The relative movement of the focal point of the laser light L along each line 5a and the relative movement of the focal point of the laser light L along each line 5b are achieved by moving the support table 230 along the X direction by the first moving mechanism 220. The relative movement of the focal point of the laser light L between each line 5a and the relative movement of the focal point of the laser light L between each line 5b are achieved by moving the support table 230 along the Y direction by the first moving mechanism 220.

[0027] 3, the laser output unit 300 includes a mounting base 301, a cover 302, and a plurality of mirrors 303 and 304. The laser output unit 300 further includes a laser oscillator (light source) 310, a shutter 320, a λ / 2 wave plate unit 330, a polarizing plate unit 340, a beam expander 350, and a mirror unit 360.

[0028] The mounting base 301 supports a plurality of mirrors 303, 304, a laser oscillator 310, a shutter 320, a λ / 2 wave plate unit 330, a polarizing plate unit 340, a beam expander 350, and a mirror unit 360. The plurality of mirrors 303, 304, the laser oscillator 310, the shutter 320, the λ / 2 wave plate unit 330, the polarizing plate unit 340, the beam expander 350, and the mirror unit 360 are attached to a main surface 301a of the mounting base 301. The mounting base 301 is a plate-shaped member, and is detachable from the device frame 210 (see FIG. 1 ). The laser output unit 300 is attached to the device frame 210 via the mounting base 301. That is, the laser output unit 300 is detachable from the device frame 210.

[0029] The cover 302 covers the plurality of mirrors 303 and 304, the laser oscillator 310, the shutter 320, the λ / 2 wave plate unit 330, the polarizing plate unit 340, the beam expander 350, and the mirror unit 360 on the main surface 301a of the mounting base 301. The cover 302 is detachable from the mounting base 301.

[0030] The laser oscillator 310 pulses linearly polarized laser light L along the X direction. The wavelength of the laser light L emitted from the laser oscillator 310 is within any one of the wavelength bands of 500 to 550 nm, 1000 to 1150 nm, or 1300 to 1400 nm. The laser light L in the wavelength band of 500 to 550 nm is suitable for internal absorption laser processing of substrates made of, for example, sapphire. The laser light L in each of the wavelength bands of 1000 to 1150 nm and 1300 to 1400 nm is suitable for internal absorption laser processing of substrates made of, for example, silicon. The polarization direction of the laser light L emitted from the laser oscillator 310 is, for example, parallel to the Y direction. The laser light L emitted from the laser oscillator 310 is reflected by the mirror 303 and enters the shutter 320 along the Y direction.

[0031] In the laser oscillator 310, the output of the laser light L is switched on / off as follows: When the laser oscillator 310 is configured with a solid-state laser, the output of the laser light L is switched on / off at high speed by switching on / off a Q switch (such as an AOM (acousto-optic modulator) or an EOM (electro-optic modulator)) provided in the resonator. When the laser oscillator 310 is configured with a fiber laser, the output of the laser light L is switched on / off at high speed by switching on / off the outputs of semiconductor lasers that constitute the seed laser and amplifier (excitation) laser. When the laser oscillator 310 uses an external modulation element, the output of the laser light L is switched on / off at high speed by switching on / off an external modulation element (such as an AOM or EOM) provided outside the resonator.

[0032] The shutter 320 uses a mechanical mechanism to open and close the optical path of the laser light L. As described above, the output of the laser light L from the laser output unit 300 is switched on and off by switching on and off the output of the laser light L in the laser oscillator 310, but the provision of the shutter 320 prevents, for example, the laser light L from being accidentally emitted from the laser output unit 300. The laser light L that has passed through the shutter 320 is reflected by the mirror 304 and sequentially enters the λ / 2 wave plate unit 330 and the polarizing plate unit 340 along the X direction.

[0033] The λ / 2 wave plate unit 330 and the polarizing plate unit 340 function as an output adjustment unit that adjusts the output (light intensity) of the laser light L. In addition, the λ / 2 wave plate unit 330 and the polarizing plate unit 340 function as a polarization direction adjustment unit that adjusts the polarization direction of the laser light L. The laser light L that has passed through the λ / 2 wave plate unit 330 and the polarizing plate unit 340 in sequence is incident on the beam expander 350 along the X direction.

[0034] The beam expander 350 adjusts the diameter of the laser light L and collimates the laser light L. The laser light L that has passed through the beam expander 350 is incident on a mirror unit 360 along the X direction.

[0035] The mirror unit 360 has a support base 361 and multiple mirrors 362 and 363. The support base 361 supports the multiple mirrors 362 and 363. The support base 361 is attached to the mounting base 301 so that its position is adjustable along the X and Y directions. The mirror 362 reflects the laser light L that has passed through the beam expander 350 in the Y direction. The mirror 362 is attached to the support base 361 so that the angle of its reflective surface is adjustable, for example, around an axis parallel to the Z direction. The mirror 363 reflects the laser light L reflected by the mirror 362 in the Z direction. The mirror 363 is attached to the support base 361 so that the angle of its reflective surface is adjustable, for example, around an axis parallel to the X direction and its position is adjustable along the Y direction. The laser light L reflected by the mirror 363 passes through an opening 361a formed in the support base 361 and enters the laser focusing unit 400 (see FIG. 1) along the Z direction. In other words, the emission direction of the laser light L from the laser output unit 300 coincides with the movement direction of the laser focusing unit 400. As described above, each mirror 362, 363 has a mechanism for adjusting the angle of the reflecting surface. In the mirror unit 360, the position of the support base 361 relative to the mounting base 301, the position of the mirror 363 relative to the support base 361, and the angle of the reflecting surface of each mirror 362, 363 are adjusted, so that the position and angle of the optical axis of the laser light L emitted from the laser output unit 300 are aligned with the laser focusing unit 400. In other words, the multiple mirrors 362, 363 are configured to adjust the optical axis of the laser light L emitted from the laser output unit 300.

[0036] As shown in FIG. 4, the laser focusing unit 400 has a housing 401. The housing 401 has a rectangular parallelepiped shape with the Y direction as the longitudinal direction. A second movement mechanism 240 is attached to one side surface 401e of the housing 401 (see FIGS. 5 and 7). A cylindrical light incident unit 401a is provided in the housing 401 so as to face the opening 361a of the mirror unit 360 in the Z direction. The light incident unit 401a causes the laser light L emitted from the laser output unit 300 to enter the housing 401. The mirror unit 360 and the light incident unit 401a are spaced apart from each other by a distance that prevents them from coming into contact with each other when the laser focusing unit 400 is moved in the Z direction by the second movement mechanism 240.

[0037] 5 and 6, the laser focusing unit 400 includes a mirror 402 and a dichroic mirror 403. The laser focusing unit 400 further includes a spatial light modulator 410, a 4f lens unit (image conversion unit) 420, a focusing lens unit (focusing unit) 430, a drive mechanism 440, and a pair of distance measurement sensors 450.

[0038] The mirror 402 is attached to the bottom surface 401b of the housing 401 so as to face the light incident unit 401a in the Z direction. The mirror 402 reflects the laser light L that enters the housing 401 through the light incident unit 401a in a direction parallel to the XY plane. The laser light L that has been collimated by the beam expander 350 of the laser output unit 300 is incident on the mirror 402 along the Z direction. That is, the laser light L is incident on the mirror 402 along the Z direction as parallel light. Therefore, even if the laser focusing unit 400 is moved along the Z direction by the second movement mechanism 240, the state of the laser light L that enters the mirror 402 along the Z direction is maintained constant. The laser light L reflected by the mirror 402 is incident on the spatial light modulator 410.

[0039] The spatial light modulator 410 is attached to an end 401c of the housing 401 in the Y direction, with a reflective surface 410a facing the inside of the housing 401. The spatial light modulator 410 is, for example, a reflective liquid crystal (LCOS: Liquid Crystal on Silicon) spatial light modulator (SLM), and reflects the laser light L in the Y direction while modulating the laser light L. The laser light L modulated and reflected by the spatial light modulator 410 is incident on the 4f lens unit 420 along the Y direction. Here, in a plane parallel to the XY plane, the angle α formed between the optical axis of the laser light L incident on the spatial light modulator 410 and the optical axis of the laser light L emitted from the spatial light modulator 410 is an acute angle (for example, 10 to 60°). That is, the laser light L is reflected at an acute angle along the XY plane by the spatial light modulator 410. This is to suppress the incident angle and reflection angle of the laser light L to suppress a decrease in diffraction efficiency and to fully demonstrate the performance of the spatial light modulator 410. In the spatial light modulator 410, for example, the thickness of the light modulation layer using liquid crystal is extremely thin, about several μm to several tens of μm, so the reflection surface 410a can be considered to be substantially the same as the light incident / exit surface of the light modulation layer.

[0040] The 4f lens unit 420 has a holder 421, a lens 422 on the spatial light modulator 410 side, a lens 423 on the condenser lens unit 430 side, and a slit member 424. The holder 421 holds the pair of lenses 422, 423 and the slit member 424. The holder 421 maintains a constant positional relationship between the pair of lenses 422, 423 and the slit member 424 in a direction along the optical axis of the laser light L. The pair of lenses 422, 423 form a double-telecentric optical system in which a reflecting surface 410a of the spatial light modulator 410 and an entrance pupil plane 430a of the condenser lens unit 430 are in an imaging relationship. As a result, an image of the laser light L on the reflecting surface 410a of the spatial light modulator 410 (an image of the laser light L modulated by the spatial light modulator 410) is transferred (imaged) on the entrance pupil plane 430a of the condenser lens unit 430. A slit 424a is formed in the slit member 424. The slit 424a is located between the lens 422 and the lens 423, near the focal plane of the lens 422. An unnecessary portion of the laser light L that has been modulated and reflected by the spatial light modulator 410 is blocked by the slit member 424. The laser light L that has passed through the 4f lens unit 420 is incident on the dichroic mirror 403 along the Y direction.

[0041] The dichroic mirror 403 reflects a portion (e.g., 95 to 99.5%) of the laser light L in the Z direction and transmits the remaining portion (e.g., 0.5 to 5%) of the laser light L along the Y direction. A portion of the laser light L is reflected at a right angle along the YZ plane by the dichroic mirror 403. The laser light L reflected by the dichroic mirror 403 enters the condenser lens unit 430 along the Z direction.

[0042] Condenser lens unit 430 is attached to end 401d of housing 401 in the Y direction (the end opposite end 401c) via drive mechanism 440. Condenser lens unit 430 has a holder 431 and a plurality of lenses 432. Holder 431 holds the plurality of lenses 432. The plurality of lenses 432 focus laser light L on target object 1 (see FIG. 1) supported by support base 230. Drive mechanism 440 moves condenser lens unit 430 along the Z direction using the driving force of a piezoelectric element.

[0043] The pair of distance measuring sensors 450 are attached to the end 401d of the housing 401 so as to be located on both sides of the condenser lens unit 430 in the X direction. Each distance measuring sensor 450 emits distance measuring light (e.g., laser light) to the laser light incident surface of the object 1 (see FIG. 1) supported on the support base 230, and detects the distance measuring light reflected by the laser light incident surface to obtain displacement data of the laser light incident surface of the object 1. Note that the distance measuring sensors 450 can be sensors using a triangulation method, a laser confocal method, a white light confocal method, a spectral interference method, an astigmatism method, or the like.

[0044] As described above, in the laser processing apparatus 200, the direction parallel to the X direction is the processing direction (the scanning direction of the laser light L). Therefore, when the focal point of the laser light L is relatively moved along each of the lines 5a, 5b, the distance measuring sensor 450 that is ahead of the condensing lens unit 430 acquires displacement data of the laser light incident surface of the object 1 along each of the lines 5a, 5b. Then, the drive mechanism 440 moves the condensing lens unit 430 along the Z direction based on the displacement data acquired by the distance measuring sensor 450 so that the distance between the laser light incident surface of the object 1 and the focal point of the laser light L is maintained constant.

[0045] The laser focusing unit 400 has a beam splitter 461, a pair of lenses 462 and 463, and a profile acquisition camera 464. The beam splitter 461 splits the laser light L that has passed through the dichroic mirror 403 into a reflected component and a transmitted component. The laser light L reflected by the beam splitter 461 is sequentially incident on the pair of lenses 462 and 463 and the profile acquisition camera 464 along the Z direction. The pair of lenses 462 and 463 form a double-telecentric optical system in which an entrance pupil plane 430a of the focusing lens unit 430 and an imaging plane of the profile acquisition camera 464 are in an imaging relationship. As a result, the image of the laser light L on the entrance pupil plane 430a of the focusing lens unit 430 is transferred (imaged) on the imaging plane of the profile acquisition camera 464. As described above, the image of the laser light L on the entrance pupil plane 430a of the condenser lens unit 430 is an image of the laser light L modulated by the spatial light modulator 410. Therefore, in the laser processing apparatus 200, by monitoring the imaging results obtained by the profile acquisition camera 464, the operating state of the spatial light modulator 410 can be grasped.

[0046] Furthermore, the laser focusing unit 400 has a beam splitter 471, a lens 472, and an optical axis position monitoring camera 473. The beam splitter 471 separates the laser light L that has passed through the beam splitter 461 into a reflected component and a transmitted component. The laser light L reflected by the beam splitter 471 is sequentially incident on the lens 472 and the optical axis position monitoring camera 473 along the Z direction. The lens 472 focuses the incident laser light L on the imaging plane of the optical axis position monitoring camera 473. In the laser processing apparatus 200, while monitoring the imaging results from the profile acquisition camera 464 and the optical axis position monitor camera 473, the position of the support base 361 relative to the mounting base 301, the position of the mirror 363 relative to the support base 361, and the angle of the reflecting surface of each mirror 362, 363 are adjusted in the mirror unit 360 (see Figures 9 and 10), thereby correcting the deviation of the optical axis of the laser light L incident on the focusing lens unit 430 (the positional deviation of the intensity distribution of the laser light relative to the focusing lens unit 430 and the angular deviation of the optical axis of the laser light L relative to the focusing lens unit 430).

[0047] The multiple beam splitters 461, 471 are disposed within a cylindrical body 404 extending from an end 401d of the housing 401 along the Y direction. A pair of lenses 462, 463 are disposed within a cylindrical body 405 erected on the cylindrical body 404 along the Z direction, and a profile acquisition camera 464 is disposed at the end of the cylindrical body 405. The lens 472 is disposed within a cylindrical body 406 erected on the cylindrical body 404 along the Z direction, and an optical axis position monitoring camera 473 is disposed at the end of the cylindrical body 406. The cylindrical bodies 405 and 406 are disposed side by side in the Y direction. The laser light L transmitted through the beam splitter 471 may be absorbed by a damper or the like provided at the end of the cylindrical body 404, or may be used for an appropriate purpose.

[0048] 6 and 7, the laser focusing unit 400 has a visible light source 481, multiple lenses 482, a reticle 483, a mirror 484, a half mirror 485, a beam splitter 486, a lens 487, and an observation camera (photodetector) 488. The visible light source 481 emits visible light V along the Z direction. The multiple lenses 482 collimate the visible light V emitted from the visible light source 481. The reticle 483 imparts a reticle mark to the visible light V. The mirror 484 reflects the visible light V collimated by the multiple lenses 482 in the X direction. The half mirror 485 separates the visible light V reflected by the mirror 484 into a reflected component and a transmitted component. The visible light V reflected by the half mirror 485 passes through the beam splitter 486 and the dichroic mirror 403 sequentially along the Z direction, and is irradiated onto the object 1 (see Figure 1) supported on the support stand 230 via the focusing lens unit 430.

[0049] The visible light V irradiated onto the object 1 is reflected by the laser light incident surface of the object 1, enters the dichroic mirror 403 via the condenser lens unit 430, and passes through the dichroic mirror 403 along the Z direction. The beam splitter 486 separates the visible light V that has passed through the dichroic mirror 403 into a reflected component and a transmitted component. The visible light V that has passed through the beam splitter 486 passes through the half mirror 485 and sequentially enters a lens 487 and an observation camera 488 along the Z direction. The lens 487 condenses the incident visible light V onto the imaging surface of the observation camera 488. In the laser processing apparatus 200, the state of the object 1 can be grasped by observing the imaging results obtained by the observation camera 488.

[0050] The mirror 484, the half mirror 485, and the beam splitter 486 are disposed in a holder 407 attached to the end 401d of the housing 401. The plurality of lenses 482 and the reticle 483 are disposed in a cylinder 408 that is erected on the holder 407 along the Z direction, and the visible light source 481 is disposed at the end of the cylinder 408. The lens 487 is disposed in a cylinder 409 that is erected on the holder 407 along the Z direction, and the observation camera 488 is disposed at the end of the cylinder 409. The cylinders 408 and 409 are arranged side by side in the X direction. Note that the visible light V that has passed through the half mirror 485 along the X direction and the visible light V that has been reflected in the X direction by the beam splitter 486 may be absorbed by a damper or the like provided on the wall of the holder 407, or may be used for an appropriate purpose.

[0051] In the laser processing apparatus 200, it is assumed that the laser output unit 300 will be replaced. This is because the wavelength of the laser light L suitable for processing varies depending on the specifications of the target object 1, the processing conditions, etc. For this reason, a plurality of laser output units 300 that emit laser light L with different wavelengths are provided. In this example, a laser output unit 300 that emits laser light L with a wavelength in the 500 to 550 nm band, a laser output unit 300 that emits laser light L with a wavelength in the 1000 to 1150 nm band, and a laser output unit 300 that emits laser light L with a wavelength in the 1300 to 1400 nm band are provided.

[0052] On the other hand, the laser processing apparatus 200 does not assume replacement of the laser focusing unit 400. This is because the laser focusing unit 400 is multi-wavelength compatible (compatible with multiple discontinuous wavelength bands). Specifically, the mirror 402, the spatial light modulator 410, the pair of lenses 422 and 423 of the 4f lens unit 420, the dichroic mirror 403, and the lens 432 of the focusing lens unit 430 are multi-wavelength compatible. Here, the laser focusing unit 400 is compatible with wavelength bands of 500 to 550 nm, 1000 to 1150 nm, and 1300 to 1400 nm. This is achieved by designing each component of the laser focusing unit 400 to achieve the desired optical performance, such as by coating each component of the laser focusing unit 400 with a predetermined dielectric multilayer film. In the laser output unit 300, the λ / 2 waveplate unit 330 includes a λ / 2 waveplate, and the polarizing plate unit 340 includes a polarizing plate. The λ / 2 wave plate and the polarizing plate are optical elements that are highly wavelength-dependent, and therefore the λ / 2 wave plate unit 330 and the polarizing plate unit 340 are provided in the laser output section 300 with different configurations for each wavelength band. [Optical path and polarization direction of laser light in laser processing equipment]

[0053] In the laser processing apparatus 200, the polarization direction of the laser light L focused on the object 1 supported by the support table 230 is parallel to the X direction, as shown in FIG. 5, and coincides with the processing direction (the scanning direction of the laser light L). Here, the spatial light modulator 410 reflects the laser light L as P-polarized light. This is because, when a liquid crystal is used in the light modulation layer of the spatial light modulator 410 and the liquid crystal is oriented so that the liquid crystal molecules are tilted in a plane parallel to a plane including the optical axis of the laser light L entering and exiting the spatial light modulator 410, the laser light L is phase-modulated with the rotation of the polarization plane suppressed. On the other hand, the dichroic mirror 403 reflects the laser light L as S-polarized light. This is because reflecting the laser light L as S-polarized light makes it easier to design the dichroic mirror 403, for example, by reducing the number of dielectric multilayer coatings required to make the dichroic mirror 403 compatible with multiple wavelengths.

[0054] Therefore, in the laser focusing unit 400, the optical path from the mirror 402 to the dichroic mirror 403 via the spatial light modulator 410 and the 4f lens unit 420 is set to be along the XY plane, and the optical path from the spatial light modulator 410 to the focusing lens unit 430 via the 4f lens unit 420 and the dichroic mirror 403 is set to be along the YZ plane.

[0055] 3, in the laser output unit 300, the optical path of the laser light L is set to be along the X direction or the Y direction. Specifically, the optical path from the laser oscillator 310 to the mirror 303 and the optical path from the mirror 304 to the mirror unit 360 via the λ / 2 wave plate unit 330, the polarizing plate unit 340, and the beam expander 350 are set to be along the X direction, and the optical path from the mirror 303 to the mirror 304 via the shutter 320 and the optical path from the mirror 362 to the mirror 363 in the mirror unit 360 are set to be along the Y direction.

[0056] 5, the laser light L that travels from the laser output unit 300 to the laser focusing unit 400 along the Z direction is reflected by the mirror 402 in a direction parallel to the XY plane and enters the spatial light modulator 410. At this time, in a plane parallel to the XY plane, the optical axis of the laser light L that enters the spatial light modulator 410 and the optical axis of the laser light L that is emitted from the spatial light modulator 410 form an acute angle α. Meanwhile, as described above, in the laser output unit 300, the optical path of the laser light L is set to be along the X direction or the Y direction.

[0057] Therefore, in the laser output section 300, the λ / 2 wave plate unit 330 and the polarizing plate unit 340 need to function not only as an output adjustment section that adjusts the output of the laser light L, but also as a polarization direction adjustment section that adjusts the polarization direction of the laser light L. [Spatial Light Modulator]

[0058] As shown in Figure 8, the spatial light modulator 410 is composed of a silicon substrate 213, a drive circuit layer 914, a plurality of pixel electrodes 214, a reflective film 215 such as a dielectric multilayer mirror, an alignment film 999a, a liquid crystal layer 216, an alignment film 999b, a transparent conductive film 217, and a transparent substrate 218 such as a glass substrate, which are stacked in this order.

[0059] The transparent substrate 218 has a surface 218a that constitutes the reflecting surface 410a of the spatial light modulator 410. The transparent substrate 218 is made of a light-transmitting material such as glass, and transmits laser light L of a predetermined wavelength that is incident on the surface 218a of the spatial light modulator 410 into the interior of the spatial light modulator 410. The transparent conductive film 217 is formed on the back surface of the transparent substrate 218, and is made of a conductive material (e.g., ITO) that transmits the laser light L.

[0060] A plurality of pixel electrodes 214 are arranged in a matrix on the silicon substrate 213 along a transparent conductive film 217. Each pixel electrode 214 is made of a metal material such as aluminum, and its surface 214a is processed to be flat and smooth. The plurality of pixel electrodes 214 are driven by an active matrix circuit provided in the drive circuit layer 914. The active matrix circuit controls the voltage applied to each pixel electrode 214 in accordance with the optical image to be output from the spatial light modulator 410.

[0061] The alignment films 999a and 999b are disposed on both end surfaces of the liquid crystal layer 216, and align the liquid crystal molecules in a certain direction. The alignment films 999a and 999b are made of a polymer material such as polyimide, and the surfaces that come into contact with the liquid crystal layer 216 are subjected to rubbing or the like.

[0062] The liquid crystal layer 216 is disposed between the plurality of pixel electrodes 214 and the transparent conductive film 217, and modulates the laser light L in accordance with an electric field formed by each pixel electrode 214 and the transparent conductive film 217. That is, when a voltage is applied to each pixel electrode 214 by the active matrix circuit of the drive circuit layer 914, an electric field is formed between the transparent conductive film 217 and each pixel electrode 214, and the alignment direction of the liquid crystal molecules 216a changes in accordance with the magnitude of the electric field formed in the liquid crystal layer 216. When the laser light L passes through the transparent substrate 218 and the transparent conductive film 217 and enters the liquid crystal layer 216, the laser light L is modulated by the liquid crystal molecules 216a while passing through the liquid crystal layer 216, is reflected by the reflective film 215, and is then modulated again by the liquid crystal layer 216 before being emitted.

[0063] At this time, the control unit 500 (see FIG. 1 ) controls the voltage applied to each pixel electrode 214, and the refractive index of the portion of the liquid crystal layer 216 sandwiched between the transparent conductive film 217 and each pixel electrode 214 changes in response to the voltage (the refractive index of the liquid crystal layer 216 at a position corresponding to each pixel electrode 214 changes). This change in refractive index allows the phase of the laser light L to be changed for each pixel electrode 214 of the liquid crystal layer 216. That is, phase modulation according to the hologram pattern can be imparted to the laser light L for each pixel electrode 214 of the liquid crystal layer 216. In other words, the spatial light modulator 410 displays a phase pattern as a hologram pattern on the liquid crystal layer 216. This phase pattern adjusts the wavefront of the laser light L, causing a phase shift in the component of each beam constituting the laser light L in a predetermined direction perpendicular to the traveling direction. Therefore, by appropriately setting the phase pattern displayed by the spatial light modulator 410, the laser light L can be modulated (for example, the intensity, amplitude, phase, polarization, etc. of the laser light L can be modulated). [4f lens unit]

[0064] As described above, the pair of lenses 422, 423 of the 4f lens unit 420 configure a double-telecentric optical system in which the reflecting surface 410a of the spatial light modulator 410 and the entrance pupil plane 430a of the condensing lens unit 430 are in an imaging relationship. Specifically, as shown in Fig. 9, the distance of the optical path between the center of the lens 422 on the spatial light modulator 410 side and the reflecting surface 410a of the spatial light modulator 410 is the first focal length f1 of the lens 422, the distance of the optical path between the center of the lens 423 on the condensing lens unit 430 side and the entrance pupil plane 430a of the condensing lens unit 430 is the second focal length f2 of the lens 423, and the distance of the optical path between the center of the lens 422 and the center of the lens 423 is the sum of the first focal length f1 and the second focal length f2 (i.e., f1 + f2). The optical path between the pair of lenses 422 and 423 from the spatial light modulator 410 to the condenser lens unit 430 is a straight line.

[0065] In the laser processing apparatus 200, from the viewpoint of increasing the effective diameter of the laser beam L at the reflection surface 410a of the spatial light modulator 410, the magnification M of the bilateral telecentric optical system satisfies 0.5 < M < 1 (reduction system). The larger the effective diameter of the laser beam L at the reflection surface 410a of the spatial light modulator 410, the more finely the laser beam L is modulated with a phase pattern. From the viewpoint of suppressing the lengthening of the optical path of the laser beam L from the spatial light modulator 410 to the condenser lens unit 430, it is more preferable that 0.6 ≤ M ≤ 0.95. Here, (the magnification M of the bilateral telecentric optical system) = (the size of the image at the entrance pupil surface 430a of the condenser lens unit 430) / (the size of the object at the reflection surface 410a of the spatial light modulator 410). In the case of the laser processing apparatus 200, the magnification M of the bilateral telecentric optical system, the first focal length f1 of the lens 422, and the second focal length f2 of the lens 423 satisfy M = f2 / f1.

[0066] Note that, from the viewpoint of reducing the effective diameter of the laser beam L at the reflection surface 410a of the spatial light modulator 410, the magnification M of the bilateral telecentric optical system may satisfy 1 < M < 2 (expansion system). The smaller the effective diameter of the laser beam L at the reflection surface 410a of the spatial light modulator 410, the smaller the magnification of the beam expander 350 (see FIG. 3) can be, and in a plane parallel to the XY plane, the angle α (see FIG. 5) formed by the optical axis of the laser beam L incident on the spatial light modulator 410 and the optical axis of the laser beam L emitted from the spatial light modulator 410 becomes smaller. From the viewpoint of suppressing the lengthening of the optical path of the laser beam L from the spatial light modulator 410 to the condenser lens unit 430, it is more preferable that 1.05 ≤ M ≤ 1.7. [Principal Component Configuration of Laser Processing Apparatus]

[0067] FIG. 10 is a configuration diagram of the main parts of the laser processing apparatus 200 shown in FIG. 1. As shown in FIG. 10, the laser processing apparatus 200 includes a support base (support unit) 230, a laser oscillator (light source) 310, a spatial light modulator 410, a condensing lens unit (condensing unit) 430, a 4f lens unit (image conversion unit) 420, an observation camera (photodetector) 488, a control unit 500, and a display unit 600. The support base 230 supports an object 1 having a first surface 1a and a second surface 1b facing each other. The laser oscillator 310 emits laser light L. The spatial light modulator 410 modulates the laser light L emitted from the laser oscillator 310. The condensing lens unit 430 condenses the laser light L modulated by the spatial light modulator 410 onto the object 1 from the first surface 1a side. The 4f lens unit 420 transfers an image of the laser light L on the spatial light modulator 410 onto an entrance pupil plane 430a of the condenser lens unit 430. The observation camera 488 detects reflected light RL of the laser light L that is incident on the object 1 from the first surface 1a side and reflected by the second surface 1b. The control unit 500 controls each unit of the laser processing apparatus 200, including the spatial light modulator 410. The display unit 600 is, for example, a GUI (Graphical User Interface) and displays various information. The display unit 600 displays the detection results of the reflected light RL when checking a reference value, which will be described later.

[0068] The laser light L reflected by the spatial light modulator 410 is focused by a lens 422 which is a relay lens of the 4f lens unit 420, and then collimated by a lens 423 which is a relay lens of the 4f lens unit 420, and enters the dichroic mirror 403. The laser light L reflected by the dichroic mirror 403 enters the condenser lens unit 430, and is condensed by the condenser lens unit 430 onto the object 1 from the first surface 1a side.

[0069] Laser light L emitted from condenser lens unit 430 travels through object 1 from first surface 1a to second surface 1b and is reflected by second surface 1b. Reflected light RL of laser light L reflected by second surface 1b travels through object 1 from second surface 1b to first surface 1a and is emitted from first surface 1a. Reflected light RL emitted from first surface 1a passes through dichroic mirror 403 and then enters observation camera 488 via lens 487.

[0070] In this embodiment, observation camera 488 is an imaging unit that acquires a point image, which is an image including a point image of reflected light RL (also referred to as a beam spot, a focused spot, or a reflected image on second surface 1b). Observation camera 488 outputs the acquired point image to control unit 500.

[0071] In order to confirm whether the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a in the X direction (first direction intersecting with the direction of the optical axis of the focusing lens unit 430) perpendicular to the optical axis of the focusing lens unit 430, the control unit 500 controls the spatial light modulator 410 as follows when a point image is acquired by the observation camera 488 (when reflected light is detected by the photodetector): That is, the control unit 500 controls the spatial light modulator 410 so that spherical aberration that occurs when the laser light L travels a predetermined distance d from the first surface 1a through the object 1 is corrected and so that coma aberration occurs on the entrance pupil plane 430a in the Y direction (second direction intersecting with the direction of the optical axis of the focusing lens unit 430 and the first direction) that is perpendicular to the optical axis of the focusing lens unit 430 and perpendicular to the X direction.

[0072] In order to check whether the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a in the Y direction, the control unit 500 controls the spatial light modulator 410 as follows when the point image is acquired by the observation camera 488. That is, the control unit 500 controls the spatial light modulator 410 so that spherical aberration that occurs when the laser light L is assumed to have traveled a predetermined distance d from the first surface 1a through the object 1 is corrected and so that coma aberration occurs in the X direction on the entrance pupil plane 430a.

[0073] Here, the predetermined distance d is a value greater than the distance t between the first surface 1a and the second surface 1b. In this embodiment, the predetermined distance d is set to satisfy (2t-0.1t)≦d≦(2t+0.1t). Note that when the first surface 1a is the outer surface of the target 1 on the incident side of the laser light L and the second surface 1b is the outer surface of the target 1 opposite to the first surface 1a, the distance t between the first surface 1a and the second surface 1b corresponds to the thickness of the target 1. Here, the target 1 used has a thickness that can cause sufficient spherical aberration in the laser light L focused by the focusing lens unit 430 (for example, a silicon wafer having a thickness of about 775 μm).

[0074] In the laser processing apparatus 200, confirmation of whether the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a (hereinafter referred to as "confirmation of the image transfer position") is performed because if the center position of the image of the laser light L transferred onto the entrance pupil plane 430a deviates from the center position of the entrance pupil plane 430a, it may not be possible to obtain the desired processing quality. The control unit 500 periodically confirms the image transfer position and sets a reference position (hereinafter simply referred to as "reference position") that is a reference for the display position of the phase pattern on the spatial light modulator 410 so that the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a. Details of confirmation of the image transfer position will be described later. [Principles for setting the reference position]

[0075] Prior to explaining confirmation of the image transfer position, the principle of setting the reference position will be explained. The two-dimensional coordinate system showing the display position of the phase pattern on the spatial light modulator 410 does not necessarily coincide with the three-dimensional coordinate system showing the spatial position of each part in the laser processing apparatus 200. However, for convenience in the following explanation, the axis of the two-dimensional coordinate system corresponding to the X axis of the three-dimensional coordinate system will be similarly regarded as the X axis, and the axis of the two-dimensional coordinate system corresponding to the Y axis of the three-dimensional coordinate system will be similarly regarded as the Y axis. The axis of the two-dimensional coordinate system corresponding to the X axis of the three-dimensional coordinate system refers to the first axis when, as the phase pattern moves to the + side (or - side) along a direction parallel to the first axis of the two-dimensional coordinate system, the "image of the laser light L transferred on the entrance pupil plane 430a" moves to the + side (or - side) along the X direction of the three-dimensional coordinate system. The axis of the two-dimensional coordinate system corresponding to the Y axis of the three-dimensional coordinate system means the second axis when the phase pattern moves to the + side (or - side) along a direction parallel to the second axis of the two-dimensional coordinate system, and the "image of the laser light L transferred to the entrance pupil plane 430a" moves to the + side (or - side) along the Y direction of the three-dimensional coordinate system.

[0076] FIG. 11 is a diagram showing the focusing state of the laser light L on the target 1. The focusing states shown in (a), (b), and (c) of FIG. 11 are when the focal point of the focusing lens unit 430 is located on the second surface 1b. FIG. 12 is a diagram showing a point image acquired by the observation camera 488. The point images shown in (a), (b), and (c) of FIG. 12 are acquired in the focusing states shown in (a), (b), and (c) of FIG. 11, respectively. In (a) of FIG. 11 and (a) of FIG. 12, spherical aberration is not corrected by the spatial light modulator 410. In (b) of FIG. 11 and (b) of FIG. 12, spherical aberration that occurs when the laser light L travels through the target 1 from the first surface 1a by a distance t (t is the distance between the first surface 1a and the second surface 1b) is corrected by the spatial light modulator 410. In (c) of Figure 11 and (c) of Figure 12, the spherical aberration that occurs when it is assumed that the laser light L travels a distance 2t from the first surface 1a through the object 1 is corrected by the spatial light modulator 410.

[0077] As shown in FIG. 11(a), when spherical aberration is not corrected by the spatial light modulator 410, the outer peripheral component of the laser light L is focused in a region deeper than the inner peripheral component of the laser light L. As shown in FIG. 11(b), when spherical aberration, which occurs when laser light L travels a distance t from the first surface 1a through the object 1, is corrected by the spatial light modulator 410, all components of the laser light L are focused in a region on the second surface 1b. Therefore, even if reflected light RL is reflected by the second surface 1b, travels further through the object 1, and is emitted from the first surface 1a, it is blurred on the imaging surface of the observation camera 488, even if it is focused by the lens 487. As a result, as shown in FIGS. 12(a) and 12(b), a point image of the reflected light RL having sufficient brightness, size, etc. cannot be confirmed in the image acquired by the observation camera 488.

[0078] 11(c), if the spherical aberration that occurs when laser light L travels a distance 2t from first surface 1a through object 1 is corrected by spatial light modulator 410, the outer peripheral component of laser light L is focused in a region shallower than the inner peripheral portion of laser light L. Therefore, reflected light RL that is reflected by second surface 1b, travels further through object 1, and is emitted from first surface 1a is focused by lens 487 and then focused in a region on the imaging surface of observation camera 488. As a result, as shown in FIG. 12(c), a point image of reflected light RL having sufficient brightness, size, etc. can be confirmed in the image acquired by observation camera 488.

[0079] Fig. 13 is a diagram showing a state where no image transfer position shift occurs (i.e., a state where the center position of the image of laser light L transferred onto entrance pupil plane 430a coincides with the center position of entrance pupil plane 430a). Fig. 14 is a diagram showing a state where image transfer position shift occurs (i.e., a state where the center position of the image of laser light L transferred onto entrance pupil plane 430a is shifted from the center position of entrance pupil plane 430a).

[0080] 13, when no image transfer position shift occurs, the center position C1 of the image 39 of the laser beam L transferred onto the entrance pupil plane 430a coincides with the center position C2 of the entrance pupil plane 430a. At this time, the center position C3 of the phase pattern 9 displayed on the liquid crystal layer 216 by the spatial light modulator 410 coincides with the optical axis center C4 of the liquid crystal layer 216, which is the reference position.

[0081] 14, when an image transfer position shift occurs, the center position C1 of the image 39 of the laser beam L transferred onto the entrance pupil plane 430a is shifted from the center position C2 of the entrance pupil plane 430a. At this time, the center position C3 of the phase pattern 9 displayed on the liquid crystal layer 216 by the spatial light modulator 410 is shifted from the optical axis center C4 of the liquid crystal layer 216, which is the reference position. In other words, when the phase pattern 9 is displayed on the liquid crystal layer 216 in a state in which the center position C3 of the phase pattern 9 is shifted from the optical axis center C4 of the liquid crystal layer 216, which is the reference position, the center position C1 of the image 39 of the laser beam L transferred onto the entrance pupil plane 430a is shifted from the center position C2 of the entrance pupil plane 430a, resulting in unintended coma aberration. For example, if the center position C3 of the phase pattern 9 is shifted by one pixel from the optical axis center C4 of the liquid crystal layer 216, i.e., by one pixel electrode 214 (see Figure 8), a transfer position shift of approximately 20 μm may occur, which may affect the processing quality.

[0082] FIG. 15 shows point image images for each display position of the phase pattern. Point image G0 is a point image acquired when the phase pattern is displayed on the liquid crystal layer 216 with its center position coinciding with the reference position. Point image G1 is a point image acquired when the phase pattern is displayed on the liquid crystal layer 216 with its center position shifted by one pixel from the reference position to the negative side along the X direction. Point image G2 is a point image acquired when the phase pattern is displayed on the liquid crystal layer 216 with its center position shifted by one pixel from the reference position to the positive side along the X direction. Point image G3 is a point image acquired when the phase pattern is displayed on the liquid crystal layer 216 with its center position shifted by one pixel from the reference position to the negative side along the Y direction. Point image G4 is a point image acquired when the phase pattern is displayed on the liquid crystal layer 216 with its center position shifted by one pixel from the reference position to the positive side along the Y direction. In other words, point image G0 is a point image acquired when no image shift occurs, and point images G1, G2, G3, and G4 are point images acquired when image shift occurs.

[0083] As shown in Figure 15, in point image images G1, G2, G3, and G4 acquired when the image rotation position shift occurs, the point images are not rotationally symmetric optical images due to the occurrence of unintended coma aberration. For example, in point image images G1, G2, G3, and G4, the point images are decentered, an arc-shaped image EZ is generated on the outside, and some parts are more blurred in the circumferential direction than other parts. On the other hand, in point image image G0 acquired when the image rotation position shift does not occur, the point images are rotationally symmetric optical images.

[0084] Rotational symmetry refers to a symmetry in which an image overlaps with itself when rotated 360 / n° (n is an integer of 2 or greater) around a certain point. Rotationally symmetric point images include those that are completely rotationally symmetric as well as those that are approximately rotationally symmetric. Rotationally symmetric point images include a point image that is not decentered, a point image that does not have an arc-shaped image EZ on the outer periphery, a point image that is not blurred in one part more than the other parts in the circumferential direction, and a point image that includes at least one of these.

[0085] FIG. 16 is a diagram showing point images (another example than FIG. 15 ) for each display position of the phase pattern. Among the numbers in the X direction shown in FIG. 16 , “0” indicates that the center position of the phase pattern coincides with the reference position in the X direction, and “−2,” “−1,” “1,” and “2” indicate that the center position of the phase pattern is shifted from the reference position in the X direction by “2 pixels to the negative side,” “1 pixel to the negative side,” “1 pixel to the positive side,” or “2 pixels to the positive side.” Among the numbers in the Y direction shown in FIG. 16 , “0” indicates that the center position of the phase pattern coincides with the reference position in the Y direction, and “−2,” “−1,” “1,” and “2” indicate that the center position of the phase pattern is shifted from the reference position in the Y direction by “2 pixels to the negative side,” “1 pixel to the negative side,” “1 pixel to the positive side,” or “2 pixels to the positive side.” FIG. 16 shows a point image when there is no image shift, a point image when there is a shift in the image position only in the X direction from a state where there is no image shift, and a point image when there is a shift in the image position only in the Y direction from a state where there is no image shift.

[0086] 16, when there is no image rotation position shift in either the X or Y direction, the point image is a rotationally symmetric optical image. In contrast, when there is an image rotation position shift in either the X or Y direction, the point image is not a rotationally symmetric optical image. Furthermore, the greater the deviation of the center position of the phase pattern from the reference position (i.e., the greater the image rotation position shift), the greater the deviation from the rotationally symmetric optical image. [Check the image position]

[0087] Based on the above-described principle regarding the setting of the reference position, the laser processing apparatus 200 checks the image transfer position (i.e., checks whether the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a). The check of the image transfer position will be described in detail below.

[0088] As described above, in order to confirm whether the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a in the Y direction, the control unit 500 controls the spatial light modulator 410 so that, when a point image is acquired by the observation camera 488, spherical aberration that occurs when it is assumed that the laser light L has traveled a predetermined distance d from the first surface 1a through the object 1 is corrected and coma aberration occurs in the X direction on the entrance pupil plane 430a. Furthermore, in order to confirm whether the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a in the X direction, the control unit 500 controls the spatial light modulator 410 so that, when a point image is acquired by the observation camera 488, spherical aberration that occurs when it is assumed that the laser light L has traveled a predetermined distance d from the first surface 1a through the object 1 is corrected and coma aberration occurs in the Y direction on the entrance pupil plane 430a.

[0089] When the spatial light modulator 410 is controlled so that spherical aberration, which occurs when the laser light L travels a predetermined distance d from the first surface 1a through the object 1, is corrected and coma aberration is generated in the X direction on the entrance pupil surface 430a, a point image of the reflected light RL appears clearly, and a fan-shaped image appears clearly on one side in the X direction, as shown in Fig. 17. In the "point image shown in the center of Fig. 17" acquired when the center position of the image of the laser light L coincides with the center position of the entrance pupil surface 430a in the Y direction, the fan-shaped image is symmetrical with respect to the X direction (i.e., line symmetrical with respect to a line parallel to the X direction). In the "point image shown in the upper part of Fig. 17" acquired when the center position of the image of the laser light L is shifted in the Y direction from the center position of the entrance pupil surface 430a to the positive side, the fan-shaped image is tilted to one side in the Y direction and is not symmetrical with respect to the X direction. 17 ” acquired in a state where the center position of the image of the laser light L is shifted to the negative side in the Y direction from the center position of the entrance pupil plane 430a, the fan-shaped image is tilted to the other side in the Y direction and is not symmetrical with respect to the X direction. As described above, the fan-shaped image that appears on one side in the X direction makes it easy to check whether the center position of the image of the laser light L coincides with the center position of the entrance pupil plane 430a in the Y direction, and therefore coma aberration in the X direction is imparted when checking the image rotation position shift in the Y direction.

[0090] When the spatial light modulator 410 is controlled so that spherical aberration, which occurs when the laser light L travels a predetermined distance d from the first surface 1a through the object 1, is corrected and coma aberration is generated in the Y direction on the entrance pupil surface 430a, a point image of the reflected light RL appears clearly, and a fan-shaped image appears clearly on one side in the Y direction, as shown in Fig. 18. In the "point image shown in the center of Fig. 18" acquired when the center position of the image of the laser light L coincides with the center position of the entrance pupil surface 430a in the X direction, the fan-shaped image is symmetrical with respect to the Y direction (i.e., line symmetrical with respect to a line parallel to the Y direction). In the "point image shown on the right side of Fig. 18" acquired when the center position of the image of the laser light L is shifted in the X direction from the center position of the entrance pupil surface 430a to the positive side, the fan-shaped image is tilted to one side in the X direction and is not symmetrical with respect to the Y direction. In the "point image shown on the left side of Fig. 18" acquired when the center position of the image of the laser light L is shifted to the negative side in the X direction from the center position of the entrance pupil plane 430a, the fan-shaped image is tilted to the other side in the X direction and is not symmetrical with respect to the Y direction. As described above, the fan-shaped image that appears on one side in the Y direction makes it easy to check whether the center position of the image of the laser light L coincides with the center position of the entrance pupil plane 430a in the X direction, and therefore coma aberration in the Y direction is imparted when checking the image rotation position shift in the X direction. [Method for setting the reference position based on a point image]

[0091] A "reference position setting method based on a point image," which is a laser processing method according to one embodiment performed in the laser processing apparatus 200, will be described with reference to Fig. 10, Fig. 19, and Fig. 20. Fig. 19 and Fig. 20 are flowcharts showing the reference position setting method based on a point image.

[0092] First, the object 1 is set on the support table 230 (step S01). This object 1 is prepared for setting a reference position, and is, for example, a wafer whose first surface 1a and second surface 1b are mirror-finished and whose resistivity is 1 Ω·cm or more. Next, the support table 230 is moved in the X and Y directions so that the condenser lens unit 430 faces the object 1 in the Z direction (step S02). The movement of the support table 230 in the X and Y directions is performed by the control unit 500 controlling the first movement mechanism 220 (see FIG. 1). Next, the condenser lens unit 430 is moved in the Z direction so that the focal point of the condenser lens unit 430 is positioned on the second surface 1b of the object 1 (step S03). The movement of the condenser lens unit 430 in the Z direction is performed by the control unit 500 controlling the second movement mechanism 240 (see FIG. 1).

[0093] Next, the control unit 500 causes the spatial light modulator 410 to display a spherical aberration correction pattern (step S04), and further causes the spatial light modulator 410 to display an X-direction coma aberration imparting pattern (step S05). The spherical aberration correction pattern is a phase pattern for correcting spherical aberration that occurs when the laser light L is assumed to have traveled a predetermined distance d from the first surface 1a through the object 1. The X-direction coma aberration imparting pattern is a phase pattern for generating coma aberration in the X direction at the entrance pupil plane 430a. Next, with the spatial light modulator 410 displaying the spherical aberration correction pattern and the X-direction coma aberration imparting pattern, the laser oscillator 310 emits the laser light L, irradiating the object 1 with the laser light L, and the observation camera 488 acquires a point image of the reflected light RL (step S06). At this time, the output of the laser light L that does not cause ablation on the object 1 may be set in advance, or the output of the laser light L may be adjusted so that ablation on the object 1 does not occur.

[0094] Next, the control unit 500 determines whether the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a in the Y direction based on the point image of the reflected light RL (the detection result of the reflected light) (step S07). Specifically, if the fan-shaped image in the point image of the reflected light RL is symmetrical with respect to the X direction (see the "point image shown in the center of FIG. 17"), the control unit 500 determines that the center position of the image of the laser light L coincides with the center position of the entrance pupil plane 430a in the Y direction. If the fan-shaped image is not symmetrical with respect to the X direction (see the "point image shown in the upper part of FIG. 17" and the "point image shown in the lower part of FIG. 17"), the control unit 500 determines that the center position of the image of the laser light L is shifted from the center position of the entrance pupil plane 430a in the Y direction. Whether the fan-shaped image is symmetrical with respect to the X direction may be recognized, for example, by a geometric method or by a known image recognition process such as pattern recognition.

[0095] As described above, in the method for setting a reference position based on a point image, when a point image of reflected light RL is acquired by observation camera 488 to check whether the center position of the image of laser light L coincides with the center position of entrance pupil plane 430a in the Y direction, the spatial light modulator 410 is controlled so that spherical aberration, which occurs when laser light L travels a predetermined distance d from first surface 1a through object 1, is corrected and coma aberration occurs in the X direction on entrance pupil plane 430a.

[0096] If the determination result of step S07 is that the center position of the image of the laser light L coincides with the center position of the entrance pupil plane 430a in the Y direction, the control unit 500 stores the Y value of the phase pattern displayed by the spatial light modulator 410 in this case (the coordinate of the second reference position of the second phase pattern in the direction corresponding to the second direction) as the Y value of the reference position (second coordinate of the reference position) (step S08). The Y value of the phase pattern is the "Y-direction coordinate" of the "reference position (second reference position) used as a reference when the spherical aberration correction pattern, the X-direction coma aberration imparting pattern, or a phase pattern in which they are superimposed (all of which are second phase patterns)" is displayed. The Y value of the reference position is the "Y-direction coordinate (second coordinate)" of the "reference position used as a reference when the phase pattern for processing the target object 1 is displayed."

[0097] If the result of the judgment in step S07 is that the center position of the image of the laser light L is shifted from the center position of the entrance pupil plane 430a in the Y direction, the control unit 500 shifts the Y value of the phase pattern displayed by the spatial light modulator 410 (step S09), and steps S06 and S07 are repeated until it is judged that the center position of the image of the laser light L coincides with the center position of the entrance pupil plane 430a in the Y direction.

[0098] Following step S08, the control unit 500 causes the spatial light modulator 410 to display a Y-direction coma aberration imparting pattern instead of the X-direction coma aberration imparting pattern (step S11). The Y-direction coma aberration imparting pattern is a phase pattern for generating coma aberration in the Y direction on the entrance pupil plane 430a. Next, while the spatial light modulator 410 is displaying the spherical aberration correction pattern and the Y-direction coma aberration imparting pattern, the laser oscillator 310 emits laser light L, which irradiates the object 1 with the laser light L, and the observation camera 488 acquires a point image of the reflected light RL (step S12). At this time, an output of the laser light L that does not cause ablation on the object 1 may be set in advance, or the output of the laser light L may be adjusted so that ablation does not occur on the object 1.

[0099] Next, the control unit 500 determines whether the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a in the X direction based on the point image of the reflected light RL (the detection result of the reflected light) (step S13). Specifically, if the fan-shaped image in the point image of the reflected light RL is symmetrical with respect to the Y direction (see the "point image shown in the center of FIG. 18"), the control unit 500 determines that the center position of the image of the laser light L coincides with the center position of the entrance pupil plane 430a in the X direction. If the fan-shaped image is not symmetrical with respect to the Y direction (see the "point image shown on the right side of FIG. 18" and the "point image shown on the left side of FIG. 18"), the control unit 500 determines that the center position of the image of the laser light L is shifted from the center position of the entrance pupil plane 430a in the X direction. Whether the fan-shaped image is symmetrical with respect to the Y direction may be recognized, for example, by a geometric method or by a known image recognition process such as pattern recognition.

[0100] As described above, in the method for setting a reference position based on a point image, when a point image of the reflected light RL is acquired by the observation camera 488 to check whether the center position of the image of the laser light L coincides with the center position of the entrance pupil plane 430a in the X direction, the spatial light modulator 410 is controlled so that spherical aberration, which occurs when the laser light L is assumed to have traveled a predetermined distance d from the first surface 1a through the object 1, is corrected and coma aberration occurs in the Y direction on the entrance pupil plane 430a.

[0101] If the determination result of step S13 indicates that the center position of the image of the laser light L coincides with the center position of the entrance pupil plane 430a in the X direction, the control unit 500 stores the X value of the phase pattern displayed by the spatial light modulator 410 in this case (the coordinate of the first reference position of the first phase pattern in the direction corresponding to the first direction) as the X value of the reference position (first coordinate of the reference position) (step S14). The X value of the phase pattern is the "Y-direction coordinate" of the "reference position (first reference position) used as a reference when the spherical aberration correction pattern, the Y-direction coma aberration imparting pattern, or a phase pattern in which they are superimposed (all of which are first phase patterns)" is displayed. The X value of the reference position is the "X-direction coordinate (first coordinate)" of the "reference position used as a reference when the phase pattern for processing the target object 1 is displayed."

[0102] If the determination result in step S13 shows that the center position of the image of the laser light L is displaced from the center position of the entrance pupil plane 430a in the X direction, the control unit 500 shifts the X value of the phase pattern displayed by the spatial light modulator 410 (step S15), and steps S12 and S13 are repeated until it is determined that the center position of the image of the laser light L coincides with the center position of the entrance pupil plane 430a in the X direction.

[0103] As described above, in the laser processing apparatus 200, the reflected light RL of the laser light L that is incident on the object 1 from the first surface 1a and reflected by the second surface 1b is detected by the observation camera 488. At this time, the spatial light modulator 410 is controlled so that spherical aberration that occurs when the laser light L is assumed to have traveled a predetermined distance d from the first surface 1a through the object 1 is corrected and so that coma aberration is generated in the Y direction on the entrance pupil plane 430a of the condenser lens unit 430. As a result, a significant difference appears in the point image of the reflected light RL between a case where the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a in the X direction and a case where the center position of the image of the laser light L transferred onto the entrance pupil plane 430a is shifted from the center position of the entrance pupil plane 430a in the X direction. Therefore, it is possible to easily and accurately check whether the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a in the X direction.

[0104] In the laser processing apparatus 200, the reflected light RL of the laser light L that is incident on the object 1 from the first surface 1a and reflected by the second surface 1b is detected by the observation camera 488. At this time, the spatial light modulator 410 is controlled so that spherical aberration that occurs when the laser light L is assumed to have traveled a predetermined distance d from the first surface 1a through the object 1 is corrected and so that coma aberration in the X direction is generated on the entrance pupil plane 430a of the condenser lens unit 430. As a result, a significant difference appears in the point image of the reflected light RL between a case where the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a in the Y direction and a case where the center position of the image of the laser light L transferred onto the entrance pupil plane 430a is shifted from the center position of the entrance pupil plane 430a in the Y direction. Therefore, it is possible to easily and accurately check whether the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a in the Y direction.

[0105] In the laser processing apparatus 200, the control unit 500 determines whether the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a in the X direction, based on the point image of the reflected light RL. This makes it possible to automatically determine whether the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a in the X direction.

[0106] In the laser processing apparatus 200, the control unit 500 determines whether the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a in the Y direction, based on the point image of the reflected light RL. This makes it possible to automatically determine whether the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a in the Y direction.

[0107] In the laser processing apparatus 200, the control unit 500 acquires information about the phase pattern displayed by the spatial light modulator 410 when the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a in the X direction, and stores the coordinates of the reference position of the phase pattern in the X direction as the X direction coordinate of the reference position. When processing the target object 1, by displaying the phase pattern on the spatial light modulator 410 using the coordinates as a reference in the X direction, the target object 1 can be processed in a state where the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a in the X direction.

[0108] In the laser processing apparatus 200, the control unit 500 acquires information about the phase pattern displayed by the spatial light modulator 410 when the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a in the Y direction, and stores the coordinates of the reference position of the phase pattern in the Y direction as the Y direction coordinate of the reference position. When processing the target object 1, by displaying the phase pattern on the spatial light modulator 410 using the coordinates as a reference in the Y direction, the target object 1 can be processed with the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coinciding with the center position of the entrance pupil plane 430a in the Y direction.

[0109] In the laser processing apparatus 200, the control unit 500 causes the spatial light modulator 410 to display a spherical aberration correction pattern for correcting spherical aberration and a coma aberration imparting pattern for generating coma aberration in the Y direction on the entrance pupil plane 430a when a point image of the reflected light RL is acquired by the observation camera 488 in order to confirm whether the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a in the X direction. This makes it possible to reliably correct the spherical aberration that occurs when the laser light L travels a predetermined distance d from the first surface 1a through the object 1, and to reliably generate coma aberration in the Y direction on the entrance pupil plane 430a of the condenser lens unit 430.

[0110] In the laser processing apparatus 200, the control unit 500 causes the spatial light modulator 410 to display a spherical aberration correction pattern for correcting spherical aberration and a coma aberration imparting pattern for generating coma aberration in the X direction on the entrance pupil plane 430a when a point image of the reflected light RL is acquired by the observation camera 488 in order to confirm whether the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a in the Y direction. This makes it possible to reliably correct the spherical aberration that occurs when the laser light L travels a predetermined distance d from the first surface 1a through the object 1, and to reliably generate coma aberration in the X direction on the entrance pupil plane 430a of the condenser lens unit 430.

[0111] In the laser processing apparatus 200, the predetermined distance d is set to satisfy (2t - 0.1t) ≦ d ≦ (2t + 0.1t), where t is the distance between the first surface 1a and the second surface 1b. This makes it possible to appropriately suppress the influence of spherical aberration on the point image of the reflected light RL. As described above, the occurrence of coma aberration in the Y direction results in a significant difference in the point image of the reflected light RL between a case where the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a in the X direction and a case where the center position of the image of the laser light L transferred onto the entrance pupil plane 430a is shifted from the center position of the entrance pupil plane 430a in the X direction. Therefore, even if the predetermined distance d is not set so as to satisfy (2t-0.1t)≦d≦(2t+0.1t), it may be possible to confirm whether the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a in the X direction. Similarly, due to the occurrence of coma in the X direction, a significant difference appears in the point image of the reflected light RL between a case where the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a in the Y direction and a case where the center position of the image of the laser light L transferred onto the entrance pupil plane 430a is shifted from the center position of the entrance pupil plane 430a in the Y direction. Therefore, even if the predetermined distance d is not set so as to satisfy (2t-0.1t)≦d≦(2t+0.1t), it may be possible to confirm whether the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a in the Y direction.

[0112] In the laser processing apparatus 200, the display unit 600 displays a point image of the reflected light RL, thereby making it possible to notify the operator of the point image of the reflected light RL.

[0113] As described above, according to the laser processing method performed in the laser processing apparatus 200, it is possible to easily and accurately check whether the center position of the image of the laser beam L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a in the X direction. Furthermore, the target object 1 can be processed in a state in which the center position of the image of the laser beam L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a in the X direction.

[0114] As described above, according to the laser processing method performed in the laser processing apparatus 200, it is possible to easily and accurately check whether the center position of the image of the laser beam L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a in the Y direction. Furthermore, the target object 1 can be processed in a state in which the center position of the image of the laser beam L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a in the Y direction.

[0115] In the laser processing apparatus 200, when a point image of the reflected light RL is acquired by the observation camera 488, the control unit 500 may display a spherical aberration correction pattern for correcting spherical aberration on the spatial light modulator 410 so that coma aberration is generated in the Y direction on the entrance pupil plane 430a in order to confirm whether the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a in the X direction. This ensures that spherical aberration generated when the laser light L travels a predetermined distance d from the first surface 1a through the object 1 is corrected and that coma aberration is generated in the Y direction on the entrance pupil plane 430a of the condenser lens unit 430. As an example, the control unit 500 controls the spatial light modulator 410 to display the spherical aberration correction pattern based on a position shifted in the Y direction from a position estimated to be the reference position. At this time, the amount by which the spherical aberration correction pattern is shifted is larger than the amount of shift in step S15 and smaller than the amount by which it deviates from the angle of view of the observation camera 488.

[0116] In the laser processing apparatus 200, when a point image of the reflected light RL is acquired by the observation camera 488, the control unit 500 may display a spherical aberration correction pattern for correcting spherical aberration on the spatial light modulator 410 so that coma aberration is generated in the X direction on the entrance pupil plane 430a in order to confirm whether the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a in the Y direction. This ensures that spherical aberration generated when the laser light L travels a predetermined distance d from the first surface 1a through the object 1 is corrected and that coma aberration is generated in the X direction on the entrance pupil plane 430a of the condenser lens unit 430. As an example, the control unit 500 controls the spatial light modulator 410 to display the spherical aberration correction pattern based on a position shifted in the X direction from a position estimated to be the reference position. At this time, the amount by which the spherical aberration correction pattern is shifted is larger than the amount of shift in step S09 and smaller than the amount by which it deviates from the angle of view of observation camera 488. [Method for setting the reference position based on the point image and processing results]

[0117] A description will be given of a "method for setting a reference position based on a point image and processing results," which is a laser processing method according to one embodiment implemented in the laser processing apparatus 200. The method for setting a reference position based on a point image and processing results is a laser processing method for setting a reference position so that the center position of the image of the laser light transferred onto the entrance pupil plane coincides with the center position of the entrance pupil plane.

[0118] The method (setting process) for setting a reference position based on a point image and a processing result includes a step (process) of acquiring a reference position (first reference position) P1 based on a point image of reflected light RL and a reference position (second reference position) P2 based on the processing result of the object 1, and a step (process) of displaying a phase pattern on the spatial light modulator 410 with reference to the reference position P2 based on the processing result of the object 1 "when processing the object 1." These steps will be described below with reference to Fig. 10 and Fig. 21. Fig. 21 is a flowchart showing the method for setting a reference position based on a point image and a processing result.

[0119] First, the object 1 is set on the support table 230 (step S21). This object 1 is prepared for setting a reference position, and is, for example, a wafer whose first surface 1a and second surface 1b are mirror-finished and whose resistivity is 1 Ω·cm or more. Next, the support table 230 is moved in the X and Y directions so that the condenser lens unit 430 faces the object 1 in the Z direction (step S22). The movement of the support table 230 in the X and Y directions is performed by the control unit 500 controlling the first movement mechanism 220 (see FIG. 1). Next, the condenser lens unit 430 is moved in the Z direction so that the focal point of the condenser lens unit 430 is positioned on the second surface 1b of the object 1 (step S23). The movement of the condenser lens unit 430 in the Z direction is performed by the control unit 500 controlling the second movement mechanism 240 (see FIG. 1).

[0120] Next, the control unit 500 acquires the X value and the Y value of the reference position P1 based on the point image of the reflected light RL (step S24). The X value is the coordinate of the reference position P1 in the X direction, and the Y value is the coordinate of the reference position P1 in the Y direction. In this way, the control unit 500 acquires the reference position P1 based on the point image of the reflected light RL (the detection result of the reflected light). As an example, the acquisition of the X value and the Y value of the reference position P1 based on the point image of the reflected light RL is performed by the "method for setting a reference position based on a point image" shown in FIGS. 19 and 20.

[0121] Note that the method for acquiring the X-value and Y-value of the reference position P1 based on the point image of the reflected light RL is not limited to the above method. For example, in order to acquire the X-value of the reference position P1 based on the point image of the reflected light RL, the control unit 500 does not have to control the spatial light modulator 410 so as to correct the spherical aberration that occurs when the laser light L is assumed to have traveled a predetermined distance d from the first surface 1a through the object 1, but does not have to control the spatial light modulator 410 so as to generate coma aberration in the Y-direction at the entrance pupil plane 430a. Similarly, in order to acquire the Y-value of the reference position P1 based on the point image of the reflected light RL, the control unit 500 does not have to control the spatial light modulator 410 so as to correct the spherical aberration that occurs when the laser light L is assumed to have traveled a predetermined distance d from the first surface 1a through the object 1, but does not have to control the spatial light modulator 410 so as to generate coma aberration in the X-direction at the entrance pupil plane 430a. Furthermore, to obtain the X and Y values ​​of the reference position P1 based on the detection results of the reflected light RL, the control unit 500 may display an axicon pattern as a phase pattern on the spatial light modulator 410 and move the condenser lens unit 430 along the Z direction in this state. In this case, if the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a, the center of the image of the reflected light RL of the laser light L reflected by the first surface 1a of the object 1 does not move. On the other hand, if the center position of the image of the laser light L transferred onto the entrance pupil plane 430a deviates from the center position of the entrance pupil plane 430a, the center of the image of the reflected light RL of the laser light L reflected by the first surface 1a of the object 1 moves. As described above, the reference position P1 based on the point image of the reflected light RL can be identified based on the detection results of the reflected light RL of the laser light L reflected by the object 1.

[0122] Next, the control unit 500 acquires the X value and the Y value of the reference position P2 based on the processing result of the object 1 (step S25). The X value is the coordinate of the reference position P2 in the X direction, and the Y value is the coordinate of the reference position P2 in the Y direction. In this way, the control unit 500 acquires the reference position P2 based on the processing result of the object 1. When acquiring the X value and the Y value of the reference position P2 based on the processing result of the object 1, the object 1 may be replaced as necessary. As an example, as shown in FIGS. 22, 23, and 24, a modified region is formed inside the object 1, and the processing state of the object 1 is observed to acquire the X value and the Y value of the reference position P2 based on the processing result of the object 1.

[0123] 22(a) is a "cross-sectional view perpendicular to the X direction" of the object 1 on which processing has been performed, with the direction parallel to the X direction (scanning direction of the laser light L) being the processing direction, and the center position of the image of the laser light L being shifted by one pixel to the positive side in the Y direction from the center position of the entrance pupil surface 430a. FIG. 22(b) is a "cross-sectional view perpendicular to the X direction" of the object 1 on which processing has been performed, with the direction parallel to the X direction being the processing direction, and the center position of the image of the laser light L being coincident with the center position of the entrance pupil surface 430a in the Y direction. FIG. 22(c) is a "cross-sectional view perpendicular to the X direction" of the object 1 on which processing has been performed, with the direction parallel to the X direction being the processing direction, and the center position of the image of the laser light L being shifted by one pixel to the negative side in the Y direction from the center position of the entrance pupil surface 430a. The crack shown in FIG. 22(b) extends along the thickness direction (ZX plane) of the object 1, compared to the cracks shown in FIGS. 22(a) and 22(c). In this case, the control unit 500 acquires the X value and Y value of the reference position of the phase pattern displayed by the spatial light modulator 410 when the processing result shown in (b) of FIG. 22 was obtained as the X value and Y value of the reference position P2.

[0124] 23A is a diagram of a cross section parallel to the X direction of the object 1 on which processing has been performed, with the processing direction being parallel to the X direction, in a state where the center position of the image of the laser light L is shifted by one pixel to the positive side from the center position of the entrance pupil surface 430a in the Y direction. FIG. 23B is a diagram of a cross section parallel to the X direction of the object 1 on which processing has been performed, with the processing direction being parallel to the X direction, in a state where the center position of the image of the laser light L coincides with the center position of the entrance pupil surface 430a in the Y direction. FIG. 23C is a diagram of a cross section parallel to the X direction of the object 1 on which processing has been performed, with the processing direction being parallel to the X direction, in a state where the center position of the image of the laser light L is shifted by one pixel to the negative side from the center position of the entrance pupil surface 430a in the Y direction. The cross section shown in FIG. 23B extends along the thickness direction (ZX plane) of the object 1, compared to the cross sections shown in FIGS. 23A and 23C. In this case, the control unit 500 acquires the X value and the Y value of the reference position of the phase pattern displayed by the spatial light modulator 410 when the processing result shown in (b) of FIG. 23 was obtained as the X value and the Y value of the reference position P2.

[0125] 24(a) is a diagram of the outer surface opposite the laser beam incident side of the object 1 on which processing has been performed with the processing direction parallel to the X direction, with the center position of the image of the laser beam L shifted by one pixel to the positive side from the center position of the entrance pupil surface 430a in the Y direction. FIG. 24(b) is a diagram of the outer surface opposite the laser beam incident side of the object 1 on which processing has been performed with the processing direction parallel to the X direction, with the center position of the image of the laser beam L coinciding with the center position of the entrance pupil surface 430a in the Y direction. FIG. 24(c) is a diagram of the outer surface opposite the laser beam incident side of the object 1 on which processing has been performed with the processing direction parallel to the X direction, with the center position of the image of the laser beam L shifted by one pixel to the negative side from the center position of the entrance pupil surface 430a in the Y direction. The processing marks shown in FIG. 24(b) are more uniformly formed on both sides of the crack that has reached the outer surface of the object 1 than the processing marks shown in FIGS. 24(a) and 24(c). In this case, the control unit 500 acquires the X value and the Y value of the reference position of the phase pattern displayed by the spatial light modulator 410 when the processing result shown in (b) of FIG. 24 was obtained as the X value and the Y value of the reference position P2.

[0126] The method for acquiring the X and Y values ​​of the reference position P2 based on the processing result of the object 1 is not limited to the above method, and any method may be used as long as it utilizes processing that produces a difference in the processing result of the object 1 between when the center position of the image of the laser light L coincides with the center position of the entrance pupil plane 430a and when the center position of the image of the laser light L is shifted from the center position of the entrance pupil plane 430a. The X and Y values ​​of the reference position P2 based on the processing result of the object 1 may be acquired by the control unit 500 specifying the reference position P2 based on the "image of the object 1 (processed object 1)" acquired by the imaging device. Alternatively, the X and Y values ​​of the reference position P2 based on the processing result of the object 1 may be acquired by the operator confirming the "image of the object 1 (processed object 1)" acquired by the imaging device on the display unit 600 and inputting the reference position P2 into the control unit 500. Alternatively, the X and Y values ​​of the reference position P2 based on the processing result of the object 1 may be obtained by the operator checking the processed object 1 and inputting the reference position P2 into the control unit 500.

[0127] Next, control unit 500 calculates and stores the difference in X value and the difference in Y value (step S26). The difference in X value is the value obtained by subtracting the X value of reference position P2 from the X value of reference position P1, and the difference in Y value is the value obtained by subtracting the Y value of reference position P2 from the Y value of reference position P1. Alternatively, the difference in X value is the value obtained by subtracting the X value of reference position P1 from the X value of reference position P2, and the difference in Y value is the value obtained by subtracting the Y value of reference position P1 from the Y value of reference position P2.

[0128] After acquiring the reference position P1 based on the point image of the reflected light RL and the reference position P2 based on the processing result of the object 1 as described above, the control unit 500 causes the spatial light modulator 410 to display a phase pattern based on the reference position P2 based on the processing result of the object 1 "during processing of the object 1." Note that "during processing of the object 1" refers to a period during which the laser processing device 200 performs a processing operation on the object 1 (which may be one type or multiple types) to be processed.

[0129] The method (setting process) for setting a reference position based on a point image and a processing result further includes a step (process) of acquiring a reference position (third reference position) P3 based on a point image of the reflected light RL when the reference position is confirmed after a certain processing of the object 1; a step (process) of calculating a reference position (fourth reference position) P4 based on the reference positions P1, P2, and P3 when the reference position P3 is deviated from the reference position P1 and storing the reference position P4; and a step (process) of displaying a phase pattern on the spatial light modulator 410 with reference to the reference position P4 at the next processing of the object 1. These steps will be described below with reference to FIGS. 10 and 25. FIG. 25 is a flowchart showing the method for setting a reference position based on a point image and a processing result. The "time to confirm the reference position" refers to the timing between a certain processing of the object 1 and the next processing of the object 1, e.g., the timing of periodic maintenance of the laser processing apparatus 200.

[0130] First, the object 1 is set on the support table 230 (step S31). This object 1 is prepared for setting a reference position, and is, for example, a wafer whose first surface 1a and second surface 1b are mirror-finished and whose resistivity is 1 Ω·cm or more. Next, the support table 230 is moved in the X and Y directions so that the condenser lens unit 430 faces the object 1 in the Z direction (step S32). The movement of the support table 230 in the X and Y directions is performed by the control unit 500 controlling the first movement mechanism 220 (see FIG. 1). Next, the condenser lens unit 430 is moved in the Z direction so that the focal point of the condenser lens unit 430 is positioned on the second surface 1b of the object 1 (step S33). The movement of the condenser lens unit 430 in the Z direction is performed by the control unit 500 controlling the second movement mechanism 240 (see FIG. 1).

[0131] Next, the control unit 500 acquires the X value and the Y value of the reference position P3 based on the point image of the reflected light RL (step S34). The X value is the coordinate of the reference position P3 in the X direction, and the Y value is the coordinate of the reference position P3 in the Y direction. In this way, the control unit 500 acquires the reference position P3 based on the point image of the reflected light RL (the detection result of the reflected light) when "confirming the reference position."

[0132] Next, the control unit 500 determines whether or not there is a deviation in the reference position P3 based on the point image of the reflected light RL (step S35). Specifically, the control unit 500 determines whether or not the currently acquired reference position P3 is deviated from the previously acquired and currently stored reference position P1 (see step S24 in FIG. 21). This determination is made by comparing the X value of the reference position P1 with the X value of the reference position P3 and by comparing the Y value of the reference position P1 with the Y value of the reference position P3. If the determination in step S35 shows that there is no deviation in the reference position P3 based on the point image of the reflected light RL, the process ends.

[0133] If the determination result in step S35 indicates that there is a deviation in reference position P3 based on the point image of reflected light RL, control unit 500 updates the X and Y values ​​of reference position P1 that were previously acquired and currently stored to the X and Y values ​​of reference position P3 that were currently acquired (step S36). That is, control unit 500 stores the X and Y values ​​of reference position P3 instead of the X and Y values ​​of reference position P1. At this time, control unit 500 retains the X and Y values ​​of reference position P1 for the subsequent processing of step S37.

[0134] Next, the control unit 500 calculates a reference position P4 based on the processing result of the object 1, based on the difference between the X value of the reference position P1 and the X value of the reference position P3 and the difference between the Y value of the reference position P1 and the Y value of the reference position P3 (step S37). Specifically, the control unit 500 calculates the X value of the reference position P4 so that the difference between the X value of the previously acquired and currently stored reference position P2 (see step S25 of FIG. 21) and the X value of the reference position P4 is the same as the difference between the X value of the reference position P1 and the X value of the reference position P3. Similarly, the control unit 500 calculates the Y value of the reference position P4 so that the difference between the Y value of the previously acquired and currently stored reference position P2 and the Y value of the reference position P4 is the same as the difference between the Y value of the reference position P1 and the Y value of the reference position P3.

[0135] Next, the control unit 500 updates the X and Y values ​​of the reference position P2 that were previously acquired and currently stored to the X and Y values ​​of the currently calculated reference position P4 (step S38). That is, the control unit 500 stores the X and Y values ​​of the reference position P4 instead of the X and Y values ​​of the reference position P2. The reference position P4 here is not the actual "reference position based on the processing result of the object 1," but an estimated "reference position based on the processing result of the object 1" obtained by calculation. In this way, the control unit 500 calculates the reference position P4 based on the reference position P1, the reference position P2, and the reference position P3, and stores the reference position P4.

[0136] After acquiring the reference position P3 based on the point image of the reflected light RL and the reference position P4 based on the processing result of the object 1 as described above, the control unit 500 causes the spatial light modulator 410 to display a phase pattern based on the reference position P4 based on the processing result of the object 1 "when processing the object 1."

[0137] As described above, the laser processing apparatus 200 acquires a reference position P1 based on the point image of the reflected light RL and a reference position P2 based on the processing result of the object 1. After the reference positions P1 and P2 are acquired, during "processing of the object 1," the spatial light modulator 410 displays a phase pattern based on the reference position P2 based on the processing result of the object 1. This allows the object 1 to be processed with the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coinciding with the center position of the entrance pupil plane 430a. During "checking of the reference position," a reference position P3 based on the point image of the reflected light RL is acquired. By comparing this reference position P3 with the reference position P1 acquired in advance based on the point image of the reflected light RL, it is possible to easily and accurately confirm whether the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a.

[0138] In the laser processing apparatus 200, if the currently acquired reference position P3 is deviated from the previously acquired and currently stored reference position P1, the control unit 500 calculates a reference position P4 based on the reference positions P1, P2, and P3, and causes the spatial light modulator 410 to display a phase pattern based on the stored reference position P4 during “processing of the object 1.” A constant positional relationship tends to be maintained between the reference position acquired based on the point image of the reflected light RL and the reference position acquired based on the processing result of the object 1. Therefore, if the reference position P3 is deviated from the reference position P1, the spatial light modulator 410 displays a phase pattern based on the reference position P4 calculated based on the reference positions P1, P2, and P3 during “processing of the object 1.” This allows the object 1 to be processed with the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coinciding with the center position of the entrance pupil plane 430a.

[0139] In the laser processing apparatus 200, the display unit 600 displays a point image of the reflected light RL when “confirming the reference position.” This makes it possible to notify the operator of the point image of the reflected light RL.

[0140] According to the laser processing method performed by the laser processing apparatus 200, as described above, after the reference positions P1 and P2 have been acquired, the spatial light modulator 410 displays a phase pattern based on the reference position P2, which is based on the processing result of the object 1, when "processing the object 1." This allows the object 1 to be processed with the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coinciding with the center position of the entrance pupil plane 430a. Then, when "confirming the reference position," a reference position P3 is acquired based on the point image of the reflected light RL. By comparing this reference position P3 with the reference position P1 acquired in advance based on the point image of the reflected light RL, it is possible to easily and accurately confirm whether the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a.

[0141] The method for setting a reference position based on a point image and a processing result (setting process) may include the following steps instead of the steps shown in the flowchart of Fig. 25. That is, the method for setting a reference position based on a point image and a processing result (setting process) may include: a step (process) of acquiring a reference position (third reference position) P3 based on the point image of reflected light RL "when confirming the reference position," a step (process) of acquiring a reference position (fourth reference position) P4 based on the processing result of the object 1 when the reference position P3 is deviated from the reference position P1, a step (process) of comparing a difference (first difference) between the reference position P1 and the reference position P2 with a difference (second difference) between the reference position P3 and the reference position P4, and a step (process) of storing the reference position P3 and the reference position P4 instead of the reference position P1 and the reference position P2 when these differences are different from each other, and a step (process) of displaying a phase pattern on the spatial light modulator 410 based on the reference position P4 "when processing the object 1." These steps will be described below with reference to Fig. 10 and Fig. 26. Fig. 26 is a flowchart showing a method for setting a reference position based on a point image and a processing result.

[0142] First, the object 1 is set on the support table 230 (step S41). This object 1 is prepared for setting a reference position, and is, for example, a wafer whose first surface 1a and second surface 1b are mirror-finished and whose resistivity is 1 Ω·cm or more. Next, the support table 230 is moved in the X and Y directions so that the condenser lens unit 430 faces the object 1 in the Z direction (step S42). The movement of the support table 230 in the X and Y directions is performed by the control unit 500 controlling the first movement mechanism 220 (see FIG. 1). Next, the condenser lens unit 430 is moved in the Z direction so that the focal point of the condenser lens unit 430 is positioned on the second surface 1b of the object 1 (step S43). The movement of the condenser lens unit 430 in the Z direction is performed by the control unit 500 controlling the second movement mechanism 240 (see FIG. 1).

[0143] Next, the control unit 500 acquires the X and Y values ​​of the reference position P3 based on the point image of the reflected light RL (step S44). The X value is the coordinate of the reference position P3 in the X direction, and the Y value is the coordinate of the reference position P3 in the Y direction. In this way, the control unit 500 acquires the reference position P3 based on the point image of the reflected light RL (the detection result of the reflected light) when "confirming the reference position."

[0144] Next, the control unit 500 determines whether or not there is a deviation in the reference position P3 based on the point image of the reflected light RL (step S45). Specifically, the control unit 500 determines whether or not the currently acquired reference position P3 is deviated from the previously acquired and currently stored reference position P1 (see step S24 in FIG. 21). This determination is made by comparing the X value of the reference position P1 with the X value of the reference position P3 and by comparing the Y value of the reference position P1 with the Y value of the reference position P3. If the determination in step S45 shows that there is no deviation in the reference position P3 based on the point image of the reflected light RL, the process ends.

[0145] If the determination in step S35 indicates that there is a deviation in the reference position P3 based on the point image of the reflected light RL, the control unit 500 issues an alarm (step S46). Specifically, the control unit 500 causes the display unit 600 to display a message indicating that the reference position P2 based on the processing result of the target object 1 should be updated. Next, the control unit 500 updates the X and Y values ​​of the reference position P1 previously acquired and currently stored to the X and Y values ​​of the reference position P3 acquired this time (step S47). That is, the control unit 500 stores the X and Y values ​​of the reference position P3 instead of the X and Y values ​​of the reference position P1. At this time, the control unit 500 retains the X and Y values ​​of the reference position P1 for the subsequent processing of step 49.

[0146] Next, the control unit 500 acquires the X value and the Y value of the reference position P4 based on the processing result of the object 1 (step S48). The X value is the coordinate of the reference position P4 in the X direction, and the Y value is the coordinate of the reference position P4 in the Y direction. In this way, the control unit 500 acquires the reference position P4 based on the processing result of the object 1.

[0147] Next, the control unit 500 calculates the difference between the reference position P1 and the reference position P2, and the difference between the reference position P3 and the reference position P4 (step S49). Specifically, the control unit 500 calculates the difference between the X value of the reference position P1 and the X value of the reference position P2, and the difference between the Y value of the reference position P1 and the Y value of the reference position P2. Similarly, the control unit 500 calculates the difference between the X value of the reference position P3 and the X value of the reference position P4, and the difference between the Y value of the reference position P3 and the Y value of the reference position P4.

[0148] Next, the control unit 500 compares the difference between the reference position P1 and the reference position P2 with the difference between the reference position P3 and the reference position P4 (step S50). Specifically, as a "comparison regarding the X value," the control unit 500 compares the difference between the X value at the reference position P1 and the X value at the reference position P2 with the difference between the X value at the reference position P3 and the X value at the reference position P4. Similarly, as a "comparison regarding the Y value," the control unit 500 compares the difference between the Y value at the reference position P1 and the Y value at the reference position P2 with the difference between the Y value at the reference position P3 and the Y value at the reference position P4. If the result of the determination in step S50 shows that the differences are not different in both the "comparison regarding the X value" and the "comparison regarding the Y value," the processing ends.

[0149] If the result of the determination in step S50 shows that the differences are different in at least one of the "comparison regarding the X value" and "comparison regarding the Y value," the control unit 500 updates the difference between the X value of reference position P1 and the X value of reference position P2 and the difference between the Y value of reference position P1 and the Y value of reference position P2 to the difference between the X value of reference position P3 and the X value of reference position P4 and the Y value of reference position P3 and the Y value of reference position P4 (step S51). That is, the control unit 500 stores the reference position P3 and the reference position P4 instead of the reference position P1 and the reference position P2.

[0150] After acquiring the reference position P3 based on the point image of the reflected light RL and the reference position P4 based on the processing result of the object 1 as described above, the control unit 500 causes the spatial light modulator 410 to display a phase pattern based on the reference position P4 based on the processing result of the object 1 "when processing the object 1."

[0151] As described above, in the laser processing apparatus 200, if the currently acquired reference position P3 deviates from the previously acquired and currently stored reference position P1, the control unit 500 acquires a reference position P4 based on the processing result of the object 1 and causes the spatial light modulator 410 to display a phase pattern based on the acquired reference position P4 as a reference “when processing the object 1.” A constant positional relationship tends to be maintained between the reference position acquired based on the point image of the reflected light RL and the reference position acquired based on the processing result of the object 1. Therefore, if the reference position P3 deviates from the reference position P1, the spatial light modulator 410 displays a phase pattern based on the newly acquired reference position P4 based on the processing result of the object 1 as a reference “when processing the object 1.” This allows the object 1 to be processed with the center position of the image of the laser light L transferred onto the entrance pupil plane 430a coinciding with the center position of the entrance pupil plane 430a.

[0152] In the laser processing apparatus 200, the control unit 500 compares a first difference between the reference position P1 and the reference position P2 with a second difference between the reference position P3 and the reference position P4. If the first difference and the second difference are different, the control unit 500 stores the reference position P3 and the reference position P4 instead of the reference position P1 and the reference position P2. If a constant positional relationship is maintained between the reference position acquired based on the point image of the reflected light RL and the reference position acquired based on the processing result of the object 1, the first difference and the second difference should be the same. Therefore, by comparing the first difference and the second difference, it is possible to confirm whether a constant positional relationship is maintained between the reference position acquired based on the point image of the reflected light RL and the reference position acquired based on the processing result of the object 1. Furthermore, if the first difference and the second difference are different, the control unit 500 stores the reference positions P3 and P4 instead of the reference positions P1 and P2, thereby updating the positional relationship between the reference position obtained based on the point image of the reflected light RL and the reference position obtained based on the processing result of the target object 1. [Variations]

[0153] The present invention is not limited to the above-described embodiments. For example, the above-described embodiments are not limited to those forming a modified region inside the object 1, but may also be those performing other laser processing such as ablation. The above-described embodiments are not limited to those focusing the laser light L inside the object 1, but may also focus the laser light L on the outer surface of the object 1 on the side where the laser light L is incident or on the outer surface opposite thereto. The device to which the present invention is applied can be applied to various laser light irradiation devices as long as it irradiates the object 1 with the laser light L. In the above-described embodiments, the lines 5a and 5b along which the laser light L is scanned are lines for cutting the object 1, but the lines along which the laser light L is scanned may be lines for other purposes. In the object 1, the first surface 1a does not have to be the outer surface of the object 1 as long as it is a surface located on the side where the laser light L is incident relative to the second surface 1b. In the object 1, the second surface 1b does not have to be the outer surface of the object 1 as long as it is a surface located on the opposite side of the first surface 1a from the side where the laser light L is incident.

[0154] The spatial light modulator 410 is not limited to a reflective type and may be a transmissive type. The image transfer unit that transfers the image of the laser light L in the spatial light modulator 410 onto the entrance pupil plane 430a is not limited to the 4f lens unit 420 having a pair of lenses 422 and 423, but may include a first lens system (e.g., a cemented lens, three or more lenses, etc.) on the spatial light modulator 410 side and a second lens system (e.g., a cemented lens, three or more lenses, etc.) on the entrance pupil plane 430a side. The photodetector that detects the reflected light RL is not limited to the observation camera 488 and may be a wavefront sensor that detects the wavefront of the reflected light RL. The wavefront sensor is, for example, composed of a microlens array and an imaging element, and acquires the local phase gradient from the image position of the light spot focused by each microlens. The wavefront sensor may be a Shack-Hartmann wavefront sensor ("WFS150-5C" manufactured by THORLABS). [Explanation of symbols]

[0155] 1...object, 1a...first surface, 1b...second surface, 200...laser processing device, 230...support base (support part), 310...laser oscillator (light source), 410...spatial light modulator, 420...4f lens unit (image conversion part), 430...condensing lens unit (condensing part), 430a...entrance pupil plane, 488...observation camera (photodetector), 500...control part, 600...display part, L...laser light, RL...reflected light.

Claims

1. a support portion for supporting an object having a first surface and a second surface facing each other; a light source that emits laser light; a spatial light modulator that modulates the laser light emitted from the light source; a focusing unit that focuses the laser light modulated by the spatial light modulator onto the object from the first surface side; an image transfer unit that transfers an image of the laser light in the spatial light modulator onto an entrance pupil plane of the light condensing unit; a photodetector that detects reflected light of the laser light reflected by the object; a control unit that controls at least the spatial light modulator, the control unit executes a setting process to set a reference position that is a reference for a display position of a phase pattern on the spatial light modulator so that a center position of the image of the laser light transferred onto the entrance pupil plane coincides with a center position of the entrance pupil plane; The setting process includes: acquiring a first reference position as the reference position based on a detection result of the reflected light, and acquiring a second reference position as the reference position based on a processing result of the object; a process of displaying the phase pattern on the spatial light modulator using the second reference position as the reference when processing the object; and acquiring a third reference position as the reference position based on a detection result of the reflected light when confirming the reference position after processing the object.

2. The setting process includes: a process of calculating a fourth reference position as the reference position based on the first reference position, the second reference position, and the third reference position when the third reference position is deviated from the first reference position, and storing the fourth reference position; The laser processing device according to claim 1 , further comprising a process of displaying the phase pattern on the spatial light modulator using the fourth reference position as the reference when processing the object.

3. The setting process includes: a process of acquiring a fourth reference position as the reference position based on a processing result of the object when the third reference position is deviated from the first reference position; The laser processing device according to claim 1 , further comprising a process of displaying the phase pattern on the spatial light modulator using the fourth reference position as the reference when processing the object.

4. The setting process includes: a process of comparing a first difference between the first reference position and the second reference position with a second difference between the third reference position and the fourth reference position; 4. The laser processing apparatus according to claim 3, further comprising a process of storing the third reference position and the fourth reference position instead of the first reference position and the second reference position when the first difference and the second difference are different.

5. 5. The laser processing device according to claim 1, further comprising a display unit that displays a detection result of the reflected light when the reference position is confirmed.

6. a support portion for supporting an object having a first surface and a second surface facing each other; a light source that emits laser light; a spatial light modulator that modulates the laser light emitted from the light source; a focusing unit that focuses the laser light modulated by the spatial light modulator onto the object from the first surface side; an image transfer unit that transfers an image of the laser light in the spatial light modulator onto an entrance pupil plane of the light condensing unit; a photodetector that detects reflected light of the laser light reflected by the object, a laser processing method for setting a reference position that is a reference for a display position of a phase pattern on the spatial light modulator so that a center position of the image of the laser light transferred onto the entrance pupil plane coincides with a center position of the entrance pupil plane, the method comprising: acquiring a first reference position as the reference position based on a detection result of the reflected light, and acquiring a second reference position as the reference position based on a processing result of the object; displaying the phase pattern on the spatial light modulator using the second reference position as the reference when processing the object; and acquiring a third reference position as the reference position based on a detection result of the reflected light when confirming the reference position after processing the object.

Images