JP2023125394A - Laser processing device and laser processing method - Google Patents

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

The present invention relates to a laser processing device and a laser processing method.

A support part that supports a target object, a light source that emits laser light, a spatial light modulator that modulates the laser light emitted from the light source, and a laser light modulated by the spatial light modulator that focuses the laser light on the target object. 2. Description of the Related Art A laser processing apparatus is known that includes a condensing section and an image transfer section that transfers an image of a laser beam in a spatial light modulator onto an entrance pupil plane of the condensing section (see, for example, Patent Document 1).

Japanese Patent Application Publication No. 2011-51011

In the above-mentioned laser beam irradiation device, if the center position of the laser beam image transferred to the entrance pupil plane of the condensing section does not match the center position of the entrance pupil plane of the condensing section, the desired processing may not be completed. There is a possibility that quality cannot be obtained.

The present invention provides a method for easily and accurately confirming whether the center position of a laser beam image transferred to the entrance pupil plane of a condenser corresponds to the center position of the entrance pupil plane of the condenser. The object of the present invention is to provide a laser processing device and a laser processing method that can perform the following steps.

The laser processing apparatus of the present invention includes a support part that supports an object having a first surface and a second surface facing each other, a light source that emits a laser beam, and a spatial light modulator that modulates the laser beam that is emitted from the light source. a condensing section that condenses the laser beam modulated by the spatial light modulator onto the object from the first surface side; and a condensing section that transfers an image of the laser beam in the spatial light modulator to an entrance pupil plane of the condensing section. The control unit includes an image transfer unit, a photodetector that detects the reflected light of the laser beam reflected by the object, and a control unit that controls at least the spatial light modulator. A setting process is executed to set a reference position, which is a reference position of the phase pattern display position in the spatial light modulator, so that the center position of the image of the laser beam coincides with the center position of the entrance pupil plane. A first reference position is acquired as a reference position based on the detection result of the reflected light, a second reference position is acquired as a reference position based on the processing result of the target object, and a second reference position is acquired when processing the target object. A third reference position is acquired as a reference position based on the detection result of reflected light during the process of displaying a phase pattern on a spatial light modulator using the reference position as a reference and when confirming the reference position after processing the object. processing.

In this laser processing device, a first reference position is acquired based on the detection result of the reflected light as a reference position which is a reference position of the display position of the phase pattern in the spatial light modulator, and a first reference position is acquired based on the result of processing the object. A second reference position is obtained. With the first reference position and the second reference position 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. do. Thereby, the object can be processed in a state in which the center position of the image of the laser beam transferred onto the entrance pupil plane of the light condensing section matches the center position of the entrance pupil plane of the light condensing section. Then, when confirming the reference position, a third reference position is acquired based on the detection result of the reflected light. By comparing this third reference position with the first reference position acquired in advance based on the detection result of the reflected light, the center position of the image of the laser beam transferred to the entrance pupil plane of the condenser can be determined. It is possible to easily and accurately confirm whether or not the center position of the entrance pupil plane of the light section coincides with the center position.

In the laser processing apparatus of the present invention, in the setting process, when the third reference position is deviated from the first reference position, the setting process is performed based on the first reference position, the second reference position, and the third reference position. The method may further include a process of calculating four reference positions and storing the fourth reference position, and a process of displaying a phase pattern on a spatial light modulator using the fourth reference position as a reference when processing the object. A certain positional relationship tends to be maintained between the reference position obtained based on the detection result of the reflected light and the reference position obtained based on the processing result of the object. Therefore, if the third reference position is deviated from the first reference position, when processing the object, the spatial light modulator may be 4 By displaying the phase pattern with reference to the reference position, the center position of the image of the laser beam transferred to the entrance pupil plane of the light condensing unit matches the center position of the entrance pupil plane of the light condensing unit. Objects can be processed.

In the laser processing apparatus of the present invention, the setting process includes a process of acquiring a fourth reference position as the reference position based on the processing result of the object when the third reference position is deviated from the first reference position; The method may further include a process of displaying a phase pattern on the spatial light modulator using the fourth reference position as a reference when processing the object. A certain positional relationship tends to be maintained between the reference position obtained based on the detection result of the reflected light and the reference position obtained based on the processing result of the object. Therefore, if the third reference position deviates from the first reference position, when processing the object, the spatial light modulator uses the fourth reference position, which is newly acquired based on the processing results of the object, as a reference, to generate a phase pattern. By displaying , the object can be processed while the center position of the image of the laser beam transferred to the entrance pupil plane of the condenser matches the center position of the entrance pupil plane of the condenser. .

In the laser processing apparatus of the present invention, the setting process includes a process of comparing a first difference between the first reference position and the second reference position and a second difference between the third reference position and the fourth reference position; The method may further include a process of storing a third reference position and a fourth reference position instead of the first reference position and the second reference position when the first difference and the second difference are different. If a certain positional relationship is maintained between the reference position obtained based on the detection result of the reflected light and the reference position obtained based on the processing result of the object, the first difference and the second The difference should be the same. Therefore, by comparing the first difference and the second difference, there is a constant difference between the reference position obtained based on the detection result of the reflected light and the reference position obtained based on the processing result of the object. It is possible to check whether the positional relationship between the two is maintained. Furthermore, when 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. It is possible to update the positional relationship between the reference position acquired based on the detection result of , and the reference position acquired based on the processing result of the target object.

The laser processing apparatus of the present invention may further include a display unit that displays the detection result of the reflected light when confirming the reference position. According to this, it is possible to notify the operator of the detection result of the reflected light.

The laser processing method of the present invention includes a support part that supports an object having a first surface and a second surface facing each other, a light source that emits a laser beam, and a spatial light modulator that modulates the laser beam that is emitted from the light source. a condensing section that condenses the laser beam modulated by the spatial light modulator onto the object from the first surface side; and a condensing section that transfers an image of the laser beam in the spatial light modulator to an entrance pupil plane of the condensing section. This is carried out in a laser processing device equipped with an image transfer section and a photodetector that detects the reflected light of the laser beam reflected by the target object, and the center position of the image of the laser beam transferred to the entrance pupil plane is the incident point. A laser processing method for setting a reference position, which is a reference for the display position of a phase pattern in a spatial light modulator, so as to match the center position of a pupil plane, the method comprising: acquiring a second reference position as a reference position based on the processing result of the object, and transmitting a phase pattern to the spatial light modulator using the second reference position as a reference when processing the object. and a step of acquiring a third reference position as the reference position based on the detection result of the reflected light when confirming the reference position after processing the object.

According to this laser processing method, as described above, in a state where the first reference position and the second reference position have been obtained, when processing the object, the spatial light modulator acquires the information based on the processing results of the object. The phase pattern is displayed based on the second reference position. Thereby, the object can be processed in a state in which the center position of the image of the laser beam transferred onto the entrance pupil plane of the light condensing section matches the center position of the entrance pupil plane of the light condensing section. Then, when confirming the reference position, a third reference position is acquired based on the detection result of the reflected light. By comparing this third reference position with the first reference position acquired in advance based on the detection result of the reflected light, the center position of the image of the laser beam transferred to the entrance pupil plane of the condenser can be determined. It is possible to easily and accurately confirm whether or not the center position of the entrance pupil plane of the light section coincides with the center position.

According to the present invention, it is possible to easily and accurately check whether the center position of the image of the laser beam transferred to the entrance pupil plane of the light condensing unit matches the center position of the entrance pupil plane of the light condensing unit. It becomes possible to provide a laser processing device and a laser processing method that can perform the following steps.

FIG. 1 is a perspective view of a laser processing device according to an embodiment. FIG. 2 is a perspective view of an object attached to the support stand shown in FIG. 1; FIG. 2 is a plan view of the laser output section shown in FIG. 1. FIG. FIG. 2 is a perspective view of a laser output section and a laser condensing section shown in FIG. 1. FIG. FIG. 2 is a cross-sectional view of the laser condenser shown in FIG. 1. FIG. FIG. 6 is a cross-sectional view of the laser condenser section taken along the line VI-VI shown in FIG. 5. FIG. 7 is a cross-sectional view of the laser condenser section taken along the line VII-VII shown in FIG. 6. FIG. 6 is a cross-sectional view of the spatial light modulator shown in FIG. 5. FIG. 6 is a diagram showing the optical arrangement relationship of the spatial light modulator, the 4f lens unit, and the condensing lens unit shown in FIG. 5. FIG. 2 is a configuration diagram of main parts of the laser processing apparatus shown in FIG. 1. FIG. It is a figure showing the condensation state of the laser beam on a target object. It is a figure showing a point image image. FIG. 7 is a diagram showing a state where no image transfer position shift occurs. FIG. 6 is a diagram illustrating a state where an image transfer position shift occurs. It is a figure which shows the point image image for each display position of a phase pattern. It is a figure which shows the point image image for each display position of a phase pattern. It is a figure which shows the point image image for each display position of a phase pattern. It is a figure which shows the point image image for each display position of a phase pattern. 3 is a flowchart illustrating a method for setting a reference position based on a point image. 3 is a flowchart illustrating a method for setting a reference position based on a point image. 3 is a flowchart illustrating a method for setting a reference position based on a point image image and processing results. It is a figure which shows the processing result for each display position of a phase pattern. It is a figure which shows the processing result for each display position of a phase pattern. It is a figure which shows the processing result for each display position of a phase pattern. 3 is a flowchart illustrating a method for setting a reference position based on a point image image and processing results. 3 is a flowchart illustrating a method for setting a reference position based on a point image image and processing results.

Embodiments of the present invention will be described in detail below with reference to the drawings. In each figure, the same or corresponding parts are denoted by the same reference numerals, and redundant explanations will be omitted.
[Overall configuration of laser processing equipment]

As shown in FIG. 1, the laser processing apparatus 200 includes an apparatus frame 210, a first movement mechanism 220, a support stand (support part) 230, and a second movement mechanism 240. Further, the laser processing apparatus 200 includes a laser output section 300, a laser condensing section 400, and a control section 500. In the following description, directions perpendicular to each other in a horizontal plane will be referred to as the X direction and the Y direction, and the vertical direction will be referred to as the Z direction.

The first moving mechanism 220 is attached to the device frame 210. The first moving mechanism 220 includes 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 and 221b extending along the Y direction. The second rail unit 222 is attached to the pair of rails 221a and 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 and 222b extending along the X direction. The movable base 223 is attached to a pair of rails 222a and 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.

The support stand 230 is attached to the movable base 223. The support stand 230 supports the object 1. The object 1 is, for example, a matrix of a plurality of functional elements (a light receiving element such as a photodiode, a light emitting element such as a laser diode, or a circuit element formed as a circuit) on the front side of a substrate made of a semiconductor material such as silicon. It is a wafer formed into a shape. When the object 1 is supported on the support stand 230, as shown in FIG. ) is pasted. The support stand 230 supports the object 1 by holding the frame 11 with a clamp and sucking the film 12 with a vacuum chuck table. On the support base 230, a plurality of mutually parallel lines 5a and a plurality of mutually parallel lines 5b are set in a grid pattern on the object 1 so as to pass between adjacent functional elements. The plurality of lines 5a and the plurality of lines 5b are lines for cutting the object 1 into functional elements.

As shown in FIG. 1, the support stand 230 is moved along the Y direction by the operation of the second rail unit 222 in the first movement mechanism 220. Further, the support stand 230 is moved along the X direction by the movement of the movable base 223 in the first moving mechanism 220. Further, the support stand 230 is rotated about an axis parallel to the Z direction as the center line by the movement of the movable base 223 in the first moving mechanism 220. In this way, the support stand 230 is attached to the device frame 210 so as to be movable along the X and Y directions and rotatable about an axis parallel to the Z direction.

The laser output section 300 is attached to the device frame 210. The laser condenser 400 is attached to the device frame 210 via the second moving mechanism 240. The laser condenser 400 is moved along the Z direction by the operation of the second moving mechanism 240. In this way, the laser condensing section 400 is attached to the device frame 210 so as to be movable along the Z direction with respect to the laser output section 300.

The control unit 500 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The control section 500 controls each section of the laser processing apparatus 200.

As an example, in the laser processing apparatus 200, a modified region is formed inside the object 1 along each line 5a, 5b (see FIG. 2) as follows.

First, the object 1 is supported on the support stand 230 so that the back surface 10b (see FIG. 2) of the object 1 becomes the laser beam entrance surface, and each line 5a of the object 1 is aligned in a direction parallel to the X direction. It will be done. Next, the laser condenser 400 is moved by the second moving mechanism 240 so that the condensing point of the laser beam L is located inside the target object 1 at a predetermined distance from the laser beam incident surface of the target object 1. be moved. Subsequently, the focal point of the laser beam L is relatively moved along each line 5a while the distance between the laser beam incident surface of the object 1 and the focal point of the laser beam L is maintained constant. Thereby, a modified region is formed inside the object 1 along each line 5a.

When the formation of the modified region along each line 5a is completed, the support base 230 is rotated by the first moving mechanism 220, and each line 5b of the object 1 is aligned in a direction parallel to the X direction. Next, the laser condenser 400 is moved by the second moving mechanism 240 so that the condensing point of the laser beam L is located inside the target object 1 at a predetermined distance from the laser beam incident surface of the target object 1. be moved. Subsequently, the focal point of the laser beam L is relatively moved along each line 5b while the distance between the laser beam incident surface of the object 1 and the focal point of the laser beam L is maintained constant. Thereby, a modified region is formed inside the object 1 along each line 5b.

Thus, in the laser processing apparatus 200, the direction parallel to the X direction is the processing direction (scanning direction of the laser beam L). The relative movement of the focal point of the laser beam L along each line 5a and the relative movement of the focal point of the laser beam L along each line 5b are controlled by the first moving mechanism 220. This is performed by moving 230 along the X direction. Further, the relative movement of the focal point of the laser beam L between each line 5a and the relative movement of the focal point of the laser beam L between each line 5b is caused by the first moving mechanism 220 moving the support base 230. This is performed by moving along the Y direction.

As shown in FIG. 3, the laser output unit 300 includes a mounting base 301, a cover 302, and a plurality of mirrors 303 and 304. Further, the laser output unit 300 includes a laser oscillator (light source) 310, a shutter 320, a λ/2 wavelength plate unit 330, a polarizing plate unit 340, a beam expander 350, and a mirror unit 360. There is.

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

The cover 302 has a plurality of mirrors 303 and 304, a laser oscillator 310, a shutter 320, a λ/2 wavelength plate unit 330, a polarizing plate unit 340, a beam expander 350, and a mirror unit 360 on the main surface 301a of the mounting base 301. covered. The cover 302 is removable from the mounting base 301.

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

In the laser oscillator 310, the output of the laser beam L is switched ON/OFF as follows. When the laser oscillator 310 is composed of a solid-state laser, by switching ON/OFF of a Q switch (AOM (acousto-optic modulator), EOM (electro-optic modulator), etc.) provided in the resonator, The output of the laser beam L can be switched ON/OFF at high speed. When the laser oscillator 310 is composed of a fiber laser, the output of the laser beam L can be turned ON/OFF quickly by switching ON/OFF of the output of the semiconductor laser that constitutes the seed laser and the amplifier (pumping) laser. can be switched to When the laser oscillator 310 uses an external modulation element, the output of the laser beam L can be turned ON/OFF quickly by switching ON/OFF of the external modulation element (AOM, EOM, etc.) provided outside the resonator. can be switched to

The shutter 320 opens and closes the optical path of the laser beam L using a mechanical mechanism. As described above, switching ON/OFF of the output of the laser beam L from the laser output section 300 is performed by switching ON/OFF of the output of the laser beam L in the laser oscillator 310. This prevents, for example, the laser light L from being unexpectedly emitted from the laser output unit 300. The laser beam L that has passed through the shutter 320 is reflected by the mirror 304 and sequentially enters the λ/2 wavelength plate unit 330 and the polarizing plate unit 340 along the X direction.

The λ/2 wavelength plate unit 330 and the polarizing plate unit 340 function as an output adjustment section that adjusts the output (light intensity) of the laser beam L. Moreover, the λ/2 wavelength plate unit 330 and the polarizing plate unit 340 function as a polarization direction adjusting section that adjusts the polarization direction of the laser beam L. The laser light L that has sequentially passed through the λ/2 wavelength plate unit 330 and the polarizing plate unit 340 enters the beam expander 350 along the X direction.

The beam expander 350 collimates the laser beam L while adjusting the diameter of the laser beam L. The laser beam L that has passed through the beam expander 350 is incident on the mirror unit 360 along the X direction.

The mirror unit 360 includes a support base 361 and a plurality of mirrors 362 and 363. The support base 361 supports a plurality of mirrors 362 and 363. The support base 361 is attached to the mounting base 301 so that its position can be adjusted along the X direction and the Y direction. The mirror 362 reflects the laser beam 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 can be adjusted, for example, around an axis parallel to the Z direction. The mirror 363 reflects the laser beam 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 can be adjusted, for example, around an axis parallel to the X direction, and the position can be adjusted along the Y direction. The laser beam L reflected by the mirror 363 passes through an opening 361a formed in the support base 361, and enters the laser condenser 400 (see FIG. 1) along the Z direction. In other words, the direction in which the laser beam L is emitted by the laser output unit 300 matches the direction in which the laser condensing unit 400 moves. As described above, each mirror 362, 363 has a mechanism for adjusting the angle of the reflective surface. In the mirror unit 360, by adjusting the position of the support base 361 with respect to the mounting base 301, adjusting the position of the mirror 363 with respect to the support base 361, and adjusting the angle of the reflective surface of each mirror 362, 363, the light from the laser output section 300 is adjusted. The position and angle of the optical axis of the emitted laser beam L are aligned with respect to the laser condenser 400. That is, the plurality of mirrors 362 and 363 are configured to adjust the optical axis of the laser beam L emitted from the laser output section 300.

As shown in FIG. 4, the laser condenser 400 has a housing 401. As shown in FIG. The housing 401 has a rectangular parallelepiped shape whose longitudinal direction is the Y direction. A second moving mechanism 240 is attached to one side 401e of the housing 401 (see FIGS. 5 and 7). A cylindrical light entrance portion 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 incidence section 401a allows the laser light L emitted from the laser output section 300 to enter the housing 401. The mirror unit 360 and the light incidence section 401a are separated from each other by a distance that prevents them from coming into contact with each other when the laser condensing section 400 is moved along the Z direction by the second moving mechanism 240.

As shown in FIGS. 5 and 6, the laser condenser 400 includes a mirror 402 and a dichroic mirror 403. Further, the laser condensing section 400 includes a spatial light modulator 410, a 4f lens unit (imaging section) 420, a condensing lens unit (condensing section) 430, a drive mechanism 440, and a pair of distance measurement sensors 450. It has .

The mirror 402 is attached to the bottom surface 401b of the housing 401 so as to face the light incidence section 401a in the Z direction. The mirror 402 reflects the laser beam L that has entered the housing 401 through the light incidence section 401a in a direction parallel to the XY plane. The laser beam 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 beam L enters the mirror 402 as parallel light along the Z direction. Therefore, even if the laser condensing section 400 is moved along the Z direction by the second moving mechanism 240, the state of the laser light L incident on the mirror 402 along the Z direction is maintained constant. Laser light L reflected by mirror 402 enters spatial light modulator 410.

The spatial light modulator 410 is attached to the end 401c of the housing 401 in the Y direction, with the reflective surface 410a facing into the housing 401. The spatial light modulator 410 is, for example, a reflective liquid crystal (LCOS) spatial light modulator (SLM), and modulates the laser light L while reflecting the laser light L in the Y direction. do. The laser light L modulated and reflected by the spatial light modulator 410 enters the 4f lens unit 420 along the Y direction. Here, in a plane parallel to the XY plane, the angle α between 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 is: It is an acute angle (for example, 10 to 60 degrees). That is, the laser beam L is reflected at an acute angle along the XY plane at the spatial light modulator 410. This is to suppress the incident angle and reflection angle of the laser beam L to suppress a decrease in diffraction efficiency and to fully demonstrate the performance of the spatial light modulator 410. Note that in the spatial light modulator 410, the thickness of the light modulation layer using liquid crystal, for example, is extremely thin, on the order of several μm to several tens of μm. can be considered to be essentially the same.

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

The dichroic mirror 403 reflects a portion (for example, 95 to 99.5%) of the laser beam L in the Z direction, and transmits the remainder (for example, 0.5 to 5%) of the laser beam L along the Y direction. let A portion of the laser beam L is reflected by the dichroic mirror 403 at right angles along the YZ plane. The laser beam L reflected by the dichroic mirror 403 enters the condenser lens unit 430 along the Z direction.

The condensing lens unit 430 is attached to an end 401d (an end opposite to the end 401c) of the housing 401 in the Y direction via a drive mechanism 440. The condensing lens unit 430 includes a holder 431 and a plurality of lenses 432. The holder 431 holds a plurality of lenses 432. The plurality of lenses 432 converge the laser beam L onto the object 1 (see FIG. 1) supported by the support stand 230. The drive mechanism 440 moves the condenser lens unit 430 along the Z direction using the drive force of the piezoelectric element.

The pair of distance measuring sensors 450 are attached to the end portion 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 measurement sensor 450 emits distance measurement light (for example, a laser beam) to the laser beam entrance surface of the object 1 (see FIG. 1) supported by the support base 230, and Displacement data of the laser beam incident surface of the target object 1 is acquired by detecting the distance measuring light reflected by. Note that the distance measuring sensor 450 may be a triangular distance measuring method, a laser confocal method, a white confocal method, a spectral interference method, an astigmatism method, or the like.

In the laser processing apparatus 200, as described above, the direction parallel to the X direction is the processing direction (the scanning direction of the laser beam L). Therefore, when the focusing point of the laser beam L is relatively moved along each line 5a, 5b, the distance measuring sensor that precedes the focusing lens unit 430 among the pair of distance measuring sensors 450 The sensor 450 acquires displacement data of the laser beam incident surface of the object 1 along each line 5a, 5b. Then, the drive mechanism 440 focuses the light based on the displacement data acquired by the ranging sensor 450 so that the distance between the laser light incident surface of the target object 1 and the focus point of the laser light L is maintained constant. The lens unit 430 is moved along the Z direction.

The laser focusing unit 400 includes a beam splitter 461, a pair of lenses 462 and 463, and a profile acquisition camera 464. The beam splitter 461 separates the laser beam L transmitted through the dichroic mirror 403 into a reflected component and a transmitted component. The laser beam L reflected by the beam splitter 461 sequentially enters a pair of lenses 462 and 463 and a profile acquisition camera 464 along the Z direction. The pair of lenses 462 and 463 constitute a double-sided telecentric optical system in which the entrance pupil plane 430a of the condenser lens unit 430 and the imaging plane of the profile acquisition camera 464 are in an imaging relationship. Thereby, the image of the laser beam L on the entrance pupil plane 430a of the condensing lens unit 430 is transferred (imaged) onto the imaging plane of the profile acquisition camera 464. As described above, the image of the laser beam L at the entrance pupil plane 430a of the condenser lens unit 430 is the image of the laser beam L modulated by the spatial light modulator 410. Therefore, in the laser processing apparatus 200, the operating state of the spatial light modulator 410 can be grasped by monitoring the imaging result by the profile acquisition camera 464.

Further, the laser condenser 400 includes a beam splitter 471, a lens 472, and a camera 473 for monitoring the optical axis position. The beam splitter 471 separates the laser beam L transmitted through the beam splitter 461 into a reflected component and a transmitted component. The laser beam L reflected by the beam splitter 471 sequentially enters the lens 472 and the optical axis position monitoring camera 473 along the Z direction. The lens 472 focuses the incident laser light L onto the imaging surface of the optical axis position monitoring camera 473. In the laser processing apparatus 200, while monitoring the imaging results by the profile acquisition camera 464 and the optical axis position monitoring camera 473, the mirror unit 360 adjusts the position of the support base 361 relative to the mounting base 301, and adjusts the mirror relative to the support base 361. 363 and the angle of the reflective surfaces of each mirror 362 and 363 (see FIGS. 9 and 10), the deviation of the optical axis of the laser beam L incident on the condensing lens unit 430 (condensing It is possible to correct the positional deviation of the intensity distribution of the laser beam with respect to the lens unit 430 and the angular deviation of the optical axis of the laser beam L with respect to the condensing lens unit 430).

The plurality of beam splitters 461 and 471 are arranged in a cylinder 404 extending from an end 401d of the housing 401 along the Y direction. The pair of lenses 462 and 463 are arranged in a cylinder 405 that stands up on the cylinder 404 along the Z direction, and the profile acquisition camera 464 is arranged at the end of the cylinder 405. . The lens 472 is arranged in a cylinder 406 that stands up on the cylinder 404 along the Z direction, and the optical axis position monitoring camera 473 is arranged at the end of the cylinder 406. The cylindrical body 405 and the cylindrical body 406 are arranged in parallel with each other in the Y direction. Note that 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. .

As shown in FIGS. 6 and 7, the laser condenser 400 includes a visible light source 481, a plurality of lenses 482, a reticle 483, a mirror 484, a half mirror 485, a beam splitter 486, and a lens 487. , and an observation camera (photodetector) 488. The visible light source 481 emits visible light V along the Z direction. The plurality of lenses 482 collimate the visible light V emitted from the visible light source 481. The reticle 483 adds a reticle mark to the visible light V. The mirror 484 reflects the visible light V collimated by the plurality of 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 sequentially passes through the beam splitter 486 and the dichroic mirror 403 along the Z direction, and passes through the condensing lens unit 430 to the object 1 supported on the support base 230 (Fig. 1)).

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 condensing lens unit 430, and is transmitted through the dichroic mirror 403 along the Z direction. . The beam splitter 486 separates the visible light V transmitted 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 the lens 487 and the observation camera 488 along the Z direction. The lens 487 focuses the incident visible light V onto the imaging surface of the observation camera 488. In the laser processing apparatus 200, the state of the target object 1 can be grasped by observing the image taken by the observation camera 488.

The mirror 484, the half mirror 485, and the beam splitter 486 are arranged in a holder 407 attached to the end 401d of the housing 401. A plurality of lenses 482 and a reticle 483 are arranged in a cylinder 408 that stands up on the holder 407 along the Z direction, and a visible light source 481 is arranged at an end of the cylinder 408. The lens 487 is arranged in a cylinder 409 that stands up on the holder 407 along the Z direction, and the observation camera 488 is arranged at the end of the cylinder 409. The cylindrical body 408 and the cylindrical body 409 are arranged in parallel with each other in the X direction. Note that the visible light V transmitted through the half mirror 485 along the X direction and the visible light V reflected in the X direction by the beam splitter 486 are each absorbed by a damper or the like provided on the wall of the holder 407. Alternatively, it may be used for an appropriate purpose.

In the laser processing apparatus 200, it is assumed that the laser output section 300 will be replaced. This is because the wavelength of the laser beam L suitable for processing differs depending on the specifications of the object 1, processing conditions, etc. Therefore, a plurality of laser output units 300 are prepared in which the wavelengths of the laser beams L that are emitted are different from each other. Here, a laser output unit 300 whose wavelength of emitted laser light L is included in a wavelength band of 500 to 550 nm, a laser output unit 300 whose wavelength of emitted laser light L is included in a wavelength band of 1000 to 1150 nm, and a laser output unit 300 whose wavelength of emitted laser light L is included in a wavelength band of 1000 to 1150 nm, A laser output section 300 is prepared in which the wavelength of the laser beam L is included in the wavelength band of 1300 to 1400 nm.

On the other hand, in the laser processing apparatus 200, it is not assumed that the laser condensing section 400 will be replaced. This is because the laser focusing section 400 supports multiple wavelengths (corresponds to a plurality of wavelength bands that are not continuous with each other). 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, the lens 432 of the condenser lens unit 430, and the like are compatible with multiple wavelengths. Here, the laser condenser 400 corresponds to 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 condenser 400 so that the desired optical performance is satisfied, such as by coating each component of the laser condenser 400 with a predetermined dielectric multilayer film. Ru. Note that in the laser output section 300, the λ/2 wavelength plate unit 330 has a λ/2 wavelength plate, and the polarizing plate unit 340 has a polarizing plate. A λ/2 wavelength plate and a polarizing plate are optical elements that are highly wavelength dependent. Therefore, the λ/2 wavelength 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]

In the laser processing apparatus 200, the polarization direction of the laser beam L focused on the object 1 supported by the support base 230 is parallel to the X direction, as shown in FIG. (scanning direction of laser beam L). Here, in the spatial light modulator 410, the laser light L is reflected as P-polarized light. This means that when liquid crystal is used in the light modulation layer of the spatial light modulator 410, liquid crystal molecules occur in a plane parallel to the plane containing the optical axis of the laser beam L entering and exiting the spatial light modulator 410. This is because when the liquid crystal is oriented so that the polarization plane is tilted, the phase modulation is applied to the laser beam L while the rotation of the plane of polarization is suppressed. On the other hand, the dichroic mirror 403 reflects the laser beam L as S-polarized light. This is because the number of dielectric multilayer coatings required to make the dichroic mirror 403 compatible with multiple wavelengths is reduced by reflecting the laser beam L as S-polarized light rather than reflecting the laser beam L as P-polarized light, etc. This is because the design of the dichroic mirror 403 becomes easier.

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 4f lens unit 420 is set along the XY plane, and from the spatial light modulator 410 The optical path leading to the condensing lens unit 430 via the 4f lens unit 420 and the dichroic mirror 403 is set along the YZ plane.

As shown in FIG. 3, in the laser output unit 300, the optical path of the laser beam L is set 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 wavelength plate unit 330, the polarizing plate unit 340, and the beam expander 350 are in the X direction. 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 follow the Y direction.

Here, as shown in FIG. 5, the laser beam L that has traveled along the Z direction from the laser output section 300 to the laser condensing section 400 is reflected by the mirror 402 in a direction parallel to the XY plane, resulting in spatial light modulation. The light enters the vessel 410. At this time, in a plane parallel to the XY plane, 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 are at an acute angle. It forms α. On the other hand, as described above, in the laser output unit 300, the optical path of the laser beam L is set along the X direction or the Y direction.

Therefore, in the laser output section 300, the λ/2 wavelength plate unit 330 and the polarizing plate unit 340 are used not only as an output adjustment section that adjusts the output of the laser beam L, but also as a polarization direction adjustment section that adjusts the polarization direction of the laser beam L. It also needs to function as a department.
[Spatial light modulator]

As shown in FIG. 8, the spatial light modulator 410 includes 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 999a, a liquid crystal layer 216, and an alignment film 999a. A film 999b, a transparent conductive film 217, and a transparent substrate 218 such as a glass substrate are laminated in this order.

Transparent substrate 218 has a surface 218a that constitutes reflective surface 410a of spatial light modulator 410. The transparent substrate 218 is made of a light-transmitting material such as glass, and transmits the laser beam L of a predetermined wavelength incident from 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 (for example, ITO) that transmits the laser beam L.

A plurality of pixel electrodes 214 are arranged in a matrix on the silicon substrate 213 along the 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 according to the optical image to be output from the spatial light modulator 410.

The alignment films 999a and 999b are arranged 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 polymeric material such as polyimide, and the surfaces in contact with the liquid crystal layer 216 are subjected to a rubbing treatment or the like.

The liquid crystal layer 216 is arranged between the plurality of pixel electrodes 214 and the transparent conductive film 217, and modulates the laser light L according to the 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 electric field formed in the liquid crystal layer 216 is The alignment direction of the liquid crystal molecules 216a changes depending on the size of the liquid crystal molecules 216a. When the laser beam L passes through the transparent substrate 218 and the transparent conductive film 217 and enters the liquid crystal layer 216, the laser beam L is modulated by the liquid crystal molecules 216a while passing through the liquid crystal layer 216, and is reflected by the reflective film 215. After that, the light is modulated again by the liquid crystal layer 216 and emitted.

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

As described above, the pair of lenses 422 and 423 of the 4f lens unit 420 implements a double-sided telecentric optical system in which the reflective 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. It consists of 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 reflective 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 between the center of the lens 422 and the entrance pupil plane 430a of the condensing lens unit 430 is The distance of the optical path from the center is the sum of the first focal length f1 and the second focal length f2 (ie, f1+f2). Among the optical paths from the spatial light modulator 410 to the condensing lens unit 430, the optical path between the pair of lenses 422 and 423 is a straight line.

In the laser processing apparatus 200, from the viewpoint of increasing the effective diameter of the laser beam L at the reflective surface 410a of the spatial light modulator 410, the magnification M of the double-sided telecentric optical system satisfies 0.5<M<1 (reduction system). Satisfied. The larger the effective diameter of the laser beam L on the reflective 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 optical path of the laser beam L from the spatial light modulator 410 to the condensing lens unit 430 from becoming long, it is more preferable that 0.6≦M≦0.95. Here, (magnification M of the double-sided telecentric optical system) = (image size at the entrance pupil plane 430a of the condenser lens unit 430)/(object size at the reflective surface 410a of the spatial light modulator 410). be. In the case of the laser processing apparatus 200, the magnification M of the double-sided 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.

Note that from the viewpoint of reducing the effective diameter of the laser beam L at the reflective surface 410a of the spatial light modulator 410, the magnification M of the double-sided telecentric optical system may satisfy 1<M<2 (magnification system). The smaller the effective diameter of the laser beam L at the reflective surface 410a of the spatial light modulator 410, the smaller the magnification of the beam expander 350 (see FIG. 3), and the smaller the magnification of the beam expander 350 (see FIG. 3), the more the spatial light modulator The angle α (see FIG. 5) between 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 optical path of the laser beam L from the spatial light modulator 410 to the condensing lens unit 430 from becoming long, it is more preferable that 1.05≦M≦1.7.
[Main part configuration of laser processing equipment]

FIG. 10 is a configuration diagram of 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 stand (support part) 230, a laser oscillator (light source) 310, a spatial light modulator 410, a condensing lens unit (condensing part) 430, It includes a 4f lens unit (image transfer section) 420, an observation camera (photodetector) 488, a control section 500, and a display section 600. The support stand 230 supports the object 1 having a first surface 1a and a second surface 1b facing each other. Laser oscillator 310 emits laser light L. Spatial light modulator 410 modulates laser light L emitted from laser oscillator 310. The condensing lens unit 430 condenses the laser beam L modulated by the spatial light modulator 410 onto the object 1 from the first surface 1a side. The 4f lens unit 420 transfers the image of the laser beam L in the spatial light modulator 410 onto the entrance pupil plane 430a of the condenser lens unit 430. The observation camera 488 detects reflected light RL of the laser beam L that enters the object 1 from the first surface 1a side and is reflected by the second surface 1b. The control section 500 controls each section 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 result of the reflected light RL when checking a reference value, which will be described later.

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

The laser beam L emitted from the condensing lens unit 430 travels through the object 1 from the first surface 1a toward the second surface 1b, and is reflected at the second surface 1b. The reflected light RL of the laser beam L reflected by the second surface 1b travels through the object 1 from the second surface 1b toward the first surface 1a, and is emitted from the first surface 1a. The reflected light RL emitted from the first surface 1a passes through the dichroic mirror 403 and then enters the observation camera 488 via the lens 487.

In the present embodiment, the observation camera 488 captures a point image that is an image including a point image of the reflected light RL (also referred to as a beam spot, a focused spot, or a reflected image on the second surface 1b). Department. The observation camera 488 outputs the acquired point image to the control unit 500.

The control unit 500 controls the center position of the image of the laser beam L transferred onto the entrance pupil plane 430a in the When a point image is acquired by the observation camera 488 (when the reflected light is detected by the photodetector), ), the spatial light modulator 410 is controlled as follows. That is, the control unit 500 controls the condensation at the entrance pupil plane 430a so that the spherical aberration that occurs when the laser beam L travels through the object 1 by a predetermined distance d from the first surface 1a is corrected. The spatial light modulator 410 is configured such that coma aberration occurs in the Y direction (the direction of the optical axis of the condenser and the second direction intersecting the first direction) perpendicular to the optical axis of the lens unit 430 and perpendicular to the X direction. control.

The control unit 500 uses the observation camera 488 to check whether the center position of the image of the laser beam L transferred to the entrance pupil plane 430a matches the center position of the entrance pupil plane 430a in the Y direction. When a point image is acquired by , the spatial light modulator 410 is controlled as follows. That is, the control unit 500 adjusts the direction in the X direction at the entrance pupil plane 430a so that the spherical aberration that occurs when it is assumed that the laser beam L travels through the object 1 by a predetermined distance d from the first surface 1a is corrected. The spatial light modulator 410 is controlled so that coma aberration occurs.

Here, the predetermined distance d is a value larger 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 object 1 on the incident side of the laser beam L and the second surface 1b is the outer surface of the object 1 on the opposite side to the first surface 1a, The distance t between the first surface 1a and the second surface 1b corresponds to the thickness of the object 1. Here, the object 1 (for example, a silicon wafer having a thickness of about 775 μm) is used that has a thickness that allows sufficient spherical aberration to occur in the laser beam L focused by the focusing lens unit 430.

In the laser processing apparatus 200, checking whether the center position of the image of the laser beam L transferred onto the entrance pupil plane 430a matches the center position of the entrance pupil plane 430a (hereinafter referred to as "confirmation of the image transfer position") ) is carried out because if the center position of the image of the laser beam L transferred to the entrance pupil plane 430a deviates from the center position of the entrance pupil plane 430a, the desired processing quality may not be obtained. This is because there is. The control unit 500 periodically checks the image transfer position and adjusts the spatial light so that the center position of the image of the laser beam L transferred to the entrance pupil plane 430a matches the center position of the entrance pupil plane 430a. A reference position (hereinafter simply referred to as "reference position") that is a reference for the display position of the phase pattern in the modulator 410 is set. Details of the confirmation of the image transfer position will be described later.
[Principle related to setting the reference position]

Prior to explaining the confirmation of the image transfer position, the principle of setting the reference position will be explained. Note that the two-dimensional coordinate system indicating the display position of the phase pattern in the spatial light modulator 410 does not necessarily match the three-dimensional coordinate system indicating the spatial position of each part in the laser processing apparatus 200. However, in the following explanation, for convenience, the axis of the two-dimensional coordinate system that corresponds to the X-axis of the three-dimensional coordinate system will be regarded as the X-axis, and the two-dimensional coordinate system that corresponds to the Y-axis of the three-dimensional coordinate system will be referred to as the X-axis. Similarly, the axis of the system is considered to be the Y axis. The axis of the two-dimensional coordinate system that corresponds to the X-axis of the three-dimensional coordinate system means that when the phase pattern moves to the + side (or - side) along the direction parallel to the first axis of the two-dimensional coordinate system, , means the first axis when the "image of the laser beam L transferred to 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 that corresponds to the Y-axis of the three-dimensional coordinate system means that when the phase pattern moves to the + side (or - side) along the direction parallel to the second axis of the two-dimensional coordinate system, , means the second axis when the "image of the laser beam L transferred to the entrance pupil plane 430a" moves to the + side (or - side) along the Y direction of the three-dimensional coordinate system.

FIG. 11 is a diagram showing a condensing state of the laser beam L on the object 1. As shown in FIG. The condensing states shown in each of FIGS. 11(a), (b), and (c) are when the focal point of the condensing lens unit 430 is located on the second surface 1b. FIG. 12 is a diagram showing a point image image acquired by the observation camera 488. The point image images shown in (a), (b), and (c) of FIG. 12 were obtained in the focused states shown in (a), (b), and (c) of FIG. 11, respectively. It is something. In FIGS. 11(a) and 12(a), spherical aberration is not corrected by the spatial light modulator 410. In FIGS. 11(b) and 12(b), the laser beam L travels through the object 1 by a distance t (t is the distance between the first surface 1a and the second surface 1b) from the first surface 1a. The spatial light modulator 410 corrects the spherical aberration that would occur if this were the case. In (c) of FIG. 11 and (c) of FIG. 12, the spherical aberration that occurs when it is assumed that the laser beam L travels through the object 1 by a distance of 2t from the first surface 1a is It has been corrected.

As shown in FIG. 11(a), when the spherical aberration is not corrected by the spatial light modulator 410, the outer peripheral component of the laser beam L is focused in a deeper region than the inner peripheral component of the laser beam L. be done. As shown in FIG. 11(b), the spherical aberration that occurs when it is assumed that the laser beam L travels through the object 1 by a distance t from the first surface 1a is corrected by the spatial light modulator 410. If there is a laser beam L, all components of the laser beam L are focused on a region on the second surface 1b. Therefore, even if the reflected light RL that is reflected by the second surface 1b, travels further through the object 1, and is emitted from the first surface 1a is focused by the lens 487, it is not reflected on the imaging surface of the observation camera 488. It becomes blurry. As a result, as shown in FIGS. 12(a) and 12(b), it is not possible to confirm the point image of the reflected light RL having sufficient brightness and size in the images acquired by the observation camera 488. Can not.

On the other hand, as shown in FIG. 11(c), the spatial light modulator 410 corrects the spherical aberration that occurs when it is assumed that the laser beam L travels through the object 1 by a distance of 2t from the first surface 1a. If so, the outer circumferential component of the laser beam L is focused on a region shallower than the inner circumferential portion of the laser beam L. Therefore, when the reflected light RL that is reflected by the second surface 1b, further travels through the object 1, and is emitted from the first surface 1a is focused by the lens 487, it is reflected on the imaging surface of the observation camera 488. The light is focused on the area. As a result, as shown in FIG. 12C, in the image acquired by the observation camera 488, a point image of the reflected light RL having sufficient brightness and size can be confirmed.

FIG. 13 shows a state in which no image transfer position shift occurs (that is, a state in which the center position of the image of the laser beam L transferred to the entrance pupil plane 430a matches the center position of the entrance pupil plane 430a). It is a diagram. FIG. 14 is a diagram showing a state in which an image transfer position shift occurs (that is, a state in which the center position of the image of the laser beam L transferred to the entrance pupil plane 430a is shifted from the center position of the entrance pupil plane 430a). It is.

As shown in FIG. 13, in a state where 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 is aligned with the center position C2 of the entrance pupil plane 430a. We are doing so. 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.

On the other hand, as shown in FIG. 14, in a state where an image transfer position shift has occurred, the center position C1 of the image 39 of the laser beam L transferred onto the entrance pupil plane 430a is changed from the center position C2 of the entrance pupil plane 430a. It's off. 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 with the center position C3 of the phase pattern 9 shifted from the optical axis center C4 of the liquid crystal layer 216, which is the reference position, the phase pattern 9 is shifted to the entrance pupil plane 430a. The center position C1 of the image 39 of the laser beam L is shifted from the center position C2 of the entrance pupil plane 430a, and unintended coma aberration occurs. For example, if the center position C3 of the phase pattern 9 deviates from the optical axis center C4 of the liquid crystal layer 216 by one pixel, that is, by one pixel electrode 214 (see FIG. 8), an image transfer position deviation of about 20 μm will occur. This may affect processing quality.

FIG. 15 is a diagram showing a point image image for each display position of a phase pattern. The point image G0 is a point image obtained when displayed on the liquid crystal layer 216 with the center position of the phase pattern matching the reference position. The point image G1 is a point image image obtained when the center position of the phase pattern is displayed on the liquid crystal layer 216 with a shift of one pixel from the reference position to the − side along the X direction. The point image G2 is a point image obtained when the center position of the phase pattern is displayed on the liquid crystal layer 216 in a state shifted from the reference position by one pixel in the + direction along the X direction. The point image G3 is a point image obtained when the center position of the phase pattern is displayed on the liquid crystal layer 216 with a shift of one pixel from the reference position to the − side along the Y direction. The point image G4 is a point image image obtained when the center position of the phase pattern is displayed on the liquid crystal layer 216 with a shift of one pixel from the reference position to the + side along the Y direction. In other words, the point image G0 is a point image image obtained in a state where no image transfer position shift has occurred, and the point image images G1, G2, G3, and G4 are obtained in a state where an image transfer position shift has occurred. This is a point image image.

As shown in FIG. 15, in the point images G1, G2, G3, and G4 acquired with image transfer position deviation, the point images are rotationally symmetrical due to the occurrence of unintended comatic aberration. It is not an optical image. For example, in the point images G1, G2, G3, and G4, the point images are eccentric, an arc-shaped image EZ is formed on the outside, and some parts are more blurred than other parts in the circumferential direction. On the other hand, in the point image G0 acquired in a state where no image transfer position shift has occurred, the point image is a rotationally symmetrical optical image.

Note that rotational symmetry means symmetry in which when rotated by 360/n° (n is an integer of 2 or more) around a certain point, the object overlaps itself. The rotationally symmetrical point image includes not only a completely rotationally symmetrical point image but also a substantially rotationally symmetrical point image. The rotationally symmetrical point image includes a point image that is not eccentric, a point image that does not have an arc-shaped image EZ on the outer circumferential side, a point image that is not blurred in one part more than the other part in the circumferential direction, and at least any of these. It is a point image that includes

FIG. 16 is a diagram showing a point image image (another example from FIG. 15) for each display position of the phase pattern. Among the numbers in the X direction shown in FIG. 16, "0" represents that the center position of the phase pattern matches the reference position in the X direction, and "-2", "-1", and "1" , "2" means that the center position of the phase pattern is "2 pixels on the - side", "1 pixel on the - side", "1 pixel on the + side", "2 pixels on the + side" from the reference position in the X direction. This indicates that the image is shifted by 1 pixel. Among the numbers in the Y direction shown in FIG. 16, "0" represents that the center position of the phase pattern matches the reference position in the Y direction, and "-2", "-1", and "1" , "2" means that the center position of the phase pattern is "2 pixels on the - side", "1 pixel on the - side", "1 pixel on the + side", "2 pixels on the + side" from the reference position in the Y direction. This indicates that the image is shifted by 1 pixel. FIG. 16 shows a point image in a state where no image transfer position deviation has occurred, a point image in a state where an image transfer position deviation has occurred only in the X direction from a state where no image transfer position deviation has occurred, and an image transfer A point image is shown in a state where the image transfer position has shifted only in the Y direction from a state where no position shift has occurred.

As shown in FIG. 16, the point image in a state where no image transfer position shift occurs in either the X direction or the Y direction is a rotationally symmetrical optical image. On the other hand, a point image in a state where an image transfer position shift occurs in the X direction or the Y direction is not a rotationally symmetric optical image. Furthermore, the larger the amount of deviation of the center position of the phase pattern from the reference position (that is, the larger the amount of deviation of the image transfer position), the larger the deviation from the optical image of the rotation target becomes.
[Checking the image transfer position]

Based on the principle of setting the reference position described above, the laser processing apparatus 200 confirms the image transfer position (that is, the center position of the image of the laser beam L transferred to the entrance pupil plane 430a is the center of the entrance pupil plane 430a). (confirmation of whether or not the position matches) is performed. Hereinafter, confirmation of the image transfer position will be explained in detail.

As described above, the control unit 500 checks whether the center position of the image of the laser beam L transferred onto the entrance pupil plane 430a matches the center position of the entrance pupil plane 430a in the Y direction. , so that the spherical aberration that occurs when it is assumed that the laser beam L travels through the object 1 by a predetermined distance d from the first surface 1a when a point image is acquired by the observation camera 488 is corrected. The spatial light modulator 410 is controlled so that coma aberration occurs in the X direction at the entrance pupil plane 430a. In addition, the control unit 500 also controls the observation When a point image is acquired by the camera 488, the spherical aberration that occurs when it is assumed that the laser beam L has traveled through the object 1 by a predetermined distance d from the first surface 1a is corrected, and the incident The spatial light modulator 410 is controlled so that coma aberration occurs in the Y direction on the pupil plane 430a.

Spherical aberration that occurs when the laser beam L travels through the object 1 by a predetermined distance d from the first surface 1a is corrected, and coma aberration occurs in the X direction at the entrance pupil surface 430a. When the spatial light modulator 410 is controlled, as shown in FIG. 17, a point image of the reflected light RL clearly appears and a fan-shaped image clearly appears on one side in the X direction. In the "point image image shown in the center of FIG. 17" acquired when the center position of the image of the laser beam L coincides with the center position of the entrance pupil plane 430a in the Y direction, the fan-shaped image is symmetrical with respect to the X direction. (In other words, line symmetry with respect to a straight line parallel to the X direction). In the "point image image shown in the upper part of FIG. 17" obtained when the center position of the image of the laser beam L is shifted to the + side from the center position of the entrance pupil plane 430a in the Y direction, the fan-shaped image is It is tilted to one side in the direction and is not symmetrical with respect to the X direction. In the "point image shown in the lower part of FIG. 17" obtained when the center position of the image of the laser beam L is shifted from the center position of the entrance pupil plane 430a to the - side in the Y direction, the fan-shaped image is It 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 appearing on one side in the X direction makes it easy to confirm whether the center position of the image of the laser beam L matches the center position of the entrance pupil plane 430a in the Y direction. Therefore, coma aberration in the X direction is added when checking the image transfer position shift in the Y direction.

Spherical aberration that occurs when the laser beam L travels through the object 1 by a predetermined distance d from the first surface 1a is corrected, and coma aberration occurs in the Y direction at the entrance pupil surface 430a. When the spatial light modulator 410 is controlled, as shown in FIG. 18, a point image of the reflected light RL clearly appears, and a fan-shaped image clearly appears on one side in the Y direction. In the "point image image shown in the center of FIG. 18" obtained when the center position of the image of the laser beam L coincides with the center position of the entrance pupil plane 430a in the X direction, the fan-shaped image is symmetrical with respect to the Y direction. (In other words, line symmetry with respect to a straight line parallel to the Y direction). In the "point image image shown on the right side of FIG. 18" obtained when the center position of the image of the laser beam L is shifted to the + side from the center position of the entrance pupil plane 430a in the X direction, the fan-shaped image is It is tilted to one side in the direction and is not symmetrical with respect to the Y direction. In the "point image image shown on the left side of FIG. 18" obtained when the center position of the image of the laser beam L is shifted from the center position of the entrance pupil plane 430a to the - side in the X direction, the fan-shaped image is It is tilted to the other side in the direction and is not symmetrical with respect to the Y direction. As described above, the fan-shaped image appearing on one side in the Y direction makes it easy to confirm whether the center position of the image of the laser beam L matches the center position of the entrance pupil plane 430a in the X direction. Therefore, comatic aberration in the Y direction is added when checking the image transfer position shift in the X direction.
[Method of setting reference position based on point image]

A "method for setting a reference position based on a point image image", which is a laser processing method of an embodiment carried out in the laser processing apparatus 200, will be described with reference to FIGS. 10, 19, and 20. 19 and 20 are flowcharts showing a method for setting a reference position based on a point image image.

First, the object 1 is set on the support stand 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 surfaces and whose resistivity is 1 Ω·cm or more. Subsequently, the support base 230 is moved in the X direction and the Y direction so that the condenser lens unit 430 faces the object 1 in the Z direction (step S02). The movement of the support base 230 in the X direction and the Y direction is carried out by the control of the first movement mechanism 220 (see FIG. 1) by the control unit 500. Subsequently, the condenser lens unit 430 is moved in the Z direction so that the focal point of the condenser lens unit 430 is located on the second surface 1b of the object 1 (step S03). The movement of the condensing lens unit 430 in the Z direction is carried out by the control of the second movement mechanism 240 (see FIG. 1) by the control section 500.

Subsequently, the control unit 500 causes the spatial light modulator 410 to display the spherical aberration correction pattern (step S04), and further causes the spatial light modulator 410 to display the X-direction coma aberration imparting pattern (step S05). The spherical aberration correction pattern is a phase pattern for correcting spherical aberration that occurs when it is assumed that the laser beam L travels through the object 1 by a predetermined distance d from the first surface 1a. The X-direction coma aberration imparting pattern is a phase pattern for generating coma aberration in the X direction on the entrance pupil plane 430a. Next, while the spatial light modulator 410 is displaying the spherical aberration correction pattern and the X-direction coma aberration imparting pattern, the laser oscillator 310 emits the laser beam L and the object 1 is irradiated with the laser beam L, A point image of the reflected light RL is acquired by the observation camera 488 (step S06). At this time, the output of the laser beam L that does not cause ablation on the object 1 may be set in advance, or the output of the laser beam L may be adjusted so that no ablation occurs on the object 1. good.

Subsequently, the control unit 500 determines whether or not the center position of the image of the laser beam L transferred onto the entrance pupil plane 430a matches the center position of the entrance pupil plane 430a in the Y direction, based on the point of the reflected light RL. The determination is made based on the image (detection result of 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 "point image shown in the center of FIG. 17"), the control unit 500 controls the It is determined that the center position of the image coincides with the center position of the entrance pupil plane 430a in the Y direction, and if the fan-shaped image is not symmetrical with respect to the X direction ("the point image shown in the upper part of FIG. 17" and " 17), it is determined that the center position of the image of the laser beam L is shifted from the center position of the entrance pupil plane 430a in the Y direction. Note that whether or not the fan-shaped image is symmetrical with respect to the X direction may be recognized, for example, by a geometric method or by known image recognition processing such as pattern recognition.

As described above, in the reference position setting method based on a point image image, observation is performed to check whether the center position of the image of the laser beam L matches the center position of the entrance pupil plane 430a in the Y direction. When a point image of the reflected light RL is acquired by the camera 488, the spherical aberration that occurs when it is assumed that the laser light L has traveled through the object 1 by a predetermined distance d from the first surface 1a is corrected. The spatial light modulator 410 is controlled so that coma aberration occurs in the X direction at the entrance pupil plane 430a.

As a result of the determination in step S07, if the center position of the image of the laser beam L coincides with the center position of the entrance pupil plane 430a in the Y direction, the control unit 500, in this case, the spatial light modulator 410 The Y value of the phase pattern (the coordinate of the second reference position of the second phase pattern in the direction corresponding to the second direction) is stored as the Y value of the reference position (the second coordinate of the reference position) (step S08). . The Y value of the phase pattern is determined by the reference position (second phase pattern) used as a reference when the spherical aberration correction pattern, the 2 reference position)” is the “coordinate in the Y direction”. The Y value of the reference position is the "coordinate in the Y direction (second coordinate)" of the "reference position used as a reference when the phase pattern for processing of the object 1 is displayed."

As a result of the determination in step S07, if the center position of the image of the laser beam L is shifted from the center position of the entrance pupil plane 430a in the Y direction, the control unit 500 controls the phase of the image displayed by the spatial light modulator 410. The Y value of the pattern is shifted (step S09), and steps S06 and S07 are repeated until it is determined that the center position of the image of the laser beam L coincides with the center position of the entrance pupil plane 430a in the Y direction. It will be done.

Following step S08, the control unit 500 causes the spatial light modulator 410 to display a coma aberration imparting pattern in the Y direction instead of the pattern imparting coma aberration in the X direction (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 comatic aberration imparting pattern, the laser oscillator 310 emits the laser beam L and the object 1 is irradiated with the laser beam L, A point image of the reflected light RL is acquired by the observation camera 488 (step S12). At this time, the output of the laser beam L that does not cause ablation on the object 1 may be set in advance, or the output of the laser beam L may be adjusted so that no ablation occurs on the object 1. good.

Subsequently, the control unit 500 determines whether or not the center position of the image of the laser beam L transferred to the entrance pupil plane 430a matches the center position of the entrance pupil plane 430a in the X direction by checking the point of the reflected light RL. The determination is made based on the image (detection result of 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 "point image shown in the center of FIG. 18"), the control unit 500 controls the point image of the laser beam L. It is determined that the center position of the image coincides with the center position of the entrance pupil plane 430a in the X direction, and if the fan-shaped image is not symmetrical in the Y direction ("the point image shown on the right side of FIG. 18" and " 18), it is determined that the center position of the image of the laser beam L is shifted from the center position of the entrance pupil plane 430a in the X direction. Note that whether or not the fan-shaped image is symmetrical with respect to the Y direction may be recognized, for example, by a geometric method or by known image recognition processing such as pattern recognition.

As described above, in the reference position setting method based on a point image image, in order to check whether the center position of the image of the laser beam L matches the center position of the entrance pupil plane 430a in the X direction, observation is performed. When a point image of the reflected light RL is acquired by the camera 488, the spherical aberration that occurs when it is assumed that the laser light L has traveled through the object 1 by a predetermined distance d from the first surface 1a is corrected. The spatial light modulator 410 is controlled so that coma aberration occurs in the Y direction at the entrance pupil plane 430a.

As a result of the determination in step S13, if the center position of the image of the laser beam L coincides with the center position of the entrance pupil plane 430a in the X direction, the control unit 500, in this case, the spatial light modulator 410 The X value of the phase pattern (the coordinate of the first reference position of the first phase pattern in the direction corresponding to the first direction) is stored as the X value of the reference position (the first coordinate of the reference position) (step S14). . The X value of the phase pattern is determined by the reference position (the first 1 reference position)” is the “coordinate in the Y direction”. The X value of the reference position is the "coordinate in the X direction (first coordinate)" of the "reference position used as a reference when the phase pattern for processing of the object 1 is displayed."

As a result of the determination in step S13, if the center position of the image of the laser beam L is shifted from the center position of the entrance pupil plane 430a in the X direction, the control unit 500 controls the phase The X value of the pattern is shifted (step S15), and steps S12 and S13 are repeated until it is determined that the center position of the image of the laser beam L coincides with the center position of the entrance pupil plane 430a in the X direction. It will be done.

As described above, in the laser processing apparatus 200, the observation camera 488 detects the reflected light RL of the laser beam L that enters the object 1 from the first surface 1a side and is reflected by the second surface 1b. At this time, the spherical aberration that occurs when it is assumed that the laser beam L travels through the object 1 by a predetermined distance d from the first surface 1a is corrected, and at the entrance pupil surface 430a of the condensing lens unit 430. Spatial light modulator 410 is controlled so that coma aberration occurs in the Y direction. As a result, the case where the center position of the image of the laser beam L transferred to the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a in the X direction, and the case where the center position of the image of the laser beam L transferred to the entrance pupil plane 430a, and A significant difference appears in the point image of the reflected light RL depending on the case where the center position of the image of L is shifted from the center position of the entrance pupil plane 430a in the X direction. Therefore, it is possible to easily and accurately confirm whether or not 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.

In the laser processing apparatus 200, the observation camera 488 detects reflected light RL of the laser beam L that enters the object 1 from the first surface 1a side and is reflected by the second surface 1b. At this time, the spherical aberration that occurs when it is assumed that the laser beam L travels through the object 1 by a predetermined distance d from the first surface 1a is corrected, and at the entrance pupil surface 430a of the condensing lens unit 430. Spatial light modulator 410 is controlled so that coma aberration occurs in the X direction. Thereby, the case where the center position of the image of the laser beam L transferred to the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a in the Y direction, and the case where the center position of the image of the laser beam L transferred to the entrance pupil plane 430a, A significant difference appears in the point image of the reflected light RL when the center position of the image of L is shifted from the center position of the entrance pupil plane 430a in the Y direction. Therefore, it is possible to easily and accurately confirm whether or not 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.

In the laser processing apparatus 200, the control unit 500 determines whether the center position of the image of the laser beam L transferred to the entrance pupil plane 430a is the center position of the entrance pupil plane 430a in the X direction based on the point image of the reflected light RL. Determine whether it matches. Thereby, it is possible to automatically determine whether the center position of the image of the laser beam L transferred onto the entrance pupil plane 430a matches the center position of the entrance pupil plane 430a in the X direction.

In the laser processing apparatus 200, the control unit 500 determines, based on the point image of the reflected light RL, that the center position of the image of the laser beam L transferred onto the entrance pupil plane 430a is the center position of the entrance pupil plane 430a in the Y direction. Determine whether it matches. Thereby, it is possible to automatically determine whether the center position of the image of the laser beam L transferred onto the entrance pupil plane 430a matches the center position of the entrance pupil plane 430a in the Y direction.

In the laser processing apparatus 200, the control unit 500 controls the spatial light modulator when 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. 410 acquires information regarding the phase pattern displayed, and stores the coordinates of the reference position of the phase pattern in the X direction as the coordinates of the reference position in the X direction. When processing the object 1, by displaying a phase pattern on the spatial light modulator 410 using the coordinates as a reference in the X direction, the center position of the image of the laser beam L transferred to the entrance pupil plane 430a can be adjusted in the X direction. The object 1 can be processed while being aligned with the center position of the entrance pupil plane 430a.

In the laser processing apparatus 200, the control unit 500 controls the spatial light modulator when 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. 410 acquires information regarding the phase pattern displayed, and stores the coordinates of the reference position of the phase pattern in the Y direction as the coordinates of the reference position in the Y direction. When processing the object 1, by displaying a phase pattern on the spatial light modulator 410 using the coordinates as a reference in the Y direction, the center position of the image of the laser beam L transferred to the entrance pupil plane 430a can be adjusted in the Y direction. The object 1 can be processed while being aligned with the center position of the entrance pupil plane 430a.

In the laser processing apparatus 200, the control unit 500 checks whether the center position of the image of the laser beam L transferred to the entrance pupil plane 430a matches the center position of the entrance pupil plane 430a in the X direction. In addition, a spherical aberration correction pattern for correcting spherical aberration when a point image of reflected light RL is acquired by the observation camera 488, and a coma for generating coma aberration in the Y direction at the entrance pupil surface 430a. The aberration imparting pattern is displayed on the spatial light modulator 410. This reliably corrects the spherical aberration that occurs when it is assumed that the laser beam L travels through the object 1 by a predetermined distance d from the first surface 1a, and also Comatic aberration can be reliably generated in the Y direction.

In the laser processing apparatus 200, the control unit 500 checks whether the center position of the image of the laser beam L transferred to the entrance pupil plane 430a matches the center position of the entrance pupil plane 430a in the Y direction. A spherical aberration correction pattern for correcting spherical aberration when a point image of the reflected light RL is acquired by the observation camera 488, and a coma for generating coma aberration in the X direction at the entrance pupil surface 430a. The aberration imparting pattern is displayed on the spatial light modulator 410. This reliably corrects the spherical aberration that occurs when it is assumed that the laser beam L travels through the object 1 by a predetermined distance d from the first surface 1a, and also Comatic aberration can be reliably generated in the X direction.

In the laser processing device 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. . Thereby, the influence of spherical aberration imparted to the point image of the reflected light RL can be appropriately suppressed. As described above, coma aberration is generated in the Y direction, so that the center position of the image of the laser beam L transferred to the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a in the X direction. , and when the center position of the image of the laser beam L transferred to the entrance pupil plane 430a is shifted from the center position of the entrance pupil plane 430a in the X direction, there is a noticeable difference in the point image of the reflected light RL. The difference appears. Therefore, even if the predetermined distance d is not set so as to satisfy (2t-0.1t)≦d≦(2t+0.1t), the center position of the image of the laser beam L transferred to the entrance pupil plane 430a is In some cases, it may be possible to confirm whether or not the direction coincides with the center position of the entrance pupil plane 430a. Similarly, when comatic aberration is generated in the X direction, the center position of the image of the laser beam L transferred to the entrance pupil plane 430a coincides with the center position of the entrance pupil plane 430a in the Y direction. A significant difference appears in the point image of the reflected light RL when the center position of the image of the laser beam L transferred to 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), the center position of the image of the laser beam L transferred to the entrance pupil plane 430a is Y In some cases, it may be possible to confirm whether or not the direction coincides with the center position of the entrance pupil plane 430a.

In the laser processing apparatus 200, the display unit 600 displays a point image of the reflected light RL. Thereby, the point image of the reflected light RL can be reported to the operator.

According to the laser processing method carried out in the laser processing apparatus 200, as described above, the center position of the image of the laser beam L transferred to the entrance pupil plane 430a is aligned with the center position of the entrance pupil plane 430a in the X direction. It is possible to easily and accurately check whether the Furthermore, the 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.

According to the laser processing method implemented in the laser processing apparatus 200, as described above, the center position of the image of the laser beam L transferred to the entrance pupil plane 430a is aligned with the center position of the entrance pupil plane 430a in the Y direction. It is possible to easily and accurately check whether the Furthermore, the 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.

In the laser processing apparatus 200, the control unit 500 checks whether the center position of the image of the laser beam L transferred to the entrance pupil plane 430a matches the center position of the entrance pupil plane 430a in the X direction. In addition, when a point image of reflected light RL is acquired by observation camera 488, a spherical aberration correction pattern for correcting spherical aberration is created such that comatic aberration occurs in the Y direction at entrance pupil surface 430a. It may also be displayed on the spatial light modulator 410. According to this, the spherical aberration that occurs when it is assumed that the laser beam L travels through the object 1 by a predetermined distance d from the first surface 1a can be reliably corrected, and the entrance pupil surface of the condensing lens unit 430 can be corrected. 430a, it is possible to reliably generate coma aberration in the Y direction. As an example, the control unit 500 causes the spatial light modulator 410 to display a 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 greater than the shift amount in step S15 and smaller than the amount by which it deviates from the viewing angle of the observation camera 488.

In the laser processing apparatus 200, the control unit 500 checks whether the center position of the image of the laser beam L transferred to the entrance pupil plane 430a matches the center position of the entrance pupil plane 430a in the Y direction. In addition, when a point image of the reflected light RL is acquired by the observation camera 488, a spherical aberration correction pattern for correcting spherical aberration is created such that coma aberration occurs in the X direction at the entrance pupil surface 430a. It may also be displayed on the spatial light modulator 410. According to this, the spherical aberration that occurs when it is assumed that the laser beam L travels through the object 1 by a predetermined distance d from the first surface 1a can be reliably corrected, and the entrance pupil surface of the condensing lens unit 430 can be corrected. 430a, it is possible to reliably generate coma aberration in the X direction. As an example, the control unit 500 causes the spatial light modulator 410 to display a 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 greater than the shift amount in step S09 and smaller than the amount by which it deviates from the viewing angle of the observation camera 488.
[Method of setting reference position based on point image image and processing results]

A "method for setting a reference position based on a point image and a processing result" which is a laser processing method of one embodiment implemented in the laser processing apparatus 200 will be described. The method for setting the reference position based on the point image and processing results is laser processing in which the reference position is set so that the center position of the laser beam image transferred to the entrance pupil plane matches the center position of the entrance pupil plane. It's a method.

The setting method (setting process) of the reference position based on the point image and the processing result is to set the reference position (first reference position) P1 based on the point image of the reflected light RL and the reference position (first reference position) based on the processing result of the object 1. 2) a step (processing) of acquiring the reference position P2 (reference position); and a step of displaying a phase pattern on the spatial light modulator 410 with reference to the reference position P2 based on the processing results of the object 1 during “processing of the object 1”. (processing). These steps will be described below with reference to FIGS. 10 and 21. FIG. 21 is a flowchart showing a method for setting a reference position based on a point image and processing results.

First, the object 1 is set on the support stand 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 surfaces and whose resistivity is 1 Ω·cm or more. Subsequently, the support base 230 is moved in the X direction and the Y direction so that the condenser lens unit 430 faces the object 1 in the Z direction (step S22). The movement of the support base 230 in the X direction and the Y direction is carried out by the control of the first movement mechanism 220 (see FIG. 1) by the control unit 500. Subsequently, the condenser lens unit 430 is moved in the Z direction so that the focal point of the condenser lens unit 430 is located on the second surface 1b of the object 1 (step S23). The movement of the condensing lens unit 430 in the Z direction is carried out by the control of the second movement mechanism 240 (see FIG. 1) by the control section 500.

Subsequently, the control unit 500 acquires the X value and 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 Y value of the reference position P1 based on the point image of the reflected light RL is performed by the "method for setting the reference position based on the point image" shown in FIGS. 19 and 20.

Note that the method of 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, assume that the control unit 500 assumes that the laser beam L has traveled through the object 1 by a predetermined distance d from the first surface 1a in order to obtain the X value of the reference position P1 based on the point image of the reflected light RL. It is not necessary to control the spatial light modulator 410 so that the spherical aberration that occurs in this case is corrected, and to control the spatial light modulator 410 so that coma aberration occurs in the Y direction at the entrance pupil plane 430a. Similarly, in order to obtain the Y value of the reference position P1 based on the point image of the reflected light RL, the control unit 500 assumes that the laser light L has traveled through the object 1 by a predetermined distance d from the first surface 1a. It is not necessary to control the spatial light modulator 410 so that the spherical aberration that occurs in the hypothetical case is corrected, and to not control the spatial light modulator 410 so that coma aberration occurs in the X direction at the entrance pupil plane 430a. . Further, in order to obtain the X value and Y value of the reference position P1 based on the detection result of the reflected light RL, the control unit 500 causes the spatial light modulator 410 to display an axicon pattern as a phase pattern, and in this state, The condensing lens unit 430 may be moved along the Z direction. In that case, if the center position of the image of the laser beam L transferred to the entrance pupil plane 430a matches the center position of the entrance pupil plane 430a, the laser beam L reflected by the first surface 1a of the object 1 The center of the image of the reflected light RL does not move. On the other hand, if the center position of the image of the laser beam L transferred to the entrance pupil plane 430a is shifted from the center position of the entrance pupil plane 430a, the reflection of the laser beam L reflected by the first surface 1a of the object 1 The center of the image of the light RL moves. As described above, the reference position P1 based on the point image of the reflected light RL can be specified based on the detection result of the reflected light RL of the laser beam L reflected by the object 1.

Subsequently, the control unit 500 acquires the X value and Y value of the reference position P2 based on the processing result of the target 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 obtains the reference position P2 based on the processing result of the object 1. When acquiring the X value and Y value of the reference position P2 based on the processing result of the target object 1, the target object 1 may be replaced as necessary. As an example, as shown in FIGS. 22, 23, and 24, by forming a modified region inside the object 1 and observing the processing state of the object 1, the processing results of the object 1 can be The X value and Y value of the base reference position P2 are acquired.

FIG. 22(a) shows a state in which the center position of the image of the laser beam L is shifted by one pixel to the + side from the center position of the entrance pupil plane 430a in the Y direction, and the direction parallel to the X direction is the processing direction ( 2 is a "cross-sectional view perpendicular to the X direction" of the object 1 processed in the scanning direction of the laser beam L. FIG. In FIG. 22(b), processing was performed with the center position of the image of the laser beam L coinciding with the center position of the entrance pupil plane 430a in the Y direction, with the processing direction parallel to the X direction. It is a "cross-sectional view perpendicular to the X direction" of the object 1. FIG. 22(c) shows a state in which the center position of the image of the laser beam L is shifted from the center position of the entrance pupil plane 430a by one pixel to the - side in the Y direction, and the processing direction is parallel to the X direction. It is a "cross-sectional view perpendicular to the X direction" of the object 1 that has been processed. 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 changes 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 FIG. 22(b) is obtained to the reference position. Obtain as the X value and Y value of P2.

In (a) of FIG. 23, the center position of the image of the laser beam L is shifted by one pixel to the + side from the center position of the entrance pupil plane 430a in the Y direction, and the processing direction is parallel to the X direction. It is a "view of a cut plane parallel to the X direction" of the object 1 that has been processed. FIG. 23(b) shows that processing was performed with the center position of the image of the laser beam L coinciding with the center position of the entrance pupil plane 430a in the Y direction, with the processing direction parallel to the X direction. It is a "view of a cut plane parallel to the X direction" of the object 1. FIG. 23(c) shows a state in which the center position of the image of the laser beam L is shifted from the center position of the entrance pupil plane 430a by one pixel to the - side in the Y direction, and the processing direction is parallel to the X direction. It is a "view of a cut plane parallel to the X direction" of the object 1 that has been processed. The cut plane shown in FIG. 23(b) extends along the thickness direction (ZX plane) of the object 1, compared to the cut planes shown in FIGS. 23(a) and (c). In this case, the control unit 500 changes 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 FIG. 23(b) is obtained to the reference position. Obtain as the X value and Y value of P2.

In (a) of FIG. 24, the center position of the image of the laser beam L is shifted by one pixel to the + side from the center position of the entrance pupil plane 430a in the Y direction, and the processing direction is parallel to the X direction. It is a "view of the outer surface on the side opposite to the laser beam incident side" of the object 1 that has been processed. In FIG. 24(b), processing was performed with the center position of the image of the laser beam L coinciding with the center position of the entrance pupil plane 430a in the Y direction, with the processing direction parallel to the X direction. This is a "view of the outer surface of the object 1 on the side opposite to the laser beam incident side." FIG. 24(c) shows a state in which the center position of the image of the laser beam L is shifted from the center position of the entrance pupil plane 430a by one pixel to the - side in the Y direction, and the processing direction is parallel to the X direction. It is a "view of the outer surface on the side opposite to the laser beam incident side" of the object 1 that has been processed. The machining 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, compared to the machining marks shown in FIGS. 24(a) and (c). . In this case, the control unit 500 changes 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 FIG. 24(b) is obtained to the reference position. Obtain as the X value and Y value of P2.

Note that the method of acquiring the X value and Y value of the reference position P2 based on the processing result of the object 1 is not limited to the above method, and the method in which the center position of the image of the laser beam L is aligned with the center position of the entrance pupil plane 430a is not limited to the above method. Any method may be used as long as the processing results of the object 1 are different depending on whether the center position of the image of the laser beam L is shifted from the center position of the entrance pupil plane 430a. Further, the control unit 500 acquires the X value and Y value of the reference position P2 based on the processing result of the object 1 based on the "image of the object 1 (processed object 1)" acquired by the imaging device. may be implemented by specifying the reference position P2. Alternatively, the acquisition of the X value and Y value of the reference position P2 based on the processing result of the object 1 can be performed by displaying the "image of the object 1 (processed object 1)" acquired by the imaging device on the display unit 600. It may be implemented by the operator confirming and inputting the reference position P2 to the control unit 500. Alternatively, the X value and Y value of the reference position P2 based on the processing result of the object 1 can be acquired by the operator checking the object 1 after processing and inputting the reference position P2 into the control unit 500. may be implemented.

Subsequently, the control unit 500 calculates and stores the difference in the X value and the difference in the Y value (step S26). The difference in X value is the value obtained by subtracting the X value of reference position P2 from the be. 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. It is a value.

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 controls the object 1 when processing the object 1. A phase pattern is displayed on the spatial light modulator 410 using the reference position P2 based on the processing result of No. 1 as a reference. Note that "while processing the object 1" means a period during which the laser processing apparatus 200 performs a processing operation on the object 1 to be processed (either one type or multiple types).

The method for setting a reference position based on a point image and processing results (setting process) is to set a reference position based on a point image of reflected light RL "when confirming the reference position" after a certain "processing of object 1". The step (processing) of acquiring the position (third reference position) P3, and the step (processing) of obtaining the reference position (third reference position) based on the reference position P1, reference position P2, and reference position P3 when the reference position P3 is deviated from the reference position P1. Step (processing) of calculating the reference position P4 (4 reference position) and storing the reference position P4, and displaying the phase pattern on the spatial light modulator 410 with reference to the reference position P4 during the next "processing of the object 1". The method further includes a step (processing). These steps will be described below with reference to FIGS. 10 and 25. FIG. 25 is a flowchart showing a method for setting a reference position based on a point image and processing results. Note that "when checking the reference position" is the timing between a certain "when processing object 1" and the next "when processing object 1", and for example, it may be carried out periodically. This refers to the timing of maintenance of the laser processing apparatus 200.

First, the object 1 is set on the support stand 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 surfaces and whose resistivity is 1 Ω·cm or more. Subsequently, the support base 230 is moved in the X direction and the Y direction so that the condenser lens unit 430 faces the object 1 in the Z direction (step S32). The movement of the support base 230 in the X direction and the Y direction is carried out by the control of the first movement mechanism 220 (see FIG. 1) by the control unit 500. Subsequently, the condenser lens unit 430 is moved in the Z direction so that the focal point of the condenser lens unit 430 is located on the second surface 1b of the object 1 (step S33). The movement of the condensing lens unit 430 in the Z direction is carried out by the control of the second movement mechanism 240 (see FIG. 1) by the control section 500.

Subsequently, the control unit 500 acquires the X value and 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 manner, the control unit 500 acquires the reference position P3 based on the point image of the reflected light RL (detection result of the reflected light) "when confirming the reference position".

Subsequently, the control unit 500 determines whether there is a shift in the reference position P3 based on the point image of the reflected light RL (step S35). Specifically, the control unit 500 determines whether the currently acquired reference position P3 deviates from the previously acquired and currently stored reference position P1 (see step S24 in FIG. 21). This determination is performed by comparing the X value of the reference position P1 and the X value of the reference position P3, and also by comparing the Y value of the reference position P1 and the Y value of the reference position P3. If the result of the determination in step S35 is that there is no deviation in the reference position P3 based on the point image of the reflected light RL, the process ends.

As a result of the determination in step S35, if there is a shift in the reference position P3 based on the point image of the reflected light RL, the control unit 500 controls the The values are updated to the X value and Y value of the reference position P3 acquired this time (step S36). That is, the control unit 500 stores the X value and Y value of the reference position P3 instead of the X value and Y value of the reference position P1. At this time, the control unit 500 leaves the X value and Y value of the reference position P1 for later processing in step 37.

Next, the control unit 500 determines the target 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. A reference position P4 is calculated based on the processing result (step S37). Specifically, the control unit 500 determines that the difference between the X value of the reference position P2 (see step S25 in FIG. 21) previously acquired and currently stored and the X value of the reference position P4 is equal to the X value of the reference position P1. The X value at the reference position P4 is calculated so that it is the same as the difference between the X value and the X value at the reference position P3. Similarly, the control unit 500 determines that the difference between the Y value of the reference position P2 acquired last time and the Y value of the reference position P4 that is currently stored is the difference between the Y value of the reference position P1 and the Y value of the reference position P3. The Y value of the reference position P4 is calculated so that it is the same as the difference.

Subsequently, the control unit 500 updates the previously acquired and currently stored X and Y values of the reference position P2 to the currently calculated X and Y values of the reference position P4 (step S38). That is, the control unit 500 stores the X value and Y value of the reference position P4 instead of the X value and Y value of the reference position P2. The reference position P4 here is not an 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.

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 controls the object 1 when processing the object 1. A phase pattern is displayed on the spatial light modulator 410 using the reference position P4 based on the processing result of No. 1 as a reference.

As described above, in the laser processing apparatus 200, 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 are acquired. In a state where the reference position P1 and the reference position P2 are acquired, "during processing of the object 1", the spatial light modulator 410 displays a phase pattern with reference to the reference position P2 based on the processing results of the object 1. do. Thereby, the object 1 can be processed in a state where 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. Then, "when confirming the reference position", the 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, the center position of the image of the laser beam L transferred to the entrance pupil plane 430a is determined on the entrance pupil plane. It is possible to easily and accurately confirm whether or not the center position of 430a coincides with the center position.

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 controls the reference position P1, the reference position P2, and the reference position P3. Based on this, a reference position P4 is calculated, and a phase pattern is displayed on the spatial light modulator 410 using the stored reference position P4 as a reference "when processing the object 1". A certain 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 changes the reference position calculated based on the reference position P1, the reference position P2, and the reference position P3 during "processing the object 1". By displaying the phase pattern with the position P4 as a reference, the object 1 is processed in a state where the center position of the image of the laser beam L transferred to the entrance pupil plane 430a matches the center position of the entrance pupil plane 430a. be able to.

In the laser processing apparatus 200, the display unit 600 displays a point image of the reflected light RL "when confirming the reference position". Thereby, the point image of the reflected light RL can be reported to the operator.

According to the laser processing method implemented in the laser processing apparatus 200, as described above, when the reference position P1 and the reference position P2 are acquired, the spatial light modulator 410 is displays the phase pattern using the reference position P2 based on the processing result of the object 1 as a reference. Thereby, the object 1 can be processed in a state where 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. Then, "when confirming the reference position", the 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, the center position of the image of the laser beam L transferred to the entrance pupil plane 430a is determined on the entrance pupil plane. It is possible to easily and accurately confirm whether or not the center position of 430a coincides with the center position.

The reference position setting method (setting process) based on the point image image and the processing result may include the following steps instead of the steps shown in the flowchart of FIG. 25. That is, the method (setting process) for setting the reference position based on the point image and the processing result is to obtain the reference position (third reference position) P3 based on the point image of the reflected light RL "when confirming the reference position". a step (processing) of obtaining 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; and a step (processing) of comparing the difference between the reference position P2 and the reference position P2 (first difference) and the difference between the reference position P3 and the reference position P4 (second difference), and when those differences are different from each other, A step (processing) of storing the reference position P3 and the reference position P4 instead of the reference position P1 and the reference position P2, and a step (processing) of storing the reference position P3 and the reference position P4 in place of the reference position P1 and the reference position P2, and a step (processing) of storing the reference position P3 and the reference position P4 in place of the reference position P1 and the reference position P2; 410 may be included. These steps will be described below with reference to FIGS. 10 and 26. FIG. 26 is a flowchart showing a method for setting a reference position based on a point image and processing results.

First, the object 1 is set on the support stand 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 surfaces and whose resistivity is 1 Ω·cm or more. Subsequently, the support base 230 is moved in the X direction and the Y direction so that the condenser lens unit 430 faces the object 1 in the Z direction (step S42). The movement of the support base 230 in the X direction and the Y direction is carried out by the control of the first movement mechanism 220 (see FIG. 1) by the control unit 500. Subsequently, the condenser lens unit 430 is moved in the Z direction so that the focal point of the condenser lens unit 430 is located on the second surface 1b of the object 1 (step S43). The movement of the condensing lens unit 430 in the Z direction is carried out by the control of the second movement mechanism 240 (see FIG. 1) by the control section 500.

Subsequently, the control unit 500 acquires the X value and Y value 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 manner, the control unit 500 acquires the reference position P3 based on the point image of the reflected light RL (detection result of the reflected light) "when confirming the reference position".

Subsequently, the control unit 500 determines whether there is a shift in the reference position P3 based on the point image of the reflected light RL (step S45). Specifically, the control unit 500 determines whether the currently acquired reference position P3 deviates from the previously acquired and currently stored reference position P1 (see step S24 in FIG. 21). This determination is performed by comparing the X value of the reference position P1 and the X value of the reference position P3, and also by comparing the Y value of the reference position P1 and the Y value of the reference position P3. As a result of the determination in step S45, if there is no deviation in the reference position P3 based on the point image of the reflected light RL, the process ends.

As a result of the determination in step S35, if there is a shift 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 that the reference position P2 based on the processing result of the object 1 should be updated. Subsequently, the control unit 500 updates the previously acquired and currently stored X and Y values of the reference position P1 to the currently acquired X and Y values of the reference position P3 (step S47). That is, the control unit 500 stores the X value and Y value of the reference position P3 instead of the X value and Y value of the reference position P1. At this time, the control unit 500 leaves the X value and Y value of the reference position P1 for the processing in step 49 later.

Subsequently, the control unit 500 acquires the X value and 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 obtains the reference position P4 based on the processing result of the object 1.

Subsequently, 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.

Subsequently, the difference between the reference position P1 and the reference position P2 is compared with the difference between the reference position P3 and the reference position P4 (step S50). 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 X value of the reference position P3 and the Compare the difference between . Similarly, 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, and the difference between the Y value at the reference position P3 and the Y value at the reference position P4, as the "comparison regarding the Y value." Compare with. As a result of the determination in step S50, if the differences are not different in either the "comparison regarding the X value" or the "comparison regarding the Y value", the process ends.

As a result of the determination in step S50, if the differences are different in at least one of the "comparison regarding the X value" and the "comparison regarding the Y value", the control unit 500 compares the X value at the reference position P1 with the reference The difference between the X value of the position P2 and the Y value of the reference position P1 and the Y value of the reference position P2 is calculated as 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 X value of the reference position P3 and the The Y value is updated to the Y value of the 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.

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 controls the object 1 when processing the object 1. A phase pattern is displayed on the spatial light modulator 410 using the reference position P4 based on the processing result of No. 1 as a reference.

As explained above, in the laser processing apparatus 200, when the currently acquired reference position P3 deviates from the previously acquired and currently stored reference position P1, the control unit 500 controls the processing result of the object 1. Based on this, a reference position P4 is acquired, and a phase pattern is displayed on the spatial light modulator 410 using the acquired reference position P4 as a reference "when processing the object 1". A certain 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 uses the reference position P4, which has been acquired anew based on the processing results of the object 1, as the reference point "during the processing of the object 1". By displaying the phase pattern as , the object 1 can be processed in a state where the center position of the image of the laser beam L transferred to the entrance pupil plane 430a matches the center position of the entrance pupil plane 430a.

In the laser processing apparatus 200, the control unit 500 compares the first difference between the reference position P1 and the reference position P2 and the second difference between the reference position P3 and the reference position P4, and determines the first difference and the second difference. If they are different, the reference position P3 and the reference position P4 are stored in place 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, the difference 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 object 1 is determined. It is possible to check whether a certain positional relationship is maintained. Furthermore, when 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, so that the point of the reflected light RL is The positional relationship between the reference position acquired based on the image and the reference position acquired based on the processing result of the target object 1 can be updated.
[Modified example]

The present invention is not limited to the above embodiments. For example, the embodiment described above is not limited to forming a modified region inside the object 1, and may also perform other laser processing such as ablation. The above embodiment is not limited to focusing the laser beam L inside the object 1, but focuses the laser beam L on the outer surface of the object 1 on the incident side of the laser beam L or the outer surface on the opposite side thereof. It may be something that shines. The device to which the present invention is applied can be applied to various laser beam irradiation devices as long as they irradiate the object 1 with the laser beam L. In the above embodiment, the lines 5a and 5b for scanning the laser beam L are lines for cutting the object 1, but the lines for scanning the laser beam L are lines for other purposes. Good too. In the object 1, the first surface 1a may not be the outer surface of the object 1 as long as it is a surface located on the incident side of the laser beam L with respect to the second surface 1b. In the object 1, the second surface 1b does not need to be the outer surface of the object 1 as long as it is a surface located on the opposite side to the incident side of the laser beam L with respect to the first surface 1a.

Spatial light modulator 410 is not limited to a reflective type, but may be a transmissive type. The image transfer unit that transfers the image of the laser beam L in the spatial light modulator 410 to the entrance pupil plane 430a is not limited to the 4f lens unit 420 having a pair of lenses 422 and 423, but is It may include one lens system (for example, a cemented lens, three or more lenses, etc.) and a second lens system (for example, a cemented lens, three or more lenses, etc.) on the side of the entrance pupil plane 430a. The photodetector that detects the reflected light RL is not limited to the observation camera 488, but may be a wavefront sensor that detects the wavefront of the reflected light RL. The wavefront sensor includes, for example, a microlens array and an image sensor, and acquires a local phase gradient from the image position of a focal spot formed by each microlens. As the wavefront sensor, a Shack-Hartmann wavefront sensor ("WFS150-5C" manufactured by THORLAB) can be used.

DESCRIPTION OF SYMBOLS 1...Target, 1a...1st surface, 1b...2nd surface, 200...Laser processing device, 230...Support stand (support part), 310...Laser oscillator (light source), 410...Spatial light modulator, 420...4f Lens unit (image transfer section), 430... Condensing lens unit (condensing section), 430a... Entrance pupil plane, 488... Observation camera (photodetector), 500... Control section, 600... Display section, L... Laser Light, RL...Reflected light.

Claims (6)

a support part that supports 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 condensing unit that condenses the laser beam 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 beam in the spatial light modulator onto an entrance pupil plane of the light condensing unit;
a photodetector that detects reflected light of the laser beam reflected by the target object;
a control unit that controls at least the spatial light modulator;
The control unit sets a reference for the display position of the phase pattern in the spatial light modulator so that the center position of the image of the laser beam transferred to the entrance pupil plane coincides with the center position of the entrance pupil plane. Execute the setting process to set the reference position,
The setting process is
A process of acquiring a first reference position as the reference position based on the detection result of the reflected light, and acquiring a second reference position as the reference position based on the processing result of the object;
when processing the object, displaying the phase pattern on the spatial light modulator using the second reference position as the reference;
A laser processing apparatus comprising: 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. The setting process is
When the third reference position is deviated from the first reference position, a fourth reference position is calculated as the reference position based on the first reference position, the second reference position, and the third reference position. , a process of storing the fourth reference position;
The laser processing apparatus according to claim 1, further comprising: displaying the phase pattern on the spatial light modulator using the fourth reference position as the reference when processing the object. The setting process is
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 apparatus according to claim 1, further comprising: displaying the phase pattern on the spatial light modulator using the fourth reference position as the reference when processing the object. The setting process is
Comparing a first difference between the first reference position and the second reference position and a second difference between the third reference position and the fourth reference position;
a process of storing the third reference position and the fourth reference position in place of the first reference position and the second reference position when the first difference and the second difference are different; The laser processing apparatus according to claim 3, further comprising: The laser processing apparatus according to any one of claims 1 to 4, further comprising a display unit that displays a detection result of the reflected light when confirming the reference position. a support part that supports 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 condensing unit that condenses the laser beam 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 beam in the spatial light modulator onto an entrance pupil plane of the light condensing unit;
Implemented in a laser processing apparatus comprising a photodetector that detects reflected light of the laser beam reflected by the target object,
A reference position, which is a reference for the display position of the phase pattern in the spatial light modulator, is set so that the center position of the image of the laser beam transferred to the entrance pupil plane coincides with the center position of the entrance pupil plane. A laser processing method to set,
acquiring a first reference position as the reference position based on the detection result of the reflected light, and acquiring a second reference position as the reference position based on the 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;
A laser processing method, comprising: 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.

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