Laser processing equipment

Abstract

This laser processing device comprises: a support unit; an irradiation unit that irradiates a target object with laser light via a condensing lens; a movement mechanism that moves the condensing lens; an imaging unit that images a laser light incidence surface; a displacement information acquisition unit that acquires displacement information for the laser light incidence surface; a first positioning unit that activates the movement mechanism so that, on the basis of results of imaging by the imaging unit, the position of the condensing lens matches a reference position; an information recording unit that, once the position of the condensing lens has been matched to the reference position by the first positioning unit, records the displacement information acquired by the displacement information acquisition unit as reference displacement information; and a second positioning unit which activates the movement mechanism so that the displacement information becomes the reference displacement information, and which matches the position of the condensing lens to the reference position.

Description

[Technical Field]

[0001] The present disclosure relates to a laser processing apparatus. [Background Art]

[0002] A laser processing apparatus that irradiates an object with laser light to form a modified region is known (see, for example, Patent Document 1). Such a laser processing apparatus includes: a support section that supports an object; an irradiation section that irradiates the object with laser light via a condenser lens; a moving mechanism that moves the condenser lens along the optical axis direction of the condenser lens; and an imaging section that images the laser light incident surface of the object. [Prior Art Literature] [Patent Literature]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-87053 [Summary of Invention] [Problem to be Solved by Invention]

[0004] In the laser processing apparatus as described above, positioning (so-called height setting) for aligning the position of the condenser lens in the optical axis direction relative to the laser light incident surface to a reference position is sometimes performed by projecting a reticle onto the laser light incident surface of the object and operating the moving mechanism such that the reticle is focused on the image captured by the imaging section. However, in this case, when an object such as a wafer having a film or a tape material on the laser light incident surface side is used, the reticle cannot be correctly identified on the image, which may make it difficult to perform the positioning of the condenser lens.

[0005] Accordingly, an object of the present disclosure is to provide a laser processing apparatus capable of positioning the position of a condenser lens in the optical axis direction relative to a laser light incident surface regardless of the object. [Means for Solving Problem]

[0006] A laser processing apparatus relating to one aspect of the present disclosure is a laser processing apparatus that irradiates a target object with laser light to form a modified region, comprising: a support unit for supporting the target object; an irradiation unit for irradiating the target object with laser light through a focusing lens; a movement mechanism for moving the focusing lens along the optical axis direction of the focusing lens; an imaging unit for imaging the laser light incident surface of the target object; a displacement information acquisition unit for acquiring displacement information that changes according to the displacement of the laser light incident surface using a measuring laser light; a first alignment unit that operates the movement mechanism based on the imaging results from the imaging unit so that the position of the focusing lens in the optical axis direction relative to the laser light incident surface matches a reference position or a predetermined height position at a predetermined distance from the reference position; an information recording unit that records the displacement information acquired by the displacement information acquisition unit as reference displacement information when the position of the focusing lens in the optical axis direction is aligned with the reference position or the predetermined height position by the first alignment unit; and a second alignment unit that operates the movement mechanism so that the displacement information acquired by the displacement information acquisition unit becomes reference displacement information, and aligns the position of the focusing lens in the optical axis direction relative to the laser light incident surface with the reference position or the predetermined height position.

[0007] In this laser processing apparatus, the first alignment unit aligns the position of the focusing lens in the optical axis direction with respect to the laser beam incident surface of the object (hereinafter, this alignment is also referred to as "height setting") based on the imaging results of the imaging unit. At this time, the displacement information acquired by the displacement information acquisition unit is recorded as reference displacement information by the information recording unit. Here, for example, when using an object in which a film or tape material exists on the laser beam incident surface side, it may be difficult to identify the laser beam incident surface from the imaging results of the imaging unit, and height setting may become difficult. Even in this case, in one aspect of this disclosure, height setting can be performed by operating the movement mechanism using the reference displacement information by the second alignment unit. In other words, in one aspect of this disclosure, both height setting by the first alignment unit and height setting by the second alignment unit are provided, making it possible to perform height setting regardless of the object.

[0008] In a laser processing apparatus relating to one aspect of this disclosure, the imaging unit receives visible light that is incident on the laser light incident surface via a reticle and reflected from the laser light incident surface, and the reference position may be the position of the focusing lens when the reticle is in focus on the image of the laser light incident surface captured by the imaging unit. In this case, the height setting can be performed using the reticle by the first alignment unit.

[0009] A laser processing apparatus relating to one aspect of this disclosure may include a processing failure determination unit that, when processing by the first alignment unit is performed and the reticle cannot be recognized as being in focus on the image of the laser beam incident surface captured by the imaging unit, determines that the object is unprocessable if reference displacement information has not been recorded by the information recording unit. This makes it possible to determine that the object is unprocessable because height setting is not possible.

[0010] A laser processing apparatus relating to one aspect of this disclosure may include a switching unit that, when processing by a first alignment unit is performed and the reticle cannot be recognized as being in focus on the image of the laser beam incident surface captured by the imaging unit, and reference displacement information is recorded by the information recording unit, then processing by a second alignment unit may be performed. In this case, the height setting by the first alignment unit is given priority, and if height setting by the first alignment unit is not possible, it is possible to switch to height setting by the second alignment unit.

[0011] In a laser processing apparatus relating to one aspect of this disclosure, the displacement information acquisition unit includes a light-emitting element that emits measuring laser light and a light-receiving element array that receives the measuring laser light reflected from the laser light incident surface, and the displacement information that changes according to the displacement of the laser light incident surface may correspond to the position where the measuring laser light is received by the light-receiving element array. In this case, it becomes possible to perform height setting by using the position where the measuring laser light is received by the light-receiving element array as displacement information.

[0012] In a laser processing apparatus relating to one aspect of this disclosure, the displacement information acquisition unit includes a light-emitting element that emits measuring laser light, a branching optical system that branches the measuring laser light reflected from the laser light incident surface into a plurality of branched measuring laser beams, and a light-receiving element array that receives the plurality of branched measuring laser beams. The displacement information, which changes according to the displacement of the laser light incident surface, may correspond to the interval between the receiving positions of the plurality of branched measuring laser beams in the light-receiving element array. In this case, it becomes possible to perform height setting by using the interval between the receiving positions of the branched measuring laser beams in the light-receiving element array as displacement information.

[0013] A laser processing apparatus relating to one aspect of this disclosure may include a light-receiving amount adjustment unit that adjusts the displacement information acquisition unit so that the amount of light received by the light-receiving element array is equal to or greater than a threshold. In this case, it becomes possible to prevent the inability to acquire effective displacement information due to a low amount of light received by the light-receiving element array.

[0014] A laser processing apparatus relating to one aspect of this disclosure may include a reference support section that supports a reference object that does not contain a film or tape material on the laser beam incident surface side. In this case, the height setting is performed on the reference object supported by the reference support section by the first alignment section, and the displacement information acquired at this time can be recorded as reference displacement information by the information recording section.

[0015] In a laser processing apparatus relating to one aspect of this disclosure, the first alignment unit may, when reference displacement information is recorded by the information recording unit, operate the movement mechanism so that the displacement information acquired by the displacement information acquisition unit becomes the reference displacement information, and then operate the movement mechanism so that the position of the focusing lens in the optical axis direction relative to the laser beam incident surface matches the reference position based on the imaging result from the imaging unit. In this case, it becomes possible to speed up the height setting by the first alignment unit (i.e., height setting based on the imaging result from the imaging unit).

[0016] In a laser processing apparatus relating to one aspect of this disclosure, the displacement information acquisition unit emits a measuring laser beam toward the laser beam incident surface and acquires displacement information by receiving the measuring laser beam reflected by the laser beam incident surface. When a modified region is formed on an object on which a transparent member that is transparent to the laser beam and the measuring laser beam is provided on the laser beam incident surface, the second alignment unit calculates an offset amount corresponding to the deviation of the optical path of the measuring laser beam when a transparent member is present compared to the optical path of the measuring laser beam when a transparent member is not present, based on the transparent member information including information on the thickness and refractive index of the transparent member, and may change the reference displacement information stored in the information recording unit in advance based on the calculated offset amount. This makes it possible to handle objects on which a transparent member (e.g., transparent tape, etc.) is provided on the laser beam incident surface.

[0017] A laser processing apparatus relating to one aspect of this disclosure includes an input unit that receives input regarding the presence or absence of a transparent member and information about the transparent member, and a second alignment unit may determine whether or not a transparent member is present based on the input from the input unit, and calculate an offset amount if it is determined that a transparent member is present. This makes it possible to handle objects on which a transparent member is provided on the laser beam incident surface by utilizing the input from the input unit. [Effects of the Invention]

[0018] According to this disclosure, it is possible to provide a laser processing apparatus that can align the position of the focusing lens in the optical axis direction with respect to the laser beam incident surface, regardless of the object being processed. [Brief explanation of the drawing]

[0019] [Figure 1] Figure 1 is a perspective view showing a laser processing apparatus according to an embodiment. [Figure 2] Figure 2 is a perspective view of an object to be attached to the support base of the laser processing apparatus according to the embodiment. [Figure 3] Figure 3 is a cross-sectional view along the XY plane of Figure 1. [Figure 4]FIG. 4 is a perspective view showing part of a laser output unit and a laser condensing unit of the laser processing apparatus according to the embodiment. [Figure 5] FIG. 5 is a cross-sectional view along the XY plane of FIG. 1. [Figure 6] FIG. 6 is a cross-sectional view along the line VI-VI of FIG. 5. [Figure 7] FIG. 7 is a cross-sectional view along the line VII-VII of FIG. 6. [Figure 8] FIG. 8 is a front view showing a schematic configuration of a separate-axis distance measuring sensor according to the embodiment. [Figure 9] FIG. 9 is a diagram showing a state where a reticle mark is in focus in an image of a laser beam incident surface captured by an observation camera according to the embodiment. [Figure 10] FIG. 10 is a flowchart showing an example of height setting. [Figure 11] FIG. 11 is a flowchart showing an example of height setting. [Figure 12] FIG. 12(a) is a front view of a separate-axis distance measuring sensor for explaining height setting. FIG. 12(b) is a front view of the separate-axis distance measuring sensor showing a continuation of FIG. 12(a). [Figure 13] FIG. 13 is a diagram showing a state where a reticle mark cannot be seen in an image of a laser beam incident surface captured by an observation camera according to the embodiment. [Figure 14] FIG. 14 is a flowchart showing an example of height setting. [Figure 15] FIG. 15 is a flowchart showing an example of height setting. [Figure 16] FIG. 16 is a schematic plan view showing a support table and a reference support table of a laser processing apparatus according to a modified example. [Figure 17] FIG. 17 is a schematic plan view showing a state where a target object and a reference target object are supported by the support table and the reference support table of FIG. 16. [Figure 18] FIG. 18(a) is a flowchart showing an example of height setting. FIG. 18(b) is a flowchart showing an example of height setting. [Figure 19]Figure 19 is a flowchart showing an example of a height set. [Figure 20] Figure 20(a) shows a schematic configuration of a modified separate-axis distance measuring sensor. Figure 20(b) shows a schematic configuration of a modified separate-axis distance measuring sensor. Figure 20(c) shows a schematic configuration of a modified separate-axis distance measuring sensor. [Figure 21] Figure 21 is a perspective view showing a modified laser processing apparatus. [Figure 22] Figure 22(a) is a side view showing an object without transparent tape. Figure 22(b) is a side view showing an object with transparent tape. [Figure 23] Figure 23 is a side view of the object used to explain the calculation of the offset amount. [Figure 24] Figure 24 is a flowchart showing an example of a height set. [Modes for carrying out the invention]

[0020] The embodiments will be described in detail below with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and redundant explanations are omitted. In the horizontal plane, the directions that are orthogonal to each other are defined as the X-axis and Y-axis directions, and the vertical direction is defined as the Z-axis direction.

[0021] As shown in Figure 1, the laser processing apparatus 200 forms a modified region on the object 1 by irradiating it with laser light. The object 1 is a plate-shaped member (e.g., a substrate, wafer, etc.) including semiconductor substrates made of semiconductor materials or piezoelectric substrates made of piezoelectric materials. As shown in Figure 2, the object 1 has a planned cutting line 5 for cutting the object 1. The planned cutting line 5 is a straight, imaginary line. When forming a modified region inside the object 1, the laser light is moved relatively along the planned cutting line 5 with the focal point (at least a part of the focal area) aligned inside the object 1. As a result, a modified region is formed on the object 1 along the planned cutting line 5.

[0022] The planned cutting line 5 is not limited to a straight line; it may also be curved, a three-dimensional shape combining both, or a line specified by coordinates. The planned cutting line 5 is not limited to a virtual line; it may also be a line actually drawn on the surface of the object 1. The modified region may be formed continuously or intermittently. The modified region may be in the form of a row or points; the point is that the modified region must be formed at least inside the object 1. Furthermore, cracks may be formed starting from the modified region, and both the cracks and the modified region may be exposed on the outer surface (front, back, or outer periphery) of the object 1. The laser beam incident surface when forming the modified region is not limited to the surface of the object 1; it may also be the back surface of the object 1.

[0023] A modified region is a region in which the density, refractive index, mechanical strength, or other physical properties differ from the surrounding area. Examples of modified regions include melted regions (meaning at least one of the following: regions that have melted and then resolidified, regions in a molten state, and regions in the state of resolidation from melting), crack regions, dielectric breakdown regions, refractive index change regions, etc., and there are also regions where these are mixed. Modified regions in the material of object 1 include regions where the density of the modified region has changed compared to the density of the unmodified region, and regions where lattice defects have formed. If the material of object 1 is single-crystal silicon, the modified region can also be called a high dislocation density region.

[0024] Regions where the density of the molten region, refractive index change region, modified region has changed compared to the density of the unmodified region, and region where lattice defects have formed may further contain cracks (fractures, microcracks) within these regions or at the interface between the modified and unmodified regions. The contained cracks may extend across the entire modified region, or be formed in only a part or multiple parts. Object 1 includes a substrate made of a crystalline material having a crystalline structure. For example, Object 1 includes a substrate formed of at least one of gallium nitride (GaN), silicon (Si), silicon carbide (SiC), LiTaO3, and sapphire (Al2O3). In other words, Object 1 includes, for example, a gallium nitride substrate, a silicon substrate, a SiC substrate, a LiTaO3 substrate, or a sapphire substrate. The crystalline material may be either anisotropic or isotropic. Furthermore, object 1 may include a substrate made of an amorphous material having an amorphous structure, for example, a glass substrate.

[0025] In this embodiment, a modified region can be formed by creating multiple modified spots (processing marks) along the planned cutting line 5. In this case, the modified region is formed by the convergence of multiple modified spots. A modified spot is a modified portion formed by one pulse shot of pulsed laser light (i.e., one pulse of laser irradiation: laser shot). Examples of modified spots include crack spots, melting spots, refractive index change spots, or a mixture of at least one of these. The size of the modified spots and the length of the cracks that are generated can be appropriately controlled considering the required cutting accuracy, the required flatness of the cut surface, the thickness and type of the object 1, the crystal orientation, etc. In this embodiment, modified spots can be formed as a modified region along the planned cutting line 5.

[0026] As shown in Figure 1, the laser processing apparatus 200 comprises an apparatus frame 210, a first moving mechanism 220, a support base (support section) 230, and a second moving mechanism (moving mechanism) 240. Furthermore, the laser processing apparatus 200 comprises a laser output unit 300, a laser focusing unit (irradiation unit) 400, and a control unit 500.

[0027] 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, 221b extending along the Y-axis. The second rail unit 222 is attached to the pair of rails 221a, 221b of the first rail unit 221 so as to be movable along the Y-axis. The second rail unit 222 is provided with a pair of rails 222a, 222b extending along the X-axis. The movable base 223 is attached to the pair of rails 222a, 222b of the second rail unit 222 so as to be movable along the X-axis. The movable base 223 is rotatable about an axis parallel to the Z-axis.

[0028] The support base 230 is attached to the movable base 223. The support base 230 supports the object 1. In the example shown in Figure 2, the object 1 is, for example, a substrate made of a semiconductor material such as silicon, on which multiple functional elements (such as photodiodes or other light-receiving elements, laser diodes or other light-emitting elements, or circuit elements formed as circuits) are formed in a matrix on the surface side. When the object 1 is supported by the support base 230, for example, the surface 1a of the object 1 (the side with the multiple functional elements) is attached to a film 12 stretched over an annular frame 11. The support base 230 supports the object 1 by holding the frame 11 with a clamp and by adsorbing the film 12 with a vacuum chuck table. On the support base 230, multiple parallel cutting lines 5a and multiple parallel cutting lines 5b are set on the object 1 in a grid pattern so as to pass between adjacent functional elements (hereinafter also referred to as "streets").

[0029] As shown in Figure 1, the support base 230 is moved along the Y-axis direction by the operation of the second rail unit 222 in the first moving mechanism 220. The support base 230 is also moved along the X-axis direction by the operation of the movable base 223 in the first moving mechanism 220. Furthermore, the support base 230 is rotated around an axis parallel to the Z-axis direction by the operation of the movable base 223 in the first moving mechanism 220. In this way, the support base 230 is attached to the device frame 210 so that it can move along the X-axis and Y-axis directions and rotate around an axis parallel to the Z-axis direction.

[0030] The laser output unit 300 is mounted on the device frame 210. The laser focusing unit 400 is mounted on the device frame 210 via a second movement mechanism 240. The laser focusing unit 400 is moved along the Z-axis direction (the optical axis direction of the focusing lens unit 430, described later) by the operation of the second movement mechanism 240. In this way, the laser focusing unit 400 is mounted on the device frame 210 so that it can move along the Z-axis direction relative to the laser output unit 300.

[0031] The control unit 500 consists of a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), and the like. The control unit 500 controls the operation of each part of the laser processing apparatus 200. Details of the processing performed by the control unit 500 will be described later.

[0032] In the laser processing apparatus 200, for example, a modified region is formed inside the object 1 along each planned cutting line 5a, 5b as follows. First, the object 1 is supported on the support base 230 so that the back surface 1b of the object 1 becomes the laser beam incident surface, and each planned cutting line 5a of the object 1 is aligned parallel to the X-axis direction. Positioning (so-called height setting) is performed to bring the position of the focusing lens unit 430, described later, in the Z-axis direction relative to the laser beam incident surface to a reference position. The laser focusing unit 400 is moved in the Z-axis direction by the second moving mechanism 240 so that the focal point of the laser beam L inside the object 1 is located at a predetermined distance from the laser beam incident surface. While the distance between the laser beam incident surface and the focal point of the laser beam L is kept constant, the focal point of the laser beam L is moved relatively along each planned cutting line 5a. As a result, a modified region is formed inside the object 1 along each planned cutting line 5a. The laser beam incident surface is not limited to the back surface 1b, but may also be the front surface 1a.

[0033] Once the formation of the modified region along each planned cutting line 5a is complete, the support base 230 is rotated by the first moving mechanism 220 so that each planned cutting line 5b of the object 1 is aligned parallel to the X-axis direction. Height setting is performed. The laser focusing unit 400 is moved by the second moving mechanism 240 so that the focal point of the laser beam L is located at a predetermined distance from the laser beam incident surface inside the object 1. While maintaining a constant distance between the laser beam incident surface and the focal point of the laser beam L, the focal point of the laser beam L is moved relative to each planned cutting line 5b. As a result, a modified region is formed inside the object 1 along each planned cutting line 5b.

[0034] Thus, in the laser processing apparatus 200, the processing direction (scanning direction of the laser beam L) is defined as the direction parallel to the X-axis direction. The relative movement of the focal point of the laser beam L along each planned cutting line 5a and along each planned cutting line 5b is performed by moving the support base 230 along the X-axis direction by the first moving mechanism 220. Furthermore, the relative movement of the focal point of the laser beam L between each planned cutting line 5a and between each planned cutting line 5b is performed by moving the support base 230 along the Y-axis direction by the first moving mechanism 220.

[0035] As shown in Figure 3, the laser output unit 300 includes a mounting base 301, a cover 302, and a plurality of mirrors 303, 304. Furthermore, the laser output unit 300 includes a laser oscillator (laser light source) 310, a shutter 320, a λ / 2 wave plate unit (output adjustment unit, polarization direction adjustment unit) 330, a polarizer unit (output adjustment unit, polarization direction adjustment unit) 340, a beam expander (laser light parallelization unit) 350, and a mirror unit 360.

[0036] The mounting base 301 supports multiple mirrors 303, 304, a laser oscillator 310, a shutter 320, a λ / 2 waveplate unit 330, a polarizer unit 340, a beam expander 350, and a mirror unit 360. The multiple mirrors 303, 304, the laser oscillator 310, the shutter 320, the λ / 2 waveplate unit 330, the polarizer unit 340, the beam expander 350, and the 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 detachable from the device frame 210 (see Figure 1). The laser output unit 300 is attached to the device frame 210 via the mounting base 301. In other words, the laser output unit 300 is detachable from the device frame 210.

[0037] The cover 302 covers multiple mirrors 303, 304, a laser oscillator 310, a shutter 320, a λ / 2 waveplate unit 330, a polarizer unit 340, a beam expander 350, and a mirror unit 360 on the main surface 301a of the mounting base 301. The cover 302 is detachable from the mounting base 301.

[0038] The laser oscillator 310 pulses linearly polarized laser light L along the X-axis. The wavelength of the laser light L emitted from the laser oscillator 310 is in one of the following wavelength bands: 500-550 nm, 1000-1150 nm, or 1300-1400 nm. Laser light L in the 500-550 nm wavelength band is suitable for internal absorption laser processing of substrates made of, for example, sapphire. Laser light L in the 1000-1150 nm and 1300-1400 nm wavelength bands is suitable for internal absorption laser processing of substrates made of, for example, silicon. The polarization direction of the laser light L emitted from the laser oscillator 310 is, for example, parallel to the Y-axis. The laser light L emitted from the laser oscillator 310 is reflected by the mirror 303 and incident on the shutter 320 along the Y-axis.

[0039] In the laser oscillator 310, the output of the laser light L can be switched ON / OFF as follows: If the laser oscillator 310 is composed of a solid-state laser, the output of the laser light L can be switched ON / OFF at high speed by switching the ON / OFF of a Q switch (AOM (acousto-optic modulator), EOM (electro-optic modulator), etc.) provided in the resonator. If the laser oscillator 310 is composed of a fiber laser, the output of the laser light L can be switched ON / OFF at high speed by switching the ON / OFF of the semiconductor lasers that constitute the seed laser and the amplifier (excitation) laser. If the laser oscillator 310 uses an external modulation element, the output of the laser light L can be switched ON / OFF at high speed by switching the ON / OFF of an external modulation element (AOM, EOM, etc.) provided outside the resonator.

[0040] The shutter 320 opens and closes the optical path of the laser beam L by a mechanical mechanism. As described above, the ON / OFF switching of the output of the laser beam L from the laser output unit 300 is performed by switching the output of the laser beam L at the laser oscillator 310, but the presence of the shutter 320 prevents, for example, the laser beam 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 incident on the λ / 2 wave plate unit 330 and the polarizer unit 340 along the X axis.

[0041] The λ / 2 waveplate unit 330 and the polarizer unit 340 function as output adjustment units that adjust the output (light intensity) of the laser light L. Furthermore, the λ / 2 waveplate unit 330 and the polarizer unit 340 function as polarization direction adjustment units that adjust the polarization direction of the laser light L. Details of these will be described later. The laser light L, having sequentially passed through the λ / 2 waveplate unit 330 and the polarizer unit 340, is incident on the beam expander 350 along the X-axis.

[0042] The beam expander 350 adjusts the diameter of the laser beam L and parallelizes it. The laser beam L that has passed through the beam expander 350 is incident on the mirror unit 360 along the X-axis.

[0043] The mirror unit 360 includes a support base 361 and a plurality of mirrors 362, 363. The support base 361 supports the plurality of mirrors 362, 363. The support base 361 is mounted on a mounting base 301 so as to be adjustable in position along the X-axis and Y-axis directions. Mirror 362 reflects the laser light L that has passed through the beam expander 350 in the Y-axis direction. Mirror 362 is mounted on the support base 361 so as to be angle-adjustable around an axis parallel to the Z-axis, for example. Mirror 363 reflects the laser light L reflected by mirror 362 in the Z-axis direction. Mirror 363 is mounted on the support base 361 so as to be angle-adjustable around an axis parallel to the X-axis, for example, and also adjustable in position along the Y-axis direction. The laser beam L reflected by the mirror 363 passes through the opening 361a formed in the support base 361 and is incident on the laser focusing unit 400 (see Figure 1) along the Z-axis direction. In other words, the direction of emission of the laser beam L from the laser output unit 300 coincides with the direction of movement of the laser focusing unit 400. As described above, each mirror 362, 363 has a mechanism for adjusting the angle of its reflective surface. In the mirror unit 360, the position of the support base 361 relative to the mounting base 301, the position of the mirror 363 relative to the support base 361, and the angle of the reflective surface of each mirror 362, 363 are adjusted so that the position and angle of the optical axis of the laser beam L emitted from the laser output unit 300 is aligned with the laser focusing unit 400. In other words, the multiple mirrors 362, 363 are configured to adjust the optical axis of the laser beam L emitted from the laser output unit 300.

[0044] As shown in Figure 4, the laser focusing unit 400 has a housing 401. The housing 401 has a rectangular parallelepiped shape with the Y-axis direction as its longitudinal direction. A second moving mechanism 240 is attached to one side surface 401e of the housing 401 (see Figures 5 and 7). The housing 401 is provided with a cylindrical light incident part 401a that faces the opening 361a of the mirror unit 360 in the Z-axis direction. The light incident part 401a causes the laser beam L emitted from the laser output unit 300 to enter the housing 401. The mirror unit 360 and the light incident part 401a are spaced apart from each other by a distance such that they do not come into contact with each other when the laser focusing unit 400 is moved along the Z-axis direction by the second moving mechanism 240.

[0045] As shown in Figures 5 and 6, the laser focusing unit 400 includes a mirror 402 and a dichroic mirror 403. Furthermore, the laser focusing unit 400 includes a reflective spatial light modulator (spatial light modulator) 410, a 4f lens unit 420, a focusing lens unit 430, a drive mechanism 440, and a pair of separate-axis distance measuring sensors (displacement information acquisition units) 450. The laser focusing unit 400 irradiates the object 1 with laser light L via the focusing lens unit 430.

[0046] Mirror 402 is mounted on the bottom surface 401b of the housing 401 so as to face the light incident section 401a in the Z-axis direction. Mirror 402 reflects the laser light L that enters the housing 401 via the light incident section 401a in a direction parallel to the XY plane. The laser light L, which has been parallelized by the beam expander 350 of the laser output section 300, is incident on mirror 402 along the Z-axis direction. In other words, the laser light L is incident on mirror 402 as parallel light along the Z-axis direction. Therefore, even if the laser focusing section 400 is moved along the Z-axis direction by the second moving mechanism 240, the state of the laser light L incident on mirror 402 along the Z-axis direction is maintained constant. The laser light L reflected by mirror 402 is incident on the reflective spatial light modulator 410.

[0047] The reflective spatial light modulator 410 is mounted on the end portion 401c of the housing 401 in the Y-axis direction, with its reflective surface 410a facing into the housing 401. The reflective spatial light modulator 410 is, for example, a reflective liquid crystal on silicon (LCOS) spatial light modulator (SLM), which modulates the laser light L and reflects the laser light L in the Y-axis direction. The laser light L modulated and reflected by the reflective spatial light modulator 410 is incident on the 4f lens unit 420 along the Y-axis direction. Here, in a plane parallel to the XY plane, the angle α between the optical axis of the laser light L incident on the reflective spatial light modulator 410 and the optical axis of the laser light L emitted from the reflective spatial light modulator 410 is acute (for example, 10 to 60°). In other words, the laser light L is reflected at an acute angle along the XY plane by the reflective spatial light modulator 410. This is to suppress the decrease in diffraction efficiency by limiting the incident and reflection angles of the laser light L, thereby allowing the reflective spatial light modulator 410 to perform to its full potential.

[0048] The 4f lens unit 420 includes a holder 421, a lens 422 on the reflective spatial light modulator 410 side, a lens 423 on the focusing lens unit 430 side, and a slit member 424. The holder 421 holds the pair of lenses 422, 423 and the slit member 424. The holder 421 maintains a constant relative position of the pair of lenses 422, 423 and the slit member 424 in the direction along the optical axis of the laser beam L. The pair of lenses 422, 423 constitute a bilateral telecentric optical system in which the reflective surface 410a of the reflective spatial light modulator 410 and the entrance pupil surface 430a of the focusing 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 reflective spatial light modulator 410 (the image of the laser beam L modulated in the reflective spatial light modulator 410) is transferred (imaged) onto the entrance pupil surface 430a of the focusing lens unit 430. A slit 424a is formed in the slit member 424. The slit 424a is located between the lens 422 and the lens 423, near the focal plane of the lens 422. Unnecessary portions of the laser beam L that have been modulated and reflected by the reflective spatial light modulator 410 are 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 axis.

[0049] The dichroic mirror 403 reflects most of the laser light L (e.g., 95-99.5%) in the Z-axis direction and transmits a portion of the laser light L (e.g., 0.5-5%) along the Y-axis direction. Most of the laser light L is reflected perpendicularly along the ZX plane by the dichroic mirror 403. The laser light L reflected by the dichroic mirror 403 is incident on the focusing lens unit 430 along the Z-axis direction.

[0050] The focusing lens unit 430 is attached to the end 401d (the end opposite to the end 401c) of the housing 401 in the Y-axis direction via a drive mechanism 440. The focusing lens unit 430 has a holder 431 and a plurality of focusing lenses 432. The holder 431 holds the plurality of focusing lenses 432. The plurality of focusing lenses 432 focus the laser beam L onto the object 1 (see Figure 1) supported on the support base 230. The drive mechanism 440 moves the focusing lens unit 430 along the Z-axis direction by the driving force of a piezoelectric element.

[0051] The separate-axis distance measuring sensor 450 is mounted on the end portion 401d of the housing 401 so as to be located on both sides of the focusing lens unit 430 in the X-axis direction. The separate-axis distance measuring sensor 450 uses a first measuring laser beam to acquire displacement information that changes according to the displacement of the laser beam incident surface of the object 1 (see Figure 1). The separate-axis distance measuring sensor 450 emits a first measuring laser beam (measuring laser beam) towards the laser beam incident surface of the object 1 (see Figure 1) supported by the support base 230, and acquires displacement information of the laser beam incident surface of the object 1 by receiving the first measuring laser beam reflected by the laser beam incident surface. The separate-axis distance measuring sensor 450 can utilize sensors such as triangulation sensors, laser confocal sensors, white light confocal sensors, spectral interferometry sensors, and astigmatism sensors.

[0052] The laser focusing unit 400 includes a beam splitter 461, a pair of lenses 462 and 463, and a camera 464 for monitoring the intensity distribution of the laser light L. The beam splitter 461 separates the laser light L that has passed through the dichroic mirror 403 into a reflected component and a transmitted component. The laser light L reflected by the beam splitter 461 is sequentially incident on the pair of lenses 462 and 463 and the camera 464 along the Z-axis. The pair of lenses 462 and 463 constitute a bilateral telecentric optical system in which the entrance pupil plane 430a of the focusing lens unit 430 and the imaging plane of the camera 464 are in an imaging relationship. As a result, the image of the laser light L at the entrance pupil plane 430a of the focusing lens unit 430 is transferred (imaged) onto the imaging plane of the camera 464. As described above, the image of the laser beam L at the entrance pupil plane 430a of the focusing lens unit 430 is the image of the laser beam L modulated in the reflective spatial light modulator 410. Therefore, the laser processing apparatus 200 can understand the operating status of the reflective spatial light modulator 410 by monitoring the imaging results from the camera 464.

[0053] Furthermore, the laser focusing unit 400 includes a beam splitter 471, a lens 472, and a camera 473 for monitoring the optical axis position of the laser beam L. The beam splitter 471 separates the laser beam L that has passed through the beam splitter 461 into a reflected component and a transmitted component. The laser beam L reflected by the beam splitter 471 is sequentially incident on the lens 472 and the camera 473 along the Z-axis direction. The lens 472 focuses the incident laser beam L onto the imaging surface of the camera 473.

[0054] Multiple beam splitters 461, 471 are arranged within a cylindrical body 404 that extends along the Y-axis from the end 401d of the housing 401. A pair of lenses 462, 463 are arranged within a cylindrical body 405 erected on the cylindrical body 404 along the Z-axis, and a camera 464 is located at the end of the cylindrical body 405. Lens 472 is arranged within a cylindrical body 406 erected on the cylindrical body 404 along the Z-axis, and a camera 473 is located at the end of the cylindrical body 406. The cylindrical bodies 405 and 406 are arranged side by side in the Y-axis direction. The laser light L that passes through the beam splitter 471 may be absorbed by a damper or the like provided at the end of the cylindrical body 404, or it may be used for an appropriate purpose.

[0055] As shown in Figures 6 and 7, the laser focusing unit 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, a lens 487, an observation camera (imaging unit) 488, and a coaxial distance measuring sensor 460. The visible light source 481 emits visible light V along the Z-axis direction. The plurality of lenses 482 parallelize the visible light V emitted from the visible light source 481. The reticle 483 marks the visible light V. The mirror 484 reflects the visible light V parallelized by the plurality of lenses 482 in the X-axis 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 is sequentially transmitted along the Z-axis direction through the beam splitter 486 and the dichroic mirror 403, and then irradiated onto the object 1 (see Figure 1) supported on the support base 230 via the focusing lens unit 430.

[0056] The visible light V irradiated onto object 1 is reflected by the laser beam incident surface of object 1, enters the dichroic mirror 403 via the focusing lens unit 430, and passes through the dichroic mirror 403 along the Z-axis. The beam splitter 486 separates the visible light V that has passed through the dichroic mirror 403 into a reflected component and a transmitted component. The beam splitter 486 also reflects the second measurement laser beam L2 and its reflected light L2R, which will be described later. The visible light V that has passed through the beam splitter 486 passes through the half mirror 485 and enters the lens 487 and observation camera 488 sequentially along the Z-axis. The lens 487 focuses the incident visible light V onto the imaging surface of the observation camera 488. The observation camera 488 images the laser beam incident surface of object 1. The observation camera 488 receives visible light V that is incident on the laser beam incident surface via the reticle 483 and reflected from the laser beam incident surface. The laser processing apparatus 200 can understand the state of the object 1 by observing the imaging results from the observation camera 488.

[0057] Mirror 484, half mirror 485, and beam splitter 486 are arranged in a holder 407 mounted on the end 401d of the housing 401. Multiple lenses 482 and reticle 483 are arranged in a cylindrical body 408 erected on the holder 407 along the Z-axis, and a visible light source 481 is located at the end of the cylindrical body 408. Lens 487 is arranged in a cylindrical body 409 erected on the holder 407 along the Z-axis, and an observation camera 488 is located at the end of the cylindrical body 409. The cylindrical bodies 408 and 409 are arranged side by side in the X-axis direction. Visible light V transmitted through the half mirror 485 along the X-axis direction, and visible light V reflected in the X-axis direction by the beam splitter 486, may be absorbed by dampers or the like provided on the wall of the holder 407, or they may be used for appropriate purposes.

[0058] The coaxial distance measuring sensor 460 is mounted on the side of the holder 407. The coaxial distance measuring sensor 460 emits a second measuring laser beam L2 towards the laser beam incident surface of the object 1 (see Figure 1) supported on the support base 230, and detects the reflected light L2R of the second measuring laser beam L2 reflected by the laser beam incident surface to obtain displacement information of the laser beam incident surface of the object 1. The second measuring laser beam L2 emitted from the coaxial distance measuring sensor 460 is reflected by the beam splitter 486, passes through the dichroic mirror 403 and is guided to the focusing lens unit 430, where it is reflected by the laser beam incident surface near the focal point of the focusing lens unit 430. This reflected light L2R returns to the coaxial distance measuring sensor 460 via the reverse path of the second measuring laser beam L2. The coaxial distance measuring sensor 460 acquires displacement information of the object 1 by utilizing the fact that the state of reflected light L2R changes depending on the position of the laser beam incident surface relative to the focusing lens unit 430. For example, as the coaxial distance measuring sensor 460, a sensor such as an astigmatism type sensor can be used.

[0059] As shown in Figure 8, the separate-axis distance measuring sensor 450 includes a light-emitting element 451, such as a laser diode, that emits a first measurement laser beam L1, and a linear photodiode array (photodetector array) 453 that receives the first measurement laser beam L1 reflected from the laser beam incident surface of the object 1. In the separate-axis distance measuring sensor 450, the first measurement laser beam L1 is emitted from the light-emitting element 451 along a direction inclined with respect to the Z-axis direction. The emitted first measurement laser beam L1 is focused toward the object 1 via a lens 452 and reflected from the laser beam incident surface. The reflected first measurement laser beam L1 travels along a direction inclined with respect to the Z-axis direction, is focused toward the linear photodiode array 453 via a lens 454, and is received at the spot position of the linear photodiode array 453. The spot position (hereinafter also simply referred to as "spot position"), which is the position of this reception in the linear photodiode array 453, has a unique relationship with respect to the displacement of the laser beam incident surface. As a result, the separate-axis distance measuring sensor 450 acquires information corresponding to the spot position (light receiving position) as displacement information. Multiple linear photodiode arrays 453 may be provided.

[0060] The control unit 500 performs a first alignment process based on the imaging results from the observation camera 488, which involves operating the second movement mechanism 240 to adjust the position of the focusing lens unit 430 (focusing lens 432) in the Z-axis direction relative to the laser beam incident surface to a reference position or a predetermined height position at a predetermined distance from the reference position (i.e., performing height setting). The reference position is the position of the focusing lens unit 430 in the Z-axis direction when the mark on the reticle 483 is in focus on the image of the laser beam incident surface captured by the observation camera 488 (hereinafter also referred to as the "reticle focus position") (see Figure 9). Here, the optical system is adjusted so that the mark on the reticle 483 is in focus on the laser beam incident surface. In other words, the reticle focus position is the position when the mark on the reticle 483 is in focus on the laser beam incident surface. To put it another way, the reticle focus position is the position of the focusing lens unit 430 in the Z-axis direction when the focus of the focusing lens unit 430 is in focus on the laser beam incident surface. Furthermore, if the optical system is adjusted so that the mark on the reticle 483 is in focus at a predetermined height and distance from the laser beam incident surface, rather than at the laser beam incident surface, then the position where the mark on the reticle 483 is in focus will be at a predetermined height and distance from the laser beam incident surface, rather than at the laser beam incident surface.

[0061] When the first alignment process aligns the position of the focusing lens unit 430 in the Z-axis direction to a reference position or a predetermined height position, the control unit 500 performs an information recording process to record the spot position acquired by the separate axis distance measuring sensor 450 as a reference spot position (reference displacement information) in the storage unit of the control unit 500.

[0062] The control unit 500 operates the second moving mechanism 240 so that the spot position acquired by the separate-axis distance measuring sensor 450 becomes the reference spot position, and performs a second alignment process to align the position of the focusing lens unit 430 in the Z-axis direction with respect to the laser beam incident surface to the reference position or a predetermined height position (i.e., height setting).

[0063] If, as a result of executing the first alignment process, the control unit 500 cannot recognize that the mark on the reticle 483 is in focus on the image of the laser beam incident surface captured by the observation camera 488, and if the reference spot position is not recorded, it executes a processing unsuitability determination process to determine that the object 1 is unsuitable for processing.

[0064] If, as a result of executing the first alignment process, the control unit 500 cannot recognize that the mark on the reticle 483 is in focus on the image of the laser beam incident surface captured by the observation camera 488, it executes a switching process to execute the second alignment process if reference displacement information has been recorded by the information recording unit.

[0065] The control unit 500 performs a light-receiving amount adjustment process to adjust the separate-axis distance measuring sensor 450 so that the amount of light received by the linear photodiode array 453 is equal to or greater than a threshold. Examples of adjustments to the separate-axis distance measuring sensor 450 include increasing at least one of the gain and exposure time, and increasing the output of the light-emitting element 451. The control unit 500 comprises a first alignment unit, an information recording unit, a second alignment unit, a processing impossibility determination unit, a switching unit, and a light-receiving amount adjustment unit.

[0066] An example of height setting performed by the laser processing device 200 will be described.

[0067] An example of the height setting process when the reference spot position is recorded in the control unit 500 (i.e., when the reference spot position is not recorded or when the reference spot position is updated) will be explained with reference to the flowchart in Figure 10. Note that in this case, height setting is performed during initial adjustment, calibration, optical axis adjustment, etc.

[0068] First, the object 1 is placed on the support base 230. Based on the image of the laser beam incident surface of the object 1 captured by the observation camera 488 (the image with the reticle 483 projected), the control unit 500 drives the second moving mechanism 240 to move the laser focusing unit 400 in the Z-axis direction so that the height position of the focusing lens unit 430 matches the reticle's focus position (step S1).

[0069] For example, in step S1 above, an observation camera 488 acquires images at each Z-axis position of the focusing lens unit 430, and image processing is performed on each image to calculate a numerical value (score) that serves as an indicator of the contrast of the reticle 483. The position in the Z-axis direction of the laser focusing unit 400 where the numerical value of the contrast is maximum (peak) for a displacement in the Z-axis direction is set as the reticle focus position. In step S1 above, an image processing method using pattern matching or Laplacian differentiation may also be used.

[0070] Next, the control unit 500 determines whether the contrast score peak of the reticle 483 is optimal (step S2). For example, in step S2, if the peak of the contrast value was not detected in step S1, it is determined to be NO, and if the peak was detected, it is determined to be YES. If the result in step S2 is NO, it is determined that the focus state of the mark on the reticle 483 cannot be recognized in the image captured by the observation camera 488, and an error has occurred (step S3). The control unit 500 determines that the object 1 on the support base 230 is unprocessable and terminates the process (step S4).

[0071] In this embodiment, since a separate-axis distance measuring sensor 450, which is on a different axis from the focusing lens unit 430, is used as the displacement information acquisition unit, for example, the optical axis position of the separate-axis distance measuring sensor 450 and the optical axis position of the focusing lens unit 430 on the laser beam incident surface are separated in the direction of processing. Therefore, if the answer to step S2 is YES, the support base 230 is moved horizontally to move the object 1 horizontally so that the first measuring laser beam L1 strikes the position on the laser beam incident surface where the reticle 483 was projected in step S1 (for example, the center position in the width direction of the street) (step S5). As an example, if the position of the support base 230 in the X-axis direction in step S1 is [X0], and the position directly below the separate-axis distance measuring sensor 450 and the focusing lens unit 430 (optical axis position on the laser beam incident surface) is separated by α in the direction of processing, then in step S5, the support base 230 is moved in the X-axis direction so that the position of the support base 230 in the X-axis direction is [X0+α]. Note that this movement of the support base 230 is unnecessary if a sensor coaxial with the condensing lens unit 430 is used as the displacement information acquisition unit. Next, the spot position detected by the linear photodiode array 453 of the separate-axis distance measuring sensor 450 is recorded in the control unit 500 as the reference spot position (step S6). With the above steps completed, the height setting is finished and the process ends (step S7).

[0072] Next, an example of the height setting process when the reference spot position is recorded in the control unit 500 will be explained with reference to the flowchart in Figure 11. First, the object 1 is placed on the support base 230. The control unit 500 operates the second moving mechanism 240 so that the spot position detected by the linear photodiode array 453 becomes the reference spot position, and moves the focusing lens unit 430 to the reticle focus position in the Z-axis direction (step S11).

[0073] Next, the control unit 500 determines whether the amount of light from the first measurement laser beam received by the linear photodiode array 453 is optimal (step S12). In step S12, if the amount of light received by the linear photodiode array 453 is above a threshold, it is determined to be YES, and if the amount of light received by the linear photodiode array 453 is below the threshold, it is determined to be NO. If the result in step S12 is NO, the control unit 500 adjusts various parameters of the separate axis distance measuring sensor 450, and then returns to step S11 (step S13).

[0074] On the other hand, if the answer in step S12 is YES, the control unit 500 operates the second moving mechanism 240 to move the position of the focusing lens unit 430 in the Z-axis direction to a predetermined height position (step S14). The predetermined height position is any height position corresponding to the depth of the modified region formed in the object 1. With this, the height setting is completed and the process is terminated (step S15).

[0075] As an example, if the reference spot position SP0 shown in Figure 8 is recorded in the control unit 500, and when performing height setting for a thick object 1, suppose that in step S11, spot position SP1 is detected as shown in Figure 12(a). In this case, as shown in Figure 12(b), the laser focusing unit 400 is moved upward by the second moving mechanism 240 so that spot position SP1 becomes the reference spot position SP0. As a result, the focusing lens unit 430 is positioned at a height corresponding to the reticle focus position, and the height setting is completed.

[0076] In the laser processing apparatus 200, height setting is performed based on the imaging results of the observation camera 488. At this time, the spot position acquired by the separate-axis distance measuring sensor 450 is recorded as the reference spot position. However, if, for example, an object 1 is used in which a film (such as an AR vapor-deposited film) or tape material exists on the laser beam incident surface side, the mark of the reticle 483 may not be visible on the image of the laser beam incident surface captured by the observation camera 488 (see Figure 13). In this case, it may become difficult to identify the laser beam incident surface from the imaging results of the observation camera 488, and height setting may become difficult. In this regard, the laser processing apparatus 200 can perform height setting by operating the second movement mechanism 240 using the reference spot position. In other words, the laser processing apparatus 200 is equipped with both height setting functions based on the imaging results of the observation camera 488 and height setting based on the detection results of the separate-axis distance measuring sensor 450, thereby enabling height setting regardless of the object 1.

[0077] In other words, the laser processing apparatus 200 links the spot position of the linear photodiode array 453 with the reticle focus position. Even if the thickness of the object 1 is varied, the relationship between the spot position and the reticle focus position remains unchanged. Therefore, if it is difficult to identify the laser beam incident surface from the imaging results of the observation camera 488, this relationship can be used to perform height setting. The laser processing apparatus 200 can use the height setting from the imaging results of the observation camera 488 to prepare a data set of height settings from the detection results of the separate-axis distance measuring sensor 450. Of course, the laser processing apparatus 200 is also effective when it is easy to identify the laser beam incident surface.

[0078] In the laser processing apparatus 200, the observation camera 488 receives visible light V that is incident on the laser beam incident surface via the reticle 483 and reflected from the laser beam incident surface. The reference position is the reticle focus position. In this case, height setting can be performed using the reticle 483.

[0079] In the laser processing apparatus 200, if the reticle 483 is not in focus on the image of the laser beam incident surface captured by the observation camera 488 and the reference spot position is not recorded (NO in step S2 above), the object 1 is determined to be unprocessable. This allows the apparatus to determine that the object 1 is unprocessable because the height setting cannot be performed.

[0080] In the laser processing apparatus 200, the separate-axis distance measuring sensor 450 includes a light-emitting element 451 that emits a first measuring laser beam L1, and a linear photodiode array 453 that receives the first measuring laser beam L1 reflected from the laser beam incident surface. Displacement information that changes according to the displacement of the laser beam incident surface corresponds to the spot position of the linear photodiode array 453. In this case, it is possible to perform height setting by using the spot position of the linear photodiode array 453 as displacement information.

[0081] The laser processing apparatus 200 adjusts the separate-axis distance measuring sensor 450 so that the amount of light received by the linear photodiode array 453 is equal to or greater than a threshold. In this case, it is possible to prevent the inability to obtain useful spot position information due to insufficient light received by the linear photodiode array 453.

[0082] In the laser processing apparatus 200, if, after performing height setting based on the imaging results of the observation camera 488, it is not possible to recognize that the reticle 483 is in focus on the image of the laser beam incident surface captured by the observation camera 488, and the reference spot position is recorded by the control unit 500, the apparatus may switch to height setting based on the detection results of the separate-axis distance measuring sensor 450 (proceeding to step S11 above). In this case, height setting based on the imaging results of the observation camera 488 is prioritized, and if that height setting is not possible, it is possible to switch to height setting based on the detection results of the separate-axis distance measuring sensor 450.

[0083] In this embodiment, the height setting process performed by the laser processing apparatus 200 is not limited to the examples shown in Figures 10 and 11. For example, the height setting may be performed as follows. Another example of the height setting process when the reference spot position is recorded in the control unit 500 will be explained with reference to the flowchart in Figure 14. First, the object 1 is placed on the support base 230. Based on the image of the laser light incident surface of the object 1 captured by the observation camera 488, the control unit 500 drives the second moving mechanism 240 to move the laser focusing unit 400 in the Z-axis direction so that the height position of the focusing lens unit 430 matches the reticle focus position (step S21).

[0084] Next, the control unit 500 determines whether the contrast score peak of the reticle is optimal (step S22). If the result in step S22 is NO, the control unit 500 determines that it cannot recognize the mark of the reticle 483 to be in focus on the image captured by the observation camera 488, and determines that an error has occurred (step S23). As a result, the control unit 500 determines that the object 1 on the support base 230 cannot be processed and terminates the process (step S24). On the other hand, if the result in step S22 is YES, the control unit 500 operates the second moving mechanism 240 to move the position of the focusing lens unit 430 in the Z-axis direction to a predetermined height position (step S25). The predetermined height position is an arbitrary height position corresponding to the depth of the modified region to be formed in the object 1. Next, similar to step S5 above, the support base 230 is moved horizontally to move the object 1 horizontally so that the first measuring laser beam L1 strikes the position on the laser beam incident surface where the reticle 483 was projected in step S21 (step S26). Subsequently, the spot position detected by the linear photodiode array 453 of the separate axis distance measuring sensor 450 is recorded in the control unit 500 as the reference spot position (step S27). With this, the height setting is completed and the process ends (step S28).

[0085] Next, an example of processing when the reference spot position is recorded in the control unit 500 will be explained with reference to the flowchart in Figure 15. First, the object 1 is placed on the support base 230. The control unit 500 operates the second moving mechanism 240 so that the spot position detected by the linear photodiode array 453 of the separate-axis distance measuring sensor 450 becomes the reference spot position, and moves the focusing lens unit 430 to a predetermined height position in the Z-axis direction (step S31).

[0086] Next, the control unit 500 determines whether the light intensity of the first measurement laser beam L1 received by the linear photodiode array 453 is optimal (step S32). If the result in step S32 is NO, the control unit 500 adjusts various parameters of the separate axis distance measuring sensor 450 and then returns to step S31 (step S33). On the other hand, if the result in step S32 is YES, the height setting is completed and the process ends (step S34).

[0087] The above describes embodiments relating to one aspect of this disclosure, but this disclosure is not limited to the embodiments described above.

[0088] The above embodiment includes a separate-axis distance measuring sensor 450 as the displacement information acquisition unit, but the displacement information acquisition unit is not particularly limited. For example, the displacement information acquisition unit may be a sensor that utilizes astigmatism, in which case it has a four-segment photodiode. As an example, the above-mentioned coaxial distance measuring sensor 460 may be used as the displacement information acquisition unit. For example, the displacement information acquisition unit may be a sensor that utilizes triangulation, in which case it has a linear photodiode array or a linear image sensor. For example, the displacement information acquisition unit may be a sensor that utilizes eccentric triangulation, in which case it has a linear photodiode array or a linear image sensor. For example, the displacement information acquisition unit may be a sensor that utilizes confocality, in which case it has a photodiode. For example, the displacement information acquisition unit may be a sensor that utilizes spectral interference, in which case it has a CCD image sensor.

[0089] Figure 16 is a schematic plan view showing the support base 230 and reference support base (reference support section) 230K of the modified laser processing apparatus 600. Figure 17 is a schematic plan view showing the state in which the object 1 and the reference object 1K are supported on the support base 230 and the reference support base 230K of Figure 16. As shown in Figures 16 and 17, the modified laser processing apparatus 600 may further include a reference support base 230K in relation to the laser processing apparatus 200.

[0090] The reference support base 230K supports the reference object 1K, which does not contain a film or tape material on the laser beam incident surface side. The reference support base 230K is positioned next to the support base 230. The reference support base 230K has a size corresponding to the size of the reference object 1K. Here, the reference support base 230K is smaller than the support base 230. The reference object 1K is an object in which the state in which the mark of the reticle 483 is in focus on the image of the laser beam incident surface captured by the observation camera 488 can be recognized. The reference object 1K is an object that is determined to be YES in step S2 above.

[0091] In the modified laser processing apparatus 600, when the reference spot position is recorded in the control unit 500, for example, the height setting shown in the flowchart of Figure 18(a) is performed. That is, the reference object 1K is placed on the reference support base 230K. The control unit 500 drives the first movement mechanism 220 and the second movement mechanism 240 to move the laser focusing unit 400 so that the optical axis of the focusing lens unit 430 is positioned on the reference object 1K (step S41). Based on the image of the laser beam incident surface of the reference object 1K captured by the observation camera 488, the control unit 500 drives the second movement mechanism 240 to move the laser focusing unit 400 in the Z-axis direction so that the height position of the focusing lens unit 430 matches the reticle focus position (step S42).

[0092] The control unit 500 operates the second moving mechanism 240 to move the position of the focusing lens unit 430 in the Z-axis direction to a predetermined height position (step S43). Subsequently, similar to step S5, the laser focusing unit 400 is moved horizontally so that the first measuring laser beam L1 strikes the position on the laser beam incident surface where the reticle 483 was projected in step S42 (step S44). Subsequently, the spot position detected by the linear photodiode array 453 of the separate axis distance measuring sensor 450 at that time is recorded in the control unit 500 as the reference spot position (step S45). With this, the height setting is completed and the process ends (step S46).

[0093] In the modified laser processing apparatus 600, if the reference spot position is recorded in the control unit 500, height setting is performed, for example, as shown in the flowchart of Figure 18(b). First, the object 1 is placed on the support base 230. The control unit 500 operates the second moving mechanism 240 so that the spot position detected by the linear photodiode array 453 of the separate-axis distance measuring sensor 450 becomes the reference spot position, and moves the focusing lens unit 430 to a predetermined height position in the Z-axis direction (step S51). With this, height setting is completed and the process ends (step S52).

[0094] According to the laser processing apparatus 600, height setting is performed on a reference object 1K supported by a reference support base 230K using imaging results from an observation camera 488, and the spot position acquired at this time can be recorded as the reference spot position. Since height setting is completed on the reference object 1K immediately before processing, it is resistant to optical axis misalignment. By performing height setting once on the reference object 1K, it is possible to reduce the number of height settings required from the second time onward, thereby improving cycle time (reduction of height setting process).

[0095] In the embodiments and modifications described above, the control unit 500 may, when the reference spot position is recorded by the control unit 500, operate the second movement mechanism 240 so that the spot position acquired by the separate-axis distance measuring sensor 450 becomes the reference spot position, and then operate the second movement mechanism 240 so that the position of the focusing lens unit 430 in the Z-axis direction relative to the laser light incident surface matches the reference position based on the imaging results from the observation camera 488.

[0096] For example, as shown in the flowchart of Figure 19, the laser focusing unit 400 is moved arbitrarily along the Z-axis so that the focal point of the focusing lens unit 430 is located in the center of the object 1 (step S61). Subsequently, the control unit 500 operates the second moving mechanism 240 so that the spot position detected by the linear photodiode array 453 of the separate-axis distance measuring sensor 450 becomes the reference spot position, and moves the focusing lens unit 430 in the Z-axis direction (step S62). From this state, the reticle focus position is searched, that is, the second moving mechanism 240 is operated to match the reference position based on the imaging results from the observation camera 488 (step S63). This makes it possible to speed up height setting compared to when height setting is performed without using the spot position of the separate-axis distance measuring sensor 450 (when height setting is performed only from the imaging results of the observation camera 488).

[0097] In the embodiments and modifications described above, the separate-axis distance measuring sensor 450 may include a branching optical system 455 that branches the first measuring laser beam L1 reflected from the laser beam incident surface of the object 1 into a plurality (here, two) branch measuring laser beams L11 and L12. The linear photodiode array 453 receives the two branch measuring laser beams L11 and L12. The displacement information that changes according to the displacement of the laser beam incident surface corresponds to the intervals H1, H2, and H3 of the receiving positions of the two branch measuring laser beams L11 and L12 in the linear photodiode array 453. The branching optical system 455 includes lenses 456 and 457. As shown in the figure, the interval between the branch measuring laser beams L11 and L12 changes to intervals H1, H2, and H3 as the distance between the laser beam incident surface and lens 454 (displacement of the laser beam incident surface) changes. In this case, the spacing H1, H2, and H3 of the light-receiving positions of the branch measurement laser beams L11 and L12 in the linear photodiode array 453 can be used as displacement information to perform height setting.

[0098] The above embodiment includes a reflective spatial light modulator 410, but the spatial light modulator is not limited to a reflective type and may also include a transmissive spatial light modulator. In the above embodiment and modifications, the modified region may be, for example, a crystalline region, a recrystallized region, or a gettering region formed inside the object 1. The crystalline region is a region that maintains the structure of the object 1 before processing. The recrystallized region is a region that solidifies as a single crystal or polycrystalline material after evaporation, plasmaification, or melting. The gettering region is a region that exhibits a gettering effect by collecting and capturing impurities such as heavy metals, and may be formed continuously or intermittently.

[0099] In the above embodiment, the control unit 500 stores the reference spot position, but the storage method is not particularly limited. For example, the reference spot position to be recorded may be prepared as a dataset based on the imaging results of the observation camera 488 and the detection results of the separate-axis distance measuring sensor 450, as described above. Such a dataset may include, for example, a coordinate table representing each position of the focusing lens unit 430 in the Z-axis direction (including the reticle focus position) and the spot position of the linear photodiode array 453 corresponding to each position. In this case, height setting independent of the object 1 is possible. Furthermore, height setting that does not require the process of detecting the position of the laser beam incident surface becomes possible.

[0100] Incidentally, there are cases where laser processing is performed on an object 1 with a transparent tape 101 (see Figure 22(b)) placed on the laser beam incident surface (in this case, the back surface 1b). The transparent tape 101 is a tape-shaped transparent member that is transparent to the laser beam L and the first measuring laser beam L1. In this case, for example, the mark of the reticle 483 (see Figure 7) may become blurred in the image of the laser beam incident surface captured by the observation camera 488, raising concerns that it may become difficult to perform height setting.

[0101] The transparency of the transparent tape 101 means that its transparency is higher than that of the parts of the object 1 other than the transparent tape 101. Transparency means, for example, that laser light L and the first measuring laser light L1 pass through it, and more specifically, that laser light L and the first measuring laser light L1 pass through while maintaining their intensity. For example, transparency may mean that the transmittance to laser light L and the first measuring laser light L1 is 85% or more. For example, the object 1 is a through-silicon via (TSV) wafer with a thickness of 30 μm.

[0102] Therefore, as shown in Figure 21, when forming a modified region on the object 1 on which the transparent tape 101 is provided, the control unit 500 of the modified laser processing apparatus 700 calculates an offset amount based on the tape information (transparent member information). Based on the calculated offset amount, the control unit 500 changes the reference spot position that has been stored in advance. In other words, the control unit 500 corrects the reference spot position based on the offset amount so that there is no misalignment of the reference spot position caused by the change in the optical path of the first measuring laser beam L1 due to the presence of the transparent tape 101.

[0103] The tape information includes information regarding the thickness and refractive index of the transparent tape 101. The offset amount corresponds to the difference between the optical path of the first measurement laser beam L1B when the transparent tape 101 is present (see Figure 22(b)) and the optical path of the first measurement laser beam L1A when the transparent tape 101 is absent (see Figure 22(a)). Specifically, the control unit 500 can calculate the offset amount T according to the following calculation formula, as illustrated in Figure 23. sinα1 = (n1 / n2)·sinα T=(2d·tanα-2d·(n1·sinα) / (n2·cosα1))·cosα n1: refractive index of the surrounding area, n2: refractive index of transparent tape 101, α1: angle of refraction

[0104] The reference spot position is acquired and stored in advance in the same manner as described above. The reference spot position is the spot position acquired by the separate-axis distance measuring sensor 450 when the position of the focusing lens unit 430 in the Z-axis direction is aligned to the reference position or a predetermined height position by the first alignment process on an object 1 that does not have the transparent tape 101.

[0105] Returning to Figure 21, the laser processing apparatus 700 includes an input unit 701 that receives input regarding the presence or absence of the transparent tape 101 and tape information. In the input unit 701, for example, the presence or absence of the transparent tape 101, the thickness of the transparent tape 101, and the refractive index of the transparent tape 101 are input by selection by the user or the like. The input unit 701 is not particularly limited and may be various devices. The control unit 500 determines whether or not the transparent tape 101 is present based on the input regarding the presence or absence of the transparent tape 101 from the input unit 701. If the control unit 500 determines that the transparent tape 101 is present, it calculates the offset amount based on the input regarding tape information from the input unit 701.

[0106] An example of the processing performed by such a laser processing apparatus 700 will be explained with reference to the flowchart in Figure 24. First, the object 1 is placed on the support base 230. The control unit 500 determines, based on the input from the input unit 701, whether or not the transparent tape 101 is on the laser beam incident surface of the object 1 (step S71). If the result in step S71 is YES, the control unit 500 calculates an offset amount based on the tape information input by the input unit 701 (step S72). The control unit 500 changes the pre-stored reference spot position based on the calculated offset amount (step S74).

[0107] Next, the control unit 500 operates the second moving mechanism 240 so that the spot position detected by the linear photodiode array 453 of the separate-axis distance measuring sensor 450 becomes the reference spot position, and moves the focusing lens unit 430 to the reticle focus position in the Z-axis direction (step S75). The control unit 500 determines whether the amount of light of the first measuring laser beam L1 received by the linear photodiode array 453 is optimal (step S76). If the result in step S76 is YES, the control unit 500 operates the second moving mechanism 240 to move the position of the focusing lens unit 430 in the Z-axis direction to a predetermined height position (step S77). If the result in step S76 is NO, the control unit 500 adjusts various parameters of the separate-axis distance measuring sensor 450 and then returns to step S75 (step S78).

[0108] On the other hand, if the answer in step S71 is NO, the control unit 500 operates the second moving mechanism 240 so that the spot position detected by the linear photodiode array 453 of the separate-axis distance measuring sensor 450 becomes the reference spot position, and moves the focusing lens unit 430 to the reticle focus position in the Z-axis direction (step S79). The control unit 500 determines whether the amount of light of the first measuring laser beam L1 received by the linear photodiode array 453 is optimal (step S80). If the answer in step S80 is YES, the control unit 500 operates the second moving mechanism 240 to move the position of the focusing lens unit 430 in the Z-axis direction to a predetermined height position (step S81). If the answer in step S80 is NO, the control unit 500 adjusts various parameters of the separate-axis distance measuring sensor 450 and then returns to step S79 (step S82). After step S77 or step S81, the height setting is completed and the process ends (step S83).

[0109] The above effects are also achieved in the laser processing apparatus 700. In the laser processing apparatus 700, the separate-axis distance measuring sensor 450 emits a first measuring laser beam L1 to the laser beam incident surface of the object 1, and receives the first measuring laser beam L1 reflected by the laser beam incident surface to acquire the spot position (receiving position, displacement information) in the linear photodiode array 453. The control unit 500 calculates an offset amount based on tape information including information on the thickness and refractive index of the transparent tape 101, and changes the pre-stored reference spot position based on the calculated offset amount. This makes it possible to handle object 1 in which a transparent tape 101 is provided on the laser beam incident surface. It is also possible to handle object 1 in which it is difficult to identify the mark on the reticle 483 (see Figure 7). This makes it possible to eliminate variations in the formation position of the modified region due to blurring of the mark on the reticle 483.

[0110] The laser processing apparatus 700 is equipped with an input unit 701. The control unit 500 determines whether or not there is a transparent tape 101 based on the input from the input unit 701, and calculates an offset amount if it determines that there is a transparent tape 101. This makes it possible to handle an object 1 on which a transparent tape 101 is placed on the laser beam incident surface using the input from the input unit 701. The correction function for the reference spot position based on the offset amount can be switched (ON / OFF).

[0111] The transparent member is not limited to the transparent tape 101, but may be other tape-shaped, film-shaped, layered, or block-shaped members. The calculation for determining the offset amount is not limited and other calculations may be used. The calculation for changing the reference spot position is not limited and other calculations may be used. Tape information may be input in advance via the input unit 701, or the refractive index and thickness of the transparent tape 101 may be measured for each laser processing.

[0112] The above embodiments may be applied to processes such as trimming, slicing, and ablation. The components in the above embodiments and modifications are not limited to the materials and shapes described above, and various materials and shapes can be applied. Furthermore, the components in the above embodiments and modifications can be arbitrarily applied to the components in other embodiments or modifications. [Explanation of Symbols]

[0113] 1...Object, 101...Transparent tape (transparent material), 200, 600, 700...Laser processing device, 230...Support base (support part), 230K...Reference support base (reference support part), 240...Second moving mechanism (movement mechanism), 400...Laser focusing unit (irradiation part), 430...Focusing lens unit (focusing lens), 450...Separate axis distance sensor (displacement information acquisition unit), 451...Light-emitting element, 453...Linear photodiode array (light-receiving element array), 483...Reticle, 488...Observation camera (imaging unit), 500...Control unit (first alignment unit, information recording unit, second alignment unit, processing failure determination unit, switching unit, light reception amount adjustment unit), 701...Input unit, L...Laser light, L1, L1A, L1B...First measurement laser light (measurement laser light).

Claims

1. A laser processing apparatus that irradiates an object with laser light to form a modified region, A support portion that supports the aforementioned object, An irradiation unit that irradiates the object with the laser light through a focusing lens, A moving mechanism for moving the focusing lens along the optical axis direction of the focusing lens, An imaging unit for imaging the laser light incident surface of the object, A displacement information acquisition unit that uses a measuring laser beam to acquire displacement information that changes according to the displacement of the laser beam incident surface, Based on the imaging results from the imaging unit, the first alignment unit operates the moving mechanism so that the position of the focusing lens in the optical axis direction relative to the laser light incident surface matches a reference position or a predetermined height position at a predetermined distance from the reference position. An information recording unit records the displacement information acquired by the displacement information acquisition unit when the position of the focusing lens in the optical axis direction is aligned with the reference position or predetermined height position by the first alignment unit, as reference displacement information linked to the reference position or predetermined height position. The system includes a second alignment unit that operates the moving mechanism so that the displacement information acquired by the displacement information acquisition unit becomes the reference displacement information, and aligns the position of the focusing lens in the optical axis direction with respect to the laser beam incident surface to the reference position or the predetermined height position, The imaging unit receives visible light that is incident on the laser light incident surface via the reticle and reflected from the laser light incident surface. The aforementioned reference position is the position of the focusing lens when the reticle is in focus on the image of the laser light incident surface captured by the imaging unit, in a laser processing apparatus.

2. The laser processing apparatus according to claim 1, further comprising a processing failure determination unit that, when processing by the first alignment unit is performed and the reticle cannot be recognized in focus on the image of the laser beam incident surface captured by the imaging unit, determines that the object cannot be processed if the reference displacement information is not recorded by the information recording unit.

3. The laser processing apparatus according to claim 1 or 2, further comprising a switching unit that, when the processing by the first alignment unit is performed and the reticle cannot be recognized as being in focus on the image of the laser beam incident surface captured by the imaging unit, the reference displacement information is recorded by the information recording unit, and the processing by the second alignment unit is performed.

4. The displacement information acquisition unit includes a light-emitting element that emits the measuring laser light and a light-receiving element array that receives the measuring laser light reflected from the laser light incident surface. The laser processing apparatus according to any one of claims 1 to 3, wherein the displacement information that changes according to the displacement of the laser light incident surface corresponds to the light receiving position of the measuring laser light in the light receiving element array.

5. The displacement information acquisition unit includes a light-emitting element that emits the measurement laser light, a branching optical system that branches the measurement laser light reflected from the laser light incident surface into a plurality of branched measurement laser beams, and a light-receiving element array that receives the plurality of branched measurement laser beams. The laser processing apparatus according to any one of claims 1 to 3, wherein the displacement information that changes according to the displacement of the laser light incident surface corresponds to the interval between the receiving positions of a plurality of branch measurement laser beams in the light receiving element array.

6. The laser processing apparatus according to claim 4 or 5, further comprising a light-receiving amount adjustment unit that adjusts the displacement information acquisition unit so that the amount of light received in the light-receiving element array is equal to or greater than a threshold.

7. The laser processing apparatus according to any one of claims 1 to 6, further comprising a reference support portion on the laser beam incident surface side for supporting a reference object that does not contain a film or tape material.

8. The first alignment part is, A laser processing apparatus according to any one of claims 1 to 7, wherein, when the reference displacement information is recorded by the information recording unit, the movement mechanism is operated so that the displacement information acquired by the displacement information acquisition unit becomes the reference displacement information, and then, based on the imaging result by the imaging unit, the movement mechanism is operated so that the position of the focusing lens in the optical axis direction with respect to the laser light incident surface matches the reference position.

9. The displacement information acquisition unit acquires the displacement information by emitting a measuring laser beam onto the laser beam incident surface and receiving the measuring laser beam reflected by the laser beam incident surface. When a transparent member having transparency to the laser light and the measuring laser light is provided on the laser light incident surface to form the modified region on the object, the second alignment portion is: Based on the information of the transparent member, including information regarding the thickness and refractive index of the transparent member, an offset amount is calculated that corresponds to the deviation of the optical path of the measuring laser beam when the transparent member is present from the optical path when the transparent member is absent. A laser processing apparatus according to any one of claims 1 to 8, wherein the reference displacement information stored in the information recording unit in advance is changed based on the calculated offset amount.

10. The system includes an input unit that receives input regarding the presence or absence of the transparent member and information about the transparent member, The second alignment part is, The laser processing apparatus according to claim 9, which determines whether or not the transparent member is present based on the input of the input unit, and calculates the offset amount if it is determined that the transparent member is present.

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