Laser processing device

Abstract

A laser processing apparatus is provided with: a support unit that supports an object; a first light source that emits processing light; a second light source that emits non-processing light; an objective lens unit that transmits the processing light and the non-processing light to the object side; a light detection unit that detects reflected light of the non-processing light that is reflected by the object and that has passed through the objective lens unit from the object side; and a processing unit that acquires information relating to contamination of the light emission surface of the objective lens unit on the basis of the detection result of the light detection unit. At least one of the optical axis of the non-processing light and the optical axis of the reflected light is shifted in a predetermined direction from the optical axis of the objective lens section on the light emission surface of the objective lens section.

Description

Technical Field

[0001] This disclosure relates to a laser processing apparatus. Background Technology

[0002] A laser processing apparatus is known, comprising a support for supporting an object, a light source for emitting processing light, a laser adjustment section for adjusting the processing light emitted from the light source, an objective lens for focusing the processing light adjusted by the laser adjustment section onto the object, and a moving section for moving the laser processing head (see, for example, Japanese Patent Application Publication No. 2020-069487). Such a laser processing apparatus is highly effective for various applications such as wafer dicing, wafer thinning, and wafer trimming. Summary of the Invention

[0003] In the laser processing apparatus described above, contamination sometimes adheres to the light-emitting surface of the objective lens in the laser processing head, which focuses the processing light onto the workpiece. In such cases, monitoring the contamination status of the light-emitting surface of the objective lens is crucial to preventing a decrease in processing quality.

[0004] Therefore, the purpose of this disclosure is to provide a laser processing apparatus that can reliably monitor the contamination status of the light exit surface of the objective lens.

[0005] One aspect of the laser processing apparatus disclosed herein is as follows: [1] "Laser processing apparatus comprising: a support portion for supporting the object; a first light source for emitting processing light; a second light source for emitting non-processing light; an objective lens portion for transmitting the processing light and the non-processing light to the object side; a light detection portion for detecting reflected light of the non-processing light reflected by the object and transmitted through the objective lens portion from the object side; and a processing portion for acquiring information related to contamination of the light emitting surface of the objective lens portion based on the detection result of the light detection portion, wherein at least one of the optical axis of the non-processing light and the optical axis of the reflected light is offset in a predetermined direction from the optical axis of the objective lens portion on the light emitting surface of the objective lens portion."

[0006] In the laser processing apparatus described above [1], non-processing light emitted from the second light source irradiates the object through the objective lens, and the reflected light of the non-processing light reflected by the object passes through the objective lens and is detected by the light detection unit. At this time, at least one of the optical axis of the non-processing light and the optical axis of the reflected light is offset from the optical axis of the objective lens in a predetermined direction on the light emission surface of the objective lens. Here, when processing of the object is performed by irradiation with processing light, contamination is more likely to adhere to the surrounding area of ​​the light emission surface of the objective lens (the area surrounding the central area) than to the central area (including the central area of ​​the optical axis) (this is an insight discovered by the inventors). Therefore, by detecting the reflected light of the non-processing light as described above, information related to the contamination of the light emission surface of the objective lens can be obtained. Thus, according to the laser processing apparatus described above [1], the contamination state of the light emission surface of the objective lens can be reliably grasped.

[0007] One aspect of the laser processing apparatus disclosed herein may also be: [2] "According to the laser processing apparatus described in [1] above, wherein the optical axis of the non-processing light is offset from the optical axis of the objective lens on one side of the predetermined direction on the light emitting surface of the objective lens, and the optical axis of the reflected light is offset from the optical axis of the objective lens on the other side of the predetermined direction on the light emitting surface of the objective lens." According to the laser processing apparatus described in [2], since the contamination state of the light emitting surface of the objective lens is easily reflected on the non-processing light and the reflected light respectively, the contamination state of the light emitting surface of the objective lens can be more reliably grasped.

[0008] One aspect of the laser processing apparatus disclosed herein may also be: [3] "The laser processing apparatus according to [1] or [2] above, wherein the predetermined direction is the direction in which the processing light irradiating the object moves relative to the object." When processing an object by irradiating it with processing light, for example, if the direction in which the processing light irradiating the object moves relative to the object is constant, then the portions on both sides of the optical axis of the objective lens in that direction are particularly prone to contamination in the area surrounding the light emitting surface of the objective lens (this is an insight discovered by the inventors). Therefore, according to the laser processing apparatus described in [3], the contamination status of the light emitting surface of the objective lens can be more reliably monitored.

[0009] One aspect of the laser processing apparatus disclosed herein may also be: [4] "The laser processing apparatus according to any one of [1] to [3] above, wherein the processing unit acquires information related to the height of a predetermined surface of the object based on the detection result of the light detection unit." According to the laser processing apparatus described in [4], the same second light source and light detection unit can be used to acquire information related to contamination of the light emitting surface of the objective lens and information related to the height of a predetermined surface of the object.

[0010] The laser processing apparatus of this disclosure may also be: [5] "the laser processing apparatus according to any one of [1] to [4] above, wherein the processing unit includes a display showing the information related to the contamination." According to the laser processing apparatus described in [5], information related to the contamination of the light-emitting surface of the objective lens can be reliably notified to the operator.

[0011] The laser processing apparatus of one aspect of this disclosure may also be: [6] "The laser processing apparatus according to any one of [1] to [5] above, wherein the objective lens comprises: at least one lens that focuses the processing light onto the object; a lens barrel that holds the at least one lens; and a protective cover that is detachable from the lens barrel and has the light emitting surface." According to the laser processing apparatus described in [6], a protective cover having a contaminated light emitting surface can be replaced with a new protective cover based on information related to contamination of the light emitting surface of the objective lens. Attached Figure Description

[0012] Figure 1 This is a perspective view of a laser processing apparatus according to one embodiment.

[0013] Figure 2 yes Figure 1 A front view of a portion of the laser processing apparatus shown.

[0014] Figure 3 yes Figure 1 The front view of the laser processing head is shown.

[0015] Figure 4 yes Figure 1 The image shows a side view of the laser processing head.

[0016] Figure 5 yes Figure 4 The diagram shows the structure of the laser processing head.

[0017] Figure 6 yes Figure 5 An exploded stereoscopic view of the objective lens section is shown.

[0018] Figure 7 yes Figure 5 The diagram shows the structure of the ranging unit.

[0019] Figure 8 yes Figure 7 The diagram shows a portion of the distance measuring unit.

[0020] Figure 9 It means Figure 7 The diagram shows the optical paths of the ranging light and the reflected light in the ranging unit.

[0021] Figure 10 It means Figure 5 A schematic diagram showing the state of the light exiting surface of the objective lens.

[0022] Figure 11 It means Figure 5 A photograph showing the state of the light exiting surface of the objective lens.

[0023] Figure 12 It is a table representing the brightness value of the reflected light of the ranging beam for each Z value.

[0024] Figure 13 It is a table representing various results for each ablation root number. Detailed Implementation

[0025] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Furthermore, in the drawings, identical or equivalent parts are labeled with the same symbols, and repeated descriptions are omitted.

[0026] [Structure of laser processing equipment]

[0027] like Figure 1 As shown, the laser processing apparatus 1 includes multiple moving mechanisms 5 and 6, a support 7, a pair of laser processing heads 10A and 10B, a light source unit 8, and a control unit 9. Hereinafter, the first direction will be referred to as the Z direction, the second direction perpendicular to the first direction will be referred to as the X direction, and the third direction perpendicular to both the first and second directions will be referred to as the Y direction. In this embodiment, the Z direction is a vertical direction, and the X and Y directions are horizontal directions.

[0028] The moving mechanism 5 includes a fixed part 51, a moving part 53, and a mounting part 55. The fixed part 51 is mounted on the device frame 1a. The moving part 53 is mounted on a track provided on the fixed part 51 and is movable along the Y direction. The mounting part 55 is mounted on a track provided on the moving part 53 and is movable along the X direction.

[0029] The moving mechanism 6 includes a fixed part 61, a pair of moving parts 63 and 64, and a pair of mounting parts 65 and 66. The fixed part 61 is mounted on the device frame 1a. The pair of moving parts 63 and 64 are respectively mounted on a track provided on the fixed part 61 and can move independently along the Y direction. The mounting part 65 is mounted on a track provided on the moving part 63 and can move along the Z direction. The mounting part 66 is mounted on a track provided on the moving part 64 and can move along the Z direction.

[0030] The support 7 is mounted on the rotation axis of the mounting portion 55 provided in the moving mechanism 5, and can rotate about an axis parallel to the Z direction as its center line. The support 7 supports the object W. The object W is, for example, a wafer.

[0031] like Figure 1 and Figure 2 As shown, laser processing head 10A is mounted on mounting portion 65 of the moving mechanism 6. When laser processing head 10A is positioned opposite support portion 7 along the Z-direction, it irradiates laser light (processing light) L onto the object W supported by support portion 7. Laser processing head 10B is mounted on mounting portion 66 of the moving mechanism 6. When laser processing head 10B is positioned opposite support portion 7 along the Z-direction, it irradiates laser light L onto the object W supported by support portion 7.

[0032] like Figure 1 As shown, the light source unit 8 has a pair of light sources (first light sources) 81 and 82. The pair of light sources 81 and 82 are mounted on the device frame 1a. The pair of light sources 81 and 82 respectively emit lasers L. The laser L emitted from the emission portion 81a of the light source 81 is guided to the laser processing head 10A by an optical fiber 2. The laser L emitted from the emission portion 82a of the light source 82 is guided to the laser processing head 10B by another optical fiber 2.

[0033] The control unit 9 controls various parts of the laser processing apparatus 1 (multiple moving mechanisms 5, 6, a pair of laser processing heads 10A, 10B, and the light source unit 8, etc.). The control unit 9 is configured as a computer device including a processor, memory, storage, and communication equipment. In the control unit 9, software (programs) loaded into the memory are executed by the processor, which controls the reading and writing of data in the memory and storage, as well as communication based on the communication equipment. Thus, the control unit 9 performs various functions. The control unit 9 has a display 91. The display 91 displays various information. The display 91 can also be configured as a touch panel that receives input from operator instructions.

[0034] The laser processing apparatus 1 configured as described above can be used for various purposes, such as dicing wafers, slicing wafers to thin them, and trimming wafers to remove the outer periphery. Here, an example of a process performed by the laser processing apparatus 1 will be described. This example is an example of cutting a wafer W into multiple chips, forming modified regions inside the wafer W along multiple lines set in a lattice pattern (i.e., an example of the first half of the dicing process).

[0035] First, the moving mechanism 5 moves the support portion 7 along the X and Y directions respectively, so that the support portion 7 supporting the object W is positioned opposite a pair of laser processing heads 10A and 10B in the Z direction. Next, the moving mechanism 5 rotates the support portion 7 about an axis parallel to the Z direction, so that multiple lines extending in one direction in the object W are aligned along the X direction.

[0036] Next, the moving mechanism 6 moves the laser processing head 10A along the Y direction, so that the focusing point of the laser L emitted from the laser processing head 10A (hereinafter referred to as "laser L of laser processing head 10A") is located on a line extending in one direction. On the other hand, the moving mechanism 6 moves the laser processing head 10B along the Y direction, so that the focusing point of the laser L emitted from the laser processing head 10B (hereinafter referred to as "laser L of laser processing head 10B") is located on another line extending in one direction. Next, the moving mechanism 6 moves the laser processing head 10A along the Z direction, so that the focusing point of the laser L of laser processing head 10A is located inside the object W. On the other hand, the moving mechanism 6 moves the laser processing head 10B along the Z direction, so that the focusing point of the laser L of laser processing head 10B is located inside the object W.

[0037] Next, light source 81 emits laser L, and laser processing head 10A irradiates object W with laser L. Simultaneously, light source 82 emits laser L, and laser processing head 10B irradiates object W with laser L. At the same time, the moving mechanism 5 moves the support 7 along the X direction, causing the focusing point of laser L from laser processing head 10A to move relative to each other along a line extending in one direction, and the focusing point of laser L from laser processing head 10B to move relative to each other along other lines extending in one direction. Thus, the laser processing apparatus 1 forms modified regions inside object W along multiple lines extending in one direction within object W.

[0038] Next, the moving mechanism 5 causes the support 7 to rotate about an axis parallel to the Z direction, so that multiple lines extending in the object W along other directions orthogonal to one direction are along the X direction.

[0039] Next, the moving mechanism 6 moves the laser processing head 10A along the Y direction, so that the focusing point of the laser L of the laser processing head 10A is located on a line extending in another direction. Conversely, the moving mechanism 6 moves the laser processing head 10B along the Y direction, so that the focusing point of the laser L of the laser processing head 10B is located on another line extending in another direction. Next, the moving mechanism 6 moves the laser processing head 10A along the Z direction, so that the focusing point of the laser L of the laser processing head 10A is located inside the object W. Conversely, the moving mechanism 6 moves the laser processing head 10B along the Z direction, so that the focusing point of the laser L of the laser processing head 10B is located inside the object W.

[0040] Next, light source 81 emits laser L, and laser processing head 10A irradiates object W with laser L. Simultaneously, light source 82 emits laser L, and laser processing head 10B irradiates object W with laser L. At the same time, the moving mechanism 5 moves the support 7 along the X direction, causing the focusing point of laser L in laser processing head 10A to move relative to each other along a line extending in another direction, and the focusing point of laser L in laser processing head 10B to move relative to each other along other lines extending in other directions. Thus, the laser processing apparatus 1 forms modified regions inside object W along multiple lines extending in other directions orthogonal to one direction.

[0041] Furthermore, in one example of the aforementioned processing, a pair of light sources 81 and 82 emit transmissive laser light L towards the object W via pulse oscillation, for example. If such laser light L is focused into the interior of the object W, the laser light L is particularly absorbed at the point corresponding to the focal point, forming a modified region within the object W. The modified region is a region whose density, refractive index, mechanical strength, and other physical properties differ from the surrounding unmodified region. Examples of modified regions include, for instance, melt-treated regions, cracked regions, insulation breakdown regions, and regions with refractive index changes.

[0042] A laser L emitted in a pulsed oscillation mode irradiates an object W. If the focal point of the laser L moves relative to a line set on the object W, multiple modification points are formed in a row along the line. A modification point is formed by irradiation with one pulse of laser L. A row of modification areas is a collection of multiple modification points arranged in a row. Adjacent modification points are sometimes connected and sometimes separated, depending on the relative movement speed of the focal point of the laser L relative to the object W and the repetition frequency of the laser L.

[0043] [Structure of the laser processing head]

[0044] like Figure 2 , Figure 3 and Figure 4 As shown, the laser processing head 10A includes a frame 11, an incident part 12, a laser adjustment part 13, and an objective lens part 14.

[0045] The frame 11 has a first wall portion 21 and a second wall portion 22, a third wall portion 23 and a fourth wall portion 24, and a fifth wall portion 25 and a sixth wall portion 26. The first wall portion 21 and the second wall portion 22 are opposite to each other in the X direction. The third wall portion 23 and the fourth wall portion 24 are opposite to each other in the Y direction. The fifth wall portion 25 and the sixth wall portion 26 are opposite to each other in the Z direction.

[0046] The distance between the third wall portion 23 and the fourth wall portion 24 is less than the distance between the first wall portion 21 and the second wall portion 22. The distance between the first wall portion 21 and the second wall portion 22 is less than the distance between the fifth wall portion 25 and the sixth wall portion 26. Furthermore, the distance between the first wall portion 21 and the second wall portion 22 may be equal to or greater than the distance between the fifth wall portion 25 and the sixth wall portion 26.

[0047] In the laser processing head 10A, the first wall portion 21 is located on the side opposite to the fixed portion 61 of the moving mechanism 6, and the second wall portion 22 is located on the side of the fixed portion 61. The third wall portion 23 is located on the side of the mounting portion 65 of the moving mechanism 6, and the fourth wall portion 24 is located on the side opposite to the mounting portion 65 and on the side of the laser processing head 10B. The fifth wall portion 25 is located on the side opposite to the support portion 7, and the sixth wall portion 26 is located on the side of the support portion 7.

[0048] The frame 11 is configured such that its third wall portion 23 is disposed on the mounting portion 65 side of the moving mechanism 6, and is mounted on the mounting portion 65. Specifically, as described below. The mounting portion 65 has a base plate 65a and a mounting plate 65b. The base plate 65a is mounted on a track provided on the moving portion 63. The mounting plate 65b is erected at the end of the base plate 65a on the side of the laser processing head 10B. With the third wall portion 23 in contact with the mounting plate 65b, the frame 11 is mounted on the mounting portion 65 by bolts 28 threadedly engaging with the mounting plate 65b via a base 27. The base 27 is respectively provided on the first wall portion 21 and the second wall portion 22. The frame 11 is detachable from the mounting portion 65.

[0049] An incident portion 12 is disposed on the fifth wall portion 25. The incident portion 12 incident a laser L into the frame 11. The incident portion 12 is biased towards the first wall portion 21 in the X direction and towards the fourth wall portion 24 in the Y direction. That is, the distance between the incident portion 12 and the first wall portion 21 in the X direction is less than the distance between the incident portion 12 and the second wall portion 22 in the X direction, and the distance between the incident portion 12 and the fourth wall portion 24 in the Y direction is less than the distance between the incident portion 12 and the third wall portion 23 in the X direction.

[0050] The exit end 2a of the optical fiber 2 is connected to the incident portion 12. Specifically, the incident portion 12 includes a hole 25a formed in the fifth wall portion 25. A mounting portion 25b is provided in the fifth wall portion 25. The main body portion 2b of the exit end 2a is mounted to the mounting portion 25b by bolts or the like. In this state, the front end portion 2c of the exit end 2a passes through the hole 25a. Thus, the exit end 2a of the optical fiber 2 is detachable from the incident portion 12. A cover 25c is disposed between the fifth wall portion 25 and the main body portion 2b. The cover 25c covers the gap formed between the hole 25a and the front end portion 2c. As an example, in the exit end 2a, an isolator that suppresses returning light is disposed in the main body portion 2b, and a collimating lens that collimates the laser L is disposed in the front end portion 2c. Furthermore, the incident portion 12 may also be configured as a connector or the like that capable of connecting the exit end 2a of the optical fiber 2.

[0051] A laser adjustment unit 13 is disposed within a frame 11. The laser adjustment unit 13 adjusts the laser L incident from the incident portion 12. The laser adjustment unit 13 is disposed within the frame 11 on the fourth wall portion 24 side relative to the partition wall portion 29. The laser adjustment unit 13 is mounted on the partition wall portion 29. The partition wall portion 29 is disposed within the frame 11, dividing the area within the frame 11 into an area on the third wall portion 23 side and an area on the fourth wall portion 24 side. The partition wall portion 29 is formed as part of the frame 11. The various structures of the laser adjustment unit 13 are mounted on the partition wall portion 29 on the fourth wall portion 24 side. The partition wall portion 29 functions as an optical substrate supporting the various structures of the laser adjustment unit 13.

[0052] The objective lens 14 is disposed on the sixth wall portion 26. Specifically, the objective lens 14 passes through a hole 26a formed in the sixth wall portion 26 (see reference). Figure 5 The objective lens 14 is positioned in the sixth wall portion 26. While focusing the laser L, adjusted by the laser adjustment unit 13, the objective lens 14 emits it outward from the frame 11. The objective lens 14 is biased towards the second wall portion 22 in the X direction and towards the fourth wall portion 24 in the Y direction. That is, the distance between the objective lens 14 and the second wall portion 22 in the X direction is less than the distance between the objective lens 14 and the first wall portion 21 in the X direction, and the distance between the objective lens 14 and the fourth wall portion 24 in the Y direction is less than the distance between the objective lens 14 and the third wall portion 23 in the X direction.

[0053] like Figure 5As shown, the laser adjustment unit 13 includes a reflector 31, an attenuator 32, and a reflector 33. The reflector 31, attenuator 32, and reflector 33 are arranged on a first straight line SL1 extending along the X direction. The reflector 31 is opposite to the incident portion 12 in the Z direction. That is, the reflector 31 is opposite to the exit end 2a of the optical fiber 2 in the Z direction. The reflector 31 reflects the laser L incident from the incident portion 12 toward the second wall portion 22. The attenuator 32 adjusts the output of the laser L reflected by the reflector 31. The reflector 33 reflects the laser L modulated by the attenuator 32 toward the sixth wall portion 26. Each reflector 31, 33 is, for example, a mirror or a prism.

[0054] The laser adjustment unit 13 also includes a beam expander 34 and a reflector 35. The reflector 33, beam expander 34, and reflector 35 are arranged on a second straight line SL2 extending along the Z direction. The beam expander 34 enlarges the diameter of the laser L reflected by the reflector 33. The reflector 35 reflects the laser L, whose diameter has been enlarged by the beam expander 34, toward the first wall portion 21 and the fifth wall portion 25. The reflector 35 is, for example, a mirror or a prism.

[0055] The laser adjustment unit 13 also includes a spatial light modulator 36 and an imaging optical system 37. The spatial light modulator 36, the imaging optical system 37, and the objective lens 14 are arranged on a third straight line SL3 extending along the Z direction. The spatial light modulator 36 modulates the laser L reflected by the reflector 35 and reflects it toward the sixth wall 26. The spatial light modulator 36 is a reflective type spatial light modulator. The spatial light modulator 36 is, for example, an LCOS (Liquid Crystal on Silicon)-SLM (Spatial Light Modulator). The imaging optical system 37 forms a telecentric optical system on both sides of the spatial light modulator 36's reflecting surface 36a and the objective lens 14's entrance pupil surface 14a, which are in an imaging relationship. The imaging optical system 37 is composed of multiple lenses.

[0056] The first straight line SL1, the second straight line SL2, and the third straight line SL3 are located on the same plane perpendicular to the Y direction. The second straight line SL2 is located on the side of the second wall portion 22 relative to the third straight line SL3. In the laser processing head 10A, the laser L incident from the incident portion 12 into the frame 11 along the Z direction is reflected by the reflecting portion 31 and travels along the first straight line SL1. The laser L traveling along the first straight line SL1 is reflected by the reflecting portion 33 and travels along the second straight line SL2. The laser L traveling along the second straight line SL2 is reflected sequentially by the reflecting portion 35 and the spatial light modulator 36 and travels along the third straight line SL3. The laser L traveling along the third straight line SL3 is emitted from the objective lens portion 14 out of the frame 11 along the Z direction.

[0057] The laser processing head 10A also includes a dichroic mirror 15, an observation section 16, a ranging section 100, a driving section 18, and a circuit section 19.

[0058] The dichroic mirror 15 is disposed on the third straight line SL3 between the imaging optical system 37 and the objective lens section 14. That is, the dichroic mirror 15 is disposed within the frame 11 between the laser adjustment section 13 and the objective lens section 14. The dichroic mirror 15 is mounted on the partition wall section 29 on the fourth wall section 24 side. The dichroic mirror 15 transmits laser L. From the viewpoint of suppressing astigmatism, the dichroic mirror 15 is preferably cubic in shape, or configured as two plates with a torsional relationship.

[0059] The observation unit 16 is disposed on the first wall portion 21 side relative to the third straight line SL3 within the frame 11. That is, the observation unit 16 is disposed on the first wall portion 21 side relative to the objective lens portion 14 in the X direction. The observation unit 16 is mounted on the partition wall portion 29 on the fourth wall portion 24 side. The observation unit 16 illuminates the surface of the object W with observation light L10 (e.g., visible light) for observing the surface of the object W (e.g., the surface on the side where the laser L is incident), and detects the observation light L10 reflected by the surface of the object W.

[0060] In this embodiment, the observation light L10 emitted from the observation unit 16 is reflected sequentially by the beam splitter 20 and the dichroic mirror 15, passes through the objective lens 14, and is emitted outside the frame 11 to illuminate the surface of the object W. The observation light L10 reflected from the surface of the object W passes through the objective lens 14 and enters the frame 11, is reflected sequentially by the dichroic mirror 15 and the beam splitter 20, and then enters the observation unit 16. Furthermore, the beam splitter 20 is mounted on the partition wall 29 on the fourth wall 24 side.

[0061] The ranging unit 100 is disposed on the first wall portion 21 side relative to the third straight line SL3 within the frame 11. That is, the ranging unit 100 is disposed on the first wall portion 21 side relative to the objective lens portion 14 in the X direction. The ranging unit 100 is mounted on the partition wall portion 29 on the fourth wall portion 24 side. The ranging unit 100 irradiates the surface of the object W with a ranging light L20 (e.g., a laser) for measuring the distance between the surface of the object W (e.g., the surface on the side where the laser L is incident) and the objective lens portion 14, and detects the ranging light L20 reflected by the surface of the object W.

[0062] In this embodiment, the ranging light L20 emitted from the ranging unit 100 passes through the beam splitter 20, is reflected by the dichroic mirror 15, passes through the objective lens 14, and is emitted outside the frame 11 to illuminate the surface of the object W. The ranging light L20 reflected from the surface of the object W passes through the objective lens 14, enters the frame 11, is reflected by the dichroic mirror 15, passes through the beam splitter 20, and enters the ranging unit 100. Furthermore, the wavelengths of the laser L, the ranging light L20, and the observation light L10 are all different (at least their center wavelengths are offset from each other).

[0063] The drive unit 18 is mounted on the partition wall 29 on the side of the fourth wall 24. The drive unit 18 moves the objective lens 14 disposed on the sixth wall 26 in the Z direction by, for example, the driving force of the piezoelectric element.

[0064] like Figure 3 and Figure 5 As shown, the circuit section 19 is disposed on the third wall 23 side relative to the partition wall 29 within the frame 11. That is, the circuit section 19 is disposed on the third wall 23 side relative to the laser adjustment section 13, the ranging section 100, and the observation section 16 within the frame 11. The circuit section 19 is separated from the partition wall 29. The circuit section 19 is, for example, a plurality of circuit boards. The circuit section 19 processes the signal output from the ranging section 100 and the signal input to the spatial light modulator 36. The circuit section 19 controls the drive section 18 based on the signal output from the ranging section 100. As an example, the circuit section 19 controls the drive section 18 in a manner that maintains the distance between the surface of the object W and the objective lens section 14 at a constant level (i.e., maintains the distance between the surface of the object W and the focusing point of the laser L at a constant level) based on the signal output from the ranging section 100.

[0065] Furthermore, the partition wall 29 has notches, holes, etc. (not shown) through which wiring for electrically connecting each of the observation section 16, the ranging section 100, the driving section 18, and the spatial light modulator 36 to the circuit section 19 passes. In addition, the frame 11 is provided with connectors (not shown) for connecting wiring for electrically connecting the circuit section 19 and the control section 9.

[0066] Like laser processing head 10A, laser processing head 10B includes a frame 11, an incident section 12, a laser adjustment section 13, an objective lens section 14, a dichroic mirror 15, an observation section 16, a ranging section 100, a driving section 18, and a circuit section 19. Among these, for example... Figure 2 As shown, each structure of the laser processing head 10B is configured to have a face-symmetric relationship with each structure of the laser processing head 10A about an imaginary plane that passes through the midpoint between a pair of mounting portions 65 and 66 and is perpendicular to the Y direction.

[0067] For example, the frame 11 of the laser processing head 10A is mounted on the mounting portion 65 such that the fourth wall portion 24 is located on the laser processing head 10B side relative to the third wall portion 23, and the sixth wall portion 26 is located on the support portion 7 side relative to the fifth wall portion 25. Conversely, the frame 11 of the laser processing head 10B is mounted on the mounting portion 66 such that the fourth wall portion 24 is located on the laser processing head 10A side relative to the third wall portion 23, and the sixth wall portion 26 is located on the support portion 7 side relative to the fifth wall portion 25.

[0068] The frame 11 of the laser processing head 10B is configured such that the frame 11 is mounted on the mounting portion 66 with the third wall portion 23 disposed on the mounting portion 66 side. Specifically, as described below. The mounting portion 66 has a base plate 66a and a mounting plate 66b. The base plate 66a is mounted on a track provided on the moving portion 63. The mounting plate 66b is erected at the end of the base plate 66a on the laser processing head 10A side. The frame 11 of the laser processing head 10B is mounted on the mounting portion 66 with the third wall portion 23 in contact with the mounting plate 66b. The frame 11 of the laser processing head 10B is detachable from the mounting portion 66.

[0069] [Structure of the objective lens]

[0070] like Figure 6 As shown, the objective lens section 14 includes multiple lenses 141, a lens barrel 142, a protective cover 143, and a nut 144. Figure 6 In this embodiment, only one lens 141 is shown, but in reality, multiple lenses 141 are arranged along the Z-direction. The multiple lenses 141 define the optical axis A of the objective lens section 14, focusing the laser L onto the object W. The lens barrel 142 holds the multiple lenses 141. A protective cover 143 has a light-transmitting plate 143a and a frame 143b. The light-transmitting plate 143a is held by the frame 143b. The protective cover 143 is disposed at one end of the lens barrel 142 (the lower end of the lens barrel 142 in the Z-direction when mounted on each laser processing head 10A, 10B). A nut 144 is threaded into one end of the lens barrel 142 with the frame 143b positioned between the nut 144 and one end of the lens barrel 142. Thus, the protective cover 143 is detachable from the lens barrel 142. In this embodiment, the surface of the light-transmitting plate 143a opposite to the lens 141 becomes the light-emitting surface 14b of the objective lens section 14. That is, the protective cover 143 has a light-emitting surface 14b. Furthermore, the objective lens section 14 may have at least one lens 141. Additionally, the shape of the light-transmitting plate 143a (i.e., the shape of the light-emitting surface 14b) when viewed from the Z direction is... Figure 6 The example shown is elliptical, but it is not limited to this; for example, it could also be circular.

[0071] As will be described later, if contamination adheres to the light exit surface 14b, or if the light exit surface 14b is damaged and the protective cover 143 is replaced, the amount of spherical aberration generated in the laser L due to the change in the thickness of the light-transmitting plate 143a will change, and the processing quality may decrease. Therefore, in the laser processing apparatus 1, a correction pattern for eliminating the change in the amount of spherical aberration generated in the laser L due to the change in the thickness of the light-transmitting plate 143a can also be applied to the laser L by the spatial light modulator 36. This correction pattern can be prepared according to the thickness of the light-transmitting plate 143a, or it can be prepared according to the difference between the thickness of the specified light-transmitting plate 143a (e.g., the light-transmitting plate 143a at the factory) and the thickness of the new light-transmitting plate 143a. The correction pattern prepared in this way can also be pre-stored by the control unit 9.

[0072] [Structure of the distance measuring unit]

[0073] like Figure 7 As shown, the ranging unit 100 includes a light source (second light source) 101, a collimating lens 102, a semi-reflecting mirror 103, an imaging lens 105, a reflective grating 106, and a light detection unit 107. Hereinafter, the ranging light L20 emitted from the ranging unit 100 (refer to...) Figure 5 This is called "rangefinding light L21", which refers to the rangefinding light L20 (refer to) reflected from the surface Wa of the object W. Figure 5 The reflected light from ( ) is called "reflected light L22". Furthermore, in Figure 7 The various structures are schematically shown in the diagram. For example, the objective lens section 14 actually has... Figure 6 The structure shown, but Figure 7 In the image, it is shown as a lens. This will be discussed later. Figure 8 and Figure 9 The same applies in China. Additionally, in... Figure 7 The beam splitter 20, which is positioned between the ranging unit 100 and the dichroic mirror 15, is omitted from the illustration.

[0074] Light source 101 emits a ranging beam (non-processing beam) L21, which is a laser. Light source 101 is, for example, a laser diode. In this embodiment, light source 101 emits the ranging beam L21 downward along the Z direction. Collimating lens 102 collimates the ranging beam L21 emitted from light source 101.

[0075] The semi-reflecting mirror 103 reflects the collimated ranging light L21, which has been collimated by the collimating lens 102, toward the dichroic mirror 15 side, so that the reflected light L22 incident from the dichroic mirror 15 side is transmitted to the imaging lens 105 side. In this embodiment, the semi-reflecting mirror 103 reflects the ranging light L21, which is incident from above along the Z direction, to one side along the X direction, and transmits the reflected light L22 from one side to the other side along the X direction.

[0076] The dichroic mirror 15 reflects the ranging light L21 reflected by the semi-reflecting mirror 103 toward the objective lens 14 side, and reflects the reflected light L22 incident from the objective lens 14 side toward the semi-reflecting mirror 103 side. In this embodiment, the dichroic mirror 15 reflects the ranging light L21 incident from the other side along the X direction downward along the Z direction, and reflects the reflected light L22 incident from the lower side along the Z direction to the other side along the X direction.

[0077] The objective lens 14 focuses the rangefinder light L21 reflected by the dichroic mirror 15 and transmits it to the object W side, while also transmitting the reflected light L22 reflected by the surface Wa of the object W to the dichroic mirror 15 side. In this embodiment, the objective lens 14 transmits the rangefinder light L21 from the top to the bottom along the Z direction, and transmits the reflected light L22 from the bottom to the top along the Z direction. The objective lens 14 transmits both the laser L and the rangefinder light L21 to the object W side.

[0078] The imaging lens 105 transmits the reflected light L22, which is reflected by the dichroic mirror 15 and passed through the semi-reflective mirror 103, to the side of the reflective grating 106. In this embodiment, the imaging lens 105 transmits the reflected light L22 from one side to the other along the X direction. The imaging lens 105 images the image at the focusing position of the rangefinder L21 or the reflected light L22 based on the objective lens 14 at the imaging position. When the focusing point of the object W's surface Wa relative to the rangefinder L21 when it is focused into the air by the objective lens 14 is located on the opposite side of the objective lens 14, this focusing position appears in the rangefinder L21. When the object W's surface Wa is located at the focusing point of the rangefinder L21 when it is focused into the air by the objective lens 14, this focusing position appears at the boundary between the rangefinder L21 and the reflected light L22. When the focal point of the object W's surface Wa relative to the ranging light L21 is focused into the air by the objective lens 14, and this focal point appears in the reflected light L22, this focal point position is located on the side of the objective lens 14. Furthermore, the imaging lens 105 can be composed of a single lens or multiple lenses.

[0079] The reflective grating 106 reflects the reflected light L22, which has passed through the imaging lens 105, toward the light detection unit 107. The reflective grating 106 is, for example, a blazed grating. In this embodiment, the reflective grating 106 reflects the reflected light L22, which is incident from one side along the X direction, upward along the Z direction. The reflective grating 106 adjusts the optical path of the reflected light L22 between the imaging lens 105 and the light detection unit 107 (details will be described later).

[0080] The light detection unit 107 detects the reflected light L22 reflected by the reflective grating 106. That is, the light detection unit 107 detects the reflected light L22 reflected by the object W and transmitted through the objective lens 14 from the object W side. The light detection unit 107 is, for example, a one-dimensional photodiode array having multiple light detection channels arranged along the X direction. The light-receiving surface 107a of the light detection unit 107 faces the reflective grating 106 side and is located on a predetermined surface S. In this embodiment, the light-receiving surface 107a faces downwards and is located on a predetermined surface S perpendicular to the Z direction. Furthermore, the light detection unit 107 can also be a two-dimensional photodiode array, etc., as long as it has multiple light detection channels arranged along the X direction.

[0081] like Figure 8 As shown, with the optical axis A1 of the rangefinder L21 offset from the optical axis A of the objective lens 14 (i.e., the optical axis A1 is separated from the optical axis A), the objective lens 14 transmits the rangefinder L21 to the object W side. The optical axis A1 of the rangefinder L21 incident on the objective lens 14 is parallel to the optical axis A of the objective lens 14. The optical axis A1 of the rangefinder L21 emitted from the objective lens 14 is tilted, such that the focal point P of the rangefinder L21 focused by the objective lens 14 is located on the optical axis A of the objective lens 14. Here, the optical axis A1 of the rangefinder L21 incident on the objective lens 14 is offset from the optical axis A of the objective lens 14 to one side in the X direction (a predetermined direction).

[0082] Therefore, as Figure 7 and Figure 8 As shown, the optical path of the reflected light L22 transmitted through the objective lens 14 changes according to the height of the surface Wa of the object W. As a result, the incident position of the reflected light L22 on the light-receiving surface 107a of the light detection unit 107 changes according to the height of the surface Wa of the object W. Therefore, the height of the surface Wa of the object W can be determined based on the incident position of the reflected light L22 on the light-receiving surface 107a of the light detection unit 107 (i.e., based on the position of the light detection channel where the reflected light L22 is incident). Furthermore, the height of the surface Wa of the object W refers to the position of the surface Wa of the object W in a direction parallel to the optical axis A of the objective lens 14 (here, the Z direction), for example, corresponding to the distance between the objective lens 14 and the surface Wa of the object W.

[0083] As an example, when the surface Wa of the object W coincides with the focal point P of the rangefinder L21 (the focal point of the rangefinder L21 when it is focused into the air by the objective lens 14), the reflected light L22... L The optical path of the objective lens 14 is symmetrical about its optical axis A with respect to the optical path of the rangefinder L21. When the surface Wa of the object W is located closer to the objective lens 14 than the focal point P of the rangefinder L21, the reflected light L22... M The optical path is more accurate than the reflected light L22. LThe side closest to the X direction is reflected. When the surface Wa of the object W is located further from the objective lens 14 than the focal point P of the ranging light L21, the reflected light L22... H The optical path is more accurate than the reflected light L22. M The side facing the X direction is reflected.

[0084] Here, as Figure 8 As shown, because the convergence and divergence of the reflected light L22 also varies depending on the height of the surface Wa of the object W, the imaging position of the reflected light L22 based on the imaging lens 105 also varies depending on the height of the surface Wa of the object W. Therefore, if a reflective grating 106 for adjusting the optical path of the reflected light L22 is not provided in the ranging unit 100, the spot size of the reflected light L22 on the light-receiving surface 107a of the light detection unit 107 will vary significantly depending on the height of the surface Wa of the object W. As a result, the accuracy of measuring the height of the surface Wa of the object W may deteriorate. Furthermore, even if the light-receiving surface 107a of the light detection unit 107 is tilted in a manner that matches the imaging position of the reflected light L22 based on the imaging lens 105, the incident angle of the reflected light L22 relative to the light-receiving surface 107a becomes larger. As a result, the size of a portion of the reflected light L22 reflected by the light-receiving surface 107a, or the spot size of the reflected light L22 on the light-receiving surface 107a, becomes larger. Consequently, the accuracy of measuring the height of the surface Wa of the object W may deteriorate.

[0085] For example, if the focal distance of the objective lens 14 is set to f1, the focal distance of the imaging lens 105 is set to f2, the height difference of the surface Wa of the object W in the direction parallel to the optical axis A of the objective lens 14 is set to ΔZ, and the difference in the imaging position of the reflected light L22 in the direction parallel to the optical axis of the imaging lens 105 is set to ΔX, then when the ranging unit 100 is not equipped with a reflective grating 106, ΔX / ΔZ = 4(f2 / f1). 2 The relationship holds true. That is, if the focal distance f1 of the objective lens 14 decreases, the difference ΔX between the imaging positions of the reflected light L22 increases, and the spot size of the reflected light L22 on the light-receiving surface 107a increases. As described above, when a modified region is formed inside the object W, the numerical aperture of the objective lens 14 increases, and the focal distance f1 of the objective lens 14 decreases. Therefore, it is particularly important to implement countermeasures to suppress the degradation of the measurement accuracy of the height of the surface Wa of the object W.

[0086] As a countermeasure, such as Figure 7 As shown, a reflective grating 106 is provided in the ranging unit 100 to adjust the optical path of the reflected light L22. The reflective grating 106 adjusts the optical path of the reflected light L22 by causing the reflected light L22 to generate an optical path length corresponding to the incident position of the reflected light L22 toward the reflective grating 106.

[0087] Furthermore, the optical path of the reflected light L22 passing through the imaging lens 105 (the optical path of the principal ray of the reflected light L22) varies along a predetermined plane (here, a plane perpendicular to the Y direction) according to the height of the surface Wa of the object W. Therefore, the reflective grating 106 is configured such that multiple slots extend along a direction perpendicular to this predetermined plane (here, the Y direction). Moreover, the reflective grating 106 is configured such that the longer the optical path length of the reflected light L22 from the imaging lens 105 to the imaging position, the further away the reflected light L22 is from the imaging lens 105, the more it is reflected by the reflective grating 106.

[0088] Therefore, the longer the optical path length of the reflected light L22 from the imaging lens 105 to the imaging position, the longer the optical path length of the reflected light L22 from the imaging lens 105 to the light-receiving surface 107a of the light detection unit 107. For example, the longer the optical path length of the reflected light L22 from the imaging lens 105 to the light-receiving surface 107a of the light detection unit 107. M The optical path length ratio from the imaging lens 105 to the light-receiving surface 107a of the photodetector 107 is L22. L The optical path length is long. The reflected light L22 travels from the imaging lens 105 to the light-receiving surface 107a of the photodetector 107. H The optical path length ratio from the imaging lens 105 to the light-receiving surface 107a of the photodetector 107 is L22. M The optical path length is long.

[0089] However, astigmatism occurs in the reflected light L22, which is imaged by the imaging lens 105 and reflected by the reflective grating 106. Specifically, the imaging position of the reflected light L22 imaged in the Y direction is farther from the predetermined surface S where the light-receiving surface 107a of the light detection unit 107 is located than the imaging position of the reflected light L22 imaged in the X direction. In the ranging unit 100, the reflective grating 106 adjusts the optical path of the reflected light L22 so that the imaging position of the reflected light L22 imaged in the X direction is closer to the predetermined surface S where the light-receiving surface 107a of the light detection unit 107 is located.

[0090] In this way, the reflective grating 106 adjusts the optical path of the reflected light L22, so that the imaging position of the reflected light L22, which is imaged in at least one direction (X direction) perpendicular to the incident direction (Z direction) of the reflected light L22 incident on the light detection unit 107, is close to a predetermined surface S perpendicular to the incident direction. Furthermore, the reflective grating 106 has a plurality of grooves extending along a direction (Y direction) parallel to the light-receiving surface 107a of the light detection unit 107 and perpendicular to the aforementioned direction (X direction). Additionally, the light detection unit 107 has a plurality of light detection channels arranged along a direction parallel to the aforementioned direction (X direction).

[0091] Here, "the incident direction of the reflected light L22 incident on the light detection unit 107" refers to the reflected light L22 that serves as a reference (e.g., the reflected light L22). L The incident direction of the reflected light L22. Furthermore, "making the imaging position of the reflected light L22 close to the predetermined surface S perpendicular to the incident direction of the reflected light L22 incident on the light detection unit 107" means that, compared to the case where the reflective grating 106 is not provided in the ranging unit 100, the imaging position of the reflected light L22 is closer to the predetermined surface S. That is, the difference in imaging position between the reflected light L22 and the incident direction of the reflected light L22 incident on the light detection unit 107 is less than the aforementioned ΔX (preferably less than 10% of ΔX) in the region including the predetermined surface S.

[0092] Furthermore, the objective lens 14 and the imaging lens 105 are configured such that the direction of the optical path (the optical path of the principal ray of the reflected light L22) emitted from the imaging lens 105 is constant. In this embodiment, as... Figure 9 As shown in (a), the optical path length between the objective lens 14 and the imaging lens 105 is the sum of the focal distance f1 of the objective lens 14 and the focal distance f2 of the imaging lens 105. That is, the focal position of the objective lens 14 on the imaging lens 105 side is the same as the focal position of the imaging lens 105 on the objective lens 14 side. Therefore, even if the height of the surface Wa of the object W changes, the direction of the optical path of the reflected light L22 emitted from the imaging lens 105 remains constant, resulting in, as Figure 9 As shown in (b), the height of the surface Wa of the object W and the position of the light detection channel into which the reflected light L22 is incident in the light detection unit 107 are linearly related. Furthermore, in Figure 9 In (a), the illustrations of the light source 101, collimating lens 102, semi-reflecting mirror 103, dichroic mirror 15, and beam splitter 20 are omitted.

[0093] In addition, such as Figure 9 As shown in (b), the image of the reflected light L22 on the light-receiving surface 107a of the light detection unit 107 is an elongated shape (elliptical in this case) with its long side perpendicular to the aforementioned direction (the direction in which the reflected light L22 is imaged close to the predetermined surface S). This allows for a slight shift of the light-receiving surface 107a of the light detection unit 107 towards the long side of the image of the reflected light L22, thus improving the accuracy of the configuration of each structure. Furthermore, the reason why the image of the reflected light L22 on the light-receiving surface 107a of the light detection unit 107 is an elongated shape with its long side perpendicular to the aforementioned direction is that, as described above, astigmatism occurs in the reflected light L22 imaged by the imaging lens 105 and reflected by the reflective grating 106.

[0094] In the ranging unit 100 configured as described above, the reflected light L22 is detected as follows. For example... Figure 7As shown, the ranging light L21 emitted from the light source 101 is collimated by the collimating lens 102. The collimated ranging light L21 is reflected by the semi-reflecting mirror 103 and passes through the beam splitter 20 (see reference). Figure 5 The ranging light L21 incident on the objective lens 14 is focused by the objective lens 14 and illuminates the surface Wa of the object W. The reflected light L22 from the surface Wa of the object W passes through the objective lens 14 and is reflected by the dichroic mirror 15. The reflected light L22 from the dichroic mirror 15 then passes sequentially through the beam splitter 20 (see reference). Figure 5 The light source L22 reflected by the reflective grating 106 is incident on the light detection unit 107 and detected by the light detection unit 107. The light source L22 reflected by the reflective grating 106 is imaged by the imaging lens 105 and reflected by the reflective grating 106.

[0095] [Managing the contamination status of the light exit surface of the objective lens]

[0096] In the laser processing apparatus 1, contamination sometimes adheres to the light emitting surface 14b of the objective lens section 14 in each laser processing head 10A and 10B. In such cases, monitoring the contamination status of the light emitting surface 14b of the objective lens section 14 is extremely important in preventing a decrease in processing quality.

[0097] Figure 10 (a) is a schematic diagram showing that there is no contamination on the light emitting surface 14b of the objective lens 14. Figure 10 (b) is a schematic diagram showing the state where contamination (illustrated as dots) adheres to the light-emitting surface 14b of the objective lens 14. Figure 10 As shown in (a) and (b), when processing the object W by irradiation with laser L, contamination tends to adhere to the area surrounding the light emitting surface 14b of the objective lens 14 (the area surrounding the central area) more easily than to the central area (including the central area containing the optical axis A). Furthermore, if the direction of relative movement of the laser L irradiating the object W relative to the object W (hereinafter referred to as the "processing direction") is constant, then... Figure 10 As shown in (b), contamination is particularly prone to adhere to the portions on both sides of the optical axis A in the processing direction in the area surrounding the light emitting surface 14b of the objective lens 14. In this embodiment, since the processing direction is the X direction, contamination is particularly prevalent on both sides of the optical axis A of the objective lens 14 in the X direction in the area surrounding the light emitting surface 14b of the objective lens 14. It is presumably because the stray particles emitted from the object W due to laser L irradiation flow toward the rear side of the objective lens 14 in the forward direction (relative to the forward direction of the object W).

[0098] Here, in the laser processing apparatus 1, as Figure 10As shown in (a) and (b), the optical axis A1 of the ranging light L21 is shifted to one side of the optical axis A of the objective lens 14 in the X direction on the light exiting surface 14b of the objective lens 14, and the optical axis A2 of the reflected light L22 (optical axis A2) L A2 M A2 H The light emanating surface 14b of the objective lens 14 is offset to the other side in the X direction from the optical axis A of the objective lens 14. Therefore, the amount of reflected light L22 incident on the light detection unit 107 of the ranging unit 100 varies depending on the contamination state of the light emanating surface 14b of the objective lens 14. Specifically, the more contamination adheres to the light emanating surface 14b of the objective lens 14, the lower the amount of reflected light L22 incident on the light detection unit 107.

[0099] Therefore, in the laser processing apparatus 1, the circuit section 19 and control section 9 of each laser processing head 10A and 10B function as processing units, acquiring information related to contamination of the light emitting surface 14b of the objective lens section 14 based on the detection results of the light detection section 107. That is, the processing unit, composed of the circuit section 19 and control section 9 of each laser processing head 10A and 10B, acquires not only information related to the height of the surface (prescribed surface) Wa of the object W, but also information related to contamination of the light emitting surface 14b of the objective lens section 14, based on the detection results of the light detection section 107. Furthermore, when acquiring information related to contamination of the light emitting surface 14b of the objective lens section 14, it is preferable to use a prescribed mirror wafer as the object W and perform the emission of the ranging light L21 and the detection of the reflected light L22 under prescribed conditions.

[0100] In this embodiment, the processing unit, comprised of the circuit section 19 and control section 9 of each laser processing head 10A, 10B, displays information related to contamination of the light emitting surface 14b of the objective lens section 14 on the display 91. For example, if the brightness value of the reflected light L22 detected by the light detection section 107 is below a predetermined value, the processing unit comprised of the circuit section 19 and control section 9 of each laser processing head 10A, 10B displays on the display 91 that the contamination of the light emitting surface 14b of the objective lens section 14 has reached a level that reduces processing quality. As described above, in the objective lens section 14, the protective cover 143 having the light emitting surface 14b is detachable from the lens barrel 142. Therefore, if the brightness value of the reflected light L22 detected by the light detection section 107 is below a predetermined value, the processing unit comprised of the circuit section 19 and control section 9 of each laser processing head 10A, 10B can also display on the display 91 that the protective cover 143 needs to be replaced.

[0101] Figure 11 (a) is a photograph showing the state of the light-emitting surface 14b of the objective lens 14 when the number of ablation roots is 0. Figure 11(b) is a photograph showing the state of the light-emitting surface 14b of the objective lens 14 when the ablation number is 1000. Here, the ablation number refers to the number of times the focal point of the laser L is moved back and forth relative to the surface Wa of the object W in the X direction (twice in one reciprocation) under conditions that allow the surface Wa of the object W to be ablated. Figure 11 As shown in (a), when the number of ablation roots is 0, there is no contamination adhering to the light emitting surface 14b of the objective lens 14. In contrast, as Figure 11 As shown in (b), when the number of ablation roots is 1000, contamination is attached to both sides of the optical axis A in the X direction in the area surrounding the light emitting surface 14b of the objective lens 14.

[0102] Figure 12 This is a table representing the brightness values ​​of the reflected light L22 under conditions 1 and 2. Here, condition 1 refers to... Figure 11 The condition corresponding to the case where the number of ablation roots shown in (a) is 0, condition 2 refers to the condition corresponding to the case where the number of ablation roots is 0. Figure 11 The conditions corresponding to the case shown in (b) where the number of ablation roots is 1000. For example... Figure 12 As shown, the brightness value of the reflected light L22 under condition 2 is significantly lower than that under condition 1, regardless of the Z value. Therefore, it can be seen that information related to contamination of the light-emitting surface 14b of the objective lens 14 can be obtained based on the detection results of the light detection unit 107. Furthermore, the Z value refers to the value representing the position of the objective lens 14 relative to the object W. "Z value: 0" indicates the position of the objective lens 14 when the focusing point of the laser L is located on the surface Wa of the object W. "Z value: negative" indicates the position where the objective lens 14 is separated from the object W based on the "Z value: 0" position, and "Z value: positive" indicates the position where the objective lens 14 is closer to the object W based on the "Z value: 0" position.

[0103] [Functions and Effects]

[0104] In the laser processing apparatus 1, a ranging light L21 emitted from the light source 101 illuminates the object W through the objective lens 14, and the reflected light L22 reflected by the object W illuminates the objective lens 14 and is detected by the light detection unit 107. At this time, the optical axis A1 of the ranging light L21 and the optical axis A2 of the reflected light L22 are both offset from the optical axis A of the objective lens 14 in the X direction on the light emission surface 14b of the objective lens 14. Here, when processing the object W by irradiation with laser L, contamination is more likely to adhere to the area around the light emission surface 14b of the objective lens 14 compared to the central area (this is an insight discovered by the inventors). Therefore, by detecting the reflected light L22 as described above, information related to the contamination of the light emission surface 14b of the objective lens 14 can be obtained. Thus, according to the laser processing apparatus 1, the contamination state of the light emission surface 14b of the objective lens 14 can be reliably determined.

[0105] In the laser processing apparatus 1, the optical axis A1 of the ranging beam L21 is offset to one side of the objective lens 14 in the X direction from the optical axis A of the objective lens 14, and the optical axis A2 of the reflected beam L22 is offset to the other side of the objective lens 14 in the X direction from the optical axis A of the objective lens 14. Therefore, since the contamination state of the optical surface 14b of the objective lens 14 is easily reflected in the ranging beam L21 and the reflected beam L22 respectively, the contamination state of the optical surface 14b of the objective lens 14 can be more reliably determined.

[0106] In the laser processing apparatus 1, the X-direction by which the optical axis A1 of the ranging light L21 and the optical axis A2 of the reflected light L22 are offset from the optical axis A of the objective lens 14 is the direction in which the laser L irradiating the object W moves relative to the object W, i.e., the processing direction. When processing the object W by irradiating it with the laser L, for example, if the direction in which the laser L irradiating the object W moves relative to the object W is constant, then the portions on both sides of the optical axis A of the objective lens 14 in that direction around the light emitting surface 14b of the objective lens 14 are particularly prone to contamination (this is an insight discovered by the inventors). Therefore, by offsetting the optical axis A1 of the ranging light L21 and the optical axis A2 of the reflected light L22 from the optical axis A of the objective lens 14 towards the processing direction, the contamination state of the light emitting surface 14b of the objective lens 14 can be more reliably monitored.

[0107] In the laser processing apparatus 1, the processing unit, which consists of the circuit section 19 and the control section 9 of each laser processing head 10A, 10B, acquires information related to the height of the surface Wa of the object W based on the detection results of the photodetector 107. Thus, using the same light source 101 and photodetector 107, it is possible to acquire information related to contamination of the light emitting surface 14b of the objective lens 14 and information related to the height of the surface Wa of the object W.

[0108] In the laser processing apparatus 1, a processing unit consisting of the circuit section 19 and the control section 9 of each laser processing head 10A, 10B displays information related to contamination of the light emitting surface 14b of the objective lens section 14 on the display 91. This allows the operator to be reliably notified of information related to contamination of the light emitting surface 14b of the objective lens section 14.

[0109] In the laser processing apparatus 1, in the objective lens section 14, a protective cover 143 having a light emitting surface 14b is detachable from the lens barrel 142. Therefore, based on information related to contamination of the light emitting surface 14b of the objective lens section 14, a new protective cover 143 with a contaminated light emitting surface 14b can be replaced.

[0110] Here, the advantage of obtaining information related to contamination of the light exit surface 14b of the objective lens 14 based on the brightness value of the reflected light L22 detected by the light detection unit 107 (i.e., the amount of light of the reflected light L22 incident on the light detection unit 107) will be explained. Figure 13 It is a table representing various results for each ablation root number.

[0111] exist Figure 13 In this context, "ablation roots" refers to the number of times the focal point of laser L is moved back and forth along the X direction (twice in one reciprocation) under conditions that allow the surface Wa of object W to ablate, with the focal point of laser L positioned at the surface Wa of object W. Figure 13 In the figure, the results of “crack amount”, “laser transmittance”, “presence or absence of indentation without aberration correction”, “presence or absence of indentation with aberration correction” and “brightness value” are the results of objective lens 14 after ablation processing with the above-mentioned “ablation roots”.

[0112] "Crack amount" refers to the average length of cracks extending from the modified region to the side opposite to the incident side of the laser L in the object W when the focusing point of the laser L is matched with the interior of the object W and the laser L is irradiated onto the object W. "Laser transmittance" refers to the ratio of "the output of the laser L after exiting the objective lens 14" to "the original output of the laser L (the output of the laser L after exiting the light source 81 or 82)". "Presence or absence of dents without aberration correction" indicates whether dents caused by laser L irradiation are generated on the surface of the object W opposite to the incident side of the laser L when aberration correction is not performed on the laser L by the spatial light modulator 36. "Presence or absence of dents with aberration correction" indicates whether dents caused by laser L irradiation are generated on the surface of the object W opposite to the incident side of the laser L when aberration correction is performed on the laser L by the spatial light modulator 36. In each of the categories "Presence or absence of indentation without aberration correction" and "Presence or absence of indentation with aberration correction," the left column represents the result when the pulse energy of laser L is 10 μJ, the middle column represents the result when the pulse energy of laser L is 5.3 μJ, and the right column represents the result when the pulse energy of laser L is 3.75 μJ. "Brightness value" refers to the brightness value of the reflected light L22 detected by the light detection unit 107.

[0113] like Figure 13 As shown, when the "number of ablation roots" is any one of the following, no significant differences were observed in "crack amount", "laser transmittance", "presence or absence of dents without aberration correction" and "presence or absence of dents with aberration correction". In contrast, a significant difference was observed in "brightness value". Therefore, it can be seen that obtaining information related to contamination of the light exit surface 14b of the objective lens 14 based on the brightness value of the reflected light L22 detected by the light detection unit 107 (i.e., the amount of reflected light L22 incident on the light detection unit 107) is extremely effective.

[0114] [Variation Example]

[0115] This disclosure is not limited to the embodiments described above. For example, the light emitting surface 14b of the objective lens 14 is not limited to the light emitting surface of the protective cover 143. As an example, even without the protective cover 143 and nut 144 provided on the objective lens 14, the light emitting surface of the lens 141 disposed at the lower end of the lens barrel 142 in the Z direction among the plurality of lenses 141 may also be the light emitting surface 14b of the objective lens 14.

[0116] In the above embodiment, both the optical axis A1 of the ranging light L21 and the optical axis A2 of the reflected light L22 are offset from the optical axis A of the objective lens 14 in the X direction on the light emitting surface 14b of the objective lens 14. However, at least one of the optical axis A1 of the ranging light L21 and the optical axis A2 of the reflected light L22 can be offset from the optical axis A of the objective lens 14 in a predetermined direction on the light emitting surface 14b of the objective lens 14.

[0117] To obtain information related to contamination of the light emitting surface 14b of the objective lens 14, non-processing light other than the ranging light L21 can also be used. As an example, a light source and a light detection unit specifically designed for obtaining information related to contamination of the light emitting surface 14b of the objective lens 14 can also be configured in the laser processing apparatus 1.

[0118] The processing unit that acquires information related to contamination of the light emitting surface 14b of the objective lens 14 is not limited to the processing unit composed of the circuit section 19 and the control section 9 of each laser processing head 10A, 10B. As an example, the processing unit that acquires information related to contamination of the light emitting surface 14b of the objective lens 14 could also be either the circuit section 19 or the control section 9. The processing unit that acquires information related to contamination of the light emitting surface 14b of the objective lens 14 could also replace displaying the information on the display 91, or in addition to displaying the information on the display 91, it could also include a notification section that notifies the operator of the information via voice or the like. The processing unit that acquires information related to contamination of the light emitting surface 14b of the objective lens 14 could also output the information to an external device other than the laser processing apparatus 1.

[0119] The surface Wa of the object W is not limited to the surface on the incident side of the laser L in the object W; each surface of the object can be set as the surface to be measured. This is because, in the ranging unit 100, the reflected light reflected by each surface is spatially separated from each other.

[0120] In the above embodiment, the dichroic mirror 15 transmits the laser L and reflects the ranging light L21 and the reflected light L22, but it can also replace the dichroic mirror 15 with an optical element that transmits the ranging light L21 and the reflected light L22 and reflects the laser L.

[0121] In the above embodiment, a reflective grating 106 disposed between the imaging lens 105 and the light detection unit 107 is used as an optical path adjustment unit to adjust the optical path of the reflected light L22. However, as long as the optical path of the reflected light L22 can be adjusted so that the imaging position of the reflected light L22 is close to the predetermined surface S, other structures are also possible. Examples of such structures include spatial light modulators, digital mirror devices, transmissive gratings, prisms, etc. A cylindrical lens may also be provided so that the image of the reflected light L22 on the light-receiving surface 107a of the light detection unit 107 is an elongated strip with the long side direction set perpendicular to a direction (the direction in which the reflected light L22 is imaged close to the predetermined surface S).

[0122] When the ranging beam L21 passes through the objective lens 14, the distance by which the optical axis A1 of the ranging beam L21 deviates from the optical axis A of the objective lens 14 can also be adjusted. For example, by adjusting... Figure 7 The position of the semi-reflective mirror 103 shown can be adjusted to change the distance by which the optical axis A1 of the ranging beam L21 is offset from the optical axis A of the objective lens 14. By adjusting this distance, the measurement range of the height of the surface Wa of the object W and the detection sensitivity of the light detection unit 107 can be adjusted.

[0123] In the above embodiment, the light-receiving surface 107a of the light detection unit 107 is located on the predetermined surface S, but the light-receiving surface 107a of the light detection unit 107 only needs to be positioned along the predetermined surface S. For example, even if the light-receiving surface 107a of the light detection unit 107 forms an angle with the predetermined surface S, as long as the angle is less than 5°, the height of the surface Wa of the object W can be measured with sufficient accuracy.

[0124] In the above embodiment, the specified surface S is a surface perpendicular to the incident direction of the reflected light L22 incident on the light detection unit 107. However, the specified surface S can be any surface that intersects the incident direction by tilting at an angle of less than 30° relative to the incident direction.

[0125] According to this disclosure, a laser processing apparatus is provided that can reliably monitor the contamination status of the light-emitting surface of the objective lens.

Claims

1. A laser processing device comprising: a supporting portion that supports an object; a first light source that emits processing light; a second light source that emits non-processing light; an objective lens portion that transmits the processing light and the non-processing light to the object side; a light detecting section that detects reflected light of the non-processing light that is reflected by the object and passes through the objective lens section from the object side; as well as a processing unit that acquires information related to contamination of the light emitting surface of the objective lens unit based on the detection result of the light detection unit, At least one of the optical axis of the non-processing light and the optical axis of the reflected light is offset from the optical axis of the objective lens section in a predetermined direction on the light emitting surface of the objective lens section.

2. The laser processing device according to claim 1, in, The optical axis of the non-processing light is offset from the optical axis of the objective lens portion to one side in the prescribed direction on the light emitting surface of the objective lens portion. The optical axis of the reflected light is offset from the optical axis of the objective lens section to the other side in the predetermined direction on the light emitting surface of the objective lens section.

3. The laser processing device according to claim 1, in, The predetermined direction is a direction in which the processing light irradiated onto the object moves relative to the object.

4. The laser processing device according to claim 1, in, The processing unit acquires information related to a height of a predetermined surface of the object based on a detection result of the light detection unit.

5. The laser processing device according to claim 1, in, The processing unit includes a display that displays the information related to the contamination.

6. The laser processing device according to claim 1, in, The objective lens portion comprises: at least one lens that focuses the processing light onto the object; a lens barrel holding the at least one lens; A protective cover is detachable from the lens barrel and has the light emitting surface.

Images