Laser processing apparatus

Abstract

To provide a laser processing device capable of detecting an abnormality of a spatial light modulator at high speed.SOLUTION: A laser processing device includes: a laser beam irradiation unit 20 arranged between an oscillator 22 and a light collector 23 and including a spatial light modulator 24 which modulates and emits a laser beam 21 incident in accordance with a phase pattern displayed on a display unit 241; a light detection unit 30 for detecting an intensity of the laser beam 21; a pattern control unit for controlling the phase pattern being displayed on the display unit 241; a storage unit for storing the intensity of the laser beam 21 detected by the light detection unit 30 as reference intensity when a branch pattern serving as a phase pattern for branching the laser beam 21 is displayed on the display unit 241; and a determination unit for determining whether or not the spatial light modulator 24 is normally operating based on whether or not the intensity of the laser beam 21 detected by the light detection unit 30 has changed from the reference intensity.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a laser processing apparatus.

Background Art

[0002] In order to manufacture a semiconductor device, there is known a processing method in which the condensing point of a laser beam is positioned inside a wafer, a modified layer is formed by irradiating along a street (a planned dividing line), and the wafer is divided by applying an external force (see Patent Document 1). In a laser processing apparatus that realizes the above-described processing method, a laser beam emitted from an oscillator is modulated by a spatial light modulator, condensed by a condenser lens, and irradiated onto a wafer.

[0003] By the way, in recent years, in order to shorten the time required for processing, a method has been used in which a laser beam is branched by a spatial light modulator and processed at a plurality of condensing points (see Patent Document 2). In this laser processing apparatus, when the spatial light modulator does not operate normally due to a defect or an abnormality, the laser beam is not properly branched, and the laser beam is irradiated in an unbranched state, which may cause a processing defect.

[0004] Therefore, various methods have been proposed to detect an operation failure of the spatial light modulator. For example, Patent Document 3 discloses a method of confirming the operation by causing the spatial light modulator to display a phase pattern including a marking that modulates a part that does not enter the pupil plane of the condenser lens and acquiring the intensity distribution of the phase pattern including the marking.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, while the method of Patent Document 3 can confirm abnormal operation during processing, it has a problem that it is necessary to obtain a two-dimensional intensity distribution and the processing takes time.

[0007] The present invention has been made in view of such problems, and an object thereof is to provide a laser processing apparatus capable of detecting an abnormality of a spatial light modulator at high speed.

Means for Solving the Problems

[0008] In order to solve the above-described problems and achieve the object, the laser processing apparatus of the present invention includes an oscillator that emits a laser beam, a condenser that condenses the laser beam emitted from the oscillator and irradiates a workpiece, and a spatial light modulator that is disposed between the oscillator and the condenser and has a display unit that displays a phase pattern, and modulates and emits the laser beam incident on the display unit according to the phase pattern. A mirror that reflects the laser beam emitted from the spatial light modulator toward the condenser; a laser beam irradiation unit including, and emitted from the spatial light modulator a condenser lens that is disposed between the mirror and the light detection unit and condenses the leakage light toward the light detection unit, the leakage light being received after passing through without being reflected by the mirror; the laser beam and a diffusion plate that is disposed between the mirror and the condenser lens and diffuses the leakage light. a light detection unit that detects the intensity of, a control unit that controls each component, the control unit having a pattern control unit that controls the phase pattern displayed on the display unit, a storage unit that stores, as a reference intensity, the intensity of the laser beam detected by the light detection unit when a branching pattern, which is the phase pattern for branching the laser beam to the display unit, is displayed by the pattern control unit, and a determination unit that determines whether the spatial light modulator is operating normally based on whether the intensity of the laser beam detected by the light detection unit has changed from the reference intensity.

[0011] Further, in the laser processing apparatus of the present invention, a focusing lens for focusing the laser beam and an aperture positioned at the focal position of the focusing lens or in the vicinity of the focal position may be disposed between the spatial light modulator and the light detection unit.

[0012] Further, in the laser processing apparatus of the present invention, the light detection unit may be a photodiode.

Advantages of the Invention

[0013] The present invention can detect an abnormality of the spatial light modulator at high speed.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

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Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0015] A mode (embodiment) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited by the content described in the following embodiments. Further, the constituent elements described below include those that can be easily assumed by those skilled in the art and substantially identical ones. Furthermore, the configurations described below can be combined as appropriate. Also, various omissions, substitutions, or changes in the configuration can be made without departing from the gist of the present invention.

[0016] 〔Embodiment〕 First, the configuration of the laser processing apparatus 1 according to the embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a configuration example of the laser processing apparatus 1 according to the embodiment. FIG. 2 is a perspective view showing an example of the workpiece 100 to be processed by the laser processing apparatus 1 shown in FIG. 1. FIG. 3 is a schematic diagram showing a schematic configuration of the laser beam irradiation unit 20 shown in FIG. 1. FIG. 4 is a schematic diagram showing an example of the phase pattern 242 displayed on the display unit 241 of the spatial light modulator 24 shown in FIG. 3. FIG. 5 is a schematic diagram of the laser beam 21 emitted from the display unit 241 on which the phase pattern 242 shown in FIG. 4 is displayed.

[0017] In the following description, the X-axis direction is a direction in a horizontal plane. The Y-axis direction is a direction in the horizontal plane that is orthogonal to the X-axis direction. The Z-axis direction is a direction orthogonal to the X-axis direction and the Y-axis direction. In the laser processing apparatus 1 of the embodiment, the processing feed direction is the X-axis direction, the indexing feed direction is the Y-axis direction, and the focusing point position adjustment direction is the Z-axis direction.

[0018] The laser processing apparatus 1 includes a holding table 10, a laser beam irradiation unit 20, a light detection unit 30 (see FIG. 3), an imaging means 31, a moving unit 60, an imaging unit 70, an input means 80, and a control unit 90. The laser processing apparatus 1 according to the embodiment is an apparatus that processes a workpiece 100 by irradiating the workpiece 100, which is an object to be processed, with a laser beam 21. The processing of the workpiece 100 by the laser processing apparatus 1 includes, for example, a modified layer forming process of forming a modified layer 106 (see FIG. 3) inside the workpiece 100 by stealth dicing, a groove processing of forming a groove on the surface 102 of the workpiece 100, or a cutting process of cutting the workpiece 100 along a planned division line 103. In the embodiment, a configuration for forming the modified layer 106 on the workpiece 100 will be described.

[0019] The workpiece 100 is, for example, a disk-shaped semiconductor device wafer, an optical device wafer, etc. having a substrate 101 (see FIG. 2) made of silicon (Si), sapphire (Al2O3), gallium arsenide (GaAs), silicon carbide (SiC), or lithium tantalate (LiTa3). Note that the workpiece 100 is disk-shaped in the embodiment, but may not be disk-shaped in the present invention. The workpiece 100 is transported and processed in a state where, for example, an annular frame 110 is attached and a tape 111 having a diameter larger than the outer diameter of the workpiece 100 is attached to the back surface 105 of the workpiece 100 and supported within the opening of the frame 110.

[0020] As shown in FIG. 2, the workpiece 100 has a planned division line 103 set in a grid pattern on the surface 102 of the substrate 101 and a device 104 formed in a region partitioned by the planned division line 103. The device 104 is, for example, an integrated circuit such as an IC (Integrated Circuit) or an LSI (Large Scale Integration), or an image sensor such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor).

[0021] In an embodiment, a modified layer 106 (see FIG. 3) is formed along a planned division line 103 on a workpiece 100. The workpiece 100 is divided into individual devices 104 along the modified layer 106 formed on the planned division line 103 and diced into chips. Note that the chips are square in shape in the embodiment, but may be rectangular in the present invention.

[0022] A holding table 10 shown in FIG. 1 etc. holds the workpiece 100 on a holding surface 11. The holding surface 11 is in a disk shape formed of a porous ceramic or the like. The holding surface 11 is a plane parallel to the horizontal direction in the embodiment. The holding surface 11 is connected to a vacuum suction source via a vacuum suction path, for example. The holding table 10 sucks and holds the workpiece 100 placed on the holding surface 11. A plurality of clamp portions 12 that sandwich an annular frame 110 for supporting the workpiece 100 are arranged around the holding table 10.

[0023] The holding table 10 is rotated around an axis parallel to the Z-axis direction by a rotation unit 13. The rotation unit 13 is supported by an X-axis direction movement plate 14. The rotation unit 13 and the holding table 10 are moved in the X-axis direction by a machining feed unit 61 described later via the X-axis direction movement plate 14. The rotation unit 13 and the holding table 10 are moved in the Y-axis direction by an indexing feed unit 62 described later via the X-axis direction movement plate 14, the machining feed unit 61, and a Y-axis direction movement plate 15.

[0024] The laser beam irradiation unit 20 is a unit that irradiates a workpiece 100 held on the holding surface 11 of the holding table 10 with a laser beam 21. Among the laser beam irradiation unit 20, at least the condenser 23 (see FIG. 3) is supported by a condensing point position adjustment unit 63, which will be described later, installed on a column 3 erected from the apparatus main body 2 of the laser processing apparatus 1. As shown in FIG. 3, the laser beam irradiation unit 20 includes an oscillator 22, a condenser 23, a spatial light modulator 24, a polarizing plate 25, a focusing lens 26, an aperture 27, a relay lens 28, and a mirror 29. Further, the laser beam irradiation unit 20 includes a focusing lens 32, a diffusing plate 33, and a filter 34 between the light detection unit 30 and the mirror 29.

[0025] The oscillator 22 emits a laser beam 21 having a predetermined wavelength for processing the workpiece 100. The laser beam 21 irradiated by the laser beam irradiation unit 20 is a laser beam having a wavelength that is transmissive or absorptive with respect to the workpiece 100, and in the embodiment of performing the modified layer formation process, it is a laser beam having a transmissive wavelength.

[0026] The condenser 23 is a condenser lens that condenses the laser beam 21 emitted from the oscillator 22 onto the workpiece 100 held on the holding surface 11 of the holding table 10 and irradiates the workpiece 100. The condenser 23 condenses the laser beam 21 modulated by the spatial light modulator 24 onto the workpiece 100. The condensing point 211 of the laser beam 21 condensed by the condenser 23 is positioned inside the workpiece 100 in the modified layer formation process of the embodiment. In the example shown in FIG. 3, the back surface 105 side of the workpiece 100 is held by the holding table 10 and the laser beam 21 is irradiated from the front surface 102 side, but in the present invention, the front surface 102 side may be held by the holding table 10 and the laser beam 21 may be irradiated from the back surface 105 side.

[0027] The spatial light modulator 24 is provided between the oscillator 22 and the condenser 23. The spatial light modulator 24 modulates the incident laser beam 21 by electrically controlling the spatial distribution such as the amplitude, phase, and polarization of the laser beam 21 emitted from the oscillator 22. In the embodiment, the spatial light modulator 24 reflects and outputs the laser beam 21, but in the present invention, the laser beam 21 may be transmitted and outputted.

[0028] The spatial light modulator 24 has a display unit 241. As shown in FIG. 4, the display unit 241 displays a predetermined phase pattern 242. The phase pattern 242 is displayed in the region 212 where the laser beam 21 hits on the display unit 241. The spatial light modulator 24 modulates and emits the laser beam 21 incident on the display unit 241 according to the phase pattern 242.

[0029] In an example shown in FIG. 4, the phase pattern 242 is a branching pattern for branching and emitting the incident laser beam 21. As shown in FIG. 4, in a state where the phase pattern 242 which is a branching pattern is displayed on the display unit 241, the laser beam 21 branches into a plurality of laser beams 21 as shown in FIG. 5.

[0030] As shown in FIG. 3, the polarizing plate 25 is provided between the oscillator 22 and the spatial light modulator 24. The polarizing plate 25 polarizes the laser beam 21 oscillated from the oscillator 22 into light in a specific direction.

[0031] The focusing lens 26 is disposed between the spatial light modulator 24 and the condenser 23. The focusing lens 26 focuses the laser beam 21. In the embodiment, the laser beam 21 transmitted through the focusing lens 26 converges and irradiates toward the aperture 27, a part of which is shielded and a part of which passes through the aperture.

[0032] The aperture 27 is disposed between the spatial light modulator 24 and the condenser 23. The aperture 27 is positioned at or near the focal position of the focusing lens 26. The laser beam 21 that has passed through the focusing lens 26 and is focused is incident on the aperture 27, and a part of it passes through the aperture 27-1. The aperture 27 allows the laser beam 21 modulated by the phase pattern 242 in the spatial light modulator 24 to pass through or partially block the light.

[0033] As shown in FIG. 5, the laser beam 21 emitted from the display unit 241 on which the phase pattern 242, which is the branching pattern shown in FIG. 4, is displayed branches into a plurality of beams, and two laser beams 21 pass through the aperture 27-1 of the aperture 27. The aperture 27 blocks, for example, the higher-order light generated by the branching pattern. Therefore, when the branching pattern is displayed as the phase pattern 242 on the display unit 241, the higher-order light is blocked by the aperture 27, so that the output of the laser beam 21 at the processing point (the focusing point 211) is lower than when the branching pattern is not displayed. Note that the aperture 27-1 of the aperture 27 is not limited to the circular shape shown in FIG. 5 and may be rectangular.

[0034] The relay lens 28 is disposed between the spatial light modulator 24 and the condenser 23. The relay lens 28 transmits the laser beam 21 that has been focused by the focusing lens 26 and passed through the aperture 27 to the mirror 29.

[0035] The mirror 29 reflects the laser beam 21 emitted from the spatial light modulator 24 toward the condenser 23. That is, the mirror 29 reflects the laser beam 21 toward the workpiece 100 held on the holding surface 11 of the holding table 10. In the embodiment, the mirror 29 reflects the laser beam 21 that has passed through the relay lens 28 toward the condenser 23. Also, the mirror 29 transmits a part of the laser beam 21 that has passed through the relay lens 28 as leakage light 213.

[0036] The light detection unit 30 detects the received light. For example, the light detection unit 30 detects the intensity of the laser beam 21 emitted from the spatial light modulator 24. More specifically, the light detection unit 30 detects the intensity of the laser beam 21 that is modulated by the phase pattern 242, emitted from the display unit 241, and passes through the aperture 27. In an embodiment, the light detection unit 30 receives the leakage light 213 of the laser beam 21 that is transmitted without being reflected by the mirror 29, and while irradiating the workpiece 100 with the laser beam 21, detects the output of the laser beam 21 that is irradiated with and modulated by the phase pattern 242.

[0037] The light detection unit 30 is, for example, a photodiode. The photodiode outputs a voltage value that changes according to the amount of received laser beam 21 to the control unit 90. The light detection unit 30 is not limited to a photodiode, and may be, for example, an imaging unit equipped with an imaging device such as a CCD imaging device or a CMOS imaging device, or a power meter.

[0038] The imaging means 31 images the processing point (focus point 211) by the laser beam 21 that irradiates the workpiece 100 held on the holding table 10. The imaging means 31 includes, for example, a CCD camera or the like. The imaging means 31 may be common with the imaging unit 70 described later.

[0039] The condenser lens 32 is disposed between the mirror 29 and the light detection unit 30. The condenser lens 32 condenses the leakage light 213 of the laser beam 21 that has passed through the mirror 29 in front of the light detection unit 30.

[0040] The diffuser plate 33 is disposed between the mirror 29 and the condenser lens 32. The diffuser plate 33 diffuses the incident leakage light 213 of the laser beam 21 to eliminate the unevenness in the intensity of the transmitted leakage light 213 of the laser beam 21.

[0041] The filter 34 is disposed between the diffusion plate 33 and the condenser lens 32. The filter 34 is a filter that transmits a part of the leakage light 213 of the laser beam 21. The filter 34 transmits, for example, only the laser beam 21 having a wavelength that the light detection unit 30 receives among the leakage light 213 of the laser beam 21. The filter 34 includes, for example, an ND (Neutral Density) filter. The ND filter is a filter that transmits while reducing the amount of light by a certain amount without selecting a wavelength in a predetermined wavelength band.

[0042] The moving unit 60 shown in FIG. 1 is a unit that relatively moves the condensing point 211 (see FIG. 3) of the laser beam 21 along a plurality of division planned lines 103 set on the workpiece 100. The moving unit 60 includes a machining feed unit 61, an indexing feed unit 62, and a condensing point position adjustment unit 63.

[0043] The machining feed unit 61 is a unit that relatively moves the holding table 10 and the condensing point 211 (see FIG. 3) of the laser beam irradiation unit 20 in the X-axis direction, which is the machining feed direction. In the embodiment, the machining feed unit 61 moves the holding table 10 in the X-axis direction. In the embodiment, the machining feed unit 61 is installed on the apparatus main body 2 of the laser processing apparatus 1. The machining feed unit 61 supports the X-axis direction moving plate 14 so as to be movable in the X-axis direction.

[0044] The indexing feed unit 62 is a unit that relatively moves the holding table 10 and the condensing point 211 (see FIG. 3) of the laser beam irradiation unit 20 in the Y-axis direction, which is the indexing feed direction. In the embodiment, the indexing feed unit 62 moves the holding table 10 in the Y-axis direction. In the embodiment, the indexing feed unit 62 is installed on the apparatus main body 2 of the laser processing apparatus 1. The indexing feed unit 62 supports the Y-axis direction moving plate 15 so as to be movable in the Y-axis direction.

[0045] The condensing point position adjustment unit 63 is a unit that relatively moves the holding table 10 and the condensing point 211 (see FIG. 3) of the laser beam irradiation unit 20 in the Z-axis direction, which is the condensing point position adjustment direction. In the embodiment, the condensing point position adjustment unit 63 moves at least the condenser 23 of the laser beam irradiation unit 20 in the Z-axis direction. In the embodiment, the condensing point position adjustment unit 63 is installed on a column 3 erected from the apparatus main body 2 of the laser processing apparatus 1. The condensing point position adjustment unit 63 movably supports at least the condenser 23 of the laser beam irradiation unit 20 in the Z-axis direction.

[0046] In the embodiment, the processing feed unit 61, the indexing feed unit 62, and the condensing point position adjustment unit 63 each include a well-known ball screw, a well-known pulse motor, and a well-known guide rail. The ball screw is rotatably provided around its axis. The pulse motor rotates the ball screw around its axis. The guide rail of the processing feed unit 61 movably supports the X-axis direction movement plate 14 in the X-axis direction. The guide rail of the processing feed unit 61 is fixedly provided on the Y-axis direction movement plate 15. The guide rail of the indexing feed unit 62 movably supports the Y-axis direction movement plate 15 in the Y-axis direction. The guide rail of the indexing feed unit 62 is fixedly provided on the apparatus main body 2. The guide rail of the condensing point position adjustment unit 63 movably supports at least the condenser 23 of the laser beam irradiation unit 20 in the Z-axis direction. The guide rail of the condensing point position adjustment unit 63 is fixedly provided on the column 3.

[0047] The imaging unit 70 images the workpiece 100 held on the holding table 10. The imaging unit 70 includes a CCD camera or an infrared camera. The imaging unit 70 is fixed, for example, adjacent to the condenser 23 (see FIG. 2) of the laser beam irradiation unit 20. The imaging unit 70 images the workpiece 100, obtains an image for performing alignment for aligning the workpiece 100 and the laser beam irradiation unit 20, and outputs the obtained image.

[0048] In the embodiment, the input means 80 is a touch panel included in a display device constituted by a liquid crystal display device or the like. The input means 80 can receive various operations such as an operator registering processing content information. The input means 80 may be an external input device such as a keyboard.

[0049] The control unit 90 controls each of the above-described components of the laser processing apparatus 1 to cause the laser processing apparatus 1 to execute a processing operation or the like on the workpiece 100. The control unit 90 is a computer including an arithmetic processing device as an arithmetic means, a storage device as a storage means, and an input / output interface device as a communication means. The arithmetic processing device includes, for example, a microprocessor such as a CPU (Central Processing Unit). The storage device has a memory such as an HDD (Hard Disk Drive), a ROM (Read Only Memory), or a RAM (Random Access Memory). The arithmetic processing device performs various arithmetic operations based on a predetermined program stored in the storage device. The arithmetic processing device outputs various control signals to the above-described components via the input / output interface device according to the arithmetic result, and controls the laser processing apparatus 1. The control unit 90 includes a pattern control unit 91, a storage unit 92, and a determination unit 93.

[0050] The pattern control unit 91 controls the phase pattern 242 to be displayed on the display unit 241 of the spatial light modulator 24. For example, the pattern control unit 91 causes the phase pattern 242 to be displayed in the area 212 where the laser beam 21 of the display unit 241 hits. For example, the pattern control unit 91 causes the display unit 241 to display a branching pattern (see FIG. 4), which is a phase pattern 242 for branching the laser beam 21.

[0051] The memory unit 92 is included in the storage device of the control unit 90. When the branching pattern is displayed on the display unit 241 by the pattern control unit 91, the memory unit 92 stores the intensity of the laser beam 21 detected by the light detection unit 30 as the reference intensity. That is, the memory unit 92 acquires and stores the intensity of the laser beam 21 irradiated on the branching pattern and branched (modulated) from the light detection unit 30.

[0052] The determination unit 93 determines whether the spatial light modulator 24 is operating normally based on the intensity of the laser beam 21 detected by the light detection unit 30. More specifically, the determination unit 93 determines whether the intensity of the laser beam 21 detected by the light detection unit 30 has changed from the reference intensity stored in the memory unit 92, and based on this determination result, determines whether the spatial light modulator 24 is operating normally.

[0053] Next, a method for determining an operation abnormality of the spatial light modulator 24 will be described. FIG. 6 is a schematic diagram showing an abnormal operation of the display unit 241 of the spatial light modulator 24 shown in FIG. 3. FIG. 7 is a schematic diagram of the laser beam 21 emitted from the display unit 241 shown in FIG. 6.

[0054] In an example shown in FIG. 6, the display unit 241 during abnormal operation cannot display the branching pattern as the phase pattern 242-1, and nothing is displayed in the region 212 (see FIG. 3) irradiated by the laser beam 21. In FIG. 6 of this specification, for the sake of explanation, the region irradiated by the laser beam 21 on the black display unit 241 is depicted in gray, but actually, the entire display unit 241, including the region irradiated by the laser beam 21, is in a black state where nothing is displayed.

[0055] At this time, as shown in FIG. 7, the laser beam 21 is not branched. The high-order light of the laser beam 21 emitted from the branching pattern (phase pattern 242 in FIG. 4) displayed on the display unit 241 during normal operation is blocked by the aperture 27, whereas the high-order light of the laser beam 21 emitted from the display unit 241 on which the branching pattern is not displayed is not blocked by the aperture 27. Therefore, the output of the laser beam 21 at the processing point (focus point 211) increases, and the intensity of the laser beam 21 detected by the light detection unit 30 increases.

[0056] Here, the storage unit 92 stores, as a reference intensity, the intensity of the laser beam 21 that is emitted from the branching pattern (phase pattern 242 in FIG. 4) displayed on the display unit 241 during normal operation and whose high-order light is blocked by the aperture 27, as detected by the light detection unit 30. When the determination unit 93 determines that the intensity of the laser beam 21 that is emitted from the display unit 241 on which the branching pattern is not displayed and whose high-order light is not blocked, as detected by the light detection unit 30, has changed from the reference intensity, the determination unit 93 determines that the spatial light modulator 24 is not operating normally.

[0057] Next, the function of the diffuser plate 33 will be described. FIG. 8 is a schematic diagram showing how the light detection unit 30 shown in FIG. 3 receives the laser beam 21. FIG. 9 is a schematic diagram showing how the light detection unit 30 receives the laser beam 21 in the laser beam irradiation unit 20-1 according to the comparative example. Note that in FIGS. 8 and 9, the drawing of the filter 34 is omitted.

[0058] As shown in FIG. 8, the leakage light 213 of the laser beam 21 enters the diffuser plate 33 in a state of being branched by the branching pattern displayed on the display unit 241. The diffuser plate 33 diffuses the incident laser beam 21 and emits it in a state where the influence of branching is evened out. The condenser lens 32 condenses the leakage light 213 of the laser beam 21, whose influence of branching is evened out, toward the light detection unit 30.

[0059] On the other hand, as shown in FIG. 9 of the comparative example, in the laser beam irradiation unit 20-1 without the diffusion plate 33, the leakage light 213 of the laser beam 21 enters the condenser lens 32 in a branched state by the branch pattern displayed on the display unit 241. The condenser lens 32 condenses the laser beam 21 in the branched state toward the light detection unit 30. However, since the branched laser beam 21 enters a plurality of locations on the light receiving surface of the light detection unit 30, the output of the laser beam 21 detected by the light detection unit 30 may become unstable.

[0060] For example, when the light detection unit 30 is a photodiode, since the light receiving surface of the photodiode is small, there is a possibility that the branched laser beam 21 cannot be received. The laser beam irradiation unit 20 including the diffusion plate 33 of the embodiment enables the light detection unit 30 to stably measure the intensity of the laser beam 21.

[0061] As described above, in the laser processing apparatus 1 according to the embodiment, when irradiating the workpiece 100 with the laser beam 21, the laser beam irradiation unit 20 modulates the laser beam 21 incident on the phase pattern 242 displayed on the display unit 241 of the spatial light modulator 24 in correspondence with the phase pattern 242. Specifically, the spatial light modulator 24 displays a branch pattern, which is a phase pattern for branching the laser beam 21, on the display unit 241, and branches and emits the laser beam 21. Further, the laser processing apparatus 1 includes a light detection unit 30 that detects the intensity of the laser beam 21 emitted from the spatial light modulator 24, and the storage unit 92 of the control unit 90 stores in advance the intensity of the laser beam 21 branched by the branch pattern.

[0062] Here, when an abnormality occurs in the spatial light modulator 24 and the branch pattern is not displayed on the display unit 241, for example, when nothing is displayed in the phase pattern 242, the output of the laser beam 21 reaching the processing point changes. In the laser processing apparatus 1 of the embodiment, while irradiating the workpiece 100 with the laser beam 21, the output of the laser beam 21 emitted from the display unit 241 is detected and compared with the reference intensity during normal operation, so that an abnormality in the spatial light modulator 24 can be detected.

[0063] As a result, it becomes possible to quickly detect an abnormality in the spatial light modulator 24 while processing one workpiece 100, so that an abnormality can be noticed even during processing, and the effect of reducing the possibility of the entire workpiece 100 being processed into a defective chip is achieved.

[0064] Note that the present invention is not limited to the above-described embodiment. That is, various modifications can be made and implemented without departing from the gist of the present invention. For example, in the laser beam irradiation unit 20 of the embodiment, the stray light 213 of the laser beam 21 whose branching effect is equalized by the diffuser plate 33 is condensed by the condenser lens 32 and received by the light detection unit 30, but it may be imaged and received as a reduction relay system. Further, by tilting the measurement optical system including the diffuser plate 33, the filter 34, and the light detection unit 30, it is possible to suppress the reflected light of the filter 34 from returning to the imaging means 31 and the oscillator 22. Thereby, it is possible to suppress the reflected light of the filter 34 from returning to the imaging means 31 and affecting the reflectance measurement of the workpiece 100, and to suppress the reflected light of the filter 34 from returning to the oscillator 22 and affecting the oscillation of the laser beam 21.

Explanation of Reference Numerals

[0065] 1 Laser processing apparatus 10 Holding table 11 Holding surface 20, 20-1 Laser beam irradiation unit 21 Laser beam 211 Focus point 212 Region 213 Leakage light 22 Oscillator 23 Condenser 24 Spatial light modulator 241 Display section 242, 242-1 Phase pattern 25 Polarizing plate 26 Focusing lens 27 Aperture 28 Relay lens 29 Mirror 30 Photodetection unit 31 Imaging means 32 Condensing lens 33 Diffuser 34 Filter 60 Moving unit 61 Machining feed unit 62 Indexing feed unit 90 Control unit 91 Pattern control section 92 Memory section 93 Judgment section 100 Workpiece 103 Division planned line 102 Surface 105 Back surface 106 Modified layer

Claims

1. A laser processing apparatus comprising: an oscillator that emits a laser beam; a condenser that condenses the laser beam emitted from the oscillator and irradiates a workpiece; a spatial light modulator disposed between the oscillator and the condenser, having a display unit that displays a phase pattern, and modulating and emitting the laser beam incident on the display unit according to the phase pattern; a mirror that reflects the laser beam emitted from the spatial light modulator toward the condenser; a laser beam irradiation unit including the above; a light detection unit that receives the leakage light of the laser beam that is emitted from the spatial light modulator and transmitted through the mirror without being reflected, and detects its intensity; a condenser lens disposed between the mirror and the light detection unit and condensing the leakage light toward the light detection unit; a diffusion plate disposed between the mirror and the condenser lens and diffusing the leakage light; a control unit that controls each component; The laser processing apparatus is provided with: The control unit includes: a pattern control unit that controls the phase pattern displayed on the display unit; a storage unit that stores, as a reference intensity, the intensity of the laser beam detected by the light detection unit when a branching pattern, which is a phase pattern for branching the laser beam, is displayed on the display unit by the pattern control unit; a determination unit that determines whether the spatial light modulator is operating normally based on whether the intensity of the laser beam detected by the light detection unit has changed from the reference intensity; Characterized by having: A laser processing apparatus.

2. Between the spatial light modulator and the light detection unit, a focusing lens that focuses the laser beam; an aperture positioned at the focal position of the focusing lens or in the vicinity of the focal position; are disposed. Characterized by this, The laser processing apparatus according to Claim 1.

3. The light detection unit is a photodiode. Characterized by this, The laser processing apparatus according to Claim 1 or 2.

Images