Laser processing apparatus

Abstract

To provide a laser processing apparatus capable of detecting an abnormality in a spatial light modulator at high speed.SOLUTION: The laser processing apparatus includes a laser beam irradiation unit 20 disposed between an oscillator 22 and a condenser 23 and including a spatial light modulator 24 that modulates and emits an incident laser beam 21 in accordance with a phase pattern displayed on a display 241, a control unit that performs switching control to switch the phase pattern displayed on the display 241 to a different phase pattern between the instant a focus point 211 of the laser beam 21 passes the end point of a planned dividing line set on a workpiece 100 and the instant the focus point reaches the start point of a next planned dividing line to be processed, an optical detection unit 30 that detects the intensity of the laser beam 21 in the phase pattern switched by the switching control, and a determination unit that determines whether or not the spatial light modulator 24 is operating properly on the basis of the intensity of the laser beam 21.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 focal point of a laser beam is positioned inside a wafer, a modified layer is formed by irradiating along a street (division planned 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. In this laser processing apparatus, when the spatial light modulator does not operate normally due to a defect or an abnormality, the laser beam may not be modulated appropriately, which may cause a processing defect.

[0003] Therefore, various methods have been proposed to detect an operation failure of the spatial light modulator. For example, Patent Document 2 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

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the method of Patent Document 2 has a problem that although an operation abnormality can be confirmed during processing, it is necessary to acquire a two-dimensional intensity distribution, which takes time for processing.

[0006] 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

[0007] In order to solve the above-described problems and achieve the object, a laser processing apparatus of the present invention is a laser processing apparatus that irradiates a workpiece on which a plurality of division planned lines are set with a laser beam and performs processing along the division planned lines, and includes an oscillator that emits a laser beam, a condenser that condenses the laser beam emitted from the oscillator and irradiates the workpiece, 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 laser beam irradiation unit including the spatial light modulator, a holding table that holds the workpiece, a processing feed unit that relatively moves the holding table and the condensing point of the laser beam in the processing feed direction, a determination feed unit that relatively moves the holding table and the condensing point of the laser beam in a determination feed direction orthogonal to the processing feed direction, a control unit that controls the phase pattern displayed on the display unit of the spatial light modulator, a light detection unit that detects the intensity of the laser beam emitted from the spatial light modulator, and a determination unit that determines whether the spatial light modulator is operating normally based on the intensity of the laser beam detected by the light detection unit. A detection unit that outputs the condensing state of the reflected light of the detection laser beam irradiated toward the workpiece held on the holding table through the condenser; Furthermore, the laser processing apparatus of the present invention further includes: Based on the condensing state, it is determined whether the position of the condensing point of the detection laser beam is above, below, or the same as the upper surface of the workpiece. Based on this, it is determined whether the condensing points of the laser beam and the detection laser beam are inside or outside the outer edge of the workpiece. When the condensing point of the laser beam is inside the outer edge of the workpiece, a processing phase pattern is displayed on the display unit. When the condensing point of the laser beam is outside the outer edge of the workpiece, switching control is performed so that a passing phase pattern different from the processing phase pattern is displayed on the display unit; The light detection unit is characterized in that it detects the intensity of the laser beam in the phase pattern switched by the switching control.

[0010] In the laser processing apparatus of the present invention, the laser beam irradiation unit may have a mirror that reflects the laser beam emitted from the spatial light modulator toward the condenser, and the light detection unit may receive the transmitted light of the laser beam that is transmitted without being reflected by the mirror, so as to detect the output of the laser beam while irradiating the workpiece with the laser beam.

[0011] Further, in the laser processing apparatus of the present invention, the light detection unit may be a photodiode.

Advantages of the Invention

[0012] The present invention can detect abnormalities of the spatial light modulator at high speed.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0014] Embodiments for carrying out the present invention (embodiments) 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.

[0015] 〔Embodiment〕 First, the configuration of the laser processing apparatus 1 according to an 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 a 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 a 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 showing another example of the phase pattern 242 displayed on the display unit 241 of the spatial light modulator 24 shown in FIG. 3. FIG. 6 is a plan view schematically showing an example of a locus 107 of a focus point 211 of the laser beam 21 when processing the workpiece 100.

[0016] In the following description, the X-axis direction is one direction in the horizontal plane. The Y-axis direction is a direction orthogonal to the X-axis direction in the horizontal plane. 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 focus point position adjustment direction is the Z-axis direction.

[0017] The laser processing apparatus 1 includes a holding table 10, a laser beam irradiation unit 20, a light detection unit 30 (see FIG. 3), imaging means 31, a moving unit 60, an imaging unit 70, input means 80, a control unit 90, and a determination unit 91. The laser processing apparatus 1 according to the embodiment is an apparatus that processes a workpiece 100 by irradiating the workpiece 100 with a laser beam 21. The processing of the workpiece 100 by the laser processing apparatus 1 is, for example, a modified layer forming process for forming a modified layer 106 (see FIG. 3) inside the workpiece 100 by stealth dicing, a groove processing for forming a groove on the surface 102 of the workpiece 100, or a cutting process for cutting the workpiece 100 along a planned cutting line 103. In the embodiment, a configuration for forming a modified layer 106 on the workpiece 100 will be described.

[0018] The workpiece 100 is, for example, a wafer such as a disk-shaped semiconductor device wafer or an optical device wafer 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 although the workpiece 100 is disk-shaped in the embodiment, it does not have to be disk-shaped in the present invention. The workpiece 100 is transported and processed while, 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.

[0019] As shown in FIG. 2, the workpiece 100 includes a dicing 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 dicing 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).

[0020] In the embodiment, a modified layer 106 (see FIG. 3) is formed along the dicing line 103 on the workpiece 100. The workpiece 100 is diced into individual devices 104 along the modified layer 106 formed on the dicing line 103 and separated into chips. Note that although the chips are square in the embodiment, they may be rectangular in the present invention.

[0021] The holding table 10 shown in Fig. 1 etc. holds the workpiece 100 on the holding surface 11. The holding surface 11 is in a disk shape formed from porous ceramic or the like. The holding surface 11 is, in the embodiment, a plane parallel to the horizontal direction. The holding surface 11 is connected to a vacuum suction source via a vacuum suction path, for example. The holding table 10 suction-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.

[0022] The holding table 10 is rotated by a rotation unit 13 around an axis parallel to the Z-axis direction. 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.

[0023] The laser beam irradiation unit 20 is a unit that irradiates a laser beam 21 onto the workpiece 100 held on the holding surface 11 of the holding table 10. Among the laser beam irradiation unit 20, at least the condenser 23 (see Fig. 3) is supported by a later-described condensing point position adjustment unit 63 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 relay lens 26, an aperture 27, a relay lens 28, and a mirror 29. Further, the laser beam irradiation unit 20 includes a condenser lens 32, a diffuser plate 33, and a filter 34 between the light detection unit 30 and the mirror 29.

[0024] 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.

[0025] 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.

[0026] 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 oscillated 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 output.

[0027] The spatial light modulator 24 has a display unit 241. As shown in FIGS. 4 and 5, the display unit 241 displays a predetermined phase pattern 242. The phase pattern 242 is displayed in the area 212 on the display unit 241 where the laser beam 21 hits. The spatial light modulator 24 modulates and emits the laser beam 21 incident on the display unit 241 according to the phase pattern 242. The spatial light modulator 24 adjusts the output of the laser beam 21 irradiated on the workpiece 100 by displaying the phase pattern 242 on the display unit 241.

[0028] Here, the focus point 211 of the laser beam 21 moves, for example, along the locus 107 shown in FIG. 6 along the division planned line 103 set on the workpiece 100. The focus point 211 of the laser beam 21 is positioned inside the workpiece 100 on the locus 107 (shown by the solid line in FIG. 6) along the division planned line 103. At this time, the display unit 241 displays, for example, the phase pattern 243 shown in FIG. 4. The phase pattern 243 is a phase pattern 243 for processing to be displayed on the display unit 241 while the focus point 211 of the laser beam 21 is processing inside the workpiece 100.

[0029] Also, until the focus point 211 of the laser beam 21 passes through the end point 103-1 of one division planned line 103 and reaches the start point 103-2 of the next division planned line 103 to be processed, that is, while on the locus 107 (shown by the broken line in FIG. 6) outside the outer edge of the workpiece 100, the display unit 241 displays, for example, the phase pattern 244 shown in FIG. 5. The phase pattern 244 is a passing phase pattern 244 for display on the display unit 241 while the focus point 211 of the laser beam 21 passes outside the workpiece 100. The phase pattern 243 is different from the phase pattern 243 for processing shown in FIG. 4.

[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 relay lens 26 is a focusing lens disposed between the spatial light modulator 24 and the condenser 23. The relay lens 26 focuses the laser beam 21. In the embodiment, the laser beam 21 transmitted through the relay lens 26 converges and irradiates toward the aperture 27, a part of which is blocked 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 relay lens 26. The laser beam 21 focused through the relay lens 26 is incident on the aperture 27, and a part of it passes through the aperture. 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 blocks it. Note that the aperture of the aperture 27 may be circular or rectangular.

[0033] 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 focused by the relay lens 26 and passed through the aperture 27 to the mirror 29.

[0034] 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 transmitted through the relay lens 28 toward the condenser 23. Also, the mirror 29 transmits the laser beam 21 transmitted through the relay lens 28 as transmitted light 213. More specifically, the mirror 29 reflects the laser beam 21 modulated by the processing phase pattern 243 in the spatial light modulator 24 toward the condenser 23 and transmits it as transmitted light 213. Also, the mirror 29 reflects the laser beam 21 modulated by the passing phase pattern 244 in the spatial light modulator 24 toward the condenser 23 and transmits it as transmitted light 213.

[0035] 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 emitted from the display unit 241 and modulated by the phase pattern 242. In the embodiment, the light detection unit 30 receives the transmitted 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 and modulated by the processing phase pattern 243 and the passing phase pattern 244.

[0036] 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 including an imaging device such as a CCD imaging device or a CMOS imaging device, or a power meter.

[0037] The imaging means 31 images the processing point (focus point 211) by the laser beam 21 irradiated on 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 to the imaging unit 70 described later.

[0038] The condenser lens 32 is disposed between the mirror 29 and the light detection unit 30. The condenser lens 32 condenses the transmitted light 213 of the laser beam 21 that has passed through the mirror 29 in front of the light detection unit 30.

[0039] The diffusion plate 33 is disposed between the mirror 29 and the condenser lens 32. The diffusion plate 33 eliminates the unevenness in the intensity of the transmitted light 213 of the laser beam 21 that is transmitted by diffusing the transmitted light 213 of the incident laser beam 21.

[0040] The filter 34 is disposed between the diffuser plate 33 and the condenser lens 32. The filter 34 is a filter that transmits a part of the transmitted 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 transmitted 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.

[0041] Here, as described above, when the laser beam irradiation unit 20 irradiates the workpiece 100 with the laser beam 21, the laser beam 21 incident on the processing phase pattern 243 by the spatial light modulator 24 is incident on the entrance pupil plane of the condenser 23 and modulated so as to process the workpiece 100 under desired processing conditions. Further, the laser beam irradiation unit 20 modulates the laser beam 21 incident on the passing phase pattern 244 by the spatial light modulator 24 so as to be incident on the light detection unit 30 until the condensing point 211 of the laser beam 21 passes through the end point 103-1 of the division planned line 103 and reaches the start point 103-2 of the division planned line 103 to be processed next. That is, while irradiating the workpiece 100 with the laser beam 21, the laser beam irradiation unit 20 irradiates the passing phase pattern 244 during the laser processing of one workpiece 100, and the light detection unit 30 detects the output of the laser beam 21 that has been modulated.

[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 processing feed unit 61, a dividing 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 the column 3 erected from the apparatus main body 2 of the laser processing apparatus 1. The condensing point position adjustment unit 63 supports at least the condenser 23 of the laser beam irradiation unit 20 so as to be movable in the Z-axis direction.

[0046] In the embodiment, the machining 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 machining feed unit 61 supports the X-axis direction movement plate 14 so as to be movable in the X-axis direction. The guide rail of the machining feed unit 61 is fixedly provided on the Y-axis direction movement plate 15. The guide rail of the indexing feed unit 62 supports the Y-axis direction movement plate 15 so as to be movable 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 supports at least the condenser 23 of the laser beam irradiation unit 20 so as to be movable 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 to obtain 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 machining 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 perform a processing operation or the like on the workpiece 100. The control unit 90 is a computer including an arithmetic processing unit as an arithmetic means, a storage device as a storage means, and an input / output interface device as a communication means. The arithmetic processing unit 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 unit performs various arithmetic operations based on a predetermined program stored in the storage device. The arithmetic processing unit outputs various control signals to each of the above-described components via the input / output interface device according to the arithmetic result, and controls the laser processing apparatus 1.

[0050] The control unit 90 controls the phase pattern 242 to be displayed on the display unit 241 of the spatial light modulator 24. For example, the control unit 90 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, when irradiating the laser beam 21 along the division planned line 103, when the condensing point 211 of the laser beam 21 is positioned inside the workpiece 100, the control unit 90 causes the display unit 241 to display a processing phase pattern 243 (see, for example, FIG. 4) for processing the inside of the workpiece 100. For example, when irradiating the laser beam 21 along the division planned line 103, the control unit 90 switches the phase pattern 242 to be displayed on the display unit 241 from the processing phase pattern 243 to the passing phase pattern 244 during the period from passing through the end point 103-1 (see FIG. 6) of the division planned line 103 to reaching the start point 103-2 of the next division planned line 103 to be processed. At this time, it is assumed that the output received by the light detection unit 30 changes to a value equal to or greater than a predetermined value when switched from the processing phase pattern 243 to the passing phase pattern 244. The control unit 90 may perform the switching control for each one division planned line 103, or may perform the switching control for every predetermined number of division planned lines 103.

[0051] The determination unit 91 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. The determination unit 91 may be configured as a part of a computer as the control unit 90. For example, when the control unit 90 switches the phase pattern 242 displayed on the display unit 241 from the processing phase pattern 243 to the passing phase pattern 244, the determination unit 91 determines whether the spatial light modulator 24 is operating normally based on whether the intensity of the laser beam 21 detected by the light detection unit 30 has changed.

[0052] As described above, in the laser processing apparatus 1 according to the embodiment, when the laser beam irradiation unit 20 irradiates the workpiece 100 with the laser beam 21, the laser beam 21 incident on the phase pattern 242 displayed on the display unit 241 of the spatial light modulator 24 is modulated corresponding to the phase pattern 242. Specifically, when the processing phase pattern 243 is being displayed, the laser beam 21 is modulated so that the laser beam 21 incident on the entrance pupil plane of the condenser 23 processes the workpiece 100 under desired processing conditions. At the same time, when the passing phase pattern 244 different from the processing phase pattern 243 is being displayed, the laser beam 21 is modulated so that the output of the transmitted light 213 of the laser beam 21 incident on the light detection unit 30 changes. That is, the laser processing apparatus 1 performs switching control to switch the phase pattern 242, so that while the laser beam irradiation unit 20 irradiates the workpiece 100 with the laser beam 21, the light detection unit 30 can detect the intensity of the laser beam 21 irradiated with and modulated by the passing phase pattern 244.

[0053] As a result, it becomes possible to quickly detect an abnormality of the spatial light modulator 24 while processing one workpiece 100, so that an abnormality can be noticed even during processing, and the possibility of processing the entire workpiece 100 into a defective chip can be reduced.

[0054] Note that the present invention is not limited to the above-described embodiments. That is, various modifications can be made and implemented without departing from the gist of the present invention.

[0055] 〔Modification Example〕 For example, the laser processing apparatus 1 may further include a detection unit 40. FIG. 7 is a schematic diagram showing a schematic configuration around the laser beam irradiation unit 20-1 according to the modification example. The laser beam irradiation unit 20-1 of the modification example is different from the laser beam irradiation unit 20 of the embodiment in that it includes a detection unit 40, and the other configurations are the same. In FIG. 7, the configuration from the oscillator 22 to the condenser 23, which is the same as that of the embodiment shown in FIG. 3, that is, the description of the polarizing plate 25, the spatial light modulator 24, the relay lens 26, the aperture 27, the relay lens 28, the mirror 29, the imaging means 31, the diffuser 33, the filter 34, the condenser lens 32, and the optical detection unit 30 is omitted.

[0056] The detection unit 40 detects the positional relationship between the condensing point 211 of the laser beam 21 and the workpiece 100. The detection unit 40 includes a dichroic mirror 41 and a height position detection unit 50.

[0057] The dichroic mirror 41 is disposed on the optical path of the laser beam 21 between the oscillator 22 and the condenser 23. The dichroic mirror 41 transmits the laser beam 21 emitted from the oscillator 22 to the holding surface 11 side of the holding table 10. Further, the dichroic mirror 41 reflects the detection laser beam 51 emitted from the light source 52 of the height position detection unit 50, which will be described later, to the holding surface 11 side of the holding table 10.

[0058] The height position detection unit 50 is a unit that detects the Z-axis position (height) of the upper surface of the workpiece 100 (in the example shown in FIG. 7, the surface 102). The Z-axis position is set with the height (Z coordinate) of the upper surface at a predetermined horizontal plane position (X-Y position) of the workpiece 100 placed on the holding surface 11 as the reference plane (0 μm). The height position detection unit 50 includes a light source 52, a beam expander 53, a mirror 54, a beam splitter 55, a lens 56, an astigmatism addition unit 57, and a detection element 58.

[0059] The light source 52 emits a detection laser beam 51 for detecting the Z-axis position (height) of the upper surface of the workpiece 100 held on the holding surface 11 of the holding table 10. The light source 52 includes, for example, an SLD (Super Luminescent Diode) light source. The light source 52 irradiates the workpiece 100 held on the holding surface 11 of the holding table 10 with the detection laser beam 51 through the condenser 23.

[0060] In a modified example, the condensing point of the detection laser beam 51 is positioned on the upper surface of the workpiece. The detection laser beam 51 emitted from the light source 52 passes through the beam expander 53, the mirror 54, the beam splitter 55, and the lens 56 in sequence and is irradiated onto the dichroic mirror 41. The dichroic mirror 41 reflects the detection laser beam 51 toward the condenser 23 side.

[0061] The beam expander 53 converts the detection laser beam 51 irradiated from the light source 52 into parallel light of a predetermined magnification. The mirror 54 reflects the detection laser beam 51 converted into parallel light by the beam expander 53 toward the beam splitter 55 side.

[0062] The beam splitter 55 reflects the detection laser beam 51 reflected by the mirror 54 toward the dichroic mirror 41 side. Also, the beam splitter 55 transmits the reflected light 511 of the detection laser beam 51 reflected by the upper surface (surface 102) of the workpiece 100, as will be described later, toward the astigmatism addition unit 57 side. The beam splitter 55 has, for example, a reflection:transmission ratio of 1:1, reflects and guides the detection laser beam 51 toward the dichroic mirror 41 side, and transmits the reflected light 511 incident from the dichroic mirror 41 side and guides it toward the astigmatism addition unit 57 side.

[0063] The lens 56 is disposed between the beam splitter 55 and the dichroic mirror 41. The lens 56 enlarges the detection laser beam 51. Note that the lens 56 for enlarging the detection laser beam 51 is necessary when the focal position of the detection laser beam 51 is different from the focal position of the laser beam 21, and is not necessary when the focal positions are the same.

[0064] The astigmatism addition unit 57 adds astigmatism to the reflected light 511 that has passed through the beam splitter 55. The astigmatism addition unit 57 includes a convex lens 571 and a cylindrical lens 572. The convex lens 571 condenses the reflected light 511 that has passed through the beam splitter 55. The reflected light 511 condensed by the convex lens 571 enters the cylindrical lens 572.

[0065] The cylindrical lens 572 has a substantially semi-cylindrical shape obtained by cutting a cylinder in half along the axial direction. The cylindrical lens 572 has a lens effect only in one direction parallel to the radial direction of the cylinder, and has no lens effect in the other direction parallel to the axial direction of the cylinder. For this reason, when the reflected light 511 of the detection laser beam 51 reflected by the upper surface of the workpiece 100 passes through the cylindrical lens 572, it enters the detection element 58 in a state where the focal positions in one direction and the other direction are shifted and astigmatism occurs. As a result, the planar shape of the reflected light 511 changes in the order of a vertically elongated ellipse, a circle, and a horizontally elongated ellipse depending on the position on the optical axis.

[0066] The detection element 58 receives the reflected light 511 to which astigmatism is added by the astigmatism addition unit 57. The detection element 58 outputs a detection signal including a detection value [V] corresponding to the condensing state (condensed image) of the received reflected light 511. Based on the condensing state of the reflected light 511 received by the detection element 58, it is possible to determine whether the position of the condensing point of the detection laser beam 51 is above, below, or the same as the upper surface of the workpiece 100. Thereby, the detection unit 40 detects the height position of the upper surface of the workpiece 100 held by the holding table 10.

[0067] As shown in FIG. 6, after processing one division planned line 103, the laser beam irradiation unit 20 causes the condensing point 211 of the laser beam 21 to pass outside the outer edge of the workpiece 100 until the next division planned line 103 is processed. Similarly, the condensing point of the detection laser beam 51 also passes through both the inside of the workpiece 100 and outside the outer edge. At this time, outside the outer edge of the workpiece 100, the height position detected by the detection unit 40 changes from the height position of the upper surface of the workpiece 100 to the height position of the holding surface 11 of the holding table 10. That is, the control unit 90 can detect the boundary position 108 that is the outer edge in the horizontal direction of the workpiece 100 based on the detection signal acquired from the detection element 58 of the height position detection unit 50. Further, the control unit 90 may perform switching control of the phase pattern 242 displayed on the display unit 241 of the spatial light modulator 24 based on the detected boundary position 108.

Explanation of Signs

[0068] 1 Laser processing apparatus 10 Holding table 11 Holding surface 20, 20-1 Laser beam irradiation unit 21 Laser beam 211 Condensing point 212 Region 213 Transmitted light 22 Oscillator 23 Condenser 24 Spatial light modulator 241 Display unit Phase patterns at positions 242, 243, and 244 Polarizer 25 Relay lens 26 Aperture 27 Relay lens 28 Mirror 29 Optical detection unit 30 Imaging means 31 Condensing lens 32 Diffuser 33 Filter 34 Detection unit 40 Height position detection unit 50 Moving unit 60 Processing feed unit 61 Indexing feed unit 62 Control unit 90 Judgment unit 91 Workpiece 100 Division planned line 103 End point 103-1 Start point 103-2 Surface 102 Back surface 105 Modified layer 106 Boundary position 108

Claims

1. A laser processing apparatus that irradiates a workpiece with a plurality of planned division lines with a laser beam and performs processing along the planned division lines, comprising: an oscillator that emits a laser beam; a condenser that condenses the laser beam emitted from the oscillator and irradiates the 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 laser beam irradiation unit including the above; a holding table that holds the workpiece; a processing feed unit that relatively moves the holding table and the condensing point of the laser beam in the processing feed direction; an indexing feed unit that relatively moves the holding table and the condensing point of the laser beam in an indexing feed direction orthogonal to the processing feed direction; a control unit that controls the phase pattern displayed on the display unit of the spatial light modulator; and comprising: a light detection unit that detects the intensity of the laser beam emitted from the spatial light modulator; a determination unit that determines whether the spatial light modulator is operating normally based on the intensity of the laser beam detected by the light detection unit; a detection unit that outputs the condensing state of the reflected light of the detection laser beam irradiated toward the workpiece held on the holding table through the condenser; further comprising: the control unit: judges whether the position of the condensing point of the detection laser beam is above, below, or the same as the upper surface of the workpiece based on the condensing state, and based on this, judges whether the condensing points of the laser beam and the detection laser beam are inside or outside the outer edge of the workpiece; when the condensing point of the laser beam is inside the outer edge of the workpiece, a phase pattern for processing is displayed on the display unit; when the condensing point of the laser beam is outside the outer edge of the workpiece, switching control is performed so that a passing phase pattern different from the phase pattern for processing is displayed on the display unit; the light detection unit: is characterized by detecting the intensity of the laser beam in the phase pattern switched by the switching control. Laser processing apparatus.

2. The laser beam irradiation unit: has a mirror that reflects the laser beam emitted from the spatial light modulator toward the condenser; the light detection unit: Detecting the output of the laser beam while irradiating the workpiece with the laser beam by receiving the transmitted light of the laser beam that is transmitted without being reflected by the mirror. The laser processing apparatus according to claim 1.

3. The light detection unit is a photodiode. The laser processing apparatus according to claim 1 or 2.

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