Laser processing apparatus and method of adjusting a laser processing apparatus

Abstract

Provided is a laser processing device and a method for adjusting a laser processing device, which can achieve low cost and suppress performance differences between devices. The laser processing device includes a laser oscillator, a condenser lens that condenses a laser beam emitted from the laser oscillator, and a phase modulation element disposed between the laser oscillator and the condenser lens. By applying a voltage corresponding to a combination pattern to the phase modulation element, individual differences in the condenser lens are suppressed, the combination pattern being obtained by combining a shape correction pattern for correcting a difference between an actual shape of the condenser lens and a design value and an adjustment pattern for adjusting an optical characteristic of the laser beam at a processing point.

Description

TECHNICAL FIELD

[0001] The present application relates to a laser processing apparatus and a method for adjusting a laser processing apparatus. BACKGROUND

[0002] As a method for dividing a processed object such as a semiconductor wafer, a technique is known in which a modified layer as a brittle region is formed by irradiating a laser beam into the processed object, and an external force is applied to divide into individual chips (see Patent Literature 1). In a laser processing apparatus that irradiates a laser beam, various optical members are used to propagate a laser beam emitted from a laser oscillator, and the laser beam is condensed by a condenser lens to be irradiated to a processed object. However, sometimes various optical distortions occur in the optical path of the laser beam, and there is a problem that the processing result differs between laser processing apparatuses due to the optical distortions (so-called inter-apparatus performance difference occurs).

[0003] Therefore, the present applicants investigated the cause of the inter-apparatus performance difference, and found that it is mostly caused by individual differences of the condenser lens. In order to eliminate such inter-apparatus performance difference, a technique has been adopted in which the condenser lens that is a main cause of the performance difference is replaced, or a wavefront sensor is used to correct the spot shape of the processing point (see Patent Literature 2).

[0004] Patent Literature 1: Japanese Patent No. 3408805

[0005] Patent Literature 2: Japanese Patent Application No. 2019-207274

[0006] However, in order to eliminate the inter-apparatus performance difference, it is necessary to select a condenser lens having a small individual difference, that is, having a similar shape, and there is a problem that not only cost is incurred but also the replacement work takes time. In addition, since the wavefront sensor used for correcting the spot shape is expensive, there is also a problem that the cost of the apparatus becomes high. SUMMARY

[0007] Therefore, an object of the present application is to provide a laser processing apparatus and a method for adjusting a laser processing apparatus that can achieve low cost and suppress inter-apparatus performance difference.

[0008] According to one aspect of the present application, there is provided a laser processing apparatus, wherein the laser processing apparatus has: a chuck table that holds a workpiece; a laser beam irradiation unit that irradiates a laser beam toward the workpiece held by the chuck table; a moving unit that relatively moves the chuck table and the laser beam irradiation unit; and a control section that controls at least the laser beam irradiation unit and the moving unit, the laser beam irradiation unit including: a laser oscillator; a condenser lens that condenses a laser beam emitted from the laser oscillator; and a phase modulation element disposed between the laser oscillator and the condenser lens, the laser processing apparatus further having an input unit that inputs a pattern obtained by patterning a voltage to be applied to the phase modulation element, a combined pattern being input from the input unit, the combined pattern being obtained by combining a shape correction pattern for correcting a difference between an actual shape of the condenser lens and a design value and an adjustment pattern for adjusting an optical characteristic of the laser beam at a processing point, the control section applying a voltage corresponding to the combined pattern to the phase modulation element, thereby suppressing individual differences of the condenser lens.

[0009] According to another aspect of the present application, there is provided an adjustment method of a laser processing apparatus in which a condensing state of a laser beam irradiated toward a workpiece is adjusted, the laser processing apparatus including: a chuck table that holds a workpiece; a laser beam irradiation unit that irradiates a laser beam toward the workpiece held by the chuck table; a moving unit that relatively moves the chuck table and the laser beam irradiation unit; a control section that controls at least the laser beam irradiation unit and the moving unit; and an input unit that inputs various information, the laser beam irradiation unit including: a laser oscillator; a condenser lens that condenses a laser beam emitted from the laser oscillator; and a phase modulation element disposed between the laser oscillator and the condenser lens, wherein the adjustment method of the laser processing apparatus has: a pattern generation step of generating a pattern obtained by patterning a voltage to be applied to the phase modulation element; an input step of inputting the pattern generated by the pattern generation step from the input unit; a voltage application step of applying a voltage corresponding to the pattern input by the input step to the phase modulation element; and a laser beam irradiation step of relatively moving the workpiece and the laser beam while emitting the laser beam after the voltage application step, and processing the workpiece, the pattern generated by the pattern generation step being a pattern obtained by combining a shape correction pattern for correcting a difference between an actual shape of the condenser lens and a design value and an adjustment pattern for adjusting an optical characteristic of the laser beam at a processing point.

[0010] According to the present application, it is possible to achieve low cost and suppress differences in performance between apparatuses. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 is a perspective view showing a structure example of the laser processing apparatus of the embodiment.

[0012] Figure 2 is a perspective view showing a structure example of the laser processing apparatus of the embodiment. Figure 1 is a perspective view showing a workpiece which is a processing target of the laser processing apparatus shown in

[0013] Figure 3 is a schematic view showing a structure of a laser beam irradiation unit of the laser processing apparatus shown in Figure 1

[0014] Figure 4 is a schematic view showing an example of a condenser lens.

[0015] Figure 5 is a graph showing an example of a relationship between a radial position from a center and a Z coordinate of a first face of the condenser lens.

[0016] Figure 6 is a graph showing an example of a shape correction pattern.

[0017] Figure 7 is a graph showing an example of an adjustment pattern.

[0018] Figure 8 is a graph showing an example of a combination pattern.

[0019] Figure 9 is a graph showing a simulation result of a condensing state derived from a design value.

[0020] Figure 10 is a graph showing a simulation result of a condensing state derived from a fitting function of an actual shape.

[0021] Figure 11 is a graph showing a simulation result of a condensing state after shape correction.

[0022] Figure 12 is a flowchart showing a flow of an adjustment method of the laser processing apparatus of the embodiment.

[0023] Explanation of Reference Signs

[0024] ​1: laser processing apparatus; 10: chuck table; 20: laser beam irradiation unit; 21: laser beam; 22: laser oscillator; 23: polarizing plate; 24: phase modulation element; 241: display portion; 242: shape correction pattern; 243: adjustment pattern; 244: combined pattern; 25: lens group; 251, 252: lens; 26: mirror; 27: condenser lens; 271: 1st surface; 2711: actual shape; 2712: fitting function; 272: 2nd surface; 28: processing point; 30: moving unit; 70: photographing unit; 80: input unit; 90: control portion; 100: workpiece. DETAILED DESCRIPTION

[0025] Embodiments of the present application will be described below in detail with reference to the accompanying drawings. The present application is not limited to the contents described in the following embodiments. In addition, among the structural elements described below, there are structural elements that are substantially the same as those that can be easily conceived by those skilled in the art. Furthermore, the structures described below can be appropriately combined. In addition, various omissions, substitutions, or alterations of the structures can be made within a scope that does not depart from the gist of the present application.

[0026] An embodiment of the laser processing apparatus 1 of the present application will be described with reference to the accompanying drawings. Figure 1 is a perspective view showing a structural example of the laser processing apparatus 1 of the embodiment. Figure 2 is a perspective view of a workpiece 100 that is a processing target of the laser processing apparatus 1 shown in Figure 1

[0027] As shown in Figure 1 The laser processing apparatus 1 has a chuck table 10, a laser beam irradiation unit 20, a moving unit 30, a photographing unit 70, an input unit 80, and a control portion 90. The moving unit 30 includes an X-axis direction moving unit 40, a Y-axis direction moving unit 50, and a Z-axis direction moving unit 60. In the following description, the X-axis direction is one direction in a horizontal plane. The Y-axis direction is a direction perpendicular to the X-axis direction in the horizontal plane. The Z-axis direction is a direction perpendicular to the X-axis direction and the Y-axis direction. The processing feed direction of the laser processing apparatus 1 of the embodiment is the X-axis direction, and the indexing feed direction is the Y-axis direction.

[0028] The laser processing apparatus 1 of the embodiment is an apparatus that processes a workpiece 100 by irradiating a laser beam 21 to the workpiece 100 that is a processing target. The processing of the workpiece 100 by the laser processing apparatus 1 is, for example, forming a modified layer 106 in the inside of the workpiece 100 by stealth dicing (refer to Figure 3 ​), grooving to form grooves on the front surface 102 of the workpiece 100, or cutting to cut the workpiece 100 along the planned dividing line 103. In the embodiment, a structure for forming a modified layer 106 on the workpiece 100 will be described. The workpiece 100 is a wafer such as a disc-shaped semiconductor wafer or an optical device wafer having a substrate 101 made of silicon (Si), sapphire (Al2O3), gallium arsenide (GaAs), or silicon carbide (SiC).

[0029] like Figure 2 As shown, the workpiece 100 has: predetermined dividing lines 103 set in a grid pattern on the front surface 102 of the substrate 101; and devices 104 formed in the area divided by the predetermined dividing lines 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). In the embodiment, the workpiece 100 has a modified layer 106 formed inside along the predetermined dividing lines 103 (see Figure 3 A belt 111 having a larger diameter than the outer diameter of the workpiece 100 is attached to the back surface 105 on the back side of the front surface 102 of the workpiece 100 , and an annular frame 110 is attached to the belt 111 , so that the workpiece 100 is supported in the opening of the annular frame 110 .

[0030] like Figure 1 As shown, the chuck table 10 holds the workpiece 100 using a holding surface 11. The holding surface 11 is a circular plate shape formed of porous ceramics or the like. In an embodiment, the holding surface 11 is a plane parallel to the horizontal direction. The holding surface 11 is connected to a vacuum suction source, for example, via a vacuum suction path. The chuck table 10 attracts and holds the workpiece 100 placed on the holding surface 11. A plurality of clamping parts 12 are arranged around the chuck table 10, and the clamping parts 12 clamp an annular frame 110 that supports the workpiece 100. The chuck table 10 rotates around an axis parallel to the Z-axis direction through a rotating unit 13. The rotating unit 13 is supported by an X-axis moving plate 14. The rotating unit 13 and the chuck table 10 move along the X-axis direction through the X-axis moving unit 40 with the aid of the X-axis moving plate 14. The rotation unit 13 and the chuck table 10 are moved in the Y-axis direction by the Y-axis moving unit 50 via the X-axis moving plate 14 , the X-axis moving unit 40 , and the Y-axis moving plate 15 .

[0031] The laser beam irradiation unit 20 is a unit that irradiates the workpiece 100 held by the chuck table 10 with a pulsed laser beam 21. At least the condensing lens 27 (refer to Figure 3 ) in the laser beam irradiation unit 20 is supported by the Z-axis direction moving unit 60 provided to the column 3 erected from the device main body 2 of the laser processing apparatus 1. The detailed structure of the laser beam irradiation unit 20 will be described later.

[0032] As shown in Figure 1 , the X-axis direction moving unit 40 is a unit that relatively moves the chuck table 10 and the laser beam irradiation unit 20 in the X-axis direction as a processing feed direction. In the embodiment, the X-axis direction moving unit 40 moves the chuck table 10 in the X-axis direction. In the embodiment, the X-axis direction moving unit 40 is provided to the device main body 2 of the laser processing apparatus 1. The X-axis direction moving unit 40 supports the X-axis direction moving plate 14 so as to be movable in the X-axis direction. The X-axis direction moving unit 40 includes a publicly known ball screw 41, a publicly known pulse motor 42, and a publicly known guide rail 43. The ball screw 41 is provided so as to be rotatable around an axis. The pulse motor 42 rotates the ball screw 41 around the axis. The guide rail 43 supports the X-axis direction moving plate 14 so as to be movable in the X-axis direction. The guide rail 43 is fixedly provided to the Y-axis direction moving plate 15.

[0033] The Y-axis direction moving unit 50 is a unit that relatively moves the chuck table 10 and the laser beam irradiation unit 20 in the Y-axis direction as an indexing feed direction. In the embodiment, the Y-axis direction moving unit 50 moves the chuck table 10 in the Y-axis direction. In the embodiment, the Y-axis direction moving unit 50 is provided to the device main body 2 of the laser processing apparatus 1. The Y-axis direction moving unit 50 supports the Y-axis direction moving plate 15 so as to be movable in the Y-axis direction. The Y-axis direction moving unit 50 includes a publicly known ball screw 51, a publicly known pulse motor 52, and a publicly known guide rail 53. The ball screw 51 is provided so as to be rotatable around an axis. The pulse motor 52 rotates the ball screw 51 around the axis. The guide rail 53 supports the Y-axis direction moving plate 15 so as to be movable in the Y-axis direction. The guide rail 53 is fixedly provided to the device main body 2.

[0034] The Z-axis direction moving unit 60 is a unit that relatively moves the chuck table 10 and the laser beam irradiation unit 20 in the Z-axis direction as a condensing point position adjustment direction. In the embodiment, the Z-axis direction moving unit 60 moves the laser beam irradiation unit 20 in the Z-axis direction. In the embodiment, the Z-axis direction moving unit 60 is provided to the column 3 erected from the device main body 2 of the laser processing apparatus 1. The Z-axis direction moving unit 60 supports at least the condensing lens 27 (refer to Figure 3) is supported so as to be movable in the Z-axis direction. The Z-axis direction movement unit 60 includes a publicly known ball screw 61, a publicly known pulse motor 62, and a publicly known guide rail 63. The ball screw 61 is disposed so as to be rotatable around an axis. The pulse motor 62 rotates the ball screw 61 around the axis. The guide rail 63 supports the laser beam irradiation unit 20 so as to be movable in the Z-axis direction. The guide rail 63 is fixed to the column 3.

[0035] The photographing unit 70 photographs the workpiece 100 held by the chuck table 10. The photographing unit 70 includes a CCD camera or an infrared camera that photographs the workpiece 100 held by the chuck table 10. The photographing unit 70 is fixed, for example, so as to be adjacent to the condenser lens 27 (see FIG. 2) of the laser beam irradiation unit 20. The photographing unit 70 photographs the workpiece 100 to obtain an image for performing alignment of the workpiece 100 with the laser beam irradiation unit 20, and outputs the obtained image to the control section 90. Figure 3 ) is supported so as to be movable in the Z-axis direction. The Z-axis direction movement unit 60 includes a publicly known ball screw 61, a publicly known pulse motor 62, and a publicly known guide rail 63. The ball screw 61 is disposed so as to be rotatable around an axis. The pulse motor 62 rotates the ball screw 61 around the axis. The guide rail 63 supports the laser beam irradiation unit 20 so as to be movable in the Z-axis direction. The guide rail 63 is fixed to the column 3.

[0036] The input unit 80 inputs various information. The input unit 80 can accept various operations such as an operation of an operator to register processing content information. The input unit 80 can accept an operation of inputting a combined pattern 244 (see FIG. 6, for example) obtained by combining a shape correction pattern 242 (see FIG. 5, for example) and an adjustment pattern 243 (see FIG. 6, for example), which will be described later. The input unit 80 can also be an external input device such as a keyboard. In the case where the laser processing apparatus 1 has a display device including a touch panel, the input unit 80 can also be included in the display device. Figure 6 Figure 7 The input unit 80 inputs various information. The input unit 80 can accept various operations such as an operation of an operator to register processing content information. The input unit 80 can accept an operation of inputting a combined pattern 244 (see FIG. 6, for example) obtained by combining a shape correction pattern 242 (see FIG. 5, for example) and an adjustment pattern 243 (see FIG. 6, for example), which will be described later. The input unit 80 can also be an external input device such as a keyboard. In the case where the laser processing apparatus 1 has a display device including a touch panel, the input unit 80 can also be included in the display device. Figure 8

[0037] The control section 90 controls the above-described respective structural elements of the laser processing apparatus 1 to cause the laser processing apparatus 1 to perform a processing operation on the workpiece 100. The control section 90 controls the laser beam irradiation unit 20, the movement unit 30, and the photographing unit 70. The control section 90 is a computer including an arithmetic processing device as an arithmetic unit, a storage device as a storage unit, and an input / output interface device as a communication unit. The arithmetic processing device includes a microprocessor such as a CPU (Central Processing Unit). The storage device has a memory such as a ROM (Read Only Memory) or a RAM (Random Access Memory). The arithmetic processing device performs various arithmetic operations in accordance with a prescribed program stored in the storage device. The arithmetic processing device outputs various control signals to the above-described respective structural elements via the input / output interface device in accordance with the arithmetic operation results, and performs control of the laser processing apparatus 1.

[0038] ​​The control section 90, for example, applies a voltage corresponding to a pattern input from the input unit 80 to the phase modulation element 24 described later. The control section 90, for example, causes the imaging unit 70 to image the workpiece 100. The control section 90, for example, performs image processing on an image imaged by the imaging unit 70. The control section 90, for example, detects a processing line of the workpiece 100 by the image processing. The control section 90, for example, drives the X-axis direction moving unit 40 and causes the laser beam irradiation unit 20 to irradiate the laser beam 21 so that a processing point 28 that is a focal point of the laser beam 21 moves along the processing line.

[0039] Next, the laser beam irradiation unit 20 is described in detail. Figure 3 is a schematic view that schematically shows Figure 1 the structure of the laser beam irradiation unit 20 of the laser processing apparatus 1 shown in FIG. 1. As shown in Figure 3 , the laser beam irradiation unit 20 includes a laser oscillator 22, a polarizing plate 23, a phase modulation element 24, a lens group 25, a reflecting mirror 26, and a condenser lens 27.

[0040] In addition, Figure 3 the arrow of the chuck table 10 at the time of processing feed. In addition, in the embodiment, a processing point 28 that is a focal point of the laser beam 21 is set inside the workpiece 100. The chuck table 10 is processed while the laser beam 21 is irradiated to the processing point 28, whereby a modified layer 106 along a division predetermined line 103 (refer to Figure 2 ) is formed inside the workpiece 100.

[0041] The modified layer 106 refers to a region in which a density, a refractive index, a mechanical strength, or other physical characteristics become a state different from those of the surroundings. The modified layer 106 is, for example, a fusion-processed region, a crack region, an insulation breakdown region, a refractive index change region, and a region in which these regions are mixed. The mechanical strength or the like of the modified layer 106 is lower than that of other portions of the workpiece 100.

[0042] The laser oscillator 22 oscillates a laser having a prescribed wavelength for processing the workpiece 100, and emits a laser beam 21. In the embodiment, the laser beam 21 irradiated by the laser beam irradiation unit 20 is a wavelength that is transmissive to the workpiece 100.

[0043] The polarizing plate 23 is provided between the laser oscillator 22 and the phase modulation element 24. The polarizing plate 23 polarizes the laser beam 21 emitted from the laser oscillator 22 into light of a specific direction.

[0044] The phase modulation element 24 is provided between the laser oscillator 22 and the condenser lens 27. The phase modulation element 24 performs phase modulation on the incident laser beam 21. The phase modulation element 24 modulates the phase of the laser beam 21 by electrically controlling the spatial distribution of the amplitude, phase, and the like of the laser beam 21 emitted from the laser oscillator 22. By applying a voltage corresponding to the pattern input from the input unit 80 to the phase modulation element 24 from the control unit 90, the phase modulation element 24 shapes the laser beam 21 into a desired beam shape. Thereby, the output and the spot shape of the laser beam 21 at the machining point 28 are adjusted.

[0045] The pattern refers to a pattern obtained by patterning the voltage applied to the phase modulation element 24. The pattern applied to the phase modulation element 24 of the embodiment is a combined pattern 244 (refer to Figure 6 ) obtained by combining a shape correction pattern 242 (refer to Figure 7 ) and an adjustment pattern 243 (refer to Figure 8 ). The shape correction pattern 242 is a pattern for correcting the aberration of the condenser lens 27. The adjustment pattern 243 is a pattern for adjusting the optical characteristics of the laser beam 21 at the machining point 28. The adjustment of the optical characteristics includes, for example, the change of the shape of the laser beam 21 and the attenuation of the intensity, and the like. The laser processing device 1 changes at least any of the shape correction pattern 242 and the adjustment pattern 243 with respect to the voltage applied to the phase modulation element 24, and thereby can adjust the output and the spot shape at the machining point 28.

[0046] In the embodiment, the phase modulation element 24 is a spatial light modulator (LCOS; Liquid Crystal On Silicon) manufactured by Hamamatsu Photonics Corporation. The phase modulation element 24 of the embodiment has a display portion 241. The display portion 241 includes an element of liquid crystal. The display portion 241 displays a pattern. When a voltage corresponding to the combined pattern 244 input from the input unit 80 is applied from the control unit 90, the phase modulation element 24 causes the display portion 241 to display the combined pattern 244. Thereby, the laser beam 21 reflected on or transmitted through the phase modulation element 24 is phase-modulated and the beam shape is shaped in accordance with the combined pattern 244, and thereby the output and the spot shape at the machining point 28 are adjusted.

[0047] In the embodiment, the phase modulation element 24 reflects the laser beam 21 to output, but in the present application, the laser beam 21 can also be transmitted to output. In addition, the phase modulation element 24 is not limited to a spatial light modulator, but can also be a deformable mirror. In the case where the phase modulation element 24 is a deformable mirror, when a voltage corresponding to the combined pattern 244 is applied, the phase modulation element 24 deforms the mirror film according to the combined pattern 244. The wavelength used by the LCOS is green of 405 nm or more, IR (infrared), and in contrast, even if the wavelength is 355 nm, a deformable mirror can be used, and thus can also be used for ablation processing by UV (ultraviolet).

[0048] The lens group 25 is provided between the phase modulation element 24 and the condenser lens 27. The lens group 25 is a 4f optical system composed of two lenses of a lens 251 and a lens 252. The 4f optical system refers to an optical system in which the rear focal plane of the lens 251 coincides with the front focal plane of the lens 252 and an image of the front focal plane of the lens 251 is imaged on the rear focal plane of the lens 252. The lens group 25 enlarges or reduces the beam diameter of the laser beam 21 output from the phase modulation element 24.

[0049] The mirror 26 reflects the laser beam 21 toward the workpiece 100 held by the holding surface 11 of the chuck table 10. In the embodiment, the mirror 26 reflects the laser beam 21 that has passed through the lens group 25 toward the condenser lens 27.

[0050] The condenser lens 27 condenses the laser beam 21 emitted from the laser oscillator 22 and irradiates the workpiece 100 held by the holding surface 11 of the chuck table 10. In the embodiment, the condenser lens 27 is a single lens. In the embodiment, the condenser lens 27 condenses the laser beam 21 reflected by the mirror 26 at the processing point 28.

[0051] Next, the pattern generation method will be described. Figure 4 is a view showing an example of the condenser lens 27. Figure 5 is a view showing an example of the relationship between the radial position from the center of the condenser lens 27 and the Z coordinate of the first surface 271. Figure 5 The horizontal axis of the graph of Figure 5 The vertical axis of the graph of Figure 5 In the graph of Figure 5 represents the difference in the Z-axis direction of each radial position of the condenser lens 27 from the center of the first surface 271.

[0052] As Figure 4As shown, the condenser lens 27 of the embodiment includes a first surface 271, which is a convex spherical surface, and a second surface 272, which is a concave spherical surface. For lenses purchased from a manufacturer, deviations from the design values ​​of the lens surface are permitted within a tolerance range. For example, to determine deviations from the design values ​​of the lens surface, the manufacturer measures the shape of each lens using a contact measuring instrument and discloses to the purchaser the distribution of the measured lens shape values ​​relative to the radial position from the center.

[0053] In the method of generating the shape correction pattern 242, first, as shown in FIG. Figure 5 As shown, the actual shape 2711 of the Z coordinate of the first surface 271 of the condenser lens 27 relative to the radial position from the center (in Figure 5 The Z coordinate of the first surface 271 is fitted with respect to the radial position of the center of the focusing lens 27 (shown by a solid line in FIG). Figure 5 (An example is shown by a dotted line in FIG. 2 ). As described above, the actual shape 2711 of the condenser lens 27 may use the measured values ​​provided by the manufacturer, or may use the measured values ​​obtained by a third party. Furthermore, a fitting function 2712 is generated using a known method using R language and numerical analysis software. The fitting function 2712 is a function that represents the Z coordinate of the first surface 271 at each radial position from the center of the condenser lens 27.

[0054] Next, assuming that the shape of first surface 271 of condenser lens 27 is represented by fitting function 2712, known ray tracing software, etc., is used to calculate the aberrations after the light passes through condenser lens 27. Based on the calculated aberration differences, correction values ​​that can achieve an ideal wavefront are calculated, and shape correction pattern 242 based on these correction values ​​is generated. The ideal wavefront refers to the wavefront of laser beam 21 after passing through condenser lens 27 having a shape of first surface 271 that matches the design value. In other words, the ideal wavefront refers to the spatial distribution of the phase of laser beam 21 that can achieve the desired processing result corresponding to the processing conditions set in laser processing apparatus 1.

[0055] Specifically, first, assuming that the shape of the first surface 271 of the condenser lens 27 is represented by a fitting function 2712, the Zernike coefficients corresponding to the aberrations of the condenser lens 27 are calculated using known ray tracing software or the like. The Zernike coefficients are values ​​calculated by applying Zernike polynomial approximation to the wavefront of the laser beam 21 after passing through the condenser lens 27, calculated using known ray tracing software or the like, and correspond to the aberrations of the condenser lens 27. The Zernike polynomials are orthogonal polynomials defined on the unit circle.

[0056] Next, a correction value of the Zernike coefficient (hereinafter, referred to as a correction value of the Zernike coefficient) for obtaining an ideal wave surface of the laser beam 21 after passing through the condensing lens 27 is calculated based on the calculated Zernike coefficient. Further, a pattern obtained by patterning a voltage to be applied to the phase modulation element 24 is generated using the correction value of the Zernike coefficient, and the generated pattern is used as the shape correction pattern 242.

[0057] Here, it is assumed that the shape of the first surface 271 of the condensing lens 27 is represented by the fitting function 2712, and the calculated Zernike coefficient is a value calculated by approximating the wave surface of the laser beam 21 after passing through the condensing lens 27 calculated using a known ray tracing software or the like with a Zernike polynomial. Therefore, the calculated Zernike coefficient is a value corresponding to the deviation of the shape of the first surface 271 of the condensing lens 27 from the design value. In addition, the correction value of the Zernike coefficient is a value for making the wave surface of the laser beam 21 after passing through the condensing lens 27 close to the ideal wave surface. Therefore, the shape correction pattern 242 is a pattern for making the wave surface of the laser beam 21 after passing through the condensing lens 27 close to the ideal wave surface.

[0058] Figure 6 is a view showing an example of the shape correction pattern 242. Figure 7 is a view showing an example of the adjustment pattern 243. Figure 8 is a view showing an example of the combined pattern 244. In Figure 6 the shape correction pattern 242 shown in Figure 7 the adjustment pattern 243 shown in Figure 8 the combined pattern 244 shown in, the black portion indicates a portion through which the laser beam 21 passes, and the white portion indicates a portion that blocks the laser beam 21. In addition, the gray portion indicates a shade, and the gray scale indicates a difference in the amount of phase modulation.

[0059] The shape correction pattern 242 and the adjustment pattern 243 are combined to form the combined pattern 244. The combined pattern 244 is input from the input unit 80 by the operator. The combined pattern 244 can also be generated by the control section 90. That is, the shape correction pattern 242 and the adjustment pattern 243 before being combined into the combined pattern 244 can also be input to the input unit 80. In addition, the shape correction pattern 242 can be generated by the control section 90 based on the actual shape 2711 of the Z coordinate of the first surface 271 with respect to the radial position from the center of the condensing lens 27 input from the operator. In addition, the adjustment pattern 243 can be generated by the control section 90 based on the set value of the adjustment optical characteristic or the like input from the operator.

[0060] Next, the effect of applying the shape correction pattern 242 is verified. Figure 9 is a view showing a simulation result of a condensing state according to the design value. Figure 10is a graph showing a simulation result of a condensing state derived from a fitting function 2712 of an actual shape 2711. Figure 11 is a graph showing a simulation result of a condensing state after shape correction. Figure 9 to Figure 11 indicates an energy distribution of the laser beam 21. In addition, in Figure 9 to Figure 11 , the upper graph indicates a spot shape in a cross-sectional direction of the workpiece 100, and the origin 0 in the Z-axis direction indicates a height of the machining point 28. In Figure 9 to Figure 11 , the lower graph indicates an energy distribution in the radial direction at the origin 0 in the Z-axis direction. In the embodiment, the numerical aperture of the condensing lens 27 is 0.8. In addition, the wavelength of the laser beam 21 is 1342 nm, and the frequency is 100 kHz. In addition, the beam diameter of the laser beam 21 incident on the condensing lens 27 is 10 mm. In addition, in the embodiment, the evaluation software used for simulation is Virtual Lab produced by T.E.M Co., Ltd.

[0061] As shown in Figure 9 , in the condensing lens 27 of the design value of the ideal wave surface, the beam diameter of the laser beam 21 condensed on the machining point 28 is about 2 μm. In addition, the energy distribution of the laser beam 21 is a Gaussian distribution. In contrast, as shown in Figure 10 , in the condensing lens 27 represented by the fitting function 2712 of the actual shape 2711, the energy distribution of the laser beam 21 condensed on the machining point 28 is blurred in the lower portion of the Gaussian, and the beam diameter is about 4 μm. In this way, the spot shape at the machining point 28 deviates from the design value of the spherical shape of the condensing lens 27, and thus is deformed with respect to the desired spot shape.

[0062] As shown in Figure 11 , in the condensing lens 27 to which the shape correction pattern 242 is applied, the beam diameter of the laser beam 21 condensed on the machining point 28 is about 2 μm. In addition, the energy distribution of the laser beam 21 is not blurred in the lower portion of the Gaussian. In this way, the condensing lens 27 to which the shape correction pattern 242 is applied can form a condensing state similar to the condensing lens 27 of the design value shown in Figure 9 .

[0063] Next, a laser machining method of the laser machining device 1 will be described. Figure 12 is a flowchart showing a flow of the laser machining method of the embodiment. The laser machining method includes a pattern generation step 501, an input step 502, a voltage application step 503, and a laser beam irradiation step 504.

[0064] The pattern generation step 501 is a step of generating a pattern in which a voltage to be applied to the phase modulation element 24 is patterned. The pattern is a combined pattern 244 obtained by combining the shape correction pattern 242 and the adjustment pattern 243. In the embodiment, in the pattern generation step 501, the combined pattern 244 displayed on the display portion 241 of the phase modulation element 24 is generated.

[0065] More specifically, in the pattern generation step 501, first, the actual shape 2711 of the first face 271 of the condenser lens 27 with respect to the Z coordinate of the radial position from the center is fitted, and a fitting function 2712 of the Z coordinate of the first face 271 of the condenser lens 27 is generated. Next, assuming that the shape of the first face 271 of the condenser lens 27 is represented by the fitting function 2712, an aberration after passing through the condenser lens 27 is calculated, and a shape correction pattern 242 is generated based on the calculated aberration, the shape correction pattern 242 being obtained based on a correction value by which an ideal wave surface can be obtained. In the pattern generation step 501, next, the shape correction pattern 242 and the adjustment pattern 243 are combined to generate the combined pattern 244.

[0066] In the input step 502, the pattern generated in the pattern generation step 501, that is, the combined pattern 244 is input from the input unit 80. Specifically, for example, an operator inputs data of the combined pattern 244 generated by an external device or the like having a pattern generation software from the input unit 80. In addition, the pattern generation software can be a dedicated software or Excel (registered trademark) or the like.

[0067] The voltage application step 503 is a step of applying a voltage corresponding to the pattern input in the input step 502, that is, the combined pattern 244 to the phase modulation element 24. More specifically, in the voltage application step 503, the control portion 90 acquires the combined pattern 244 input from the input unit 80. The control portion 90 outputs a control signal to the phase modulation element 24 so as to apply a voltage corresponding to the combined pattern 244. In the embodiment, when the voltage corresponding to the combined pattern 244 is applied from the control portion 90, the phase modulation element 24 causes the display portion 241 to display the combined pattern 244.

[0068] The laser beam irradiation step 504 is a step of relatively moving the workpiece 100 and the chuck table 10 while irradiating the laser beam 21 after the voltage application step 503, and performing processing on the workpiece 100. Specifically, in the laser beam irradiation step 504, the moving unit 30 is moved to a processing position of the laser processing device 1. Next, by capturing the workpiece 100 by the capturing unit 70, the division predetermined line 103 is detected. If the division predetermined line 103 is detected, alignment of the division predetermined line 103 of the workpiece 100 and the condensing point of the laser processing device 1 is performed.

[0069] In the laser beam irradiation step 504, the laser beam 21 is then irradiated to the workpiece 100. At this time, the moving unit 30 moves in the X-axis direction and the Y-axis direction and rotates around the axis parallel to the Z-axis direction in accordance with the processing content information registered by the operator.

[0070] In the laser beam irradiation step 504, the processing point 28 as the condensing point is positioned inside the workpiece 100, and the laser beam 21 having a wavelength that is transmissive to the workpiece 100 and being pulsed is irradiated from the front surface 102 side of the workpiece 100. Since the laser processing apparatus 1 irradiates the laser beam 21 having a wavelength that is transmissive to the workpiece 100, a modified layer 106 along the division predetermined line 103 is formed inside the substrate 101.

[0071] As described above, in the laser processing apparatus 1 of the embodiment, the laser beam irradiation unit 20 includes the phase modulation element 24 that is provided between the laser oscillator 22 and the condensing lens 27 that condenses the laser beam 21 emitted from the laser oscillator 22, and that is capable of suppressing individual differences of the condensing lens 27 by applying a voltage corresponding to a prescribed pattern. The prescribed pattern is a combined pattern 244 obtained by combining a shape correction pattern 242 for correcting a difference between an actual shape of the condensing lens 27 and a design value and an adjustment pattern 243 for adjusting an optical characteristic of the laser beam 21 at the processing point 28.

[0072] The existing laser processing apparatus is equipped with the phase modulation element 24 such as an LCOS, a deformable mirror, or the like that applies a voltage corresponding to the adjustment pattern 243 for adjusting the optical characteristic of the laser beam 21 at the processing point 28. Therefore, by inputting the combined pattern 244 obtained by combining the shape correction pattern 242 for correcting the difference between the actual shape of the condensing lens 27 and the design value in addition to the existing adjustment pattern 243, it is possible to irradiate the laser beam 21 that is corrected for the individual differences of the condensing lens 27. Thus, the laser processing apparatus 1 of the embodiment is capable of suppressing inter-apparatus performance differences. In addition, the phase modulation element 24 can use an element already equipped in the existing laser processing apparatus, and thus does not require additional costs such as additional components or changes to the apparatus. Therefore, the laser processing apparatus 1 of the embodiment can be implemented at low cost.

[0073] In addition, the present application is not limited to the above-described embodiments. That is, various modifications can be made within the scope of the gist of the present application to implement the present application. For example, in the embodiment, the individual differences of the shape of the first surface 271 of the condensing lens 27 are corrected, but the individual differences of the shape of the second surface 272 can also be corrected, and the shapes of both the first surface 271 and the second surface 272 can also be corrected.

Claims

1. A laser processing device, wherein: The laser processing device has: A chuck table that holds the workpiece; a laser beam irradiation unit for irradiating a laser beam toward a workpiece held by the chuck table; a moving unit that relatively moves the chuck table and the laser beam irradiation unit; and a control section that controls at least the laser beam irradiation unit and the moving unit, The laser beam irradiation unit comprises: Laser oscillator; a condensing lens for condensing the laser beam emitted from the laser oscillator, the condensing lens including a first surface and a second surface; and A phase modulation element is disposed between the laser oscillator and the focusing lens. The laser processing device further includes an input unit that inputs a pattern obtained by patterning the voltage applied to the phase modulation element. A combination pattern is input from the input unit, the combination pattern being a combination of a shape correction pattern for correcting a difference between an actual shape of the condensing lens and a design value and an adjustment pattern for adjusting the optical characteristics of the laser beam at a processing point. The control unit applies a voltage corresponding to the combination pattern to the phase modulation element, thereby suppressing individual differences in the condensing lens. In the step of generating the shape correction pattern, a fitting function is used. The fitting function is a fitting function of the Z coordinate of the first surface of the focusing lens generated by fitting the actual shape of the Z coordinate of the first surface relative to the radial position of the focusing lens from its center. The Z coordinate of the first surface is the coordinate of the first surface in a direction perpendicular to the processing feed direction and the graduation feed direction of the laser processing device.

2. The laser processing device according to claim 1, wherein: The first surface of the condenser lens is a convex spherical surface, and the second surface of the condenser lens is a concave spherical surface.

3. A method for adjusting a laser processing device, wherein the method comprises adjusting a focusing state of a laser beam irradiated onto a workpiece in the laser processing device, The laser processing device comprises: A chuck table that holds the workpiece; a laser beam irradiation unit for irradiating a laser beam toward a workpiece held by the chuck table; a moving unit that relatively moves the chuck table and the laser beam irradiation unit; a control section that controls at least the laser beam irradiation unit and the movement unit; and Input unit, which inputs various information, The laser beam irradiation unit comprises: Laser oscillator; a condensing lens for condensing the laser beam emitted from the laser oscillator, the condensing lens including a first surface and a second surface; and A phase modulation element is disposed between the laser oscillator and the focusing lens. in, The adjustment method of the laser processing device has the following steps: a pattern generating step of generating a pattern by patterning the voltage applied to the phase modulation element; an input step of inputting the pattern generated by the pattern generating step from the input unit; a voltage applying step of applying a voltage corresponding to the pattern input in the input step to the phase modulation element; as well as a laser beam irradiation step, after the voltage application step, emitting the laser beam while moving the workpiece and the laser beam relative to each other to process the workpiece, The pattern generated by the pattern generating step is a combination of a shape correction pattern for correcting a difference between an actual shape of the condenser lens and a design value and an adjustment pattern for adjusting the optical characteristics of the laser beam at a processing point. In the step of generating the shape correction pattern, a fitting function is used. The fitting function is a fitting function of the Z coordinate of the first surface of the focusing lens generated by fitting the actual shape of the Z coordinate of the first surface relative to the radial position of the focusing lens from its center. The Z coordinate of the first surface is the coordinate of the first surface in a direction perpendicular to the processing feed direction and the graduation feed direction of the laser processing device.

4. The method for adjusting a laser processing device according to claim 3, wherein: The first surface of the condenser lens is a convex spherical surface, and the second surface of the condenser lens is a concave spherical surface.

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