阅读说明：本技术 激光加工装置和激光加工装置的调整方法 (Laser processing apparatus and method for adjusting laser processing apparatus ) 是由 植木笃 木村展之 于 2021-03-05 设计创作，主要内容包括：本发明提供激光加工装置和激光加工装置的调整方法,能够实现低成本且抑制装置间性能差异。激光加工装置的激光束照射单元包含：激光振荡器；聚光透镜,其对从激光振荡器射出的激光束进行聚光；以及相位调制元件,其配设在激光振荡器与聚光透镜之间。通过对相位调制元件施加与组合图案对应的电压,抑制聚光透镜的个体差异,该组合图案是将用于校正聚光透镜的实际形状与设计值之差的形状校正图案和用于调整激光束在加工点处的光学特性的调整图案组合而得的。(The invention provides a laser processing apparatus and an adjusting method of the laser processing apparatus, which can realize low cost and restrain performance difference between apparatuses. The laser beam irradiation unit of the laser processing device comprises: a laser oscillator; a condensing lens that condenses the 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 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 optical characteristics of the laser beam at the processing point to the phase modulation element, individual differences of the condenser lens are suppressed.)

1. A laser processing apparatus, wherein,

the laser processing device comprises:

a chuck table for holding a workpiece;

a laser beam irradiation unit for irradiating a laser beam to the workpiece held by the chuck table;

a moving unit relatively moving 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 includes:

a laser oscillator;

a condensing lens that condenses the 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 has an input unit that inputs a pattern obtained by patterning a voltage applied to the phase modulation element,

a combined pattern is input from the input unit, the combined pattern is obtained by combining a shape correction pattern for correcting the difference between the actual shape and the designed value of the condensing lens and an adjustment pattern for adjusting the optical characteristics of the laser beam at the processing point, and the control part applies a voltage corresponding to the combined pattern to the phase modulation element, thereby suppressing the individual difference of the condensing lens.

2. An adjustment method of a laser processing device, which adjusts the condensing state of a laser beam irradiated to a processed object,

the laser processing apparatus includes:

a chuck table for holding a workpiece;

a laser beam irradiation unit for irradiating a laser beam to the workpiece held by the chuck table;

a moving unit relatively moving 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 which inputs various kinds of information,

the laser beam irradiation unit includes:

a laser oscillator;

a condensing lens that condenses the laser beam emitted from the laser oscillator; and

a phase modulation element disposed between the laser oscillator and the condenser lens,

wherein the content of the first and second substances,

the method for adjusting the laser processing device comprises the following steps:

a pattern generation step of generating a pattern in which a voltage applied to the phase modulation element is patterned;

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 in the input step to the phase modulation element; and

a laser beam irradiation step of irradiating the laser beam and moving the workpiece and the laser beam relative to each other to perform processing on the workpiece,

the pattern generated by the pattern generating step is a pattern in which 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 optical characteristics of the laser beam at the processing point are combined.

Technical Field

The present invention relates to a laser processing apparatus and an adjustment method for the laser processing apparatus.

Background

As a method for dividing a workpiece such as a semiconductor wafer, the following techniques are known: a laser beam is irradiated into a workpiece to form a modified layer as a brittle region, and an external force is applied to divide the modified layer into individual chips (see patent document 1). In a laser processing apparatus for irradiating a laser beam, the laser beam emitted from a laser oscillator is propagated by using various optical members, and is condensed by a condenser lens to be irradiated to a workpiece. However, there is a problem that various optical distortions may occur on the optical path of the laser beam, and the processing results may vary among laser processing apparatuses due to the optical distortions (so-called performance difference between apparatuses may occur).

Therefore, the present inventors have investigated the cause of the performance difference between the apparatuses, and have found that the cause is often caused by individual difference of the condenser lens. In order to eliminate such performance difference between devices, the following techniques have been employed: replacing the condenser lens which is a main cause of the performance difference; or the spot shape of the machining point is corrected by using a wavefront sensor (see patent document 2).

Patent document 1: japanese patent No. 3408805

Patent document 2: japanese patent application No. 2019-207274

However, in order to eliminate the performance difference between apparatuses, it is necessary to select a condensing lens having a similar shape with a small individual difference, which is problematic in that not only the cost but also the replacement work takes a lot of time. Further, the wavefront sensor used for correcting the spot shape is expensive, and therefore, there is a problem that the apparatus cost increases.

Disclosure of Invention

Therefore, an object of the present invention is to provide a laser processing apparatus and a method of adjusting a laser processing apparatus, which can suppress performance variation between apparatuses at low cost.

According to an aspect of the present invention, there is provided a laser processing apparatus, wherein the laser processing apparatus has: a chuck table for holding a workpiece; a laser beam irradiation unit for irradiating a laser beam to the workpiece held by the chuck table; a moving unit relatively moving 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 condensing lens that condenses the laser beam emitted from the laser oscillator; and a phase modulation element disposed between the laser oscillator and the condenser lens, wherein the laser processing apparatus further includes an input unit that inputs a pattern obtained by patterning a voltage applied to the phase modulation element, and inputs a combination pattern obtained by combining a shape correction pattern for correcting a difference between an actual shape and a design value of the condenser lens and an adjustment pattern for adjusting an optical characteristic of the laser beam at a processing point from the input unit, and the control unit applies a voltage corresponding to the combination pattern to the phase modulation element, thereby suppressing an individual difference of the condenser lens.

According to another aspect of the present invention, there is provided a method of adjusting a laser processing apparatus for adjusting a condensing state of a laser beam applied to a workpiece, the method including: a chuck table for holding a workpiece; a laser beam irradiation unit for irradiating a laser beam to the workpiece held by the chuck table; a moving unit relatively moving 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 which inputs various kinds of information, the laser beam irradiation unit including: a laser oscillator; a condensing lens that condenses the laser beam emitted from the laser oscillator; and a phase modulation element disposed between the laser oscillator and the condenser lens, wherein the method for adjusting the laser processing apparatus includes the steps of: a pattern generation step of generating a pattern in which a voltage applied to the phase modulation element is patterned; 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 in the input step to the phase modulation element; and a laser beam irradiation step of performing processing on the workpiece by relatively moving the workpiece and the laser beam while emitting the laser beam after the voltage application step, wherein the pattern generated by the pattern generation step is a pattern in which a shape correction pattern for correcting a difference between an actual shape and a design value of the condenser lens and an adjustment pattern for adjusting optical characteristics of the laser beam at a processing point are combined.

According to the present invention, it is possible to suppress performance differences between apparatuses at low cost.

Drawings

Fig. 1 is a perspective view showing a configuration example of a laser processing apparatus according to an embodiment.

Fig. 2 is a perspective view of a workpiece to be processed in the laser processing apparatus shown in fig. 1.

Fig. 3 is a schematic diagram schematically illustrating a structure of a laser beam irradiation unit of the laser processing apparatus shown in fig. 1.

Fig. 4 is a schematic diagram showing an example of the condenser lens.

Fig. 5 is a graph showing an example of the relationship between the radial position of the condenser lens from the center and the Z-coordinate of the 1 st surface.

Fig. 6 is a diagram illustrating an example of the shape correction pattern.

Fig. 7 is a diagram showing an example of the adjustment pattern.

Fig. 8 is a diagram showing an example of the combination pattern.

Fig. 9 is a graph showing a simulation result of the light condensing state according to the design value.

Fig. 10 is a graph showing a simulation result of the light condensing state based on the fitting function of the actual shape.

Fig. 11 is a diagram showing a simulation result of the light condensing state after the shape correction.

Fig. 12 is a flowchart illustrating a flow of an adjustment method of the laser processing apparatus according to the embodiment.

Description of the reference symbols

1: a laser processing device; 10: a chuck table; 20: a laser beam irradiation unit; 21: a laser beam; 22: a laser oscillator; 23: a polarizing plate; 24: a phase modulation element; 241: a display unit; 242: a shape correction pattern; 243: adjusting the pattern; 244: combining the patterns; 25: a lens group; 251. 252: a lens; 26: a mirror; 27: a condenser lens; 271: the 1 st surface; 2711: the actual shape; 2712: fitting a function; 272: the 2 nd surface; 28: a processing point; 30: a mobile unit; 70: a shooting unit; 80: an input unit; 90: a control unit; 100: a workpiece is processed.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiments. The components described below include substantially the same components as can be easily conceived by those skilled in the art. The following structures can be combined as appropriate. Various omissions, substitutions, and changes in the structure can be made without departing from the spirit of the invention.

A 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 a laser processing apparatus 1 according to an embodiment. Fig. 2 is a perspective view of a workpiece 100 to be processed in the laser processing apparatus 1 shown in fig. 1.

As shown in fig. 1, the laser processing apparatus 1 includes a chuck table 10, a laser beam irradiation unit 20, a moving unit 30, an imaging unit 70, an input unit 80, and a control unit 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 on a horizontal plane. The Z-axis direction is a direction perpendicular to the X-axis direction and the Y-axis direction. The laser processing apparatus 1 of the embodiment has a processing feed direction in the X-axis direction and an indexing feed direction in the Y-axis direction.

The laser processing apparatus 1 of the embodiment is an apparatus that processes a workpiece 100 by irradiating the workpiece 100 to be processed with a laser beam 21. The processing of the workpiece 100 by the laser processing apparatus 1 is, for example, modified layer forming processing for forming a modified layer 106 (see fig. 3) in the workpiece 100 by stealth dicing, groove processing for forming a groove in the front surface 102 of the workpiece 100, or cutting processing for cutting the workpiece 100 along the lines to divide 103. In the embodiment, a structure in which the modified layer 106 is formed 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).

As shown in fig. 2, the workpiece 100 includes: lines to divide 103 set in a grid pattern on the front surface 102 of the substrate 101; and devices 104 formed in the regions demarcated by the 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 modified layer 106 is formed inside the object 100 along the lines to divide 103 (see fig. 3). A tape 111 having a diameter larger 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 tape 111, whereby the workpiece 100 is supported in the opening of the annular frame 110.

As shown in fig. 1, the chuck table 10 holds a workpiece 100 by a holding surface 11. The holding surface 11 is a disk shape formed of porous ceramics or the like. In the embodiment, the holding surface 11 is 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 chuck table 10 sucks and holds the workpiece 100 placed on the holding surface 11. A plurality of clamping portions 12 are arranged around the chuck table 10, and the clamping portions 12 clamp an annular frame 110 that supports the workpiece 100. The chuck table 10 is rotated by the rotation unit 13 about an axis parallel to the Z-axis direction. The rotating unit 13 is supported by the X-axis direction moving plate 14. The rotation unit 13 and the chuck table 10 are moved in the X-axis direction by the X-axis direction moving unit 40 by the X-axis direction moving plate 14. The rotation unit 13 and the chuck table 10 are moved in the Y-axis direction by the Y-axis direction moving unit 50 via the X-axis direction moving plate 14, the X-axis direction moving unit 40, and the Y-axis direction moving plate 15.

The laser beam irradiation unit 20 is a unit that irradiates the workpiece 100 held by the chuck table 10 with a pulse-shaped laser beam 21. At least the condenser lens 27 (see fig. 3) of the laser beam irradiation unit 20 is supported by a Z-axis direction moving unit 60, and the Z-axis direction moving unit 60 is provided on the column 3 erected from the apparatus main body 2 of the laser processing apparatus 1. The detailed structure of the laser beam irradiation unit 20 will be described later.

As shown in fig. 1, the X-axis direction moving unit 40 is a unit that moves the chuck table 10 and the laser beam irradiation unit 20 relative to each other in the X-axis direction, which is a machining 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 in the apparatus main body 2 of the laser processing apparatus 1. The X-axis direction moving unit 40 supports the X-axis direction moving plate 14 to be movable in the X-axis direction. The X-axis direction moving means 40 includes a known ball screw 41, a known pulse motor 42, and a known guide rail 43. The ball screw 41 is provided to be rotatable about the axial center. The pulse motor 42 rotates the ball screw 41 around the axis. The guide rail 43 supports the X-axis direction moving plate 14 to be movable in the X-axis direction. The guide rail 43 is fixedly provided to the Y-axis direction moving plate 15.

The Y-axis direction moving unit 50 is a unit that moves the chuck table 10 and the laser beam irradiation unit 20 relative to each other in the Y-axis direction, which is an index feeding 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 on the apparatus main body 2 of the laser processing apparatus 1. The Y-axis direction moving unit 50 supports the Y-axis direction moving plate 15 to be movable in the Y-axis direction. The Y-axis direction moving unit 50 includes a known ball screw 51, a known pulse motor 52, and a known guide rail 53. The ball screw 51 is provided to be rotatable about the axial center. The pulse motor 52 rotates the ball screw 51 about the axis. The guide rail 53 supports the Y-axis direction moving plate 15 to be movable in the Y-axis direction. The guide rail 53 is fixedly provided to the apparatus main body 2.

The Z-axis direction moving unit 60 is a unit that moves the chuck table 10 and the laser beam irradiation unit 20 relative to each other in the Z-axis direction, which is a focal 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 on the column 3 erected from the apparatus main body 2 of the laser processing apparatus 1. The Z-axis direction moving unit 60 supports at least the condenser lens 27 (see fig. 3) of the laser beam irradiation unit 20 to be movable in the Z-axis direction. The Z-axis direction moving means 60 includes a known ball screw 61, a known pulse motor 62, and a known guide rail 63. The ball screw 61 is provided to be rotatable about the axial center. The pulse motor 62 rotates the ball screw 61 around the axis. The guide rail 63 supports the laser beam irradiation unit 20 to be movable in the Z-axis direction. The guide rail 63 is fixedly provided to the column 3.

The imaging unit 70 images the workpiece 100 held by the chuck table 10. The imaging unit 70 includes a CCD camera or an infrared camera that images the workpiece 100 held by the chuck table 10. The imaging unit 70 is fixed adjacent to the condenser lens 27 (see fig. 3) of the laser beam irradiation unit 20, for example. The imaging unit 70 images the workpiece 100, obtains an image for performing alignment for aligning the workpiece 100 with the laser beam irradiation unit 20, and outputs the obtained image to the control unit 90.

The input unit 80 inputs various information. The input unit 80 can receive various operations such as registration of processing content information by an operator. The input unit 80 can receive an operation of inputting a combination pattern 244 (see fig. 8 as an example) in which a shape correction pattern 242 (see fig. 6 as an example) and an adjustment pattern 243 (see fig. 7 as an example) to be described later are combined. The input unit 80 may be an external input device such as a keyboard. When the laser processing apparatus 1 includes a display device including a touch panel, the input unit 80 may be included in the display device.

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 on the workpiece 100. The control section 90 controls the laser beam irradiation unit 20, the moving unit 30, and the imaging unit 70. The control unit 90 is a computer including an arithmetic processing device as arithmetic means, a storage device as storage means, and an input/output interface device as communication means. The arithmetic Processing Unit includes a microprocessor such as a CPU (Central Processing Unit). The storage device includes a Memory such as a ROM (Read Only Memory) or a RAM (Random Access Memory). The arithmetic processing device performs various calculations 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 based on the arithmetic result, and controls the laser processing device 1.

The control unit 90 applies a voltage corresponding to the pattern input from the input unit 80 to the phase modulation element 24, which will be described later, for example. The control unit 90 causes the imaging unit 70 to image the workpiece 100, for example. The control unit 90 performs image processing on an image captured by the imaging unit 70, for example. The control unit 90 detects a machining line of the workpiece 100 by, for example, image processing. The control section 90 drives the X-axis direction moving unit 40, for example, and causes the laser beam irradiation unit 20 to irradiate the laser beam 21 so as to move the machining point 28, which is the converging point of the laser beam 21, along the machining line.

Next, the laser beam irradiation unit 20 will be described in detail. Fig. 3 is a schematic diagram schematically illustrating the structure of the laser beam irradiation unit 20 of the laser processing apparatus 1 illustrated in fig. 1. As shown in fig. 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 mirror 26, and a condenser lens 27.

In addition, an arrow in fig. 3 indicates a moving direction of the chuck table 10 at the time of the machining feed. In the embodiment, the machining point 28, which is the converging point of the laser beam 21, is set inside the workpiece 100. By processing and feeding the chuck table 10 while irradiating the processing point 28 with the laser beam 21, a modified layer 106 along the lines to divide 103 (see fig. 2) is formed inside the object 100.

Modified layer 106 is a region in which the density, refractive index, mechanical strength, or other physical properties are different from those of the surroundings. The modified layer 106 is, for example, a melt-processed region, a crack region, an insulation breakdown region, a refractive index change region, a region in which these regions are mixed, or the like. The modified layer 106 has a mechanical strength or the like lower than that of the other parts of the workpiece 100.

The laser oscillator 22 emits a laser beam 21 by oscillating a laser beam having a predetermined wavelength for processing the workpiece 100. In the embodiment, the laser beam 21 irradiated by the laser beam irradiation unit 20 has a wavelength that is transparent to the workpiece 100.

The polarizing plate 23 is disposed 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 in a specific direction.

The phase modulation element 24 is disposed between the laser oscillator 22 and the condenser lens 27. The phase modulation element 24 phase-modulates 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 section 90, the phase modulation element 24 shapes the laser beam 21 into a desired beam shape. Thereby, the output and spot shape of the laser beam 21 at the machining point 28 are adjusted.

The pattern is a pattern obtained by patterning a 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 (see fig. 8) obtained by combining the shape correction pattern 242 (see fig. 6) and the adjustment pattern 243 (see fig. 7). 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 processing point 28. The adjustment of the optical characteristics includes, for example, a change in the shape of the laser beam 21 and an attenuation of the intensity. The laser processing apparatus 1 can adjust the output and spot shape at the processing point 28 by changing at least any one of the shape correction pattern 242 and the adjustment pattern 243 with respect to the voltage applied to the phase modulation element 24.

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 a liquid crystal element. 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 section 90, the phase modulation element 24 causes the display section 241 to display the combined pattern 244. Thereby, the laser beam 21 reflected on the phase modulation element 24 or transmitted through the phase modulation element 24 is phase-modulated and the beam shape is shaped in accordance with the combined pattern 244, thereby adjusting the output and spot shape at the machining point 28.

In the embodiment, the phase modulation element 24 reflects the laser beam 21 and outputs the reflected laser beam, but in the present invention, the laser beam 21 may be transmitted and output. The phase modulation element 24 is not limited to the spatial light modulator, and may 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 in accordance with the combined pattern 244. LCOS uses green light having a wavelength of 405nm or more and IR (infrared light), but can be used for ablation processing by UV (ultraviolet light) because a deformable mirror can be used even if the wavelength is 355 nm.

The lens group 25 is disposed between the phase modulation element 24 and the condenser lens 27. The lens group 25 is a 4f optical system constituted by 2 lenses of the lens 251 and the lens 252. The 4f optical system is 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 formed 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.

The mirror 26 reflects the laser beam 21 and reflects the laser beam 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 having passed through the lens group 25 toward the condenser lens 27.

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

Next, a pattern generation method will be described. Fig. 4 is a diagram showing an example of the condenser lens 27. Fig. 5 is a view showing an example of the relationship between the radial position of the condenser lens 27 from the center and the Z coordinate of the 1 st surface 271. The horizontal axis of fig. 5 represents the radial position of the condenser lens 27 from the center, and the vertical axis of fig. 5 represents the Z coordinate of the 1 st surface 271. In fig. 5, the origin 0 in the Z-axis direction indicates the position in the Z-axis direction at the center in the radial direction of the 1 st surface 271. That is, fig. 5 shows the difference in the Z-axis direction with respect to the center of the 1 st surface 271 for each radial position from the center of the condenser lens 27.

As shown in fig. 4, the condenser lens 27 of the embodiment includes a 1 st surface 271 which is a convex spherical surface and a 2 nd surface 272 which is a concave spherical surface. With regard to lenses purchased from manufacturers, deviations of the lens surface from the design values are allowed within the range of tolerances. For example, regarding the deviation of the lens surface from the design value, the manufacturer performs a measurement of the lens shape for each lens, for example, using a contact type measurer, and discloses the distribution of the measured value of the lens shape with respect to the radial position from the center to the purchaser.

In the method of generating the shape correction pattern 242, first, as shown in fig. 5, an actual shape 2711 (indicated by a solid line in fig. 5) of the Z coordinate of the 1 st surface 271 with respect to the radial position from the center of the condenser lens 27 is fitted, and a fitting function 2712 (an example is indicated by a broken line in fig. 5) of the Z coordinate of the 1 st surface 271 with respect to the radial position from the center of the condenser lens 27 is generated. As described above, the actual shape 2711 of the condenser lens 27 may use a measurement value provided by the manufacturer, or may use a measurement value measured by a manufacturer. The fitting function 2712 is generated by a known method using an R language, numerical analysis software, or the like. The fitting function 2712 is a function representing the Z coordinate of the 1 st surface 271 of each radial position from the center of the condenser lens 27.

Next, assuming that the shape of the 1 st surface 271 of the condenser lens 27 is represented by a fitting function 2712, the aberration after passing through the condenser lens 27 is calculated by a known ray tracing software or the like. From the calculated aberration difference, a correction value that can obtain an ideal wavefront is calculated, and the shape correction pattern 242 based on the correction value is generated. The ideal wavefront is the wavefront of the laser beam 21 after passing through the condenser lens 27 having the shape of the 1 st surface 271 matching the design value. That is, the ideal wavefront means a spatial distribution of the phase of the laser beam 21 that can obtain a desired processing result according to the processing conditions set in the laser processing apparatus 1.

Specifically, first, assuming that the shape of the 1 st surface 271 of the condenser lens 27 is represented by the fitting function 2712, the zernike coefficients corresponding to the aberration of the condenser lens 27 are calculated by known ray tracing software or the like. The zernike coefficient is a value calculated by zernike polynomial approximation of the wave surface of the laser beam 21 after passing through the condenser lens 27, which is calculated by known ray tracing software or the like, and corresponds to the aberration of the condenser lens 27. In addition, the zernike polynomial means an orthogonal polynomial defined on a unit circle.

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 obtained from the calculated zernike coefficient. Further, a pattern obtained by patterning the voltage 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.

Here, assuming that the shape of the 1 st surface 271 of the condenser lens 27 is represented by a fitting function 2712, the calculated zernike coefficient is a value calculated by performing zernike polynomial approximation on the wave surface of the laser beam 21 having passed through the condenser lens 27 calculated by known ray tracing software or the like. Therefore, the calculated zernike coefficient is a value corresponding to a deviation of the shape of the 1 st surface 271 of the condenser lens 27 from the design value. The correction value of the zernike coefficient is a value for bringing the wavefront of the laser beam 21 after passing through the condenser lens 27 close to an ideal wavefront. Therefore, the shape correction pattern 242 is a pattern for making the wave surface of the laser beam 21 transmitted through the condenser lens 27 close to an ideal wave surface.

Fig. 6 is a diagram illustrating an example of the shape correction pattern 242. Fig. 7 is a diagram illustrating an example of the adjustment pattern 243. Fig. 8 is a diagram illustrating an example of the combination pattern 244. In the shape correction pattern 242 shown in fig. 6, the adjustment pattern 243 shown in fig. 7, and the combination pattern 244 shown in fig. 8, a black portion indicates a portion through which the laser beam 21 is transmitted, and a white portion indicates a portion blocking the laser beam 21. In addition, the gray portion indicates the shade, that is, the gray level indicates the difference in the phase modulation amount.

The shape correction pattern 242 and the adjustment pattern 243 are combined to form a combined pattern 244. The combined pattern 244 is input from the input unit 80 by the operator. The combined pattern 244 may be generated by the control unit 90. That is, the shape correction pattern 242 and the adjustment pattern 243 before being combined into the combined pattern 244 may be input to the input unit 80. The shape correction pattern 242 may be generated by the control unit 90 based on the actual shape 2711 of the Z coordinate of the 1 st surface 271 with respect to the radial position from the center of the condenser lens 27, which is input from the operator. The adjustment pattern 243 may be generated by the control unit 90 based on a set value for adjusting the optical characteristics, which is input from the operator.

Next, the effect of applying the shape correction pattern 242 is verified. Fig. 9 is a graph showing a simulation result of the light condensing state according to the design value. Fig. 10 is a graph showing a simulation result of the light condensing state from the fitting function 2712 of the actual shape 2711. Fig. 11 is a diagram showing a simulation result of the light condensing state after the shape correction. Fig. 9 to 11 show the energy distribution of the laser beam 21. In fig. 9 to 11, the upper diagram shows the spot shape of the workpiece 100 in the cross-sectional direction, and the origin 0 in the Z-axis direction shows the height of the machining point 28. In fig. 9 to 11, the lower graph shows the radial energy distribution at the origin 0 in the Z-axis direction. In the embodiment, the numerical aperture of the condenser lens 27 is 0.8. The laser beam 21 had a wavelength of 1342nm and a frequency of 100 kHz. The beam diameter of the laser beam 21 incident on the condenser lens 27 was 10 mm. In the embodiment, the evaluation software used for the simulation was a Virtual laboratory (Virtual Lab) manufactured by t.e.m.

As shown in fig. 9, the beam diameter of the laser beam 21 condensed at the machining point 28 is about 2 μm in the condenser lens 27 which is a design value of an ideal wavefront. In addition, the energy distribution of the laser beam 21 is gaussian distribution. On the other hand, as shown in fig. 10, in the condenser lens 27 represented by the fitting function 2712 of the actual shape 2711, the energy distribution of the laser beam 21 condensed at the machining point 28 is blurred in the downward swing of 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 condenser lens 27, and is thus deformed from the desired spot shape.

As shown in fig. 11, in the condenser lens 27 to which the shape correction pattern 242 is applied, the beam diameter of the laser beam 21 condensed at the processing point 28 is about 2 μm. In addition, the energy distribution of the laser beam 21 does not produce a blur in the skirt portion of the gaussian. In this way, the condenser lens 27 to which the shape correction pattern 242 is applied can be brought into a condensing state similar to the condenser lens 27 of the design value shown in fig. 9.

Next, a laser processing method of the laser processing apparatus 1 will be described. Fig. 12 is a flowchart illustrating a flow of a laser processing method of the embodiment. The laser processing method includes a pattern generation step 501, an input step 502, a voltage application step 503, and a laser beam irradiation step 504.

The pattern generation step 501 is a step of generating a pattern in which a voltage 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, a combined pattern 244 to be displayed on the display section 241 of the phase modulation element 24 is generated.

More specifically, in the pattern generating step 501, first, the actual shape 2711 of the condenser lens 27 with respect to the Z coordinate of the 1 st surface 271 at the radial position from the center is fitted to generate the fitting function 2712 of the Z coordinate of the 1 st surface 271 of the condenser lens 27. Next, assuming that the shape of the 1 st surface 271 of the condenser lens 27 is represented by the fitting function 2712, the aberration after passing through the condenser lens 27 is calculated, and the shape correction pattern 242 is generated from the calculated aberration, the shape correction pattern 242 being obtained from the correction value by which an ideal wavefront can be obtained. In the pattern generation step 501, the shape correction pattern 242 and the adjustment pattern 243 are combined to generate a combined pattern 244.

In the input step 502, the combined pattern 244, which is the pattern generated in the pattern generation step 501, is input from the input unit 80. Specifically, for example, the operator inputs data of the combined pattern 244 generated by an external device having pattern generating software or the like from the input unit 80. The pattern generation software may be dedicated software, or may be Excel (registered trademark) or the like.

The voltage applying step 503 is a step of applying a voltage corresponding to the pattern (i.e., the combined pattern 244) input in the input step 502 to the phase modulation element 24. More specifically, in the voltage applying step 503, the control section 90 acquires the combined pattern 244 input from the input unit 80. The control section 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 a voltage corresponding to the combined pattern 244 is applied from the control section 90, the phase modulation element 24 causes the display section 241 to display the combined pattern 244.

The laser beam irradiation step 504 is a step of: after the voltage applying step 503, the workpiece 100 is processed by relatively moving the workpiece 100 and the chuck table 10 while emitting the laser beam 21. Specifically, in the laser beam irradiation step 504, the moving unit 30 is moved to the processing position of the laser processing apparatus 1. Next, the object 100 is imaged by the imaging unit 70, and the line to divide 103 is detected. If the line 103 is detected, alignment is performed to align the line 103 to be divided of the object 100 and the converging point of the laser processing apparatus 1.

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

In the laser beam irradiation step 504, the machining point 28, which is a converging point, is positioned inside the workpiece 100, and the pulsed laser beam 21 having a wavelength that is transparent to the workpiece 100 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 transparent to the workpiece 100, the modified layer 106 is formed inside the substrate 101 along the lines to divide 103.

As described above, in the laser processing apparatus 1 of the embodiment, the laser beam irradiation unit 20 includes the phase modulation element 24, and the individual difference of the condenser lens 27 can be suppressed by applying a voltage corresponding to a predetermined pattern to the phase modulation element 24, the phase modulation element 24 is disposed between the laser oscillator 22 and the condenser lens 27, and the condenser lens 27 condenses the laser beam 21 emitted from the laser oscillator 22. The predetermined pattern is a combined pattern 244 obtained by combining a shape correction pattern 242 for correcting the difference between the actual shape of the condenser lens 27 and the design value and an adjustment pattern 243 for adjusting the optical characteristics of the laser beam 21 at the processing point 28.

A conventional laser processing apparatus is mounted with a phase modulation element 24 such as an LCOS or a deformable mirror that applies a voltage corresponding to an adjustment pattern 243 for adjusting the optical characteristics of the laser beam 21 at the processing point 28. Therefore, by inputting a combination pattern 244 obtained by combining the shape correction patterns 242 for correcting the difference between the actual shape of the condenser lens 27 and the design value in addition to the conventional adjustment pattern 243, it is possible to irradiate the laser beam 21 in which the individual difference of the condenser lens 27 is corrected. Thus, the laser processing apparatus 1 of the embodiment can suppress performance variation between apparatuses. Further, since the phase modulation element 24 can be an element already mounted in an existing laser processing apparatus, it is not necessary to increase the cost of additional parts, modification of the apparatus, or the like. Therefore, the laser processing apparatus 1 of the embodiment can be realized at low cost.

The present invention is not limited to the above embodiments. That is, various modifications can be made without departing from the scope of the present invention. For example, in the embodiment, the individual difference in the shape of the 1 st surface 271 of the condenser lens 27 is corrected, but the individual difference in the shape of the 2 nd surface 272 may be corrected, or the shapes of both the 1 st surface 271 and the 2 nd surface 272 may be corrected.