Laser processing device

Abstract

The present application provides a laser processing device that can easily perform adjustment without increasing the size of the device. The laser processing device includes an energy distribution correction unit (30, 40) that forms a lower portion of a Gaussian distribution of an energy distribution in a Y-axis direction of a laser beam (21) emitted from a laser oscillator (22) into a vertical distribution, an imaging lens group (23) that is composed of two or more lenses and images a beam shape of the laser beam whose energy distribution is corrected by the energy distribution correction unit on an upper surface of an object to be processed (100), and a cylindrical lens (24) that adjusts an energy density in an X-axis direction of the laser beam whose energy distribution is corrected by the energy distribution correction unit. The distance between the imaging lens group and the cylindrical lens is relatively moved to adjust a spot shape of the laser beam on the upper surface of the object to be processed.

Description

TECHNICAL FIELD

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

[0002] In order to process a workpiece such as a semiconductor wafer, a laser processing apparatus is known which forms a division groove by irradiating a laser beam to the workpiece. In such a laser processing apparatus, various components such as a mask, a relay lens, and a cylindrical lens are assembled in an optical system (see Patent Document 1).

[0003] Patent Document 1: Japanese Patent Application Publication No. 2010-158710

[0004] However, there is a problem that adjustment of the above components is very difficult and time-consuming. In particular, it is difficult to adjust the generatrix of the pair of cylindrical lenses, which becomes a cause of generating mechanical errors between processing apparatuses, and therefore research has been conducted to make adjustment easy by reducing the cylindrical lenses to one piece instead of two pieces. However, there are problems that it is difficult to maintain mechanical accuracy because the moving distance of the cylindrical lenses becomes large at the time of adjustment, and the size of the apparatus becomes large. SUMMARY

[0005] Therefore, an object of the present application is to provide a laser processing apparatus which can easily adjust the spot shape of a laser beam on the upper surface of a workpiece without making the size of the apparatus large.

[0006] According to the present application, there is provided a laser processing apparatus characterized by comprising: a chuck table which holds a workpiece; a laser beam irradiation unit which irradiates a laser beam of a wavelength having absorbance with respect to the workpiece held by the chuck table; an X-axis direction moving unit which relatively moves the chuck table and the laser beam irradiation unit in an X-axis direction which is a processing feed direction; and a Y-axis direction moving unit which relatively moves the chuck table and the laser beam irradiation unit in a Y-axis direction which is an indexing feed direction perpendicular to the processing feed direction, the laser beam irradiation unit including: a laser oscillator; a condensing lens which condenses a laser beam emitted from the laser oscillator; an energy distribution correction unit which is provided between the laser oscillator and the condensing lens, forms a lower swing portion of a Gaussian distribution of energy distribution in the Y-axis direction of the laser beam emitted from the laser oscillator into a vertical distribution; an imaging lens group which is composed of two or more lenses, images a beam shape of the laser beam whose energy distribution is corrected by the energy distribution correction unit on the upper surface of the workpiece; and a single cylindrical lens which adjusts the energy density in the X-axis direction of the laser beam whose energy distribution is corrected by the energy distribution correction unit, relatively moves a distance between the imaging lens group and the cylindrical lens to adjust the spot shape of the laser beam on the upper surface of the workpiece.

[0007] It is preferable that the imaging lens group include a relay lens and an expander.

[0008] According to the present application, it is possible to easily adjust the spot shape of the laser beam on the upper surface of the workpiece without increasing the size of the device. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 is a perspective view showing a structure example of a laser processing device of an embodiment.

[0010] Figure 2 is Figure 1 is a perspective view of a workpiece, which is a processing target of the laser processing device shown.

[0011] Figure 3 is a schematic view showing a structure of a laser beam irradiation unit of the laser processing device shown. Figure 1

[0012] Figure 4 is a perspective view showing an example of an energy distribution correction unit of an embodiment.

[0013] Figure 5 is a schematic view showing an example of a beam shape at a condensing spot.

[0014] Figure 6 is a perspective view showing another example of an energy distribution correction unit of an embodiment.

[0015] Figure 7 is a graph showing an example of an energy distribution in the Y-axis direction of a laser beam.

[0016] Figure 8 is a schematic view schematically showing a structure of a laser beam irradiation unit of a comparative example.

[0017] Figure 9 is a schematic view showing a structure of an imaging lens group of a first modified example.

[0018] Figure 10 is a schematic view showing a structure of an imaging lens group of a second modified example.

[0019] REFERENCE NUMERALS

[0020] ​1: laser processing apparatus; 10: chuck table; 20, 20-2: laser beam irradiation unit; 21: laser beam; 22: laser oscillator; 23: imaging lens group; 24: cylindrical lens; 25: mirror; 26: condenser lens; 27: condensing spot; 28: relay lens; 29: cylindrical lens pair; 30, 40: energy distribution correction unit; 50: X-axis direction moving unit; 60: Y-axis direction moving unit; 70: Z-axis direction moving unit; 80: imaging unit; 85: display unit; 90: control unit; 100: workpiece. DETAILED DESCRIPTION

[0021] 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 included structural elements that are substantially the same as those that can be easily thought of 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 the scope of the gist of the present application.

[0022] A laser processing apparatus 1 according to an embodiment will be described with reference to the accompanying drawings. Figure 1 is a perspective view showing a structure example of the laser processing apparatus 1 according to 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

[0023] As shown in Figure 1 , the laser processing apparatus 1 has a chuck table 10, a laser beam irradiation unit 20, an X-axis direction moving unit 50, a Y-axis direction moving unit 60, a Z-axis direction moving unit 70, an imaging unit 80, a display unit 85, and a control unit 90. In the following description, the X-axis direction is one direction on a horizontal plane. The Y-axis direction is a direction perpendicular to the X-axis direction on 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 according to the embodiment is the X-axis direction, and the indexing feed direction is the Y-axis direction.

[0024] The laser processing apparatus 1 according to the embodiment is an apparatus that forms a laser processing groove 106 (refer to Figure 5 ) on a workpiece 100 by irradiating a laser beam 21 to the workpiece 100 that is a processing target. In the embodiment, a structure that performs groove processing on the workpiece 100 is described, but perforation processing can be performed on the workpiece 100. The workpiece 100 is a wafer such as a semiconductor wafer, an optical device wafer, or the like, which is a circular plate-shaped wafer having silicon (Si), sapphire (Al2O3), gallium arsenide (GaAs), silicon carbide (SiC), or the like as a substrate 101.

[0025] As​Figure 2 As shown, the workpiece 100 has predetermined dividing lines 103 arranged in a grid pattern on the front surface 102 of the substrate 101 and devices 104 formed in the areas divided by the predetermined dividing lines 103. The devices 104 are, for example, integrated circuits such as IC (Integrated Circuit) or LSI (Large Scale Integration), or image sensors such as CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor). In the embodiment, the workpiece 100 is formed with laser-processed grooves 106 (see FIG. 1 ) along the predetermined dividing lines 103. Figure 5 In the embodiment, a belt 111 having a larger diameter than the outer diameter of the workpiece 100 and attached to the annular frame 110 is attached to the back surface 105 on the back side of the front surface 102 , and the workpiece 100 is supported in the opening of the annular frame 110 .

[0026] like Figure 1 As shown, the chuck table 10 holds the workpiece 100 using a holding surface 11. The holding surface 11 is a disk-shaped surface 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 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 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 via the X-axis moving plate 14 through the X-axis moving unit 50. The rotation unit 13 and the chuck table 10 are moved in the Y-axis direction by the Y-axis direction moving unit 60 via the X-axis direction moving plate 14 , the X-axis direction moving unit 50 , and the Y-axis direction moving plate 15 .

[0027] The laser beam irradiation unit 20 irradiates the workpiece 100 held by the chuck table 10 with a pulsed laser beam 21. At least the focusing lens 26 of the laser beam irradiation unit 20 is supported by a Z-axis direction moving unit 70, which is provided on a column 3 extending from the main body 2 of the laser processing apparatus 1. The detailed structure of the laser beam irradiation unit 20 will be described later.

[0028] The X-axis direction moving unit 50 is a unit that relatively moves the chuck table 10 and the laser beam irradiation unit 20 in the X-axis direction as a machining feed direction. In the embodiment, the X-axis direction moving unit 50 moves the chuck table 10 in the X-axis direction. In the embodiment, the X-axis direction moving unit 50 is provided on the device main body 2 of the laser processing device 1. The X-axis direction moving unit 50 supports the X-axis direction moving plate 14 so as to be movable in the X-axis direction. The X-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 X-axis direction moving plate 14 so as to be movable in the X-axis direction. The guide rail 53 is fixedly provided to the Y-axis direction moving plate 15.

[0029] The Y-axis direction moving unit 60 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 60 moves the chuck table 10 in the Y-axis direction. In the embodiment, the Y-axis direction moving unit 60 is provided on the device main body 2 of the laser processing device 1. The Y-axis direction moving unit 60 supports the Y-axis direction moving plate 15 so as to be movable in the Y-axis direction. The Y-axis direction moving 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 provided 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 Y-axis direction moving plate 15 so as to be movable in the Y-axis direction. The guide rail 63 is fixedly provided to the device main body 2.

[0030] The Z-axis direction moving unit 70 is a unit that relatively moves the chuck table 10 and the laser beam irradiation unit 20 in the Z-axis direction as a focal point position adjustment direction. In the embodiment, the Z-axis direction moving unit 70 moves the laser beam irradiation unit 20 in the Z-axis direction. In the embodiment, the Z-axis direction moving unit 70 is provided to the column 3 that is provided upright from the device main body 2 of the laser processing device 1. The Z-axis direction moving unit 70 supports at least the condensing lens 26 (see FIG. 1) in the laser beam irradiation unit 20 so as to be movable in the Z-axis direction. The Z-axis direction moving unit 70 includes a publicly known ball screw 71, a publicly known pulse motor 72, and a publicly known guide rail 73. The ball screw 71 is provided so as to be rotatable around an axis. The pulse motor 72 rotates the ball screw 71 around the axis. The guide rail 73 supports the laser beam irradiation unit 20 so as to be movable in the Z-axis direction. The guide rail 73 is fixedly provided to the column 3. Figure 3

[0031] ​The photographing unit 80 photographs the workpiece 100 held by the chuck table 10. The photographing unit 80 includes a CCD (Charge Coupled Device) camera or an infrared camera that photographs the workpiece 100 held by the chuck table 10. The photographing unit 80 is fixed, for example, adjacent to the condenser lens 26 (see FIG. 1) of the laser beam irradiation unit 20. The photographing unit 80 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 unit 90. Figure 3

[0032] The display unit 85 includes a display surface 86 that displays a state of a processing operation or an image, and the like. The display unit 85 is a display section constituted by a liquid crystal display device, or the like. In a case where the display surface 86 includes a touch panel, the display unit 85 can also include an input section. The input section can accept various operations such as registration of processing content information by an operator. The input section can also be an external input device such as a keyboard. The display unit 85 switches information or an image displayed on the display surface 86 by an operation from the input section, or the like. The display unit 85 can also include a notification section. The notification section emits at least one of sound and light to notify an operator of the laser processing device 1 of predetermined notification information. The notification section can also be an external notification device such as a speaker or a light emitting device. The display unit 85 is connected to the control unit 90.

[0033] The control unit 90 controls each of the above-described structural elements of the laser processing device 1 to cause the laser processing device 1 to perform a processing operation on the workpiece 100. The control unit 90 controls the laser beam irradiation unit 20, the X-axis direction moving unit 50, the Y-axis direction moving unit 60, the Z-axis direction moving unit 70, the photographing unit 80, and the display unit 85. The control unit 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, for example, 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 computations according to a prescribed program stored in the storage device. The arithmetic processing device outputs various control signals to each of the above-described structural elements via the input / output interface device according to a computation result, and performs control of the laser processing device 1.

[0034] ​The control unit 90 causes the imaging unit 80 to image the workpiece 100, for example. The control unit 90 performs image processing on an image imaged by the imaging unit 80, for example. The control unit 90 detects a processing line of the workpiece 100 by the image processing, for example. The control unit 90 drives the X-axis direction moving unit 50 and causes the laser beam irradiation unit 20 to irradiate the laser beam 21 so that the condensing spot 27 of the laser beam 21 moves along the processing line, for example.

[0035] Next, the laser beam irradiation unit 20 will be 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. As shown in Figure 3 the laser beam irradiation unit 20 includes a laser oscillator 22, an energy distribution modification unit 30, 40, an imaging lens group 23, a cylindrical lens 24, a mirror 25, and a condensing lens 26.

[0036] The laser oscillator 22 emits a laser beam 21 having a prescribed wavelength for processing the workpiece 100. The laser beam 21 irradiated by the laser beam irradiation unit 20 is a wavelength that is absorbable by the workpiece 100. The beam diameter of the laser beam 21 is 1 mm, for example.

[0037] The energy distribution modification unit 30, 40 is disposed between the laser oscillator 22 and the condensing lens 26. In an embodiment, the energy distribution modification unit 30, 40 is disposed between the laser oscillator 22 and the imaging lens group 23. The energy distribution modification unit 30, 40 includes a mask that is disposed at a prescribed position on the optical path of the laser beam 21, and shapes the beam shape into a prescribed shape by light-shielding a part of the laser beam 21.

[0038] Figure 4 is a perspective view showing an example of the energy distribution modification unit 30 of the embodiment. Figure 5 is a schematic view showing an example of the beam shape at the condensing spot 27. As shown in Figure 4 the energy distribution modification unit 30 includes a mask substrate 31, a transmission portion 32, and a light-shielding portion 33. The mask substrate 31 is in a plate shape that can light-shield the laser beam 21. The mask substrate 31 is disposed at a prescribed position on the optical path of the laser beam 21. The transmission portion 32 is a hole formed in the mask substrate 31. The transmission portion 32 is a portion that transmits the laser beam 21. In an embodiment, the transmission portion 32 is in a slit shape having a slit width of 0.5 mm. The light-shielding portion 33 is a portion that surrounds the transmission portion 32 and shields a part of the laser beam 21. A part of the laser beam 21 that is irradiated to the mask substrate 31 is shielded by the light-shielding portion 33, and the remaining part passes through the transmission portion 32. Thus, the energy distribution modification unit 30 shapes the beam shape of the laser beam 21 into a prescribed shape. Figure 5The beam shape of the laser beam 21 in the Y-axis direction at the focused spot 27 is shown. The processing width of the laser-processed groove 106 is determined by the focused spot width W in the Y-axis direction at the focused spot 27 .

[0039] Figure 6 FIG. 4 is a perspective view showing another example of the energy distribution correction unit 40 according to the embodiment. Figure 6 As shown in FIG. 1 , the energy distribution correction unit 40 includes a mask base 41, a plurality of transmissive portions 42, and a light shielding portion 43. The mask base 41 is in the shape of a plate capable of shielding the laser beam 21. Figure 4 The mask base 41 is similar to the mask base 31 of the example shown. The mask base 41 is disposed at a predetermined position on the optical path of the laser beam 21. The transmissive portion 42 is a hole formed in the mask base 41. The transmissive portion 42 is a portion that transmits the laser beam 21. The light-shielding portion 43 surrounds the transmissive portion 42 and blocks a portion of the laser beam 21. A portion of the laser beam 21 that is irradiated into any hole in the transmissive portion 42 of the mask base 41 is blocked by the light-shielding portion 43, while the remaining portion passes through the transmissive portion 42.

[0040] The transmissive portion 42 includes five transmissive portions 42-1, 42-2, 42-3, 42-4, and 42-5. The transmissive portion 42-3 is a circular hole. The transmissive portions 42-1, 42-2, 42-4, and 42-5 are slit-shaped holes. The transmissive portion 42-3 allows the laser beam 21 to pass through without being blocked. The transmissive portions 42-1, 42-2, 42-4, and 42-5 block a portion of the laser beam 21. The transmissive portions 42-1, 42-2, 42-4, and 42-5 have different slit widths. The slit width of the transmissive portion 42-1 is smaller than the slit width of the transmissive portion 42-2. The slit width of the transmissive portion 42-2 is smaller than the slit width of the transmissive portion 42-4. The slit width of the transmissive portion 42-4 is smaller than the slit width of the transmissive portion 42-5. That is, among the transmissive portions 42-1, 42-2, 42-4, and 42-5, the transmissive portion 42-1 has the smallest slit width, and the transmissive portion 42-5 has the largest slit width. The smaller the slit width, the smaller the passing rate of the laser beam 21. Figure 5 The beam shape of the laser beam 21 in the Y-axis direction at the focused spot 27 is shown. That is, the processing width of the laser processed groove 106 is changed according to the slit width of the transmission portion 42.

[0041] The energy distribution correction unit 40 is configured to be movable in a direction perpendicular to the optical axis of the laser beam 21 by means of a mask moving unit 44. The mask moving unit 44 includes, for example, a micrometer and a motor. Figure 1The control unit 90 shown controls. The energy distribution correction unit 40, for example, in a case where a prescribed operation is accepted from an input section or the like, moves the energy distribution correction unit 40 so that a prescribed transmission portion 42 of the energy distribution correction unit 40 is located on the optical path of the laser beam 21. For example, in a case where the operator selects the transmission portion 42-1 via an input section or the like, the mask moving unit 44 moves the energy distribution correction unit 40 so that the transmission portion 42-1 is located on the optical path of the laser beam 21.

[0042] Figure 7 is a graph showing the energy E0, E C distribution in the Y-axis direction of the laser beam 21. As Figure 7 shown, the energy E0distribution in the Y-axis direction of the laser beam 21 emitted from the laser oscillator 22 is a Gaussian distribution. Since the laser beam 21 is blocked by the light-blocking portions 33, 43, the energy E C of the laser beam 21 passing through the energy distribution correction units 30, 40 is 0 in a portion corresponding to the lower portion of the Gaussian distribution of the energy E0. That is, the energy distribution correction units 30, 40 transmit the central portion of the laser beam 21, in which the energy is strong, by the transmission portions 32, 42, and block the portions of the end portions, in which the energy is weak, by the light-blocking portions 33, 43. Thus, the energy distribution correction units 30, 40 form the lower portion of the Gaussian distribution of the energy E C distribution in the Y-axis direction of the laser beam 21 into a substantially vertical distribution.

[0043] Thus, the forming of the lower portion of the Gaussian distribution of the energy distribution in the Y-axis direction of the laser beam 21 emitted from the laser oscillator 22 into a vertical distribution in the present application means that the transmission portions 32, 42 of the energy distribution correction units 30, 40 transmit the central portion of the laser beam 21 in the Y-axis direction emitted from the laser oscillator 22, the light-blocking portions 33, 43 block the portions of the end portions of the laser beam 21 in the Y-axis direction, and the lower portion of the Gaussian distribution of the energy E C distribution in the Y-axis direction of the laser beam 21 is formed into a substantially vertical distribution.

[0044] Further, in the graph shown in Figure 7 , the lower portion of the Gaussian distribution of the energy E C distribution is recorded vertically, but due to the detouring of light or the like, the graph shape of the lower portion of the Gaussian distribution formed by the blocking of the actual laser beam 21 is not a perfect vertical shape, but is sometimes a steep shape. That is, the substantially vertical can be a perfect vertical shape, or can be a steep shape. When the detouring of light or the like occurs from the light-blocking portions 33, 43, the lower portion of the Gaussian distribution is not a perfect vertical shape, but is a steep shape.

[0045] As Figure 3As shown, the imaging lens group 23 is composed of two or more lenses. In the imaging lens group 23, other lenses having a function of a composite focal length are arranged within the individual focal length of one lens that contributes to imaging. The relative positions between the two or more lenses of the imaging lens group 23 can also be fixed. The imaging lens group 23 can also be installed to the housing of the laser beam irradiation unit 20 in a state where the relative positions between the two or more lenses are fixed. In the embodiment, the imaging lens group 23 is a two-piece combined lens composed of a lens 231 that is a biconcave lens and a lens 232 that is a biconvex lens. The lens 232 has a function of shortening the imaging distance, and the component of one direction of the spherical surface has a function of a cylindrical lens.

[0046] The imaging lens group 23 images the light beam shape of the laser beam 21 whose energy distribution is corrected by the energy distribution correction units 30, 40 on the upper surface of the workpiece 100. The imaging lens group 23 can be relatively moved with respect to the cylindrical lens 24 along the optical axis of the laser beam 21. The imaging lens group 23 can be housed in one housing as in the embodiment, or can be configured to be housed in different housings and the housings can be integrally moved with each other. In addition, the two or more lenses 231, 232 that constitute the imaging lens group 23 are arranged close to each other, and the two or more lenses function as a so-called composite focal length.

[0047] The cylindrical lens 24 adjusts the energy density in the X-axis direction of the laser beam 21 whose energy distribution is corrected by the energy distribution correction units 30, 40. Thereby, Figure 5 The X-axis direction condensing spot length L0 at the condensing spot 27 of the laser beam 21 shown is changed to a condensing spot length L. Only one cylindrical lens 24 is provided on the optical path of the laser beam irradiation unit 20. In the embodiment, the cylindrical lens 24 is a plano-concave lens, but in the present application, it can also be a plano-convex lens.

[0048] The cylindrical lens 24 can be relatively moved with respect to the imaging lens group 23 along the optical path of the laser beam 21. The cylindrical lens 24 is relatively moved with respect to the imaging lens group 23 along the optical path of the laser beam 21, thereby adjusting the energy density in the X-axis direction of the laser beam 21. In this way, the laser beam irradiation unit 20 of the laser processing apparatus 1 of the embodiment moves only one cylindrical lens 24 along the optical path of the laser beam 21, thereby adjusting the energy density in the X-axis direction of the laser beam 21. In addition, in the embodiment, the cylindrical lens 24 is arranged at a position farther back than the imaging lens group 23, but in the present application, the positional relationship between the imaging lens group 23 and the cylindrical lens 24 can also be reversed.

[0049] The mirror 25 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 25 reflects the laser beam 21 that has passed through the cylindrical lens 24.

[0050] The condenser lens 26 condenses the laser beam 21 emitted from the laser oscillator 22 on the workpiece 100 to irradiate the workpiece 100. In the embodiment, the condenser lens 26 condenses the laser beam 21 reflected by the mirror 25. In the embodiment, the focal length of the condenser lens 26 is 100 mm.

[0051] As described above, the laser processing apparatus 1 of the embodiment uses the imaging lens group 23 composed of the plurality of lenses 231, 232 as a relay lens, whereby the main surfaces of the lenses 231, 232 constituting the imaging lens group 23 can be moved along the optical path to the vicinity of the energy distribution correction units 30, 40. In the conventional engineering system, no lens having an effect of changing the focal length, i.e., having a composite focal length, is disposed within the focal length of the lens contributing to imaging, in contrast to which, in the imaging lens group 23, another lens having an effect of a composite focal length is disposed within the focal length of the lens contributing to imaging. Thereby, the distance between the energy distribution correction units 30, 40 and the imaging lens group 23 can be shortened, and thus the miniaturization of the apparatus can be facilitated.

[0052] Further, by assembling an element having a surface of a curvature of a cylindrical lens in the imaging lens group 23, the cylindrical lens used in pairs in the conventional art can be reduced to one piece, and thus the adjustment of the generatrix is not required, and the adjustment can be easily performed. In addition, since the function of a composite focal length can be exerted and the focal length of the relay lens can be shortened, the moving distance of the cylindrical lens 24 can be reduced, and thus the adjustment time can be shortened while maintaining the accuracy of the processing point of the conventional apparatus.

[0053] In addition, the inventors of the present application confirmed the effects of the embodiment. At the time of confirmation, the laser beam irradiation unit 20-2 of the comparative example shown in FIG. 8 was compared with the laser beam irradiation unit 20 of the embodiment. Figure 8 The comparative example is a laser beam irradiation unit 20-2 of a laser processing apparatus of the conventional art. The laser beam irradiation unit 20-2 of the comparative example is different from the laser beam irradiation unit 20 of the embodiment in that the laser beam irradiation unit 20-2 does not include the energy distribution correction units 30, 40. Figure 8 is a schematic view schematically showing the structure of the laser beam irradiation unit 20-2 of the comparative example. In the comparative example, the laser beam irradiation unit 20-2 includes the laser oscillator 22, the mirror 25, and the condenser lens 26. Figure 8 In the comparative example, the same parts as those of the laser beam irradiation unit 20 of the embodiment are denoted by the same reference numerals, and the description thereof is omitted.

[0054] The laser beam irradiation unit 20-2 of the comparative example has a relay lens 28 and a cylindrical lens pair 29 instead of the imaging lens group 23 and the cylindrical lens 24 compared to the laser beam irradiation unit 20 of the embodiment. The relay lens 28 transmits the laser beam 21 whose energy distribution is corrected by the energy distribution correction units 30, 40 to the cylindrical lens pair 29. The relay lens 28 is a spherical biconvex lens. The cylindrical lens pair 29 is composed of two cylindrical lenses. The cylindrical lens pair 29 is a two-piece combined lens composed of a cylindrical lens 291 which is a plano-concave lens and a cylindrical lens 292 which is a plano-concave lens. The two cylindrical lenses 291, 292 which compose the cylindrical lens pair 29 can move the relative positions to each other. In addition, the lens 232 which is a biconvex lens of the imaging lens group 23 of the embodiment and the relay lens 28 of the comparative example are both f = -600.

[0055] In the laser beam irradiation unit 20-2 of the comparative example, the distance D2 between the energy distribution correction units 30, 40 and the relay lens 28 is 600 mm. In contrast, in the laser beam irradiation unit 20 of the embodiment, the distance Dl between the energy distribution correction units 30, 40 and the imaging lens group 23 is 173 mm. Therefore, it is known that the distance between the energy distribution correction units 30, 40 and the imaging lens group 23 can be shortened by using the imaging lens group 23 composed of the plurality of lenses 231, 232 as a relay lens.

[0056] In addition, in the laser beam irradiation unit 20-2 of the comparative example, the maximum moving distance D4 of each of the cylindrical lenses 291, 292 of the cylindrical lens pair 29 for adjustment in the optical path direction is 72 mm. In contrast, in the laser beam irradiation unit 20 of the embodiment, the maximum moving distance D3 of the cylindrical lens 24 for adjustment in the optical path direction is 41 mm. Therefore, it is known that the laser processing apparatus 1 can shorten the distance between the energy distribution correction units 30, 40 and the imaging lens group 23 and can reduce the moving distance of the cylindrical lens 24 by using the imaging lens group 23 composed of the plurality of lenses 231, 232 as a relay lens.

[0057] 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.

[0058] For example, the imaging lens group of the present application is not limited to the combination of the embodiment. Figure 9This is a schematic diagram illustrating the structure of imaging lens group 23-1 in the first modification. Imaging lens group 23-1 is a three-lens combination, with lens 233 (a spherical biconcave lens), lens 234 (a plano-concave lens), and lens 235 (a plano-convex lens) arranged sequentially along the optical path. In the first modification, lenses 233, 234, and 235 are housed in a single housing. Lenses 234 and 235 are positioned within the focal length of lens 233. Lenses 234 and 235 function as a composite focal length, facilitating focal length changes.

[0059] In addition, the imaging lens group of the present invention is not limited to a combined lens. Figure 10 This is a schematic diagram showing the structure of the imaging lens group 23-2 of the second modified example. The imaging lens group 23-2 is composed of a relay lens 236 and an expander 237. In the second modified example, the relay lens 236 is a biconvex lens. The expander 237 includes a lens 238, which is a plano-concave lens, and a lens 239, which is a plano-convex lens, which can adjust the distance between the lenses. The expander 237 is arranged within the individual focal lengths of the relay lens 236. The expander 237 has the function of synthesizing the focal length, which helps to change the focal length.

Claims

1. A laser processing device, characterized in that: The laser processing device has: A chuck table that holds the workpiece; a laser beam irradiation unit for irradiating a laser beam having a wavelength that is absorptive to a workpiece held by the chuck table; an X-axis direction moving unit that moves the chuck table and the laser beam irradiation unit relative to each other in the X-axis direction as a processing feed direction; and a Y-axis direction moving unit which moves the chuck table and the laser beam irradiation unit relative to each other in the Y-axis direction which is an indexing feed direction perpendicular to the machining feed direction; The laser beam irradiation unit comprises: Laser oscillator; a condenser lens for condensing the laser beam emitted from the laser oscillator; an energy distribution correction unit disposed between the laser oscillator and the condensing lens, which corrects the lower portion of the Gaussian distribution of the energy distribution in the Y-axis direction of the laser beam emitted from the laser oscillator into a vertical distribution; an imaging lens group consisting of two or more lenses, which forms an image of the beam shape of the laser beam whose energy distribution has been corrected by the energy distribution correction unit on the upper surface of the workpiece, wherein the relative positions of the two or more lenses of the imaging lens group are fixed, and the imaging lens group includes a spherical biconcave lens; and A cylindrical lens adjusts the energy density in the X-axis direction of the laser beam whose energy distribution has been corrected by the energy distribution correction unit. The distance between the imaging lens group and the cylindrical lens is relatively moved to adjust the spot shape of the laser beam on the upper surface of the workpiece.

2. The laser processing device according to claim 1, wherein The imaging lens group includes a relay lens and an expander.

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