Laser processing equipment

Abstract

To provide a laser processing device capable of detecting a stain of a condenser lens.SOLUTION: A laser processing device includes: an oscillator 41 for irradiating a held plate-like object 100 with a laser beam 4 for processing; a condenser 42 for condensing the laser beam 4 for processing; a light source 61 for irradiating the plate-like object 100 with a laser beam 5 for detection through the condenser 42; an astigmatism addition unit 66 for adding astigmatism to reflected light 6 of the laser beam 5 for detection reflected on an upper surface 101 of the plate-like object 100; a detection element 69 for outputting a detection value according to the condensed state of the reflected light 6 added with the astigmatism; a storage part for storing relative relation information between each position in a Z-axis direction of the condenser 42 and the detection value; a comparison part for comparing newly acquired relative relation information at a predetermined timing with relative relation information already stored in the storage part; and a determination part for determining whether or not to have a predetermined or more difference in the compared relative relation information.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] One method known for dividing a semiconductor wafer into device chips involves irradiating the wafer with a laser beam of a wavelength that is transparent to the wafer, with a focal point positioned inside the wafer, to form a modified layer that serves as the starting point for division (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3408805 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when laser processing is performed using the method described in Patent Document 1, the focal point is positioned near the upper surface of the wafer, so ablation may occur on the upper surface of the wafer, generating debris. If debris scatters and adheres to the focusing lens, the laser beam passing through the focusing lens is blocked by the debris, and the amount of energy of the laser beam focused at the focusing point becomes insufficient. This may adversely affect the formation of the modified layer, making it difficult to divide the wafer along the modified layer.

[0005] The present invention has been made in view of the above problems, and an object of the present invention is to provide a laser processing apparatus capable of detecting dirt on a condenser lens. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, the laser processing apparatus of the present invention includes a chuck table having a holding surface for holding a plate-like object, a laser beam irradiation unit including an oscillator for irradiating a processing laser beam having a wavelength that is transparent to the plate-like object held on the holding surface and a condenser for condensing the processing laser beam, a Z-axis movement unit for moving the condenser in the Z-axis direction that is a direction perpendicular to the holding surface, a height position detection unit for detecting the height of the upper surface of the plate-like object held on the holding surface, and a control unit for controlling each component, and the height position detection unit detects the height of the upper surface of the plate-like object held on the holding surface. a light source which irradiates a detection laser beam through the condenser onto the held plate-like object; an astigmatism adding unit which adds astigmatism to reflected light of the detection laser beam which is irradiated from the light source onto the plate-like object and reflected by an upper surface of the plate-like object; and a detection element which receives the reflected light to which astigmatism has been added and outputs a detection value according to a condensing state of the received reflected light, wherein the control unit includes a detection section which acquires the detection value by the detection element when the detection laser beam is irradiated onto the plate-like object while moving the condenser in the Z-axis direction; and a first phase shifter which indicates a relative relationship between each position of the condenser in the Z-axis direction and the detection value. versus a storage unit that stores relational information; a comparison unit that compares second relative relation information indicating a relative relation between each position in the Z-axis direction of the collector and the detection value newly acquired at a predetermined timing with the first relative relation information already stored in the storage unit; and versus and a determination unit that determines whether or not there is a difference of a predetermined value or more with respect to the relationship information and outputs a determination result.

[0007] In the laser processing apparatus of the present invention, a detection value obtained when the focal point of the detection laser beam is positioned on the upper surface of the plate-like object is set as a reference value, and the comparison unit compares the position of the condenser in the Z-axis direction where the detection value becomes the reference value with the position of the condenser that has already been stored in the storage unit. 1. In relational information 1. The position and the newly acquired corresponding Second In relational information SecondThe determining unit compares the position of the The first position and the second position position Toga It may be possible to determine whether or not there is a difference equal to or greater than a predetermined value and output the determination result.

[0008] In addition, the present invention Another aspect Laser processing equipment teeth , the control unit for controlling each component, and the height position detection unit includes a light source that irradiates the plate-like object held on the holding surface with a detection laser beam through the light condenser, and a control unit for controlling each component. The height position detection unit detects the height of the upper surface of the plate-like object held on the holding surface by detecting the height of the detection laser beam. The height position detection unit detects the height of the upper surface of the plate-like object held on the holding surface by detecting the height of the detection laser beam through the light condenser. the control unit includes an astigmatism adding unit which adds astigmatism to the reflected light, and a detection element which receives the reflected light to which astigmatism has been added and outputs a detection value according to a focusing state of the received reflected light, the control unit including a detection section which acquires a detection value detected by the detection element when the detection laser beam is irradiated onto the plate-like object while moving the collector in the Z-axis direction, a memory section which stores relative relationship information between each position of the collector in the Z-axis direction and the detection value, a comparison section which compares the relative relationship information newly acquired at a predetermined timing with the relative relationship information already stored in the memory section, and a determination section which determines whether or not there is a difference of a predetermined value or more between the relative relationship information compared by the comparison section and outputs a determination result; The focus of the detection laser beam is located between the focus of the collector and the collector. It is characterized by . Effect of the Invention

[0009] The present invention can detect dirt on the condenser lens. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view showing an example of the configuration of a laser processing device according to an embodiment. [Diagram 2] FIG. 2 is a schematic diagram showing a schematic configuration of the periphery of the processing point including the laser beam irradiation unit shown in FIG. [Diagram 3] FIG. 3 is an explanatory diagram of the astigmatism of the height position detection unit shown in FIG. [Figure 4] FIG. 4 is an explanatory diagram showing a case where the planar shape of reflected light at a detection element of the height position detection unit shown in FIG. 2 is a vertically elongated ellipse. [Diagram 5] FIG. 5 is an explanatory diagram showing a case where the planar shape of reflected light at a detection element of the height position detection unit shown in FIG. 2 is circular. [Figure 6] FIG. 6 is an explanatory diagram showing a case where the planar shape of reflected light at a detection element of the height position detection unit shown in FIG. 2 is a horizontally elongated ellipse. [Figure 7] FIG. 7 is an explanatory diagram showing the relationship between the position of the collector in the Z-axis direction and the detection value by the detection element. [Figure 8] FIG. 8 is a schematic diagram showing another example of the light collecting position in the collector shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The form (embodiment) for carrying out 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 embodiment. Furthermore, the components described below include those that a person skilled in the art can easily imagine and those that are substantially the same. Furthermore, the configurations described below can be appropriately combined. Furthermore, various omissions, substitutions, or modifications of the configurations can be made without departing from the gist of the present invention.

[0012] [Embodiment] First, the configuration of the laser processing device 1 according to the embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing an example of the configuration of the laser processing device 1 according to the embodiment. FIG. 2 is a schematic diagram showing a schematic configuration of the periphery of the processing point including the laser beam irradiation unit 40 shown in FIG. 1. FIG. 3 is an explanatory diagram of astigmatism of the height position detection unit 60 shown in FIG. 2. FIG. 4 is an explanatory diagram showing a case where the planar shape of the reflected light 6 at the detection element 69 of the height position detection unit 60 shown in FIG. 2 is a vertically elongated ellipse. FIG. 5 is an explanatory diagram showing a case where the planar shape of the reflected light 6 at the detection element 69 of the height position detection unit 60 shown in FIG. 2 is a circular shape. FIG. 6 is an explanatory diagram showing a case where the planar shape of the reflected light 6 at the detection element 69 of the height position detection unit 60 shown in FIG. 2 is a horizontally elongated ellipse. FIG. 7 is an explanatory diagram showing the relationship between the position of the condenser 42 in the Z-axis direction and the detection value by the detection element 69.

[0013] 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 a horizontal plane. The Z-axis direction is a direction perpendicular to the X-axis and Y-axis directions. In the laser processing apparatus 1 of the embodiment, the processing feed direction is the X-axis direction, and the indexing feed direction is the Y-axis direction.

[0014] The laser processing apparatus 1 includes a chuck table 10, a processing feed unit 20, an indexing feed unit 30, a laser beam irradiation unit 40, a Z-axis direction moving unit 50, a height position detection unit 60, an imaging unit 70, a display unit 80, and a control unit 90. The laser processing apparatus 1 according to the embodiment is an apparatus for processing the plate-like object 100 by irradiating the plate-like object 100 held on the chuck table 10 with a processing laser beam 4 by the laser beam irradiation unit 40. The processing of the plate-like object 100 by the laser processing apparatus 1 is, for example, a modified layer forming process in which a modified layer is formed inside the plate-like object 100 by the processing laser beam 4 having a wavelength that is transparent to the plate-like object 100.

[0015] The plate-like object 100 is made of, for example, silicon (Si), sapphire (Al 2 O 3 ), gallium arsenide (GaAs), silicon carbide (SiC), or lithium tantalate (LiTa 3 ) or the like as a substrate, such as a disk-shaped semiconductor device wafer or an optical device wafer. Note that, although the plate-shaped object 100 is disk-shaped in the embodiment, it does not have to be disk-shaped in the present invention. The plate-shaped object 100 is transported and processed in a state in which it is supported within an opening of the frame 110, for example, with an annular frame 110 attached and a tape 111 having a diameter larger than the outer diameter of the plate-shaped object 100 attached to the back surface of the plate-shaped object 100.

[0016] The chuck table 10 holds the plate-like object 100 on a holding surface 11. The holding surface 11 is a disk shape made 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, for example, via a vacuum suction path. The chuck table 10 holds the plate-like object 100 placed on the holding surface 11 by suction. A plurality of clamps 12 are arranged around the chuck table 10 to clamp an annular frame 110 that supports the plate-like object 100.

[0017] The chuck table 10 is rotated about an axis parallel to the Z-axis direction by a rotation unit 13. The rotation unit 13 is supported by an X-axis direction moving plate 14. The rotation unit 13 and the chuck table 10 are moved in the X-axis direction by a processing feed unit 20 via the X-axis direction moving plate 14. The rotation unit 13 and the chuck table 10 are moved in the Y-axis direction by an indexing feed unit 30 via the X-axis direction moving plate 14, the processing feed unit 20, and the Y-axis direction moving plate 15.

[0018] The processing feed unit 20 is a unit that relatively moves the chuck table 10 and the laser beam irradiation unit 40 in the X-axis direction, which is the processing feed direction. In the embodiment, the processing feed unit 20 moves the chuck table 10 in the X-axis direction. In the embodiment, the processing feed unit 20 is installed on the device body 2 of the laser processing device 1.

[0019] The processing feed unit 20 supports the X-axis moving plate 14 so as to be movable in the X-axis direction. In an embodiment, the processing feed unit 20 includes a well-known ball screw 21, a well-known pulse motor 22, and a well-known guide rail 23. The ball screw 21 is provided so as to be rotatable about its axis. The pulse motor 22 rotates the ball screw 21 about its axis. The guide rail 23 supports the X-axis moving plate 14 so as to be movably in the X-axis direction. The guide rail 23 is provided fixed to the Y-axis moving plate 15.

[0020] The indexing feed unit 30 is a unit that relatively moves the chuck table 10 and the laser beam irradiation unit 40 in the Y-axis direction, which is the indexing feed direction. In the embodiment, the indexing feed unit 30 moves the chuck table 10 in the Y-axis direction. In the embodiment, the indexing feed unit 30 is installed on the device body 2 of the laser processing device 1.

[0021] The indexing feed unit 30 supports the Y-axis moving plate 15 so as to be movable in the Y-axis direction. In this embodiment, the indexing feed unit 30 includes a well-known ball screw 31, a well-known pulse motor 32, and a well-known guide rail 33. The ball screw 31 is provided so as to be rotatable about its axis. The pulse motor 32 rotates the ball screw 31 about its axis. The guide rail 33 supports the Y-axis moving plate 15 so as to be movably in the Y-axis direction. The guide rail 33 is provided and fixed to the device body 2.

[0022] The laser beam irradiation unit 40 is a unit that irradiates a processing laser beam 4 having a wavelength that is transparent to the plate-like object 100 held on the holding surface 11 of the chuck table 10. As shown in FIG. 2, the laser beam irradiation unit 40 includes an oscillator 41 and a condenser 42.

[0023] The oscillator 41 emits a processing laser beam 4 having a predetermined wavelength for processing the plate-like object 100. The processing laser beam 4 emitted by the laser beam irradiation unit 40 has a wavelength that is transparent or absorbent to the plate-like object 100. The processing laser beam 4 emitted by the oscillator 41 is, for example, a YAG laser beam or a YVO laser beam. The wavelength of the processing laser beam 4 is, for example, 1064 nm in the embodiment, but is not limited to this in the present invention.

[0024] The condenser 42 is a focusing lens that focuses the processing laser beam 4 emitted from the oscillator 41 onto the plate-like object 100 held on the holding surface 11 of the chuck table 10, and irradiates the plate-like object 100. In the embodiment, the condenser 42 focuses the processing laser beam 4 that has passed through the dichroic mirror 43 onto the plate-like object 100.

[0025] The dichroic mirror 43 is disposed on the optical path of the processing laser beam 4 between the oscillator 41 and the condenser 42. The dichroic mirror 43 transmits the processing laser beam 4 emitted from the oscillator 41 toward the holding surface 11 of the chuck table 10. The dichroic mirror 43 also reflects the detection laser beam 5 emitted from a light source 61 of a height position detection unit 60 (described later) toward the holding surface 11 of the chuck table 10.

[0026] The Z-axis direction moving unit 50 shown in Fig. 1 is a unit that moves the focal point of the processing laser beam 4 focused by the focusing device 42 shown in Fig. 2 in the optical axis direction. The optical axis direction is the Z-axis direction that is perpendicular to the holding surface 11 of the chuck table 10. The Z-axis direction moving unit 50 moves the chuck table 10 and at least the focusing device 42 of the laser beam irradiation unit 40 relatively in the Z-axis direction. In the embodiment, the Z-axis direction moving unit 50 is installed on the vertical wall portion 3 that stands upright from the device body 2 of the laser processing device 1.

[0027] The Z-axis movement unit 50 supports at least the condenser 42 of the laser beam irradiation unit 40 so as to be movable in the Z-axis direction. In the embodiment, the Z-axis movement unit 50 includes a well-known ball screw 51, a well-known pulse motor 52, and a well-known guide rail 53. The ball screw 51 is provided so as to be rotatable about its axis. The pulse motor 52 rotates the ball screw 51 about its axis. The guide rail 53 supports the laser beam irradiation unit 40 so as to be movably in the Z-axis direction. The guide rail 53 is provided and fixed to the vertical wall portion 3.

[0028] 2 is a unit that detects the Z-axis position (height) of the top surface 101 of the plate-like object 100. In the embodiment, the Z-axis position is the height (Z coordinate) of the top surface of the workpiece 100 placed on the holding surface 11 at a predetermined position (XY position) in a horizontal plane, which is the reference plane (0 μm). The laser processing apparatus 1 of the embodiment uses the height position detection unit 60 to detect dirt on the lens of the condenser 42 (described later). The height position detection unit 60 includes a light source 61, a beam expander 62, a mirror 63, a beam splitter 64, an astigmatism adding unit 66, and a detection element 69.

[0029] The light source 61 emits a detection laser beam 5 for detecting the Z-axis position (height) of the upper surface 101 of the plate-like object 100 held on the holding surface 11 of the chuck table 10. The light source 61 includes, for example, an SLD (Super Luminescent Diode) light source. The light source 61 irradiates the detection laser beam 5 through a condenser 42 to the plate-like object 100 held on the holding surface 11 of the chuck table 10.

[0030] In the embodiment, the focal point of the detection laser beam 5 is positioned at the same position as the focal point of the processing laser beam 4. In the embodiment, the light source 61 irradiates the dichroic mirror 43 through a beam expander 62, a mirror 63, and a beam splitter 64 in this order. The dichroic mirror 43 reflects the detection laser beam 5 to the condenser 42 side.

[0031] The beam expander 62 converts the detection laser beam 5 emitted from the light source 61 into parallel light of a predetermined magnification. The mirror 63 reflects the detection laser beam 5 converted into parallel light by the beam expander 62 toward the beam splitter 64.

[0032] The beam splitter 64 reflects the detection laser beam 5 reflected by the mirror 63 toward the dichroic mirror 43. The beam splitter 64 also transmits the reflected light 6 of the detection laser beam 5 reflected by the upper surface 101 of the plate-like object 100 toward the astigmatism adding unit 66, as described below. The beam splitter 64 has a reflection:transmission ratio of, for example, 1:1, and reflects and guides the detection laser beam 5 toward the dichroic mirror 43, and also transmits and guides the reflected light 6 incident from the dichroic mirror 43 side toward the astigmatism adding unit 66.

[0033] The astigmatism adding unit 66 adds astigmatism to the reflected light 6 that has passed through the beam splitter 64. The astigmatism adding unit 66 includes a convex lens 67 and a cylindrical lens 68. The convex lens 67 collects the reflected light 6 that has passed through the beam splitter 64. The reflected light 6 collected by the convex lens 67 enters the cylindrical lens 68.

[0034] As shown in Fig. 3, the cylindrical lens 68 has a substantially semi-cylindrical shape obtained by halving a cylinder along the axial direction. The cylindrical lens 68 has a lens effect only in the α direction, for example, and has no lens effect in the β direction. That is, when the reflected light 6 of the detection laser beam 5 reflected by the upper surface 101 of the plate-like object 100 passes through the cylindrical lens 68, the focal position in the α direction is shifted from the focal position in the β direction, causing astigmatism, and enters the detection element 69 (see Figs. 4, 5, and 6).

[0035] 3, 4, 5, and 6, the planar shape of the reflected light 6-1, 6-2, 6-3 that has passed through the cylindrical lens 68 changes from vertically elongated ellipse to circle to horizontally elongated ellipse depending on the position on the optical axis. Therefore, when the reflected light 6-1, 6-2, 6-3 is received by the detection element 69 consisting of a four-segment photodiode, the balance of the amount of light incident on each of the divided regions 69-1, 69-2, 69-3, 69-4 changes depending on the planar shape of the reflected light 6-1, 6-2, 6-3.

[0036] 4, when the reflected light 6-1 has a vertically elongated ellipse, the amount of light incident on divided regions 69-1 and 69-3 in the detection element 69 is greater than the amount of light incident on divided regions 69-2 and 69-4. In this case, the difference between the sum of the amount of light incident on divided regions 69-1 and 69-3 and the sum of the amount of light incident on divided regions 69-2 and 69-4 is a positive value (a value greater than 0). When the difference is a positive value, the focal point of the detection laser beam 5 is located below the upper surface 101 of the plate-like object 100.

[0037] 5, when the reflected light 6-2 is circular, the amounts of light incident on divided regions 69-1, 69-2, 69-3, and 69-4 in the detection element 69 are equal. In this case, the difference between the sum of the amounts of light incident on divided regions 69-1 and 69-3 and the sum of the amounts of light incident on divided regions 69-2 and 69-4 is 0. When the difference is 0, the focal point of the detection laser beam 5 is located on the upper surface 101 of the plate-like object 100.

[0038] 6, when the reflected light 6-1 has a horizontally elongated ellipse, the amount of light incident on divided regions 69-2 and 69-4 in the detection element 69 is greater than the amount of light incident on divided regions 69-1 and 69-3. In this case, the difference between the sum of the amount of light incident on divided regions 69-1 and 69-3 and the sum of the amount of light incident on divided regions 69-2 and 69-4 is a negative value (a value smaller than 0). When the difference is a negative value, the focal point of the detection laser beam 5 is located above the upper surface 101 of the plate-like object 100.

[0039] The detection element 69 receives the reflected light 6 to which astigmatism has been added by the astigmatism adding unit 66. The detection element 69 outputs a detection value [V] corresponding to the focusing state (focused image) of the received reflected light 6 to a control unit 90 described later. If the detection value is H, the amount of incident light detected by the divided area 69-1 is A, the amount of incident light detected by the divided area 69-2 is B, the amount of incident light detected by the divided area 69-3 is C, and the amount of incident light detected by the divided area 69-4 is D, the detection value is calculated from the formula shown below: H={(A+C)-(B+D)} / (A+B+C+D).

[0040] 1 captures an image of the plate-like object 100 held on the holding surface 11 of the chuck table 10. The imaging unit 70 includes a CCD (Charge Coupled Device) camera or an infrared camera that captures an image of the plate-like object 100 held on the holding surface 11. The imaging unit 70 is fixed, for example, adjacent to the condenser 42 (see FIG. 2) of the laser beam irradiation unit 40. The imaging unit 70 captures an image of the plate-like object 100 to obtain an image for performing alignment between the plate-like object 100 and the laser beam irradiation unit 40, and outputs the obtained image to the control unit 90.

[0041] The display unit 80 is a display section configured by a liquid crystal display device or the like. The display unit 80 displays, for example, a setting screen for processing conditions, the state of the plate-like object 100 captured by the imaging unit 70, the state of the processing operation, detection information by the height position detection unit 60, and the like on the display surface. When the display surface of the display unit 80 includes a touch panel, the display unit 80 may include an input unit. The input unit can receive various operations such as an operator registering processing content information. The input unit may be an external input device such as a keyboard. The display unit 80 switches information and images displayed on the display surface by operations from the input unit or the like. The display unit 80 may include an alarm device. The alarm device emits at least one of sound and light to notify the operator of the laser processing device 1 of predetermined alarm information. The alarm device may be an external alarm device such as a speaker or a light-emitting device.

[0042] The control unit 90 controls each of the above-mentioned components of the laser processing device 1, and causes the laser processing device 1 to execute processing operations and the like for the plate-like object 100. The control unit 90 controls the processing feed unit 20, the indexing feed unit 30, the laser beam irradiation unit 40, the Z-axis direction moving unit 50, the height position detection unit 60, the imaging unit 70, and the display unit 80. The control unit 90 is a computer including an arithmetic processing device as a calculation means, a storage device as a storage means, and an input / output interface device as a communication means. The arithmetic processing device includes, for example, a microprocessor such as a CPU (Central Processing Unit). The storage device has a memory such as 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 each of the above-mentioned components via the input / output interface device according to the calculation results, and controls the laser processing device 1.

[0043] The control unit 90, for example, causes the imaging unit 70 to capture an image of the plate-like object 100. The control unit 90, for example, performs image processing of the image captured by the imaging unit 70. The control unit 90, for example, detects the processing line of the plate-like object 100 by image processing. The control unit 90, for example, drives the processing feed unit 20 so that the processing point, which is the focal point of the processing laser beam 4, moves along the processing line, and causes the laser beam irradiation unit 40 to irradiate the processing laser beam 4. The control unit 90 acquires the detection result by the height position detection unit 60. As shown in FIG. 1, the control unit 90 has a detection unit 91, a memory unit 92, a comparison unit 93, a determination unit 94, and a notification unit 95.

[0044] The detection unit 91 acquires a detection value by the detection element 69. For example, the detection unit 91 acquires a detection value when the detection laser beam 5 is irradiated onto the plate-like object 100 held on the holding surface 11 of the chuck table 10 while the Z-axis direction moving unit 50 moves the condenser 42 in the Z-axis direction.

[0045] The memory unit 92 stores relative relationship information 200 between each position of the condenser 42 in the Z-axis direction and the detection value when the detection laser beam 5 is irradiated onto the plate-like object 100 when the condenser 42 is at each position (see FIG. 7). In FIG. 7, the relative relationship information 201 is data that is acquired in a state in which no debris or the like is attached to the condenser 42 and the condenser 42 is normally collecting light, and is stored in advance. Also, in FIG. 7, the relative relationship information 202 is data that is newly acquired at a predetermined timing, such as when the laser processing apparatus 1 is calibrated. The predetermined timing is, for example, every time a predetermined number of plate-like objects 100 are processed, which means, in other words, after at least one plate-like object 100 is processed after cleaning or replacing the condenser 42.

[0046] The comparison unit 93 compares the newly acquired relative relationship information (for example, relative relationship information 202 in FIG. 7) at a predetermined timing with the relative relationship information already stored in the storage unit 92 (for example, relative relationship information 201 in FIG. 7). When debris or the like is attached to the collector 42, the detection laser beam 5 passing through the collector 42 is blocked by the debris or the like, thereby reducing the amount of incident light entering the detection element 69. Furthermore, when the detection laser beam 5 passing through the collector 42 is blocked by the debris or the like, the position of the focal point of the detection laser beam 5 in the Z-axis direction changes.

[0047] The comparison unit 93 compares, for example, a position 211 in the relative relationship information 201 already stored in the storage unit 92 with a position 212 in the relative relationship information 202 newly acquired at a predetermined timing, for the position [μm] in the Z-axis direction where the detection value becomes a reference value 210. In the embodiment, the reference value 210 is a detection value obtained in a state where the focal point of the detection laser beam 5 is positioned on the upper surface 101 of the plate-like object 100 held on the holding surface 11 of the chuck table 10, i.e., 0.

[0048] The determination unit 94 acquires the comparison result by the comparison unit 93. The determination unit 94 determines whether or not there is a difference of a predetermined value or more between the relative relationships 92-1 and 92-2 compared by the comparison unit 93, and outputs the determination result. For example, the determination unit 94 determines whether or not there is a difference of a predetermined value or more between the positions 211 and 212 in the Z-axis direction compared by the comparison unit 93. That is, the determination unit 94 determines whether or not the difference between the position 211 in the relative relationship information 201 already stored in the storage unit 92 and the position 212 in the relative relationship information 202 newly acquired at a predetermined timing is a predetermined threshold value 220 or more. If the difference between the positions 211 and 212 in the Z-axis direction is the predetermined threshold value 220 or more, the determination unit 94 determines that the light collector 42 is dirty.

[0049] The notification unit 95 issues a warning when the determination unit 94 determines that the relative relationship information 201, 202 compared by the comparison unit 93 has a difference of a predetermined value or more. The notification unit 95 issues a preset warning to the operator of the laser processing device 1, for example, by emitting at least one of sound and light. The notification unit 95 may cause a warning device included in the display unit 80 or an external warning device to issue the warning. Moreover, the notification unit 95 does not issue a warning when the determination unit 94 determines that the relative relationship information 201, 202 compared by the comparison unit 93 does not have a difference of a predetermined value or more.

[0050] As described above, the laser processing apparatus 1 according to the embodiment detects lens contamination by utilizing the phenomenon in which the position of the focal point in the Z-axis direction changes when the condenser 42 (condensing lens) is contaminated by debris, etc. Specifically, astigmatism is added to the reflected light 6 of the detection laser beam 5 irradiated onto the plate-like object 100, and the position in the Z-axis direction (focused position) when the condenser 42 positions the focal point on the upper surface 101 of the plate-like object 100 is detected based on a detection value corresponding to the focused state (focused image).

[0051] When the light collecting position moves from position 211 before contamination of collector 42 to position 212 after contamination, and the movement distance exceeds a predetermined threshold value 220, it can be determined that collector 42 is contaminated and requires cleaning or replacement. As a result, contamination of collector 42 can be detected at an early stage, and collector 42 can be cleaned or replaced before a splitting failure occurs, which contributes to improving yield.

[0052] The present invention is not limited to the above embodiment. In other words, various modifications can be made without departing from the gist of the present invention. For example, the astigmatism adding unit 66 may include a toric lens instead of the cylindrical lens 68.

[0053] In addition, for example, the focal point of the detection laser beam 5 is positioned at the same position as the focal point of the processing laser beam 4 in the embodiment, but in the present invention, it may be positioned between the focal point of the processing laser beam 4 and the collector 42. Fig. 8 is a schematic diagram showing another example of the focal position in the collector 42 shown in Fig. 2.

[0054] 8, the processing laser beam 4 is incident on the collector 42 as parallel light. That is, the focal position of the collector 42 is equal to the position of the focal point 4-1 of the processing laser beam 4. In the example shown in FIG. 8, the focal point 5-1 of the detection laser beam 5 is positioned at the position of the focal point 4-1 of the processing laser beam 4, that is, between the focal point of the collector 42 and the collector 42.

[0055] When the positions of the focusing points 4-1 and 5-1 are different in this way, for example, a lens or the like for expanding the diameter of the detection laser beam 5 may be provided in the optical path between the beam splitter 64 and the dichroic mirror 43 shown in Fig. 2. The detection laser beam 5 is expanded in diameter by the lens or the like and enters the condenser 42 in a condensed state such that the spot diameter gradually decreases toward the condenser 42. As a result, the focal position of the detection laser beam 5 becomes shallower and the spot diameter of the reflected light 6 detected by the detection element 69 becomes smaller, so that the focal position is easily changed even by a small amount of dirt, and the accuracy of dirt detection can be further improved. [Explanation of symbols]

[0056] 1 Laser processing equipment 4. Laser beam for processing 5 Detection laser beam 6, 6-1, 6-2, 6-3 Reflected light 10 Chuck table 11 Holding surface 40 Laser beam irradiation unit 41 Oscillator 42 Concentrator 50 Z-axis direction movement unit 60 Height position detection unit 61 Light source 66 Astigmatism Add-on Unit 69 Detector element 90 Control Unit 91 Detection unit 92 Memory section 93 Comparison Section 94 Judgment section 95 Notification Department 100 Plate-shaped objects 101 Top surface 200, 201, 202 Relative relationship information 210 Reference Value 211, 212 position 220 Threshold

Claims

1. A laser processing apparatus comprising: a chuck table having a holding surface for holding a plate-like object; a laser beam irradiation unit including an oscillator for irradiating a processing laser beam having a wavelength that is transparent to the plate-like object held on the holding surface and a condenser for condensing the processing laser beam; a Z-axis direction moving unit that moves the condenser in a Z-axis direction that is a direction perpendicular to the holding surface; a height position detection unit for detecting the height of an upper surface of the plate-like object held on the holding surface; A control unit for controlling each of the components; Including, The height position detection unit includes: a light source that irradiates a detection laser beam through the condenser onto the plate-like object held on the holding surface; an astigmatism adding unit that adds astigmatism to reflected light of a detection laser beam that is irradiated from the light source to the plate-like object and reflected by an upper surface of the plate-like object; a detection element that receives the reflected light to which astigmatism has been added and outputs a detection value according to a focusing state of the received reflected light; Equipped with The control unit a detection unit that acquires a detection value detected by the detection element when the detection laser beam is irradiated onto the plate-like object while moving the condenser in a Z-axis direction; a storage unit configured to store first relative relationship information indicating a relative relationship between each position of the collector in the Z-axis direction and the detection value; a comparison unit that compares second relative relationship information indicating a relative relationship between each position of the collector in the Z-axis direction and the detection value newly acquired at a predetermined timing with the first relative relationship information already stored in the storage unit; a determination unit that determines whether or not the first relative relationship information and the second relative relationship information compared by the comparison unit have a difference of a predetermined value or more, and outputs a determination result; The present invention is characterized in that it comprises Laser processing equipment.

2. a detection value obtained when the focal point of the detection laser beam is positioned on the upper surface of the plate-like object is defined as a reference value; the comparison unit compares a first position in the first relative relationship information already stored in the storage unit with a second position in the second relative relationship information newly acquired at a predetermined timing, for a position in the Z-axis direction of the collector at which the detection value becomes a reference value; the determining unit determines whether or not there is a difference between the first position and the second position compared by the comparing unit that is equal to or greater than a predetermined value, and outputs a determination result. The laser processing apparatus according to claim 1.

3. A laser processing apparatus comprising: a chuck table having a holding surface for holding a plate-like object; a laser beam irradiation unit including an oscillator for irradiating a processing laser beam having a wavelength that is transparent to the plate-like object held on the holding surface and a condenser for condensing the processing laser beam; a Z-axis direction moving unit that moves the condenser in a Z-axis direction that is a direction perpendicular to the holding surface; a height position detection unit for detecting the height of an upper surface of the plate-like object held on the holding surface; A control unit for controlling each of the components; Including, The height position detection unit includes: a light source that irradiates a detection laser beam through the condenser onto the plate-like object held on the holding surface; an astigmatism adding unit that adds astigmatism to reflected light of a detection laser beam that is irradiated from the light source to the plate-like object and reflected by an upper surface of the plate-like object; a detection element that receives the reflected light to which astigmatism has been added and outputs a detection value according to a focusing state of the received reflected light; Equipped with The control unit a detection unit that acquires a detection value detected by the detection element when the detection laser beam is irradiated onto the plate-like object while moving the condenser in a Z-axis direction; a storage unit that stores relative relationship information between each position of the collector in the Z-axis direction and the detection value; a comparison unit that compares the relative relationship information newly acquired at a predetermined timing with the relative relationship information already stored in the storage unit; a determination unit that determines whether or not the relative relationship information compared by the comparison unit has a difference equal to or greater than a predetermined value and outputs a determination result; Equipped with The focusing point of the detection laser beam is located between the focus of the collector and the collector. Laser processing equipment.

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