Laser processing equipment

Abstract

To provide a laser processing device that is able to efficiently confirm whether a crack has occurred from a modified layer.SOLUTION: A laser processing device 1 includes: a condenser lens 52 to which a laser beam 37 is emitted to form a converging point of the laser beam 37 and form a focal point of a camera 41; a focal-point adjustment unit 43 that adjusts a height of the focal point of the camera 41 by moving a base 21, to which the camera 41 and the condenser lens 52 are fixed, in a height direction perpendicular to a holding surface 11 of a chuck table 10; a converging-point adjustment unit 32 disposed between a laser oscillator 31 and the condenser lens 52 and that changes a position of a height of the converging point of the laser beam 37 without changing a height of the condenser lens 52; and a control unit 60 having a registration unit 61 for registering the heights of the converging point and the focal point and controls the focal-point adjustment unit 43 and the converging-point adjustment unit 32, on the basis of information of the registration unit 61.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] When manufacturing various device chips such as ICs (Integrated Circuits), LSIs (Large Scale Integration), LEDs (Light Emitting Diodes), and power devices, devices are formed on a semiconductor wafer, which is a workpiece, and then the device is divided into individual chips. Dicing using a cutting blade has been used to divide the device into individual chips, but this requires a street (planned dividing line) width that is greater than or equal to the blade thickness, and there is a risk that a large amount of cutting waste will be generated and adhere to the device. Therefore, as a dividing method that can reduce the street width and suppress the generation of cutting waste, a dividing method is known in which a laser beam with a wavelength that is transparent to the workpiece is focused inside the workpiece to form a modified layer that becomes the starting point of fracture (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-084923 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in order to break the wafer due to cracks occurring in the modified layer, there was a demand to check whether the cracks occurred continuously on all lines. While it is possible to detect cracks by photographing the line after processing with a camera, this increases the inspection time, which is an issue that reduces production efficiency.

[0005] The present invention has been made in consideration of the above problems, and has an object to provide a laser processing device that can efficiently check whether a crack has occurred in a modified layer. [Means for solving the problem]

[0006] In order to solve the above problems and achieve the object, the laser processing apparatus of the present invention provides , covered a light source for illuminating an imaging area of ​​the camera; a condenser lens onto which the laser beam is irradiated and which forms a focal point of the camera and which is irradiated with the laser beam and which forms a focal point of the camera; a focus adjustment unit for moving a base to which the camera and the condenser lens are fixed in a height direction perpendicular to the holding surface to adjust the height of the focal point of the camera; and a focus adjustment unit for adjusting the height of the focal point of the camera and which is disposed between the laser oscillator and the condenser lens and which changes the height of the focal point of the laser beam without changing the height of the condenser lens. the focal point adjustment unit adjusts the focal point of the laser beam to a focal point that is greater than the focal point of the laser beam, and a control unit that registers the focal point and the height of the focal point and controls the focus adjustment unit and the focal point adjustment unit based on information from the registration unit, and while setting the focal point inside the workpiece to form a modified layer along the planned division line inside the workpiece, the camera focused on the exposed surface of the workpiece is used to photograph cracks from the modified layer that have extended onto the exposed surface, and the registration unit registers as information registration data that corresponds to the height of the focal point of the laser beam, the adjustment conditions of the focal point adjustment unit that realizes the height of the focal point of the laser beam, the focal height of the camera, and the adjustment conditions of the focus adjustment unit that realizes the focal height of the camera. The control unit may adjust the height of the focal point of the laser beam and the height of the focus of the camera simultaneously by adjusting the focus adjustment unit based on the registered data, and then adjust the height of the focal point of the laser beam by adjusting the focal point adjustment unit.

[0007] The focus adjustment unit may be a spatial light phase modulator or a beam expander. Effect of the Invention

[0008] The present invention can efficiently check whether or not cracks are occurring in the modified layer. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of a laser processing device according to an embodiment. [Diagram 2] FIG. 2 is a perspective view showing an example of a workpiece to be processed by the laser processing apparatus of FIG. [Diagram 3] FIG. 3 is a diagram showing an example of registration data registered by the registration unit of the laser processing apparatus of FIG. [Figure 4] FIG. 4 is a cross-sectional view showing an example of the operation of the laser processing apparatus of FIG. [Diagram 5] FIG. 5 is a cross-sectional view showing another example of the operation of the laser processing apparatus of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] 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.

[0011] [Embodiment] 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 diagram showing an example of the configuration of the laser processing apparatus 1 according to the embodiment. As shown in Fig. 1, the laser processing apparatus 1 according to the embodiment includes a chuck table 10, a laser processing unit 20, and a control unit 60.

[0012] FIG. 2 is a perspective view showing an example of a workpiece 100 to be processed by the laser processing apparatus 1 of FIG. 1. In this embodiment, the workpiece 100 to be processed by the laser processing apparatus 1 is, for example, a disk-shaped semiconductor wafer or an optical device wafer made of silicon, sapphire, silicon carbide (SiC), gallium arsenide, or the like, as shown in FIG. 2. The workpiece 100 has a flat surface 101 on which a chip-sized device 103 is formed in an area partitioned by a plurality of planned division lines (streets) 102 formed in a lattice pattern. In this embodiment, the workpiece 100 has an adhesive tape 105 attached to the surface 101, and an annular frame 106 attached to the outer edge of the adhesive tape 105, but the present invention is not limited to this. In addition, the workpiece 100 may be a rectangular package substrate, a ceramic plate, a glass plate, or the like having a plurality of devices sealed with resin.

[0013] The chuck table 10 includes a disk-shaped frame body with a recess formed therein and a disk-shaped suction part fitted into the recess. The suction part of the chuck table 10 is formed of a porous ceramic or the like with a large number of porous holes, and is connected to a vacuum suction source (not shown) via a vacuum suction path (not shown). The upper surface of the suction part of the chuck table 10 is a holding surface 11 on which the workpiece 100 is placed and which suction-holds the placed workpiece 100. In this embodiment, the holding surface 11 is a surface on which the workpiece 100 is placed with the back surface 104 on the back side of the front surface 101 facing upward as the exposed surface, and suction-holds the placed workpiece 100 from the front surface 101 side via an adhesive tape 105. The holding surface 11 and the upper surface of the frame body of the chuck table 10 are arranged on the same plane and are formed parallel to the XY plane, which is a horizontal plane. The chuck table 10 is movable in one horizontal direction, that is, the X-axis direction, by an X-axis moving unit (not shown), and in another horizontal direction, that is, the Y-axis direction, which is perpendicular to the X-axis direction, by a Y-axis moving unit (not shown), and is rotatable around a Z-axis in the vertical direction, which is perpendicular to the XY plane, by a rotary drive source (not shown).

[0014] As shown in Fig. 1, the laser processing unit 20 includes a base 21, a laser oscillation unit 30, an imaging unit 40, and a coaxial irradiation unit 50. As shown in Fig. 1, the laser oscillation unit 30 includes a laser oscillator 31, a focal point adjustment unit 32, and a reflecting mirror 33. The laser oscillator 31, the focal point adjustment unit 32, and the reflecting mirror 33 are all fixed to the base 21, and their relative positions are maintained. The laser oscillation unit 30 adjusts the oscillation and optical characteristics of a laser beam 37 and guides it to the coaxial irradiation unit 50.

[0015] The laser oscillator 31 oscillates a laser beam 37 having a wavelength that is transparent to the workpiece 100. In this embodiment, the laser oscillator 31 oscillates a pulsed laser beam 37, but the present invention is not limited to this. The focal point adjustment unit 32 is disposed between the laser oscillator 31 and the dichroic mirror 51 of the coaxial irradiation unit 50, and displaces a height 39 (see FIGS. 4 and 5) in the Z-axis direction (thickness direction of the workpiece 100) of a focal point 38 (see FIGS. 4 and 5) of the laser beam 37 oscillated from the laser oscillator 31 without changing the height of the focusing lens 52 of the coaxial irradiation unit 50. In this embodiment, the height 39 of the focal point 38 of the laser beam 37 is shown as a relative height based on the height of the back surface 104 of the workpiece 100 held on the chuck table 10.

[0016] In this embodiment, the focal point adjustment unit 32 is a so-called LCOS-SLM (Liquid Crystal On Silicon-Spatial Light Modulator) that adjusts the optical characteristics of the laser beam 37 oscillated from the laser oscillator 31 and emits the laser beam 37 with the adjusted optical characteristics. The optical characteristics of the laser beam 37 adjusted by the LCOS-SLM are, for example, at least one of the phase, polarization plane, amplitude, intensity, and propagation direction of the laser beam 37. In the present invention, the focal point adjustment unit 32 is not limited to an LCOS-SLM, and may be a beam expander that expands the outer diameter of the spot of the laser beam 37 while keeping the laser beam 37 as a parallel beam.

[0017] The reflecting mirror 33 is disposed between the laser oscillator 31 and the focal point adjustment unit 32. The reflecting mirror 33 reflects the laser beam 37 oscillated from the laser oscillator 31 and guides it to the focal point adjustment unit 32. Although one reflecting mirror 33 is provided in this embodiment, the present invention is not limited to this, and it may not be provided, or two or more reflecting mirrors may be provided.

[0018] 1, the imaging unit 40 includes a camera 41, a light source 42, a focus adjustment unit 43, a dichroic mirror 44, and an optical system 45. The camera 41, the light source 42, the dichroic mirror 44, and the optical system 45 are all fixed to the base 21, and their relative positions are maintained together with the respective components of the laser oscillation unit 30. The focus adjustment unit 43 is attached to the base 21. The imaging unit 40 guides illumination light 47 that illuminates the imaging region of the camera 41 to the coaxial irradiation unit 50, and also guides incident light 48 from the imaging region to the camera 41 via the coaxial irradiation unit 50, and images the imaging region with the camera 41 based on the incident light 48 from the imaging region.

[0019] The camera 41 is provided with an imaging element that images the back surface 104 of the workpiece 100 positioned in the imaging area before and after laser processing or during laser processing, the planned division line 102, and the crack 300 that appears on the back surface 104 of the workpiece 100 after laser processing (see Figs. 4 and 5) based on the incident light 48 from the imaging area. The imaging element is, for example, a CCD (Charge-Coupled Device) imaging element or a CMOS (Complementary MOS) imaging element. The camera 41 images the back surface 104 of the workpiece 100 held on the chuck table 10 during or after laser processing, etc., to obtain an image for confirming the crack 300 that appears on the back surface 104 of the workpiece 100, and outputs the obtained image to the control unit 60. The camera 41 may also image the workpiece 100 held on the chuck table 10 to obtain an image for detecting the area to be processed, and output the obtained image to the control unit 60. In this embodiment, the camera 41 is a visible light camera, but the present invention is not limited to this, and may be an infrared (IR) camera, etc. The camera 41 is preferably a visible light camera, in which case the modified layer 200 (see Figs. 4 and 5) formed inside the workpiece 100 and the crack 300 are imaged in an overlapping manner, which has the effect of preventing difficulty in distinguishing between the modified layer 200 and the crack 300.

[0020] In addition to the camera 41, the laser processing apparatus 1 may be provided with a separate camera that captures an image of the workpiece 100 held on the chuck table 10 to obtain an image for performing alignment to detect an area to be processed, and outputs the obtained image to the control unit 60. This separate camera may be a visible light camera or an IR camera.

[0021] The light source 42 emits illumination light 47 that illuminates the imaging area of ​​the camera 41. The light source 42 is, for example, a xenon flash lamp that emits white light, a white LED, or the like.

[0022] The focus adjustment unit 43 adjusts the height of the focal point 49 (see FIGS. 4 and 5) of the camera 41 and the height 39 of the condensing point 38 of the laser beam 37 by moving the base 21 in a height direction (Z-axis direction, thickness direction of the workpiece 100) perpendicular to the holding surface 11 of the chuck table 10. In this embodiment, the height of the focal point 49 of the camera 41 is shown as a relative height based on the height of the back surface 104 of the workpiece 100 held on the chuck table 10, similar to the height 39 of the condensing point 38 of the laser beam 37. The focus adjustment unit 43 moves all the components fixed to the base 21, i.e., the components of the laser oscillation unit 30, the camera 41, the light source 42, the dichroic mirror 44 and the optical system 45 of the imaging unit 40, and the components of the coaxial irradiation unit 50 (the dichroic mirror 51 and the condensing lens 52) as a whole without changing their relative positions. Therefore, the focus adjustment unit 43 can move the focus 49 of the camera 41 and the focal point 38 of the laser beam 37 in the vertical direction without changing the focal length of the camera 41 and without changing the state in which the laser beam 37, the incident light 48 to the camera 41, and the illumination light 47 are coaxially superimposed.

[0023] Dichroic mirror 44 is disposed between camera 41 and dichroic mirror 51 and between light source 42 and dichroic mirror 51, i.e., at the intersection of incident light 48 and illumination light 47. Dichroic mirror 44 reflects illumination light 47 from light source 42 and guides it to condenser lens 52, and transmits incident light 48 from condenser lens 52 and guides it to camera 41.

[0024] The optical system 45 is disposed between the camera 41 and the dichroic mirror 44. The optical system 45 collects the incident light 48 from the collecting lens 52 that has passed through the dichroic mirror 44, and guides the light to the camera 41. Although one optical system 45 is provided in this embodiment, the present invention is not limited to this, and two or more optical systems may be provided.

[0025] The coaxial irradiation unit 50 includes a dichroic mirror 51 and a condenser lens 52. The dichroic mirror 51 and the condenser lens 52 are both fixed to the base 21, and their relative positions are maintained together with the components of the laser oscillation unit 30, and the camera 41, light source 42, dichroic mirror 44, and optical system 45 of the imaging unit 40.

[0026] The dichroic mirror 51 is disposed between the focal point adjustment unit 32 and the condenser lens 52 and between the dichroic mirror 44 and the condenser lens 52, i.e., at the intersection of the laser beam 37, the illumination light 47, and the incident light 48. The dichroic mirror 51 reflects the laser beam 37 from the focal point adjustment unit 32 and guides it to the condenser lens 52, and also transmits the illumination light 47 that has passed through the dichroic mirror 44 and guides it to the condenser lens 52, and transmits the incident light 48 from the condenser lens 52 and guides it to the dichroic mirror 44, thereby coaxially overlapping the laser beam 37, the illumination light 47, and the incident light 48 on the condenser lens 52 side. By coaxially overlapping the laser beam 37, the illumination light 47, and the incident light 48 in this manner, the dichroic mirror 51 positions the processing area of ​​the workpiece 100 by the laser beam 37, the illumination area by the illumination light 47, and the imaging area of ​​the camera 41 so as to overlap with each other.

[0027] The condenser lens 52 is disposed closer to the imaging area of ​​the camera 41 than the dichroic mirror 51, that is, closer to the holding surface 11 of the chuck table 10. The condenser lens 52 is irradiated with the laser beam 37 from the dichroic mirror 44, forms a focal point 38 of the laser beam 37, and irradiates the laser beam 37 onto the processing area of ​​the workpiece 100 held on the chuck table 10, thereby laser processing the processing area of ​​the workpiece 100 to form a modified layer 200. The condenser lens 52 is irradiated with the illumination light 47 from the dichroic mirror 44, and irradiates the illumination light 47 onto the illumination area of ​​the workpiece 100 held on the chuck table 10, thereby illuminating the imaging area of ​​the camera 41. The condenser lens 52 forms a focal point 49 of the camera 41, and guides the incident light 48 reflected from the imaging area of ​​the camera 41 illuminated by the illumination light 47 to the dichroic mirror 51.

[0028] The control unit 60 controls the operation of each component of the laser processing device 1 to cause the laser processing device 1 to perform laser processing of the workpiece 100. The control unit 60 has a registration unit 61. The control unit 60 causes the registration unit 61 to register registration data 400 (see FIG. 3) including the height 39 of the condensing point 38 and the height of the focal point 49 of the camera 41. The control unit 60 refers to the registration data 400 registered in the registration unit 61, and controls the laser oscillator 31, the condensing point adjustment unit 32, and the focus adjustment unit 43 based on the registration data 400 to control the optical characteristics of the laser beam 37 and the height 39 of the condensing point 38 of the laser beam 37 in the Z-axis direction, and controls the focus adjustment unit 43 to control the height 39 of the condensing point 38 of the laser beam 37 and the height of the focal point 49 of the camera 41. The control unit 60 also controls the light source 42 to control the illuminance of the illumination light 47, etc.

[0029] Fig. 3 is a diagram showing an example of registration data (registration data 400) registered by the registration unit 61 of the laser processing apparatus 1 of Fig. 1. As shown in Fig. 3, the registration unit 61 stores in the registration data 400, for each processing order of irradiation of the laser beam 37 and imaging by the camera 41, the height 39 of the focal point 38 of the laser beam 37, the adjustment condition of the focal point adjustment unit 32 that realizes the height 39 of the focal point 38 of the laser beam 37, the height of the focal point 49 of the camera 41, and the adjustment condition of the focus adjustment unit 43 that realizes the height of the focal point 49 of the camera 41, in association with each other.

[0030] Furthermore, the control unit 60 controls the X-axis moving unit and the Y-axis moving unit (not shown) based on images captured by the camera 41 for performing alignment and the like, thereby controlling the relative positional relationship between the chuck table 10 and the laser processing unit 20. In this way, the control unit 60 controls the positions of the processing area of ​​the workpiece 100 by the laser beam 37, the illumination area of ​​the illumination light 47, and the imaging area of ​​the camera 41 on the surface 101 of the workpiece 100 held on the chuck table 10.

[0031] Furthermore, the control unit 60 detects the crack 300 that has expanded to the back surface 104 of the workpiece 100 based on the image for confirming the crack 300 captured by the camera 41. In the image for confirming the crack 300, the back surface 104 of the workpiece 100 favorably reflects the illumination light 47, so that the amount of light 48 incident on the camera 41 is large and the image is captured with high brightness. On the other hand, in the image for confirming the crack 300, the crack 300 that has expanded to the back surface 104 of the workpiece 100 reflects less illumination light 47 than the back surface 104 of the workpiece 100, so that the amount of light 48 incident on the camera 41 is small and the image is captured with low brightness. As a result, the control unit 60 identifies the crack 300 in the image for confirming the crack 300.

[0032] In this embodiment, the control unit 60 includes a computer system. The computer system included in the control unit 60 includes an arithmetic processing unit having a microprocessor such as a CPU (Central Processing Unit), a storage device having a memory such as a ROM (Read Only Memory) or a RAM (Random Access Memory), and an input / output interface device. In this embodiment, the function of the control unit 60 is realized by the arithmetic processing unit of the computer system included in the control unit 60 executing a computer program stored in the storage device of the computer system included in the control unit 60. The arithmetic processing unit of the control unit 60 performs arithmetic processing according to the computer program stored in the storage device of the control unit 60, and outputs a control signal for controlling the laser processing device 1 to each component of the laser processing device 1 via the input / output interface device of the control unit 60. In this embodiment, the function of the registration unit 61 is realized by the storage device of the computer system included in the control unit 60.

[0033] Next, this specification will explain the operation and processing of the laser processing device 1 according to the embodiment with reference to the drawings. Fig. 4 is a cross-sectional view showing an example of the operation of the laser processing device 1 of Fig. 1. Fig. 4 shows the operation of the laser processing device 1 when the control unit 60 performs the control processing of the laser processing device 1 based on the registered data 400 shown in Fig. 3.

[0034] 4, the laser processing apparatus 1 according to the embodiment performs processing to form modified layers 200 in regions at different depths from the rear surface 104 inside the workpiece 100 by setting heights 39 of focus points 38 of a laser beam 37 and irradiating the workpiece with the laser beam 37. When the modified layer 200 is formed inside the workpiece 100, a crack 300 extends from the modified layer 200 into the workpiece 100 along the height direction (Z-axis direction, thickness direction of the workpiece 100).

[0035] When performing such operation of the laser processing apparatus 1, the control unit 60 first selects registered data 400 to be referenced when performing the control process of the laser processing apparatus 1, based on various processing conditions such as the thickness of the workpiece 100 and the number of depth levels at which the modified layer 200 is formed by irradiating the laser beam 37 and performing laser processing.

[0036] The control unit 60 then forms the modified layer 200 in each layer inside the workpiece 100 based on the selected registered data 400. In this embodiment, the control unit 60 forms the modified layer 200 in order from the lower layer. That is, in the example shown in FIG. 4, the control unit 60 first forms the modified layer 200 in the fourth layer, which is the deepest layer as viewed from the back surface 104 side of the workpiece 100, then forms the modified layer 200 in the third layer immediately above the fourth layer, the second layer further above, and the first layer closest to the back surface 104 of the workpiece 100. Then, the crack 300 extends from the modified layer 200 formed in the first layer to the back surface 104 of the workpiece 100. Note that the control unit 60 is not limited to this in the present invention, and may form the modified layer 200 in each layer in any order.

[0037] The control unit 60 adjusts the height 39 of the focal point 38 of the laser beam 37 and the height of the focal point 49 of the camera 41 simultaneously by adjusting the focus adjustment unit 43 based on the selected registered data 400, and then adjusts the height 39 of the focal point 38 of the laser beam 37 by adjusting the focal point adjustment unit 32. For example, when forming the modified layer 200 first in the fourth layer, the control unit 60 sets the condition of the focus adjustment unit 43 to "focus adjustment condition 1" in Fig. 3 to set the height 39 of the focal point 38 of the laser beam 37 and the height of the focal point 49 of the camera 41 on the back surface 104 of the workpiece 100 (the height of the focal point in Fig. 3 is "0"), and then sets the condition of the focus adjustment unit 32 to "focus adjustment condition 1" in Fig. 3 to set the height 39 of the focal point 38 of the laser beam 37 to the depth of the fourth layer ("height 1" in Fig. 3). For example, the difference in height between the focal point 38 of the laser beam 37 and the focal point 49 of the camera 41 is about 10 to 120 μm.

[0038] Furthermore, when forming the modified layer 200 on the third, second and first layers, the control unit 60 does not need to set the conditions of the focus adjustment unit 43 again because the height of the focus 49 of the camera 41 has already been set on the back surface 104 of the workpiece 100 when the modified layer 200 was formed on the fourth layer. Instead, the control unit 60 sets the conditions of the focus adjustment unit 32 to "focus point adjustment condition 2," "focus point adjustment condition 3," and "focus point adjustment condition 4" in Figure 3, respectively, thereby setting the height 39 of the focus point 38 of the laser beam 37 to the depth of the third, second and first layers, respectively ("height 2," "height 3," and "height 4" in Figure 3).

[0039] In this embodiment, when forming the modified layer 200 on the fourth, third and second layers, the control unit 60 does not perform observation by the camera 41 at the same time as irradiating the laser beam 37, so it may control the focus adjustment unit 43 to set both the height 39 of the focal point 38 of the laser beam 37 and the height of the focal point 49 of the camera 41 to the height of the layer to be processed of the workpiece 100.

[0040] When forming the modified layer 200 in the fourth, third and second layers, the control unit 60 sets the height 39 of the focal point 38 of the laser beam 37 and the height of the focal point 49 of the camera 41, and then sets the positions of the processing area of ​​the workpiece 100 by the laser beam 37, the illumination area of ​​the illumination light 47 and the imaging area of ​​the camera 41 on the planned division line 102 formed on the surface 101 of the workpiece 100 held on the chuck table 10. The control unit 60 controls the laser processing unit 20 to irradiate the laser beam 37 while relatively moving the laser processing unit 20 and the chuck table 10 holding the workpiece 100 along the planned division line 102, thereby forming the modified layer 200 along the planned division line 102 in the area of ​​the depth of the fourth, third and second layers inside the workpiece 100 where the height 39 of the focal point 38 of the laser beam 37 is set.

[0041] When forming the modified layer 200 in the first layer, the control unit 60 performs various settings in the same manner as when forming the modified layer 200 in the fourth, third and second layers, and then irradiates the laser beam 37 to form the modified layer 200 along the planned division line 102 in the area at the depth of the first layer, while further capturing an image of the back surface 104 of the workpiece 100 along the planned division line 102 with a camera 41 having a focus 49 set on the back surface 104, which is the exposed surface of the workpiece 100.

[0042] When the crack 300 extending from the modified layer 200 formed inside the workpiece 100 extends to the back surface 104, the control unit 60 can image the crack 300 extending to the back surface 104 by imaging the back surface 104 of the workpiece 100 with the camera 41. Based on the image captured by the camera 41, the control unit 60 detects whether the crack 300 extending from the modified layer 200 inside the workpiece 100 has extended to the back surface 104.

[0043] Fig. 5 is a cross-sectional view showing another example of the operation of the laser processing apparatus 1 of Fig. 1. The example shown in Fig. 5 is an example in which the depth and the number of levels at the depth at which the modified layer 200 is formed by irradiating the laser beam 37 are changed from the example shown in Fig. 4. Note that, in the examples shown in Figs. 4 and 5, the laser processing apparatus 1 has four and three levels at the depth at which the modified layer 200 is formed by irradiating the laser beam 37, respectively, but the present invention is not limited thereto, and the number of levels at the depth at which the modified layer 200 is formed by irradiating the laser beam 37 may be two or less or five or more.

[0044] The laser processing apparatus 1 according to the embodiment having the above-mentioned configuration can image the processing area of ​​the workpiece 100 during or immediately after laser processing by coaxially irradiating a single condenser lens 52 with a laser beam 37 for laser processing and an illumination light 47 for imaging. In addition, the laser processing apparatus 1 according to the embodiment can set the height 39 of the condenser point 38 of the laser beam 37 and the height of the focal point 49 of the camera 41 for imaging to different heights by the condenser point adjustment unit 32 and the focus adjustment unit 43. Therefore, the laser processing apparatus 1 according to the embodiment can immediately image the crack 300 extending from the modified layer 200 to the back surface 104 when the modified layer 200 is formed near the exposed surface (back surface 104) of the workpiece 100 almost in parallel with the laser processing process from the side where the laser beam 37 is irradiated and the laser processing is performed, thereby achieving the effect of efficiently confirming whether the crack 300 has occurred from the modified layer 200 and extended to the back surface 104.

[0045] In addition, in the laser processing apparatus 1 according to the embodiment, the focal point adjustment unit 32 is a spatial light phase modulator or a beam expander. Therefore, in the laser processing apparatus 1 according to the embodiment, the focal point adjustment unit 32 can precisely displace the height 39 of the focal point 38 of the laser beam 37 without moving one focusing lens 52. In other words, the height 39 of the focal point 38 of the laser beam 37 can precisely displace the height 39 of the focal point 38 of the laser beam 37 without displacing the height of the focal point 49 of the camera 41. Therefore, the height 39 of the focal point 38 of the laser beam 37 and the height of the focal point 49 of the camera 41 for capturing images can be precisely set to different desired heights.

[0046] It should be noted that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. [Explanation of symbols]

[0047] 1 Laser processing equipment 10 Chuck table 11 Holding surface 21 Foundation 31 Laser Oscillator 32 Focus point adjustment unit 37 Laser Beam 38 Focus point 39 (height of focal point 38) 41 Camera 42 Light source 43 Focus Adjustment Unit 49 focus 52 Condenser Lens 61 Registration Department 60 Control section 100 Workpiece 102 Division line 200 Modified layer 300 Crack

Claims

1. A laser processing device that irradiates a workpiece with a laser beam along a planned dividing line set on the workpiece, a chuck table that holds the workpiece on a holding surface; A laser oscillator that emits a laser beam having a wavelength that is transparent to the workpiece; A camera for capturing an image of a workpiece; A light source that illuminates an imaging area of ​​the camera; a condenser lens onto which the laser beam is projected, forming a condensing point of the laser beam and forming a focal point of the camera; a focus adjustment unit that adjusts the height of the focus of the camera by moving a base to which the camera and the condenser lens are fixed in a height direction perpendicular to the holding surface; a focus adjustment unit disposed between the laser oscillator and the condenser lens and configured to change the height of the focus of the laser beam without changing the height of the condenser lens; a control unit that has a registration unit that registers the focal point and the height of the focal point, and controls the focus adjustment unit and the focal point adjustment unit based on information from the registration unit; The focus point is set inside the workpiece to form a modified layer along the planned division line inside the workpiece, while the camera, which is focused on the exposed surface of the workpiece, photographs cracks extending from the modified layer on the exposed surface, and The registration unit of the laser processing apparatus registers as information registration data the height of the focal point of the laser beam, the adjustment conditions of the focal point adjustment unit that realizes the height of the focal point of the laser beam, the focal height of the camera, and the adjustment conditions of the focus adjustment unit that realizes the focal height of the camera, which correspond to each other.

2. 2. The laser processing apparatus according to claim 1, wherein the control unit adjusts the height of the focal point of the laser beam and the height of the focal point of the camera simultaneously by adjusting the focus adjustment unit based on the registered data, and then adjusts the height of the focal point of the laser beam by adjusting the focal point adjustment unit.

3. 3. The laser processing apparatus according to claim 1, wherein the focal point adjustment unit is a spatial light phase modulator or a beam expander.

Images