Inspection wafer, method of using the inspection wafer, and inspection device

Abstract

To suppress oversight of detection of deterioration of a metal layer while suppressing work man-hours.SOLUTION: An inspection wafer for inspecting leakage light of a laser beam that affects a device on the surface side of the wafer when a modified layer is formed in a laser processing device includes an inspection substrate 61, and a metal layer 62 formed with a predetermined thickness on one surface 63 of the inspection substrate 61, the metal layer 62 includes a target 65 for automatically adjusting the amount of light in the laser processing device. The target 65 is imaged in the laser processing device, and it is possible to appropriately detect the leakage light of the laser beam by automatically adjusting the amount of light applied to the processing area such that the target 65 appears as desired in the captured target image.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to an inspection wafer, a method for using the inspection wafer, and an inspection device. [Background technology]

[0002] One method for dividing a workpiece such as a semiconductor wafer into individual devices involves, for example, positioning the focal point of a laser beam having a wavelength that is transparent to the workpiece inside the workpiece corresponding to the intended dividing line, and scanning the laser beam relatively to the workpiece to form a modified layer inside the wafer, and then applying an external force along the intended dividing line whose strength has been reduced, to divide the workpiece starting from the modified layer (see, for example, Patent Document 1).

[0003] However, it was found that forming a modified layer using the method shown in Patent Document 1 causes a problem in that the laser beam scatters on a device formed on the surface opposite to the surface irradiated with the laser beam (back surface), damaging the device. This problem is believed to be caused by leakage light of the laser beam that is refracted or reflected when it hits fine cracks extending from the modified layer in the wafer thickness direction.

[0004] Therefore, the present inventors developed a test wafer to find processing conditions that allow good division of the wafer while minimizing damage to the device (see, for example, Patent Document 2). This test wafer has a metal layer laminated on a substrate, and the maximum width of the alteration of the metal layer caused by leakage light of a laser beam when a modified layer is formed is measured to identify the damage range and adjust the processing conditions. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3408805 [Patent Document 2] JP 2018-64049 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, since the inspection wafer shown in Patent Document 2 has minute thickness variations in the metal layer, the appearance of the deterioration of the metal layer changes depending on the intensity of the light irradiated onto the processing area of ​​the equipment, and there is a risk that actual deterioration of the metal layer may be overlooked, making it impossible to set appropriate processing conditions.

[0007] To avoid this problem, currently an operator adjusts the light intensity for each wafer being inspected, but this creates a breeding ground for human error, as different operators set different values.

[0008] The present invention has been made in consideration of the above-mentioned facts, and its object is to provide an inspection wafer, a method of using the inspection wafer, and an inspection device that can reduce the amount of work required while preventing oversight of detection of alteration in the metal layer. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems and achieve the object, the inspection wafer of the present invention is an inspection wafer for inspecting leakage light of a laser beam that affects devices on the front side of a wafer when forming a modified layer in a laser processing apparatus that irradiates a laser beam of a wavelength that is transparent to a substrate constituting the wafer from the back side of the wafer, the substrate having a plurality of devices formed in each area partitioned by a plurality of planned dividing lines set on the front side, along the planned dividing lines to form a modified layer inside the substrate, the inspection wafer having an inspection substrate and a metal layer formed with a predetermined thickness on one side of the inspection substrate, the metal layer having a target for automatically adjusting the amount of light in the laser processing apparatus, and the target is imaged in the laser processing apparatus, and the amount of light irradiated to the processing area is automatically adjusted so that the target appears in the imaged image in a desired manner, thereby making it possible to appropriately detect leakage light of the laser beam.

[0010] In the inspection wafer, the target may be a two-dimensional code.

[0011] The method of using an inspection wafer of the present invention is a method of using the inspection wafer, comprising: an imaging step of imaging a target formed on the inspection wafer; a comparison step of comparing the target image imaged in the imaging step with a reference image obtained by previously imaging the target with an amount of light capable of properly detecting leakage light of the laser beam; and an adjustment step of adjusting the amount of light based on the result of the comparison step so that the target image becomes the same as the reference image. After performing the adjustment step, an inspection step is performed, including a modified layer formation step of irradiating a laser beam of a wavelength that is transparent to the inspection substrate from the surface of the inspection wafer opposite to the surface on which the metal layer is formed, and forming a modified layer by relatively moving the focal point of the light focused inside the inspection substrate and the inspection wafer; and a width measurement step of imaging the metal layer of the inspection wafer after the modified layer formation step, and measuring the maximum width of the location where the metal layer has been altered.

[0012] The inspection apparatus of the present invention is an inspection apparatus that performs inspection using the inspection wafer, and includes a chuck table that holds the inspection wafer, a laser beam irradiation unit equipped with a condenser that condenses and irradiates a laser beam onto the inspection wafer held on the chuck table, a moving unit that relatively moves the chuck table and the focal point of the laser beam, an imaging unit equipped with a light source that irradiates light onto a target formed on the inspection wafer and images the target by irradiating light from the light source, and a control unit, wherein the control unit includes a memory section that stores a reference image of the target previously imaged with an amount of light that can appropriately detect leakage light of the laser beam, a comparison section that compares the reference image stored in the memory section with a target image newly imaged by the imaging unit, a judgment section that judges whether the amount of light from the light source is appropriate based on the comparison result by the comparison section, and a light amount adjustment section that automatically adjusts the amount of light from the light source so that the target image and the reference image are the same when the judgment section judges that the amount of light is not appropriate. Effect of the Invention

[0013] The present invention has an effect of suppressing oversight of detection of alteration of a metal layer while suppressing the number of work steps. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a perspective view of a test wafer according to the first embodiment. [Diagram 2] FIG. 2 is a perspective view showing a configuration example of a laser processing apparatus which is an inspection apparatus using the inspection wafer shown in FIG. [Diagram 3] FIG. 3 is an enlarged cross-sectional view of a portion of a wafer, illustrating a state in which the laser processing apparatus shown in FIG. 2 forms a modified layer on the wafer. [Figure 4] FIG. 4 is a cross-sectional view that illustrates a schematic configuration of an imaging unit of the laser processing apparatus illustrated in FIG. [Diagram 5]FIG. 5 is a plan view of the inspection wafer shown in FIG. 1 as viewed from below. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. [Figure 7] FIG. 7 is a diagram showing an example of a reference image stored in the storage unit of the control unit of the laser processing apparatus shown in FIG. [Figure 8] FIG. 8 is a diagram showing an example of a target image compared by a comparison unit of the control unit of the laser processing apparatus shown in FIG. [Figure 9] FIG. 9 is a diagram showing another example of the target image compared by the comparison unit of the control unit of the laser processing apparatus shown in FIG. [Figure 10] FIG. 10 is a flowchart showing a flow of a method of using the inspection wafer according to the first embodiment. [Figure 11] FIG. 11 is a side view, partially in section, showing a schematic diagram of an imaging step in the method of using the wafer shown in FIG. [Figure 12] FIG. 12 is a side view, partially in cross section, illustrating a modified layer forming step of the inspection step in the method of using the inspection wafer shown in FIG. [Figure 13] FIG. 13 is an enlarged cross-sectional view showing a part of the inspection wafer shown in FIG. [Figure 14] FIG. 14 is a diagram showing an example of an image captured by the imaging unit in the width measurement step of the inspection step in the method of using the inspection wafer shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] 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.

[0016] [Embodiment 1] An inspection wafer 60 according to a first embodiment of the present invention and a laser processing device 1 which is an inspection device will be described with reference to the drawings. The inspection wafer 60 according to the first embodiment shown in Fig. 1 is used in the laser processing device 1 which is an inspection device shown in Fig. 2. The laser processing device 1 shown in Fig. 2 is a processing device which irradiates a pulsed laser beam 21 onto a wafer 200 and performs laser processing (corresponding to processing) on ​​the wafer 200. First, the wafer 200 to be processed by the laser processing device 1 and the laser processing device 1 will be described.

[0017] Fig. 1 is a perspective view of an inspection wafer according to embodiment 1. Fig. 2 is a perspective view showing a configuration example of a laser processing device which is an inspection device using the inspection wafer shown in Fig. 1. Fig. 3 is an enlarged cross-sectional view of a part of a wafer, which shows a state in which the laser processing device shown in Fig. 2 forms a modified layer on the wafer. Fig. 4 is a cross-sectional view showing a configuration of an imaging unit of the laser processing device shown in Fig. 2.

[0018] (Wafer) 2 is a disk-shaped semiconductor wafer, an optical device wafer, or the like having a substrate 201 made of silicon, sapphire, gallium arsenide, etc. In the wafer 200, a plurality of mutually intersecting division lines 203 are set on a surface 202 of the substrate 201, and devices 204 are formed in each region partitioned by the plurality of division lines 203 set on the surface 202.

[0019] The device 204 is, for example, an integrated circuit such as an integrated circuit (IC) or a large scale integration (LSI), or an image sensor such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS).

[0020] Moreover, in the embodiment 1, the wafer 200 has an adhesive tape 208 attached to a front surface 202, the adhesive tape 208 having a circular plate shape with a diameter larger than the outer diameter of the wafer 200 and an annular frame 207 attached to its outer edge, and is supported within an opening 209 of the frame 207. Moreover, in the embodiment 1, the wafer 200 has the front surface 202 attached to the adhesive tape 208, and the back surface 205 behind the front surface 202 faces upward.

[0021] In the first embodiment, the wafer 200 is divided into individual devices 204 along the intended division lines 203 by, for example, laser processing using the laser processing device 1 while being supported in an opening 209 of a frame 207 by an adhesive tape 208. Also, in the first embodiment, the wafer 200 has a substrate 201 made of silicon.

[0022] (Laser processing equipment) The laser processing device 1 is a processing device that irradiates a laser beam 21 having a wavelength that is transparent to a substrate 201 constituting the wafer 200 from a back surface 205 of the wafer 200 along a planned dividing line 203 to form a modified layer 206 shown in FIG. 3 inside the substrate 201. The modified layer 206 means a region in which the density, refractive index, mechanical strength and other physical properties are different from those of the surroundings, and examples of the modified layer 206 include a melting process region, a crack region, an insulation breakdown region, a refractive index change region, and a region in which these regions are mixed. The modified layer 206 has a lower mechanical strength than other parts of the substrate 201 of the wafer 200.

[0023] As shown in FIG. 2, the laser processing apparatus 1 has a chuck table 10 that holds a wafer 200, a sub-chuck table 15 that holds an inspection wafer 60, a laser beam irradiation unit 20, a moving unit 30, an imaging unit 40, and a control unit 50.

[0024] The chuck table 10 holds the wafer 200 on a holding surface 11 parallel to the horizontal direction. The holding surface 11 is disk-shaped and made of porous ceramics or the like, and is connected to a vacuum suction source (not shown) via a vacuum suction path (not shown). The chuck table 10 is sucked by the vacuum suction source to suction and hold the wafer 200 placed on the holding surface 11. A plurality of clamps 12 are arranged around the chuck table 10 to clamp a frame 207 that supports the wafer 200 in an opening 209.

[0025] Furthermore, the chuck table 10 is rotated by the rotary movement unit 34 of the moving unit 30 about an axis parallel to the Z-axis direction which is perpendicular to the holding surface 11 and parallel to the vertical direction. The chuck table 10, together with the rotary movement unit 34, is moved in the X-axis direction parallel to the horizontal direction by the X-axis movement unit 31 of the moving unit 30, and is moved in the Y-axis direction which is parallel to the horizontal direction and perpendicular to the X-axis direction by the Y-axis movement unit 32. The chuck table 10 is moved by the moving unit 30 between a processing region below the laser beam irradiation unit 20 and a carry-in / out region which is away from below the laser beam irradiation unit 20 and where the wafer 200 is carried in and out.

[0026] The sub-chuck table 15 is a chuck table that holds the inspection wafer 60 on a holding surface 16. In the first embodiment, the sub-chuck table 15 is formed in a flat plate shape with a rectangular surface shape, and the holding surface 16 is formed from porous ceramics or the like. The holding surface 16 of the sub-chuck table 15 is connected to a vacuum suction source (not shown) via a vacuum suction path (not shown). The sub-chuck table 15 is sucked by the vacuum suction source to suck and hold the inspection wafer 60 placed on the holding surface 16. In the first embodiment, a plurality of sub-chuck tables 15 (four in the first embodiment) are arranged around the chuck table 10.

[0027] The sub-chuck table 15, together with the chuck table 10 and the rotary movement unit 34, is moved in the X-axis direction parallel to the horizontal direction by the X-axis movement unit 31 of the movement unit 30, and is moved in the Y-axis direction parallel to the horizontal direction and perpendicular to the X-axis direction by the Y-axis movement unit 32. The sub-chuck table 15, together with the chuck table 10, is moved by the movement unit 30 across the above-mentioned processing area and carry-in / out area. In the processing area, the sub-chuck table 15 can be positioned below the imaging unit 40. In the carry-in / out area, the sub-chuck table 15 can carry an inspection wafer 60 into and out of the holding surface 16.

[0028] The laser beam irradiation unit 20 is a unit that includes a condenser 23 that condenses and irradiates a pulsed laser beam 21 onto the wafer 200 or the inspection wafer 60 held on the chuck tables 10, 15, and performs laser processing on the wafer 200. Incidentally, condensing and irradiating means irradiating the wafer 200 with the laser beam 21 condensed at a condensing point 22.

[0029] In the first embodiment, a part of the laser beam irradiation unit 20 is supported by a lifting member 4 that is moved in the Z-axis direction by a Z-axis moving unit 33 of a moving unit 30 provided on an erect wall 3 erected from an apparatus body 2, as shown in Fig. 2. The laser beam irradiation unit 20 includes a laser oscillator that emits a pulsed laser beam 21 having a wavelength that is transparent to the substrate 201 of the wafer 200 and the inspection wafer 60, and a condenser 23 that condenses the laser beam 21 emitted from the laser oscillator onto the wafer 200 or the inspection wafer 60 held on the holding surfaces 11, 16 of the chuck tables 10, 15.

[0030] The condenser 23 includes a condenser lens (not shown) arranged at a position facing the holding surfaces 11, 16 of the chuck tables 10, 15 in the Z-axis direction. The condenser lens transmits the laser beam 21 emitted from the laser oscillator and condenses the laser beam 21 at a condensing point 22 (shown in FIG. 3). The laser beam irradiation unit 20 configured as described above sets the condensing point 22 of the pulsed laser beam 21 having a wavelength that is transparent to the wafer 200 or the inspection wafer 60 held on the chuck tables 10, 15 inside the wafer 200 or the inspection wafer 60, and irradiates the laser beam 21 onto the back surface 205 of the wafer 200 or the inspection wafer 60 to form a modified layer 206 inside the wafer 200 or the inspection wafer 60.

[0031] In addition, when the modified layer 206 is formed on the wafer 200, fine cracks may be generated extending in the thickness direction from the modified layer 206. When fine cracks are generated, the laser beam 21 irradiated to the wafer 200 may hit the fine cracks and be refracted or reflected to reach the front surface 202 side, as shown in Fig. 3, and may have an effect such as damage on the device 204 (i.e., may alter the metal constituting the device 204). The laser beam 21 that hits the fine cracks and is refracted or reflected to reach the front surface 202 side is hereinafter referred to as leakage light 24 of the laser beam 21.

[0032] The moving unit 30 relatively moves the chuck tables 10, 15 and the focal point 22 of the laser beam 21 irradiated by the laser beam irradiation unit 20 in the X-axis direction, the Y-axis direction, the Z-axis direction, and around an axis parallel to the Z-axis direction. The X-axis direction and the Y-axis direction are perpendicular to each other and parallel to the holding surface 11 (i.e., the horizontal direction). The moving unit 30 includes an X-axis moving unit 31 which is a processing feed unit that moves the chuck tables 10, 15 in the X-axis direction, a Y-axis moving unit 32 which is an indexing feed unit that moves the chuck tables 10, 15 in the Y-axis direction, a Z-axis moving unit 33 which moves the condenser 23 included in the laser beam irradiation unit 20 in the Z-axis direction, and a rotation moving unit 34 which rotates the chuck table 10 around an axis parallel to the Z-axis direction.

[0033] The Y-axis moving unit 32 is a unit that relatively indexes and feeds the chuck tables 10, 15 and the laser beam irradiation unit 20. In the first embodiment, the Y-axis moving unit 32 is installed on the device body 2 of the laser processing device 1. The Y-axis moving unit 32 supports the moving plate 5 that supports the X-axis moving unit 31 so as to be freely movable in the Y-axis direction.

[0034] The X-axis moving unit 31 is a unit that relatively processes and feeds the chuck tables 10, 15 and the laser beam irradiation unit 20. The X-axis moving unit 31 is installed on the moving plate 5. The X-axis moving unit 31 supports a second moving plate 6 that supports a rotational moving unit 34 that rotates the chuck table 10 around an axis parallel to the Z-axis direction, so as to be movable in the X-axis direction. The second moving plate 6 supports the rotational moving unit 34, the chuck table 10, and the sub-chuck table 15. The Z-axis moving unit 33 is installed on the standing wall 3, and supports the lifting member 4 so as to be movable in the Z-axis direction. The rotational moving unit 34 supports the chuck table 10.

[0035] The X-axis moving unit 31, the Y-axis moving unit 32 and the Z-axis moving unit 33 each include a well-known ball screw rotatably provided about its axis, a well-known pulse motor for rotating the ball screw about its axis, and a well-known guide rail for supporting the moving plates 5, 6 movably in the X-axis or Y-axis direction and supporting the lifting member 4 movably in the Z-axis direction. The rotational movement unit 34 includes a motor for rotating the chuck table 10 about its axis, etc.

[0036] The laser processing apparatus 1 also includes an X-axis position detection unit (not shown) for detecting the position of the chuck table 10 in the X-axis direction, a Y-axis position detection unit (not shown) for detecting the position of the chuck table 10 in the Y-axis direction, and a Z-axis position detection unit for detecting the position of the condenser 23 included in the laser beam irradiation unit 20 in the Z-axis direction. Each position detection unit outputs a detection result to the control unit 50.

[0037] The imaging unit 40 captures an image of the wafer 200 or the inspection wafer 60 held on the chuck table 10. As shown in Fig. 4, the imaging unit 40 includes a housing 41, a light source 42, an objective lens 43, a mirror 44, and an imaging element 45. The housing 41 is a container having a space therein, and is attached to the tip of the housing of the laser beam irradiation unit 20 and supported by the lifting member 4 together with the housing of the laser beam irradiation unit 20.

[0038] The light source 42 is attached to the housing 41 and emits light 46 into the housing 41. In the first embodiment, the light 46 emitted by the light source 42 includes at least infrared light. The objective lens 43 is installed in the housing 41 and disposed at a position capable of facing the holding surface 11 of the chuck table 10 in the Z-axis direction. In the first embodiment, the objective lens 43 is disposed at a position aligned with the condenser lens of the laser beam irradiation unit 20 in the X-axis direction. The objective lens 43 condenses the light 46 emitted from the light source 42 onto an object facing the light source 42 in the Z-axis direction, and transmits light 47 reflected from the object facing the light source 42 in the Z-axis direction.

[0039] The mirror 44 is installed in the housing 41 and guides the light 46 emitted from the light source 42 to the objective lens 43. In the first embodiment, two mirrors 44 are provided, but in the present invention, the number of mirrors 44 is not limited to two. One of the two mirrors 44 faces the light source 42 in the Z-axis direction, is disposed below the light source 42, and reflects the light 46 horizontally toward the upper side of the objective lens 43. The other mirror 44 faces the objective lens 43 in the Z-axis direction, is disposed above the objective lens 43 and to the side of the one mirror 44, and reflects the light 46 reflected by the one mirror 44 toward the objective lens 43. The other mirror 44 transmits the light 47 described above. In this way, at least the other mirror 44 is a half mirror that reflects the light 46 and transmits the light 47.

[0040] In the first embodiment, the light source 42 is a light source that constitutes epi-illumination (also called coaxial illumination) in which light 46 irradiated to an object facing the objective lens 43 in the Z-axis direction is coaxial with the optical axis of the image sensor 45 and the objective lens 43. However, in the present invention, the imaging unit 40 may be provided with a light source that constitutes oblique illumination in which the optical axis of light 46 irradiated to an object facing the objective lens 43 in the Z-axis direction intersects with the optical axis of the image sensor 45 and the objective lens 43.

[0041] The imaging element 45 is disposed in a direction opposite to the direction in which the light 46 passes through the objective lens 43, as viewed from the objective lens 43. In the first embodiment, the imaging element 45 is attached to the housing 41, faces the objective lens 43 in the Z-axis direction, and is disposed above the objective lens 43. The imaging element 45 receives infrared light from the light 47 that passes through the objective lens 43, and captures an image of the object that the objective lens 43 faces in the Z-axis direction using infrared light. The imaging element 45 is a CCD (Charge Coupled Device) imaging element, a CMOS (Complementary MOS) imaging element, or the like. In this way, the imaging unit 40 is configured such that the objective lens 43, the imaging element 45, and the like are covered by the housing 41, and no light from the outside enters the housing 41 except for the objective lens 43.

[0042] The imaging element 45 outputs the captured image to the control unit 50. In the first embodiment, the image captured by the imaging element 45 is a grayscale image in which the amount of infrared light in the light 47 is defined by multiple gradations (for example, 256 gradations).

[0043] The imaging unit 40 acquires the image captured by the imaging element 45, and outputs the acquired image to the control unit 50. The imaging unit 40 also acquires an image of the wafer 200 held on the holding surface 11 of the chuck table 10, and acquires an image for performing alignment between the wafer 200 and the laser beam irradiation unit 20.

[0044] The control unit 50 controls each of the above-mentioned components of the laser processing apparatus 1 to cause the laser processing apparatus 1 to perform laser processing operations on the wafer 200. The control unit 50 is a computer having an arithmetic processing device 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. The arithmetic processing device of the control unit 50 performs arithmetic processing according to a computer program stored in the storage device, and outputs control signals for controlling the laser processing apparatus 1 to the above-mentioned components of the laser processing apparatus 1 via the input / output interface device, thereby realizing the functions of the control unit 50.

[0045] The control unit 50 is connected to a display unit 51 configured with a liquid crystal display device or the like for displaying the status and images of the machining operation, an input unit used by the operator to register machining content information, and an alarm unit for emitting at least one of sound and light to notify the operator. The input unit is configured with at least one of a touch panel provided on the display unit 51 and an external input device such as a keyboard.

[0046] (Inspection wafer) Next, the inspection wafer 60 according to the first embodiment will be described. Fig. 5 is a plan view of the inspection wafer shown in Fig. 1 as seen from below. Fig. 6 is a cross-sectional view taken along line VI-VI in Fig. 5. The inspection wafer 60 is used to inspect leakage light 24 of the laser beam 21 that affects the device 204 on the front surface 202 side of the wafer 200 when a modified layer 206 is formed on the wafer 200.

[0047] The inspection wafer 60 corresponds to the wafer 200 to be processed by the laser processing apparatus 1. The inspection wafer 60 has an inspection substrate 61 and a metal layer 62, as shown in FIG.

[0048] The inspection substrate 61 is a flat plate with both surfaces 63, 64 that are flat and parallel to each other and have a uniform thickness. The inspection substrate 61 is formed in a rectangular shape that is the same as the planar shape of the sub-chuck table 15. The inspection substrate 61 is made of a material that forms a modified layer 206 by irradiating the laser beam 21 with a focal point 22 set inside, similar to the substrate 201 of the wafer 200. The inspection substrate 61 is made of, for example, the same material as the substrate 201 of the corresponding wafer 200 of the inspection wafer 60, and has a thickness equal to that of the substrate 201 of the corresponding wafer 200 of the inspection wafer 60. In the first embodiment, the inspection substrate 61 is made of the same silicon as the substrate 201 of the corresponding wafer 200.

[0049] The metal layer 62 is formed with a predetermined thickness on one surface 63 of the inspection substrate 61. As shown in Fig. 5 and Fig. 6, the metal layer 62 includes a target 65, and is formed on the entire one surface 63 of the inspection substrate 61 except for the target 65. The metal layer 62 is formed by deposition on the one surface 63 of the inspection substrate 61, and is made of a metal that can be altered when irradiated with the leakage light 24 of the laser beam 21, like the metal that constitutes the device 204 of the wafer 200.

[0050] The metal layer 62 is preferably made of the same material as the metal constituting the device 204, or a metal having a melting point close thereto. The metal layer 62 is made of a metal such as aluminum (Al), tin (Sn), platinum (Pt), gold (Au), silver (Ag), indium (In), lead (Pb), copper (Cu), or chromium (Cr). The thickness of the metal layer 62 is not particularly limited, but is preferably formed to a thickness that is easily altered by the leakage light 24 of the laser beam 21. In the first embodiment, the metal layer 62 is made of tin (Sn) and is formed to a thickness of 1 μm or less.

[0051] Furthermore, in the present invention, the testing wafer 60 may have an underlayer between one surface 63 of the testing substrate 61 and the metal layer 62. The underlayer is formed on one surface 63 of the testing substrate 61 by vapor deposition, and the metal layer 62 is formed on the underlayer by vapor deposition. The underlayer is desirably made of a metal that can favorably adhere the metal layer 62 to the testing substrate 61. The underlayer is desirably made of, for example, titanium (Ti) or chromium (Cr).

[0052] The inspection board 61 having the above-described configuration has the metal layer 62 placed on the holding surface 16 and is suction-held to the holding surface 16 of the sub-chuck table 15. The inspection board 61 is imaged from the other side 64 of the inspection board 61 by the imaging unit 40, and the laser beam irradiation unit 20 sets a focal point 22 inside the inspection board 61 from the other side 64 of the inspection board 61 and irradiates the laser beam 21.

[0053] As shown in Fig. 5 and Fig. 6, only one target 65 is formed at a corner of one surface 63 of the inspection board 61. When the metal layer 62 side of the inspection board 61 is sucked to the holding surface 16 of the sub-chuck table 15 and an image is taken from the other surface 64 side by the imaging unit 40, the target 65 has a first region 66 (shown with a black background in Fig. 5) in which the amount of reflected infrared light is a first amount of light out of the light 47 that reflects the light 46 from the light source 42, and a second region 67 (shown with a white background in Fig. 5) in which the amount of reflected infrared light is lower than the first amount of light by a predetermined value or more. The first amount of infrared light reflected by the first region 66 is equal to the amount of infrared light reflected by the metal layer 62.

[0054] In the first embodiment, the target 65 is configured by arranging the first region 66 and the second region 67 in two mutually orthogonal directions on one surface 63, similar to a two-dimensional code. That is, in the first embodiment, the target 65 is a two-dimensional code in which the first region 66 and the second region 67 are arranged in two mutually orthogonal directions on one surface 63. However, in the present invention, the target 65 may be a one-dimensional code (so-called barcode) in which the first region 66 and the second region 67 are arranged in one direction on one surface 63 and the first region 66 and the second region 67 are formed in a rod shape perpendicular to the arrangement direction. In the first embodiment, the arrangement of the first region 66 and the second region 67 of the target 65 is the same even if the corresponding wafer 200 of the inspection wafer 60 is different.

[0055] In the first embodiment, the first region 66 of the target 65 is made of the same metal as the metal layer 62, and when the metal layer 62 is deposited on the one surface 63, the first region 66 is deposited on the one surface 63 at the same time as the metal layer 62. In the first embodiment, the second region 67 of the target 65 is formed without deposition of the metal constituting the metal layer 62 and the first region 66 when the metal layer 62 and the first region 66 are deposited on the one surface 63, and is a region that exposes the one surface 63 of the inspection board 61. That is, the second region 67 is formed by the one surface 63 of the inspection board 61. In this way, the target 65 is provided with the first region 66 and the second region 67, and is used to automatically adjust the light amount of the light 46 of the light source 42 of the imaging unit 40 when imaging in the laser processing device 1. The light amount adjustment means adjusting the light amount of the light 46 of the light source 42 of the imaging unit 40. In the present invention, the target 65 may be created by processing with a laser marker. In this case, the area processed with the laser marker becomes the second region 67 with a small amount of light.

[0056] (Control Unit) Next, the function of the control unit 50 of the laser processing device 1 will be described. Fig. 7 is a diagram showing an example of a reference image stored in the storage unit of the control unit of the laser processing device shown in Fig. 2. Fig. 8 is a diagram showing an example of a target image compared by the comparison unit of the control unit of the laser processing device shown in Fig. 2. Fig. 9 is a diagram showing another example of a target image compared by the comparison unit of the control unit of the laser processing device shown in Fig. 2.

[0057] 2, the control unit 50 includes a storage unit 52 capable of storing information, a comparison unit 53, a determination unit 54, and a light amount adjustment unit 55. The storage unit 52 stores a reference image 70 shown in Fig. 7. The reference image 70 is an image obtained by the imaging unit 40 capturing an image of a target 65 of the inspection wafer 60 from the other surface 64 side with a light amount that allows the leakage light 24 of the laser beam 21 to be appropriately detected.

[0058] The reference image 70 is an image in which the amount of infrared light reflected from the first region 66 of the target 65 is equal to or greater than a first predetermined value, and the amount of infrared light reflected from the second region 67 is equal to or less than a second predetermined value that is less than the first predetermined value. The reference image 70 makes the contrast between the first region 66 and the second region 67 clear by having the amount of infrared light reflected from the first region 66 of the target 65 be equal to or greater than the first predetermined value, and the amount of infrared light reflected from the second region 67 be equal to or less than the second predetermined value.

[0059] The comparison unit 53 compares the reference image 70 stored in the storage unit 52 with images 71, 72 (shown in Figs. 8 and 9, hereinafter referred to as target images) of the target 65 of the inspection wafer 60 newly captured from the other surface 64 side by the imaging unit 40. The comparison unit 53 compares the reference image 70 with the target images 71, 72 by well-known image processing such as pattern matching. In the first embodiment, the comparison unit 53 calculates the Q value of the reference image 70 and the Q values ​​of the target images 71, 72, and calculates the difference between these Q values.

[0060] The determination unit 54 determines whether the amount of light 46 from the light source 42 is appropriate based on the comparison result by the comparison unit 53. The determination unit 54 determines whether the reference image 70 and the target images 71, 72 are similar based on the comparison result by the comparison unit 53. If the determination unit 54 determines that the reference image 70 and the target images 71, 72 are similar, it determines that the amount of light 46 from the light source 42 is appropriate, and if it determines that the reference image 70 and the target images 71, 72 are not similar, it determines that the amount of light 46 from the light source 42 is not appropriate.

[0061] In the first embodiment, if the difference between the Q value of the reference image 70 and the Q values ​​of the target images 71, 72 is less than a predetermined value, the determination unit 54 determines that the reference image 70 and the target images 71, 72 are similar to each other and determines that the amount of light 46 from the light source 42 is appropriate. If the difference between the Q value of the reference image 70 and the Q values ​​of the target images 71, 72 is equal to or greater than a predetermined value, the determination unit 54 determines that the reference image 70 and the target images 71, 72 are not similar to each other and determines that the amount of light 46 from the light source 42 is not appropriate.

[0062] When the determination unit 54 determines that the amount of light 46 from the light source 42 is inappropriate, the light amount adjustment unit 55 automatically adjusts the amount of light 46 from the light source 42 so that the target images 71, 72 and the reference image 70 are the same. When the determination unit 54 determines that the amount of light 46 from the light source 42 is inappropriate, the light amount adjustment unit 55 extracts a first region 66 and a second region 67 from the target images 71, 72 by well-known image processing, and calculates the average light amount of the first region 66 and the average light amount of the second region 67.

[0063] The light amount adjustment unit 55 judges whether the average value of the light amount of the first region 66 of the target images 71, 72 is less than a first predetermined value, and whether the average value of the light amount of the second region 67 of the target images 71, 72 exceeds a second predetermined value. When the light amount adjustment unit 55 judges that the average value of the light amount of the first region 66 of the target images 71, 72 is less than the first predetermined value, the light amount adjustment unit 55 increases the light amount of the light 46 of the light source 42 by a predetermined value, thereby automatically adjusting the light amount of the light 46 from the light source 42. When the light amount adjustment unit 55 judges that the average value of the light amount of the second region 67 of the target images 71, 72 exceeds the second predetermined value, the light amount adjustment unit 55 decreases the light amount of the light 46 of the light source 42 by a predetermined value, thereby automatically adjusting the light amount of the light 46 from the light source 42.

[0064] In the first embodiment, the target image 71 shown in Fig. 8 is an image acquired when the average value of the light amount in the second region 67 exceeds a second predetermined value and the amount of light 46 from the light source 42 is excessively greater than an appropriate amount of light. The target image 72 shown in Fig. 9 is an image acquired when the average value of the light amount in the first region 66 is less than a first predetermined value and the amount of light 46 from the light source 42 is excessively less than an appropriate amount of light.

[0065] The function of the storage unit 52 is realized by the above-mentioned storage device. The functions of the comparison unit 53, the determination unit 54, and the light amount adjustment unit 55 are realized by the calculation processing device performing calculation processing in accordance with the computer program stored in the storage device.

[0066] Next, a method of using the inspection wafer according to embodiment 1 will be described. Fig. 10 is a flow chart showing the flow of the method of using the inspection wafer according to embodiment 1. The method of using the inspection wafer is a method of using the inspection wafer 60 having the above-mentioned configuration, and is also a method of setting processing conditions when the laser processing apparatus 1 performs laser processing on the wafer 200 to be processed to form the modified layer 206.

[0067] The processing conditions include the wavelength of the laser beam 21, the cross-sectional shape of the focal point 22 perpendicular to the optical axis (hereinafter referred to as the spot shape), the average output, the repetition frequency, the pulse width, the numerical aperture of the focusing lens of the collector 23, the position of the focal point 22 in the Z-axis direction, and the moving speed of the chuck table 10 in the X-axis direction when the laser beam 21 is irradiated (hereinafter referred to as the processing feed speed).

[0068] The method of using the inspection wafer is a method in which the laser processing apparatus 1 performs inspection using the inspection wafer 60, and includes a reference image storage step 301, an imaging step 302, a comparison step 303, an adjustment step 304, and an inspection step 305, as shown in FIG. 10.

[0069] (Reference image storage step) The reference image storage step 301 is a step in which the storage unit 52 stores the reference image 70. In the first embodiment, in the reference image storage step 301, the control unit 50 receives the processing conditions for the inspection step 305 input by the operator by operating the input unit or the like, and the metal layer 62 of a predetermined inspection wafer 60 is placed on the holding surface 16 of the sub-chuck table 15 positioned in the carry-in / out area. In the first embodiment, when the control unit 50 receives an instruction from the operator to start an operation for setting the processing conditions from the input unit, the operation for setting the processing conditions is started.

[0070] In the reference image storage step 301, the control unit 50 suction-holds the inspection wafer 60 on the holding surface 16 of the sub-chuck table 15, controls the moving unit 30 to position the sub-chuck table 15, which is suction-holding the inspection wafer 60, in the processing area, and positions the target 65 of the inspection wafer 60, which is suction-held on the sub-chuck table 15, below the imaging unit 40.

[0071] In the reference image storage step 301, the control unit 50 adjusts the amount of light 46 from the light source 42 to an amount of light capable of properly detecting an area 68 in the metal layer 62 of the inspection wafer 60 where deterioration has occurred due to the leakage light 24 of the laser beam 21, and the imaging unit 40 images the target 65 from the back surface 205 side of the inspection wafer 60 that is held by suction on the sub-chuck table 15 (step 301-1).

[0072] In the reference image storage step 301, the control unit 50 images the target 65 from the back surface 205 side of the inspection wafer 60 and displays the image acquired on the display unit 51. The operator visually checks the image of the target 65 displayed on the display unit 51 and checks whether the brightness of the image of the target 65, i.e., the amount of light from the light source 42 of the imaging unit 40, is appropriate.

[0073] In the reference image storage step 301, if the brightness of the image of the target 65, i.e., the amount of light of the light source 42 of the imaging unit 40, is not appropriate, the operator operates the input unit to adjust the amount of light of the light source 42 of the imaging unit 40 (step 301-2). Specifically, in the reference image storage step 301, if the operator determines that the image of the target 65 is too bright, he operates the input unit to decrease the amount of light of the light source 42 of the imaging unit 40, and if he determines that the image of the target 65 is too dark, he operates the input unit to increase the amount of light of the light source 42 of the imaging unit 40.

[0074] In the reference image storage step 301, when the operator confirms that the brightness of the image of the target 65, i.e., the amount of light from the light source 42 of the imaging unit 40, is appropriate, the operator operates the input unit to store the image of the target 65 captured by the imaging unit 40 in the memory section 52 as the reference image 70 (step 301-3).

[0075] (imaging step) Fig. 11 is a side view showing a schematic partial cross section of an imaging step of the method of using a wafer shown in Fig. 10. The imaging step 302 is a step of imaging a target 65 formed on an inspection wafer 60. In the first embodiment, in the imaging step 302, if the inspection wafer 60 that is sucked and held on the sub-chuck table 15 and from which the reference image 70 is obtained does not correspond to the wafer 200 to be processed, the laser processing apparatus 1 temporarily moves the sub-chuck table 15 and the like to a carry-in / out area, and replaces the inspection wafer 60 on the sub-chuck table 15 with the inspection wafer 60 that corresponds to the wafer 200 to be processed. The laser processing apparatus 1 sucks and holds the replaced inspection wafer 60 on the sub-chuck table 15.

[0076] In the imaging step 302, if the inspection wafer 60 suction-held on the sub-chuck table 15 in the reference image storage step 301 corresponds to the wafer 200 to be processed, or after the inspection wafer 60 suction-held on the sub-chuck table 15 is replaced with one corresponding to the wafer 200 to be processed, the control unit 50 controls the moving unit 30 to position the sub-chuck table 15 which suction-holds the inspection wafer 60 in the processing area. In the imaging step 302, the laser processing apparatus 1 positions the target 65 of the inspection wafer 60 suction-held on the sub-chuck table 15 below the imaging unit 40, as shown in FIG.

[0077] In the imaging step 302, the control unit 50 adjusts the amount of light 46 from the light source 42 to a predetermined value, and images the target 65 from the other surface 64 side of the inspection wafer 60 suction-held on the sub-chuck table 15 by the imaging unit 40. Thus, the imaging unit 40 includes a light source 42 that irradiates the light 46 onto the target 65 formed on the inspection wafer 60, and images the target 65 by irradiating the light 46 from the light source 42. The imaging unit 40 outputs target images 71, 72 acquired by imaging the target 65 to the control unit 50.

[0078] (Comparison step) The comparison step 303 is a step of comparing the target images 71, 72 acquired by the imaging unit 40 in the imaging step 302 with the reference image 70 stored in the storage section 52 to determine whether the amount of light 46 from the light source 42 when the target images 71, 72 were acquired in the imaging step 302 is appropriate or not. In the comparison step 303, the comparison section 53 compares the reference image 70 stored in the storage section 52 with the target images 71, 72 of the inspection wafer 60 newly acquired by imaging the other surface 64 side by the imaging unit 40 (step 303-1).

[0079] In the comparison step 303, the determination unit 54 determines whether the amount of light 46 from the light source 42 is appropriate or not based on the comparison result by the comparison unit 53 (step 303-2). In the comparison step 303, if the determination unit 54 determines that the amount of light 46 from the light source 42 is not appropriate (step 303-2: No), the process proceeds to the adjustment step 304. Also, in the comparison step 303, if the determination unit 54 determines that the amount of light 46 from the light source 42 is appropriate (step 303-2: Yes), the process proceeds to the inspection step 305.

[0080] (Adjustment steps) The adjustment step 304 is a step of automatically adjusting the amount of light 46 from the light source 42 based on the result of the comparison step 303 so that the target images 71, 72 and the reference image 70 become the same. In the adjustment step 304, the light amount adjustment unit 55 automatically adjusts the amount of light 46 from the light source 42, and the process returns to the imaging step 302.

[0081] In the wafer inspection method according to the first embodiment, the imaging step 302, the comparison step 303, and the adjustment step 304 are repeated until the determination unit 54 determines that the amount of light 46 from the light source 42 is appropriate. In addition, by repeating the imaging step 302, the comparison step 303, and the adjustment step 304 in the wafer inspection method according to the first embodiment until the determination unit 54 determines that the amount of light 46 from the light source 42 is appropriate, the laser processing device 1 automatically adjusts the amount of light 46 from the light source 42 irradiated onto the area including the target 65, which is the processing area of ​​the inspection wafer 60, so that the appearance of the target 65 in the target images 71 and 72 captured by the imaging unit 40 becomes a desired appearance that is close to the reference image 70. The laser processing device 1 automatically adjusts the amount of light 46 from the light source 42 that is irradiated onto the area including the target 65, which is the processing area of ​​the inspection wafer 60, so that the inspection wafer 60 can properly detect the area 68 where the metal layer 62 has been altered due to the leakage light 24 of the laser beam 21.

[0082] (Inspection step) Fig. 12 is a side view, partially in cross section, showing a modified layer forming step in the inspection step of the method of using the inspection wafer shown in Fig. 10. Fig. 13 is a cross-sectional view showing an enlarged portion of the inspection wafer shown in Fig. 12. Fig. 14 is a diagram showing a schematic example of an image captured by an imaging unit in a width measuring step in the inspection step of the method of using the inspection wafer shown in Fig. 10.

[0083] The inspection step 305 is performed after the determination unit 54 determines that the amount of light 46 from the light source 42 is appropriate in the comparison step 303. That is, the inspection step 305 may be performed after the adjustment step 304. The inspection step 305 includes a modified layer formation step 306 and a width measurement step 307.

[0084] The modified layer forming step 306 is a step in which a laser beam 21 of a wavelength that is transparent to the inspection substrate 61 is irradiated from the other surface 64 opposite to the surface 63 on which the metal layer 62 of the inspection wafer 60 is formed, and the focal point 22 inside the inspection substrate 61 and the inspection wafer 60 are moved relative to each other to form a modified layer 206.

[0085] In the modified layer forming step 306, the control unit 50 sets the focal point 22 inside the inspection substrate 61 of the inspection wafer 60 sucked and held on the sub-chuck table 15 based on the processing conditions, and controls the laser beam application unit 20 and the moving unit 30 to irradiate the inspection wafer 60 with a pulsed laser beam 21 from the laser beam application unit 20 from the other surface 64 side while moving the sub-chuck table 15 in the X-axis direction, as shown in Fig. 12. Since the laser beam 21 has a wavelength that is transparent to the inspection substrate 61 of the inspection wafer 60, a modified layer 206 is formed inside the inspection substrate 61 of the inspection wafer 60.

[0086] In addition, when the modified layer 206 is formed, the laser beam 21 hits the fine cracks extending through the modified layer 206, and the refracted or reflected leakage light 24 reaches one side 63 and partially alters the metal layer 62, resulting in areas 68 where the metal layer 62 has been altered.

[0087] The width measuring step 307 is a step of imaging the metal layer 62 of the inspection wafer 60 after the modified layer forming step 306, and measuring the maximum width of the location 68 where the metal layer 62 has been altered. In the width measuring step 307, the control unit 50 controls the moving unit 30 to move the sub-chuck table 15 in the X-axis direction while the imaging unit 40 images the region of the inspection wafer 60 where the modified layer 206 has been formed from the other surface 64 side, thereby obtaining an image 73 shown in FIG.

[0088] In addition, in embodiment 1, in image 73, the amount of infrared light reflected by area 74 (shown by white background in Figure 14) where modified layer 206 of metal layer 62 is not formed and no deterioration has occurred is greater than the amount of infrared light reflected by area 75 (shown by parallel diagonal lines in Figure 14) where modified layer 206 is formed and area 76 where deterioration point 68 (shown by black background in Figure 14) has been formed.

[0089] In the width measurement step 307, the determination section 54 of the control unit 50 extracts the locations 68 where the deterioration of the metal layer 62 has occurred from the image 73, an example of which is shown in Fig. 14, and measures the distance 77 between the two locations 68 where the deterioration has occurred that are furthest apart in the Y-axis direction (corresponding to the maximum width of the locations 68 where the deterioration has occurred) (step 307-1). In the width measurement step 307, the determination section 54 determines whether the measured distance 77 between the two locations 68 where the deterioration has occurred, i.e., the maximum width described above, is appropriate or not (step 307-2).

[0090] In the width measurement step 307, the judgment unit 54 judges whether or not the distance 77 between the two measured altered locations 68 exceeds the width of the planned division line 203 of the wafer 200 to be processed, and judges whether or not the distance 77, i.e., the maximum width mentioned above, is appropriate.

[0091] In the width measurement step 307, if the judgment unit 54 determines that the distance 77 between the two measured altered locations 68 exceeds the width of the planned division line 203 of the wafer 200 to be processed, it judges that the maximum width is not appropriate (step 307-2: No), changes the processing conditions so that the maximum width becomes appropriate (step 307-3), and returns to the modified layer formation step 306.

[0092] Furthermore, in the width measurement step 307, if the distance 77 between the two measured altered locations 68 is less than or equal to the width of the planned division line 203 of the wafer 200 to be processed, the judgment unit 54 judges that the maximum width is appropriate (step 307-2: Yes), and the method of using the inspection wafer relating to embodiment 1 is terminated.

[0093] As described above, the inspection wafer according to the first embodiment includes the target 65 for which the metal layer 62 is automatically adjusted in the laser processing device 1, so that the laser processing device 1 can compare the reference image 70 in which the target 65 is previously captured with an appropriate amount of light with the target images 71, 72 in which the target 65 of the newly prepared inspection wafer 60 is captured, and automatically adjust the amount of light so that the target 65 in the reference image 70 and the target 65 in the newly captured target images 71, 72 look the same. As a result, the inspection wafer 60 has an effect of suppressing oversight of detection of alteration of the metal layer 62 while suppressing the number of steps required by the operator.

[0094] Moreover, the method of using the inspection wafer 60 according to the first embodiment compares a reference image 70 in which the target 65 is previously captured with an appropriate amount of light with target images 71, 72 in which the target 65 of a newly prepared inspection wafer 60 is captured, and automatically adjusts the amount of light so that the target 65 in the reference image 70 and the target 65 in the newly captured target images 71, 72 look the same. As a result, the method of using the inspection wafer has the effect of suppressing oversight of detection of alteration of the metal layer 62 while suppressing the number of steps of the operator's work.

[0095] Moreover, the laser processing apparatus 1 according to the first embodiment includes a light amount adjustment unit 55 that compares a reference image 70 in which the target 65 is previously captured with an appropriate light amount with target images 71, 72 in which the target 65 of a newly prepared inspection wafer 60 is captured, and automatically adjusts the light amount so that the target 65 in the reference image 70 and the target 65 in the newly captured target images 71, 72 look the same. As a result, the laser processing apparatus 1 exhibits the effect of suppressing oversight of detection of alteration of the metal layer 62 while suppressing the number of work steps by the operator.

[0096] The method of using the inspection wafer 60 and the laser processing apparatus 1 of embodiment 1 compare the reference image 70 with the target images 71, 72 and automatically adjust the amount of light so that the target 65 in the reference image 70 and the target 65 in the target images 71, 72 look the same, thereby suppressing operator error and achieving the effect of preventing human error while reducing operator work.

[0097] The present invention is not limited to the above embodiment. In other words, the present invention can be implemented in various modifications without departing from the gist of the present invention. For example, in the present invention, the target 65 may be arranged in a first region 66 and a second region 67 according to a certain rule to indicate information such as numbers, letters, and symbols indicating the rod number of the inspection wafer 60. In this case, the laser processing device 1 may read the information indicated by the target 65 from the target images 71 and 72, and store the read information in association with the images 70, 71, 72, and 73, so that they can be tracked later. [Explanation of symbols]

[0098] 1 Laser processing equipment (inspection equipment) 15 Sub chuck table (chuck table) 20 Laser beam irradiation unit (processing unit) 21 Laser Beam 22 Focus point 23 Concentrator 24 Light Leak 30 Mobile Units 40 Imaging unit 42 Light source 46 light 50 Control Unit 52 Storage section 53 Comparison section 54 Judgment section 55 Light intensity adjustment section 60 Inspection wafer 61 Test board 62 Metal layer 63 One Side 64 The other side (opposite side) 65 Target 68 Location where deterioration occurred 70 Reference Images 71,72 Target image 77 distance (maximum width) 200 wafers 201 Substrate 202 Surface 203 Division line 204 Devices 205 Back side 206 Modified layer 302 Imaging Step 303 Comparison Step 304 Adjustment Steps 305 Inspection Steps 306 Modified layer formation step 307 Width measurement step

Claims

1. In a laser processing apparatus for forming a modified layer inside a substrate by irradiating a laser beam having a wavelength that is transparent to a substrate constituting the wafer from the back surface of the wafer along the planned dividing lines, the wafer having a plurality of devices formed in each region defined by the planned dividing lines, the inspection wafer is used to inspect leakage light of the laser beam that affects devices on the front surface side of the wafer when forming the modified layer, A test board; a metal layer formed on one surface of the testing substrate with a predetermined thickness; the metal layer is provided with a target for automatically adjusting the amount of light in the laser processing device; An inspection wafer capable of properly detecting leakage light from the laser beam by imaging the target in the laser processing device and automatically adjusting the amount of light irradiated to the processing area so that the target appears as desired in the captured image.

2. 2. The inspection wafer according to claim 1, wherein the target is a two-dimensional code.

3. A method for using the inspection wafer according to claim 1 or 2, comprising: an imaging step of imaging a target formed on the inspection wafer; A target image captured in the imaging step; and a comparison step of comparing the image with a reference image obtained by previously capturing an image of the target with an amount of light that allows the leakage light of the laser beam to be appropriately detected; and an adjustment step of adjusting the amount of light based on a result of the comparison step so that the target image becomes the same as the reference image. After carrying out the adjustment step, Irradiating the inspection wafer from a surface opposite to the surface on which the metal layer is formed with a laser beam having a wavelength that is transparent to the inspection substrate; a modified layer forming step of forming a modified layer by relatively moving a focal point of the light focused inside the inspection substrate and the inspection wafer; a width measuring step of imaging the metal layer of the inspection wafer after the modified layer forming step and measuring the maximum width of a portion where the metal layer has been altered; 4. A method of using a wafer for inspection, comprising carrying out an inspection step comprising:

4. An inspection apparatus for performing an inspection using the inspection wafer according to claim 1 or 2, a chuck table for holding the inspection wafer; a laser beam irradiation unit including a condenser for condensing and irradiating a laser beam onto the inspection wafer held on the chuck table; a moving unit for relatively moving the chuck table and the focal point of the laser beam; an imaging unit that includes a light source that irradiates light onto a target formed on the inspection wafer and images the target by irradiating the light from the light source; A control unit, The control unit a storage unit for storing a reference image obtained by previously capturing an image of the target with an amount of light that allows the leakage light of the laser beam to be appropriately detected; a comparison unit that compares a reference image stored in the storage unit with a target image newly captured by the imaging unit; a determination unit that determines whether or not the amount of light from the light source is appropriate based on a comparison result by the comparison unit; a light amount adjustment unit that automatically adjusts the amount of light from the light source when the determination unit determines that the light amount is not appropriate so that the target image and the reference image become the same; An inspection device comprising:

Images