JP2022164422A - Inspection wafer, usage of inspection wafer, and inspection device - Google Patents

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

The present invention relates to an inspection wafer, a method of using the inspection wafer, and an inspection apparatus.

As a method of dividing a workpiece such as a semiconductor wafer into individual devices, for example, a laser beam having a wavelength that is transparent to the workpiece is focused inside the workpiece corresponding to the line to be divided. By positioning and relatively scanning the laser beam and the workpiece, a modified layer is formed inside the wafer, and then an external force is applied along the planned division line with reduced strength to start the modified layer. There is a method of dividing a workpiece into two (see, for example, Patent Document 1).

However, when the modified layer is formed using the method disclosed in Patent Document 1, the laser beam scatters in the device formed on the surface opposite to the surface irradiated with the laser beam (back surface) and damages the device. It turned out that there was a problem. This problem is presumed to be caused by leakage light of the laser beam refracted or reflected by hitting fine cracks extending in the thickness direction of the wafer from the modified layer.

Therefore, the present inventors have developed an inspection wafer for searching for processing conditions that allow the wafer to be satisfactorily divided while minimizing damage to devices (see, for example, Patent Document 2). This wafer for inspection has a metal layer laminated on the substrate, and the range of damage was specified by measuring the maximum width of the alteration of the metal layer caused by the leakage light of the laser beam when the modified layer was formed. Adjusting processing conditions.

Japanese Patent No. 3408805 JP 2018-64049 A

However, in the inspection wafer disclosed in Patent Document 2, the metal layer has minute variations in thickness. If the metal layer is changed, it may be overlooked even though it is actually changed, and it may become impossible to set appropriate processing conditions.

In order to avoid this problem, an operator currently adjusts the light intensity for each wafer for inspection, but this has been a breeding ground for human error, such as different set values depending on the operator.

The present invention has been made in view of the above facts, and its object is to provide an inspection wafer and a method of using the inspection wafer that can suppress oversight of detection of deterioration of a metal layer while suppressing the number of work steps. and to provide inspection equipment.

In order to solve the above-described problems and achieve the object, a wafer for inspection according to the present invention has a plurality of devices formed in respective regions partitioned by a plurality of planned division lines set on the front surface. When forming a modified layer in a laser processing apparatus that forms a modified layer inside the substrate by irradiating a laser beam having a wavelength that is transparent to the substrate that constitutes the wafer along the dividing line to form the modified layer An inspection wafer for inspecting leakage light of a laser beam that affects devices on the surface side of the wafer, comprising: an inspection substrate; and a metal layer formed with a predetermined thickness on one surface of the inspection substrate. , wherein the metal layer is provided with a target for automatically adjusting the amount of light in the laser processing apparatus, the target is imaged in the laser processing apparatus, and the appearance of the target in the imaged image is desired. It is characterized in that it is possible to appropriately detect leaked light of the laser beam by automatically adjusting the amount of light irradiated to the processing area so as to make it visible.

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

A 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 target image captured in the imaging step, and the laser beam. a comparison step of comparing the target image with a reference image in which the target is captured in advance with a light amount that can appropriately detect the leaked light of the beam; and based on the result of the comparison step, the target image is the same as the reference image. and an adjusting step of adjusting the amount of light so that the amount of light is adjusted so that after performing the adjusting step, the light is transmitted from the surface of the inspection wafer opposite to the surface on which the metal layer is formed to the inspection substrate a modified layer forming step of irradiating a laser beam having a wavelength having a property and relatively moving a condensed point condensed inside the inspection substrate and the inspection wafer to form a modified layer; and a width measurement step of imaging the metal layer of the inspection wafer and measuring the maximum width of the portion where the metal layer is altered, after the modified layer forming step. characterized by

The inspection apparatus of the present invention is an inspection apparatus that performs inspection using the inspection wafer, and comprises a chuck table that holds the inspection wafer, and a laser beam to the inspection wafer held on the chuck table. a laser beam irradiation unit equipped with a condenser for converging and irradiating the laser beam, a moving unit for relatively moving the chuck table and the focal point of the laser beam, and a target formed on the inspection wafer. an imaging unit that has a light source that emits light from the light source and images the target by irradiating light from the light source; and a control unit that can appropriately detect leakage light of the laser beam. A storage unit that stores a reference image of the target captured in advance with a possible amount of light, and a comparison unit that compares the reference image stored in the storage unit with the 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 the comparison result of the comparison unit; and if the determination unit determines that the amount of light is not appropriate, the target image and the reference image are: and a light amount adjusting unit that automatically adjusts the amount of light from the light source so that it becomes the same.

ADVANTAGE OF THE INVENTION This invention is effective in the ability to suppress the oversight of the detection of the deterioration of a metal layer, while suppressing a work man-hour.

FIG. 1 is a perspective view of an inspection wafer according to Embodiment 1. FIG. 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. FIG. 3 is a cross-sectional view showing an enlarged part of a wafer schematically showing a state in which the laser processing apparatus shown in FIG. 2 forms a modified layer on the wafer. 4 is a cross-sectional view schematically showing the configuration of an imaging unit of the laser processing apparatus shown in FIG. 2. FIG. FIG. 5 is a plan view of the wafer for inspection shown in FIG. 1 as viewed from below. FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 7 is a diagram showing an example of a reference image stored in a storage section of a control unit of the laser processing apparatus shown in FIG. 2; FIG. 8 is a diagram showing an example of target images compared by a comparison section of a control unit of the laser processing apparatus shown in FIG. 2. FIG. FIG. 9 is a diagram showing another example of target images compared by the comparison section of the control unit of the laser processing apparatus shown in FIG. FIG. 10 is a flow chart showing the flow of the method of using the wafer for inspection according to the first embodiment. FIG. 11 is a side view schematically showing an imaging step in the method of using the wafer shown in FIG. 10, partially in cross section. FIG. 12 is a side view schematically showing a modified layer forming step in the inspection step of the method of using the wafer for inspection shown in FIG. 10, partially in cross section. FIG. 13 is a cross-sectional view showing an enlarged part of the wafer for inspection shown in FIG. FIG. 14 is a diagram schematically showing an example of an image captured by the imaging unit in the width measurement step of the inspection step of the method of using the wafer for inspection shown in FIG.

A form (embodiment) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited by the contents described in the following embodiments. In addition, the components described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the configurations described below can be combined as appropriate. In addition, various omissions, substitutions, or changes in configuration can be made without departing from the gist of the present invention.

[Embodiment 1]
An inspection wafer 60 and a laser processing apparatus 1 as an inspection apparatus according to Embodiment 1 of the present invention will be described with reference to the drawings. An inspection wafer 60 according to Embodiment 1 shown in FIG. 1 is used in the laser processing apparatus 1, which is the inspection apparatus shown in FIG. The laser processing apparatus 1 shown in FIG. 2 is a processing apparatus that irradiates a wafer 200 with a pulsed laser beam 21 to perform laser processing (corresponding to processing) on the wafer 200 . First, the wafer 200 to be processed by the laser processing apparatus 1 and the laser processing apparatus 1 will be described.

FIG. 1 is a perspective view of an inspection wafer according to Embodiment 1. FIG. 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. FIG. 3 is a cross-sectional view showing an enlarged part of a wafer schematically showing a state in which the laser processing apparatus shown in FIG. 2 forms a modified layer on the wafer. 4 is a cross-sectional view schematically showing the configuration of an imaging unit of the laser processing apparatus shown in FIG. 2. FIG.

(wafer)
A wafer 200 to be processed by the laser processing apparatus 1 shown in FIG. 2 is a disk-shaped semiconductor wafer, an optical device wafer, or the like having a substrate 201 made of silicon, sapphire, gallium arsenide, or the like. A wafer 200 has a plurality of division lines 203 that intersect each other on a surface 202 of a substrate 201 , and devices 204 are formed in each area partitioned by the plurality of division lines 203 set on the surface 202 .

The device 204 is, for example, an integrated circuit such as an IC (Integrated Circuit) or LSI (Large Scale Integration), a CCD (Charge Coupled Device), or an image sensor such as a CMOS (Complementary Metal Oxide Semiconductor).

In the first embodiment, the wafer 200 has an adhesive tape 208 having a disk shape with a larger diameter than the outer diameter of the wafer 200 and an annular frame 207 attached to the outer edge of the adhesive tape 208, which is attached to the surface 202 of the wafer 200. It is supported within an opening 209 in frame 207 . Further, in Embodiment 1, the wafer 200 has the front surface 202 adhered to the adhesive tape 208 and the rear surface 205 on the back side of the front surface 202 faces upward.

In the first embodiment, the wafer 200 is laser-processed by the laser processing apparatus 1 while being supported in the opening 209 of the frame 207 by the adhesive tape 208, thereby forming individual wafers along the dividing line 203. It is divided into devices 204 . Further, in the first embodiment, the substrate 201 of the wafer 200 is made of silicon.

(laser processing equipment)
The laser processing apparatus 1 irradiates a laser beam 21 having a wavelength that is transparent to the substrate 201 constituting the wafer 200 from the back surface 205 of the wafer 200 along the division lines 203 to produce the inside of the substrate 201 as shown in FIG. 1 is a processing apparatus for forming a modified layer 206 shown in FIG. 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 surrounding area. , a refractive index change region, and a region in which these regions are mixed can be exemplified. The modified layer 206 has lower mechanical strength than other portions of the substrate 201 of the wafer 200 .

As shown in FIG. 2, the laser processing apparatus 1 includes 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, and an imaging unit. 40 and a control unit 50 .

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

Further, the chuck table 10 is rotated by the rotary movement unit 34 of the movement 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 is moved in the X-axis direction parallel to the horizontal direction by the X-axis movement unit 31 of the movement unit 30 together with the rotary movement unit 34, and is moved parallel to the horizontal direction and perpendicular to the X-axis direction by the Y-axis movement unit 32. is moved in the Y-axis direction. The chuck table 10 is moved by the moving unit 30 between a processing area below the laser beam irradiation unit 20 and a loading/unloading area away from the laser beam irradiation unit 20 where the wafer 200 is loaded and unloaded.

The sub-chuck table 15 is a chuck table that holds the inspection wafer 60 on the holding surface 16 . In the first embodiment, the sub-chuck table 15 is formed in a flat plate shape with a deformed surface shape, and the holding surface 16 is formed of porous ceramic or the like. The holding surface 16 of the sub-chuck table 15 is connected to a vacuum suction source (not shown) through a vacuum suction path (not shown). The sub-chuck table 15 sucks and holds the inspection wafer 60 placed on the holding surface 16 by being sucked by the vacuum suction source. In Embodiment 1, a plurality of (four in Embodiment 1) sub-chuck tables 15 are arranged around the chuck table 10 .

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 parallel to the horizontal direction by the Y-axis movement unit 32. It is moved in the Y-axis direction perpendicular to the X-axis direction. The sub-chuck table 15 is moved by the moving unit 30 together with the chuck table 10 over the above-described processing area and loading/unloading area. Note that the sub-chuck table 15 can be positioned below the imaging unit 40 in the processing area. In the loading/unloading area, the inspection wafer 60 can be loaded/unloaded onto/from the holding surface 16 of the sub-chuck table 15 .

The laser beam irradiation unit 20 includes a condenser 23 for condensing and irradiating a pulsed laser beam 21 onto the wafer 200 held on the chuck tables 10 and 15 or the wafer 60 for inspection, so that the wafer 200 is laser-processed. It is a unit that It should be noted that the converged irradiation means irradiation with the laser beam 21 condensed at the condensing point 22 .

In the first embodiment, as shown in FIG. 2, part of the laser beam irradiation unit 20 is moved in the Z-axis direction by a Z-axis moving unit 33 of a moving unit 30 provided on an erected wall 3 erected from the apparatus main body 2. is supported by the elevating member 4 which is moved to 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 holding surfaces 11 and 16 of the chuck tables 10 and 15. and a condenser 23 for condensing the laser beam 21 emitted from the laser oscillator onto the wafer 200 or the inspection wafer 60 held in the chamber.

The condenser 23 has a condenser lens (not shown) disposed at a position facing the holding surfaces 11 and 16 of the chuck tables 10 and 15 in the Z-axis direction. The condensing lens transmits the laser beam 21 emitted from the laser oscillator and converges the laser beam 21 to a condensing point 22 (shown in FIG. 3). The laser beam irradiation unit 20 configured as described above directs the converging 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 and 15 to the wafer. 200 or the inside of the inspection wafer 60 , the back surface 205 of the wafer 200 or the inspection wafer 60 is irradiated with the laser beam 21 to form a modified layer 206 inside the wafer 200 or the inspection wafer 60 .

In addition, when the modified layer 206 is formed on the wafer 200 , fine cracks extending in the thickness direction from the formed modified layer 206 may occur. When a fine crack occurs, as shown in FIG. 3, the laser beam 21 irradiated to the wafer 200 hits the fine crack, is refracted or reflected, reaches the surface 202 side, and damages the device 204. (ie, altering the metal that makes up the device 204). The laser beam 21 that hits the fine cracks, is refracted or reflected, and reaches the surface 202 side is hereinafter referred to as the leaked light 24 of the laser beam 21 .

The moving unit 30 moves the chuck tables 10 and 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 the axis parallel to the Z-axis direction. to move relative to The X-axis direction and the Y-axis direction are directions orthogonal to each other and parallel to the holding surface 11 (that is, the horizontal direction). The moving unit 30 includes an X-axis moving unit 31 that is a processing feed unit that moves the chuck tables 10 and 15 in the X-axis direction, and a Y-axis moving unit that is an indexing feed unit that moves the chuck tables 10 and 15 in the Y-axis direction. 32, a Z-axis movement unit 33 that moves the condenser 23 included in the laser beam irradiation unit 20 in the Z-axis direction, and a rotary movement unit 34 that rotates the chuck table 10 around an axis parallel to the Z-axis direction. Prepare.

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

The X-axis movement unit 31 is a unit that relatively feeds the chuck tables 10 and 15 and the laser beam irradiation unit 20 . The X-axis movement unit 31 is installed on the movement plate 5 . The X-axis moving unit 31 movably supports the second moving plate 6 supporting a rotary moving unit 34 that rotates the chuck table 10 about an axis parallel to the Z-axis direction. The second moving plate 6 supports the rotary moving unit 34 , the chuck table 10 and the sub-chuck table 15 . The Z-axis movement 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 rotary movement unit 34 supports the chuck table 10 .

The X-axis moving unit 31, the Y-axis moving unit 32, and the Z-axis moving unit 33 include a well-known ball screw provided rotatably around the axis, a well-known pulse motor for rotating the ball screw around the axis, and a moving plate. 5 and 6 are movably supported in the X-axis direction or the Y-axis direction, and known guide rails are provided to support the lifting member 4 movably in the Z-axis direction. The rotary movement unit 34 includes a motor or the like that rotates the chuck table 10 around its axis.

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, and a Y-axis position detection unit (not shown) for detecting the position of the chuck table 10 in the Y-axis direction. A direction position detection unit and a Z-axis direction position detection unit for detecting the position of the collector 23 included in the laser beam irradiation unit 20 in the Z-axis direction are provided. Each position detection unit outputs a detection result to the control unit 50 .

The imaging unit 40 images the wafer 200 or the inspection wafer 60 held on the chuck table 10 . The imaging unit 40 includes a housing 41, a light source 42, an objective lens 43, a mirror 44, and an imaging device 45, as shown in FIG. The housing 41 is a container having a space inside, is attached to the tip of the housing of the laser beam irradiation unit 20 , and is supported by the elevating member 4 together with the housing of the laser beam irradiation unit 20 .

Light source 42 is attached to housing 41 and emits light 46 within housing 41 . In Embodiment 1, the light 46 emitted by the light source 42 contains at least infrared rays. The objective lens 43 is installed inside the housing 41 and arranged at a position capable of facing the holding surface 11 of the chuck table 10 in the Z-axis direction. In Embodiment 1, the objective lens 43 is arranged at a position aligned with the condenser lens of the laser beam irradiation unit 20 in the X-axis direction. The objective lens 43 converges the light 46 emitted from the light source 42 on the object facing in the Z-axis direction and transmits the light 47 reflected from the object facing in the Z-axis direction.

The mirror 44 is installed inside the housing 41 and guides the light 46 emitted from the light source 42 to the objective lens 43 . Although two mirrors 44 are provided in the first embodiment, the number of mirrors 44 is not limited to two in the present invention. One mirror 44 of the two mirrors 44 faces the light source 42 in the Z-axis direction, is arranged below the light source 42 , and reflects the light 46 upwardly of the objective lens 43 in the horizontal direction. The other mirror 44 faces the objective lens 43 in the Z-axis direction, is arranged above the objective lens 43 and to the side of the one mirror 44 , and directs the light 46 reflected by the one mirror 44 to the objective lens 43 . reflect towards. Also, the other mirror 44 transmits the light 47 described above. Thus, at least the other mirror 44 is a half mirror that reflects light 46 and transmits light 47 .

In the first embodiment, the light source 42 is epi-illumination (also referred to as coaxial illumination) in which the light 46 emitted to the object facing the objective lens 43 in the Z-axis direction is coaxial with the optical axis of the imaging device 45 and the objective lens 43. It is the light source that constitutes. However, in the present invention, the imaging unit 40 constitutes oblique illumination in which the optical axis of the light 46 irradiated to the object facing the objective lens 43 in the Z-axis direction intersects the optical axes of the imaging element 45 and the objective lens 43. A light source may be provided.

The imaging device 45 is arranged in a direction opposite to the direction in which the light 46 passes through the objective lens 43 when viewed from the objective lens 43 . In Embodiment 1, the imaging element 45 is attached to the housing 41 , faces the objective lens 43 in the Z-axis direction, and is arranged above the objective lens 43 . The imaging element 45 receives infrared rays of the light 47 transmitted through the objective lens 43 and captures an infrared image of what the objective lens 43 faces in the Z-axis direction. The imaging element 45 is a CCD (Charge Coupled Device) imaging element, a CMOS (Complementary MOS) imaging element, or the like. In this manner, the imaging unit 40 is configured such that the objective lens 43 and the imaging device 45 are covered by the housing 41 so that light does not enter the housing 41 except for the objective lens 43 from the outside.

The imaging device 45 outputs the acquired 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 a plurality of gradations (for example, 256 gradations).

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

The control unit 50 controls the above-described components of the laser processing apparatus 1 to cause the laser processing apparatus 1 to perform laser processing operations on the wafer 200 . Note that the control unit 50 includes an arithmetic processing unit having a microprocessor such as a CPU (central processing unit), a storage device having a memory such as ROM (read only memory) or RAM (random access memory), an input/output A computer having an interface device. The arithmetic processing unit of the control unit 50 performs arithmetic processing according to a computer program stored in the storage device, and outputs a control signal for controlling the laser processing apparatus 1 to the laser processing apparatus 1 via the input/output interface device. The functions of the control unit 50 are implemented by outputting to the components described above.

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

(Wafer for inspection)
Next, an inspection wafer 60 according to Embodiment 1 will be described. FIG. 5 is a plan view of the wafer for inspection shown in FIG. 1 as viewed from below. FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. The inspection wafer 60 inspects the leakage light 24 of the laser beam 21 that affects the devices 204 on the surface 202 side of the wafer 200 when forming the modified layer 206 on the wafer 200 .

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.

The test substrate 61 is a flat plate having flat surfaces 63 and 64 parallel to each other and having a uniform thickness. The inspection substrate 61 is formed to have a rectangular planar shape that is the same as the planar shape of the sub-chuck table 15 . As with the substrate 201 of the wafer 200 , the inspection substrate 61 is made of a material that forms the modified layer 206 when the laser beam 21 is irradiated with the focal point 22 set inside. 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 the same thickness as the substrate 201 of the corresponding wafer 200 of the inspection wafer 60 . In Embodiment 1, the inspection substrate 61 is made of the same silicon as the substrate 201 of the corresponding wafer 200 .

The metal layer 62 is formed with a predetermined thickness on one surface 63 of the inspection board 61 . As shown in FIGS. 5 and 6, the metal layer 62 has 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 vapor deposition on one surface 63 of the substrate for inspection 61, and like the metal forming the device 204 of the wafer 200, the metal layer 62 can be transformed when irradiated with the leakage light 24 of the laser beam 21. It is composed of

The metal layer 62 is desirably made of the same material as the metal forming the device 204 or a metal having a melting point close to that of the metal. The metal layer 62 is made of, for example, aluminum (Al), tin (Sn), platinum (Pt), gold (Au), silver (Ag), indium (In), lead (Pb), copper (Cu), or chromium (Cr ) and other metals. Also, the thickness of the metal layer 62 is not particularly limited, but it is desirable that the metal layer 62 be formed to a thickness that is easily altered by the leakage light 24 of the laser beam 21 . In Embodiment 1, the metal layer 62 is made of tin (Sn) and has a thickness of 1 μm or less.

Further, in the present invention, the inspection wafer 60 may be provided with an underlying layer between the one surface 63 of the inspection substrate 61 and the metal layer 62 . The base layer is formed on one surface 63 of the inspection substrate 61 by vapor deposition, and the metal layer 62 is formed on the base layer by vapor deposition. The underlying layer is preferably made of a metal that allows the metal layer 62 to adhere well to the test substrate 61 . The underlayer is desirably made of, for example, titanium (Ti) or chromium (Cr).

The inspection substrate 61 configured as described above has the metal layer 62 placed on the holding surface 16 and is held by suction on the holding surface 16 of the sub-chuck table 15 . The image is captured from the side, and the laser beam irradiating unit 20 irradiates the laser beam 21 from the other surface 64 side of the inspection substrate 61 by setting the condensing point 22 inside the inspection substrate 61 .

As shown in FIGS. 5 and 6, only one target 65 is formed at the corner of one surface 63 of the inspection substrate 61. As shown in FIG. The target 65 reflects the light 46 from the light source 42 when the metal layer 62 side of the inspection substrate 61 is attracted 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 . A first area 66 (indicated by a black background in FIG. 5) in which the amount of reflected infrared light of the reflected light 47 is the first amount of light, and a second area 66 (indicated by a black 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. and a region 67 (shown in white in FIG. 5). The first amount of infrared light reflected by the first region 66 is equivalent to the amount of infrared light reflected by the metal layer 62 .

In the first embodiment, the target 65 is configured by arranging the first regions 66 and the second regions 67 in two directions perpendicular to each other on one surface 63, like the two-dimensional code. That is, in the first embodiment, the target 65 is a two-dimensional code in which the first area 66 and the second area 67 are arranged in two directions on one surface 63 perpendicular to each other. However, in the present invention, the target 65 has the first region 66 and the second region 67 arranged in one direction of the one surface 63, and the first region 66 and the second region 67 are formed in a bar shape orthogonal to the arrangement direction. A one-dimensional code (so-called bar code) may be used. In Embodiment 1, the arrangement of the first regions 66 and the second regions 67 of the target 65 is the same arrangement even if the corresponding wafers 200 of the inspection wafer 60 are different.

In Embodiment 1, the first region 66 is made of the same metal as the metal layer 62 , and the target 65 is deposited on the one surface 63 simultaneously with the metal layer 62 when the metal layer 62 is deposited on the one surface 63 . be done. In the first embodiment, the target 65 is such that the metal forming the metal layer 62 and the first region 66 is deposited when the second region 67 is deposited on the one surface 63 of the metal layer 62 and the first region 66 . This is a region that is formed without a substrate and exposes one surface 63 of the inspection substrate 61 . That is, the second area 67 is configured by one surface 63 of the inspection substrate 61 . In this way, the target 65 has the first region 66 and the second region 67, so that the laser processing apparatus 1 automatically adjusts the light amount of the light 46 emitted from the light source 42 of the imaging unit 40 when an image is captured. used for It should be noted that light amount adjustment refers to adjusting the light amount of the light 46 from the light source 42 of the imaging unit 40 . Moreover, in the present invention, the target 65 may be created by processing with a laser marker. In this case, the portion processed with the laser marker becomes the second region 67 where the amount of light is small.

(Controller unit)
Next, functions of the control unit 50 of the laser processing apparatus 1 will be described. 7 is a diagram showing an example of a reference image stored in a storage section of a control unit of the laser processing apparatus shown in FIG. 2; FIG. 8 is a diagram showing an example of target images compared by a comparison section of a control unit of the laser processing apparatus shown in FIG. 2. FIG. FIG. 9 is a diagram showing another example of target images compared by the comparison section of the control unit of the laser processing apparatus shown in FIG.

The control unit 50 includes a storage section 52 capable of storing information, a comparison section 53, a determination section 54, and a light amount adjustment section 55, as shown in FIG. The storage unit 52 stores the reference image 70 shown in FIG. The reference image 70 is an image obtained by previously imaging the target 65 of the inspection wafer 60 from the other surface 64 side by the imaging unit 40 with a light amount that can appropriately detect the leakage light 24 of the laser beam 21 . .

In the reference image 70, 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 less than the first predetermined value. 2 It is an image of a predetermined value or less. In the reference image 70, the amount of infrared light reflected from the first area 66 of the target 65 is greater than or equal to a first predetermined value and the amount of infrared light reflected from the second area 67 is less than or equal to a second predetermined value. The contrast between the first area 66 and the second area 67 is clarified.

The comparison unit 53 compares the reference image 70 stored in the storage unit 52 and the images 71 and 72 of the target 65 of the wafer for inspection 60 (see FIG. 8 and FIG. 9, hereinafter referred to as a target image). The comparison unit 53 compares the reference image 70 and the target images 71 and 72 by image processing such as known 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 and 72, and calculates the difference between these Q values.

The determination unit 54 determines whether or not the light amount of the 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 or not the reference image 70 and the target images 71 and 72 are similar based on the comparison result of the comparison unit 53 . When determining that the reference image 70 and the target images 71 and 72 are similar to each other, the determination unit 54 determines that the light amount of the light 46 from the light source 42 is appropriate. are not approximate, it is determined that the amount of light 46 from the light source 42 is not appropriate.

In the first embodiment, when the difference between the Q value of the reference image 70 and the Q values of the target images 71 and 72 is less than a predetermined value, the determination unit 54 separates the reference image 70 and the target images 71 and 72 from each other. are similar to each other, and it is determined 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 and 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 and 72 are close to each other. It is determined that the amount of light 46 from the light source 42 is not appropriate.

When the determination unit 54 determines that the light amount of the light 46 from the light source 42 is not appropriate, the light amount adjustment unit 55 adjusts the light amount of the light 46 from the light source 42 so that the target images 71 and 72 and the reference image 70 are the same. is automatically adjusted. When the determination unit 54 determines that the light amount of the light 46 from the light source 42 is not appropriate, the light amount adjustment unit 55 extracts the first area 66 and the second area 67 from the target images 71 and 72 by well-known image processing. , the average value of the light intensity of the first region 66 and the average value of the light intensity of the second region 67 are calculated.

The light intensity adjustment unit 55 determines whether the average value of the light intensity of the first regions 66 of the target images 71 and 72 is less than the first predetermined value, and determines whether the average value of the light intensity of the second regions 67 of the target images 71 and 72 is the first predetermined value. 2 Determine whether or not a predetermined value is exceeded. When the light amount adjustment unit 55 determines that the average value of the light amounts of the first regions 66 of the target images 71 and 72 is less than the first predetermined value, the light amount adjustment unit 55 increases the light amount of the light 46 from the light source 42 by a predetermined value. to automatically adjust the amount of light 46 from the light source 42 . If the light amount adjustment unit 55 determines that the average value of the light amounts of the second regions 67 of the target images 71 and 72 exceeds the second predetermined value, the light amount adjustment unit 55 reduces the light amount of the light 46 from the light source 42 by a predetermined value. Then, the amount of light 46 from the light source 42 is automatically adjusted.

In the first embodiment, the target image 71 shown in FIG. 8 is such that the average value of the light intensity of the second region 67 exceeds the second predetermined value, and the light intensity of the light 46 from the light source 42 is lower than the appropriate light intensity. This is an image acquired when there are too many. The target image 72 shown in FIG. 9 was acquired when the average value of the light intensity of the first region 66 was less than the first predetermined value and the light intensity of the light 46 from the light source 42 was excessively less than the appropriate light intensity. It is an image.

The function of the storage unit 52 is implemented by the storage device described above. The functions of the comparison unit 53, the determination unit 54, and the light amount adjustment unit 55 are realized by the arithmetic processing unit performing arithmetic processing according to a computer program stored in the storage device.

Next, a method of using the wafer for inspection according to the first embodiment will be described. FIG. 10 is a flow chart showing the flow of the method of using the wafer for inspection according to the first embodiment. The method of using the inspection wafer is the method of using the inspection wafer 60 configured as described above, and the processing conditions for forming the modified layer 206 by laser processing the wafer 200 to be processed by the laser processing apparatus 1. is also a way to set

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

The inspection wafer usage method is a method in which the laser processing apparatus 1 performs inspection using the inspection wafer 60. As shown in FIG. , an adjustment step 304 and an inspection step 305 .

(Reference image storage step)
A 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 of the inspection step 305 input by the operator by operating the input unit or the like, and the holding surface of the sub-chuck table 15 positioned in the loading/unloading area. A metal layer 62 of a predetermined inspection wafer 60 is placed on 16 . In the first embodiment, when the control unit 50 receives an operator's instruction to start the operation of setting the machining conditions from the input unit, the operation of setting the machining conditions is started.

In the reference image storage step 301, the control unit 50 sucks and holds the inspection wafer 60 on the holding surface 16 of the sub-chuck table 15, controls the moving unit 30, and processes the sub-chuck table 15 holding the inspection wafer 60 by suction. The target 65 of the wafer 60 for inspection, which is positioned in the region and held by the sub-chuck table 15 by suction, is positioned below the imaging unit 40 .

In the reference image storage step 301, the control unit 50 can appropriately detect the portion 68 where the light intensity of the light 46 from the light source 42 is altered by the leakage light 24 of the laser beam 21 in the metal layer 62 of the inspection wafer 60. The target 65 is imaged from the rear surface 205 side of the wafer 60 for inspection held by the sub-chuck table 15 by the imaging unit 40 (step 301-1).

In the reference image storage step 301 , the control unit 50 displays an image acquired by imaging the target 65 from the back surface 205 side of the inspection wafer 60 on the display unit 51 , and the operator can display the image of the target 65 displayed on the display unit 51 . to check whether the brightness of the image of the target 65, that is, the amount of light from the light source 42 of the imaging unit 40 is appropriate.

In the reference image storage step 301, if the brightness of the image of the target 65, that is, the light amount of the light source 42 of the imaging unit 40 is not appropriate, the operator operates the input unit to adjust the light amount of the light source 42 of the imaging unit 40. (Step 301-2). Specifically, in the reference image storage step 301, when the operator determines that the image of the target 65 is too bright, he operates the input unit to reduce the amount of light from the light source 42 of the imaging unit 40 so that the image of the target 65 is dark. If it is determined that it is too much, the input unit is operated to increase the light amount of the light source 42 of the imaging unit 40 .

In the reference image storage step 301 , when the operator confirms that the brightness of the image of the target 65 , that is, the light quantity of the light source 42 of the imaging unit 40 is appropriate, the operator operates the input unit to store the image in the storage section 52 . The image of the target 65 captured by the unit 40 is stored as the reference image 70 (step 301-3).

(imaging step)
FIG. 11 is a side view schematically showing an imaging step in the method of using the wafer shown in FIG. 10, partially in cross section. The imaging step 302 is a step of imaging the targets 65 formed on the inspection wafer 60 . In the first embodiment, in the imaging step 302, if the inspection wafer 60 sucked and held on the sub-chuck table 15 to obtain the reference image 70 does not correspond to the wafer 200 to be processed, the laser processing apparatus 1 Once the sub-chuck table 15 and the like are moved to the loading/unloading area, the inspection wafer 60 on the sub-chuck table 15 is replaced with an inspection wafer 60 corresponding to the wafer 200 to be processed. The laser processing apparatus 1 sucks and holds the inspection wafer 60 after replacement on the sub-chuck table 15 .

In the imaging step 302, if the inspection wafer 60 sucked and held on the sub-chuck table 15 in the reference image storage step 301 corresponds to the wafer 200 to be processed, or if the inspection wafer 60 sucked and 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 sucking and holding 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 held by the sub-chuck table 15 under the imaging unit 40, as shown in FIG.

In the imaging step 302, the control unit 50 adjusts the light intensity of the light 46 of the light source 42 to a predetermined value, and the other side of the inspection wafer 60 sucked and held on the sub-chuck table 15 by the imaging unit 40 is detected. An image of the target 65 is taken from the 64 side. Thus, the imaging unit 40 includes the light source 42 that irradiates the target 65 formed on the inspection wafer 60 with the light 46 , and the target 65 is imaged by irradiating the light 46 from the light source 42 . The imaging unit 40 outputs target images 71 and 72 acquired by imaging the target 65 to the control unit 50 .

(comparison step)
In a comparison step 303, the target images 71 and 72 obtained by the imaging unit 40 in the imaging step 302 are compared with the reference image 70 stored in the storage unit 52, and the target images 71 and 72 are obtained in the imaging step 302. is a step of determining whether or not the amount of light 46 from the light source 42 is appropriate. In the comparison step 303 , the comparison unit 53 compares the reference image 70 stored in the storage unit 52 and the target images 71 and 72 of the inspection wafer 60 newly acquired by imaging from the other surface 64 side by the imaging unit 40 . is compared with (step 303-1).

In the comparison step 303, the determination unit 54 determines whether or not the light amount of the light 46 from the light source 42 is appropriate 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 light amount of the 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, when the determination unit 54 determines that the light amount of the light 46 from the light source 42 is appropriate (step 303-2: Yes), the process proceeds to the inspection step 305. FIG.

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

In the wafer inspection method according to the first embodiment, the imaging step 302, comparison step 303, and adjustment step 304 are repeated until the determination unit 54 determines that the amount of light 46 from the light source 42 is appropriate. Further, 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 light amount of the light 46 from the light source 42 is appropriate. The laser processing apparatus 1 adjusts 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 similar to the reference image 70. automatically adjusts the amount of light 46 emitted from the light source 42 to irradiate the region including . The inspection wafer 60 is processed by automatically adjusting the amount of light 46 emitted from the light source 42 with which the laser processing apparatus 1 irradiates a region including a target 65, which is a processing region of the inspection wafer 60, so that the leakage light 24 of the laser beam 21 is Therefore, it is possible to appropriately detect the location 68 where the metal layer 62 is altered.

(Inspection step)
FIG. 12 is a side view schematically showing a modified layer forming step in the inspection step of the method of using the wafer for inspection shown in FIG. 10, partially in cross section. FIG. 13 is a cross-sectional view showing an enlarged part of the wafer for inspection shown in FIG. FIG. 14 is a diagram schematically showing an example of an image captured by the imaging unit in the width measurement step of the inspection step of the method of using the wafer for inspection shown in FIG.

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

In the modified layer forming step 306, a laser beam 21 having a wavelength that is transparent to the inspection substrate 61 is emitted from the other surface 64 of the inspection wafer 60 opposite to the one surface 63 on which the metal layer 62 is formed. is irradiated, and the converging point 22 condensed inside the inspection substrate 61 and the inspection wafer 60 are relatively moved to form the modified layer 206 .

In the modified layer forming step 306, based on the processing conditions, the control unit 50 sets the condensing point 22 inside the inspection substrate 61 of the inspection wafer 60 held by suction on the sub-chuck table 15, as shown in FIG. As shown, the laser beam irradiation unit 20 and the moving unit 30 are controlled to move the sub-chuck table 15 in the X-axis direction, and the pulsed laser beam 21 emitted from the laser beam irradiation unit 20 is inspected from the other surface 64 side. The wafer 60 for use is irradiated. Since the laser beam 21 has a wavelength that is transparent to the inspection substrate 61 of the inspection wafer 60, the modified layer 206 is formed inside the inspection substrate 61 of the inspection wafer 60. .

When the modified layer 206 is formed, the laser beam 21 strikes fine cracks in which the modified layer 206 extends, and leaked light 24 refracted or reflected reaches the one surface 63 side, and reaches the metal layer. 62 is partially denatured to produce denatured locations 68 in the metal layer 62 .

The width measurement step 307 is a step of imaging the metal layer 62 of the inspection wafer 60 after the modified layer formation step 306 and measuring the maximum width of the location 68 where the metal layer 62 is altered. In the width measurement 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 moves the region of the inspection wafer 60 where the modified layer 206 is formed. An image 73 shown in FIG. 14 is acquired by imaging from the surface 64 side of the .

In Embodiment 1, in the image 73, the amount of infrared light reflected by a region 74 (indicated by a white background in FIG. 14) where the modified layer 206 of the metal layer 62 is not formed and where deterioration has not occurred is From the amount of infrared rays reflected by the region 75 (indicated by parallel hatching in FIG. 14) where the modified layer 206 is formed and the region 76 (indicated by black background in FIG. 14) where alteration occurs (shown by black background in FIG. 14) There are many.

In the width measurement step 307, the determination unit 54 of the control unit 50 extracts the location 68 where the alteration of the metal layer 62 occurs from the image 73 whose example is shown in FIG. A distance 77 (corresponding to the maximum width of the altered locations 68) is measured (step 307-1). In the width measurement step 307, the judging section 54 judges whether or not the distance 77 between the two measured locations 68 where deterioration has occurred, that is, the aforementioned maximum width is appropriate (step 307-2).

In the width measurement step 307, the determination unit 54 determines whether or not the measured distance 77 between the two altered locations 68 exceeds the width of the dividing line 203 of the wafer 200 to be processed. 77, that is, it is determined whether the maximum width described above is appropriate.

In the width measurement step 307, if the determination unit 54 determines that the measured distance 77 between the two altered locations 68 exceeds the width of the dividing line 203 of the wafer 200 to be processed, the maximum width is not appropriate. (step 307-2: No), the processing conditions are changed so that the maximum width is appropriate (step 307-3), and the process returns to the modified layer forming step 306.

In the width measurement step 307, the determination unit 54 determines that the maximum width is appropriate if the measured distance 77 between the two altered locations 68 is equal to or less than the width of the dividing line 203 of the wafer 200 to be processed. It is determined that there is (step 307-2: Yes), and the method of using the inspection wafer according to the first embodiment is terminated.

As described above, in the wafer for inspection according to the first embodiment, the metal layer 62 has the target 65 for automatically adjusting the light amount in the laser processing apparatus 1. A reference image 70 obtained by imaging the target 65 is compared with target images 71 and 72 obtained by imaging the target 65 of the inspection wafer 60 newly prepared, and the target 65 of the reference image 70 and the newly imaged target image 71 are compared. , 72 can be automatically adjusted so that the targets 65 appear the same. As a result, the wafer for inspection 60 has the effect of suppressing oversight of detection of deterioration of the metal layer 62 while suppressing the man-hours of the operator.

Further, the method of using the inspection wafer 60 according to the first embodiment includes a reference image 70 obtained by imaging the target 65 in advance with an appropriate amount of light, a target image 71 obtained by imaging the target 65 of the newly prepared inspection wafer 60, 72, and the amount of light is automatically adjusted so that the target 65 in the reference image 70 and the target 65 in the newly captured target images 71 and 72 look the same. As a result, the method of using the wafer for inspection has the effect of suppressing oversight of detection of deterioration of the metal layer 62 while suppressing the man-hours of the operator.

Further, the laser processing apparatus 1 according to the first embodiment prepares a reference image 70 obtained by imaging the target 65 in advance with an appropriate amount of light, and target images 71 and 72 obtained by imaging the target 65 of the inspection wafer 60 newly prepared. For comparison, the target 65 of the reference image 70 and the targets 65 of the newly captured target images 71 and 72 are provided with a light quantity adjustment unit 55 that automatically adjusts the light quantity so that they look the same. As a result, the laser processing apparatus 1 has the effect of suppressing oversight of detection of deterioration of the metal layer 62 while suppressing the operator's man-hours.

The method of using the inspection wafer 60 and the laser processing apparatus 1 according to the first embodiment compare the reference image 70 and the target images 71 and 72, and the target 65 of the reference image 70 and the target 65 of the target images 71 and 72 are Since the light quantity is automatically adjusted so that the appearance is the same, human error by the operator can be suppressed, and it is possible to prevent human error while reducing the work of the operator.

It should be noted that the present invention is not limited to the above embodiments. That is, it can be modified in various ways without departing from the gist of the present invention. For example, in the present invention, the target 65 arranges the first area 66 and the second area 67 according to a certain rule, and indicates information such as numbers, characters, and symbols indicating the rod number of the inspection wafer 60. But it's okay. In this case, the laser processing apparatus 1 reads the information indicated by the target 65 from the target images 71 and 72, associates the read information with the images 70, 71, 72, and 73, stores them, and can track them later. You can do it.

1 Laser processing equipment (inspection equipment)
15 Sub-chuck table (chuck table)
20 laser beam irradiation unit (processing unit)
21 Laser beam 22 Condensing point 23 Concentrator 24 Leakage light 30 Moving unit 40 Imaging unit 42 Light source 46 Light 50 Control unit 52 Storage unit 53 Comparing unit 54 Judging unit 55 Light amount adjusting unit 60 Wafer for inspection 61 Substrate for inspection 62 Metal Layer 63 One side 64 The other side (opposite side)
65 target 68 location where alteration occurs 70 reference image 71, 72 target image 77 distance (maximum width)
200 wafer 201 substrate 202 front surface 203 division line 204 device 205 back surface 206 modified layer 302 imaging step 303 comparison step 304 adjustment step 305 inspection step 306 modified layer formation step 307 width measurement step

Claims (4)

A laser beam having a wavelength that is transparent to the substrate constituting the wafer is applied from the back surface of the wafer, in which a plurality of devices are formed in each region partitioned by a plurality of planned division lines set on the front surface, along the planned division lines. In a laser processing apparatus that forms a modified layer inside a substrate by irradiating along the surface of the substrate, an inspection wafer for inspecting leakage light of the laser beam that affects the devices on the surface side of the wafer when forming the modified layer. and
an inspection substrate;
a metal layer formed with a predetermined thickness on one surface of the inspection substrate;
The metal layer has a target for automatically adjusting the light amount in the laser processing device,
An image of the target is captured by the laser processing apparatus, and the amount of light irradiated to the processing area is automatically adjusted so that the appearance of the target in the captured image becomes a desired appearance, thereby reducing the leakage light of the laser beam. Inspection wafers that can be properly detected. 2. The wafer for inspection according to claim 1, wherein said target is a two-dimensional code. A method for using the wafer for inspection according to claim 1 or claim 2,
an imaging step of imaging a target formed on the inspection wafer;
a target image captured in the imaging step;
a comparison step of comparing the target with a reference image obtained by imaging the target in advance with a light amount that can appropriately detect the leakage light of the laser beam;
an adjusting step of adjusting the amount of light so that the target image is the same as the reference image based on the result of the comparing step;
After performing the adjustment step,
irradiating a laser beam having 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;
a modified layer forming step of forming a modified layer by relatively moving a condensed point of light collected inside the inspection substrate and the inspection wafer;
After the modified layer forming step, a width measuring step of imaging the metal layer of the inspection wafer and measuring the maximum width of the portion where the metal layer is modified;
A method of using a wafer for inspection, characterized by performing an inspection step comprising: An inspection apparatus for performing inspection using the inspection wafer according to claim 1 or claim 2,
a chuck table holding the inspection wafer;
a laser beam irradiation unit having a condenser for condensing and irradiating a laser beam onto the wafer for inspection 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 having a light source for irradiating light onto a target formed on the inspection wafer and irradiating light from the light source to image the target;
a control unit;
The control unit is
a storage unit that stores a reference image of the target captured in advance with an amount of light that allows the leaked light of the laser beam to be detected appropriately;
a comparison unit that compares the reference image stored in the storage unit and the 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 the comparison result of the comparison unit;
a light amount adjustment unit 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 determination unit determines that the amount of light is not appropriate;
An inspection device comprising:

Images