TW202302263A - Observation device, observation method, and object to be observed - Google Patents

Abstract

The invention provides an observation device, an observation method, and an object to be observed, which can more accurately acquire information about the position of a modified region. This observation device is provided with: an imaging unit which has a condensing lens for condensing, on an object, transmitted light that is trans missive with respect to the object, and which images the object by means of the transmitted light; a moving unit for moving the condenser lens relative to the object; and a control unit for controlling at least the imaging unit and the moving unit, the object has a first surface and a second surface on the opposite side of the first surface, and the object is provided with a mark in which the measured value of the position in the Z direction intersecting the first surface and the second surface is known.

Description

Observation device, observation method and observation object

The present invention relates to an observation device, an observation method, and an observation object.

There is known a laser processing apparatus that irradiates laser light on the wafer from the back side of the semiconductor substrate in order to cut a wafer including a semiconductor substrate and a functional element layer formed on the surface of the semiconductor substrate along a plurality of lines, respectively. light to form multiple rows of modified regions inside the semiconductor substrate along multiple lines respectively. The laser processing apparatus described in Patent Document 1 (Japanese Patent Laid-Open No. 2017-64746) includes an infrared camera, and can observe the modified region formed inside the semiconductor substrate and the processing damage formed on the functional element layer from the back side of the semiconductor substrate. wait.

However, when observing an object using transmitted light transmitted from the object, for example, by moving an imaging unit including a light source of the transmitted light and a detector in the Z direction (for example, the direction of the optical axis of the transmitted light), while The case of photographing an object at a plurality of positions while moving the focused point of the transmitted light in the Z direction. In this case, it is conceivable to calculate the position of the modified region inside the object by multiplying the movement amount of the imaging unit when the modified region is detected by a correction coefficient corresponding to the NA of the objective lens and the refractive index of the object. The estimated value of . However, according to the findings of the inventors of the present invention, as the state of the device and the depth of observation (the distance in the Z direction from the incident surface of the transmitted light to the condensing point) change, the imaging unit when the modified region is detected The amount of movement sometimes deviates. As the cause, first, the shift of the observation position due to the focus blur of the objective lens is considered. That is, when the spherical aberration correction amount of the objective lens of the imaging unit is constant, the constant spherical aberration correction may be weakly corrected in an ideal state. In this case, the converging position of transmitted light in the object becomes relatively shallow, and as a result, the movement amount of the imaging unit when a certain modified region is detected becomes relatively large (observation position becomes deeper). Similarly, when the spherical aberration correction amount of the objective lens of the imaging unit is constant, and the constant spherical aberration correction is overcorrected for the ideal state, the condensing position of the transmitted light in the object is relatively As a result, the movement amount of the imaging unit when a certain modified region is detected becomes relatively small (observation position becomes shallower). In addition, as a cause of variation in the amount of movement, a deviation before and after the operation of the correction ring lens is considered. That is, when the objective lens of the imaging unit is a correction ring lens, even if the correction ring is operated to adjust the aberration correction amount of the correction ring, the operation amount of the correction ring may not be constant with respect to the change amount of the aberration correction amount. , as a result, the viewing position sometimes shifts before and after the operation of the correction collar. In addition, mechanical differences of the objective lens of the imaging unit, detachment of the objective lens, and the like are also one cause of the variation in the amount of movement. In this way, when the movement amount of the imaging unit when the modified region is detected is deviated due to various reasons, when the estimated value of the position of the modified region is calculated by multiplying the movement amount by a fixed correction coefficient, the estimated Values can also be biased. As a result, it is difficult to obtain an accurate position of the modified region. Therefore, an object of the present invention is to provide an observation device, an observation method, and an observation object capable of obtaining more accurate information on the position of a modified region. The observation device of the present invention includes: an imaging unit having a condenser lens for condensing transmitted light having transmittance with respect to the object to the object, for photographing the object with the transmitted light; A moving part that the optical lens relatively moves with respect to the object; and a control part for at least controlling the photographing part and the moving part, the object has a first surface and a second surface on the opposite side of the first surface, and the object is provided with The control unit executes the imaging processing and export processing of the marker whose actual measurement value of the position in the Z direction intersecting the first surface and the second surface is known. In the imaging processing, the imaging unit and the moving unit are controlled so that the transmitted light It enters the inside of the object from the first surface, moves the condenser lens in the Z direction, and shoots the object with the transmitted light to obtain a marker image including a marker image as an internal image of the object, and collects The export process exports correction coefficients such that the calculated value, which is the product of the correction coefficient and the movement amount of the condenser lens when the marker image is captured, becomes the actual measured value after the photographing process. The observation method of the present invention includes: a preparation step of preparing an object, the object has a first surface and a second surface on the opposite side of the first surface, and the object is formed in the Z direction intersecting the first surface and the second surface. In the photographing step, the transmitted light that is transparent to the object is injected into the inside of the object from the first surface, and the condensing lens for condensing the transmitted light is used in the Z direction moving and photographing the object with transmitted light to obtain an image including a mark as an internal image of the object; and an exporting step of exporting a correction coefficient after the photographing step such that the correction coefficient is consistent with the photographed mark The calculated value, which is the product of the moving amount of the condenser lens at the time of imaging, becomes the actual measured value. The objects of these observation devices and observation methods are provided with marks whose actual measured values are known at positions in the Z direction intersecting the first surface and the second surface. In these observation devices and observation methods, by imaging such an object while moving the condenser lens, it is possible to acquire a marker image including an image of the marker as an internal image of the object. Then, a correction coefficient is exported so that the value (measured value) of the product of the correction coefficient and the movement amount of the condenser lens when the mark image is captured is an actual value of the known position of the mark. That is, according to the observation device and observation method, it is possible to derive correction coefficients corresponding to the state of the device when the marker image is captured and the amount of movement of the condenser lens when the marker image is captured (that is, the observation depth). Thereby, when calculating the estimated value of the position of the modified region by observing the modified region with transmitted light, the information on the position of the modified region can be obtained more accurately by using the correction coefficient. The observation device of the present invention may also be configured such that the object is formed with a plurality of marks whose positions in the Z direction are different from each other and whose actual measured values are known, and the control unit moves the condensing lens along the Z direction during the photographing process. Directions are relatively moved so that the focal point of the transmitted light is located at a plurality of positions inside the object in the Z direction to photograph the object, thereby acquiring a plurality of marker images including images of the plurality of markers. In the export process, the control unit may export a plurality of correction coefficients, and the value of the product of the correction coefficient and each movement amount of the condenser lens when each of the plurality of marker images is captured is calculated. Each of the values is each of the measured values of the plurality of markers. In this case, correction coefficients corresponding to a plurality of movement amounts can be exported. Therefore, when calculating the estimated position of the modified region by observing the modified region with transmitted light, more accurate information on the position of the modified region can be obtained in a wider range in the Z direction. The observation device of the present invention may be configured such that modified regions aligned in the X-direction along the first surface and the second surface and cracks extending from the modified regions are formed as marks on the object, and in the imaging process , moving the condenser lens along the Z direction to move the condensing point of the transmitted light and photographing the object with the transmitted light, thereby acquiring cracks including cracks extending in a direction intersecting the X direction and the Z direction. The internal image of the image is used as the marker image. According to the findings of the inventors of the present invention, when a modified region is formed inside an object by, for example, laser processing, cracks extending in various directions from the modified region may be formed. Moreover, among the cracks, the crack extending in the direction intersecting the Z direction intersecting the laser incident surface of the object and the X direction which is the advancing direction of the laser processing can be compared with the modified region by utilizing the The transmitted transmitted light is precisely detected. Therefore, as described above, if the internal image including the image of the crack is used as the marker image, it is possible to reduce the variation in the amount of movement of the condenser lens when the marker image is captured. As a result, more accurate correction coefficients can be exported. The observation device of the present invention may be configured such that the imaging unit has a correction ring lens including a condenser lens and a correction ring provided on the condenser lens for correcting aberrations occurring in the object. Thus, in the case where the condenser lens is provided with a correction ring, there is a problem that the state of the device changes before and after the operation of the correction ring. Therefore, it is more effective to export the correction coefficient according to the state of the device as described above. The observation device of the present invention may be configured to include: a setting unit for setting an object; and an object set on the setting unit. In this way, by always setting the marked object, it is possible to export the correction coefficient at any time. The observation device of the present invention includes: a photographing unit having a condensing lens for converging the transmitted light having transmittance to the target object on the target object for photographing the target object with the transmitted light; A moving part that the optical lens relatively moves with respect to the object; and a control part for controlling at least the photographing part and the moving part, the object has a first surface and a second surface on the opposite side of the first surface, and the object is provided with There is a modified region and a crack extending from the modified region, and the control unit executes imaging processing and calculation processing, wherein in the imaging processing, the imaging unit and the moving unit are controlled so that transmitted light enters the object from the first surface, so that The condenser lens is moved in the Z direction intersecting the first surface and the second surface, and the object is photographed with transmitted light to obtain a detection image including a modified region and/or a crack image as an internal image, and the calculation Processing After the photographing process, the correction coefficient is multiplied by the movement amount of the condenser lens when the detection image is captured to calculate the estimated value of the position of the modified region and/or crack in the Z direction, and the control unit saves and moves The amount of corresponding multiple correction coefficients. This observation device stores a correction coefficient corresponding to the movement amount of the condenser lens as described above. Therefore, by calculating the estimated value of the position of the modified region using the correction coefficient, more accurate information on the position of the modified region can be obtained. The observation object of the present invention has a first surface and a second surface on the opposite side of the first surface, on which a mark is provided, and the observation object is used to derive a correction coefficient for calculating and calculating from an actual measured value at the position of the mark. The measured value of the position of the mark in the Z direction where the first surface and the second surface intersect. Using this observation object, it is possible to derive the correction coefficient as described above. According to the present invention, it is possible to provide an observation device, an observation method, and an observation object capable of more accurately acquiring information on the position of a modified region.

Hereinafter, an embodiment will be described in detail with reference to the drawings. However, in the description of each drawing, the same reference numerals may be assigned to the same or corresponding parts, and overlapping descriptions may be omitted. In addition, in each drawing, a rectangular coordinate system defined by an X axis, a Y axis, and a Z axis may be shown. As an example, the X direction and the Y direction are a first horizontal direction and a second horizontal direction intersecting (orthogonal) with each other, and the Z direction is a vertical direction intersecting (orthogonal) the X direction and the Y direction. As shown in FIG. 1 , the laser processing apparatus 1 includes a stage 2, a laser irradiation unit 3 (irradiation unit), a plurality of imaging units 4, 5, 6, a drive unit 7, a control unit 8, and a display 150 (display unit). The laser processing apparatus 1 is an apparatus for forming a modified region 12 on an object 11 by irradiating the object 11 with laser light L. The stage 2 supports the object 11 by, for example, a film adhered to the object 11 by suction. The mounting table 2 is movable along the X direction and the Y direction, and is rotatable about an axis parallel to the Z direction as a center line. The laser irradiation unit 3 condenses the laser light L having transmittance to the object 11 to irradiate the object 11 . When the laser light L is condensed to the inside of the object 11 supported by the stage 2, the laser light L is particularly absorbed at the part corresponding to the condensing point C of the laser light L, and a laser light L can be formed inside the object 11. Modified area 12. The modified region 12 is a region that differs in density, refractive index, mechanical strength, or other physical properties from the surrounding non-modified region. As the modified region 12, there are, for example, a melt-processed region, a crack region, a dielectric breakdown region, a refractive index change region, and the like. The modified region 12 has a characteristic that cracks easily extend from the modified region 12 to the incident side of the laser light L and the opposite side. Such properties of the modified region 12 are utilized for cutting the object 11 . As an example, when the stage 2 is moved in the X direction and the focused point C is relatively moved in the X direction with respect to the object 11, a plurality of modified spots are formed in a row along the X direction. 12s. One modified spot 12s is formed by irradiating one pulse of laser light L. One row of modified regions 12 is a collection of a plurality of modified spots 12s arranged in one row. Adjacent modified spots 12s may be connected to each other or may be separated from each other depending on the relative movement speed of the focused spot C with respect to the object 11 and the repetition frequency of the laser light L. The imaging unit 4 photographs the modified region 12 formed in the object 11 and the tip of a crack extending from the modified region 12 . The imaging unit 5 and the imaging unit 6 image the object 11 supported by the mounting table 2 using the light transmitted from the object 11 under the control of the control unit 8 . Images captured by the imaging units 5 and 6 are used, for example, to align the irradiation position of the laser light L. FIG. The driving unit 7 supports the laser irradiation unit 3 and the plurality of imaging units 4 , 5 , 6 . The driving unit 7 moves the laser irradiation unit 3 and the plurality of imaging units 4, 5, 6 in the Z direction. The control unit 8 controls the operations of the mounting table 2 , the laser irradiation unit 3 , the plurality of imaging units 4 , 5 , and 6 , and the driving unit 7 . The control unit 8 is configured as a computer device including a processor, a memory, a register, a communication device, and the like. In the control unit 8 , the processor executes software (program) read from the memory, etc., and controls reading or writing of data in the memory and temporary register, and communication by the communication device. The display 150 has a function as an input unit that accepts input of information from a user, and a function as a display unit that displays information to the user. [Structure of Object] The object 11 of this embodiment is a wafer 20 as shown in FIGS. 2 and 3 . The wafer 20 includes a semiconductor substrate 21 and a functional element layer 22 . In this embodiment, it is described that the wafer 20 includes the functional element layer 22 , but the wafer 20 may have the functional element layer 22 or may not have the functional element layer 22 , or may be a bare wafer. The semiconductor substrate 21 has a front surface 21a (second surface) and a back surface 21b (first surface). The semiconductor substrate 21 is, for example, a silicon substrate. The functional element layer 22 is formed on the surface 21 a of the semiconductor substrate 21 . The functional element layer 22 includes a plurality of functional elements 22a arranged two-dimensionally along the surface 21a. The functional element 22a is, for example, a light receiving element such as a photodiode, a light emitting element such as a laser diode, or a circuit element such as a memory. The functional element 22a may also be formed three-dimensionally by stacking a plurality of layers. In addition, although the notch 21c showing the crystal orientation is provided in the semiconductor substrate 21, an orientation flat may be provided instead of the notch 21c. The wafer 20 is cut along the plurality of lines 15 for each functional element 22a. The plurality of lines 15 pass between each of the plurality of functional elements 22 a when viewed from the thickness direction of the wafer 20 . More specifically, the line 15 passes through the center of the ruled line region 23 (the center in the width direction) when viewed from the thickness direction of the wafer 20 . The ruled line region 23 extends in the functional element layer 22 so as to pass between adjacent functional elements 22a. In this embodiment, a plurality of functional elements 22a are arranged in a matrix along the surface 21a, and a plurality of lines 15 are set in a grid. In addition, although the line 15 is an imaginary line, it may be an actually drawn line. [Structure of Laser Irradiating Unit] As shown in FIG. 4 , the laser irradiating unit 3 has a light source 31 , a spatial light modulator 32 and a condenser lens 33 . The light source 31 outputs laser light L by, for example, pulse oscillation. The spatial light modulator 32 modulates the laser light L output from the light source 31 . The spatial light modulator 32 is, for example, a reflective liquid crystal (LCOS: Liquid Crystal on Silicon) spatial light modulator (SLM: Spatial Light Modulator). The condensing lens 33 condenses the laser light L modulated by the spatial light modulator 32 . Wherein, the condenser lens 33 may also be a correction ring lens. In the present embodiment, the laser irradiation unit 3 irradiates the laser light L to the wafer 20 from the back surface 21b side of the semiconductor substrate 21 along the plurality of lines 15, thereby irradiating the laser light L inside the semiconductor substrate 21 along the plurality of lines 15 respectively. Two rows of modified regions 12a, 12b are formed. The modified region 12a is the modified region closest to the surface 21a among the two rows of modified regions 12a and 12b. The modified region 12b is the modified region closest to the modified region 12a among the two rows of modified regions 12a and 12b, and is the modified region closest to the back surface 21b. The two rows of modified regions 12 a and 12 b are adjacent to each other in the thickness direction (Z direction) of the wafer 20 . The two rows of modified regions 12 a and 12 b are formed by relatively moving the two light-converging points C1 and C2 along the line 15 with respect to the semiconductor substrate 21 . The laser light L is modulated by the spatial light modulator 32 , so that, for example, the focal point C2 is located on the rear side of the traveling direction and on the incident side of the laser light L relative to the focal point C1 . Here, regarding the formation of the modified region, it may be single focus or multi focus, and may be one path or multiple paths. The laser irradiation unit 3 irradiates the wafer 20 with laser light L along each of the plurality of lines 15 from the back surface 21 b side of the semiconductor substrate 21 . As an example, with respect to the semiconductor substrate 21 which is a single-crystal silicon <100> substrate with a thickness of 400 μm, two light-converging points C1 and C2 are respectively focused on a position 54 μm away from the surface 21 a and a position 128 μm away from the surface 21 a. Each line 15 of 15 irradiates laser light L to the wafer 20 from the back surface 21 b side of the semiconductor substrate 21 . At this time, for example, under the condition that the cracks 14 throughout the two rows of modified regions 12a, 12b reach the surface 21a of the semiconductor substrate 21, the wavelength of the laser light L is 1099nm, the pulse width is 700n seconds, and the repetition frequency is 120kHz. . In addition, let the output of the laser light L at the converging point C1 be 2.7 W, and the output of the laser light L at the converging point C2 be 2.7 W, and let the relative moving speeds of the two converging points C1 and C2 with respect to the semiconductor substrate 21 be 800mm/sec. Wherein, for example, when the number of processing passes is 5, for the above-mentioned wafer 20, ZH80 (position 328 μm away from surface 21a), ZH69 (position 283 μm away from surface 21a), ZH57 (position 283 μm away from surface 21a) and ZH57 (position 328 μm away from surface 21a) can also be used for the above-mentioned wafer 20, for example. 21a at a distance of 234 μm), ZH26 (a position at a distance of 107 μm from the surface 21a), and ZH12 (a position at a distance of 49.2 μm from the surface 21a) are processing positions. In this case, for example, the laser light L may have a wavelength of 1080 nm, a pulse width of 400 nsec, a repetition frequency of 100 kHz, and a moving speed of 490 mm/sec. The formation of such two rows of modified regions 12a, 12b and cracks 14 is carried out as follows. That is, in subsequent steps, for example, by grinding the back surface 21b of the semiconductor substrate 21, the semiconductor substrate 21 is thinned, and the cracks 14 are exposed to the back surface 21b, and the wafer 20 is cut into multiple pieces along the plurality of lines 15, respectively. case of a semiconductor element. [Structure of Imaging Unit for Inspection] As shown in FIG. The photographing unit 4 photographs the wafer 20 . The light source 41 outputs light I1 that is transparent to the semiconductor substrate 21 . The light source 41 is composed of, for example, a halogen lamp and a filter, and outputs light I1 in the near-infrared region. The light I1 output from the light source 41 is reflected by the mirror 42 , passes through the objective lens 43 , and is irradiated to the wafer 20 from the rear surface 21 b side of the semiconductor substrate 21 . At this time, the stage 2 supports the wafer 20 on which the two rows of modified regions 12 a and 12 b are formed as described above. The objective lens 43 is used to condense light (transmitted light) I1 that is transparent to the semiconductor substrate 21 toward the semiconductor substrate 21 . The objective lens 43 passes the light I1 reflected by the surface 21 a of the semiconductor substrate 21 . That is, the objective lens 43 passes the light I1 having propagated through the semiconductor substrate 21 . The numerical aperture (NA) of the objective lens 43 is 0.45 or more, for example. The objective lens 43 has a correction ring 43a. The correction ring 43 a corrects the aberration generated by the light I1 in the semiconductor substrate 21 by, for example, adjusting the distance between a plurality of lenses constituting the objective lens 43 . Here, the means for correcting aberrations is not limited to the correction ring 43a, and other correction means such as a spatial light modulator may also be used. The light detection unit 44 detects the light I1 transmitted through the objective lens 43 and the reflection mirror 42 . The photodetector 44 is composed of, for example, an InGaAs camera, and detects the light I1 in the near-infrared region. However, the means for detecting (imaging) the light I1 in the near-infrared region is not limited to an InGaAs camera, and other imaging means that perform transmission-type imaging such as a transmission confocal microscope may be used. The imaging unit 4 is capable of imaging each of the two rows of modified regions 12a, 12b and the front ends of each of the plurality of cracks 14a, 14b, 14c, and 14d (details will be described later). The crack 14a is a crack extending from the modified region 12a toward the surface 21a. The crack 14b is a crack extending from the modified region 12a to the rear surface 21b side. The crack 14c is a crack extending from the modified region 12b to the surface 21a side. The crack 14d is a crack extending from the modified region 12b to the rear surface 21b side. [Structure of Imaging Unit for Alignment Correction] As shown in FIG. 6 , the imaging unit 5 has a light source 51 , a mirror 52 , a lens 53 , and a photodetector 54 . The light source 51 outputs light I2 that is transparent to the semiconductor substrate 21 . The light source 51 is composed of, for example, a halogen lamp and a filter, and outputs light I2 in the near-infrared region. The light source 51 can also be shared with the light source 41 of the imaging unit 4 . The light I2 output from the light source 51 is reflected by the mirror 52 , passes through the lens 53 , and is irradiated onto the wafer 20 from the rear surface 21 b side of the semiconductor substrate 21 . The lens 53 passes the light I2 reflected by the surface 21 a of the semiconductor substrate 21 . That is, the lens 53 passes the light I2 that has propagated through the semiconductor substrate 21 . The numerical aperture of the lens 53 is 0.3 or less. That is, the numerical aperture of the objective lens 43 of the imaging unit 4 is larger than the numerical aperture of the lens 53 . The light detection unit 54 detects the light I2 passing through the lens 53 and the reflection mirror 52 . The photodetector 54 is composed of, for example, an InGaAs camera, and detects the light I2 in the near-infrared region. Under the control of the control unit 8 , the imaging unit 5 irradiates the wafer 20 with light I2 from the back surface 21b side, and detects the light I2 returned from the surface 21a (functional element layer 22 ), thereby imaging the functional element layer 22 . Also, under the control of the control unit 8, the imaging unit 5 irradiates the wafer 20 with light I2 from the back surface 21b side, and detects the light I2 returning from the positions where the modified regions 12a, 12b are formed on the semiconductor substrate 21, whereby An image of a region including the modified regions 12a, 12b is acquired. These images are used to calibrate the irradiation position of the laser beam L. FIG. The photographing unit 6 has the same structure as the photographing unit 5 except that it has a lower magnification than the lens 53 (for example, 6 times in the photographing unit 5 and 1.5 times in the photographing unit 6), and has the same structure as the photographing unit 5. 5 is also used for calibration. [Principle of imaging by imaging unit for inspection] Using imaging unit 4 shown in FIG. 5, as shown in FIG. (The focal point of the objective lens 43) moves from the back surface 21b side to the surface 21a side. In this case, when the focal point F is focused on the front end 14e of the crack 14 extending from the modified region 12b to the back side 21b side from the rear surface 21b side, the front end 14e can be confirmed (right image in FIG. 7 ). However, even if the focal point F is focused on the crack 14 itself and the tip 14e of the crack 14 that has reached the surface 21a from the back surface 21b side, it cannot be confirmed (the image on the left side of FIG. 7 ). In addition, when the focal point F is focused on the front surface 21 a of the semiconductor substrate 21 from the rear surface 21 b side, the functional element layer 22 can be confirmed. And, using the imaging unit 4 shown in FIG. 5, as shown in FIG. 8, for the semiconductor substrate 21 in which the crack 14 spanning the two rows of modified regions 12a, 12b has not reached the surface 21a, the focal point F is directed from the back surface 21b side to the surface 21a. Move sideways. In this case, even if the focal point F is focused on the front end 14e of the crack 14 extending from the modified region 12a to the front surface 21a side from the rear surface 21b side, the front end 14e cannot be confirmed (the left image in FIG. 8 ). However, if the focal point F is focused from the rear surface 21b side to a region located on the opposite side to the rear surface 21b with respect to the surface 21a (that is, a region located on the functional element layer 22 side with respect to the surface 21a), the focal point F is symmetrical with respect to the surface 21a. When the virtual focal point Fv is positioned at the front end 14e, the front end 14e can be confirmed (the image on the right side of FIG. 8 ). In addition, the virtual focal point Fv is a point symmetrical to the focal point F with respect to the surface 21 a in consideration of the refractive index of the semiconductor substrate 21 . It is presumed that the crack 14 cannot be confirmed as described above because the width of the crack 14 is smaller than the wavelength of the light I1 which is the illumination light. 9 and 10 are SEM (Scanning Electron Microscope) images of modified regions 12 and cracks 14 formed inside semiconductor substrate 21 which is a silicon substrate. (b) of FIG. 9 is an enlarged image of the region A1 shown in (a) of FIG. 9 , (a) of FIG. 10 is an enlarged image of the region A2 shown in (b) of FIG. 9 , and ( b) is an enlarged image of the area A3 shown in (a) of FIG. 10 . Thus, the width of the crack 14 is about 120 nm, which is smaller than the wavelength (for example, 1.1 to 1.2 μm) of the light I1 in the near-infrared region. The principle of photography conceived from the above matters is as follows. As shown in (a) of FIG. 11 , since the light I1 does not return when the focal point F is placed in the air, a pitch-black image (image on the right side of (a) of FIG. 11 ) is obtained. As shown in (b) of FIG. 11 , if the focal point F is located inside the semiconductor substrate 21, the light I1 reflected by the surface 21a will return, so a clean image (the figure on the right side of (b) of FIG. 11 ) will be obtained. picture). As shown in (c) of FIG. 11 , if the focal point F is focused on the modified region 12 from the rear surface 21b side, part of the light I1 returned after being reflected by the surface 21a is absorbed, scattered, etc. by the modified region 12, Therefore, an image (image on the right side of (c) of FIG. 11 ) showing the jet-black modified region 12 against a clean background is obtained. As shown in (a) and (b) of FIG. 12, if the focal point F is focused on the front end 14e of the crack 14 from the back surface 21b side, for example, due to optical specificity (stress concentration, distortion, atomic crack) generated near the front end 14e, Density discontinuity, etc.) makes the light localized near the front end 14e, etc., thereby causing a part of the light I1 reflected by the surface 21a to be scattered, reflected, interfered, absorbed, etc., so it will be displayed in a white background An image of the jet-black front end 14e is obtained (images on the right side of (a) and (b) of FIG. 12 ). As shown in (c) of FIG. 12 , if the focal point F is focused from the back surface 21b side to a portion other than the vicinity of the front end 14e of the crack 14, at least a part of the light I1 reflected by the surface 21a will return, so that a clean white image will be obtained. image (the image on the right side of (c) in FIG. 12 ). [Example of Internal Observation] FIG. 13 is a view showing an object on which a modified region is formed. (a) of FIG. 13 is a cross-sectional photograph of an object cut so as to expose a modified region. (b) of FIG. 13 is an example of an image of an object captured by light transmitted through the object. (c) of FIG. 13 is another example of an image of an object captured by light transmitted through the object. As shown in (a) of FIG. 13 , the modified region 12 formed on the object (here, the semiconductor substrate 21 ) by condensing the laser light L includes: Void region 12m on the side opposite to surface 21a; and Void region 12n on the back surface 21b side, which is a surface where laser light L is incident from defect region 12m. When the semiconductor substrate 21 on which such a modified region 12 is formed is photographed by light I1 which is transparent to the semiconductor substrate 21, as shown in (b) and (c) of FIG. An image of a crack 14k extending in a direction intersecting the Z direction and the X direction (having an angle with respect to the X direction). When viewed from the Z direction, the crack 14k is approximately parallel to the Y direction in the example of FIG. 13( b ), and is slightly inclined relative to the Y direction in the example of FIG. 13( c ). When the image of these cracks 14k is photographed at a plurality of positions on the semiconductor substrate 21 while moving the converging point of the light I1 in the Z direction, the range in the Z direction can be limited compared with that of the modified region 12 was clearly detected. FIG. 14 is a graph regarding the location of modified regions and cracks in the Z direction. In FIG. 14 , the plots of the lower end of the defect, the upper end of the defect, the lower end of the area above the defect, and the upper end of the area above the defect are actual measured values actually measured by cross-sectional observation. The lower end means the end on the front surface 21a side, and the upper end means the end on the back surface 21b side. Therefore, for example, the lower end of the region above the defect refers to the end of the region 12n above the defect on the surface 21a side. In addition, the drawing of the direct observation and the back reflection observation in the graph of FIG. 14 is based on the movement of the objective lens 43 in the Z direction when the internal image including the clear image of the crack 14k in the image obtained by using the light I1 is photographed. The measured value obtained by calculation of the amount (hereinafter sometimes simply referred to as "movement amount") is, for example, a value obtained by image judgment based on AI. Direct observation is the case where light I1 is incident from the back surface 21b, and the converging point of light I1 is directly aligned with the crack 14k without being reflected by the surface 21a (in the above example, the focal point F is aligned with the crack 14k from the back surface 21b side). 14k), the back reflection observation is the case where light I1 is incident from the back surface 21b, and the converging point of the light I1 reflected by the surface 21a is aligned with the crack 14k (in the above example, with respect to the surface 21a, When the focal point F is aligned with the area on the opposite side of the rear surface 21b from the rear surface 21b side, and the virtual focal point Fv symmetrical to the focal point F with respect to the surface 21a is aligned with the crack 14k). As shown in FIG. 14 , in direct observation, in the cases C1 to C4 where the formation positions of the modified regions 12 are located at four different positions in the Z direction, all detection is between the lower end of the region above the defect and the upper end of the region above the defect. A crack 14k is detected. In the back reflection observation, the crack 14k is detected at approximately the same position as the lower end of the area above the defect in case C1, and the crack 14k is detected between the lower end of the area above the defect and the upper end of the defect in cases C2~C4. The width of the modified region 12 in the Z direction is the distance between the lower end of the defect and the upper end of the region above the defect. In this way, the crack 14 k can be detected more accurately in the Z direction than the modified region 12 itself. Therefore, by acquiring the movement amount of the internal image when the crack 14k appears in the Z direction, information on the position of the modified region 12 can be acquired more accurately. Here, the vertical axis in FIG. 14 represents the distance from the back surface, where the back surface is the back surface with respect to the incident surface of the light I1 , and is the surface 21 a for the semiconductor substrate 21 . In addition, Fig. 15 is obtained by plotting the detection results in the case C1 on the cross-sectional photograph. In this embodiment, based on the above findings, the crack 14k is detected by internal observation, and the information on the position of the modified region 12 is acquired. Next, the observation method of this embodiment will be described. In this observation method, the crack 14k is a crack to be detected. In this embodiment, when obtaining information on the position of the modified region 12, first, the position of the crack 14k in the Z direction is calculated. At this time, the movement amount of the objective lens 43 in the Z direction when the internal image of the detected crack 14k is captured is multiplied by a predetermined correction coefficient. As shown in FIGS. 14 and 15 , cracks 14 k are detected within the range of the modified region 12 in the Z direction. Therefore, the calculated position of the crack 14 k is the calculated value of the position of the modified region 12 in the Z direction. First, the discovery about the correction coefficient will be described. As shown in FIG. 16 , in order to adjust the position of the converging point of the light I1 in the semiconductor substrate 21 , the imaging unit 4 is moved by a movement amount Fz in the Z direction using the drive unit 7 . At this time, if there is no semiconductor substrate 21, the moving amount of the converging point of the light I1 is also the moving amount Fz. However, when the converging point of the light I1 is formed inside the semiconductor substrate 21 , the moving amount of the converging point of the light I1 is a moving amount Hz different from the moving amount Fz (magnified in the illustrated example). The amount of movement Hz defines the actual imaging position in the semiconductor substrate 21 , that is, the position of the detection target (for example, the modified region 12 and the crack 14 k ). On the other hand, the information that can be directly acquired by the control unit 8 is the movement amount Fz of the imaging unit 4 (that is, the movement amount Fz of the focal point when there is no semiconductor substrate 21 ) as an input value for the control of the drive unit 7 . ). Therefore, in order to obtain the actual position of the detection target in the semiconductor substrate 21 , the control unit 8 needs to multiply the movement amount Fz by a certain coefficient. The coefficient applied at this time is the correction coefficient. This correction coefficient can be set to a constant value (for example, about 4 when the semiconductor substrate 21 is silicon) in consideration of the NA of the objective lens 43 and the refractive index of the semiconductor substrate 21 . However, when the correction coefficient is set to a constant value, the following problems may arise. 17 is a graph showing the relationship between the position of the detection target in the Z direction and the movement amount when the detection target is detected. The "depth position" on the horizontal axis of the graph in FIG. 17 is the position in the Z direction where the detection object is set (the position where the light I1 is aligned), and the "Z-axis movement amount" on the vertical axis of the graph in FIG. 17 is " is the movement amount Fz when the detection object is detected at each position in the Z direction. The detection objects are arranged at intervals of about 40 μm in the semiconductor substrate 21 so that the detection objects can be detected when the movement amount Fz is 10 μm. In FIG. 17 , graphs in a plurality of cases with different device states are collectively described. In the case of focusing on one device state (one graph), when the position of the detection object in the Z direction is different, the original The amount of movement Fz that should be fixed at 10 μm deviates. The same applies when comparing a plurality of device states (a plurality of graphs). The cause of the shift in the amount of movement Fz in this way is, first, the shift in the observation position due to the focus blur of the objective lens 43 . That is, when the amount of spherical aberration correction of the objective lens 43 of the imaging unit 4 is constant, the constant spherical aberration correction is weak correction relative to the ideal state. In this case, the condensing position of the light I1 in the semiconductor substrate 21 becomes relatively shallow, and as a result, the movement amount Fz of the imaging unit 4 when a certain modified region 12 is detected becomes relatively large (the observation position becomes Deeper). Similarly, when the spherical aberration correction amount of the objective lens 43 of the imaging unit 4 is constant, and the constant spherical aberration correction is overcorrected compared to the ideal state, the condensing position of the light I1 in the semiconductor substrate 21 is relatively changed. As a result, the movement amount Fz of the imaging unit 4 when a certain modified region 12 is detected becomes relatively small (the observation position becomes shallower). In addition, as a cause of variation in the amount of movement Fz, it is conceivable to consider a deviation before and after the operation of the correction ring lens. That is, in the case where the objective lens 43 of the photographing unit 4 is a correction ring lens, even if the correction ring 43a is operated in order to adjust the aberration correction amount by the correction ring 43a, the operation amount of the correction ring 43a is equal to the change amount of the aberration correction amount. It may not always be the case, and as a result, the observation position may be shifted before and after the operation of the correction ring 43a. Furthermore, mechanical error of the objective lens 43 of the imaging unit 4, attachment and detachment of the objective lens 43, and the like are also causes of variation in the movement amount Fz. When calculating the measured value by multiplying the shifted amount of movement Fz by a certain correction coefficient in this way, the calculation result also deviates. Accordingly, in order to obtain information about the exact position of the detection object, it is necessary to use an appropriate correction coefficient according to the state of the device and the position in the Z direction. Therefore, in the observation method of the present embodiment, exporting of the correction coefficients is performed as follows. The timing of exporting the correction coefficient is arbitrary, and as an example, it is a timing when the state of the device changes such as when the objective lens 43 is attached or detached. Fig. 18 is a flowchart showing the procedure for exporting the correction coefficients in the observation method of this embodiment. As shown in FIG. 18 , the object (observation object) 60 for exporting the correction coefficient is moved to the lower part of the objective lens 43 of the imaging unit 4 (step S1 ). As shown in FIG. 1 , the laser processing apparatus 1 further includes a mounting table (installation portion) 2A different from the mounting table 2 , and an object 60 is mounted on the mounting table 2A. The mounting table 2A is movable in the X direction and the Y direction by the drive unit 7, for example. Fig. 19 is a side view showing an object for exporting correction coefficients. As shown in FIG. 19 , the object 60 includes a rear surface 60 b and a surface (second surface) 60 a opposite to the rear surface (first surface) 60 b. In object 60 , modified regions 12 aligned in the X direction along back surface 60 b and surface 60 a and cracks (cracks 14 , 14 k ) extending from modified regions 12 are formed by laser processing. In particular, cracks 14 k extending from the modified region 12 in a direction intersecting the Z direction and the X direction are formed in the object 60 . In addition, in the object 60, a plurality of rows of modified regions 12 are formed so as to be aligned in the Z direction. The distance between the modified regions 12 in the Z direction is equal to or less than 10 μm in terms of the amount of movement Fz. In the object 60, a cut surface is formed so that the modified region 12 is exposed, and the position of each modified region 12 in the Z direction, for example, the position of the crack 14k, is actually measured by observing the cut surface. rather known. The known measured values may be stored by the control unit 8 or may be stored in any storage device that the control unit 8 can communicate with. In this way, here, the preparation step of preparing the object 60 including the back surface 60b and the surface 60a on the opposite side of the back surface 60b is carried out, and the actual measurement value of the position in the Z direction intersecting the back surface 60b and the surface 60a is known. , the modified region 12 and the crack 14k are formed in the object 60 . In the next step, as shown in FIG. 20 , the object 60 is photographed using light (transmitted light) I1 having a transmittance to the object 60 (step S2: photographing step). In this step S2, by controlling the imaging unit 4 (imaging unit), the following imaging processing is performed: using the light I1 to scan cracks extending from the modified region 12 in the direction intersecting the Z direction and the X direction. Extended crack 14k for photography. The Y direction is an example of a direction intersecting the X direction and the Z direction. The X direction is the processing advance direction of laser processing for forming the modified regions 12 on the object 60 (that is, the direction in which the modified regions 12 are arranged), and the Z direction is the direction in which the modified regions 12 are arranged. A direction intersecting the back surface 60b and the surface 60a. In this step S2, the control unit 8 controls the imaging unit 4 and the driving unit 7 to cause the light I1 to enter the object 60 from the back surface 60b of the object 60, and moves the imaging unit 4 in the Z direction to make the light I1 The focal point (focus F, virtual focal point Fv) of the light I1 is moved in the Z direction so that the focal point of the light I1 is positioned at a plurality of positions inside the object 60 and the object 60 is photographed multiple times. Thereby, a plurality of internal images GD are acquired. In this embodiment, the objective lens 43 moves integrally with the imaging unit 4 . Therefore, to move the imaging unit 4 is to move the objective lens 43 , and the moving amount of the imaging unit 4 is equal to the moving amount of the objective lens 43 . The range in which the converging point of the light I1 is moved may be the entire range of the thickness of the object 60, but here, a part of the range RA can be selected. One example is the position in the Z direction where the laser beam focus point is aligned by modifying the regions 12a, 12b). The moving interval of the imaging unit 4 in the Z direction when performing multiple imaging, that is, the imaging interval of the object 60 is arbitrary, and it is preferable to set it more finely from the viewpoint of detecting the crack 14k more accurately. The imaging interval is within 1 μm as an example, and here is 0.2 μm. Further, here, the control unit 8 controls the imaging unit 4 and the driving unit 7 so as to perform direct observation and rear reflection observation of the object 60 . More specifically, the control unit 8 firstly executes the first photographing process of causing the light I1 to enter the object 60 from the back surface 60b, and moving the photographing unit 4 in the Z direction, while moving the light I1 that does not pass through the surface 60a. The converging point (focal point F) of the reflected light I1 moves from the back surface 60b side to the front surface 60a side, and the object 60 is photographed at a plurality of positions in the Z direction, and a plurality of first internal images are acquired as the internal image GD. GD1. This first photographing process is direct observation. In addition, the control unit 8 executes the second photographing process of causing the light I1 to enter the object from the back surface 60b and moving the photographing unit 4 in the Z direction, thereby reducing the intensity of the light I1 reflected by the surface 60a. The focus point (virtual focal point Fv) is moved from the front 60a side to the back 60b side, and the object 60 is photographed at a plurality of positions, thereby acquiring a plurality of second internal images GD2 as the internal image GD. This second photographing process is observation from the back side of the incident surface of the light I1 (here, referred to as the front surface 60 a in relation to the front and back of the semiconductor substrate 21 ) side, and thus is back reflection observation. In the next step, photographing data on the internal image GD acquired by photographing in step S2 is saved (step S3). As described above, in step S2 , the control unit 8 performs imaging while moving the imaging unit 4 (that is, the focal point of the light I1 ) in the Z direction by controlling the driving unit 7 . Therefore, the control unit 8 can acquire the movement amount Fz when each internal image is captured. Here, the information on the amount of movement Fz of each internal image GD can be associated with each internal image GD and stored as photographic data. The photographic data can be stored in any storage device that can be communicated with the control unit 8 regardless of inside or outside the control unit 8 and the laser processing apparatus 1 . The amount of movement Fz of the imaging unit 4 (objective lens 43) is, as an example, from the position where the light I1 is aligned with the back surface 21b of the semiconductor substrate 21 so that the light I1 is aligned with the semiconductor substrate. The amount of movement of the imaging unit 4 when the imaging unit 4 is moved in the Z direction according to a desired position inside 21 . Next, the control unit 8 inputs photographic data from a predetermined storage device (step S4). Then, the control unit 8 judges the formation state of the crack 14k (step S5). Here, as an example, the control unit 8 automatically judges an internal image GD (marker image) in which the image of the crack 14k is relatively clear among a plurality of internal images GD by image recognition (performs AI judgment). Here, an example of an algorithm for detecting cracks and modified regions by AI judgment will be described. 29 and 30 are diagrams illustrating crack detection. FIG. 29 illustrates internal observation results (internal images of the semiconductor substrate 21 ). The control unit 8 first detects the straight line group 140 with respect to the internal image of the semiconductor substrate 21 shown in (a) of FIG. 29 . For the detection of the straight line group 140 , for example, algorithms such as Hough transform and LSD (Line Segment Detector: straight line segment detection algorithm) can be used. The Hough transform is a method of detecting all straight lines passing through all points on an image, and assigning weights to straight lines passing more feature points to detect straight lines. LSD is a method of detecting a straight line by estimating an area to be a line segment by calculating the slope and angle of luminance values in an image, and approximating the area to a rectangle. Next, the control unit 8 detects the crack 14 from the straight line group 140 by calculating the similarity with the crack line for the straight line group 140 as shown in FIG. 30 . The crack line, as shown in the upper graph of Fig. 30, has the characteristic of being very bright front and back in the Y direction relative to the brightness value on the line. Therefore, the control unit 8 compares, for example, the brightness values of all the pixels in the detected straight line group 140 with those before and after in the Y direction, and uses the number of pixels whose difference is equal to or greater than the threshold value as a similarity score. Then, among the plurality of detected straight line groups 140 , the one with the highest similarity score to the crack line is taken as the representative value of the image. The higher the representative value, the higher the probability that the crack 14 exists is an index. The control unit 8 compares representative values of a plurality of images, and selects an image with a relatively high score as a crack image candidate. 31 to 33 are diagrams illustrating flaw detection. FIG. 31 illustrates internal observation results (internal images of the semiconductor substrate 21 ). For the image inside the semiconductor substrate 21 shown in (a) of FIG. 31 , the control unit 8 detects corners (gathering of edges) in the image as key points, detects the position, size, and direction of the key points, and detects features. 250 points. The method of detecting feature points in this way is known as Eigen, Harris, Fast, SIFT, SURF, STAR, MSER, ORB, AKAZE, etc. Here, as shown in FIG. 32 , since the scars 280 are arranged at regular intervals in shapes such as circles and rectangles, they have strong characteristics as corners. Therefore, the flaw 280 can be detected with high precision by counting the feature quantities of the feature points 250 in the image. As shown in FIG. 33 , by comparing the sum of the feature values for each image taken by shifting in the depth direction, it is possible to confirm the change in the value indicating the crack displacement for each modified layer. The control unit 8 estimates the peak value of the change as the position of the flaw 280 . By statistical feature quantities in this way, not only the position of the scar but also the pulse interval can be estimated. The description of the above AI judgment is about the crack 14 and the flaw 280 extending in the X direction, but the crack 14k extending in the direction intersecting the Z direction and the X direction can also use the same algorithm, by comparing more The representative value of the internal image ID, and the relatively higher score is judged as the internal image ID with a relatively clear image of the crack 14k. As an example, FIG. 21 shows a plurality of internal images GD taken at positions different from each other in the Z direction. In FIG. 21 , centering on the shooting position of the internal image GDd shown in (d), (c) is the internal image GDc at the shooting position 1 μm away from the back 60 b side, and (b) is the inside image GDc cut away from the back 60 b side. The internal image GDb of the shooting position of 3 μm, (a) is the internal image GDa of the shooting position 5 μm away from the back 60 b side, (e) is the internal image GDe of the shooting position 1 μm away from the front 60 a side, (f ) is an internal image GDf of an imaging position offset by 3 μm from the surface 60 a side, and (g) is an internal image GDg of an imaging position offset by 5 μm from the surface 60 a side. The imaging position here is a value inside the object 60 . In the example shown in FIG. 21 , the image of the crack 14k is the clearest in the internal image GDd, so the control unit 8 judges that the internal image GDd has a relatively high score and the image of the crack 14k is relatively clear. That is, here, it is judged that the crack 14k is detected in the internal image GDd (let the internal image GDd be a marker image). The control unit 8 can acquire the movement amount Fz when the internal image GDd is captured. By performing the same steps and processing on the multiple rows of modified regions 12 with different positions in the Z direction and the cracks 14k extending from each modified region 12, the control unit 8 can acquire and detect each row of modified regions 12 from multiple rows. Or the amount of movement Fz when the crack 14k is extended. That is, in the present embodiment, a plurality of modified regions 12 and cracks 14k having different positions in the Z direction and known as measured values indicating the positions are formed in the object 60, and in the imaging process, The control unit 8 moves the photographing unit 4 in the Z direction so that the converging point of the light I1 is located at a plurality of positions inside the object 60 in the Z direction to photograph the object 60 , thereby acquiring images including multiple A plurality of internal images GD (an image corresponding to the above-described internal image GDd, that is, a marker image) of each crack 14k extending in each modified region 12 is a clear image. Then, as shown in the second column Q2 of FIG. 22 , the control unit 8 acquires the movement amount Fz when each marker image is captured. As shown in the first column Q1 of FIG. 22 , the control unit 8 uses the actual measurement value of the position of the multi-row modified region 12 (crack 14k) in the Z direction as the position relative to the back surface of the object 60 (with respect to the light I1). The back side of the incident surface, here the distance from the surface 60a) is obtained. Next, the control unit 8 exports the correction coefficient (step S6: export step). As shown in FIG. 22 , the control unit 8 acquires and detects cracks extending from each modified region 12 as information for calculating the measured values of the respective positions of the plurality of modified regions 12 arranged in the Z direction. The amount of movement Fz at 14k (column 2 Q2). On the other hand, the control unit 8 can acquire actual measurement values of the respective positions of the plurality of modified regions 12 arranged in the Z direction (first column Q1 ). Therefore, the control unit 8 can correspond to each of the plurality of modified regions 12 arranged in the Z direction by multiplying the movement amount Fz by the correction coefficient, that is, the estimated value of the position of the modified region 12. Export the correction coefficient in the form of actual measured value. In other words, the control unit 8 outputs the correction coefficient as correction coefficient=actually measured value/movement amount Fz. That is, the control unit 8 executes the export process of multiplying the movement amount Fz when the internal image GD of a clear image including the crack 14k, that is, the marker image is taken, that is, the estimated value, multiplied by the correction coefficient, The correction coefficients are exported in such a manner that the actual measured value of the position of the modified region 12 in the Z direction is obtained. The third column Q3 in FIG. 22 shows the correction coefficients thus exported. Thereafter, the control unit 8 saves the data indicating the exported correction coefficient (step S7), and ends the process. The correction coefficients derived in the above manner are derived based on the internal image GD captured by the light I1 from the imaging unit 4 . Therefore, the correction coefficient reflects the device state of the imaging unit 4 when the internal image GD is captured. In addition, the correction coefficients are exported based on internal images GD captured at a plurality of positions of the object 60 in the Z direction. Therefore, the correction coefficient is obtained by taking into account the position in the Z direction where the converging point of the light I1 is aligned within the object 60 , and the aberration correction amount corresponding to the position. Next, in the observation method of this embodiment, by observing an object including the modified region 12 whose position in the Z direction is not actually measured, the method for obtaining the position of the modified region 12 in the Z direction is implemented. A series of steps for information. Fig. 23 is a flow chart showing the procedure for acquiring information on the position of the modified region in the Z direction in the observation method of the present embodiment. As shown in FIG. 23 , here, an object in which a modified region is formed is prepared. Here, laser processing is performed (step S11: preparation step). However, as a step of the observation method, the step of laser processing is not essential, and for example, an object in which the modified region 12 is formed using another laser processing device (or at another time using the laser processing device 1) may also be prepared. . In this step S11 , as shown in FIG. 24 , an object including a semiconductor substrate 21 is prepared. The semiconductor substrate 21 includes a rear surface (first surface) 21b and a surface (second surface) 21a opposite to the rear surface 21b. In the semiconductor substrate 21, the lines 15 extending in the X direction along the back surface 21b and the front surface 21a are set. The semiconductor substrate 21 is supported by the stage 2 so that the back surface 21 b faces the laser irradiation unit 3 so that the back surface 21 b becomes the incident surface of the laser light L. In this state, while controlling the laser irradiation unit 3, the control unit 8 controls the driving unit 7 and/or the moving mechanism of the mounting table 2 to relatively move the semiconductor substrate 21 along the X direction so that the converging point C of the laser light L is along the line 15 moves relative to the semiconductor substrate 21 . At this time, the control unit 8 displays patterns for causing the spatial light modulator 32 to divide the laser light L into a plurality of (here, two) laser beams L1 and L2. As a result, the converging points C1 and C2 of the laser beams L1 and L2 are formed at a distance Dz in the Z direction and a distance Dx in the X direction inside the semiconductor substrate 21 . As a result, in the semiconductor substrate 21 , a plurality of (here, two rows) modified regions 12 a and 12 b are formed along the line 15 . Therefore, here, the X direction is the process advancing direction in which the light-converging points C1 and C2 advance. Thus, here, the control section 8 executes the following laser processing: by controlling the laser irradiation unit 3 (irradiation section), the semiconductor substrate 21 is irradiated with the laser light L along the X direction which is the extending direction of the line 15. In the semiconductor substrate 21, a plurality of modified regions 12 arranged in the X direction and cracks (cracks 14, 14k) extending from the modified regions 12 are formed. In FIG. 24 and subsequent figures, the functional element layer 22 formed on the surface 21 a of the semiconductor substrate 21 is omitted. Next, look inside. That is, in the next step, the semiconductor substrate 21 is moved to the observation position (step S12). More specifically, the control unit 8 relatively moves the semiconductor substrate 21 to directly below the objective lens 43 of the imaging unit 4 by controlling the driving unit 7 and/or the moving mechanism of the stage 2 . In addition, when the semiconductor substrate 21 on which the modified region 12 is formed is separately prepared, for example, the user may place the semiconductor substrate 21 at the observation position. Next, as shown in FIG. 25 , the semiconductor substrate 21 is photographed using light (transmitted light) I1 having transmittance to the semiconductor substrate 21 (step S13: photographing step). In this step S13, the following photographing process is executed: by controlling the photographing unit 4 (photographing section), the light I1 is made to enter the inside of the semiconductor substrate 21 from the back surface 21b of the semiconductor substrate 21, and the light I1 is used to Among the cracks extending from the modified region 12 , a target crack 14 k extending in a direction intersecting the Z direction and the X direction is photographed. The Y direction is an example of the direction intersecting the X direction which is a process advancing direction, and the Z direction which intersects the back surface 21b and the surface 21a. More specifically, in step S13, the control unit 8 moves the imaging unit 4 in the Z direction by controlling the driving unit 7 (moving unit) and the imaging unit 4, so that the converging point of the light I1 is positioned inside the semiconductor substrate 21. The semiconductor substrate 21 is photographed at a plurality of positions, thereby acquiring a plurality of internal image IDs. As mentioned above, in this embodiment, the objective lens 43 moves integrally with the imaging unit 4 . Therefore, to move the imaging unit 4 is to move the objective lens 43 , and the moving amount of the imaging unit 4 is equal to the moving amount of the objective lens 43 . At this time, the control unit 8 moves the imaging unit 4 in the Z direction by controlling the driving unit 7, and moves the focus point (focus F, virtual focus Fv) of the light I1 in the Z direction while performing multiple operations. Photograph of the sub-semiconductor substrate 21 . The range in which the converging point of the light I1 is moved may be the entire range of the thickness of the semiconductor substrate 21, but here, during the laser processing in step S11, a part of the range RA can be selected, and this part of the range RA includes the range for forming the modified laser beam. The positions in the Z direction where the focal points C1 and C2 of the laser beams L1 and L2 are aligned according to the regions 12a and 12b. The moving interval of the imaging unit 4 in the Z direction when performing multiple imaging, that is, the imaging interval of the semiconductor substrate 21 is arbitrary, but it is preferable to set it more finely from the viewpoint of detecting the crack 14k more accurately. The imaging interval is within 1 μm as an example, and it is 0.2 μm here. Further, here, the control section 8 controls the imaging unit 4 and the drive unit 7 to perform direct observation and rear reflection observation of the semiconductor substrate 21 . More specifically, the control unit 8 first executes the following first photographing process, making the light I1 incident on the semiconductor substrate 21 from the back surface 21b, and moving the photographing unit 4 in the Z direction, thereby making the light I1 not pass through the surface 21a The converging point (focal point F) of the reflected light I1 is moved from the back surface 21b side to the front surface 21a side, and the semiconductor substrate 21 is photographed at a plurality of positions in the Z direction, thereby acquiring a plurality of first images as internal image IDs. 1 internal image ID1. This first photographing process is direct observation. In addition, the control unit 8 executes the second photographing process of causing the light I1 to enter the object from the back surface 21b, moving the photographing unit 4 in the Z direction, thereby concentrating the light I1 reflected on the surface 21a. The light spot (virtual focal point Fv) moves from the front surface 21a side to the rear surface 21b side, and the semiconductor substrate 21 is imaged at a plurality of positions, thereby acquiring a plurality of second internal images ID2 as internal image IDs. This second photographing process is observation performed from the back side (here, in the structure of the semiconductor substrate 21 , referred to as the surface 21 a ) side with respect to the incident surface of the light I1 , and thus is back reflection observation. In the next step, photographing data on the internal image ID acquired by photographing in step S13 is saved (step S14). As described above, in step S13 , the control unit 8 performs imaging while moving the imaging unit 4 (that is, the converging point of the light I1 ) in the Z direction by controlling the driving unit 7 . Therefore, the control unit 8 can acquire the movement amount Fz of the imaging unit 4 when each internal image is captured. Here, the information on the amount of movement Fz of each internal image ID can be associated with each internal image ID and stored as photographic data. The photographic data can be stored in any storage device that can be communicated with the control unit 8 regardless of inside or outside the control unit 8 and the laser processing apparatus 1 . The amount of movement of the imaging unit 4 (objective lens 43), as an example, can be selected from the position where the light I1 is aligned with the back surface 21b of the semiconductor substrate 21, so that the light I1 is aligned with the semiconductor substrate. The movement amount of the imaging unit 4 when the imaging unit 4 is moved in the Z direction according to a desired position inside the substrate 21 . Next, the control unit 8 inputs photographic data from a predetermined storage device (step S15). Then, the control unit 8 judges the formation state of the crack 14k (step S16). Here, as an example, the control unit 8 automatically judges an internal image ID whose image of the crack 14k is relatively clear among a plurality of internal image IDs by image recognition (performs AI judgment). An example of AI judgment is as described above. FIG. 26 shows a plurality of internal image IDs taken at positions different from each other in the Z direction. In FIG. 26 , centering on the shooting position of the internal image IDd shown in (d), (c) is the internal image IDc at the shooting position 1 μm away from the rear surface 21b side, and (b) is the internal image IDc cut away from the rear surface 21b side. The internal image IDb of the photographing position of 3 μm, (a) is the internal image IDa of the photographing position 5 μm removed from the back 21 b side, (e) is the internal image IDe of the photographing position 1 μm removed from the front 21 a side, (f ) is an internal image IDf of an imaging position offset by 3 μm from the surface 21 a side, and (g) is an internal image IDg of an imaging position offset by 5 μm from the surface 21 a side. However, the imaging position here is a value inside the semiconductor substrate 21 . In the example shown in FIG. 26 , according to the fact that the image of the crack 14k is the clearest in the internal image IDd, the control unit 8 judges that the internal image IDd has a relatively high score and the image of the crack 14k is relatively clear. (that is, it is determined that the crack 14k is detected in the internal image IDd). The control unit 8 can acquire the amount of movement when the internal image IDd is captured. Therefore, the control unit 8 can calculate the crack position of the crack 14k based on the movement amount when the internal image IDd is captured. In this way, the control unit 8 executes the following imaging process: by controlling the imaging unit 4 and the driving unit 7, the light I1 is incident on the semiconductor substrate 21 from the back surface 21b, and the imaging unit 4 (objective lens 43) is aligned in the Z direction. The semiconductor substrate 21 is photographed with the light I1 while moving, thereby acquiring a detection image which is an internal image ID including a clear image of the crack 14k. In addition, the control unit 8 executes a calculation process of calculating a moving distance Fz extending in a direction intersecting the Z direction and the X direction based on a plurality of internal image IDs and the movement amount Fz of the imaging unit 4 when each internal image ID is captured. The crack 14k is the position of the target crack in the Z direction, that is, the crack position. More specifically, in the calculation process, the control unit 8 determines an internal image ID with a clear image of the crack 14k among a plurality of internal image IDs, and calculates based on the movement amount Fz when the determined internal image ID is captured. Crack location. The crack position can be calculated by multiplying the movement amount Fz by a predetermined correction coefficient, for example. The calibration coefficients have been exported through the above steps S1-7. That is, the control unit 8 stores a plurality of correction coefficients corresponding to the movement amount Fz, and calculates the correction coefficient corresponding to the crack position of the crack 14k using the correction coefficients corresponding to the movement amount Fz when the detected image is captured in the calculation process. The estimated value of the position of the mass region 12. The control part 8 can perform the above-mentioned calculation of the crack position of the crack 14k for both the 1st internal image ID1 acquired by direct observation, and the 2nd internal image ID2 acquired by back reflection observation. Thus, the control unit 8 can calculate the crack position of the crack 14k corresponding to the first internal image ID1 and located relatively on the back surface 21b side, and the crack position of the crack 14k corresponding to the second internal image ID2 and located relatively on the front surface 21a side. Crack location. That is, in this case, the control unit 8 executes the first arithmetic processing and the second arithmetic processing. In the first arithmetic processing, the first internal image in which the crack 14k is clear among the plurality of first internal images ID1 is judged, The first crack position Z1 as the crack position is calculated based on the movement amount of the imaging unit 4 when the determined first internal image is captured, and in the second calculation process, among the plurality of second internal images ID2 is determined The second internal image of the crack 14k is clear, and the second crack position Z2 (for the first crack position Z1 and For an example of the second crack position Z2, refer to FIG. 15). The distance between the first crack position Z1 relatively located on the back surface 21b side and the second crack position Z2 relatively located on the surface 21a side defines the portion (crack initiation portion) in the modified region 12 where the crack 14k is formed. width. Next, in step S16 , the control unit 8 estimates the position of the modified region 12 and the like based on the acquired crack position and the like. That is, here, the control unit 8 executes an estimation process of estimating the end (defect) on the rear surface 21b side of the modified region 12 based on the formation conditions of the modified region 12 (here, the processing conditions of laser processing) and the position of the crack. upper end of the upper region) in the Z direction, the position of the end of the modified region 12 on the surface 21a side (defect lower end) in the Z direction, and the width of the modified region 12 in the Z direction (the upper end of the defect upper region and At least one of the spacing at the lower end of the defect). Here, the control unit 8 calculates the first crack position Z1 of the crack 14k (upper crack) on the back surface 21b side based on direct observation, and calculates the second crack position Z2 of the crack 14k (lower crack) on the surface 21a side based on back reflection observation. Therefore, the control unit 8 can calculate the width of the crack initiation portion inside the semiconductor substrate 21 as the distance between the first crack position Z1 of the upper crack and the second crack position Z2 of the lower crack. Then, the control unit 8 can calculate the width of the modified region 12 inside the semiconductor substrate 21 in the Z direction by, for example, multiplying the calculated width of the crack initiation portion by a coefficient related to the processing conditions of laser processing. The coefficient here is determined based on various conditions that affect the formation of the modified region 12 , such as the wavelength of the laser light L during laser processing, the amount of aberration correction, the pulse width, and the pulse energy. The coefficient here is about 3.0 in one example. In this way, in the estimation process, the control unit 8 can estimate the position of the modified region 12 in the Z direction based on the formation conditions of the modified region 12 (processing conditions of laser processing) and the distance between the first crack position Z1 and the second crack position Z2. width. On the other hand, the control unit 8 can calculate the lower end of the modified region 12 on the surface 21a side by subtracting the assumed modified region width, that is, the assumed modified region width, from the first crack position Z1 of the upper crack. s position. The modified region width can be determined based on various conditions affecting the formation of the modified region 12 such as the wavelength of the laser light L during laser processing, the amount of aberration correction, the pulse width, and the pulse energy, for example. Assume that the width of the modified region is about 20 μm as an example. Furthermore, the control unit 8 can calculate the position of the lower end of the surface 21a of the modified region 12 by subtracting the width of the assumed defect region 12m, that is, the assumed defect region width, from the second crack position Z2 of the lower crack. The hypothetical defect region width can be determined based on, for example, various conditions affecting the formation of the modified region 12 such as the wavelength of the laser L during laser processing, the amount of aberration correction, the pulse width, and the pulse energy. Assume that the defect region width is about 10 μm as an example. Further, the control unit 8 can calculate the position of the upper end of the modified region 12 on the rear surface 21b side by adding the width of the assumed defect upper region 12n, that is, the assumed defect upper region width, to the second crack position Z2 of the lower crack. The width of the region above the hypothetical defect can be determined based on various conditions that affect the formation of the modified region 12 such as the wavelength of the laser light L during laser processing, the amount of aberration correction, the pulse width, and the pulse energy. Assume that the width of the region above the defect is about 10 μm as an example. As described above, the control unit 8 estimates and acquires various information on the position of the modified region 12 in step S16. In the next step, the control unit 8 outputs the information of the judgment result of step S16 to an arbitrary storage device (step S17), and stores it in the storage device (step S18). Thereafter, as necessary, various information is displayed on the display 150 in a state where the user's input can be accepted (step S19), and the processing is completed. The information displayed on the display 150 is, for example, the first crack position Z1, the second crack position Z2, the width of the initial part, the position of the end of the modified region 12, and the width of the modified region 12 in the Z direction. In this way, in step S19 , the control unit 8 controls the display 150 to execute display processing for displaying information on the crack position on the display 150 . As described above, the observation method using the laser processing apparatus 1 is completed. In this embodiment, the observation method is performed by the imaging unit 4 , the driving unit 7 and the control unit 8 in the laser processing device 1 . In other words, in the laser processing apparatus 1, the observation device 1A (refer to FIG. 1 ) is constituted by the imaging unit 4, the drive unit 7, and the control unit 8. The object 60 and the semiconductor substrate 21 are photographed by the permanent light I1, the driving unit 7 is used to move the imaging unit 4 relative to the object 60 and the semiconductor substrate 21, and the control unit 8 is used to control at least the imaging unit 4 and the driving unit 7. . FIG. 27 is a graph showing the error between the measured value and the actual measured value of the position of the modified region. As shown in FIG. 27 , in the observation method of this embodiment, the correction coefficients derived in consideration of the state of the device, the position in the Z direction (the depth position in FIG. 27 ), and the amount of aberration correction in steps S1 to S7 are used, In steps S11 to S19, the estimated value of the modified region 12 is calculated. Therefore, the error between the measured value and the actual measured value in this embodiment is approximately within 6 μm. However, the error of the comparative example using a certain (fixed) correction coefficient is as large as about 19 μm compared with the present embodiment. As described above, in the observation device 1A of the present embodiment and the object 60 of the observation method, a mark (here, a modified mark) whose measured value is known at a position in the Z direction intersecting the back surface 60b and the front surface 60a is provided. quality region 12 and crack 14k). In the observation device 1A and the observation method of the present embodiment, by imaging such an object 60 while moving the imaging unit 4, an image including the crack 14k as an internal image GD of the object 60 can be obtained. Tag the image. Then, the correction coefficient is derived so that the value (measured value) obtained by multiplying the movement amount Fz when the marker image is obtained by the correction coefficient is an actual measurement value of the known position of the modified region 12 . That is, according to the observation device 1A and the observation method, correction coefficients corresponding to the state of the device when the marker image is captured and the movement amount of the imaging unit 4 (that is, the observation depth) when the marker image is captured can be derived. Therefore, when the modified region 12 is observed with the light I1 to calculate the estimated value of the modified region 12 position, if this correction coefficient is used, more accurate information on the modified region 12 position can be obtained. In addition, in the observation device 1A of the present embodiment, a plurality of modified regions 12 and cracks 14k whose positions in the Z direction are different from each other and whose actual measurement values are known are formed on the object 60 . In this case, the control unit 8 photographs the object 60 by positioning the focusing point at a plurality of positions inside the object 60 in the Z direction, and obtains the image including the area extending from each modified region 12 of the plurality of modified regions 12. Multiple marker images of images of individual cracks 14k. Then, in the export process, the control unit 8 converts each value obtained by multiplying each movement amount Fz of the imaging unit 4 by a correction coefficient, that is, an estimated value, into a plurality of modified cracks 14k. A plurality of correction coefficients are exported in the form of the actual measured values of the respective positions of the regions 12 . Therefore, when the modified region 12 is observed with the light I1 and the estimated value of the modified region 12 position is calculated, information on the modified region 12 position can be acquired more accurately over a wider range in the Z direction. In addition, in the observation device 1A, the modified region 12 aligned in the Z direction and the cracks 14, 14k extending from the modified region 12 are formed in the object 60, and in the imaging process, by moving the imaging unit 4 along the Moving in the Z direction, while moving the focus point of the light I1, the object 60 is photographed with the light I1, and cracks extending in a direction intersecting the X direction and the Z direction, including the cracks 14 and 14k, are acquired as marker images. 14k like internal image GD. According to the findings of the inventors of the present invention, when the modified region 12 is formed by, for example, laser processing inside the object 60 , cracks extending in various directions from the modified region 12 may be formed. Furthermore, among the cracks, the crack 14k extending in the direction intersecting the Z direction and the X direction is accurately detected by the light I1 transmitted from the object 60 compared with the modified region 12, wherein the Z direction It is a direction intersecting the back surface 60b which is the laser beam incident surface of the object 60, and the X direction is the advancing direction of laser processing. Therefore, if the internal image GD including the image of the crack 14k is used as the marker image as described above, it is possible to reduce the variation in the movement amount Fz of the imaging unit 4 when the marker image is captured. As a result, more accurate correction coefficients can be exported. In the observation device 1A of the present embodiment, the imaging unit 4 has a correction ring lens including an objective lens 43 and a correction ring 43 a provided on the objective lens 43 for correcting aberrations generated in the object 60 . In this way, when the objective lens 43 for condensing the light I1 toward the object 60 is provided with the correction ring 43a, the state of the device may change before and after the operation of the correction ring 43a. Therefore, it is more effective to export the correction coefficient according to the state of the device as described above. Here, the observation device 1A of the present embodiment includes: an imaging unit 4 having an objective lens 43 for converging light I1 having transmittance with respect to the semiconductor substrate 21 toward the semiconductor substrate 21, and for imaging the semiconductor substrate 21 with the light I1. The substrate 21 performs imaging; the driving unit 7 for moving the objective lens 43 relative to the semiconductor substrate 21 ; and the control unit 8 for controlling at least the imaging unit 4 and the driving unit 7 . The semiconductor substrate 21 has a back surface 21b and a surface 21a opposite to the back surface 21b, and the semiconductor substrate 21 is provided with a modified region 12 and cracks 14, 14k extending from the modified region 12. The control unit 8 executes imaging processing and arithmetic processing. In the aforementioned imaging processing, by controlling the imaging unit 4 and the driving unit 7, the light I1 is incident on the semiconductor substrate 21 from the back surface 21b, and the imaging unit 4 is moved along the Z direction. While moving, the semiconductor substrate 21 is photographed with the light I1, thereby acquiring the internal image ID of the image including the crack 14k, that is, the inspection image. The movement amount Fz of the imaging unit 4 is multiplied by the correction coefficient to calculate the position of the crack 14k in the Z direction, that is, the crack position. The control unit 8 stores a plurality of correction coefficients corresponding to the movement amount Fz. This observation device 1A stores a correction coefficient corresponding to the movement amount Fz of the imaging unit 4 as described above. Therefore, by calculating the estimated value of the position of the crack 14k using this correction coefficient, more accurate information on the position of the modified region 12 can be obtained. The object 60 of this embodiment has a back surface 60b and a surface 60a on the opposite side of the back surface 60b, and a modified region 12 and a crack 14k extending from the modified region 12 are provided as marks, and the object 60 is used for export correction. This correction coefficient is used to calculate the measured values of the positions of the modified regions 12 and the cracks 14 k in the Z direction intersecting the back surface 60 b and the surface 60 a from the measured values of the modified regions 12 positions. Using this object 60, the correction coefficients can be exported as described above. The above-mentioned embodiment is for explaining one aspect of this invention. Therefore, the present invention is not limited to the above-mentioned embodiments, and can be arbitrarily modified. For example, in the above-described embodiment, the drive unit 7 for moving the objective lens 43 together with the imaging unit 4 was illustrated as means for moving the objective lens 43 in the Z direction relative to the semiconductor substrate 21 . However, for example, an actuator may be used to move only the objective lens 43 in the Z direction. In addition, in the above-mentioned embodiment, the example in which the control unit 8 automatically judges the image in steps S5 and S16 is described, but the control unit 8 may acquire the crack position of the crack 14k based on the judgment result of the user. In this case, for example, the control unit 8 causes the display 150 to display a plurality of internal images GD, ID, and displays one internal image prompting the determination (selection) of the image of the crack 14k from the plurality of internal images GD, ID. like information. Then, the control unit 8 can receive the input of the judgment result through the display 150, and calculate the crack position of the crack 14k based on the internal image GD and the movement amount Fz of the ID corresponding to the judgment result. In this case, the display 150 is a display unit for displaying information, and is also an input receiving unit for receiving input. In this case, the processing load on the control unit 8 for performing image recognition and the like is reduced. In addition, in the above-mentioned embodiment, in steps S2 and S13, the observation of one modified region 12 was performed both of direct observation and rear reflection observation, and the first internal images as internal images GD and ID were acquired. GD1, ID1 and the second internal image GD2, ID2. However, in steps S2 and S13, only one of direct observation and back reflection observation may be performed. In this case, since one of the first internal image GD1, ID1 and the second internal image GD2, ID2 can be obtained, the export of the correction coefficient and the modification of the modified region 12 can also be performed based on this one. Estimation of the position and width of the end. Here, in the observation apparatus 1A, the object 60 for exporting the correction coefficient may always be provided. That is, the observation apparatus 1A may include a setting unit (for example, the mounting table 2A in FIG. 1 ) for setting the object 60 and the object 60 set on the setting unit. In this way, by always setting the object 60 provided with the modified region 12 and the crack 14k as a mark, it is possible to export the correction coefficient at any timing. Further, in the above-mentioned embodiment, when exporting the correction coefficient, the internal image including the crack 14k is used as the marker image, and the movement amount Fz when the marker image is obtained by photographing is used. That is, by detecting the crack 14k, the correction coefficient is exported based on the position where the crack 14k is detected. However, in the observation device 1A and the observation method, when exporting the correction coefficients, the modified region 12 itself may be detected. In this case, the processing of the control unit 8 is as follows. That is, the control unit 8 executes the imaging process and the exporting process. In the imaging process, by controlling the imaging unit 4 and the drive unit 7, the light I1 is made to enter the inside of the object 60 from the back surface 60b, and the imaging unit 4 Move in the Z direction to move the focus point of the light I1 in the Z direction, and image the object 60 with the light I1, thereby acquiring an image including the modified region 12 as an internal image GD of the object 60 In the export process, after the photographing process, the value obtained by multiplying the movement amount Fz of the imaging unit 4 when the marker image is obtained by multiplying the correction coefficient, that is, the estimated value is the value of the modified region 12 in the export process. Export the correction coefficient in the form of the measured value of the position. In this way, when the modified region 12 itself is the detection object, in order to export the correction coefficients at more positions in the Z direction, it is necessary to use smaller intervals in the Z direction (for example, the movement amount Fz is 5 μm, and the object 60 inside is about 20 μm) to capture an internal image, there is a problem that an image of one modified region 12 is captured across a plurality of internal images. In this case, the image of the modified region 12 at a certain position in the Z direction and the image of the modified region 12 at another position in the Z direction overlap in one internal image. In order to solve such a problem, when the modified regions 12 are the detection targets, it is conceivable to shift rows of modified regions 12 arranged in the Z direction from each other in the Y direction as shown in FIG. 28 . In this way, it can be avoided that the image of the modified region 12 at a certain position in the Z direction and the image of the modified region 12 at another position in the Z direction overlap in one internal image, so that internal images can be imaged at a smaller interval. The image is photographed, and the correction coefficients of more positions can be exported. In addition, when the detection target for exporting the correction coefficient is the modified region 12, in the subsequent step of acquiring information on the position of the modified region 12 of the semiconductor substrate 21, the crack 14k may be replaced by The detection is performed to detect the modified region 12 itself. Here, in the above-mentioned embodiment, when exporting the correction coefficients, an example was given of using the object 60 in which the modified region 12 and the crack 14k whose actual measurement values are known are set as marks. However, the object for exporting the correction coefficient is not limited to this. For example, one surface of a wafer with a known thickness may be affixed with a test icon as a mark, or a predetermined pattern may be formed as a mark on one surface of a wafer with a known thickness. Get something as an object. In these cases, by preparing a plurality of objects having different thicknesses, it is possible to export correction coefficients for a plurality of positions in the Z direction.

1: Laser processing device 1A: Observation device 2: Carrying table 2A: Carrying table 3: Laser irradiation unit 4: Photography unit 5: Photography unit 6: Photography unit 7: Drive unit 8: Control Department 11: object 12:Modified area 12a: Modified area 12b:Modified area 12s: modification point 12m: defect area 12n: area above the defect 14: Crack 14a: Crack 14b: Crack 14c: crack 14d: Crack 14e: front end 14k: crack 15: line 20: Wafer 21: Semiconductor substrate 21a: Surface 21b: back 21c: Gap 22: Functional component layer 22a: Functional elements 23: grid area 31: light source 32: Spatial light modulator 33: Concentrating lens 41: light source 42: Mirror 43: objective lens 43a: Calibration ring 44: Light detection unit 51: light source 52: Mirror 53: lens 54: Light detection unit 60: object 60a: surface 60b: back 140:Detect line group 150: display 250: Feature points 280: scars A1: area A2: area A3: area C: focus point C1: focus point C2: focus point Dx: separation distance Dz: separation distance RA: range ID: internal image ID1: internal image ID2: internal image IDa: internal image IDb: internal image IDc: internal image IDd: internal image IDe: internal image IDf: internal image IDg: internal image L: laser light L1: laser light L2: laser light I1: light I2: light F: focus Fv: virtual focus Z1: The first crack position Z2: The second crack position S1: Move object for export S2: Photography S3: save photographic data S4: input data S5: Judgment status S6: Export correction coefficient S7: save data S11:Laser processing S12: Object movement S13: Photography S14: Save photographic data S15: input data S16: Judgment status S17: output judgment result S18: save data S19: display GD: internal image GD1: Internal image GD2: Internal Image GDa: Internal Image GDb: internal image GDc: internal image GDd: internal image GDe: internal image GDf: internal image GDg: internal image Hz: amount of movement

[FIG. 1] It is a block diagram of the laser processing apparatus of one embodiment. [ Fig. 2 ] is a plan view of a wafer of an embodiment. [ Fig. 3 ] is a cross-sectional view of a part of the wafer shown in Fig. 2 . [ Fig. 4 ] is a configuration diagram of the laser irradiation unit shown in Fig. 1 . [ Fig. 5 ] is a configuration diagram of the imaging unit for inspection shown in Fig. 1 . [FIG. 6] It is a block diagram of the imaging unit for alignment correction shown in FIG. 1. [FIG. [ Fig. 7] Fig. 7 is a cross-sectional view of a wafer for explaining the imaging principle of the inspection imaging unit shown in Fig. 5 , and images at various locations obtained by the inspection imaging unit. [ Fig. 8] Fig. 8 is a cross-sectional view of a wafer for explaining the imaging principle of the inspection imaging unit shown in Fig. 5 , and images at various locations obtained by the inspection imaging unit. [ Fig. 9 ] is an SEM image of a modified region and cracks formed inside a semiconductor substrate. [ Fig. 10 ] is an SEM image of a modified region and cracks formed inside a semiconductor substrate. [ Fig. 11 ] is a schematic diagram for explaining the imaging principle of the inspection imaging unit shown in Fig. 5 . [ Fig. 12 ] is a schematic diagram for explaining the imaging principle of the inspection imaging unit shown in Fig. 5 . [ Fig. 13 ] is a diagram showing an object on which a modified region is formed. [ Fig. 14 ] is a graph regarding the positions of modified regions and cracks in the Z direction. [ Fig. 15 ] is a diagram obtained by plotting detection results on cross-sectional photographs of objects. [ Fig. 16 ] is a schematic diagram for explaining correction coefficients. [ Fig. 17 ] is a graph showing the relationship between the position of the detection target in the Z direction and the movement amount when the detection target is detected. [FIG. 18] It is a flowchart which shows the procedure for exporting the correction coefficient in the observation method of this embodiment. [ Fig. 19 ] is a side view showing an object for exporting correction coefficients. [ Fig. 20 ] is a diagram showing one step of the observation method shown in Fig. 18 . [ Fig. 21 ] are a plurality of internal images taken at positions different from each other in the Z direction. [ Fig. 22 ] is a table showing the relationship between the actually measured value of the position of the modified region, the amount of movement, and the correction coefficient. [ Fig. 23 ] is a flowchart showing a procedure for acquiring information on the position of the modified region in the Z direction in the observation method of the present embodiment. [ Fig. 24 ] is a diagram showing one step of the observation method shown in Fig. 23 . [ Fig. 25 ] is a diagram showing one step of the observation method shown in Fig. 23 . [ Fig. 26 ] is a table showing the relationship between the actually measured value of the position of the modified region, the amount of movement, and the correction coefficient. [ Fig. 27 ] is a graph showing the error between the measured value and the actual measured value of the position of the modified region. [ Fig. 28 ] is a schematic cross-sectional view showing an object of a modified example. [ Fig. 29 ] is a diagram illustrating crack detection. [ Fig. 30 ] is a diagram illustrating crack detection. [ Fig. 31 ] is a diagram illustrating flaw detection. [ Fig. 32 ] is a diagram illustrating flaw detection. [ Fig. 33 ] is a diagram illustrating flaw detection.

Claims (8)

An observation device, characterized in that it comprises: an imaging unit having a condensing lens for condensing transmitted light having transmittance with respect to the object toward the object, and for photographing the object with the transmitted light; a moving unit for relatively moving the condensing lens relative to the object; and a control unit for controlling at least the aforementioned photographing unit and the aforementioned moving unit, The aforementioned object has a first surface and a second surface opposite to the first surface, A mark whose measured value is known at a position in the Z direction intersecting the first surface and the second surface is provided on the object, The aforementioned control unit executes the photographing process and the exporting process, wherein, In the photographing process, the photographing unit and the moving unit are controlled so that the transmitted light enters the inside of the object from the first surface, the condenser lens is moved in the Z direction, and the transmitted light is used to control the The object is photographed to obtain a marker image including the image of the marker as an internal image of the object, The export process exports a correction coefficient after the photographing process so that the measured value obtained by multiplying the correction coefficient by the moving amount of the condenser lens when the marker image is captured becomes the actual measured value. The observation device as claimed in claim 1, wherein: In the aforementioned object, a plurality of the aforementioned marks having different positions in the Z direction and whose aforementioned actually measured values of the positions are known are formed, In the photographing process, the control unit relatively moves the condensing lens in the Z direction so that the condensing points of the transmitted light are located at a plurality of positions inside the target object in the Z direction, so that the target object is scanned. photography, whereby a plurality of images of the aforementioned markers are obtained comprising images of respective images of the plurality of aforementioned markers, In the export process, the control unit exports a plurality of the correction coefficients such that the correction coefficients are consistent with each of the condenser lenses when each of the plurality of marker images is captured. The value of the product of the movement amount, that is, the measured value is each of the above-mentioned actual measurement values of the plurality of the above-mentioned marks. The observation device as claimed in claim 1 or 2, wherein: In the object, modified regions aligned in the X direction along the first surface and the second surface and cracks extending from the modified regions are formed as the marks, In the photographing process, the condensing lens is moved in the Z direction to move the converging point of the transmitted light, and the object is photographed with the transmitted light, thereby obtaining the edge including the crack and the X The aforementioned internal image of an image of a crack extending in a direction intersecting with the aforementioned Z direction is used as the aforementioned marker image. The observation device as described in any one of claim items 1 to 3, wherein: The imaging unit has a correction ring lens including the condenser lens and a correction ring provided on the condenser lens for correcting aberrations occurring in the object. The observation device as described in any one of claims 1 to 4, wherein: a setting part for setting the aforementioned object; and The aforementioned object installed in the aforementioned setting portion. A kind of observation method is characterized in that, has: A preparation step for preparing an object, wherein the object has a first surface and a second surface opposite to the first surface, and a position in the Z direction intersecting the first surface and the second surface is formed on the object The marker whose measured value is known; In the photographing step, the transmitted light having transmittance with respect to the object is made to enter the inside of the object from the first surface, and the condensing lens for condensing the transmitted light is moved in the Z direction to utilize the transmitted light. photographing the object with light to acquire an image including the mark as an internal image of the object; and In the exporting step, after the photographing step, a correction coefficient is exported so that the measured value obtained by multiplying the correction coefficient and the moving amount of the condenser lens when the marker image is captured becomes the actual measured value. An observation device, characterized in that it has: an imaging unit having a condensing lens for condensing transmitted light having transmittance with respect to the object toward the object, and for photographing the object with the transmitted light; a moving unit for relatively moving the condensing lens relative to the object; and a control unit for controlling at least the aforementioned photographing unit and the aforementioned moving unit, The aforementioned object has a first surface and a second surface opposite to the first surface, A modified region and a crack extending from the modified region are provided in the object, The aforementioned control unit executes imaging processing and calculation processing, wherein, In the photographing process, the photographing unit and the moving unit are controlled so that the transmitted light enters the object from the first surface, and the condenser lens is moved along a Z direction intersecting the first plane and the second plane. moving in the direction and using the transmitted light to photograph the aforementioned object to obtain a detection image including the image of the aforementioned modified region and/or the aforementioned crack as an internal image, After the aforementioned photographing process, the calculation process multiplies the correction coefficient by the moving amount of the condenser lens when the detection image is captured, to calculate the position of the modified region and/or the crack in the Z direction. value, The control unit stores a plurality of correction coefficients corresponding to the movement amount. An observation object having a first surface and a second surface opposite to the first surface and provided with a mark, characterized in that: The observation object is used to export a correction coefficient for calculating a measured value of the position of the mark in the Z direction intersecting the first surface and the second surface from the actual measured value of the position of the mark. .

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