TW202235194A - Observation device and observation method capable of more accurately acquiring information on the position of the modified region - Google Patents

Abstract

The observation device and observation method of the invention can more accurately acquire information on the position of the modified region. The observation device includes: an imaging unit for imaging an object using transmitted light having transmissivity with respect to the object, and a control unit for controlling at least the imaging unit, the object having a first surface and a second surface opposite to the first surface, the object formed with a modified region arranged along the first surface and the second surface in X-direction and a crack extended from the modified region. The control unit controls the imaging unit to perform imaging process as the following: enabling the transmitted light to irradiate into the inside of the object from the first surface, and using the transmitted light to photograph the target crack, wherein the target crack is the crack upwardly extended in the Z direction intersecting the first surface and the second surface and in the direction intersecting the X direction among the cracks.

Description

Observation device and observation method

The invention relates to an observation device and an observation method.

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) is equipped with an infrared camera, and can observe the modified region formed inside the semiconductor substrate and the processing damage formed in the functional element layer from the back side of the semiconductor substrate. Wait.

As described above, when observing the modified region formed inside the semiconductor substrate with an infrared camera, it may not be clear which part of the modified region is detected in the thickness direction of the semiconductor substrate. Therefore, in the above-mentioned technical field, it is required to obtain more accurate information on the position of the modified region, such as the upper end position, the lower end position, and the width of the modified region in the thickness direction of the semiconductor substrate. An object of the present invention is to provide an observation device and an observation method capable of more accurately obtaining information on the position of a modified region. The inventors of the present invention conducted intensive studies to solve the above-mentioned technical problems, and obtained the following findings. That is, when a modified region is formed by, for example, laser processing in the above object such as a semiconductor substrate, cracks extending in various directions from the modified region may be formed. Moreover, among the cracks, the cracks intersecting the Z direction intersecting the laser light incident surface of the same object and the X direction which is the advancing direction of the laser processing can utilize the transmittance transmitted from the object compared with the modified region. Light is precisely detected. Therefore, if information on the position at which the crack intersecting the X-direction and the Z-direction is photographed can be obtained, based on this position, information on the position of the modified region can be obtained more accurately. The present invention has been accomplished based on such findings. That is, the observation device of the present invention includes: an imaging unit for imaging an object by using transmitted light having transmittance to the object; and a control unit for controlling at least the imaging unit, and the object has a first surface and On the second surface on the opposite side of the first surface, modified regions aligned in the X direction along the first surface and the second surface and cracks extending from the modified regions are formed on the object, and the control unit controls the imaging unit to The following photographing process is performed: the transmitted light is injected into the inside of the object from the first surface, and the target crack is photographed by the transmitted light, wherein the target crack is Z in the crack that intersects the first surface and the second surface. Cracks extending in the direction and in the direction crossing the X direction. In addition, 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 opposite to the first surface, and an X along the first surface and the second surface is formed on the object. modified regions aligned in the direction and cracks extending from the modified regions; and a photographing step of, after the preparation step, causing transmitted light transmitted from the object to enter the object from the first surface, and using the transmitted light to detect the cracks in the object The photography was performed, and the target crack was a crack extending in the Z direction intersecting the first surface and the second surface and the direction intersecting the X direction among the cracks. In the target object of these devices and methods, modified regions aligned in the X direction and cracks extending from the modified regions are formed. Furthermore, for such an object, it is possible to photograph a target crack intersecting the X direction and the Z direction using the transmitted light transmitted from the object. As in the above findings, the target crack intersecting the X direction and the Z direction from the modified region can be imaged (detected) more accurately in the Z direction than the modified region. Therefore, if information such as the amount of movement of the condensing lens when photographing a target crack can be acquired, information on the position of the modified region can be acquired more accurately based on the amount of movement. The observation device of the present invention may also be configured to include a moving unit for relatively moving the condensing lens relative to the object, wherein the condensing lens is used to condense the transmitted light on the object, and in the imaging process, the control unit Control the photographing unit and the moving unit to move the condensing lens relatively in the Z direction, so that the condensing point is located at multiple positions inside the object to photograph the object, thereby acquiring a plurality of internal images, and the control unit, in After the photographing process, an arithmetic process is performed based on a plurality of internal images and the movement amount of the condenser lens in the Z direction when each of the internal images is photographed, for the position of the target crack in the Z direction. Calculate the location of the crack. In this way, by calculating the crack position based on the movement amount of the condensing lens when photographing the target crack, information on the position of the modified region can be acquired more accurately. The observation device of the present invention may be configured such that, in the arithmetic processing, the control unit judges that the image of the target crack in the plurality of internal images is a clear internal image, The movement amount of the optical lens is used to calculate the crack position. In this way, the position of the crack can be calculated more accurately by the determination of the internal image of the target crack that is clear by the control unit. The observation device of the present invention may be configured such that the control unit, after the arithmetic processing, executes an estimation process of estimating the position of the end of the modified region on the first surface side at Z based on the formation conditions of the modified region and the position of the crack. direction, the position of the end of the modified region on the second surface side in the Z direction, and the width of the modified region in the Z direction. The shape and size of the modified region may vary depending on the formation conditions of the modified region such as laser processing conditions (such as laser wavelength, pulse width, pulse energy, and aberration correction amount, etc.). Therefore, by using the conditions for forming the modified region and the position of the crack in this way, information on the position of the modified region can be estimated more accurately. The observation device of the present invention may be configured such that, in the imaging process, the control unit executes the first imaging process and the second imaging process, wherein in the first imaging process, the transmitted light is made to enter the object from the first surface, The condensing lens is relatively moved in the Z direction to move the condensing point of the transmitted light that has not been reflected by the second surface from the first surface side to the second surface side, and photograph the object at multiple positions. In this way, a plurality of first internal images are obtained as internal images. In the second photographing process, the transmitted light is made to enter the object from the first surface, and the condenser lens is relatively moved in the Z direction, while using The converging point of the transmitted light reflected on the second surface is moved from the second surface side to the first surface side, and the object is photographed at a plurality of positions, thereby acquiring a plurality of second internal images as internal images. In this way, if the transmitted light incident from the first surface of the object but not reflected by the second surface is used for photography (direct observation) of the object, in addition By photographing the object with the reflected transmitted light (rear reflection observation), and acquiring internal images separately, it is possible to more accurately obtain the position of the crack by using the position of the crack obtained based on the amount of movement of the condenser lens when the internal image was photographed. Information about the location of the modified area. The observation device of the present invention may be configured such that, in the arithmetic processing, the control unit executes the first arithmetic processing and the second arithmetic processing, wherein in the first arithmetic processing, it is determined that the target crack in the plurality of first internal images is clear. The first internal image of the first internal image is calculated based on the movement amount of the condenser lens when the determined first internal image is taken, and the first crack position as the crack position is calculated. In the second calculation process, a plurality of In the second internal image in which the target crack is clear, the second crack position is calculated as the crack position based on the movement amount of the condenser lens when the determined second internal image is captured, In the estimation process, the control unit estimates the width of the modified region in the Z direction based on the formation conditions of the modified region and the distance between the first crack position and the second crack position. As described above, in this case, information on the width of the modified region can be acquired more accurately based on the interval between the crack position acquired by direct observation and the crack position acquired by back reflection observation. The observation device of the present invention may be configured to further include a display unit for displaying information, and a control unit for controlling the display unit after the calculation processing to execute display processing for displaying information on the crack position on the display unit. In this case, the user can grasp the information of the crack position through the display unit. Here, the information on the crack position refers to at least one of various information included in the crack position itself and the information on the position of the modified region that can be estimated based on the crack position. According to the present invention, it is possible to provide an observation device and an observation method capable of more accurately obtaining information on the position of the 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 around 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 has 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, the two focusing 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, and along a plurality of lines 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 (image on the right side of 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 can be obtained (the figure on the right side of (b) in FIG. 11 picture). As shown in (c) of FIG. 11 , if the focal point F is focused on the modified region 12 from the back surface 21b side, the modified region 12 causes absorption, scattering, etc., of part of the light I1 reflected by the surface 21a and returned, 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 confined near the front end 14e, etc., thereby causing a part of the light I1 reflected by the surface 21a to scatter, reflect, interfere, absorb, 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 area 12m on the side opposite to surface 21a; and Void area 12n on the back surface 21b side, which is the incident surface of laser light L from defect area 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 actually 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 plotting 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 is photographed in the image obtained by using the light I1. 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. Fig. 16 is a flow chart showing an example of the observation method of this embodiment. Here, as shown in FIG. 16 , laser processing is performed in order to prepare the object on which the modified region is formed (step S11 : preparation step). However, as one step of the observation method, the step of laser processing is not essential, and for example, an object on which the modified region 12 is formed using another laser processing device (or at another time using the laser processing device 1 ) may be prepared. In this step S11 , as shown in FIG. 17 , 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. On 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 relatively moves with respect to the semiconductor substrate 21 . At this time, the control unit 8 displays a pattern 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 condensing points C1 and C2 of the laser beams L1 and L2 are formed within the semiconductor substrate 21 so as to be separated by a distance Dz in the Z direction and separated by a distance Dx in the X direction. As a result, a plurality of (here, two rows) modified regions 12 a and 12 b are formed along the line 15 in the semiconductor substrate 21 . Therefore, here, the X direction is the process advancing direction in which the light-converging points C1 and C2 advance. In this way, here, by controlling the laser irradiation unit 3 (irradiation unit), the control unit 8 irradiates the semiconductor substrate 21 with the laser light L along the X direction, which is the extension direction of the wire 15, and executes the formation of the semiconductor substrate 21 along the X direction. Laser processing of a plurality of modified regions 12 and cracks (cracks 14, 14k) extending from the modified regions 12. In FIG. 17 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 a position 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 . 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. 18 , the semiconductor substrate 21 is photographed using the light (transmitted light) I1 having transmittance to the semiconductor substrate 21 (step S13: photographing step). In this step S13, by controlling the photographing unit 4 (photographing section), the following photographing process is executed: the light I1 is incident into the inside of the semiconductor substrate 21 from the back surface 21b of the semiconductor substrate 21, Among the cracks extending in 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, and a plurality of internal image IDs are acquired. In this embodiment, the objective lens 43 moves integrally with the imaging unit 4 . Therefore, moving the imaging unit 4 also moves 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: Modify the regions 12a, 12b to align the focal points C1, C2 of the laser beams L1, L2 to the positions in the Z direction. The movement 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, and is preferably set more finely from the viewpoint of detecting the crack 14k more accurately. The imaging interval is, for example, within 1 μm, and here it is 0.2 μm. Furthermore, here, the control unit 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 first photographing process of 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, while moving the photographing unit 4 to the surface 21a that is not reflected by the surface 21a. The converging point (focal point F) of the 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 to acquire a plurality of first internal images ID1 as internal image IDs. 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, and moving the photographing unit 4 in the Z direction to adjust the condensing point of the light I1 reflected by the surface 21a (Virtual Focus Fv) The semiconductor substrate 21 is photographed at a plurality of positions while moving from the front surface 21a side to the rear surface 21b side, 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, referred to as the surface 21 a in terms of the structure of the semiconductor substrate 21 ) 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 of the imaging unit 4 when each internal image is captured. Here, the information on the amount of movement can be associated with each internal image ID and stored as photographic data. Among them, the imaging data can be stored in any storage device that can be accessed by 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) can be, as an example, from the position where the converging point of the light I1 is aligned with the back surface 21b of the semiconductor substrate 21, and the imaging unit 4 is moved in the Z direction to make the light I1 move. The amount of movement of the imaging unit 4 when the focal point is aligned with a desired position inside the semiconductor substrate 21 . Next, the control unit 8 inputs photographic data from a predetermined storage device (step S15). Then, the control part 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 with a relatively clear image of the crack 14k among a plurality of internal image IDs by image recognition (performs AI judgment). Here, an example of an algorithm for detecting cracks and modified regions by AI judgment will be described. 20 and 21 are diagrams illustrating crack detection. FIG. 20 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. 20 . 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. Hough transform is a method of detecting all straight lines passing through all points on an image, and assigning weights to more straight lines passing through feature points to detect straight lines. LSD is a method of detecting a straight line by calculating the slope and angle of the luminance value in an image to estimate an area to be a line segment, and treating the area as a rectangle. Next, the control part 8 detects the crack 14 from the straight line group 140 by calculating the similarity with a crack line with respect to the straight line group 140 as shown in FIG. The crack line, as shown in the upper graph of Fig. 21, 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 multiple 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. 22 to 24 are diagrams illustrating flaw detection. FIG. 22 illustrates internal observation results (internal images of the semiconductor substrate 21 ). For the image inside the semiconductor substrate 21 shown in (a) of FIG. 22 , the control unit 8 detects corners (gathering of edges) in the image as key points, and detects its position, size, and direction to detect 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. 23 , 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. 24 , by comparing the sum of feature values for each image taken by shifting in the depth direction, it is possible to confirm the change of the mountain representing the crack displacement for each modified layer. The control unit 8 estimates the peak of this 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. 19 shows a plurality of internal image IDs photographed at positions different from each other in the Z direction. In FIG. 19 , 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 back surface 21b side, and (b) is the shooting position taken away from the back surface 21b side. The internal image IDb of the imaging position of 3 μm, (a) is the internal image IDa of the imaging position 5 μm removed from the back surface 21 b side, (e) the internal image IDe of the imaging position 1 μm away from the front surface 21 a side, (f) is the internal image IDf of the imaging position offset by 3 μm from the surface 21 a side, and (g) is the internal image IDg of the imaging position offset by 5 μm from the surface 21 a side. The imaging position here is a value inside the semiconductor substrate 21 . In the example shown in FIG. 19 , the image of the crack 14k is the clearest in the internal image IDd. Based on this, the control unit 8 can judge that the internal image IDd is a relatively high score and the image of the crack 14k is relatively clear. image (that is, it can be 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 calculation process of calculating the internal image IDs extending in the direction intersecting the Z direction and the X direction based on the movement amount 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 is calculated. More specifically, the control unit 8 judges an internal image ID with a clear image of the crack 14k among a plurality of internal image IDs in the calculation process, and calculates the crack position based on the movement amount when the determined internal image ID is captured. . The crack position can be computed, for example, by multiplying the movement amount by a predetermined correction coefficient. The correction coefficient can be obtained from, for example, the NA of the objective lens 43, the refractive index of the semiconductor substrate 21, and the like. 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 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 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 . In the above manner, the observation method using the laser processing device 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, an observation device 1A (refer to FIG. 1 ) is constituted by an imaging unit 4 , a drive unit 7 , and a control unit 8 . To photograph the semiconductor substrate 21 , the driving unit 7 is used to relatively move the photographing unit 4 relative to the semiconductor substrate 21 , and the control unit 8 is used to at least control the photographing unit 4 and the driving unit 7 . As described above, in the semiconductor substrate 21 to be observed by the observation method of the present embodiment and the observation device 1A implementing the observation method, the modified regions 12 and the sub-modified regions 12 arranged in the X direction are formed. Extended cracks 14, 14k. With such a semiconductor substrate 21 , the crack 14 k extending in the direction intersecting the Z direction and the X direction can be photographed using the light I1 transmitted through the semiconductor substrate 21 . The crack 14k intersecting the Z direction and the X direction can be imaged (detected) more accurately in the Z direction than the modified region 12 itself. Therefore, for example, if information such as the amount of movement of the imaging unit 4 when imaging the crack 14 k is acquired, information on the position of the modified region 12 can be acquired more accurately based on the amount of movement. In addition, the observation device 1A of the present embodiment includes a drive unit 7 for relatively moving the converging point of the light I1 with respect to the semiconductor substrate 21 . In the photographing process, the control unit 8 moves the photographing unit 4 in the Z direction by controlling the photographing unit 4 and the driving unit 7, so that the light I1 focuses on multiple positions inside the semiconductor substrate 21 to capture the semiconductor light. The substrate 21 takes pictures and acquires a plurality of internal image IDs. In addition, after the photographing process, the control unit 8 executes calculation processing of calculating the crack 14k in the Z direction based on a plurality of internal image IDs and the movement amount of the photographing unit 4 in the Z direction when the respective internal image IDs are obtained by photographing. The position in the direction of the crack position (the first crack position Z1 and the second crack position Z2) is calculated. In this way, information on the position of the modified region 12 can be acquired more accurately based on the amount of movement of the imaging unit 4 when imaging the crack 14k. In addition, in the observation device 1A of the present embodiment, in the arithmetic processing, the control unit 8 judges a clear internal image of the crack 14k among the plurality of internal images ID, and obtains the judged internal image based on photography. The crack position of the crack 14k is calculated based on the movement amount of the imaging unit 4. In this manner, the position of the crack 14k can be more accurately calculated by judging a clear internal image of the crack 14k by the control unit 8 . In addition, in the observation device 1A of the present embodiment, the control unit 8 executes an estimation process of estimating the back surface 21b of the modified region 12 based on the formation conditions of the modified region 12 and the crack positions of the cracks 14k after the arithmetic processing. At least one of the Z-direction position of the side end, the Z-direction position of the surface 21 a side end of the modified region 12 , and the Z-direction width of the modified region 12 . The shape and size of the modified region 12 may vary depending on the formation conditions of the modified region such as laser processing conditions (such as laser wavelength, pulse width, pulse energy, and aberration correction amount, etc.). Therefore, if the conditions for forming the modified region 12 such as the processing conditions of laser processing and the position of the crack 14k are used, information on the position of the modified region 12 can be obtained more accurately. In addition, in the observation device of this embodiment, in the imaging process, the control unit 8 executes the first imaging process and the second imaging process. substrate 21, and the imaging unit 4 is moved, whereby the converging point of the light I1 not reflected by the surface 21a is moved from the back surface 21b side to the surface 21a side, and the semiconductor substrate 21 is photographed at a plurality of positions, as The internal image ID acquires a plurality of first internal images ID1, and in the second photographing process, the light I1 is made incident on the semiconductor substrate 21 from the back surface 21b, and the photographing unit 4 is moved, whereby the light reflected by the surface 21a The semiconductor substrate 21 is photographed at a plurality of positions while moving the condensing point of the light I1 from the front surface 21 a side to the rear surface 21 b side, and a plurality of second internal images ID2 are acquired as internal image IDs. In this way, if the imaging (direct observation) of the semiconductor substrate 21 is performed by using the light I1 incident from the back surface 21b of the semiconductor substrate 21 but not reflected by the surface 21a, and using the light incident from the back surface 21b of the semiconductor substrate 21 and being The imaging of the semiconductor substrate 21 by the light I1 reflected on the surface 21a (rear reflection observation) acquires internal images separately, and the position of the crack can be obtained based on the movement amount of the imaging unit 4 when the internal image is acquired, and more accurate The information on the position of the modified region 12 can be obtained accurately. In addition, in the observation device 1A of the present embodiment, the control unit 8 executes the first and second arithmetic processing in the arithmetic processing, wherein in the first arithmetic processing, a plurality of first internal image ID1s are judged to be The clear first internal image of the middle crack 14k is calculated based on the movement amount of the imaging unit 4 when the determined first internal image is captured, and the first crack position Z1 as the crack position is calculated. Among the plurality of second internal images ID2, the second internal image in which the crack 14k is clear is judged, based on the movement amount of the imaging unit 4 when the judged second internal image is captured, the second internal image as the crack position is determined. The crack position Z2 is calculated. In addition, in the estimation process, the control unit 8 can estimate the width of the modified region 12 in the Z direction based on the formation conditions of the modified region 12 and the distance between the first crack position Z1 and the second crack position Z2 . As described above, in this case, information on the width of the modified region 12 can be obtained more accurately based on the distance between the first crack position Z1 obtained by direct observation and the second crack position Z2 obtained by rear reflection observation. . Furthermore, the observation device 1A of this embodiment further includes a display 150 for displaying information. Furthermore, the control unit 8 may execute display processing for displaying information on crack positions on the display 150 by controlling the display 150 after the calculation processing. In this case, the user can grasp the crack location information through the display 150 . Here, the information on the crack position is at least one of various information included in the crack position itself and information on the position of the modified region 12 that can be estimated based on the crack position. The above-mentioned embodiment is an example for explaining the present invention. Therefore, the present invention is not limited to the above-mentioned embodiments, and can be arbitrarily changed. For example, in the above-mentioned embodiment, the drive unit 7 for moving the objective lens 43 together with the imaging unit 4 was illustrated as means for relatively moving the objective lens 43 in the Z direction with respect 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 embodiment, the example in which the control unit 8 automatically judges the image in step S16 was described, but the control unit 8 may acquire the crack position of the crack 14k based on the user's judgment result. In this case, the control unit 8 displays, for example, a plurality of internal image IDs on the display 150 and displays information prompting determination (selection) of one internal image of the crack 14k from the plurality of internal image IDs. 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 movement amount of the internal image 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 step S13, observation of one modified region 12 was performed both of direct observation and rear reflection observation, and the first internal image ID1 and the internal image ID were acquired. 2nd internal image ID2. However, in step S13, only one of direct observation and back reflection observation may be performed. In this case, since one of the first internal image ID1 and the second internal image ID2 can be obtained, the position and width of the end of the modified region 12 can also be estimated based on this one.

1: Laser processing device 1A: Observation device 2: 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 14k: crack 14e: front end 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 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 F: focus Fv: virtual focus I1: light I2: light 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 RA: range 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 Z1: The first crack position Z2: The second crack position

[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 in which detection results are plotted in a cross-sectional photograph of an object. [FIG. 16] It is a flowchart which shows an example of the observation method of this embodiment. [ Fig. 17 ] is a diagram showing one step of the observation method shown in Fig. 17 . [ Fig. 18 ] is a diagram showing one step of the observation method shown in Fig. 17 . [ Fig. 19 ] are a plurality of internal images taken at positions different from each other in the Z direction. [ Fig. 20 ] is a diagram illustrating crack detection. [ Fig. 21 ] is a diagram illustrating crack detection. [ Fig. 22 ] is a diagram illustrating flaw detection. [ Fig. 23 ] is a diagram illustrating flaw detection. [ Fig. 24 ] is a diagram illustrating flaw detection.

2: Carrying table

3: Laser irradiation unit

12:Modified area

12a: Modified area

12b:Modified area

15: line

21b: back

21: Semiconductor substrate

21a: Surface

31: light source

32: Spatial light modulator

33: Concentrating lens

C: focus point

C1: focus point

C2: focus point

Dx: separation distance

Dz: separation distance

L: laser light

L1: laser light

L2: laser light

Claims (8)

An observation device, characterized in that it has: an imaging unit for photographing the object by using transmitted light having transmittance with respect to the object; and a control unit for controlling at least the aforementioned photographing unit, The aforementioned object has a first surface and a second surface opposite to the first surface, A modified region aligned in the X direction along the first surface and the second surface and a crack extending from the modified region are formed on the object, The control unit controls the imaging unit to perform the following imaging process: the transmitted light enters the inside of the object from the first surface, and the target crack is captured by the transmitted light, wherein the target crack is It is the said crack extending in the Z direction intersecting with the said 1st surface and the said 2nd surface, and the direction intersecting with the said X direction among the said cracks. The observation device as claimed in claim 1, wherein: a moving part for relatively moving a condensing lens relative to the object, the condensing lens for condensing the transmitted light on the object, In the photographing process, the control unit controls the photographing unit and the moving unit to relatively move the condensing lens in the Z direction so that the condensing points of the transmitted light are positioned at a plurality of positions inside the object. The aforementioned object is photographed to obtain a plurality of internal images, The control unit executes an arithmetic process after the photographing process based on the plurality of internal images and the amount of movement of the condenser lens in the Z direction when each of the internal images is photographed. The crack position is calculated as the position of the target crack in the Z direction. The observation device as claimed in claim 2, wherein: In the arithmetic processing, the control unit judges the internal image with a clear image of the target crack in the plurality of internal images based on the movement of the condenser lens when the determined internal image is captured. Quantity to calculate the aforementioned crack position. The observation device as claimed in claim 3, wherein: The control unit executes an estimation process of estimating a position of an end portion of the modified region on the first surface side in the Z direction based on the formation condition of the modified region and the position of the crack after the arithmetic processing. at least one of the position, the position of the end portion of the modified region on the second surface side in the Z direction, and the width of the modified region in the Z direction. The observation device as described in any one of claim items 2 to 4, wherein: In the photographing process, the control unit executes the first photographing process and the second photographing process, In the first photographing process, the transmitted light is made to enter the object from the first surface, and the condenser lens is relatively moved in the Z direction, so that the light that has not been reflected by the second surface The focusing point of the transmitted light is moved from the first surface side to the second surface side, and the object is photographed at a plurality of positions, whereby a plurality of first internal images are acquired as the internal images, In the second photographing process, the transmitted light reflected on the second surface is made to enter the target object from the first surface, and the condenser lens is relatively moved in the Z direction, so that the transmitted light reflected on the second surface The focusing point is moved from the second surface side to the first surface side, and the object is photographed at a plurality of positions, thereby acquiring a plurality of second internal images as the internal images. The observation device as claimed in claim 5, wherein: In the arithmetic processing, the control unit executes the first arithmetic processing and the second arithmetic processing, In the first arithmetic processing, the first internal image in which the target crack is clear among the plurality of first internal images is judged based on the condenser lens used when capturing the judged first internal image. The aforementioned movement amount is used to calculate the first crack position as the aforementioned crack position, In the second arithmetic processing, the second internal image in which the target crack is clear among the plurality of second internal images is determined based on the condenser lens used when capturing the determined second internal image. The aforementioned movement amount is used to calculate the second crack position as the aforementioned crack position, The control unit estimates the width of the modified region in the Z direction based on the formation conditions of the modified region and the distance between the first crack position and the second crack position. The observation device as described in any one of claim items 2 to 6, wherein: further comprising a display unit for displaying information, The control unit controls the display unit after the arithmetic processing, and executes a display process of causing the display unit to display information on the position of the crack. 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 on the opposite side of the first surface, and the object is formed with objects arranged in the X direction along the first surface and the second surface. modified regions and cracks extending from the aforementioned modified regions; and In the photographing step, after the preparation step, the transmitted light transmitted from the object is made to enter the object from the first surface, and the crack of the target is photographed by the transmitted light, and the crack of the target is the same as the crack in the crack. The cracks extending in the Z direction intersecting the first surface and the second surface and in the direction intersecting the X direction.

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