JP2022117060A - Observation device and method for observation - Google Patents

Abstract

To provide an observation device and a method for observation that can acquire information on the position of a modified region more accurately.SOLUTION: An observation device 1A includes: an imaging unit 4 for imaging a semiconductor substrate 21 by light I1 transmissive for the semiconductor substrate 21; and a control unit 8 for controlling the imaging unit 4. The control unit 8 images a crack 14k extending in a direction that intersects with a Z-direction and an X-direction, with the light I1, while causing the light I1 to enter from a back surface 21b of the semiconductor substrate 21 to the inside of the semiconductor substrate 21 by controlling the imaging unit 4.SELECTED DRAWING: Figure 17

Description

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

By irradiating the wafer with a laser beam from the back side of the semiconductor substrate in order to cut the wafer including the semiconductor substrate and the functional element layer formed on the surface of the semiconductor substrate along each of the plurality of lines, 2. Description of the Related Art A laser processing apparatus is known that forms a plurality of rows of modified regions inside a semiconductor substrate along each of a plurality of lines. The laser processing apparatus described in Patent Document 1 is equipped with an infrared camera, and can observe the modified region formed inside the semiconductor substrate, the processing damage formed in the functional element layer, etc. from the back side of the semiconductor substrate. is possible.

JP 2017-64746 A

As described above, when the modified region formed inside the semiconductor substrate is observed 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 technical field, there is a demand for obtaining 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.

SUMMARY OF THE INVENTION An object of the present invention is to provide an observation apparatus and an observation method that enable more accurate acquisition of information about the position of a modified region.

The present inventor has obtained the following knowledge by proceeding with earnest research in order to solve the above problems. That is, when a modified region is formed inside an object such as the semiconductor substrate by, for example, laser processing, cracks extending in various directions from the modified region may also be formed. Among the cracks, the cracks that intersect the Z direction that intersects the laser beam incident surface of the object and the X direction that is the progress direction of the laser processing are compared with the modified region. Detected pinpoint by light. Therefore, if it is possible to obtain information about the positions where the cracks intersecting the X and Z directions are imaged, it is possible to more accurately obtain information about the positions of the modified regions based on the positions. The present invention has been made based on such findings.

That is, an observation apparatus according to the present invention includes an imaging unit for imaging an object with transmitted light that is permeable to the object, and a control unit for controlling at least the imaging unit. The object includes a first surface and a second surface opposite the first surface, the object having modified regions arranged in an X direction along the first surface and the second surface and cracks extending from the modified regions. Under the control of the imaging unit, the control unit controls the Z direction and the X direction intersecting the first surface and the second surface of the crack while allowing the transmitted light to enter the object from the first surface. A target crack, which is a crack extending in a direction intersecting with , is imaged with transmitted light.

Further, the observation method according to the present invention includes a first surface and a second surface opposite to the first surface, and includes modified regions and modified regions arranged in the X direction along the first surface and the second surface. a preparing step of preparing an object in which a crack extending from the region is formed; an imaging step of imaging a target crack, which is a crack extending in a direction intersecting the Z direction and the X direction intersecting the two planes, with transmitted light.

The target object of these devices and methods has modified regions arranged along the X direction and cracks extending from the modified regions. Then, with respect to such an object, an image of a target crack that intersects in the X direction and the Z direction is captured using transmitted light that passes through the object. As described above, the target cracks intersecting the modified region in the X direction and the Z direction are imaged (detected) more pinpointally than the modified region in the Z direction. Therefore, if information such as the amount of movement of the condenser lens when the target crack is imaged is obtained, information regarding the position of the modified region can be obtained more accurately based on the amount of movement.

The observation apparatus according to the present invention includes a movement unit for moving a condenser lens for condensing transmitted light onto the object relative to the object. And by controlling the moving unit, the condenser lens is relatively moved along the Z direction, so that the condensing point is positioned at a plurality of positions inside the object and the object is imaged, thereby obtaining a plurality of internal images. After the imaging process, the control unit obtains the position of the target crack in the Z direction 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 captured. You may perform the calculation process which calculates a certain crack position. By calculating the crack position based on the amount of movement of the condenser lens when the image of the target crack is captured in this way, it is possible to acquire information on the position of the modified region more accurately.

In the observation device according to the present invention, in the calculation process, the control unit determines an internal image in which the image of the target crack is clear among the plurality of internal images, and the condenser lens when the determined internal image is captured. The crack position may be calculated based on the amount of movement. In this way, the crack position can be calculated more accurately by determining the internal image in which the target crack is clear by the control unit.

In the observation device according to the present invention, after the calculation process, the control unit determines the position in the Z direction of the end of the modified region on the first surface side based on the conditions for forming the modified region and the crack position. An estimation process of estimating at least one of the position in the Z direction of the end of the modified region on the second surface side and the width of the modified region in the Z direction may be performed. The shape and size of the modified region may change depending on the conditions for forming the modified region, such as laser processing conditions (for example, laser beam wavelength, pulse width, pulse energy, aberration correction amount, etc.). be. Therefore, by using the formation condition of the modified region and the crack position in this way, it is possible to more accurately estimate the information on the position of the modified region.

In the observation apparatus according to the present invention, in the imaging process, the control unit relatively moves the condensing lens along the Z direction while causing the transmitted light to enter the object from the first surface. A plurality of first internal images are acquired as internal images by imaging the object at a plurality of positions while moving the focal point of transmitted light that has not undergone reflection from the first surface side toward the second surface side. In the first imaging process, while the transmitted light is incident on the object from the first surface, the condensing lens is relatively moved along the Z direction, so that the condensing point of the transmitted light reflected by the second surface is moved to the second surface. and a second imaging process of acquiring a plurality of second internal images as internal images by imaging the object at a plurality of positions while moving from the surface side toward the first surface side. In this way, imaging (direct observation) of an object using transmitted light that is incident from the first surface of the object and has not been reflected by the second surface, and imaging (direct observation) of the object using transmitted light that is incident from the first surface of the object and undergoing second observation. If an internal image is acquired by imaging the object using transmitted light reflected by the surface (back surface reflection observation), and by acquiring an internal image respectively, the internal image is acquired based on the amount of movement of the condenser lens when the internal image is captured. Information on the position of the modified region can be obtained more accurately by using the crack position.

In the observation device according to the present invention, in the calculation process, the control unit determines the first internal image in which the target crack is clear among the plurality of first internal images, and determines the image of the determined first internal image. A first calculation process for calculating a first crack position as a crack position based on the amount of movement of the condenser lens, and a second internal image in which the target crack is clear among the plurality of second internal images is determined, and the determined a second calculation process for calculating the second crack position as the crack position based on the amount of movement of the condenser lens when the second internal image was captured; and in the estimation process, the control unit The width of the modified region in the Z direction may be estimated based on the conditions for forming the modified region and the distance between the first crack position and the second crack position. As described above, in this case, based on the distance between the crack position acquired based on direct observation and the crack position acquired based on back reflection observation, more accurately, the width of the modified region Information can be obtained.

The observation device according to the present invention further includes a display unit for displaying information, and the control unit executes display processing for displaying information related to the crack position on the display unit by controlling the display unit after the calculation processing. You may In this case, the user can grasp the information related to the crack position via the display unit. The information about the crack position is at least one of the crack position itself and various information included in the information about the position of the modified region that can be estimated based on the crack position.

ADVANTAGE OF THE INVENTION According to this invention, the observation apparatus and observation method which can acquire the information regarding the position of a modified region more correctly can be provided.

1 is a configuration diagram of a laser processing apparatus according to one embodiment; FIG. 1 is a plan view of a wafer in one implementation; FIG. 3 is a cross-sectional view of a portion of the wafer shown in FIG. 2; FIG. FIG. 2 is a configuration diagram of a laser irradiation unit shown in FIG. 1; 2 is a configuration diagram of an imaging unit for inspection shown in FIG. 1; FIG. 2 is a configuration diagram of an imaging unit for alignment correction shown in FIG. 1. FIG. 6A and 6B are cross-sectional views of a wafer for explaining the principle of imaging by the imaging unit for inspection shown in FIG. 5 and images at various locations by the imaging unit for inspection; 6A and 6B are cross-sectional views of a wafer for explaining the principle of imaging by the imaging unit for inspection shown in FIG. 5 and images at various locations by the imaging unit for inspection; 4 is an SEM image of a modified region and cracks formed inside a semiconductor substrate; 4 is an SEM image of a modified region and cracks formed inside a semiconductor substrate; FIG. 6 is a schematic diagram for explaining the principle of imaging by the imaging unit for inspection shown in FIG. 5; FIG. 6 is a schematic diagram for explaining the principle of imaging by the imaging unit for inspection shown in FIG. 5; FIG. 4 is a diagram showing an object on which a modified region is formed; FIG. 10 is a graph of modified regions and crack locations in the Z direction; FIG. The detection results are plotted on a cross-sectional photograph of the object. 4 is a flow chart showing an example of an observation method according to the present embodiment; FIG. 18 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; 4A and 4B are a plurality of internal images captured at different positions in the Z direction; It is a figure explaining crack detection. It is a figure explaining crack detection. It is a figure explaining mark detection. It is a figure explaining mark detection. It is a figure explaining mark detection.

Hereinafter, one embodiment will be described in detail with reference to the drawings. In addition, in description of each figure, the same code|symbol may be attached|subjected to the part which is the same or corresponds, and the overlapping description may be abbreviate|omitted. Each figure may also show an orthogonal coordinate system defined by the X-axis, the Y-axis, and the Z-axis. As an example, the X direction and the Y direction are the first horizontal direction and the second horizontal direction that intersect (perpendicularly) with each other, and the Z direction is the vertical direction that intersects (perpendicularly) with 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 section), a plurality of imaging units 4, 5, 6, a drive unit 7, a control section 8, 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 a laser beam L. As shown in FIG.

The stage 2 supports the object 11 by sucking a film attached to the object 11, for example. The stage 2 is movable along each of the X and Y directions, and is rotatable about an axis parallel to the Z direction.

The laser irradiation unit 3 condenses a laser beam L having transparency to the object 11 and irradiates the object 11 with the laser beam L. As shown in FIG. When the laser beam L is condensed inside the object 11 supported by the stage 2, the laser beam L is particularly absorbed in a portion corresponding to the converging point C of the laser beam L, and the inside of the object 11 is reformed. A textured region 12 is formed.

Modified region 12 is a region that differs in density, refractive index, mechanical strength, and other physical properties from surrounding unmodified regions. The modified region 12 includes, for example, a melting process 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 tend to 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 used for cutting the object 11 .

As an example, when the stage 2 is moved along the X direction and the focal point C is moved along the X direction relative to the object 11, the plurality of modified spots 12s are aligned along the X direction. formed in rows. One modified spot 12s is formed by one pulse of laser light L irradiation. A row of modified regions 12 is a set of a plurality of modified spots 12s arranged in a row. Adjacent modified spots 12 s may be connected to each other or separated from each other depending on the relative moving speed of the focal point C with respect to the object 11 and the repetition frequency of the laser light L.

The imaging unit 4 images the modified region 12 formed in the object 11 and the tip of the crack extending from the modified region 12 .

The imaging unit 5 and the imaging unit 6 image the object 11 supported by the stage 2 under the control of the control unit 8 using light that passes through the object 11 . Images obtained by imaging by the imaging units 5 and 6 are used for alignment of the irradiation position of the laser light L as an example.

The drive unit 7 supports the laser irradiation unit 3 and a plurality of imaging units 4, 5, 6. The drive unit 7 moves the laser irradiation unit 3 and the plurality of imaging units 4, 5, 6 along the Z direction.

A control unit 8 controls operations of the stage 2 , the laser irradiation unit 3 , the plurality of imaging units 4 , 5 , 6 , and the driving unit 7 . The control unit 8 is configured as a computer device including a processor, memory, storage, communication device, and the like. In the control unit 8, the processor executes software (program) read into the memory or the like, and controls reading and writing of data in the memory and storage, and communication by the communication device.

The display 150 has a function as an input unit for receiving input of information from the user and a function as a display unit for displaying information to the user.
[Object configuration]
The object 11 in this implementation is a wafer 20, as shown in FIGS. A wafer 20 includes a semiconductor substrate 21 and a functional element layer 22 . In this embodiment, the wafer 20 is described as having the functional element layer 22, but the wafer 20 may or may not have the functional element layer 22, and 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, a circuit element such as a memory, or the like. The functional element 22a may be configured three-dimensionally by stacking a plurality of layers. Although the semiconductor substrate 21 is provided with the notch 21c indicating the crystal orientation, an orientation flat may be provided instead of the notch 21c.

The wafer 20 is cut along each of the plurality of lines 15 into functional elements 22a. The plurality of lines 15 pass between each of the plurality of functional elements 22a when viewed from the thickness direction of the wafer 20. As shown in FIG. More specifically, line 15 passes through the center of street region 23 (the center in the width direction) when viewed from the thickness direction of wafer 20 . The street region 23 extends between adjacent functional elements 22 a in the functional element layer 22 . In this embodiment, the plurality of functional elements 22a are arranged in a matrix along the surface 21a, and the plurality of lines 15 are set in a lattice. Although the line 15 is a virtual line, it may be an actually drawn line.

[Configuration of laser irradiation unit]
As shown in FIG. 4 , the laser irradiation 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, a pulse oscillation method. 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). A condenser lens 33 collects the laser light L modulated by the spatial light modulator 32 . Note that the condenser lens 33 may be a correction ring lens.

In this embodiment, the laser irradiation unit 3 irradiates the wafer 20 with the laser light L from the back surface 21 b side of the semiconductor substrate 21 along each of the plurality of lines 15 , thereby causing the semiconductor wafer 20 to be irradiated along each of the plurality of lines 15 . Two rows of modified regions 12 a and 12 b are formed inside the substrate 21 . The modified region 12a is the modified region closest to the surface 21a among the two rows of modified regions 12a and 12b. Of the two rows of modified regions 12a and 12b, the modified region 12b is the modified region closest to the modified region 12a and the modified region closest to the rear 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 focal points C 1 and C 2 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 the condensing point C2 is located behind the condensing point C1 in the traveling direction and on the incident side of the laser light L, for example. The formation of the modified region may be single focus or multifocal, and may be one pass or multiple passes.

The laser irradiation unit 3 irradiates the wafer 20 with the laser light L from the rear surface 21 b side of the semiconductor substrate 21 along each of the plurality of lines 15 . As an example, two condensing points C1 and C2 are aligned at positions of 54 μm and 128 μm from the surface 21a of the semiconductor substrate 21, which is a single crystal silicon <100> substrate with a thickness of 400 μm, and a plurality of lines 15 are formed. The wafer 20 is irradiated with the laser light L from the back surface 21b side of the semiconductor substrate 21 along each of . At this time, for example, when the crack 14 extending over the two rows of modified regions 12a and 12b reaches the surface 21a of the semiconductor substrate 21, the wavelength of the laser light L is 1099 nm, the pulse width is 700 nsec, and the repetition frequency is 120 kHz. be done. The output of the laser light L at the condensing point C1 is 2.7 W, and the output of the laser light L at the condensing point C2 is 2.7 W. The moving speed is 800 mm/sec. For example, when the number of processing passes is 5, ZH80 (position of 328 μm from the surface 21a), ZH69 (position of 283 μm from the surface 21a), ZH57 (position of 234 μm from the surface 21a) are applied to the wafer 20 described above. position), ZH26 (position 107 μm from surface 21a), and ZH12 (position 49.2 μm from surface 21a) may be processing positions. In this case, for example, the wavelength of the laser light L may be 1080 nm, the pulse width may be 400 nsec, the repetition frequency may be 100 kHz, and the moving speed may be 490 mm/sec.

Formation of such two rows of modified regions 12a, 12b and cracks 14 is performed in the following cases. That is, in a later process, for example, the semiconductor substrate 21 is thinned by grinding the back surface 21b of the semiconductor substrate 21, the cracks 14 are exposed on the back surface 21b, and the wafers 20 are separated along the lines 15 respectively. This is the case of cutting into semiconductor devices.

[Configuration of imaging unit for inspection]
As shown in FIG. 5 , the imaging unit 4 (imaging section) has a light source 41 , a mirror 42 , an objective lens (collecting lens) 43 , and a light detection section 44 . The imaging unit 4 images the wafer 20 . The light source 41 outputs light I<b>1 that is transmissive 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 onto the wafer 20 from the back surface 21b side of the semiconductor substrate 21. FIG. At this time, the stage 2 supports the wafer 20 on which the two rows of modified regions 12a and 12b are formed as described above.

The objective lens 43 is for condensing the light (transmitted light) I<b>1 having transparency to the semiconductor substrate 21 toward the semiconductor substrate 21 . The objective lens 43 allows the light I1 reflected by the surface 21a of the semiconductor substrate 21 to pass therethrough. That is, the objective lens 43 allows the light I1 propagated through the semiconductor substrate 21 to pass therethrough. The numerical aperture (NA) of the objective lens 43 is, for example, 0.45 or more. The objective lens 43 has a correction ring 43a. The correction ring 43a corrects the aberration occurring in the light I1 within the semiconductor substrate 21 by adjusting the mutual distances of the plurality of lenses constituting the objective lens 43, for example. Note that the means for correcting aberration is not limited to the correction ring 43a, and other correction means such as a spatial light modulator may be used. The photodetector 44 detects the light I1 transmitted through the objective lens 43 and the mirror 42 . The photodetector 44 is composed of, for example, an InGaAs camera, and detects light I1 in the near-infrared region. The means for detecting (imaging) the light I1 in the near-infrared region is not limited to the InGaAs camera, and other imaging means such as a transmission confocal microscope may be used as long as they perform transmission imaging.

The imaging unit 4 can image the two rows of modified regions 12a and 12b and the tips 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. Crack 14b is a crack extending from modified region 12a toward back surface 21b. The crack 14c is a crack extending from the modified region 12b toward the surface 21a. The crack 14d is a crack extending from the modified region 12b toward the rear surface 21b.

[Configuration 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 . The light source 51 outputs light I<b>2 that is transmissive 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 may 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 irradiates the wafer 20 from the back surface 21b side of the semiconductor substrate 21. FIG.

The lens 53 allows the light I2 reflected by the surface 21a of the semiconductor substrate 21 to pass therethrough. That is, the lens 53 allows the light I2 propagated through the semiconductor substrate 21 to pass therethrough. The numerical aperture of 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 photodetector 54 detects the light I2 that has passed through the lens 53 and the mirror 52 . The photodetector 54 is composed of, for example, an InGaAs camera, and detects light I2 in the near-infrared region.

Under the control of the control unit 8, the imaging unit 5 irradiates the wafer 20 with the light I2 from the rear surface 21b side, and detects the light I2 returning from the front surface 21a (functional element layer 22) to detect the functional element layer. 22 is imaged. Similarly, under the control of the control unit 8, the imaging unit 5 irradiates the wafer 20 with the light I2 from the rear surface 21b side, and also emits light returning from the formation positions of the modified regions 12a and 12b in the semiconductor substrate 21. By detecting I2, an image of the region including the modified regions 12a and 12b is acquired. These images are used for alignment of the irradiation position of the laser beam L. FIG. Imaging unit 6 has a configuration similar to that of imaging unit 5, except that lens 53 has a lower magnification (e.g., 6x in imaging unit 5 and 1.5x in imaging unit 6). , is used for alignment in the same manner as the imaging unit 5 .

[Imaging principle by inspection imaging unit]
Using the imaging unit 4 shown in FIG. 5, as shown in FIG. 7, the semiconductor substrate 21 in which the cracks 14 extending over the two rows of modified regions 12a and 12b reach the front surface 21a, is exposed from the back surface 21b side to the front surface. The focal point F (the focal point of the objective lens 43) is moved toward the 21a side. In this case, when the tip 14e of the crack 14 extending from the modified region 12b to the back surface 21b side is focused on from the back surface 21b side, the tip 14e can be confirmed (image on the right side in FIG. 7). However, even if the crack 14 itself and the tip 14e of the crack 14 reaching the front surface 21a are focused from the rear surface 21b side, they cannot be confirmed (left image in FIG. 7). The functional element layer 22 can be confirmed by focusing on the front surface 21a of the semiconductor substrate 21 from the rear surface 21b side.

Also, using the imaging unit 4 shown in FIG. 5, as shown in FIG. , the focal point F is moved toward the surface 21a side. In this case, even if the tip 14e of the crack 14 extending from the modified region 12a to the surface 21a side is focused from the back surface 21b side, the tip 14e cannot be confirmed (left image in FIG. 8). However, the focal point F is adjusted from the back surface 21b side to the area opposite to the back surface 21b with respect to the surface 21a (that is, the area on the side of the functional element layer 22 with respect to the surface 21a), and the focal point F is symmetrical with respect to the surface 21a. When the virtual focus Fv is positioned at the tip 14e, the tip 14e can be confirmed (right image in FIG. 8). The virtual focal point Fv is a point symmetrical with respect to the focal point F considering the refractive index of the semiconductor substrate 21 and the surface 21a.

The reason why the crack 14 itself cannot be confirmed as described above is assumed to be that 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 the modified region 12 and cracks 14 formed inside the semiconductor substrate 21, which is a silicon substrate. FIG. 9(b) is an enlarged image of area A1 shown in FIG. 9(a), FIG. 10(a) is an enlarged image of area A2 shown in FIG. 9(b), and FIG. b) is an enlarged image of the area A3 shown in FIG. 10(a). Thus, the width of the crack 14 is approximately 120 nm, which is smaller than the wavelength of the light I1 in the near-infrared region (for example, 1.1 to 1.2 μm).

The imaging principle assumed based on the above is as follows. As shown in FIG. 11(a), when the focal point F is placed in the air, the light I1 does not return, resulting in a dark image (right image in FIG. 11(a)). As shown in FIG. 11(b), when the focal point F is positioned inside the semiconductor substrate 21, the light I1 reflected by the surface 21a returns, resulting in a whitish image ((b) in FIG. 11). ) in the right image). As shown in (c) of FIG. 11, when the modified region 12 is focused on from the rear surface 21b side, part of the light I1 reflected by the surface 21a and returned is absorbed by the modified region 12. Due to scattering and the like, an image in which the modified region 12 appears dark in a whitish background is obtained (right image in FIG. 11(c)).

As shown in FIGS. 12A and 12B, when the tip 14e of the crack 14 is focused from the back surface 21b side, for example, optical peculiarities (stress concentration, strain, discontinuity of atomic density, etc.), confinement of light generated near the tip 14e, etc., causes scattering, reflection, interference, absorption, etc. of part of the light I1 that has been reflected by the surface 21a and returned, resulting in a whitish background. An image in which the tip 14e appears dark inside is obtained (images on the right in FIGS. 12(a) and 12(b)). As shown in FIG. 12(c), when the focus F is adjusted from the rear surface 21b side to a portion other than the vicinity of the tip 14e of the crack 14, at least part of the light I1 reflected by the surface 21a returns, A whitish image is obtained (right image in FIG. 12(c)).

[Embodiment related to internal observation]
FIG. 13 is a diagram showing an object on which modified regions are formed. FIG. 13(a) is a cross-sectional photograph of an object cut so as to expose the modified region. (b) of FIG. 13 is an example of an image of an object captured by light passing through the object. (c) of FIG. 13 is another example of an image of an object captured by light passing through the object. As shown in (a) of FIG. 13 , the modified region 12 formed in the object (in this case, the semiconductor substrate 21 ) by condensing the laser beam L is opposite to the incident surface of the laser beam L in the semiconductor substrate 21 . The void region 12m located on the side of the front surface 21a, which is the side surface, and the void upper region 12n located on the side of the back surface 21b, which is the incident surface of the laser light L, than the void region 12m.

When the semiconductor substrate 21 having the modified region 12 formed thereon is imaged with light I1 having transparency to the semiconductor substrate 21, as shown in FIGS. An image of a crack 14k extending along the cross direction (at an angle to the X direction) may be identified. When viewed from the Z direction, the crack 14k is substantially parallel to the Y direction in the example of FIG. 13(b), and is slightly inclined with respect to the Y direction in the example of FIG. 13(c). Images of these cracks 14k are limited in the Z direction compared to the modified region 12 when the semiconductor substrate 21 is imaged at a plurality of positions while moving the focal point of the light I1 along the Z direction. clearly detected in the widest range.

FIG. 14 is a graph of modified regions and crack locations in the Z direction. In FIG. 14, plots of the void bottom end, the void top end, the void top region bottom end, and the void top region top end are actually measured values obtained 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 void upper region is the end of the void upper region 12n on the surface 21a side.

In addition, the plots of the direct observation and the back surface reflection observation in the graph of FIG. It is a measured value calculated based on the amount of movement (hereinafter sometimes simply referred to as “amount of movement”), and is, for example, a value obtained by image determination by AI. In the direct observation, while the light I1 is incident from the back surface 21b, the light I1 is directly focused on the crack 14k without being reflected by the surface 21a (in the above example, the crack 14k is observed from the back surface 21b side. 14k), and in the back surface reflection observation, while the light I1 is incident from the back surface 21b, the condensing point of the light I1 reflected by the surface 21a is aligned with the crack 14k (the above example Then, the focus F is adjusted from the back surface 21b side to the region on the opposite side of the surface 21a from the back surface 21b, and the virtual focus Fv symmetrical with the focus F with respect to the surface 21a is aligned with the crack 14k).

As shown in FIG. 14, in direct observation, in four cases C1 to C4 in which the formation position of the modified region 12 is different in the Z direction, all cracks occur between the lower end of the void upper region and the upper end of the void upper region. 14k is detected, and in the back surface reflection observation, the crack 14k is detected at approximately the same position as the lower end of the void upper region in case C1, and the crack 14k is detected between the lower end of the void upper region and the upper end of the void in cases C2 to C4. be done. The width of the modified region 12 in the Z-direction is the distance between the lower end of the void and the upper end of the void upper region. Thus, the crack 14k is more pinpoint detected in the Z direction than the modified region 12 itself.

Therefore, by obtaining the amount of movement of the internal image when the crack 14k appears in the Z direction, it is possible to obtain information regarding the position of the modified region 12 more accurately. The vertical axis in FIG. 14 indicates the distance from the back surface, and the back surface here is the back surface with respect to the incident surface of the light I1, which is the front surface 21a of the semiconductor substrate 21. FIG. 15 is a cross-sectional photograph plotted with the detection results for case C1.

In the present embodiment, based on the above findings, the crack 14k is detected by internal observation, and information on the position of the modified region 12 is acquired. Subsequently, an observation method according to this embodiment will be described. In this observation method, the crack 14k is the target crack to be detected.

FIG. 16 is a flowchart showing an example of an observation method according to this embodiment. As shown in FIG. 16, here, laser processing is performed in order to prepare an object on which a modified region is formed (step S11: preparation step). However, as one step of the observation method, the laser processing step is not essential. You can prepare things.

In this step S11, as shown in FIG. 17, an object including a semiconductor substrate 21 is prepared. The semiconductor substrate 21 includes a back surface (first surface) 21b and a surface (second surface) 21a opposite to the back surface 21b. A line 15 extending in the X direction along the back surface 21 b and the front surface 21 a is set on the semiconductor substrate 21 . 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 serves as the incident surface of the laser light L. As shown in FIG. In this state, the control unit 8 controls the driving unit 7 and/or the movement mechanism of the stage 2 so as to relatively move the semiconductor substrate 21 along the X direction while controlling the laser irradiation unit 3. is moved relative to the semiconductor substrate 21 along the line 15 .

At this time, the controller 8 causes the spatial light modulator 32 to display a pattern for splitting the laser light L into a plurality of (here, two) laser lights L1 and L2. As a result, condensing points C1 and C2 of the laser beams L1 and L2 are formed inside the semiconductor substrate 21 so as to be separated by a distance Dz in the Z direction and 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 lines 15 in the semiconductor substrate 21 . Therefore, here, the X direction is the processing progress direction along which the condensing points C1 and C2 progress.

Thus, here, the control unit 8 irradiates the semiconductor substrate 21 with the laser light L along the X direction, which is the extending direction of the line 15, under the control of the laser irradiation unit 3 (irradiation unit). A laser machining process is performed to form a plurality of modified regions 12 arranged along the X direction and cracks (cracks 14 and 14k) extending from the modified regions 12 in the semiconductor substrate 21 . Note that the functional element layer 22 formed on the surface 21a of the semiconductor substrate 21 is omitted in FIG. 17 and subsequent figures.

An internal observation is then performed. That is, in the subsequent step, the semiconductor substrate 21 is moved to the observation position (step S12). More specifically, the control unit 8 controls the drive unit 7 and/or the movement mechanism of the stage 2 to relatively move the semiconductor substrate 21 so that it is positioned immediately below the objective lens 43 of the imaging unit 4. . When the semiconductor substrate 21 on which the modified region 12 is formed is separately prepared, the semiconductor substrate 21 may be placed at the observation position by the user, for example.

Subsequently, as shown in FIG. 18, the semiconductor substrate 21 is imaged with light (transmitted light) I1 having transparency to the semiconductor substrate 21 (step S13: imaging step). In this step S13, under the control of the imaging unit 4 (imaging section), the light I1 is caused to enter the inside of the semiconductor substrate 21 from the rear surface 21b of the semiconductor substrate 21, while the cracks extending from the modified region 12 are detected in the Z direction and the X direction. Imaging processing is performed to image the target crack, which is the crack 14k extending along the direction intersecting the direction, with the light I1. The Y direction is an example of a direction that intersects the X direction, which is the processing progress direction, and the Z direction, which intersects the back surface 21b and the front surface 21a.

More specifically, in step S13, the control unit 8 controls the driving unit 7 (moving unit) and the imaging unit 4 to move the imaging unit 4 along the Z direction, thereby moving the semiconductor substrate 21. A plurality of internal image IDs are obtained by capturing an image of the semiconductor substrate 21 with the condensing points of the light I1 positioned at a plurality of positions inside. In this embodiment, the objective lens 43 is moved integrally with the imaging unit 4 . Therefore, moving the imaging unit 4 is also moving the objective lens 43 , and the amount of movement of the imaging unit 4 is the same as the amount of movement of the objective lens 43 .

At this time, the control unit 8 moves the imaging unit 4 in the Z direction under the control of the drive unit 7, and while moving the condensing point (focus F, virtual focus Fv) of the light I1 in the Z direction, An image of the semiconductor substrate 21 is taken. The range in which the focal point of the light I1 is moved may be the entire range of the thickness of the semiconductor substrate 21, but here, the laser beam L1 for forming the modified regions 12a and 12b during the laser processing in the step S11. , L2 can be defined as a partial range RA including the position in the Z direction where the condensing points C1 and C2 of the light beams C1 and C2 are combined. Note that the interval of movement of the imaging unit 4 in the Z direction when performing multiple imagings, that is, the imaging interval of the semiconductor substrate 21 is arbitrary, but from the viewpoint of more accurately detecting the crack 14k, it is more A detailed setting is desirable. The imaging interval is within 1 μm as an example, and is 0.2 μm here.

Furthermore, here, the control section 8 controls the imaging unit 4 and the driving unit 7 so that the direct observation and the back reflection observation of the semiconductor substrate 21 are performed. More specifically, the control unit 8 moves the imaging unit 4 along the Z direction while allowing the light I1 to enter the semiconductor substrate 21 from the back surface 21b, so that the light that has not been reflected by the front surface 21a is By imaging the semiconductor substrate 21 at a plurality of positions in the Z direction while moving the focal point (focus F) of I1 from the back surface 21b side to the front surface 21a side, a plurality of first internal images ID1 are obtained as internal image IDs. The first imaging process to be acquired is executed. This first imaging process is direct observation.

At the same time, the control unit 8 causes the light I1 to enter the object from the back surface 21b, and moves the imaging unit 4 along the Z direction, so that the condensing point (virtual focus Fv ) is moved from the front surface 21a side toward the back surface 21b side, the semiconductor substrate 21 is imaged at a plurality of positions, thereby executing a second imaging process of acquiring a plurality of second internal images ID2 as internal image IDs. Since this second imaging process is observation from the back side (here, referred to as the front surface 21a due to the configuration of the semiconductor substrate 21) with respect to the incident surface of the light I1, it is a rear reflection observation.

In the subsequent step, the imaging data relating to the internal image ID acquired by the imaging in step S13 is saved (step S14). As described above, in step S<b>13 , the control unit 8 performs imaging while moving the imaging unit 4 (that is, the focal point of the light I<b>1 ) along the Z direction under the control of the drive unit 7 . Therefore, the control section 8 can acquire the amount of movement of the imaging unit 4 when each internal image is captured. Here, information about the amount of movement can be associated with each internal image ID and stored as imaging data. Note that the imaging data can be stored in any storage device that can be accessed by the control unit 8 regardless of whether it is inside or outside the control unit 8 and the laser processing apparatus 1 .

As an example, the amount of movement of the imaging unit 4 (objective lens 43) is such that the light I1 moves from the position where the condensing point of the light I1 is aligned with the back surface 21b of the semiconductor substrate 21 to the desired position inside the semiconductor substrate 21. It can be the amount of movement of the imaging unit 4 when the imaging unit 4 is moved along the Z direction so as to align the condensing point of I1.

Subsequently, the control unit 8 inputs imaging data from a predetermined storage device (step S15). Then, the control unit 8 determines the state of formation of the crack 14k (step S16). Here, as an example, the control unit 8 automatically determines, by image recognition, an internal image ID in which the image of the crack 14k is relatively clear among the plurality of internal image IDs (performs AI determination). Here, an example of an algorithm for detecting cracks and modified regions by AI determination will be described.

20 and 21 are diagrams for explaining crack detection. FIG. 20 shows the internal observation result (internal image of the semiconductor substrate 21). The control unit 8 first detects a group of straight lines 140 in the internal image of the semiconductor substrate 21 as shown in FIG. 20(a). Algorithms such as Hough transform or LSD (Line Segment Detector) are used to detect the straight line group 140 . The Hough transform is a method of detecting all straight lines passing through a point on an image and weighting the straight lines passing through more feature points. LSD is a method of estimating a line segment area by calculating the gradient and angle of luminance values in an image, and detecting a straight line by approximating the area to a rectangle.

Subsequently, the control unit 8 detects the crack 14 from the straight line group 140 by calculating the degree of similarity between the straight line group 140 and the crack line as shown in FIG. 21 . As shown in the upper diagram of FIG. 21, the crack line has the characteristic that the front and back in the Y direction are very bright with respect to the luminance value on the line. For this reason, the control unit 8 compares, for example, the brightness values of all pixels of the detected straight line group 140 with those before and after in the Y direction, and sets the number of pixels whose difference is equal to or greater than the threshold both before and after as the similarity score. . Then, among the plurality of detected straight line groups 140, the straight line with the highest similarity score to the crack line is taken as the representative value in the image. The higher the representative value, the higher the possibility that the crack 14 exists. The control unit 8 compares the representative values of a plurality of images, and selects those with relatively high scores as crack image candidates.

FIGS. 22 to 24 are diagrams for explaining the detection of scars. FIG. 22 shows the internal observation result (internal image of the semiconductor substrate 21). The control unit 8 detects corners (concentration of edges) in the image of the inside of the semiconductor substrate 21 as shown in (a) of FIG. Then, the feature point 250 is detected. Methods for detecting feature points in this manner include Eigen, Harris, Fast, SIFT, SURF, STAR, MSER, ORB, AKAZE, and the like.

Here, as shown in FIG. 23, the grooves 280 have a strong feature as corners because shapes such as circles and rectangles are arranged at regular intervals. Therefore, it is possible to detect the dent 280 with high accuracy by totalizing the feature amounts of the feature points 250 in the image. As shown in FIG. 24, when comparing the total feature amount for each image taken while shifting in the depth direction, it is possible to confirm a change in the mountain that indicates the amount of crack rows for each modified layer. The control unit 8 estimates the peak of the change as the position of the scar 280 . By summarizing the feature amounts in this way, it becomes possible to estimate not only the dart position but also the pulse pitch.

The above description of the AI determination relates to the crack 14 and the scar 280 extending along the X direction, but for the crack 14k extending along the direction intersecting the Z direction and the X direction, the same algorithm is used to By comparing the representative values of a plurality of internal image IDs, an internal image ID with a relatively high score can be determined as an internal image ID with a relatively clear image of the crack 14k.

As an example, FIG. 19 shows a plurality of internal image IDs captured at different positions in the Z direction. In FIG. 19, centering on the imaging position of the internal image IDd shown in (d), (c) is the internal image IDc at the imaging position on the back surface 21b side by 1 μm, and (b) is the imaging position on the back surface 21b side by 3 μm. (a) is an internal image IDa at the imaging position on the back surface 21b side by 5 μm, (e) is an internal image IDe by 1 μm at the imaging position on the front surface 21a side, (f) is an internal image IDe by 3 μm on the surface 21a The internal image IDf at the imaging position on the side, and (g) is the internal image IDg at the imaging position on the surface 21a side by 5 μm. Note that 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. (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 amount of movement when the internal image IDd is captured.

In this way, the control unit 8 controls the crack 14k extending in the direction intersecting the Z direction and the X direction based on the plurality of internal image IDs and the amount of movement of the imaging unit 4 when each of the internal image IDs is captured. Calculation processing is executed to calculate the crack position, which is the position of a target crack in the Z direction. More specifically, in the calculation process, the control unit 8 determines the internal image ID in which the image of the crack 14k is clear among the plurality of internal image IDs, and calculates the movement amount when the determined internal image ID is captured. Calculate the crack position based on. The crack position can be calculated, for example, by multiplying the amount of movement 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 unit 8 performs the above calculation of the crack position of the crack 14k for both the first internal image ID1 acquired by direct observation and the second internal image ID2 acquired by back reflection observation. can be done. As a result, the control unit 8 determines the crack position of the crack 14k relatively located on the back surface 21b side according to the first internal image ID1 and the crack position relatively located on the front surface 21a side according to the second internal image ID2. 14k crack locations can be calculated.

That is, in this case, the control unit 8 determines the first internal image in which the crack 14k is clear among the plurality of first internal images ID1, and the imaging unit 4 when the determined first internal image is captured. A first calculation process for calculating a first crack position Z1 as a crack position based on the movement amount of , and a second internal image in which the crack 14k is clear among the plurality of second internal images ID2. and a second calculation process of calculating a second crack position Z2 as a crack position based on the amount of movement of the imaging unit 4 when the second internal image was captured (first crack position Z1 and FIG. 15 for an example of the second crack position Z2). The distance between the first crack position Z1 relatively on the back surface 21b side and the second crack position Z2 relatively on the front surface 21a side is the portion of the modified region 12 where the crack 14k is formed (crack initiation portion ) width.

Subsequently, in step S16, the control unit 8 estimates the position and the like of the modified region 12 based on the acquired crack positions and the like. That is, here, the control unit 8 controls the edge of the modified region 12 on the back surface 21b side (the upper end of the void upper region) based on the formation conditions of the modified region 12 (here, processing conditions in laser processing) and the crack position. ) in the Z direction, the position in the Z direction of the end (void lower end) of the modified region 12 on the surface 21a side, and the width of the modified region 12 in the Z direction (void upper region upper end and void lower end ) is performed.

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 first crack position Z1 of the crack 14k (lower crack) on the front surface 21a side based on the back reflection observation. The second crack position Z2 is calculated. Therefore, the control unit 8 can calculate the width of the crack starting portion inside the semiconductor substrate 21 as the interval between the first crack position Z1 of the upper crack and the second crack position Z2 of the lower crack.

Then, for example, the control unit 8 multiplies the calculated width of the crack initiation portion by a coefficient related to the processing conditions of the laser processing to obtain the width of the modified region 12 in the Z direction inside the semiconductor substrate 21. can be calculated. The coefficients here are 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 aberration correction amount, the pulse width, and the pulse energy. The coefficient here is around 3.0 as an example.

Thus, in the estimation process, the control unit 8 determines the modified region 12 based on the conditions for forming the modified region 12 (processing conditions for laser processing) and the distance between the first crack position Z1 and the second crack position Z2. can be estimated for the Z direction.

On the other hand, the control unit 8 subtracts the assumed modified region width, which is the entire width of the assumed modified region 12, from the first crack position Z1 of the upper crack, thereby obtaining the surface 21a side of the modified region 12. The position of the bottom edge can be calculated. The assumed modified region width is determined based on various conditions that affect the formation of the modified region 12, such as the wavelength of the laser beam L during laser processing, the aberration correction amount, the pulse width, and the pulse energy. An assumed modified region width is, for example, about 20 μm.

In addition, the control unit 8 calculates the position of the lower end of the surface 21a of the modified region 12 by subtracting the assumed void region width, which is the width of the assumed void region 12m, from the second crack position Z2 of the lower crack. can do. The assumed void region width is determined based on various conditions that affect the formation of the modified region 12, such as the wavelength of the laser beam L during laser processing, the aberration correction amount, the pulse width, and the pulse energy. An assumed void region width is, for example, about 10 μm.

Furthermore, the control unit 8 adds the assumed void upper region width, which is the width of the assumed void upper region 12n, to the second crack position Z2 of the lower crack, thereby obtaining the The position of the top edge can be calculated. The estimated void upper region width is determined based on various conditions that affect formation of the modified region 12, such as the wavelength of the laser beam L during laser processing, the aberration correction amount, the pulse width, and the pulse energy. An assumed void upper region width is, for example, about 10 μm.

As described above, the control unit 8 estimates and acquires various types of information regarding the position of the modified region 12 in step S16. In the subsequent step, the control unit 8 outputs the information related to the determination result of step S16 to an arbitrary storage device (step S17), and stores the information in the storage device (step S18). After that, if necessary, various information is displayed on the display 150 in a state in which input from the user can be accepted (step S19), and the process ends. The information to be displayed on the display 150 includes, for example, the first crack position Z1, the second crack position Z2, the starting width, the position of the edge of the modified region 12, and the width of the modified region 12 in the Z direction. is. In this way, in step S19, the control unit 8 controls the display 150 to perform display processing for displaying the information related to the crack position on the display 150. FIG.

By the above, the observation method by the laser processing apparatus 1 is completed. In this embodiment, the observation method is performed by the imaging unit 4, the drive unit 7, and the controller 8 of the laser processing apparatus 1. FIG. In other words, in the laser processing apparatus 1, the imaging unit 4 for imaging the semiconductor substrate 21 with the light I1 that is transparent to the semiconductor substrate 21 and the imaging unit 4 for moving the imaging unit 4 relative to the semiconductor substrate 21. and a controller 8 for controlling at least the imaging unit 4 and the driving unit 7 constitute an observation device 1A (see FIG. 1).

As described above, the observation method according to the present embodiment and the semiconductor substrate 21 to be observed by the observation apparatus 1A that implements the observation method include the modified regions 12 and the modified regions 12 arranged along the X direction. Cracks 14, 14k are formed extending from the textured region 12. FIG. Then, an image of the crack 14k extending in the direction intersecting the Z direction and the X direction is captured in the semiconductor substrate 21 using the light I1 that is transmitted through the semiconductor substrate 21 . The crack 14k intersecting the Z direction and the X direction is imaged (detected) more pinpointally than the modified region 12 itself in the Z direction. Therefore, for example, if information such as the amount of movement of the imaging unit 4 when the crack 14k is imaged is obtained, information regarding the position of the modified region 12 can be obtained more accurately based on the amount of movement.

The observation device 1A according to this embodiment also includes a drive unit 7 for moving the focal point of the light I1 relative to the semiconductor substrate 21. As shown in FIG. In the imaging process, the control unit 8 moves the imaging unit 4 along the Z direction under the control of the imaging unit 4 and the drive unit 7, so that the condensing points of the light I1 are located at a plurality of positions inside the semiconductor substrate 21. By positioning the semiconductor substrate 21 and imaging the semiconductor substrate 21, a plurality of internal image IDs are acquired. Then, after the imaging process, the control unit 8 determines the Z direction of the crack 14k based on the plurality of internal image IDs and the amount of movement of the imaging unit 4 in the Z direction when each of the internal image IDs is captured. Calculation processing for calculating crack positions (first crack position Z1 and second crack position Z2) is executed. In this way, it is possible to more accurately acquire information about the position of the modified region 12 based on the amount of movement of the imaging unit 4 when the crack 14k is imaged.

In addition, in the observation device 1A according to the present embodiment, in the calculation process, the control unit 8 determines an internal image with a clear image of the crack 14k among the plurality of internal image IDs, and captures the determined internal image. The crack position of the crack 14k is calculated based on the amount of movement of the imaging unit 4 at that time. Thus, the position of the crack 14k can be calculated more accurately by the determination of the internal image in which the crack 14k is clear by the control unit 8. FIG.

Further, in the observation device 1A according to the present embodiment, after the calculation process, the control unit 8 calculates the edge of the modified region 12 on the back surface 21b side based on the formation conditions of the modified region 12 and the crack position of the crack 14k. an estimation process for estimating at least one of the position of the portion in the Z direction, the position in the Z direction of the end of the modified region 12 on the side of the surface 21a, and the width of the modified region 12 in the Z direction. . When the shape and size of the modified region 12 change according to the formation conditions of the modified region, such as laser processing conditions (for example, laser beam wavelength, pulse width, pulse energy, aberration correction amount, etc.) There is Therefore, by using the forming conditions of the modified region 12 such as the processing conditions of the laser processing and the positions of the cracks 14k in this way, it is possible to more accurately estimate information about the positions of the modified regions 12 .

Further, in the observation apparatus according to the present embodiment liquid, in the imaging process, the control unit 8 causes the light I1 to enter the semiconductor substrate 21 from the rear surface 21b, and moves the imaging unit 4 to reflect the light I1 on the front surface 21a. The semiconductor substrate 21 is imaged at a plurality of positions while moving the focal point of the light I1 from the back surface 21b side toward the front surface 21a side, thereby obtaining a plurality of first internal images ID1 as internal image IDs. By moving the imaging unit 4 while performing the imaging process and causing the light I1 to enter the semiconductor substrate 21 from the back surface 21b, the focal point of the light I1 reflected by the surface 21a is moved from the surface 21a side toward the back surface 21b side. and a second imaging process of acquiring a plurality of second internal images ID2 as internal image IDs by imaging the semiconductor substrate 21 at a plurality of positions while moving.

In this way, imaging (direct observation) of the semiconductor substrate 21 using the light I1 which is incident from the back surface 21b of the semiconductor substrate 21 and has not been reflected by the front surface 21a, and the light I1 which is incident from the back surface 21b of the semiconductor substrate 21 and is reflected from the surface 21a. If an internal image is obtained by imaging the semiconductor substrate 21 using the light I1 reflected by (back reflection observation) and by each of the above, the internal image is obtained based on the amount of movement of the imaging unit 4 when the internal image is captured. Information on the position of the modified region 12 can be obtained more accurately by using the crack position.

In addition, in the observation device 1A according to the present embodiment, in the calculation process, the control unit 8 determines the first internal image in which the crack 14k is clear among the plurality of first internal images ID1, and determines the determined first internal image ID1. A first calculation process for calculating a first crack position Z1 as a crack position based on the amount of movement of the imaging unit 4 when an image is captured; a second calculation process of determining the internal image and calculating the second crack position Z2 as the crack position based on the amount of movement of the imaging unit 4 when the determined second internal image is captured; . In the estimation process, the control unit 8 estimates the width of the modified region 12 in the Z direction based on the conditions for forming the modified region 12 and the distance between the first crack position Z1 and the second crack position Z2. be able to. As described above, in this case, based on the distance between the first crack position Z1 obtained based on direct observation and the second crack position Z2 obtained based on back surface reflection observation, more accurately, Information about the width of the modified region 12 can be obtained.

Furthermore, the observation device 1A according to this embodiment further includes a display 150 for displaying information. Then, after the calculation process, the control unit 8 may perform a display process for displaying information related to the crack position on the display 150 by controlling the display 150 . In this case, the display 150 enables the user to grasp information about the crack position. The information about the crack position is at least one of the crack position itself and various information included in the information about the position of the modified region 12 that can be estimated based on the crack position.

The above embodiment describes one aspect of the present invention. Therefore, the present invention is not limited to the above embodiments, and can be arbitrarily modified.

For example, in the above embodiment, the drive unit 7 that moves the imaging unit 4 together with the objective lens 43 is illustrated as means for moving the objective lens 43 relative to the semiconductor substrate 21 along the Z direction. However, for example, only the objective lens 43 may be moved along the Z direction by an actuator.

Further, in the above-described embodiment, an example in which the control unit 8 automatically determines the image in step S16 has been described. good too. In this case, the control unit 8, for example, causes the display 150 to display a plurality of internal image IDs, and displays information prompting determination (selection) of one internal image with a clear image of the crack 14k from the plurality of internal image IDs. Display at 150. Then, the control unit 8 can receive input of the determination result via the display 150 and calculate the crack position of the crack 14k based on the amount of movement of the internal image ID corresponding to the determination result. In this case, the display 150 is both a display unit for displaying information and an input reception unit for receiving input. In this case, the processing load of the control unit 8 for image recognition and the like is reduced.

Further, in the above-described embodiment, in step S13, both direct observation and back surface reflection observation are performed for observation of one modified region 12, and the first internal image ID1 and the second internal image ID as the internal image ID. Got ID2. However, in step S13, only one of the direct observation and the rear reflection observation may be performed. In this case, since one of the first internal image ID1 and the second internal image ID2 is obtained, the position and width of the end portion of the modified region 12 may be estimated based on the one.

DESCRIPTION OF SYMBOLS 1A... Observation apparatus, 4... Imaging unit (imaging part), 7... Driving unit (moving part), 8... Control part, 12... Modified area, 14... Crack, 14k... Crack (target crack), 21... Semiconductor substrate (Object) 21a front surface (second surface) 21b back surface (first surface) I1 light (transmitted light) ID internal image ID1 first internal image ID2 second internal image Z1... 1st crack position, Z2... 2nd crack position.

Claims (8)

an imaging unit for capturing an image of an object with transmitted light that is permeable to the object;
a control unit for controlling at least the imaging unit;
with
the object includes a first surface and a second surface opposite the first surface;
The object has modified regions arranged in the X direction along the first surface and the second surface, and cracks extending from the modified regions are formed,
The control unit causes the transmitted light to enter the object from the first surface under the control of the imaging unit, and transmits light in a Z direction intersecting the first surface and the second surface of the crack. and performing an imaging process of imaging the target crack, which is the crack extending in the direction intersecting the X direction, with the transmitted light,
Observation device. a moving unit for relatively moving a condenser lens for condensing the transmitted light onto the object with respect to the object;
In the imaging process, the control unit relatively moves the condenser lens along the Z direction under the control of the imaging unit and the moving unit, thereby moving the transmission light to a plurality of positions inside the object. obtaining a plurality of internal images by imaging the object by positioning a light converging point;
After the imaging process, the control unit determines the Z direction of the target crack 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 captured. Perform a calculation process to calculate the crack position, which is the position with respect to the direction,
The observation device according to claim 1. In the calculation process, the control unit determines the internal image in which the image of the target crack is clear among the plurality of internal images, and determines the movement of the condenser lens when the determined internal image is captured. calculating the crack location based on the amount;
The observation device according to claim 2. After the calculation process, the control unit determines the position in the Z direction of the end of the modified region on the first surface side based on the conditions for forming the modified region and the crack position. performing an estimation process of estimating at least one of a position in the Z direction of the end of the modified region on the second surface side and a width of the modified region in the Z direction;
The observation device according to claim 3. In the imaging process, the control unit
By relatively moving the condenser lens along the Z direction while allowing the transmitted light to enter the object from the first surface, the transmitted light that has not been reflected by the second surface is collected. A first imaging process of acquiring a plurality of first internal images as the internal images by imaging the object at a plurality of positions while moving the light spot from the first surface side toward the second surface side. When,
The condensing point of the transmitted light reflected by the second surface is shifted by relatively moving the condensing lens along the Z direction while allowing the transmitted light to enter the object from the first surface. a second imaging process of acquiring a plurality of second internal images as the internal images by imaging the object at a plurality of positions while moving from the second surface side toward the first surface side;
run the
An observation device according to any one of claims 2 to 4. In the calculation process, the control unit
The first internal image in which the target crack is clear among the plurality of first internal images is determined, and based on the movement amount of the condenser lens when the determined first internal image is captured, the A first calculation process for calculating a first crack position as a crack position;
The second internal image in which the target crack is clear among the plurality of second internal images is determined, and based on the movement amount of the condenser lens when the determined second internal image is captured, the A second calculation process for calculating a second crack position as a crack position;
and run
The control unit estimates the width of the modified region in the Z direction based on conditions for forming the modified region and the distance between the first crack position and the second crack position.
The observation device according to claim 5. further comprising a display for displaying information,
After the calculation process, the control unit controls the display unit to perform display processing for displaying information related to the crack position on the display unit.
An observation device according to any one of claims 2 to 6. A modified region including a first surface and a second surface opposite to the first surface and arranged in the X direction along the first surface and the second surface and a crack extending from the modified area are formed. a preparation step of preparing the target object;
After the preparation step, the Z direction and the X direction that intersect the first surface and the second surface of the crack while allowing transmitted light that passes through the object to enter the object from the first surface. An imaging step of imaging the target crack, which is the crack extending in the direction intersecting with the transmitted light,
Observation method comprising

Images