Observation device and observation method

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

[Technical field]

[0001] The present invention relates to an observation device and an observation method. [Background technology]

[0002] A laser processing device is known that cuts a wafer, which includes a semiconductor substrate and a functional element layer formed on the surface of the semiconductor substrate, along each of a plurality of lines by irradiating the wafer with laser light from the back side of the semiconductor substrate to form a plurality of rows of modified regions inside the semiconductor substrate along each of the plurality of lines. The laser processing device described in Patent Document 1 is equipped with an infrared camera, and makes it possible to observe the modified regions formed inside the semiconductor substrate and processing damage formed in the functional element layer from the back side of the semiconductor substrate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-64746 A Summary of the Invention [Problem to be solved by the invention]

[0004] As described above, when a modified region formed inside a 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 and lower end positions and width of the modified region in the thickness direction of the semiconductor substrate.

[0005] An object of the present invention is to provide an observation device and an observation method that are capable of acquiring information relating to the position of a modified region more accurately. [Means for solving the problem]

[0006] The present inventor has conducted intensive research to solve the above problems, and has come to the following findings. That is, when a modified region is formed inside an object such as the above semiconductor substrate by, for example, laser processing, cracks extending in various directions from the modified region may also be formed. Among the cracks, cracks intersecting the Z direction intersecting the laser light incident surface of the object and the X direction, which is the proceeding direction of the laser processing, are pinpoint detected by the transmitted light that passes through the object, compared with the modified region. Therefore, if information on the position where the crack intersecting the X direction and the Z direction is imaged can be obtained, information on the position of the modified region can be obtained more accurately based on the position. The present invention has been made based on such findings.

[0007] In other words, the observation device of the present invention comprises an imaging unit for imaging an object using transmitted light that is transparent to the object, and a control unit for controlling at least the imaging unit, wherein the object includes a first surface and a second surface opposite the first surface, and the object has modified areas arranged in the X direction along the first surface and the second surface and cracks extending from the modified areas, and the control unit controls the imaging unit to cause the transmitted light to enter the interior of the object from the first surface, while using the transmitted light to image a target crack, which is a crack among the cracks that extends in a direction that intersects the Z direction and the X direction that intersects the first surface and the second surface.

[0008] In addition, the observation method of the present invention includes a preparation step of preparing an object including a first surface and a second surface opposite the first surface, and having modified regions arranged in the X direction along the first surface and the second surface and cracks extending from the modified regions, and an imaging step of, after the preparation step, allowing transmitted light that passes through the object to be incident on the object from the first surface, and imaging a target crack, which is a crack that extends in a direction that intersects the Z direction and the X direction that intersects the first surface and the second surface, using the transmitted light.

[0009] In the target object of these devices and methods, modified regions arranged along the X direction and cracks extending from the modified regions are formed. Then, for such an object, target cracks intersecting in the X direction and Z direction are imaged using transmitted light passing through the object. As found above, target cracks intersecting in the X direction and Z direction from the modified region are imaged (detected) with pinpoint accuracy in the Z direction compared to the modified region. Therefore, by obtaining information such as the amount of movement of the focusing lens when the target crack is imaged, it is possible to obtain information regarding the position of the modified region more accurately based on the amount of movement.

[0010] The observation device according to the present invention includes a moving unit for moving a condenser lens for focusing transmitted light on an object relative to the object, and in the imaging process, the control unit controls the imaging unit and the moving unit to relatively move the condenser lens along the Z direction to position the focusing point at multiple positions inside the object and capture multiple internal images by imaging the object, and the control unit may execute a calculation process after the imaging process to calculate a crack position, which is the position of the target crack in the Z direction, based on the multiple internal images and the amount of movement of the condenser lens in the Z direction when each of the internal images is captured. In this way, by calculating the crack position based on the amount of movement of the condenser lens when the target crack is imaged, it is possible to more accurately obtain information regarding the position of the modified region.

[0011] In the observation device according to the present invention, in the calculation process, the control unit may determine an internal image in which the image of the target crack is clear among the multiple internal images, and calculate the crack position based on the movement amount of the focusing lens when the determined internal image is captured. In this way, the crack position can be calculated more accurately by the control unit determining an internal image in which the target crack is clear.

[0012] In the observation device according to the present invention, the control unit may execute an estimation process after the calculation process to estimate at least one of the position of the end of the modified region on the first surface side in the Z 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 based on the formation conditions of the modified region and the crack position. The shape and size of the modified region may change depending on the formation conditions of the modified region, such as the processing conditions of the laser processing (e.g., the wavelength of the laser light, the pulse width, the pulse energy, and the amount of aberration correction, etc.). Therefore, by using the formation conditions of the modified region and the crack position in this way, information regarding the position of the modified region can be more accurately estimated.

[0013] In the observation device of the present invention, in the imaging process, the control unit may execute a first imaging process in which transmitted light is incident on the object from the first surface while moving the focusing lens relatively along the Z direction to image the object at multiple positions while moving the focusing point of the transmitted light that has not been reflected on the second surface from the first surface side toward the second surface side, thereby acquiring multiple first internal images as internal images, and a second imaging process in which transmitted light is incident on the object from the first surface while moving the focusing lens relatively along the Z direction to image the object at multiple positions while moving the focusing point of the transmitted light reflected on the second surface from the second surface side toward the first surface side, thereby acquiring multiple second internal images as internal images. In this way, by obtaining internal images by imaging the object using transmitted light that is incident on the first surface of the object and has not been reflected on the second surface (direct observation), and by imaging the object using transmitted light that is incident on the first surface of the object and has been reflected on the second surface (rear-surface reflection observation), it is possible to obtain more accurate information regarding the position of the modified area by using the crack position obtained based on the amount of movement of the focusing lens when the internal image is obtained.

[0014] In the observation device according to the present invention, in the calculation process, the control unit executes a first calculation process in which a first internal image in which the target crack is clear among the multiple first internal images is determined, and calculates a first crack position as a crack position based on the movement amount of the condenser lens when the determined first internal image is captured, and a second calculation process in which a second internal image in which the target crack is clear among the multiple second internal images is determined, and calculates a second crack position as a crack position based on the movement amount of the condenser lens when the determined second internal image is captured, and in the estimation process, the control unit may estimate the width of the modified region in the Z direction based on the formation condition of the modified region and the interval between the first crack position and the second crack position. As described above, in this case, information about the width of the modified region can be obtained more accurately based on the interval between the crack position acquired based on direct observation and the crack position acquired based on back surface reflection observation.

[0015] The observation device according to the present invention may further include a display unit for displaying information, and the control unit may execute a display process for controlling the display unit to display information related to the crack position on the display unit after the calculation process. In this case, the user can grasp the information related to the crack position via the display unit. Note that the information related to the crack position is at least one of various pieces of information included in the information related to the crack position itself and the position of the modified region that can be estimated based on the crack position. Effect of the Invention

[0016] According to the present invention, it is possible to provide an observation device and an observation method that are capable of acquiring information relating to the position of a modified region more accurately. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a configuration diagram of a laser processing apparatus according to one embodiment. [Diagram 2] FIG. 2 is a plan view of a wafer of one implementation. [Diagram 3] 3 is a cross-sectional view of a portion of the wafer shown in FIG. 2. [Figure 4] FIG. 2 is a configuration diagram of a laser irradiation unit shown in FIG. [Diagram 5] FIG. 2 is a configuration diagram of an inspection imaging unit shown in FIG. [Figure 6] FIG. 2 is a configuration diagram of an alignment correction imaging unit shown in FIG. [Figure 7] 6A to 6C are cross-sectional views of a wafer for explaining the imaging principle by the inspection imaging unit shown in FIG. 5, and images at various locations by the inspection imaging unit. [Figure 8] 6A to 6C are cross-sectional views of a wafer for explaining the imaging principle by the inspection imaging unit shown in FIG. 5, and images at various locations by the inspection imaging unit. [Figure 9] 1 is a SEM image of modified regions and cracks formed within a semiconductor substrate. [Figure 10] 1 is a SEM image of modified regions and cracks formed within a semiconductor substrate. [Figure 11] 6 is a schematic diagram for explaining the imaging principle of the inspection imaging unit shown in FIG. 5. [Figure 12] 6 is a schematic diagram for explaining the imaging principle of the inspection imaging unit shown in FIG. 5. [Figure 13] FIG. 1 is a diagram showing an object on which a modified region is formed. [Figure 14] 1 is a graph of the position of the modified region and the crack in the Z direction. [Figure 15] The detection results are plotted on a cross-sectional photograph of the target object. [Figure 16] 4 is a flowchart showing an example of an observation method according to the present embodiment. [Figure 17] FIG. 18 is a diagram showing one step of the observation method shown in FIG. [Figure 18] FIG. 18 is a diagram showing one step of the observation method shown in FIG. [Figure 19] These are multiple internal images taken at different positions in the Z direction. [Figure 20] FIG. 13 is a diagram illustrating crack detection. [Figure 21] FIG. 13 is a diagram illustrating crack detection. [Figure 22] FIG. 13 is a diagram illustrating a scratch detection. [Figure 23] FIG. 13 is a diagram illustrating a scratch detection. [Figure 24] FIG. 13 is a diagram illustrating a scratch detection. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] An embodiment will be described in detail below with reference to the drawings. In the description of each drawing, the same or corresponding parts are given the same reference numerals, and duplicated descriptions may be omitted. In addition, each drawing may show an orthogonal coordinate system defined by an X-axis, a Y-axis, and a Z-axis. As an example, the X-direction and the Y-direction are a first horizontal direction and a second horizontal direction that intersect (are perpendicular to) each other, and the Z-direction is a vertical direction that intersects (are perpendicular to) the X-direction and the Y-direction.

[0019] 1, the laser processing apparatus 1 includes a stage 2, a laser irradiation unit 3 (irradiation section), a plurality of imaging units 4, 5, and 6, a drive unit 7, a control section 8, and a display 150 (display section). The laser processing apparatus 1 is an apparatus that forms a modified region 12 in an object 11 by irradiating the object 11 with laser light L.

[0020] The stage 2 supports the object 11, for example, by adsorbing a film attached to the object 11. The stage 2 is movable along both the X direction and the Y direction, and is rotatable about an axis parallel to the Z direction.

[0021] The laser irradiation unit 3 focuses laser light L, which is transparent to the object 11, and irradiates the object 11. When the laser light L is focused inside the object 11 supported by the stage 2, the laser light L is particularly absorbed in a portion corresponding to a focusing point C of the laser light L, and a modified region 12 is formed inside the object 11.

[0022] The modified region 12 is a region that differs from the surrounding non-modified region in terms of density, refractive index, mechanical strength, and other physical properties. Examples of the modified region 12 include a melting treatment region, a crack region, a dielectric breakdown region, and a refractive index change region. The modified region 12 has a property that cracks tend to extend from the modified region 12 to the incident side of the laser light L and to the opposite side. Such a property of the modified region 12 is utilized for cutting the target object 11.

[0023] 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, multiple modified spots 12s are formed in a row along the X direction. One modified spot 12s is formed by irradiating one pulse of laser light L. One row of modified regions 12 is a collection of multiple modified spots 12s lined up in a row. Adjacent modified spots 12s 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.

[0024] The imaging unit 4 captures an image of the modified region 12 formed in the object 11 and the tip of the crack extending from the modified region 12 .

[0025] Under the control of the control unit 8, the imaging units 5 and 6 capture an image of the object 11 supported on the stage 2 by light transmitted through the object 11. The images obtained by the imaging units 5 and 6 are used, for example, to align the irradiation position of the laser light L.

[0026] The drive unit 7 supports the laser irradiation unit 3 and the multiple imaging units 4, 5, and 6. The drive unit 7 moves the laser irradiation unit 3 and the multiple imaging units 4, 5, and 6 along the Z direction.

[0027] The control unit 8 controls the operations of the stage 2, the laser irradiation unit 3, the multiple imaging units 4, 5, and 6, and the drive unit 7. The control unit 8 is configured as a computer device including a processor, a memory, a storage, a communication device, etc. In the control unit 8, the processor executes software (programs) loaded into the memory, etc., and controls the reading and writing of data in the memory and storage, as well as communication by the communication device.

[0028] The display 150 functions as an input unit that accepts information input from the user, and as a display unit that displays information to the user. [Object composition] The object 11 in this embodiment is a wafer 20, as shown in FIG. 2 and FIG. 3. The wafer 20 includes a semiconductor substrate 21 and a functional device layer 22. In this embodiment, the wafer 20 is described as having the functional device layer 22, but the wafer 20 may or may not have the functional device 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 device layer 22 is formed on the front surface 21a of the semiconductor substrate 21. The functional device layer 22 includes a plurality of functional devices 22a arranged two-dimensionally along the front surface 21a. The functional device 22a is, for example, a light receiving device such as a photodiode, a light emitting device such as a laser diode, a circuit device such as a memory, or the like. The functional device 22a may be configured three-dimensionally by stacking a plurality of layers. Although the semiconductor substrate 21 has a notch 21c indicating the crystal orientation, an orientation flat may be provided instead of the notch 21c.

[0029] The wafer 20 is cut into functional elements 22a along each of the lines 15. The lines 15 pass between the functional elements 22a when viewed in the thickness direction of the wafer 20. More specifically, the lines 15 pass through the center (the center in the width direction) of the street region 23 when viewed in the thickness direction of the wafer 20. The street region 23 extends in the functional element layer 22 so as to pass between adjacent functional elements 22a. In this embodiment, the functional elements 22a are arranged in a matrix along the surface 21a, and the lines 15 are set in a lattice pattern. The lines 15 are virtual lines, but may be lines that are actually drawn.

[0030] [Laser irradiation unit configuration] 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, for example, by 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). The condenser lens 33 condenses the laser light L modulated by the spatial light modulator 32. The condenser lens 33 may be a correction ring lens.

[0031] In this embodiment, the laser irradiation unit 3 irradiates the wafer 20 with laser light L from the back surface 21b side of the semiconductor substrate 21 along each of the multiple lines 15, thereby forming two rows of modified regions 12a, 12b inside the semiconductor substrate 21 along each of the multiple lines 15. The modified region 12a is the modified region closest to the front surface 21a among the two rows of modified regions 12a, 12b. The modified region 12b is the modified region closest to the modified region 12a among the two rows of modified regions 12a, 12b, and is the modified region closest to the back surface 21b.

[0032] The two rows of modified regions 12a, 12b are adjacent to each other in the thickness direction (Z direction) of the wafer 20. The two rows of modified regions 12a, 12b are formed by moving the two focusing points C1, C2 along the line 15 relative to the semiconductor substrate 21. The laser light L is modulated by the spatial light modulator 32, for example, so that the focusing point C2 is located on the rear side of the focusing point C1 in the traveling direction and on the incident side of the laser light L. The modified regions may be formed by a single focus or multiple focuses, and may be formed by one pass or multiple passes.

[0033] The laser irradiation unit 3 irradiates the wafer 20 with laser light L from the back surface 21b side of the semiconductor substrate 21 along each of the multiple lines 15. As an example, a single crystal silicon <100> The two focal points C1 and C2 are aligned at positions 54 μm and 128 μm from the front surface 21a of the semiconductor substrate 21, respectively, and the laser light L is irradiated from the back surface 21b of the semiconductor substrate 21 along each of the multiple lines 15 to the wafer 20. At this time, for example, when the condition is that the cracks 14 across the two rows of modified regions 12a and 12b reach the front surface 21a of the semiconductor substrate 21, the wavelength of the laser light L is 1099 nm, the pulse width is 700 ns, and the repetition frequency is 120 kHz. The output of the laser light L at the focal point C1 is 2.7 W, the output of the laser light L at the focal point C2 is 2.7 W, and the relative moving speed of the two focal points C1 and C2 with respect to the semiconductor substrate 21 is 800 mm / sec. In addition, for example, when the number of processing passes is 5, ZH80 (position 328 μm from the surface 21a), ZH69 (position 283 μm from the surface 21a), ZH57 (position 234 μm from the surface 21a), ZH26 (position 107 μm from the surface 21a), and ZH12 (position 49.2 μm from the surface 21a) may be set as processing positions for the above-mentioned wafer 20. 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.

[0034] The formation of the two rows of modified regions 12a, 12b and the cracks 14 is performed in the following case: That is, in a later process, for example, by grinding the back surface 21b of the semiconductor substrate 21 to thin the semiconductor substrate 21 and expose the cracks 14 on the back surface 21b, and then cutting the wafer 20 into a plurality of semiconductor devices along each of the plurality of lines 15.

[0035] [Configuration of the inspection imaging unit] As shown in FIG. 5, the imaging unit 4 (imaging section) has a light source 41, a mirror 42, an objective lens (condenser lens) 43, and a light detection section 44. The imaging unit 4 captures an image of 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 onto the wafer 20 from the back surface 21b side of the semiconductor substrate 21. 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.

[0036] The objective lens 43 is for collecting light I1 (transmitted light) having transparency to the semiconductor substrate 21 toward the semiconductor substrate 21. The objective lens 43 passes the light I1 reflected by the surface 21a of the semiconductor substrate 21. In other words, the objective lens 43 passes the light I1 propagated through the semiconductor substrate 21. 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 aberrations occurring in the light I1 in the semiconductor substrate 21, for example, by adjusting the distances between the multiple lenses constituting the objective lens 43. Note that the means for correcting the aberrations is not limited to the correction ring 43a, and may be other correction means such as a spatial light modulator. The light detection unit 44 detects the light I1 transmitted through the objective lens 43 and the mirror 42. The light detection unit 44 is, for example, configured by an InGaAs camera, and detects the light I1 in the near-infrared region. The means for detecting (capturing) the light I1 in the near-infrared region is not limited to an InGaAs camera, and may be any other imaging means that captures images in a transmission type, such as a transmission confocal microscope.

[0037] The imaging unit 4 can capture images of each of the two rows of modified regions 12a, 12b and the tips of each of the multiple cracks 14a, 14b, 14c, and 14d (details will be described later). The crack 14a is a crack that extends from the modified region 12a to the front surface 21a. The crack 14b is a crack that extends from the modified region 12a to the back surface 21b. The crack 14c is a crack that extends from the modified region 12b to the front surface 21a. The crack 14d is a crack that extends from the modified region 12b to the back surface 21b.

[0038] [Configuration of the imaging unit for alignment correction] 6, the imaging unit 5 has a light source 51, a mirror 52, a lens 53, and a light detection unit 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 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 and passes through the lens 53, and is irradiated onto the wafer 20 from the back surface 21b side of the semiconductor substrate 21.

[0039] The lens 53 passes the light I2 reflected by the surface 21a of the semiconductor substrate 21. That is, the lens 53 passes the light I2 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 that has passed through the lens 53 and the mirror 52. The light detection unit 54 is configured by, for example, an InGaAs camera, and detects the light I2 in the near-infrared region.

[0040] The imaging unit 5, under the control of the control unit 8, irradiates the wafer 20 with light I2 from the back surface 21b side and detects the light I2 returning from the front surface 21a (functional element layer 22), thereby capturing an image of the functional element layer 22. Similarly, under the control of the control unit 8, the imaging unit 5, under the control of the control unit 8, 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 and 12b are formed in the semiconductor substrate 21, thereby acquiring an image of the region including the modified regions 12a and 12b. These images are used for alignment of the irradiation position of the laser light L. The imaging unit 6 has a similar configuration to the imaging unit 5, except that the lens 53 has a lower magnification (for example, 6x in the imaging unit 5 and 1.5x in the imaging unit 6), and is used for alignment in the same manner as the imaging unit 5.

[0041] [Principle of imaging by inspection imaging unit] Using the imaging unit 4 shown in FIG. 5, the focal point F (the focal point of the objective lens 43) is moved from the back surface 21b side to the front surface 21a side with respect to the semiconductor substrate 21 in which the cracks 14 extending across the two rows of modified regions 12a, 12b reach the front surface 21a as shown in FIG. 7. In this case, when the focal point F is adjusted from the back surface 21b side to the tip 14e of the crack 14 extending from the modified region 12b to the back surface 21b side, the tip 14e can be confirmed (the image on the right side in FIG. 7). However, even if the focal point F is adjusted from the back surface 21b side to the cracks 14 themselves and the tip 14e of the cracks 14 reaching the front surface 21a, they cannot be confirmed (the image on the left side in FIG. 7). It should be noted that when the focal point F is adjusted from the back surface 21b side to the front surface 21a of the semiconductor substrate 21, the functional element layer 22 can be confirmed.

[0042] 5, the focal point F is moved from the back surface 21b side to the front surface 21a side for the semiconductor substrate 21 in which the cracks 14 extending across the two rows of modified regions 12a, 12b have not yet reached the front surface 21a, as shown in FIG. 8. In this case, even if the focal point F is aligned from the back surface 21b side to the tip 14e of the crack 14 extending from the modified region 12a to the front surface 21a side, the tip 14e cannot be confirmed (the image on the left side in FIG. 8). However, when the focal point F is aligned from the back surface 21b side to the region on the opposite side of the back surface 21b with respect to the front surface 21a (i.e., the region on the functional element layer 22 side with respect to the front surface 21a) and a virtual focal point Fv symmetrical to the focal point F with respect to the front surface 21a is positioned at the tip 14e, the tip 14e can be confirmed (the image on the right side in FIG. 8). The virtual focal point Fv is a point symmetrical with respect to the front surface 21a to the focal point F taking into account the refractive index of the semiconductor substrate 21.

[0043] As described above, the reason why the crack 14 itself cannot be confirmed is assumed to be because the width of the crack 14 is smaller than the wavelength of the light I1, which is the illumination light. Figures 9 and 10 are SEM (Scanning Electron Microscope) images of the modified region 12 and the crack 14 formed inside the semiconductor substrate 21, which is a silicon substrate. (b) of Figure 9 is an enlarged image of the region A1 shown in (a) of Figure 9, (a) of Figure 10 is an enlarged image of the region A2 shown in (b) of Figure 9, and (b) of Figure 10 is an enlarged image of the region A3 shown in (a) of Figure 10. Thus, the width of the crack 14 is about 120 nm, which is smaller than the wavelength (e.g., 1.1 to 1.2 μm) of the light I1 in the near-infrared region.

[0044] Based on the above, the imaging principle is assumed as follows. As shown in FIG. 11(a), when the focal point F is located in air, the light I1 does not return, and a dark image is obtained (the image on the right side of FIG. 11(a)). As shown in FIG. 11(b), when the focal point F is located inside the semiconductor substrate 21, the light I1 reflected by the front surface 21a returns, and a whitish image is obtained (the image on the right side of FIG. 11(b)). As shown in FIG. 11(c), when the focal point F is aligned with the modified region 12 from the rear surface 21b side, the modified region 12 absorbs, scatters, or the like a part of the light I1 reflected by the front surface 21a and returned, and an image is obtained in which the modified region 12 appears dark against a whitish background (the image on the right side of FIG. 11(c)).

[0045] As shown in (a) and (b) of FIG. 12, when the focal point F is focused on the tip 14e of the crack 14 from the back surface 21b side, for example, due to optical singularities (stress concentration, distortion, discontinuity of atomic density, etc.) occurring near the tip 14e, light confinement occurring near the tip 14e, etc., scattering, reflection, interference, absorption, etc. occur for a part of the light I1 reflected by the surface 21a and returned, so an image is obtained in which the tip 14e appears dark on a whitish background (the right image in (a) and (b) of FIG. 12). As shown in (c) of FIG. 12, when the focal point F is focused on a part other than the vicinity of the tip 14e of the crack 14 from the back surface 21b side, at least a part of the light I1 reflected by the surface 21a returns, so a whitish image is obtained (the right image in (c) of FIG. 12).

[0046] [Embodiments relating to internal observation] FIG. 13 is a diagram showing an object in which a modified region is formed. FIG. 13(a) is a cross-sectional photograph of an object cut so that a modified region is exposed. FIG. 13(b) is an example of an image of an object captured by light passing through the object. FIG. 13(c) is another example of an image of an object captured by light passing through the object. As shown in FIG. 13(a), the modified region 12 formed in the object (here, a semiconductor substrate 21) by focusing the laser light L includes a void region 12m located on the front surface 21a side, which is the surface opposite to the incident surface of the laser light L in the semiconductor substrate 21, and a void upper region 12n located on the back surface 21b side, which is the incident surface of the laser light L, of the void region 12m.

[0047] When the semiconductor substrate 21 on which such modified regions 12 are formed is imaged by light I1 that is transparent to the semiconductor substrate 21, images of cracks 14k extending along a direction intersecting the Z direction and the X direction (at an angle with respect to the X direction) may be confirmed, as shown in (b) and (c) of Figure 13. When viewed from the Z direction, the cracks 14k are roughly parallel to the Y direction in the example of (b) of Figure 13, and are slightly inclined with respect to the Y direction in the example of (c) of Figure 13. When the semiconductor substrate 21 is imaged at multiple positions while moving the focal point of the light I1 along the Z direction, the images of these cracks 14k are clearly detected in a limited range in the Z direction, as compared with the modified regions 12.

[0048] Fig. 14 is a graph showing the positions of the modified region and the cracks in the Z direction. In Fig. 14, the plots of the void lower end, the void upper end, the void upper region lower end, and the void upper region upper end are actual values ​​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 void upper region lower end is the end on the front surface 21a side of the void upper region 12n.

[0049] 14, the plots of direct observation and back surface reflection observation are measured values ​​calculated based on the movement amount (hereinafter, sometimes simply referred to as "movement amount") of the objective lens 43 in the Z direction when an internal image including a clear image of the crack 14k is captured among images captured by the light I1, and are values ​​obtained by image judgment by AI as an example. Direct observation is a case where the light I1 is incident from the back surface 21b and the focal point of the light I1 is directly aligned with the crack 14k without being reflected on the front surface 21a (in the above example, the focal point F is aligned with the crack 14k from the back surface 21b side), and back surface reflection observation is a case where the light I1 is incident from the back surface 21b and the focal point of the light I1 reflected on the front surface 21a is aligned with the crack 14k (in the above example, the focal point F is aligned with the area on the opposite side of the back surface 21b with respect to the front surface 21a from the back surface 21b side, and a virtual focal point Fv symmetrical to the focal point F with respect to the front surface 21a is aligned with the crack 14k).

[0050] 14, in the direct observation, in the four cases C1 to C4 in which the formation position of the modified region 12 is different in the Z direction, the crack 14k is detected between the lower end of the region above the void and the upper end of the region above the void, while in the back surface reflection observation, in the case C1, the crack 14k is detected at approximately the same position as the lower end of the region above the void, and in the cases C2 to C4, the crack 14k is detected between the lower end of the region above the void and the upper end of the void. 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 region above the void. Thus, the crack 14k is detected more pinpoint in the Z direction compared to the modified region 12 itself.

[0051] Therefore, by acquiring the amount of movement of the internal image when the crack 14k appears in the Z direction, it is possible to acquire information regarding the position of the modified region 12 more accurately. Note that the vertical axis of Fig. 14 indicates the distance from the back surface, which is the back surface relative to the incident surface of the light I1 and is the front surface 21a of the semiconductor substrate 21. Fig. 15 plots the detection results for case C1 on the cross-sectional photograph.

[0052] In this embodiment, based on the above findings, the crack 14k is detected by internal observation to obtain information on the position of the modified region 12. Next, an observation method according to this embodiment will be described. In this observation method, the crack 14k is a target crack to be detected.

[0053] Fig. 16 is a flow chart showing an example of the observation method according to the present embodiment. As shown in Fig. 16, laser processing is performed here 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, and for example, an object on which a modified region 12 is formed may be prepared using another laser processing device (or at a separate timing by the laser processing device 1).

[0054] 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 front surface (second surface) 21a opposite to the back surface 21b. A line 15 extending in the X direction along the back surface 21b and the front surface 21a is set on the semiconductor substrate 21. The semiconductor substrate 21 is supported by the stage 2 such that the back surface 21b faces the laser irradiation unit 3 in order to make the back surface 21b an incident surface of the laser light L. In this state, the control unit 8 controls the laser irradiation unit 3 while controlling the driving unit 7 and / or the moving mechanism of the stage 2 to relatively move the semiconductor substrate 21 along the X direction, thereby moving the focal point C of the laser light L along the line 15 relative to the semiconductor substrate 21.

[0055] At this time, the control unit 8 causes the spatial light modulator 32 to display a pattern for splitting the laser light L into a plurality (two in this case) of laser lights L1 and L2. As a result, focal points C1 and C2 of the laser lights L1 and L2 are formed inside the semiconductor substrate 21 at a distance Dz apart in the Z direction and a distance Dx apart in the X direction. As a result, a plurality (two rows in this case) of modified regions 12a and 12b are formed along the line 15 in the semiconductor substrate 21. Therefore, in this case, the X direction is the processing direction in which the focal points C1 and C2 proceed.

[0056] In this manner, the control unit 8 controls the laser irradiation unit 3 (irradiation unit) to irradiate the semiconductor substrate 21 with laser light L along the X direction, which is the extension direction of the lines 15, thereby performing a laser processing process to form, in the semiconductor substrate 21, a plurality of modified regions 12 arranged along the X direction and cracks (cracks 14, 14k) extending from the modified regions 12. Note that in Fig. 17 and the subsequent figures, the functional element layer 22 formed on the surface 21a of the semiconductor substrate 21 is omitted.

[0057] Next, the inside is observed. That is, in the next step, the semiconductor substrate 21 is moved to the observation position (step S12). More specifically, the control unit 8 controls the driving unit 7 and / or the moving mechanism of the stage 2 to relatively move the semiconductor substrate 21 so that it is positioned directly below the objective lens 43 of the imaging unit 4. Note that, 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, for example, a user.

[0058] 18, the semiconductor substrate 21 is imaged by light (transmitted light) I1 having transparency to the semiconductor substrate 21 (step S13: imaging step). In this step S13, the imaging unit 4 (imaging section) is controlled to cause the light I1 to enter the inside of the semiconductor substrate 21 from the back surface 21b of the semiconductor substrate 21, and an imaging process is performed to image a target crack, which is a crack 14k extending along a direction intersecting the Z direction and the X direction among the cracks extending from the modified region 12, by the light I1. The Y direction is an example of a direction intersecting the X direction, which is the processing progress direction, and the Z direction intersecting the back surface 21b and the front surface 21a.

[0059] More specifically, in step S13, the control unit 8 controls the drive unit 7 (moving unit) and the imaging unit 4 to move the imaging unit 4 along the Z direction, thereby positioning the focal point of the light I1 at multiple positions inside the semiconductor substrate 21 and capturing images of the semiconductor substrate 21, thereby acquiring multiple internal images ID. In this embodiment, the objective lens 43 is moved integrally with the imaging unit 4. Therefore, moving the imaging unit 4 also means moving the objective lens 43, and the amount of movement of the imaging unit 4 is equivalent to the amount of movement of the objective lens 43.

[0060] At this time, the control unit 8 controls the drive unit 7 to move the imaging unit 4 in the Z direction, and images the semiconductor substrate 21 multiple times while moving the focal point (focal point F, virtual focal point Fv) of the light I1 in the Z direction. 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, it can be a partial range RA including the Z-direction position where the focal points C1, C2 of the laser beams L1, L2 are aligned to form the modified regions 12a, 12b during the laser processing in step S11. Note that the interval of the movement of the imaging unit 4 in the Z direction when imaging multiple times, that is, the imaging interval of the semiconductor substrate 21, is arbitrary, but it is desirable to set it more finely from the viewpoint of detecting the crack 14k more accurately. The imaging interval is, for example, within 1 μm, and is 0.2 μm here.

[0061] Further, here, the control unit 8 controls the imaging unit 4 and the drive unit 7 so that direct observation and back surface reflection observation of the semiconductor substrate 21 are performed. More specifically, the control unit 8 first performs a first imaging process in which light I1 is incident on the semiconductor substrate 21 from the back surface 21b, and the imaging unit 4 is moved along the Z direction to move the focal point (focal point F) of the light I1 that has not been reflected on the front surface 21a from the back surface 21b side to the front surface 21a side, thereby imaging the semiconductor substrate 21 at multiple positions in the Z direction to obtain multiple first internal images ID1 as internal images ID. This first imaging process is direct observation.

[0062] At the same time, the control unit 8 executes a second imaging process in which the light I1 is incident on the object from the back surface 21b, while the imaging unit 4 is moved along the Z direction, thereby imaging the semiconductor substrate 21 at multiple positions while moving the focal point (virtual focal point Fv) of the light I1 reflected on the front surface 21a from the front surface 21a side toward the back surface 21b side, thereby acquiring multiple second internal images ID2 as internal images ID. This second imaging process is an observation from the back surface (here, referred to as the front surface 21a in view of the configuration of the semiconductor substrate 21) side with respect to the incident surface of the light I1, and therefore is a back surface reflection observation.

[0063] In the next step, imaging data relating to the internal image ID acquired by imaging in step S13 is stored (step S14). As described above, in step S13, the control unit 8 performs imaging while moving the imaging unit 4 (i.e., the focal point of the light I1) along the Z direction by controlling the drive unit 7. Therefore, the control unit 8 can acquire the amount of movement of the imaging unit 4 when each internal image is captured. Here, information regarding the amount of movement is associated with each internal image ID and can be stored as imaging data. The imaging data can be stored in any storage device accessible to the control unit 8, regardless of whether it is inside or outside the control unit 8 and the laser processing apparatus 1.

[0064] As an example, the amount of movement of the imaging unit 4 (objective lens 43) can be the amount of movement of the imaging unit 4 when the imaging unit 4 is moved along the Z direction from a position where the focal point of the light I1 is aligned with the back surface 21b of the semiconductor substrate 21 to a desired position inside the semiconductor substrate 21.

[0065] Next, the control unit 8 inputs the imaging data from a predetermined storage device (step S15). Then, the control unit 8 judges the formation state of the crack 14k (step S16). Here, as an example, the control unit 8 automatically judges, by image recognition, an internal image ID in which the image of the crack 14k is relatively clear among the multiple internal image IDs (performs AI judgment). Here, an example of an algorithm for detecting cracks and modified regions by AI judgment will be described.

[0066] 20 and 21 are diagrams for explaining crack detection. FIG. 20 shows an internal observation result (internal image of the semiconductor substrate 21). The control unit 8 first detects a group of straight lines 140 from the internal image of the semiconductor substrate 21 as shown in FIG. 20(a). For the detection of the group of straight lines 140, an algorithm such as Hough transformation or LSD (Line Segment Detector) is used. The Hough transformation is a method of detecting straight lines by detecting all straight lines passing through a point on an image and weighting the straight lines that pass through more characteristic points. The LSD is a method of detecting straight lines by calculating the gradient and angle of the brightness value in the image to estimate an area that will be a line segment, and approximating the area to a rectangle.

[0067] Next, the control unit 8 detects the crack 14 from the straight line group 140 by calculating the similarity between the straight line group 140 and the crack line as shown in FIG. 21. The crack line has a characteristic that the front and rear of the crack line are very bright in the Y direction compared to the luminance value on the line, as shown in the upper diagram of FIG. 21. For this reason, the control unit 8, for example, compares the luminance values ​​of all pixels of the detected straight line group 140 with the front and rear in the Y direction, and sets the number of pixels whose difference is equal to or greater than a threshold both before and after as the similarity score. Then, the one of the detected multiple straight line groups 140 with the highest similarity score with the crack line is set as the representative value in the image. The higher the representative value, the more likely the crack 14 is to exist. The control unit 8 compares the representative values ​​in multiple images to set the one with a relatively high score as a crack image candidate.

[0068] 22 to 24 are diagrams for explaining the detection of scratches. In FIG. 22, an internal observation result (internal image of the semiconductor substrate 21) is shown. The control unit 8 detects corners (concentration of edges) in the image of the inside of the semiconductor substrate 21 as shown in FIG. 22(a) as key points, and detects the positions, sizes, and directions to detect feature points 250. Known methods for detecting feature points in this way include Eigen, Harris, Fast, SIFT, SURF, STAR, MSER, ORB, AKAZE, and the like.

[0069] Here, as shown in FIG. 23, the dent 280 has a strong characteristic as a corner, since shapes such as circles and rectangles are arranged at regular intervals. Therefore, by collecting the feature amounts of the feature points 250 in the image, it is possible to detect the dent 280 with high accuracy. As shown in FIG. 24, when comparing the total feature amounts of the images captured by shifting in the depth direction, a change in a mountain indicating the amount of crack rows for each modified layer can be confirmed. The control unit 8 estimates the peak of the change as the position of the dent 280. By collecting the feature amounts in this way, it is possible to estimate not only the dent position but also the pulse pitch.

[0070] The above explanation of the AI ​​judgment is related to the crack 14 and the scar 280 extending along the X direction, but a similar algorithm can also be used for the crack 14k extending along a direction intersecting the Z direction and the X direction, and by comparing the representative values ​​of multiple internal image IDs, the one with a relatively high score can be judged to be the internal image ID in which the image of the crack 14k is relatively clear.

[0071] As an example, Fig. 19 shows a plurality of internal images ID captured at different positions in the Z direction. In Fig. 19, with the imaging position of the internal image IDd shown in (d) as the center, (c) is an internal image IDc at an imaging position 1 μm away from the back surface 21b, (b) is an internal image IDb at an imaging position 3 μm away from the back surface 21b, (a) is an internal image IDa at an imaging position 5 μm away from the back surface 21b, (e) is an internal image IDe at an imaging position 1 μm away from the front surface 21a, (f) is an internal image IDf at an imaging position 3 μm away from the front surface 21a, and (g) is an internal image IDg at an imaging position 5 μm away from the front surface 21a. The imaging positions here are values ​​within the semiconductor substrate 21.

[0072] In the example shown in Fig. 19, since the image of the crack 14k is the clearest in the internal image IDd, the control unit 8 determines that the internal image IDd has a relatively high score and is an internal image in which the image of the crack 14k is relatively clear (i.e., it is determined that the crack 14k is detected in the internal image IDd). The control unit 8 can obtain 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.

[0073] In this way, the control unit 8 executes a calculation process to calculate the crack position in the Z direction of the target crack, which is the crack 14k extending in a direction intersecting the Z direction and the X direction, based on the multiple internal image IDs and the movement amount of the imaging unit 4 when each of the internal image IDs is imaged. More specifically, in the calculation process, the control unit 8 determines an internal image ID in which the image of the crack 14k is clear among the multiple internal image IDs, and calculates the crack position based on the movement amount when the determined internal image ID is imaged. The crack position can be calculated, for example, by multiplying the movement amount by a predetermined correction coefficient. The correction coefficient can be obtained, for example, from the NA of the objective lens 43, the refractive index of the semiconductor substrate 21, etc.

[0074] The control unit 8 can calculate 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 surface reflection observation. This allows the control unit 8 to calculate the crack position of the crack 14k located relatively on the back surface 21b side according to the first internal image ID1, and the crack position of the crack 14k located relatively on the front surface 21a side according to the second internal image ID2.

[0075] That is, in this case, the control unit 8 executes a first calculation process of determining a first internal image in which the crack 14k is clear among the multiple first internal images ID1, and calculating a first crack position Z1 as a crack position based on the movement amount of the imaging unit 4 when the determined first internal image was captured, and a second calculation process of determining a second internal image in which the crack 14k is clear among the multiple second internal images ID2, and calculating a second crack position Z2 as a crack position based on the movement amount of the imaging unit 4 when the determined second internal image was captured (see FIG. 15 for an example of the first crack position Z1 and 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 defines the width of the portion (crack starting portion) where the crack 14k is formed in the modified region 12.

[0076] Subsequently, in step S16, the control unit 8 estimates the position of the modified region 12, etc., based on the acquired crack position, etc. That is, here, the control unit 8 executes an estimation process to estimate at least one of the position in the Z direction of the end of the modified region 12 on the back surface 21b side (upper end of the region above the void), the position in the Z direction of the end of the modified region 12 on the front surface 21a side (lower end of the void), and the width of the modified region 12 in the Z direction (the distance between the upper end of the region above the void and the lower end of the void) based on the formation conditions of the modified region 12 (here, the processing conditions in the laser processing) and the crack position.

[0077] 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 front surface 21a side based on back surface reflection observation. Therefore, the control unit 8 can calculate the width of the crack starting part 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.

[0078] Then, the control unit 8 can calculate the width in the Z direction of the modified region 12 inside the semiconductor substrate 21, for example, by multiplying the calculated width of the crack start portion by a coefficient related to the processing conditions of the laser processing. The coefficient here is determined based on various conditions that affect the formation of the modified region 12, such as the wavelength, aberration correction amount, pulse width, and pulse energy of the laser light L during the laser processing. The coefficient here is, for example, around 3.0.

[0079] In this way, in the estimation process, the control unit 8 can estimate the width of the modified area 12 in the Z direction based on the formation conditions of the modified area 12 (laser processing conditions) and the distance between the first crack position Z1 and the second crack position Z2.

[0080] Meanwhile, the control unit 8 can calculate the position of the lower end of the modified region 12 on the surface 21a side by subtracting the assumed modified region width, which is the assumed overall width of the modified region 12, from the first crack position Z1 of the upper crack. The assumed modified region width is determined based on various conditions that affect the formation of the modified region 12, such as the wavelength, aberration correction amount, pulse width, and pulse energy of the laser light L during laser processing. The assumed modified region width is, for example, about 20 μm.

[0081] 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 assumed void region width, which is the width of the assumed void region 12m, from the second crack position Z2 of the lower crack. The assumed void region width is determined based on various conditions that affect the formation of the modified region 12, such as the wavelength, aberration correction amount, pulse width, and pulse energy of the laser light L during laser processing. The assumed void region width is, for example, about 10 μm.

[0082] Furthermore, the control unit 8 can calculate the position of the upper end of the modified region 12 on the back surface 21b side by adding an 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. The assumed void upper region width is determined based on various conditions that affect the formation of the modified region 12, such as the wavelength, aberration correction amount, pulse width, and pulse energy of the laser light L during laser processing. The assumed void upper region width is, for example, about 10 μm.

[0083] As described above, in step S16, the control unit 8 estimates and acquires various pieces of information related to the position of the modified region 12. In the next step, the control unit 8 outputs information related to the judgment result of step S16 to an arbitrary storage device (step S17) and stores the information in the storage device (step S18). Thereafter, as necessary, various pieces of information are displayed on the display 150 in a state in which input from the user can be accepted (step S19), and the process ends. Examples of information displayed on the display 150 include the first crack position Z1, the second crack position Z2, the starting portion width, the position of the end of the modified region 12, and the width of the modified region 12 in the Z direction. Thus, in step S19, the control unit 8 controls the display 150 to execute a display process for displaying information related to the crack position on the display 150.

[0084] This completes the observation method using the laser processing apparatus 1. In this embodiment, the observation method is performed by the imaging unit 4, drive unit 7, and control unit 8 of the laser processing apparatus 1. In other words, in the laser processing apparatus 1, an observation device 1A is configured by the imaging unit 4 for imaging the semiconductor substrate 21 with light I1 that is transparent to the semiconductor substrate 21, the drive unit 7 for moving the imaging unit 4 relatively to the semiconductor substrate 21, and the control unit 8 for controlling at least the imaging unit 4 and the drive unit 7 (see FIG. 1).

[0085] As described above, the semiconductor substrate 21 to be observed by the observation method according to the present embodiment and the observation device 1A for carrying out the observation method has the modified regions 12 arranged along the X direction and the cracks 14, 14k extending from the modified regions 12. Then, for such a semiconductor substrate 21, the cracks 14k extending in a direction intersecting the Z direction and the X direction are imaged using the light I1 transmitted through the semiconductor substrate 21. The cracks 14k intersecting the Z direction and the X direction are imaged (detected) more pinpoint-wise in the Z direction than the modified regions 12 themselves. Therefore, for example, by acquiring information such as the amount of movement of the imaging unit 4 when the cracks 14k are imaged, it is possible to acquire information on the position of the modified regions 12 more accurately based on the amount of movement.

[0086] The observation device 1A according to the present embodiment also includes a drive unit 7 for moving the focal point of the light I1 relative to the semiconductor substrate 21. In the imaging process, the control unit 8 controls the imaging unit 4 and the drive unit 7 to move the imaging unit 4 along the Z direction, thereby positioning the focal point of the light I1 at multiple positions inside the semiconductor substrate 21 and imaging the semiconductor substrate 21, thereby acquiring multiple internal image IDs. After the imaging process, the control unit 8 executes a calculation process for calculating the crack position (first crack position Z1 and second crack position Z2), which is the position of the crack 14k in the Z direction, based on the multiple internal image IDs and the movement amount of the imaging unit 4 in the Z direction when each of the internal image IDs is imaged. In this way, information regarding the position of the modified region 12 can be acquired more accurately based on the movement amount of the imaging unit 4 when the crack 14k is imaged.

[0087] In the observation device 1A according to the present embodiment, in the calculation process, the control unit 8 determines an internal image in which the image of the crack 14k is clear among the multiple internal images ID, and calculates the crack position of the crack 14k based on the movement amount of the imaging unit 4 when the determined internal image was captured. In this way, the control unit 8 determines an internal image in which the crack 14k is clear, and the position of the crack 14k can be calculated more accurately.

[0088] Furthermore, in the observation device 1A according to this embodiment, the control unit 8 executes an estimation process to estimate at least one of the position of the end of the modified region 12 on the back surface 21b side in the Z direction, the position of the end of the modified region 12 on the front surface 21a side in the Z direction, and the width of the modified region 12 in the Z direction, based on the formation conditions of the modified region 12 and the crack position of the crack 14k after the calculation process. The shape and size of the modified region 12 may change depending on the formation conditions of the modified region, such as the processing conditions of the laser processing (for example, the wavelength of the laser light, the pulse width, the pulse energy, and the amount of aberration correction, etc.). Therefore, by using the formation conditions of the modified region 12, such as the processing conditions of the laser processing, and the position of the crack 14k in this way, information on the position of the modified region 12 can be more accurately estimated.

[0089] In addition, in the observation device for the present embodiment liquid, in the imaging process, the control unit 8 executes a first imaging process in which light I1 is incident on the semiconductor substrate 21 from the back surface 21b while moving the imaging unit 4, thereby imaging the semiconductor substrate 21 at multiple positions while moving the focal point of light I1 that has not been reflected on the front surface 21a from the back surface 21b side toward the front surface 21a side, thereby acquiring multiple first internal images ID1 as internal image IDs, and a second imaging process in which light I1 is incident on the semiconductor substrate 21 from the back surface 21b while moving the imaging unit 4, thereby imaging the semiconductor substrate 21 at multiple positions while moving the focal point of light I1 reflected on the front surface 21a from the front surface 21a side toward the back surface 21b side, thereby acquiring multiple second internal images ID2 as internal image IDs.

[0090] In this way, by acquiring internal images by imaging the semiconductor substrate 21 using light I1 that is incident on the back surface 21b of the semiconductor substrate 21 and has not been reflected on the front surface 21a (direct observation), and by acquiring internal images by imaging the semiconductor substrate 21 using light I1 that is incident on the back surface 21b of the semiconductor substrate 21 and has been reflected on the front surface 21a (back surface reflection observation), it is possible to acquire information regarding the position of the modified region 12 more accurately by utilizing the crack position acquired based on the amount of movement of the imaging unit 4 when the internal image is acquired.

[0091] In the observation device 1A according to the present embodiment, in the calculation process, the control unit 8 executes a first calculation process in which the control unit 8 determines a first internal image in which the crack 14k is clear among the multiple first internal images ID1, and calculates a first crack position Z1 as a crack position based on the movement amount of the imaging unit 4 when the determined first internal image is captured, and executes a second calculation process in which the control unit 8 determines a second internal image in which the crack 14k is clear among the multiple second internal images ID2, and calculates a second crack position Z2 as a crack position based on the movement amount of the imaging unit 4 when the determined second internal image is captured. 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 condition of the modified region 12 and the interval 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 acquired more accurately based on the interval between the first crack position Z1 acquired based on direct observation and the second crack position Z2 acquired based on back surface reflection observation.

[0092] Furthermore, the observation device 1A according to this embodiment further includes a display 150 for displaying information. Then, the control unit 8 may execute a display process for controlling the display 150 to display information related to the crack position on the display 150 after the calculation process. In this case, the user can grasp the information related to the crack position via the display 150. Note that the information related to the crack position is at least one of various pieces of information included in the information related to the crack position itself and the position of the modified region 12 that can be estimated based on the crack position.

[0093] The above embodiment is a description of one aspect of the present invention, therefore the present invention is not limited to the above embodiment and may be modified as desired.

[0094] For example, in the above embodiment, the drive unit 7 that moves the imaging unit 4 together with the objective lens 43 is exemplified as the means for relatively moving the objective lens 43 in the Z direction with respect to the semiconductor substrate 21. However, for example, only the objective lens 43 may be moved in the Z direction by an actuator.

[0095] In the above embodiment, the control unit 8 automatically judges the image in step S16. However, the control unit 8 may obtain the crack position of the crack 14k based on the judgment result of the user. In this case, the control unit 8, for example, displays a plurality of internal image IDs on the display 150 and displays information on the display 150 that prompts the user to judge (select) one internal image in which the image of the crack 14k is clear from the plurality of internal image IDs. The control unit 8 then accepts an input of the judgment result via the display 150, and can calculate the crack position of the crack 14k based on the amount of movement of the internal image ID corresponding to the judgment result. In this case, the display 150 is a display unit for displaying information and also an input receiving unit for receiving input. In this case, the processing load of the control unit 8 for image recognition and the like is reduced.

[0096] In the above embodiment, in step S13, both direct observation and back surface reflection observation were performed on one modified region 12 to obtain a first internal image ID1 and a second internal image ID2 as internal image IDs. However, in step S13, only one of direct observation and back surface reflection observation may be performed. In this case, one of the first internal image ID1 and the second internal image ID2 is obtained, and the position and width of the end of the modified region 12 may be estimated based on that one. [Explanation of symbols]

[0097] 1A...observation device, 4...imaging unit (imaging section), 7...driving unit (moving section), 8...control section, 12...modified area, 14...crack, 14k...crack (target crack), 21...semiconductor substrate (target 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...first crack position, Z2...second crack position.

Claims

1. an imaging unit for imaging an object using transmitted light having transparency to the object; A control unit for controlling at least the imaging unit; a moving unit for moving a condensing lens for condensing the transmitted light on the object relatively to the object; Equipped with the object includes a first surface and a second surface opposite the first surface; The object has modified regions arranged in an X direction along the first surface and the second surface and cracks extending from the modified regions, The control unit controls the imaging unit to cause the transmitted light to enter the inside of the object from the first surface, and performs an imaging process to image a target crack, which is a crack among the cracks extending in a direction intersecting the Z direction and the X direction intersecting the first surface and the second surface, using the transmitted light; In the imaging process, the control unit relatively moves the condensing lens along the Z direction by controlling the imaging unit and the moving unit, thereby positioning a condensing point of the transmitted light at a plurality of positions inside the object and imaging the object to obtain a plurality of internal images, The control unit, after the imaging process, executes a calculation process to calculate a crack position, which is the position of the target crack in the Z direction, based on the multiple internal images and the movement amount of the condenser lens in the Z direction when each of the internal images is captured, In the calculation process, the control unit determines the internal image in which the image of the target crack is clearest among the multiple internal images, and calculates the crack position based on the movement amount of the condenser lens when the determined internal image is captured. Observation equipment.

2. After the calculation process, the control unit executes an estimation process to estimate at least one of a position of an end of the modified region on the first surface side in the Z direction, a position of an end of the modified region on the second surface side in the Z direction, and a width of the modified region in the Z direction based on the formation condition of the modified region and the crack position. The observation device according to claim 1.

3. In the imaging process, the control unit a first imaging process for imaging the object at a plurality of positions while moving the focusing lens relatively along the Z direction while causing the transmitted light to be incident on the object from the first surface, thereby acquiring a plurality of first internal images as the internal image; and a second imaging process for imaging the object at a plurality of positions while moving the focusing lens relatively along the Z direction while causing the transmitted light to be incident on the object from the first surface, thereby acquiring a plurality of second internal images as the internal image; and Execute 3. The observation device according to claim 1 or 2.

4. In the calculation process, the control unit A first calculation process for determining the first internal image in which the target crack is clearest among the plurality of first internal images, and calculating a first crack position as the crack position based on the movement amount of the focusing lens when the determined first internal image is captured; A second calculation process for determining the second internal image in which the target crack is the clearest among the plurality of second internal images, and calculating a second crack position as the crack position based on the movement amount of the condenser lens when the determined second internal image is captured; Run The control unit estimates a width of the modified region in the Z direction based on a formation condition of the modified region and an interval between the first crack position and the second crack position. The observation device according to claim 3.

5. Further comprising a display unit for displaying information, The control unit executes a display process to cause the display unit to display information related to the crack position after the calculation process. The observation device according to any one of claims 1 to 4.

6. A preparation step of preparing an object including a first surface and a second surface opposite to 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; After the preparation process, an imaging process is performed in which transmitted light passing through the object is incident on the object from the first surface, and a target crack, which is a crack among the cracks extending in a direction intersecting the Z direction and the X direction intersecting the first surface and the second surface, is imaged by the transmitted light. Equipped with In the imaging step, a condenser lens for condensing the transmitted light on the object is relatively moved along the Z direction to position the condensing points of the transmitted light at a plurality of positions inside the object, thereby acquiring a plurality of internal images by imaging the object; After the imaging step, a crack position, which is the position of the target crack in the Z direction, is calculated based on the multiple internal images and the movement amount of the condenser lens in the Z direction when each of the internal images is captured; In the calculation of the crack position, the internal image in which the image of the target crack is clearest is determined among the multiple internal images, and the crack position is calculated based on the movement amount of the condenser lens when the determined internal image is captured. Observation method.

7. an imaging unit for imaging an object using transmitted light having transparency to the object; A control unit for controlling at least the imaging unit; a moving unit for moving a condensing lens for condensing the transmitted light on the object relatively to the object; Equipped with the object includes a first surface and a second surface opposite the first surface; The object has modified regions arranged in an X direction along the first surface and the second surface and cracks extending from the modified regions, The control unit controls the imaging unit to cause the transmitted light to enter the inside of the object from the first surface, and performs an imaging process to image a target crack, which is a crack among the cracks extending in a direction intersecting the Z direction and the X direction intersecting the first surface and the second surface, using the transmitted light; In the imaging process, the control unit relatively moves the condensing lens along the Z direction by controlling the imaging unit and the moving unit, thereby positioning a condensing point of the transmitted light at a plurality of positions inside the object and imaging the object to obtain a plurality of internal images, The control unit, after the imaging process, executes a calculation process to calculate a crack position, which is the position of the target crack in the Z direction, based on the multiple internal images and the movement amount of the condenser lens in the Z direction when each of the internal images is captured, In the imaging process, the control unit a first imaging process for imaging the object at a plurality of positions while moving the focusing lens relatively along the Z direction while causing the transmitted light to be incident on the object from the first surface, thereby acquiring a plurality of first internal images as the internal image; and a second imaging process for imaging the object at a plurality of positions while moving the focusing lens relatively along the Z direction while causing the transmitted light to be incident on the object from the first surface, thereby acquiring a plurality of second internal images as the internal image; and Run In the calculation process, the control unit A first calculation process for determining the first internal image in which the target crack is clearest among the plurality of first internal images, and calculating a first crack position as the crack position based on the movement amount of the focusing lens when the determined first internal image is captured; A second calculation process for determining the second internal image in which the target crack is the clearest among the plurality of second internal images, and calculating a second crack position as the crack position based on the movement amount of the condenser lens when the determined second internal image is captured; Run The control unit estimates a width of the modified region in the Z direction based on a formation condition of the modified region and an interval between the first crack position and the second crack position. Observation equipment.

8. A preparation process for preparing an object including 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; After the preparation process, an imaging process is performed in which transmitted light passing through the object is incident on the object from the first surface, and a target crack, which is a crack among the cracks extending in a direction intersecting the Z direction and the X direction intersecting the first surface and the second surface, is imaged by the transmitted light. Equipped with In the imaging step, a condenser lens for condensing the transmitted light on the object is relatively moved along the Z direction to position the condensing points of the transmitted light at a plurality of positions inside the object, thereby acquiring a plurality of internal images by imaging the object; After the imaging step, a crack position, which is the position of the target crack in the Z direction, is calculated based on the multiple internal images and the movement amount of the condenser lens in the Z direction when each of the internal images is captured; In the imaging step, While the transmitted light is incident on the object from the first surface, the condensing lens is relatively moved along the Z direction, and the condensing point of the transmitted light that has not been reflected at the second surface is moved from the first surface side toward the second surface side to capture an image of the object at a plurality of positions, thereby acquiring a plurality of first internal images as the internal image, and While the transmitted light is incident on the object from the first surface, the condensing lens is relatively moved along the Z direction to move the condensing point of the transmitted light reflected on the second surface from the second surface side toward the first surface side, thereby capturing an image of the object at a plurality of positions, thereby acquiring a plurality of second internal images as the internal image; In the calculation of the crack position, Among the plurality of first internal images, the first internal image in which the target crack is most clearly determined is determined, and a first crack position as the crack position is calculated based on the amount of movement of the condenser lens when the determined first internal image is captured, and Among the plurality of second internal images, the second internal image in which the target crack is clearest is determined, and a 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; estimating a width of the modified region in the Z direction based on a formation condition of the modified region and an interval between the first crack position and the second crack position; Observation method.

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