Observation device and observation method

Abstract

The observation device and the observation method of the present application can more accurately acquire information about the position of a modified region. The observation device includes an imaging unit configured to image an object using a transmission light having a transmissivity with respect to the object, the object having a first surface and a second surface opposite to the first surface, a modified region arranged in an X direction along the first surface and the second surface being formed in the object, and a crack extending from the modified region, and a control unit configured to control at least the imaging unit, the control unit performing an imaging process of causing the transmission light to be incident on the inside of the object from the first surface and imaging an object crack using the transmission light, the object crack being the crack extending in a Z direction intersecting the first surface and the second surface and a direction intersecting the X direction among the cracks.

Description

Technical Field

[0001] This invention relates to observation apparatus and observation methods. Background Technology

[0002] A laser processing apparatus is known to form multiple rows of modified regions inside the semiconductor substrate along multiple lines by irradiating the wafer with a laser from the back side of the semiconductor substrate in order to cut a wafer comprising a semiconductor substrate and a functional element layer formed on the front side of the semiconductor substrate along multiple lines. Patent Document 1 (Japanese Patent Application Publication No. 2017-64746) describes a laser processing apparatus that includes an infrared camera, enabling observation from the back side of the semiconductor substrate of the modified regions formed inside the semiconductor substrate and processing damage formed on the functional element layer. Summary of the Invention

[0003] As described above, when observing modified regions formed inside a semiconductor substrate using an infrared camera, it is unclear which portion of the modified region is detected along the thickness direction of the semiconductor substrate. Therefore, in the aforementioned technical field, there is a need to obtain more accurate information regarding the location of the modified region along the thickness direction of the semiconductor substrate, such as the upper and lower positions and the width of the modified region.

[0004] The purpose of this invention is to provide an observation device and method that can more accurately obtain information about the location of the modified region.

[0005] The inventors of this invention conducted intensive research to solve the aforementioned technical problems, and thus made the following discovery. Specifically, when a modified region is formed inside an object such as a semiconductor substrate, for example by laser processing, cracks sometimes form extending from the modified region in various directions. Furthermore, cracks that intersect the Z-direction (intersecting the laser incident surface of the object) and the X-direction (serving as the laser processing advance direction) can be accurately detected using transmitted light transmitted from the object, compared to the modified region. Therefore, if information about the location of the cracks intersecting the X and Z directions can be obtained, information about the location of the modified region can be obtained more accurately based on that location. This invention was made based on this discovery.

[0006] That is, the observation device of the present invention includes: an imaging unit for imaging an object using transmitted light that is transmissive to the object; and a control unit for controlling at least the imaging unit, wherein the object has a first surface and a second surface opposite to the first surface, and modified regions arranged in the X direction along the first surface and the second surface and cracks extending from the modified regions are formed on the object, and the control unit performs the following imaging process by controlling the imaging unit: causing transmitted light to enter the interior of the object from the first surface, and imaging the cracks of the object using the transmitted light, wherein the cracks of the object are cracks that extend in the Z direction intersecting the first surface and the second surface and in the direction intersecting the X direction.

[0007] Furthermore, the observation method of the present invention includes: a preparation step of preparing an object having a first surface and a second surface opposite to the first surface, wherein modified regions arranged in the X direction along the first surface and the second surface and cracks extending from the modified regions are formed on the object; and an imaging step, after the preparation step, wherein transmitted light transmitted from the object is incident on the object from the first surface, and the object crack is imaged using the transmitted light, wherein the object crack is a crack extending in the Z direction intersecting the first surface and the second surface and in the direction intersecting the X direction.

[0008] In the object to which these devices and methods are applied, modified regions arranged along the X-direction and cracks extending from the modified regions are formed. Furthermore, for such an object, the cracks intersecting the X and Z directions can be imaged using transmitted light transmitted from the object. As discovered above, the cracks intersecting the X and Z directions from the modified regions can be imaged (detected) more precisely in the Z direction than the modified regions. Therefore, if information such as the amount of movement of the condenser lens during image capture of the cracks can be obtained, information about the position of the modified regions can be obtained more accurately based on that amount of movement.

[0009] The observation device of the present invention can also be configured to include a moving unit for moving a condenser lens relative to an object, wherein the condenser lens is used to focus transmitted light onto the object. During image processing, a control unit controls an imaging unit and a moving unit to move the condenser lens relative to each other along the Z-direction, so that the focusing point of the transmitted light is located at multiple positions inside the object to capture images of the object, thereby acquiring multiple internal images. After the image processing, the control unit performs the following calculation: based on the multiple internal images and the amount of movement of the condenser lens in the Z-direction during the capture of each internal image, it calculates the crack position, which is the location of the crack in the Z-direction. Thus, by calculating the crack position based on the amount of movement of the condenser lens during the capture of the crack in the object, information about the location of the modified region can be obtained more accurately.

[0010] The observation device of the present invention can also be configured such that, during computational processing, the control unit determines a clear internal image of the object crack from among multiple internal images, and calculates the crack location based on the amount of movement of the condenser lens when capturing the determined internal image. In this way, by determining a clear internal image of the object crack through the control unit, the crack location can be calculated more accurately.

[0011] The observation device of the present invention can also be configured such that, after computational processing, the control unit performs the following estimation process: based on the formation conditions of the modified region and the crack location, it estimates at least one of the following: the position of the end of the first surface side of the modified region in the Z direction, the position of the end of the second surface side of the modified region in the Z direction, and the width of the modified region in the Z direction. The shape and size of the modified region may vary, for example, depending on the processing conditions of the laser processing (e.g., the wavelength, pulse width, pulse energy, and aberration correction amount of the laser). Therefore, by utilizing the formation conditions and crack location of the modified region in this way, information about the position of the modified region can be estimated more accurately.

[0012] The observation device of the present invention can also be configured such that, in the image processing, the control unit performs a first image processing and a second image processing. In the first image processing, transmitted light is incident on the object from the first surface, and a condenser lens is moved relative to it in the Z direction. This moves the focal point of the transmitted light that has not been reflected by the second surface from the first surface side to the second surface side, while simultaneously capturing images of the object at multiple positions, thereby acquiring multiple first internal images as internal images. In the second image processing, transmitted light is incident on the object from the first surface, and a condenser lens is moved relative to it in the Z direction. This moves the focal point of the transmitted light reflected by the second surface from the second surface side to the first surface side, while simultaneously capturing images of the object at multiple positions, thereby acquiring multiple second internal images as internal images. In this way, if we use transmitted light incident from the first surface of the object but not reflected by the second surface to photograph the object (direct observation), and also use transmitted light incident from the first surface of the object and reflected by the second surface to photograph the object (rear reflection observation), and acquire internal images respectively, we can obtain more accurate information about the location of the modified area by using the crack location obtained based on the amount of movement of the condenser lens when photographing the internal image.

[0013] The observation device of the present invention can also be configured such that, in the calculation process, the control unit performs a first calculation process and a second calculation process. In the first calculation process, a first internal image with a clearly visible object crack is determined from among a plurality of first internal images. Based on the amount of movement of the condenser lens when capturing the determined first internal image, a first crack position, which is the crack location, is calculated. In the second calculation process, a second internal image with a clearly visible object crack is determined from among a plurality of second internal images. Based on the amount of movement of the condenser lens when capturing the determined second internal image, a second crack position, which is the crack location, is calculated. In the estimation process, the control unit estimates the width of the modified region in the Z direction based on the formation conditions of the modified region and the interval between the first crack position and the second crack position. As described above, in this case, based on the interval between the crack position obtained through direct observation and the crack position obtained through back reflection observation, information about the width of the modified region can be obtained more accurately.

[0014] The observation device of the present invention can also be configured to include a display unit for displaying information, and a control unit that controls the display unit after computational processing to perform display processing to cause the display unit to display information about the crack location. In this case, the user can obtain information about the crack location through the display unit. The crack location information refers to at least one of various types of information included in the crack location itself and information about the location of the modified region that can be deduced based on the crack location.

[0015] According to the present invention, an observation apparatus and observation method are provided that can more accurately obtain information about the location of the modified region. Attached Figure Description

[0016] Figure 1 This is a structural diagram of a laser processing apparatus according to one implementation method.

[0017] Figure 2 This is a top view of a chip in one implementation method.

[0018] Figure 3 yes Figure 2 A cross-sectional view of a portion of the wafer shown.

[0019] Figure 4 yes Figure 1 The diagram shows the structure of the laser irradiation unit.

[0020] Figure 5 yes Figure 1 The diagram shown is a structural diagram of the inspection camera unit.

[0021] Figure 6 yes Figure 1 The diagram shows the structure of the camera unit used for alignment and correction.

[0022] Figure 7 It is used for explanation Figure 5 The diagram shows a cross-sectional view of the wafer based on the imaging principle of the inspection camera unit, and images of various locations obtained by the inspection camera unit.

[0023] Figure 8 It is used for explanation Figure 5 The diagram shows a cross-sectional view of the wafer based on the imaging principle of the inspection camera unit, and images of various locations obtained by the inspection camera unit.

[0024] Figure 9 These are SEM images of modified regions and cracks formed inside a semiconductor substrate.

[0025] Figure 10 These are SEM images of modified regions and cracks formed inside a semiconductor substrate.

[0026] Figure 11 It is used for explanation Figure 5 The diagram shown illustrates the imaging principle of the inspection camera unit.

[0027] Figure 12 It is used for explanation Figure 5 The diagram shown illustrates the imaging principle of the inspection camera unit.

[0028] Figure 13 It is a diagram representing the object that has formed the modified region.

[0029] Figure 14 It is a graph showing the location of the modified region and cracks in the Z direction.

[0030] Figure 15 It is a diagram obtained by plotting the detection results on a cross-sectional photograph of the object.

[0031] Figure 16 This is a flowchart illustrating an example of the observation method of this embodiment.

[0032] Figure 17 It means Figure 17 A diagram illustrating one step of the observation method shown.

[0033] Figure 18 It means Figure 17 A diagram illustrating one step of the observation method shown.

[0034] Figure 19 These are multiple internal images captured by cameras at different positions along the Z-axis.

[0035] Figure 20 This is a diagram illustrating crack detection.

[0036] Figure 21 This is a diagram illustrating crack detection.

[0037] Figure 22 This is a diagram illustrating the detection of scars.

[0038] Figure 23 This is a diagram illustrating the detection of scars.

[0039] Figure 24 This is a diagram illustrating the detection of scars. Detailed Implementation

[0040] Hereinafter, an embodiment will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same or equivalent parts are sometimes given the same reference numerals, and repeated descriptions are omitted. Furthermore, in the drawings, a rectangular coordinate system defined by the X-axis, Y-axis, and Z-axis is sometimes indicated. As an example, the X-direction and Y-direction are first and second horizontal directions that intersect (orthogonal) each other, and the Z-direction is a vertical direction that intersects (orthogonal) the X-direction and Y-direction.

[0041] like Figure 1 As shown, the laser processing apparatus 1 includes a stage 2, a laser irradiation unit 3 (irradiation section), multiple camera units 4, 5, and 6, a drive unit 7, a control unit 8, and a display 150 (display section). The laser processing apparatus 1 is a device that forms a modified region 12 on a workpiece 11 by irradiating the workpiece 11 with a laser L.

[0042] The mounting stage 2 supports the object 11, for example, by adsorbing and attaching a film to the object 11. The mounting stage 2 is movable along the X and Y directions respectively, and can rotate about an axis parallel to the Z direction.

[0043] The laser irradiation unit 3 focuses a transmissive laser L onto the object 11. When the laser L is focused into the interior of the object 11 supported by the stage 2, the laser L is particularly absorbed in the part corresponding to the focusing point C of the laser L, thus forming a modified region 12 inside the object 11.

[0044] The modified region 12 is a region whose density, refractive index, mechanical strength, or other physical properties differ from those of the surrounding unmodified region. Examples of modified regions 12 include melt-treated regions, cracked regions, regions with insulation failure, and regions with refractive index changes. The modified region 12 has the characteristic that cracks can easily extend from it to the incident side of the laser L and to the opposite side. This characteristic of the modified region 12 is utilized in the cutting of the object 11.

[0045] As an example, when the stage 2 is moved along the X direction and the focusing point C is moved relative to the object 11 along the X direction, multiple modification points 12s are formed in a row along the X direction. Each modification point 12s is formed by irradiation with a single pulse of laser L. A row of modification regions 12 is a collection of multiple modification points 12s arranged in a row. Adjacent modification points 12s may be connected to each other or separated from each other, depending on the relative moving speed of the focusing point C relative to the object 11 and the repetition frequency of the laser L.

[0046] The camera unit 4 captures images of the modified region 12 formed in the object 11, and the tip of the crack extending from the modified region 12.

[0047] Under the control of the control unit 8, camera units 5 and 6 use light transmitted from the object 11 to photograph the object 11 supported by the stage 2. The images obtained by camera units 5 and 6 are used, for example, to align the position of the laser L.

[0048] The drive unit 7 supports the laser irradiation unit 3 and multiple camera units 4, 5, and 6. The drive unit 7 causes the laser irradiation unit 3 and the multiple camera units 4, 5, and 6 to move along the Z direction.

[0049] The control unit 8 controls the operation of the stage 2, the laser irradiation unit 3, the multiple camera units 4, 5, and 6, and the drive unit 7. The control unit 8 is configured as a computer device including a processor, memory, storage device, and communication device. In the control unit 8, the processor executes software (programs) read from memory, controls the reading and writing of data in the memory and storage device, and manages communication performed by the communication device.

[0050] The display 150 has the functions of an input section for receiving information input from the user and a display section for displaying information to the user.

[0051] [Structure of the object]

[0052] The object 11 in this embodiment is as follows: Figure 2 and Figure 3The image shows a wafer 20. The wafer 20 includes a semiconductor substrate 21 and a functional element layer 22. In this embodiment, the wafer 20 is described as including the functional element layer 22; however, the wafer 20 may or may not include the functional element layer 22, or it may be a carrier wafer. The semiconductor substrate 21 has a front side 21a (second side) and a back side 21b (first side). The semiconductor substrate 21 is, for example, a silicon substrate. The functional element layer 22 is formed on the front side 21a of the semiconductor substrate 21. The functional element layer 22 includes a plurality of functional elements 22a arranged two-dimensionally along the front side 21a. The functional elements 22a are, for example, light-receiving elements such as photodiodes, light-emitting elements such as laser diodes, circuit elements such as memory, etc. The functional elements 22a may also be stacked in multiple layers and configured in three dimensions. Furthermore, although a notch 21c indicating the crystal orientation is provided in the semiconductor substrate 21, an orientation plane may be provided instead of the notch 21c.

[0053] The wafer 20 is cut along multiple lines 15 for each functional element 22a. When viewed from the thickness direction of the wafer 20, the multiple lines 15 pass between each of the multiple functional elements 22a. More specifically, when viewed from the thickness direction of the wafer 20, the lines 15 pass through the center (center in the width direction) of the grid line region 23. The grid line region 23 extends in the functional element layer 22 in a manner that passes between adjacent functional elements 22a. In this embodiment, the multiple functional elements 22a are arranged in a matrix along the front surface 21a, and the multiple lines 15 are set in a grid pattern. Furthermore, although the lines 15 are virtual lines, they can also be actually drawn lines.

[0054] [Structure of the laser irradiation unit]

[0055] like Figure 4 As shown, the laser irradiation unit 3 includes a light source 31, a spatial light modulator 32, and a focusing lens 33. The light source 31 outputs laser light L, for example, via pulse oscillation. The spatial light modulator 32 modulates the laser light L output from the light source 31. The spatial light modulator 32 is, for example, a spatial light modulator (SLM) of a reflective liquid crystal on silicon (LCOS). The focusing lens 33 focuses the laser light L modulated by the spatial light modulator 32. The focusing lens 33 can also be a correction ring lens.

[0056] In this embodiment, the laser irradiation unit 3 irradiates the wafer 20 with laser L from the back side 21b of the semiconductor substrate 21 along multiple lines 15, thereby forming two rows of modified regions 12a and 12b inside the semiconductor substrate 21 along the multiple lines 15. Modified region 12a is the modified region closest to the front side 21a among the two rows of modified regions 12a and 12b. Modified region 12b is the modified region closest to modified region 12a among the two rows of modified regions 12a and 12b, and is also the modified region closest to the back side 21b.

[0057] Two rows of modified regions 12a and 12b are adjacent in the thickness direction (Z direction) of the wafer 20. These two rows of modified regions 12a and 12b are formed by moving two focusing points C1 and C2 relative to the semiconductor substrate 21 along line 15. The laser L is modulated by a spatial light modulator 32, such that, for example, focusing point C2 is located behind focusing point C1 in the travel direction and on the incident side of laser L. The formation of the modified regions can be single-focus or multi-focus, and can involve one path or multiple paths.

[0058] The laser irradiation unit irradiates the wafer 20 with laser L from the back side 21b side of the semiconductor substrate 21 along each of the plurality of lines 15. As an example, relative to the semiconductor substrate 21, which is a single-crystal silicon <100> substrate with a thickness of 400 μm, two focusing points C1 and C2 are focused to positions 54 μm and 128 μm away from the front side 21a, respectively, and the wafer 20 is irradiated with laser L from the back side 21b side of the semiconductor substrate 21 along each of the plurality of lines 15. At this time, for example, if the condition is selected that the crack 14 covering the two rows of modified regions 12a, 12b reaches the front side 21a of the semiconductor substrate 21, the wavelength of the laser L is set to 1099 nm, the pulse width is 700 nm, and the repetition frequency is 120 kHz. Furthermore, the output of laser L at focal point C1 is set to 2.7W, and the output of laser L at focal point C2 is set to 2.7W. The relative moving speed of the two focal points C1 and C2 relative to the semiconductor substrate 21 is set to 800 mm / s. For example, when the number of processing paths is 5, for the aforementioned wafer 20, processing positions could be set as follows: ZH80 (position 328 μm from the front surface 21a), ZH69 (position 283 μm from the front surface 21a), ZH57 (position 234 μm from the front surface 21a), ZH26 (position 107 μm from the front surface 21a), and ZH12 (position 49.2 μm from the front surface 21a). In this case, for example, the wavelength of laser L could be 1080 nm, the pulse width 400 nsec, the repetition frequency 100 kHz, and the moving speed 490 mm / s.

[0059] The formation of such two rows of modified regions 12a, 12b and crack 14 is carried out under the following conditions. That is, in subsequent steps, for example, the semiconductor substrate 21 is thinned by grinding the back side 21b of the semiconductor substrate 21 and the crack 14 is exposed to the back side 21b, and the wafer 20 is cut into multiple semiconductor devices along multiple lines 15 respectively.

[0060] [Inspection of the camera unit's structure]

[0061] like Figure 5 As shown, the imaging unit 4 (imaging section) includes a light source 41, a reflector 42, an objective lens 43 (condenser lens), and a light detection unit 44. The imaging unit 4 captures an image of the wafer 20. The light source 41 outputs light I1 that is transmissive relative to the semiconductor substrate 21. The light source 41 is, for example, composed of 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 reflector 42 and passes through the objective lens 43, illuminating the wafer 20 from the back side 21b of the semiconductor substrate 21. At this time, the stage 2 supports the wafer 20, on which two rows of modified regions 12a and 12b are formed, as described above.

[0062] Objective lens 43 is used to focus light (transmitted light) I1, which is transmissive relative to semiconductor substrate 21, toward semiconductor substrate 21. Objective lens 43 allows light I1, which is reflected by the front surface 21a of semiconductor substrate 21, to pass through. That is, objective lens 43 allows light I1, which has propagated in semiconductor substrate 21, to pass through. The numerical aperture (NA) of objective lens 43 is, for example, 0.45 or greater. Objective lens 43 has a correction ring 43a. The correction ring 43a corrects aberrations caused by light I1 in semiconductor substrate 21, for example, by adjusting the distance between the multiple lenses constituting objective lens 43. The means of correcting aberrations is not limited to the correction ring 43a, but may also be other correction means such as a spatial light modulator. Light detection unit 44 detects light I1 transmitted from objective lens 43 and mirror 42. Light detection unit 44 is, for example, composed of an InGaAs camera, and detects light I1 in the near-infrared region. Among them, the means of detecting (photographing) light I1 in the near-infrared region is not limited to InGaAs cameras, but can also be other imaging means of transmission imaging, such as transmission confocal microscopes.

[0063] Camera unit 4 can capture images of each of the two rows of modified regions 12a and 12b, as well as the front ends of multiple cracks 14a, 14b, 14c, and 14d (details described later). Crack 14a extends from modified region 12a towards the front side 21a. Crack 14b extends from modified region 12a towards the back side 21b. Crack 14c extends from modified region 12b towards the front side 21a. Crack 14d extends from modified region 12b towards the back side 21b.

[0064] [Structure of the camera unit for alignment and correction]

[0065] like Figure 6 As shown, the imaging unit 5 includes a light source 51, a reflector 52, a lens 53, and a light detection unit 54. The light source 51 outputs light I2 that is transmissive relative to the semiconductor substrate 21. The light source 51 is, for example, composed of a halogen lamp and a filter, and outputs light I2 in the near-infrared region. The light source 51 may also be shared with the light source 41 of the imaging unit 4. The light I2 output from the light source 51 is reflected by the reflector 52 and passes through the lens 53, illuminating the wafer 20 from the back side 21b of the semiconductor substrate 21.

[0066] Lens 53 allows light I2, reflected by the front surface 21a of semiconductor substrate 21, to pass through. That is, lens 53 allows light I2, after propagating within semiconductor substrate 21, to pass through. The numerical aperture of lens 53 is 0.3 or less. That is, the numerical aperture of the objective lens 43 of imaging unit 4 is larger than the numerical aperture of lens 53. Light detection unit 54 detects the light I2 passing through lens 53 and mirror 52. Light detection unit 54 is, for example, an InGaAs camera, and detects light I2 in the near-infrared region.

[0067] Under the control of the control unit 8, the imaging unit 5 illuminates the wafer 20 with light I2 from the back side 21b and detects the light I2 returning from the front side 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 illuminates the wafer 20 with light I2 from the back side 21b and detects the light I2 returning from the formation locations of the modified regions 12a and 12b on the semiconductor substrate 21, thereby acquiring an image of the region containing the modified regions 12a and 12b. These images are used for aligning the irradiation position of the laser L. The imaging unit 6 has the same structure as the imaging unit 5, except that it has a lower magnification (e.g., 6x in the imaging unit 5, 1.5x in the imaging unit 6) compared to the lens 53, and is used for alignment in the same way.

[0068] [Inspection of the shooting principle of the camera unit]

[0069] use Figure 5 The camera unit 4 shown is as follows: Figure 7 As shown, for a crack 14 spanning two rows of modified regions 12a and 12b that reaches the semiconductor substrate 21 on the front side 21a, the focal point F (the focal point of the objective lens 43) is moved from the back side 21b to the front side 21a. In this case, if the focal point F is focused from the back side 21b to the tip 14e of the crack 14 extending from the modified region 12b to the back side 21b, the tip 14e ( Figure 7(Image on the right). However, even when focusing from the back side 21b side F to the crack 14 itself and the front end 14e of the crack 14 reaching the front side 21a, confirmation is not possible. Figure 7 (Image on the left). Alternatively, if the focus F is shifted from the back side 21b to the front side 21a of the semiconductor substrate 21, the functional element layer 22 can be identified.

[0070] And, using Figure 5 The camera unit 4 shown is as follows: Figure 8 As shown, for the semiconductor substrate 21 where the crack 14 spanning the two rows of modified regions 12a and 12b does not reach the front side 21a, the focus F is moved from the back side 21b to the front side 21a. In this case, even if the focus F is focused from the back side 21b to the tip 14e of the crack 14 extending from the modified region 12a to the front side 21a, the tip 14e cannot be identified. Figure 8 (Image on the left). However, if the focus F is focused from the back side 21b to the area located on the opposite side of the front side 21a (i.e., the area located on the side of the functional element layer 22 relative to the front side 21a), and a virtual focus Fv symmetrical to the focus F about the front side 21a is located at the front end 14e, then the front end 14e can be confirmed ( Figure 8 (Image on the right). In addition, the virtual focus Fv is a point that takes into account the refractive index of the semiconductor substrate 21 and is symmetrical with respect to the focus F about the front surface 21a.

[0071] The inability to identify crack 14 as described above is presumably because the width of crack 14 is smaller than the wavelength of light I1, which serves as illumination. Figure 9 and Figure 10 These are SEM (Scanning Electron Microscope) images of the modified region 12 and crack 14 formed inside the semiconductor substrate 21, which is a silicon substrate. Figure 9 (b) is Figure 9 A magnified image of region A1 shown in (a). Figure 10 (a) is Figure 9 A magnified image of region A2 shown in (b). Figure 10 (b) is Figure 10 A magnified image of region A3 shown in (a). As such, the width of crack 14 is approximately 120 nm, which is smaller than the wavelength of light I1 in the near-infrared region (e.g., 1.1–1.2 μm).

[0072] The camera principle envisioned based on the above is as follows. Figure 11 As shown in (a), if the focal point F is placed in the air, light I1 will not return, thus resulting in a completely black image. Figure 11 (The image to the right of (a)). Figure 11 As shown in (b), if the focal point F is located inside the semiconductor substrate 21, the light I1 reflected by the front surface 21a will return, thus obtaining a clean white image. Figure 11 (Image to the right of (b)). Figure 11 As shown in (c), if the focus F is focused from the back side 21b to the modified region 12, the modified region 12 will cause absorption and scattering of a portion of the light I1 reflected back from the front side 21a, resulting in an image where the modified region 12 appears completely black against a white background. Figure 11 (Image to the right of (c)).

[0073] like Figure 12 As shown in (a) and (b), if the focal point F is focused from the back side 21b to the tip 14e of the crack 14, the light will be confined to the vicinity of the tip 14e due to optical specificities (stress concentration, distortion, atomic density discontinuities, etc.) generated near the tip 14e. As a result, a portion of the light I1 reflected back from the front side 21a will be scattered, reflected, interfered with, absorbed, etc., thus obtaining an image in which the tip 14e appears black against a clean white background. Figure 12 (Images to the right of (a) and (b)). Figure 12 As shown in (c), if the focus F is adjusted from the back side 21b to a portion beyond the vicinity of the front end 14e of the crack 14, at least a portion of the light I1 reflected by the front side 21a will return, thus obtaining a clean white image. Figure 12 (Image to the right of (c)).

[0074] [Implementation of Internal Observation]

[0075] Figure 13 It is a diagram representing the object that has formed the modified region. Figure 13 (a) is a cross-sectional photograph of the object cut in a manner that exposes the modified region. Figure 13 (b) is an example of an image of an object obtained by taking a photograph using light transmitted from the object. Figure 13 (c) is another example of an image of an object obtained by photographing light transmitted from the object. For example... Figure 13 As shown in (a), the modified region 12 formed on the object (here, the semiconductor substrate 21) by focusing the laser L includes: a defect (Void) region 12m on the side opposite to the incident surface of the laser L on the semiconductor substrate 21, i.e., the front side 21a side; and a defect-above region 12n on the side closer to the incident surface of the laser L than the defect region 12m, i.e., the back side 21b side.

[0076] When the semiconductor substrate 21, which has such a modified region 12, is imaged using light I1 that is transmissive relative to the semiconductor substrate 21, such as Figure 13 As shown in (b) and (c), images of crack 14k extending along directions intersecting the Z and X directions (at an angle relative to the X direction) can sometimes be confirmed. When viewed from the Z direction, crack 14k appears as... Figure 13 In example (b), it is roughly parallel to the Y direction. Figure 13 In example (c), the cracks are slightly tilted relative to the Y direction. When the semiconductor substrate 21 is photographed at multiple locations while the focus point of the light I1 is moved along the Z direction, the images of these cracks 14k can be clearly detected within a defined range in the Z direction, compared with the modified region 12.

[0077] Figure 14 This is a graph showing the modified region and crack location along the Z-axis. Figure 14 In the diagram, the lower end of the defect, the upper end of the defect, the lower end of the region above the defect, and the upper end of the region above the defect are drawn based on actual measured values ​​obtained through cross-sectional observation. The lower end refers to the end on the front side 21a, and the upper end refers to the end on the back side 21b. Therefore, for example, the lower end of the region above the defect refers to the end of the region above the defect 12n on the front side 21a.

[0078] also, Figure 14 The diagrams for direct observation and back-reflection observation are calculated based on the amount of movement (hereinafter sometimes simply referred to as "movement") of the objective lens 43 in the Z direction when the internal image containing a clear image of crack 14k is captured using the image captured by light I1. As an example, the value is obtained through AI-based image judgment. Direct observation is the case where light I1 is incident from the back side 21b and the focal point of light I1 is directly aligned with crack 14k without reflection from the front side 21a (in the example above, the focal point F is aligned with crack 14k from the back side 21b). Back-reflection observation is the case where light I1 is incident from the back side 21b and the focal point of light I1 reflected by the front side 21a is aligned with crack 14k (in the example above, the focal point F is aligned with the area opposite to the back side 21b from the back side 21b relative to the front side 21a, and the virtual focal point Fv symmetrical about the front side 21a and the focal point F is aligned with crack 14k).

[0079] like Figure 14As shown, in direct observation, in four different cases C1 to C4 where the modified region 12 is located in the Z direction, crack 14k is detected between the lower end and the upper end of the region above the defect. In back-reflection observation, in case C1, crack 14k is detected at approximately the same position as the lower end of the region above the defect; in cases C2 to C4, crack 14k is detected between the lower end and the upper end of the region above the defect. The width of the modified region 12 in the Z direction is the distance between the lower end of the defect and the upper end of the region above the defect. Thus, crack 14k can be detected more accurately in the Z direction compared to the modified region 12 itself.

[0080] Therefore, by acquiring the amount of movement of the internal image when the crack 14k appears in the Z direction, information about the location of the modified region 12 can be obtained more accurately. Figure 14 The vertical axis represents the distance from the back surface, where the back surface is the back surface relative to the incident surface of light I1, and for the semiconductor substrate 21, it is the front surface 21a. Furthermore, Figure 15 It is obtained by plotting the detection results under case C1 based on the cross-sectional photograph.

[0081] In this embodiment, based on the findings described above, information about the location of the modified region 12 is obtained by internally observing and detecting the crack 14k. Next, the observation method of this embodiment will be described. In this observation method, the crack 14k is the target crack being inspected.

[0082] Figure 16 This is a flowchart illustrating an example of the observation method of this embodiment. For example... Figure 16 As shown, here, in order to prepare the object with the modified region, laser processing is performed (step S11: preparation step). However, as a step in the observation method, the laser processing step is not essential. For example, the object with the modified region 12 formed using other laser processing devices (or using laser processing device 1 at another time) can also be prepared.

[0083] In step S11, as Figure 17As shown, 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 21b and the front surface 21a is provided on the semiconductor substrate 21. The semiconductor substrate 21 is supported by the stage 2 with the back surface 21b facing the laser irradiation unit 3 so that the back surface 21b is the incident surface of the laser L. In this state, the control unit 8 controls the laser irradiation unit 3 and the moving mechanism of the drive unit 7 and / or the stage 2 to move the semiconductor substrate 21 relative to the laser in the X direction, so that the focusing point C of the laser L moves relative to the semiconductor substrate 21 along the line 15.

[0084] At this time, the control unit 8 displays a pattern for causing the spatial light modulator 32 to divide the laser L into multiple (here, two) lasers L1 and L2. Consequently, within the semiconductor substrate 21, focusing points C1 and C2 for each of the lasers L1 and L2 are formed such that they are spaced apart by a distance Dz in the Z direction and a distance Dx in the X direction. As a result, multiple (here, two rows) modified regions 12a and 12b are formed along line 15 in the semiconductor substrate 21. Therefore, the X direction is the processing advance direction for the focusing points C1 and C2.

[0085] Thus, here, the control unit 8, through control of the laser irradiation unit 3 (irradiation unit), irradiates the semiconductor substrate 21 with laser L along the extension direction of line 15, i.e., the X direction, and performs laser processing to form multiple modified regions 12 arranged along the X direction on the semiconductor substrate 21, and to extend cracks (cracks 14, 14k) from the modified regions 12. Figure 17 The functional element layer 22 formed on the front side 21a of the semiconductor substrate 21 is omitted in the accompanying drawings.

[0086] Next, internal observation is performed. That is, in the following step, the semiconductor substrate 21 is moved to the observation position (step S12). More specifically, the control unit 8 moves the semiconductor substrate 21 relative to the objective lens 43 of the imaging unit 4 by controlling the movement mechanism of the drive unit 7 and / or the stage 2. If a semiconductor substrate 21 with the modified region 12 formed is prepared separately, the semiconductor substrate 21 can also be placed at the observation position by the user, for example.

[0087] Next, as Figure 18As shown, an image of the semiconductor substrate 21 is captured using light (transmitted light) I1 that is transmissive relative to the semiconductor substrate 21 (step S13: image capture step). In this step S13, by controlling the image capture unit 4 (image capture section), the following image capture process is performed: light I1 is incident from the back surface 21b of the semiconductor substrate 21 into the interior of the semiconductor substrate 21, and the image capture process is performed using light I1 to capture the crack 14k, i.e., the target crack, which extends from the crack extending from the modified region 12 in a direction intersecting the Z and X directions. The Y direction is an example of a direction that intersects the X direction, which is the processing advance direction, and the Z direction, which intersects the back surface 21b and the front surface 21a.

[0088] 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, so that the focusing point of light I1 is located at multiple positions inside the semiconductor substrate 21, thereby capturing images of the semiconductor substrate 21 and acquiring multiple internal images ID. In this embodiment, the objective lens 43 moves integrally with the imaging unit 4. Therefore, moving the imaging unit 4 also moves the objective lens 43, and the amount of movement of the imaging unit 4 is equal to the amount of movement of the objective lens 43.

[0089] At this time, the control unit 8 controls the drive unit 7 to move the imaging unit 4 in the Z direction, while moving the focusing point (focal point F, virtual focal point Fv) of light I1 in the Z direction, and performs multiple imaging operations on the semiconductor substrate 21. The range in which the focusing point of light I1 is moved can be the entire thickness range of the semiconductor substrate 21, but here, during the laser processing in step S11, a portion of the range RA can be selected. This portion of the range RA includes the Z-direction positions where the focusing points C1 and C2 of lasers L1 and L2 are aligned in order to form the modified regions 12a and 12b. The interval between the movement of the imaging unit 4 in the Z direction during multiple imaging operations, i.e., the imaging interval of the semiconductor substrate 21, is arbitrary, but from the viewpoint of more accurately detecting crack 14k, it is preferable to set it more precisely. The imaging interval is, for example, within 1 μm, and here it is 0.2 μm.

[0090] Furthermore, here, the control unit 8 controls the imaging unit 4 and the driving unit 7 to perform direct observation and back-reflection observation of the semiconductor substrate 21. More specifically, the control unit 8 first performs the following first imaging process: light I1 is incident on the semiconductor substrate 21 from the back side 21b, and the imaging unit 4 is moved along the Z direction. While moving the focal point (focus F) of the light I1 that has not been reflected by the front side 21a from the back side 21b side to the front side 21a side, images are captured on the semiconductor substrate 21 at multiple positions in the Z direction, and multiple first internal images ID1 are acquired as internal image IDs. This first imaging process is direct observation.

[0091] Furthermore, the control unit 8 performs the following second imaging process: light I1 is incident on the object from the back surface 21b, and the imaging unit 4 is moved along the Z direction. While moving the focal point (virtual focus Fv) of the light I1 reflected by the front surface 21a from the front surface 21a side towards the back surface 21b side, images are captured on the semiconductor substrate 21 at multiple positions, thereby acquiring multiple second internal images ID2 as internal image IDs. This second imaging process is an observation performed from the back surface (here, referred to as the front surface 21a in the structure of the semiconductor substrate 21) relative to the incident surface of light I1, therefore it is a back reflection observation.

[0092] In the next step, image data regarding the internal image IDs acquired through step S13 is saved (step S14). As described above, in step S13, the control unit 8 performs image capture while controlling the drive unit 7 to move the camera unit 4 (i.e., the focusing point of light I1) along the Z direction. Therefore, the control unit 8 can acquire the amount of movement of the camera unit 4 when capturing each internal image. Here, information about this amount of movement can be associated with each internal image ID and saved as image data. The image data can be saved 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.

[0093] 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 in which the focusing point of the light I1 is aligned with the back surface 21b of the semiconductor substrate 21, so that the focusing point of the light I1 is aligned with the desired position inside the semiconductor substrate 21.

[0094] Next, the control unit 8 inputs camera data from the designated storage device (step S15). Then, the control unit 8 determines the formation state of the crack 14k (step S16). Here, as an example, the control unit 8 automatically determines the internal image ID with the relatively clear image of the crack 14k among multiple internal image IDs through image recognition (performing AI judgment). Here, an example of an algorithm for detecting cracks and modified regions by AI judgment will be explained.

[0095] Figure 20 and Figure 21 This is a diagram illustrating crack detection. Figure 20 The illustration shows the internal observation results (internal image of semiconductor substrate 21). Control unit 8 for... Figure 20In the internal image of the semiconductor substrate 21 shown in (a), firstly, a group of straight lines 140 is detected. In detecting the group of straight lines 140, algorithms such as Hough transform or LSD (Line Segment Detector) can be used, for example. Hough transform is a method that detects straight lines by assigning weights to lines that pass through more feature points, while detecting all straight lines passing through all points in the image. LSD is a method that calculates the slope and angle of brightness values ​​within the image to estimate regions that constitute line segments, and detects straight lines by approximating these regions as rectangles.

[0096] Next, control unit 8, through, as... Figure 21 As shown, the similarity between the line group 140 and the crack line is calculated, and crack 14 is detected from the line group 140. Crack line, as... Figure 21 As shown in the image above, the line has a characteristic of being very bright both before and after the crack line in the Y direction. Therefore, the control unit 8 compares the brightness values ​​of all pixels in the detected line group 140 with the before and after values ​​in the Y direction, and uses the number of pixels whose difference is above a threshold in both directions as a similarity score. Then, the line group 140 with the highest similarity score to the crack line among the detected line groups 140 is taken as the representative value of that image. The higher the representative value, the higher the probability of the presence of the crack 14. The control unit 8 compares the representative values ​​of multiple images and selects the image with the relatively higher score as a crack image candidate.

[0097] Figures 22-24 This is a diagram illustrating the detection of scars. Figure 22 The illustration shows the internal observation results (internal image of semiconductor substrate 21). Control unit 8 for... Figure 22 The image of the interior of the semiconductor substrate 21 shown in (a) is used to detect feature points 250 by identifying the corners (convergence of edges) within the image as key points and detecting their position, size, and orientation. Known methods for detecting feature points include Eigen, Harris, Fast, SIFT, SURF, STAR, MSER, ORB, and AKAZE.

[0098] Here, as Figure 23 As shown, the scratches 280, due to their circular, rectangular, and other shapes arranged at certain intervals, have strong corner features. Therefore, by statistically analyzing the feature values ​​of feature points 250 within the image, scratches 280 can be detected with high precision. Figure 24 As shown, by comparing the sum of the feature values ​​of each image obtained by imaging while shifting in the depth direction, the variation in the crack displacement of each modified layer can be identified. The control unit 8 deduces the location of the scratch 280 from the peak of this variation. By statistically analyzing the feature values ​​in this way, not only the location of the scratch can be deduced, but also the pulse interval can be calculated.

[0099] The above AI judgment refers to crack 14 and scratch 280 extending along the X direction. However, crack 14k extending along the direction intersecting the Z and X directions can also be judged using the same algorithm by comparing the representative values ​​of multiple internal image IDs, and the internal image ID with the relatively higher score is judged as the relatively clear internal image ID of crack 14k.

[0100] As an example, Figure 19 These are multiple internal image IDs obtained by taking pictures at different positions along the Z-axis. Figure 19 Centered on the imaging position of the internal image IDd shown in (d), (c) is the internal image IDc located 1 μm away from the back side 21b, (b) is the internal image IDb located 3 μm away from the back side 21b, (a) is the internal image IDa located 5 μm away from the back side 21b, (e) is the internal image IDe located 1 μm away from the front side 21a, (f) is the internal image IDf located 3 μm away from the front side 21a, and (g) is the internal image IDg located 5 μm away from the front side 21a. Here, the imaging position is a value inside the semiconductor substrate 21.

[0101] exist Figure 19 In the example shown, the image of crack 14k is the clearest in the internal image IDd. Based on this, the control unit 8 can determine that the internal image IDd has a relatively high score and the image of crack 14k is relatively clear (i.e., it can be determined that 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 crack 14k based on the amount of movement when the internal image IDd is captured.

[0102] Thus, the control unit 8 performs the following calculation: based on multiple internal image IDs and the movement amount of the camera unit 4 when acquiring each internal image ID, it calculates the position of the crack 14k, i.e., the object crack, in the Z direction, which extends in a direction intersecting the Z and X directions. More specifically, in the calculation process, the control unit 8 determines the internal image ID in which the image of crack 14k is clear among the multiple internal image IDs, and calculates the crack position based on the movement amount when acquiring the determined internal image ID. The crack position can be calculated, for example, by multiplying the movement amount by a predetermined correction factor. The correction factor can be obtained, for example, based on the NA of the objective lens 43, the refractive index of the semiconductor substrate 21, etc.

[0103] The control unit 8 is capable of calculating the crack position of the crack 14k as described above on both the first internal image ID1 acquired through direct observation and the second internal image ID2 acquired through back reflection observation. Therefore, the control unit 8 can calculate the crack position of the crack 14k located on the back side 21b corresponding to the first internal image ID1, and the crack position of the crack 14k located on the front side 21a corresponding to the second internal image ID2.

[0104] That is, in this case, the control unit 8 performs a first arithmetic process and a second arithmetic process. In the first arithmetic process, it determines the first internal image with a clear crack 14k among multiple first internal images ID1, and calculates the first crack position Z1 as the crack location based on the movement amount of the camera unit 4 when the determined first internal image is obtained by imaging. In the second arithmetic process, it determines the second internal image with a clear crack 14k among multiple second internal images ID2, and calculates the second crack position Z2 as the crack location based on the movement amount of the camera unit 4 when the determined second internal image is obtained by imaging (for an example of the first crack position Z1 and the second crack position Z2, see [reference]). Figure 15 The distance between the first crack position Z1 located on the back side 21b and the second crack position Z2 located on the front side 21a defines the width of the portion (crack initiation portion) in the modified region 12 where the crack 14k is formed.

[0105] Next, in step S16, the control unit 8 calculates the position of the modified region 12 based on the acquired crack location, etc. That is, here, the control unit 8 performs the following calculation process: based on the formation conditions of the modified region 12 (here, the processing conditions of laser processing) and the crack location, it calculates at least one of the following: the position of the end of the modified region 12 on the back side 21b side (the upper end of the defect upper region) in the Z direction, the position of the end of the modified region 12 on the front side 21a side (the lower end of the defect) in the Z direction, and the width of the modified region 12 in the Z direction (the interval between the upper end of the defect upper region and the lower end of the defect).

[0106] Here, the control unit 8 calculates the first crack position Z1 of the crack 14k (upper crack) on the back side 21b based on direct observation, and calculates the second crack position Z2 of the crack 14k (lower crack) on the front side 21a based on back reflection observation. Therefore, the control unit 8 can calculate the width of the crack initiation portion inside the semiconductor substrate 21 by using the interval between the first crack position Z1 of the upper crack and the second crack position Z2 of the lower crack.

[0107] Then, the control unit 8, for example, can calculate the width of the modified region 12 inside the semiconductor substrate 21 in the Z direction by multiplying the width of the crack initiation portion obtained from the calculation by a coefficient related to the processing conditions of the laser processing. This coefficient is determined, for example, based on various factors affecting the formation of the modified region 12, such as the wavelength of the laser L during laser processing, the aberration correction amount, the pulse width, and the pulse energy. In one example, this coefficient is around 3.0.

[0108] In this way, during the calculation process, the control unit 8 can calculate the width of the modified region 12 in the Z direction based on the formation conditions of the modified region 12 (the processing conditions of laser processing) and the interval between the first crack position Z1 and the second crack position Z2.

[0109] On the other hand, the control unit 8 can calculate the position of the lower end of the front side 21a of the modified region 12 by subtracting the assumed overall width of the modified region 12, i.e., the assumed modified region width, from the first crack position Z1 of the upper crack. The assumed modified region width can be determined, for example, based on various conditions that affect the formation of the modified region 12, such as the wavelength of the laser L during laser processing, the aberration correction amount, the pulse width, and the pulse energy. The assumed modified region width is, for example, about 20 μm.

[0110] Furthermore, the control unit 8 can calculate the position of the lower end of the front surface 21a of the modified region 12 by subtracting the assumed width of the defect region 12m, i.e., the assumed defect region width, from the second crack position Z2 below the crack. The assumed defect region width can be determined, for example, based on various conditions affecting the formation of the modified region 12, such as the wavelength of the laser L during laser processing, the aberration correction amount, the pulse width, and the pulse energy. An example of the assumed defect region width is approximately 10 μm.

[0111] Furthermore, the control unit 8 can calculate the position of the upper end of the back surface 21b side of the modified region 12 by adding the assumed width of the defect upper region 12n to the second crack position Z2 of the lower crack. The assumed width of the defect upper region can be determined, for example, based on various conditions affecting the formation of the modified region 12, such as the wavelength of the laser L during laser processing, aberration correction amount, pulse width, and pulse energy. An example of the assumed width of the defect upper region is approximately 10 μm.

[0112] As described above, in step S16, the control unit 8 calculates and obtains various information regarding the position of the modified region 12. In the next step, the control unit 8 outputs the judgment result from step S16 to an arbitrary storage device (step S17) and saves it in that storage device (step S18). Then, as needed, the display 150 displays various information in a state that can accept user input (step S19), completing the processing. The information displayed on the display 150 includes, for example, the first crack position Z1, the second crack position Z2, the width of the starting portion, 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 performs display processing to make the display 150 display information about the crack position by controlling the display 150.

[0113] The observation method using the laser processing apparatus 1 is concluded in the manner described above. In this embodiment, the observation method is performed using the imaging unit 4, the driving unit 7, and the control unit 8 in the laser processing apparatus 1. In other words, the laser processing apparatus 1 comprises the imaging unit 4, the driving unit 7, and the control unit 8, wherein the imaging unit 4 is used to image the semiconductor substrate 21 using light I1 that is transmissive relative to the semiconductor substrate 21, the driving unit 7 is used to move the imaging unit 4 relative to the semiconductor substrate 21, and the control unit 8 is used to control at least the imaging unit 4 and the driving unit 7 (see reference). Figure 1 ).

[0114] As explained above, in the semiconductor substrate 21, which is the object of observation in the observation method of this embodiment and the observation apparatus 1A that implements the observation method, modified regions 12 arranged along the X direction and cracks 14, 14k extending from the modified regions 12 are formed. For such a semiconductor substrate 21, the cracks 14k extending in directions intersecting the Z and X directions can be imaged using light I1 transmitted from the semiconductor substrate 21. The cracks 14k intersecting the Z and X directions can be imaged (detected) more accurately in the Z direction than the modified regions 12 themselves. Therefore, for example, if information such as the amount of movement of the imaging unit 4 when imaged on the cracks 14k is obtained, information about the position of the modified regions 12 can be obtained more accurately based on this amount of movement.

[0115] Furthermore, the observation device 1A of this embodiment includes a drive unit 7 for moving the focusing point of light I1 relative to the semiconductor substrate 21. During image processing, the control unit 8 controls the imaging unit 4 and the drive unit 7 to move the imaging unit 4 along the Z direction, positioning the focusing point of light I1 at multiple locations within the semiconductor substrate 21 to capture images of the semiconductor substrate 21 and acquire multiple internal image IDs. After the image processing, the control unit 8 performs the following calculation: based on the multiple internal image IDs and the amount of movement of the imaging unit 4 in the Z direction when each internal image ID is acquired, it calculates the position of the crack 14k in the Z direction, i.e., the crack position (first crack position Z1 and second crack position Z2). In this way, information about the position of the modified region 12 can be obtained more accurately based on the amount of movement of the imaging unit 4 when the crack 14k is captured.

[0116] Furthermore, in the observation device 1A of this embodiment, during the calculation process, the control unit 8 determines the internal image of the crack 14k that is clear among multiple internal image IDs, and calculates the crack position of the crack 14k based on the amount of movement of the camera unit 4 when the determined internal image is obtained by imaging. In this way, by using the control unit 8 to determine the internal image of the crack 14k that is clear, the position of the crack 14k can be calculated more accurately.

[0117] Furthermore, in the observation device 1A of this embodiment, the control unit 8 performs the following calculation process after the computational processing: based on the formation conditions of the modified region 12 and the crack position of the crack 14k, it calculates at least one of the following: the position of the end of the modified region 12 on the back side 21b side in the Z direction, the position of the end of the modified region 12 on the front side 21a side in the Z direction, and the width of the modified region 12 in the Z direction. The shape and size of the modified region 12 may sometimes change in accordance with the formation conditions of the modified region, such as the laser processing conditions (e.g., the wavelength, pulse width, pulse energy, and aberration correction amount of the laser). Therefore, by utilizing the formation conditions of the modified region 12, such as the laser processing conditions, and the position of the crack 14k, information about the position of the modified region 12 can be obtained more accurately.

[0118] Furthermore, in the observation device of this embodiment, during the image processing, the control unit 8 performs a first image processing and a second image processing. In the first image processing, light I1 is incident on the semiconductor substrate 21 from the back side 21b, and the imaging unit 4 is moved. As a result, the focusing point of the light I1 that has not been reflected by the front side 21a is moved from the back side 21b side to the front side 21a side, and images of the semiconductor substrate 21 are captured at multiple positions, acquiring multiple first internal images ID1 as internal image IDs. In the second image processing, light I1 is incident on the semiconductor substrate 21 from the back side 21b, and the imaging unit 4 is moved. As a result, the focusing point of the light I1 that has been reflected by the front side 21a is moved from the front side 21a side to the back side 21b side, and images of the semiconductor substrate 21 are captured at multiple positions, acquiring multiple second internal images ID2 as internal image IDs.

[0119] In this way, if internal images of the semiconductor substrate 21 are obtained by using light I1 incident from the back side 21b of the semiconductor substrate 21 but not reflected by the front side 21a, and by using light I1 incident from the back side 21b of the semiconductor substrate 21 and reflected by the front side 21a, respectively, information about the location of the modified region 12 can be obtained more accurately by using the crack location obtained based on the amount of movement of the imaging unit 4 when the internal image is obtained.

[0120] Furthermore, in the observation device 1A of this embodiment, during the calculation process, the control unit 8 performs a first calculation process and a second calculation process. In the first calculation process, it determines a first internal image from among multiple first internal images ID1 where the crack 14k is clearly visible, and calculates the first crack position Z1, which is the crack location, based on the movement amount of the camera unit 4 when the determined first internal image is captured. In the second calculation process, it determines a second internal image from among multiple second internal images ID2 where the crack 14k is clearly visible, and calculates the second crack position Z2, which is the crack location, based on the movement amount of the camera unit 4 when the determined second internal image is captured. Furthermore, in the estimation process, the control unit 8 can estimate the width of the modified region 12 in the Z direction based on the formation conditions of the modified region 12 and the interval between the first crack position Z1 and the second crack position Z2. As described above, in this case, information about the width of the modified region 12 can be obtained more accurately based on the interval between the first crack location Z1 obtained by direct observation and the second crack location Z2 obtained by back reflection observation.

[0121] Furthermore, the observation device 1A of this embodiment also includes a display 150 for displaying information. Moreover, after computational processing, the control unit 8 can also perform display processing by controlling the display 150 to display information about the crack location. In this case, the user can obtain information about the crack location through the display 150. The crack location information includes at least one of various types of information, including the crack location itself and information about the location of the modified region 12 that can be deduced based on the crack location.

[0122] The above-described embodiments are intended to illustrate one aspect of the present invention. Therefore, the present invention is not limited to the above-described embodiments and can be modified in any way.

[0123] For example, in the above embodiment, a drive unit 7 is shown as a means for moving the objective lens 43 relative to the semiconductor substrate 21 in the Z direction. This means for moving the objective lens 43 together with the imaging unit 4. However, for example, an actuator may be used to move the objective lens 43 only in the Z direction.

[0124] Furthermore, in the above embodiment, an example was described where the control unit 8 automatically performs image judgment in step S16. However, it is also possible for the control unit 8 to obtain the crack position of crack 14k based on the user's judgment result. In this case, the control unit 8, for example, causes the display 150 to display multiple internal image IDs and displays information prompting the user to judge (select) the internal image with the clearest image of crack 14k from the multiple internal image IDs. The control unit 8 can also accept the judgment result as input through the display 150 and calculate the crack position of crack 14k based on the movement amount of the internal image ID corresponding to the judgment result. In this case, the display 150 is both a display unit for displaying information and an input receiving unit for receiving input. In this case, the processing load for image recognition and other operations performed by the control unit 8 is reduced.

[0125] Furthermore, in the above embodiment, in step S13, the modified region 12 is observed by both direct observation and back-reflection observation, obtaining 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-reflection observation may be performed. In this case, since one of the first internal image ID1 and the second internal image ID2 can be obtained, the position and width of the end of the modified region 12 can also be deduced based on that one.

Claims

1. An observation device, characterized in that, include: An imaging unit for capturing an image of the object using transmitted light that is transmissible relative to the object; A control unit for at least controlling the camera unit; and A movable part for moving a condenser lens relative to the object, wherein the condenser lens is used to focus the transmitted light onto the object. The object has a first surface and a second surface opposite to the first surface. The object has modified regions arranged in the X direction along the first and second surfaces, and cracks extending from the modified regions. The control unit controls the camera unit to perform the following imaging process: the transmitted light is incident from the first surface into the interior of the object, and the transmitted light is used to image a crack in the object, wherein the crack is a crack extending in the Z direction intersecting the first and second surfaces and in the X direction intersecting the X direction. In the image processing, the control unit controls the imaging unit and the moving unit to move the condenser lens relative to each other along the Z direction, so that the focusing point of the transmitted light is located at multiple positions inside the object to capture an image of the object, thereby acquiring multiple internal images. The control unit performs the following calculation after the image processing: 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, it calculates the crack position, which is the location of the object crack in the Z direction. In the calculation process, the control unit determines the internal image of the object crack that is clear among the multiple internal images, and calculates the crack position based on the amount of movement of the condenser lens when the determined internal image is captured.

2. The observation device as described in claim 1, characterized in that: The control unit performs the following calculation process after the calculation: based on the formation conditions of the modified region and the location of the crack, it calculates at least one of the following: the position of the end of the first surface side of the modified region in the Z direction, the position of the end of the second surface side of the modified region in the Z direction, and the width of the modified region in the Z direction.

3. The observation device as described in claim 1, characterized in that: In the aforementioned camera processing, the control unit executes the first camera processing and the second camera processing, wherein, In the first imaging process, the transmitted light is incident on the object from the first surface, and the condenser lens is moved relative to it along the Z direction. This causes the focal point of the transmitted light, which has not been reflected by the second surface, to move from the first surface side to the second surface side, while simultaneously capturing images of the object at multiple positions, thereby acquiring multiple first internal images as the internal images. In the second imaging process, the transmitted light is incident on the object from the first surface, and the condenser lens is moved relative to it along the Z direction. This causes the focal point of the transmitted light reflected from the second surface to move from the second surface side to the first surface side, while imaging the object at multiple positions, thereby acquiring multiple second internal images as the internal images.

4. The observation device as described in claim 2, characterized in that: In the aforementioned camera processing, the control unit executes the first camera processing and the second camera processing, wherein, In the first imaging process, the transmitted light is incident on the object from the first surface, and the condenser lens is moved relative to it along the Z direction. This causes the focal point of the transmitted light, which has not been reflected by the second surface, to move from the first surface side to the second surface side, while simultaneously capturing images of the object at multiple positions, thereby acquiring multiple first internal images as the internal images. In the second imaging process, the transmitted light is incident on the object from the first surface, and the condenser lens is moved relative to it along the Z direction. This causes the focal point of the transmitted light reflected from the second surface to move from the second surface side to the first surface side, while imaging the object at multiple positions, thereby acquiring multiple second internal images as the internal images.

5. The observation device as described in claim 3, characterized in that: In the aforementioned arithmetic processing, the control unit executes the first arithmetic processing and the second arithmetic processing, wherein, In the first calculation process, a first internal image with a clear object crack is selected from among the multiple first internal images. Based on the amount of movement of the condenser lens when the selected first internal image is captured, a first crack position is calculated as the crack location. In the second calculation process, a second internal image with a clear object crack is selected from among the multiple second internal images. Based on the amount of movement of the condenser lens when the selected second internal image is captured, a second crack position is calculated as the crack location. The control unit calculates the width of the modified region in the Z direction based on the formation conditions of the modified region and the interval between the first crack position and the second crack position.

6. The observation device as described in claim 4, characterized in that: In the aforementioned arithmetic processing, the control unit executes the first arithmetic processing and the second arithmetic processing, wherein, In the first calculation process, a first internal image with a clear object crack is selected from among the multiple first internal images. Based on the amount of movement of the condenser lens when the selected first internal image is captured, a first crack position is calculated as the crack location. In the second calculation process, a second internal image with a clear object crack is selected from among the multiple second internal images. Based on the amount of movement of the condenser lens when the selected second internal image is captured, a second crack position is calculated as the crack location. The control unit calculates the width of the modified region in the Z direction based on the formation conditions of the modified region and the interval between the first crack position and the second crack position.

7. The observation device as described in any one of claims 1 to 6, characterized in that: It also includes a display unit for displaying information. The control unit controls the display unit after the computational processing to perform display processing that causes the display unit to display information about the location of the crack.

8. An observation device, characterized in that, include: An imaging unit for capturing an image of the object using transmitted light that is transmissible relative to the object; A control unit for at least controlling the camera unit; and A movable part for moving a condenser lens relative to the object, wherein the condenser lens is used to focus the transmitted light onto the object. The object has a first surface and a second surface opposite to the first surface. The object has modified regions arranged in the X direction along the first and second surfaces, and cracks extending from the modified regions. The control unit controls the camera unit to perform the following imaging process: the transmitted light is incident from the first surface into the interior of the object, and the transmitted light is used to image a crack in the object, wherein the crack is a crack extending in the Z direction intersecting the first and second surfaces and in the X direction intersecting the X direction. In the image processing, the control unit controls the imaging unit and the moving unit to move the condenser lens relative to each other along the Z direction, so that the focusing point of the transmitted light is located at multiple positions inside the object to capture an image of the object, thereby acquiring multiple internal images. The control unit performs the following calculation after the image processing: 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, it calculates the crack position, which is the location of the object crack in the Z direction. In the aforementioned camera processing, the control unit executes the first camera processing and the second camera processing, wherein, In the first imaging process, the transmitted light is incident on the object from the first surface, and the condenser lens is moved relative to it along the Z direction. This causes the focal point of the transmitted light, which has not been reflected by the second surface, to move from the first surface side to the second surface side, while simultaneously capturing images of the object at multiple positions, thereby acquiring multiple first internal images as the internal images. In the second imaging process, the transmitted light is incident on the object from the first surface, and the condenser lens is moved relative to it along the Z direction. This moves the focal point of the transmitted light reflected from the second surface from the second surface side to the first surface side, while simultaneously capturing images of the object at multiple positions, thereby acquiring multiple second internal images as the internal images. In the aforementioned arithmetic processing, the control unit executes the first arithmetic processing and the second arithmetic processing, wherein, In the first calculation process, a first internal image with a clear object crack is selected from among the multiple first internal images. Based on the amount of movement of the condenser lens when the selected first internal image is captured, a first crack position is calculated as the crack location. In the second calculation process, a second internal image with a clear object crack is selected from among the multiple second internal images. Based on the amount of movement of the condenser lens when the selected second internal image is captured, a second crack position is calculated as the crack location. The control unit calculates the width of the modified region in the Z direction based on the formation conditions of the modified region and the interval between the first crack position and the second crack position.

9. An observation method, characterized in that, include: The preparation steps for preparing an object, the object having a first surface and a second surface opposite to 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 formed on the object. and In the imaging step, after the preparation step, transmitted light from the object is incident from the first surface into the interior of the object, and the transmitted light is used to image the crack in the object, wherein the crack is a crack that extends in the Z direction intersecting the first and second surfaces and in the X direction intersecting the first surface. In the imaging step, by using a focusing lens to concentrate the transmitted light and moving it relative to the object along the Z direction, the focusing point of the transmitted light is located at multiple positions inside the object to capture images of the object, thereby obtaining multiple internal images. It also includes a calculation step, which, after the imaging step, calculates the crack position, which is the location of the object 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 the calculation step, the internal image of the object crack in the plurality of internal images is determined to be clear, and the position of the crack is calculated based on the amount of movement of the condenser lens when the determined internal image is captured.

10. An observation method, characterized in that, include: The preparation steps for preparing an object, the object having a first surface and a second surface opposite to 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 formed on the object. and In the imaging step, after the preparation step, transmitted light from the object is incident from the first surface into the interior of the object, and the transmitted light is used to image the crack in the object, wherein the crack is a crack that extends in the Z direction intersecting the first and second surfaces and in the X direction intersecting the first surface. In the imaging step, by using a focusing lens to concentrate the transmitted light and moving it relative to the object along the Z direction, the focusing point of the transmitted light is located at multiple positions inside the object to capture images of the object, thereby obtaining multiple internal images. It also includes a calculation step, which, after the imaging step, calculates the crack position, which is the location of the object 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 the aforementioned camera recording steps, steps 1 and 2 are performed, wherein, In the first imaging step, the transmitted light is incident on the object from the first surface, and the condenser lens is moved relative to it along the Z direction. This causes the focal point of the transmitted light, which has not been reflected by the second surface, to move from the first surface side to the second surface side, while simultaneously imaging the object at multiple positions, thereby acquiring multiple first internal images as the internal images. In the second imaging step, the transmitted light is incident on the object from the first surface, and the condenser lens is moved relative to it along the Z direction. This causes the focal point of the transmitted light reflected from the second surface to move from the second surface side towards the first surface side, while simultaneously imaging the object at multiple positions, thereby acquiring multiple second internal images as the internal images. In the aforementioned calculation steps, the first calculation step and the second calculation step are performed, wherein, In the first calculation step, a first internal image with a clear crack is selected from among the multiple first internal images. Based on the amount of movement of the condenser lens when the selected first internal image is captured, a first crack position is calculated as the crack location. In the second calculation step, a second internal image with a clearly defined object crack is selected from among the multiple second internal images. Based on the amount of movement of the condenser lens when capturing the selected second internal image, a second crack position is calculated as the crack location. After the calculation step, the width of the modified region in the Z direction is calculated based on the formation conditions of the modified region and the interval between the first crack position and the second crack position.

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