KR20220110083A - Observation device and observation method - Google Patents

Abstract

An observation device comprises: an imaging unit for imaging an object by means of transmitted light which is transmissive to an object; and a control unit for controlling at least the imaging unit. The object has a first surface and a second surface on the opposite side of the first surface, modified regions aligned in an X direction along the first surface and the second surface, and cracks extending from the modified regions are formed in the object. The control unit performs, by controlling the imaging unit, an imaging process of causing the transmitted light to enter the inside of the object from the first surface and imaging an object crack using the transmitted light, wherein the object crack is the cracks extending in a Z direction intersecting the first surface and the second surface and in a direction intersecting the X direction. The observation device can more accurately acquire information about the position of the modified region.

Description

OBSERVATION DEVICE AND OBSERVATION METHOD

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

In order to cut a wafer having 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, the semiconductor substrate along each of the plurality of lines There is known a laser processing apparatus for forming a plurality of rows of modified regions in the inside. The laser processing apparatus described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2017-64746) is provided with an infrared camera, and the modified region formed inside the semiconductor substrate, processing damage formed in the functional element layer, etc. It is possible to observe from the side.

As described above, when the modified region formed inside the semiconductor substrate is observed with the 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 to acquire more accurate information about the position of the modified region, such as the upper end position, the lower end position, and the width of the modified region with respect to the thickness direction of the semiconductor substrate.

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

MEANS TO SOLVE THE PROBLEM This inventor came to acquire the following knowledge by advancing earnestly research in order to solve the said subject. That is, when a modified region is formed in an object such as the semiconductor substrate by, for example, laser processing, cracks extending in various directions from the modified region may also be formed. And, among the cracks, a crack that intersects the Z-direction that intersects the laser beam incident surface of the object and the X-direction that is the progress direction of laser processing is pinpointed by the transmitted light passing through the object, compared with the modified region. . Therefore, if information on the position at which the crack intersecting the X and Z directions is imaged can be acquired, then based on the position, information on the position of the modified region can be more accurately acquired. The present disclosure has been made based on such knowledge.

That is, the observation apparatus according to the present disclosure includes an imaging unit for imaging an object with transmitted light having transparency to the object, and at least a control unit for controlling the imaging unit, wherein the object is on the opposite side of the first surface and the first surface. The object includes a second surface, and modified regions arranged in the X direction along the first surface and the second surface and cracks extending from the modified region are formed, and the control unit removes the transmitted light under the control of the imaging unit. A target crack, which is a crack extending in a direction crossing the Z-direction and the X-direction crossing the first and second planes among cracks while being incident into the interior of the target object from the first surface, is imaged by transmitted light.

Further, the observation method according to the present disclosure includes a first surface and a second surface opposite to the first surface, and a modified region arranged in the X direction along the first surface and the second surface and a crack extending from the modified region After the preparation process of preparing the formed object, and after the preparation process, while the transmitted light passing through the object is incident on the object from the first surface, the direction intersecting the Z-direction and the X-direction intersecting the first and second surfaces during cracking and an imaging process of imaging a target crack, which is a crack extending to the , with transmitted light.

In the object to be subjected to these apparatuses and methods, modified regions arranged along the X direction and cracks extending from the modified regions are formed. And with respect to such a target object, the target crack which cross|intersects the X direction and Z direction is imaged using the transmitted light which penetrates the target object. As described above, the target crack intersecting the X direction and the Z direction from the modified region is imaged (detected) in pinpoint in the Z direction rather than the modified region. Therefore, for example, if information such as the movement amount of the condensing lens when the target crack is imaged is acquired, information on the position of the modified region can be more accurately obtained based on the movement amount.

In the observation apparatus according to the present disclosure, a moving unit for moving a condensing lens for condensing transmitted light onto an object is provided relative to the object, and in the imaging process, the control unit selects the Z direction by controlling the image pickup unit and the moving unit. Accordingly, by moving the condensing lens relative to each other, a plurality of internal images are acquired by positioning the condensing point at a plurality of positions inside the object and imaging the object, and the control unit captures each of the plurality of internal images and the internal images after the imaging process. Based on the amount of movement of the condensing lens in the Z direction at the time of doing so, calculation processing for calculating the crack position, which is the position of the target crack in the Z direction, may be performed. In this way, by calculating the crack position based on the movement amount of the condensing lens when the target crack is imaged, it becomes possible to more accurately acquire information about the position of the modified region.

In the observation apparatus according to the present disclosure, in the calculation processing, the control unit determines an internal image in which the image of the target crack is clear from among the plurality of internal images, and the amount of movement of the condensing lens when the determined internal image is captured. Based on this, the crack position may be calculated. In this way, the crack position can be more accurately calculated by the control part's determination of the internal image in which the target crack is clear.

In the observation apparatus according to the present disclosure, after the calculation processing, the control unit includes a position in the Z direction of the end of the first face of the modified region and the end of the second face of the modified region, based on the formation conditions and the crack position of the modified region, after the calculation processing. Estimation processing for estimating at least one of the position in the Z direction of , and the width of the modified region in the Z direction may be performed. The shape and size of the modified region may change depending on the formation conditions of the modified region, such as, for example, laser processing processing conditions (for example, laser light wavelength, pulse width, pulse energy, and aberration correction amount). . Accordingly, by using the formation conditions and crack positions of the modified region as described above, information on the position of the modified region can be more accurately estimated.

In the observation apparatus according to the present disclosure, in the imaging process, the control unit relatively moves the condenser lens along the Z-direction while injecting transmitted light from the first surface to the object, thereby condensing transmitted light that has not been reflected on the second surface. A first imaging process for acquiring a plurality of first internal images as internal images by imaging an object at a plurality of positions while moving a point from the first surface side toward the second surface side, and injecting transmitted light from the first surface to the object , by moving the condensing lens relative to each other along the Z-direction to move the converging point of transmitted light reflected from the second surface from the second surface side toward the first surface side while imaging an object at a plurality of positions to form a plurality of second images as internal images. You may perform the 2nd imaging process which acquires an internal image. In this way, imaging (direct observation) of an object using transmitted light incident from the first surface of the object and not passing through reflection on the second surface, and an object using transmitted light incident from the first surface of the object and reflected from the second surface When an internal image is acquired by each imaging (backside reflection observation) of will do

In the observation apparatus according to the present disclosure, in the calculation processing, the control unit determines a first internal image in which the target crack is clear among the plurality of first internal images, and the amount of movement of the condensing lens when the determined first internal image is captured. Based on the first calculation processing for calculating the first crack position as the crack position, and a second internal image in which the target crack is clear among the plurality of second internal images is determined, and the determined second internal image is captured A second calculation process for calculating a second crack position as a crack position is executed based on the movement amount of the condensing lens of Based on the spacing, the width of the modified region in the Z direction may be estimated. As described above, in this case, based on the interval between the crack position acquired based on direct observation and the crack position acquired based on backside reflection observation, information on the width of the modified region can be acquired more accurately. do.

The observation apparatus according to the present disclosure may further include a display unit for displaying information, and the control unit may perform a display processing in which information regarding a crack position is displayed on the display unit under control of the display unit after the calculation processing. In this case, it becomes possible for a user to grasp|ascertain information about a crack position through a display part. In addition, the information on the crack location is at least one of various information included in the crack location itself or the information about the location of the modified region that can be estimated based on the crack location.

ADVANTAGE OF THE INVENTION According to this indication, the observation apparatus and observation method which enable the acquisition of the information regarding the position of a modified area|region more accurately can be provided.

1 is a configuration diagram of a laser processing apparatus of one embodiment.
2 is a plan view of a wafer in one implementation.
3 is a cross-sectional view of a portion of the wafer shown in FIG. 2 .
FIG. 4 is a configuration diagram of the laser irradiation unit shown in FIG. 1 .
FIG. 5 is a configuration diagram of an imaging unit for inspection shown in FIG. 1 .
It is a block diagram of the imaging unit for alignment correction shown in FIG. 1. FIG.
7 is a cross-sectional view of a wafer for explaining the imaging principle by the inspection imaging unit shown in FIG. 5 , and an image at each location by the inspection imaging unit.
Fig. 8 is a cross-sectional view of a wafer for explaining the imaging principle by the inspection imaging unit shown in Fig. 5, and an image at each location by the inspection imaging unit.
9 is an SEM image of a modified region and a crack formed inside a semiconductor substrate.
10 is an SEM image of a modified region and a crack formed inside a semiconductor substrate.
It is a schematic diagram for demonstrating the imaging principle by the imaging unit for inspection shown in FIG.
It is a schematic diagram for demonstrating the imaging principle by the imaging unit for a test|inspection shown in FIG.
13 is a diagram illustrating an object on which a modified region is formed.
14 is a graph relating to the modified region and the position of cracks in the Z direction.
15 is a plot of a detection result on a cross-sectional photograph of an object.
16 is a flowchart showing an example of the observation method according to the present embodiment.
FIG. 17 is a diagram showing one step of the observation method shown in FIG. 16 .
FIG. 18 is a diagram showing one step of the observation method shown in FIG. 16 .
19 is a plurality of internal images captured at different positions with respect to the Z direction.
It is a figure explaining crack detection.
It is a figure explaining crack detection.
22 is a diagram for explaining scratch detection.
23 is a diagram for explaining scratch detection.
24 is a diagram for explaining scratch detection.

EMBODIMENT OF THE INVENTION Hereinafter, one Embodiment is described in detail with reference to drawings. In addition, in description of each drawing, the same code|symbol is attached|subjected to the same or corresponding part, and overlapping description may be abbreviate|omitted. In addition, in each figure, the Cartesian coordinate system prescribed|regulated by an X-axis, a Y-axis, and a Z-axis may be shown. As an example, the X direction and the Y direction are a first horizontal direction and a second horizontal direction intersecting (orthogonal) to each other, and the Z direction is a vertical direction intersecting (orthogonal) to the X direction and the Y direction.

As shown in FIG. 1 , the laser processing apparatus 1 includes a stage 2 , a laser irradiation unit 3 (irradiation unit), a plurality of imaging units 4 , 5 , 6 , and a drive unit 7 . and a control unit 8 and a display 150 (display unit). The laser processing apparatus 1 is an apparatus which forms the modified region 12 in the object 11 by irradiating the laser beam L to the object 11 .

The stage 2 supports the object 11 by, for example, adsorbing a film pasted on the object 11 . The stage 2 is movable along each of the X and Y directions, and is rotatable with an axis parallel to the Z direction as a center line.

The laser irradiation unit 3 condenses the laser beam L having transmittance with respect to the object 11 and irradiates it on the object 11 . When the laser beam L is condensed inside the object 11 supported by the stage 2, the laser beam L is particularly absorbed in the portion corresponding to the converging point C of the laser beam L, A modified region 12 is formed inside the object 11 .

The modified region 12 is a region different from the surrounding unmodified region in density, refractive index, mechanical strength, and other physical properties. The modified region 12 includes, for example, a melt processing region, a crack region, a dielectric breakdown region, and a refractive index change region. The modified region 12 has a characteristic that cracks easily extend from the modified region 12 to the incident side of the laser beam L and the opposite side. Such characteristics of the modified region 12 are used for cutting the object 11 .

As an example, when the stage 2 is moved along the X direction and the light-converging point C is relatively moved along the X direction with respect to the object 11, a plurality of modified spots 12s are arranged in one row along the X direction. formed to line up. One modified spot 12s is formed by irradiation of one pulse of laser light L. The modified region 12 in one row is a set of a plurality of modified spots 12s arranged in one row. The adjacent modified spots 12s may be connected to each other or separated from each other by the relative movement speed of the light-converging point C with respect to the object 11 and the repetition frequency of the laser light L.

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

The imaging unit 5 and the imaging unit 6, under the control of the control unit 8 , image the target 11 supported on the stage 2 by the light passing through the target 11 . The image obtained by imaging the imaging units 5 and 6 is provided for alignment of the irradiation position of the laser beam L as an example.

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

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

The display 150 has a function as an input unit for accepting input of information from a user, and a function as a display unit for displaying information to the user.

[Configuration of object]

The object 11 of the present embodiment is a wafer 20 as shown in FIGS. 2 and 3 . The wafer 20 includes a semiconductor substrate 21 and a functional element layer 22 . In this embodiment, the wafer 20 is described as having the functional element layer 22 . However, the wafer 20 may or may not have the functional element layer 22 , and may be a bare wafer. The semiconductor substrate 21 has a front surface 21a (second surface) and a rear surface 21b (first surface). The semiconductor substrate 21 is, for example, a silicon substrate. The functional element layer 22 is formed on the surface 21a of the semiconductor substrate 21 . The functional element layer 22 includes a plurality of functional elements 22a arranged two-dimensionally along the surface 21a. The functional element 22a is, for example, a light receiving element such as a photodiode, a light emitting element such as a laser diode, or a circuit element such as a memory. The functional element 22a may be formed three-dimensionally by stacking a plurality of layers. Moreover, although the notch 21c which shows a crystal orientation is provided in the semiconductor substrate 21, the orientation flat may be provided instead of the notch 21c.

The wafer 20 is cut for each functional element 22a along each of the plurality of lines 15 . The plurality of lines 15 pass through each of the plurality of functional elements 22a when viewed from the thickness direction of the wafer 20 . More specifically, the line 15 passes through the center (center in the width direction) of the street region 23 when viewed from the thickness direction of the wafer 20 . The street region 23 extends so as to pass between the functional elements 22a adjacent to each other in the functional element layer 22 . In the present embodiment, the plurality of functional elements 22a are arranged in a matrix shape along the surface 21a, and the plurality of lines 15 are set in a grid shape. In addition, although the line 15 is an imaginary line, it may be an actual drawn line.

[Configuration of laser irradiation unit]

As shown in FIG. 4 , the laser irradiation unit 3 includes a light source 31 , a spatial light modulator 32 , and a condensing lens 33 . The light source 31 outputs the laser beam L by a pulse oscillation method, for example. 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: Spatial Light Modulator) of a reflective liquid crystal (LCOS: Liquid Crystal™ Silicon). The condensing lens 33 condenses the laser light L modulated by the spatial light modulator 32 . In addition, the condensing lens 33 may be a correction ring lens.

In the present embodiment, the laser irradiation unit 3 irradiates a laser beam L to the wafer 20 from the back surface 21b side of the semiconductor substrate 21 along each of the plurality of lines 15 , thereby generating a plurality of Two rows of modified regions 12a and 12b are formed in the semiconductor substrate 21 along each of the lines 15 . The modified region 12a is a modified region closest to the surface 21a among the two rows of modified regions 12a and 12b. The modified region 12b is a modified region closest to the modified region 12a among the two rows of modified regions 12a and 12b, and is a modified region closest to the back surface 21b.

The two rows of modified regions 12a and 12b are adjacent to each other in the thickness direction (Z direction) of the wafer 20 . The two rows of modified regions 12a and 12b are formed by relatively moving the two light-converging points C1 and C2 along the line 15 with respect to the semiconductor substrate 21 . The laser light L is modulated by the spatial light modulator 32, for example, so that the light converging point C2 is located on the back side of the traveling direction and on the incident side of the laser light L with respect to the light converging point C1. In addition, regarding formation of a modified area|region, a monofocal point or a multifocal point may be sufficient, and one pass or multiple passes may be sufficient.

The laser irradiation unit 3 irradiates the laser beam L to the wafer 20 from the back surface 21b side of the semiconductor substrate 21 along each of the plurality of lines 15 . As an example, with respect to the semiconductor substrate 21, which is a single crystal silicon <100> substrate with a thickness of 400 μm, two light-converging points C1 and C2 are respectively aligned at a position of 54 μm and a position of 128 μm from the surface 21a, The laser beam L is irradiated to the wafer 20 from the back surface 21b side of the semiconductor substrate 21 along each of the plurality of lines 15 . At this time, for example, when the conditions are that the cracks 14 spanning the two rows of modified regions 12a and 12b reach the surface 21a of the semiconductor substrate 21, the wavelength of the laser light L is 1099 nm, and the pulse width is 1099 nm. is 700 n seconds, and the repetition frequency is 120 kHz. In addition, the output of the laser beam L at the converging point C1 is 2.7 W, and the output of the laser light L at the converging point C2 is 2.7 W, and the output of the laser beam L at the converging point C1 is 2 The relative moving speed of the light-converging points C1 and C2 is 800 mm/sec. Further, for example, when the number of processing passes is 5, with respect to the above-described wafer 20, for example, ZH80 (at a position of 328 µm from the surface 21a), ZH69 (at a position of 283 µm from the surface 21a) ), ZH57 (at a position of 234 µm from the surface 21a), ZH26 (at a position of 107 µm from the surface 21a), and ZH12 (at a position of 49.2 µm from the surface 21a) may be the machining positions. In this case, for example, the wavelength of the laser beam L is 1080 nm, the pulse width is 400 nsec, the repetition frequency is 100 kHz, and the moving speed may be 490 mm/sec.

The formation of these two rows of modified regions 12a and 12b and cracks 14 is performed in the following case. That is, in a subsequent step, for example, by grinding the back surface 21b of the semiconductor substrate 21 to thin the semiconductor substrate 21, the cracks 14 are exposed on the back surface 21b, and a plurality of This is a case where the wafer 20 is cut into a plurality of semiconductor devices along each of the lines 15 .

[Configuration of the imaging unit for inspection]

As shown in FIG. 5 , the imaging unit 4 (imaging unit) includes a light source 41 , a mirror 42 , an objective lens (condensing lens) 43 , and a light detection unit 44 . The imaging unit 4 images the wafer 20 . The light source 41 outputs the light I1 having transparency to the semiconductor substrate 21 . The light source 41 is constituted by, 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 modified regions 12a and 12b in two rows are formed as described above.

The objective lens 43 is for condensing the light (transmitted light) I1 having transparency to the semiconductor substrate 21 toward the semiconductor substrate 21 . The objective lens 43 passes the light I1 reflected from the surface 21a of the semiconductor substrate 21 . That is, the objective lens 43 allows the light I1 to pass 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 the aberration generated in the light I1 in the semiconductor substrate 21 by, for example, adjusting the distances between the plurality of lenses constituting the objective lens 43 . In addition, the means for correcting the aberration is not limited to the correction ring 43a, and other correction means such as a spatial light modulator may be used. 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 constituted by, for example, an InGaAs camera, and detects the light I1 in the near-infrared region. In addition, the means for detecting (imaging) the light I1 in the near-infrared region is not limited to the InGaAs camera, and other imaging means such as a transmission confocal microscope or the like may be used as long as transmission-type imaging is performed.

The imaging unit 4 can image each of the two rows of modified regions 12a and 12b and the tip of each of the plurality of cracks 14a, 14b, 14c, and 14d (the details will be described later). The crack 14a is a crack extending from the modified region 12a to the surface 21a side. The crack 14b is a crack extending from the modified region 12a to the back surface 21b side. The crack 14c is a crack extending from the modified region 12b to the surface 21a side. The crack 14d is a crack that extends from the modified region 12b to the back surface 21b side.

[Configuration of the imaging unit for alignment correction]

As shown in FIG. 6 , the imaging unit 5 includes a light source 51 , a mirror 52 , a lens 53 , and a light detection unit 54 . The light source 51 outputs the light I2 having transparency to the semiconductor substrate 21 . The light source 51 is constituted by, for example, a halogen lamp and a filter, and outputs light I2 in the near-infrared region. The light source 51 may be shared with the light source 41 of the imaging unit 4 . The light I2 output from the light source 51 is reflected by the mirror 52 , passes through the lens 53 , and is irradiated onto the wafer 20 from the back surface 21b side of the semiconductor substrate 21 .

The lens 53 passes the light I2 reflected from the surface 21a of the semiconductor substrate 21 . That is, the lens 53 allows the light I2 to pass through the semiconductor substrate 21 . The numerical aperture of the lens 53 is 0.3 or less. That is, the numerical aperture of the objective lens 43 of the imaging unit 4 is larger than the numerical aperture of the lens 53 . The light detection unit 54 detects the light I2 passing through the lens 53 and the mirror 52 . The light detection unit 55 is constituted by, for example, an InGaAs camera, and detects light I2 in the near-infrared region.

The imaging unit 5 irradiates the wafer 20 with the light I2 from the back surface 21b side under the control of the control part 8, and returns from the front surface 21a (functional element layer 22). By detecting the incoming light I2, the functional element layer 22 is imaged. In addition, the imaging unit 5 irradiates the wafer 20 with the light I2 from the back surface 21b side under the control of the control part 8 similarly, and the modified area|region in the semiconductor substrate 21 is similar. By detecting the light I2 returning from the formation position of (12a, 12b), an image of the region including the modified regions (12a, 12b) is acquired. These images are used for alignment of the irradiation position of the laser beam L. The imaging unit 6 has the imaging unit 5 except that the lens 53 has a lower magnification (eg, 6 times in the imaging unit 5 and 1.5 times in the imaging unit 6 ). ), and is used for alignment similarly to the imaging unit 5 .

[Principle of Imaging by Inspection Imaging Unit]

Using the imaging unit 4 shown in FIG. 5, as shown in FIG. 7, cracks 14 spanning two rows of modified regions 12a and 12b reach the surface 21a of a semiconductor substrate 21. , the focal point F (the focal point of the objective lens 43) is moved from the rear surface 21b side toward the front surface 21a side. In this case, if the focal point F from the back surface 21b side is focused on 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 (Fig. 7 on the right). However, even if the focus F is focused on the crack 14 itself and the tip 14e of the crack 14 reaching the surface 21a from the back surface 21b side, they cannot be confirmed (in FIG. 7 ). image on the left). In addition, when the focus F is focused on the front surface 21a of the semiconductor substrate 21 from the back surface 21b side, the functional element layer 22 can be confirmed.

Further, using the imaging unit 4 shown in FIG. 5 , as shown in FIG. 8 , cracks 14 spanning two rows of modified regions 12a and 12b do not reach the surface 21a of the semiconductor substrate. With respect to (21), the focal point F is moved from the back surface 21b side toward the front surface 21a side. In this case, even if the focus F from the back surface 21b side is focused on the tip 14e of the crack 14 extending from the modified region 12a to the surface 21a side, the tip 14e cannot be confirmed ( image on the left in Fig. 8). However, focusing F from the back surface 21b side to the area on the side opposite to the back surface 21b with respect to the front surface 21a (that is, the area on the side of the functional element layer 22 with respect to the surface 21a), When a virtual focal point Fv symmetrical to the focal point F with respect to the surface 21a is positioned at the tip 14e, the tip 14e can be confirmed (image on the right in Fig. 8). In addition, the virtual focus Fv is the point symmetrical with respect to the focus F and the surface 21a which considered the refractive index of the semiconductor substrate 21. As shown in FIG.

The reason that the crack 14 itself cannot be confirmed as mentioned above is assumed because the width|variety of the crack 14 is smaller than the wavelength of the light I1 which is illumination light. 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. Fig. 9(b) is an enlarged image of the area A1 shown in Fig. 9(a), Fig. 10(a) is an enlarged image of the area A2 shown in Fig. 9(b), Fig. 10B is an enlarged image of the region A3 shown in Fig. 10A. In this way, the width of the crack 14 is about 120 nm, and is smaller than the wavelength of the light I1 in the near-infrared region (for example, 1.1 to 1.2 µm).

The imaging principle assumed based on the above is as follows. As shown in Fig. 11A, when the focus F is positioned in the air, the light I1 does not return, so a dark image is obtained (the image on the right in Fig. 11A). ). As shown in Fig. 11(b), when the focal point F is positioned inside the semiconductor substrate 21, the light I1 reflected from the surface 21a is returned, so that a white image is obtained ( The image on the right in Fig. 11 (b)). As shown in FIG. 11C , when the focus F is focused on the modified region 12 from the back surface 21b side, the light I1 reflected from the front surface 21a by the modified region 12 and returned. ), an image in which the modified region 12 is reflected darkly in a white background is obtained (image on the right in Fig. 11C).

12A and 12B, when the focus F is focused on the tip 14e of the crack 14 from the back surface 21b side, for example, generated near the tip 14e Due to optical specificity (stress concentration, strain, discontinuity in atomic density, etc.), confinement of light generated near the tip 14e, etc., scattering, reflection, interference, Since absorption or the like occurs, an image in which the tip 14e is darkly reflected in a white background is obtained (images on the right in Figs. 12(a) and 12(b)). As shown in Fig. 12(c), when the focus F is focused on the portion other than the vicinity of the tip 14e of the crack 14 from the back surface 21b side, the light I1 reflected from the surface 21a Since at least a part of is returned, a white image is obtained (the image on the right in Fig. 12(c)).

[Embodiment related to inside observation]

13 is a diagram illustrating an object on which a modified region is formed. 13A is a cross-sectional photograph of an object cut to expose a modified region. Fig. 13B is an example of an image of an object captured by light passing through the object. 13C is another example of an image of an object captured by light passing through the object. As shown in FIG.13(a), the modified area|region 12 formed in the target object (the semiconductor substrate 21 here) by the condensing of the laser beam L is a laser beam in the semiconductor substrate 21. The void area 12m located on the surface 21a side which is the surface on the opposite side to the incident surface of L, and the void upper side located on the back surface 21b side which is the incident surface of the laser beam L rather than the void area 12m. region 12n.

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

14 is a graph relating to the modified region and the position of cracks in the Z direction. In FIG. 14, the plot of a void lower end, a void upper end, a void upper area|region lower end, and a void upper area|region upper end are actually measured values by cross-sectional observation. The lower end means the end on the side of the front surface 21a, and the upper end means the end on the side of the back surface 21b. Therefore, for example, the lower end of the void upper region is an end portion on the surface 21a side of the void upper region 12n.

In addition, the plots of direct observation and back reflection observation in the graph of Fig. 14 are in the Z direction when an internal image including a clear image of the crack 14k among the images captured by the light I1 is captured. It is a measured value calculated based on the movement amount of the objective lens 43 (hereinafter, simply referred to as "movement amount" in some cases), and is, as an example, a value obtained by image determination by AI. Direct observation is a case in which the light I1 is incident from the back surface 21b and the converging point of the light I1 is directly aligned with the crack 14k without being reflected on the surface 21a (in the above example, When the focus F is focused on the crack 14k from the rear surface 21b side), the rear surface reflection observation is the light I1 reflected by the surface 21a while the light I1 is incident from the rear surface 21b. When the light-converging point of is set to the crack 14k (in the above example, with respect to the surface 21a, the focus F is focused from the back surface 21b side to the area on the opposite side to the back surface 21b, the surface 21a) with respect to the case where an imaginary focal point Fv symmetrical to the focal point F is set at the crack 14k).

As shown in FIG. 14, in direct observation, in four cases C1 to C4 in which the formation position of the modified region 12 was different in the Z direction, between the lower end of the void upper region and the upper end of the void upper region. The crack 14k is detected, and in back reflection observation, in case C1, the crack 14k is detected at the same position as the lower end of the void upper region in general, and the lower end of the void upper region and the void in cases C2 to C4 A crack 14k is detected between the upper end and the upper end. 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. In this way, the crack 14k is detected more pinpoint with respect to the Z direction, compared to the modified region 12 itself.

Accordingly, by acquiring the movement amount of the internal image when the crack 14k appears with respect to the Z direction, it becomes possible to more accurately acquire information about the position of the modified region 12 . In addition, although the vertical axis|shaft in FIG. 14 has shown the distance from the back surface, the back surface here is the back surface with respect to the incident surface of the light I1, and the front surface 21a with respect to the semiconductor substrate 21. As shown in FIG. In addition, FIG. 15 is a plot of the detection result of case C1 in a cross-sectional photograph.

In this embodiment, based on the above knowledge, the crack 14k is detected by internal observation, and information regarding the position of the modified area|region 12 is acquired. Then, the observation method which concerns on this embodiment is demonstrated. In this observation method, the crack 14k is a target crack to be detected.

16 is a flowchart showing an example of the observation method according to the present embodiment. As shown in FIG. 16, here, in order to prepare the target object in which the modified area|region was formed, laser processing is performed (process S11: preparation process). However, as one step of the observation method, the laser processing step is not essential, for example, using another laser processing apparatus (or at a separate timing by the laser processing apparatus 1) the modified region 12 is You may prepare the formed object.

In this process S11, as shown in FIG. 17, the target object containing the semiconductor substrate 21 is prepared. The semiconductor substrate 21 includes a rear surface (first surface) 21b and a surface (second surface) 21a opposite to the rear surface 21b. A line 15 extending in the X direction along the back surface 21b and the front surface 21a is set in the semiconductor substrate 21 . The semiconductor substrate 21 is supported by the stage 2 so that the back surface 21b faces the laser irradiation unit 3 in order to make the back surface 21b the incident surface of the laser light L. In that state, while controlling the laser irradiation unit 3 , the control unit 8 moves the driving unit 7 and/or the stage 2 so as to relatively move the semiconductor substrate 21 along the X direction. control to move the converging point C of the laser light L relative to the semiconductor substrate 21 along the line 15 .

At this time, the control unit 8 causes the spatial light modulator 32 to display a pattern for branching the laser light L into a plurality (here, two) of the laser light L1 and L2 . Thereby, in the inside of the semiconductor substrate 21, the converging points C1 and C2 of each of the laser beams L1 and L2 are spaced apart only by the distance Dz with respect to the Z direction, and spaced apart by the distance Dx with respect to the X direction. ) is formed. As a result, a plurality (here, two rows) of modified regions 12a and 12b are formed along the line 15 in the semiconductor substrate 21 . Therefore, here, the X direction becomes the processing advancing direction in which the light-converging points C1 and C2 advance.

As described above, here, the control unit 8 transmits the laser beam L to the semiconductor substrate 21 along the X direction, which is the extension direction of the line 15 , under the control of the laser irradiation unit 3 (irradiation unit). By irradiating, a laser processing process for forming in the semiconductor substrate 21 a plurality of modified regions 12 arranged along the X direction and cracks (cracks 14 and 14k) extending from the modified region 12 is performed. In addition, in FIG. 17 and subsequent drawings, the functional element layer 22 formed on the surface 21a of the semiconductor substrate 21 is abbreviate|omitted.

Then, an inside observation is made. That is, in the subsequent process, the semiconductor substrate 21 is moved to an observation position (process S12). More specifically, the control unit 8 controls the driving unit 7 and/or the moving mechanism of the stage 2 to move the semiconductor substrate 21 directly under the objective lens 43 of the imaging unit 4 . move relative to position. In addition, when the semiconductor substrate 21 in which the modified area|region 12 was formed is prepared separately, the said semiconductor substrate 21 may be mounted in the observation position by a user, for example.

Next, as shown in FIG. 18 , the semiconductor substrate 21 is imaged by the light (transmitted light) I1 having transparency to the semiconductor substrate 21 (Step S13: Imaging step). In this step S13 , under the control of the imaging unit 4 (imaging unit), the light I1 is made incident on the inside of the semiconductor substrate 21 from the back surface 21b of the semiconductor substrate 21 , while the modified region 12 is ), an imaging process of imaging a target crack that is a crack 14k extending along a direction intersecting with the Z and X directions among cracks extending from the light I1 is performed. In addition, the Y direction is an example of the direction which intersects the X direction which is a processing advancing direction, and the Z direction which intersects the back surface 21b and the front surface 21a.

More specifically, in step S13 , the control unit 8 controls the driving unit 7 (moving unit) and the imaging unit 4 to move the imaging unit 4 along the Z direction, whereby the semiconductor A plurality of internal images ID are acquired by imaging the semiconductor substrate 21 by locating the converging point of the light I1 at a plurality of positions inside the substrate 21 . In this embodiment, the objective lens 43 is moved integrally with the imaging unit 4 . Therefore, moving the imaging unit 4 is also moving the objective lens 43 , and the moving amount of the imaging unit 4 is equal to the moving amount of the objective lens 43 .

At this time, under the control of the drive unit 7 , the control unit 8 moves the imaging unit 4 with respect to the Z direction, and the converging point of the light I1 (focus F, virtual focus Fv) The semiconductor substrate 21 is imaged a plurality of times while moving in the Z direction. The range in which the converging point of the light I1 is moved may be the entire range of the thickness of the semiconductor substrate 21 . It can be set as the partial range RA including the Z-direction position where the converging points C1 and C2 of the lights L1 and L2 were matched. In addition, although the movement interval of the imaging unit 4 with respect to the Z direction when imaging is performed a plurality of times, that is, the imaging interval of the semiconductor substrate 21 is arbitrary, from the viewpoint of more accurately detecting the crack 14k, more It is preferable to set it in detail. The imaging interval is, for example, within 1 µm, and here it is 0.2 µm.

In addition, here, the control part 8 controls the imaging unit 4 and the drive unit 7 so that direct observation and back reflection observation of the semiconductor substrate 21 are performed. More specifically, the control unit 8 first moves the imaging unit 4 along the Z-direction while making the light I1 incident on the semiconductor substrate 21 from the back surface 21b, so that the By imaging the semiconductor substrate 21 at a plurality of positions in the Z direction while moving the converging point (focus F) of the light I1 that has not undergone reflection from the back surface 21b side to the front surface 21a side, A first imaging process for acquiring a plurality of first internal images ID1 as the image ID is executed. This 1st imaging process is direct observation.

At the same time, the control unit 8 moves the imaging unit 4 along the Z-direction while injecting the light I1 from the back surface 21b to the object, thereby condensing the light I1 reflected from the front surface 21a. By imaging the semiconductor substrate 21 at a plurality of positions while moving the point (virtual focus Fv) from the front surface 21a side toward the back surface 21b side, a plurality of second internal images ( A second imaging process for acquiring ID2) is executed. Since this 2nd imaging process is observation from the back side (here, it is called the front surface 21a in the structure of the semiconductor substrate 21) with respect to the incident surface of the light I1, it is back reflection observation.

In the subsequent step, the imaging data relating to the internal image ID acquired by the imaging in step S13 is saved (step S14). As described above, in step S13, the control unit 8 performs imaging while moving the imaging unit 4 (that is, the converging point of the light I1) along the Z direction under the control of the driving unit 7 . . Therefore, the control part 8 can acquire the movement amount of the imaging unit 4 when each internal image is imaged. Here, for each of the internal images ID, information about the movement amount is associated, and can be saved as imaged data. In addition, the imaged data can be stored in any storage device accessible to the control unit 8 , regardless of the inside or outside of the control unit 8 and the laser processing apparatus 1 .

The amount of movement of the imaging unit 4 (objective lens 43 ) is, for example, from a position in which the converging point of the light I1 is aligned with the back surface 21b of the semiconductor substrate 21 , the semiconductor substrate 21 ) can be the amount of movement of the imaging unit 4 when the imaging unit 4 is moved along the Z direction so as to align the converging point of the light I1 at a desired position inside the .

Next, the control unit 8 inputs the image pickup data from a predetermined storage device (step S15). And the control part 8 determines the formation state of the crack 14k (step S16). Here, as an example, the control unit 8 automatically determines an internal image ID in which the image of the crack 14k is relatively clear from among the plurality of internal images ID by image recognition (AI judgment is performed) ). Here, an example of an algorithm for detecting cracks or modified regions by AI judgment will be described.

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

Next, as shown in FIG. 21 , the control unit 8 detects the crack 14 from the straight line group 140 by calculating the degree of similarity with the crack line for the straight line group 140 . As shown in the upper drawing of FIG. 21, the crack line has the characteristic that the front and back are very bright in the Y direction with respect to the linear luminance value. For this reason, for example, the control unit 8 compares the luminance values of all the pixels in the detected straight line group 140 with the front and rear in the Y direction, and determines the number of pixels whose difference is equal to or greater than the threshold value even before and after the similarity. score it. And let the thing with the highest score of the similarity with a crack line among the several detected straight line group 140 be a representative value in the image. It becomes an index|index that the possibility that the crack 14 exists, so that a representative value is high. The control part 8 makes the thing with a relatively high score a crack image candidate by comparing the representative value in a some image.

22 to 24 are diagrams for explaining scratch detection. In FIG. 22, the internal observation result (internal image of the semiconductor substrate 21) is shown. The control unit 8 detects an image inside the semiconductor substrate 21 as shown in FIG. 22A using a corner (edge concentration) in the image as a key point, and determines the position, size, and direction of the image. The feature point 250 is detected by detection. As a method for detecting a feature point in this way, Eigen, Harris, Fast, SIFT, SURF, STAR, MSER, ORB, AKAZE, and the like are known.

Here, as shown in FIG. 23, since the shape of a circle, a rectangle, etc. is lined up at regular intervals, the scratch 280 has a strong characteristic as a corner. For this reason, by counting the feature amount of the feature point 250 in the image, it becomes possible to detect the scratch 280 with high precision. As shown in FIG. 24, when the sum total of the feature amounts for each image shifted in the depth direction is compared, the change of the mountain|mountain which shows the crack calorific value for every modified layer can be confirmed. The control unit 8 estimates the peak of the change as the position of the scratch 280 . By accumulating the feature amount in this way, it becomes possible to estimate not only the scratch position but also the pulse pitch.

The above explanation of the AI determination relates to the crack 14 and the scratch 280 extending along the X direction, but also for the crack 14k extending along the direction intersecting the Z direction and the X direction, the same algorithm By comparing the representative values in the plurality of internal images ID, it is possible to determine a relatively high score as an internal image ID in which the image of the crack 14k is relatively clear.

As an example, FIG. 19 is a plurality of internal images ID captured at different positions with respect to the Z direction. In Fig. 19, centering on the imaging position of the internal image IDd shown in (d), (c) is 1 µm, the internal image IDc at the imaging position on the back surface 21b side, (b) is 3 The internal image IDb at the imaging position on the back surface 21b side by µm (a) by 5 µm, the internal image IDa at the imaging position on the back surface 21b side by 1 µm (e) by 1 µm ( The internal image IDe at the imaging position on the 21a side, (f) the internal image IDf at the imaging position on the surface 21a side by 3 µm, (g) by 5 µm on the surface 21a side It is an internal image IDg at the imaging position. In addition, the imaging position here is a value inside the semiconductor substrate 21. As shown in FIG.

In the example shown in FIG. 19, since the image of the crack 14k is the clearest in the internal image IDd, the internal image IDd has a relatively high score by the control part 8, and the crack 14k. It is determined that the image of is a relatively clear internal image (that is, it is determined that the crack 14k is detected in the internal image IDd). The control part 8 can acquire the movement amount at the time of imaging the internal image IDd. Therefore, the control part 8 can calculate the crack position of the crack 14k based on the movement amount when the internal image IDd is imaged.

In this way, the control unit 8 extends in the direction intersecting the Z direction and the X direction based on the movement amount of the imaging unit 4 when the plurality of internal images ID and each of the internal images ID are imaged. Calculation processing for calculating the crack position, which is the position in the Z direction of the target crack, which is the crack 14k to be formed, is performed. More specifically, in the calculation processing, the control unit 8 determines an internal image ID with a clear image of the crack 14k among the plurality of internal images ID, and captures the determined internal image ID. The crack position is calculated based on the amount of movement at the time. The crack position can be calculated, for example, by multiplying the movement amount by a predetermined correction factor. The correction coefficient can be calculated|required from the NA of the objective lens 43, the refractive index of the semiconductor substrate 21, etc., for example.

The control unit 8 can calculate the crack position of the above crack 14k for both the first internal image ID1 acquired by direct observation and the second internal image ID2 acquired by back reflection observation. . Thereby, the control part 8 controls the crack position of the crack 14k located on the relatively back surface 21b side according to the first internal image ID1, and the relatively surface ( The crack position of the crack 14k located on the 21a) side can be calculated.

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

Then, in process S16, the control part 8 estimates the position of the modified area|region 12 etc. based on the acquired crack position etc. That is, here, the control part 8 controls the edge part of the back surface 21b side of the modified area|region 12 based on the formation conditions of the modified area|region 12 (processing conditions in laser processing here) and the crack location. The position in the Z direction of (the upper end of the region above the void), the position in the Z direction of the end (the lower end of the void) on the surface 21a side of the modified region 12, and the width in the Z direction of the modified region 12 ( The estimation process for estimating at least one of the space|interval of the upper part of a void upper area|region and a void bottom) is performed.

Here, the control part 8 calculates the 1st crack position Z1 of the crack 14k (upper crack) of the back surface 21b side based on direct observation, and the surface 21a side based on back surface reflection observation. The second crack position Z2 of the crack 14k (bottom crack) of . Therefore, the control unit 8 can calculate the width of the crack origin in the semiconductor substrate 21 as the interval between the first crack position Z1 of the upper crack and the second crack position Z2 of the lower crack. have.

Then, for example, the control unit 8 multiplies the calculated width of the crack initiation portion by a coefficient related to the processing conditions of laser processing, whereby Z of the modified region 12 in the semiconductor substrate 21 is You can calculate the width for the direction. The coefficient here is determined based on various conditions affecting the formation of the modified region 12, such as the wavelength of the laser light L at the time of laser processing, the aberration correction amount, the pulse width, and the pulse energy, for example. do. The coefficient here is about 3.0 as an example.

Thus, in the estimation process, the control part 8 is based on the formation conditions of the modified area|region 12 (processing conditions of laser processing) and the space|interval of the 1st cracking position Z1 and the 2nd cracking position Z2. , the width of the modified region 12 in the Z direction may be estimated.

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

In addition, the control unit 8 subtracts the assumed void region width, which is the width of the assumed void region 12m, from the second cracking position Z2 of the downward crack, so that the lower end of the surface 21a of the modified region 12 is location can be calculated. The assumed void region width is determined based on various conditions affecting the formation of the modified region 12, such as the wavelength of the laser light L during laser processing, the aberration correction amount, the pulse width, and the pulse energy, for example. do. The assumed void region width is, for example, about 10 µm.

In addition, the control unit 8 adds the assumed void upper region width, which is the assumed void upper region 12n width, to the second cracking position Z2 of the downward cracking, thereby forming the rear surface 21b of the modified region 12 . The position of the top of the side can be calculated. The assumed void upper region width is, for example, based on various conditions affecting the formation of the modified region 12 such as the wavelength of the laser light L at the time of laser processing, the aberration correction amount, the pulse width, and the pulse energy. it is decided The assumed void upper region width is, for example, about 10 µm.

As described above, in step S16 , the control unit 8 estimates and acquires various types of information regarding the position of the modified region 12 . In the subsequent step, the control unit 8 outputs the information according to the determination result of the step S16 to an arbitrary storage device (step S17), and saves the information in the storage device (step S18). Thereafter, if necessary, various types of information are displayed on the display 150 in a state in which input from the user can be accepted (step S19), and the processing is ended. The information to be displayed on the display 150 is, for example, the first crack position Z1 , the second crack position Z2 , the width of the origin, the position of the end of the modified region 12 , and the position of the modified region 12 . width in the Z direction, and the like. In this way, in step S19 , the control unit 8 executes a display process in which the information regarding the crack position is displayed on the display 150 under the control of the display 150 .

By the above, the observation method by the laser processing apparatus 1 is complete|finished. In the present embodiment, the observation method is performed by the imaging unit 4 , the drive unit 7 , and the control unit 8 in the laser processing apparatus 1 . In other words, in the laser processing apparatus 1, the imaging unit 4 for imaging the semiconductor substrate 21 by the light I1 which has transparency to the semiconductor substrate 21, and the imaging unit 4 is a semiconductor substrate The observation device 1A is constituted by a drive unit 7 for moving it relative to 21 and a control unit 8 for controlling at least the imaging unit 4 and the drive unit 7 ( see Fig. 1).

As described above, in the semiconductor substrate 21 to be observed in the observation method and the observation apparatus 1A for implementing the observation method according to the present embodiment, the modified region 12 and the modified region are arranged along the X direction. Cracks 14 and 14k extending from (12) are formed. Then, a crack 14k extending in a direction crossing the Z direction and the X direction is imaged with respect to the semiconductor substrate 21 as described above using the light I1 transmitted through the semiconductor substrate 21 . The crack 14k that intersects the Z and X directions is imaged (detected) by pinpoint in the Z direction rather than the modified region 12 itself. Therefore, for example, if information such as the amount of movement of the imaging unit 4 when the crack 14k is imaged is acquired, information on the position of the modified region 12 can be more accurately obtained based on the amount of movement. do.

Further, the observation apparatus 1A according to the present embodiment includes a driving unit 7 for relatively moving the converging point of the light I1 with respect to the semiconductor substrate 21 . In the imaging process, the control unit 8 moves the imaging unit 4 along the Z-direction under the control of the imaging unit 4 and the driving unit 7 , whereby a plurality of positions inside the semiconductor substrate 21 are performed. A plurality of internal images ID are acquired by locating the converging point of the light I1 to image the semiconductor substrate 21 . Then, the control unit 8, after the imaging process, based on the amount of movement of the imaging unit 4 in the Z direction when the plurality of internal images ID and each of the internal images ID are imaged, the crack 14k Calculation processing for calculating the crack positions (the first crack position Z1 and the second crack position Z2) which is a position in the Z direction of is performed. In this way, based on the amount of movement of the imaging unit 4 when the crack 14k is imaged, it is possible to more accurately acquire information about the position of the modified region 12 .

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

Further, in the observation apparatus 1A according to the present embodiment, the control unit 8 controls the modified region 12 after the calculation processing, based on the formation conditions of the reformed region 12 and the crack position of the crack 14k. At least one of a position in the Z direction of the end of the back surface 21b side, a position in the Z direction of the end of the surface 21a side of the modified region 12, and a width in the Z direction of the modified region 12 Estimation processing for estimating is performed. The shape and size of the modified region 12 varies depending on the formation conditions of the modified region, such as, for example, laser processing processing conditions (eg, laser light wavelength, pulse width, pulse energy, aberration correction amount, etc.). There are cases. Accordingly, by using the formation conditions of the modified region 12 and the position of the crack 14k, such as the processing conditions of laser processing, information on the position of the modified region 12 can be more accurately estimated.

Further, in the observation apparatus according to the present embodiment, in the imaging process, the control unit 8 moves the imaging unit 4 while making the light I1 incident on the semiconductor substrate 21 from the back surface 21b, By imaging the semiconductor substrate 21 at a plurality of positions while moving the converging point of the light I1 that has not undergone reflection on the front surface 21a from the back surface 21b side toward the front surface 21a side, the internal image ID ), a first imaging process for acquiring a plurality of first internal images ID1, By imaging the semiconductor substrate 21 at a plurality of positions while moving the converging point of the light I1 reflected by 21a) from the front surface 21a side toward the back surface 21b side, a plurality of second images are formed as internal images ID. 2 The second imaging process for acquiring the internal image ID2 is executed.

In this way, imaging (direct observation) of the semiconductor substrate 21 using the light I1 incident from the back surface 21b of the semiconductor substrate 21 and not passing through reflection on the surface 21a, and the semiconductor substrate 21 When an internal image is acquired by each imaging (rear reflection observation) of the semiconductor substrate 21 using the light I1 incident from the back surface 21b and reflected by the front surface 21a of By using the crack position acquired based on the movement amount of the imaging unit 4, it becomes possible to acquire information regarding the position of the modified area|region 12 more accurately.

Further, in the observation apparatus 1A according to the present embodiment, in the calculation processing, the control unit 8 determines a first internal image in which the crack 14k is clear among the plurality of first internal images ID1, and determines A first calculation process for calculating a first crack position Z1 as a crack position based on the amount of movement of the imaging unit 4 when the first internal image is imaged, and a plurality of second internal images ID2 A second crack position Z2 as a crack position is calculated based on the amount of movement of the imaging unit 4 when a second internal image in which the middle crack 14k is clear is determined, and the determined second internal image is imaged. A second calculation process is executed. In the estimation process, the control unit 8 controls the Z-direction of the modified region 12 based on the formation conditions of the modified region 12 and the interval between the first cracking position Z1 and the second cracking position Z2. width can be estimated. As described above, in this case, based on the interval between the first cracking position Z1 acquired based on direct observation and the second cracking position Z2 acquired based on backside reflection observation, the modification is more accurately performed. Information regarding the width of the region 12 can be acquired.

Further, the observation device 1A according to the present embodiment further includes a display 150 for displaying information. In addition, after the calculation process, the control part 8 may perform the display process in which the information regarding the crack position is displayed on the display 150 by control of the display 150. In this case, through the display 150, the user can grasp information about the crack location. In addition, the information on the crack location is at least one of the crack location itself or various pieces of information included in the information about the location of the modified region 12 that can be estimated based on the crack location.

The above embodiments have described one aspect of the present disclosure. Accordingly, the present disclosure is not limited to the above embodiment, but is arbitrarily modified.

For example, in the above embodiment, as a means for moving the objective lens 43 relative to the semiconductor substrate 21 along the Z direction, a driving unit for moving the imaging unit 4 for each objective lens 43 ( 7) is exemplified. However, for example, only the objective lens 43 may be moved along the Z direction by an actuator.

In addition, in the said embodiment, in the process S16, although the example in which the control part 8 judges an image automatically was demonstrated, the control part 8 based on a user's judgment result determines the crack position of the crack 14k. may be acquired In this case, the control unit 8 displays, for example, a plurality of internal images ID on the display 150, and one internal image in which the image of the crack 14k is clear from the plurality of internal images ID. Information prompting the determination (selection) of is displayed on the display 150 . Then, the control unit 8 receives the input of the determination result through the display 150, and can calculate the crack position of the crack 14k based on the movement amount of the internal image ID corresponding to the determination result. have. In this case, the display 150 is not only a display unit for displaying information, but also an input reception unit for accepting input. In this case, the processing load for image recognition etc. of the control part 8 is reduced.

In the above embodiment, in step S13, both direct observation and back reflection observation are performed for observation of one modified region 12, and the first internal image ID1 and the second internal image ID as the internal image ID. An internal image ID2 was acquired. 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 is obtained, the position and width of the edge portion of the modified region 12 may be estimated based on the one.

Claims (8)

an imaging unit for imaging the object by means of transmitted light having transparency to the object;
at least a control unit for controlling the imaging unit;
The object includes a first surface and a second surface opposite to the first surface,
A modified region arranged in the X direction along the first surface and the second surface and a crack extending from the modified region are formed in the object;
The control unit, under the control of the imaging unit, while injecting the transmitted light from the first surface into the interior of the object, the Z-direction intersecting the first surface and the second surface of the crack and the X-direction intersection An observation device for performing an imaging process of imaging a target crack, which is the crack, extending in the following direction with the transmitted light. The method according to claim 1,
and a moving unit for relatively moving a condensing lens for condensing the transmitted light on the object with respect to the object,
In the imaging process, the control unit relatively moves the condensing lens along the Z-direction under the control of the imaging unit and the moving unit to position the converging points of the transmitted light at a plurality of positions inside the object, acquiring a plurality of internal images by imaging the object;
The control unit is, after the imaging processing, based on the amount of movement of the condensing lens in the Z direction when the plurality of internal images and each of the internal images are imaged, a crack that is a position of the target crack in the Z direction An observation device that executes calculation processing for calculating a position. 3. The method according to claim 2,
In the calculation processing, the control unit determines the internal image in which the image of the target crack is clear from among the plurality of internal images, and based on the movement amount of the condenser lens when the determined internal image is captured. an observation device for calculating the crack location. 4. The method of claim 3,
After the calculation processing, based on the formation conditions of the modified region and the crack position, the control unit includes: a position of an end of the first surface side of the modified region in the Z direction, a position of the second surface side of the modified region, An observation apparatus for performing estimation processing for estimating at least one of a position of an end portion in the Z direction and a width of the modified region in the Z direction. 5. The method according to any one of claims 2 to 4,
In the imaging process, the control unit,
By relatively moving the condensing lens along the Z-direction while the transmitted light is incident on the object from the first surface, the converging point of the transmitted light that has not undergone reflection on the second surface is set from the first surface side. a first imaging process of acquiring a plurality of first internal images as the internal images by imaging the target at a plurality of positions while moving toward a second surface side;
By relatively moving the condensing lens along the Z-direction while the transmitted light is incident on the object from the first surface, the converging point of the transmitted light reflected by the second surface is moved from the second surface side to the first surface side. An observation apparatus for executing a second imaging process for acquiring a plurality of second internal images as the internal images by imaging the target at a plurality of positions while moving toward the . 6. The method of claim 5,
In the calculation processing, the control unit,
Determine the first internal image in which the target crack is clear among a plurality of the first internal images, and based on the movement amount of the condensing lens when the determined first internal image is captured, the first internal image as the crack position is determined. a first calculation process for calculating a crack location;
Determine the second internal image in which the target crack is clear from among the plurality of second internal images, and based on the amount of movement of the condensing lens when the determined second internal image is captured, a second as the crack position performing a second calculation process for calculating a crack location;
The control unit is an observation device for 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 cracking position and the second cracking position. 7. The method according to any one of claims 2 to 6,
Further comprising a display unit for displaying information,
The said control part is an observation apparatus which performs the display process which displays the information regarding the said crack position on the said display part under the control of the said display part after the said calculation process. It includes a first surface and a second surface opposite to the first surface, and a modified region arranged in the X direction along the first surface and the second surface, and a crack extending from the modified region to prepare an object preparation process,
After the preparation process, while the transmitted light passing through the object is incident on the object from the first surface, it extends in the Z direction and the X direction crossing the first surface and the second surface during the cracking The observation method provided with the imaging process of imaging the target crack which is the said crack with the said transmitted light.

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