JP7313127B2 - IMAGING DEVICE, LASER PROCESSING DEVICE, AND IMAGING METHOD - Google Patents

Description

The present invention relates to an imaging device, a laser processing device, and an imaging method.

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

JP 2017-64746 A

Like the laser processing apparatus described in Patent Document 1, there is a demand for non-destructive confirmation of the modified region formed inside the wafer. On the other hand, in the laser processing apparatus disclosed in Patent Document 1, the imaging position of the wafer by the infrared camera is arranged on a straight line downstream in the wafer movement direction with respect to the processing position of the wafer by the processing optical system.

As a result, the infrared camera captures an image of the wafer on the same planned cutting line as the wafer processing position by the processing optical system, so that the formation position of the modified region formed inside the wafer, processing damage, etc. can be confirmed and measured in real time. However, it takes a certain amount of time to confirm and measure the modified region using an infrared camera or the like. Therefore, if the formation of the modified region and the confirmation of the modified region, etc., are performed at the same time as in the laser processing apparatus described in Patent Document 1, the speed at which the modified region is formed is limited, which may reduce the processing efficiency.

Accordingly, an object of the present invention is to provide an imaging device, a laser processing device, and an imaging method that enable non-destructive confirmation while suppressing a decrease in processing efficiency.

An imaging apparatus according to the present invention is an imaging apparatus for imaging a modified region formed in an object by irradiation with a laser beam and/or a crack extending from the modified region, and includes a first imaging unit that images the object with light that passes through the object, and a first control unit that controls the first imaging unit. performing a first imaging process for controlling the first imaging unit to image the modified region formed along and/or the region including the crack extending from the modified region;

In this device, the first control unit performs a first imaging process of imaging the modified region in the object and/or the region including the crack extending from the modified region using light passing through the object. Therefore, images of the modified region and the like (the modified region and/or cracks extending from the modified region (the same shall apply hereinafter)) can be acquired without destroying the object, and they can be confirmed. In particular, in this apparatus, the first control unit executes the above-described first imaging process after the modified region is formed on the object along the first line and at the timing when the irradiation position of the laser light is aligned with the first line. Therefore, it is possible to confirm the modified region and the like without affecting the speed at which the modified region is formed. That is, according to this device, it is possible to perform non-destructive confirmation while suppressing a decrease in processing efficiency.

In the imaging device according to the present invention, after the modified region is formed on the object along the second line that intersects the first line, the first control unit may execute a second imaging process of controlling the first imaging unit so as to capture an image of the modified region formed along the second line and/or the region including the crack extending from the modified region at the timing at which the laser beam irradiation position is aligned with the second line. In this case, it is possible to non-destructively check the modified regions formed along the lines intersecting each other while suppressing the deterioration of the processing efficiency.

A laser processing apparatus according to the present invention includes the imaging device described above, a laser irradiation unit for irradiating an object with a laser beam, and a drive unit to which the laser irradiation unit is attached and which moves the laser irradiation unit in a direction intersecting the incident surface of the laser beam on the object, and the first imaging unit is attached to the drive unit together with the laser irradiation unit.

This device includes the imaging device described above. Therefore, according to this device, it is possible to perform non-destructive confirmation while suppressing a decrease in processing efficiency. This apparatus also includes a drive unit that moves the laser irradiation unit in a direction (incident direction) that intersects the incident surface of the laser beam on the object. A first imaging unit is attached to the drive unit together with the laser irradiation unit. Therefore, it becomes easy to share the positional information of the incident direction between the formation of the modified region by laser light irradiation and the first imaging process.

A laser processing apparatus according to the present invention includes a second imaging unit that captures an image of an object using light that passes through the object, and a laser irradiation unit and a second control unit that controls the second imaging unit. The first imaging unit has a first lens that passes light that has passed through the object, and a first photodetector that detects the light that has passed through the first lens. and a detection unit, and the second control unit may perform alignment processing for controlling the laser irradiation unit and the second imaging unit so as to align the irradiation position of the laser light based on the detection result of the second photodetection unit. In this way, by separately using the second imaging unit for aligning the irradiation position of the laser light in addition to the first imaging unit for imaging the modified region, etc., it is possible to use an optical system suitable for each.

In the laser processing apparatus according to the present invention, the numerical aperture of the first lens may be larger than the numerical aperture of the second lens. In this case, it is possible to image the modified region or the like with a relatively large numerical aperture while ensuring alignment by observation with a relatively small numerical aperture.

In the laser processing apparatus according to the present invention, the second control unit may perform alignment processing after forming a plurality of rows of modified regions along the laser beam incident surface of the object. In this way, performing alignment after forming a plurality of rows of modified regions is more efficient from the viewpoint of both formation of the modified regions and imaging of the modified regions.

An imaging method according to the present invention is an imaging method for imaging a modified region formed in an object by irradiating a laser beam and/or a crack extending from the modified region, comprising a first imaging step of imaging the modified region formed along the first line and/or the region including the crack extending from the modified region formed along the first line after the modified region is formed in the object along the first line and at the timing of aligning the irradiation position of the laser beam with the first line. .

In this method, a modified region in the object and/or a region containing a crack extending from the modified region is imaged with light passing through the object. Therefore, it is possible to confirm the modified region and the like without destroying the object. In particular, in this method, the imaging is performed after the modified region is formed on the object along the first line and at the timing when the irradiation position of the laser beam is aligned with the first line. Therefore, it is possible to confirm the modified region and the like without affecting the speed at which the modified region is formed. That is, according to this method, it is possible to check nondestructively while suppressing a decrease in processing efficiency.

The imaging method according to the present invention includes a second imaging step of imaging the modified region formed along the second line and/or the region including the crack extending from the modified region with light passing through the object at the timing of aligning the irradiation position of the laser beam with the second line after the modified region is formed in the object along the second line intersecting the first line. In this case, it is possible to non-destructively check the modified regions formed along the lines intersecting each other while suppressing the deterioration of the processing efficiency.

Advantageous Effects of Invention According to the present invention, it is possible to provide an imaging device, a laser processing device, and an imaging method that enable non-destructive confirmation while suppressing a decrease in processing efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram of the laser processing apparatus provided with the test|inspection apparatus of one Embodiment. 1 is a plan view of a wafer in one embodiment; FIG. 3 is a cross-sectional view of a portion of the wafer shown in FIG. 2; FIG. FIG. 2 is a configuration diagram of a laser irradiation unit shown in FIG. 1; 2 is a configuration diagram of an imaging unit for inspection shown in FIG. 1; FIG. 2 is a configuration diagram of an imaging unit for alignment correction shown in FIG. 1. FIG. 6A and 6B are cross-sectional views of a wafer for explaining the principle of imaging by the imaging unit for inspection shown in FIG. 5 and images at various locations by the imaging unit for inspection; 6A and 6B are cross-sectional views of a wafer for explaining the principle of imaging by the imaging unit for inspection shown in FIG. 5 and images at various locations by the imaging unit for inspection; 4 is an SEM image of a modified region and cracks formed inside a semiconductor substrate; 4 is an SEM image of a modified region and cracks formed inside a semiconductor substrate; FIG. 6 is an optical path diagram for explaining the principle of imaging by the imaging unit for inspection shown in FIG. 5 and a schematic diagram showing an image at a focus by the imaging unit for inspection; FIG. 6 is an optical path diagram for explaining the principle of imaging by the imaging unit for inspection shown in FIG. 5 and a schematic diagram showing an image at a focus by the imaging unit for inspection; 6A and 6B are a cross-sectional view of a wafer, an image of a cut surface of the wafer, and an image at each location by the inspection imaging unit for explaining the principle of inspection by the inspection imaging unit shown in FIG. 5; 6A and 6B are a cross-sectional view of a wafer, an image of a cut surface of the wafer, and an image at each location by the inspection imaging unit for explaining the principle of inspection by the inspection imaging unit shown in FIG. 5; 1 is a flowchart of a semiconductor device manufacturing method according to one embodiment; 16 is a cross-sectional view of a portion of the wafer in the grinding and cutting steps of the semiconductor device manufacturing method shown in FIG. 15; FIG. 16 is a cross-sectional view of a portion of the wafer in the grinding and cutting steps of the semiconductor device manufacturing method shown in FIG. 15; FIG. 4 is a flow chart showing a laser processing method and an imaging method according to one embodiment. It is a block diagram of the laser processing system provided with the imaging device of a modification.

An embodiment will be described in detail below with reference to the drawings. In addition, in each figure, the same elements or corresponding elements may be denoted by the same reference numerals, and overlapping descriptions may be omitted. Also, the drawing may show an orthogonal coordinate system defined by the X-axis, the Y-axis, and the Z-axis.

As shown in FIG. 1, the laser processing apparatus 1 includes a stage 2, a laser irradiation unit 3, a plurality of imaging units 4, 5, 6, a drive unit 7, and a controller 8. The laser processing apparatus 1 is an apparatus that forms a modified region 12 on an object 11 by irradiating the object 11 with a laser beam L. As shown in FIG.

The stage 2 supports the object 11 by sucking a film attached to the object 11, for example. The stage 2 is movable along each of the X and Y directions, and is rotatable about an axis parallel to the Z direction. Note that the X direction and the Y direction are the first horizontal direction and the second horizontal direction perpendicular to each other, and the Z direction is the vertical direction.

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

Modified region 12 is a region that differs in density, refractive index, mechanical strength, and other physical properties from surrounding unmodified regions. The modified region 12 includes, for example, a melting process region, a crack region, a dielectric breakdown region, a refractive index change region, and the like. The modified region 12 has a characteristic that cracks tend to extend from the modified region 12 to the incident side of the laser light L and the opposite side. Such properties of the modified region 12 are used for cutting the object 11 .

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

An imaging unit (first imaging unit) 4 images an object 11 supported by the stage 2 with light passing through the object 11 under the control of a control section (first control section) 8 . More specifically, the imaging unit 4 images the modified region 12 formed in the object 11 and the tip of the crack extending from the modified region 12 . In this embodiment, the imaging unit 4 and the control section 8 that controls the imaging unit 4 function as an imaging device 10 .

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

The drive unit 7 supports the laser irradiation unit 3 and a plurality of imaging units 4, 5, 6. In other words, the drive unit 7 is attached with the laser irradiation unit 3 . The imaging units 4 , 5 and 6 are attached to the drive unit 7 together with the laser irradiation unit 3 . The driving unit 7 moves the laser irradiation unit 3 and the plurality of imaging units 4, 5, 6 along the Z direction. Here, the Z direction is a direction that intersects the plane of incidence of the laser light L on the object 11 (for example, the back surface 21b described later).

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

The object 11 of this embodiment is a wafer 20, as shown in FIGS. A wafer 20 includes a semiconductor substrate 21 and a functional element layer 22 . The semiconductor substrate 21 has a front surface 21a and a back surface 21b. The semiconductor substrate 21 is, for example, a silicon substrate. The functional element layer 22 is formed on the surface 21 a of the semiconductor substrate 21 . The functional element layer 22 includes a plurality of functional elements 22a arranged two-dimensionally along the surface 21a. The functional element 22a is, for example, a light receiving element such as a photodiode, a light emitting element such as a laser diode, a circuit element such as a memory, or the like. The functional element 22a may be configured three-dimensionally by stacking a plurality of layers. Although the semiconductor substrate 21 is provided with the notch 21c indicating the crystal orientation, an orientation flat may be provided instead of the notch 21c.

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

The lines 15 include a plurality of first lines 15a and a plurality of second lines 15b crossing (perpendicular to) the first lines 15a. Here, the first lines 15a are parallel to each other, and the second lines 15b are parallel to each other. Thus, a pair of first lines 15a adjacent to each other and a pair of second lines 15b adjacent to each other define one rectangular parallelepiped functional element 22a. In other words, wafer 20 (object 11) includes a plurality of functional elements 22a defined by first lines 15a and second lines 15b when viewed in the Z direction. The intersection of the first line 15a and the second line 15b defines the corner of the functional element 22a, and each of the first line 15a and the second line 15b defines the sides of the functional element 22a.
[Configuration of laser irradiation unit]

As shown in FIG. 4 , the laser irradiation unit 3 has a light source 31 , a spatial light modulator 32 and a condenser lens 33 . The light source 31 outputs laser light L by, for example, a pulse oscillation method. The spatial light modulator 32 modulates the laser light L output from the light source 31 . The spatial light modulator 32 is, for example, a reflective liquid crystal (LCOS: Liquid Crystal on Silicon) spatial light modulator (SLM: Spatial Light Modulator). A condenser lens 33 collects the laser light L modulated by the spatial light modulator 32 .

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

The two rows of modified regions 12 a and 12 b are adjacent to each other in the thickness direction (Z direction) of the wafer 20 . The two rows of modified regions 12 a and 12 b are formed by relatively moving the two focal points C 1 and C 2 along the line 15 with respect to the semiconductor substrate 21 . The laser light L is modulated by the spatial light modulator 32 so that the condensing point C2 is located behind the condensing point C1 in the traveling direction and on the incident side of the laser light L, for example.

The laser irradiation unit 3 irradiates the wafer 20 with the laser light L from the rear surface 21b side of the semiconductor substrate 21 along each of the plurality of lines 15 under the condition that the crack 14 extending over the two rows of modified regions 12a and 12b reaches the front surface 21a of the semiconductor substrate 21. As an example, a semiconductor substrate 21, which is a single crystal silicon substrate having a thickness of 775 μm, is irradiated with laser light L from the rear surface 21b side of the semiconductor substrate 21 to the wafer 20 along each of the plurality of lines 15 by aligning the two focal points C1 and C2 at positions 54 μm and 128 μm from the surface 21a. At this time, the wavelength of the laser light L is 1099 nm, the pulse width is 700 ns, and the repetition frequency is 120 kHz. The power of the laser light L at the condensing point C1 is 2.7 W, the power of the laser light L at the condensing point C2 is 2.7 W, and the relative moving speed of the two condensing points C1 and C2 with respect to the semiconductor substrate 21 is 800 mm/sec.

Formation of such two rows of modified regions 12a, 12b and cracks 14 is carried out in the following cases. That is, in a later process, the semiconductor substrate 21 is thinned by grinding the back surface 21b of the semiconductor substrate 21, the cracks 14 are exposed on the back surface 21b, and the wafer 20 is cut into a plurality of semiconductor devices along the plurality of lines 15.
[Configuration of imaging unit for inspection]

As shown in FIG. 5 , the imaging unit 4 has a light source 41 , a mirror 42 , an objective lens (first lens) 43 , and a photodetector (first photodetector) 44 . The light source 41 outputs light I<b>1 having transparency to the semiconductor substrate 21 . The light source 41 is composed of, for example, a halogen lamp and a filter, and outputs light I1 in the near-infrared region. The light I1 output from the light source 41 is reflected by the mirror 42, passes through the objective lens 43, and is irradiated onto the wafer 20 from the rear surface 21b side of the semiconductor substrate 21. FIG. At this time, the stage 2 supports the wafer 20 on which the two rows of modified regions 12a and 12b are formed as described above.

The objective lens 43 allows the light I1 reflected by the surface 21a of the semiconductor substrate 21 to pass therethrough. That is, the objective lens 43 allows the light I1 propagated (transmitted) through the semiconductor substrate 21 to pass therethrough. The numerical aperture (NA) of the objective lens 43 is 0.45 or more. The objective lens 43 has a correction ring 43a. The correction ring 43a corrects the aberration occurring in the light I1 within the semiconductor substrate 21 by adjusting the mutual distances of the plurality of lenses constituting the objective lens 43, for example. The photodetector 44 detects the light I1 that has passed through the objective lens 43 and the mirror 42 . The photodetector 44 is composed of, for example, an InGaAs camera, and detects light I1 in the near-infrared region.

The imaging unit 4 can image the two rows of modified regions 12a and 12b and the tips of the plurality of cracks 14a, 14b, 14c and 14d (details will be described later). The crack 14a is a crack extending from the modified region 12a toward the surface 21a. Crack 14b is a crack extending from modified region 12a toward back surface 21b. The crack 14c is a crack extending from the modified region 12b toward the surface 21a. The crack 14d is a crack extending from the modified region 12b toward the rear surface 21b. The control unit 8 causes the laser irradiation unit 3 to irradiate the laser beam L under the condition that the cracks 14 extending over the two rows of modified regions 12a and 12b reach the surface 21a of the semiconductor substrate 21 (see FIG. 4).
[Configuration of imaging unit for alignment correction]

As shown in FIG. 6 , the imaging unit 5 has a light source 51 , a mirror 52 , a lens (second lens) 53 , and a photodetector (second photodetector) 54 . The light source 51 outputs light I<b>2 that is transmissive to the semiconductor substrate 21 . The light source 51 is composed of, for example, a halogen lamp and a filter, and outputs light I2 in the near-infrared region. The light source 51 may be shared with the light source 41 of the imaging unit 4 . The light I2 output from the light source 51 is reflected by the mirror 52, passes through the lens 53, and irradiates the wafer 20 from the back surface 21b side of the semiconductor substrate 21. FIG.

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

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

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

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

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

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

As shown in FIGS. 12A and 12B, when the tip 14e of the crack 14 is focused from the rear surface 21b side, for example, due to optical peculiarities (stress concentration, strain, discontinuity of atomic density, etc.) occurring near the tip 14e, light confinement occurring near the tip 14e, and the like, part of the light I1 that has been reflected and returned from the surface 21a is scattered, reflected, interfered, absorbed, etc., so that the tip 14e appears dark against a whitish background. (right images in FIGS. 12a and 12b). As shown in FIG. 12(c), when the focus F is adjusted from the rear surface 21b side to a portion other than the vicinity of the tip 14e of the crack 14, at least part of the light I1 reflected by the front surface 21a returns, resulting in a whitish image (right image in FIG. 12(c)).
[Inspection principle by inspection imaging unit]

The control unit 8 causes the laser irradiation unit 3 to irradiate the laser beam L under the condition that the crack 14 extending over the two rows of modified regions 12a and 12b reaches the surface 21a of the semiconductor substrate 21. As a result, when the crack 14 extending over the two rows of modified regions 12a and 12b reaches the surface 21a as planned, the state of the tip 14e of the crack 14 is as follows. That is, as shown in FIG. 13, the tip 14e of the crack 14 does not appear in the region between the modified region 12a and the surface 21a and in the region between the modified region 12a and the modified region 12b. The position of the tip 14e of the crack 14 extending from the modified region 12b to the back surface 21b side (hereinafter simply referred to as "tip position") is located on the back surface 21b side with respect to the reference position P between the modified region 12b and the back surface 21b.

On the other hand, when the control unit 8 causes the laser irradiation unit 3 to irradiate the laser beam L under the condition that the crack 14 extending over the two rows of modified regions 12a and 12b reaches the surface 21a of the semiconductor substrate 21, the crack 14 extending over the two rows of modified regions 12a and 12b does not reach the surface 21a due to some problem, contrary to the schedule, the state of the tip 14e of the crack 14 is as follows. That is, as shown in FIG. 14, a tip 14e of a crack 14a extending from the modified region 12a toward the surface 21a appears in the region between the modified region 12a and the surface 21a. A tip 14e of a crack 14b extending from the modified region 12a toward the back surface 21b and a tip 14e of a crack 14c extending from the modified region 12b toward the surface 21a appear in the region between the modified regions 12a and 12b. The tip position of the crack 14 extending from the modified region 12b toward the back surface 21b is located on the surface 21a with respect to the reference position P between the modified region 12b and the back surface 21b.

As described above, if the control unit 8 performs at least one of the following first inspection, second inspection, third inspection, and fourth inspection, it is possible to evaluate whether or not the crack 14 extending over the two rows of modified regions 12a and 12b reaches the surface 21a of the semiconductor substrate 21. In the first inspection, an inspection area R1 is defined as an area between the modified area 12a and the surface 21a, and an inspection is performed to determine whether or not the tip 14e of the crack 14a extending from the modified area 12a toward the surface 21a exists in the inspection area R1. In the second inspection, an inspection area R2 is defined between the modified areas 12a and 12b, and an inspection is performed to determine whether or not the tip 14e of the crack 14b extending from the modified area 12a toward the rear surface 21b exists in the inspection area R2. The third inspection is an inspection of whether or not the tip 14e of the crack 14c extending from the modified region 12b toward the surface 21a exists in the inspection region R2. In the fourth inspection, a region extending from the reference position P toward the back surface 21b but not reaching the back surface 21b is defined as an inspection region R3, and an inspection is performed to determine whether or not the tip position of the crack 14 extending from the modified region 12b toward the back surface 21b is located in the inspection region R3.

Each of the inspection region R1, the inspection region R2, and the inspection region R3 can be set based on the positions where the two focal points C1 and C2 are aligned with the semiconductor substrate 21 before forming the two rows of modified regions 12a and 12b. When the crack 14 extending over the two rows of modified regions 12a and 12b reaches the front surface 21a of the semiconductor substrate 21, the tip position of the crack 14 extending from the modified region 12b to the rear surface 21b side is stable, so the reference position P and the inspection region R3 can be set based on the results of the test machining. 13 and 14, the imaging unit 4 can image each of the two modified regions 12a and 12b. Therefore, after forming the two rows of modified regions 12a and 12b, the inspection region R1, the inspection region R2, and the inspection region R3 may be set based on the respective positions of the two modified regions 12a and 12b.
[Laser processing method and semiconductor device manufacturing method]

A semiconductor device manufacturing method according to the present embodiment will be described with reference to FIG. In addition, the semiconductor device manufacturing method of the present embodiment includes a laser processing method performed by the laser processing apparatus 1 .

First, a wafer 20 is prepared and placed on the stage 2 of the laser processing apparatus 1 . Subsequently, the laser processing apparatus 1 irradiates the wafer 20 with laser light L from the back surface 21b side of the semiconductor substrate 21 along each of the plurality of lines 15, thereby forming two rows of modified regions 12a and 12b inside the semiconductor substrate 21 along each of the plurality of lines 15 (S01, first step). In this step, the laser processing apparatus 1 irradiates the wafer 20 with the laser beam L from the rear surface 21b side of the semiconductor substrate 21 along each of the plurality of lines 15 under the condition that the crack 14 extending over the two rows of modified regions 12a and 12b reaches the surface 21a of the semiconductor substrate 21.

Subsequently, the laser processing apparatus 1 inspects whether or not the tip 14e of the crack 14b extending from the modified region 12a toward the back surface 21b exists in the inspection region R2 between the modified region 12a and the modified region 12b (S02, second step). In this step, the laser processing apparatus 1 focuses F on the inspection region R2 from the back surface 21b side, and detects the light I1 propagating (transmitting) through the semiconductor substrate 21 from the front surface 21a side to the back surface 21b side, thereby inspecting whether or not the tip 14e of the crack 14b exists in the inspection region R2. Thus, in this embodiment, the laser processing apparatus 1 performs the second inspection.

More specifically, the objective lens 43 of the imaging unit 4 focuses F on the inspection region R2 from the back surface 21b side, and the photodetector 44 of the imaging unit 4 detects the light I1 propagating (transmitting) through the semiconductor substrate 21 from the front surface 21a side to the back surface 21b side. At this time, the imaging unit 4 is moved along the Z direction by the driving unit 7, and the focal point F is relatively moved along the Z direction within the inspection region R2. Thereby, the photodetector 44 acquires image data at each location in the Z direction. Then, the control unit 8 inspects whether or not the tip 14e of the crack 14b exists in the inspection region R2 based on the signal output from the photodetector 44 (that is, the image data at each location in the Z direction).

Subsequently, the control unit 8 evaluates the processing result in step S01 based on the inspection result in step S02 (S03, third step). In this step, if the tip 14e of the crack 14b does not exist in the inspection region R2, the control unit 8 evaluates that the crack 14 extending over the two rows of modified regions 12a and 12b reaches the surface 21a of the semiconductor substrate 21. On the other hand, when the tip 14e of the crack 14b exists in the inspection region R2, the control unit 8 evaluates that the crack 14 extending over the two rows of modified regions 12a and 12b has not reached the surface 21a of the semiconductor substrate 21.

Subsequently, when it is evaluated that the crack 14 extending over the two rows of modified regions 12a and 12b reaches the surface 21a of the semiconductor substrate 21, the control unit 8 performs acceptance processing (S04). In this step, the control unit 8 causes the display provided in the laser processing apparatus 1 to display the passing result, the display of the image data on the display, the recording of the passing result in the storage unit provided in the laser processing apparatus 1 (storage as a log), the storage of the image data in the storage unit, and the like. In this manner, the display provided in the laser processing apparatus 1 functions as a notification unit that notifies the operator of the acceptance.

On the other hand, when it is evaluated that the crack 14 extending over the two rows of modified regions 12a and 12b does not reach the surface 21a of the semiconductor substrate 21, the control unit 8 performs rejection processing (S05). In this step, the control unit 8 causes the lamp included in the laser processing device 1 to turn on a lamp indicating the failure, the display included in the laser processing device 1 to indicate the failure, and the storage unit included in the laser processing device 1 to record the failure (storage as a log). In this manner, at least one of the lamp and the display provided in the laser processing apparatus 1 functions as a notification unit that notifies the operator of the failure.

The above steps S01 to S05 are the laser processing method performed in the laser processing apparatus 1. FIG.

When the passing process of step S04 is performed (that is, when it is evaluated in step 03 that the crack 14 extending over the two rows of modified regions 12a and 12b reaches the front surface 21a of the semiconductor substrate 21), the grinding device grinds the back surface 21b of the semiconductor substrate 21 to expose the cracks 14 extending over the two rows of modified regions 12a and 12b on the back surface 21b. Cut into devices (S06, fourth step).

The above steps S01 to S06 are the semiconductor device manufacturing method including the laser processing method performed in the laser processing apparatus 1. FIG. In addition, when the rejection process of step S05 is performed (that is, when it is evaluated that the crack 14 extending over the two rows of modified regions 12a and 12b does not reach the surface 21a of the semiconductor substrate 21 in step 03), inspection and adjustment of the laser processing apparatus 1, laser processing (recovery processing) again on the wafer 20, etc. are performed.

Here, the grinding and cutting of the wafer 20 in step S06 will be described more specifically. As shown in FIG. 16 , a grinding apparatus 200 grinds (polishes) the back surface 21 b of the semiconductor substrate 21 to thin the semiconductor substrate 21 and expose the cracks 14 on the back surface 21 b, and cuts the wafer 20 into a plurality of semiconductor devices 20 a along each of the plurality of lines 15. In this step, the grinding device 200 grinds the back surface 21b of the semiconductor substrate 21 to the reference position P for the fourth inspection.

As described above, when the crack 14 extending over the two rows of modified regions 12a and 12b reaches the front surface 21a of the semiconductor substrate 21, the tip position of the crack 14 extending from the modified region 12b to the back surface 21b side is located on the back surface 21b side with respect to the reference position P. Therefore, by grinding the back surface 21b of the semiconductor substrate 21 to the reference position P, the crack 14 extending over the two rows of modified regions 12a and 12b can be exposed on the back surface 21b. In other words, the wafer 20 is irradiated with the laser beam L from the rear surface 21b side of the semiconductor substrate 21 along each of the plurality of lines 15 under the condition that the predetermined grinding end position is the reference position P and the crack 14 extending over the two rows of modified regions 12a and 12b reaches the front surface 21a of the semiconductor substrate 21 and the reference position P.

Subsequently, as shown in FIG. 17, the expanding device 300 expands the expanding tape 201 attached to the back surface 21b of the semiconductor substrate 21 to separate the plurality of semiconductor devices 20a from each other. The expanding tape 201 is, for example, a DAF (Die Attach Film) made up of a substrate 201a and an adhesive layer 201b. In that case, the adhesive layer 201b arranged between the back surface 21b of the semiconductor substrate 21 and the base material 201a is cut for each semiconductor device 20a by expanding the expandable tape 201. FIG. The cut adhesive layer 201b is picked up together with the semiconductor device 20a.

Here, as described above, an image of the wafer 20 is taken when inspecting whether or not the tip 14e of the crack 14b exists in a predetermined region. The imaging of the wafer 20 is performed by an imaging device 10 composed of the imaging unit 4 and the control section 8 . In the above example, after the two rows of modified regions 12a and 12b were formed inside the semiconductor substrate 21 along all the lines 15, the image of the wafer 20 was taken along with the implementation of the second inspection. However, the timing of the second inspection (imaging of wafer 20) is not limited to this.

For example, the timing of performing the second inspection may be after the modified regions 12a and 12b are formed along one or more first lines 15a and at the timing when the irradiation position of the laser beam L is aligned with the first line 15a. In this case, after the modified regions 12a and 12b are formed along one or more second lines 15b, the second inspection may be performed at the timing when the irradiation position of the laser light L is aligned with the second lines 15b. This case will be described in detail below.

The laser processing method shown in FIG. 18 includes an imaging method. As shown in FIG. 18, first, alignment of the processing start position is performed with the wafer 20 placed on the stage 2 of the laser processing apparatus 1 (S11). In this process, for example, the imaging unit 5 images the wafer 20 under the control of the controller 8, thereby performing alignment. More specifically, in this step, the control section 8 controls the imaging unit 5 to image the functional element layer 22 .

On the other hand, initial information including the size (chip size) of the functional element 22a, the work size (size of processing range) on the wafer 20, and the reference image of the functional element layer 22 is registered in advance in the laser processing apparatus 1 (for example, the control unit 8). Then, the control unit 8 aligns the irradiation position of the laser light L (the position of the laser irradiation unit 3 in the X direction and the Y direction) based on the image obtained by the imaging unit 5 and the initial information.

In the subsequent step, the controller 8 sets the processing height (position in the Z direction) of the laser irradiation unit 3 by controlling the drive unit 7 (S12). Subsequently, the controller 8 starts forming the modified regions 12a and 12b (S13). Here, as an example, processing along the first line 15a is performed. That is, in this step, the laser processing apparatus 1 irradiates the wafer 20 with laser light L along one first line 15a from the back surface 21b side of the semiconductor substrate 21, thereby forming two rows of modified regions 12a and 12b inside the semiconductor substrate 21 along the first line 15a.

Subsequently, after the processing on one first line 15a is completed, the control unit 8 determines whether or not the position of the first line 15a is the preset alignment position (S14). The alignment here is re-alignment for correcting the positional deviation that occurs with respect to the alignment performed in step S11. This re-alignment may be performed each time the processing of one first line 15a is completed, but it is efficient to perform this alignment after a plurality of first lines 15a are completed. That is, the alignment position may be set for each first line 15a, but it is efficient to set one alignment position for a plurality of first lines 15a.

As a result of this step, if the position of the first line 15a processed in step S13 is not the alignment position, the process returns to step S13 to continue forming the modified regions 12a and 12b along another first line 15a. On the other hand, as a result of this step, if the position of the first line 15a that has been processed in step S13 is the alignment position, then alignment is to be performed again. That is, in this case, the formation of the modified regions 12a and 12b is temporarily stopped, and it is time to perform alignment.

Therefore, the second inspection is performed at this timing. That is, in the subsequent process, the control unit 8 controls the imaging unit 4 to image the wafer 20 (S15, first imaging process). Here, the control unit 8 moves the imaging unit 4 along the Z direction, thereby relatively moving the focus F within the wafer 20 along the Z direction. As a result, the imaging unit 4 captures an image at each location in the Z direction and obtains an image. Therefore, the obtained image may include only the modified regions 12a and 12b, may include the modified regions 12a and 12b and the crack 14, or may include only the crack 14.

That is, here, after the modified regions 12a and 12b are formed on the wafer 20 along the first line 15a, the control unit 8 controls the imaging unit 4 so as to image the modified regions 12a and 12b formed along the first line 15a and/or the region including the crack 14 extending from the modified regions 12a and 12b at the timing at which the irradiation position of the laser beam L is aligned with the first line 15a. An imaging process (first imaging step) is executed. The image obtained in this step is provided to the control section 8 . Therefore, the control unit 8 can perform the second inspection based on the supplied image data and based on the above method/principle.

In the subsequent process, the alignment is performed again as described above (the control unit 8 executes the alignment process) (S16). An example of alignment here is as follows. That is, the control unit 8 controls the imaging unit 5 to image the functional element layer 22 at the alignment correction position. Further, the control section 8 controls the imaging unit 5 to capture an image of a region including the modified regions 12a and 12b at the same position. Then, based on the two images, the control unit 8 detects the displacement amount of the modified regions 12a and 12b with respect to a predetermined position (for example, the central position) of the street region 23. FIG. The controller 8 aligns the irradiation position of the laser light L again based on the detected deviation amount.

Alternatively, another example of alignment here is as follows. That is, the control unit 8 controls the imaging unit 5 to image the functional element layer 22 at the alignment correction position. Then, the control unit 8 performs pattern matching between the image of the functional element layer 22 at the alignment correction position acquired in advance before processing and the image of the functional element layer 22 acquired in this process, thereby detecting the amount of deviation between characteristic points such as alignment marks. The controller 8 adjusts the irradiation position of the laser light L based on the detected deviation amount.

In the subsequent step, the control unit 8 determines whether or not the formation of the modified regions 12a and 12b along all the first lines 15a has been completed (S17). As a result of this determination, if the formation of the modified regions 12a and 12b along all the first lines 15a has not been completed, the process returns to step S13 to continue forming the modified regions 12a and 12b along the remaining first lines 15a. On the other hand, if the result of this determination is that the formation of the modified regions 12a and 12b along all the first lines 15a has been completed, then the formation of the modified regions 12a and 12b along the second lines 15b is started. That is, in this case, the formation of the modified regions 12a and 12b is temporarily stopped, and the timing is set to switch between the formation of the modified regions 12a and 12b along the first line 15a and the formation of the modified regions 12a and 12b along the second line 15b.

That is, in the subsequent step, the laser processing apparatus 1 irradiates the wafer 20 with laser light L from the back surface 21b side of the semiconductor substrate 21 along one second line 15b, thereby forming two rows of modified regions 12a and 12b inside the semiconductor substrate 21 along the second line 15b (S18).

Subsequently, after the processing on one second line 15b is completed, the control unit 8 determines whether or not the position of the second line 15b is the preset alignment position (S19). The alignment here is realignment for correcting the positional deviation that occurs with respect to the alignment performed in step S16. This re-alignment may be performed each time the processing of one second line 15b is completed, but it is efficient to perform this alignment after a plurality of second lines 15b are completed. That is, the alignment position here may also be set for each second line 15b, but it is efficient to set one alignment position for a plurality of second lines 15b.

As a result of this step, if the position of the second line 15b processed in step S18 is not the alignment position, the process returns to step S18 to continue forming the modified regions 12a and 12b along another second line 15b. On the other hand, as a result of this step, if the position of the second line 15b that has been processed in step S18 is the alignment position, then alignment is to be performed again. That is, in this case, the formation of the modified regions 12a and 12b is temporarily stopped, and it is time to perform alignment.

Therefore, the second inspection is further performed at this timing. That is, in the subsequent process, the controller 8 controls the imaging unit 4 to image the wafer 20 (S20, second imaging process). The mode of imaging is the same as in step S15.

That is, after the modified regions 12a and 12b are formed on the wafer 20 along the second line 15b, the control unit 8 controls the imaging unit 4 to capture an image of the modified regions 12a and 12b formed along the second line 15b and/or the region including the cracks 14 extending from the modified regions 12a and 12b at the timing when the irradiation position of the laser beam L is aligned with the second line 15b. second imaging step). The image obtained in this step is provided to the control section 8 . Therefore, the control unit 8 can perform the second inspection based on the supplied image data and based on the above method/principle.

In the subsequent step, alignment is performed again as described above (S21). The mode of alignment here is the same as in step S16.

In the subsequent step, the control unit 8 determines whether or not the formation of the modified regions 12a, 12b along all the second lines 15b has been completed (S22). As a result of this determination, if the formation of the modified regions 12a and 12b along all the second lines 15b has not been completed, the process returns to step S18 to continue forming the modified regions 12a and 12b along the remaining second lines 15b. On the other hand, if the result of this determination is that the formation of the modified regions 12a and 12b along all the second lines 15b has been completed, the process is completed.

Note that the location where the second inspection is performed (that is, the imaging area when viewed from the Z direction) may be at least one location among the plurality of lines 15 set in a grid pattern, but as an example, it may be a side of the functional element 22a. As described above, the functional element 22a is defined by the first line 15a and the second line 15b when viewed from the Z direction. Therefore, the location where the second inspection is performed can be a side area corresponding to the first line 15a and/or the second line 15b of the functional element 22a when viewed from the Z direction. In other words, the location where the second inspection is performed can be a location other than the corner region, which is the intersection of the first line 15a and the second line 15b in the functional element 22a when viewed in the Z direction.

Further, in the laser processing method and the imaging method described with reference to FIG. 18, the second inspection was exemplified as the inspection of the crack 14, but the second inspection is not limited to the first inspection, the third inspection, or the fourth inspection.

[Actions and Effects of Laser Processing Method and Semiconductor Device Manufacturing Method]

In the laser processing method described above, the focus F is adjusted from the back surface 21b side of the semiconductor substrate 21 to the inspection region R2 between the modified regions 12a and 12b, and the light I1 propagating through the semiconductor substrate 21 from the front surface 21a side to the back surface 21b side is detected. By detecting the light I1 in this way, the tip 14e of the crack 14b extending from the modified region 12a to the back surface 21b side can be confirmed when the tip 14e of the crack 14b exists in the inspection region R2. Then, when the tip 14e of the crack 14b exists in the inspection region R2, it is assumed that the crack 14 extending over the two rows of modified regions 12a and 12b does not reach the surface 21a of the semiconductor substrate 21. FIG. Therefore, according to the laser processing method described above, it is possible to confirm whether or not the crack 14 extending over the two rows of modified regions 12 a and 12 b reaches the surface 21 a of the semiconductor substrate 21 .

Further, in the laser processing method described above, when the tip 14e of the crack 14b does not exist in the inspection region R2, it is evaluated that the crack 14 extending over the two rows of modified regions 12a and 12b reaches the surface 21a of the semiconductor substrate 21, and when the tip 14e of the crack 14b exists in the inspection region R2, it is evaluated that the crack 14 spanning the two rows of modified regions 12a and 12b does not reach the surface 21a of the semiconductor substrate 21. Thereby, it is possible to determine the embodiment of the subsequent steps based on the evaluation results.

Further, in the laser processing method described above, two rows of modified regions 12a and 12b are formed as the plurality of rows of modified regions 12 . As a result, the formation of multiple rows of modified regions 12 and the inspection of cracks 14 extending over the multiple rows of modified regions 12 can be efficiently performed.

Further, according to the semiconductor device manufacturing method described above, when it is evaluated that the crack 14 extending over the two rows of modified regions 12a and 12b does not reach the front surface 21a of the semiconductor substrate 21, the rear surface 21b of the semiconductor substrate 21 is not ground, so that it is possible to prevent the wafer 20 from being reliably cut along each of the plurality of lines 15 after the grinding process.
[Imaging device, imaging method, action and effect of laser processing device]

The imaging device 10 described above is for imaging the modified regions 12a and 12b formed in the object 11 (semiconductor substrate 21 of the wafer 20) and/or the cracks 14 extending from the modified regions 12a and 12b by the irradiation of the laser light L. The imaging device 10 includes an imaging unit 4 that images the wafer 20 with light I<b>1 that passes through at least the semiconductor substrate 21 of the wafer 20 , and a control unit 8 that controls the imaging unit 4 . After the modified regions 12a and 12b are formed on the semiconductor substrate 21 along the first line 15a, the control unit 8 performs a first imaging process of controlling the imaging unit 4 so as to capture an image of the modified regions 12a and 12b formed along the first line 15a and/or the region including the crack 14 extending from the modified regions 12a and 12b at the timing when the irradiation position of the laser beam L is aligned with the first line 15a. execute.

In the imaging device 10, the control unit 8 performs a first imaging process of imaging the modified regions 12a and 12b in the semiconductor substrate 21 and/or the regions including the cracks 14 extending from the modified regions 12a and 12b with the light I1 that passes through the semiconductor substrate 21. Therefore, images of the modified regions 12a, 12b, etc. (modified regions 12a, 12b and/or cracks 14 extending from the modified regions 12a, 12b (the same shall apply hereinafter)) can be acquired and confirmed without destroying the wafer 20. In particular, in the imaging device 10, the control unit 8 executes the above-described first imaging process after the modified regions 12a and 12b are formed in the semiconductor substrate 21 along the first line 15a and at the timing when the irradiation position of the laser beam L is aligned with the first line 15a. Therefore, the modified regions 12a and 12b can be confirmed without affecting the speed at which the modified regions 12a and 12b are formed. That is, according to the imaging device 10, it is possible to perform non-destructive confirmation while suppressing a decrease in processing efficiency.

In the imaging device 10, after the modified regions 12a and 12b are formed in the semiconductor substrate 21 along the second line 15b that intersects the first line 15a, the controller 8 controls the modified regions 12a and 12b formed along the second line 15b and/or the regions including the cracks 14 extending from the modified regions 12a and 12b at the timing when the irradiation position of the laser beam L is aligned with the second line 15b. A second imaging process is executed to control the imaging unit 4 so as to take an image. Therefore, it is possible to check the modified regions 12a and 12b formed along the lines 15 intersecting each other in a non-destructive manner while suppressing a decrease in processing efficiency.

Further, the laser processing apparatus 1 described above includes the imaging device 10 described above, a laser irradiation unit 3 for irradiating the wafer 20 with the laser light L, and a driving unit 7 to which the laser irradiation unit 3 is attached and which moves the laser irradiation unit 3 in the Z direction. The imaging unit 4 is attached to the driving unit 7 together with the laser irradiation unit 3 .

The laser processing device 1 includes the imaging device 10 described above. Therefore, according to the laser processing apparatus 1, it is possible to perform non-destructive confirmation while suppressing a decrease in processing efficiency. The laser processing apparatus 1 also includes a drive unit 7 that moves the laser irradiation unit 3 in the Z direction. An imaging unit 4 is attached to the drive unit 7 together with the laser irradiation unit 3 . Therefore, it becomes easy to share positional information in the Z direction between the formation of the modified regions 12a and 12b by the irradiation of the laser light L and the first imaging process.

The laser processing apparatus 1 also includes an imaging unit 5 that captures an image of the wafer 20 with light I2 that passes through at least the semiconductor substrate 21 of the wafer 20, and a controller 8 that controls the laser irradiation unit 3 and the imaging unit 5 (common with the imaging device 10). The imaging unit 4 has an objective lens 43 that allows the light I1 that has passed through the semiconductor substrate 21 to pass therethrough, and a photodetector 44 that detects the light I1 that has passed through the objective lens 43 . The imaging unit 5 also has a lens 53 that allows the light I2 that has passed through the semiconductor substrate 21 to pass therethrough, and a photodetector 54 that detects the light I2 that has passed through the lens 53 . Then, the control unit 8 performs alignment processing for controlling the laser irradiation unit 3 and the imaging unit 5 so as to align the irradiation position of the laser light L based on the detection result of the light detection unit 54 . In this way, by separately using the imaging unit 5 for aligning the irradiation position of the laser light L in addition to the imaging unit 4 for imaging the modified regions 12a and 12b, it is possible to use an optical system suitable for each.

Moreover, in the laser processing apparatus 1 , the numerical aperture of the objective lens 43 is larger than that of the lens 53 . In this case, it is possible to image the modified regions 12a, 12b, etc., with a relatively large numerical aperture while ensuring alignment by observation with a relatively small numerical aperture.

In the laser processing apparatus 1 , the control unit 8 may perform alignment processing after forming a plurality of rows of modified regions 12 a and 12 b along the laser beam incident surface (back surface 21 b ) of the wafer 20 . In this way, alignment after forming a plurality of rows of modified regions 12a and 12b is more efficient from the viewpoint of both formation of modified regions 12a and 12b and imaging of modified regions 12a and 12b.

The imaging method described above is an imaging method for imaging the modified regions 12a and 12b formed in the semiconductor substrate 21 by the irradiation of the laser beam L and/or the cracks 14 extending from the modified regions 12a and 12b. a first imaging step of imaging the modified regions 12a and 12b and/or the regions including the cracks 14 extending from the modified regions 12a and 12b with the light I1 that passes through the semiconductor substrate 21;

In this method, the modified regions 12 a and 12 b in the semiconductor substrate 21 and/or the regions including the cracks 14 extending from the modified regions 12 a and 12 b are imaged with light I 1 passing through the semiconductor substrate 21 . Therefore, the modified regions 12a, 12b and the like can be checked without destroying the wafer 20. FIG. In particular, in this method, after the modified regions 12a and 12b are formed in the semiconductor substrate 21 along the first line 15a, the imaging is performed at the timing when the irradiation position of the laser beam L is aligned with the first line 15a. Therefore, the modified regions 12a and 12b can be confirmed without affecting the speed at which the modified regions 12a and 12b are formed. That is, according to this method, it is possible to check nondestructively while suppressing a decrease in processing efficiency.

In the imaging method described above, after the modified regions 12a and 12b are formed in the semiconductor substrate 21 along the second line 15b that intersects the first line 15a, at the timing of aligning the irradiation position of the laser beam L with the second line 15b, the modified regions 12a and 12b formed along the second line 15b and/or the regions including the cracks 14 extending from the modified regions 12a and 12b are removed from the semiconductor substrate 21. A second imaging step of imaging with the transmitted light I1 is provided. Therefore, it is possible to check the modified regions 12a and 12b formed along the lines 15 intersecting each other in a non-destructive manner while suppressing a decrease in processing efficiency.
[Modification]

The invention is not limited to the embodiments described above. For example, in the above-described embodiment, the laser processing apparatus 1 forms two rows of modified regions 12a and 12b inside the semiconductor substrate 21 along each of the plurality of lines 15, but the laser processing device 1 may form one row or three or more rows of modified regions 12 inside the semiconductor substrate 21 along each of the plurality of lines 15. The number of rows, positions, etc. of the modified regions 12 formed for one line 15 can be appropriately set in consideration of the thickness of the semiconductor substrate 21 in the wafer 20, the thickness of the semiconductor substrate 21 in the semiconductor device 20a, and the like. The multiple rows of modified regions 12 may be formed by performing relative movement of the focal point C of the laser light L multiple times on one line 15 .

15, the grinding device 200 may grind the back surface 21b of the semiconductor substrate 21 beyond the reference position P in the grinding and cutting step S06 shown in FIG. The expected grinding end position can be appropriately set according to whether the modified region 12 is left on the side surface (cut surface) of the semiconductor device 20a. If the semiconductor device 20a is, for example, a DRAM (Dynamic Random Access Memory), the modified region 12 may remain on the side surface of the semiconductor device 20a.

Further, as shown in FIG. 19 , the imaging device 10 may be configured separately from the laser processing device 1 . An imaging apparatus 10 shown in FIG. 19 includes an imaging unit 4, a stage 101, a drive unit 102, and a control section (first control section) 103. A stage 101 is configured in the same manner as the stage 2 described above, and supports a wafer 20 on which a plurality of rows of modified regions 12 are formed. The drive unit 102 supports the imaging unit 4 and moves the imaging unit 4 along the Z direction. The control unit 103 is configured similarly to the control unit 8 described above. In the laser processing system shown in FIG. 19, the wafer 20 is transported between the laser processing device 1 and the imaging device 10 by a transport device such as a robot hand.

Further, the irradiation conditions of the laser light L when the wafer 20 is irradiated with the laser light L from the back surface 21b side of the semiconductor substrate 21 along each of the plurality of lines 15 are not limited to those described above. For example, the irradiation condition of the laser light L may be, as described above, a condition in which the crack 14 extending over the multiple rows of modified regions 12 (for example, two rows of modified regions 12a and 12b) reaches the interface between the semiconductor substrate 21 and the functional element layer 22. Alternatively, the irradiation conditions of the laser light L may be such that the cracks 14 extending over the plurality of rows of the modified regions 12 reach the surface of the functional element layer 22 opposite to the semiconductor substrate 21 . Alternatively, the irradiation condition of the laser light L may be a condition that the cracks 14 extending over the plurality of lines of the modified regions 12 reach the vicinity of the surface 21 a in the semiconductor substrate 21 . In this manner, the irradiation conditions of the laser light L may be any conditions as long as the cracks 14 extending over the plurality of rows of the modified regions 12 are formed. In either case, it is possible to confirm whether or not the cracks 14 extending over the rows of the modified regions 12 sufficiently extend toward the surface 21a of the semiconductor substrate 21 .

In addition, various materials and shapes can be applied to each configuration in the above-described embodiments without being limited to the materials and shapes described above. Moreover, each configuration in one embodiment or modified example described above can be arbitrarily applied to each configuration in another embodiment or modified example.

DESCRIPTION OF SYMBOLS 1... Laser processing apparatus, 3... Laser irradiation unit, 4... Imaging unit (first imaging unit), 5... Imaging unit (second imaging unit), 7... Driving unit, 8... Control part (first control part, second control part), 10... Imaging device, 12, 12a, 12b... Modified area, 11... Object, 14... Crack, 15a... First line, 15b... Second line.

Claims (9)

An imaging device for imaging a modified region formed in an object by irradiation with a laser beam and/or a crack extending from the modified region,
a first imaging unit that captures an image of the object using light that passes through the object;
a first control unit that controls the first imaging unit;
with
After the modified region is formed on the object along the first line, the first control unit performs a first imaging process of controlling the first imaging unit to capture an image of the modified region formed along the first line and/or a region including the crack extending from the modified region at a timing when the irradiation position of the laser beam is aligned with the first line,
The alignment with respect to the first line includes alignment correction for correcting a deviation amount of the irradiation position of the laser light,
The alignment correction is performed when the position of the first line forming the modified region is a preset alignment position.
Imaging device. After the modified region is formed on the object along a second line that intersects the first line, the first control unit performs a second imaging process of controlling the first imaging unit to capture an image of the modified region formed along the second line and/or a region including the crack extending from the modified region at a timing when the irradiation position of the laser beam is aligned with the second line.
The imaging device according to claim 1 . An imaging device according to claim 1 or 2;
a laser irradiation unit for irradiating the object with the laser light;
a driving unit to which the laser irradiation unit is attached and which moves the laser irradiation unit in a direction intersecting the incident surface of the laser light on the object;
with
The first imaging unit is attached to the drive unit together with the laser irradiation unit,
Laser processing equipment. a second imaging unit that captures an image of the object using light that passes through the object;
a second control unit that controls the laser irradiation unit and the second imaging unit;
with
The first imaging unit has a first lens that passes light that has passed through the object, and a first photodetector that detects the light that has passed through the first lens,
The second imaging unit has a second lens that passes light that has passed through the object, and a second photodetector that detects the light that has passed through the second lens,
The second control unit performs alignment processing for controlling the laser irradiation unit and the second imaging unit so as to align the irradiation position of the laser light based on the detection result of the second photodetection unit.
The laser processing apparatus according to claim 3. The numerical aperture of the first lens is greater than the numerical aperture of the second lens,
The laser processing apparatus according to claim 4. The second control unit performs the alignment process after forming a plurality of rows of the modified regions along the laser light incident surface of the object.
The laser processing apparatus according to claim 4 or 5. An imaging method for imaging a modified region formed in an object by laser light irradiation and/or a crack extending from the modified region,
After the modified region is formed in the object along the first line and at the timing of aligning the irradiation position of the laser beam with the first line, the modified region formed along the first line and / or the region containing the crack extending from the modified region is imaged with light passing through the object;
The alignment with respect to the first line includes alignment correction for correcting a deviation amount of the irradiation position of the laser light,
The alignment correction is performed when the position of the first line forming the modified region is a preset alignment position.
Imaging method. After the modified region is formed on the object along a second line that intersects the first line and at the timing of aligning the irradiation position of the laser beam with the second line, the modified region formed along the second line and / or the region containing the crack extending from the modified region is imaged with light passing through the object.
The imaging method according to claim 7. An imaging device for imaging a modified region formed in an object by laser light irradiation and/or a crack extending from the modified region, the imaging device comprising: a first imaging unit for imaging the object with light passing through the object; and a first control section for controlling the first imaging unit;
a laser irradiation unit for irradiating the object with the laser light;
a driving unit to which the laser irradiation unit is attached and which moves the laser irradiation unit in a direction intersecting the incident surface of the laser light on the object;
a second imaging unit that captures an image of the object using light that passes through the object;
a second control unit that controls the laser irradiation unit and the second imaging unit;
with
After the modified region is formed on the object along the first line, the first control unit performs a first imaging process of controlling the first imaging unit to capture an image of the modified region formed along the first line and/or a region including the crack extending from the modified region at a timing when the irradiation position of the laser beam is aligned with the first line,
The first imaging unit is attached to the drive unit together with the laser irradiation unit,
The first imaging unit has a first lens that passes light that has passed through the object, and a first photodetector that detects the light that has passed through the first lens,
The second imaging unit has a second lens that passes light that has passed through the object, and a second photodetector that detects the light that has passed through the second lens,
The second control unit performs alignment processing for controlling the laser irradiation unit and the second imaging unit so as to align the irradiation position of the laser light based on the detection result of the second photodetection unit,
The numerical aperture of the first lens is greater than the numerical aperture of the second lens,
Laser processing equipment.

Images