KR102697247B1 - Imaging device, laser processing device, and imaging method - Google Patents

Abstract

An imaging device comprising a first imaging unit (4) for imaging an object (11) by light passing through the object, and a first control unit (8) for controlling the first imaging unit, wherein the first control unit executes a first imaging process for controlling the first imaging unit to image the modified area (12) formed along the first line (15a) on the object at a timing when alignment of the irradiation position of laser light with respect to the first line is performed, and/or an area including the crack extending from the modified area.

Description

Imaging device, laser processing device, and imaging method

One aspect of the present disclosure relates to an imaging device, a laser processing device, and an imaging method.

A laser processing device is known which forms a plurality of rows of modified regions inside a semiconductor substrate along each of a plurality of lines by irradiating the wafer with laser light from the back side of the semiconductor substrate to 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. The laser processing device described in Patent Document 1 is equipped with an infrared camera, and is capable of observing the modified regions formed inside the semiconductor substrate, processing damage formed in the functional element layer, and the like, from the back side of the semiconductor substrate.

Patent Document 1: Japanese Patent Publication No. 2017-64746

As with the laser processing device described in the above-mentioned patent document 1, there is a demand for non-destructively confirming a modified region, etc. formed inside a wafer. Regarding this, in the laser processing device described in patent document 1, the position of capturing the image of the wafer by the infrared camera is arranged in a straight line on the downstream side in the direction of wafer movement with respect to the position of processing the wafer by the processing optical system.

As a result, it is attempted to confirm and measure in real time the formation position of a modified region formed inside a wafer, processing damage, etc., by having an infrared camera capture an image of the wafer on the same cutting line as the processing position of the wafer by the processing optical system. However, confirmation and measurement of a modified region, etc. using an infrared camera, etc. requires a certain amount of time. Therefore, if the formation of a modified region and confirmation of the modified region, etc. are attempted simultaneously, as in the laser processing device described in Patent Document 1, there is a concern that the processing efficiency may decrease because the speed at which the modified region is formed is limited.

Therefore, one aspect of the present disclosure is to provide an imaging device, a laser processing device, and an imaging method that enable non-destructive verification while suppressing a decrease in processing efficiency.

An imaging device according to one aspect of the present disclosure is an imaging device for imaging a modified region formed in a target object by irradiation with laser light, and/or a crack extending from the modified region, comprising: a first imaging unit for imaging the target object by light passing through the target object; and a first control section for controlling the first imaging unit, wherein the first control section executes a first imaging process for controlling the first imaging unit to image the modified region formed along the first line, and/or an area including the crack extending from the modified region, at a timing when alignment of the irradiation position of the laser light with respect to the first line is performed after the modified region is formed in the target object along the first line.

In this device, the first control unit executes a first imaging process for capturing an image of a region including a modified region in the target object and/or a crack extending from the modified region by light passing through the target object. Therefore, it is possible to acquire an image of the modified region, etc. (the modified region and/or the crack extending from the modified region (the same applies hereinafter)) without destroying the target object, and confirmation of them becomes possible. In particular, in this device, the first control unit executes the first imaging process at a timing when alignment of the irradiation position of the laser light with respect to the first line is performed after the modified region is formed in the target object along the first line. Therefore, confirmation of the modified region, etc. becomes possible without affecting the speed at which the modified region is formed. That is, according to this device, non-destructive confirmation becomes possible while suppressing a decrease in processing efficiency.

In an imaging device according to one aspect of the present disclosure, the first control unit may execute a second imaging process for controlling the first imaging unit to image a modified region formed along the second line and/or a region including a crack extending from the modified region at a timing when alignment of the irradiation position of the laser light with respect to the second line is performed after a modified region is formed in the target object along the second line intersecting the first line. In this case, non-destructive confirmation of the modified region, etc. formed along the intersecting lines becomes possible while suppressing a decrease in processing efficiency.

A laser processing device according to one aspect of the present disclosure comprises the above-described imaging device, a laser irradiation unit for irradiating a target object with laser light, and a drive unit equipped with the laser irradiation unit and moving the laser irradiation unit in a direction intersecting an incident surface of the laser light on the target object, wherein the first imaging unit is mounted on the drive unit together with the laser irradiation unit.

This device is equipped with the above-mentioned imaging device. Therefore, with this device, non-destructive confirmation is possible while suppressing a decrease in processing efficiency. In addition, this device is equipped with a drive unit that moves a laser irradiation unit in a direction (incident direction) intersecting an incident surface of laser light on a target object. Then, the first imaging unit is mounted on the drive unit together with the laser irradiation unit. Therefore, it becomes easy to share positional information of the incident direction in the formation of a modified area by irradiation of laser light and the first imaging process.

A laser processing device according to one aspect of the present disclosure comprises a second imaging unit that images an object by light passing through the object, and a second control unit that controls the laser irradiation unit and the second imaging unit, wherein the first imaging unit has a first lens that passes light that has passed through the object, and a first light detection unit 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 light detection unit that detects the light that has passed through the second lens, and the second control unit may execute an alignment process that controls the laser irradiation unit and the second imaging unit to align an irradiation position of the laser light based on a detection result of the second light detection 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 a modified area, etc., it becomes possible to use an optical system suitable for each.

In a laser processing device according to one aspect of the present disclosure, the numerical aperture of the first lens may be larger than the numerical aperture of the second lens. In this case, alignment can be reliably performed by observation with a relatively small numerical aperture, while imaging of a modified area, etc., with a relatively large numerical aperture is possible.

In the laser processing device according to one aspect of the present disclosure, the second control unit may perform alignment processing after forming multiple rows of modified regions along the incident surface of the laser light on the target object. In this way, performing alignment after forming multiple rows of modified regions is more efficient from the viewpoints of both forming the modified regions and capturing images of the modified regions, etc.

An imaging method according to one aspect of the present disclosure is an imaging method for imaging a modified region formed in a target object by irradiation with laser light, and/or a crack extending from the modified region, comprising: a first imaging process for imaging, by light transmitted through the target object, a region including the modified region formed along a first line, and/or the crack extending from the modified region, at a timing at which alignment is performed with respect to a first line of an irradiation position of laser light after the modified region is formed in the target object along a first line.

In this method, a region including a modified region in a target object and/or a crack extending from the modified region is imaged by light passing through the target object. Therefore, confirmation of the modified region, etc. can be performed without destroying the target object. In particular, in this method, the image is performed at a timing when alignment of the irradiation position of the laser light with respect to the first line is performed after the modified region is formed in the target object along the first line. Therefore, confirmation of the modified region, etc. can be performed without affecting the speed at which the modified region is formed. That is, according to this method, confirmation by non-destruction is possible while suppressing a decrease in processing efficiency.

An imaging method according to one aspect of the present disclosure comprises a second imaging process for imaging, by means of light transmitted through the object, a modified area formed along the second line and/or an area including a crack extending from the modified area at a timing when alignment of an irradiation position of laser light with respect to a second line is performed after a modified area is formed in the object along a second line intersecting the first line. In this case, non-destructive confirmation of the modified area, etc. formed along the intersecting lines is made possible while suppressing a decrease in processing efficiency.

According to one aspect of the present disclosure, it is possible to provide an imaging device, a laser processing device, and an imaging method that enable non-destructive verification while suppressing a decrease in processing efficiency.

Figure 1 is a configuration diagram of a laser processing device having an inspection device of one embodiment.
Figure 2 is a plan view of a wafer of one embodiment.
Figure 3 is a cross-sectional view of a portion of the wafer shown in Figure 2.
Figure 4 is a configuration diagram of the laser irradiation unit shown in Figure 1.
Figure 5 is a configuration diagram of the inspection imaging unit shown in Figure 1.
Figure 6 is a configuration diagram of the imaging unit for alignment correction shown in Figure 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 images 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 images at each location by the inspection imaging unit.
Figure 9 is an SEM image of a modified region and crack formed inside a semiconductor substrate.
Figure 10 is an SEM image of a modified region and crack formed inside a semiconductor substrate.
Fig. 11 is a schematic diagram showing an optical path for explaining the imaging principle by the inspection imaging unit shown in Fig. 5, and an image at a focus by the inspection imaging unit.
Fig. 12 is a schematic diagram showing an optical path for explaining the imaging principle by the inspection imaging unit shown in Fig. 5, and an image at a focus by the inspection imaging unit.
Fig. 13 is a cross-sectional view of a wafer, an image of a cut surface of the wafer, and images at each location by the inspection imaging unit for explaining the inspection principle by the inspection imaging unit shown in Fig. 5.
Fig. 14 is a cross-sectional view of a wafer, an image of a cut surface of the wafer, and images at each location by the inspection imaging unit for explaining the inspection principle by the inspection imaging unit shown in Fig. 5.
Figure 15 is a flow chart of a semiconductor device manufacturing method according to one embodiment.
FIG. 16 is a cross-sectional view of a portion of a wafer in the grinding and cutting process of the semiconductor device manufacturing method shown in FIG. 15.
Fig. 17 is a cross-sectional view of a portion of a wafer in the grinding and cutting process of the semiconductor device manufacturing method shown in Fig. 15.
Fig. 18 is a flow chart showing a laser processing method and an imaging method according to one embodiment.
Fig. 19 is a configuration diagram of a laser processing system equipped with an imaging device of a modified example.

Hereinafter, one embodiment will be described in detail with reference to the drawings. In addition, in each drawing, the same elements or corresponding elements are given the same symbols and redundant descriptions are omitted. In addition, the drawings sometimes show an orthogonal coordinate system defined by the X-axis, the Y-axis, and the Z-axis.

As shown in Fig. 1, a laser processing device (1) is equipped with a stage (2), a laser irradiation unit (3), a plurality of imaging units (4, 5, 6), a driving unit (7), and a control unit (8). The laser processing device (1) is a device that forms a modified area (12) on a target object (11) by irradiating the target object (11) with laser light (L).

The stage (2) supports the object (11), for example, by absorbing a film attached to the object (11). The stage (2) is movable along the X direction and the Y direction, respectively, and is rotatable about an axis line parallel to the Z direction as a center line. In addition, the X direction and the Y direction are a first horizontal direction and a second horizontal direction that are perpendicular to each other, and the Z direction is a vertical direction.

The laser irradiation unit (3) focuses laser light (L) that is transparent to the target object (11) and irradiates the target object (11). When the laser light (L) is focused inside the target object (11) supported on the stage (2), the laser light (L) is particularly absorbed at a portion corresponding to the focusing point (C) of the laser light (L), and a modified region (12) is formed inside the target object (11).

The modified region (12) is a region whose density, refractive index, mechanical strength, and other physical properties are different from those of the surrounding non-modified region. Examples of the modified region (12) include a melt processing region, a crack region, an insulation breakdown region, a refractive index change region, etc. The modified region (12) has a characteristic that cracks are likely to extend from the modified region (12) to the incident side of the laser light (L) and the opposite side. This characteristic of the modified region (12) is utilized for cutting the target object (11).

As an example, when the stage (2) is moved along the X direction and the focusing point (C) is moved relatively along the X direction with respect to the object (11), a plurality of modified spots (12s) are formed to be lined up in one row along the X direction. One modified spot (12s) is formed by irradiation with one pulse of laser light (L). A row of modified areas (12) is a collection of a plurality of modified spots (12s) lined up in one row. The adjacent modified spots (12s) may be connected to each other or separated from each other depending on the relative movement speed of the focusing point (C) with respect to the object (11) and the repetition frequency of the laser light (L).

The imaging unit (first imaging unit) (4) captures an image of an object (11) supported on a stage (2) by light passing through the object (11) under the control of the control unit (first control unit) (8). More specifically, the imaging unit (4) captures an image of a modified region (12) formed on the object (11) and a tip of a crack extending from the modified region (12). In the present embodiment, the imaging unit (4) and the control unit (8) controlling the imaging unit (4) function as an imaging device (10).

The imaging unit (second imaging unit) (5) and the imaging unit (6) capture an image of an object (11) supported on a stage (2) by light passing through the object (11) under the control of the control unit (second control unit) (8). The image obtained by capturing the image by the imaging units (5, 6) is provided, for example, for alignment of the irradiation position of the laser light (L).

The drive unit (7) supports the laser irradiation unit (3) and a plurality of imaging units (4, 5, 6). In other words, the laser irradiation unit (3) is mounted on the drive unit (7). In addition, the imaging units (4, 5, 6) are mounted on the drive unit (7) together with the laser irradiation unit (3). The drive 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 intersecting the incident surface of the laser light (L) on the target object (11) (for example, the back surface (21b) described later).

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 device including a processor, a memory, a storage, a communication device, and the like. In the control unit (8), the processor executes software (program) read into the memory, etc., and controls reading and writing of data from the memory and storage, and communication by the communication device.

[Composition of the object]

The object (11) of the present embodiment is a wafer (20), as shown in FIGS. 2 and 3. The wafer (20) has a semiconductor substrate (21) and a functional element layer (22). The semiconductor substrate (21) has a 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 (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 elements (22a) are, for example, light-receiving elements such as photodiodes, light-emitting elements such as laser diodes, circuit elements such as memories, etc. The functional elements (22a) may be configured three-dimensionally by stacking a plurality of layers. In addition, a notch (21c) indicating the crystal orientation is provided on the semiconductor substrate (21), but an orientation flat may be provided instead of the notch (21c).

The wafer (20) is cut along each of the plurality of lines (15) for each functional element (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). More specifically, the lines (15) pass through the center (center in the width direction) of the street regions (23) when viewed from the thickness direction of the wafer (20). The street regions (23) extend so as to pass between adjacent functional elements (22a) 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, the lines (15) are virtual lines, but may be lines that are actually drawn.

The line (15) includes a plurality of first lines (15a) and a plurality of second lines (15b) intersecting (orthogonal 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. As a result, a single functional element (22a) in the shape of a rectangular parallelepiped is defined by a pair of adjacent first lines (15a) and a pair of adjacent second lines (15b). In other words, the wafer (20) (object (11)) includes a plurality of functional elements (22a) defined by the first lines (15a) and the second lines (15b) when viewed from the Z direction. The intersection of the first line (15a) and the second line (15b) defines an angle (corner) of the functional element (22a), and each of the first line (15a) and the second line (15b) defines a side of the functional element (22a).

[Laser irradiation unit configuration]

As shown in Fig. 4, the laser irradiation unit (3) has a light source (31), a spatial light modulator (32), and a focusing 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 spatial light modulator (SLM: Spatial Light Modulator) of a reflective liquid crystal (LCOS: Liquid Crystal on Silicon). The focusing lens (33) focuses the laser light (L) modulated by the spatial light modulator (32).

In this embodiment, the laser irradiation unit (3) forms two rows of modified regions (12a, 12b) inside the semiconductor substrate (21) along each of the plurality of lines (15) by irradiating 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). The modified region (first modified region) (12a) is the modified region closest to the surface (21a) among the two rows of modified regions (12a, 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, 12b) and is the modified region closest to the back surface (21b).

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

The laser irradiation unit (3) irradiates laser light (L) to the wafer (20) from the back surface (21b) of the semiconductor substrate (21) along each of a plurality of lines (15) under the condition that the crack (14) spanning the two rows of modified regions (12a, 12b) reaches the surface (21a) of the semiconductor substrate (21). As an example, for a semiconductor substrate (21) which is a single crystal silicon substrate having a thickness of 775 μm, two focusing points (C1, C2) are respectively aligned at positions 54 μm and 128 μm from the surface (21a), and laser light (L) is irradiated to the wafer (20) from the back surface (21b) of the semiconductor substrate (21) along each of a plurality of lines (15). At this time, the wavelength of the laser light (L) is 1099 nm, the pulse width is 700 nm, and the repetition frequency is 120 kHz. In addition, the output of the laser light (L) at the focusing point (C1) is 2.7 W, the output of the laser light (L) at the focusing point (C2) is 2.7 W, and the relative movement speed of the two focusing points (C1, C2) with respect to the semiconductor substrate (21) is 800 mm/sec.

The formation of these two rows of modified regions (12a, 12b) and cracks (14) is carried out in the following case. That is, in a subsequent process, the semiconductor substrate (21) is thinned by grinding the back surface (21b) of the semiconductor substrate (21) and the cracks (14) are exposed on the back surface (21b), and the wafer (20) is cut into a plurality of semiconductor devices along each of a plurality of lines (15).

[Configuration of the 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 objective lens) (43), and a light detection unit (first light detection unit) (44). The light source (41) outputs light (I1) that is transparent to the semiconductor substrate (21). The light source (41) is composed of, for example, a halogen lamp and a filter, and outputs light (I1) in the near-infrared region. The light (I1) output from the light source (41) is reflected by the mirror (42), passes through the objective lens (43), and is irradiated onto the wafer (20) from the back surface (21b) side of the semiconductor substrate (21). At this time, the stage (2) supports the wafer (20) on which two rows of modified regions (12a, 12b) are formed as described above.

The objective lens (43) passes light (I1) reflected from the surface (21a) of the semiconductor substrate (21). That is, the objective lens (43) passes light (I1) that has transmitted the semiconductor substrate (21). 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 aberrations occurring in the light (I1) within the semiconductor substrate (21), for example, by adjusting the distance between a plurality of lenses constituting the objective lens (43). The light detection unit (44) detects light (I1) that has passed through the objective lens (43) and the mirror (42). The light detection unit (44) is composed of, for example, an InGaAs camera and detects light (I1) in the near-infrared region.

The imaging unit (4) can capture images of the tips of each of the two rows of modified regions (12a, 12b) and each of the plurality of cracks (14a, 14b, 14c, 14d) (details will be described later). The crack (14a) is a crack extending from the modified region (12a) toward the surface (21a). The crack (14b) is a crack extending from the modified region (12a) toward the 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 back surface (21b). The control unit (8) irradiates the laser irradiation unit (3) with laser light (L) under the condition that the crack (14) spanning the two rows of modified regions (12a, 12b) reaches the surface (21a) of the semiconductor substrate (21) (see Fig. 4). However, if the crack (14) does not reach the surface (21a) due to some problem, etc., a plurality of such cracks (14a, 14b, 14c, 14d) are formed.

[Configuration of the 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 light detection unit (second light detection unit) (54). The light source (51) outputs light (I2) that is transparent to the semiconductor substrate (21). The light source (51) is composed of, for example, a halogen lamp and a filter, and outputs light (I2) in the near-infrared region. The light source (51) may be common 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 light (I2) reflected from the surface (21a) of the semiconductor substrate (21). That is, the lens (53) passes light (I2) transmitted 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 light (I2) that has passed through the lens (53) and the mirror (52). The light detection unit (55) is configured by, for example, an InGaAs camera and detects light (I2) in the near-infrared region.

The imaging unit (5), under the control of the control unit (second control unit) (8), irradiates light (I2) to the wafer (20) from the back side (21b) side and detects light (I2) returning from the surface (21a) (functional element layer (22)), thereby capturing an image of the functional element layer (22). In addition, the imaging unit (5), similarly, under the control of the control unit (8), irradiates light to the wafer (20) from the back side (21b) side and detects light (I2) returning from the formation position of the modified area (12a, 12b) on the semiconductor substrate (21), thereby acquiring an image of an area including the modified area (12a, 12b). These images are used for the alignment of the irradiation position of the laser light (L). The imaging unit (6) has the same configuration as the imaging unit (5), except that the lens (53) has a lower magnification (e.g., 6x in the imaging unit (5) and 1.5x in the imaging unit (6)), and is used for alignment like the 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 a semiconductor substrate (21) in which a crack (14) spanning two rows of modified areas (12a, 12b) reaches the surface (21a), the focus (F) (the focus of the objective lens (43)) is moved from the back side (21b) side toward the surface (21a). In this case, when the focus (F) is adjusted from the back side (21b) side to the tip (14e) of the crack (14) extending from the modified area (12b) to the back side (21b) side, the tip (14e) can be confirmed (right image in Fig. 7). 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 side (21b) side, they cannot be confirmed (left image in Fig. 7). Also, if the focus (F) is focused on the surface (21a) of the semiconductor substrate (21) from the back side (21b) side, the functional element layer (22) can be confirmed.

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

As described above, it is assumed that the reason why the crack (14) itself cannot be confirmed is because the width of the crack (14) is smaller than the wavelength of the illuminating light (I1). FIGS. 9 and 10 are SEM (Scanning Electron Microscope) images of a modified region (12) and a crack (14) formed inside a semiconductor substrate (21), which is a silicon substrate. FIG. 9 (b) is an enlarged image of the region (A1) shown in FIG. 9 (a), FIG. 10 (a) is an enlarged image of the region (A2) shown in FIG. 9 (b), and FIG. 10 (b) is an enlarged image of the region (A3) shown in FIG. 10 (a). As described above, the width of the crack (14) is about 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).

Based on the above, the imaging principle assumed is as follows. As shown in Fig. 11 (a), 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. 11 (a)). As shown in Fig. 11 (b), when the focus (F) is positioned inside the semiconductor substrate (21), the light (I1) reflected from the surface (21a) returns, so a white image is obtained (the image on the right in Fig. 11 (b)). As shown in (c) of Fig. 11, when the focus (F) is focused on the modified area (12) from the back surface (21b) side, absorption, scattering, etc. occur for a portion of the light (I1) reflected from the surface (21a) by the modified area (12), so an image is obtained in which the modified area (12) appears dark against a white background (right image in (c) of Fig. 11).

As shown in (a) and (b) of Fig. 12, when a focus (F) is focused on the tip (14e) of the crack (14) from the back surface (21b), for example, due to optical singularities (stress concentration, deformation, discontinuity of atomic density, etc.) occurring near the tip (14e), light confinement occurring near the tip (14e), etc., scattering, reflection, interference, absorption, etc. occur for a portion of the light (I1) reflected from the surface (21a) and returned, so that an image is obtained in which the tip (14e) appears dark against a white background (right image in (a) and (b) of Fig. 12). As shown in (c) of Fig. 12, when the focus (F) is focused from the back surface (21b) on a part other than the vicinity of the tip (14e) of the crack (14), at least a part of the light (I1) reflected from the surface (21a) returns, so a white image is obtained (the image on the right in (c) of Fig. 12).

[Inspection principle by inspection imaging unit]

When the control unit (8) irradiates the laser irradiation unit (3) with laser light (L) under the condition that the crack (14) spanning the modified regions (12a, 12b) of the two rows reaches the surface (21a) of the semiconductor substrate (21), and as a result, the crack (14) spanning the modified regions (12a, 12b) of the two rows reaches the surface (21a) as scheduled, 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 area between the modified region (12a) and the surface (21a), and in the area between the modified region (12a) and the modified region (12b). The position of the tip (14e) of the crack (14) extending from the modified area (12b) to the back surface (21b) (hereinafter, simply referred to as the “tip position”) is located on the back surface (21b) side with respect to the reference position (P) between the modified area (12b) and the back surface (21b).

In this case, when the control unit (8) irradiates the laser irradiation unit (3) with laser light (L) under the condition that the crack (14) spanning the modified regions (12a, 12b) of the two rows reaches the surface (21a) of the semiconductor substrate (21), if, contrary to the plan, due to some problem, the crack (14) spanning the modified regions (12a, 12b) of the two rows does not reach the surface (21a), the state of the tip (14e) of the crack (14) becomes as follows. That is, as shown in Fig. 14, in the region between the modified region (12a) and the surface (21a), the tip (14e) of the crack (14a) extending from the modified region (12a) toward the surface (21a) appears. In the region between the modified region (12a) and the modified region (12b), 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. The tip position of the crack (14) extending from the modified region (12b) toward the back surface (21b) is located at the surface (21a) with respect to the reference position (P) between the modified region (12b) and the back surface (21b).

By the above, when the control unit (8) performs at least one of the following first, second, third and fourth inspections, it is possible to evaluate whether or not the crack (14) spanning the two rows of modified regions (12a, 12b) reaches the surface (21a) of the semiconductor substrate (21). The first inspection is an inspection of whether or not a tip (14e) of a crack (14a) extending from the modified region (12a) toward the surface (21a) exists in the inspection region (R1), with the region between the modified region (12a) and the surface (21a) being an inspection region (R1). The second inspection is an inspection area (R2) between the modified area (12a) and the modified area (12b), and is an inspection area to check whether a tip (14e) of a crack (14b) extending from the modified area (12a) toward the back surface (21b) exists in the inspection area (R2). The third inspection is an inspection area to check whether a tip (14e) of a crack (14c) extending from the modified area (12b) toward the front surface (21a) exists in the inspection area (R2). The fourth inspection is an inspection area (R3) to check whether a tip position of a crack (14) extending from the modified area (12b) toward the back surface (21b) is located in the inspection area (R3), and is an inspection area to check whether a tip position of a crack (14) extending from the modified area (12b) toward the back surface (21b) exists in the inspection area (R3).

Each of the inspection region (R1), the inspection region (R2), and the inspection region (R3) can be set based on the positions at which two focusing points (C1, C2) are aligned with respect to the semiconductor substrate (21) before forming the two rows of modified regions (12a, 12b). When the crack (14) spanning the two rows of modified regions (12a, 12b) reaches the 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) is stable, so the reference position (P) and the inspection region (R3) can be set based on the results of the test processing. In addition, since the imaging unit (4) can capture images of each of the two modified regions (12a, 12b) as shown in FIGS. 13 and 14, after forming two rows of modified regions (12a, 12b), it is okay to set each of the inspection region (R1), the inspection region (R2), and the inspection region (R3) based on the positions of each of the two modified regions (12a, 12b).

[Laser processing method and semiconductor device manufacturing method]

The semiconductor device manufacturing method of the present embodiment will be described with reference to Fig. 15. In addition, the semiconductor device manufacturing method of the present embodiment includes a laser processing method implemented in a laser processing device (1).

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

Next, the laser processing device (1) inspects whether a tip (14e) of a crack (14b) extending from the modified region (12a) to the back surface (21b) side exists in the inspection region (R2) between the modified region (12a) and the modified region (12b) (S02, second process). In this process, the laser processing device (1) focuses (F) from the back surface (21b) side within the inspection region (R2) and detects light (I1) that propagates (transmits) through the semiconductor substrate (21) from the front surface (21a) side to the back surface (21b) side, thereby inspecting whether a tip (14e) of a crack (14b) exists in the inspection region (R2). In this way, in the present embodiment, the laser processing device (1) performs the second inspection.

More specifically, the objective lens (43) of the imaging unit (4) focuses (F) from the back surface (21b) side within the inspection area (R2), and the light detection unit (44) of the imaging unit (4) detects light (I1) that propagates (transmits) 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 focus (F) is relatively moved along the Z direction within the inspection area (R2). Thereby, the light detection unit (44) acquires image data at each location in the Z direction. Then, the control unit (8) inspects whether or not a tip (14e) of a crack (14b) exists in the inspection area (R2) based on the signal output from the light detection unit (44) (i.e., image data at each location in the Z direction).

Next, the control unit (8) evaluates the processing result in the process S01 based on the inspection result in the process S02 (S03, the third process). In this process, if the tip (14e) of the crack (14b) does not exist in the inspection area (R2), the control unit (8) evaluates that the crack (14) spanning the two rows of modified areas (12a, 12b) reaches the surface (21a) of the semiconductor substrate (21). On the other hand, if the tip (14e) of the crack (14b) exists in the inspection area (R2), the control unit (8) evaluates that the crack (14) spanning the two rows of modified areas (12a, 12b) does not reach the surface (21a) of the semiconductor substrate (21).

Next, if it is evaluated that the crack (14) spanning the modified regions (12a, 12b) of the two rows reaches the surface (21a) of the semiconductor substrate (21), the control unit (8) performs a passing process (S04). In this process, the control unit (8) performs, as a passing process, display of the intent of passing by the display provided in the laser processing device (1), display of image data by the display, recording of the intent of passing by the memory provided in the laser processing device (1) (memory as a log), and storage of the image data by the memory. In this way, the display provided in the laser processing device (1) functions as a notification unit that informs the operator of the intent of passing.

Meanwhile, if it is evaluated that the crack (14) spanning the modified regions (12a, 12b) of the two rows does not reach the surface (21a) of the semiconductor substrate (21), the control unit (8) performs a failure processing (S05). In this process, the control unit (8) performs, as a failure processing, lighting of the meaning of failure by the lamp provided in the laser processing device (1), display of the meaning of failure by the display provided in the laser processing device (1), and recording (memory as a log) of the meaning of failure by the memory provided in the laser processing device (1). In this way, at least one of the lamp and the display provided in the laser processing device (1) functions as a notification unit that informs the operator of the meaning of failure.

The above processes S01 to S05 are laser processing methods performed in a laser processing device (1).

When the pass processing of process S04 is performed (i.e., when it is evaluated in process 03 that the crack (14) spanning the two rows of modified regions (12a, 12b) reaches the surface (21a) of the semiconductor substrate (21), the grinding device grinds the back surface (21b) of the semiconductor substrate (21), thereby exposing the crack (14) spanning the two rows of modified regions (12a, 12b) to the back surface (21b), and cuts the wafer (20) into a plurality of semiconductor devices along each of the plurality of lines (15) (S06, fourth process).

The above processes S01 to S06 are a semiconductor device manufacturing method including a laser processing method performed in a laser processing device (1). In addition, in the case where the failure treatment of process S05 is performed (i.e., in the case where it is evaluated that the crack (14) spanning the two rows of modified regions (12a, 12b) in process S03 does not reach the surface (21a) of the semiconductor substrate (21), inspection and adjustment of the laser processing device (1), re-laser processing (recovery processing) of the wafer (20), etc. are performed.

Here, the grinding and cutting of the wafer (20) of process S06 will be described in more detail. As shown in Fig. 16, the grinding device (200) grinds (polishes) the back surface (21b) of the semiconductor substrate (21), thereby thinning the semiconductor substrate (21) and exposing cracks (14) on the back surface (21b), and cuts the wafer (20) into a plurality of semiconductor devices (20a) along each of a plurality of lines (15). In this process, 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) spanning the two rows of modified regions (12a, 12b) reaches the 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) 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) spanning the two rows of modified regions (12a, 12b) can be exposed to the back surface (21b). In other words, with the grinding end position as the reference position (P), a laser light (L) is irradiated onto the wafer (20) from the back side (21b) of the semiconductor substrate (21) along each of a plurality of lines (15) under the condition that the crack (14) spanning the two rows of modified areas (12a, 12b) reaches the surface (21a) of the semiconductor substrate (21) and the reference position (P).

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

Here, as described above, when examining whether a tip (14e) of a crack (14b) exists in a predetermined region, imaging of the wafer (20) is performed. Imaging of the wafer (20) is performed by an imaging device (10) configured by an imaging unit (4) and a control unit (8). In the above example, after forming two rows of modified regions (12a, 12b) inside the semiconductor substrate (21) along each of all lines (15), imaging of the wafer (20) was performed according to the implementation of the second inspection. However, the timing of the second inspection (imaging of the wafer (20)) is not limited to this.

For example, the timing of performing the second inspection may be the timing at which alignment of the first line (15a) of the irradiation position of the laser light (L) is performed after the modified region (12a, 12b) is formed along one or more first lines (15a). In this case, the second inspection may be further performed at the timing at which alignment of the second line (15b) of the irradiation position of the laser light (L) is performed after the modified region (12a, 12b) is formed along one or more 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, here, first, in a state where a wafer (20) is placed on the stage (2) of a laser processing device (1), alignment of the processing start position is performed (S11). In this process, for example, alignment is performed by the imaging unit (5) imaging the wafer (20) under the control of the control unit (8). More specifically, in this process, the control unit (8) controls the imaging unit (5) to image the functional element layer (22).

On the one hand, the laser processing device (1) (e.g., the control unit (8)) has initial information registered in advance, including the size of the functional element (22a) (chip size), the work size (size of the processing range) on the wafer (20), and the reference image of the functional element layer (22). 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 process, the control unit (8) sets the processing height (position in the Z direction) of the laser irradiation unit (3) by controlling the drive unit (7) (S12). Next, the control unit (8) initiates the formation of the modified regions (12a, 12b) (S13). Here, as an example, processing is performed along the first line (15a). That is, in this process, the laser processing device (1) irradiates the wafer (20) with laser light (L) from the back surface (21b) side of the semiconductor substrate (21) along one first line (15a), thereby forming two rows of modified regions (12a, 12b) inside the semiconductor substrate (21) along the first line (15a).

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

As a result of this process, if the position of the first line (15a) whose processing was completed in process S13 was not the alignment position, the process returns to process S13 and the formation of the modified region (12a, 12b) along another first line (15a) is continued. On the other hand, as a result of this process, if the position of the first line (15a) whose processing was completed in process S13 was the alignment position, the alignment is performed again. That is, in this case, the formation of the modified region (12a, 12b) is temporarily stopped, and the timing for performing the alignment is set.

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 capture an image of the wafer (20) (S15, first imaging process). Here, the control unit (8) moves the imaging unit (4) along the Z direction, so that the focus (F) is relatively moved along the Z direction within the wafer (20). Thereby, the imaging unit (4) captures an image at each location in the Z direction and acquires an image. Therefore, the obtained image may include only the modified areas (12a, 12b), may include both the modified areas (12a, 12b) and the crack (14), or may include only the crack (14).

That is, here, after the modified area (12a, 12b) is formed on the wafer (20) along the first line (15a), at a timing when alignment of the irradiation position of the laser light (L) with respect to the first line (15a) is performed, the control unit (8) executes a first imaging process (first imaging process) that controls the imaging unit (4) to capture an image of the modified area (12a, 12b) formed along the first line (15a) and/or an area including a crack (14) extending from the modified area (12a, 12b). The image obtained in this process is provided to the control unit (8). Therefore, the control unit (8) can execute a second inspection based on the supplied image data and based on the above-described method and principle.

In the subsequent process, re-alignment is performed as described above (the control unit (8) performs alignment processing) (S16). An example of the alignment here is as follows. That is, the control unit (8) controls the imaging unit (5) to capture an image of the functional element layer (22) at the alignment correction position. In addition, the control unit (8) controls the imaging unit (5) to capture an image of an area including the modified areas (12a, 12b) at the same position. Then, the control unit (8) detects the amount of misalignment of the modified areas (12a, 12b) with respect to a predetermined position (for example, the center position) of the street area (23) based on the two images. The control unit (8) performs re-alignment of the irradiation position of the laser light (L) based on the detected amount of misalignment.

Alternatively, another example of alignment here is as follows. That is, the control unit (8) controls the imaging unit (5) to capture an image of the functional element layer (22) at the alignment correction position. Then, the control unit (8) detects the amount of misalignment between feature points such as alignment marks by pattern matching between the image of the functional element layer (22) at the alignment correction position that was previously captured before processing and the image of the functional element layer (22) captured in this process. The control unit (8) adjusts the irradiation position of the laser light (L) based on the detected amount of misalignment.

In the continuing process, the control unit (8) determines whether the formation of the modified regions (12a, 12b) along all of the first lines (15a) is completed (S17). If, as a result of this determination, the formation of the modified regions (12a, 12b) along all of the first lines (15a) is not completed, the process returns to step S13, and the formation of the modified regions (12a, 12b) along the remaining first lines (15a) is continued. On the other hand, if, as a result of this determination, the formation of the modified regions (12a, 12b) along all of the first lines (15a) is completed, the formation of the modified regions (12a, 12b) along the second lines (15b) is subsequently initiated. That is, in this case, the formation of the modified region (12a, 12b) is stopped once, and the timing for the formation of the modified region (12a, 12b) along the first line (15a) and the formation of the modified region (12a, 12b) along the second line (15b) is switched.

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

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

As a result of this process, if the position of the second line (15b) whose processing was completed in process S18 was not the alignment position, the process returns to process S18, and the formation of the modified region (12a, 12b) along another second line (15b) is continued. On the other hand, as a result of this process, if the position of the second line (15b) whose processing was completed in process S18 was the alignment position, the alignment is performed again. That is, in this case, the formation of the modified region (12a, 12b) is temporarily stopped, and the timing for performing the alignment is set.

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

That is, after the modified areas (12a, 12b) are formed on the wafer (20) along the second line (15b), the control unit (8) controls the imaging unit (4) to perform a second imaging process (second imaging process) to capture an image of the modified areas (12a, 12b) formed along the second line (15b) and/or an area including a crack (14) extending from the modified areas (12a, 12b) at a timing when alignment of the irradiation position of the laser light (L) with respect to the second line (15b) is performed. The image obtained in this process is provided to the control unit (8). Therefore, the control unit (8) can perform the second inspection based on the supplied image data and the above-described method and principle.

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

In the continuing process, the control unit (8) determines whether the formation of the modified regions (12a, 12b) along all of the second lines (15b) is completed (S22). If, as a result of this determination, the formation of the modified regions (12a, 12b) along all of the second lines (15b) is not completed, the process returns to step S18, and the formation of the modified regions (12a, 12b) along the remaining second lines (15b) is continued. On the other hand, if, as a result of this determination, the formation of the modified regions (12a, 12b) along all of the second lines (15b) is completed, the processing is completed.

In addition, the location where the second inspection is performed (i.e., the imaging area when viewed from the Z direction) may be at least one location among a plurality of lines (15) set in a grid shape, and as an example, may be the 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 may be the area of the side 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 may be a location excluding the area of the angle (corner) that is the intersection of the first line (15a) and the second line (15b) of the functional element (22a) when viewed from the Z direction.

Also, in the laser processing method and imaging method explained using Fig. 18, the second inspection was exemplified as an inspection for cracks (14), but it is not limited to the second inspection and may be a first inspection, a third inspection, or a fourth inspection.

[Laser processing method, semiconductor device manufacturing method, operation and effect]

In the laser processing method described above, a focus (F) is focused from the back surface (21b) side of the semiconductor substrate (21) within the inspection area (R2) between the modified area (12a) and the modified area (12b), and 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, if a tip (14e) of a crack (14a) extending from the modified area (12a) to the back surface (21b) side exists in the inspection area (R2), the tip (14e) of the crack (14b) can be confirmed. And, in the case where the tip (14e) of the crack (14b) exists in the inspection area (R2), it is assumed that the crack (14) spanning the two rows of modified areas (12a, 12b) does not reach the surface (21a) of the semiconductor substrate (21). Therefore, according to the laser processing method described above, it is possible to check whether the crack (14) spanning the two rows of modified areas (12a, 12b) reaches the surface (21a) of the semiconductor substrate (21).

In addition, in the laser processing method described above, if the tip (14e) of the crack (14b) does not exist in the inspection area (R2), it is evaluated that the crack (14) spanning the two rows of modified areas (12a, 12b) reaches the surface (21a) of the semiconductor substrate (21), and if the tip (14e) of the crack (14b) exists in the inspection area (R2), it is evaluated that the crack (14) spanning the two rows of modified areas (12a, 12b) does not reach the surface (21a) of the semiconductor substrate (21). Thereby, the implementation form of the subsequent process can be determined based on the evaluation result.

In addition, in the laser processing method described above, two rows of modified regions (12a, 12b) are formed as the multiple rows of modified regions (12). As a result, the formation of the multiple rows of modified regions (12) and the inspection of cracks (14) spanning the multiple rows of modified regions (12) can be efficiently performed.

In addition, according to the semiconductor device manufacturing method described above, if it is evaluated that the crack (14) spanning the two rows of modified regions (12a, 12b) does not reach the surface (21a) of the semiconductor substrate (21), the back surface (21b) of the semiconductor substrate (21) is not ground, so that it is possible to prevent a situation in which the wafer (20) cannot be reliably cut along each of the plurality of lines (15) after the grinding process from occurring.

[Operation and effect of imaging device, imaging method, laser processing device]

The above-described imaging device (10) is for capturing a modified region (12a, 12b) formed on a target object (11) (a semiconductor substrate (21) of a wafer (20)) by irradiation with laser light (L), and/or a crack (14) extending from the modified region (12a, 12b). The imaging device (10) comprises an imaging unit (4) that captures an image of a wafer (20) by light (I1) that passes through at least a semiconductor substrate (21) of the wafer (20), and a control unit (8) that controls the imaging unit (4). The control unit (8) executes a first imaging process to control the imaging unit (4) to capture an image of the modified area (12a, 12b) formed along the first line (15a) and/or an area including a crack (14) extending from the modified area (12a, 12b) at a timing when alignment of the irradiation position of the laser light (L) with respect to the first line (15a) is performed after the modified area (12a, 12b) is formed on the semiconductor substrate (21) along the first line (15a).

In the imaging device (10), the control unit (8) executes a first imaging process of capturing an image of a region including a modified region (12a, 12b) in a semiconductor substrate (21) and/or a crack (14) extending from the modified region (12a, 12b) by light (I1) passing through the semiconductor substrate (21). Therefore, without destroying the wafer (20), it is possible to acquire images of the modified region (12a, 12b), etc. (the modified region (12a, 12b), and/or the crack (14) extending from the modified region (12a, 12b) (hereinafter the same)), and their confirmation becomes possible. In particular, in the imaging device (10), the control unit (8) executes the first imaging process at a timing when alignment of the irradiation position of the laser light (L) with respect to the first line (15a) is performed after the modified region (12a, 12b) is formed on the semiconductor substrate (21) along the first line (15a). For this reason, confirmation of the modified region (12a, 12b), etc., becomes possible without affecting the speed at which the modified region (12a, 12b) is formed. That is, with the imaging device (10), confirmation through non-destruction becomes possible while suppressing a decrease in processing efficiency.

In addition, in the imaging device (10), the control unit (8) executes a second imaging process for controlling the imaging unit (4) to capture an image of the modified region (12a, 12b) formed along the second line (15b) and/or an area including a crack (14) extending from the modified region (12a, 12b) at a timing when alignment of the irradiation position of the laser light (L) with respect to the second line (15b) is performed after the modified region (12a, 12b) is formed along the second line (15b) intersecting the first line (15a). For this reason, non-destructive confirmation of the modified region (12a, 12b), etc. formed along the intersecting lines (15), is possible while suppressing a decrease in processing efficiency.

In addition, the laser processing device (1) described above is equipped with the above-described imaging device (10), a laser irradiation unit (3) for irradiating a wafer (20) with laser light (L), and a drive unit (7) on which the laser irradiation unit (3) is mounted and which moves the laser irradiation unit (3) in the Z direction. The imaging unit (4) is mounted on the drive unit (7) together with the laser irradiation unit (3).

The laser processing device (1) is equipped with the above-described imaging device (10). Therefore, the laser processing device (1) enables non-destructive confirmation while suppressing a decrease in processing efficiency. In addition, the laser processing device (1) is equipped with a drive unit (7) that moves the laser irradiation unit (3) in the Z direction. Then, the imaging unit (4) is mounted on the drive unit (7) together with the laser irradiation unit (3). Therefore, it becomes easy to share positional information in the Z direction in the formation of the modified area (12a, 12b) by irradiation with the laser light (L) and in the first imaging process.

In addition, the laser processing device (1) has an imaging unit (5) that captures an image of the wafer (20) by light (I2) that passes through at least a semiconductor substrate (21) of the wafer (20), and a control unit (8) (common with the imaging device (10)) that controls the laser irradiation unit (3) and the imaging unit (5). The imaging unit (4) has an objective lens (43) that passes light (I1) that passes through the semiconductor substrate (21), and a light detection unit (44) that detects the light (I1) that passes through the objective lens (43). In addition, the imaging unit (5) has a lens (53) that passes light (I2) that passes through the semiconductor substrate (21), and a light detection unit (54) that detects the light (I2) that passes through the lens (53). And, the control unit (8) executes an alignment process to control 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 alignment of the irradiation position of the laser light (L) in addition to the imaging unit (4) for imaging the modified area (12a, 12b), it becomes possible to use an optical system suitable for each.

In addition, in the laser processing device (1), the numerical aperture of the objective lens (43) is larger than the numerical aperture of the lens (53). In this case, alignment can be reliably performed by observation with a relatively small numerical aperture, while imaging of the modified area (12a, 12b) and the like with a relatively large numerical aperture is possible.

In addition, in the laser processing device (1), the control unit (8) may perform alignment processing after forming multiple rows of modified areas (12a, 12b) along the incident surface (back surface (21b)) of the laser light on the wafer (20). In this way, performing alignment after forming multiple rows of modified areas (12a, 12b) is more efficient from the viewpoints of both forming the modified areas (12a, 12b) and capturing images of the modified areas (12a, 12b), etc.

The above-described imaging method is an imaging method for imaging a modified region (12a, 12b) formed in a semiconductor substrate (21) by irradiation with laser light (L), and/or a crack (14) extending from the modified region (12a, 12b), comprising: a first imaging process for imaging, by light (I1) transmitting through the semiconductor substrate (21), a region including the modified region (12a, 12b) formed along the first line (15a) and/or the crack (14) extending from the modified region (12a, 12b), at a timing at which alignment of the irradiation position of the laser light (L) with respect to the first line (15a) is performed after the modified region (12a, 12b) is formed in the semiconductor substrate (21) along the first line (15a).

In this method, a region including a modified region (12a, 12b) in a semiconductor substrate (21) and/or a crack (14) extending from the modified region (12a, 12b) is imaged by light (I1) passing through the semiconductor substrate (21). Therefore, the modified region (12a, 12b), etc. can be confirmed without destroying the wafer (20). In particular, in this method, after the modified region (12a, 12b) is formed in the semiconductor substrate (21) along the first line (15a), the image is captured at a timing when alignment of the irradiation position of the laser light (L) with respect to the first line (15a) is performed. Therefore, the modified region (12a, 12b), etc. can be confirmed without affecting the speed at which the modified region (12a, 12b) is formed. That is, this method enables non-destructive confirmation while suppressing the decline in processing efficiency.

In addition, the above imaging method comprises a second imaging process of imaging the modified regions (12a, 12b) formed along the second line (15b) and/or the region including the crack (14) extending from the modified regions (12a, 12b) by using light (I1) transmitted through the semiconductor substrate (21) at a timing when alignment of the irradiation position of the laser light (L) with respect to the second line (15b) is performed after the modified regions (12a, 12b) are formed along the second line (15b) intersecting the first line (15a). Therefore, non-destructive confirmation of the modified regions (12a, 12b), etc. formed along the intersecting lines (15) is possible while suppressing a decrease in processing efficiency.

[Variations]

The present disclosure is not limited to the above-described embodiment. For example, in the above-described embodiment, the laser processing device (1) formed two rows of modified regions (12a, 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), etc. In addition, the multiple rows of modified regions (12) may be formed by performing the relative movement of the focusing point (C) of the laser light (L) multiple times for one line (15).

In addition, in the grinding and cutting process of process S06 shown in Fig. 15, the grinding device (200) may grind the back surface (21b) of the semiconductor substrate (21) beyond the reference position (P). The grinding end position can be appropriately set depending on whether or not a modified region (12) is left on the side surface (cut surface) of the semiconductor device (20a). In addition, when the semiconductor device (20a) is, for example, a DRAM (Dynamic Random Access Memory), it is okay for a modified region (12) to remain on the side surface of the semiconductor device (20a).

In addition, as shown in Fig. 19, the imaging device (10) may be configured separately from the laser processing device (1). The imaging device (10) shown in Fig. 19 has, in addition to the imaging unit (4), a stage (101), a driving unit (102), and a control unit (first control unit) (103). The 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 driving unit (102) supports the imaging unit (4) and moves the imaging unit (4) along the Z direction. The control unit (103) is configured in the same manner as the control unit (8) described above. In the laser processing system shown in Fig. 19, a wafer (20) is returned between a laser processing device (1) and an imaging device (10) by a return device such as a robot hand.

In addition, the irradiation conditions of the laser light (L) when irradiating the wafer (20) 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 conditions of the laser light (L) may be conditions such that a crack (14) spanning multiple rows of modified regions (12) (for example, two rows of modified regions (12a, 12b)) reaches the interface between the semiconductor substrate (21) and the functional element layer (22), as described above. Alternatively, the irradiation conditions of the laser light (L) may be conditions such that a crack (14) spanning multiple rows of modified regions (12) reaches the surface on the opposite side of the semiconductor substrate (21) in the functional element layer (22). Alternatively, the irradiation conditions of the laser light (L) may be conditions in which a crack (14) spanning the multiple rows of modified regions (12) reaches the vicinity of the surface (21a) within the semiconductor substrate (21). In this way, the irradiation conditions of the laser light (L) may be conditions in which a crack (14) spanning the multiple rows of modified regions (12) is formed. In either case, it is possible to check whether the crack (14) spanning the multiple rows of modified regions (12) sufficiently extends to the surface (21a) side of the semiconductor substrate (21).

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

[Industrial applicability]

It is possible to provide an imaging device, a laser processing device, and an imaging method that enable non-destructive verification while suppressing a decrease in processing efficiency.

1 - Laser processing device 3 - Laser irradiation unit
4 - Shooting unit (first shooting unit) 5 - Shooting unit (second shooting unit)
7 - Drive unit 8 - Control unit (1st control unit, 2nd control unit)
10 - Image device 12, 12a, 12b - Modified area
11 - Object 14 - Crack
15a - 1st line 15b - 2nd line

Claims (11)

An imaging device for capturing at least one of a modified region formed in a target object by irradiation with laser light and a crack extending from the modified region,
A first imaging unit that captures an image of the object by light passing through the object,
It has a first control unit that controls the first imaging unit,
The first control unit executes a first imaging process for controlling the first imaging unit to image an area including at least one of the modified area formed along the first line and the crack extending from the modified area at a timing when alignment of the irradiation position of the laser light with respect to the first line is performed after the modified area is formed on the target object along the first line.
The alignment for the above first line includes alignment correction for correcting the amount of misalignment in the irradiation position of the laser light,
An imaging device in which the alignment correction is performed when the position of the first line forming the modified area is a preset alignment position. In claim 1,
The first control unit executes a second imaging process for controlling the first imaging unit to image an area including at least one of the modified area formed along the second line and the crack extending from the modified area at a timing when alignment of the irradiation position of the laser light with respect to the second line is performed after the modified area is formed on the target object along the second line intersecting the first line. An imaging device as described in claim 1 or claim 2,
A laser irradiation unit for irradiating the laser light to the above target object,
The laser irradiation unit is mounted and has a driving unit that moves the laser irradiation unit in a direction intersecting the incident surface of the laser light on the target object.
The above first imaging unit is a laser processing device mounted on the driving unit together with the laser irradiation unit. In claim 3,
A second imaging unit that captures an image of the object by light passing through the object,
A second control unit is provided for controlling the laser irradiation unit and the second imaging unit,
The above first imaging unit has a first lens that passes light transmitted through the object, and a first light detection unit that detects the light passing through the first lens.
The second imaging unit has a second lens that passes light transmitted through the object, and a second light detection unit that detects the light passing through the second lens.
A laser processing device in which the second control unit executes alignment processing to control 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 light detection unit. In claim 4,
A laser processing device wherein the numerical aperture of the first lens is larger than the numerical aperture of the second lens. In claim 4,
The second control unit is a laser processing device that performs the alignment process after forming a plurality of rows of the modified areas along the incident surface of the laser light on the target object. In claim 5,
The second control unit is a laser processing device that performs the alignment process after forming a plurality of rows of the modified areas along the incident surface of the laser light on the target object. An imaging method for capturing at least one of a modified region formed in a target object by irradiation with laser light and a crack extending from the modified region,
At a timing at which alignment of the irradiation position of the laser light with respect to the first line is performed after the modified region is formed on the target object along the first line, a first imaging process is provided for imaging an area including at least one of the modified region formed along the first line and the crack extending from the modified region by light transmitted through the target object.
The alignment for the above first line includes alignment correction for correcting the amount of misalignment in the irradiation position of the laser light,
The above alignment correction is an imaging method performed when the position of the first line forming the modified area is a preset alignment position. In claim 8,
An imaging method comprising: a second imaging process for imaging an area including at least one of the modified area formed along the second line and the crack extending from the modified area, by light transmitted through the object, at a timing at which alignment of the irradiation position of the laser light with respect to the second line is performed after the modified area is formed on the object along the second line intersecting the first line. A laser irradiation unit for irradiating a target object with laser light,
A driving unit equipped with the laser irradiation unit and moving the laser irradiation unit in a direction intersecting the incident surface of the laser light on the target object;
A first imaging unit, which is mounted on the driving unit together with the laser irradiation unit and has a first lens for passing light transmitted through the object and a first light detection unit for detecting the light transmitted through the first lens, and captures an image of the object by the light transmitted through the object;
A first control unit for controlling the first imaging unit,
A second imaging unit having a second lens for passing light transmitted through the object and a second light detection unit for detecting the light transmitted through the second lens, and for capturing an image of the object by light transmitted through the object;
A second control unit is provided for controlling the laser irradiation unit and the second imaging unit,
The first control unit executes a first imaging process for controlling the first imaging unit to image an area including at least one of the modified area formed along the first line and a crack extending from the modified area at a timing when alignment of the irradiation position of the laser light with respect to the first line is performed after a modified area is formed on the target object along the first line.
A laser processing device in which the second control unit executes alignment processing to control the laser irradiation unit and the second imaging unit to align the first line of the irradiation position of the laser light based on the detection result of the second light detection unit. In claim 10,
A laser processing device wherein the numerical aperture of the first lens is larger than the numerical aperture of the second lens.

Images