Inspection apparatus and inspection method

Abstract

The control section of the laser processing apparatus of the present application is configured to perform: control of the laser irradiation unit so as to irradiate laser light along each of the forward and return paths in the X direction for each of a plurality of lines of the wafer, thereby forming one or a plurality of modified regions inside the wafer; determination, based on a signal output from a shooting unit that detects light, of whether or not a BHC in which a crack extending from each of the modified regions of the forward and return paths of the plurality of lines reaches the surface side; and determination, based on information related to the average crack amount of the forward and return paths in which the processing depth of the laser light involved in the formation of the modified regions is shallowest and the difference in crack amount of the paths, of whether or not the irradiation conditions of the laser light are acceptable.

Description

Technical Field

[0001] One aspect of the present invention relates to an inspection apparatus and an inspection method. Background Technology

[0002] Patent Document 1 discloses a laser processing apparatus comprising: an evaluation unit that captures an image of the cut surface obtained by laser cutting, generates an evaluation value representing the processing quality of each of multiple processing defect modes using feature quantities obtained based on the image, and then outputs a combination pattern of multiple evaluation values ​​corresponding to each of the multiple processing defect modes; and a correction amount calculation unit that calculates a correction amount for the processing parameters of the laser cutting based on the combination pattern. Existing technical documents Patent documents

[0003] Patent Document 1: Japanese Patent Application Publication No. 2020-121338 Summary of the Invention The problem the invention aims to solve

[0004] For laser processing devices like those described above, it is necessary to confirm whether the actual processing results meet the specified conditions at the time of manufacture, delivery, or during periodic inspections by end users. If not, the processing parameters may be adjusted.

[0005] The purpose of one aspect of the present invention is to provide an inspection apparatus and inspection method that can improve the accuracy of inspection. Technical means to solve the problem

[0006] (1) An inspection apparatus according to one aspect of the present invention comprises: a stage supporting a wafer having a semiconductor substrate, the semiconductor substrate having a first surface and a second surface; a laser irradiation unit irradiating the wafer with a laser using the second surface as an incident surface; an imaging unit outputting light that is transmissive to the semiconductor substrate and detecting light propagating in the semiconductor substrate; and a control unit configured to perform: controlling the laser irradiation unit to form one or more modified regions inside the semiconductor substrate by irradiating each of a plurality of lines extending along a first direction and adjacent to each other in a second direction with a laser along each of the forward and reverse paths in the first direction; determining, based on a signal output from the imaging unit that detects the light, whether a crack reaching the first surface side of the semiconductor substrate is a crack arrival state extending from the modified regions of each of the multiple lines; and determining whether the laser irradiation conditions are qualified based on information related to the average amount of cracks in the shallowest reverse path within the reverse path where the laser processing depth involved in the formation of the modified region is determined to be in the crack arrival state, and the difference in the amount of cracks in the reverse path.

[0007] In one aspect of the inspection apparatus of the present invention, lasers are irradiated along multiple lines to form modified regions, and the inspection results of the imaging unit determine whether cracks extending from the modified regions of each of the multiple lines have reached the first surface side (whether it is a crack-reaching state). Then, by combining information related to the average amount of cracks and the difference in crack amounts of the shortest-depth laser processing path within the short-path determined to be a crack-reaching state, the irradiation conditions of the laser are determined to be acceptable. The average amount of cracks in the short-path with the shallowest processing depth that is a crack-reaching state is an important indicator of the processing performance of laser processing that has formed a crack-reaching state. In addition, information related to the difference in crack amounts of the short-path is an important indicator of whether the same laser processing state can be achieved in the short-path. By comprehensively evaluating these indicators to determine whether the irradiation conditions of the laser are acceptable, the accuracy of the acceptance / acceptance determination can be improved. Thus, the inspection accuracy related to laser irradiation conditions can be improved.

[0008] (2) The inspection device described in (1) above may include information related to the difference in the amount of cracks in the round trip path, which includes information indicating the difference in the amount of cracks in the round trip path and information indicating the difference in the laser processing depth of the round trip path. The information indicating the difference in the amount of cracks in the round trip path is information on the difference in the amount of cracks evaluated based on a real numerical value. The information indicating the difference in the laser processing depth of the round trip path is information on the difference in the amount of cracks evaluated based on a cutting machine input value. By taking into account such information on the difference in the amount of cracks evaluated based on a cutting machine input value when determining whether the result is acceptable, for example, even if the same value is input into the cutting machine, deviations in the processing result can be avoided. As described above, by including the above two pieces of information as information related to the difference in the amount of cracks in the round trip path, the inspection accuracy can be improved.

[0009] (3) The inspection device described in (2) above may involve the control unit adding points to each of the information representing the average amount of cracks on the round trip path, the information representing the difference in the amount of cracks on the round trip path, and the information representing the difference in the laser processing depth on the round trip path, and determining whether the laser irradiation conditions are qualified or not based on their total value. With this structure, the above three pieces of information can be quantitatively evaluated, thus standardizing the evaluation. This improves the accuracy of the qualification / disqualification determination.

[0010] (4) The inspection device described in (2) or (3) above may be such that the control unit adds a weighted sum of the average crack amount of the round trip path, the information indicating the difference in crack amount of the round trip path, and the information indicating the difference in laser processing depth of the round trip path, and determines whether the laser irradiation conditions are qualified based on the total value. With such a structure, the best evaluation can be performed by weighting according to the evaluation criteria.

[0011] (5) The inspection device as described in any one of (1) to (4) above may have a control unit configured to further perform: adjusting the laser irradiation conditions based on information related to the average amount of cracks on the round trip path and the difference between the amounts of cracks on the round trip path when the laser irradiation conditions are not satisfactory. With such a structure, the laser irradiation conditions can be repeatedly adjusted based on the average amount of cracks on the round trip path, etc., until the laser irradiation conditions become satisfactory, and the laser irradiation conditions can be appropriately set.

[0012] (6) The inspection apparatus as described in any one of (1) to (5) above may be used to perform a series of inspections using only one wafer. By performing a series of inspections using only one wafer, the evaluation bias caused by the individual differences of each wafer can be eliminated, and the pass / fail status can be correctly determined and the laser irradiation conditions can be appropriately adjusted.

[0013] (7) The inspection apparatus as described in any one of (1) to (6) above may include a laser irradiation unit comprising: a light source that emits laser light; a spatial light modulator that modulates the laser light emitted from the light source; and a condenser lens that focuses the laser light modulated by the spatial light modulator onto the wafer. The control unit further considers information representing the coordinates of the aberration correction pattern of the spatial light modulator and the position of the pupil plane of the condenser lens to determine whether the laser irradiation conditions are qualified. The closer the center coordinates of the aberration correction pattern of the spatial light modulator are to the center of the condenser lens, the stronger the time-dependent changes during laser irradiation. Therefore, by incorporating such information into the difference consideration, the inspection accuracy can be improved.

[0014] (8) The inspection apparatus described in any one of (1) to (7) above may include a control unit that further considers additional parameters used in the assessment of the average crack amount to determine whether the laser irradiation conditions are acceptable. For example, considering the expectation that the smaller the crack amount of a thin object, the better, the assessment of the average crack amount may change. In this regard, by considering additional parameters used in the assessment of the average crack amount, the average crack amount can be appropriately assessed, and the inspection accuracy can be improved.

[0015] (9) The inspection apparatus as described in any one of (1) to (8) above may include a control unit that further considers information indicating the cross-sectional state of the processed wafer to determine whether the laser irradiation conditions are qualified. By considering the actual cross-sectional state after processing, the inspection accuracy related to the laser irradiation conditions can be improved.

[0016] (10) An inspection method according to one aspect of the present invention comprises: a first step of preparing a wafer having a semiconductor substrate, the semiconductor substrate having a first surface and a second surface, and forming one or more modified regions inside the semiconductor substrate by irradiating each of a plurality of lines extending along a first direction and adjacent to each other in a second direction with a laser along each of the forward and reverse paths in the first direction; a second step of outputting light that is transmissible to the semiconductor substrate having the modified regions formed in the first step, and detecting the light propagating in the semiconductor substrate; a third step of determining, based on the light detected in the second step, whether it is a crack arrival state where cracks extending from the modified regions reach the first surface side of the semiconductor substrate; and a fourth step of determining whether the laser irradiation conditions are qualified based on information related to the average amount of cracks in the reverse path where the laser processing depth involved in the formation of the modified regions is shallowest within the reverse path where the crack arrival state is determined, and the difference in the amount of cracks in the reverse path. The effects of the invention

[0017] According to one aspect of the present invention, the accuracy of inspection can be improved. Attached Figure Description

[0018] Figure 1 This is a structural diagram of a laser processing apparatus having an inspection device according to one embodiment. Figure 2 This is a plan view of a wafer according to one embodiment. Figure 3 for Figure 2 A cross-sectional view of a portion of the wafer shown. Figure 4 for Figure 1 The diagram shows the structure of the laser irradiation unit. Figure 5 for Figure 1 The diagram shown is a structural diagram of the inspection imaging unit. Figure 6 for Figure 1 The diagram shows the structure of the camera unit used for calibration and correction. Figure 7 For illustrative purposes Figure 5 The diagram shows a cross-sectional view of the wafer based on the imaging principle involved in the inspection imaging unit, and images obtained by the inspection imaging unit at various locations. Figure 8 For illustrative purposes Figure 5 The diagram shows a cross-sectional view of the wafer based on the imaging principle involved in the inspection imaging unit, and images obtained by the inspection imaging unit at various locations. Figure 9 SEM images of the modified region and cracks formed inside the semiconductor substrate. Figure 10SEM images of the modified region and cracks formed inside the semiconductor substrate. Figure 11 For illustrative purposes Figure 5 The diagram shows the optical path of the imaging principle involved in the inspection imaging unit and the schematic diagram showing the image obtained by the imaging unit at the focal point. Figure 12 For illustrative purposes Figure 5 The diagram shows the optical path of the imaging principle involved in the inspection imaging unit and the schematic diagram showing the image obtained by the imaging unit at the focal point. Figure 13 A schematic diagram showing the formation of the modified area for inspection. Figure 14 A flowchart to show the processing sequence. Figure 15 A diagram showing an example of the processing result. Figure 16 A diagram showing the cross-sectional state of the processed wafer. Figure 17 This is a table showing an example of processing conditions and inspection standards. Figure 18 A diagram showing the rules for weighting, scoring, and adjustment processing. Figure 19 A diagram illustrating the processing and export cycle. Figure 20 A diagram illustrating the processing and export cycle. Figure 21 This is a flowchart to show the inspection method. Detailed Implementation

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Furthermore, the same reference numerals are used for the same or corresponding parts in each drawing, and repeated descriptions are omitted. [Structure of laser processing equipment]

[0020] like Figure 1 As shown, the laser processing apparatus 1 (inspection apparatus) includes a stage 2, a laser irradiation unit 3, multiple imaging units 4, 5, and 6, a drive unit 7, and a control unit 8. The laser processing apparatus 1 is a device that forms a modified region 12 on a workpiece 11 by irradiating the workpiece 11 with a laser L.

[0021] The stage 2 supports the object 11, for example, by adsorbing and attaching a thin film to the object 11. The stage 2 can move along both the X direction (first direction) and the Y direction (second direction), and can rotate with an axis parallel to the Z direction as its center line. Furthermore, the X and Y directions are horizontal directions perpendicular to each other, and the Z direction is a vertical direction.

[0022] The laser irradiation unit 3 concentrates a transmissive laser L onto the object 11. If the laser L is focused inside the object 11 supported by the stage 2, the part corresponding to the focusing point C of the laser L will particularly absorb the laser L, thus forming a modified region 12 inside the object 11.

[0023] The modified region 12 is a region that differs from the surrounding unmodified region in terms of density, refractive index, mechanical strength, and other physical properties. For example, the modified region 12 may have a melt-processed region, a cracked region, an insulation-damaged region, or a region with a changing refractive index. The modified region 12 has the characteristic that cracks easily extend from the modified region 12 on the incident side of the laser L and on the opposite side. This characteristic of the modified region 12 is used to cut the object 11.

[0024] As an example, it is formed as follows: if the stage 2 is moved along the X direction, and the focusing point C is moved relative to the object 11 along the X direction, then multiple modified particles 12s are arranged in a row along the X direction. Each modified particle 12s is formed by irradiation with a single pulse of laser L. The modified region 12 of a row is a collection of multiple modified particles 12s arranged in a row. Adjacent modified particles 12s may be linked together or separated from each other by the relative movement speed of the focusing point C relative to the object 11 and the repetition frequency of the laser L.

[0025] The imaging unit 4 captures images of the modified area 12 formed by the object 11 and the front end of the crack extending from the modified area 12.

[0026] Under the control of the control unit 8, the imaging units 5 and 6 capture images of the object 11 supported by the stage 2 using light transmitted through the object 11. The images captured by the imaging units 5 and 6 are used, as an example, for calibrating the irradiation position of the laser L.

[0027] The drive unit 7 supports the laser irradiation unit 3 and multiple imaging units 4, 5, and 6. The drive unit 7 causes the laser irradiation unit 3 and the multiple imaging units 4, 5, and 6 to move along the Z direction.

[0028] The control unit 8 controls the operation of the stage 2, the laser irradiation unit 3, the multiple imaging units 4, 5, and 6, and the drive unit 7. The control unit 8 is configured as a computer device including a processor, memory, storage device, and communication device. In the control unit 8, the processor executes software (programs) read from the memory, etc., and controls the reading and writing of data in the memory and storage device, as well as the communication performed by the communication device.

[0029] [Structure of the object] The object 11 in this embodiment is as follows: Figure 2 and Figure 3The image shows a wafer 20. The wafer 20 includes a semiconductor substrate 21 and a functional element layer 22. In this embodiment, the wafer 20 is described as having the functional element layer 22, but the wafer 20 may or may not have the functional element layer 22, and may also be a bare wafer. The semiconductor substrate 21 has a surface 21a (first surface) and a back surface 21b (second surface, incident surface). The semiconductor substrate 21 is, for example, a silicon substrate. The functional element layer 22 is formed on the surface 21a of the semiconductor substrate 21. The functional element layer 22 includes a plurality of functional elements 22a arranged in a two-dimensional manner along the surface 21a. The functional elements 22a are, for example, light-receiving elements such as photodiodes, light-emitting elements such as laser diodes, and circuit elements such as memory. The functional elements 22a may be constructed in a three-dimensional manner by stacking multiple layers. Furthermore, a notch 21c indicating the crystal orientation is provided on the semiconductor substrate 21, but an orientation plane may be provided instead of a notch 21c.

[0030] The wafer 20 is cut into individual functional elements 22a along multiple lines 15. Each of the multiple lines 15 passes through multiple 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 channel region 23 when viewed from the thickness direction of the wafer 20. The channel region 23 extends in the functional element layer 22 between adjacent functional elements 22a. In this embodiment, the multiple functional elements 22a are arranged in a matrix along the surface 21a, and the multiple lines 15 are arranged in a lattice pattern. Furthermore, the lines 15 are virtual lines, but can be actually stretched lines.

[0031] [Structure of the laser irradiation unit] like Figure 4 As shown, the laser irradiation unit 3 includes a light source 31, a spatial light modulator 32, and a focusing lens 33. The light source 31 outputs laser light L, for example, through pulse oscillation. The spatial light modulator 32 modulates the laser light L output from the light source 31. The spatial light modulator 32 is, for example, a spatial light modulator (SLM) of a reflective liquid crystal on silicon (LCOS). The focusing lens 33 concentrates the laser light L modulated by the spatial light modulator 32.

[0032] In this embodiment, the laser irradiation unit 3 irradiates the wafer 20 with laser L from the back surface 21b side of the semiconductor substrate 21 along multiple lines 15, thereby forming two rows of modified regions 12a and 12b inside the semiconductor substrate 21 along the multiple lines 15. 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 also the modified region closest to the back surface 21b.

[0033] The two rows of modified regions 12a and 12b are adjacent in the thickness direction (Z direction) of wafer 20. The two rows of modified regions 12a and 12b are formed by two focusing points C1 and C2 moving relative to the semiconductor substrate 21 along line 15. The laser L is modulated, for example, by a spatial light modulator 32, such that focusing point C2 is located behind focusing point C1 in the direction of propagation and on the incident side of laser L. Furthermore, the formation of the modified regions can be single-focus or multi-focus, and can be a single operation or multiple operations.

[0034] The laser irradiation unit 3 irradiates the wafer 20 with laser L along multiple lines 15 from the back side 21b of the semiconductor substrate 21, under the condition that the cracks 14 spanning the two columns of modified regions 12a and 12b reach the surface 21a of the semiconductor substrate 21. As an example, for a single-crystal silicon substrate with a thickness of 775μm, i.e., the semiconductor substrate 21, two focusing points C1 and C2 are aligned at positions 54μm and 128μm respectively from the surface 21a, and the wafer 20 is irradiated with laser L along multiple lines 15 from the back side 21b of the semiconductor substrate 21. At this time, the wavelength of laser L is 1099nm, the pulse width is 700ns, and the repetition frequency is 120kHz. In addition, the output of laser L at focusing point C1 is 2.7W, the output of laser L at focusing point C2 is 2.7W, and the relative moving speed of the two focusing points C1 and C2 relative to the semiconductor substrate 21 is 800mm / s.

[0035] The formation of the two rows of modified regions 12a and 12b and the crack 14 is carried out in the following manner. That is, in a subsequent process, the semiconductor substrate 21 is thinned by grinding the back side 21b of the semiconductor substrate 21 and the crack 14 is exposed on the back side 21b, and the wafer 20 is cut into multiple semiconductor devices along multiple lines 15.

[0036] [Inspect the structure of the imaging unit] like Figure 5As shown, the imaging unit 4 includes a light source 41, a mirror 42, an objective lens 43, and a light detection unit 44. The light source 41 outputs light I1 that is transmissive to the semiconductor substrate 21. The light source 41 is, for example, composed of a halogen lamp and a filter, and outputs light I1 in the near-infrared region. The light I1 output from the light source 41 is reflected by the mirror 42 and passes through the objective lens 43, and then illuminates the wafer 20 from the back side 21b side of the semiconductor substrate 21. At this time, the stage 2 forms the wafer 20 in the modified regions 12a and 12b of the support row 2 as described above.

[0037] Objective lens 43 allows light I1 reflected from the surface 21a of semiconductor substrate 21 to pass through. In other words, objective lens 43 allows light I1 propagating on semiconductor substrate 21 to pass through. The numerical aperture (NA) of objective lens 43 is 0.45 or greater. Objective lens 43 has a correction ring 43a. The correction ring 43a corrects aberrations caused by light I1 within semiconductor substrate 21, for example, by adjusting the distances between the multiple lenses constituting objective lens 43. Light detection unit 44 detects light I1 transmitted through objective lens 43 and mirror surface 42. Light detection unit 44 is, for example, constructed using an InGaAs camera, and detects light I1 in the near-infrared region.

[0038] The imaging unit 4 can capture images of the front ends of each of the two rows of modified regions 12a and 12b, and each of the multiple cracks 14a, 14b, 14c, and 14d (details are described later). Crack 14a is a crack extending from the modified region 12a to the surface 21a side. Crack 14b is a crack extending from the modified region 12a to the back side 21b side. Crack 14c is a crack extending from the modified region 12b to the surface 21a side. Crack 14d is a crack extending from the modified region 12b to the back side 21b side. The control unit 8, under the condition that the cracks 14 spanning the two rows of modified regions 12a and 12b reach the surface 21a of the semiconductor substrate 21, causes the laser L to irradiate the laser irradiation unit 3 (see reference). Figure 4 However, as long as no defect or other abnormality causes crack 14 to reach surface 21a, multiple cracks 14a, 14b, 14c, and 14d will be formed. In this embodiment, as a pre-processing step for irradiating laser L from laser irradiation unit 3 to cut wafer 20 into multiple semiconductor devices, the following process is performed: to check the length of cracks and other defects as described above, and then adjust the laser irradiation conditions based on the inspection results. Specifically, as the above-mentioned pre-processing step, the following process is performed: a modified region for inspection is formed on wafer 20, and then the irradiation conditions are determined to be acceptable based on the length of cracks extending from the modified region, and the laser irradiation conditions are adjusted if necessary (details are described later). Furthermore, this pre-processing step can be performed, for example, at the time of manufacture or delivery of the laser processing equipment, or during periodic inspections by the end user.

[0039] [Structure of the imaging unit for calibration and correction] like Figure 6 As shown, the imaging unit 5 includes a light source 51, a mirror 52, a lens 53, and a light detection unit 54. The light source 51 outputs light I2 that is transmissive to the semiconductor substrate 21. The light source 51 is, for example, composed of a halogen lamp and a filter, and outputs light I2 in the near-infrared region. The light source 51 can also be used as the light source 41 of the imaging unit 4. The light I2 output from the light source 51 is reflected by the mirror 52 and passes through the lens 53, illuminating the wafer 20 from the back side 21b of the semiconductor substrate 21.

[0040] Lens 53 allows light I2 reflected from the surface 21a of the semiconductor substrate 21 to pass through. In other words, lens 53 allows light I2 propagating on the semiconductor substrate 21 to pass through. The numerical aperture of lens 53 is 0.3 or less. That is, the numerical aperture of the objective lens 43 of the imaging unit 4 is larger than the numerical aperture of lens 53. Light detection unit 54 detects the light I2 passing through lens 53 and mirror 52. Light detection unit 55, for example, is configured as an InGaAs camera, and detects light I2 in the near-infrared region.

[0041] Under the control of the control unit 8, the imaging unit 5 illuminates the wafer 20 with light I2 from the back side 21b and detects the light I2 returning from the surface 21a (functional element layer 22), thereby capturing an image of the functional element layer 22. Similarly, under the control of the control unit 8, the imaging unit 5 illuminates the wafer 20 with light I2 from the back side 21b and detects the light I2 returning from the formation locations of the modified regions 12a and 12b of the semiconductor substrate 21, thereby acquiring an image of the region including the modified regions 12a and 12b. These images are used for calibration of the irradiation position of the laser L. The imaging unit 6 has the same structure as the imaging unit 5, except that the lens 53 has a low magnification (e.g., 6x for imaging unit 5, 1.5x for imaging unit 6), and is used for calibration in the same way.

[0042] [Examine the shooting principles involved in the shooting unit] use Figure 5 As shown in the image unit 4, Figure 7 As shown, relative to the semiconductor substrate 21 where the crack 14 spans two columns of modified regions 12a and 12b reaches the surface 21a, the focal point F (the focal point of the objective lens 43) is moved from the back side 21b toward the surface 21a. At this time, if the focal point F is aligned with the tip 14e of the crack 14 extending from the modified region 12b to the back side 21b from the back side 21b side, then the tip 14e (…) can be confirmed. Figure 7 (Image on the right). However, if the focal point F is aligned with the crack 14 itself and the front end 14e of the crack 14 reaching the surface 21a from the back side 21b side, it cannot be confirmed ( Figure 7(Image on the left). Furthermore, if the focal point F is aligned with the surface 21a of the semiconductor substrate 21 from the back side 21b, the functional element layer 22 can be identified.

[0043] Additionally, using Figure 5 As shown in the image unit 4, Figure 8 As shown, for the semiconductor substrate 21 where the crack 14 spanning the two columns of modified regions 12a and 12b does not reach the surface 21a, the focal point F is moved from the back side 21b towards the surface 21a. At this time, even if the focal point F is aligned with the tip 14e of the crack 14 extending from the modified region 12a towards the surface 21a from the back side 21b, the tip 14e cannot be confirmed. Figure 8 (Image on the left). However, if the focal point F is aligned with the area opposite to the back surface 21b (that is, the area on the side of the functional element layer 22 relative to the surface 21a) from the back surface 21b side, and the imaginary focal point Fv symmetrical to the focal point F is located at the front end 14e across the surface 21a, then the front end 14e can be confirmed ( Figure 8 (Image on the right). Furthermore, the imaginary focal point Fv is a point that is symmetrical to the focal point F, which takes into account the refractive index of the semiconductor substrate 21, across surface 21a.

[0044] As mentioned above, the reason why it is impossible to confirm the nature of crack 14 is speculated to be that the width of crack 14 is smaller than the wavelength of the illumination light, i.e., light I1. Figure 9 and Figure 10 The image shows a SEM (Scanning Electron Microscope) image of the modified region 12 and the crack 14 formed inside the silicon substrate, i.e., the semiconductor substrate 21. Figure 9 (b) is Figure 9 The magnified image of region A1 shown in (a), Figure 10 (a) is Figure 9 The magnified image of region A2 shown in (b), Figure 10 (b) is Figure 10 The magnified image of region A3 shown in (a). In this way, the width of the crack 14 is 120 nm, which is smaller than the wavelength of light I1 in the near-infrared region (e.g., 1.1 to 1.2 μm).

[0045] The shooting principle assumed based on the above description is as follows. Figure 11 As shown in (a), if the focal point F is located in the air, light I1 will not return, thus resulting in a dark image. Figure 11 (The image on the right side of (a)). Figure 11 As shown in (b), if the focal point F is located inside the semiconductor substrate 21, the light I1 reflected from the surface 21a will return, thus resulting in a washed-out image. Figure 11 (Image to the right of (b)). Figure 11 As shown in (c), if the focal point F is aligned with the modified region 12 from the back side 21b, the modified region 12 causes absorption and scattering of a portion of the light I1 reflected back from the surface 21a, resulting in a blackish image of the modified region 12 against a white background. Figure 11 (The image on the right of (c)).

[0046] like Figure 12 As shown in (a) and (b), if the focal point F is aligned with the front end 14e of the crack 14 from the back side 21b, due to optical specificities (stress concentration, strain, atomic density discontinuities, etc.) generated near the front end 14e, and light retention generated near the front end 14e, a portion of the light I1 reflected back from the surface 21a undergoes scattering, reflection, interference, absorption, etc., resulting in a blackish image of the front end 14e against a white background. Figure 12 (Images to the right of (a) and (b)). Figure 12 As shown in (c), if the focal point F is aligned with the portion other than the front end 14e of the crack 14 from the back side 21b, at least a portion of the light I1 reflected from the surface 21a will be reflected back, thus resulting in a whitish image. Figure 12 (The image on the right of (c)).

[0047] The following describes the inspection and adjustment process of laser irradiation conditions performed in the preprocessing for forming modified regions for purposes such as wafer dicing 20. The control unit 8 is configured to perform: controlling the laser irradiation unit 3 to form one or more modified regions 12 for inspection inside the semiconductor substrate 21 by irradiating the wafer 20 with laser L (forming process); determining, based on the image obtained by the imaging unit 4 (the signal output from the imaging unit 4), whether the crack 14 extending from the modified region 12 reaches the surface 21a side of the semiconductor substrate 21 (first determination process); determining whether the laser irradiation conditions are qualified or not based on the average crack amount, etc. (second determination process); and adjusting the laser irradiation conditions based on the average crack amount, etc., if the laser irradiation conditions are unqualified (adjustment process).

[0048] (Forming process) like Figure 13 As shown, in the forming process, the control unit 8 controls the laser irradiation unit 3 so that the modified region 12 is formed along multiple lines of the wafer 20. Figure 13The display shows multiple lines extending along the X direction and adjacent in the Y direction. The control unit 8 controls the laser irradiation unit 3 to irradiate each of the multiple lines of the wafer 20 with laser light along the X-direction (forward) and (backward) paths, thereby forming one or more modified regions 12 inside the wafer 20. The control unit 8 controls the laser irradiation unit 3 to form modified regions 12 with varying depths between the multiple lines. (The last sentence appears to be incomplete and possibly refers to a different context.) Figure 13 In the example shown, the modified region 12 of the line marked "Z167" has the shallowest formation depth. In the Y direction, the formation depth of the modified region 12 gradually increases as one moves further away from the line marked "Z167," with the modified region of the line marked "Z178" having the deepest formation depth. This difference in the formation depth of the modified regions originates from the processing depth (height) of the laser processing apparatus 1, i.e., the difference in Z-height. The Z-height setting value of each line is changed to alter the formation depth of the modified region 12 of each line.

[0049] The modified regions 12 of each line are formed by moving the wafer 20 relative to the laser L output from the laser irradiation unit 3 along the X direction. The movement of the wafer 20 in the X direction is divided into forward (forward path) and reverse (reverse path), forming a modified region 12 for the forward path and a modified region 12 for the reverse path on each line. In the determination process described later, it is determined whether a crack has been reached for each forward path and each reverse path. This is because the optical axis of the laser L is different on the forward and reverse paths, so it is preferred to determine them separately. Furthermore, in Figure 13 For each of the 12 modified regions, only one modified region is displayed, but in reality, two modified regions 12a and 12b can be formed as described above. The number of focal points can be single focal, dual focal, or more.

[0050] Figure 14 To show the sequence of processes involved in the formation process ( Figure 13 The flowchart shows the processing sequence of the formation process example. Figure 14 In the example shown, initially, laser processing is performed on the forward path of "Z178" with the deepest processing depth (Z height) (step S1). Then, indexing feed is performed to change the processing position in the Y direction (step S2), and laser processing is performed on the return path of "Z178" (step S3).

[0051] Next, the Z-height is reset and indexed feed is performed to enable laser processing of the line adjacent to "Z178", namely "Z177", in the forward path (step S4), and laser processing is performed on the forward path of "Z177" (step S5). Then, the indexing feed enables laser processing of the return path of "Z178" (step S6), and laser processing is performed on the return path of "Z177" (step S7). Similarly, the Z-height is reset and indexed feed is repeated until laser processing is performed on the return path of "Z167", which has the shallowest processing depth (Z-height) (step S8).

[0052] (First judgment and processing) In the first determination process, the control unit 8 determines, based on the signal output from the imaging unit 4 of the detection light, that is, the image acquired in the imaging unit 4, whether the crack 14 extending from the modified region 12 of each of the multiple return paths reaches the surface 21a side of the wafer 20 in a crack arrival state (BHC: Bottom side half-cut). The determination process for whether it is a crack arrival state can be performed, for example, by techniques disclosed in Japanese Patent Application Publication No. 2021-048235. Furthermore, the state where the crack 14 does not reach the surface 21a side of the wafer 20 may be referred to below as ST (Stealth). Figure 13 The examples shown are as follows: Figure 15 As shown, for the outbound path, the line from "Z178" (the deepest Z-height) to "Z174" is designated as BHC, and the line with a shallower Z-height than "Z173" is designated as ST. Similarly, for the return path, the line from "Z178" (the deepest Z-height) to "Z175" is designated as BHC, and the line with a shallower Z-height than "Z174" is designated as ST. The following may refer to lines that would otherwise be designated as BHC: the line with the shallowest Z-height for the outbound path, "Z174," is recorded as the shallowest BHC line for the outbound path, and the line with the shallowest Z-height for the return path, "Z175," is recorded as the shallowest BHC line for the return path. (Second Judgment Processing) In the second determination process, the control unit 8 determines whether the laser irradiation conditions are qualified based on information related to the shallowest laser processing depth (Z height) involved in the formation of the modified region 12 within the round-trip path determined to be BHC, the average crack amount of the shallowest BHC line in the forward path and the shallowest BHC line in the return path, and the difference in crack amount between the shallowest BHC line in the forward path and the shallowest BHC line in the return path. Specifically, the information related to the difference in crack amount between the shallowest BHC line in the forward path and the shallowest BHC line in the return path includes information representing the difference in crack amount between the shallowest BHC line in the forward path and the shallowest BHC line in the return path, and information representing the difference in laser processing depth between the shallowest BHC line in the forward path and the shallowest BHC line in the return path.

[0053] The average cracking amount of the shallowest forward BHC line and the shallowest return BHC line is an important indicator of the processing performance of laser processing that forms BHC. For example, if the cracking amount of the shallowest forward BHC line is 60 μm and the cracking amount of the shallowest return BHC line is 40 μm, the average cracking amount of the shallowest forward BHC line and the shallowest return BHC line is 50 μm. Hereinafter, the average cracking amount of the shallowest forward BHC line and the shallowest return BHC line may only be recorded as "average cracking amount of both forward and return paths".

[0054] The information regarding the difference in crack amount between the shallowest BHC line on the outgoing path and the shallowest BHC line on the returning path is an important indicator of whether the same laser processing state can be set on both paths. This information, representing the difference in crack amount between the shallowest BHC line on the outgoing and returning paths, is based on a real-valued assessment of the difference in crack amount between the two paths. For example, if the crack amount of the shallowest BHC line on the outgoing path is 60 μm and the crack amount of the shallowest BHC line on the returning path is 40 μm, the information representing the difference in crack amount between the shallowest BHC line on the outgoing and returning paths is 20 μm. Hereinafter, the information representing the difference in crack amount between the shallowest BHC line on the outgoing and returning paths may only be recorded as "difference in crack amount between the two paths".

[0055] The information representing the difference in processing depth between the shallowest forward BHC line and the shallowest return BHC line is information about the difference in cracking amount between the forward and return paths, expressed as Z-height, which is information evaluated based on the cutting machine input value. By considering this information about the difference in cracking amount evaluated based on the cutting machine input value, the adjustment process described later can be performed so that, for example, even if the same value is input through the cutting machine (setting the same Z-height), the situation where the forward and return paths are offset can be avoided in the processing results. For example, if the processing depth of the shallowest forward BHC line is "Z174" and the processing depth of the shallowest return BHC line is "Z175", the difference in processing depth between the shallowest forward BHC line and the shallowest return BHC line is "1" (175-174=1). Hereinafter, the information representing the difference in processing depth between the shallowest forward BHC line and the shallowest return BHC line may only be recorded as "forward and return path ZH difference".

[0056] The control unit 8 can add points for each of the average crack amount of the round-trip path, the difference in crack amount of the round-trip path, and the ZH difference of the round-trip path, and then determine whether the laser irradiation conditions are qualified based on their total value. The control unit 8 can add points for each of the average crack amount of the round-trip path, the difference in crack amount of the round-trip path, and the ZH difference of the round-trip path by comparing the predetermined target value with the actual value as an inspection standard. The control unit 8 can perform the above point addition operation in such a way that the smaller the difference between the target value and the actual value, the higher the point count. The target value for the average crack amount of the round-trip path is set to a preset reference value, and the target values ​​for the difference in crack amount of the round-trip path and the ZH difference of the round-trip path are, for example, set to 0.

[0057] The control unit 8 can perform the above-mentioned point addition operation by weighting the average crack amount of the round-trip path, the difference in crack amount between the round-trip path, and the ZH difference between the round-trip path, and then determine whether the laser irradiation conditions are qualified based on the total value. The control unit 8 can increase the weight of key indicators according to the evaluation policy and then perform the above-mentioned point addition operation.

[0058] In addition to considering the main parameters consisting of the average crack amount of the round-trip path, the difference in crack amount of the round-trip path, and the ZH difference of the round-trip path, the control unit 8 can also consider secondary parameters to determine whether the laser irradiation conditions are qualified. For example, the control unit 8 can further consider information representing the coordinates of the aberration correction pattern of the spatial light modulator 32 and the position of the pupil plane of the condenser lens 33 (an example of secondary parameters) to determine whether the laser irradiation conditions are qualified. At this time, the control unit 8 can, for example, make the center of the coordinates of the aberration correction pattern of the spatial light modulator 32 closer to the center of the pupil plane of the condenser lens 33 (closer to the mechanical center) so that the time-varying change during laser irradiation is stronger, and thus add a higher number of points.

[0059] The control unit 8 can further consider additional parameters (an example of a sub-parameter) used in the evaluation of the average crack amount to determine whether the laser irradiation conditions are acceptable. Such additional parameters can be set according to the end-user's expectations or goals. For example, in the case of laser processing specifically for thin objects, the larger the crack amount, the more difficult it is to combine the conditions; therefore, when the crack amount is small, information indicating a higher number of dots can be set as an additional parameter. For example, in the case of laser processing for SD memory engines, since the end-user expects to increase the crack amount, information indicating a higher number of dots can be set as an additional parameter when the crack amount is large.

[0060] The control unit 8 can further consider information on the cross-sectional state of the processed wafer 20 (an example of a sub-parameter) to determine whether the laser irradiation conditions are qualified. Figure 16 This is a diagram showing the cross-sectional state of the processed wafer 20. The control unit 8, for example... Figure 16 As shown in (a), the point count can be lowered in cases with recessed areas or black stripes. Control unit 8, for example, Figure 16 As shown in (b), the number of points can be increased when there is a clear cross section.

[0061] (Adjustments) If the laser irradiation conditions are unqualified in the second process, the control unit 8 adjusts the laser irradiation conditions based on information related to the average crack amount on the round trip path, the difference in crack amount on the round trip path, and the ZH difference on the round trip path. For example, if the average crack amount on the round trip path is smaller than the target value determined by the inspection standard, the control unit 8 adjusts the focusing correction amount of the spatial light modulator 32 to match the difference from the target value and thus increase the crack amount. If the average crack amount on the round trip path is larger than the target value determined by the inspection standard, the control unit 8 adjusts the focusing correction amount of the spatial light modulator 32 to match the difference from the target value and thus decrease the crack amount.

[0062] For example, if the difference in crack amount between the round-trip path or the ZH difference between the round-trip path is larger than the target value determined by the inspection standard, the control unit 8 adjusts the modulation pattern of the spatial light modulator 32 to reduce the difference in crack amount between the round-trip path or the ZH difference between the round-trip path. The control unit 8 reduces the difference in crack amount between the round-trip path or the ZH difference between the round-trip path by shifting the modulation pattern along the X direction.

[0063] Next, refer to Figures 17-20 This section provides specific examples of the processes described above.

[0064] Figure 17 To display processing conditions ( Figure 17 (a) and inspection standards ( Figure 17 A table of example (b) is shown. Figure 17 As shown in (a), the processing conditions display the initial conditions for the focus correction amount and the offset (offset X) in the X direction of the modulation pattern. The initial condition for the focus correction amount is set to a reference value (focus correction level ±0), and the initial condition for the offset X is also set to a reference value (X=±0). The adjustment process adjusts the values ​​of the focus correction amount and the offset X. Figure 17 The example shown in (b) serves as the inspection standard, with the target crack length set as follows: 50 μm, target crack length (standard): 50 μm ± 8 μm, target ZH: Z174, and ZH difference between the round trip: within 3.

[0065] Figure 18 A diagram illustrating the rules for pre-defined weighting, score derivation, and adjustment processing. Figure 18 (a) is a table showing the rules governing the average amount of cracking on the round-trip road. Figure 18In the example shown in (a), when the average crack amount on the round-trip path is 50 μm, the weighted number of points is 10; when it is 50 ± 4 μm, the weighted number of points is 5; and when it exceeds 50 ± 4 μm, the weighted number of points is 0. In the adjustment process, when the number of points for the average crack amount on the round-trip path is 10, no adjustment is needed. When there are 5 points and the crack amount is greater than 50 μm, the focusing correction level is set to -2; when there are 5 points and the crack amount is less than 50 μm, the focusing correction level is set to +2; when there are 0 points and the crack amount is greater than 50 μm, the focusing correction level is set to -4; and when there are 0 points and the crack amount is less than 50 μm, the focusing correction level is set to +4. Furthermore, "level +" indicates the focusing correction amount adjustment in the direction where the crack amount increases, and "level -" indicates the focusing correction amount adjustment in the direction where the crack amount decreases. The larger the value after + (or -), the larger the adjustment amount.

[0066] Figure 18 (b) shows a table of rules relating to the difference in crack volume between the forward and reverse routes. (In such cases...) Figure 18 In the example shown in (b), when the difference in crack size between the two sides is 0 to 4 μm, the weighted number of points is 5; when it is 5 to 12 μm, the weighted number of points is 2; and when it exceeds 13 μm, the weighted number of points becomes 0. Figure 18 (c) is a table showing the rules involved in the ZH difference between the round trip route. Figure 18 In the example shown in (c), when the ZH difference between the outbound and return routes is 0-1, the weighted number of points is 5; when it is 2-3, the weighted number of points is 2; and when it exceeds 4, the weighted number of points becomes 0. During the adjustment process, when the total number of points for the outbound and return route crack difference and the ZH difference is 10, no adjustment is needed. When there are 7 points and the outbound route is larger, offset X is set to +1; when there are 7 points and the outbound route is smaller, offset X is set to -1; when there are 4 points and the outbound route is larger, offset X is set to +2; when there are 4 points and the outbound route is smaller, offset X is set to -2; when there are 0 points and the outbound route is larger, offset X is set to +3; and when there are 0 points and the outbound route is smaller, offset X is set to -3. In addition, "Offset X+" is the offset adjustment in the direction where the crack amount on the outgoing path decreases and the crack amount on the returning path increases, and "Offset X-" is the offset adjustment in the direction where the crack amount on the outgoing path increases and the crack amount on the returning path decreases. The larger the value after + (or -), the greater the adjustment amount.

[0067] Under such circumstances, for example, Figure 19 As shown in (a), the first (cycle 1) formation process is performed with the initial focusing correction level and offset X, as follows: Figure 19As shown in (b), based on internal observations, the Z-height of the shallowest BHC line in the outward path is set to Z172, the Z-height of the shallowest BHC line in the return path is set to Z176, the cracking amount of the shallowest BHC line in the outward path is set to 60 μm, and the cracking amount of the shallowest BHC line in the return path is set to 40 μm. At this time, as... Figure 19 As shown in (c), the average crack size of the round-trip path is 50 μm, the crack size difference between the round-trip path is 20 μm, and the ZH difference between the round-trip path is 4. (Compared to the above...) Figure 18 Under the given conditions, the weighted score of the average crack amount on the round trip is 10, the weighted score of the crack amount difference on the round trip is 0, and the score of the ZH difference on the round trip is 0, for a total of 10 points, which is considered unqualified. In this case, instead of increasing the score for the average crack amount on the round trip, adjustments must be made to the crack amount difference and the ZH difference on the round trip, using an offset of X+3.

[0068] Then, proceed as follows Figure 19 The processing of loop 2 is shown in (d) to (f). Figure 19 As shown in (d), after the adjustment process of cycle 1, the focusing correction level is maintained at the initial condition, and the offset X is set to the initial condition +3. In this state, the second (cycle 2) formation process is performed, as follows... Figure 19 As shown in (e), the results of internal observation show that the Z-height of the shallowest BHC line in the outward path is Z174, the Z-height of the shallowest BHC line in the return path is Z174, the cracking amount of the shallowest BHC line in the outward path is 45 μm, and the cracking amount of the shallowest BHC line in the return path is 55 μm. At this time, as... Figure 19 As shown in (f), the average crack size of the round-trip path is 50 μm, the crack size difference between the round-trip path is 10 μm, and the ZH difference between the round-trip path is 0. (Compared to the above...) Figure 18 Under the given conditions, the weighted score of the average crack amount of the round trip is 10, the weighted score of the crack amount difference of the round trip is 2, and the score of the ZH difference of the round trip is 5, for a total of 17 points, which is considered unqualified. In this case, it is not necessary to increase the score for the average crack amount of the round trip; instead, adjustments must be made to the crack amount difference and the ZH difference of the round trip, requiring an offset adjustment of X-1.

[0069] Then, proceed Figure 20 The processing of loop 3 is shown in (d) to (f). Figure 20 As shown in (d), after the adjustment process in cycle 2, the focusing correction level is maintained at the initial condition, and the offset X is set to the initial condition +2. In this state, the third (cycle 3) formation process is performed, as follows... Figure 20As shown in (e), the results of internal observation show that the Z-height of the shallowest BHC line in the outward path is Z173, and the Z-height of the shallowest BHC line in the return path is Z174. The cracking amount of the shallowest BHC line in the outward path is 50 μm, and the cracking amount of the shallowest BHC line in the return path is 50 μm. At this time, as... Figure 20 As shown in (f), the average crack size of the round-trip path is 50 μm, the crack size difference between the round-trip path is 0 μm, and the ZH difference between the round-trip path is 1. (Compared to the above...) Figure 18 Under the given conditions, the weighted score of the average crack amount on the round trip is 10, the weighted score of the crack amount difference on the round trip is 5, and the score of the ZH difference on the round trip is 5, for a total score of 20 (full marks), which is considered acceptable. At this point, no adjustment is required, and the series of inspections ends. Furthermore, this series of inspections can be performed using only one wafer (20).

[0070] The number of cycles can be predetermined. Then, the process of adjusting the laser irradiation conditions can end at the point when the number of cycles is reached. For example, setting the maximum number of cycles to 9, while time-consuming, allows for very precise adjustment of the laser irradiation conditions. Therefore, in situations requiring critical checks or optimal processing conditions, such as basic certification or the delivery of new engines, a maximum number of cycles of 9 is suitable. Conversely, setting the maximum number of cycles to 2 shortens the cycle time but makes it more difficult to derive optimal irradiation conditions. Specifically, there are concerns that it may be difficult to distinguish whether a defect is due to hardware issues with the object or problems with the irradiation conditions. Therefore, in situations such as periodic processing checks or when processing conditions have been derived and acceptance / failure can be determined, a maximum number of cycles of 2 is suitable. Furthermore, setting the maximum number of cycles to 3 allows for a comparison of the accuracy of the derived results, balancing process time and irradiation conditions. For factory checks or startup checks, a maximum number of cycles of 3 is suitable.

[0071] Figure 21 This is a flowchart to show the inspection method.

[0072] like Figure 21 As shown, the initial conditions for checking the processing conditions are set as the reference focusing correction level and offset X (LBA initial center). And set the inspection standard (processing inspection benchmark) (step S101). For the inspection standard, the number of qualified points for the inspection items and the number of inspection processing cycles can be entered. In addition, for the inspection standard, the point allocation for each inspection item can be entered. At this time, weighting is performed by the point allocation. Then, wafer 20 is inserted (step S102), wafer calibration is performed (step S103), and Z height is set (step S104). Setting Z height (setting height) refers to the following operation: the reticle is projected onto the laser irradiation surface of wafer 20 and then photographed by the imaging unit. The laser processing head is moved so that the focus of the reticle is focused on the captured image. Then, the position of the condenser lens relative to the optical axis direction of the laser incident surface is aligned with the benchmark position.

[0073] Then, while changing the Z-height, a modified region 12 is formed for each line's return path (step S105). Next, the internal structure of the processed wafer 20 is observed (step S106), and the above-mentioned average crack amount of the return path, the difference in crack amount of the return path, and the ZH difference of the return path are derived (step S107).

[0074] Next, based on the exported information, additional points are calculated (step S108). The calculation of additional points can be performed by weighting or by considering secondary parameters.

[0075] Then, it is determined whether the specified number of cycles has been reached (step S109). If not, the laser irradiation conditions are adjusted. Specifically, the focusing correction level and the offset X are changed (step S110), and then the processing after step S105 is performed again.

[0076] In addition, when the specified number of cycles is reached, the cycle with the highest number of points is identified, and the number of points and irradiation conditions of that cycle are extracted (step S111). Then, it is determined whether the extracted number of points meets the processing inspection criteria (step S112).

[0077] If the result is non-compliant, the non-compliant data is displayed and recorded (step S113), and then the process of step S110 is repeated. Further, if the result is compliant, the compliant data is displayed and recorded (step S114), and the inspection method process ends.

[0078] Next, the effects of the laser processing apparatus 1 involved in this embodiment will be explained.

[0079] The laser processing apparatus 1 according to this embodiment includes: a stage 2 supporting a wafer 20; a laser irradiation unit 3 irradiating the wafer 20 with laser light; an imaging unit 4 outputting light that is transmissible to the wafer 20 and detecting the light propagating on the wafer 20; and a control unit 8. The control unit 8 is configured to perform: controlling the laser irradiation unit 3 so that each of the laser irradiates multiple lines of the wafer 20 along the forward and reverse paths in the X direction, thereby forming one or more modified regions 12 inside the wafer 20; determining, based on the signal output from the imaging unit 4 that detects the light, whether the cracks extending from the modified regions 12 of the multiple lines to the surface 21a side reach the BHC side; and determining whether the laser irradiation conditions are qualified based on information related to the average amount of cracks in the shallowest reverse path within the reverse path where the laser processing depth involved in the formation of the modified region 12 is determined to be BHC, and the difference in the amount of cracks in that reverse path.

[0080] In the laser processing apparatus 1 of this embodiment, each region is irradiated with laser along multiple back-and-forth paths to form a modified region 12. Based on the detection results of the imaging unit 4, it is determined whether the cracks extending from the modified regions 12 along the multiple back-and-forth paths reach the surface 21a side (whether it is a BHC). Then, by combining the information related to the average amount of cracks and the difference in crack amounts of the back-and-forth paths with the shallowest processing depth within the BHC back-and-forth paths, the suitability of the laser irradiation conditions is determined. The average amount of cracks in the back-and-forth paths with the shallowest processing depth that are BHC back-and-forth paths is an important indicator for representing the processing performance of laser processing that forms BHC. In addition, the information related to the difference in crack amounts of these back-and-forth paths is an important indicator showing whether the back-and-forth paths can form the same laser processing state. By comprehensively evaluating these indicators to determine whether the laser irradiation conditions are suitable, the accuracy of the suitability determination can be improved. As a result, the inspection accuracy related to laser irradiation conditions can be improved.

[0081] Information related to the difference in crack amount between the two paths can include information indicating the difference in crack amount between the two paths and information indicating the difference in laser processing depth between the two paths. The information indicating the difference in crack amount between the two paths is based on a real-valued assessment of the crack amount. The information indicating the difference in laser processing depth between the two paths is based on a cutting machine input value assessment of the crack amount. By considering this information on the difference in crack amount based on the cutting machine input value when determining whether the result is acceptable, for example, deviations in processing results can be avoided even if the same value is input into the cutting machine. As described above, including these two pieces of information as information related to the difference in crack amount between the two paths improves inspection accuracy.

[0082] The control unit 8 can assign additional points to each of the information on the difference between the average crack amount of the reciprocating path and the crack amount representing the reciprocating path, and the information on the difference representing the laser processing depth of the reciprocating path, and then determine whether the laser irradiation condition is acceptable or not from the total value. According to such a configuration, the above three pieces of information are quantitatively evaluated, so that the evaluation can be standardized. This can improve the determination accuracy of pass or fail.

[0083] The control unit 8 can weight each of the information on the difference between the average crack amount of the reciprocating path and the crack amount representing the reciprocating path, and the information on the difference representing the laser processing depth of the reciprocating path before assigning additional points, and then determine whether the laser irradiation condition is acceptable or not from the total value. According to such a configuration, optimal evaluation can be performed by weighting in accordance with the evaluation policy.

[0084] The control unit 8 can be configured to further execute: adjusting the laser irradiation condition based on the information related to the average crack amount of the reciprocating path and the difference in the crack amount of the reciprocating path when the laser irradiation condition is not acceptable. According to such a configuration, until the laser irradiation condition becomes acceptable, the laser irradiation condition can be repeatedly adjusted based on the average crack amount of the reciprocating path and the like, and the laser irradiation condition can be appropriately set.

[0085] The laser processing apparatus 1 can perform a series of inspections using only one wafer 20. By performing a series of inspections using only one wafer 20, evaluation deviations caused by individual differences of each wafer 20 (such as inspection value offsets caused by differences in the thickness of the wafer 20) can be eliminated, so that pass or fail can be correctly determined and the laser irradiation condition can be appropriately adjusted. In addition, according to such a configuration, since processing is performed at the same time point, it is less susceptible to the influence of the laser state or temporal change, and the inspection accuracy can be improved.

[0086] The control unit 8 can further consider the information representing the coordinates of the aberration correction pattern of the spatial light modulator 32 and the position of the pupil plane of the condenser lens 33 to determine whether the laser irradiation condition is acceptable or not. The closer the center coordinate of the aberration correction pattern of the spatial light modulator 32 is to the center of the condenser lens 33, the stronger the temporal change during laser irradiation. Therefore, by taking such information into account in the difference consideration, the inspection accuracy can be improved.

[0087] The control unit 8 can further consider additional parameters used for evaluation of the average crack amount to determine whether the laser irradiation condition is acceptable or not. For example, in consideration of expectations such as that the smaller the crack amount of a thin object, the better, the evaluation of the average crack amount will change. In this regard, by considering the additional parameters used for the evaluation of the average crack amount, the average crack amount can be appropriately evaluated, and the inspection accuracy can be improved.

[0088] The control unit 8 can further consider information indicating the cross-sectional state of the processed wafer 20 to determine whether the laser irradiation conditions are qualified. By considering the actual cross-sectional state after processing, the accuracy of the inspection related to the laser irradiation conditions can be improved. Symbol Explanation

[0089] 1…laser processing apparatus; 2…stage; 3…laser irradiation unit (laser irradiation section); 4…image unit (image section); 8…control section; 12…modification area; 20…wafer; 21…semiconductor substrate; 21a…surface (first surface); 21b…back side (second surface); 31…light source; 32…spatial light modulator; 33…condenser lens.

Claims

1. An inspection device, wherein, have: A stage that supports a wafer having a semiconductor substrate, the semiconductor substrate having a first surface and a second surface; A laser irradiation unit that uses the second surface as the incident surface to irradiate the wafer with a laser; The imaging unit outputs light that is transmissive to the semiconductor substrate and detects the light propagating on the semiconductor substrate; and Control Department The control unit is configured to control the laser irradiation unit in such a way as to form one or more modified regions inside the semiconductor substrate by irradiating the laser along each of a plurality of lines extending along a first direction and adjacent to each other in a second direction, along each of the forward and return paths in the first direction. Based on the signal output from the imaging unit that detects the light, it is determined whether the crack reaches the first surface side of the semiconductor substrate from the modified region extending from the round-trip path of each of the multiple lines. Based on information related to the average amount of cracks in the shallowest round trip within the round trip where the cracking state is determined to have occurred, and the difference in the amount of cracks in the round trip, the laser irradiation conditions are determined to be qualified.

2. The inspection device as claimed in claim 1, wherein, The information related to the difference in the amount of cracks in the round trip path includes information indicating the difference in the amount of cracks in the round trip path and information indicating the difference in the processing depth of the laser in the round trip path.

3. The inspection device as described in claim 2, wherein, The control unit adds points to each of the average crack amount of the round trip path, the information representing the difference in crack amount of the round trip path, and the information representing the difference in the laser processing depth of the round trip path, and determines whether the laser irradiation conditions are qualified based on their total value.

4. The inspection device as described in claim 2 or 3, wherein, The control unit weights the average crack amount of the round trip path, the information representing the difference in crack amount of the round trip path, and the information representing the difference in the laser processing depth of the round trip path, and adds a point count, and determines whether the laser irradiation conditions are qualified or not based on the total value.

5. The inspection device according to any one of claims 1 to 4, wherein, The control unit is configured to further perform the following: if the laser irradiation conditions are unqualified, adjust the laser irradiation conditions based on information related to the average amount of cracks on the round trip path and the difference in the amount of cracks on the round trip path.

6. The inspection device according to any one of claims 1 to 5, wherein, A series of checks are performed using only one of the aforementioned wafers.

7. The inspection device according to any one of claims 1 to 6, wherein, The laser irradiation unit includes: a light source that emits laser light; a spatial light modulator that modulates the laser light emitted from the light source; and a focusing lens that focuses the laser light modulated by the spatial light modulator onto the wafer. The control unit further considers information representing the coordinates of the aberration correction pattern of the spatial light modulator and the position of the pupil plane of the condenser lens to determine whether the laser irradiation conditions are qualified.

8. The inspection device according to any one of claims 1 to 7, wherein, The control unit further considers the additional parameters used in the assessment of the average amount of cracks to determine whether the laser irradiation conditions are qualified.

9. The inspection device according to any one of claims 1 to 8, wherein, The control unit further considers information representing the cross-sectional state of the processed wafer to determine whether the laser irradiation conditions are qualified.

10. An inspection method, wherein, have: In the first step, a wafer with a semiconductor substrate is prepared. The semiconductor substrate has a first surface and a second surface. One or more modified regions are formed inside the semiconductor substrate by irradiating each of a plurality of lines extending along a first direction and adjacent to each other in the second direction with laser light along the forward and return paths of the first direction. In the second step, light that is transmissible to the semiconductor substrate having the modified region formed in the first step is output, and the light propagating on the semiconductor substrate is detected. The third step involves determining, based on the light detected in the second step, whether the crack extends from the modified region to the first surface side of the semiconductor substrate and reaches a crack arrival state. and In the fourth step, based on information related to the average amount of cracks in the round trip with the shallowest laser processing depth involved in the formation of the modified region within the round trip path determined to be in the state of cracking, and the difference in the amount of cracks in that round trip path, the laser irradiation conditions are determined to be qualified.

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