Inspection apparatus and inspection method

Abstract

The inspection device includes: a light source that irradiates a wafer with laser light; an AF unit that measures displacement of a back surface (a measurement target surface) that is an incident surface of the laser light L on the wafer, as a measurement unit; and a control unit configured to perform operations of: controlling the light source in a manner that forms one or more modified regions inside the wafer by irradiating the wafer with the laser light; and controlling the AF unit in a manner that measures a post-processing displacement that is displacement of the back surface after the laser light is irradiated, and derives information related to estimation of a processing state of the wafer based on the post-processing displacement measured by the AF unit.

Description

Technical Field

[0001] This disclosure relates to inspection devices and inspection methods. Background Technology

[0002] An inspection apparatus is known that, in order to cut a wafer having a semiconductor substrate and a functional element layer formed on one surface of the semiconductor substrate along multiple lines, forms multiple rows of modified regions inside the semiconductor substrate along each of the multiple lines by irradiating the wafer with a laser from the other side of the semiconductor substrate. The inspection apparatus described in Japanese Patent Application Publication No. 2017-64746 includes an infrared camera, capable of observing the modified regions formed inside the semiconductor substrate and processing damage formed in the functional element layer from the back side of the semiconductor substrate. In this inspection apparatus, for example, the crack state of the processed wafer is estimated based on such internal observation results, and the processing is determined to be acceptable (whether the desired processing can be performed under set processing conditions) based on the estimated crack state. Summary of the Invention

[0003] According to the inspection apparatus described above, the crack state of a wafer can be estimated with high precision through internal observation using an infrared camera. In this technical field, there is a demand for high-precision estimation of the crack state (processing state) of a wafer, and for easier estimation of the crack state (processing state). In view of the above-mentioned practical situation, this disclosure relates to an inspection apparatus and inspection method that can more easily estimate the processing state of a wafer.

[0004] The inventors focused on the correlation between the displacement (undulation) on the incident surface or the surface opposite to the incident surface after laser processing and the processing state of the wafer, and devised an inspection device for deriving information related to the estimation of the processing state of the wafer based on such post-processing displacement of the wafer.

[0005] That is, one aspect of the inspection apparatus disclosed herein includes: a laser irradiation unit that irradiates a wafer with a laser; a measurement unit that measures the displacement of the laser incident surface or the surface opposite to the incident surface on the wafer, i.e., the measurement target surface; and a control unit configured to perform the following operations: control the laser irradiation unit to form one or more modified regions inside the wafer by irradiating the wafer with a laser; control the measurement unit to measure the displacement of the measurement target surface after laser irradiation, i.e., the post-processing displacement; and derive information related to estimating the processing state of the wafer based on the post-processing displacement measured by the measurement unit.

[0006] In one aspect of the inspection apparatus disclosed herein, the post-processing displacement of the incident surface or the surface opposite to the incident surface on the wafer irradiated by a laser, i.e., the target surface, is measured, and information relating to the estimation of the wafer's processing state is derived based on this post-processing displacement. As described above, the post-processing displacement (undulation shape) on the target surface is correlated with the wafer's processing state. Therefore, by deriving information relating to the estimation of the wafer's processing state based on the post-processing displacement, the wafer's processing state can be appropriately estimated based on this estimated information. Moreover, the process of measuring the post-processing displacement of the target surface is much easier than the process of determining the processing state (crack state) of a specific wafer through internal observation of the wafer, such as by using an infrared camera. Therefore, the inspection apparatus according to one aspect of the present disclosure allows for easier estimation of the wafer's processing state.

[0007] Alternatively, the aforementioned inspection device may also include a display unit, which is controlled by the control unit to display information related to the estimation of the processing status of the exported wafer. By displaying this information on the display unit, for example, if the information used to estimate the processing status is displayed as information related to the estimation of the processing status, the user can easily estimate the wafer's processing status based on the displayed content. Furthermore, if the estimation result of the processing status itself is displayed as information related to the estimation of the processing status, the user can confirm the appropriateness of the estimation result.

[0008] Alternatively, the measuring unit may include a measuring unit that measures the displacement on the surface of the object being measured by illuminating measuring light onto it and receiving and detecting the reflected light from the surface. With this structure, the displacement on the surface of the object being measured can be measured with high precision through a simple structure and processing.

[0009] Alternatively, the measuring unit can be an autofocus unit that measures the displacement on the surface to be measured by adjusting the focusing point of the laser irradiating the wafer from the laser irradiation unit. With this structure, the autofocus unit, typically installed in inspection apparatuses that irradiate wafers with lasers, can be used to measure the displacement on the surface to be measured. That is, with this structure, the autofocus unit can be used to measure the displacement (bump and concavity) of the wafer surface, and the wafer's processing state can be easily estimated based on this displacement.

[0010] Alternatively, the control unit can derive the difference between the post-processing displacement and the reference displacement measured by the measurement unit for each region of the measurement target surface, and derive information related to estimating the wafer's processing state based on this difference. The difference between the post-processing displacement and the reference displacement more accurately represents the amount of displacement caused by the effects of processing. Therefore, by deriving information related to estimating the processing state based on this difference, the wafer's processing state can be estimated more accurately.

[0011] Alternatively, the control unit can control the measurement unit to further measure the displacement of the measurement object surface before laser irradiation, i.e., the pre-processing displacement. Using this pre-processing displacement as a reference displacement, information related to estimating the wafer's processing state can be derived. In this way, by actually measuring the displacement of the measurement object surface before laser irradiation, i.e., the pre-processing displacement, and using this pre-processing displacement as a reference displacement, the difference between the post-processing displacement and the reference displacement more accurately represents the amount of displacement caused by the processing effect. Therefore, by deriving information related to estimating the processing state based on this difference, the wafer's processing state can be estimated more accurately.

[0012] Alternatively, the control unit can estimate the state of cracks extending from the modified region formed inside the wafer by laser irradiation based on the difference. There is a correlation between the difference between the post-processing displacement and the reference displacement (the displacement on the measurement surface after laser processing) and the state of cracks extending from the modified region. Therefore, by estimating the crack state based on the difference, the crack state (i.e., the wafer processing state) can be estimated with high accuracy.

[0013] Alternatively, from the perspective of the control unit, for regions where the absolute value of the difference is greater than a first threshold, the crack is presumed to be in a state where it reaches the incident surface but not the opposite surface, or in a state where it does not reach the incident surface but reaches the opposite surface. For regions where the absolute value of the difference is less than the first threshold, the crack is presumed to be in a state where it does not reach either the incident surface or the opposite surface, or in a state where it reaches either the incident surface or the opposite surface. The inventors have discovered that for regions where the absolute value of the difference between the processed displacement and the reference displacement (the displacement on the measurement object surface after laser processing) is large, the crack is in a state where it reaches only one of the incident surface or the opposite surface (the so-called BHC or HC state). For regions where the difference is small, the crack is in a state where it does not reach either the incident surface or the opposite surface (the so-called ST state) or in a state where it reaches either the incident surface or the opposite surface (the so-called FC state). Based on this idea, by presuming the state of the crack based on whether the difference is greater than a certain threshold (the first threshold), the state of the crack (i.e., the processing state of the wafer) can be estimated with higher accuracy.

[0014] Alternatively, from the control unit's perspective, for regions where the absolute value of the difference with the surrounding area is greater than a second threshold, the crack is presumed to be either reaching the incident surface and also reaching the opposite side, or not reaching the incident surface but reaching the opposite side. For regions where the absolute value of the difference is less than the second threshold, the crack is presumed to be either not reaching the incident surface or the opposite side, or reaching the incident surface or the opposite side. When presuming the crack state based on the difference, it is sometimes easier and more accurate to judge based on the absolute value of the difference and the difference with the surrounding area (judging based on the relative value) than to judge based on the absolute value of the difference. Based on this idea, by presuming the crack state based on whether the difference with the surrounding area is greater than a certain threshold (second threshold), the crack state (i.e., the wafer processing state) can be estimated with higher accuracy and ease.

[0015] Alternatively, the aforementioned inspection device may also include an imaging unit that outputs light that is transparent to the wafer and detects the light propagating on the wafer. The control unit further considers the signal output from the imaging unit that detects the light and estimates the crack state. With this structure, processing can be performed such as: estimating the basic wafer processing state based on the displacement on the object surface, and simultaneously estimating the crack state of only a portion of the area (such as areas where the crack state needs to be investigated in more detail) based on the signal output from the imaging unit, thus enabling more accurate estimation of the crack state. Furthermore, even in this case, compared to estimating the entire crack state based solely on the signal output from the imaging unit, the wafer processing state can be estimated more easily (significantly reducing the cycle time).

[0016] Alternatively, the control unit can control the measurement unit to measure the pre-processing displacement in each region along the first direction by irradiating measurement light onto the target surface along the first direction and detecting the reflected light of the measurement light on the target surface. The laser irradiation unit can control the laser to irradiate multiple lines of laser light onto the wafer along a second direction intersecting the first direction to form multiple processing lines. The control measurement unit can also control the post-processing displacement in each region along the first direction by irradiating measurement light onto the target surface along the first direction in a manner spanning multiple processing lines and detecting the reflected light of the measurement light on the target surface. For each corresponding region, the difference between the post-processing displacement and the pre-processing displacement is derived, and information related to estimating the processing state of each region is derived based on this difference. In this way, by measuring the post-processing displacement and the pre-processing displacement in each region along the direction spanning multiple processing lines (the first direction) and deriving the difference between the post-processing displacement and the pre-processing displacement for each region, the degree of post-laser processing displacement of each of the multiple processing lines can be specified, and the processing state of each of the multiple processing lines can be appropriately estimated. Based on this structure, for example, by making the processing conditions of multiple processing lines different from each other and estimating the processing state under each processing condition, it is possible to efficiently determine whether multiple processing conditions are appropriate. Moreover, since the degree of displacement of multiple processing lines is specified, by comparing the displacements of different processing lines with each other, not only the absolute displacement amount, but also the relative information of the displacement amount compared with other processing lines, it is possible to easily and accurately estimate the processing state of each processing line.

[0017] Alternatively, regarding the control unit, the control measurement unit measures the pre-processing displacement in each region along the first direction by irradiating measurement light onto the target surface along the first direction and detecting the reflected light of the measurement light on the target surface; the control measurement unit measures the pre-processing displacement in each region along the second direction by irradiating measurement light onto the target surface along the second direction and detecting the reflected light of the measurement light on the target surface; the control laser irradiation unit measures the pre-processing displacement in each region along the second direction by irradiating multiple lines of laser light onto the wafer to form multiple processing lines; and the control measurement unit measures the pre-processing displacement in each region along the second direction by irradiating multiple lines of laser light onto the wafer along the first direction to form multiple processing lines. A measurement unit is controlled to irradiate the surface of the object to be measured with measurement light in a second direction and detect the reflected light of the measurement light on the surface of the object to be measured to measure the post-processing displacement in each region along the second direction. The measurement unit is controlled to irradiate the surface of the object to be measured with measurement light in a manner that spans multiple processing lines along the first direction and detect the reflected light of the measurement light on the surface of the object to be measured to measure the post-processing displacement in each region along the second direction. The difference between the post-processing displacement and the pre-processing displacement is derived for each corresponding region along the first direction, and information related to the estimation of the processing state related to each region is derived based on the difference. The difference between the post-processing displacement and the pre-processing displacement is derived for each corresponding region along the second direction, and information related to the estimation of the processing state related to each region is derived based on the difference.

[0018] Based on this structure, even when multiple processing lines are formed along intersecting directions (in the case of a lattice-like pattern), information relevant to estimating the processing state can be appropriately derived. Specifically, the post-processing displacement and pre-processing displacement are measured for each region along a direction spanning the multiple processing lines formed along the first direction (the second direction), and the difference between the post-processing displacement and the pre-processing displacement is derived for each region. Thus, the processing state of each of the multiple processing lines formed along the first direction can be appropriately estimated. Furthermore, the post-processing displacement and pre-processing displacement are measured for each region along a direction spanning the multiple processing lines formed along the second direction (the first direction), and the difference between the post-processing displacement and the pre-processing displacement is derived for each region. Thus, the processing state of each of the multiple processing lines formed along the second direction can be appropriately estimated. Moreover, since the formation of the multiple processing lines along the first direction and the measurement of the post-processing displacement in each region along the first direction (spanning the multiple processing lines along the second direction) are processes performed in the same direction, they can be performed simultaneously. However, by performing these processes together (simultaneously), processing efficiency can be significantly improved.

[0019] Alternatively, the control unit controls the measurement unit and the laser irradiation unit such that the irradiation line of the measurement light irradiated along the first direction for measuring the post-processing displacement overlaps with any one of the multiple processing lines along the first direction, and controls the measurement unit and the laser irradiation unit such that the irradiation line of the measurement light irradiated along the second direction for measuring the post-processing displacement does not overlap with the multiple processing lines along the second direction. Currently, in order to measure the post-processing displacement with high accuracy, it is desirable to eliminate the influence of processing lines whose processing direction is different from the processing line of the object whose post-processing displacement is to be measured. That is, when measuring the post-processing displacement of multiple processing lines along a certain direction, it is desirable to eliminate the influence of processing lines along directions different from that certain direction. In this case, it is necessary that the irradiation line of the measurement light irradiated along the direction different from that certain direction, in a manner that spans multiple processing lines along the certain direction, does not overlap with the processing lines along the direction different from that certain direction. At this point, since the irradiation line of the measurement light along the second direction does not overlap with the multiple processing lines along the second direction, it is possible to measure the post-processing displacement related to the multiple processing lines along the first direction with high accuracy. Here, as described above, in this process, after forming the machining line along the second direction, the formation of the machining line along the first direction and the measurement of the post-machining displacement along the first direction are performed together. Thus, when the formation of the machining line and the measurement of the post-machining displacement are performed together along the same direction, even if the irradiation lines of the measurement light used for machining line and displacement measurement overlap, the post-machining displacement of the formed machining line can be measured without being affected by the newly formed machining line, by performing the irradiation of the measurement light used for displacement measurement before the formation of the machining line (performed together, and controlled to prioritize the irradiation of the measurement light over the formation of the machining line). That is, in this process, because the formation of the machining line along the first direction and the measurement of the post-machining displacement along the first direction are performed together, even if any one of the machining lines along the first direction overlaps with the irradiation line of the measurement light irradiated along the first direction, the post-machining displacement related to multiple machining lines along the second direction can be estimated with high accuracy without being affected by the formation of the machining line along the first direction. Furthermore, since any of the processing lines along the first direction overlaps with the irradiation line of the measurement light irradiated along the first direction, the processing related to the formation of the processing lines and the irradiation of the measurement light can be simplified (simplified).

[0020] Alternatively, the control unit can control a measurement unit to measure the pre-processing displacement in each region along the first direction by irradiating measurement light onto the target surface along the first direction and detecting the reflected light of the measurement light on the target surface. It can also control a laser irradiation unit to irradiate a laser onto the wafer along the first direction to form a processing line. Furthermore, it can control a measurement unit to measure the post-processing displacement in each region along the processing line by irradiating measurement light onto the target surface along the processing line and detecting the reflected light of the measurement light on the target surface. For each corresponding region along the processing line, it can derive the difference between the post-processing displacement and the pre-processing displacement, and based on this difference, derive information related to the estimation of the processing state of each region. In this way, by unifying the irradiation direction of the measurement light used to measure the pre-processing displacement, the formation direction of the processing line, and the irradiation direction of the measurement light used to measure the post-processing displacement, processing such as wafer rotation is eliminated, thereby improving processing efficiency. Furthermore, in this method of irradiating the measurement light along the processing line, unlike the case of irradiating the measurement light across multiple processing lines, although the processing state cannot be estimated based on the relative information of the displacement of multiple processing lines relative to each other, the processing state of the processing line can be estimated based on the absolute displacement after processing.

[0021] Alternatively, the control unit can control the processing based on prescribed processing conditions, determine whether the processing is qualified based on information related to the estimation of the wafer's processing state, and modify the processing conditions if the determination result is unqualified. With this structure, the processing conditions can be changed considering the estimation result of the wafer's processing state, enabling centralized and automatic optimization of the processing conditions.

[0022] One aspect of the inspection method disclosed herein includes: a laser processing step, irradiating a wafer with a laser to form one or more modified regions inside the wafer; a post-processing measurement step, measuring the displacement of the measurement object surface of the laser-processed wafer, i.e., the post-processing displacement; and an estimation step, correcting the processing state of the wafer based on the post-processing displacement.

[0023] Alternatively, the above inspection method may include a pre-processing measurement process before the laser processing process, which measures the displacement of the object surface, i.e., the pre-processing displacement. In the estimation process, the difference between the post-processing displacement and the pre-processing displacement is derived for each area of ​​the object surface, and the processing status of the wafer is estimated based on the difference.

[0024] Alternatively, in the pre-processing measurement process, measurement light is irradiated onto the surface of the object to be measured along a first direction, and the reflected light from the measurement light on the surface of the object to be measured is received and detected, thereby measuring the pre-processing displacement in each region along the first direction. In the laser processing process, multiple lines of laser light are irradiated onto the wafer along a second direction that intersects the first direction to form multiple processing lines. In the post-processing measurement process, measurement light is irradiated onto the surface of the object to be measured along the first direction in a manner that spans multiple processing lines, and the reflected light from the measurement light on the surface of the object to be measured is received and detected, thereby measuring the post-processing displacement in each region along the first direction.

[0025] Alternatively, the pre-processing measurement process can include a first pre-processing process and a second pre-processing process. In the first pre-processing process, measurement light is irradiated onto the surface of the object to be measured along a first direction, and the reflected light from the measurement light on the surface of the object to be measured is received and detected to measure the pre-processing displacement in each region along the first direction. In the second pre-processing process, measurement light is irradiated onto the surface of the object to be measured along a second direction intersecting the first direction, and the reflected light from the measurement light on the surface of the object to be measured is received and detected to measure the pre-processing displacement in each region along the second direction. The laser processing process can also include a first processing process and a second processing process. In the first processing process, multiple lines of laser light are irradiated onto the wafer along the second direction to form multiple processing lines. In the second processing process, multiple lines of laser light are irradiated along the second direction to form multiple processing lines. Multiple processing lines are formed by irradiating the wafer with multiple lines of laser light in a first direction. The post-processing measurement process includes a first post-processing process and a second post-processing process. In the first post-processing process, measurement light is irradiated onto the surface to be measured along the first direction in a manner that spans multiple processing lines along the second direction. The reflected light from the measurement light on the surface to be measured is received and detected, and the post-processing displacement in each region along the first direction is measured. In the second post-processing process, measurement light is irradiated onto the surface to be measured along the second direction in a manner that spans multiple processing lines along the first direction. The reflected light from the measurement light on the surface to be measured is received and detected, and the pre-processing displacement in each region along the second direction is measured. The first post-processing process and the second post-processing process are performed together.

[0026] Alternatively, in the pre-processing measurement process, measurement light is irradiated onto the surface of the object to be measured along a first direction, and the reflected light from the measurement light on the surface of the object to be measured is received and detected to measure the pre-processing displacement in each region along the first direction. In the laser processing process, a laser is irradiated onto the wafer along the first direction to form a processing line. In the post-processing measurement process, measurement light is irradiated onto the surface of the object to be measured along the processing line, and the reflected light from the measurement light on the surface of the object to be measured is received and detected to measure the post-processing displacement in each region along the processing line.

[0027] According to this disclosure, it is easier to estimate the processing status of the wafer. Attached Figure Description

[0028] Figure 1 This is a structural diagram of an inspection device according to one embodiment.

[0029] Figure 2 This is a top view of a wafer in one implementation method.

[0030] Figure 3 yes Figure 2 A cross-sectional view of a portion of the wafer shown.

[0031] Figure 4 yes Figure 1 The diagram shows the structure of the laser irradiation unit.

[0032] Figure 5 yes Figure 1 The diagram shown is a structural diagram of the inspection imaging unit.

[0033] Figure 6 yes Figure 1 The diagram shows the structure of the imaging unit used for alignment correction.

[0034] Figure 7 It is a diagram schematically representing a cross-section of a wafer in each state of cracking.

[0035] Figure 8 This is a diagram representing the inspection process.

[0036] Figure 9 This is an example of a screen displaying the presumed result.

[0037] Figure 10 yes Figure 8 The flowchart of the inspection process (inspection method).

[0038] Figure 11 This is a flowchart of the inspection method for the variant example.

[0039] Figure 12 This is an example of a modified display screen.

[0040] Figure 13 It is a diagram schematically representing a cross-section of a wafer in each state of cracking.

[0041] Figure 14 This is a diagram showing the inspection process for a modified example.

[0042] Figure 15 yes Figure 14 The flowchart of the inspection process (inspection method).

[0043] Figure 16 This is a diagram showing the inspection process for a modified example.

[0044] Figure 17 yes Figure 16 The flowchart of the inspection process (inspection method).

[0045] Figure 18 This is a diagram showing the inspection process for a modified example.

[0046] Figure 19 This is a diagram schematically representing a portion of the structure of an inspection device with variations.

[0047] Figure 20 This is an example of a modified display screen.

[0048] Figure 21 This is an example of a modified display screen.

[0049] Figure 22 This is a diagram schematically representing a portion of the structure of an inspection device with variations.

[0050] Figure 23 This diagram illustrates the inspection method for the modified example. Detailed Implementation

[0051] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Furthermore, in the drawings, the same or equivalent parts are labeled with the same symbols, and repeated descriptions are omitted.

[0052] [Structure of the inspection device]

[0053] like Figure 1 As shown, the inspection device 1 includes a stage 2, a laser irradiation unit 3, multiple imaging units 4, 5, and 6, a drive unit 7, a control unit 8, and a display 150 (display unit). The inspection device 1 is a device that forms a modified region 12 on a workpiece 11 by irradiating the workpiece 11 with a laser L.

[0054] 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 the X and Y directions respectively, and can rotate about an axis parallel to the Z direction. Furthermore, the X and Y directions are a first horizontal direction and a second horizontal direction that are perpendicular to each other, and the Z direction is a vertical direction.

[0055] The laser irradiation unit 3 focuses a laser L that is transmissive to the object 11 and irradiates the object 11. If the laser L is focused into the interior of the object 11 supported by the stage 2, the laser L is particularly absorbed in the part corresponding to the focusing point C, forming a modified region 12 inside the object 11.

[0056] The modified region 12 is a region whose density, refractive index, mechanical strength, and other physical properties differ from the surrounding unmodified region. Examples of modified regions 12 include melt-treated regions, cracked regions, insulation breakdown regions, and regions with refractive index changes. The modified region 12 has the characteristic that cracks easily extend from the modified region 12 towards the incident side of the laser L and the opposite side. This characteristic of the modified region 12 is used for cutting the object 11.

[0057] As an example, if the stage 2 is moved along the X direction, and the focusing point C moves relative to the object 11 along the X direction, then multiple modification points 12s are formed in a row along the X direction. A modification point 12s is formed by irradiation with a pulse of laser L. A row of modification regions 12 is a collection of multiple modification points 12s arranged in a row. Adjacent modification points 12s may be connected or separated depending on the relative movement speed of the focusing point C relative to the object 11 and the repetition frequency of the laser L.

[0058] The imaging unit 4 is configured to capture images of the modified region 12 formed on the object 11 and the tip of the crack extending from the modified region 12. Furthermore, the imaging unit 4 is not a necessary component, but in this embodiment, it is described as having the imaging unit 4 in the inspection device 1.

[0059] Under the control of the control unit 8, the imaging units 5 and 6 photograph the object 11 supported by the stage 2 using light transmitted through the object 11. As an example, the images obtained by the imaging units 5 and 6 are used for aligning the irradiation position of the laser L. Furthermore, while the imaging units 5 and 6 are not essential components, they are described as being present in this embodiment.

[0060] 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.

[0061] 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 modules, a memory, and communication devices. In the control unit 8, the processor executes software (programs) that reads data from the memory modules, controls the reading and writing of data in the memory modules and the memory, and controls communication performed by the communication devices.

[0062] The display 150 has the functions of an input section for receiving information from the user and a display section for displaying information to the user.

[0063] [Structure of the object]

[0064] like Figure 2 and Figure 3 As shown, the object 11 in this embodiment is 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 a functional element layer 22, but the wafer 20 may have a functional element layer 22, or it may not have a functional element layer 22, or it may be a bare wafer. 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 in two dimensions 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 modules. Sometimes, multiple layers of functional elements 22a are stacked to form a three-dimensional structure. In addition, a notch 21c indicating crystal orientation is provided on the semiconductor substrate 21, but an orientation plane may be provided instead of the notch 21c.

[0065] The wafer 20 is cut along each of the plurality of lines 15 for each functional element 22a. Viewed from the thickness direction of the wafer 20, the plurality of lines 15 pass between each of the plurality of functional elements 22a. More specifically, viewed from the thickness direction of the wafer 20, the lines 15 pass through the center (center in the width direction) of the trace region 23. The trace region 23 extends in the functional element layer 22 in such a way that it passes between adjacent functional elements 22a. In this embodiment, the plurality of functional elements 22a are arranged in a matrix along the surface 21a, and the plurality of lines 15 are set in a lattice pattern. Furthermore, the lines 15 are imaginary lines, but can also be actually drawn lines.

[0066] [Structure of the laser irradiation unit]

[0067] like Figure 4 As shown, the laser irradiation unit 3 includes a light source 31 (laser irradiation unit), a spatial light modulator 32, and a focusing lens 33. The light source 31 outputs laser light L via, for example, pulse oscillation. The spatial light modulator 32 modulates the laser light L output from the light source 31. The spatial light modulator 32 is, for example, a spatial light modulator (SLM) of a reflective liquid crystal on silicon (LCOS). The focusing lens 33 focuses the laser light L modulated by the spatial light modulator 32. Alternatively, the focusing lens 33 may also be a correction ring lens.

[0068] In this embodiment, the laser irradiation unit 3 forms two rows of modified regions 12a, 12b along each of the plurality of lines 15 inside the semiconductor substrate 21 by irradiating laser L from the back side 21b of the semiconductor substrate 21 toward the wafer 20. Modified region 12a is the modified region closest to surface 21a among the two rows of modified regions 12a, 12b. Modified region 12b is the modified region closest to modified region 12a among the two rows of modified regions 12a, 12b, and is the modified region closest to the back side 21b.

[0069] 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 moving two focusing points C1 and C2 relative to the semiconductor substrate 21 along line 15. The laser L is modulated by a spatial light modulator 32, such that, for example, focusing point C2 is located behind focusing point C1 in the forward direction 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 one-pass or multi-pass.

[0070] Laser irradiation unit 3 irradiates laser L from the back surface 21b side of semiconductor substrate 21 onto wafer 20 along each of multiple lines 15. For example, relative to a single-crystal silicon substrate, i.e., semiconductor substrate 21, with a thickness of 775 μm, two focusing points C1 and C2 are matched to positions 54 μm and 128 μm away from surface 21a, respectively, and laser L is irradiated from the back surface 21b side of semiconductor substrate 21 onto wafer 20 along each of multiple lines 15. At this time, for example, under the condition that the cracks 14 covering the two rows of modified regions 12a, 12b reach the surface 21a of semiconductor substrate 21, the wavelength of laser L is set to 1099 nm, the pulse width to 700 nm, and the repetition frequency to 120 kHz. In addition, the output of laser L in focus point C1 is set to 2.7W, the output of laser L in focus point C2 is set to 2.7W, and the relative moving speed of the two focus points C1 and C2 relative to the semiconductor substrate 21 is set to 800mm / second.

[0071] The formation of the two rows of modified regions 12a, 12b and the crack 14 is carried out under the following conditions. That is, in subsequent processes, for example, the semiconductor substrate 21 is sometimes 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 each of the multiple lines 15.

[0072] like Figure 4As shown, the laser irradiation unit 3 also includes an AF (autofocus) unit 71 (measuring unit). When there is a displacement (undulation) in the thickness direction (Z direction) on the incident surface, i.e., the back surface 21b, on the wafer 20, the AF unit 71 is also a structure used to precisely match the focusing point of the laser L with a position located at a predetermined distance from the back surface 21b. The AF unit 71 measures the displacement on the back surface 21b (the surface to be measured) to adjust the focusing point of the laser L irradiated onto the wafer 20 by the light source 31. Specifically, the AF unit 71 irradiates the back surface 21b with an AF laser LA (measuring light) and receives and detects the reflected light of the AF laser LA on the back surface 21b, thereby acquiring displacement data (measured displacement) of the back surface 21b.

[0073] The AF unit 71 includes an AF light source 71a that outputs an AF laser LA and a displacement detection unit 71b that receives and detects the reflected light from the AF laser LA. The AF laser LA emitted from the AF light source 71a is reflected by an AF dichroic mirror 72 and then illuminates the back surface 21b via a condenser lens 33. Thus, the AF laser LA and laser L are illuminated onto the wafer 20 from the same condenser lens 33 (coaxially). Furthermore, the reflected light from the AF laser LA on the back surface 21b is reflected by the AF dichroic mirror 72 and detected by the displacement detection unit 71b. The displacement detection unit 71b is configured, for example, with a 4-segment photodiode. The 4-segment photodiode is a structure that receives and outputs a voltage value corresponding to each light quantity by dividing the condenser image of the reflected light from the AF laser LA into segments. Because this condenser image adds non-point aberrations to the reflected light from the AF laser LA, its shape (longitudinal, circular, transverse) varies depending on the position of the back surface 21b of the wafer 20 relative to the condenser point of the AF laser LA. That is, the focusing image varies depending on the position of the back surface 21b of wafer 20 relative to the focusing point. Therefore, the voltage value output from the 4-segment photodiode varies depending on the position of the back surface 21b of wafer 20 relative to the focusing point of the AF laser LA.

[0074] The voltage value output from the four-segment photodiode of the displacement detection unit 71b is input to the control unit 8. The control unit 8 calculates a value based on the voltage value output from the four-segment photodiode of the displacement detection unit 71b, which serves as position information related to the position of the back surface 21b of the wafer 20 relative to the focusing point of the AF laser LA. Furthermore, based on this calculated value, the control unit 8 controls the drive unit 7 (actuator) to finely adjust the position of the focusing lens 33 in the up-down direction, so that the focusing point of the laser L irradiated from the light source 31 is at a constant depth away from the back surface 21b. Thus, control is performed based on the ranging results generated by the AF unit 71 along with the laser processing (before laser processing), thereby ensuring that even if there are undulations on the incident surface, i.e., the back surface 21b, the focusing point of the laser L is always precisely matched to the position at a predetermined distance away from the back surface 21b.

[0075] In this embodiment, the AF unit 71 functions as a measurement unit, which measures the displacement of the back surface 21b (the measurement target surface) used when estimating the processing state (cracked state) of the wafer 20 (details will be described later).

[0076] [Inspect the structure of the imaging unit]

[0077] like Figure 5 As shown, the imaging unit 4 (imaging section) includes a light source 41, a reflector 42, an objective lens 43, and a light detection unit 44. The imaging unit 4 images the wafer 20. The light source 41 outputs transmissive light I1 to the semiconductor substrate 21. The light source 41 is, for example, composed of a halogen lamp and a filter, and outputs light I1 in the near-infrared region. The light I1 output from the light source 41 is reflected by the reflector 42, passes through the objective lens 43, and illuminates the wafer 20 from the back side 21b side of the semiconductor substrate 21. At this time, the stage 2 supports the wafer 20 on which the two rows of modified regions 12a and 12b as described above are formed.

[0078] Objective lens 43 allows light I1 reflected from the surface 21a of semiconductor substrate 21 to pass through. That is, objective lens 43 allows light I1 propagating on semiconductor substrate 21 to pass through. The aperture number (NA) of objective lens 43 is, for example, 0.45 or more. Objective lens 43 has a correction ring 43a. The correction ring 43a corrects aberrations generated in light I1 within semiconductor substrate 21, for example, by adjusting the distance between the plurality of lenses constituting objective lens 43. Furthermore, the aberration correction unit is not limited to correction ring 43a, but may also be other correction units such as a spatial light modulator. Light detection unit 44 detects light I1 transmitted through objective lens 43 and mirror 42. Light detection unit 44 is, for example, composed of an InGaAs camera, and detects light I1 in the near-infrared region. Furthermore, the unit that detects (images) light I1 in the near-infrared region is not limited to an InGaAs camera; as long as transmission-type imaging is performed, it may also be other imaging units such as a transmission-type confocal microscope.

[0079] The imaging unit 4 is capable of imaging the front ends of each of the two modified regions 12a and 12b, and multiple cracks 14a, 14b, 14c, and 14d. Crack 14a extends from the modified region 12a toward the surface 21a. Crack 14b extends from the modified region 12a toward the back surface 21b. Crack 14c extends from the modified region 12b toward the surface 21a. Crack 14d extends from the modified region 12b toward the back surface 21b.

[0080] [Structure of the camera unit for alignment correction]

[0081] like Figure 6 As shown, the imaging unit 5 includes a light source 51, a reflector 52, a lens 53, and a light detection unit 54. The light source 51 outputs transmissive light I2 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 combined with the light source 41 of the imaging unit 4. The light I2 output from the light source 51 is reflected by the reflector 52, passes through the lens 53, and illuminates the wafer 20 from the back side 21b of the semiconductor substrate 21.

[0082] Lens 53 allows light I2 reflected from the surface 21a of the semiconductor substrate 21 to pass through. That is, lens 53 allows light I2 propagating on the semiconductor substrate 21 to pass through. The number of apertures in lens 53 is 0.3 or less. That is, the number of apertures in the objective lens 43 of the imaging unit 4 is greater than the number of apertures in lens 53. Light detection unit 54 detects light I2 passing through lens 53 and mirror 52. Light detection unit 55, for example, is an InGaAs camera, detecting light I2 in the near-infrared region. Alternatively, light detection unit 55 can be an SD camera or a device that detects non-transparent light.

[0083] Under the control of the control unit 8, the imaging unit 5 irradiates light I2 onto the wafer 20 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 irradiates light I2 onto the wafer 20 from the back side 21b and detects the light I2 returning from the formation locations of the modified regions 12a and 12b in the semiconductor substrate 21, thereby acquiring an image of the region including the modified regions 12a and 12b. These images are used for alignment of the irradiation location of the laser L. The imaging unit 6 has the same structure as the imaging unit 5, except that the lens 53 has a lower magnification (e.g., 6x in the imaging unit 5, 1.5x in the imaging unit 6), and is used for alignment in the same way as the imaging unit 5.

[0084] [Wafer inspection performed by the inspection device]

[0085] The following process will be explained: When a modified region is formed for the purpose of cutting wafer 20, the processing state (cracked state) of wafer 20 when laser processing of wafer 20 is performed under set processing conditions is estimated, and the appropriateness of the processing conditions is determined based on the estimation result (checking whether it is qualified). In this embodiment, the inspection device 1 measures the displacement of the back surface 21b (measurement object surface) of the wafer irradiated by laser through AF unit 71, and estimates the processing state of wafer 20 based on the measured displacement of the back surface 21b.

[0086] First, refer to Figure 7 The principle for estimating the processing state (cracked state) is explained. Figure 7 This is a schematic diagram of a cross-section (longitudinal section) of wafer 20 showing each state of cracking after laser processing. Figure 7 (a) indicates the “BHC (Bottom side half-cut) state” in which the crack 14 does not reach the incident surface of laser L, i.e., the back surface 21b, but reaches the opposite side surface, i.e., the surface 21a. Figure 7 (b) indicates that the crack 14 has not reached either the back side 21b or the surface 21a, which is in the "ST (Stealth) state". Figure 7 (c) indicates that the crack 14 reaches either the back surface 21b or the surface 21a in the "FC (Full-cut) state". Figure 7 (d) indicates the "HC (Half-cut) state" where the crack 14 reaches the back surface 21b but not the surface 21a. Hereinafter, each state will be referred to as BHC, ST, FC, and HC.

[0087] Here, the cracking state of wafer 20 is related to the displacement (convexity / concavity shape) on the incident surface (back side 21b) after laser processing. That is, under BHC, the back side 21b is concave (refer to...). Figure 7 (a)), under ST or FC, the back surface 21b is flat (without bumps) (see reference). Figure 7 (b) and Figure 7 (c) Under HC, the back surface 21b is convex. Therefore, by measuring the displacement of the back surface 21b after laser processing using the AF unit 71, the inspection device 1 can determine whether the measured area is BHC, ST (or FC), or HC. Furthermore, ST and FC cannot be determined solely based on the displacement on the back surface 21b after laser processing; as described later, the inspection device 1 can determine ST and FC based on the imaging results of the back surface 21b captured by the imaging units 4, 5, and 6. Figure 7 (b) and Figure 7As can be seen from (c), in order to distinguish between ST and FC, the imaging results inside wafer 20 are not required; the imaging results on the back side 21b of wafer 20 are sufficient. Therefore, in terms of distinguishing between ST and FC, the photodetector units of imaging units 4, 5, and 6 may not be InGaAs cameras but SD cameras, etc.

[0088] Figure 8 This is a diagram showing the specific inspection procedures when the material is in a presumed processing state (cracked state). For example... Figure 8 As shown in (a), firstly, the displacement of each region before laser processing (pre-processing displacement) is measured along a direction (first direction) that intersects (e.g., orthogonally) with the multiple processing lines PL formed by laser processing. Next, as... Figure 8 As shown in (b), the wafer 20 is rotated 90°, and multiple lines of laser L are irradiated onto the wafer 20 along a direction intersecting the first direction (the second direction) to form multiple processing lines PL. In this case, the multiple processing lines PL are processed, for example, under mutually different processing conditions. Moreover, as... Figure 8 As shown in (c), wafer 20 is rotated 90° here (let's say it's parallel to the wafer). Figure 8 (a) In the same direction), the displacement (displacement after processing) of each region is measured along the first direction. After such measurement, the inspection device 1 derives the difference between the displacement after processing and the displacement before processing for each corresponding region. Thus, the displacement caused by the laser processing (the uneven shape of the back surface 21b) is derived for each processing line PL. Based on the displacement (the uneven shape of the back surface 21b) of each processing line PL, the inspection device 1 estimates the processing state (cracked state) of each processing line PL, and determines whether the processing conditions set for each processing line PL are appropriate (whether the inspection is qualified) based on the estimation result. The processing of the inspection device 1 in this inspection process will be specifically described below.

[0089] The control unit 8 performs the following operations: controls the light source 31 to form one or more modified regions inside the wafer 20 by irradiating the wafer 20 with laser L; controls the AF unit 71 to measure the displacement of the back surface 21b (the measurement target surface) after irradiation with laser L, i.e., the post-processing displacement; and derives information related to the estimation of the processing state of the wafer 20 based on the post-processing displacement measured by the AF unit 71. The control unit 8 controls the display 150 to display the derived information related to the estimation of the processing state of the wafer 20. Figure 9 This is an example of a display screen shown on monitor 150. The information involved in estimating the processing state can be the estimation result of the processing state itself, or information used to estimate the processing state. The estimation result of the processing state itself is, for example... Figure 9The information displayed includes "BHC", "ST", "HC", etc. This information, used to indicate the processing status, is, for example, information that allows the user to infer the processing status (BHC, etc.) based on the information displayed on the monitor 150. Figure 9 The information on the displacement on the back side 21b is shown. In this embodiment, the control unit 8 is configured to not only export information for estimating the processing state, but also export the estimation result of the processing state itself, and display any information on the display 150 for explanation. However, the control unit 8 may only export information for estimating the processing state, and the display 150 may only display information for estimating the processing state.

[0090] Specifically, the control unit 8 derives the difference between the post-processing displacement and the reference displacement measured by the AF unit 71 for each region of the back surface 21b, and estimates the processing state of the wafer 20 based on this difference. In this way, by deriving the difference between the post-processing displacement and the reference displacement, the displacement (change in unevenness) of the back surface 21b caused by the laser processing is derived more accurately. For example, if the pre-processing displacement of each region of the back surface 21b is known in advance, the reference displacement can also be this known pre-processing displacement. In this embodiment, the control unit 8 uses the pre-processing displacement actually measured before laser processing as the reference displacement. That is, the control unit 8 controls the AF unit 71 to further measure the displacement of the back surface 21b before laser irradiation, i.e., the pre-processing displacement (refer to...). Figure 8 (a)) The pre-processing displacement is used as a reference displacement to estimate the processing state of wafer 20. That is, the control unit 8 outputs the post-processing displacement measured by the AF unit 71 (refer to...). Figure 8 (c) and the pre-processing displacement measured by AF unit 71 (refer to) Figure 8 The difference between (b) and the processing status of wafer 20 is estimated based on the difference.

[0091] Based on the difference between the post-processing displacement and the pre-processing displacement in each region of the measurement target surface, the control unit 8 estimates the state of the crack 14 extending from the modified region formed inside the wafer 20 by irradiation with laser L in each region. Here, each region is... Figure 8 The processing lines PL shown in (b) are as follows.

[0092] Alternatively, the control unit 8 may define regions where the absolute value of the difference is greater than a certain threshold (first threshold) as BHC or HC, and regions where the absolute value of the difference is less than or equal to the threshold (first threshold) as ST or FC. In this way, the control unit 8 can also determine the cracking state of each region based on the absolute value of the difference. Alternatively, the control unit 8 may define regions where the difference between the absolute value of the difference and the surrounding regions is greater than a threshold (second threshold) as BHC or HC, and regions where the difference between the absolute value of the difference and the surrounding regions is less than or equal to the threshold (second threshold) as ST or FC.

[0093] Control unit 8 controls each structure to perform the following actions: Figure 8 The inspection procedures shown are performed. For example... Figure 8 As shown in (a), the control unit 8 controls the AF unit 71 to measure the pre-processing displacement in each region along the first direction by irradiating the back surface 21b with an AF laser LA along the irradiation line AL1 in the first direction and detecting the reflected light of the AF laser LA on the back surface 21b. The AF unit 71 irradiates the back surface 21b with the AF laser LA, receives and detects the reflected light of the AF laser LA on the back surface 21b, thereby acquiring displacement data of the back surface 21b in each region of the irradiation line AL1, and outputs the displacement data (voltage value) to the control unit 8. In addition, the AF unit 71 outputs information (voltage value) indicating the total amount of light detected by receiving the reflected light of the AF laser LA to the control unit 8.

[0094] Next, as Figure 8 As shown in (b), the control unit 8 controls the light source 31 to irradiate the wafer 20 with multiple lines of laser L along a second direction intersecting the first direction, thereby forming multiple processing lines PL. Next, as... Figure 8As shown in (c), the control unit 8 controls the AF unit 71 to measure the post-processing displacement in each region along the first direction by irradiating the back surface 21b with an AF laser LA along the irradiation line AL2 in a manner spanning multiple processing lines PL and detecting the reflected light of the AF laser LA on the back surface 21b. The AF unit 71 acquires the displacement data of the back surface 21b in each region of the irradiation line AL2 and outputs the displacement data (voltage value) to the control unit 8. In addition, the AF unit 71 outputs information (voltage value) indicating the total amount of light detected by receiving the reflected light of the AF laser LA to the control unit 8. Furthermore, if the irradiation lines AL1 and AL2 have corresponding regions, the regions do not necessarily have to be identical. That is, the irradiation line AL2 for measuring the post-processing displacement can completely overlap with the irradiation line AL1 for measuring the pre-processing displacement, or they can partially overlap, or they can correspond to each other (approach each other to a certain extent) but not overlap. Finally, the control unit 8 derives the difference between the displacement after machining and the displacement before machining for each corresponding region of the reference rays AL1 and AL2, and estimates the crack state related to each region based on the difference. Specifically, the control unit 8 estimates the crack state for each machining line PL.

[0095] To estimate the crack state of each processing line PL as described above, the control unit 8 needs to specifically determine whether the displacement data (signals representing displacement) of the back surface 21b obtained by irradiating the laser LA used for AF with reference rays AL1 and AL2 corresponds to the displacement data of any processing line PL. The control unit 8 performs wafer-end specific processing and processing line specific processing to correlate the displacement data with the processing line PL, thereby estimating the crack state of each processing line PL. Hereinafter, refer to... Figure 9 The specific processing at the wafer end and the specific processing line are explained.

[0096] exist Figure 9 In the diagram, the horizontal axis represents time, the left vertical axis represents the voltage value corresponding to the total light intensity detected in AF unit 71, and the right vertical axis represents the voltage value corresponding to the displacement amount. This displacement amount represents the difference between the displacement data of the back surface 21b after laser processing and the displacement data of the back surface 21b before laser processing (specifically, a 30-interval moving average of the difference). Figure 9In the diagram, the total light intensity is represented by a solid line, and the displacement is represented by a dashed line. The control unit 8 first performs a wafer end designation process, identifying two points of change in the total light intensity as the two ends of the wafer 20. When the wafer 20 is not irradiated by the AF laser LA, its reflected light is not detected; conversely, when the wafer 20 is irradiated by the AF laser LA, its reflected light is detected. Therefore, the wafer end can be designated based on the detected total light intensity. Furthermore, the control unit 8 can also designate two points where the displacement is not a constant value as the two ends of the wafer 20. Because the positions of the wafer 20 ends are designated, the difference between the displacement data of the irradiation line AL1 (displacement data before laser processing) and the displacement data of the irradiation line AL2 (displacement data after laser processing) at corresponding time intervals is obtained to represent... Figure 9 The data shows the displacement amount of the difference. Next, the control unit 8 performs machining line-specific processing on the displacement data of a specific machining line PL based on the machining parameters and the scanning speed of the AF unit 71. Currently, for example, if the machining parameters are set to 5mm and the scanning speed of the AF unit 71 is 5mm / sec, the interval of the displacement data of each machining line PL is specified as 1sec. In this case, as Figure 9 As shown, displacement data at 1 sec, 2 sec, 3 sec, 4 sec, 5 sec, 6 sec... from the wafer end are specified as displacement data for each processing line PL. The difference (displacement amount) in the displacement data of each processing line PL is specified through the processing so far.

[0097] Alternatively, the control unit 8 may define machining lines whose absolute value of the difference (displacement amount) in the displacement data is greater than a certain threshold (first threshold) as BHC or HC, and machining lines whose absolute value of the displacement amount is less than the first threshold as ST or FC. Currently, for example, in... Figure 9 In the example shown, the first threshold is set to 0.04V. Therefore, as Figure 9 As shown, machining lines PL for 1 second, 2 seconds, and 6 seconds, where the absolute value of the difference (displacement amount) in the displacement data is greater than 0.04V, are assumed to be BHC or HC. Furthermore, under BHC, the back surface 21b is concave (see reference). Figure 7 In contrast, under HC, the back surface 21b is convex, therefore, the positive and negative values ​​of the displacement are opposite. Currently, it is pre-set that the displacement is negative in the case of BHC and positive in the case of HC. In this case, as... Figure 9As shown, machining lines PL for 1 second and PL for 2 seconds, where the absolute value of the displacement is greater than 0.04V and the displacement is negative, are defined as BHC. Similarly, machining lines PL for 6 seconds, where the absolute value of the displacement is greater than 0.04V and the displacement is positive, are defined as HC. Furthermore, machining lines PL for 3 seconds, PL for 4 seconds, and PL for 5 seconds, where the absolute value of the difference in displacement data (displacement) is less than 0.04V, are defined as ST or FC. Moreover, the control unit 8 can determine ST and FC based on the imaging results of the back side 21b captured by any of the imaging units 4, 5, and 6. Figure 9 In the example shown, the 3-second processing line PL, the 4-second processing line PL, and the 5-second processing line are presumed to be ST.

[0098] Alternatively, the control unit 8 may define machining lines PL where the absolute value of the difference (displacement amount) between their displacement data and the surrounding area is greater than a threshold (second threshold) as BHC or HC, and machining lines PL where the absolute value of the difference (displacement amount) between their displacement data and the surrounding area is less than the second threshold as ST or FC. Here, the displacement amount of the surrounding area is, for example, the displacement amount of the area outside the machining line PL (between machining lines PL). Because such areas are not laser-processed, the difference (displacement amount) in the displacement data is reduced. Through this processing, as... Figure 9 The machining lines PL with a large absolute difference in displacement from the surrounding area (1 sec, 2 sec, and 6 sec) are presumed to be BHC or HC, while the machining lines PL with a small absolute difference in displacement from the surrounding area (3 sec, 4 sec, and 5 sec) are presumed to be ST or FC.

[0099] Through the above processing, the control unit 8 estimates the processing state (crack state) of each processing line PL and displays the estimation result on the display 150. Furthermore, the control unit 8 determines whether the processing is qualified (whether the processing conditions are appropriate) based on the crack state of each processing line PL. If the crack state of each processing line PL meets the assumption (meets the inspection conditions), the processing conditions are set to appropriate, and the inspection is qualified. On the other hand, if there is a processing line PL whose crack state does not meet the assumption, the control unit 8 determines that the inspection is unqualified, performs processing condition correction, and performs the inspection again. Corrections to the processing conditions include, for example, corrections to the output of the light source 31, corrections to laser parameters, corrections to various aberrations, and corrections to the CP value.

[0100] [Inspection Method]

[0101] Reference Figure 10 The inspection method of this embodiment will be described. Figure 10 yes Figure 8 The flowchart of the inspection process (inspection method).

[0102] like Figure 10 As shown, firstly, the display 150 receives the selection input for inspection conditions, and selects the inspection conditions (step S1). For example, the formation position of the modified region, the distance from the lower end of the modified region, and the crack state are set for each of the multiple processing lines PL. Furthermore, processing conditions are set so that the processing indicated by the inspection conditions can be performed. Processing conditions include, for example, the output of the light source 31, laser parameters, corrections for various aberrations, and CP value.

[0103] Next, by controlling the imaging units 5 and 6, alignment processing related to the irradiation position of the laser L is performed, and height setting processing (step S2) is performed to set the processing depth (height) of the laser processing, i.e., the Z height.

[0104] Next, as Figure 8 As shown in (a), the AF laser LA is irradiated onto the back surface 21b, and the reflected light of the AF laser LA on the back surface 21b is detected to obtain the displacement data of the back surface 21b in each region along the irradiation line AL1 in the first direction, i.e., the AF waveform before processing (step S3).

[0105] Next, as Figure 8 As shown in (b), the wafer 20 rotates 90° due to the rotation of the stage 2 (step S4), and multiple processing lines PL are formed by irradiating the wafer 20 with multiple lines of laser L along the direction intersecting the first direction (second direction) (step S5).

[0106] Next, as Figure 8 As shown in (c), due to the rotation of the stage 2, the wafer 20 rotates 90°, becoming... Figure 8 In the same direction (step S6), the AF laser LA is irradiated onto the back surface 21b, and the reflected light of the AF laser LA on the back surface 21b is detected to obtain the displacement data of the back surface 21b in each region along the irradiation line AL2 in the first direction, i.e., the AF waveform after processing (step S7).

[0107] Next, in the inspection device 1, various signal processing is performed to estimate the processing status of each processing line PL, and the estimation results are displayed on the display 150 (step S8). Specifically, after performing wafer-end specific processing and processing line specific processing, the inspection device 1 estimates the crack status of each processing line PL based on the difference (displacement amount) of displacement data on the back side 21b.

[0108] Furthermore, based on the cracking state of each processing line PL, it is determined whether the inspection is qualified (whether the processing conditions are appropriate) (step S9). If the inspection is qualified, the process ends. On the other hand, if the cracking state does not conform to the assumed processing line PL and the inspection is unqualified, a correction process to modify the processing conditions is performed (step S10), and the process starting from step S1 is performed again under the new processing conditions.

[0109] [Effects]

[0110] Next, the effects of the inspection device 1 in this embodiment will be explained.

[0111] The inspection device 1 includes: a light source 31 that irradiates a laser onto a wafer 20; an AF unit 71, which serves as a measurement unit, that measures the displacement of the incident surface of the laser L on the wafer 20, i.e., the back surface 21b (the surface to be measured); and a control unit 8 configured to perform the following operations: control the light source 31 to form one or more modified regions inside the wafer 20 by irradiating the wafer 20 with the laser L; control the AF unit 71 to measure the displacement of the back surface 21b after irradiation with the laser L, i.e., the post-processing displacement; and derive information related to estimating the processing state of the wafer 20 based on the post-processing displacement measured by the AF unit 71.

[0112] In the inspection apparatus 1 of this embodiment, the post-processing displacement of the back surface 21b (the measurement target surface) on the wafer 20 irradiated by the laser L is measured, and information related to estimating the processing state of the wafer 20 is derived based on this post-processing displacement. As described above, the post-processing displacement (undulation shape) on the back surface 21b is correlated with the processing state of the wafer 20. Therefore, by deriving the information related to estimating the processing state of the wafer 20 based on the post-processing displacement, the processing state of the wafer 20 can be appropriately estimated based on this estimated information. Moreover, the process of measuring the post-processing displacement of the back surface 21b (the measurement target surface) is much easier than the process of determining the processing state (crack state) of a specific wafer 20 by, for example, internal observation of the wafer 20 using an infrared camera. Therefore, according to the inspection apparatus 1 of this embodiment, the processing state of the wafer 20 can be estimated more easily.

[0113] The inspection device 1 includes a display 150, and the control unit 8 controls the display 150 to display information related to the estimation of the processing status of the derived wafer 20. By displaying the information related to the estimation of the wafer's processing status derived by the control unit 8 on the display 150, for example, when displaying information used to estimate the processing status as information related to the estimation of the processing status, the user can easily estimate the processing status of the wafer 20 based on the displayed content. Furthermore, when displaying the estimation result of the processing status itself as information related to the estimation of the processing status, the user can confirm the appropriateness of the estimation result.

[0114] The AF unit 71 illuminates the back surface 21b with an AF laser LA, and receives and detects the reflected light from the AF laser LA on the back surface 21b, thereby measuring the displacement on the back surface 21b. Based on this structure, the displacement on the back surface 21b can be measured with high precision through a simple structure and processing.

[0115] Furthermore, in the inspection apparatus 1, since the measuring unit for measuring the displacement on the back surface 21b is the AF unit 71 for measuring the displacement on the back surface 21b in order to adjust the focusing point of the laser L irradiating the wafer 20 from the light source 31, the autofocus unit, which is typically installed in an inspection apparatus that irradiates the wafer 20 with laser, can be used to measure the displacement on the back surface 21b. That is, according to this structure, the displacement (convexity / concave shape) of the back surface 21b can be measured using the autofocus unit, and the processing state of the wafer 20 can be easily estimated based on this displacement.

[0116] The control unit 8 derives the difference between the post-processing displacement and the reference displacement measured by the AF unit 71 for each region of the back surface 21b, and derives information related to the estimation of the processing state of the wafer 20 based on this difference. The difference between the post-processing displacement and the reference displacement more accurately represents the amount of displacement caused by the effects of processing. Therefore, by deriving the information related to the estimation of the processing state based on this difference, the processing state of the wafer 20 can be estimated more accurately.

[0117] The control unit 8 controls the AF unit 71 to further measure the displacement of the back surface 21b before irradiation by the laser L, i.e., the pre-processing displacement, and uses this pre-processing displacement as a reference displacement to derive information related to the estimation of the processing state of the wafer 20. In this way, by actually measuring the displacement of the back surface 21b before irradiation by the laser L, i.e., the pre-processing displacement, and using this pre-processing displacement as a reference displacement, the difference between the post-processing displacement and the reference displacement more accurately represents the amount of displacement caused by the processing effect. Therefore, by deriving the information related to the estimation of the processing state based on this difference, the processing state of the wafer 20 can be estimated more accurately.

[0118] The control unit 8 estimates the state of the crack 14 extending from the modified region formed inside the wafer 20 by irradiation with laser L based on the aforementioned difference. The difference between the post-processing displacement and the reference displacement (the displacement on the back surface 21b after laser processing) is correlated with the state of the crack extending from the modified region. Therefore, by estimating the state of the crack based on the difference, the state of the crack (i.e., the processing state of the wafer 20) can be estimated with high accuracy.

[0119] The control unit 8 presumes regions where the absolute value of the difference is greater than a first threshold as BHC or HC, and regions where the absolute value of the difference is less than the first threshold as ST or FC. The inventors discovered that for regions where the absolute value of the difference between the processed displacement and the reference displacement (displacement on the measurement surface after laser processing) is large, the crack 14 is in a state where it reaches only one of the incident surface and the opposite surface (the so-called BHC or HC state); for regions where the difference is small, the crack 14 is in a state where it does not reach either the incident surface or the opposite surface (the so-called ST state), or the crack 14 reaches either the incident surface or the opposite surface (the so-called FC state). Based on this idea, by presuming the state of the crack 14 according to whether the difference is greater than a certain threshold (the first threshold), the state of the crack 14 (i.e., the processing state of the wafer 20) can be presumed with higher accuracy.

[0120] Alternatively, the control unit 8 may presume regions where the absolute value of the difference between the aforementioned difference and the surrounding regions is greater than a second threshold as BHC or HC, and regions where the absolute value of the difference is less than or equal to the second threshold as ST or HC. When prescribing the state of crack 14 based on the difference, it is sometimes easier and more accurate to judge based on the absolute value of the difference and the difference with the surrounding regions (judging based on the relative value) than to judge based on the absolute value of the difference. Based on this idea, by prescribing the state of crack 14 based on whether the difference with the surrounding regions is greater than a certain threshold (second threshold), the state of crack 14 (i.e., the processing state of wafer 20) can be predicted with higher accuracy and ease.

[0121] The control unit 8 controls the AF unit 71 to irradiate the back surface 21b with an AF laser LA along a first direction, and measures the pre-processing displacement in each region along the first direction by detecting the reflected light of the AF laser LA on the back surface 21b. The control unit 8 controls the light source 31 to irradiate the wafer 20 with multiple lines of laser light along a second direction that intersects the first direction to form multiple processing lines PL. The control unit 8 controls the AF unit 71 to irradiate the back surface 21b with an AF laser LA along the first direction in a manner that spans multiple processing lines PL, and measures the post-processing displacement in each region along the first direction by detecting the reflected light of the AF laser LA on the back surface 21b. The control unit 8 derives the difference between the post-processing displacement and the pre-processing displacement for each corresponding region, and derives information related to the estimation of the processing state of each region based on the difference. In this way, by measuring the post-processing displacement and pre-processing displacement of each region along the direction (first direction) spanning multiple processing lines PL, and deriving the difference between the post-processing displacement and pre-processing displacement for each region, the degree of post-laser processing displacement of each of the multiple processing lines PL can be specified, and the processing state of each of the multiple processing lines PL can be appropriately estimated. Based on this structure, for example, by making the inspection conditions of the multiple processing lines PL different from each other, the appropriateness of the processing conditions can be efficiently determined by estimating the processing state under each inspection condition. Moreover, since the degree of displacement of the multiple processing lines PL is specified, by comparing the displacements of different processing lines PL with each other, not only the absolute displacement amount, but also the relative information based on the displacement amount compared with other processing lines, the processing state of each of the multiple processing lines PL can be easily and accurately estimated.

[0122] The control unit 8 performs processing control based on prescribed processing conditions, and determines whether the processing is qualified based on information related to the estimation of the processing state of the wafer 20. If the determination result is unqualified, the processing conditions can also be modified. According to this structure, the processing conditions can be changed considering the estimation result of the processing state of the wafer 20, and the optimization of processing conditions can be implemented centrally and automatically.

[0123] [Variation Example]

[0124] The above description describes this embodiment, but the present invention is not limited to the above embodiment. For example, the description was given to determine whether the inspection is qualified and to modify the processing conditions as needed, but the inspection device 1 may not modify the processing conditions and may only display the estimated result of the processing state on the display 150. In addition, the inspection device 1 may only perform processing until the information involved in the estimation of the processing state is derived, and may not display the estimation result on the display 150, etc.

[0125] Furthermore, in the inspection apparatus 1, as described above, the processing state (crack state) can be estimated based on the displacement of the incident surface of the laser on the wafer 20 without using a camera such as an InGaAs camera that detects light that is transparent to the wafer 20. However, by further utilizing the function of the imaging unit 4, which includes a camera such as an InGaAs camera that detects light that is transparent to the wafer 20, the processing state of the wafer 20 can be estimated in more detail. That is, the inspection apparatus 1 may also include an imaging unit 4 that outputs light that is transparent to the wafer 20 and detects the light propagating on the wafer 20. The control unit 8 further considers the signal output from the imaging unit 4 that detects the light and estimates the state of the crack 14. In this case, the inspection apparatus 1, using the imaging unit 4, can estimate the processing state of the wafer 20 in more detail based on the internal observation results of the wafer 20. Regarding the inspection device 1, for example, among the multiple processing lines PL that are estimated to be BHC based solely on the displacement of the incident surface, the processing line PL where the formation position of the modified region is set to the shallowest position under inspection conditions (i.e., the boundary between BHC and ST is the processing line PL) is measured by an InGaAs camera to determine the position of the modified region and the length of the crack 14. This reduces the number of processing lines PL that need to be observed internally, significantly shortens the cycle time, and ensures the accuracy of the inspection.

[0126] Figure 11 This is a flowchart of the inspection method when further considering the internal observation results based on the InGaAs camera. Figure 11 Steps S101 to S108 shown are the same as those described above. Figure 10 Steps S1 to S8 are the same. After step S108, in inspection device 1, only specific machining lines PL (e.g., machining lines PL that become BHC at the shallowest position) are internally observed using an InGaAs camera (step S109). Furthermore, in inspection device 1, the internal observation results based on the InGas camera are further considered, and the inspection is judged to be qualified (whether the machining conditions are appropriate) based on the crack state of each machining line PL (step S110). The subsequent correction process (step S111) is the same as... Figure 10 The process of step S10 is the same.

[0127] Furthermore, in the above embodiment, the information involved in deriving the difference between the post-processing displacement and the pre-processing displacement and deriving the estimation of the processing state of the wafer 20 based on the difference has been described, but it is not limited to this. It is also possible to derive the estimation information of the processing state (more specifically, the cracked state) of the wafer 20 based solely on, for example, the post-processing displacement. Figure 12 This is an example of a display shown on the monitor 150 when the crack state of wafer 20 is inferred solely from post-processing displacement. In the above... Figure 9 In the example, the difference between the displacement after machining and the displacement before machining is expressed as the displacement amount. In contrast, in Figure 12 In the example, the post-processing displacement is expressed as a displacement amount. Thus, even when only the post-processing displacement is displayed as a displacement amount, for example, when it can be guaranteed that the wafer 20 before processing is to a certain extent flat, the crack state of the wafer 20 can be estimated with high accuracy based on the displayed state. Furthermore, in Figure 9 In the example shown, the presumed result of the cracked state (BHC, etc.) is displayed on monitor 150, but as Figure 12 As shown, it is also possible to export only the information used by the user to estimate the processing status (cracked status) and display it on the monitor 150.

[0128] Furthermore, in the above embodiment, it is assumed that the cracked state of wafer 20 is correlated with the displacement (convexity / concave shape) on the incident surface (back side 21b) after laser processing (see reference). Figure 7 The description assumes that the cracking state of the wafer 20 is estimated by measuring the displacement of the back surface 21b after laser processing. However, it is not limited to this. For example, the cracking state of the wafer 20 can also be estimated by measuring the displacement of the surface (surface 21a) opposite to the incident surface of the laser L after laser processing. That is, the inspection device 1 can also take the surface 21a, which is opposite to the incident surface of the laser L on the wafer 20, as the measurement object, measure the displacement of the surface 21a, and estimate the cracking state of the wafer 20 based on the displacement. Figure 13 This is a schematic diagram of a cross-section (longitudinal section) of wafer 20 showing each state of cracking after laser processing. Figure 13 (a) represents the states of BHC. Figure 13 (b) represents the states of ST. Figure 13 (c) represents the states of FC. Figure 13 (d) represents the various states of HC. For example... Figure 13 As shown in (a), under BHC, surface 21a is convex, as... Figure 13 (b) and Figure 13 As shown in (c), under ST and FC conditions, surface 21a is flat (without bumps), as... Figure 13 As shown in (d), under HC, surface 21a is concave. Thus, the crack state of wafer 20 is correlated with the displacement (convex / concave shape) on surface 21a after laser processing. Therefore, by measuring the displacement of surface 21a after laser processing using AF unit 71, inspection device 1 can also determine whether the measured location is BHC, ST (or FC), or HC.

[0129] In addition, for example Figure 8 and Figure 10The following steps are illustrated as a specific inspection procedure for estimating the processing state (crack state): measuring the displacement before processing, rotating the wafer 20 by 90°, laser processing, rotating the wafer 20 by 90°, measuring the displacement after processing, and estimating the crack state. However, the inspection procedure for estimating the crack state is not limited to this. Figure 14 This is a diagram showing the inspection process for a modified example. In Figure 14 In the inspection method shown, firstly, the displacement before laser processing is measured along the irradiation line AL1 in the first direction. Figure 14 Next, multiple processing lines PL1 are formed along a second direction intersecting the first direction by laser processing (CH1), and multiple processing lines PL2 are formed along the first direction by laser processing (CH2). Figure 14 (b) Next, the displacement after laser processing is measured along the irradiation line AL2 in the first direction. Figure 14 (c)). Irradiation lines AL1 and AL2 are, for example, lines that completely overlap each other, and lines that do not overlap with multiple processing lines PL2. After such measurements are performed, the inspection device 1 derives the difference between the displacement after processing and the displacement before processing for each processing line PL1. Thus, the displacement caused by the laser processing (the uneven shape of the back surface 21b) is derived for each processing line PL1. Based on the displacement (the uneven shape of the back surface 21b) of each processing line PL1, the inspection device 1 estimates the processing state (cracked state) of each processing line PL1, and determines whether the processing conditions set for each processing line PL1 are appropriate (checking whether it is qualified) based on the estimation results. In addition, in Figure 14 In the example shown, since only the displacement of the irradiation lines AL1 and AL2 along the first direction is measured, the processing state of multiple processing lines PL1 can only be estimated. However, by measuring the displacement of the irradiation lines in the second direction before and after processing, the processing state of multiple processing lines PL2 can also be estimated.

[0130] Figure 15 yes Figure 14 The flowchart of the inspection process (inspection method). Figure 15 Steps S201 and S202 shown are the same as those described above. Figure 10 Steps S1 and S2 are the same. After step S202, in the inspection device 1, as... Figure 14 As shown in (a), an AF laser LA is irradiated onto the back surface 21b, and the reflected light from the AF laser LA on the back surface 21b is detected. Displacement data of the back surface 21b in each region along the irradiation line AL1 in the first direction is obtained, i.e., the AF waveform before processing (step S203). Next, as... Figure 14As shown in (b), multiple lines of laser L (CH1) are irradiated onto the wafer 20 along a direction intersecting the first direction (the second direction) to form multiple processing lines PL1, and multiple lines of laser L (CH2) are irradiated onto the wafer 20 along the first direction to form multiple processing lines PL2 (step S204). Next, as... Figure 14 As shown in (c), an AF laser LA is irradiated onto the back surface 21b, and the reflected light from the AF laser LA on the back surface 21b is detected. Displacement data of the back surface 21b in each region along the irradiation line AL2 in the first direction is obtained, i.e., the processed AF waveform (step S205). Subsequent steps S206 to S208 are the same as described above. Figure 10 Steps S8 to S10 are the same.

[0131] Figure 16 This is a diagram illustrating the inspection process in another variation. In Figure 16 In the inspection method shown, when multiple opposing processing lines PL1 and PL2 are formed, the displacement of each opposing processing line PL1 and PL2 is derived, and the processing state (cracked state) is estimated. In this inspection method, firstly, the displacement before laser processing is measured along the irradiation line AL11 in the first direction. Secondly, the displacement before laser processing is measured along the irradiation line AL21 in the second direction intersecting the first direction. Figure 16 (a)). Next, multiple processing lines PL1 are formed along the second direction by laser processing (CH1) (refer to...). Figure 16 (b)). Next, multiple processing lines PL2 are formed along the first direction by laser processing (CH2), and (simultaneously with the formation of the processing lines PL2) the displacement after laser processing is measured along the irradiation line AL12 in the first direction. Figure 16 (c)). Finally, the displacement after laser processing was measured along the irradiation line AL22 in the second direction (refer to...). Figure 16 (d) Irradiation lines AL11 and AL12 are, for example, completely overlapping lines, and AL21 and AL22 are, for example, completely overlapping lines. Furthermore, AL11 and AL12 overlap with any one of the multiple processing lines PL2, while AL21 and AL22 do not overlap with any of the multiple processing lines PL1. After such measurements are performed, the inspection device 1 derives the difference between the displacement after processing and the displacement before processing for each processing line PL1, PL2. Thus, the displacement caused by the laser processing (the uneven shape of the back surface 21b) is derived for each processing line PL1, PL2. Based on the displacement (the uneven shape of the back surface 21b) of each processing line PL1, PL2, the inspection device 1 estimates the processing state (cracked state) of each processing line PL1, PL2, and determines whether the processing conditions set for each processing line PL1, PL2 are appropriate (checking for compliance) based on the estimation results.

[0132] In the case of the above processing, the control unit 8 controls the AF unit 71 to irradiate the back surface 21b with an AF laser LA along the irradiation line AL11 in the first direction, and detects the reflected light of the AF laser LA on the back surface 21b to determine the pre-processing displacement in each region along the irradiation line AL11. The control unit 8 also controls the AF unit 71 to irradiate the back surface 21b with an AF laser LA along the irradiation line AL21 in the second direction intersecting the first direction, and detects the reflected light of the AF laser LA on the back surface 21b to determine the pre-processing displacement in each region along the irradiation line AL21. The control unit 8 controls the light source 31 to irradiate the wafer 20 with multiple lines of laser L (CH1) along the second direction to form multiple processing lines PL1. The control unit 8 also performs the following operations: controls the light source 31 to irradiate the wafer 20 with multiple lines of laser (CH2) along the first direction to form multiple processing lines PL2; controls the AF unit 71 to irradiate the wafer 20 with multiple processing lines across the second direction. The AF unit 71 is controlled to irradiate the back surface 21b with an AF laser LA along the irradiation line AL12 in the first direction in a manner PL1, and to measure the post-processing displacement in each region along the irradiation line AL12 in the first direction by detecting the reflected light of the AF laser LA on the back surface 21b. The AF unit 71 is controlled to irradiate the back surface 21b with an AF laser LA along the irradiation line AL22 in the second direction in a manner spanning multiple processing lines PL2 in the first direction, and to measure the post-processing displacement in each region along the irradiation line AL22 in the second direction by detecting the reflected light of the AF laser LA on the back surface 21b. The difference between the post-processing displacement and the pre-processing displacement is derived for each corresponding region along the first direction, and information related to the estimation of the processing state of each region is derived based on the difference. The difference between the post-processing displacement and the pre-processing displacement is derived for each corresponding region along the second direction, and information related to the estimation of the processing state of each region is derived based on the difference.

[0133] Based on this structure, when multiple machining lines PL1 and PL2 are formed along intersecting directions (the machining lines are formed in a grid pattern), information related to estimating the machining state can be appropriately derived. Specifically, the post-machining displacement and pre-machining displacement are measured for each region along the direction spanning the multiple machining lines PL2 formed along the first direction (the second direction), and the difference between the post-machining displacement and the pre-machining displacement is derived for each region. Thus, the machining state of each of the multiple machining lines PL2 formed along the first direction can be appropriately estimated. Furthermore, the post-machining displacement and pre-machining displacement are measured for each region along the direction spanning the multiple machining lines PL1 formed along the second direction (the first direction), and the difference between the post-machining displacement and the pre-machining displacement is derived for each region. Thus, the machining state of each of the multiple machining lines PL1 formed along the second direction can be appropriately estimated. Moreover, since the formation of the multiple machining lines PL2 along the first direction and the measurement of the post-machining displacement in each region along the first direction (spanning the multiple machining lines along the second direction) are performed in the same direction, simultaneous operation is possible. Figure 16 (c) However, by performing these processes together (simultaneously), processing efficiency can be greatly improved.

[0134] In the above process, the control unit 8 may control the AF unit 71 and the light source 31 such that the irradiation line AL12 of the AF laser LA irradiating along the first direction for measuring the post-processing displacement overlaps with any one of the plurality of processing lines PL2 along the first direction, and control the AF unit 71 and the light source 31 such that the irradiation line AL22 of the AF laser LA irradiating along the second direction for measuring the post-processing displacement does not overlap with the plurality of processing lines PL1 along the second direction. Currently, in order to measure the post-processing displacement with high accuracy, it is desirable to eliminate the influence of processing lines whose processing direction is different from that of the processing line of the object whose post-processing displacement is to be measured. That is, when measuring the post-processing displacement of multiple processing lines along a certain direction, it is desirable to eliminate the influence of processing lines along directions different from that certain direction. In this case, it is necessary that the irradiation line of the AF laser LA irradiating along directions different from that certain direction, in a manner that spans multiple processing lines along a certain direction, does not overlap with the processing lines along directions different from that certain direction. In this respect, since the irradiation line AL22 of the laser LA along the second direction and the multiple machining lines PL1 along the second direction do not overlap, it is possible to measure the post-machining displacement related to the multiple machining lines PL2 along the first direction with high precision. Here, as described above, in this process, after forming the machining lines PL1 along the second direction, the formation of the machining lines PL2 along the first direction and the measurement of the post-machining displacement along the first direction are performed together. Figure 16 (b) and Figure 16(c) In this way, when the formation of the machining line and the measurement of the post-machining displacement are performed together along the same direction, even if the irradiation lines of the AF laser LA used for machining line and displacement measurement overlap, the post-machining displacement of the formed machining line can be measured without being affected by the newly formed machining line by performing the irradiation of the AF laser LA used for displacement measurement before the formation of the machining line (controlled to be performed together, and the irradiation of the AF laser LA is performed before the formation of the machining line). That is, in this process, since the formation of the machining line PL2 along the first direction and the measurement of the post-machining displacement along the irradiation line AL12 along the first direction are performed together, even if any one of the machining lines PL2 along the first direction overlaps with the irradiation line AL12 of the AF laser LA irradiated along the first direction, the post-machining displacement related to the multiple machining lines PL1 along the second direction can be estimated with high accuracy without being affected by the formation of the machining line PL2 along the first direction. Furthermore, since any one of the processing lines PL2 along the first direction overlaps with the irradiation line AL12 of the AF laser LA irradiating along the first direction, the processing related to the formation of the processing lines PL2 and the irradiation of the AF laser LA can be simplified (simplified).

[0135] Figure 17 yes Figure 16 The flowchart of the inspection process (inspection method). Figure 17 Steps S301 and S302 shown are the same as those described above. Figure 10 Steps S1 and S2 are the same. After step S302, in the inspection device 1, as... Figure 16 As shown in (a), by irradiating the back surface 21b with an AF laser LA and detecting the reflected light of the AF laser LA on the back surface 21b, displacement data of the back surface 21b in each region along the irradiation line AL11 in the first direction, i.e., the AF waveform before processing, is obtained. Similarly, displacement data of the back surface 21b in each region along the irradiation line AL21 in the second direction, i.e., the AF waveform before processing, is obtained (step S303). Next, as... Figure 16 As shown in (b), multiple lines of laser L (CH1) are irradiated onto wafer 20 along the second direction to form multiple processing lines PL1 (step S304). Next, as... Figure 16 As shown in (c), multiple lines of laser L (CH2) are irradiated onto the wafer 20 along the first direction to form multiple processing lines PL2, and displacement data of the back surface 21b in each region of the irradiation line AL12 along the first direction is acquired, i.e., the processed AF waveform (step S305). Next, as... Figure 16 As shown in (d), the displacement data of the back surface 21b in each region along the irradiation line AL22 in the second direction is obtained, i.e., the AF waveform after processing (step S306). Subsequent steps S307 to S309 are the same as described above. Figure 10Steps S8 to S10 are the same.

[0136] Furthermore, in the above embodiment, it was described that the processing state of each processing line was estimated by irradiating the AF laser LA in a manner that spans multiple processing lines and detecting its reflected light. However, it is not limited to this, and the processing state of the processing line can also be estimated by irradiating the AF laser LA along the processing line and detecting its reflected light. Figure 18 This diagram illustrates an inspection process where the machining condition of a machining line is estimated by irradiating it with an AF (Anatomical Focusing) laser (LA). Figure 18 In the inspection process shown, the control unit 8 first controls the AF unit 71 to irradiate the back surface 21b with an AF laser LA along the irradiation line AL1 in the first direction, and detects the reflected light of the AF laser LA on the back surface 21b to determine the pre-processing displacement in each region along the irradiation line AL1 in the first direction. Figure 18 (a)). In this case, the control unit 8 can use all predetermined processing lines as irradiation lines AL1, or only a portion (e.g., one) of the predetermined processing lines as irradiation lines AL1. Next, the control unit 8 controls the light source 31 to irradiate the wafer 20 with laser along the first direction to form multiple processing lines PL. Figure 18 (b) The control unit 8 can also control the AF unit 71 and the light source 31 to simultaneously measure the pre-processing displacement and form multiple processing lines PL. Next, the control unit 8 controls the light source 31 to irradiate the back surface 21b with the AF laser LA along the irradiation line AL2 that overlaps with the processing line PL, and detects the reflected light of the AF laser LA on the back surface 21b to measure the post-processing displacement in each region along the irradiation line AL2 that overlaps with the processing line PL. Figure 18 (c) Irradiation lines AL1 and AL2 are, for example, overlapping lines. The control unit 8 can use all the machining lines PL as irradiation lines AL2, or it can use only a portion (e.g., one) of the machining lines PL as irradiation lines AL2. Furthermore, the control unit 8 derives the difference between the displacement after machining and the displacement before machining for each corresponding region along irradiation lines AL1 and AL2, and estimates the machining state (crack state) related to each region based on the difference.

[0137] In this way, by unifying the irradiation direction of the AF laser LA used to measure the displacement before processing, the formation direction of the processing line PL, and the irradiation direction of the AF laser LA used to measure the displacement after processing, the process of rotating the wafer 20 as described in the embodiment is eliminated, thereby improving processing efficiency. Furthermore, in this method of irradiating the AF laser LA along the processing line PL, unlike the case where the AF laser LA is irradiated across multiple processing lines PL, the processing state cannot be estimated based on the relative information of the displacement amounts of multiple processing lines PL, but the processing state of the processing line PL can be estimated based on the absolute displacement amount after processing.

[0138] In the above implementation Figure 18 In the case of the inspection process shown, the inspection device 1 can also simultaneously perform the irradiation of the AF laser LA for measuring the displacement before processing, the formation of the processing line PL, and the irradiation of the AF laser LA for measuring the displacement after processing by setting a structure that irradiates the AF laser LA with an axis different from that of the laser L (setting two-sided split-axis AF). Figure 19 This is a schematic diagram illustrating a portion of the structure of an inspection device with two-sided split-axis AF units. Figure 19 In the structure shown, AF units 571 and 671 are provided that irradiate the AF laser LA with an axis different from that of the laser L irradiating the wafer 20 through the focusing lens 33. AF unit 571 irradiates the AF laser LA forward of the laser L in the laser processing forward direction. AF unit 571 irradiates the AF laser LA backward of the laser L in the laser processing forward direction. When the laser processing forward directions are opposite in the outgoing and returning paths, the functions of AF units 571 and 671 are opposite. According to this structure of AF units with two separate axes, it is possible to measure the pre-processing displacement achieved by irradiating the AF laser LA from AF unit 571 and the post-processing displacement achieved by irradiating the AF laser LA from AF unit 671, together with the process of irradiating the AF laser LA in the laser processing forward direction. Thus, in the implementation of... Figure 18 In the case of the inspection procedures shown, the processing status can be estimated more efficiently.

[0139] Figure 20 This is an example of a display screen showing the presupposition of the machining line PL based on the structure of the two side axes AF. Figure 20 (b) represents the pre-machining displacement (pre-machining AF waveform) measured by AF unit 571. Figure 20 (c) represents the post-machining displacement (post-machining AF waveform) measured by AF unit 671. The pre-machining displacement is derived from this. Figure 20 (b) and displacement after processing Figure 20 The difference of (c) shows Figure 20The difference in displacement data shown in (a) represents the displacement amount. Figure 20 In (a), the displacement is shown when the crack state is HC.

[0140] As mentioned above, when estimating the machining state of machining line PL based on the structure of the two side-axis AF, since only the displacement of one machining line PL is measured, it is impossible to estimate the machining state based on comparing the relative information of the displacements of multiple machining lines PL. However, if... Figure 21 As shown, based on the cracking condition, the difference in displacement data—that is, the absolute value and sign of the displacement—is different. Therefore, the processing state of the machining line PL can be appropriately estimated based on this information. For example, in... Figure 21 In the example shown in (a), based on the fact that the average value of the absolute values ​​of the displacements (the values ​​shown by the solid lines) is large and positive, it can be inferred that the cracked state is HC. Additionally, for example in... Figure 21 In the example shown in (b), the case where the average value of the absolute value of the displacement (the value shown by the solid line) is small can be presumed to be a cracked state of ST or FC. By further considering the shooting results of the shooting unit, the cracked state can be presumed to be ST.

[0141] The structure that simultaneously performs the measurement of displacement before processing, the formation of the processing line PL, and the measurement of displacement after processing is not limited to Figure 19 The structure of the two-sided split axis AF. For example, as Figure 22 As shown in (a), the inspection device 1 can also replace the AF unit 671 that irradiates the AF laser LA to a position further back than the laser L. Figure 19 The structure uses a general-purpose distance sensor 871 for measuring the concavity and convexity of the back surface 21b as a means of measuring displacement after machining. Furthermore, as... Figure 22 As shown in (b), the inspection device 1 can also replace the AF unit 571 that irradiates the AF laser LA to a position further forward than the laser L. Figure 19 The general-purpose distance sensor 771, which has a concavity / convexity measurement feature on the back side 21b, serves as the structure for measuring displacement after machining. Figure 22 In structure (b), since the split-axis AF structure is not required, it is possible to adopt a structure similar to... Figure 4 The laser irradiation unit 3 is similar to the structure (coaxial AF) that irradiates laser L and AF with laser LA from a condenser lens 33. In addition, for example, a two-dimensional laser displacement sensor can be used as a ranging sensor 771, 871.

[0142] Additionally, the inspection device 1 can also automatically set the pattern offset (LCOS pattern offset) of the spatial light modulator 32. It is known that by offsetting the center of the modulation pattern of the spatial light modulator 32 by an appropriate amount relative to the center of the incident pupil plane of the condenser lens 33, the formation state of the modified region can be appropriately controlled. The automatic setting of the LCOS pattern offset is achieved by automatically deriving and setting a preferred offset amount for the center of the modulation pattern. Currently, for example, the offset amount (pattern offset value) is changed in 1.0 increments for five processing lines PL. That is, as... Figure 23 As shown, using the third line (center), considered to be of appropriate offset, as a reference, the offset of the first line is set to center -2.0, the offset of the second line is set to center -1.0, the offset of the fourth line is set to center +1.0, and the offset of the fifth line is set to center +2.0. Furthermore, the cracking state of each processing line PL is estimated by the inspection device 1 under the inspection conditions of the two patterns, as follows: Figure 23 As shown, only one crack state of the third line is BHC. In this case, the inspection device 1 estimates the offset of the third line that is BHC under any inspection condition as the preferred offset. The inspection device 1 assumes that the offset assumed to be appropriate before inspection is actually appropriate, and sets the offset of the third line as the offset during inspection. On the other hand, if only another line becomes BHC, the inspection device 1 sets the offset of that other line as the optimal value.

[0143] Furthermore, in this embodiment, the inspection device 1 is described as determining whether the predetermined processing conditions are appropriate, but the inspection device 1 can also re-derive the processing conditions by estimating the crack state (proposing conditions). In addition, the inspection device 1 can be used not only for invisible cutting devices, but also for automatically determining the crack state in slicing devices and edge trimming devices.

Claims

1. An inspection device, wherein, have: The laser irradiation section irradiates the wafer with laser light; The measuring unit measures the displacement of the target surface, which is the incident surface of the laser on the wafer or the surface opposite to the incident surface; and The control unit is configured to perform the following operations: controlling the laser irradiation unit to form one or more modified regions inside the wafer by irradiating the wafer with the laser; controlling the measurement unit to measure the post-processing displacement, which is the displacement of the measurement object surface after irradiation with the laser; and deriving information related to estimating the processing state of the wafer based on the post-processing displacement measured by the measurement unit. The control unit outputs the difference between the post-processing displacement and the reference displacement measured by the measurement unit for each region of the measurement object surface, and derives information related to the estimation of the wafer's processing state based on this difference. The control unit estimates the state of cracks extending from the modified region formed inside the wafer by irradiating the laser based on the difference.

2. The inspection device according to claim 1, wherein, It also features: a display unit, The control unit controls the display unit in a manner that displays information related to the estimated processing status of the derived wafer.

3. The inspection device according to claim 1, wherein, The measuring unit has a measuring unit that measures the displacement on the surface of the object being measured by irradiating measuring light onto the surface of the object being measured and receiving and detecting the reflected light from the measuring light on the surface of the object being measured.

4. The inspection device according to claim 2, wherein, The measuring unit has a measuring unit that measures the displacement on the surface of the object being measured by irradiating measuring light onto the surface of the object being measured and receiving and detecting the reflected light from the measuring light on the surface of the object being measured.

5. The inspection device according to claim 3, wherein, The measuring unit is an autofocusing unit for measuring the displacement on the surface of the object being measured by adjusting the focusing point of the laser irradiating the wafer by the laser irradiation unit.

6. The inspection device according to claim 4, wherein, The measuring unit is an autofocusing unit for measuring the displacement on the surface of the object being measured by adjusting the focusing point of the laser irradiating the wafer by the laser irradiation unit.

7. The inspection device according to any one of claims 1 to 6, wherein, The control unit: The measuring unit is controlled in a manner that further measures the pre-processing displacement of the surface to be measured before irradiation with the laser. Using the pre-processing displacement as the reference displacement, information related to the estimation of the wafer's processing state is derived.

8. The inspection device according to any one of claims 1 to 6, wherein, The control unit: For regions where the absolute value of the difference is greater than a first threshold, it is presumed that the crack reaches the incident surface but not the opposite side, or does not reach the incident surface but reaches the opposite side. For regions where the absolute value of the difference is below a first threshold, it is presumed that the crack either does not reach either the incident surface or the opposite side, or reaches either the incident surface or the opposite side.

9. The inspection device according to claim 7, wherein, The control unit: For regions where the absolute value of the difference is greater than a first threshold, it is presumed that the crack reaches the incident surface but not the opposite side, or does not reach the incident surface but reaches the opposite side. For regions where the absolute value of the difference is below a first threshold, it is presumed that the crack either does not reach either the incident surface or the opposite side, or reaches either the incident surface or the opposite side.

10. The inspection device according to any one of claims 1 to 6, wherein, The control unit: For regions where the absolute value of the difference with the surrounding region is greater than a second threshold, it is presumed that the crack is in a state where it reaches the incident surface but not the opposite side, or in a state where it does not reach the incident surface but reaches the opposite side. For regions where the absolute value of the difference is below a second threshold, it is presumed that the crack either does not reach either the incident surface or the opposite side, or reaches either the incident surface or the opposite side.

11. The inspection device according to claim 7, wherein, The control unit: For regions where the absolute value of the difference with the surrounding region is greater than a second threshold, it is presumed that the crack is in a state where it reaches the incident surface but not the opposite side, or in a state where it does not reach the incident surface but reaches the opposite side. For regions where the absolute value of the difference is below a second threshold, it is presumed that the crack either does not reach either the incident surface or the opposite side, or reaches either the incident surface or the opposite side.

12. The inspection apparatus according to claim 8, wherein, The control unit: For regions where the absolute value of the difference with the surrounding region is greater than a second threshold, it is presumed that the crack is in a state where it reaches the incident surface but not the opposite side, or in a state where it does not reach the incident surface but reaches the opposite side. For regions where the absolute value of the difference is below a second threshold, it is presumed that the crack either does not reach either the incident surface or the opposite side, or reaches either the incident surface or the opposite side.

13. The inspection apparatus according to claim 9, wherein, The control unit: For regions where the absolute value of the difference with the surrounding region is greater than a second threshold, it is presumed that the crack is in a state where it reaches the incident surface but not the opposite side, or in a state where it does not reach the incident surface but reaches the opposite side. For regions where the absolute value of the difference is below a second threshold, it is presumed that the crack either does not reach either the incident surface or the opposite side, or reaches either the incident surface or the opposite side.

14. The inspection device according to any one of claims 1 to 6, wherein, It also includes a camera unit that outputs translucent light to the wafer and detects the light propagating on the wafer. The control unit further considers the signal output from the imaging unit that detects light to estimate the state of the crack.

15. The inspection device according to any one of claims 1 to 6, wherein, The control unit: The measuring unit is controlled by measuring the pre-processing displacement in each region along the first direction by irradiating measuring light onto the surface of the object to be measured along the first direction and detecting the reflected light of the measuring light on the surface of the object to be measured. The laser irradiation unit is controlled to form multiple processing lines by irradiating the wafer with multiple lines of laser light along a second direction intersecting the first direction. The measuring unit is controlled by irradiating the measuring object surface with measuring light along the first direction in a manner that spans the multiple processing lines, and detecting the reflected light of the measuring light on the measuring object surface to measure the post-processing displacement in each region along the first direction. For each corresponding region, the difference between the post-processing displacement and the pre-processing displacement is derived, and based on the difference, information related to the estimation of the processing state associated with each region is derived.

16. The inspection device according to any one of claims 1 to 6, wherein, The control unit: The measuring unit is controlled by measuring the pre-processing displacement in each region along the first direction by irradiating measuring light onto the surface of the object to be measured along the first direction and detecting the reflected light of the measuring light on the surface of the object to be measured. The measuring unit is controlled by illuminating the measuring object surface with measuring light along a second direction intersecting the first direction, and detecting the reflected light of the measuring light on the measuring object surface to detect the pre-processing displacement in each region along the second direction. The laser irradiation unit is controlled to form multiple processing lines by irradiating the wafer with multiple lines of laser light along the second direction. The following operations are performed together: the laser irradiation unit is controlled to form multiple processing lines by irradiating the wafer with multiple lines of laser light along the first direction; the measurement unit is controlled to detect the post-processing displacement in each region along the first direction by irradiating the measurement object surface with measurement light along the first direction in a manner that spans the multiple processing lines along the second direction, and detecting the reflected light of the measurement light on the measurement object surface. The measuring unit is controlled by irradiating the measuring object surface with measuring light along the second direction in a manner that spans the plurality of processing lines along the first direction, and detecting the reflected light of the measuring light on the measuring object surface to detect the post-processing displacement in each region along the second direction. For each corresponding region along the first direction, the difference between the post-processing displacement and the pre-processing displacement is derived, and information related to the estimation of the processing state associated with each region is derived based on the difference. For each corresponding region along the second direction, the difference between the post-processing displacement and the pre-processing displacement is derived, and information related to the estimation of the processing state associated with each region is derived based on the difference.

17. The inspection apparatus according to claim 16, wherein, The control unit: The measuring unit and the laser irradiation unit are controlled such that the irradiation line of the measuring light illuminating along the first direction for measuring the post-processing displacement overlaps with any one of the plurality of processing lines along the first direction. The measuring unit and the laser irradiation unit are controlled in such a way that the irradiation line of the measuring light irradiating along the second direction for measuring the post-processing displacement and the plurality of processing lines along the second direction do not overlap.

18. The inspection device according to any one of claims 1 to 6, wherein, The control unit: The measuring unit is controlled by measuring the pre-processing displacement in each region along the first direction by irradiating measuring light onto the surface of the object to be measured along the first direction and detecting the reflected light of the measuring light on the surface of the object to be measured. The laser irradiation section is controlled in such a way that a processing line is formed by irradiating the wafer with a laser along the first direction. The measuring unit is controlled by measuring the post-processing displacement in each region along the processing line by irradiating the measuring object surface with measuring light along the processing line and detecting the reflected light of the measuring light on the measuring object surface. For each corresponding region along the machining line, the difference between the post-machining displacement and the pre-machining displacement is derived, and information related to the estimation of the machining state associated with each region is derived based on the difference.

19. The inspection device according to any one of claims 1 to 6, wherein, The control unit performs processing control based on the prescribed processing conditions, determines whether the processing is qualified based on the information involved in the estimation of the processing state of the wafer, and corrects the processing conditions if the determination result is unqualified.

20. An inspection method, wherein, include: A laser processing step in which a laser is irradiated onto the wafer in a manner that forms one or more modified regions inside the wafer; The post-processing measurement process measures the post-processing displacement of the measurement object surface of the wafer after laser processing. as well as The estimation process, based on the displacement after processing, estimates the processing state of the wafer. For each region of the measured object surface, the difference between the post-processing displacement and the reference displacement measured in the post-processing measurement process is derived, and information related to estimating the processing state of the wafer is derived based on this difference. The state of the crack extending from the modified region formed inside the wafer by irradiation with the laser is estimated based on the difference.

21. The inspection method according to claim 20, wherein, Before the laser processing step, a pre-processing measurement step is also included to measure the pre-processing displacement, which is the displacement of the surface to be measured. In the estimation process, the difference between the post-processing displacement and the pre-processing displacement is derived for each region of the measured object surface, and the processing state of the wafer is estimated based on the difference.

22. The inspection method according to claim 21, wherein, In the pre-processing measurement process, by irradiating the surface of the object being measured with measurement light along a first direction, receiving and detecting the reflected light from the surface of the object being measured, the pre-processing displacement in each region along the first direction is measured. In the laser processing step, multiple laser beams of varying intensity are irradiated onto the wafer along a second direction intersecting the first direction, forming multiple processing lines. In the post-processing measurement process, measurement light is irradiated onto the surface of the object to be measured along the first direction in a manner that spans the multiple processing lines. The reflected light from the measurement light on the surface of the object to be measured is received and detected, thereby measuring the post-processing displacement in each region along the first direction.

23. The inspection method according to claim 21, wherein, The pre-processing measurement process includes: a first pre-processing process, which involves irradiating the surface of the object to be measured with measuring light along a first direction, receiving and detecting the reflected light from the surface of the measuring light, thereby measuring the pre-processing displacement in each region along the first direction; and a second pre-processing process, which involves irradiating the surface of the object to be measured with measuring light along a second direction intersecting the first direction, receiving and detecting the reflected light from the surface of the measuring light, thereby measuring the pre-processing displacement in each region along the second direction. The laser processing steps include: a first processing step, in which multiple lines of laser light are irradiated onto the wafer along the second direction to form multiple processing lines; and a second processing step, in which multiple lines of laser light are irradiated onto the wafer along the first direction to form multiple processing lines. The post-processing measurement process includes: a first post-processing process, in which measurement light is irradiated onto the surface of the object to be measured along the first direction in a manner spanning the plurality of processing lines along the second direction, and the reflected light from the surface of the object to be measured is received and detected, thereby measuring the post-processing displacement in each region along the first direction; and a second post-processing process, in which measurement light is irradiated onto the surface of the object to be measured along the second direction in a manner spanning the plurality of processing lines along the first direction, and the reflected light from the surface of the object to be measured is received and detected, thereby measuring the pre-processing displacement in each region along the second direction. The first post-processing step is performed together with the second processing step.

24. The inspection method according to claim 21, wherein, In the pre-processing measurement process, by irradiating the surface of the object being measured with measurement light along a first direction, receiving and detecting the reflected light from the surface of the object being measured, the pre-processing displacement in each region along the first direction is measured. In the laser processing step, a laser is irradiated onto the wafer along the first direction to form a processing line. In the post-processing measurement process, by irradiating the surface of the object to be measured with measuring light along the processing line, receiving and detecting the reflected light of the measuring light on the surface of the object to be measured, the post-processing displacement in each region along the processing line is measured.

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