KR20220015325A - Inspection device and inspection method - Google Patents

Abstract

The present invention relates to an inspection device and an inspection method capable of more easily estimating a processing state of a wafer. The inspection device comprises: a light source for irradiating a laser beam (L) to a wafer; an AF unit as a measuring unit for measuring displacement of the back surface (surface to be measured) that is an incident surface of the laser beam (L) on the wafer; and a control unit which is configured to control the light source so that one or multiple modified regions are formed inside the wafer by irradiating the wafer with the laser beam (L), control the AF unit so that displacement after processing, which is the displacement of the back surface after the laser beam (L) is irradiated, is measured, and derive, based on the processed displacement measured by the AF unit, information about estimation of a processing state of the wafer.

Description

INSPECTION DEVICE AND INSPECTION METHOD

The present disclosure relates to an inspection apparatus and an inspection method.

In order to cut a wafer having a semiconductor substrate and a functional element layer formed on one surface of the semiconductor substrate along each of a plurality of lines, the wafer is irradiated with a laser beam from the other surface side of the semiconductor substrate to form a plurality of lines. Inspection apparatuses are known which form a plurality of rows of modified regions in the interior of a semiconductor substrate along each of them. The inspection apparatus described in Japanese Patent Laid-Open No. 2017-64746 is equipped with an infrared camera, and it is possible to observe the modified region formed inside the semiconductor substrate, processing damage formed in the functional element layer, and the like from the back side of the semiconductor substrate. it is to be done In the inspection apparatus, for example, based on such internal observation results, the state of cracking of the wafer after processing is estimated, and based on the estimation result of the state of cracks, whether processing has been passed or not (desired under the set processing conditions) Whether one processing can be performed) is determined.

Patent Document 1: Japanese Patent Laid-Open No. 2017-64746

According to the inspection apparatus demonstrated above, the state of the crack of a wafer can be estimated with high precision by internal observation with an infrared camera. Here, in this technical field, while estimating the state (processed state) of a crack of a wafer with high precision, it is calculated|required more easily to estimate the state (processed state) of a crack. The present disclosure has been made in view of the above circumstances, and relates to an inspection apparatus and an inspection method capable of more easily estimating a processing state of a wafer.

The present inventors pay attention to the correlation between the displacement (concave-convex shape) on the incident surface after laser processing or the surface opposite to the incident surface, and the processing state of the wafer, and based on the displacement after processing of the wafer, the processing state of the wafer We came up with the idea of an inspection device that derives information on the estimation of

That is, the inspection apparatus according to one aspect of the present disclosure includes a laser irradiation unit that irradiates a laser beam to a wafer, and a measurement unit that measures the displacement of a measurement target surface that is an incident surface of the laser light on the wafer or a surface opposite to the incident surface and controlling the laser irradiation unit so that one or a plurality of modified regions are formed inside the wafer by irradiating laser light onto the wafer, and measuring the post-processing displacement, which is the displacement of the measurement target surface after laser light irradiation and a control unit configured to execute controlling the portion and deriving information about the estimation of the processing state of the wafer based on the post-processing displacement measured by the measuring portion.

In the inspection apparatus according to one aspect of the present disclosure, the post-processing displacement of the measurement target surface, which is the incident face or the surface opposite to the incident face on the wafer to which the laser light is irradiated, is measured, and based on the post-processing displacement, the wafer Information regarding the estimation of the machining state is derived. As described above, there is a correlation between the post-processing displacement (concave-convex shape) on the measurement target surface and the processing state of the wafer. Therefore, by deriving information on the estimation of the processing state of the wafer based on the displacement after processing, it is possible to appropriately estimate the processing state of the wafer based on the information on the estimation. In addition, the processing of measuring the displacement after processing of the measurement target surface is very easy compared with the processing of specifying the processing state (state of cracks) of the wafer by, for example, internal observation of the wafer with an infrared camera or the like. For this reason, according to the inspection apparatus which concerns on one aspect of this indication, the processing state of a wafer can be estimated more easily.

The inspection apparatus may further include a display unit, and the control unit may control the display unit so that the derived information related to the estimation of the processing state of the wafer is displayed. When the information about the estimation of the processing state of the wafer derived by the control unit is displayed on the display unit, for example, when information for estimating the processing state is displayed as information about the estimation of the processing state, the user, Based on the displayed content, the processing state of the wafer can be easily estimated. Moreover, when the estimation result of a processing state itself is displayed as information about estimation of a processing state, the validity of the estimation result of a processing state can be confirmed to a user.

The measurement unit may have a measurement unit that measures the displacement on the measurement object surface by irradiating the measurement light onto the measurement object surface and by receiving and detecting the reflected light of the measurement light on the measurement object surface. According to such a configuration, it is possible to measure the displacement on the measurement target surface with high precision by simple and easy configuration and processing.

The measurement unit may be an autofocus unit that measures a displacement on the measurement target surface in order to adjust the converging point of the laser beam irradiated to the wafer by the laser irradiation unit. According to this structure, the displacement in the measurement target surface can be measured using the autofocus unit normally provided in the inspection apparatus which laser-irradiates a wafer. That is, according to this configuration, the displacement (concave-convex shape) of the wafer surface is measured using the autofocus unit, and the processing state of the wafer can be easily estimated based on the displacement.

The control unit may derive the difference between the post-processing displacement and the reference displacement measured by the measuring unit for each region of the measurement target surface, and based on the difference, derive information about the estimation of the processing state of the wafer. The difference between the displacement after machining and the reference displacement more accurately represents the amount of displacement due to the influence of machining. For this reason, the processing state of a wafer can be estimated more accurately by deriving information regarding the estimation of a processing state based on the said difference.

The control unit may control the measurement unit so that the pre-processing displacement, which is the displacement of the measurement target surface before the laser beam is irradiated, is further measured, and may derive information about the estimation of the processing state of the wafer by using the pre-processing displacement as the reference displacement. In this way, the displacement before processing, which is the displacement of the measurement target surface before laser light irradiation, is actually measured, and the displacement before processing becomes the reference displacement. It becomes a more accurate representation of the amount of displacement by For this reason, the processing state of a wafer can be estimated more accurately by deriving information regarding the estimation of a processing state based on the said difference.

The control part may estimate the state of the crack extending from the modified area|region formed in the inside of a wafer by irradiating a laser beam based on a difference. There is a correlation between the difference between the displacement after machining and the reference displacement (displacement on the measurement target surface after laser machining) and the state of cracks extending from the modified region. For this reason, by estimating the state of a crack based on the difference, the state of a crack (that is, the processing state of a wafer) can be estimated with high precision.

In the region where the absolute value of the difference is larger than the first threshold value, the control unit is in a state in which the crack has reached the incident surface and has not reached the opposite surface, or has not reached the incident surface and is on the opposite side. It is assumed that the surface of is reached, and in the region where the absolute value of the difference is less than or equal to the first threshold value, the crack has not reached both the incident surface and the opposite surface, or the incident surface and the opposite surface It is okay to assume that everything has been reached. The present inventors found that, in a region where the absolute value of the difference between the displacement after machining and the reference displacement (displacement on the measurement target surface after laser machining) is large, the crack reaches only one of the incident face and the opposite face (so-called BHC or HC), and in the region where the difference is small, either the crack has not reached both the incident surface and the opposite surface (so-called ST state), or the crack is located on both the incident surface and the opposite surface. It was found that it is in a state that has been reached (the so-called state of FC). Based on this idea, by estimating the state of the crack depending on whether or not the difference is greater than a certain threshold value (first threshold value), the state of the crack (that is, the processing state of the wafer) can be estimated with higher precision.

The control unit determines that, in a region where the difference in the absolute value of the difference with the surrounding region is larger than the second threshold value, the crack has reached the incident surface and has not reached the opposite surface, or It is assumed that the state has not reached and has reached the opposite surface, and in the region where the difference in the absolute value of the difference is equal to or less than the second threshold value, the crack has not reached both the incident surface and the opposite surface, or . When estimating the state of a crack based on the difference, it may be easier and more accurate to judge from the difference around the absolute value of the difference (judgment from the relative value) than from the absolute value of the difference. Based on this idea, by estimating the state of the crack depending on whether or not the difference in the difference with the surrounding area is larger than a certain threshold (second threshold), the state of the crack (that is, the processing state of the wafer) can be obtained more precisely Roads can also be easily estimated.

The inspection apparatus further includes an imaging unit that outputs light having transparency to the wafer and detects light propagating through the wafer, wherein the control unit further includes a signal output from the imaging unit that has detected the light Considering this, you may estimate the state of a crack. According to this configuration, the basic wafer processing state is estimated based on the displacement on the measurement target plane, and for example, cracks in a part of the region (the region where the state of cracks are to be investigated in more detail). It becomes possible to process only the estimation of the state based on the signal output from the imaging unit, and the like, so that the estimation of the state of the crack can be performed more accurately. Moreover, even in this case, compared with the case where the state of all cracks is estimated from only the signal output from the imaging part, the processing state of a wafer can be estimated easily (by shortening tact significantly).

The control unit includes the measurement unit so that the measurement light is irradiated to the measurement target surface along the first direction, and the displacement before processing in each region along the first direction is measured by detecting the reflected light of the measurement light on the measurement target surface. Control, along a second direction intersecting the first direction, a plurality of lines (minutes), so that the laser beam is irradiated to the wafer to form a plurality of processing lines, and to control the laser irradiation unit, so as to span the plurality of processing lines , control the measuring unit so that the measurement light is irradiated to the measurement target surface along the first direction, and the post-processing displacement in each area along the first direction is measured by detecting the reflected light of the measurement light on the measurement target surface, , may derive the difference between the displacement after machining and the displacement before machining for each region corresponding to each other, and based on the difference, information about the estimation of the machining state for each region may be derived. In this way, the displacement after machining and the displacement before machining are measured for each region along the direction (first direction) spanning the plurality of machining lines, and the difference between the displacement after machining and the displacement before machining is derived for each region. The degree of displacement after laser processing in each of the processing lines can be specified, and the processing state of each of the plurality of processing lines can be appropriately estimated. According to this configuration, for example, by making the processing conditions of a plurality of processing lines different from each other and estimating the processing state in each processing condition, it is possible to efficiently determine the suitability of the plurality of processing conditions. And by specifying the degree of displacement of a plurality of processing lines, by comparing displacements between different processing lines, not only the absolute displacement amount, but also based on the relative information of the displacement amount compared with other processing lines, it is easy and Precisely, the machining state of each of the plurality of machining lines can be estimated.

The control unit includes the measurement unit so that the measurement light is irradiated to the measurement target surface along the first direction, and the displacement before processing in each region along the first direction is measured by detecting the reflected light of the measurement light on the measurement target surface. Control, the measurement light is irradiated to the measurement target surface along a second direction intersecting the first direction, and the reflected light of the measurement light on the measurement target surface is detected, whereby the pre-processing displacement in each area along the second direction Controls the measuring unit to measure , and controls the laser irradiation unit to form a plurality of processing lines by irradiating the wafer with laser light for a plurality of lines along the second direction, and for a plurality of lines along the first direction; Controlling the laser irradiation unit so that the wafer is irradiated with laser light to form a plurality of processing lines, and the measurement light is irradiated to the measurement target surface along the first direction to span the plurality of processing lines along the second direction, By detecting the reflected light of the measurement light on the measurement target surface, the measurement unit is controlled so that the displacement after processing in each area along the first direction is measured, and a plurality of processing lines along the first direction are controlled. controlling the measuring unit so that the measurement light is irradiated to the measurement target surface along the second direction, and the post-processing displacement in each region along the second direction is measured by detecting the reflected light of the measurement light on the measurement target surface, For each region corresponding to each other along the first direction, the difference between the displacement after machining and the displacement before machining is derived, and based on the difference, information about the estimation of the machining state for each region is derived, and For each region corresponding to each other, the difference between the displacement after machining and the displacement before machining may be derived, and based on the difference, information about the estimation of the machining state for each region may be derived.

According to such a configuration, even when a plurality of processing lines are formed in each of the mutually intersecting directions (when the processing lines are formed in a grid pattern), information regarding the estimation of the processing state is appropriately derived. That is, the displacement after machining and the displacement before machining are measured for each area along the direction (second direction) crossing the plurality of machining lines formed along the first direction, and the difference between the displacement after machining and the displacement before machining is calculated for each area. By being derived, it is possible to appropriately estimate the processing state of each of the plurality of processing lines formed along the first direction. In addition, the displacement after machining and the displacement before machining are measured for each area along the direction (first direction) crossing the plurality of machining lines formed along the second direction, and the difference between the displacement after machining and the displacement before machining is calculated for each area. By being derived, it is possible to appropriately estimate the processing state of each of the plurality of processing lines formed along the second direction. And, the formation of the plurality of processing lines along the first direction and the measurement of the displacement after processing in each region along the first direction (over the plurality of processing lines along the second direction) are processing along the same direction. Therefore, it is possible to execute them simultaneously. By executing these processes together (simultaneously), the processing efficiency can be greatly improved.

The control unit controls the measuring unit and the laser irradiation unit so that any of the plurality of processing lines along the first direction and the irradiation line of the measurement light irradiated along the first direction overlaps with each other for measuring the displacement after processing, For measurement, you may control the measuring part and the laser irradiation part so that the irradiation line of the measurement light irradiated along the 2nd direction and the some processing line along the 2nd direction may not overlap. Now, in order to measure the displacement after machining with high precision, it is desired to exclude the influence of a machining line having a different machining direction from the machining line for which the post machining displacement is to be measured. That is, in the case of measuring the displacement after machining with respect to a plurality of machining lines along a certain direction, it is desired to exclude the influence of the machining lines along a direction different from the one direction. In this case, it is necessary that the irradiation line of the measurement light irradiated along a direction different from the one direction does not overlap the processing line along the direction different from the one direction so as to span a plurality of processing lines along a certain direction. In this respect, since the irradiation line of the measurement light along the second direction and the plurality of processing lines along the second direction do not overlap, the displacement after processing with respect to the plurality of processing lines along the first direction can be measured with high precision. . Here, as described above, in this process, after the processing line along the second direction is formed, the formation of the processing line along the first direction and the measurement of the displacement after processing along the first direction are performed together. As described above, in the case where the formation of the processing line and the measurement of the displacement after processing are performed together along the same direction, even if the processing line and the irradiation line of the measurement light for measuring the displacement overlap, the irradiation of the measurement light for measuring the displacement is processed Post-machining displacement of a previously formed processing line without being affected by a newly formed processing line by executing prior to line formation (acting together, controlling so that the irradiation of measurement light precedes formation of the processing line) can be measured. That is, in this process, since the formation of the machining line along the first direction and the measurement of the displacement after machining along the first direction are performed together, any of the machining lines along the first direction and the irradiated along the first direction are performed. Even if the irradiation lines of the measurement light overlap, the post-processing displacement with respect to the plurality of processing lines along the second direction can be estimated with high accuracy without being affected by the formation of the processing line along the first direction. And, by overlapping any of the processing lines along the first direction and the irradiation line of the measurement light irradiated along the first direction, the processing related to the formation of the processing line and the irradiation of the measurement light can be simplified (facilitated).

The control unit includes the measurement unit so that the measurement light is irradiated to the measurement target surface along the first direction, and the displacement before processing in each region along the first direction is measured by detecting the reflected light of the measurement light on the measurement target surface. control, and control the laser irradiation unit so that the laser beam is irradiated to the wafer along the first direction to form a processing line, and the measurement light is irradiated to the measurement target surface along the processing line, and reflected light of the measurement light on the measurement target surface By this detection, the measurement unit is controlled so that the displacement after machining in each area along the machining line is measured, and the difference between the displacement after machining and the displacement before machining is derived for each region corresponding to each other along the machining line, and this difference Based on this, you may derive information regarding the estimation of the processing state regarding each area|region. In this way, since the irradiation direction of the measurement light for measuring the displacement before processing, the formation direction of the processing line, and the irradiation direction of the measurement light for measuring the displacement after processing are common, processing of rotating the wafer, etc. becomes unnecessary, The processing efficiency can be improved. In addition, in this form in which the measurement light is irradiated along the processing line, unlike the case where the measurement light is irradiated to span a plurality of processing lines, estimation of the processing state based on the relative information of the amount of displacement comparing the plurality of processing lines is performed. However, it is possible to estimate the machining state of the machining line based on the absolute amount of displacement after machining.

The control unit performs processing control based on predetermined processing conditions, determines whether processing has passed based on information about the estimation of the processing state of the wafer, and may correct processing conditions when the determination result is unpassed . According to such a configuration, the processing conditions can be changed in consideration of the estimation result of the processing state of the wafer, and even optimization of the processing conditions can be performed integrally and automatically.

An inspection method according to one embodiment of the present disclosure includes a laser processing step of irradiating a laser beam to a wafer so that one or a plurality of modified regions are formed inside the wafer, and a displacement of a measurement target surface of the wafer after laser processing It includes a post-processing measurement process of measuring the displacement after processing, and an estimation process of estimating the processing state of the wafer based on the displacement after processing.

The inspection method further includes a pre-processing measurement step of measuring a pre-processing displacement that is a displacement of the measurement target surface before the laser processing step, and in the estimation step, post-processing and pre-processing displacements for each area of the measuring target surface You may derive a difference from and and estimate the processing state of a wafer based on this difference.

In the pre-processing measurement step, the measurement light is irradiated to the measurement target surface along the first direction, and the reflected light of the measurement light on the measurement target surface is received and detected, thereby pre-processing in each region along the first direction. Displacement is measured, and in the laser processing step, laser light is irradiated to the wafer for a plurality of lines along a second direction intersecting the first direction to form a plurality of processing lines, and in the post-processing measurement step, a plurality of After processing in each area along the first direction by irradiating the measurement light to the measurement target surface along the first direction so as to cross the processing line, and receiving and detecting the reflected light of the measurement light on the measurement target surface It is okay to measure displacement.

In the pre-processing measurement step, the measurement light is irradiated to the measurement target surface along the first direction, and the reflected light of the measurement light on the measurement target surface is received and detected, thereby pre-processing displacement in each region along the first direction. In the first pre-processing process of measuring a second pre-processing process of measuring the pre-processing displacement in each region along A first processing step and a second processing step of forming a plurality of processing lines by irradiating laser light to the wafer for a plurality of lines along the first direction, wherein the post-processing measurement step includes a plurality of lines along the second direction Displacement after processing in each region along the first direction by irradiating measurement light to the measurement target surface along the first direction so as to span the processing line of In the first post-processing step of measuring the measurement light, the measurement light is irradiated to the measurement target surface along the second direction so as to span a plurality of processing lines along the first direction, and the reflected light of the measurement light on the measurement target surface is received. A second post-machining step of measuring a pre-machining displacement in each region along the second direction by detecting may be included, and the first post-machining step may be performed together with the second machining step.

In the pre-processing measurement step, the measurement light is irradiated to the measurement target surface along the first direction, and the reflected light of the measurement light on the measurement target surface is received and detected, thereby pre-processing in each region along the first direction. Displacement is measured, and in the laser processing step, laser light is irradiated to the wafer along the first direction to form a processing line, and in the post-processing measurement step, the measurement light is irradiated to the measurement target surface along the processing line, and this You may measure the displacement after processing in each area|region along a processing line by receiving and detecting the reflected light of the measurement light on the measurement target surface.

ADVANTAGE OF THE INVENTION According to this indication, the processing state of a wafer can be estimated more easily.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram of the test|inspection apparatus of one Embodiment.
2 is a plan view of a wafer according to an embodiment.
3 is a cross-sectional view of a portion of the wafer shown in FIG. 2 .
Fig. 4 is a configuration diagram of the laser irradiation unit shown in Fig. 1;
FIG. 5 is a configuration diagram of an imaging unit for inspection shown in FIG. 1 .
It is a block diagram of the imaging unit for alignment correction shown in FIG.
Fig. 7 is a diagram schematically showing a cross section of a wafer for each state of cracks.
It is a figure which shows an inspection process.
9 is an example of a display screen of an estimation result.
It is a flowchart of the inspection process (inspection method) of FIG.
11 is a flowchart of an inspection method according to a modification.
12 is an example of a display screen according to a modification.
Fig. 13 is a diagram schematically showing a cross section of a wafer for each state of cracks.
It is a figure which shows the inspection process which concerns on a modified example.
It is a flowchart of the inspection process (inspection method) of FIG. 14. FIG.
It is a figure which shows the inspection process which concerns on a modification.
It is a flowchart of the inspection process (inspection method) of FIG. 16. FIG.
It is a figure which shows the inspection process which concerns on a modified example.
It is a figure which shows typically a part of the structure of the inspection apparatus which concerns on a modification.
20 is an example of a display screen according to a modification.
21 is an example of a display screen according to a modification.
It is a figure which shows typically a part of the structure of the inspection apparatus which concerns on a modification.
It is a figure explaining the inspection method which concerns on a modified example.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described in detail with reference to drawings. In addition, in each drawing, the same code|symbol is attached|subjected to the same or equivalent part, and overlapping description is abbreviate|omitted.

[Configuration of inspection device]

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

The stage 2 supports the object 11 by, for example, adsorbing a film pasted on the object 11 . The stage 2 is movable along each of the X direction and the Y direction, and is rotatable with an axis parallel to the Z direction as a center line. In addition, the X direction and the Y direction are a first horizontal direction and a second horizontal direction perpendicular to each other, and the Z direction is a vertical direction.

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

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

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

The imaging unit 4 is configured to be capable of imaging the modified region 12 formed on the object 11 and the tip of the crack extending from the modified region 12 . In addition, about the imaging unit 4, although it is not an essential component, it demonstrates assuming that the inspection apparatus 1 has the imaging unit 4 in this embodiment.

The imaging unit 5 and the imaging unit 6, under the control of the control unit 8 , image the target 11 supported on the stage 2 by the light passing through the target 11 . The image obtained by imaging by the imaging units 5 and 6 is provided for alignment of the irradiation position of the laser beam L as an example. In addition, about the imaging units 5 and 6, although it is not an essential component, it demonstrates assuming that the inspection apparatus 1 has the imaging units 5 and 6 in this embodiment.

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

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

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

[Configuration of object]

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

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

[Configuration of laser irradiation unit]

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

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

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

The laser irradiation unit 3 irradiates the laser beam L to the wafer 20 from the back surface 21b side of the semiconductor substrate 21 along each of the plurality of lines 15 . As an example, for a semiconductor substrate 21 that is a single crystal silicon substrate having a thickness of 775 μm, two light-converging points C1 and C2 are respectively aligned at a position of 54 μm and a position of 128 μm from the surface 21a, and a plurality of lines ( 15) A laser beam L is irradiated to the wafer 20 from the back surface 21b side of the semiconductor substrate 21 along each. At this time, for example, when the condition that the cracks 14 crossing the two rows of modified regions 12a and 12b reach the surface 21a of the semiconductor substrate 21, the wavelength of the laser beam L is 1099 nm. , the pulse width is 700 n seconds, and the repetition frequency is 120 kHz. In addition, the output of the laser light L at the converging point C1 is 2.7 W, and the output of the laser light L at the converging point C2 is 2.7 W, and the two condensing beams on the semiconductor substrate 21 are The relative moving speed of the points C1 and C2 is 800 mm/sec.

The formation of these two rows of modified regions 12a and 12b and cracks 14 is performed in the following cases. That is, in a later step, for example, by grinding the back surface 21b of the semiconductor substrate 21 , the semiconductor substrate 21 is thinned and the crack 14 is applied to the back surface 21b. This is a case where the wafer 20 is cut into a plurality of semiconductor devices along each of the plurality of lines 15 by exposing them.

As shown in FIG. 4 , the laser irradiation unit 3 further includes an AF (auto focus) unit 71 (a measurement unit, a measurement unit). The AF unit 71 is positioned at a predetermined distance from the back surface 21b of the wafer 20 even when displacement (undulations) in the thickness direction (Z direction) exists on the back surface 21b, which is the incident surface, of the wafer 20. It is a structure for precisely matching the condensing point of the light L. The AF unit 71 measures the displacement on the back surface 21b (measurement target surface) in order to adjust the converging point of the laser light L irradiated onto the wafer 20 by the light source 31 . The AF unit 71 specifically irradiates the laser beam LA for AF (measurement light) to the back surface 21b, and receives the reflected light of the laser beam LA for AF on the back surface 21b. and by detecting it, the displacement data of the back surface 21b is acquired (displacement is measured).

The AF unit 71 has the AF light source 71a which outputs the AF laser beam LA, and the displacement detection part 71b which receives and detects the reflected light of the AF laser beam LA. The laser beam LA for AF emitted from the light source 71a for AF is reflected by the dichroic mirror 72 for AF, and is irradiated to the back surface 21b through the condensing lens 33. As shown in FIG. In this way, the laser beam LA and the laser beam L for AF are irradiated to the wafer 20 from the same condensing lens 33 (they are on the same axis). And the reflected light of the laser beam LA for AF on the back surface 21b is reflected by the dichroic mirror 72 for AF, and is detected by the displacement detection part 71b. The displacement detection unit 71b includes, for example, a quadruple photodiode. The quadruple photodiode is configured to divide and receive a condensed image of the reflected light of the AF laser light LA, and output a voltage value according to the amount of each light. Since astigmatism is added to the reflected light of the AF laser light LA, the focused image has a position of the back surface 21b of the wafer 20 with respect to the converging point of the AF laser light LA. Accordingly, the shape (vertical length, roundness, transverse length) changes. That is, the light-converging image changes depending on the position of the back surface 21b of the wafer 20 with respect to the light-converging point. Therefore, the voltage value output from the quadrant photodiode changes according to the position of the back surface 21b of the wafer 20 with respect to the converging point of the AF laser light LA.

The voltage value output from the quadruple photodiode of the displacement detection unit 71b is input to the control unit 8 . The control unit 8 relates to the position of the back surface 21b of the wafer 20 with respect to the converging point of the AF laser light LA based on the voltage value output from the quadruple photodiode of the displacement detecting unit 71b. Calculates the calculated value as position information. And the control part 8 controls the drive unit 7 (actuator) based on the said calculation value, and the position of the converging point of the laser beam L irradiated from the light source 31 is from the back surface 21b. The position of the condensing lens 33 is finely adjusted in the vertical direction so as to have a constant depth. In this way, control based on the result of the distance range by the AF unit 71 is performed together with the laser processing by the laser beam L (prior to the laser processing), so that the back surface 21b which is the incident surface ), the converging point of the laser beam L can always be precisely aligned with the position at a predetermined distance from the back surface 21b.

In this embodiment, the AF unit 71 also functions as a measurement unit that measures the displacement of the back surface 21b (measurement target surface) used when estimating the processing state (crack state) of the wafer 20 ( Details will be described later).

[Configuration of the imaging unit for inspection]

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

The objective lens 43 allows the light I1 reflected from the surface 21a of the semiconductor substrate 21 to pass therethrough. That is, the objective lens 43 transmits the light I1 propagating through the semiconductor substrate 21 . The numerical aperture NA of the objective lens 43 is, for example, 0.45 or more. The objective lens 43 has a correction ring 43a. The correction ring 43a corrects aberrations generated in the light I1 in the semiconductor substrate 21 by, for example, adjusting the distances between the plurality of lenses constituting the objective lens 43 . In addition, the means for correcting the aberration is not limited to the correction ring 43a, and other correction means such as a spatial light modulator may be used. The photodetector 44 detects the light I1 transmitted through the objective lens 43 and the mirror 42 . The photodetector 44 is constituted by, for example, an InGaAs camera, and detects the light I1 in the near-infrared region. In addition, the means for detecting (imaging) the light I1 in the near-infrared region is not limited to the InGaAs camera, and other imaging means may be used as long as it performs transmission-type imaging, such as a transmission confocal microscope.

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

[Configuration of the imaging unit for alignment correction]

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

The lens 53 transmits the light I2 reflected from the surface 21a of the semiconductor substrate 21 . That is, the lens 53 transmits the light I2 propagating through the semiconductor substrate 21 . The numerical aperture of the lens 53 is 0.3 or less. That is, the numerical aperture of the objective lens 43 of the imaging unit 4 is larger than the numerical aperture of the lens 53 . The photodetector 54 detects the light I2 that has passed through the lens 53 and the mirror 52 . The photodetector 54 is constituted by, for example, an InGaAs camera, and detects light I2 in the near-infrared region. In addition, an SD camera may be sufficient as the photodetection part 54, and what detects the light which does not have transparency may be sufficient as it.

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

[Inspection of wafer by inspection device]

Hereinafter, in the case of performing a process for forming a modified region for the purpose of cutting the wafer 20 , processing of the wafer 20 when laser processing of the wafer 20 is performed under set processing conditions A process for estimating the state (the state of cracks) and determining the suitability of the processing conditions (whether or not the inspection is passed) based on the estimation result will be described. In the inspection apparatus 1 according to the present embodiment, the displacement of the back surface 21b (measurement target surface) of the wafer irradiated with laser light is measured by the AF unit 71, and the displacement of the measured back surface 21b is Based on this, the processing state of the wafer 20 is estimated.

First, with reference to FIG. 7, the estimation principle of a processing state (state of a crack) is demonstrated. 7 : is a figure which shows typically the cross section (vertical cross-section) of the wafer 20 for each crack state after laser processing. Fig. 7(a) shows "BHC (Bottom side half-) in which the crack 14 does not reach the back surface 21b which is the incident surface of the laser beam L, and has reached the surface 21a which is the opposite surface. cut) state”. Fig. 7(b) shows the "ST (Stealth) state" in which the crack 14 does not reach both the back surface 21b and the front surface 21a. Fig. 7(c) shows the "FC (Full-cut) state" in which the crack 14 has reached both the back surface 21b and the front surface 21a. Fig. 7(d) shows the "HC (half-cut) state" in which the crack 14 has reached the back surface 21b and has not reached the front surface 21a. Hereinafter, each state is simply described as BHC, ST, FC, and HC.

Here, the state of the crack of the wafer 20 has a correlation with the displacement (concave-convex shape) on the incident surface (rear surface 21b) after laser processing. That is, in the BHC, the back surface 21b is concave (see Fig. 7(a)), and in the ST or FC, the back surface 21b is flat (no irregularities) (Fig. 7(b) and Fig. 7). (c)), in the HC, the back surface 21b is convex. For this reason, the inspection apparatus 1 measures the displacement of the back surface 21b after laser processing by the AF unit 71 to determine whether the measured location is BHC, ST (or FC), or HC. can be estimated In addition, although ST and FC cannot be discriminated only by the displacement on the back surface 21b after laser processing, as will be described later, the inspection device 1 includes the back surface 21b imaged by the imaging units 4, 5, 6 ST and FC can be discriminated based on the imaging result of . 7(b) and 7(c), in order to discriminate ST and FC, the imaging result of the inside of the wafer 20 is not required, and the imaging of the back surface 21b of the wafer 20 to know the results. Therefore, in discriminating ST and FC, the photodetector of the imaging units 4, 5, 6 may not be an InGaAs camera but may be an SD camera or the like.

8 : is a figure which shows the specific inspection process at the time of estimating a processing state (state of a crack). As shown in Fig. 8(a) , first, along a direction (first direction) that intersects (for example, orthogonal) with a plurality of processing lines PL formed by laser processing, each region before laser processing is The displacement (displacement before machining) is measured. Next, as shown in FIG. 8B , the wafer 20 is rotated by 90°, and laser beams are applied to the wafer 20 for a plurality of lines along a direction intersecting the first direction (second direction). (L) is irradiated to form a plurality of processing lines (PL). In this case, the plurality of processing lines PL are processed under different processing conditions, for example. Then, as shown in FIG. 8C , the wafer 20 is rotated by 90° again (the same direction as in FIG. 8A ), and displacement (processing) of each region along the first direction after displacement) is measured. After performing such a measurement, the inspection apparatus 1 derives the difference between the displacement after machining and the displacement before machining for each region corresponding to each other. Thereby, with respect to each processing line PL, the displacement (uneven|corrugated shape of the back surface 21b) by the influence of laser processing is derived. The inspection apparatus 1 estimates the processing state (crack state) of each processing line PL based on the displacement (the uneven shape of the back surface 21b) with respect to each processing line PL, and is based on the estimation result. Based on it, suitability of the processing conditions set with respect to each processing line PL (test|inspection pass or not) is judged. Hereinafter, the process of the inspection apparatus 1 in the said inspection process is demonstrated concretely.

The control unit 8 controls the light source 31 so that one or a plurality of modified regions are formed in the inside of the wafer 20 by irradiating the laser beam L onto the wafer 20 , and the laser beam L ) controlling the AF unit 71 so that the post-processing displacement, which is the displacement of the back surface 21b (measurement target surface) after irradiating , is measured, and based on the post-processing displacement measured by the AF unit 71, the wafer (20) derivation of information about the estimation of the processing state is performed. The control unit 8 controls the display 150 to display the derived information about the estimation of the processing state of the wafer 20 . 9 is an example of a display screen displayed on the display 150 . The information about the estimation of a processing state may be the estimation result of a processing state itself, and may be information for estimating a processing state. The estimation result itself of a processing state is information, such as "BHC", "ST" and "HC" shown in FIG. 9, for example. The information for estimating the processing state is information that enables the user to estimate the processing state (BHC, etc.) based on the information displayed on the display 150, for example, the back surface ( It is information indicating the amount of displacement in 21b). In the present embodiment, the control unit 8 derives not only the information for estimating the processing state, but also the estimation result of the processing state itself, and explains that any information is displayed on the display 150 , but the control unit 8 ) may derive only information for estimating the processing state, and the display 150 may display only information for estimating the processing state.

Specifically, the control unit 8 derives a difference between the post-processing displacement and the reference displacement measured by the AF unit 71 for each area of the back surface 21b, and based on the difference, the wafer 20 Estimate the processing state of In this way, by the difference between the displacement after processing and the reference displacement is derived, the displacement (change in the uneven state) of the back surface 21b under the influence of laser processing is more accurately derived. The reference displacement may be, for example, a displacement before processing grasped in advance in the case where the displacement before processing of each region of the back surface 21b is grasped in advance. In this embodiment, the control part 8 makes the pre-processing displacement actually measured before laser processing the reference displacement. That is, the control unit 8 controls the AF unit 71 so that the pre-processing displacement, which is the displacement of the back surface 21b before the laser beam is irradiated, is additionally measured (refer to FIG. 8(a)), and before the processing The processing state of the wafer 20 is estimated by using the displacement as the reference displacement. That is, the control unit 8 controls the post-processing displacement measured by the AF unit 71 (see FIG. 8(c) ) and the pre-processing displacement measured by the AF unit 71 (see FIG. 8(b) ). ) is derived, and the processing state of the wafer 20 is estimated based on the difference.

The control unit 8 is formed inside the wafer 20 by irradiating the laser beam L with respect to each region based on the difference between the displacement after processing and the displacement before processing in each region of the measurement target surface. Estimate the state of the crack 14 extending from the modified region to be Each area here is each processing line PL shown in FIG.8(b).

The control unit 8 estimates that the region in which the absolute value of the difference is greater than a certain threshold value (first threshold value) is BHC or HC, and the region in which the absolute value of the difference is equal to or less than the threshold value (first threshold value). As for , it may be assumed to be ST or FC. In this way, the control unit 8 may estimate the state of cracks in each region based on the absolute value of the difference. In addition, the control unit 8 estimates that the difference between the absolute value of the difference with the surrounding area is greater than a threshold value (second threshold) is BHC or HC, and the absolute difference of the difference with the surrounding area is BHC or HC. About the area|region where the difference of values is equal to or less than the said threshold value (2nd threshold value), you may estimate to be ST or FC.

The control part 8 controls each structure so that a test|inspection may be performed in the test|inspection process shown in FIG. As shown in FIG. 8(a), the control part 8 is irradiated with the laser beam LA for AF to the back surface 21b along the irradiation line AL1 of a 1st direction, and the back surface 21b The AF unit 71 is controlled so that the pre-processing displacement in each area along the 1st direction is measured by the reflected light of the laser beam LA for AF being detected. The AF unit 71 irradiates the laser beam LA for AF to the back surface 21b, and receives and detects the reflected light of the laser beam LA for AF on the back surface 21b, whereby the irradiation line ( The displacement data of the back surface 21b in each area|region of AL1 is acquired, and this displacement data (voltage value) is output to the control part 8. As shown in FIG. In addition, the AF unit 71 outputs information (voltage value) indicating the total amount of light detected by receiving the reflected light of the laser beam LA for AF to the control unit 8 .

Next, as shown in FIG. 8B , the control unit 8 irradiates the laser beam L to the wafer 20 for a plurality of lines along a second direction intersecting the first direction, and a plurality of The light source 31 is controlled so that the processing line PL is formed. Next, as shown in FIG.8(c), the control part 8 is laser beam for AF on the back surface 21b along irradiation line AL2 of a 1st direction so that several processing lines PL may be spanned. The AF unit 71 is controlled so that the post-processing displacement in each area along the first direction is measured by irradiating LA and detecting the reflected light of the AF laser light LA on the back surface 21b thereof. do. The AF unit 71 acquires displacement data of the back surface 21b in each area of the irradiation line AL2 and outputs the displacement data (voltage value) to the control unit 8 . Moreover, the AF unit 71 outputs, to the control part 8, information (voltage value) indicating the total amount of light detected by receiving the reflected light of the laser beam LA for AF. In addition, as long as the irradiation lines AL1 and AL2 have regions corresponding to each other, the regions may not necessarily coincide with each other. That is, the irradiation line AL2 at the time of displacement measurement after machining may completely overlap the irradiation line AL1 at the time of displacement measurement before machining, and may overlap partially, and correspond to each other (close to each other to some extent). It doesn't matter if they don't overlap. Finally, the control unit 8 derives a difference between the displacement after machining and the displacement before machining for each region corresponding to each other of the irradiation lines AL1 and AL2, and based on the difference, the state of cracks in each region is determined estimate Specifically, the control part 8 estimates the state of a crack for each processing line PL.

In order to estimate the state of the crack for each processing line PL described above, the control unit 8 is a back surface ( It is necessary to specify which processing line PL the displacement data (signal indicating displacement) of 21b) corresponds to. The control unit 8 associates the displacement data with the processing line PL by performing wafer end specification processing and processing line identification processing, and estimates the state of cracks for each processing line PL. is realizing Hereinafter, the wafer end specification process and the processing line specification process are demonstrated with reference to FIG.

In FIG. 9 , the horizontal axis indicates time, the left vertical axis indicates a voltage value corresponding to the total amount of light detected by the AF unit 71 , and the right vertical axis indicates displacement data of the back surface 21b after laser processing and the laser The voltage value corresponding to the displacement amount indicating the difference (in detail, the 30-section moving average of the difference) with the displacement data of the back surface 21b before processing is shown. In Fig. 9, the total amount of light is indicated by a solid line, and the amount of displacement is indicated by a dotted line. The control unit 8 first performs a wafer end specification process for specifying two change points of the total amount of light as both ends of the wafer 20 . In this case, the reflected light is not detected when the wafer 20 is not irradiated with the AF laser light LA, whereas the reflected light is detected when the wafer 20 is irradiated with the AF laser light LA. Therefore, the wafer edge can be specified from the total amount of light detected. In addition, the control unit 8 may specify two points at which the displacement amount is not a constant value as both ends of the wafer 20 . Since the position of the end of the wafer 20 is specified, 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) of the time corresponding to each other When the difference of the displacement data is derived, the data of the displacement amount representing the difference shown in FIG. 9 is obtained. Next, the control unit 8 performs processing line specifying processing for specifying displacement data of the processing line PL from the processing index and the scanning speed of the AF unit 71 . Now, for example, assuming that the processing index is 5 mm and the scanning speed of the AF unit 71 is 5 mm/sec, the interval of the displacement data of each processing line PL is specified as 1 sec. In this case, 1 sec, 2 sec, 3 sec, 4 sec, 5 sec, 6 sec... The displacement data of are specified as displacement data of each processing line PL. By the processing up to this point, the difference (displacement amount) of the displacement data for every processing line PL is specified.

The control unit 8 estimates that the absolute value of the difference (displacement amount) of the displacement data is BHC or HC for the processing line PL greater than a certain threshold value (first threshold value), and the absolute value of the displacement amount is the first threshold You may estimate that it is ST or FC about the processing line PL below a value. Now, for example, in the example shown in FIG. 9, the said 1st threshold value is 0.04V. For this reason, as shown in FIG. 9, the 1 sec processing line PL, 2 sec processing line PL, and 6 sec processing line ( PL) is estimated to be BHC or HC. In the BHC, the back surface 21b has a concave shape (refer to Fig. 7(a) ), whereas in the HC, the back surface 21b has a convex shape, so the positive and negative displacement amounts are opposite to each other. Now, suppose that it is set in advance so that the displacement amount is negative in the case of BHC, and the displacement amount becomes positive in the case of HC. In this case, as shown in FIG. 9 , the processing line PL of 1 sec and the processing line PL of 2 sec in which the absolute value of the displacement amount is larger than 0.04 V and the displacement amount is a negative value is estimated to be BHC. Moreover, it is estimated that the processing line PL of 6 sec whose absolute value of a displacement amount is larger than 0.04 V and a displacement amount is a positive value is HC. And it is estimated that the 3 sec processing line PL, 4 sec processing line PL, and 5 sec processing line PL of which the absolute value of the difference (displacement amount) of the displacement data is 0.04 V or less is ST or FC do. Moreover, the control part 8 can discriminate|determine ST and FC based on the imaging result of the back surface 21b imaged by any imaging unit 4, 5, 6. In the example shown in FIG. 9, it is estimated as ST about the processing line PL of 3 sec, the processing line PL of 4 sec, and the processing line of 5 sec.

Moreover, the control part 8 estimates that the difference in the absolute value of the difference (displacement amount) of the displacement data with the surrounding area is BHC or HC with respect to the processing line PL whose difference is larger than the threshold value (2nd threshold value), and, You may estimate that the difference of the absolute value of the displacement amount with the area|region of is ST or FC about the processing line PL whose 2nd threshold value or less is less. The displacement amount of the peripheral region here is, for example, the displacement amount of the region (between the processing lines PL) other than the processing lines PL. Since such a region is not subjected to laser processing, the difference (displacement amount) of the displacement data becomes small. Even with this process, as shown in FIG. 9, the processing line PL of 1 sec, the processing line PL of 2 sec, and the processing line PL of 6 sec with a large difference in the absolute value of the displacement amount from the surrounding area|region ) is estimated to be BHC or HC, and the 3 sec processing line PL, 4 sec processing line PL, and 5 sec processing line PL with a small difference in the absolute value of the displacement amount from the surrounding area is , ST or FC.

By the above process, the control part 8 estimates the processing state (state of a crack) for every processing line PL, and makes the display 150 display the estimation result. And the control part 8 determines whether or not a process passes (suitability of a process condition) based on the state of the crack of each process line PL. When the state of the crack of each processing line PL is as assumed (according to an inspection condition), it is said that processing conditions are appropriate, and it becomes an inspection pass. On the other hand, when the processing line PL which is not as the state of a crack exists as assumed, the control part 8 determines with an inspection failure, performs the process which correct|amends a processing condition, and performs an inspection again. The correction of the processing conditions is, for example, correction of the output of the light source 31 , correction of laser parameters, correction of various aberrations, correction of CP values, and the like.

[method of inspection]

The inspection method of this embodiment is demonstrated with reference to FIG. Fig. 10 is a flowchart of the inspection step (inspection method) of Fig. 8 .

As shown in FIG. 10, first, the selection input of an inspection condition is received by the display 150, and an inspection condition is selected (step S1). As inspection conditions, the formation position of a modified area|region, the lower end distance of a modified area|region, the state of a crack, etc. are set for every several processing line PL, for example. Then, the processing conditions are set so that the processing shown in the inspection conditions becomes possible. The processing conditions are, for example, the output of the light source 31 , laser parameters, correction of various aberrations, CP values, and the like.

Next, while the alignment processing regarding the irradiation position of the laser beam L is performed by the imaging units 5 and 6 being controlled, the height set which sets the Z height which is a processing depth (height) at the time of laser processing A process is performed (step S2).

Next, as shown to Fig.8 (a), while the laser beam LA for AF is irradiated to the back surface 21b, the reflected light of the laser beam LA for AF in the back surface 21b is detected, and the 1st A pre-processing AF waveform, which is displacement data of the back surface 21b in each area of the irradiation line AL1 along the direction, is acquired (step S3).

Next, as shown in FIG. 8B , as the stage 2 rotates, the wafer 20 rotates 90 degrees (step S4), along a direction intersecting the first direction (second direction). , for a plurality of lines, the laser beam L is irradiated to the wafer 20 to form a plurality of processing lines PL (step S5).

Next, as shown in FIG. 8(c) , as the stage 2 rotates, the wafer 20 rotates 90° and becomes the same direction as in FIG. 8(a) (step S6), and the AF laser The light LA is irradiated to the rear surface 21b, and the reflected light of the AF laser light LA is detected on the rear surface 21b, and the rear surface 21b in each area of the irradiation line AL2 along the first direction. A post-processing AF waveform that is displacement data of is acquired (step S7).

Next, in the inspection apparatus 1, various signal processing is performed, the processing state of each processing line PL is estimated, and the estimation result is displayed on the display 150 (step S8). Specifically, the inspection apparatus 1 performs the wafer end specification processing and the processing line identification processing, and then, for each processing line PL, the state of the crack based on the difference (displacement amount) of the displacement data of the back surface 21b. to estimate

And based on the state of the crack of each processing line PL, it is judged whether the test|inspection passed (suitability of processing conditions) (step S9). If the inspection is passed, the processing is finished. On the other hand, if there is a processing line PL in which the state of the crack is not as expected and the inspection is unsuccessful, a correction process for correcting the processing conditions is executed (step S10), and the steps are repeated again with the new processing conditions. The processing from S1 is executed.

[action effect]

Next, the operation and effect of the inspection apparatus 1 which concerns on this embodiment is demonstrated.

The inspection apparatus 1 detects the displacement of a light source 31 irradiating laser light onto the wafer 20 and a back surface 21b (measurement target surface) that is an incident surface of the laser light L on the wafer 20 . The AF unit 71 as a measuring unit to measure and the light source 31 to control the light source 31 so that one or a plurality of modified regions are formed inside the wafer 20 by irradiating the laser beam L to the wafer 20 and controlling the AF unit 71 so that the post-processing displacement, which is the displacement of the back surface 21b after the laser light L is irradiated, is measured, and based on the post-processing displacement measured by the AF unit 71, and a control unit 8 configured to execute deriving information on the estimation of the processing state of the wafer 20 .

In the inspection apparatus 1 according to the present embodiment, the displacement after processing of the back surface 21b (the measurement target surface) of the wafer 20 to which the laser beam L is irradiated is measured, and based on the displacement after processing , information regarding the estimation of the processing state of the wafer 20 is derived. As described above, the displacement (concave-convex shape) after processing on the back surface 21b and the processing state of the wafer 20 have a correlation. Therefore, by deriving information on the estimation of the processing state of the wafer 20 based on the displacement after processing, the processing state of the wafer 20 can be appropriately estimated based on the information on the estimation. The processing for measuring the displacement after processing of the back surface 21b (measurement target surface) is, for example, the processing state (crack state) of the wafer 20 by internal observation of the wafer 20 with an infrared camera or the like. It is very easy compared to the process of specifying For this reason, according to the inspection apparatus 1 which concerns on this embodiment, the processing state of the wafer 20 can be estimated more easily.

The inspection apparatus 1 is provided with a display 150 , and the control unit 8 controls the display 150 so that the derived information regarding the estimation of the processing state of the wafer 20 is displayed. By displaying the information on the estimation of the processing state of the wafer derived by the control unit 8 on the display 150, for example, information for estimating the processing state as information on the estimation of the processing state is displayed. In this case, the user can easily estimate the processing state of the wafer 20 based on the displayed content. Moreover, when the estimation result of a processing state itself is displayed as information about estimation of a processing state, the validity of the estimation result of a processing state can be confirmed to a user.

The AF unit 71 irradiates the back surface 21b with the laser beam LA for AF, and receives and detects the reflected light of the laser beam LA for AF on the back surface 21b, thereby detecting the back surface 21b ) to measure the displacement. According to this structure, the displacement in the back surface 21b can be measured with high precision by a simple and easy structure and process.

In addition, in the inspection apparatus 1, the measuring unit for measuring the displacement on the back surface 21b adjusts the converging point of the laser light L irradiated to the wafer 20 by the light source 31 on the back surface ( With the AF unit 71 for measuring the displacement at 21b), the displacement at the back surface 21b can be measured using an autofocus unit normally provided in an inspection apparatus that irradiates the wafer 20 with a laser. can That is, according to this configuration, the displacement (concavo-convex shape) of the back surface 21b is measured using the autofocus unit, and the processing state of the wafer 20 can be easily estimated based on the displacement.

The control unit 8 derives a difference between the post-processing displacement and the reference displacement measured by the AF unit 71 for each area of the back surface 21b, and based on the difference, the processing state of the wafer 20 is determined. Derive information about the estimate. The difference between the displacement after machining and the reference displacement more accurately represents the amount of displacement due to the influence of machining. For this reason, the processing state of the wafer 20 can be estimated more accurately by deriving information regarding the estimation of a processing state based on the said difference.

The control unit 8 controls the AF unit 71 so that the pre-processing displacement, which is the displacement of the back surface 21b before the laser beam L is irradiated, is further measured, and the wafer 20 with the pre-processing displacement as the reference displacement. ) to derive information on the estimation of the processing state of In this way, the displacement before processing, which is the displacement of the back surface 21b before the laser beam L is irradiated, is actually measured, and since the displacement before processing becomes the reference displacement, the difference between the displacement after processing and the reference displacement is It becomes to show the displacement amount by the influence of processing more accurately. For this reason, the processing state of the wafer 20 can be estimated more accurately by deriving information regarding the estimation of a processing state based on the said difference.

Based on the difference, the control unit 8 estimates the state of the crack 14 extending from the modified region formed inside the wafer 20 when the laser beam L is irradiated. There is a correlation between the difference between the displacement after machining and the reference displacement (displacement on the back surface 21b after laser machining) and the state of cracks extending from the modified region. For this reason, by estimating the state of a crack based on the difference, the state of a crack (that is, the processing state of the wafer 20) can be estimated with high precision.

The control unit 8 estimates a region in which the absolute value of the difference is greater than the first threshold value as BHC or HC, and estimates it as ST or FC in a region in which the absolute value of the difference is equal to or less than the first threshold value. The present inventors found that, in a region where the absolute value (displacement on the measurement target surface after laser processing) of the difference between the displacement after processing and the reference displacement is large, the crack 14 reaches only one of the incident surface and the opposite surface. state (so-called BHC or HC state), and in the region where the difference is small, a state in which the crack 14 does not reach both the incident surface and the opposite surface (so-called ST state) or the crack 14 It was discovered that it was in the state (so-called FC state) reaching both the incident surface and the surface on the opposite side. Based on this idea, by estimating the state of the crack 14 according to whether the difference is greater than a certain threshold (first threshold) or not, the state of the crack 14 (ie, the processing state of the wafer 20) can be estimated with higher precision.

The control unit 8 estimates that the region where the difference in the absolute value of the difference with the surrounding region is greater than the second threshold value is BHC or HC, and in the region where the difference in the absolute value of the difference is equal to or less than the second threshold value, It's okay to assume ST or HC. When estimating the state of the crack 14 based on the difference, it is easier and more accurate to judge from the difference with the surroundings of the absolute value of the difference (judgment from the relative value) rather than judge from the absolute value of the difference there is Based on this idea, by estimating the state of the crack 14 depending on whether or not the difference in difference with the surrounding area is greater than a certain threshold (second threshold), the state of the crack 14 (that is, the wafer ( 20) can be estimated more accurately and easily.

The control part 8 irradiates the laser beam LA for AF to the back surface 21b along a 1st direction, The reflected light of the laser beam LA for AF on the back surface 21b is detected, and the 1st The AF unit 71 is controlled so that the displacement before processing in each area along the direction is measured, and the laser beam is irradiated to the wafer 20 for a plurality of lines along the second direction intersecting the first direction. The laser light LA for AF is irradiated to the back surface 21b along the first direction to control the light source 31 so as to form a processing line PL of The AF unit 71 is controlled so that the post-processing displacement in each area along the 1st direction is measured by the reflected light of the laser beam LA for AF on the back surface 21b being detected, and the area|regions corresponding to each other For each, a difference between the displacement after machining and the displacement before machining is derived, and based on the difference, information on the estimation of the machining state for each region is derived. In this way, the displacement after processing and the displacement before processing are measured for each region along the direction (first direction) spanning the plurality of processing lines PL, and the difference between the displacement after processing and the displacement before processing is derived for each region. Accordingly, the degree of displacement after laser processing in each of the plurality of processing lines PL can be specified, and the processing state of each of the plurality of processing lines PL can be appropriately estimated. According to this configuration, for example, by making the inspection conditions of the plurality of processing lines PL different from each other and estimating the processing state in the respective inspection conditions, it is possible to efficiently determine whether the processing conditions are appropriate. . And, by specifying the degree of displacement of the plurality of processing lines PL, by comparing the displacements of the different processing lines PL, not only the absolute displacement amount, but also relative information of the displacement amount compared with other processing lines Based on this, it is possible to easily and accurately estimate the processing state of each of the plurality of processing lines PL.

The control unit 8 performs processing control based on predetermined processing conditions, determines whether processing has been passed or not, based on the information on the estimation of the processing state of the wafer 20, and if the determination result is not, It is okay to correct the processing conditions. According to this configuration, the processing conditions can be changed in consideration of the result of the estimation of the processing state of the wafer 20, so that even optimization of the processing conditions can be performed integrally and automatically.

[Variation]

As mentioned above, although this embodiment was demonstrated, this invention is not limited to the said embodiment. For example, although the description has been made as to whether the inspection has been passed or not and to correct the processing conditions as necessary, the inspection apparatus 1 does not correct the processing conditions and only displays the estimated results of the processing state on the display 150 It is okay to mark on In addition, the inspection apparatus 1 does not need to perform only processing until the information regarding the estimation of a processing state is derived|leading-out, and to display an estimation result etc. on the display 150. FIG.

In addition, in the inspection apparatus 1, as described above, from the displacement of the incident surface of the laser light on the wafer 20, without using a camera that detects light having transmittance to the wafer 20, such as an InGaAs camera. The processing state (the state of cracks) can be estimated, but furthermore, by using the function of the imaging unit 4 configured including a camera that detects light having a transmittance with respect to the wafer 20 such as an InGaAs camera, In more detail, the processing state of the wafer 20 may be estimated. That is, the inspection apparatus 1 includes an imaging unit 4 that outputs light having transmittance to the wafer 20 and detects light propagating through the wafer 20 , and the control unit 8 includes You may estimate the state of the crack 14 by further considering the signal output from the imaging unit 4 which detected . In this case, the inspection apparatus 1 can estimate a more detailed processing state of the wafer 20 from the internal observation result of the wafer 20 using the imaging unit 4 . The inspection apparatus 1 includes, for example, a processing line PL, in which the formation position of the modified region is the shallowest position among the plurality of processing lines PL estimated to be BHC from the displacement of the incident surface ( That is, only the processing line PL that is the boundary between BHC and ST), the position of the modified region and the length of the crack 14 are measured with the InGaAs camera, so that the processing line PL for internal observation is reduced and wide. This can shorten the tact and guarantee the accuracy of the inspection.

11 is a flowchart of an inspection method in the case where the result of internal observation by an InGaAs camera is further taken into consideration. Steps S101 to S108 shown in FIG. 11 are the same as steps S1 to S8 of FIG. 10 described above. Following step S108, in the inspection apparatus 1, only the specific processing line PL (for example, the processing line PL serving as BHC at the shallowest position) is internally observed with an InGaAs camera (step S109). ). And in the inspection apparatus 1, the internal observation result by the InGas camera is also considered further, and based on the state of the crack of each processing line PL, it is judged whether the inspection passed (suitability of processing conditions) ( step S110). The subsequent correction processing (step S111) is the same as the processing of step S10 in FIG. 10 .

Further, in the above embodiment, the difference between the displacement after processing and the displacement before processing is derived, and based on the difference, information on the estimation of the processing state of the wafer 20 is derived. , for example, information regarding the estimation of the processing state (specifically, the state of cracks) of the wafer 20 may be derived from only the displacement after processing. 12 is an example of the display screen displayed on the display 150 in the case of estimating the state of the crack of the wafer 20 only from the displacement after processing. In the example of FIG. 9 described above, the difference between the displacement after machining and the displacement before machining is shown as the displacement amount, whereas in the example of FIG. 12 , the displacement after machining is shown as the displacement amount. In this way, even when only the displacement after processing is displayed as the displacement amount, for example, if it can be ensured that the wafer 20 before processing is flat to some extent, based on the displayed state, The state of the crack can be estimated. Moreover, in the example shown in FIG. 9, although the estimation result of the crack state itself (BHC etc.) was displayed on the display 150, as shown in FIG. 12, as shown in FIG. Only information may be derived and displayed on the display 150 .

Moreover, in the said embodiment, the state of the crack of the wafer 20 and the displacement (concavo-convex shape) in the incident surface (rear surface 21b) after laser processing have a correlation (refer FIG. 7), and laser processing Although it has been described that the state of the crack of the wafer 20 is estimated by measuring the displacement of the rear surface 21b later, it is not limited to this, for example, the surface on the opposite side of the incident surface after laser processing ( You may estimate the state of the crack of the wafer 20 by measuring the displacement of the surface 21a). That is, the inspection apparatus 1 measures the displacement of the surface 21a of the wafer 20 with the surface 21a on the opposite side to the incident surface of the laser light L as the measurement target surface. You may estimate the state of the crack of the wafer 20 based on a displacement. 13 is a diagram schematically illustrating a cross-section (longitudinal cross-section) of the wafer 20 in each crack state after laser processing. Fig. 13 (a) shows the BHC, Fig. 13 (b) shows the ST, Fig. 13 (c) shows the FC, and Fig. 13 (d) shows the HC state. As shown in Fig. 13(a), in BHC, the surface 21a is convex, and in ST and FC, as shown in Figs. 13(b) and 13(c), the surface 21a is flat ( There is no unevenness), and as shown in Fig. 13(d), in the HC, the surface 21a is concave. In this way, the state of the crack of the wafer 20 and the displacement (concavo-convex shape) on the surface 21a after laser processing have a correlation. For this reason, the inspection apparatus 1 measures the displacement of the surface 21a after laser processing by the AF unit 71 to determine whether the measured location is BHC, ST (or FC), or HC. can be estimated

In addition, as a specific inspection step for estimating the processing state (the state of cracks), as shown in FIGS. 8 and 10 , measurement of the displacement before processing, 90° rotation of the wafer 20, laser processing, and 90° of the wafer 20 An example of rotating, measuring displacement after machining, and estimating the crack state has been described in order, but the inspection process for estimating the crack state is not limited thereto. It is a figure which shows the inspection process which concerns on a modified example. In the inspection method shown in FIG. 14, first, the displacement before laser processing is measured along the irradiation line AL1 of a 1st direction (FIG. 14(a)), Then, by laser processing CH1, the 1st direction and A plurality of processing lines PL1 are formed in a second direction that intersects, and a plurality of processing lines PL2 are formed in a first direction by laser processing CH2 (FIG. 14(b)), and then, Displacement is measured after laser processing along the irradiation line AL2 in the first direction (FIG. 14(c)). Irradiation line AL1 and irradiation line AL2 are lines which mutually completely overlap, for example, and are lines which do not overlap with some processing line PL2. After such a measurement is performed, the inspection apparatus 1 derives the difference between the displacement after processing and the displacement before processing for each processing line PL1. Thereby, with respect to each processing line PL1, the displacement (uneven|corrugated shape of the back surface 21b) by the influence of laser processing is derived. The inspection apparatus 1 estimates the processing state (crack state) of each processing line PL1 based on the displacement (the uneven shape of the back surface 21b) with respect to each processing line PL1, and, according to the estimation result, Based on it, suitability of the processing conditions set with respect to each processing line PL1 (test|inspection pass or not) is judged. Moreover, in the example shown in FIG. 14, since only the displacement along irradiation line AL1, AL2 of 1st direction is measured, only the processing state of some processing line PL1 is estimated, but irradiation of 2nd direction By measuring the displacement before and after the processing of the line, the processing state of the plurality of processing lines PL2 can also be estimated.

Fig. 15 is a flowchart of the inspection step (inspection method) of Fig. 14 . Steps S201 and S202 shown in FIG. 15 are the same as steps S1 and S2 of FIG. 10 described above. Following step S202, in the inspection apparatus 1, as shown in FIG. 14(a), while irradiating the back surface 21b with the laser beam LA for AF, the laser beam for AF on the back surface 21b ( LA) is detected, and the pre-processing AF waveform, which is displacement data of the back surface 21b in each area of the irradiation line AL1 along the first direction, is acquired (step S203). Next, as shown in FIG. 14B , laser beams L (CH1) are irradiated to the wafer 20 for a plurality of lines along a direction crossing the first direction (second direction), and a plurality of While the processing line PL1 is formed, the laser beam L (CH2) is irradiated to the wafer 20 for several lines along the 1st direction, and the several processing line PL2 is formed (step S204). . Next, as shown in FIG.14(c), while the laser beam LA for AF is irradiated to the back surface 21b, the reflected light of the laser beam LA for AF in the back surface 21b is detected, and the 1st A post-processing AF waveform that is displacement data of the back surface 21b in each area of the irradiation line AL2 along the direction is acquired (step S205). Subsequent steps S206 to S208 are the same as steps S8 to S10 of FIG. 10 described above.

16 : is a figure which shows the inspection process which concerns on another modified example. In the inspection method shown in FIG. 16 , when a plurality of processing lines PL1 and PL2 opposing each other are formed, displacement is derived for each of the plurality of processing lines PL1 and PL2 opposed to each other, and the processing state ( state of the crack) is estimated. In this inspection method, first, the displacement before laser processing is measured along the irradiation line AL11 in the first direction, and the displacement before laser processing is measured along the irradiation line AL21 in the second direction intersecting the first direction. measured (FIG. 16(a)). Next, a plurality of processing lines PL1 are formed in the second direction by laser processing CH1 (see FIG. 16B ). Subsequently, a plurality of processing lines PL2 are formed in the first direction by laser processing CH2 (simultaneous with the formation of processing line PL2), and displacement after laser processing along the irradiation line AL12 in the first direction is measured (FIG. 16(c)). Finally, the displacement after laser processing is measured along the irradiation line AL22 in the second direction (refer to FIG. 16(d) ). The irradiation line AL11 and the irradiation line AL12 are lines that completely overlap each other, for example, and the irradiation line AL21 and the irradiation line AL22 are lines that completely overlap each other, for example. Moreover, irradiation line AL11 and irradiation line AL12 overlap with any one of several processing line PL2, and irradiation line AL21 and irradiation line AL22 are any one of several processing line PL1. not overlapping After such measurement is performed, the inspection apparatus 1 derives the difference between the displacement after processing and the displacement before processing for each processing line PL1 and PL2. Thereby, with respect to each processing line PL1, PL2, the displacement (uneven|corrugated shape of the back surface 21b) by the influence of laser processing is derived. The inspection apparatus 1 estimates the processing state (crack state) of each processing line PL1, PL2 based on the displacement (the uneven shape of the back surface 21b) with respect to each processing line PL1, PL2, , based on the estimation result, it is determined whether the processing conditions set for each of the processing lines PL1 and PL2 are appropriate (whether the inspection has been passed or not).

When the processing described above is performed, the control unit 8 irradiates the back surface 21b with the laser beam LA for AF along the irradiation line AL11 in the first direction, and the AF on the back surface 21b The AF unit 71 is controlled so that the pre-processing displacement in each area along the irradiation line AL11 is measured by detecting the reflected light of the laser light LA, and irradiation in the second direction intersecting the first direction The laser beam LA for AF is irradiated to the back surface 21b along the line AL21, and the reflected light of the laser beam LA for AF on the back surface 21b is detected. The AF unit 71 is controlled so that the displacement before processing in each area is measured, and the laser beam L (CH1) is irradiated to the wafer 20 for a plurality of lines along the second direction, and a plurality of processing lines The light source 31 is controlled so that the PL1 is formed, and the laser beam CH2 is irradiated to the wafer 20 for a plurality of lines along the first direction to form a plurality of processing lines PL2. A laser beam LA for AF is irradiated to the back surface 21b along the irradiation line AL12 in the first direction to control 31 and to span the plurality of processing lines PL1 along the second direction, The AF unit 71 is controlled so that the post-processing displacement in each area along the irradiation line AL12 in the first direction is measured by detecting the reflected light of the laser beam LA for AF on the back surface 21b. The laser beam LA for AF is irradiated to the back surface 21b along the irradiation line AL22 of the 2nd direction so that it may cross the some processing line PL2 along the 1st direction, and the back surface The AF unit 71 is controlled so that the post-processing displacement in each area along the irradiation line AL22 in the second direction is measured by detecting the reflected light of the laser light LA for AF in 21b, For each region corresponding to each other along the first direction, a difference between the displacement after machining and the displacement before machining is derived, and based on the difference, the estimation of the machining state for each region is performed. information is derived, and for each region corresponding to each other along the second direction, the difference between the displacement after machining and the displacement before machining is derived, and based on the difference, information about the estimation of the machining state for each region is derived. .

According to this configuration, when a plurality of processing lines PL1 and PL2 are formed in each of the mutually intersecting directions (when the processing lines are formed in a grid shape), information regarding the estimation of the processing state is appropriately derived. That is, the displacement after processing and the displacement before processing are measured for each region along the direction (the second direction) crossing the plurality of processing lines PL2 formed along the first direction, and the displacement after processing and displacement before processing for each region When the difference of is derived, the processing state of each of the plurality of processing lines PL2 formed along the first direction can be appropriately estimated. In addition, the displacement after machining and the displacement before machining are measured for each region along the direction (first direction) crossing the plurality of machining lines PL1 formed along the second direction, and the displacement after machining and the displacement before machining for each region When the difference of is derived, the processing state of each of the plurality of processing lines PL1 formed along the second direction can be appropriately estimated. In addition, the formation of the plurality of processing lines PL2 along the first direction and the measurement of the displacement after processing in each region along the first direction (over the plurality of processing lines along the second direction) are performed in the same direction. Since these processes can be executed simultaneously (FIG. 16(c)), the processing efficiency can be greatly improved by executing these processes together (simultaneously).

In the above processing, the control unit 8 includes an irradiation line AL12 of the laser beam LA for AF irradiated along a first direction and the plurality of processing lines along the first direction ( Control the AF unit 71 and the light source 31 so that any of PL2) overlaps, and the irradiation line AL22 of the laser beam LA for AF irradiated along the second direction for measurement of the displacement after processing; The AF unit 71 and the light source 31 may be controlled so that the plurality of processing lines PL1 along the second direction do not overlap. Now, in order to measure the displacement after machining with high precision, it is desired to exclude the influence of a machining line having a different machining direction from the machining line for which the post machining displacement is to be measured. That is, in the case of measuring the displacement after machining with respect to a plurality of machining lines along a certain direction, it is desired to exclude the influence of the machining lines along a direction different from the one direction. In this case, the irradiation line of the laser beam LA for AF irradiated along a direction different from the one direction so as to span a plurality of processing lines along the certain direction does not overlap the processing line along the other direction from the one direction. will be needed In this point, when the irradiation line AL22 of the laser beam LA for AF along the 2nd direction and the some processing line PL1 along the 2nd direction do not overlap, the some processing line along a 1st direction Displacement after machining for (PL2) can be measured with high precision. Here, as described above, in this process, after the processing line PL1 along the second direction is formed, the formation of the processing line PL2 along the first direction and the measurement of the displacement after processing along the first direction are performed. are executed together (FIGS. 16(b) and 16(c)). As described above, in the case where the formation of the processing line and the measurement of the displacement after processing are performed together along the same direction, the displacement measurement is performed even if the processing line and the irradiation line of the AF laser beam LA for displacement measurement overlap. A new formation is performed by performing irradiation of the laser beam LA for AF for the purpose prior to the formation of the processing line (while executing it, control so that the irradiation of the laser beam LA for AF precedes the formation of the processing line) It is possible to measure the displacement after processing of the processing line that has been formed without being affected by the processing line. That is, in this process, since the formation of the processing line PL2 along the first direction and the measurement of the displacement after processing along the irradiation line AL12 in the first direction are performed together, the processing line PL2 along the first direction ( Even if any one of PL2) and the irradiation line AL12 of the laser beam LA for AF irradiated along the 1st direction overlap, it is not influenced by formation of the processing line PL2 along the 1st direction, 2nd direction It is possible to estimate with high precision the displacement after machining with respect to the plurality of processing lines PL1 along the . And by overlapping any one of the processing lines PL2 along the 1st direction and the irradiation line AL12 of the laser beam LA for AF irradiated along the 1st direction, the formation and AF of the processing line PL2 The processing related to the irradiation of the laser beam LA for use can be simplified (facilitated).

Fig. 17 is a flowchart of the inspection step (inspection method) of Fig. 16 . Steps S301 and S302 shown in FIG. 17 are the same as steps S1 and S2 of FIG. 10 described above. Following step S302, in the inspection apparatus 1, as shown in FIG. 16(a), while the laser beam LA for AF is irradiated to the back surface 21b, the laser beam for AF in the back surface 21b ( When the reflected light of LA) is detected, a pre-processing AF waveform that is displacement data of the back surface 21b in each area of the irradiation line AL11 along the first direction is acquired, and the irradiation line AL21 along the second direction is obtained. ), the pre-processing AF waveform which is the displacement data of the back surface 21b in each area is acquired (step S303). Subsequently, as shown in FIG. 16B , laser beams L (CH1) are irradiated to the wafer 20 for a plurality of lines along the second direction, thereby forming a plurality of processing lines PL1 ( step S304). Subsequently, as shown in FIG. 16(c) , laser beams L (CH2) are irradiated to the wafer 20 for a plurality of lines along the first direction, thereby forming a plurality of processing lines PL2. , a post-processing AF waveform that is displacement data of the back surface 21b in each area of the irradiation line AL12 along the first direction is acquired (step S305). Next, as shown in FIG. 16(d), the AF waveform after processing which is the displacement data of the back surface 21b in each area|region of the irradiation line AL22 along the 2nd direction is acquired (step S306). Subsequent steps S307 to S309 are the same as steps S8 to S10 of FIG. 10 described above.

In addition, in the said embodiment, although the processing state of each processing line is estimated by irradiating the laser beam LA for AF so that it may span multiple processing lines, and detecting the reflected light, it is not limited to this. , You may estimate the processing state of a processing line by irradiating the laser beam LA for AF along a processing line, and detecting the reflected light. 18 : is a figure which shows the inspection process of the form of irradiating the laser beam LA for AF along a processing line, and estimating the processing state of a processing line. In the inspection process shown in FIG. 18, first, the control part 8 is irradiated with the laser beam LA for AF to the back surface 21b along the irradiation line AL1 of a 1st direction, and the back surface 21b The AF unit 71 is controlled so that the pre-processing displacement in each area along the irradiation line AL1 in the first direction is measured by detecting the reflected light of the AF laser light LA (FIG. 18(a)) )). In this case, the control part 8 may make all the processing schedule lines into irradiation line AL1, and may make only some (for example, one) processing schedule lines into irradiation line AL1. Next, the control unit 8 controls the light source 31 so that the laser beam is irradiated to the wafer 20 along the first direction to form a plurality of processing lines PL ( FIG. 18B ). The control unit 8 may control the AF unit 71 and the light source 31 so that the pre-processing displacement is measured and the plurality of processing lines PL are formed simultaneously. Next, the control unit 8 irradiates the laser beam LA for AF to the back surface 21b along the irradiation line AL2 overlapping the processing line PL, and the laser beam for AF on the back surface 21b ( The light source 31 is controlled so that the post-processing displacement in each area along the irradiation line AL2 overlapping with the processing line PL is measured by detecting the reflected light of LA) (FIG. 18(c)). The irradiation line AL1 and the irradiation line AL2 are, for example, overlapping lines. The control part 8 may use all the processing lines PL as the irradiation line AL2, and may make only one part (for example, one) processing line PL into the irradiation line AL2. Then, the control unit 8 derives a difference between the displacement after machining and the displacement before machining for each region corresponding to each other along the irradiation line AL1 and the irradiation line AL2, and based on this difference, Estimate the machining state (the state of cracks).

In this way, the irradiation direction of the laser beam LA for AF for measuring the displacement before processing, the formation direction of the processing line PL, and the irradiation direction of the laser beam LA for AF for measuring the displacement after processing are common. As a result, processing for rotating the wafer 20 as described in the embodiment becomes unnecessary, and processing efficiency can be improved. Moreover, in this form to which the laser beam LA for AF is irradiated along the processing line PL, unlike the case where the laser beam LA for AF is irradiated so that several processing lines PL may be irradiated, a plurality of processing Although the processing state cannot be estimated based on the relative information of the displacement amount compared with the lines PL, the processing state of the processing line PL can be estimated based on the absolute displacement amount after processing.

In the case of performing the inspection process shown in FIG. 18 described above, the inspection apparatus 1 provides a configuration for irradiating the laser beam LA for AF with an axis separate from the irradiation of the laser beam L ( By providing both side separate axis AF), the AF laser light LA for measuring the displacement before processing, the formation of the processing line PL, and the AF laser for measuring the displacement after processing The light LA may be irradiated simultaneously. Fig. 19 is a diagram schematically showing a part of the configuration of an inspection apparatus having both side-axis separate-axis AF units. In the configuration shown in FIG. 19 , AF units 571 and 671 for irradiating the laser beam LA for AF on a separate axis from the laser beam L irradiated to the wafer 20 via the condensing lens 33 are provided. . The AF unit 571 irradiates the laser beam LA for AF to the front side rather than the laser beam L in the laser processing advancing direction. The AF unit 571 irradiates the laser beam LA for AF to the rear side rather than the laser beam L in the laser processing advancing direction. In the case where the laser processing advance direction is reversed on the outgoing route and the return route, the roles of the AF units 571 and 671 are reversed. According to this configuration of the separate axis AF on both sides, along with the step of irradiating the laser beam LA for AF in the laser processing direction, the displacement before processing by irradiating the laser beam LA for AF from the AF unit 571 Measurement and post-processing displacement measurement by irradiating the AF laser beam LA from the AF unit 671 can be performed. Thereby, when performing the inspection process shown in FIG. 18 WHEREIN: It is possible to estimate a processing state more efficiently.

Fig. 20 is a diagram showing an example of a display screen in the case of estimating the processing state of the processing line PL by the configuration of the two separate axes AF described above. Fig. 20(b) shows the displacement before machining (AF waveform before machining) measured by the AF unit 571, and Fig. 20(c) shows the displacement after machining (machining) measured by the AF unit 671. AF waveform) is shown. By deriving the difference between the displacement before machining (FIG. 20(b)) and the displacement after machining (FIG. 20(c)), the displacement amount that is the difference between the displacement data shown in FIG. 20(a) is displayed. In Fig. 20(a), the displacement amount when the crack state is HC is shown.

As described above, in the case of estimating the processing state of the processing line PL by the configuration of the separate axis AF on both sides, since only the displacement in one processing line PL is measured, the plurality of processing lines PL Although it is not possible to estimate the processing state based on the relative information of the displacement amount compared with each other, as shown in FIG. 21 , the absolute value and positive value of the displacement amount, which is the difference between displacement data, differ depending on the state of the crack, so this information Based on this, the processing state of the processing line PL can be estimated appropriately. For example, in the example shown in Fig. 21(a), the average value (value indicated by the solid line) of the absolute values of the displacement is relatively large, and based on the positive value, it can be estimated that the state of the crack is HC. Further, for example, in the example shown in Fig. 21 (b), the state of the crack can be estimated to be ST or FC based on the fact that the average value (the value indicated by the solid line) of the absolute values of the displacement amounts is relatively small, and further By considering the imaging result of the imaging unit, it can be estimated that the state of the crack is ST.

The configuration for simultaneously measuring the displacement before processing, forming the processing line PL, and measuring the displacement after processing is not limited to the configuration of the separate axes AF on both sides of FIG. 19 . For example, as shown in FIG. 22(a), the inspection apparatus 1 replaces the AF unit 671 (FIG. 19) which irradiates the laser beam LA for AF behind the laser beam L. In addition, you may provide the general ranging sensor 871 for the unevenness|corrugation measurement of the back surface 21b as a structure related to the measurement of the displacement after processing. Moreover, as shown in FIG.22(b), the inspection apparatus 1 replaces with the AF unit 571 (FIG. 19) which irradiates the laser beam LA for AF on the front side rather than the laser beam L, and the back surface The general ranging sensor 771 for measuring the unevenness of (21b) may be provided as a configuration related to the measurement of the displacement after processing. In the configuration of Fig. 22 (b), since the configuration of the separate axis AF becomes unnecessary, the laser beam L and the AF laser beam ( LA) can be irradiated (coaxial AF). In addition, as the range sensors 771 and 871, for example, a two-dimensional laser displacement sensor can be used.

Further, the inspection device 1 may 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 with respect to the center of the pupil plane of the condensing lens 33, the formation state of the modified region can be controlled very appropriately. The automatic setting of the LCOS pattern offset is to automatically derive and set the desired offset amount of the center of the modulation pattern. Now, for example, it is assumed that the offset amount (pattern offset value) is changed by 1.0 for each of the five processing lines PL. That is, as shown in Fig. 23, on the basis of the third line (center), which is considered to be an appropriate offset amount, the offset amount of the first line is -2.0, the offset amount of the second line is -1.0, and the fourth line is the center. Assume that the offset amount of the 1st line is set to +1.0 at the center, and the offset amount at the 5th line is set at the center +2.0. Then, as a result of the inspection apparatus 1 estimating the crack state of each processing line PL under the inspection conditions of two patterns, as shown in FIG. 23 , in only the third line, the crack state is BHC. said to have been In this case, the test|inspection apparatus 1 estimates the offset amount of the 3rd line which became BHC in any test|inspection condition as a preferable offset amount. The test|inspection apparatus 1 sets the offset amount of the said 3rd line to the offset amount in test|inspection because the offset amount assumed to be an appropriate offset amount before test|inspection was actually appropriate. On the other hand, the inspection apparatus 1 sets the offset amount of the said other line as an optimal value, when it becomes BHC only in another line.

Moreover, in embodiment, although the test|inspection apparatus 1 demonstrated that it judged the suitability of predetermined processing conditions, the inspection apparatus 1 derives a processing condition newly by estimating the state of a crack (condition) making a bet) is fine. Moreover, the thing used for the automatic determination of the state of the crack in not only a stealth dicing apparatus but a slicing apparatus and a trimming apparatus may be sufficient as the inspection apparatus 1.

Claims (20)

A laser irradiation unit for irradiating a laser beam to the wafer;
a measuring unit for measuring a displacement of a surface to be measured which is an incident surface of the laser beam or a surface opposite to the incident surface in the wafer;
Controlling the laser irradiator so that one or a plurality of modified regions are formed inside the wafer by irradiating the laser beam to the wafer, and the post-processing displacement that is the displacement of the measurement target surface after the laser beam is irradiated An inspection apparatus comprising: a control unit configured to control the measuring unit to measure , and deriving information on estimation of a processing state of the wafer based on the post-processing displacement measured by the measuring unit. The method according to claim 1,
Further comprising a display unit,
The control unit controls the display unit to display the derived information on the estimation of the processing state of the wafer. The method according to claim 1 or 2,
The measurement unit includes a measurement unit configured to measure a displacement on the measurement object surface by irradiating measurement light onto the measurement object surface and receiving and detecting reflected light of the measurement light on the measurement object surface . 4. The method according to claim 3,
and the measurement unit is an autofocus unit that measures a displacement on the measurement target surface in order to adjust a converging point of the laser light irradiated to the wafer by the laser irradiation unit. 5. The method according to claim 3 or 4,
The control unit derives a difference between the post-processing displacement and the reference displacement measured by the measuring unit for each area of the measurement target surface, and based on the difference, information on the estimation of the processing state of the wafer deriving inspection device. 6. The method of claim 5,
The control unit is
controlling the measuring unit so that the pre-processing displacement, which is the displacement of the measurement target surface before the laser light is irradiated, is additionally measured,
An inspection apparatus for deriving information on estimation of a processing state of the wafer by using the displacement before processing as the reference displacement. 7. The method of claim 6,
The said control part is an inspection apparatus which estimates the state of the crack extending from the said modified area|region formed in the inside of the said wafer by the said laser beam irradiation based on the said difference. 8. The method of claim 7,
The control unit is
For a region in which the absolute value of the difference is larger than the first threshold value, the crack has reached the incident surface and has not reached the opposite surface, or has not reached the incident surface In addition, it is assumed that the state has reached the surface on the opposite side,
In the region where the absolute value of the difference is equal to or less than the first threshold, the crack has not reached both the incident surface and the opposite surface, or has reached both the incident surface and the opposite surface. A test device that assumes a condition. 9. The method according to claim 7 or 8,
The control unit is
In a region where the difference in the absolute value of the difference from the surrounding region is larger than the second threshold value, the crack has reached the incident surface and has not reached the opposite surface, or It is assumed that the surface has not been reached and has reached the surface on the opposite side,
In the region where the difference in the absolute value of the difference is equal to or less than the second threshold, the crack has not reached both the incident surface and the opposite surface, or has reached both the incident surface and the opposite surface. A test device that presumes to exist. 10. The method according to any one of claims 7 to 9,
Further comprising an imaging unit that outputs light having transparency to the wafer and detects light propagating through the wafer,
The control unit further considers a signal output from the imaging unit that has detected the light, and estimates the state of the crack. 11. The method according to any one of claims 6 to 10,
The control unit is
The measurement light is irradiated to the measurement target surface along the first direction, and the displacement before processing in each region along the first direction is measured by detecting the reflected light of the measurement light on the measurement target surface, control the measurement unit,
controlling the laser irradiation unit so that a plurality of lines are irradiated with laser light to the wafer to form a plurality of processing lines along a second direction intersecting the first direction,
Each region along the first direction by irradiating the measurement light to the measurement target surface along the first direction so as to span the plurality of processing lines, and detecting the reflected light of the measurement light on the measurement target surface to control the measuring unit to measure the displacement after processing in
An inspection apparatus for deriving a difference between the displacement after machining and the displacement before machining for each region corresponding to each other, and deriving information about the estimation of the machining state for each region based on the difference. 11. The method according to any one of claims 6 to 10,
The control unit is
The measurement light is irradiated to the measurement target surface along the first direction, and the displacement before processing in each region along the first direction is measured by detecting the reflected light of the measurement light on the measurement target surface, control the measurement unit,
The measurement light is irradiated to the measurement target surface along a second direction intersecting the first direction, and reflected light of the measurement light on the measurement target surface is detected, so that the measurement light is detected in each region along the second direction. Control the measuring unit so that the displacement is measured before machining,
controlling the laser irradiation unit so that a plurality of lines are irradiated to the wafer to form a plurality of processing lines along the second direction;
In the first direction, the laser beam is irradiated to the wafer for a plurality of lines to form a plurality of processing lines, and controlling the laser irradiation unit so as to span the plurality of processing lines along the second direction. The measurement light is irradiated to the measurement target surface along the first direction, and the post-processing displacement in each region along the first direction is measured by detecting the reflected light of the measurement light on the measurement target surface, Controlling the measurement unit is performed together,
The measurement light is irradiated to the measurement target surface along the second direction so as to span the plurality of processing lines along the first direction, and reflected light of the measurement light on the measurement target surface is detected, whereby the second controlling the measuring unit so that the displacement after machining in each area along the direction is measured,
For each region corresponding to each other along the first direction, a difference between the displacement after machining and the displacement before machining is derived, and based on the difference, information about the estimation of the machining state for each region is derived, and the An inspection apparatus for deriving a difference between the displacement after machining and the displacement before machining for each region corresponding to each other along the second direction, and deriving information about the estimation of the machining state for each region based on the difference. 13. The method of claim 12,
The control unit is
Control the measuring unit and the laser irradiation unit so that any of the plurality of processing lines along the first direction and the irradiation line of the measurement light irradiated along the first direction for measuring the displacement after the processing overlap,
Inspection apparatus for controlling the measuring unit and the laser irradiation unit so that the irradiation line of the measurement light irradiated along the second direction and the plurality of processing lines along the second direction do not overlap for measuring the displacement after the processing. 11. The method according to any one of claims 6 to 10,
The control unit is
The measurement light is irradiated to the measurement target surface along the first direction, and the displacement before processing in each region along the first direction is measured by detecting the reflected light of the measurement light on the measurement target surface, control the measurement unit,
Controls the laser irradiation unit so that the laser beam is irradiated to the wafer along the first direction to form a processing line,
The measurement light is irradiated to the measurement target surface along the processing line, and the displacement after processing in each region along the processing line is measured by detecting the reflected light of the measurement light on the measurement target surface, control the measurement unit,
An inspection apparatus for deriving a difference between the displacement after machining and the displacement before machining for each region corresponding to each other along the machining line, and deriving information about the estimation of the machining state for each region based on the difference. 15. The method according to any one of claims 1 to 14,
The control unit performs processing control based on a predetermined processing condition, determines whether processing has passed based on information about the estimation of the processing state of the wafer, and, if the determination result is not, determines the processing condition calibrating inspection device. A laser processing process of irradiating laser light to the wafer so that one or a plurality of modified regions are formed inside the wafer;
a post-processing measurement step of measuring a post-processing displacement that is a displacement of the measurement target surface of the wafer after the laser processing;
and an estimation step of estimating a processing state of the wafer based on the displacement after processing. 17. The method of claim 16,
Before the laser processing process, further comprising a pre-processing measuring process of measuring a pre-processing displacement that is a displacement of the measurement target surface,
In the estimation step, a difference between the displacement after processing and the displacement before processing is derived for each region of the measurement target surface, and the processing state of the wafer is estimated based on the difference. 18. The method of claim 17,
In the pre-processing measurement step, each region along the first direction by irradiating measurement light to the measurement target surface along the first direction and receiving and detecting reflected light of the measurement light on the measurement target surface Measure the displacement before machining in
In the laser processing step, laser light is irradiated to the wafer for a plurality of lines along a second direction intersecting the first direction to form a plurality of processing lines,
In the post-processing measurement step, the measurement light is irradiated to the measurement target surface along the first direction so as to span the plurality of processing lines, and the reflected light of the measurement light on the measurement target surface is received and detected. an inspection method for measuring the displacement after machining in each region along the first direction. 18. The method of claim 17,
In the measurement step before processing, in each region along the first direction by irradiating measurement light to the measurement target surface along a first direction, and receiving and detecting reflected light of the measurement light on the measurement target surface In the first pre-processing process of measuring the displacement before processing of and a second pre-processing process of measuring the pre-processing displacement in each region along the second direction by detecting
The laser processing step includes a plurality of lines along the second direction, a first processing step of irradiating laser light to the wafer to form a plurality of processing lines, and a plurality of lines along the first direction, the A second processing step of forming a plurality of processing lines by irradiating the wafer with laser light,
In the post-processing measurement step, the measurement light is irradiated to the measurement target surface along the first direction so as to span the plurality of processing lines along the second direction, and the reflected light of the measurement light on the measurement target surface is measured A first post-processing process of measuring the post-processing displacement in each region along the first direction by receiving and detecting light, and the second direction so as to span the plurality of processing lines along the first direction Therefore, after the second processing of measuring the displacement before processing in each region along the second direction by irradiating the measurement light to the measurement target surface, receiving and detecting the reflected light of the measurement light on the measurement target surface process, including
The first post-processing step is an inspection method performed together with the second machining step. 18. The method of claim 17,
In the pre-processing measurement step, each region along the first direction by irradiating measurement light to the measurement target surface along the first direction and receiving and detecting reflected light of the measurement light on the measurement target surface Measure the displacement before machining in
In the laser processing process, a processing line is formed by irradiating a laser beam to the wafer along the first direction,
In the post-processing measurement step, measurement light is irradiated to the measurement target surface along the processing line, and the reflected light of the measurement light on the measurement target surface is received and detected, so that in each region along the processing line Inspection method to measure the displacement after the above machining of.

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