Shape measurement system, processing apparatus, shape measurement method, processing method, and chip manufacturing method

Abstract

This technology shortens the measurement time when measuring the three-dimensional shape of an object using interferometric light. [Solution] A shape measurement system for measuring the three-dimensional shape of an object, comprising a measuring optical system, a moving unit for moving the measuring optical system and the object relative to each other, and a controller for controlling the moving unit, wherein the measuring optical system comprises a light source that emits low-coherence light, a branching unit that splits the light from the light source into reference light that irradiates a reference surface which is a reflective surface and measurement light that irradiates the object, and a photoelectric conversion device having a photoelectric conversion element that receives interference light resulting from the interference of the reference light reflected from the reference surface and the measurement light reflected from the object, and the photoelectric conversion device has an event camera that outputs event data to the controller that can identify the position of the photoelectric conversion element where there has been a change in brightness.

Description

Technical Field

[0001] The present invention relates to a shape measurement system for measuring a three-dimensional shape of an object, a processing apparatus for processing a workpiece, a shape measurement method for measuring a three-dimensional shape of an object, a processing method for processing a workpiece, and a chip manufacturing method for manufacturing chips from a workpiece.

Background Art

[0002] In a wafer having an insulating film (that is, a Low-k film) formed of a Low-k material (that is, a material having a lower dielectric constant than silicon dioxide) provided on the surface, the wafer may be divided into a plurality of chips along a plurality of planned division lines set on the surface of the wafer.

[0003] At the time of division, a method has been proposed in which first, a laser beam is irradiated along each planned division line to form thin processed grooves (that is, grooves) from which the Low-k film has been removed by ablation processing, and then a cutting blade is cut into the processed grooves to divide the wafer into a plurality of chips (see, for example, Patent Document 1).

[0004] A laser processing apparatus that removes a Low-k film to form grooves may be equipped with a white light interference microscope in order to determine the processing quality of ablation processing by measuring the three-dimensional shape of the processed grooves (see, for example, Patent Document 2).

[0005] When measuring the three-dimensional shape of a processed groove formed on one surface (that is, the surface to be measured) of a workpiece such as a wafer with a white light interference microscope, the white light interference microscope is moved along the thickness direction (that is, the height direction) of the workpiece, and an image of a predetermined range is captured using interference light at each height position.

[0006] After measuring the three-dimensional shape of a predetermined area of ​​the surface to be measured in this manner, the workpiece and the white light interference microscope are slightly moved parallel to each other along the surface to be measured. Then, similarly, the white light interference microscope is moved along the height direction, and a predetermined area is imaged using interference light at each height position, thereby measuring the three-dimensional shape of this predetermined area (i.e., the imaged area).

[0007] In this way, by repeatedly moving the white light interference microscope along the height direction of the workpiece and moving it parallel to the surface of the workpiece and the white light interference microscope being measured, the entire machined groove can be imaged and the overall three-dimensional shape of the machined groove can be measured.

[0008] However, since a predetermined range is imaged at each height position, the movement speed of the white light interference microscope along the height direction is limited by the frame rate of the image sensor in the white light interference microscope (i.e., the number of still images that can be captured by the image sensor per unit time). Therefore, it is difficult to simply increase the movement speed in the height direction.

[0009] On the other hand, a single workpiece may have numerous machining grooves, and it may be necessary to measure multiple workpieces, each with numerous machining grooves, one after the other. Therefore, there is a need to improve the efficiency of measurement when measuring the three-dimensional shape of an object using interference light. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2005-64231 [Patent Document 2] Japanese Patent Publication No. 2015-85397 [Overview of the Initiative] [Problems that the invention aims to solve]

[0011] This invention has been made in view of the aforementioned problems, and aims to shorten the measurement time when measuring the three-dimensional shape of an object using interference light. [Means for solving the problem]

[0012] According to one aspect of the present invention, a shape measuring system for measuring the three-dimensional shape of an object is provided, comprising: a measuring optical system; a moving unit for moving the measuring optical system and the object relative to each other; and a controller for controlling the moving unit, wherein the measuring optical system comprises: a light source emitting low-coherence light; a branching unit for splitting the light from the light source into reference light for irradiating a reference surface which is a reflective surface and measurement light for irradiating the object; and a photoelectric conversion device having a photoelectric conversion element that receives interference light resulting from the interference of the reference light reflected from the reference surface and the measurement light reflected from the object, wherein the photoelectric conversion device has an event camera that outputs event data to the controller that can identify the position of the photoelectric conversion element where a change in brightness has occurred.

[0013] Preferably, the controller controls the moving unit to change the relative position of the measuring optical system and the object, causing the photoelectric converter to receive the interference light of the measurement light reflected from the area to be measured on the object and the reference light, and to measure the shape of the area to be measured on the object based on the occurrence of an event in the event camera within that area to be measured.

[0014] According to another aspect of the present invention, a processing apparatus for processing a workpiece is provided, comprising: a holding unit for holding the workpiece; a processing unit for processing the workpiece; a measuring optical system; a moving unit for moving the measuring optical system and the holding unit relative to each other; and a controller for controlling the moving unit, wherein the measuring optical system comprises: a light source emitting low-coherence light; a branching unit for splitting the light from the light source into reference light for irradiating a reference surface which is a reflective surface and measuring light for irradiating the workpiece; and a photoelectric conversion device having a photoelectric conversion element that receives interference light resulting from the interference of the reference light reflected from the reference surface and the measuring light reflected from the workpiece, wherein the photoelectric conversion device has an event camera that outputs event data to the controller that can identify the position of the photoelectric conversion element where a change in brightness has occurred.

[0015] According to yet another aspect of the present invention, a shape measurement method for measuring the three-dimensional shape of an object is provided, comprising: irradiating the object with low-coherence light that has been split into a reference light irradiated onto a reference surface and a measurement light irradiated onto the object; receiving interference light obtained by the interference of the reference light reflected from the reference surface and the measurement light reflected from the object using a photoelectric converter; and changing the relative position of the photoelectric converter and the object along a first direction in which the photoelectric converter and the object move closer to or further away from each other, wherein the photoelectric converter includes a photoelectric conversion element that receives the interference light obtained by the interference of the reference light reflected from the reference surface and the measurement light reflected from the object, and has an event camera that outputs event data capable of identifying the position of the photoelectric conversion element where there has been a change in brightness, and a shape measurement method is provided for measuring the three-dimensional shape of the object based on the event data obtained by receiving the interference light with the photoelectric converter and changing the relative position of the photoelectric converter and the object.

[0016] According to yet another aspect of the present invention, a processing method for processing a workpiece, comprising: processing the workpiece with a processing unit to form a processing mark; after the formation of the processing mark, irradiating the processing mark with low-coherence light, which is split into a reference light irradiated onto a reference surface and a measurement light irradiated onto the processing mark, and receiving the interference light obtained by the interference of the reference light reflected from the reference surface and the measurement light reflected from the processing mark with a photoelectric converter; and after the formation of the processing mark, along a first direction in which the photoelectric converter and the processing mark move closer to and further apart, A processing method is provided for measuring the three-dimensional shape of a processing mark based on event data obtained by receiving the interference light with the photoelectric conversion device and changing the relative position between the photoelectric conversion device and the processing mark. The photoelectric conversion device includes a photoelectric conversion element that receives interference light resulting from the interference of the reference light reflected from the reference surface and the measurement light reflected from the processing mark, and has an event camera that outputs event data capable of identifying the position of the photoelectric conversion element where there has been a change in brightness.

[0017] According to yet another aspect of the present invention, a method for manufacturing a chip from a workpiece comprises: processing the workpiece with a processing unit to form a processing groove having a depth that does not completely cut the workpiece; measuring the three-dimensional shape of the processing groove after its formation; and, after measuring the three-dimensional shape of the processing groove, cutting the workpiece so as to pass through the bottom of the processing groove to divide it into chips, wherein the three-dimensional shape of the processing groove is measured by irradiating the processing groove with low-coherence light that has been split into a reference light irradiated onto a reference surface and a measuring light irradiated onto the processing groove, and the interference light resulting from the interference of the reference light reflected from the reference surface and the measuring light reflected from the processing groove is converted by a photoelectric converter. A chip manufacturing method is provided, comprising receiving light and changing the relative position of the photoelectric converter and the workpiece along a first direction in which the photoelectric converter and the workpiece move closer to and further apart, wherein the photoelectric converter includes a photoelectric converter element that receives interference light resulting from the interference of the reference light reflected from the reference surface and the measurement light reflected from the workpiece, and has an event camera that outputs event data capable of identifying the position of the photoelectric converter element where there has been a change in brightness, and for measuring the three-dimensional shape of the workpiece, the chip manufacturing method is provided, which measures the three-dimensional shape of the workpiece based on the event data obtained by receiving the interference light with the photoelectric converter and changing the relative position of the photoelectric converter and the workpiece.

[0018] According to yet another aspect of the present invention, a method for manufacturing a chip from a workpiece comprises: processing the workpiece with a processing unit to form a processing groove that completely cuts the workpiece and divides it into chips; and measuring the three-dimensional shape of the processing groove after its formation, wherein the three-dimensional shape of the processing groove is measured by irradiating the processing groove with low-coherence light that has been split into a reference light irradiated onto a reference surface and a measuring light irradiated onto the processing groove, and receiving the interference light resulting from the interference of the reference light reflected from the reference surface and the measuring light reflected from the processing groove with a photoelectric converter, and the photoelectric converter and the workpiece move in close proximity to each other. A chip manufacturing method is provided, which involves changing the relative position of the photoelectric converter and the processed groove along a first separating direction, wherein the photoelectric converter includes a photoelectric converter element that receives interference light resulting from the interference of the reference light reflected from the reference surface and the measurement light reflected from the processed groove, and has an event camera that outputs event data capable of identifying the position of the photoelectric converter element where there has been a change in brightness, and in measuring the three-dimensional shape of the processed groove, the chip is manufactured by measuring the three-dimensional shape of the processed groove based on the event data obtained by receiving the interference light with the photoelectric converter and changing the relative position of the photoelectric converter and the processed groove. [Effects of the Invention]

[0019] A measurement optical system in a shape measurement system according to one aspect of the present invention comprises a light source that emits low-coherence light, a branching unit that splits the light from the light source into reference light and measurement light, and a photoelectric conversion device having a photoelectric conversion element that receives interference light. The photoelectric conversion device also includes an event camera that outputs event data capable of identifying the location of the photoelectric conversion element where a change in brightness has occurred to a controller.

[0020] Firstly, by receiving the interfering light with an event camera, the amount of image information output to the controller can be significantly reduced compared to when the interfering light is received with a general image sensor different from the event camera, thus allowing for a sufficiently high frame rate.

[0021] Secondly, since the interference light of low-coherence light with a short coherence length is received by the event camera, when the optical path difference between the measurement light and the reference light is outside the range of the coherence length, almost no light and dark of the interference light is formed on the event camera. Therefore, no event indicating a luminance change occurs either.

[0022] In this way, the synergistic effect of using low-coherence light and an event camera allows the frame rate to be sufficiently increased, so the relative moving speed of the measurement optical system can be increased. Therefore, the measurement time when measuring a three-dimensional shape can be shortened.

[0023] A processing apparatus according to another aspect of the present invention also includes the above-described measurement optical system. Therefore, by the synergistic effect of using low-coherence light and an event camera, the frame rate can be sufficiently increased, and the measurement time when measuring a three-dimensional shape can be shortened.

[0024] In the shape measurement method, the processing method, and the chip manufacturing method according to still other aspects of the present invention, since the interference light of low-coherence light with a short coherence length is received by an event camera, the synergistic effect of using low-coherence light and the event camera allows the frame rate to be sufficiently increased, so the measurement time when measuring a three-dimensional shape can be shortened. Brief Description of the Drawings

[0025] [Figure 1] It is a schematic diagram of a processing apparatus. [Figure 2] FIG. 2(A) is a schematic diagram of a shape measurement system, and FIG. 2(B) is a schematic diagram of an event camera. [Figure 3] This is a simulation result showing the interference of low-coherence light. [Figure 4] It is a schematic diagram showing an example of irregularities along the X-axis direction on the surface of a workpiece. [Figure 5] It is a flowchart showing a processing method for a workpiece. [Figure 6] It is a perspective view of a workpiece. [Figure 7]Figure 7(A) shows the ablation process applied to a workpiece, and Figure 7(B) is a cross-sectional view of the workpiece including the processing marks. [Figure 8] Figure 8(A) shows the imaging of the first region of the measurement area, Figure 8(B) shows the imaging of the second region adjacent to the first region, and Figure 8(C) shows the imaging of the Nth region. [Figure 9] This is a flowchart showing an example of a device chip manufacturing method. [Figure 10] Figure 10(A) shows the modification region formation process, Figure 10(B) shows the back surface grinding process, and Figure 10(C) is a perspective view of the device chip. [Figure 11] This flowchart shows a modified example of a device chip manufacturing method. [Figure 12] This is a cross-sectional view of a workpiece cut by ablation. [Modes for carrying out the invention]

[0026] (First Embodiment) An embodiment according to one aspect of the present invention will be described with reference to the attached drawings. Figure 1 is a schematic diagram of a processing apparatus 2 for processing a workpiece (i.e., object) 11. In Figure 1, some of the components of the processing apparatus 2 are simply shown as functional blocks. The X axis, Y axis and Z axis shown in Figure 1 are orthogonal to each other (i.e., intersect).

[0027] In Figure 1, the positive direction of the X-axis is defined as the +X direction, and the negative direction of the X-axis is defined as the -X direction. The +X and -X directions are opposite directions. In this specification, the +X and -X directions are sometimes collectively referred to as the X-axis direction (or machining feed direction).

[0028] In Figure 1, the positive direction of the Y-axis is defined as the +Y direction, and the negative direction of the Y-axis is defined as the -Y direction. The +Y and -Y directions are opposite directions. In this specification, the +Y and -Y directions are sometimes collectively referred to as the Y-axis direction (or indexing feed direction).

[0029] Furthermore, in Figure 1, the positive direction of the Z-axis is defined as the +Z direction, and the negative direction of the Z-axis is defined as the -Z direction. The +Z and -Z directions are opposite to each other. For example, the -Z direction is the vertical direction (i.e., the direction of gravity). In this case, the -Z direction is downward, and the +Z direction is upward. In this specification, the +Z and -Z directions are sometimes collectively referred to as the Z-axis direction (or the first direction or height direction).

[0030] The processing apparatus 2 includes a disc-shaped chuck table (holding unit) 4 that holds the workpiece 11 by suction using negative pressure. The chuck table 4 has a disc-shaped frame made of a metal such as stainless steel. A disc-shaped recess with a diameter smaller than the outer diameter of the frame is formed in the radial center of the frame.

[0031] A disc-shaped porous plate (not shown) made of porous ceramics is placed in the recess of the frame, and the porous plate is fixed to the frame using an adhesive or the like. The upper surfaces of the frame and the porous plate are substantially flush and exposed facing upward.

[0032] A suction source (not shown), such as an ejector or vacuum pump, is connected to the frame, and the negative pressure from the suction source is transmitted to the upper surface of the porous plate via the frame. The upper surface of the frame and the upper surface of the porous plate form a holding surface 4a that holds the workpiece 11 by suction.

[0033] The workpiece 11 is held by suction on the holding surface 4a in the form of a workpiece unit 21 integrated with the frame 17 via a dicing tape 19, as shown in Figure 6, for example. However, for convenience, the dicing tape 19 and the frame 17 are omitted from the illustration in Figure 1 (and similarly in Figures 2(A), 7(A), and 8(A) to 8(C)).

[0034] By the way, instead of the chuck table 4, an electrostatic chuck that holds the workpiece 11 by electrostatic attraction may be used. Alternatively, the workpiece 11 may be fixed directly or indirectly to the holding surface by a holding unit having a pressing mechanism including a clamp that can be opened and closed by an actuator, instead of or in combination with negative pressure or electrostatic force.

[0035] In this embodiment, the holding surface 4a of the chuck table 4 is exposed upwards, but it may be reversed so that the holding surface 4a is exposed downwards. Similarly, when employing an electrostatic chuck, a pressing mechanism, etc., the holding surface may also be exposed downwards.

[0036] The chuck table 4 is supported by a moving mechanism 6. The moving mechanism 6 has a θ-table (not shown) that rotates the chuck table 4 around a rotation axis arranged along the Z-axis. Furthermore, the moving mechanism 6 has a first moving plate (not shown) that supports the chuck table 4 and the θ-table.

[0037] The first movable plate is slidably supported by a pair of X-axis guide rails (not shown), each of which has its longitudinal portion aligned along the X-axis. Between the pair of X-axis guide rails is a first screw shaft (not shown), whose longitudinal portion is aligned along the X-axis. A first nut portion (not shown) is provided on the lower surface of the first movable plate.

[0038] A first screw shaft, whose longitudinal portion is arranged along the X-axis, is rotatably connected to the first nut portion via a plurality of balls (not shown). A first drive source (not shown), such as a servo motor, is connected to one end of the first screw shaft. When the first drive source is operated, the first movable plate moves along the X-axis.

[0039] The first moving plate, a pair of X-axis guide rails, a first screw shaft, a first nut section, a first drive source, etc. constitute the X-axis movement mechanism. The pair of X-axis guide rails, the first screw shaft, etc. are supported by a second moving plate (not shown).

[0040] The second movable plate is slidably supported by a pair of Y-axis guide rails (not shown), each of which has its longitudinal portion aligned along the Y-axis. Between the pair of Y-axis guide rails is a second screw shaft (not shown), whose longitudinal portion is aligned along the Y-axis.

[0041] A second nut portion (not shown) is provided on the lower surface of the second movable plate, and a second screw shaft, whose longitudinal portion is arranged along the Y-axis, is rotatably connected to the second nut portion via a plurality of balls (not shown).

[0042] A second drive source (not shown), such as a servo motor, is connected to one end of the second screw shaft. When the second drive source is activated, the second moving plate moves along the Y-axis direction. The second moving plate, a pair of Y-axis direction guide rails, the second screw shaft, the second nut section, the second drive source, etc., constitute a Y-axis direction movement mechanism.

[0043] A light concentrator 10, which constitutes the laser beam irradiation unit (i.e., processing unit) 8, is positioned above the chuck table 4. The laser beam irradiation unit 8 has a laser oscillator 12. The laser oscillator 12 has a laser medium, which is a crystal such as Nd:YAG.

[0044] By irradiating the laser medium with excitation light from a light source such as a flash lamp or laser diode, the laser oscillator 12 emits a pulsed laser beam having a predetermined wavelength (for example, 1064 nm).

[0045] The laser beam emitted from the laser oscillator 12 is converted to a wavelength absorbed by the workpiece 11 (for example, 355 nm) by a wavelength conversion device (not shown) that includes a nonlinear optical crystal such as an LBO (i.e., LiB3O5) crystal, and then enters the light concentrator 10.

[0046] Then, after the direction of travel is changed by the mirror 10a located inside the light concentrator 10, the light passes through the focusing lens 10b located inside the light concentrator 10 and is irradiated toward the holding surface 4a (i.e., along the Z-axis direction) approximately perpendicular to it.

[0047] With the focal point of the pulsed laser beam L positioned near the surface 11a of the workpiece 11 held by the holding surface 4a, the focal point and the chuck table 4 are moved relative to each other along the X-axis direction by the moving mechanism 6, thereby enabling ablation processing on the workpiece 11 (i.e., the workpiece 11 can be processed).

[0048] The laser beam L emitted from the laser oscillator 12 may also be irradiated from the light concentrator 10 toward the holding surface 4a after passing through an optical modulator such as an AOM (Acousto-Optic Modulator), EOM (Electro-Optic Modulator), or LCOS-SLM (Liquid Crystal on Silicon - Spatial Light Modulator).

[0049] The optical modulator has various functions. For example, the optical modulator adjusts the power of the laser beam L (i.e., average output, peak power, etc.). The optical modulator may also control whether or not to irradiate the laser beam L onto the focuser 10.

[0050] Within the processing apparatus 2, the position of the light concentrator 10 is substantially fixed, but the focusing lens 10b is configured to be adjustable along the Z-axis direction by a piezoelectric actuator. Therefore, the position of the focusing point of the laser beam L can be adjusted along the Z-axis direction.

[0051] Near the light concentrator 10, a lifting mechanism (i.e., a moving unit) 14 is provided for moving the measuring optical system 20, which will be described later, along the Z-axis. The lifting mechanism 14 has a movable plate 16 that can move along the Z-axis.

[0052] The movable plate 16 is slidably supported by a pair of Z-axis guide rails (not shown) whose respective longitudinal portions are arranged along the Z-axis. Between the pair of Z-axis guide rails is a screw shaft (not shown) whose longitudinal portion is arranged along the Z-axis.

[0053] The movable plate 16 is provided with a nut portion (not shown), to which a screw shaft is rotatably connected via multiple balls (not shown). A drive source (not shown), such as a voice coil motor, is connected to one end of the screw shaft.

[0054] When the drive source is activated, the movable plate 16 moves along the Z-axis direction. By employing a voice coil motor as the drive source, the movable plate 16 can be positioned with high precision within a relatively narrow range in the Z-axis direction (for example, between 0 μm and 10 μm).

[0055] Alternatively, instead of using a ball screw to move the movable plate 16 by rotating the screw shaft, the movable plate 16 may be moved along the Z-axis direction by a piezoelectric actuator. Even when using a piezoelectric actuator, the movable plate 16 can be positioned with high precision within a relatively narrow range in the Z-axis direction.

[0056] A measuring optical system 20 is fixed to the movable plate 16. When measuring the three-dimensional shape of the surface (i.e., the surface to be measured) 11a of the workpiece 11 held by the holding surface 4a by imaging (i.e., receiving interference light with the event camera 38), the lifting mechanism 14 moves the measuring optical system 20 and the workpiece 11 relative to each other along the Z-axis direction while imaging is performed.

[0057] Figure 2(A) is a schematic diagram of a shape measurement system 42 including a measuring optical system 20. The measuring optical system 20 has a housing 22, and a white light source (i.e., light source) 24 is fixed inside the housing 22. The white light source 24 has a light source such as an SLD (Superluminescent Diode) or an LED (Light Emitting Diode).

[0058] The white light source 24 emits light containing a variety of wavelengths continuously across a relatively wide wavelength band. In this example, the white light source 24 emits white light with a central wavelength of 465 nm, but this white light does not have to be perfectly white in the strict sense.

[0059] The white light source 24 of this embodiment emits low-coherence light 24a. Low-coherence light 24a is characterized by a short coherence distance 24b (see Figure 3). In this specification, low-coherence light 24a means so-called white light in which the coherence distance 24b is greater than 0 μm and 36 μm or less (more preferably greater than 0 μm and 10 μm or less).

[0060] A first beam splitter 26 is provided at a predetermined distance from the white light source 24 in the -X direction. A second beam splitter 28 is provided directly below the first beam splitter 26. Furthermore, an objective lens 30 is provided directly below the second beam splitter (i.e., the branching section) 28.

[0061] In this example, the first beam splitter 26 and the second beam splitter 28 are half-mirrors. Near the second beam splitter 28, a mirror 32 is provided to which light reflected by the second beam splitter 28 is incident. The mirror 32 has a reference surface 32a which is a reflective surface.

[0062] A portion of the low-coherence light 24a emitted from the white light source 24 sequentially passes through the second beam splitter 28 and the objective lens 30, becoming measurement light 24a1 that is irradiated onto the surface 11a of the workpiece 11. The objective lens 30 has the function of focusing the measurement light 24a1 onto the surface 11a of the workpiece 11.

[0063] After passing through the objective lens 30 and irradiating the surface 11a, the measurement light 24a1 reflected from the surface 11a proceeds sequentially through the second beam splitter 28 and the first beam splitter 26 to the imaging lens 34 located directly above the first beam splitter 26.

[0064] In contrast, the remaining portion of the low-coherence light 24a irradiated from the white light source 24 is sequentially reflected by the first beam splitter 26 and the second beam splitter 28 to become the reference light 24a2 irradiated on the reference surface 32a.

[0065] Thus, the second beam splitter 28 has the function of splitting the low-coherence light 24a into measurement light 24a1 and reference light 24a2. The reference light 24a2 reflected by the reference surface 32a proceeds sequentially through the second beam splitter 28 and the first beam splitter 26 to the imaging lens 34.

[0066] An event camera (i.e., a photoelectric converter) 38, including a solid-state image sensor 36, is provided directly above the imaging lens 34. The event camera 38 receives interference light resulting from the interference of the measurement light 24a1 and the reference light 24a2.

[0067] The measuring optical system 20 in this embodiment is a so-called Michelson type, but it may also be a Mirau type. In the case of a Mirau type, a mirror 32 having a reference surface 32a is positioned between the objective lens 30 and the holding surface 4a on the optical axis of the objective lens 30.

[0068] Figure 2(B) is a schematic diagram of the event camera 38. The event camera 38 is also called an EVS (Event-based Vision Sensor). The event camera 38 has a solid-state image sensor 36. Multiple photoelectric conversion elements 36a capable of receiving interference light are arranged regularly (for example, in a grid) on the imaging surface of the solid-state image sensor 36.

[0069] In Figure 2(B), two photoelectric conversion elements 36a are shown as black dots on the grid points as an example, but each grid point is provided with a photoelectric conversion element 36a. Each photoelectric conversion element 36a includes, for example, a photodiode and a current-voltage conversion circuit, and the current-voltage conversion circuit generates a voltage signal corresponding to the brightness of the light received by the photodiode.

[0070] The solid-state image sensor 36 includes a brightness change detection circuit 36b which is integrally provided with the region where multiple photoelectric conversion elements 36a are located. Unlike a typical CMOS (Complementary Metal-Oxide-Semiconductor) image sensor, the brightness change detection circuit 36b does not always output voltage signals from all photoelectric conversion elements 36a to the controller 40, which will be described later.

[0071] The brightness change detection circuit 36b selectively outputs event data 36c to the controller 40 in response to a change in brightness at the photoelectric conversion element 36a. The event data 36c includes information that can identify (A) the coordinates (x,y) (i.e., position) of the photoelectric conversion element 36a where the brightness change occurred, and (B) information (i) indicating that there was a positive or negative brightness change at the photoelectric conversion element 36a, and further includes (C) the time (t) (i.e., timestamp) at which the brightness change occurred.

[0072] Because the event data 36c includes a timestamp, even if the controller 40 cannot receive images in real time based on the event data 36c, the controller 40 can create images that are correctly arranged in chronological order based on the event data 36c that it receives retrospectively.

[0073] Furthermore, whether or not there has been a change in brightness in the photoelectric conversion element 36a is determined by the brightness change detection circuit 36b, for example, by comparing the measured brightness with a threshold value. However, this threshold value is updated as appropriate for each photoelectric conversion element 36a over time.

[0074] The brightness change detection circuit 36b does not output voltage signals from all photoelectric conversion elements 36a to the controller 40 for each frame, but rather outputs event data 36c for only the photoelectric conversion elements 36a that have experienced a brightness change to the controller 40.

[0075] Therefore, the amount of information in each frame can be reduced compared to a typical CMOS image sensor. Figure 2(B) shows how multiple photoelectric conversion elements 36a are arranged on a two-dimensional plane defined by x and y, but x and y may be the same as or different from the X and Y that define the spatial axes described above.

[0076] As shown in Figure 2(A), the lifting mechanism 14, the measuring optical system 20, and the controller 40 constitute a shape measuring system 42 for measuring the three-dimensional shape of the workpiece 11, and also constitute a measurement method called coherence scanning interferometry (CSI) which has relatively high vertical resolution.

[0077] When the shape measurement system 42 measures the shape of at least a portion of the surface 11a of the workpiece 11 held by suction on the holding surface 4a (i.e., the measurement area 11c), the measurement area 11c is imaged by a vertical scanning method in which the measurement optical system 20 and the workpiece 11 are moved relative to each other along the Z-axis.

[0078] Figure 3 shows the simulation results illustrating the interference of low-coherence light 24a. The horizontal axis of Figure 3 represents the optical path difference (μm) between the measurement light 24a1 and the reference light 24a2 from the event camera 38 to the measurement area 11c, and the vertical axis of Figure 3 represents the luminance (au) of the interference light received by the event camera 38.

[0079] When the optical path difference is 0 (μm), the measurement light 24a1 and the reference light 24a2 reinforce each other at all wavelengths, and the brightness of the interference light reaches its peak value. Even when the optical path difference is not 0 (μm), although weaker than when the optical path difference is 0 (μm), the brightness and darkness of the interference light are still present on the imaging surface of the solid-state image sensor 36.

[0080] In the example shown in Figure 3, outside the range of ±1 μm for the optical path difference (i.e., the coherence distance 24b), the interference between the measurement light 24a1 and the reference light 24a2 cancels out due to their different wavelengths, and virtually no brightness or darkness of interference light occurs on the imaging surface of the solid-state image sensor 36.

[0081] Therefore, during the process of moving the measuring optical system 20 upward along the Z-axis from a predetermined reference height position Z0 (not shown), the brightness of the interference light from a certain photoelectric conversion element 36a becomes strongest (i.e., the interference becomes strongest).

[0082] The height position of the measurement optical system 20 in the Z-axis direction when the interference is strongest corresponds to the height of the measurement area 11c in the XY plane that corresponds to the photoelectric conversion element 36a. The predetermined reference height position Z0 is a position in the +Z direction with respect to the holding surface 4a, and is determined appropriately according to the thickness of the workpiece 11.

[0083] When measuring the three-dimensional shape of the measurement area 11c, the controller 40 controls the lifting mechanism 14 to change the relative position of the measurement optical system 20, the workpiece 11, and the photoelectric conversion element 36a, while receiving the interference light of the measurement light 24a1 and the reference light 24a2 reflected from the measurement area 11c (see Figure 8(A)).

[0084] Then, the height of the area to be measured 11c is determined based on the occurrence of an event in the event camera 38 within the area to be measured 11c (i.e., the optical path difference between the measurement light 24a1 and the reference light 24a2 when a change in brightness occurs).

[0085] Specifically, by moving the measurement optical system 20 upward with the lifting mechanism 14 and tracking the occurrence of events for each photoelectric conversion element 36a, the height of the measurement area 11c at the time of strongest interference for each photoelectric conversion element 36a is determined. This allows the three-dimensional shape of the measurement area 11c within the range that can be imaged by multiple photoelectric conversion elements 36a to be measured based on the event data 36c.

[0086] In particular, since this embodiment uses an event camera 38, the amount of image information output to the controller 40 can be significantly reduced compared to the case where interference light is received by a general CMOS image sensor different from the event camera 38, so the relative movement speed of the measurement optical system 20 can be increased. Therefore, the frame rate can be sufficiently high.

[0087] In addition, since the event camera 38 receives the interference light of the low-coherence light 24a, which has a short coherence distance 24b, when the optical path difference between the measurement light 24a1 and the reference light 24a2 is outside the range of the coherence distance 24b, almost no brightness or darkness of interference light is formed in the event camera 38. Therefore, no events indicating changes in brightness occur.

[0088] In this way, the synergistic effect of using low-coherence light 24a and event camera 38 allows for a sufficiently high frame rate, thus shortening the measurement time when measuring 3D shapes.

[0089] Furthermore, the controller 40, upon receiving event data 36c from the brightness change detection circuit 36b, determines for each photoelectric conversion element 36a the time midway between the time when brightness changes begin to occur (i.e., the time when events begin to occur) t1 and the time when brightness changes cease to occur (i.e., the time when events cease to occur) t2. 12 The shape of the measurement region 11c may be determined based on the relative position of the measurement optical system 20 and the workpiece 11.

[0090] This makes measurement easier and improves resistance to noise compared to the case where the brightness change detection circuit 36b determines whether or not there has been a brightness change in the photoelectric conversion element 36a by comparing the measured brightness with a predetermined threshold.

[0091] After moving the measurement optical system 20 along the Z-axis from the reference height position Z0, the imaging area of ​​the event camera 38 is shifted by a predetermined distance in the X-axis direction, and then the measurement optical system 20 is similarly moved along the Z-axis direction (see Figure 8(B)).

[0092] The reference height position Z0 at the point where the X-axis direction is shifted may be the same as the reference height position Z0 before the X-axis direction shift, and may be changed as appropriate considering the expected thickness of the workpiece 11 depending on the position in the X-axis direction.

[0093] Figure 4 is a schematic diagram showing an example of irregularities along the X-axis direction of the surface 11a of the workpiece 11. The height of the measurement area 11c is determined by identifying the height Z at which the interference is strongest. In Figure 4, the shape of the surface 11a is shown with a dashed line, and black circles are placed in the range of position X1 (or X2, X3, X4) + ΔX on the surface 11a that constitutes the measurement area 11c.

[0094] Note that in Figure 4, for the sake of explanation, five black circles are shown in the range of ΔX, but in an actual event camera 38, the number of black circles is equal to the number of photoelectric conversion elements 36a provided in a predetermined direction (for example, the x-direction) on the solid-state image sensor 36.

[0095] Furthermore, although Figure 4 shows the measurement of the height shape within the ΔX range of the measurement area 11c for ease of explanation, in reality, the three-dimensional shape of the measurement area 11c in a two-dimensional plane that can be imaged by multiple photoelectric conversion elements 36a can be measured by moving the measurement optical system 20 along the Z-axis direction.

[0096] After measuring the 3D shape in the range (position X1 + ΔX), the imaging area of ​​the measurement optical system 20 is shifted by a predetermined distance in the X-axis direction (for example, refer to the range (position X2 + ΔX)). Then, similarly, the 3D shape in the new imaging area is measured while moving the measurement optical system 20 along the Z-axis direction. Of course, position X1 may be equal to (position X2 + ΔX).

[0097] In this manner, by repeatedly moving the measurement optical system 20 in the Z-axis direction and shifting the imaging area of ​​the measurement optical system 20 by a predetermined distance in the X-axis direction, the three-dimensional shape of the surface 11a of the workpiece 11 in a band-shaped region along the X-axis direction is measured (see Figure 8(C)). Subsequently, the imaging area of ​​the event camera 38 is shifted in the Y-axis direction.

[0098] Similarly, the movement of the measurement optical system 20 along the Z-axis and the movement of the imaging area along the X-axis are repeated. In this way, the three-dimensional shape of the entire surface 11a of the workpiece 11 is measured.

[0099] In this embodiment, if no significant change in brightness occurs during the process of moving the measurement optical system 20 along the Z-axis, the event camera 38 does not output event data 38c to the controller 40, thus allowing for a higher frame rate and a higher relative movement speed of the measurement optical system 20.

[0100] Now, let's return to Figure 1. The controller 40 controls the moving mechanism 6, the laser beam irradiation unit 8, the lifting mechanism 14, the measurement optical system 20, etc. The controller 40 is composed of a computer including, for example, a processor 40a represented by a CPU (Central Processing Unit) and memory 40b.

[0101] Memory 40b includes a main memory such as DRAM (Dynamic Random Access Memory) and an auxiliary memory such as flash memory, a hard disk drive, or a solid-state drive.

[0102] The auxiliary storage device stores software, including a predetermined program. The controller 40's functions are realized by operating the processor 40a and other components according to this software.

[0103] This software includes a program that measures the three-dimensional shape of the measurement area 11c by determining the height of the measurement area 11c when the interference is strongest by tracking the occurrence of events for each photoelectric conversion element 36a, and displays this three-dimensional shape on the display device 44.

[0104] The display device 44 is, for example, a touch panel display that also functions as an input device. The operator can set processing conditions and perform other operations through the display device 44.

[0105] Next, with reference to Figures 5 to 8, a processing method for performing laser processing on a workpiece 11 using the processing apparatus 2 (i.e., processing the workpiece 11) will be described. This processing method includes a shape measurement method for measuring the three-dimensional shape of the workpiece 11 (see S20, S30, and S40 in Figure 5).

[0106] Figure 5 is a flowchart showing the processing method for the workpiece 11. In this embodiment, each step is performed in the order of S10 to S40. First, the workpiece 11 is subjected to ablation processing with the laser beam irradiation unit 8 (i.e., the workpiece 11 is processed) to form processing marks 11d (see Figure 7(B)) on the workpiece 11 (processing step S10).

[0107] Figure 6 is a perspective view of the workpiece 11 before processing. The workpiece 11 includes a disc-shaped wafer made of single-crystal silicon, a semiconductor material. The workpiece 11 has a circular front surface 11a and a circular back surface 11b. Multiple mutually orthogonal division lines 13 are set on the front surface 11a.

[0108] Each of the multiple rectangular regions demarcated by multiple division lines 13 is provided with a device 15 such as an IC (Integrated Circuit). Each division line 13 and each device 15 is covered with a low-k film (not shown). However, the low-k film is not mandatory.

[0109] Furthermore, there are no restrictions on the material, shape, structure, size, etc. of the wafer. The workpiece 11 may have a substrate made of semiconductors other than silicon (GaAs, SiC, GaN, etc.), diamond, sapphire, glass, ceramics, resin, metal, etc. There are also no restrictions on the type, number, shape, structure, size, arrangement, etc. of the devices 15. The workpiece 11 does not have to have devices 15.

[0110] An annular metal frame 17 is positioned around the outer periphery of the workpiece 11, enclosing the workpiece 11. A dicing tape 19 with a diameter larger than the opening of the frame 17 is attached to one surface of the frame 17 and the back surface 11b of the workpiece 11.

[0111] In other words, the workpiece 11 is supported by the frame 17 via the dicing tape 19. The workpiece 11, the frame 17, and the dicing tape 19 constitute the workpiece unit 21.

[0112] When forming the processing marks 11d, the workpiece 11 is held by the chuck table 4 via the dicing tape 19 so that the surface 11a is exposed upwards (see Figure 7(A)). Note that in Figure 7(A), the frame 17 and dicing tape 19 are omitted as described above.

[0113] Then, after adjusting the position of the chuck table 4 so that the focal point of the laser beam L is located near the surface 11a in the Z-axis direction and on the extension of one planned division line 13 in the X-axis direction, the chuck table 4 is moved along the X-axis direction while the laser beam L is irradiated. The laser processing conditions are set as follows, for example.

[0114] Wavelength: 355nm Average output: 0.7W Repeat frequency: 200kHz Pulse width: 9 ps Machining feed rate: 600 mm / s

[0115] Figure 7(A) shows the process of performing ablation on the workpiece 11. After machining one division line 13 from one end in the X-axis direction to the other, the chuck table 4 is moved along the Y-axis direction by a predetermined index feed amount. Then, ablation is performed in the same manner on other division lines 13 adjacent to the machined division line 13 in the Y-axis direction.

[0116] After ablation processing is performed on all planned division lines 13 along the X-axis in this manner, the chuck table 4 is rotated by approximately 90 degrees using the θ table of the moving mechanism 6. Then, ablation processing is performed similarly on each of the unprocessed planned division lines 13.

[0117] Figure 7(B) is a cross-sectional view of a workpiece 11 including a processing mark 11d formed on the surface 11a by ablation. The processing mark 11d is a processing groove having a predetermined depth from the surface 11a (i.e., having a depth that does not completely cut the workpiece 11), and comprises a processing groove 11d1 and molten deposit portions 11d2 located at both edges of the processing groove 11d1.

[0118] Note that the molten deposit area 11d2 shown in Figure 7(B) is explicitly shown for explanatory purposes, but it is not always formed uniformly along the longitudinal direction of the planned division line 13. When the processed mark 11d is viewed from above, there are also regions where the molten deposit area 11d2 is partially formed.

[0119] Furthermore, it is not essential to form machining marks 11d on all planned division lines 13; machining marks 11d may be formed on at least one planned division line 13. Alternatively, to confirm the machining performance, circular or elliptical machining marks 11d may be formed on a portion of one planned division line 13 or on a portion of a test piece.

[0120] In this embodiment, after forming a processing mark 11d on at least one division line 13 (i.e., after the processing step S10), the relative position between the measuring optical system 20 and the workpiece 11 is changed continuously or intermittently along the Z-axis direction, and a portion of the processing mark 11d is imaged (imaging step S20).

[0121] In the imaging step S20, as described above, the measurement light 24a1 is irradiated onto the surface 11a of the workpiece 11, and the interference light resulting from the interference between the reference light 24a2 and the measurement light 24a1 reflected by the workpiece 11 held by the holding surface 4a is received by the event camera 38 (light receiving step), and the relative position of the event camera 38 and the workpiece 11 is changed along the Z-axis direction (Z-axis direction movement step).

[0122] For example, in the imaging step S20, the measuring optical system 20 is continuously moved upward along the Z-axis so as to move away from the workpiece 11, and the first region 11c1 (see Figure 8(A)) of the measurement region 11c on the surface 11a of the workpiece 11 is imaged with the measuring optical system 20.

[0123] Alternatively, in the imaging step S20, the first region 11c1 may be imaged with the measuring optical system 20 while intermittently moving the measuring optical system 20 upward so that it moves away from the workpiece 11 along the Z-axis direction. That is, the process of imaging the first region 11c1 with the measuring optical system 20 stationary and moving the measuring optical system 20 along the Z-axis direction may be repeated.

[0124] Figure 8(A) shows the imaging of the first region 11c1 of the measurement region 11c. In Figure 8(A), the case where the measurement optical system 20 is moved upward is shown, but instead, the measurement optical system 20 may be moved downward so that it is closer to the workpiece 11.

[0125] As described above, the measurement optical system 20 measures the three-dimensional shape of the area to be measured 11c based on event data 36c, so the frame rate can be made significantly higher compared to when interference light is received by a general CMOS image sensor different from the event camera 38.

[0126] Furthermore, the synergistic effect of using low-coherence light 24a and the event camera 38 allows for a sufficiently high frame rate, thus increasing the relative movement speed of the measurement optical system 20. Therefore, the measurement time when measuring three-dimensional shapes can be shortened.

[0127] After the imaging process S20 for the first region 11c1, the controller 40 determines whether or not the entire processing mark 11d along one of the planned division lines 13 has been imaged (determination process S30 in Figure 5).

[0128] For example, the controller 40 determines whether or not it has captured an image of the entire processing mark 11d along one of the planned division lines 13 by comparing the length of one division line 13 in the X-axis direction with the relative movement distance of the measurement optical system 20 and the chuck table 4 in the X-axis direction.

[0129] If the entire processing mark 11d has not been imaged (NO in S30), the measuring optical system 20 and the workpiece 11 are moved a predetermined distance relative to each other along the X-axis in order to similarly image the second region 11c2 adjacent to the first region 11c1 in the X-axis direction (index feed step S40). Then, the process returns to the imaging step S20, and the second region 11c2 is imaged in the same manner.

[0130] Figure 8(B) shows the process of imaging the second region 11c2 adjacent to the first region 11c1. The imaging process S20 and the index feeding process S40 are repeated until the Nth region 11c N The image is taken. Figure 8(C) shows the Nth region 11c N This diagram shows the process of imaging (where N is a natural number greater than or equal to 3).

[0131] In contrast, if the entire processing mark 11d along one planned division line 13 is imaged (YES in S30), the controller 40 determines whether all processing marks 11d have been imaged. If all processing marks 11d have been imaged (YES in the determination step S50), the flow ends.

[0132] If not all processing marks 11d have been imaged (NO in S50), the relative position of the measurement optical system 20 is adjusted to the unimaged division line 13 (movement step S60). After the movement step S60, the process returns to the imaging step S20.

[0133] Incidentally, the event data 36c mentioned above includes information indicating that there was a change in brightness in the photoelectric conversion element 36a, but it may also include the amount of brightness change itself. This amount of brightness change can be considered as the derivative of brightness with respect to time (or position in the Z-axis direction).

[0134] Therefore, the controller 40 can determine the brightness at each time (or Z-axis position) by integrating the change in brightness over time (or position in the Z-axis direction), and based on this result, it can determine the time (or Z-axis position) at which interference is maximized.

[0135] Furthermore, if event data 36c includes a change in brightness, the time (or position in the Z-axis direction) when the change in brightness is maximum can be simply considered as the time (or position in the Z-axis direction) when the interference is maximum. Alternatively, the time (or position in the Z-axis direction) when the brightness is maximum may be considered as the time (or position in the Z-axis direction) when the interference is maximum.

[0136] (Second Embodiment) Next, a second embodiment will be described with reference to Figures 9 to 10(C). The second embodiment relates to a method for manufacturing a device chip 23, in which a plurality of device chips 23 (see Figure 10(C)) are manufactured from a workpiece 11.

[0137] Figure 9 is a flowchart showing an example of a method for manufacturing the device chip 23. In the second embodiment, as in the processing step S10 of the first embodiment, processing grooves (i.e., the processing marks 11d described above) are formed on each planned division line 13 by ablation processing using a laser beam L (processing step S12).

[0138] After the machining process S12, the imaging process S20, the judgment process S30, and the index feeding process S40 in the first embodiment (see Figure 5) are repeated as appropriate (shape measurement process S22). This allows for imaging of one machined groove and measurement of its three-dimensional shape.

[0139] If not all machined grooves have been imaged (NO in judgment step S52), the shape measurement step S22 is repeated until all machined grooves have been imaged. Of course, the synergistic effect of using low-coherence light 24a and event camera 38 allows the frame rate to be sufficiently high, so the relative movement speed of the measurement optical system 20 can be increased. Therefore, the measurement time when measuring three-dimensional shapes can be shortened.

[0140] After imaging all the machined grooves and measuring the three-dimensional shape of each machined groove (YES in S52), the process proceeds to the workpiece division process S70. In the division process S70 of this embodiment, first, a modified region 11e with reduced mechanical strength is formed along each planned division line 13 between the bottom 11d3 of the machined groove 11d1 and the back surface 11b of the workpiece 11 (see modified region formation process in division process S70, Figure 10(A)).

[0141] Figure 10(A) shows the modification region formation process. The modification region formation process can use essentially the same processing apparatus 2 as the ablation process. Therefore, in Figure 10(A), components having the same function as processing apparatus 2 are denoted by the same reference numerals as the components shown in processing apparatus 2 in Figure 1.

[0142] However, the laser beam irradiation unit 8 shown in Figure 10(A) irradiates the workpiece 11 with a pulsed laser beam L from the condenser 10 that has a wavelength that can penetrate the workpiece 11 (for example, 1064 nm), rather than a wavelength that is absorbed by the workpiece 11.

[0143] In the modification region formation process, the chuck table 4 is moved along the X-axis while the focusing point of the laser beam L is positioned between the bottom 11d3 of the processing groove 11d1 and the back surface 11b of the workpiece 11 in the Z-axis direction. The laser processing conditions are set as follows, for example.

[0144] Wavelength: 1064nm Average output: 1.0W Repeat frequency: 30kHz Pulse width: 3ns Machining feed rate: 165 mm / s Number of passes: 2

[0145] In the modification region formation process, the depth position of the focusing point of the laser beam L in the Z-axis direction can be adjusted by utilizing the three-dimensional shape of the processed groove (i.e., the processed mark 11d) obtained in the shape measurement process S22.

[0146] For example, the position of the focusing point may vary for each division line 13 due to rough surface conditions at the bottom 11d3 of the processed groove 11d1. However, by fine-tuning the position of the focusing device 10 in the Z-axis direction, the possibility of the modified region 11e varying for each division line 13 due to the surface conditions at the bottom 11d3 can be reduced.

[0147] After forming a modified region 11e along each planned division line 13, the back surface 11b of the workpiece 11 is ground with the grinding device 50 (back surface grinding step in division step S70, see Figure 10(B)). The grinding device 50 has a disc-shaped chuck table 52.

[0148] The chuck table 52 has a holding surface 52a that holds the workpiece 11 by suction. The holding surface 52a has a conical shape in which the central part protrudes slightly (for example, by only 20 μm) compared to the outer circumference, but since the amount of protrusion is small, the holding surface 52a is shown as substantially flat in Figure 10(B).

[0149] A rotational drive source (not shown), such as a servo motor, is provided at the bottom of the chuck table 52. The chuck table 52 is rotatable around a rotation axis 52b located at the radial center of the chuck table 52.

[0150] The rotating shaft 52b is tilted such that a portion of the holding surface 52a is approximately parallel to the XY plane. However, since the tilt is slight, in Figure 10(B), the rotating shaft 52b is shown as approximately parallel to the Z-axis direction. A grinding unit 54 is provided above the chuck table 52.

[0151] The grinding unit 54 is configured to be movable along the Z-axis direction by a Z-axis direction movement mechanism (not shown). It has a cylindrical spindle 56 arranged along the Z-axis direction. A disc-shaped mount 58 is fixed to the lower end of the spindle 56.

[0152] An annular grinding wheel 60 is mounted on the lower surface of the mount 58. The grinding wheel 60 has an annular wheel base 60a. Multiple grinding wheels 60b are arranged on the lower surface of the wheel base 60a at approximately equal intervals along the circumferential direction of the wheel base 60a.

[0153] In the back grinding process using the grinding device 50, the workpiece 11 is first held in place by suction on the holding surface 52a. In this example, the surface 11a of the workpiece 11 is covered with a resin protective member 25, and then the workpiece 11 is held in place by suction on the holding surface 52a so that the back surface 11b is exposed.

[0154] Next, the chuck table 52 and spindle 56 are rotated at predetermined speeds, and the grinding unit 54 is fed downward at a predetermined speed. The area of ​​the back surface 11b that is arranged approximately parallel to the XY plane is ground by contacting the multiple grinding wheels 60b.

[0155] The grinding area on the back surface 11b is semi-circular, but as the chuck table 52 rotates around the rotation axis 52b, the entire back surface 11b is ground almost uniformly, and the workpiece 11 is thinned. In the back surface grinding process, the workpiece 11 is thinned, and the impact applied to the workpiece 11 is used to propagate cracks from the modified area 11e.

[0156] As the cracks reach the surface 11a and back surface 11b, the workpiece 11 is cut along each planned division line 13 so as to pass through the bottom 11d3 of the machining groove, and is divided into multiple device chips 23. Figure 10(B) shows the back surface grinding process, and Figure 10(C) is a perspective view of one of the multiple device chips 23.

[0157] In this embodiment, the division process S70 is performed by a modified region formation process and a back grinding process. However, after measuring the three-dimensional shape of each processed groove, instead of the modified region formation process and grinding process, the workpiece 11 may be cut at each planned division line 13 by blade dicing using a cutting device (not shown) to divide it into multiple device chips 23.

[0158] (Modification of the second embodiment) Next, a modification of the second embodiment will be described with reference to Figures 11 and 12. Figure 11 is a flowchart showing a modification of the method for manufacturing the device chip 23.

[0159] In this modified example, an ablation process is performed on the unprocessed workpiece 11 to form processing grooves 11f that completely cut the workpiece 11 at each planned division line 13, thereby dividing the workpiece 11 into multiple device chips 23 (processing step S14). Figure 12 is a cross-sectional view of the workpiece 11 cut by the ablation process.

[0160] After the machining process S14, the shape measurement process S22 is performed (i.e., the imaging process S20, the judgment process S30, and the index feeding process S40 in the first embodiment are repeated as appropriate). This allows one machined groove 11f to be imaged and its three-dimensional shape to be measured. If not all machined grooves 11f have been imaged (NO in S52), the shape measurement process S22 is repeated until all machined grooves 11f have been imaged.

[0161] In response to this, after imaging all the machined grooves 11f and measuring the three-dimensional shape of each machined groove 11f (YES in S52), the controller 40 determines whether the three-dimensional shape of the machined groove 11f obtained in the shape measurement step S22 is outside a predetermined tolerance range (determination step S72). After the determination step S72, the flow ends.

[0162] In this modified configuration, the synergistic effect of using low-coherence light 24a and the event camera 38 allows for a sufficiently high frame rate, thus increasing the relative movement speed of the measurement optical system 20. Therefore, the measurement time when measuring three-dimensional shapes can be shortened.

[0163] Furthermore, in this modified example, if the three-dimensional shape of the machined groove 11f obtained in the shape measurement step S22 falls outside a predetermined tolerance range, the controller 40 determines that the device chip 23 constituting the machined groove 11f that falls outside the tolerance range is a defective product.

[0164] By inspecting the micro-shape after laser processing in this way, for example, the worker can choose to discard the defective device chip 23. This reduces the possibility of malfunctions occurring in products equipped with the device chip 23.

[0165] Furthermore, the structures, methods, etc., of the embodiments described above can be modified as appropriate without departing from the scope of the object of the present invention. In the embodiments and modifications described above, the case in which a three-dimensional shape such as a processing mark 11d formed by laser processing is measured by the measuring optical system 20 has been explained, but the three-dimensional shape of a region processed by mechanical processing such as cutting, grinding, polishing may also be measured by the measuring optical system 20. [Explanation of symbols]

[0166] 2: Processing equipment 4: Chuck table (holding unit), 4a: Holding surface, 6: Moving mechanism 8: Laser beam irradiation unit (processing unit) 10: Focuser, 10a: Mirror, 10b: Focusing lens 11: Workpiece (object), 11a: Surface (surface to be measured), 11b: Back surface 11c: Measured area, 11c1: First area, 11c2: Second area, 11c N :Nth area 11d: Machining marks (machined groove area), 11d1: Machined groove, 11d2: Molten deposit area, 11d3: Bottom 11e: Modified area, 11f: Machined groove 12: Laser Oscillator 13: Planned splitting line, 15: Device 14: Lifting mechanism (moving unit), 16: Moving plate 17: Frame, 19: Dicing tape 20: Measuring optical system, 22: Housing 21: Workpiece unit, 23: Device chip, 25: Protective member 24: White light source (light source), 24a: Low coherence light 24a1: Measurement light, 24a2: Reference light, 24b: Coherence distance 26: First beam splitter, 28: Second beam splitter (branching point) 30: Objective lens, 32: Mirror, 32a: Reference plane, 34: Imaging lens 36: Solid-state image sensor, 36a: Photoelectric conversion element, 36b: Brightness change detection circuit 36c: Event data, 38: Event camera (photoelectric converter) 40: Controller, 40a: Processor, 40b: Memory 42: Shape measurement system, 44: Display device 50: Grinding equipment 52: Chuck table, 52a: Holding surface, 52b: Rotating shaft 54: Grinding unit, 56: Spindle, 58: Mount 60: Grinding wheel, 60a: Wheel base, 60b: Grinding wheel L: Laser beam S10,S12,S14: Machining process S20: Imaging process, S30: Decision process, S40: Index feeding process S22: Shape measurement process S50: Judgment process, S60: Movement process, S70: Division process S52, S72: Judgment process X1,X2,X3,X4:Position

Claims

1. A shape measuring system for measuring the three-dimensional shape of an object, Measurement optical system and A moving unit that moves the measuring optical system and the object relative to each other, A controller for controlling the mobile unit, Equipped with, The measuring optical system is, A light source that emits low-coherence light, A branching unit that splits the light from the light source into a reference light that irradiates a reference surface which is a reflective surface, and a measurement light that irradiates the object, A photoelectric conversion device having a photoelectric conversion element that receives interference light resulting from the interference of the reference light reflected from the reference surface and the measurement light reflected from the object, It has, The photoelectric conversion device is a shape measurement system characterized by having an event camera that outputs event data to the controller that can identify the location of the photoelectric conversion element where a change in brightness has occurred.

2. The controller is, By controlling the moving unit, the relative position of the measuring optical system and the object is changed, and the photoelectric converter receives the interference light of the measurement light reflected from the area to be measured in the object and the reference light. The shape measurement system according to claim 1, which measures the shape of a region to be measured of an object based on the occurrence of an event in the event camera within that region to be measured.

3. A processing device for processing a workpiece, A holding unit for holding the workpiece, A processing unit for processing the workpiece, Measurement optical system and A moving unit that moves the measuring optical system and the holding unit relative to each other, A controller for controlling the mobile unit, Equipped with, The measuring optical system is, A light source that emits low-coherence light, A branching unit that splits the light from the light source into a reference light that irradiates a reference surface which is a reflective surface, and a measuring light that irradiates the workpiece, A photoelectric conversion device having a photoelectric conversion element that receives interference light resulting from the interference of the reference light reflected from the reference surface and the measurement light reflected from the workpiece, It has, The photoelectric conversion device is a processing apparatus characterized by having an event camera that outputs event data to the controller that can identify the location of the photoelectric conversion element where a change in brightness has occurred.

4. A shape measurement method for measuring the three-dimensional shape of an object, The low-coherence light is split into a reference light irradiated onto a reference surface and a measurement light irradiated onto the object, and the measurement light is irradiated onto the object. The interference light resulting from the interference between the reference light reflected from the reference surface and the measurement light reflected from the object is received by a photoelectric converter. The relative positions of the photoelectric converter and the object are changed along a first direction in which the photoelectric converter and the object move closer to and further apart from each other. Equipped with, The photoelectric conversion device includes a photoelectric conversion element that receives the interference light resulting from the interference of the reference light reflected from the reference surface and the measurement light reflected from the object, and has an event camera that outputs event data capable of identifying the position of the photoelectric conversion element where a change in brightness has occurred. A shape measurement method characterized by measuring the three-dimensional shape of an object based on event data obtained by receiving the interference light with the photoelectric converter and changing the relative position between the photoelectric converter and the object.

5. A processing method for processing a workpiece, The process involves processing the workpiece with a processing unit to form processing marks, After the formation of the processing mark, the measurement light is irradiated onto the processing mark from the low-coherence light that is split into a reference light irradiated onto the reference surface and a measurement light irradiated onto the processing mark, and the interference light resulting from the interference between the reference light reflected from the reference surface and the measurement light reflected from the processing mark is received by a photoelectric converter. After the formation of the processing mark, the relative positions of the photoelectric conversion device and the processing mark are changed along a first direction in which the photoelectric conversion device and the processing mark move closer to and further apart. Equipped with, The photoelectric conversion device includes a photoelectric conversion element that receives interference light resulting from the interference of the reference light reflected from the reference surface and the measurement light reflected from the processing mark, and has an event camera that outputs event data capable of identifying the position of the photoelectric conversion element where a change in brightness has occurred. A processing method characterized by measuring the three-dimensional shape of a processing mark based on event data obtained by receiving the interference light with the photoelectric converter and changing the relative position between the photoelectric converter and the processing mark.

6. A method for manufacturing chips from a workpiece, The workpiece is processed by a processing unit to form a processing groove having a depth that does not completely cut through the workpiece, After the formation of the machined groove, the three-dimensional shape of the machined groove is measured, After measuring the three-dimensional shape of the machined groove, the workpiece is cut so as to pass through the bottom of the machined groove and divided into chips. Equipped with, Measuring the three-dimensional shape of the machined groove is The low-coherence light is split into a reference light irradiated onto a reference surface and a measurement light irradiated onto the machining groove, and the measurement light is irradiated onto the machining groove. The interference light resulting from the interference between the reference light reflected from the reference surface and the measurement light reflected from the machining groove is received by a photoelectric converter. The relative position of the photoelectric conversion device and the workpiece is changed along a first direction in which the photoelectric conversion device and the workpiece move closer to and further apart from each other. It has, The photoelectric conversion device includes a photoelectric conversion element that receives interference light resulting from the interference of the reference light reflected from the reference surface and the measurement light reflected from the processing groove, and has an event camera that outputs event data capable of identifying the position of the photoelectric conversion element where a change in brightness has occurred. By measuring the three-dimensional shape of the machined groove, A method for manufacturing a chip, characterized by receiving the interference light with the photoelectric converter, changing the relative position between the photoelectric converter and the processed groove, and measuring the three-dimensional shape of the processed groove based on the event data obtained by these actions.

7. A method for manufacturing chips from a workpiece, The workpiece is processed by a processing unit to form a processing groove that completely cuts the workpiece and divides it into chips, After the formation of the machined groove, the three-dimensional shape of the machined groove is measured, Equipped with, Measuring the three-dimensional shape of the machined groove is The low-coherence light is split into a reference light irradiated onto a reference surface and a measurement light irradiated onto the machining groove, and the measurement light is irradiated onto the machining groove. The interference light resulting from the interference between the reference light reflected from the reference surface and the measurement light reflected from the machining groove is received by a photoelectric converter. The relative position of the photoelectric conversion device and the workpiece is changed along a first direction in which the photoelectric conversion device and the workpiece move closer to and further apart from each other. It has, The photoelectric conversion device includes a photoelectric conversion element that receives interference light resulting from the interference of the reference light reflected from the reference surface and the measurement light reflected from the processing groove, and has an event camera that outputs event data capable of identifying the position of the photoelectric conversion element where a change in brightness has occurred. By measuring the three-dimensional shape of the machined groove, A method for manufacturing a chip, characterized by receiving the interference light with the photoelectric converter, changing the relative position between the photoelectric converter and the processed groove, and measuring the three-dimensional shape of the processed groove based on the event data obtained by these actions.

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