JP2018161733A - Method for processing wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To determine a quality of edge trimming at an early stage.SOLUTION: A method for processing a wafer by which an outer peripheral edge of the wafer having a chamfered portion on an outer periphery thereof is cut from a front side thereof. This method comprises: an outer peripheral edge position detection step at which the outer peripheral edge of the wafer is imaged by a camera, and a position of the outer peripheral edge of the wafer is detected; a processing step at which a cutting blade is cut in the outer peripheral edge from the front side thereof; an edge position detection step at which a cut annular region is imaged, and a position of an edge of a newly formed surface of the wafer is detected; a cut width calculation step at which a width of the annular region is calculated from the detected position of the outer peripheral edge of the wafer and the position of the edge of the surface of the wafer; a calculation step at which the surface of the wafer and a step part formed on a bottom of the annular region are respectively imaged by the camera, and a cut depth of the cutting blade is calculated; and a determination step at which whether or not respectively calculated values fall within a previously registered allowable range.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a wafer processing method.

  The surface of the wafer made of a semiconductor is partitioned by a plurality of division lines arranged in a lattice pattern, and a device such as an IC is formed in each partitioned region. When the wafer is finally divided along the division lines, individual device chips are formed.

  In recent years, with the downsizing and thinning of electronic devices, there is an increasing demand for downsizing and thinning of device chips mounted on the electronic devices. In order to form a thinned device chip, for example, the back surface of the wafer having a plurality of devices formed on the front surface is ground to thin the wafer to a predetermined thickness, and then, along the planned dividing line. The wafer is divided.

  By the way, chamfering is performed on the outer peripheral edge of the wafer in order to prevent cracking and dust generation of the wafer. A chamfered portion having a circular cross section is formed on the outer periphery of the wafer. When forming a thinned device chip using such a wafer having the chamfered portion formed on the outer periphery, the back surface of the wafer is ground to thin the wafer.

  However, when a wafer having a chamfered portion formed on the outer periphery is thinned, the cross-sectional shape is sharpened like a knife edge on the outer periphery of the wafer. Then, chipping and cracking are likely to occur from the outer periphery of the wafer, which causes a problem that the wafer is easily damaged. In particular, when damage such as cracks reaches the device, the device is damaged and the device chip becomes defective.

  Therefore, a technique called edge trimming has been proposed in which the outer peripheral edge of the wafer is cut before grinding. When the chamfered portion is partially removed in advance by edge trimming, the outer periphery of the wafer is not sharpened even if the wafer is ground from the back surface. Therefore, it is possible to reduce the number of damages that occur on the outer peripheral edge of the wafer during grinding.

  A cutting blade having an annular cutting blade is used for edge trimming. The annular cutting blade is formed, for example, by sintering a binder in which abrasive grains are dispersed. In edge trimming, the cutting blade is rotated in a plane perpendicular to the wafer, and the rotating cutting blade is cut in the vicinity of the outer peripheral edge of the wafer (see Patent Document 1). In edge trimming, an annular region having a predetermined width including the outer peripheral edge of a wafer is cut to a predetermined depth, but an error or the like may occur and cutting as expected may not be performed.

  For example, when an annular region having a width exceeding a predetermined width is cut from the outer peripheral edge of the wafer, a device formed on the surface of the wafer may be cut to cause damage to the device. Also, the cutting blade may not reach a predetermined depth due to an error or the like, and when the wafer is finally ground and thinned, a large chip or a step may be generated on the outer periphery of the wafer. Therefore, it is necessary to sufficiently manage the area where the edge trimming is performed, the implementation status, and the like.

  In order to manage the state of execution of edge trimming, it is necessary to measure the width of the cut region and the depth of cutting (hereinafter referred to as cutting depth) for the wafer subjected to edge trimming. Conventionally, measurement is performed after a wafer having been subjected to edge trimming is taken out from the cutting apparatus.

JP 2006-93333 A

  The wafer is cleaned inside the cutting apparatus after the edge trimming is performed and before the wafer is taken out of the cutting apparatus. For this reason, it takes man-hours from the time when edge trimming is performed to the time when the measurement is performed outside the cutting apparatus.

  Then, even if an abnormality occurs in the processing situation and the content that does not allow the edge trimming is not allowed, edge trimming of the content that is not allowed is performed on the subsequent wafers one after another until it becomes clear. End up. Therefore, defective wafers continue to be manufactured one after another between the occurrence of the abnormality and the confirmation of the abnormality, and the wafer is wasted.

  The present invention has been made in view of such a problem, and an object of the present invention is to calculate a width and a cutting depth of a region cut in edge trimming, and determine whether or not the edge trimming is good at an early stage. It is to provide a processing method.

  According to one aspect of the present invention, a chuck table having a holding surface for holding a wafer and rotatable about an axis perpendicular to the holding surface, and a cutting blade for cutting the wafer held on the chuck table are mounted. A device region in which a device is formed, and an outer peripheral surplus region surrounding the device region using a cutting apparatus comprising: a cutting unit comprising: a cutting unit comprising: a cutting unit comprising: a cutting unit including: A wafer processing method in which the outer peripheral edge of a wafer having a chamfered portion on the outer periphery is cut from the surface side, the holding step for exposing the surface and holding the wafer by the chuck table, and the chuck table The outer periphery of the wafer held on the surface is imaged by the camera, and three or more points on the outer periphery are parallel to the holding surface. An outer periphery position detecting step for detecting a position of the outer periphery of the wafer from the acquired coordinates, and a depth greater than a finished thickness due to the thinning of the wafer from the surface side to the outer periphery. While cutting the cutting blade, the chuck table is rotated around the axis one or more times to cut the annular region including the outer peripheral edge of the wafer, so that a stepped portion is formed at the bottom of the cut annular region. A processing step of forming a new edge of the surface of the wafer along the inner periphery of the annular region, and imaging the annular region cut in the processing step from the surface side of the wafer, An edge position detecting step of acquiring coordinates in a plane parallel to the holding surface for three or more points on the edge of the surface of the wafer, and detecting a position of the edge of the surface of the wafer from the acquired coordinates; A cutting width calculating step for calculating the width of the annular region cut in the processing step from the position of the outer peripheral edge of the wafer and the position of the edge of the surface of the wafer; and the surface of the wafer The step formed on the bottom of the annular region in the processing step is imaged with the camera, and the height of the camera when the surface is in focus and the step when the step is in focus. The values calculated in the cutting depth calculation step for calculating the cutting depth of the cutting blade from the difference between the height of the camera, the cutting width calculation step, and the cutting depth calculation step are registered in advance. A wafer processing method comprising: a determination step for determining whether or not the difference is within an allowable range; and a notification step for notifying an operator of a determination result in the determination step. It is.

  In one aspect of the present invention, the image processing apparatus further includes a chip detection step for detecting a size of a chip formed on the edge from the captured image obtained in the edge position detection step, and the determination step includes the detected chip. It may be a wafer processing method for determining whether or not the size of the wafer is within an allowable range.

  In the wafer processing method according to one aspect of the present invention, before and after performing edge trimming on a wafer, the vicinity of the outer peripheral edge of the wafer is imaged using a camera (imaging unit) provided in the cutting apparatus. By comparing the positions of the outer peripheral edge of the wafer before processing and the edge of the wafer surface after processing, the width of the cut annular region can be calculated.

  In addition, after performing edge trimming, the surface of the wafer and the stepped portion of the annular region are imaged so that the camera is in focus. At this time, the cutting depth of the cutting blade can be calculated by comparing the height position of the camera focused on the wafer surface and the height position of the camera focused on the stepped portion of the annular region.

  If the calculated cutting width and cutting depth of the cutting blade are within the allowable range, it is confirmed that edge trimming is appropriately performed. If the calculated cutting width or cutting depth is not within the allowable range, it is confirmed that an abnormality has occurred in the machining status. In the wafer processing method according to one embodiment of the present invention, the determination is performed using the camera included in the cutting apparatus. Therefore, the determination can be performed immediately after the wafer is cut. Therefore, the determination result can be notified to an operator of the cutting apparatus at an early stage.

  When an abnormality occurs in the processing, the operator or the like can stop the cutting device before starting the processing of the next wafer, and can inspect the cutting device. Therefore, edge trimming is not performed one after another in an abnormal state, and wafer loss can be suppressed.

  Therefore, according to one aspect of the present invention, a wafer processing method is provided in which the width and depth of cut of a region cut in edge trimming are calculated, and the quality of edge trimming can be determined at an early stage.

It is a perspective view which shows a wafer typically. It is a perspective view which shows a cutting device typically. FIG. 3A is a side view schematically showing the position detection step, and FIG. 3B is a top view schematically showing the position detection step. FIG. 4A is a side view schematically showing the processing step, and FIG. 4B is a side view schematically showing the edge position detecting step. It is a figure which shows an example of a captured image typically. It is a fragmentary sectional view showing a grinding step typically.

  Embodiments according to one aspect of the present invention will be described with reference to the accompanying drawings. First, a wafer that is a workpiece in the processing method according to the present embodiment will be described with reference to FIG. FIG. 1 is a perspective view schematically showing a wafer. The wafer 1 is, for example, a substantially disk-shaped substrate made of a material such as silicon, SiC (silicon carbide), or other semiconductor, or a material such as sapphire, glass, or quartz.

  The surface 1a of the wafer 1 is partitioned by a plurality of scheduled division lines 3 arranged in a lattice pattern, and devices 5 such as ICs are formed in the respective areas partitioned by the plurality of scheduled division lines 3. Finally, the wafer 1 is divided along the streets 3 to form individual device chips. A region where a plurality of devices 5 are formed in the surface 1a is called a device region, and an outer peripheral side surrounding the device region is called an outer peripheral surplus region.

  If the front surface 1a and back surface 1b of the wafer 1 and the side surface between the two are corners, the wafer 1 is damaged when an external impact or the like is applied to the corners. , Debris may soar into the air and generate dust. Therefore, a chamfering process is performed in advance on the outer peripheral edge of the wafer 1, and a chamfered portion 1c having an arcuate cross section is formed on the outer peripheral edge.

  Next, a cutting apparatus used in the processing method according to the present embodiment will be described with reference to FIG. FIG. 2 is a side view schematically showing the cutting device 2. As shown in FIG. 2, the cutting device 2 includes a device base 4 that supports each component. A rectangular opening 4 a that is long in the X-axis direction is formed on the upper surface of the apparatus base 4.

  In the opening 4a, there are an X-axis moving table 6, an X-axis moving mechanism (not shown) for moving the X-axis moving table 6 in the X-axis direction, and a dust-proof and drip-proof cover 8 that covers the X-axis moving mechanism. Is provided. The X-axis movement mechanism includes a pair of X-axis guide rails (not shown) parallel to the X-axis direction, and an X-axis movement table 6 is slidably attached to the X-axis guide rails.

  A nut portion (not shown) is provided on the lower surface side of the X-axis moving table 6, and an X-axis ball screw (not shown) parallel to the X-axis guide rail is screwed to the nut portion. . An X-axis pulse motor (not shown) is connected to one end of the X-axis ball screw. When the X-axis ball screw is rotated by the X-axis pulse motor, the moving table 6 moves in the X-axis direction along the X-axis guide rail.

  On the X-axis moving table 6, a chuck table 10 for sucking and holding a workpiece is provided. The chuck table 10 is connected to a rotation drive source (not shown) such as a motor, and rotates around a rotation axis substantially parallel to the Z-axis direction (vertical direction). Further, the chuck table 10 is sent in the X-axis direction by the X-axis moving mechanism described above.

  The surface (upper surface) of the chuck table 10 serves as a holding surface 10a for sucking and holding a workpiece. The holding surface 10 a is connected to a suction source (not shown) through a flow path (not shown) formed inside the chuck table 10.

  A protruding portion 12 that protrudes laterally from the device base 4 is provided at a corner in front of the device base 4 away from the opening 4a. A space is formed inside the protrusion 12, and a cassette elevator 16 that can be raised and lowered is installed in this space. A cassette 18 that can accommodate a plurality of workpieces is placed on the upper surface of the cassette elevator 16.

  A transport unit (not shown) for transporting the above-described workpiece to the chuck table 10 is provided at a position close to the opening 4a. The workpiece drawn from the cassette 18 by the transport unit is placed on the holding surface 10 a of the chuck table 10.

  On the upper surface of the apparatus base 4, a support structure 20 that supports a cutting unit 14 that cuts a workpiece is disposed so as to protrude above the opening 4 a. A cutting unit moving mechanism 22 that moves the cutting unit 14 in the Y-axis direction (index feed direction) and the Z-axis direction is provided on the upper front surface of the support structure 20.

  The cutting unit moving mechanism 22 includes a pair of Y-axis guide rails 24 arranged in front of the support structure 20 and parallel to the Y-axis direction. A Y-axis moving plate 26 constituting the cutting unit moving mechanism 22 is slidably attached to the Y-axis guide rail 24. A nut portion (not shown) is provided on the back surface side (rear surface side) of the Y-axis moving plate 26, and a Y-axis ball screw 28 parallel to the Y-axis guide rail 24 is screwed into the nut portion. ing.

  A Y-axis pulse motor (not shown) is connected to one end of the Y-axis ball screw 28. When the Y-axis ball screw 28 is rotated by the Y-axis pulse motor, the Y-axis moving plate 26 moves in the Y-axis direction along the Y-axis guide rail 24. A pair of Z-axis guide rails 30 parallel to the Z-axis direction are provided on the surface (front surface) of the Y-axis moving plate 26. A Z-axis moving plate 32 is slidably attached to the Z-axis guide rail 30.

  A nut portion (not shown) is provided on the back surface side (rear surface side) of the Z-axis moving plate 32, and a Z-axis ball screw 34 parallel to the Z-axis guide rail 30 is screwed into the nut portion. ing. A Z-axis pulse motor 36 is connected to one end of the Z-axis ball screw 34. When the Z-axis ball screw 34 is rotated by the Z-axis pulse motor 36, the Z-axis moving plate 32 moves in the Z-axis direction along the Z-axis guide rail 30.

  A cutting unit 14 for processing a workpiece and an imaging unit (camera) 38 are fixed to the lower part of the Z-axis moving plate 32. If the Y-axis moving plate 26 is moved in the Y-axis direction by the cutting unit moving mechanism 22, the cutting unit 14 and the imaging unit 38 are moved in the Y-axis direction, and the Z-axis moving plate 32 is moved in the Z-axis direction. For example, the cutting unit 14 and the imaging unit 38 move up and down.

  The imaging unit 38 can capture an image of the workpiece held on the chuck table 10. The imaging unit 38 is positioned so that a predetermined part of the workpiece can be imaged by operating the cutting unit moving mechanism 22 and the X-axis moving mechanism. Further, by moving the Z-axis moving plate 32 in the Z-axis direction, the imaging unit can be positioned at a height at which a predetermined point of the workpiece is in focus (focus). The imaging unit 38 has a function of sending the obtained captured image and information such as the height when the image is captured to the control unit 44 described later.

  The cutting unit 14 includes an annular cutting blade 14b (see FIG. 4) attached to one end side of a spindle 14a (see FIG. 4) constituting a rotation axis parallel to the Y-axis direction. A rotation drive source (not shown) such as a motor is connected to the other end side of the spindle 14a, and the cutting blade 14b mounted on the spindle 14a can be rotated.

  The cutting blade 14b has a disk-shaped base 14c. A substantially circular mounting hole penetrating through the base 14c is provided at the center of the base 14c. An annular cutting blade 14d for cutting into the workpiece is fixed to the outer periphery of the base 14c. The cutting device 2 can cut the workpiece by cutting the cutting blade 14b into the workpiece held on the chuck table 10.

  The cutting device 2 includes a cleaning unit 40 at a position adjacent to the opening 4 a of the device base 4. The cleaning unit 40 has a function of cleaning the workpiece after processing. The cleaning unit 40 includes a spinner table 42 that sucks and holds a workpiece in a cylindrical cleaning space. A rotation drive source (not shown) that rotates the spinner table 42 at a predetermined speed is connected to the lower portion of the spinner table 42. The processed workpiece is transported from the chuck table 10 onto the spinner table 42 by a transport mechanism (not shown), and is sucked and held.

  Above the spinner table 42, an injection nozzle (not shown) for injecting a cleaning fluid (typically two fluids in which water and air are mixed) is arranged toward the workpiece. The workpiece can be cleaned by rotating the spinner table 42 holding the workpiece and ejecting a cleaning fluid from the spray nozzle. The workpiece cleaned by the cleaning unit 40 is accommodated in the cassette 18 by, for example, a transport mechanism (not shown).

  The cutting device 2 further includes a control unit 44. The control unit 44 has a function of controlling each component of the cutting apparatus 2 such as the cutting unit 14, the chuck table 10, each moving mechanism, the imaging unit 38, the cleaning unit 40, and a transport mechanism (not shown). The control unit 44 also includes a captured image captured by the imaging unit, information regarding the height of the imaging unit 38 when the captured image is captured, and information regarding a position on the workpiece where the captured image is captured. , From the cutting device 2.

  The control unit 44 further calculates the width of the cut annular region and the cutting depth of the cutting blade 14b for the cutting of the annular region including the outer peripheral edge of the workpiece based on the received information and the like. It has the function to do. To the control unit 44, the allowable range for the width of the annular region and the depth of cut is input in advance by the manufacturer of the cutting device 2, an operator, or the like, and the control unit 44 stores the value of the allowable range. it can. The control unit 44 has a function of determining whether or not the calculated value is within the allowable range.

  The control unit 44 has a storage unit (not shown) for storing each piece of information in order to realize these functions. The storage unit stores allowable ranges for the width of the annular region and the cutting depth. In addition, the storage unit stores values of the width of the cut annular region and the cutting depth of the cutting blade 14b. The control unit 44 can write information stored in the storage unit to an external storage medium removably connected to the cutting device 2. The function of the control unit 44 is realized as software on a device control PC, for example.

  The cutting device 2 has a display unit 46 electrically connected to the control unit 44 on the outer surface. The display unit 46 is, for example, a display panel equipped with a touch panel, and an operator of the cutting apparatus 2 can input information such as processing conditions to the control unit 44 using the touch panel. The display unit 46 has a function of displaying an interface image for inputting information and the like and operating the cutting apparatus 2, and further has a function of displaying a result of the determination performed by the control unit 44.

  Next, a wafer processing method in which edge trimming is performed by cutting the chamfered portion 1c on the outer peripheral edge of the wafer 1 as a workpiece from the surface 1a side using the cutting apparatus 2 will be described.

  In the wafer processing method, first, a holding step is performed. In the holding step, the wafer 1 is placed on the holding surface 10 a of the chuck table 10 with the surface 1 a facing upward so as to expose the surface 1 a of the workpiece 1. At this time, the position of the wafer 1 is aligned so that an axis perpendicular to the holding surface 10 a serving as the rotation axis of the chuck table 10 passes through the center of the wafer 1. Then, the suction source of the chuck table 10 is operated to suck and hold the wafer 1 on the chuck table 10.

  Next, an outer periphery position detecting step for detecting the position of the outer periphery of the wafer is performed. The outer periphery position detection step will be described with reference to FIGS. 3 (A) and 3 (B). FIG. 3A is a side view schematically showing the outer periphery position detection step, and FIG. 3B is a top view schematically showing the outer periphery position detection step.

  In the outer periphery position detecting step, first, the imaging unit (camera) 38 captures an image of the outer periphery of the wafer 1 held on the chuck table 10. Imaging is performed at three or more imaging locations 1d on the outer peripheral edge. A captured image is obtained by imaging, and coordinates on a plane parallel to the holding surface 10 a of the imaging location 1 d are acquired from the relative positions of the imaging unit 38 and the chuck table 10.

  The acquired captured image and information regarding the coordinates of the imaging location 1d are sent to the control unit 44 (see FIG. 2), and the control unit 44 uses the received coordinates of the three or more imaging locations 1d as a wafer. The position of the outer peripheral edge of 1 is detected. Information on the position of the outer peripheral edge is stored in the storage unit of the control unit 44.

  Next, in the processing method according to the present embodiment, the processing step of cutting the annular region including the outer peripheral edge of the wafer 1 from the surface 1a side is performed by the cutting blade 14b. FIG. 4A is a side view schematically showing processing steps. First, the chuck table 10 is moved, and the cutting blade 14b is positioned above the wafer 1 so that the inner peripheral edge of the annular region and the end of the cutting blade 14d of the cutting blade 14b are aligned in the horizontal direction.

  Then, the spindle 14a is rotated to rotate the cutting blade 14b, and the chuck table 10 is rotated about the axis perpendicular to the holding surface 10a. Then, the cutting blade 14 b is lowered to a predetermined height, and the cutting blade 14 b is cut into the outer peripheral edge of the wafer 1. When the chuck table 10 is rotated more than once around the axis while the cutting blade 14b is lowered to a predetermined height, the annular region including the outer peripheral edge of the wafer 1 is cut. Thereafter, the cutting blade 14b is raised to finish the processing step.

  In the processing method according to the present embodiment, an edge position detection step of detecting the position of the edge of the surface 1a of the wafer 1 newly formed in the processing step is performed. Here, the edge coincides with the inner peripheral edge of the surface 1a of the cut annular region. FIG. 4B is a side view schematically showing the edge position detection step. In the edge position detection step, the edge 1e of the surface 1a of the wafer 1 is imaged by the imaging unit 38 as in the above-described outer periphery position detection step.

  Imaging is performed at three or more imaging locations on the edge 1e. A captured image is obtained by imaging, and coordinates on a plane parallel to the holding surface 10a of the imaging location are acquired. The acquired captured image and information regarding the coordinates of the imaging location are sent to the control unit 44 (see FIG. 2). The control unit 44 uses the edge 1e based on the received coordinates of three or more imaging locations. The position of is detected. Information on the detected position of the edge 1 e is stored in the storage unit of the control unit 44.

  An example of a captured image captured in the edge position detecting step is shown in FIG. In the captured image 7, a surface 1a of the wafer 1 whose outer peripheral edge is cut, an edge 1e of the surface 1a, and a step portion 1f exposed by cutting are shown. Furthermore, as shown in FIG. 5, when a chipping (chipping) 9 occurs in the edge 1 e of the surface 1 a by cutting, the chipping 9 is also copied in the captured image 7.

  Therefore, the edge position detection step may further include a chip detection step for detecting the size of the chip formed on the edge 1e. In the missing detection step, for example, the control unit 44 that has received the captured image 7 determines whether or not the edge 1e shown in the captured image 7 is missing. If the edge 1 e is chipped, the size of the chip is detected from the captured image 7 and information about the chip is stored in the storage unit of the control unit 44.

  In the processing method according to the present embodiment, the width of the annular region cut in the processing step from the detected position of the outer peripheral edge of the wafer 1 and the detected position of the edge 1e of the surface 1a. A cutting width calculating step for calculating 1 g (see FIG. 4) is performed. For example, the radius of the outer peripheral edge of the wafer 1 is calculated from the position of the outer peripheral edge of the wafer 1 before cutting, and the radius of the edge 1e is calculated from the position of the edge 1e of the surface 1a. Then, the difference between the two calculated radii is the width 1 g of the cut annular region.

  In the processing method according to the present embodiment, a cutting depth calculation step of calculating a cutting depth 1h (see FIG. 4) of the cutting blade 14b is performed. In the cutting depth calculation step, the imaging unit 38 images each of the surface 1a of the wafer 1 and the step portion 1f of the annular region formed in the processing step.

  When imaging the surface 1a of the wafer 1 held on the chuck table 10, the imaging unit 38 causes the cutting unit moving mechanism 22 of the cutting device 2 to focus the imaging unit 38 on the surface 1a. The height position is adjusted. The height position of the image pickup unit 38 when the image is taken is recorded at the same time as the picked-up image is formed. Similarly, when imaging the stepped portion 1f, the height position of the imaging unit 38 is adjusted so that the focal point (focus) of the imaging unit 38 is aligned with the stepped portion 1f, and the height position is recorded.

  Here, the in-focus position of the imaging unit 38 does not change unless there is a special operation. Therefore, the difference between the height position of the imaging unit 38 when the surface 1a of the wafer 1 is in focus and the height position of the imaging unit 38 when the step 1f is focused is the surface. This is the difference in height between 1a and the stepped portion 1f. Therefore, the difference in height position of the imaging unit 38 when the surface 1a and the stepped portion 1f are imaged is recorded in the storage unit of the control unit 44 as the cutting depth 1h of the cutting blade 14b.

  Next, a determination step is performed to determine whether or not the values calculated in the cutting width calculation step and the cutting depth calculation step are within a registered allowable range. The control unit 44 stores an allowable range input in advance by the manufacturer or operator of the cutting device 2. First, the control unit 44 reads the calculated cutting width value, the allowable range of the cutting width, the calculated cutting depth value, and the allowable range of the cutting depth from the storage unit.

  First, the control unit 44 determines whether or not the value of the cutting width (annular region width 1 g) calculated in the cutting width calculation step is within the allowable range of the cutting width. For example, the cutting width is set to any value of 1 mm to 2 mm, while the allowable range of the cutting width is a range having a width of 50 μm above and below the set cutting width value. Is set.

  If the cutting width (the width 1g of the annular region, see FIG. 4B) is too large, the device region of the wafer 1 may be cut and the device 5 may be damaged. On the other hand, if the cutting width is too small, the chamfered portion 1c of the wafer 1 is not sufficiently removed, and when the wafer 1 is thinned, the outer peripheral edge may be damaged. Therefore, when the cutting width is not within the allowable range, it is necessary to check the processing conditions.

  Further, the control unit 44 determines whether or not the value of the cutting depth of the cutting blade calculated in the cutting depth calculation step is within the allowable range of the cutting depth. For example, the cut depth is set to any value of 50 μm to 100 μm, while the allowable range of the cut depth is a width of 15 μm above and below the set cut depth value. It is set to the range it has.

  The cutting depth 1h (see FIG. 4B) when the cutting blade 14d of the cutting blade 14b cuts into the wafer 1 is set to a depth greater than the finished thickness of the wafer 1 where the back surface 1b side of the wafer 1 is thinned later. The When the cutting depth 1h is less than the finished thickness, when the wafer 1 is thinned, a part of the chamfered portion 1c of the wafer 1 is not removed, and the outer peripheral edge of the wafer 1 is sharp like a knife edge, This is because the wafer 1 is likely to be damaged.

  On the other hand, when the cutting depth 1h becomes larger than necessary, the amount of consumption of the cutting blade 14d increases, so that the replacement frequency of the cutting blade 14b increases and the machining efficiency decreases. Therefore, when the value of the cutting depth 1h is not within the allowable range, it is necessary to check the machining status.

  In the determination step, the control unit 44 may determine whether the size of the chip 9 generated on the edge 1e formed by cutting on the surface 1a of the wafer 1 is within an allowable range. In the edge position detection step, when the chip detection step for detecting the size of the chip 9 generated in the edge 1e is performed, the size of the chip 9 detected in the determination step is an allowance for the size of the chip registered in advance. It can be determined whether it is within the range.

  As the size of the chip 9 generated at the edge 1e increases, the wafer 1 is more likely to be damaged from the chip 9 as a starting point. Therefore, when the size of the chip 9 is not within a predetermined allowable range (for example, 20 μm or less), it is necessary to check the processing status.

  The control unit 44 stores the determined result in the storage unit of the control unit 44. Then, the operator of the cutting apparatus 2 can verify the determination result and information such as the cutting width and the cutting depth from the storage unit. In addition, the control unit 44 sends a determination result to the display unit 46.

  Next, in the processing method according to the present embodiment, a notification step of notifying the operator of the determination result in the determination step is performed. When the determination result is sent from the control unit 44, the display unit 46 of the cutting apparatus 2 displays the determination result so that an operator of the cutting apparatus 2 can visually recognize the determination result. When the calculated cutting width and the calculated cutting depth are not within the allowable range, the display unit 46 displays that fact and informs the operator of the determination result to check the processing status and perform the cutting processing. Prompt to stop.

  According to the machining method according to the present embodiment, when an abnormality occurs in the machining situation, the time from when the abnormality occurs until the operator senses it can be shortened. Therefore, since edge trimming can be stopped soon after an abnormality occurs in the processing state, the wafer 1 is not wasted by performing abnormal edge trimming on a large number of wafers 1. If the cutting device 2 can be inspected to remove the cause of the abnormality, the edge trimming by the cutting device 2 can be resumed.

  Note that when the calculated cutting width and the calculated cutting depth without any abnormality in the machining state are within the allowable range, the display unit 46 may display the fact. Alternatively, the determination result may be notified to the operator by not displaying the determination result. Further, the determination result may be notified to the operator by means other than the display unit 46, and when it is determined that the calculated cutting width, the calculated cutting depth, etc. are not within the allowable range, for example, The determination result may be notified to the operator by emitting a warning sound.

  The edge trimmed wafer 1 is then thinned by applying a protective tape (protective member) 11 on the front surface 1a side and grinding on the back surface 1b side. The protective tape 11 has a function of protecting the surface 1a of the wafer 1 during the grinding process.

  A protective member (protective tape) 11 attached to the surface 1a of the wafer 1 includes a flexible film-like base material, and a glue layer (adhesive layer) formed on one surface of the base material. Have. For example, PO (polyolefin) is used for the base material. PET (polyethylene terephthalate), polyvinyl chloride, polystyrene, or the like having higher rigidity than PO may be used. For the glue layer (adhesive layer), for example, silicone rubber, acrylic material, epoxy material or the like is used.

  Next, a grinding step for thinning the wafer 1 by grinding the back surface 1b of the wafer 1 is performed. FIG. 6 is a partial cross-sectional view schematically showing the grinding step. As shown in FIG. 6, the grinding device 48 includes a chuck table 54 that sucks and holds the wafer 1, and a grinding unit 48 a above the chuck table 54. The chuck table 54 has the same configuration as the chuck table 10 described above, and the upper surface serves as a holding surface 54 a that holds the wafer 1. The chuck table 10 is rotatable around an axis perpendicular to the holding surface 10a.

  The grinding unit 48a includes a spindle 50 that rotatably supports an annular grinding wheel 52. The grinding wheel 52 is attached to the tip of the spindle 50, and a plurality of grinding wheels 56 arranged in an annular shape are fixed to the lower surface side of the grinding wheel 52.

  In order to grind the back surface 1 b side of the wafer 1, the wafer 1 is placed on the holding surface 54 a of the chuck table 54 through the protective tape 11 with the front surface 1 a side facing downward. At this time, the wafer 1 is positioned so that the center of the wafer 1 is aligned with the rotation axis of the chuck table 54. Then, the wafer 1 is sucked and held on the chuck table 54, and the back surface 1b side of the wafer 1 is exposed upward.

  Next, the spindle 50 of the grinding unit 48a is rotated to rotate the grinding wheel 52, and the chuck table 54 is rotated. When the grinding wheel 52 is lowered toward the wafer 1 and the grinding wheel 56 fixed to the rotating grinding wheel 52 touches the back surface 1b of the wafer 1, the wafer 1 is ground. When the grinding wheel 56 is positioned at a predetermined height, the wafer 1 is thinned to a predetermined thickness.

  The chamfered portion formed on the outer peripheral edge of the wafer 1 to be ground is cut from the surface 1a side by edge trimming. Therefore, even if the wafer 1 is ground and thinned, the outer peripheral edge of the wafer 1 is not sharp like a knife edge. Then, the occurrence of damage on the outer periphery of the wafer 1 is suppressed.

  In the above-described embodiment, the case where the wafer is directly held by the chuck table of the cutting apparatus when the chamfered portion of the wafer is cut from the front side in the edge trimming has been described. However, one embodiment of the present invention is not limited thereto. . In edge trimming, the back surface of the wafer may be held on the chuck table in a state of being attached to a tape stretched on an annular frame.

  In addition, the structure, method, and the like according to the above-described embodiment can be appropriately modified and implemented without departing from the scope of the object of the present invention.

DESCRIPTION OF SYMBOLS 1 Wafer 1a Front surface 1b Back surface 1c Chamfered part 1d Image pick-up location 1e Edge 1f Step part 1g Width 1h Depth of cut 3 Line to be divided 5 Device 7 Captured image 9 Chipping (chipping)
DESCRIPTION OF SYMBOLS 11 Protective tape 2 Cutting device 4 Device base 4a Opening 6 X-axis moving table 8 Dust-proof drip-proof cover 10, 54 Chuck table 10a, 54a Holding surface 12 Protrusion 14 Cutting unit 14a Spindle 14b Cutting blade 14c Base 14d Cutting blade 16 Cassette elevator 18 Cassette 20 Support structure 22 Cutting unit moving mechanism 24 Y-axis guide rail 26 Y-axis moving plate 28 Y-axis ball screw 30 Z-axis guide rail 32 Z-axis moving plate 34 Z-axis ball screw 36 Z-axis pulse motor 38 Imaging unit (camera)
40 Cleaning Unit 42 Spinner Table 44 Control Unit 46 Display Unit 48 Grinding Device 48a Grinding Unit 50 Spindle 52 Grinding Wheel 56 Grinding Wheel

Claims (2)

A chuck table having a holding surface for holding a wafer and rotatable about an axis perpendicular to the holding surface, a cutting unit to which a cutting blade for cutting the wafer held on the chuck table is mounted, and the chuck table The imaging unit having a camera for imaging the wafer held on the surface, and using a cutting device, the device region in which the device is formed and an outer peripheral surplus region surrounding the device region are provided on the surface, and the outer periphery is chamfered. A wafer processing method of cutting the outer peripheral edge of a wafer having a portion from the surface side,
A holding step for exposing the surface and holding the wafer on the chuck table;
The outer peripheral edge of the wafer held on the chuck table is imaged by the camera, and coordinates on a plane parallel to the holding surface are obtained for three or more points on the outer peripheral edge. An outer periphery position detecting step for detecting the position of the outer periphery;
While the cutting blade is cut into the outer peripheral edge from the surface side at a depth equal to or greater than the finished thickness due to the thinning of the wafer, the chuck table is rotated around the axis one or more times to move the outer peripheral edge of the wafer. A step of forming a stepped portion at the bottom of the cut annular region and cutting a new edge of the surface of the wafer along the inner periphery of the annular region by cutting the annular region including
The annular region cut in the processing step is imaged from the front side of the wafer, and coordinates in a plane parallel to the holding surface are obtained for three or more points on the edge of the wafer surface. An edge position detecting step for detecting the position of the edge of the surface of the wafer from the coordinates;
A cutting width calculating step for calculating the width of the annular region cut in the processing step from the detected position of the outer peripheral edge of the wafer and the position of the edge of the surface of the wafer;
The surface of the wafer and the step formed on the bottom of the annular region in the processing step are respectively imaged by the camera, and the height of the camera when focused on the surface and the focus on the step Cutting depth calculation step of calculating the cutting depth of the cutting blade from the difference between the height of the camera when
A determination step of determining whether the values calculated in the cutting width calculation step and the cutting depth calculation step are within a pre-registered allowable range;
And a notifying step for notifying an operator of a determination result in the determining step. A chip detection step for detecting the size of the chip formed at the edge from the captured image obtained in the edge position detection step;
The wafer processing method according to claim 1, wherein in the determining step, it is determined whether or not the detected size of the chip is within an allowable range.