JP2014239134A - Wafer processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wafer processing method capable of accurately detecting an outer peripheral edge of a wafer and appropriately cutting an outer peripheral part of the wafer.SOLUTION: A wafer processing method for cutting and removing an outer peripheral edge of a wafer (11) comprises the steps of: mounting the wafer on a holding surface (4a) of a chuck table (4) (wafer holding step); detecting three XY coordinate points or more from the outer peripheral edge of the wafer (outer peripheral edge detecting step); calculating an XY coordinate in a center (O1) position of the wafer from the XY coordinate of the outer peripheral edge (center position calculating step); calculating an amount of misregistration between the center position of the wafer and a rotation center (O2) position of the chuck table (misregistration calculating step); and cutting the outer peripheral edge of the wafer (outer peripheral edge removing step). The outer peripheral edge detecting step scans a laser beam (34) by relatively moving a laser displacement gauge (8) and the chuck table while irradiating the holding surface with the laser beam from the laser displacement gauge.

Description

  The present invention relates to a wafer processing method for cutting and removing a peripheral portion of a chamfered wafer.

  In recent years, in order to realize a small and lightweight device, it is required to thinly process a wafer made of a semiconductor material such as silicon or gallium arsenide. For example, after a device such as an IC is formed in each region partitioned by streets (division lines) on the front surface, the wafer is thinned by grinding the back surface side. The thinned wafer is divided into a plurality of chips corresponding to each device along the street.

  Wafers used in the manufacture of such devices are chamfered to prevent chipping during transportation. However, if the chamfered wafer is thinned by grinding, the outer peripheral portion (chamfered portion) of the wafer is sharpened like a knife edge, and chipping is likely to occur.

  Therefore, a wafer processing method has been proposed in which a chamfered portion is cut and removed before thinning by grinding (see, for example, Patent Document 1). In this processing method, the chamfered portion is cut and removed by cutting a cutting blade before grinding the wafer, thereby preventing the outer peripheral portion from being thinly sharp like a knife edge.

  By the way, in this processing method, the chuck table is rotated after the wafer is sucked and held on the chuck table, and a cutting blade is cut into the outer peripheral portion of the wafer. Therefore, if the rotation center of the chuck table and the center of the wafer are deviated, the outer peripheral portion of the wafer cannot be appropriately cut.

  In order to solve this problem, a processing method has been proposed in which the outer peripheral edge of the wafer is detected based on the density of the captured image obtained by imaging the outer peripheral portion of the wafer, and the cutting position of the cutting blade is corrected (for example, Patent Documents). 2).

JP 2003-273053 A JP 2006-93333 A

  However, for example, when a metal film or the like is formed on the outer peripheral portion of the wafer, or when the optical characteristics (color, etc.) between the chuck table and the wafer are close, the boundary between the chuck table and the wafer in the captured image Tends to be unclear. For this reason, it is not always easy to detect the outer peripheral edge of the wafer with high accuracy by the above-described method, and the cutting position of the wafer may not be appropriately corrected.

  The present invention has been made in view of such problems, and an object thereof is to provide a wafer processing method capable of accurately detecting the outer peripheral edge of a wafer and appropriately cutting the outer peripheral portion of the wafer. It is.

  According to the present invention, a chuck table having a holding surface for holding a wafer and a cutting blade in which the wafer held on the chuck table is mounted on a spindle having an axis in the Y-axis direction are orthogonal to the Y-axis direction. A wafer processing method for cutting and removing the outer peripheral edge of the wafer using a cutting device having a cutting means for processing in the X-axis direction, wherein the wafer is placed on the holding surface of the chuck table. A wafer holding step, an outer edge detecting step for detecting three or more XY coordinates of the outer edge of the wafer on the holding surface after the wafer holding step, and the outer edge detected in the outer edge detecting step. A center position calculating step for calculating the XY coordinates of the center position of the wafer from the XY coordinates of the periphery, and the center of the wafer calculated in the center position calculating step And a positional deviation calculating step for calculating a positional deviation amount between the chuck table and the rotational center position of the chuck table, and after the positional deviation calculating step, the rotational center of the chuck table is positioned on an extension line of the shaft center of the spindle. The outer peripheral edge of the wafer is moved while moving the cutting blade in the Y-axis direction passing through the center of rotation of the chuck table based on the amount of displacement and the rotation angle of the chuck table while rotating the chuck table. A peripheral edge removing step of cutting the peripheral edge of the wafer in the circumferential direction at substantially the same distance from the center position of the wafer, and in the outer peripheral edge detecting step, the laser beam is emitted from a laser displacement meter toward the holding surface The displacement gauge and the chuck table are moved relative to each other in the X axis direction and the Y axis direction to scan the laser beam. Processing method of the wafer and detecting the XY coordinates of the outer peripheral edge by intersecting the outer peripheral edge of the wafer is provided.

  According to the present invention, since the outer periphery of the wafer is detected by scanning with a laser beam, imaging is performed when a film is formed up to the outer periphery of the wafer or when the optical characteristics of the chuck table and the wafer are close. Even in a situation where sufficient contrast cannot be obtained in the image, the outer periphery of the wafer can be detected with high accuracy.

  Therefore, the amount of positional deviation between the center of the wafer and the rotation center of the chuck table can be accurately calculated, and the outer peripheral portion of the wafer can be appropriately cut.

FIG. 1A is a perspective view illustrating a configuration example of a wafer processed by the wafer processing method of the present embodiment, and FIG. 1B is a cross-sectional view illustrating a configuration example of the wafer. It is a top view which shows typically the structural example of the cutting device used for the processing method of the wafer of this Embodiment. It is a partial cross section side view which shows typically the wafer holding step of this Embodiment. FIG. 4A is a partial cross-sectional side view schematically showing the outer periphery detection step of the present embodiment, and FIG. 4B is a plan view schematically showing the outer periphery detection step. It is a graph which shows the example of the data output from a laser displacement meter in the outer periphery detection step of this Embodiment. It is a top view which shows typically the center position calculation step of this Embodiment. It is a top view which shows typically the position shift calculation step of this Embodiment. FIG. 8A is a plan view schematically showing the outer peripheral edge removing step of the present embodiment, and FIG. 8B is a partial cross section schematically showing the outer peripheral edge removing step of the present embodiment. It is a side view.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. The wafer processing method of the present embodiment includes a wafer holding step (see FIG. 3), an outer peripheral edge detecting step (see FIGS. 4 and 5), a center position calculating step (see FIG. 6), and a misalignment calculating step (FIG. 7). And a peripheral edge removing step (see FIG. 8).

  In the wafer holding step, the wafer is held on the chuck table of the cutting apparatus (see FIG. 3). In the outer periphery detection step, the coordinates of a plurality of points on the outer periphery of the wafer are detected using a laser displacement meter (see FIGS. 4 and 5). In the center position calculating step, the coordinates of the center of the wafer are calculated based on the detected coordinates of a plurality of points on the outer periphery (see FIG. 6).

  In the positional deviation calculation step, the positional deviation amount between the center of the wafer and the center of rotation of the chuck table is calculated (see FIG. 7). In the outer peripheral edge removing step, the outer peripheral edge of the wafer is removed by cutting while changing the cutting position of the cutting blade based on the amount of positional deviation between the center of the wafer and the center of rotation of the chuck table (see FIG. 8). Hereinafter, the wafer processing method according to the present embodiment will be described in detail.

  FIG. 1A is a perspective view illustrating a configuration example of a wafer processed by the wafer processing method of the present embodiment, and FIG. 1B is a cross-sectional view illustrating a configuration example of the wafer. As shown in FIG. 1A and FIG. 1B, a wafer 11 to be processed is, for example, a semiconductor wafer having a disk-shaped outer shape, and a central device region 13 and a peripheral excess surrounding the device region 13 Region 15.

  The device region 13 on the surface 11a side of the wafer 11 is partitioned into a plurality of regions by streets (division planned lines) 17 arranged in a lattice pattern, and a device 19 such as an IC is formed in each region. The outer peripheral portion 11c of the wafer 11 is chamfered, and the cross-sectional shape is an arc shape.

  In the wafer processing method of the present embodiment, first, a wafer holding step of holding the wafer 11 on the chuck table of the processing apparatus is performed. FIG. 2 is a plan view schematically showing a configuration example of a cutting apparatus used in the wafer processing method of the present embodiment.

  As shown in FIG. 2, the cutting apparatus 2 includes a chuck table (holding means) 4 that holds the wafer 11 by suction. Above the chuck table 4, a blade unit (cutting means) 6 for cutting the wafer 11 and a laser displacement meter 8 capable of detecting the height position of the wafer 11 held on the chuck table 4 are arranged.

  Below the chuck table 4 is provided an X-axis moving mechanism (machining feed means) 10 for moving the chuck table 4 in the machining feed direction (X-axis direction). A Y axis moving mechanism (not shown) for moving the blade unit 6 and the laser displacement meter 8 in the indexing feed direction (Y axis direction) is disposed at a position adjacent to the X axis moving mechanism 10. On the Y-axis moving mechanism, a Z-axis moving mechanism (not shown) that moves the blade unit 6 and the laser displacement meter 8 in the vertical direction (Z-axis direction) is provided.

  The chuck table 4 is connected to a rotation mechanism (not shown) and rotates around the Z axis. The surface of the chuck table 4 is a holding surface 4 a that holds the wafer 11 by suction. A negative pressure of a suction source (not shown) acts on the holding surface 4 a through a flow path (not shown) formed inside the chuck table 4, and a suction force for sucking the wafer 11 is generated.

  The blade unit 6 includes a spindle 14 that is rotatably supported in the spindle housing 12. The axis of the spindle 14 is oriented in the Y-axis direction. An annular cutting blade 16 is attached to one end side of the spindle 14.

  A motor (not shown) is connected to the other end side of the spindle 14, and the cutting blade 16 attached to the spindle 14 rotates with the rotational force transmitted from the motor. The wafer 11 is cut by rotating the cutting blade 16 and cutting it into the wafer 11 held on the chuck table 4.

  The laser displacement meter 8 includes an irradiation unit 18 that irradiates a laser beam toward the holding surface 4 a of the chuck table 4 and a light receiving unit 20 that receives the reflected laser beam. The irradiation unit 18 includes, for example, a laser oscillator such as a semiconductor laser, and is configured to be able to irradiate a laser beam downward. The light receiving unit 20 includes a light receiving element such as a CMOS or a CCD, and converts a laser beam incident from below into an electrical signal corresponding to the amount of light received.

  An X-axis scale 22 extending in the X-axis direction is disposed in the vicinity of the chuck table 4. The chuck table 4 is provided with an X-axis sensor 24 that detects the distance from the origin X0 to the chuck table 4 in the X-axis direction based on the X-axis scale 22.

  A Y-axis scale 26 extending in the Y-axis direction orthogonal to the X-axis direction is disposed in the vicinity of the blade unit 6 and the laser displacement meter 8. The blade unit 6 is provided with a Y-axis sensor 28 that detects the distance from the origin Y0 in the Y-axis direction to the blade unit 6 and the laser displacement meter 8 based on the Y-axis scale 26.

  The components such as the chuck table 4, the blade unit 6, the laser displacement meter 8, the X-axis moving mechanism 10, the Y-axis moving mechanism, and the Z-axis moving mechanism are controlled by a control device (control means) 30 including an arithmetic unit and the like. Is done. A storage device (storage means) 32 is connected to the control device 30. The control device 30 stores information necessary for controlling each component in the storage device 32, and reads and uses the information as necessary.

  In the wafer holding step, the wafer 11 is sucked and held on the chuck table 4 of the processing apparatus 2 described above. FIG. 3 is a partial cross-sectional side view schematically showing the wafer holding step of the present embodiment.

  First, the chuck table 4 and the wafer 11 are aligned so that the holding surface 4a of the chuck table 4 and the back surface 11b of the wafer 11 face each other. Then, the wafer 11 is placed on the holding surface 4a of the chuck table 4 and a negative pressure of the suction source is applied. As a result, the wafer 11 is held on the chuck table 4 with the front surface 11a facing upward.

  After the wafer holding step, an outer peripheral edge detecting step for detecting coordinates of a plurality of points on the outer peripheral edge of the wafer 11 is performed. FIG. 4A is a partial cross-sectional side view schematically showing the outer periphery detection step of the present embodiment, and FIG. 4B is a plan view schematically showing the outer periphery detection step.

  In the outer periphery detection step, as shown in FIG. 4, first, the laser displacement meter 8 is positioned above the chuck table 4 using the X-axis moving mechanism 10, the Y-axis moving mechanism, and the Z-axis moving mechanism. Specifically, above the starting point 38 that does not overlap the wafer 11 so that the irradiation line (orbit) 36 of the laser beam 34 irradiated from the laser displacement meter 8 passes through the points 11d and 11e on the outer peripheral edge of the wafer 11. Position the laser displacement meter 8 at

  Next, the chuck table 4 is moved in the X-axis direction while irradiating the laser beam 34 from the laser displacement meter 8. At this time, the position of the laser displacement meter 8 in the Y-axis direction is fixed. As a result, the laser displacement meter 8 can scan the laser beam 34 along the irradiation planned line 36 that is relatively moved in the X-axis direction so as to cross the wafer 11 and extends in the X-axis direction.

  The chuck table 4 is moved until the laser beam 34 reaches the end point 40 of the irradiation scheduled line 36. The end point 40 is located on the opposite side of the start point 38 across the wafer 11, and does not overlap the wafer 11 like the start point 38. As described above, the laser beam 34 is scanned along the irradiation planned line 36 that intersects the outer peripheral edge of the wafer 11 at two points (points 11d and 11e).

  After the scanning of the irradiation planned line 36 is completed, the laser displacement meter 8 is moved in the Y-axis direction to scan the irradiation planned line (orbit) 42 passing through the points 11f and 11g on the outer peripheral edge of the wafer 11. Do.

  That is, the laser displacement meter 8 is positioned above the starting point 44 different from the starting point 38, and the chuck table 4 is moved in the X-axis direction while irradiating the laser beam 34 from the laser displacement meter 8.

  The chuck table 4 is moved until the laser beam 34 reaches the end point 46 of the irradiation scheduled line 42. Thereby, the laser beam 34 is scanned along the irradiation planned line 42 that intersects the outer peripheral edge of the wafer 11 at two points (points 11f and 11g).

  FIG. 5 is a graph showing an example of data output from the laser displacement meter 8 in the outer periphery detection step of the present embodiment. The laser beam 34 irradiated from the irradiation unit 18 of the laser displacement meter 8 toward the holding surface 4 a of the chuck table 4 is reflected by the holding surface 4 a of the chuck table 4 or the surface 11 a of the wafer 11 and received by the laser displacement meter 8. Incident on the part 20.

  Since the laser displacement meter 8 is relatively moved in the X-axis direction, the amount of light received by the light receiving unit 20 changes with time. The laser displacement meter 8 outputs data relating to the height position of the wafer 11 in the X-axis direction as shown in FIG.

  The control device 30 detects coordinates (X coordinates) in the X-axis direction of points on the outer peripheral edge of the wafer 11 based on data output from the laser displacement meter 8. Specifically, as shown in FIG. 5, coordinates at which the height position changes rapidly are detected as X coordinates of points 11 d (11 f) and 11 e (11 g) on the outer peripheral edge of the wafer 11.

  In the control device 30, since the coordinates (Y coordinate) of the irradiation scheduled lines 36 and 42 in the Y-axis direction are known based on the Y-axis scale 26, the Y-axis sensor 28, and the like, the control device 30 detects the point 11d on the outer periphery. , 11e, 11f, and 11g can be recognized. The control device 30 stores the XY coordinates of the points 11d, 11e, 11f, and 11g on the outer peripheral edge in the storage device 32.

  After the outer peripheral edge detecting step, a center position calculating step for calculating the coordinates of the center of the wafer 11 is performed. FIG. 6 is a plan view schematically showing the center position calculating step of the present embodiment.

  The control device 30 reads out the XY coordinates of the points 11d, 11e, 11f, and 11g on the outer peripheral edge detected in the outer peripheral edge detection step from the storage device 32, and from these four XY coordinates, as shown in FIG. 11 XY coordinates of the center O1 are calculated.

  The XY coordinates of the center O1 can be calculated by using, for example, a method of obtaining the center of a circumscribed circle of a triangle having any one of the points 11d, 11e, 11f, and 11g on the outer peripheral edge as a vertex. However, the calculation method of the XY coordinates of the center O1 is not particularly limited. Thereafter, the control device 30 stores the calculated XY coordinates of the center O1 in the storage device 32.

  After the center position calculating step, a position shift calculating step for calculating a position shift amount between the center O1 of the wafer 11 and the rotation center of the chuck table 4 is performed. FIG. 7 is a plan view schematically showing the positional deviation calculation step of the present embodiment.

  As shown in FIG. 7, the control device 30 reads the XY coordinates of the center O1 of the wafer 11 from the storage device 32, and the amount of misalignment between the center O1 and the rotation center O2 of the chuck table 4 (eccentric distance d and eccentric angle). φ) is calculated based on the following formulas (1) and (2). The eccentric distance d corresponds to the distance between the center O1 and the rotation center O2, and the eccentric angle φ corresponds to an angle formed by a line segment connecting the center O1 and the rotation center O2 with respect to the X-axis direction.

In the following formulas (1) and (2), X1 represents the X coordinate of the center O1, Y1 represents the Y coordinate of the center O1, X2 represents the X coordinate of the rotation center O2, and Y2 represents the rotation center O2. Represents the Y coordinate. X2 and Y2 are determined based on the X-axis scale 22, the X-axis sensor 24, the Y-axis scale 26, the Y-axis sensor 28, and the like.

  After the positional deviation calculation step, an outer peripheral edge removing step for cutting and removing the outer peripheral edge of the wafer 11 while changing the cutting position of the cutting blade 16 based on the positional deviation amount (eccentric distance d and eccentric angle φ) is performed. To do. FIG. 8A is a plan view schematically showing the outer peripheral edge removing step of the present embodiment, and FIG. 8B is a partial cross section schematically showing the outer peripheral edge removing step of the present embodiment. It is a side view.

  In the outer peripheral edge removing step, first, the rotation center O2 of the chuck table 4 is positioned on the extension line of the spindle 14 axis. Then, the cutting blade 16 that rotates at high speed is cut into the outer peripheral portion 11 c of the wafer 11 while rotating the chuck table 4 at a predetermined speed.

Here, the cutting blade 16 is cut into the wafer 11 while being moved in the Y-axis direction based on the positional shift amount calculated in the positional shift calculation step. The distance y from the rotation center O2 to the cutting position P of the cutting blade 16 is expressed by the following formula (3) using the distance r from the center O1 of the wafer 11 to the cutting position P, the rotation angle θ of the chuck table 4, and the like. Is done.

  The distance r from the center O1 of the wafer 11 to the cutting position P of the cutting blade 16 corresponds to the finished radius of the wafer 11. As this distance r, a value equal to or smaller than the radius of the wafer 11 can be arbitrarily set.

  In this way, the cutting blade 16 is cut while moving in the Y-axis direction based on the positional deviation amount (eccentric distance d and eccentric angle φ) calculated in the positional deviation calculating step and the rotation angle θ of the chuck table 4. Thus, a position at a certain distance r from the center O1 of the wafer 11 can be cut in the circumferential direction.

  According to the wafer processing method of the present embodiment, since the outer peripheral edge of the wafer 11 is detected by scanning with the laser beam 34, a film is formed even on the outer peripheral portion 11c of the wafer 11, or the chuck table 4 and the wafer The outer periphery of the wafer 11 can be accurately detected even in a situation where sufficient contrast cannot be obtained in the captured image as in the case where the optical characteristics of the wafer 11 are close.

  Therefore, the amount of positional deviation between the center O1 of the wafer 11 and the rotation center O2 of the chuck table can be accurately calculated, and the outer peripheral portion 11c of the wafer 11 can be appropriately cut.

  In addition, this invention is not limited to description of the said embodiment, A various change can be implemented. For example, in the above embodiment, the XY coordinates of four points (points 11d, 11e, 11f, and 11g) on the outer periphery are detected in the outer periphery detection step, but the present invention is not limited to this. If at least three or more XY coordinates on the outer periphery can be detected, the coordinates of the center O1 of the wafer 11 can be calculated.

  Moreover, in the said embodiment, although the semiconductor wafer is used as the wafer 11 of a process target, the process target of this invention is not limited to this. For example, a bonded wafer such as a TSV (Through Silicon Via) wafer may be processed.

  In addition, the configurations, methods, and the like according to the above-described embodiments can be changed as appropriate without departing from the scope of the object of the present invention.

DESCRIPTION OF SYMBOLS 11 Wafer 11a Front surface 11b Back surface 11c Peripheral part 11d, 11e, 11f, 11g Point 13 Device area 15 Peripheral surplus area 17 Scheduled division line (street)
19 Device 2 Cutting device 4 Chuck table (holding means)
4a Holding surface 6 Blade unit (cutting means)
8 Laser displacement meter 10 X-axis movement mechanism (processing feed means)
DESCRIPTION OF SYMBOLS 12 Spindle housing 14 Spindle 16 Cutting blade 18 Irradiation part 20 Light-receiving part 22 X-axis scale 24 X-axis sensor 26 Y-axis scale 28 Y-axis sensor 30 Control apparatus (control means)
32 Storage device (storage means)
34 Laser beam 36, 42 Scheduled irradiation line (orbit)
38,44 Start point 40,46 End point

Claims (1)

A chuck table having a holding surface for holding a wafer, and the wafer held on the chuck table are processed in an X-axis direction orthogonal to the Y-axis direction by a cutting blade mounted on a spindle having an axis in the Y-axis direction. A wafer processing method for cutting and removing the outer peripheral edge of the wafer using a cutting device comprising a cutting means,
A wafer holding step of placing and holding a wafer on the holding surface of the chuck table;
After the wafer holding step, an outer peripheral edge detecting step for detecting three or more XY coordinates of the outer peripheral edge of the wafer on the holding surface;
A center position calculating step of calculating an XY coordinate of the center position of the wafer from the XY coordinates of the outer periphery detected in the outer periphery detecting step;
A positional deviation calculating step for calculating a positional deviation amount between the central position of the wafer calculated in the central position calculating step and the rotational center position of the chuck table;
After the misalignment calculating step, the center of rotation of the chuck table is positioned on an extension line of the shaft center of the spindle, and based on the misalignment amount and the rotation angle of the chuck table while rotating the chuck table, An outer peripheral edge removing step of cutting the outer peripheral edge of the wafer in the circumferential direction at substantially the same distance from the center position of the wafer while moving the cutting blade in the Y-axis direction passing through the rotation center of the chuck table; Prepared,
In the outer periphery detection step, the laser displacement meter and the chuck table are relatively moved in the X-axis direction and the Y-axis direction while irradiating the laser beam from the laser displacement meter toward the holding surface, and the laser beam is scanned. A method of processing a wafer, comprising detecting an XY coordinate of the outer periphery when the scanned trajectory intersects the outer periphery of the wafer.

Images