Cutting device and cutting method

Abstract

This invention provides a cutting apparatus and a cutting method that effectively detects foreign objects on the holding surface. In the cutting method of this invention, the height of the wafer's outer periphery is measured to calculate height distribution data, and the rate of change of the wafer's outer periphery height is calculated. Furthermore, the presence of foreign objects on the back side of the wafer, i.e., on the holding surface of the chuck table, is determined based on a comparison of the height change rate with a threshold. Therefore, the presence of foreign objects on the holding surface can be effectively detected. In addition, if foreign objects are present on the holding surface, this information is communicated to the operator, and the grinding operation is terminated. Therefore, the presence of foreign objects on the holding surface can be effectively communicated to the operator, and cutting operations can be effectively avoided when foreign objects are present on the holding surface.

Description

Technical Field

[0001] This invention relates to cutting apparatus and cutting method. Background Technology

[0002] A silicon wafer with multiple ICs, LSIs, and other devices formed on its front side is ground to a specified thickness on its back side and then divided into individual device chips by a cutting device. The resulting device chips are used in electronic devices such as mobile phones and personal computers.

[0003] When dividing the workpiece, such as a silicon wafer, into individual device chips, a cutting device is typically used. This cutting device includes a chuck stage with a holding surface that attracts and holds the workpiece, and a cutting tool (e.g., Patent Document 1). The cutting tool is, for example, a hub tool that is electrodeposited on a substrate using Ni plating.

[0004] Furthermore, in the cutting device, the workpiece is attracted and held by the chuck table, and the cutting tool performs cutting operations on the workpiece.

[0005] Patent Document 1: Japanese Patent Application Publication No. 2000-087282

[0006] Patent Document 2: Japanese Patent Application Publication No. 2000-216227

[0007] In cutting devices like those described above, when foreign objects adhere to the holding surface of the chuck table, the workpiece may sometimes break while being held on the chuck table. Therefore, currently, before holding the workpiece on the chuck table, an imaging unit is used to photograph the holding surface to check for the presence of foreign objects (e.g., Patent Document 2).

[0008] However, sometimes the foreign object is so small that it is difficult to detect even through the imaging unit. In this case, even if the workpiece is not damaged, a part of the workpiece may bulge due to the foreign object, and the machining quality may be reduced when cutting is performed in this state. Summary of the Invention

[0009] Therefore, the object of the present invention is to provide a cutting device and a cutting method that can effectively detect foreign objects on the retaining surface.

[0010] According to one aspect of the present invention, a cutting device is provided for cutting a chamfered portion of an outer periphery of a workpiece, wherein the cutting device comprises: a chuck table having a holding surface for holding the workpiece; a machining unit for machining the workpiece held by the chuck table; a height measuring unit for measuring the height of the workpiece held by the chuck table; and a controller for controlling at least the chuck table, the machining unit, and the height measuring unit of the cutting device, the controller comprising: a height distribution calculation unit that rotates the chuck table... For at least one week, the height of the workpiece is measured from a predetermined distance inward from the outer periphery using the height measurement unit, thereby calculating the height distribution data of the workpiece's outer periphery; a change rate calculation unit calculates the change rate of the height of the workpiece's outer periphery, i.e., the height change rate, based on the height distribution data calculated by the height distribution calculation unit; a determination unit determines whether there is a foreign object on the back side of the workpiece based on the comparison result of the height change rate and a threshold; and an error notification unit notifies of an error if it is determined that there is a foreign object on the back side of the workpiece.

[0011] According to another aspect of the present invention, a cutting method is provided for cutting the outer peripheral chamfer of a workpiece, wherein the cutting method comprises the following steps: a holding step, wherein the workpiece is held by a chuck table having a holding surface; a height distribution calculation step, wherein after the holding step, the height of the workpiece at a predetermined distance from the outer peripheral end to the inward side is measured while the chuck table is rotated at least one revolution, thereby calculating the height distribution data of the outer periphery of the workpiece; a rate of change calculation step, wherein the rate of change of the height of the outer periphery of the workpiece is calculated based on the height distribution data calculated in the height distribution calculation step; a determination step, wherein the presence of a foreign object on the back side of the workpiece is determined based on a comparison result of the height rate of change with a threshold; and a processing step, wherein an error is notified if the determination step determines that a foreign object is present, and cutting of the outer peripheral chamfer is performed if the determination step does not determine that a foreign object is present.

[0012] In this invention, the height of the outer periphery of the workpiece is measured to calculate height distribution data, and the height change rate of the outer periphery of the workpiece is calculated. Furthermore, based on a comparison of the height change rate with a threshold, it is determined whether foreign objects exist on the back side of the workpiece, i.e., whether foreign objects exist on the holding surface of the chuck table. Therefore, in this embodiment, it is possible to effectively detect the presence of foreign objects attached to the holding surface.

[0013] Furthermore, in this invention, the presence of foreign matter on the back side of the workpiece is communicated. Therefore, the presence of foreign matter on the holding surface can be effectively communicated to, for example, the operator. Attached Figure Description

[0014] Figure 1 This is a perspective view showing the structure of the cutting device.

[0015] Figure 2 This is a cross-sectional view showing the structure of the chuck table and height measuring unit.

[0016] Figure 3 This is a 3D diagram illustrating the steps involved in calculating the height distribution.

[0017] Figure 4 (a) and Figure 4 (b) is a cross-sectional view showing a foreign object attached to the wafer.

[0018] Figure 5 This is a graph showing an example of height distribution data when foreign matter is attached to a wafer.

[0019] Figure 6 This is a graph showing an example of height distribution data when no foreign matter is attached to the wafer.

[0020] Figure 7 This is a graph showing an example of height distribution data when foreign matter is attached to the front side of a wafer.

[0021] Figure 8 This is a graph showing an example of height distribution data when there is a foreign object on the back side of the wafer.

[0022] Label Explanation

[0023] 1: Cutting device; 2: Holding part; 7: Controller; 8: Touch panel; 9: Speaker; 10: Base; 11: X-axis moving mechanism; 12: Y-axis moving mechanism; 13: Cutting unit moving mechanism; 14: Portal column; 16: First Z-axis moving mechanism; 17: Second Z-axis moving mechanism; 18: First cutting unit; 19: Second cutting unit; 20: Chuck table; 21: Holding component; 22: Holding surface; 23: Frame; 24: Frame surface; 25: θ stage; 30: Height measuring unit; 31: Irradiation part; 32: Position adjustment part; 33: Ball screw; 34: Motor; 35: Housing; 36: Vibration part; 37: Light receiving part 40: Support arm; 71: Height distribution calculation unit; 72: Change rate calculation unit; 73: Judgment unit; 74: Error notification unit; 100: Wafer; 101: Front side; 102: Back side; 103: Device; 105: Outer peripheral chamfer; 110: Ball screw; 111: Guide rail; 112: Motor; 113: X-axis worktable; 120: First ball screw; 121: Guide rail; 122: Second ball screw; 123: First Y-axis worktable; 124: First motor; 125: Second Y-axis worktable; 160: Ball screw; 161: Guide rail; 162: Motor; 163: Support component; 181: Cutting tool; 182: Imaging unit. Detailed Implementation

[0024] Figure 1 The wafer 100 shown is an example of a workpiece and has a generally circular shape. Multiple devices 103 are formed on the front side 101 of the wafer 100. The back side 102 of the wafer 100 is the surface to be ground using a grinding tool or the like.

[0025] In addition, such as Figure 2 As shown, the outer periphery of the wafer 100 is chamfered, forming a chamfered portion 105 with an arc-shaped cross-section. Furthermore, Figure 1 The cutting device 1 shown cuts (edge ​​trimming) the outer peripheral chamfer 105 of such a wafer 100.

[0026] The cutting device 1 is referred to as a dual-axis cutting machine. The cutting device 1 includes: a base 10; a portal column 14 erected on the base 10; and a controller 7 for controlling the various components of the cutting device 1.

[0027] An X-axis moving mechanism 11 is provided on the base 10. The X-axis moving mechanism 11 moves the chuck table 20 along the cutting feed direction (X-axis direction). The X-axis moving mechanism 11 includes: a pair of guide rails 111 extending along the X-axis direction; an X-axis table 113 mounted on the guide rails 111; a ball screw 110 extending parallel to the guide rails 111; and a motor 112 that rotates the ball screw 110.

[0028] A pair of guide rails 111 are arranged parallel to the X-axis direction on the upper surface of the base 10. The X-axis worktable 113 is mounted on the pair of guide rails 111 in a manner that allows it to slide along these guide rails 111. A holding part 2, including a chuck worktable 20, is mounted on the X-axis worktable 113.

[0029] The ball screw 110 is screwed into a nut (not shown) provided on the X-axis worktable 113. The motor 112 is connected to one end of the ball screw 110, driving the ball screw 110 to rotate. Driven by the rotation of the ball screw 110, the X-axis worktable 113 and the holding part 2 move along the guide rail 111 in the X-axis direction.

[0030] The holding part 2 includes: a chuck stage 20 having a holding surface 22 for holding the wafer 100; and a θ stage 25, which is a rotating shaft that supports the chuck stage 20 and rotates.

[0031] like Figure 2 As shown, the chuck stage 20 has a generally circular frame 23, and a holding member 21 made of a porous material such as porous ceramic is provided in a recess of the frame 23. The upper surface of the holding member 21 serves as a holding surface 22 for attracting and holding the wafer 100. In the chuck stage 20, the holding member 21 is in communication with an attraction source (not shown), thereby enabling the wafer 100 to be attracted and held through the holding surface 22.

[0032] like Figure 1 As shown, the chuck table 20 is supported on an θ-stage 25, which is disposed on the bottom side of the chuck table 20. The θ-stage 25 is mounted on the upper surface of the X-axis table 113 in a manner that allows it to rotate in the XY plane. Therefore, the θ-stage 25 can support the chuck table 20 and enable the chuck table 20 to rotate in the XY plane.

[0033] A portal column 14 is erected on the rear side (-X direction side) of the base 10 in a manner that allows it to move across the X-axis direction via a mechanism 11.

[0034] A cutting unit moving mechanism 13 is provided on the front surface (the surface on the +X direction side) of the portal column 14 to move the first cutting unit 18 and the second cutting unit 19. The cutting unit moving mechanism 13 performs indexing feed of the first cutting unit 18 and the second cutting unit 19 in the Y-axis direction and cutting feed in the Z-axis direction.

[0035] The cutting unit moving mechanism 13 includes: a first Z-axis moving mechanism 16 that moves the first cutting unit 18 on the +Y direction side in the Z-axis direction, a second Z-axis moving mechanism 17 that moves the second cutting unit 19 on the -Y direction side in the Z-axis direction, and a Y-axis moving mechanism 12 that moves the first cutting unit 18 and the second cutting unit 19 in the Y-axis direction.

[0036] Y-axis moving mechanism 12 is disposed on the front surface of portal column 14. Y-axis moving mechanism 12 causes first Z-axis moving mechanism 16, which includes first cutting unit 18, and second Z-axis moving mechanism 17, which includes second cutting unit 19, to reciprocate along the Y-axis direction.

[0037] The Y-axis moving mechanism 12 includes: a pair of guide rails 121 extending along the Y-axis direction, a first Y-axis worktable 123 and a second Y-axis worktable 125 mounted on the guide rails 121, a first ball screw 120 and a second ball screw 122 extending parallel to the guide rails 121, a first motor 124 that rotates the first ball screw 120, and a second motor (not shown) that rotates the second ball screw 122.

[0038] A pair of guide rails 121 are arranged parallel to the Y-axis direction on the front surface of the portal column 14. A first Y-axis worktable 123 and a second Y-axis worktable 125 are mounted on the pair of guide rails 121 in a manner that allows them to slide along these guide rails 121. A first Z-axis direction moving mechanism 16 and a first cutting unit 18 are mounted on the first Y-axis worktable 123. A second Z-axis direction moving mechanism 17 and a second cutting unit 19 are mounted on the second Y-axis worktable 125.

[0039] The first ball screw 120 is screwed into a nut portion (not shown) disposed on the first Y-axis worktable 123. The first motor 124 is connected to one end of the first ball screw 120, thereby driving the first ball screw 120 to rotate. Driven by the rotation of the first ball screw 120, the first Y-axis worktable 123, the first Z-axis moving mechanism 16, and the first cutting unit 18 move along the guide rail 121 in the Y-axis direction.

[0040] Similarly, the second ball screw 122 is screwed into the nut portion (not shown) of the second Y-axis worktable 125 and is driven to rotate by a second motor connected to one end of the second ball screw 122. As a result, the second Y-axis worktable 125, the second Z-axis moving mechanism 17, and the second cutting unit 19 move along the guide rail 121 in the Y-axis direction.

[0041] The first Z-axis moving mechanism 16 causes the first cutting unit 18 to reciprocate in the Z-axis direction. The first Z-axis moving mechanism 16 includes: a pair of guide rails 161 extending along the Z-axis direction, a support member 163 disposed on the guide rails 161, a ball screw 160 extending parallel to the guide rails 161, and a motor 162 that rotates the ball screw 160.

[0042] A pair of guide rails 161 are arranged parallel to the Z-axis direction on the first Y-axis worktable 123. A support member 163 is mounted on the pair of guide rails 161 in a manner that allows it to slide along these guide rails 161. A first cutting unit 18 is mounted on the lower end of the support member 163.

[0043] The ball screw 160 is screwed into a nut portion (not shown) provided on the support member 163. The motor 162 is connected to one end of the ball screw 160, driving the ball screw 160 to rotate. Driven by the rotation of the ball screw 160, the support member 163 and the first cutting unit 18 move along the guide rail 161 in the Z-axis direction.

[0044] The second Z-axis moving mechanism 17 also causes the second cutting unit 19 to reciprocate in the Z-axis direction. The second Z-axis moving mechanism 17 has the same structure as the first Z-axis moving mechanism 16, so its description is omitted.

[0045] The first cutting unit 18 and the second cutting unit 19 are examples of processing units that process the wafer 100 held by the chuck stage 20. The first cutting unit 18 cuts the wafer 100 held by the chuck stage 20 and includes a cutting tool 181 and an imaging unit 182. The imaging unit 182 images the wafer 100 held by the holding surface 22 of the chuck stage 20 and detects the outer peripheral chamfer 105, which is the cutting part of the wafer 100. The cutting tool 181 is used to cut the outer peripheral chamfer 105 of the wafer 100.

[0046] The second cutting unit 19 also cuts the wafer 100 held by the chuck stage 20 in the same way as the first cutting unit 18. The second cutting unit 19 has the same structure as the first cutting unit 18, so its description is omitted.

[0047] Additionally, a height measuring unit 30 is mounted on the lower end of the support member 163 in the first Z-axis moving mechanism 16 and the second Z-axis moving mechanism 17 via a support arm 40.

[0048] The height measuring unit 30 is configured to be adjacent to the first cutting unit 18 and the second cutting unit 19. The height measuring unit 30 is capable of moving together with the first cutting unit 18 and the second cutting unit 19 in the Y-axis and Z-axis directions via a cutting unit moving mechanism 13 that includes a Y-axis moving mechanism 12, a first Z-axis moving mechanism 16, and a second Z-axis moving mechanism 17.

[0049] Furthermore, the height measuring unit 30 is configured to measure the height of the wafer 100 held by the chuck stage 20. Specifically, for example, Figure 2 As shown, the height measuring unit 30 includes: an irradiation section 31 disposed within the housing 35 to irradiate a laser L; a position adjustment section 32 to adjust the position of the irradiation section 31 along the Y-axis; an oscillation section 36 to control the irradiation of the laser L from the irradiation section 31; and a light receiving section 37 to receive the reflected light of the laser L.

[0050] The position adjustment unit 32 includes a ball screw 33 extending along the Y-axis direction and a motor 34 for rotating the ball screw 33. The ball screw 33 is screwed into a nut (not shown) provided on the irradiation unit 31. The irradiation unit 31 moves in the Y-axis direction by rotating the ball screw 33 driven by the motor 34.

[0051] For example, Figure 2 As shown, the height measuring unit 30, with such a structure, irradiates laser L from the irradiation unit 31 onto the vicinity of the outer peripheral chamfer 105 of the wafer 100 held by the holding surface 22 of the chuck stage 20 and onto the frame surface 24, which is the upper surface of the frame 23. Furthermore, the height measuring unit 30 can measure the height of the frame surface 24 and the height near the outer peripheral chamfer 105 of the wafer 100, i.e., the height of the wafer 100 at a predetermined distance inward from its outer peripheral end (outer edge of the outer peripheral chamfer 105), based on the reflected light from laser L.

[0052] In addition, such as Figure 1 As shown, the cutting device 1 has a touch panel 8 mounted on a housing (not shown). Various information related to the cutting device 1 is displayed on the touch panel 8. Additionally, the touch panel 8 is used to set various information. Thus, the touch panel 8 functions as a display component for displaying information and also as an input component for inputting information.

[0053] Additionally, a speaker 9 is located near the touch panel 8 to transmit information to the operator via sound.

[0054] In addition, a controller 7 is provided in the cutting device 1. The controller 7 has a CPU that performs calculations according to the control program and a storage medium such as a memory. The controller 7 performs various processes and controls the various components of the cutting device 1.

[0055] In addition, the controller 7 has a height distribution calculation unit 71, a change rate calculation unit 72, a determination unit 73 and an error notification unit 74. The controller 7 uses these to detect foreign objects on the front side of the wafer 100 while grinding the wafer 100.

[0056] The following describes a cutting method for the wafer 100 controlled by the controller 7. This cutting method is a cutting method for cutting the outer peripheral chamfer 105 of the wafer 100.

[0057] (1) Maintaining steps

[0058] In this step, the wafer 100 is held by the chuck stage 20 having the holding surface 22. Specifically, in this step, an operator or a transfer device (not shown) places the wafer 100 onto the holding surface 22 in the chuck stage 20 of the holding section 2. Furthermore, the controller 7 controls an attraction source (not shown) to transmit an attraction force to the holding surface 22. Thus, the wafer 100 is attracted and held by the holding surface 22.

[0059] (2) Steps for calculating height distribution

[0060] Next, controller 7 controls the X-axis moving mechanism 11, the cutting unit moving mechanism 13, and the θ-stage 25, such as... Figure 3 As shown, the position of the height measuring unit 30 is set such that the laser L from the height measuring unit 30 irradiates the outer peripheral chamfer 105 of the wafer 100 and its vicinity.

[0061] Then, while controlling the θ stage 25 to rotate the chuck stage 20 at least one revolution, the height distribution calculation unit 71 of the controller 7 uses the height measurement unit 30 to measure the height of the wafer 100 at a predetermined distance from the outer periphery to the inward side along the outer periphery of the wafer 100, and uses this height as the height of the outer periphery of the wafer 100. Thus, the height distribution calculation unit 71 calculates the height distribution data of the outer periphery of the wafer 100. This height distribution data shows the distribution of the height of the wafer 100 along its outer periphery.

[0062] Here, an example illustrating the relationship between foreign matter attached to the wafer 100 and its height distribution data is given. For example... Figure 4 As shown in (a), when the foreign object F is attached to a portion of the front surface 101 of the outer periphery of the wafer 100, the measured height Ta of the outer periphery of the wafer 100 only increases in the portion where the foreign object F is attached. Therefore, the height distribution data calculated by the height distribution calculation unit 71 is also as shown in (a). Figure 5 As shown in the curve (a), it only increases locally at and near the measurement point corresponding to the foreign object F.

[0063] On the other hand, such as Figure 4 As shown in (b), when the foreign object F is attached to a portion of the back surface 102 of the outer periphery of the wafer 100, that is, when the foreign object is present on the holding surface 22 of the chuck stage 20, the measured height Tb of the outer periphery of the wafer 100 gradually increases towards the portion where the foreign object F is attached. Therefore, the height distribution data calculated by the height distribution calculation unit 71 is also as follows. Figure 5 As shown in graph (b), the curve gradually increases towards the measurement point corresponding to the foreign object F.

[0064] (3) Steps for calculating the rate of change

[0065] Next, the change rate calculation unit 72 of the controller 7 calculates the change rate of the height of the outer periphery of the wafer 100, i.e., the height change rate, based on the height distribution data calculated by the height distribution calculation unit 71 in the height distribution calculation step.

[0066] At this time, the change rate calculation unit 72 obtains the height of multiple measurement points on the outer periphery of the wafer 100 based on the height distribution data. Furthermore, the change rate calculation unit 72 calculates the height change rate, for example, using the following equation (1).

[0067] Rate of change of height = ((change in height) / (distance between measurement points)) × 100%...(1)

[0068] Here, the change in height refers, for example, "the difference in height measured between measurement points". Additionally, the distance between measurement points is, for example, "the distance between measurement points along the outer perimeter of the wafer 100".

[0069] For example, four measurement points A to D are arranged sequentially on the outer periphery of the wafer 100. Furthermore, the positions of measurement points A to D on the outer periphery of the wafer 100 are r, respectively. A r B r c r D The heights measured at measurement points A through D are H, respectively. A H B H c H D .

[0070] In this case, the height change rate between AB, BC, and CD is calculated using the change in height between AB (H). B -H A ), the change in height between B and C (H) C -H B The change in height between CDs (H) D -H C ) and the distance between A and B (r) B -rA ), the distance between B and C (r) C -r B The distance between CD and r D -r C The calculations are as follows.

[0071] The rate of change of height between A and B = ((H) B -H A ) / (r B -r A ))×100%

[0072] Rate of change of height between B and C = ((H) C -H B ) / (r C -r B ))×100%

[0073] The rate of change in height between CDs = ((H) D -H C ) / (r D -r C ))×100%

[0074] (4) Judgment Steps

[0075] Next, the determination unit 73 of the controller 7 determines whether there is a foreign object on the back side 102 of the wafer 100 based on the comparison result of the height change rate calculated by the change rate calculation unit 72 and the predetermined threshold.

[0076] In this embodiment, the determination unit 73 sets a relatively small first threshold and a relatively large second threshold. The determination unit 73 uses these two thresholds to determine whether there is no foreign matter attached to the wafer 100, whether there is foreign matter attached to the front side 101 of the wafer 100, or whether there is foreign matter attached to the back side 102 of the wafer 100.

[0077] The following example uses the four measurement points A to D to illustrate the determination example of the determination unit 73. If no foreign matter is attached to the wafer 100, such as... Figure 6 As shown, the height H was measured at four measurement points A to D. A H B H c H D In essence, they are the same value. Therefore, in this case, the maximum values ​​of the height change rates between AB, BC, and CD are very small, less than the relatively small first threshold. Therefore, when the maximum value of the height change rate calculated by the change rate calculation unit 72 is less than the first threshold, the determination unit 73 determines that no foreign matter is attached to the wafer 100.

[0078] Additionally, suppose a foreign object is attached near the measurement point D on the front side 101 of the wafer 100. In this case, if using... Figure 4 and Figure 5 As explained, the height of the outer periphery of the wafer 100 locally increases near the presence of foreign matter. Therefore, in this case, as... Figure 7 As shown, the measured height of the outer periphery of the wafer 100 locally increases at measurement point D and its nearby measurement point C, while decreasing at measurement points A and B, which are far from measurement point D. Therefore, the maximum values ​​of the height change rates between A and B, between B and C, and between C and D are greater than a relatively large second threshold. Therefore, if the maximum value of the height change rate calculated by the change rate calculation unit 72 is greater than the second threshold, the determination unit 73 determines that a foreign object is attached to the front surface 101 of the wafer 100.

[0079] Additionally, suppose a foreign object is attached near the measurement point D on the back surface 102 of the wafer 100. In this case, if using... Figure 4 and Figure 5 As explained, the height of the outer periphery of the wafer 100 gradually increases toward the portion where the foreign matter is attached. Therefore, in this case, as... Figure 8 As shown, the measured height of the outer periphery of the wafer 100 increases gradually towards the measurement point D. Therefore, the maximum values ​​of the height change rates between AB, BC, and CD are greater than a first threshold and less than a second threshold. Therefore, if the maximum value of the height change rate calculated by the change rate calculation unit 72 is greater than the first threshold and less than the second threshold, the determination unit 73 determines that there is a foreign object on the back surface 102 of the wafer 100 (i.e., there is a foreign object on the holding surface 22 of the chuck stage 20).

[0080] (5) Processing steps

[0081] Next, the error notification unit 74 of the controller 7 controls the error notification based on the determination result of the determination unit 73. For example, if the determination unit 73 determines that there is a foreign object on the back surface 102 of the chip 100, the error notification unit 74 notifies the operator of an error. That is, the error notification unit 74 uses... Figure 1 The speaker 9 notifies the operator of the presence of a foreign object on the back surface 102 of the wafer 100 via sound (e.g., an alarm), and also provides notification via text and / or images using the touch panel 8. Furthermore, the controller 7, for example, terminates the cutting method on the wafer 100.

[0082] On the other hand, if the determination unit 73 determines that no foreign matter is attached to the wafer 100, the error notification unit 74, for example, does not issue an error notification. Furthermore, in this case, the controller 7 controls the aforementioned structural components in the cutting device 1 to perform cutting of the outer peripheral chamfer 105 of the wafer 100. That is, the controller 7 rotates the chuck table 20 via the θ stage 25 while the rotating cutting tool 181 in the first cutting unit 18 or the second cutting unit 19 cuts the outer peripheral chamfer 105 of the wafer 100 circumferentially.

[0083] Furthermore, if the determination unit 73 determines that there is a foreign object attached to the front surface 101 of the wafer 100, the error notification unit 74 notifies the operator of this information, for example, using the touch panel 8. Also, the controller 7 controls each structural component of the cutting device 1, for example, in the same manner as when there is no foreign object attached to the wafer 100, to perform cutting on the outer peripheral chamfer 105 of the wafer 100.

[0084] As described above, in this embodiment, the height of the outer periphery of the wafer 100 is measured to calculate height distribution data, and the height change rate of the outer periphery of the wafer 100 is calculated. Furthermore, based on the comparison result of the height change rate and a threshold, it is determined whether there are foreign objects on the back surface 102 of the wafer 100, i.e., whether there are foreign objects on the holding surface 22 of the chuck stage 20. Therefore, in this embodiment, it is possible to effectively detect situations where foreign objects are attached to the holding surface 22.

[0085] Furthermore, in this embodiment, if a foreign object is present on the back surface 102 of the wafer 100, a notification component including a touch panel 8 and a speaker 9 is used to notify the operator. Therefore, this embodiment can effectively communicate to the operator the situation where a foreign object is attached to the holding surface 22. Additionally, in this embodiment, the controller 7 terminates the grinding operation in this situation. Therefore, it is possible to effectively avoid performing cutting operations while a foreign object is attached to the holding surface 22.

[0086] Furthermore, in this embodiment, the determination unit 73 uses two thresholds, including a first threshold and a second threshold, to determine whether there is no foreign matter attached to the wafer 100, whether there is foreign matter attached to the front side 101 of the wafer 100, or whether there is foreign matter attached to the back side 102 of the wafer 100. Therefore, in this embodiment, in addition to determining whether there is foreign matter attached to the wafer 100, it is also possible to determine the location (front side 101 or back side 102) where foreign matter is attached.

[0087] Furthermore, the determination unit 73 can be configured to use a threshold to determine whether there is a foreign object attached to the back surface 102 of the wafer 100. In this case, the determination unit 73 can be configured to determine that there is a foreign object on the back surface 102 of the wafer 100 if the maximum value of the height change rate calculated by the change rate calculation unit 72 is greater than the threshold, and on the other hand, to determine that there is no foreign object on the back surface 102 of the wafer 100 if the maximum value of the height change rate is less than the threshold.

[0088] Furthermore, the change rate calculation unit 72 can be configured to extract data on local height variations (measurement points and measured heights) from the height distribution data during the change rate calculation step, and use the extracted data and data before and after it to calculate the thickness change rate. In this configuration, the thickness change rate can be calculated focusing on the portion of the wafer 100 where foreign matter is believed to be attached. Therefore, the thickness change rate useful for determining the attachment of foreign matter to the wafer 100 can be calculated effectively.

Claims

1. A cutting device for cutting the outer peripheral chamfer of a workpiece, wherein, The cutting device has the following features: A chuck table having a holding surface for holding the workpiece; A processing unit that processes the workpiece held by the chuck table; A height measuring unit that measures the height of the workpiece held by the chuck table; and The controller controls at least the chuck table, the machining unit, and the height measuring unit of the cutting device. The controller contains: The height distribution calculation unit rotates the chuck table at least one revolution while measuring the height of the workpiece at a predetermined distance from the outer periphery end to the inward side via the height measurement unit, thereby calculating the height distribution data of the workpiece's outer periphery. The change rate calculation unit calculates the change rate of the height of the outer periphery of the workpiece, i.e., the height change rate, based on the height distribution data calculated by the height distribution calculation unit. The determination unit determines whether there are foreign objects on the back side of the workpiece based on a comparison between the height change rate and a threshold; and The error notification unit notifies an error when it determines that there is a foreign object on the back of the workpiece.

2. A cutting method for cutting the outer peripheral chamfer of a workpiece, wherein, The cutting method has the following steps: The workpiece is held in place by a chuck table with a holding surface. The height distribution calculation step involves, after the holding step, rotating the chuck table at least one revolution while measuring the height of the workpiece at a specified distance from the outer periphery to the inside, thereby calculating the height distribution data of the workpiece's outer periphery. The change rate calculation step calculates the change rate of the outer perimeter height of the workpiece, i.e., the height change rate, based on the height distribution data calculated in the height distribution calculation step. The determination step involves comparing the height change rate with a threshold to determine whether there are foreign objects on the back side of the workpiece; and The processing steps are as follows: if the determination step determines that a foreign object is present, an error is notified; if the determination step does not determine that a foreign object is present, the outer peripheral chamfer is cut.

Images