WORKPIECE CUTTING PROCESS

Abstract

A workpiece cutting method for cutting a workpiece having an upper surface and a lower surface, comprising: a tape attaching step of attaching a tape to the bottom surface of the workpiece; a holding step of holding the lower surface of the workpiece by the belt on a holding table including a holding plate, the holding plate having a holding surface for holding the workpiece, at least a part of the holding surface being an image area formed of a material transparent to visible light; a machining step of cutting the workpiece held on the holding table to divide the workpiece, thereby forming a dividing groove having a depth reaching the tape; an image capturing step of capturing at least a part of the dividing groove from the upper surface side of the workpiece using an upper camera portion located above the holding plate, thereby obtaining an upper image, and also capturing the part of the dividing groove from the lower surface side of the workpiece through the image area of ​​the holding plate and the belt using a lower camera portion located below the holding plate, thereby obtaining a lower image, and an image comparison step for comparing the upper image and the lower image obtained in the image acquisition step wherein the image comparing step includes a step of comparing at least a difference in width between the dividing groove on the upper image or the dividing groove on the lower image and a deviation in position between the dividing groove on the upper image and the dividing groove on the lower image with a previously set allowable condition, wherein the workpiece cutting method further comprises: a warning step for issuing a warning in a case that at least one of the width difference and the position deviation does not satisfy the allowed condition.

Description

BACKGROUND OF THE INVENTIONTechnical field

[0001] The present invention relates to a workpiece cutting method for cutting a workpiece to divide it into a plurality of chips. Description of the state of the art

[0002] Conventionally, a cutting device is known that includes an annular cutting blade for cutting a plate-shaped workpiece such as a semiconductor wafer. When cutting the workpiece, the cutting blade is rotated at high speed and then fed into the workpiece. At the same time, the cutting blade and the workpiece are moved relative to each other, thereby cutting the workpiece along a path of this relative movement. A plurality of intersecting dividing lines are preliminarily set on the workpiece. When performing a gap inspection, the workpiece is cut along a predetermined number of dividing lines to form a dividing groove (gap) in the workpiece along each dividing line. Afterward, the position and shape of these dividing grooves are inspected.Typically, a gap inspection is performed using a camera or the like positioned above the workpiece to capture the workpiece's upper surface and thereby obtain an image of the parting groove. Then, based on this image, it is checked whether the workpiece has been properly cut along each parting line, or whether the size of the chipping that has occurred in the parting line or the gap width is less than or equal to an allowable value (see Japanese Patent Application Laid-Open No. 2009-246015 A and Japanese Patent Application Laid-Open No. 2013-74198 A).

[0003] JP 2012-256749 A relates to a cutting device.

[0004] US 2010 / 0181681 A1 relates to the structure of semiconductor components and a manufacturing method for semiconductor components. PRESENTATION OF THE INVENTION

[0005] The workpiece is cut using the cutting device to obtain a plurality of chips. If chipping with a size larger than an allowable value occurs on the upper surface of a chip, that chip is treated as a defective chip. However, if chipping with a size larger than an allowable value occurs on the lower surface of a chip, that chip is also treated as a defective chip. Furthermore, if the parting line is inclined with respect to the direction along the thickness of the workpiece (i.e., an oblique cut) or if the position of the parting groove deviates from the position of the parting line, defective chips may be produced. In a normal joint inspection, only the upper surface of the workpiece is inspected. Accordingly, if the lower surface of the workpiece is defective, there is a high probability that defective chips may be produced.

[0006] It is therefore an object of the present invention to provide a workpiece cutting method which can prevent the production of defective chips or reduce the possibility of producing a large amount of defective chips.

[0007] In accordance with one aspect of the present invention, there is provided a workpiece cutting method for cutting a workpiece having an upper surface and a lower surface, including an attaching step of attaching a tape to the lower surface of the workpiece; a holding step of holding the lower surface of the workpiece by the tape on a holding table including a holding plate, the holding plate having a holding surface for holding the workpiece, at least a part of the holding surface being an image area formed of a material transparent to visible light; a machining step of cutting the workpiece held on the holding table to divide the workpiece, thereby forming a dividing groove having a depth reaching the tape;and an image capturing step of capturing at least a part of the dividing groove from the upper surface side of the workpiece using an upper camera portion located above the holding plate, thereby obtaining an upper image, and also capturing the part of the dividing groove from the lower surface side of the workpiece through the imaging portion of the holding plate and the belt using a lower camera portion located below the holding plate, thereby obtaining a lower image.;

[0008] Preferably, the workpiece cutting method further includes an image comparing step of comparing the upper image and the lower image obtained in the image capturing step.

[0009] Preferably, the image comparison step includes a step of comparing at least a difference in width between the dividing groove in the upper image and the dividing groove in the lower image and a deviation in position between the dividing groove on the upper surface and the dividing groove in the lower image with a permitted condition set in advance. The workpiece cutting method further includes a warning step of issuing a warning in a case where at least one of the difference in width and the deviation in position does not satisfy the permitted condition.

[0010] In the image capturing step of the workpiece cutting method according to the present invention, the division groove is imaged from the upper surface side of the workpiece by the upper camera portion located above the holding plate, thereby obtaining an upper image. At the same time, the division groove is imaged from the lower surface side of the workpiece by the lower camera portion located below the holding plate, thereby obtaining the lower image. Accordingly, when the upper end of the division groove is inspected, the lower end of the division groove can also be inspected, so that not only defective machining on the upper surface of the workpiece but also defective machining on the lower surface of the workpiece can be detected. If defective machining has occurred on the lower surface of the workpiece, the defective machining can be eliminated by any means.Accordingly, compared to the case where joint inspection is not performed on the lower surface of the workpiece, but only on the upper surface of the workpiece, the production of defective chips can be prevented. If defective chips are produced, it is possible to reduce the possibility of producing a large number of defective chips.

[0011] The above and other features, objects and advantages of the present invention and the mode of carrying them out will become clearer and the invention itself best understood by studying the following description and appended claims with reference to the appended figures which show a preferred embodiment of the invention. SHORT DESCRIPTION OF THE CHARACTERS Fig. 1A is a perspective view of a workpiece; Fig. 1B is a perspective view of a workpiece unit; Fig. 2 is a perspective view of a cutting device; Fig. 3 is a perspective view of a chuck table supported on a support member; Fig. 4 is a plan view of a holding plate; Fig. 5 is a perspective view of the lower image pickup unit; Fig. 6A is a side sectional view, partly in cross section, illustrating a holding step for holding the workpiece on the chuck table; Fig. 6B is a partial cross-sectional side view illustrating a cutting step for cutting the workpiece held on the holding surface using a cutting blade; Fig. 7 is a partial cross-sectional side view illustrating an image capturing step for capturing the upper surface and the lower surface of the workpiece; Fig. 8A is a plan view illustrating an example of an upper image obtained in the image pickup step; Fig. 8B is a plan view illustrating an example of a lower image obtained in the image pickup step; Fig. Figure 8C is a schematic sectional view of a workpiece in a region corresponding to that shown in Fig. 8A and Fig. 8B; Fig. 9A is a plan view showing another example of the above image; Fig. 9B is a top view showing another example of the lower image; Fig. Figure 9C is a schematic sectional view of the workpiece in a region corresponding to that shown in Fig. 9A and 9B are shown; and Fig. 10 is a flowchart illustrating the workpiece cutting method according to a preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0012] A preferred embodiment of the present invention will now be described with reference to the attached figures. A workpiece 11 is first described. Fig. 1A is a perspective view of the workpiece 11. The workpiece 11 is a circular, plate-shaped semiconductor wafer (disk-shaped). The workpiece 11 has a front surface 11a and a back surface 11b opposite the front surface 11a. A plurality of intersecting dividing lines (streets) 13 are set on one side of the front surface 11a of the workpiece 11 to define a plurality of separated regions on which a plurality of devices 15 are respectively formed. The intersecting dividing lines 13 are formed from a plurality of parallel dividing lines extending in a first direction and a plurality of parallel dividing lines extending in a second direction perpendicular to the first direction.

[0013] The workpiece 11 is not limited in terms of material, shape, structure, size, etc. While the workpiece 11 is formed from a semiconductor such as silicon in the preferred embodiment, the workpiece 11 may be formed from any other semiconductor such as gallium arsenide (GaAs) and silicon carbide (SiC). Furthermore, the workpiece 11 may also be formed from a dielectric, metal oxide such as LiTaO3 and LiNbO3, glass, or a ceramic, for example. Furthermore, the workpiece 11 may be a semiconductor package substrate having a plastic molded layer. The components 15 formed on the workpiece 11 are also not limited in their type, number, shape, structure, size, arrangement, etc. Furthermore, the components 15 do not have to be formed on the workpiece 11.

[0014] A ring frame 17 having a circular opening 17a is arranged around the workpiece 11. The circular opening 17a has a larger diameter than the workpiece 11. The ring frame 17 is made of metal. The workpiece 11 lies in the circular opening 17a of the ring frame 17. A circular band 19 is attached to the workpiece 11 and the ring frame 17. The circular band 19 has a larger diameter than that of the circular opening 17a of the ring frame 17. The ring frame 17 has a first surface 17b (lower surface as in Fig. 1B) and a second surface 17c (upper surface as shown in Fig. 1B). The circular belt 19 is attached to the rear surface 11b of the workpiece 11 and the first surface 17b of the ring frame 17. The belt 19 is a plastic film having a layered structure formed of a base layer (not shown) and an adhesion-promoting layer (not shown) formed on the base layer. The base layer is a non-adherent plastic layer, and the adhesion-promoting layer is, for example, an ultraviolet-curing plastic layer. The adhesion-promoting layer is formed on the entire one side surface of the base layer. Consequently, the workpiece 11 and the ring frame 17 are bonded by the belt 19, thereby forming a workpiece unit 21 formed in Fig. 1B is shown. Fig. 1B is a perspective view of the workpiece unit 21. The ring frame 17 is not essential. In the case where the ring frame 17 is not used, the belt 19 has a diameter equal to that of the workpiece 11, and the belt 19 is attached to one side of the rear surface 11b of the workpiece 11, thereby forming the workpiece unit 21, with the ring frame 17 omitted.

[0015] The workpiece 11 is machined using a cutting device 2 which is Fig. 2 is shown. Fig. Figure 2 is a perspective view of the cutting device 2. The cutting device 2 has a stationary base 4 formed of a metal such as stainless steel. A pair of guide rails 14 are provided on the stationary base 4 so as to extend in the X direction indicated by an arrow X in Fig. 2. A ball screw 8 is provided between the pair of guide rails 14 so as to extend in the X direction. A pulse motor 10 for rotating the ball screw 8 is connected to one end of the ball screw 8. An X-moving plate 6 is provided above the ball screw 8 so as to be slidably attached to the pair of guide rails 14. The X-moving plate 6 is formed of a metal such as stainless steel. A nut portion (not shown) is formed on the lower surface of the X-moving plate 6 so as to be in screw engagement with the ball screw 8. The ball screw 8 and the pulse motor 10 constitute an X-moving mechanism 12. Accordingly, when the ball screw 8 is rotated by the pulse motor 10, the X-moving plate 6 is moved in the X direction along the pair of guide rails 14.

[0016] A linear scale 14a is provided on the upper surface of the stationary base 4 so as to extend along the guide rails 14. A reading head (not shown) for reading the mark on the linear scale 14a is provided on the lower surface of the X-movable plate 6. The linear scale 14a and this reading head constitute a detection unit 14b for detecting a feed amount as the amount of movement of the workpiece 11 in the X direction. A pair of guide rails 24 are provided on the upper surface of the X-movable plate 6 so as to extend in the Y direction indicated by an arrow Y in Fig. 2. A ball screw 18 is provided between the pair of guide rails 24 so as to extend in the Y direction. A pulse motor 20 for rotating the ball screw 18 is connected to one end of the ball screw 18. A support member 16 is provided above the ball screw 18 so as to be slidably attached to the pair of guide rails 24. The support member 16 is formed of a metal such as stainless steel. A nut portion (not shown) is formed on the lower surface of the support member 16 so as to be in screw engagement with the ball screw 18. The ball screw 18 and the pulse motor 20 constitute a Y-movement mechanism 22. Accordingly, when the ball screw 18 is rotated by the pulse motor 20, the support member 16 is moved in the Y direction along the pair of guide rails 24.

[0017] A linear scale 24a is provided on the upper surface of the X-movable plate 6 so as to extend along the guide rails 24. A reading head (not shown) for reading the mark of the linear scale 24a is provided on the lower surface of the support member 16. The linear scale 24a and this reading head form a detection unit 24b for detecting an index amount as the movement amount of the workpiece 11 in the Y direction. As shown in Fig. 3, the support member 16 includes a lower plate 16a adapted to be fixed to the guide rails 24, an upper plate 16b provided above the lower plate 16a so as to be opposite thereto, and a connecting plate 16c for connecting one end of the lower plate 16a and one end of the upper plate 16b. The upper plate 16b has a circular opening (not shown), and a substantially cylindrical chuck table (holding table) 28 is rotatably mounted in this circular opening of the upper plate 16b. Fig. 3 is a perspective view of the chuck table 28 supported on the support member 16. An upper portion of the chuck table 28 projects upward from the upper plate 16b.

[0018] Several clamping mechanisms 56 (see Fig. 6A and Fig. 6B) are provided on the cylindrical surface of the upper portion of the clamping table 28 at a predetermined vertical position. These multiple clamping mechanisms 56 are located at different positions in the circumferential direction of the clamping table 28. In Fig. 3, the plurality of clamping mechanisms 56 are not shown. Each clamping mechanism 56 serves to fix the ring frame 17 of the workpiece unit 21 placed on the chuck table 28 by holding a part of the ring frame 17. A belt 30 for rotating the chuck table 28 is wound around the cylindrical surface of the upper portion of the chuck table 28 in a region between the clamping mechanism 56 and the upper plate 16b in the vertical direction of the chuck table 28 (in the Z direction indicated by an arrow Z in Fig. 3). That is, this area of ​​the upper section of the clamping table 28 is a belt winding section.

[0019] A motor 32 having a shaft is fixed to the connecting plate 16c of the support member 16, and a pulley 34 is connected to the shaft of the motor 32. The belt 30 is wound around the pulley 34 and the belt winding portion of the chuck table 28. Accordingly, when the motor 32 is actuated, the chuck table 28 is rotated by the belt 30. The motor 32 is, for example, a pulse motor. When performing alignment, the motor 32 is actuated a predetermined number of pulses, and the chuck table 28 is rotated about its vertical axis by a predetermined angle θ. Accordingly, the dividing lines 13 extending in the first direction are aligned parallel to the X direction.

[0020] A circular holding plate 54 is provided on the upper surface of the chuck table 28. The holding plate 54 is made of a transparent material (silica glass) that is transparent to visible light. The holding plate 54 has an upper surface as a holding surface 54a for holding the workpiece 11. A plurality of fine holes (not shown) are formed on the entire holding surface 54a of the holding plate 54. Each fine hole is connected to a suction passage (not shown) formed in the holding plate 54. Each suction passage is connected to a vacuum source (not shown). Accordingly, when the workpiece 11 of the workpiece unit 21 is placed on the holding plate 54 by the belt 19 and the vacuum source is actuated, the workpiece 11 is held under suction on the holding surface 54a of the holding plate 54.In the case that the rear surface 11b side of the workpiece 11 is held on the chuck table 28, the rear surface 11b of the workpiece 11 becomes a lower surface of the workpiece 11 and the front surface 11a of the workpiece 11 becomes a surface of the workpiece 11.

[0021] The structure of the holding plate 54 will now be described with reference to Fig. 4 described. Fig. 4 is a plan view of the holding plate 54. The holding plate 54 has a suction passage, excluding a region 54b where no suction passage is formed. The region 54b without a suction passage has a cross shape in a plan view, so that the holding plate 54 is divided into four section regions, each having a central angle of 90°. Each section region is a suction passage, which includes a region 54c where a plurality of suction passages are formed. In each region 54c including a suction passage, the suction passages are arranged in rows and columns like a grid over the entire surface.

[0022] Each suction passage extends through the thickness of the holding plate 54 at a predetermined position near a curved circumferential portion of each suction passage-including region 54c and reaches the rear side of the holding plate 54 opposite the holding surface 54a. Each suction passage is connected to a vacuum source such as a pump at the rear side of the holding plate 54. Further, the remaining annular region formed outside the suction passage-free region 54b and the suction passage-including region 54c is a suction passage-free circumferential region 54d.Since no suction passages are formed in the region 54b including no suction passage and the peripheral region 54d, light is less likely to be scattered in the region 54b in which no suction passage is formed and the peripheral region 54d than in the region 54c in which a suction passage is formed.

[0023] However, the region 54b having no suction passage, the region 54c having a suction passage, and the peripheral region 54d are all transparent to visible light. Accordingly, in the case of picking up the workpiece 11 placed on the holding surface 54a from the lower side of the holding surface 54, the region 54b having no suction passage, the regions 54c having a suction passage, and the peripheral region 54d all serve as an image pickup area that allows visible light to pass through the holding plate 54 from its rear side (lower surface) to its front side (surface). As a modification, the entire plate 54 does not need to be formed of a transparent material. That is, a part of the holding plate 54 may be formed of an opaque material that is not transparent to visible light.For example, the suction passage region 54c and the peripheral region 54d may be made of an opaque material such as a porous ceramic. In this case, the suction passage region 54c and the peripheral region 54d do not serve as the image region.

[0024] Back to Fig. 2, a plate-shaped first vertical column 36 is provided on the stationary base 4 so as to extend vertically in the Z direction. The lower end of the first vertical column 36 is fixed to the stationary base 4. A pair of guide rails 44 are provided on one side surface of the first vertical column 36 so as to extend in the Z direction. A ball screw 38 is provided between the upper pair of guide rails 44 so as to extend in the Z-axis direction. A pulse motor 40 for rotating the ball screw 38 is connected to one end of the ball screw 38. A cutting unit 46 is slidably mounted on the pair of guide rails 44 so as to be movable in the Z-axis direction. The cutting unit 46 has a spindle housing 48 extending in the Y direction. The spindle housing 48 has a rectangular prism shape.

[0025] The spindle housing 48 has a first side surface 48a opposite the first vertical column 36 and a second side surface 48b opposite the first side surface 48a. The first side surface 48a of the spindle housing 48 is provided with a nut portion (not shown) that is in screw engagement with the ball screw 38. The ball screw 38 and the pulse motor 40 constitute a Z-axis moving mechanism 42. Accordingly, when the ball screw 38 is rotated by the pulse motor 40, the spindle housing 48 is moved in the Z direction along the pair of guide rails 44. A spindle (not shown) extending in the Y direction is rotatably supported in the spindle housing 48. A motor (not shown) for rotating the spindle is connected to one end of the spindle. The other end of the spindle protrudes from the spindle housing 48, and a cutting blade 50 is removably attached to the other end of the spindle.Accordingly, when the spindle is rotated by the motor, the cutting blade 50 is rotated.

[0026] An arm portion 52a extends from the second side surface 48b of the spindle housing 48, and an upper camera portion 52b is provided at the front end of the arm portion 52a so as to face downward. The upper camera portion 52b is set higher than the support plate 54. The arm portion 52a and the upper camera portion 52b constitute an upper imaging unit 52. The upper camera portion 52b includes an illumination unit (not shown) for applying visible light to the workpiece 11 and an image pickup element (not shown) such as a charge-coupled device (CCD) for detecting visible light reflected by the workpiece 11 to thereby image the workpiece 11. A lower imaging unit 62 is provided so as to be opposite to the upper imaging unit 52 in the Z-axis direction. Fig. 5 is a perspective view of the lower image pickup unit 62.

[0027] As in Fig. As shown in Figure 5, the lower image pickup unit 62 includes a plate-shaped second vertical column 64 extending in the Z direction. The lower end of the second vertical column 64 is fixed to the stationary base 4. A pair of guide rails 66 are provided on one side surface of the second vertical column 64 so as to extend in the Z direction. A ball screw 68 is provided between the pair of guide rails 66 so as to extend in the Z-axis direction. A pulse motor 70 for rotating the ball screw 68 is connected to one end of the ball screw 78. A Z-movement plate 74 is slidably mounted on the pair of guide rails 66 so as to be movable in the Z direction. The Z-movable plate 74 has a first side surface 74a opposite the second vertical column 64 and a second side surface 74b opposite the first side surface 74a.The first side surface 74a of the Z-movable plate 74 is connected to a nut portion (not shown) in screw engagement with the ball screw 68.

[0028] The ball screw 68 and the pulse motor 70 constitute a second Z-movement mechanism 72. Accordingly, when the ball screw 68 is rotated by the pulse motor 70, the Z-movable plate 74 is moved in the Z direction along the pair of guide rails 66. A support plate 76 is fixed at one end portion to the second side surface 74b of the Z-movable plate 74. The support plate 67 extends in the Y direction. A lower camera portion 78 is fixed to the other end portion of the support plate 76. The lower camera portion 78 is set lower than the support plate 54. The lower camera portion 68 has a camera body portion 80 including an image pickup element (not shown) for detecting reflected light from the workpiece 11 and converting it into an electrical signal. The lower camera section 78 further comprises an illumination unit 82 for applying visible light to the workpiece 11.The illumination unit 82 is fixed to a side surface of the camera body portion 80 opposite to the support plate 76 in the Y direction.

[0029] The camera body portion 80 in the lower camera portion 78 includes an objective lens (not shown), and the upper camera portion 52b also includes an objective lens (not shown). The lower camera portion 78 is positioned so that the optical axis of the objective lens in the lower camera portion 78 coincides with the optical axis of the objective lens in the upper camera portion 52b. Accordingly, a portion of the workpiece 11 that is to be photographed from the upper side by the upper camera portion 52b can be photographed from the lower side by the lower camera portion 78 at the same XY coordinate position. Back to Fig. 2, the upper portion and the side portions (front, rear, right, and left sides) of the stationary base 4 are enclosed by a cover member (not shown), and an operation panel (not shown) is provided on the front surface of the cover member. The operation panel serves as both an input unit for allowing an operator to input instructions to the cutting device 2 and a display unit for displaying an image of the workpiece 11, machining states, etc. The operation panel can also display letters and the like representing a warning. The operator is notified by the warning displayed by the operation panel, thereby detecting the occurrence of faulty machining. Further, a warning lamp (not shown) is also provided on the upper surface of the cover member. When the operator is warned of the above information, the warning lamp is turned off.As a modification, a speaker (not shown) for issuing the warning may be further provided in the cutting device 2 in addition to the control panel and the warning lamp mentioned above. In this case, when a defective machining operation has occurred, the warning is issued through the speaker.

[0030] The cutting device 2 further includes a control unit 60 such as a computer. The control unit 60 includes a central processing unit (CPU), read-only memory (ROM), random access memory (RAM), a hard disk, etc., connected to each other by a control controller. The ROM, RAM, and hard disk constitute a storage section, and the CPU performs calculations according to a program and data stored in this storage section. The control unit 60 can serve as a dedicated means such that the CPU reads the program stored in the storage section to perform cooperation between software and hardware resources. For example, the control unit 60 serves as a drive section for controlling the operation of the X-movement mechanism 12, the Y-movement mechanism 22, the first Z-movement mechanism 42, and the second Z-movement mechanism 72.When the X-movement mechanism 12 is actuated by the drive section, an electrical signal indicating the feed amount detected by the detection unit 14b is received by the drive section to detect the feed amount. When the Y-movement mechanism 22 is actuated by the drive section, an electrical signal indicating the index amount detected by the detection unit 24b is received by the drive section to detect the index amount.

[0031] The control unit 60 also serves as an image pickup section for executing and controlling the image pickup operation of the upper camera section 52b and the lower camera section 78, and also serves as an image forming section for forming an image from the electrical signal received from the upper camera section 52b and the lower camera section 78. That is, the reflected light from the workpiece 11 is detected by the image pickup element and then converted into an electrical signal, which is next sent to the image forming section. The image forming section next forms an image according to the received electrical signal.The control unit 60 also serves as a comparison section for comparing an upper image obtained using the upper camera section 52b to capture the upper surface of the workpiece 11 and a lower image obtained using the lower camera section 78 to capture the lower surface of the workpiece 11. For example, the comparison section compares the difference in width between a dividing groove 11c (described below) in the upper image and the dividing groove 11c in the lower image with an allowable value (i.e., an allowable condition) with respect to the difference in width previously stored in the storage section.

[0032] Further, the comparison section compares the positional deviation amount between the dividing groove 11c in the upper image and the dividing groove 11c in the lower image with a positional deviation allowable value (a allowable condition) previously stored and set in the storage section. If at least one of the width difference of the dividing groove 11c and the positional deviation amount of the dividing groove 11c exceeds the previously set allowable value (that is, if at least the width difference and the positional deviation amount do not meet the previously allowed conditions), the control unit 60 operates the operation panel to issue a warning. At this time, the control unit 60 may turn on the warning lamp instead of operating the operation panel.Alternatively, the control unit 60 can illuminate the warning lamp along with the operation of the control panel (the display warning on the control panel). Additionally, a loudspeaker can be activated to issue a warning. Accordingly, the operator can detect the occurrence of a defective machining operation.

[0033] Now, a method of cutting the workpiece 11 using the cutting device 2 to divide the workpiece 11 will be described. Fig. Figure 10 is a flow chart illustrating the cutting process for the workpiece 11 according to a preferred embodiment. The cutting process is carried out using the steps shown in Fig. 10. First, the adhesion-promoting layer of the tape 19 is applied to the rear surface 11b of the workpiece 11 and the first surface 17b of the ring frame 17. Accordingly, the workpiece unit 21 shown in Fig. 1B (tape attachment step S10). In the tape attachment step S10, the tape 19 is attached to the workpiece 11 and the ring frame 17 using a frame attachment device (not shown) or manually by the operator.

[0034] After performing the tape attachment step S10, the tape 19 of the workpiece unit 21 is placed on the holding plate 54, and the ring frame 17 is fixed to the clamping mechanism 56. Thereafter, the vacuum source is actuated to hold the rear surface 11b side of the workpiece 11 by the tape 19 to the holding surface 54a of the holding plate 54 under suction (holding step S20). Fig. 6A illustrates the holding step S20 for holding the workpiece 11 on the chuck table 28. In the holding step S20, the rear surface 11b side of the workpiece 11 is held on the holding plate 54 as described above. Accordingly, the rear surface 11b of the workpiece 11 becomes a lower surface, and the front surface 11a of the workpiece 11 becomes an upper surface. As a modification, the belt 19 may be attached to the front surface 11a of the workpiece 11. In this case, the front surface of the workpiece 11 becomes a lower surface, and the rear surface 11b of the workpiece 11 becomes an upper surface.

[0035] After performing the holding step S20, the front surface 11a side of the workpiece 11 is imaged by the upper camera section 52b, thereby capturing a predetermined one of the dividing lines 13 extending in the first direction. Thereafter, the chuck table 28 is rotated by the motor 32 so that the predetermined dividing line 13 detected above is parallel to the X-axis direction. After that, the cutting blade 50 is positioned directly above the predetermined dividing line 13 and then rotated at high speed. After that, the cutting blade 50 is lowered to cut the front surface 11a (i.e., the upper surface) of the workpiece 11 until the rear surface 11b of the workpiece 11 is reached. After that, the X-movement mechanism 12 is actuated to move the chuck table 28 and the cutting blade 50 relative to each other in the X-direction.

[0036] Accordingly, the workpiece 11 is completely cut along the path of this relative movement (ie, along the predetermined dividing line 13). That is, the workpiece 11 is divided along the predetermined dividing line 13 (cutting step (processing step) S30). By performing the cutting step S30, the cutting blade 11c is formed in the workpiece 11 along the predetermined dividing line 13 so that it reaches the tape 19. Fig. 6B illustrates the cutting step S30 for cutting the workpiece 11 held on the holding surface 54a using the cutting blade 50. In the cutting step S30, the workpiece 11 is cut along the predetermined dividing line 13 to form the dividing groove 11c along the predetermined dividing line 13.

[0037] After performing the cutting step S30, the control unit 60 determines whether the workpiece 11 has been cut along all the dividing lines 13 extending in the first direction (cutting completion confirmation step S40). The control unit 60 previously calculates the total number of dividing lines 13 extending in the first direction according to the size of the workpiece 11, the index size (i.e., the distance between adjacent dividing lines 13), etc., which were previously acquired, and then pre-stores this total number. Accordingly, the control unit 60 can determine whether the workpiece 11 has been cut along all the dividing lines 13 extending in the first direction according to the number of dividing lines 13 along which the workpiece 11 has been cut by performing the cutting steps S30 once or multiple times, and the number of dividing lines 13 which was previously stored.

[0038] In the case where the workpiece 11 has been cut along all the dividing lines 13 extending in the first direction (YES in S40), the cutting operation along all the dividing lines 13 extending in the first direction is completed. In contrast, in the case where the workpiece 11 has not been cut along all the dividing lines 13 extending in the first direction (NO in S40), the control unit determines whether the dividing groove 11c formed in the cutting step S30 is subjected to a gap inspection (gap inspection confirmation step S50). For example, the control unit 60 is previously set to perform a gap inspection every time a predetermined number of dividing lines 11 are formed.Accordingly, in the case that the last division groove 11c formed is not a division groove 11C corresponding to the predetermined number subjected to a gap check (NO in S50), the program returns to the cutting step S30.

[0039] In the case that the last division groove 11c is the division groove 11c corresponding to the predetermined number subjected to a gap check (YES in S50), the cutting unit 56 is lifted to stop the cutting operation once, and the program proceeds to the image capturing step S60. Fig. 7 illustrates the image capturing step S60 for capturing the upper surface and the lower surface of the workpiece 11. In the image capturing step S60, the support member 16 is moved in the X direction and the Y direction so that the holding plate 54 and the upper plate 16b are positioned between the upper imaging unit 52 and the lower imaging unit 62.

[0040] Thereafter, the upper camera section 52 is operated to capture at least a part of the division groove 11c as a joint inspection target from the front surface 11a (upper surface) side of the workpiece 11, thereby obtaining an upper image. Further, the lower camera section 78 is operated to capture the part of the same division groove 11c having the same coordinate position as that of the upper image from the rear surface 11b (lower surface) side of the workpiece 11 through the image pickup area of ​​the holding plate 54 and the belt 19, thereby obtaining a lower image. In this way, the division groove 11c is captured as a joint inspection target from the upper and lower sides of the workpiece 11. Fig. Figure 8A shows an example of the upper image and Fig. 8B shows an example of the lower image. Fig. Figure 8C is a schematic sectional view of the workpiece 11 in a region corresponding to the recorded Fig. 8A and Fig. 8B. Fig. 8A, Fig. 8B and Fig. 8C illustrates an example of inclined cutting such that the cutting blade 50 is inclined with respect to the Z direction to form an inclined dividing groove 11c.

[0041] The upper end of the division band 11c, which is in Fig. 8A, has a width L1 in the Y direction. As shown in Fig. 8C, the width L1 is the distance from one end P A1 in the Y-direction (+Y-direction indicated by an arrow Y in Fig. 8C) to the other end P A2 in the Y-direction (for example, -Y-direction versus +Y-direction). On the other hand, the lower end of the dividing groove 11c, which is in Fig. 8B, has a width L2 in the Y direction.

[0042] As in Fig. 8C, the width L2 is the distance from one end P B1in the Y direction (for example +Y direction) to the other end P B2 in the Y direction (for example -Y direction).

[0043] The width L1 of the upper end is equal to the width L2 of the lower end. However, one end P deviates B1 from the position of one end P A1 in the Y-direction (for example -Y-direction) and the lower end P B2 also deviates from the position of the other end P A2 in the Y direction (for example, -Y direction). In this way, the lower end of the dividing groove 11c (ie, the bottom of the dividing groove 11c that reaches the belt 19) deviates in position from the upper end of the dividing groove 11c (ie, the upper opening of the dividing groove 11c exposed on the front surface 11a) in the Y direction (for example, -Y direction).

[0044] Fig. Figure 9A shows another example of the above image and Fig. 9B show another example of the lower image. Fig. Figure 9C is a schematic sectional view of the workpiece 11 in a region corresponding to the illustrated Fig. 9A and Fig. 9B. Fig. 9A, Fig. 9B and Fig. 9C illustrate an example in which the cutting blade 50 is tapered to form a tapered dividing groove 11c. The upper end of the dividing band 11c, which is Fig. 9A, has a width L1 in the Y direction. As shown in Fig. As shown in Figure 9C, the width L1 is the distance from one end P A1 in the Y direction (for example +Y direction, indicated by an arrow Y in Fig. 9C) to the other end P A2 in the Y direction (for example, -Y direction versus +Y direction).

[0045] On the other hand, the lower end of the dividing groove 11c, which is in Fig. 9B, has a width L3 in the Y-direction. As shown in Fig. 9C, the width L3 is the distance from one end P C1 in the Y direction (for example + direction) to the other end P C2 in the Y-direction (for example, Y-direction). The width L3 of the lower end is smaller than the width L1 of the upper end. Furthermore, one end P deviates C1 in the position of the one P A1 in the Y-direction (for example -Y-direction) and the other end P C2 deviates in position from the other end P A1 the Y direction (for example, +Y direction). In this way, the lower end of the dividing groove 11c is positioned within the dividing groove 11c in the XY plane.

[0046] After performing image acquisition step S60, the upper image and the lower image are compared with each other (image comparison step S70). In image comparison step S70, the control unit 60, as a comparison section, compares the difference in width between the dividing groove 11c in the upper image and the dividing groove 11c in the lower image with a permissible value (permissible condition) regarding the difference in width previously set and stored in the storage section in the control unit 60. For example, the difference in width of the dividing groove 11c is the difference between the width L1 and the width L2 or the difference between the width L1 and the width L3 mentioned above.In the case that the difference in the width of the dividing groove 11c is less than or equal to the allowable value (the difference in the width of the dividing groove 11c satisfies the allowable conditions (YES in S70), the support member 16 returns to the position below the cutting blade 50 and the program proceeds to the cutting step S30.

[0047] In contrast, in the case where the difference in the width of the cutting groove 11c is greater than the allowable value (i.e., the difference in the width of the dividing groove 11c does not meet the allowable conditions) (NO in S70), the control unit 60 operates at least one of the operation panel, the warning lamp, and the speaker to issue a warning to the operator (warning step S80). After performing the warning step, the operator corrects the cutting blade 50 or replaces the cutting blade 50 (correcting step S90). In particular, when inclined cutting has occurred, as in Fig. 8C, the cutting blade 50 is preferably replaced.

[0048] In contrast, when the cutting blade 50 is tapered or unevenly worn, the width of the dividing groove 11c on the lower surface side (rear surface 11b) of the workpiece 11 becomes smaller than that on the upper surface side (front surface 11a) of the workpiece 11, which is in Fig. 9C. In this case, sharpening is performed for the cutting blade 50 to thereby correct the cutting blade 50. For example, the workpiece unit 21 is removed from the chuck table 28, and a sharpening plate (not shown) is next transferred to the chuck table 28. The sharpening plate is next held on the chuck table 28. Thereafter, the cutting blade 50 is rotated and lowered to abut against the sharpening plate, thereby performing sharpening of the cutting blade 50. After performing this sharpening, the sharpening plate is removed from the chuck table 28, and the workpiece unit 21 is held on the chuck table 28. As a modification, an auxiliary chuck table (not shown) may be provided adjacent to the chuck table 28, and a sharpening plate (not shown) may be set on the auxiliary chuck table.In this case, if the control unit 60 has detected that the permissible condition is not met or a warning has been issued, the cutting unit 46 is moved to the position above the sharpening plate set on the auxiliary chuck table. Thereafter, the cutting blade 50 is rotated and then lowered to abut against the sharpening plate, thereby sharpening the cutting blade 50. After performing the correction step S30, the program returns to the cutting step S30.

[0049] In the image capturing step according to the preferred embodiment, the upper chamber portion 52b and the lower camera portion 78 are operated to capture a part of the dividing groove 11c located at the same coordinate position on the holding surface 54a. Not only when defective machining occurs on the upper surface of the workpiece 11, but also when defective machining has occurred on the lower surface of the workpiece 11, defective machining can be detected. When defective machining has occurred on the lower surface of the workpiece 11, defective machining can be eliminated by any means. Accordingly, compared with the case where joint inspection is not performed on the lower surface of the workpiece 11 but joint inspection is performed only on the surface of the workpiece 11, production of defective chips can be prevented.If defective chips are produced, it is possible to reduce the possibility of a large number of defective chips being produced.

[0050] In a conventional method of joint inspection, the cutting blade 50 is rotated to cut the front side of an inspection member such as a silicon piece or a carbon piece, which has a rectangular prism shape, to a depth corresponding to half the depth of the inspection member (i.e., the inspection member is half-cut from the front side). Thereafter, an end surface of the inspection member is inspected on a plane perpendicular to the longitudinal direction of the dividing groove 11c using a microscope. In this way, it is very difficult to inspect the condition of the cutting blade 50 using the conventional method. Furthermore, the condition of the inclined cutting changes according to the material and depth of cut of the workpiece 11 and the feed speed of the chuck table 28, for example.Furthermore, the inclined cutting condition sometimes changes on a front surface of the workpiece 11 where the cutting blade 50 enters the workpiece 11, a rear surface of the workpiece 11 where the cutting blade 50 exits the workpiece, and in an intermediate region of the workpiece 11 between the front surface and the rear surface. In the conventional inspection method using an inspection element described above, the inclined cutting condition in the workpiece 11 cannot be inspected during the formation of the parting groove 11c. In contrast, according to the preferred embodiment, the inclined cutting condition can be easily detected by temporarily stopping the cutting operation and then picking up the workpiece 11. Furthermore, whether the cutting blade 50 is unevenly worn can be easily detected.

[0051] Further, in the image comparison step S70, the control unit 60, as a comparison section, may compare the positional deviation between the dividing groove 11c in the upper image and the dividing groove in the lower image with a permissible value (permissible condition) for the deviation amount previously stored and set in the storage section in the control unit 60. For example, the positional deviation is the offset amount between the one end P A1 and the other end P B1 or the offset between one end P A1 and one end P C1 . In the case that the deviation of the position is less than or equal to a permissible value (ie, the deviation amount of the position satisfies the permissible condition) (YES in S70), the support member 16 is returned to the position below the cutting blade 50 and the program returns to cutting step S30.

[0052] In contrast, in the case where the positional deviation amount is greater than the allowable value (i.e., the positional deviation amount does not satisfy the allowable condition) (NO in S70), the control unit 60 operates at least one of the operation panel, warning lamp, and speaker to issue a warning to the operator (warning step S80). After performing the warning step S80, the cutting blade 50 is corrected (correction step S90). After performing the correction step S90, the program returns to the cutting step S30. In the image comparison step S60, either the difference in the width of the dividing groove 11c or the positional deviation of the dividing groove 11c is compared with the allowable value. Alternatively, both the difference in the width and the positional deviation amount may be compared with the allowable value.

[0053] As a modification in the image comparison step S70, at least one of the average value, maximum value, and minimum value of chipping sizes on the upper image and a lower image may be compared with a previously set allowable value. In the case that at least one of the average value, maximum value, and minimum value is less than or equal to the allowable value (i.e., the allowable condition is satisfied) (YES in S70), the program returns to cutting step S30. As another modification, the positional deviation between the dividing line 13 and the dividing groove 11c on the upper image may be compared with a previously set allowable value. In the case that the positional deviation is less than or equal to the allowable value (i.e., the allowable condition is satisfied) (YES in S70), the program returns to cutting step S30.In contrast, if the allowable condition is not met (NO in S70), the warning step S80 is executed, and the correction step S90 is next executed to replace or correct the cutting blade 50. After that, the program returns to the cutting step S30.

[0054] Furthermore, the method or structure according to the preferred embodiment may be appropriately modified without departing from the scope of the present invention. For example, the cutting unit 46 may be replaced by a laser application unit for applying a laser beam having an absorption wavelength in the workpiece 11. In this case, the machining step (corresponding to the cutting step S30 in Fig.10) the steps of applying the laser beam to the workpiece 11 and relatively moving the laser application unit and the chuck table 28 to thereby form the dividing groove 11c. Accordingly, the workpiece 11 is cut by the laser beam. Also in this case, the image acquisition step S60 is next performed to obtain an upper image and a lower image, and the image comparison step S70 is next performed using the upper image and the lower image obtained as described above.

[0055] Furthermore, in the above preferred embodiment, the upper camera section 52b and the lower camera section 78 are fixed with respect to the X direction and Y direction and movable only in the Z direction. As a modification, the upper camera section 52b and the lower camera section 78 can be moved in all of the X direction, the Y direction, and the Z direction. In this case, too, a relative positional relationship can be specified between the upper camera section 52b and the lower camera section 78. Accordingly, the lower camera section 78 can capture any object at the same coordinate position as the position captured by the upper camera section 52b.

[0056] For example, in the state where the workpiece unit 21 is not placed on the holding plate 54, the lower camera section 78 may pick up the upper camera section 52b to thereby specify the XY coordinate position of the upper camera section 52b. If the optical axis of the lower camera section does not coincide with the optical axis of the upper camera section 52b, the position of the lower camera section 78 relative to the upper camera section 52b is corrected so that the optical axis of the lower camera section 78 coincides with the optical axis of the upper camera section 52b. Alternatively, the upper camera section 52b may pick up the lower camera section 78, and the position of the upper camera section 52b relative to the lower camera section 78 is corrected next.

[0057] In the case where the upper camera section 52b and the lower camera section 78 can be moved in the X direction, the Y direction, and the Z direction, the lower camera section 78 may further include an infrared camera section having an image pickup element for detecting infrared light and converting it into an electrical signal, and an infrared light application unit for applying infrared light. In this case, a target pattern (not shown) may be formed on the front surface 11a (upper surface) side of the workpiece 11, and this target pattern may be captured by the upper chamber section 52b and also captured by the infrared camera section of the lower camera section 78. Accordingly, the control unit 60 may specify a part of the dividing groove 11c at the same XY coordinate position on the support surface 54a.Furthermore, while the X-movement mechanism 12 and the Y-movement mechanism 22 are actuated to move the support member 16 in the X-direction and the Y-direction in the above preferred embodiment, the Y-movement mechanism 22 may be omitted. In this case, the first vertical column 36 may be connected to the other Y-movement mechanism instead of the fixed stationary base 4. Accordingly, the cutting unit 46 and the image pickup unit 52 become movable in the Y-axis direction and the Z-direction.

[0058] In the case where the regions 54c including a suction passage and the peripheral region 54d are formed of an opaque material, the upper image and a lower image can be obtained only in the intersecting region 54b not including the suction passage (image acquisition step S60). According to the upper image and the lower image obtained as above, the comparison step S70 can be performed. In the remaining region except for the region 54b not including a suction passage, a lower image cannot be obtained and only an upper image can be obtained. In this case, the image comparison step S70 is not performed, but a conventional gap inspection is performed according to the upper image.

Claims

[1] A workpiece cutting method for cutting a workpiece having an upper surface and a lower surface, comprising: a tape attaching step of attaching a tape to the bottom surface of the workpiece; a holding step of holding the lower surface of the workpiece by the belt on a holding table including a holding plate, the holding plate having a holding surface for holding the workpiece, at least a part of the holding surface being an image area formed of a material transparent to visible light; a machining step of cutting the workpiece held on the holding table to divide the workpiece, thereby forming a dividing groove having a depth reaching the tape; an image capturing step of capturing at least a part of the dividing groove from the upper surface side of the workpiece using an upper camera portion located above the holding plate, thereby obtaining an upper image, and also capturing the part of the dividing groove from the lower surface side of the workpiece through the image area of ​​the holding plate and the belt using a lower camera portion located below the holding plate, thereby obtaining a lower image, and an image comparison step for comparing the upper image and the lower image obtained in the image acquisition step wherein the image comparing step includes a step of comparing at least a difference in width between the dividing groove on the upper image or the dividing groove on the lower image and a deviation in position between the dividing groove on the upper image and the dividing groove on the lower image with a previously set allowable condition, wherein the workpiece cutting method further comprises: a warning step for issuing a warning in a case that at least one of the width difference and the position deviation does not satisfy the allowed condition.

Images