CN116475863A

CN116475863A - Grinding device

Info

Publication number: CN116475863A
Application number: CN202211708007.XA
Authority: CN
Inventors: 万波秀年; 斋藤良信
Original assignee: Disco Corp
Current assignee: Disco Corp
Priority date: 2022-01-13
Filing date: 2022-12-28
Publication date: 2023-07-25
Also published as: JP2023102923A; TW202327779A; KR20230109551A

Abstract

The invention provides a grinding device which can attract and hold a processed object by a chuck workbench even when the tilting force of the processed object is large. Before the wafer (100) is held by the holding surface (22) of the chuck table (20), a groove is formed in the wafer (100) to weaken the tilting force of the wafer (100). Therefore, even when the force of tilting the wafer (100) is large, the wafer (100) can be easily sucked and held by the holding surface (22) of the chuck table (20). In addition, the time taken for the holding surface (22) to hold the wafer (100) can be shortened, and therefore the overall processing time of the grinding device (1) on the wafer (100) can be shortened.

Description

Grinding device

Technical Field

The present invention relates to a grinding device.

Background

When a plate-shaped workpiece having a force of tilting an outer peripheral portion is sucked and held by a holding surface and ground by a grinding wheel, the outer peripheral portion of the workpiece may float from the holding surface, and the workpiece may be peeled off from the holding surface by the grinding wheel. Accordingly, in the technique of patent document 1, a cutting tool is used to form a cutting groove in the upper surface of a workpiece held by a holding surface, thereby reducing the raising force.

Patent document 1: japanese patent laid-open No. 2015-223667

When the cutting groove is formed, cutting water is used to discharge cutting chips generated during cutting. Therefore, the cutting groove is formed in the processing chamber while the workpiece is held by the chuck table. Therefore, when the workpiece is raised so much that the chuck table is difficult to hold the workpiece by suction, it is difficult to form the cutting groove and grind the workpiece.

Disclosure of Invention

Accordingly, an object of the present invention is to reduce the tilting force when grinding a workpiece having a tilting force of an outer peripheral portion, and to suction and hold the workpiece by a chuck table.

The grinding device (the present grinding device) of the present invention comprises: a chuck table that holds a lower surface of a workpiece by suction with a force of raising an outer peripheral portion; and a grinding mechanism that grinds an upper surface of the work held by the holding surface by a grinding wheel, wherein the grinding device has a groove forming unit that forms a groove having a depth equal to or less than a depth ground by the grinding wheel on the upper surface of the work before the work is held by the holding surface, the groove forming unit having: a supporting unit that supports a workpiece; and a laser processing unit that irradiates the upper surface of the object to be processed supported by the support unit with a laser beam having a wavelength that is absorptive to the object to be processed, wherein the laser processing unit positions a converging point of the laser beam in accordance with a height of the upper surface of the object to be processed supported by the support unit, and the groove is formed in the upper surface of the object to be processed by the laser beam, thereby reducing a warp force of the object to be processed.

In the present grinding apparatus, the groove forming unit may have: a height measuring device for measuring the height of the tilted outer peripheral edge of the workpiece supported by the supporting unit and the height of the central upper surface of the workpiece supported by the supporting unit; and a warp amount calculation section that calculates a difference between the height of the outer peripheral edge measured by the height measurer and the height of the central upper surface, the groove forming unit may have a groove condition determination section that determines at least the number of grooves based on the difference calculated by the warp amount calculation section.

In the grinding device, a groove is formed in the workpiece by the groove forming means before the chuck table is held in the holding surface of the workpiece, so that the tilting force of the workpiece is reduced. Therefore, even when the tilting force of the workpiece is large, the workpiece can be easily sucked and held by the holding surface of the chuck table.

Further, since the time taken for the holding surface to hold the workpiece can be shortened, the overall processing time of the workpiece by the grinding apparatus can be shortened.

Drawings

Fig. 1 is a perspective view showing the structure of a grinding apparatus according to an embodiment.

Fig. 2 is a perspective view showing the structure of the processing unit.

Fig. 3 is an explanatory diagram showing a structure of the Y-axis direction moving mechanism in the processing unit.

Fig. 4 is an explanatory diagram showing a configuration example of the laser processing unit.

Fig. 5 is an explanatory diagram showing a configuration example of a processing head in the laser processing unit.

Fig. 6 is an explanatory view showing an example of a groove formed in the back surface of a wafer.

Fig. 7 is an explanatory diagram showing another configuration example of the laser processing unit.

Description of the reference numerals

1: a grinding device; 7: a control unit; 8: a tank condition determining section; 10: 1 st device base; 11: a 2 nd device base; 12: a crumple cover; 13: an opening portion; 15: a column; 20: a chuck table; 21: a porous member; 22: a holding surface; 23: a frame; 24: a frame surface; 39: a cover plate; 60: grinding and feeding mechanism; 61: a Z-axis guide rail; 62: a Z-axis ball screw; 63: a Z-axis moving stage; 64: a Z-axis motor; 65: a Z-axis encoder; 66: a support; 70: a grinding mechanism; 71: a spindle housing; 72: a main shaft; 73: a spindle motor; 74: a grinding wheel mounting seat; 75: grinding the grinding wheel; 76: a grinding wheel base; 77: grinding tool; 80: a thickness measurer; 81: a holding surface altimeter; 82: an upper surface altimeter; 100: a wafer; 101: a front face; 102: a back surface; 110: a processing unit; 111: a gate-type column; 112: a housing; 120: an X-axis direction moving mechanism; 121: an X-axis guide rail; 122: an X-axis ball screw; 123: an X-axis moving stage; 124: an X-axis motor; 125: an X-axis encoder; 130: a photographing unit; 131: 1 st camera; 132: illumination; 133: a camera housing; 134: a 1 st opening portion; 135: a laser processing unit; 136: a processing head; 137: a laser housing portion; 138: a 2 nd opening portion; 139: a front end portion; 140: a Y-axis direction moving mechanism; 141: a Y-axis guide rail; 142: a Y-axis ball screw; 143: a Y-axis moving stage; 144: a Y-axis motor; 145: a Y-axis encoder; 146: a holding table; 150: a holding member; 151: a rotation mechanism; 152: a temporary placing mechanism; 153: an alignment member; 154: a temporary placing table; 155: a robot; 156: a rotary cleaning mechanism; 157: a rotary table; 158: a nozzle; 160: a 1 st cassette stage; 161: a 1 st case; 162: a 2 nd cassette stage; 163: a 2 nd case; 170: a carry-in mechanism; 171: a suction pad; 172: a carrying-out mechanism; 173: a suction pad; 180: a laser oscillator; 182: a condenser; 184: a dichroic mirror; 186: a lifting mechanism; 187: a 2 nd camera; 191: a fluid ejection nozzle; 192: a fluid source; 193: a fluid recovery nozzle; 194: a suction source; 201: an oscillator; 205: an X-axis current mirror section; 206: an X-axis mirror; 207: an X-axis actuator; 210: a Y-axis current mirror section; 211: a Y-axis mirror; 212: a Y-axis actuator; 215: a direction changing mirror; 217: fθ lens; 300: a laser beam; 301: a laser beam; 310: a processing point; 401: a groove.

Detailed Description

As shown in fig. 1, a grinding apparatus 1 according to the present embodiment is an apparatus for grinding a wafer 100 as a workpiece. Wafer 100 is, for example, a circular plate-like workpiece having a front side 101 and a back side 102. A device, not shown, is formed on the front surface 101 of the wafer 100, and a protective tape 103 is attached thereto. The back surface 102 of the wafer 100 serves as a surface to be processed by grinding. In addition, the wafer 100 has a force of raising the outer peripheral portion. That is, as shown in fig. 4, the outer peripheral portion (outer peripheral edge) of the wafer 100 is tilted toward the back surface 102, which is the upper surface of the wafer 100.

The grinding device 1 includes: 1 st device base 10; and a 2 nd device base 11 disposed behind (+y direction side) the 1 st device base 10.

A 1 st cartridge stage 160 and a 2 nd cartridge stage 162 are provided on the front side (-Y direction side) of the 1 st apparatus base 10. A 1 st cassette 161 for accommodating the wafer 100 before processing is mounted on the 1 st cassette stage 160. A 2 nd pod 163 for accommodating the processed wafer 100 is mounted on the 2 nd pod stage 162.

The 1 st cassette 161 and the 2 nd cassette 163 have a plurality of shelves therein, and each of the shelves accommodates one wafer 100. That is, the 1 st cassette 161 and the 2 nd cassette 163 store a plurality of wafers 100 in a shelf shape.

The openings (not shown) of the 1 st case 161 and the 2 nd case 163 face the +y direction side. A robot 155 is disposed on the +y direction side of these openings. The robot 155 has a holding member 150 for holding the wafer 100. The robot 155 carries (stores) the processed wafer 100 in the 2 nd cassette 163. The robot 155 takes out the wafer 100 before processing from the 1 st cassette 161 and places the wafer on the stocker 154 of the stocker 152.

The stocker 152 is provided adjacent to the robot 155 for stocker the wafer 100 taken out from the 1 st cassette 161. The temporary setting mechanism 152 includes: a stocker 154 for supporting the wafer 100; a positioning member 153 for performing wafer positioning; and a rotation mechanism 151 that rotates the temporary placement stage 154.

The alignment member 153 includes: a plurality of alignment pins arranged outside so as to surround the temporary placement stage 154; and a slider that moves the alignment pin in the radial direction of the landing 154. In the alignment member 153, the alignment pins move toward the center in the radial direction of the stage 154, thereby reducing the diameter of a circle connecting the plurality of alignment pins. Thus, the wafer 100 supported by the stage 154 is aligned (centered) at a predetermined position. The stocker 152 (stocker 154) functions as a supporting unit for supporting the wafer 100.

The machining unit 110 is provided on the +y direction side of the stocker 152. The processing unit 110 and the setting mechanism 152 as the supporting unit are included in the groove forming unit in the present embodiment. The processing unit 110 will be described later.

Further, a carry-in mechanism 170 is provided adjacent to the temporary storage mechanism 152. The carry-in mechanism 170 has a suction pad 171 for sucking and holding the wafer 100. The carry-in mechanism 170 sucks and holds the wafer 100 taken out by the robot 155 and temporarily placed on the temporary placement stage 154 by the suction pad 171, and places the wafer on the holding surface 22 of the chuck table 20. In this way, the loading mechanism 170 conveys the wafer 100 held by the robot 155 to the chuck table 20.

An opening 13 is provided on the upper surface side of the 2 nd apparatus base 11. A chuck table 20 having a holding surface 22 for holding the wafer 100 is disposed in the opening 13.

The chuck table 20 has: a porous member 21; and a housing 23 that houses the porous member 21 so that the upper surface of the porous member 21 is exposed. The upper surface of the porous member 21 is a holding surface 22 for suction-holding the wafer 100. The holding surface 22 communicates with a suction source (not shown), and thereby suction-holds the front surface 101 side of the wafer 100. That is, the chuck table 20 attracts and holds the front surface 101, which is the lower surface of the wafer 100, through the holding surface 22. The housing surface 24, which is the upper surface of the housing 23, surrounds the holding surface 22 and is formed to be flush (coplanar) with the holding surface 22.

The chuck table 20 is rotatable about a rotation axis passing through the center of the holding surface 22 in a state where the wafer 100 is held by the holding surface 22 by a table rotation mechanism, not shown, provided below the chuck table.

The chuck table 20 is movable in the Y-axis direction by a table moving mechanism, not shown, provided in the 2 nd apparatus base 11.

In the present embodiment, the chuck table 20 is moved in the Y-axis direction between a workpiece placement position for holding the wafer 100 on the-Y-direction side of the holding surface 22 and a grinding position on the +y-direction side for grinding the wafer 100 held by the holding surface 22.

A cover plate 39 that moves in the Y-axis direction together with the chuck table 20 is provided around the chuck table 20. Further, a bellows cover 12 extending and contracting in the Y-axis direction is connected to the cover plate 39.

Further, a column 15 is erected on the +y direction side of the 2 nd apparatus base 11. A grinding mechanism 70 and a grinding feed mechanism 60 for grinding the wafer 100 are provided on the front surface of the post 15.

The grinding feed mechanism 60 relatively moves the chuck table 20 and the grinding tools 77 of the grinding mechanism 70 in the Z-axis direction (grinding feed direction) perpendicular to the holding surface 22. In the present embodiment, the grinding feed mechanism 60 is configured to move the grinding wheel 77 in the Z-axis direction with respect to the chuck table 20.

The grinding feed mechanism 60 has: a pair of Z-axis guide rails 61 parallel to the Z-axis direction; a Z-axis moving stage 63 that slides on the Z-axis guide rail 61; a Z-axis ball screw 62 parallel to the Z-axis guide rail 61; a Z-axis motor 64; a Z-axis encoder 65 for detecting the rotation angle of the Z-axis ball screw 62; and a bracket 66 mounted to the Z-axis moving stage 63. The holder 66 supports the grinding mechanism 70.

The Z-axis moving stage 63 is slidably provided on the Z-axis guide rail 61. A nut portion, not shown, is fixed to the Z-axis moving stage 63. The Z-axis ball screw 62 is screwed to the nut portion. The Z-axis motor 64 is coupled to one end of the Z-axis ball screw 62.

In the grinding feed mechanism 60, the Z-axis motor 64 rotates the Z-axis ball screw 62, whereby the Z-axis moving table 63 moves in the Z-axis direction along the Z-axis guide rail 61. Accordingly, the holder 66 attached to the Z-axis moving stage 63 and the grinding mechanism 70 supported by the holder 66 also move in the Z-axis direction together with the Z-axis moving stage 63.

The Z-axis encoder 65 rotates the Z-axis ball screw 62 by the Z-axis motor 64, and can recognize the rotation angle of the Z-axis ball screw 62. The Z-axis encoder 65 can detect the height position of the grinding wheel 77 of the grinding mechanism 70 moving in the Z-axis direction based on the identification result.

The grinding mechanism 70 grinds the back surface 102, which is the upper surface of the wafer 100 held by the chuck table 20, with the grinding tool 77. The grinding mechanism 70 has: a spindle case 71 fixed to the bracket 66; a spindle 72 rotatably held by the spindle case 71; a spindle motor 73 for rotationally driving the spindle 72; a grinding wheel mount 74 mounted to the lower end of the spindle 72; and a grinding wheel 75 supported by the wheel mount 74.

The spindle case 71 is held by the holder 66 so as to extend in the Z-axis direction. The spindle 72 extends in the Z-axis direction so as to be perpendicular to the holding surface 22 of the chuck table 20, and is rotatably supported by the spindle housing 71.

The spindle motor 73 is coupled to the upper end side of the spindle 72. By the spindle motor 73, the spindle 72 rotates about a rotation axis extending in the Z-axis direction.

The grinding wheel mount 74 is formed in a circular plate shape and is fixed to the lower end (front end) of the spindle 72. The grinding wheel mount 74 supports a grinding wheel 75.

Grinding wheel 75 is formed to have an outer diameter substantially the same as that of wheel mount 74. The grinding wheel 75 includes an annular wheel base 76 formed of a metallic material. A plurality of grinding tools 77 are fixed to the lower surface of the grinding wheel base 76 along the entire circumference in an annular arrangement. The grinding wheel 77 rotates with the spindle 72 about its center by the spindle motor 73, and grinds the back surface 102 of the wafer 100 held by the chuck table 20.

As shown in fig. 1, a thickness measuring device 80 is disposed on the side of the opening 13 in the 2 nd device base 11.

The thickness gauge 80 has a holding surface altimeter 81 and an upper surface altimeter 82. The holding surface height gauge 81 measures the height of the holding surface 22 by contacting the frame surface 24 of the frame 23 which is flush with the holding surface 22 of the chuck table 20. The upper surface height gauge 82 measures the height of the upper surface, i.e., the height of the back surface 102 of the wafer 100 by contacting the back surface 102, i.e., the upper surface of the wafer 100 held by the holding surface 22. The thickness measuring device 80 calculates the thickness of the wafer 100 from the difference between the measured value of the holding surface altimeter 81 and the measured value of the upper surface altimeter 82.

The holding surface altimeter 81 and the upper surface altimeter 82 of the thickness measuring device 80 may be noncontact altimeters.

For example, the holding surface height gauge 81 and the upper surface height gauge 82 may be configured to measure the height of the holding surface 22 and the height of the back surface 102 of the wafer 100 from reflected light (reflected wave) of laser light (or acoustic wave) irradiated to the frame surface 24 of the frame 23 and the back surface 102 of the wafer 100.

The ground wafer 100 is carried out by the carrying-out mechanism 172. The carry-out mechanism 172 has a suction pad 173 for sucking and holding the wafer 100. The carry-out mechanism 172 sucks and holds the wafer 100 held by the chuck table 20 via the suction pad 173, and conveys the wafer to the spin table 157 of the single-wafer spin cleaning mechanism 156.

The spin cleaning mechanism 156 is a spin cleaning unit that cleans the wafer 100 ground by the grinding mechanism 70. The spin cleaning mechanism 156 includes: a rotary table 157 for holding the wafer 100; and a nozzle 158 to spray the washing water and the drying air toward the rotary table 157.

In the spin cleaning mechanism 156, a spin table 157 holding the wafer 100 rotates, and the wafer 100 is rotated by spraying cleaning water toward the wafer 100. Then, dry air is blown to the wafer 100, and the wafer 100 is dried.

The wafer 100 cleaned by the spin cleaning mechanism 156 is carried out of the spin cleaning mechanism 156 by the robot 155 and carried into the 2 nd cassette 163.

Here, the structure of the processing unit 110 will be described. The processing unit 110 forms a groove having a depth equal to or less than the depth ground by the grinding tool 77 on the back surface 102, which is the upper surface of the wafer 100, before the wafer 100 is held by the holding surface 22 of the chuck table 20 together with the setting mechanism 152, which is the supporting unit.

As shown in fig. 2, the processing unit 110 has a gate post 111 standing on the 2 nd apparatus base 11 (see fig. 1).

The gate-shaped column 111 has: a housing 112 having a photographing unit 130 and a laser processing unit 135; and an X-axis direction moving mechanism 120 that moves the housing 112 in an X-axis direction parallel to a stage 154 (see fig. 1) of the stage mechanism 152.

The X-axis direction moving mechanism 120 includes: a pair of X-axis guide rails 121 parallel to the X-axis direction; an X-axis moving stage 123 that slides on the X-axis guide rail 121; an X-axis ball screw 122 parallel to the X-axis guide rail 121; an X-axis motor 124; and an X-axis encoder 125 for detecting a rotation angle of the X-axis ball screw 122.

The X-axis moving table 123 is slidably provided on the X-axis guide 121, and holds the housing 112. The X-axis moving stage 123 has a nut portion not shown. An X-axis ball screw 122 is screwed to the nut portion. The X-axis motor 124 is coupled to one end of the X-axis ball screw 122.

In the X-axis direction moving mechanism 120, the X-axis motor 124 rotates the X-axis ball screw 122, whereby the X-axis moving stage 123 moves in the X-axis direction along the X-axis guide rail 121. Thereby, the housing 112 held by the X-axis moving stage 123 also moves in the X-axis direction together with the X-axis moving stage 123.

The X-axis encoder 125 rotates the X-axis ball screw 122 by the X-axis motor 124, and can recognize the rotation angle of the X-axis ball screw 122. The X-axis encoder 125 can detect the position of the housing 112 moving in the X-axis direction, that is, the position of the 1 st camera 131 of the imaging unit 130 and the processing head 136 of the laser processing unit 135 held by the housing 112 in the X-axis direction, based on the identification result.

As shown in fig. 3, the photographing unit 130 has: a 1 st camera 131 of a cylindrical shape disposed outside the housing 112; an annular illumination 132 provided at the front end of the 1 st camera 131; and a camera housing 133 supporting the 1 st camera 131.

The camera housing 133 is provided in the housing 112 so as to penetrate the 1 st opening 134 provided in the-Y direction side surface of the housing 112. The front end of the camera housing 133 on the-Y direction side has the 1 st camera 131. The +y direction side portion of the camera housing 133 is attached to the upper surface of a Y-axis moving stage 143 described later.

The imaging unit 130 having such a configuration functions as a height measurer and a warp amount calculating section. That is, the imaging unit 130 measures, as a height measuring instrument, the height of the raised outer peripheral edge of the wafer 100 supported by the rest table 154 (see fig. 1) of the rest mechanism 152 as a supporting unit and the height of the center (center upper surface) of the back surface 102 of the wafer 100 supported by the rest table 154. In addition, the photographing unit 130 calculates a height difference, which is a difference between the measured height of the outer peripheral edge and the height of the central upper surface, as a warpage amount calculating section. The imaging unit 130 transmits the calculated height difference to the tank condition determining unit 8 shown in fig. 2 in the housing 112. The level difference of the wafer 100 is a value corresponding to the warp amount of the wafer 100.

The laser processing unit 135 held in the housing 112 together with the photographing unit 130 irradiates the back surface 102 of the wafer 100 supported by the stage 154 with laser light having a wavelength that is absorptive to the wafer 100.

The laser processing unit 135 has: a processing head 136 disposed outside the housing 112; and a laser housing 137 for supporting the processing head 136.

The laser housing 137 is provided in the housing 112 so as to penetrate a 2 nd opening 138 provided in the-Y direction side surface of the housing 112. The laser housing 137 has a processing head 136 at its tip on the-Y direction side. The +y direction side portion of the laser housing 137 is attached to the upper surface of the Y-axis moving stage 143.

The laser processing unit 135 includes, for example, as shown in fig. 4, therein: a 2 nd camera 187 capable of photographing the wafer 100; a laser oscillator 180 for oscillating a laser beam 300 having a wavelength that is absorptive to the wafer 100; a condenser 182; a dichroic mirror 184 that directs the laser light 300 to the condenser 182; and a lifting mechanism 186 that lifts and lowers the condenser 182 in the up-down direction.

Of these, for example, the laser oscillator 180 is disposed in the laser housing 137, and the 2 nd camera 187, the dichroic mirror 184, the condenser 182, and the elevating mechanism 186 are disposed in the processing head 136.

The laser processing unit 135 positions the focal point of the laser beam 300 according to the height (upper surface height) of the back surface 102 of the wafer 100 supported by the platen 154 of the platen 152, and forms a groove having a depth equal to or less than the depth ground by the grinding tool 77 on the back surface 102 by the laser beam 300.

That is, in the laser processing unit 135, the height of the converging point of the laser beam 300 can be adjusted by adjusting the position of the condenser 182 in the Z-axis direction by the elevating mechanism 186. In the laser processing unit 135, the laser beam is irradiated onto the back surface 102 of the wafer 100 while the height of the converging point of the laser beam 300 is adjusted so that the converging point is arranged on the back surface 102 of the wafer 100, whereby a groove is formed in the back surface 102 to reduce the tilting force of the wafer 100.

As shown in fig. 5, the processing head 136 of the laser processing unit 135 may have a fluid ejection nozzle 191 and a fluid recovery nozzle 193 in the vicinity of the tip 139 from which the laser beam 300 is emitted.

Fluid ejection nozzle 191 is connected to a fluid source 192. The fluid ejection nozzle 191 ejects the fluid supplied from the fluid source 192 toward the processing point 310, which is a portion irradiated with the laser beam 300 on the back surface 102 of the wafer 100, as indicated by an arrow 311. The fluid is, for example, air, water, or a mixed fluid of air and water (two fluids).

The fluid recovery nozzle 193 is connected to a suction source 194. The fluid collection nozzle 193 sucks fluid from the vicinity of the processing point 310 as indicated by an arrow 312 by the suction force applied by the suction source 194.

In the processing head 136 having such a structure, processing scraps generated by processing of the laser beam 300 can be removed from the processing point 310 by the fluid ejected from the fluid ejection nozzle 191. Further, the machining chips removed from the machining point 310 can be sucked and recovered together with the fluid by the fluid recovery nozzle 193. Therefore, the machining chips can be removed well from the vicinity of the machining point 310 and the tip of the machining head 136 and recovered. Therefore, the wafer 100 and the processing head 136 can be suppressed from being contaminated with processing scraps.

As shown in fig. 3, a Y-axis direction moving mechanism 140 for moving the imaging unit 130 and the laser processing unit 135 in the Y-axis direction parallel to a stage 154 (see fig. 1) of the stage mechanism 152 is provided in the housing 112.

The Y-axis direction moving mechanism 140 includes: a pair of Y-axis guide rails 141 parallel to the Y-axis direction; a Y-axis moving stage 143 that slides on the Y-axis guide rail 141; a Y-axis ball screw 142 parallel to the Y-axis guide rail 141; a Y-axis motor 144; a Y-axis encoder 145 for detecting a rotation angle of the Y-axis ball screw 142; and a holding table 146 for holding them.

The Y-axis moving stage 143 is slidably provided on the Y-axis guide rail 141, and holds the camera housing 133 and the laser housing 137. The Y-axis moving stage 143 has a nut portion not shown. The nut portion is screwed with a Y-axis ball screw 142. The Y-axis motor 144 is coupled to one end of the Y-axis ball screw 142.

In the Y-axis direction moving mechanism 140, the Y-axis ball screw 142 is rotated by the Y-axis motor 144, and the Y-axis moving table 143 moves along the Y-axis guide rail 141 in the Y-axis direction. Thereby, the camera housing 133 and the laser housing 137 held by the Y-axis moving stage 143, and the 1 st camera 131 and the processing head 136 provided at the tips thereof also move in the Y-axis direction together with the Y-axis moving stage 143.

The Y-axis encoder 145 rotates the Y-axis ball screw 142 by the Y-axis motor 144, and can recognize the rotation angle of the Y-axis ball screw 142. The Y-axis encoder 145 can detect the Y-axis positions of the 1 st camera 131 and the processing head 136, which move in the Y-axis direction, based on the recognition result.

As shown in fig. 1, the grinding apparatus 1 includes a control unit 7 for controlling the grinding apparatus 1. The control unit 7 includes a CPU, a memory, and other storage media for performing arithmetic processing according to a control program. The control unit 7 executes various processes, and centrally controls the respective components of the grinding apparatus 1.

For example, the control unit 7 controls the above-described components of the grinding apparatus 1 to perform the grinding process for the wafer 100.

Hereinafter, a method of grinding the wafer 100 in the grinding apparatus 1 controlled by the control unit 7 will be described.

[ procedure for measuring warpage ]

First, the control unit 7 takes out the wafer 100 before processing from the 1 st cassette 161 by the robot 155 shown in fig. 1, places the wafer 100 on the stocker 154 of the stocker 152 so that the back surface 102 faces upward, and supports the wafer 100 on the stocker 154 to be positioned at a predetermined position.

Then, the control unit 7 controls the rotation mechanism 151 of the stocker 152 and the X-axis direction moving mechanism 120 (see fig. 2) and the Y-axis direction moving mechanism 140 (see fig. 3) of the processing unit 110, and places the 1 st camera 131 of the imaging unit 130 directly above the outer peripheral edge of the back surface 102 of the wafer 100 supported by the stocker 154.

The imaging unit 130 irradiates the back surface 102 with the illumination 132, and measures the height of the outer periphery of the back surface 102 with the 1 st camera 131. That is, the 1 st camera 131 measures the height of the outer periphery of the back surface 102 by focusing the focal point on the outer periphery of the back surface 102 to determine the height of the focal point.

Next, the control unit 7 controls the rotation mechanism 151 of the stocker 152 and the X-axis direction moving mechanism 120 and the Y-axis direction moving mechanism 140 of the processing unit 110, and places the 1 st camera 131 of the imaging unit 130 directly above the center (central upper surface) of the back surface 102 of the wafer 100 supported by the stocker 154.

The imaging unit 130 irradiates the back surface 102 with the illumination 132, and measures the height of the center of the back surface 102 with the 1 st camera 131. That is, the 1 st camera 131 measures the height of the center of the back surface 102 by focusing the center of the back surface 102 to determine the height of the focus.

Then, the photographing unit 130 calculates a difference between the measured height of the outer periphery of the rear surface 102 and the height of the center of the rear surface 102, i.e., a height difference. As described above, the level difference is a value corresponding to the warp amount of the wafer 100. The photographing unit 130 transfers the calculated height difference to the slot condition determining section 8.

The groove condition determining section 8 determines the number of grooves formed in the back surface 102 of the wafer 100 by the processing unit 110 based on the height difference of the back surface 102 calculated by the imaging unit 130. The groove condition determining unit 8 sets the number of grooves, for example, so as to reduce the warpage amount of the wafer 100 to such an extent that the wafer 100 can be held well by the holding surface 22 of the chuck table 20 by the grooves formed in the back surface 102.

In addition, the warpage amount may be measured by photographing the wafer 100 held by the robot 155 by the photographing unit 130. At this time, the wafer 100 may be moved in the X-axis direction and the Y-axis direction by the robot 155.

[ groove formation Process ]

Next, the control unit 7 controls the rotation mechanism 151 of the stocker 152 and the X-axis direction moving mechanism 120 and the Y-axis direction moving mechanism 140 of the processing unit 110, and irradiates the back surface 102 of the wafer 100 with the laser beam 300 from the processing head 136 while adjusting the position of the processing head 136 of the laser processing unit 135 with respect to the wafer 100, thereby forming a plurality of parallel grooves 401 as shown in fig. 6 on the back surface 102.

At this time, the control unit 7 adjusts the output of the laser beam 300, the position of the converging point, and the like so that the depth of the groove 401 formed in the back surface 102 becomes equal to or less than the depth (grinding amount) of the back surface 102 of the wafer 100 by the grinding tool 77 in a grinding step described later. The control unit 7 forms the number of grooves 401 determined by the groove condition determining unit 8 on the back surface 102 of the wafer 100.

By forming such grooves 401 in the back surface 102, the force of tilting in the wafer 100 is reduced, and the amount of warpage of the wafer 100 is reduced to such an extent that the wafer 100 can be held well by the holding surface 22 of the chuck table 20.

[ holding step ]

Next, the control unit 7 controls a table moving mechanism, not shown, to place the chuck table 20 shown in fig. 1 at the work holding position on the-Y direction side. The control unit 7 controls the carry-in mechanism 170 to hold the wafer 100 on the stocker 152, and places the wafer on the holding surface 22 of the chuck table 20 with the back surface 102 facing upward.

Then, the control unit 7 controls the table moving mechanism to place the chuck table 20 at the +y-direction grinding position, which is the lower side of the grinding mechanism 70.

[ grinding Process ]

Next, the control unit 7 rotates the grinding wheel 75 of the grinding mechanism 70 and the chuck table 20, and performs grinding feed in the-Z direction of the grinding mechanism 70 including the grinding wheel 77 by the grinding feed mechanism 60. Thereby, the grinding tool 77 of the rotating grinding wheel 75 contacts the back surface 102 of the wafer 100 held by the rotating chuck table 20, and grinds the back surface 102.

In this grinding step, the control unit 7 measures the thickness of the ground wafer 100 by the thickness measuring device 80. The control unit 7 performs grinding by the grinding wheel 77 until the thickness of the wafer 100 reaches a predetermined thickness set in advance. As described above, the groove 401 formed in the back surface 102 of the wafer 100 has a depth equal to or less than the grinding amount of the grinding tool 77. Therefore, the groove 401 disappears from the back surface 102 by this grinding process.

[ cleaning procedure ]

After the grinding process, the control unit 7 holds the wafer 100 held by the chuck table 20 by the carry-out mechanism 172, and places the wafer on the spin table 157 of the spin cleaning mechanism 156. The control unit 7 cleans the wafer 100 using the spin cleaning mechanism 156.

Then, the control unit 7 uses the robot 155 to take out the wafer 100 from the spin cleaning mechanism 156 and carry it into the 2 nd cassette 163 on the 2 nd cassette stage 162.

As described above, in the present embodiment, before the wafer 100 is held by the holding surface 22 of the chuck table 20, the groove 401 is formed in the wafer 100, and the force for raising the wafer 100 is reduced. Therefore, even when the force for tilting the wafer 100 is large, the wafer 100 can be easily sucked and held by the holding surface 22 of the chuck table 20.

In addition, since the time taken for holding the wafer 100 by the holding surface 22 can be shortened, the processing time of the entire wafer 100 by the grinding device 1 can be shortened.

In the present embodiment, the laser beam 300 emitted from the laser processing unit 135 is used to form the groove 401 in the back surface 102 of the wafer 100. Therefore, unlike the structure in which the groove is formed by the cutting tool, the groove 401 can be formed by dry processing without using a large amount of processing water. Therefore, the structure of supplying and recovering the processing water can be omitted or simplified, and thus the enlargement of the grinding apparatus 1 can be avoided.

In the present embodiment, the wafer 100 carried to the stocker 154 by the robot 155 and supported by the stocker 154 is formed with the groove 401 by the laser processing unit 135, so that the warpage amount is reduced.

As described above, in the present embodiment, in order to form the groove 401 by the laser processing unit 135, the robot 155 and the stage 154 are used as conventional structures. Therefore, since the structure added to form the groove 401 can be reduced, the groove 401 can be formed in the grinding device 1 without increasing the size of the grinding device 1.

In the present embodiment, in the groove forming step, the laser processing unit 135 forms the groove 401 in the back surface 102 of the wafer 100 supported by the stage 154. In this regard, the laser processing unit 135 may irradiate the back surface 102 of the wafer 100 held by the carry-in mechanism 170 with the laser beam 300 to form the groove 401.

In addition, the groove 401 can be formed by irradiating the wafer 100 held by the robot 155 with the laser beam 300, so that the warpage of the wafer 100 can be reduced. At this time, the wafer 100 may be moved in the X-axis direction and the Y-axis direction with respect to the processing head 136 of the laser processing unit 135 by the robot 155.

When the groove 401 is formed in the wafer 100 held by the carry-in mechanism 170, the control unit 7 sucks and holds the wafer 100 supported by the stocker 154 via the suction pad 171 of the carry-in mechanism 170 after the warp measuring step using the imaging unit 130. The control unit 7 also places the wafer 100 held by the suction pad 171 below the laser processing unit 135 in the processing unit 110.

The control unit 7 controls the X-axis direction moving mechanism 120, the Y-axis direction moving mechanism 140, and the carry-in mechanism 170 of the processing unit 110, and irradiates the back surface 102 of the wafer 100 with the laser beam 300 from the processing head 136 while adjusting the position of the processing head 136 of the laser processing unit 135 relative to the wafer 100 held by the suction pad 171, thereby forming a plurality of parallel grooves 401 on the back surface 102.

In this configuration, the carry-in mechanism 170 preferably has a suction pad 171 having a relatively small area.

In addition, the processing unit 110 including the photographing unit 130 and the laser processing unit 135 may be disposed in the vicinity of the spin cleaning mechanism 156.

In this case, in the warp amount measurement step, the control unit 7 takes out the wafer 100 before processing from the 1 st cassette 161 by the robot 155, and places the wafer on the spin table 157 of the spin cleaning mechanism 156 with the back surface 102 facing upward. Then, the photographing unit 130 of the processing unit 110 measures the height difference of the wafer 100, and transmits to the tank condition determining section 8.

The control unit 7 forms a groove 401 in the back surface 102 of the wafer 100 supported by the rotary table 157 by the laser processing unit 135. Then, the control unit 7 performs cleaning of the wafer 100 by the spin cleaning mechanism 156.

Next, the control unit 7 uses the robot 155 to take out the cleaned wafer 100 from the spin cleaning mechanism 156, and conveys the wafer 100 to the stocker 152, thereby performing the holding step, the grinding step, and the cleaning step described above.

In this configuration, the wafer 100 after the groove 401 is formed can be easily cleaned by the spin cleaning mechanism 156. Therefore, processing scraps generated when the grooves 401 are formed using the laser beam 300 can be removed well from the wafer 100.

In addition, the laser processing unit 135 may have an optical system using a galvanometer mirror. In this case, as shown in fig. 7, the laser processing unit 135 has: an oscillator 201 that oscillates out laser light 301; an X-axis galvano mirror section 205 and a Y-axis galvano mirror section 210 that deflect the laser beam 301; a direction changing mirror 215 that changes the direction of the laser light 301; and an fθ lens 217.

In this configuration, for example, the oscillator 201, the X-axis galvanometer mirror 205, and the Y-axis galvanometer mirror 210 are disposed in the laser housing 137 of the laser processing unit 135 shown in fig. 3, and the direction changing mirror 215 and the fθ lens 217 are disposed in the processing head 136 of the laser processing unit 135.

The X-axis galvanometer mirror section 205 includes an X-axis mirror 206 and an X-axis actuator 207 that adjusts the rotation angle of the X-axis mirror 206. In the X-axis galvanometer mirror section 205, the rotation angle of the X-axis mirror 206 is adjusted by the X-axis actuator 207, thereby deflecting the optical axis of the laser beam 301 from the oscillator 201 in the X-axis direction.

The Y-axis galvanometer mirror section 210 includes a Y-axis mirror 211 and a Y-axis actuator 212 that adjusts the rotation angle of the Y-axis mirror 211. In the Y-axis galvanometer mirror section 210, the rotation angle of the Y-axis mirror 211 is adjusted by the Y-axis actuator 212, so that the optical axis of the laser beam 301 from the X-axis galvanometer mirror section 205 is deflected in the Y-axis direction.

The direction changing mirror 215 changes the direction of the laser beam 301 deflected by the X-axis galvano mirror 205 and the Y-axis galvano mirror 210 downward.

The fθ lens 217 irradiates the laser beam 301 deflected by the X-axis galvano mirror 205 and the Y-axis galvano mirror 210 substantially perpendicularly to the back surface 102 of the wafer 100 as parallel beams having equal converging heights.

In the laser processing unit 135 having such a configuration, the deflection state of the laser beam 301 reflected by the X-axis mirror 206 and the Y-axis mirror 211 is adjusted by adjusting the rotation angles of these mirrors, so that the laser beam 301 can be irradiated to an arbitrary position on the back surface 102 of the wafer 100 located below the fθ lens 217.

In the case of using the laser processing unit 135 having such a configuration, the control unit 7 can control the irradiation position of the laser beam 301 irradiated from the processing head 136 to the back surface 102 of the wafer 100 by adjusting the rotation angles of the X-axis mirror 206 and the Y-axis mirror 211 by using the X-axis actuator 207 and the Y-axis actuator 212, thereby forming a plurality of parallel grooves 401 on the back surface 102 of the wafer 100.

In the present embodiment, when the groove 401 is formed in the back surface 102 of the wafer 100 in the groove forming step, the control unit 7 controls the rotation mechanism 151 of the setting mechanism 152 and the X-axis direction moving mechanism 120 and the Y-axis direction moving mechanism 140 in the processing unit 110 to adjust the position of the processing head 136 of the laser processing unit 135. In this regard, the control unit 7 may adjust the position of the processing head 136 using only the X-axis direction moving mechanism 120 and the Y-axis direction moving mechanism 140. Alternatively, the control unit 7 may adjust the position of the processing head 136 using the rotation mechanism 151 and any one of the X-axis direction moving mechanism 120 and the Y-axis direction moving mechanism 140.

In the present embodiment, the groove condition determining unit 8 determines the number of grooves formed in the back surface 102 of the wafer 100 by the processing unit 110 based on the difference between the height of the outer peripheral edge and the height of the center of the wafer 100 calculated by the imaging unit 130. In this regard, the groove condition determining unit 8 may determine at least the number of grooves based on the difference in height between the wafers 100. That is, the groove condition determining unit 8 may set the groove depth and/or the groove interval based on the number of grooves based on the difference in height between the wafers 100. For example, the groove condition determining unit 8 increases the depth of the groove as the level difference of the wafer 100 increases. The groove condition determining unit 8 narrows the groove intervals as the level difference of the wafer 100 increases.

The groove condition determining unit 8 may set the number, depth, and/or interval of grooves formed in the back surface 102 of the wafer 100 according to the height difference of the wafer 100 and the thickness of the wafer 100. In this case, the photographing unit 130 may calculate the thickness of the wafer 100 when calculating the height difference of the wafer 100 supported by the stage 154 (refer to fig. 1). For example, the imaging unit 130 calculates a difference between the height of the center of the back surface 102 of the wafer 100 and the height of the holding surface 22 of the chuck table 20 acquired in advance, and transmits the difference as the thickness of the wafer 100 to the groove condition determining unit 8.

In the present embodiment, a wafer 100 is shown as a workpiece, which is a circular plate-like workpiece. In this regard, the shape of the workpiece in the present embodiment is not limited to this circular shape, and may be a polygon such as a quadrangle.

The grooves formed in the workpiece are not limited to the plurality of parallel linear grooves 401 shown in fig. 6, and may be formed in a lattice shape. In addition, when the workpiece is circular like the wafer 100, concentric or radial grooves may be formed in the workpiece.

In the present embodiment, the imaging unit 130 obtains a difference between the height of the outer peripheral edge on the back surface 102 of the wafer 100 and the height of the center, that is, a difference in height, as a value corresponding to the warpage amount of the wafer 100. In this regard, the imaging unit 130 may calculate a difference between the height of the outer peripheral edge on the back surface 102 of the wafer 100 and the height of the holding surface 22 of the chuck table 20 acquired in advance as a value corresponding to the warp amount of the wafer 100, and the groove condition determining unit 8 may determine the number of grooves formed on the back surface 102 of the wafer 100 based on the difference. In this structure, the height measurement of the center of the back surface 102 of the wafer 100 may be omitted.

In the present embodiment, in the warp measurement step, the 1 st camera 131 of the imaging unit 130 measures the height of the outer peripheral edge and the height of the center of the rear surface 102 of the wafer 100 mounted on the stage 154 of the stage mechanism 152. In this regard, in order to measure the height of the outer periphery and the height of the center of the rear surface 102 of the wafer 100, the 2 nd camera 187 of the laser processing unit 135 shown in fig. 4 may be used. The 2 nd camera 187 can be focused on the outer periphery and the center of the back surface 102 of the wafer 100 held by the stage 154 via the dichroic mirror 184 and the condenser 182.

Claims

1. A grinding apparatus, comprising:

a chuck table that holds a lower surface of a workpiece by suction with a force of raising an outer peripheral portion; and

a grinding mechanism for grinding the upper surface of the processed object held by the holding surface by a grinding tool,

wherein,,

the grinding device comprises a groove forming unit for forming a groove with a depth smaller than the grinding depth of the grinding tool on the upper surface of the processed object before the processed object is held by the holding surface,

the groove forming unit includes:

a supporting unit that supports a workpiece; and

a laser processing unit for irradiating the upper surface of the object to be processed supported by the support unit with laser light having a wavelength which is absorptive to the object to be processed,

the laser processing unit positions a converging point of the laser beam according to the height of the upper surface of the object to be processed supported by the supporting unit, and the groove is formed on the upper surface of the object to be processed by the laser beam, so that the warping force of the object to be processed is weakened.

2. The grinding apparatus of claim 1, wherein,

the groove forming unit includes:

a height measuring device for measuring the height of the tilted outer peripheral edge of the workpiece supported by the supporting unit and the height of the central upper surface of the workpiece supported by the supporting unit; and

a warp amount calculating section that calculates a difference between the height of the outer peripheral edge measured by the height measuring instrument and the height of the central upper surface,

the groove forming unit has a groove condition determining section that determines at least the number of grooves based on the difference calculated by the warp amount calculating section.