Chuck workbench

Abstract

A chuck table is provided, which can maintain the holding surface in a clean state without machining chips even if the holding surface is not cleaned by a cleaning grinder, and can form a workpiece held by the chuck table into a uniform thickness by grinding or lapping. The chuck table (3) comprises: a porous plate (30) having a holding surface (30a) for attracting and holding the workpiece; a frame having a recess (310) for exposing the holding surface and accommodating the porous plate; a groove formed on the bottom surface of the recess of the frame; and a supply path connecting the groove with a fluid supply source, wherein the porous plate has an inverted bowl-shaped recess with an inverted bowl-shaped cross section, and the inverted bowl-shaped recess is formed on the opposite surface of the porous plate opposite to the holding surface in a manner corresponding to the groove when the porous plate is accommodated in the recess. The groove is connected to the fluid supply source, and the fluid supplied to the inverted bowl-shaped recess flows radially from the inverted bowl-shaped recess toward the holding surface, causing the fluid to be ejected from the holding surface.

Description

Technical Field

[0001] The present invention relates to a chuck table for sucking and holding a workpiece such as a semiconductor wafer. Background Art

[0002] The grinding device connects the holding surface of a chuck table, which has a holding surface formed of a porous member, to a suction source such as a vacuum generator. The workpiece is held on the holding surface by suction generated by the suction source, and then ground to a desired thickness using a grinding tool. The chuck table is constructed, for example, by supporting the plate-shaped porous member using a frame having a plurality of concentric suction grooves on its inner bottom surface.

[0003] After grinding, the holding surface of the chuck table is connected to a fluid supply source that provides a mixed fluid of water and air (two-fluid). The mixed fluid is ejected from the holding surface to eliminate the vacuum suction force remaining between the holding surface and the workpiece, allowing the workpiece to be removed from the holding surface. Furthermore, after the workpiece is removed from the holding surface, the mixed fluid is also ejected from the holding surface to eject and remove grinding chips that were sucked into the porous component during grinding.

[0004] However, the grinding chips ejected from the holding surface are removed in a concentric stripe pattern on the holding surface by the suction grooves that eject the mixed fluid toward the porous member. Therefore, grinding chips remain in a concentric stripe pattern on the holding surface outside the suction grooves. Therefore, there are inventions that use a cleaning tool to clean the holding surface, such as the removal tool and removal method disclosed in Patent Document 1.

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2015-030081

[0006] However, when the holding surface is cleaned using a cleaning tool, there is a problem that the grinding chips are shaved off along with the holding surface, thereby changing the shape of the holding surface and reducing the flatness of the holding surface (the parallelism of the holding surface with respect to the grinding surface of the grinding tool), making it impossible to grind the workpiece to a uniform thickness.

[0007] Therefore, in a chuck table having a holding surface for sucking and holding the workpiece, there is the following problem: even if the holding surface is not cleaned by a cleaning tool, the holding surface is maintained in a clean state without machining chips attached, and the workpiece held by the chuck table can be formed into a uniform thickness during grinding or polishing. Summary of the Invention

[0008] The present invention provides a chuck table for sucking and holding a workpiece such as a semiconductor wafer.

[0009] The present invention for solving the above-mentioned problems is a chuck worktable, which has a holding surface for sucking and holding a workpiece, wherein the chuck worktable has: a porous plate, which has the holding surface; a frame, which has a recess for exposing the holding surface and accommodating the porous plate; a groove, which is formed on the bottom surface of the recess of the frame; and a supply path, which connects the groove with a fluid supply source, and the porous plate has an inverted bowl-shaped recess with an inverted bowl-shaped cross-section, and the inverted bowl-shaped recess is formed on the opposite surface of the porous plate opposite to the holding surface in a manner corresponding to the groove when the porous plate is accommodated in the recess, so that the groove is connected to the fluid supply source and the fluid provided to the inverted bowl-shaped recess flows radially from the inverted bowl-shaped recess toward the holding surface, and the fluid is ejected from the holding surface.

[0010] The chuck table of the present invention preferably includes a mask portion that masks a predetermined range of the inverted bowl-shaped recess centered at a most recessed position.

[0011] The chuck table of the present invention having a holding surface for sucking and holding a workpiece comprises: a porous plate having a holding surface; a frame having a recess that exposes the holding surface and accommodates the porous plate; a groove formed on the bottom surface of the recess of the frame; and a supply path that connects the groove with a fluid supply source, and the porous plate has an inverted bowl-shaped recess with an inverted bowl-shaped cross-section, and the inverted bowl-shaped recess is formed on the opposite surface of the porous plate opposite to the holding surface in a manner corresponding to the groove when the porous plate is accommodated in the recess. Therefore, for processing chips that enter the porous component from the holding surface during grinding, for example, when the workpiece is detached from the chuck table, the groove is connected to the fluid supply source so that the fluid provided to the inverted bowl-shaped recess flows radially from the inverted bowl-shaped recess toward the holding surface, so that the fluid can be ejected from the entire holding surface and the grinding chips can be ejected from the entire holding surface and removed.

[0012] The chuck worktable of the present invention has a shield portion, which shields a specified range of the inverted bowl-shaped recess centered on the most depressed position, thereby preventing the fluid ejected from the groove toward the inverted bowl-shaped recess from flowing only from the most depressed position of the inverted bowl-shaped recess toward the retaining surface, and enables the fluid to flow radially from the inverted bowl-shaped recess more efficiently and be ejected in a manner that expands toward the entire retaining surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a perspective view showing an example of a grinding device.

[0014] Figure 2 (A) is a perspective view showing the holding surface side of the porous plate, Figure 2 (B) is a perspective view showing the opposite surface side of the multi-well plate opposite to the holding surface.

[0015] Figure 3 It is a perspective view showing the multi-well plate and the frame.

[0016] Figure 4 is a cross-sectional view showing the multi-well plate and the frame.

[0017] Figure 5 It is a perspective view showing an example of a chuck table.

[0018] Figure 6 This is a cross-sectional view illustrating a state in which a workpiece is sucked and held by a chuck table.

[0019] Figure 7 This is a cross-sectional view illustrating a state in which the workpiece can be separated from the holding surface of the chuck table and grinding chips adhering to or entering the holding surface are ejected and removed by supplying fluid.

[0020] Label Description

[0021] W: workpiece; Wa: front face; Wb: back face; 1: grinding device; 10: base; 11: column; 3: chuck table; 30: porous plate; 30a: holding surface; 306: inverted bowl-shaped recess; 307: shield; 31: frame; 310: recess; 310a: bottom surface; 310c: groove; 312: annular wall; 313: bolt insertion hole; 33: rotating unit; 330: spindle; 331: motor; 332: driving pulley; 333: endless belt; 334: Driven pulley; 36: workbench base; 39: cover; 39a: corrugated cover; 38: thickness measuring unit; 5: grinding feed unit; 50: ball screw; 51: guide rail; 52: motor; 53: lifting plate; 7: grinding unit; 70: spindle; 71: housing; 72: motor; 73: mounting seat; 74: grinding wheel; 740: grinding tool; 75: support; 80: fluid supply source; 81: suction source; 86: rotary joint; 870: piping; 871: solenoid valve. DETAILED DESCRIPTION

[0022] Figure 1 The grinding device 1 shown is a device for grinding a workpiece W held on a chuck table 3 of the present invention using a grinding unit 7. The front portion (-Y direction side) on the base 10 of the grinding device 1 is an area where the workpiece W is loaded and unloaded relative to the chuck table 3, and the rear portion (+Y direction side) on the base 10 is an area where the workpiece W held on the chuck table 3 is ground by the grinding unit 7.

[0023] In addition, the processing device equipped with the chuck worktable 3 of the present invention can be a grinding device that uses a rotating grinding pad to grind the workpiece W to increase the bending strength or make the ground surface into a mirror surface, or it can be a cutting device that uses a rotating cutting tool to cut the workpiece W.

[0024] The workpiece W is a circular semiconductor wafer made of a silicon matrix, for example. Figure 1 The front surface Wa of the workpiece W, facing downward, is formed with multiple devices and protected by a protective tape (not shown). The back surface Wb of the workpiece W serves as the surface to be ground. Besides silicon, the workpiece W can be made of gallium arsenide, sapphire, gallium nitride, ceramic, resin, or silicon carbide, and can also be a rectangular package substrate.

[0025] The chuck table 3 is surrounded by a cover 39 and can be rotated around the axis in the Z-axis direction by a rotating unit 33 disposed below. Figure 1 The cover 39 shown and the bellows cover 39 a connected to the cover 39 are reciprocated in the Y-axis direction by a moving unit (not shown) below the cover 39 .

[0026] A column 11 is erected in the grinding area, and a grinding feed unit 5 is disposed on the front surface of the column 11 for grinding and feeding the grinding unit 7 in the Z-axis direction (vertical direction) relative to or away from the chuck table 3. The grinding feed unit 5 includes a ball screw 50 having an axis in the vertical direction; a pair of guide rails 51 disposed parallel to the ball screw 50; a motor 52 connected to the upper end of the ball screw 50 to rotate the ball screw 50; and a lifting plate 53 having a nut inside that is threadedly engaged with the ball screw 50. The side of the lifting plate 53 is in sliding contact with the guide rails 51. When the motor 52 rotates the ball screw 50, the lifting plate 53 is guided by the guide rails 51 and reciprocates in the Z-axis direction, thereby grinding and feeding the grinding unit 7 fixed to the lifting plate 53 in the Z-axis direction.

[0027] The grinding unit 7 for grinding the workpiece W held by the chuck worktable 3 includes: a spindle 70 whose axial direction is the Z-axis direction; a housing 71, which supports the spindle 70 so that it can rotate; a motor 72, which drives the spindle 70 to rotate; an annular mounting seat 73, which is connected to the lower end of the spindle 70; a grinding wheel 74, which is mounted on the lower surface of the mounting seat 73 in a manner that allows it to be loaded and unloaded; and a support 75, which supports the housing 71 and has a side surface fixed to the lifting plate 53 of the grinding feed unit 5.

[0028] The grinding wheel 74 includes a grinding wheel base 741 and a plurality of substantially rectangular parallelepiped grinding tools 740 arranged in a ring on the bottom surface of the grinding wheel base 741. The grinding tools 740 are formed by bonding diamond abrasive grains with a suitable adhesive, and their lower surfaces mainly serve as grinding surfaces.

[0029] An unillustrated flow path is provided inside the spindle 70 along the axial direction (Z-axis direction) of the spindle 70 and is connected to the grinding water supply source to serve as a channel for grinding water. The flow path also flows through the mounting seat 73 and opens at the bottom surface of the grinding wheel base 741 in a manner that allows grinding water to be sprayed toward the grinding tool 740.

[0030] A thickness measuring unit 38 for measuring the thickness of the workpiece W in a contact manner during grinding is provided at a position adjacent to the chuck table 3 that moves in the +Y direction to the grinding position.

[0031] The chuck table 3 of the present invention comprises: a porous plate 30 having a holding surface 30a for sucking and holding the workpiece W; and a frame 31 having a recess 310 (see FIG. 1 ) for exposing the holding surface 30a and accommodating the porous plate 30. Figure 3 ).

[0032] like Figure 2 As shown in (A) and (B) of FIG. 1 , the porous plate 30 is made of, for example, porous ceramics, porous metal, porous polytetrafluoroethylene, or porous carbon, and has a circular outer shape. The holding surface 30a on the upper surface thereof is an extremely gentle conical surface with the rotation center of the chuck table 3 as its vertex. Alternatively, the holding surface 30a may be a flat surface.

[0033] Figure 3 、 Figure 4 The frame 31 shown is made of, for example, a metal such as stainless steel or ceramic, and its outer shape is formed into a circular plate shape. An annular wall 312 of a predetermined height is erected on the outer peripheral side of the upper surface of the frame 31, and the area inside the annular wall 312 becomes a recess 310 for accommodating the porous plate 30. The diameter of the recess 310 (the inner diameter of the annular wall 312) is, for example, set to be slightly smaller than the diameter of the porous plate 30, so that the porous plate 30 can be fitted into the recess 310.

[0034] like Figure 3 As shown, a plurality of bolt insertion holes 313 (for example, 8 at 45-degree intervals) are formed around the outer periphery of the annular wall 312 on the upper surface of the frame body 31 at regular intervals along the circumferential direction and penetrating in the thickness direction (Z-axis direction).

[0035] The bottom surface 310a of the recessed portion 310 of the frame 31 is formed with a plurality of concentric circles (in the center of the rotation center of the frame 31) formed concentrically. Figure 3In the illustrated example, there are three annular suction or air supply grooves 310c; and a circular suction or air supply groove 310d overlapping the center of the frame 31. The grooves formed in the recessed portion 310 of the frame 31 are not limited to those in this embodiment. Connecting grooves may be formed that radially extend from the annular grooves 310c so as to evenly connect the annular suction grooves 310c in the circumferential direction.

[0036] At the bottom of each annular groove 310c, there are formed equal intervals in the circumferential direction and through the Z-axis direction, so that the groove 310c is connected to the fluid supply source 80 (see Figure 6 ) is connected to the supply path 314. In addition, a supply path 314 is formed in the center position of the frame 31 in the Z-axis direction to connect the circular groove 310d with the fluid supply source 80.

[0037] The fluid supply source 80 in this embodiment includes, for example, at least one of a water supply source such as a pump and an air supply source such as a compressor. The fluid that can be supplied by the fluid supply source 80 is, for example, a mixture of water and air. Alternatively, the fluid may be water or air.

[0038] The porous plate 30 has an inverted bowl-shaped recess 306 with an inverted bowl-shaped cross section. The inverted bowl-shaped recess 306 is received in the porous plate 30. Figure 4 The recessed portion 310 shown is formed on the opposite surface 30 b of the porous plate 30 opposite to the holding surface 30 a in a manner corresponding to the groove 310 c.

[0039] In this embodiment, Figure 2 (B) and Figure 4 The inverted bowl-shaped recess 306 shown includes: three inverted bowl-shaped recesses 306a, which are formed in a concentric circle shape with the rotation center of the porous plate 30 as the center when viewed from above; and one inverted bowl-shaped recess 306b, which is formed in the center of the porous plate 30 as a circle when viewed from above. That is, the inverted bowl-shaped recess 306a is a groove formed by cutting the opposite surface 30b of the porous plate 30 in an annular shape so that the cross section becomes an inverted bowl shape, and the inverted bowl-shaped recess 306b is a depression formed by cutting the opposite surface 30b of the porous plate 30 in a roughly hemispherical shape so that the cross section becomes an inverted bowl shape. Figure 4 As shown, the inverted bowl-shaped recess 306 a faces the plurality of annular grooves 310 c of the frame 31 , and the inverted bowl-shaped recess 306 b faces the groove 310 d formed in the center of the frame 31 .

[0040] In addition, instead of the annular inverted bowl-shaped recess 306a, a plurality of inverted bowl-shaped recesses 306b that are circular in plan view may be dispersed in an annular shape.

[0041] For example, as in this embodiment, it is preferable that Figure 4 The chuck table 3 shown has a mask portion 307a and a mask portion 307b that mask a predetermined area centered around the most depressed position of each inverted bowl-shaped recess 306a and inverted bowl-shaped recess 306b. Specifically, the predetermined area of ​​each inverted bowl-shaped recess 306a, which is annular in plan view, is masked by applying a sealant such as a non-water-soluble resin to form the mask portion 307a, or by attaching a sealing tape to form a circular shape when viewed from above. Separately, the predetermined area of ​​the inverted bowl-shaped recess 306b, which is circular in plan view, is masked by applying a sealant such as a non-water-soluble resin to form the mask portion 307b, or by attaching a sealing tape to form a circular shape when viewed from above.

[0042] The chuck table 3 is formed by applying adhesive on the opposite surface 30b of the porous plate 30 and pasting the opposite surface 30b to the bottom surface 310a of the recess 310 of the frame 31. Figure 5 The completed body shown. And, the chuck table 3 is fixed on Figure 6 The workbench base 36 is arranged on the circular workbench base 36 in the top view shown in FIG. Figure 1 That is, the lower surface of the frame 31 is brought into contact with the upper surface of the table base 36, the threaded hole (not shown) formed on the upper surface of the table base 36 is made to overlap with the bolt insertion hole 313, and the fixing bolt 368 passing through the bolt insertion hole 313 is screwed and fastened to the threaded hole (not shown), thereby achieving a state in which the chuck table 3 is fixed to the table base 36.

[0043] The rotation unit 33 connected to the bottom surface of the table base 36 to rotate the chuck table 3 is, for example, a pulley mechanism. The rotation unit 33 includes a spindle 330, whose axial direction is in the Z-axis direction and whose upper end is connected to the bottom surface of the table base 36; and a motor 331, which serves as a drive source for rotating the chuck table 3 about the center of the chuck table 3. A driving pulley 332 is mounted on the shaft of the motor 331, around which an endless belt 333 is wound. A driven pulley 334 is mounted on the spindle 330, around which the endless belt 333 is also wound. The motor 331 rotates the driving pulley 332, and as the driving pulley 332 rotates, the endless belt 333 rotates. The rotation of the endless belt 333 causes the driven pulley 334 and the spindle 330 to rotate.

[0044] A first flow path 361 is formed from the top to the bottom surface of the table base 36, communicating with the supply paths 314 of the frame 31. The upper end of the first flow path 361 has a plurality of openings on the top surface of the table base 36, corresponding to the supply paths 314. The first flow paths 361 merge into one channel, for example, within the frame 31, and the lower ends of the merged first flow paths 361 open on the bottom surface of the table base 36.

[0045] A second flow path 330b is formed inside the spindle 330, communicating with the first flow path 361 of the table base 36. Furthermore, a rotary joint 86 is connected to the spindle 330. This rotary joint 86 transfers the suction force generated by a suction source 81, such as an ejector mechanism or a vacuum generator, and the fluid supplied by the fluid supply source 80 to the rotating spindle 330 without any omission.

[0046] The second flow path 330b can communicate with the fluid supply source 80 via a rotary joint 86 and a pipe 870 such as a metal pipe or a flexible resin pipe. The pipe 870 is provided with a solenoid valve 871, which can selectively connect the fluid supply source 80 and the suction source 81.

[0047] Below, the above Figure 1 The operation of each part of the grinding device 1 , particularly the operation of the chuck table 3 , when grinding the back surface Wb of the workpiece W using the grinding device 1 shown will be described.

[0048] First, the workpiece W is placed on the holding surface 30a with the back surface Wb facing upward so that the center of the chuck table 3 is roughly aligned with the center of the workpiece W. Figure 6 The solenoid valve 871 shown connects the suction source 81 and the pipe 870. In this state, Figure 6 The suction force generated by the operation of the suction source 81 shown is transmitted to the holding surface 30a of the porous plate 30 through the rotary joint 86, the second flow path 330b of the main shaft 330, the first flow path 361 of the worktable base 36, the supply path 314 of the frame 31, and the grooves 310c and 310d, so that the chuck worktable 3 attracts and holds the workpiece W with the back side Wb facing upward.

[0049] Then, the chuck table 3 holding the workpiece W moves in the +Y direction to Figure 1 Below the grinding unit 7 shown, the chuck table 3 is positioned in such a way that the rotation center of the grinding wheel 74 of the grinding unit 7 is horizontally offset by a specified distance relative to the rotation center of the workpiece W and the rotation trajectory of the grinding tool 740 passes through the rotation center of the workpiece W.

[0050] The grinding unit 7 is fed in the -Z direction by the grinding feed unit 5. The grinding tool 740, which rotates as the spindle 70 rotates, comes into contact with the back surface Wb of the workpiece W and performs grinding. During grinding, as the chuck table 3 rotates by the rotation unit 33, the workpiece W held on the holding surface 30a also rotates, so that the grinding tool 740 grinds the entire back surface Wb of the workpiece W. Furthermore, grinding water is supplied to the contact area between the grinding tool 740 and the workpiece W to cool and clean the contact area.

[0051] The workpiece W is ground to a desired thickness while the thickness is measured by the thickness measuring unit 38 , and then the grinding feed unit 5 raises the grinding unit 7 and moves it away from the workpiece W.

[0052] The chuck table 3 holding the workpiece W moves in the −Y direction and returns to the loading and unloading area of ​​the grinding device 1 .

[0053] right Figure 7 The electromagnetic valve 871 shown is energized, and the fluid supply source 80 and the pipe 870 are connected through the electromagnetic valve 871. In this state, the fluid supply source 80 sends a mixed fluid of, for example, water and air. This mixed fluid reaches the rotary joint 86, the second flow path 330b of the main shaft 330, the first flow path 361 of the workbench base 36, the supply path 314 of the frame 31, and the grooves 310c and 310d, and flows to the entire circumference of the groove 310c. In addition, the mixed fluid rises in the +Z direction from the grooves 310c and 310d toward the inverted bowl-shaped recesses 306a and 306b with an inverted bowl-shaped cross section formed on the opposite side 30b of the porous plate 30.

[0054] And, as Figure 7 As shown, the mixed fluid spreads radially upward through the inverted bowl-shaped recesses 306a and 306b and flows to the holding surface 30a. This allows the mixed fluid to be uniformly ejected from the entire holding surface 30a, allowing grinding chips and the like that have entered the porous structure to be ejected and removed from the entire holding surface 30a. Furthermore, the vacuum suction force remaining between the holding surface 30a and the front surface Wa of the workpiece W is eliminated, allowing the workpiece W to be released from the holding surface 30a. Even after the workpiece W is released from the holding surface 30a by the unillustrated transfer pad, the mixed fluid continues to be ejected from the entire holding surface 30a for a specified period of time, ensuring a more thorough cleaning of the holding surface 30a.

[0055] In particular, in this embodiment, the shielding portions 307a and 307b shield a predetermined area centered on the most depressed position of the inverted bowl-shaped recesses 306a and 306b, thereby preventing the mixed fluid from flowing upward only from the most depressed position of the inverted bowl-shaped recesses 306a and 306b. Furthermore, the mixed fluid has a strong upward flow when moving from the grooves 310c and 310d toward the inverted bowl-shaped recesses 306a and 306b, so some of the mixed fluid may flow directly above the shielding portions 307a and 307b from the surrounding areas. Therefore, the mixed fluid does not fail to be ejected from the retaining surface 30a located directly above the shielding portions 307a and 307b.

[0056] The chuck table 3 of the present invention is not limited to the above-described embodiment and can be implemented in various different ways within the scope of its technical concept. In addition, the shapes of the various structures of the grinding device 1 illustrated in the accompanying drawings are not limited thereto and can be appropriately changed within the scope of being able to exert the effects of the present invention.

Claims

1. A chuck table having a holding surface for sucking and holding a workpiece, wherein: The chuck table features: a multi-well plate having the retaining surface; a frame having a recessed portion for housing the porous plate while exposing the holding surface; a groove formed on a bottom surface of the recessed portion of the frame; and providing a path connecting the tank to a fluid supply source, Furthermore, the porous plate has an inverted bowl-shaped recess having an inverted bowl-shaped cross section and a mask portion, wherein the inverted bowl-shaped recess is formed on a surface of the porous plate opposite to the holding surface in a manner corresponding to the groove when the porous plate is accommodated in the recess, and the mask portion masks a predetermined range of the inverted bowl-shaped recess centered at the most depressed position. The fluid provided to the inverted bowl-shaped recess by connecting the groove to the fluid supply source is shielded by the shield portion to prevent the fluid from flowing directly upward. The fluid flows radially from the inverted bowl-shaped recess toward the retaining surface and is ejected from the retaining surface.

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