JP2008049445A - Processing equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a machining apparatus capable of surely and stably performing a feeding operation of machining means by enabling a load detection of the machining means without depending on a load current value or a load sensor. <P>SOLUTION: The gap amount in the thrust direction or the radial direction of an air-bearing spindle which varies according to the feeding action of a working unit 30 is recognized by the variation of an air pressure generated in the gap, and the feeding action of the working unit 30 is safely controlled. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  In the present invention, a processing means for processing a workpiece and a holding means for holding the workpiece are rotatably held by an air bearing spindle, and the workpiece is held by the holding means by a feeding operation of the processing means. Relates to the device.

  In response to the recent demand for lighter, thinner and smaller semiconductor devices and increased capacity, a semiconductor package in which a plurality of semiconductor chips such as SIP (system in package) and MCP (multi-chip package) are stacked is used. There is an example. In order to manufacture such a stacked package, it is necessary to make the semiconductor wafer, which is a material of the semiconductor chip, thinner. The thinning process includes grinding with a grindstone. When the thinning process is performed by thinning, the polishing process is performed to remove mechanical damage remaining on the ground surface.

  As a processing apparatus that performs grinding or polishing, a type that is pressed against a processing surface while rotating a polishing or grinding tool is generally used, and such a processing apparatus is inserted into a spindle housing. One that employs an air bearing spindle that holds the spindle shaft portion with high-pressure air is often used (see Patent Document 1, etc.).

  In such a processing apparatus, conventionally, in order to prevent the pressing load of the processing tool on the workpiece from becoming excessive, the feeding operation of the processing tool is controlled while detecting the load current value of the motor. In addition, a load sensor is provided on the processing tool side or the holding means side for holding the workpiece to control the pressing load (see Patent Document 2, etc.).

Japanese Patent Laid-Open No. 11-138432 JP 2003-326456 A

  By the way, in the semiconductor wafer thinning process by grinding, there is a technique for securing rigidity with the thickness of the outer peripheral portion even if the device forming region is thinned while leaving the outer peripheral portion of the wafer. In such a grinding process, in order to control the pressing load on the workpiece of a processing tool such as a grinding wheel with the load current value of the motor, the fluctuation of the load value is small because the grinding wheel diameter of the grinding tool is relatively small. There is a problem that grinding failure such as excessive pressing load is difficult to detect. In addition, when a load sensor is provided on the processing tool side or the holding means side for holding the workpiece, the rigidity of the member provided with the load sensor is reduced, and when the pressing load of the processing means is applied to the member, There has been a problem that deformation and inclination occur and the processing of an accurate and uniform amount is hindered.

  Therefore, the present invention can detect the fluctuation reliably even when the fluctuation of the load value of the machining means is small, and does not cause a problem as in the case of being equipped with a load sensor. An object of the present invention is to provide a processing apparatus capable of reliably and stably performing the feeding operation of the means.

  The present invention provides a holding means for holding a workpiece and a machining tool for machining the workpiece, which is rotatably held by an air bearing spindle, and machining the workpiece by a feed operation approaching the holding means. The air bearing spindle is formed in the spindle housing, a spindle shaft portion rotatably inserted into the spindle housing and supporting the machining tool, and the spindle housing and the spindle. An air supply path for supplying air to the gap between the shaft portion and an air exhaust path formed in the spindle housing for exhausting the air supplied to the gap. An air pressure sensor for detecting the pressure of the air passing through the air pressure sensor, and a detection signal of the air pressure sensor. Is input, and a gap pressure measuring unit that measures the pressure of the gap based on the detection signal and monitors the pressure of the gap, and a memory that stores the load value received by the machining means by the feeding operation as a predetermined target load value And a control unit that controls the feeding operation of the processing means based on information received from the gap pressure measurement unit and the storage unit.

  Further, in the above-mentioned configuration, the present invention also has a similar configuration in which an air bearing spindle is provided on the holding means side instead of the processing means side. That is, the invention provides a holding means for rotatably holding a workpiece by means of an air bearing spindle, and a workpiece that is rotatably held by a processing tool for processing the workpiece, and is fed by a feed operation approaching the holding means. The air bearing spindle is formed in the spindle housing, a spindle shaft portion rotatably inserted into the spindle housing and supporting the holding means, and a spindle housing. An air supply path for supplying air to a gap between the spindle housing and the spindle shaft portion; and an air exhaust path formed in the spindle housing for exhausting the air supplied to the gap. An air pressure sensor for detecting the pressure of air passing through the air exhaust passage, and the air A detection signal of the pressure sensor is input, a gap pressure measurement unit that measures the pressure of the gap based on the detection signal and monitors the pressure of the gap, and a load value received by the processing means by the feeding operation is set to a predetermined target load. It is characterized by comprising a storage unit that stores values, a gap pressure measurement unit, and a control unit that controls the feeding operation of the processing means based on information received from the storage unit.

  According to the present invention, the machining tool performs a predetermined process on the workpiece held by the holding unit by feeding the machining unit. At the time of machining, the spindle shaft portion of the air bearing spindle moves relative to the spindle housing in accordance with the feed operation of the machining tool, and the gap amount between the spindle housing and the spindle shaft portion changes. In the pressure measurement unit, the pressure of the gap is monitored one by one according to the change in the gap amount. Here, the control unit compares the monitored gap pressure with the target load value stored in the storage unit, and controls the feeding operation of the machining means so that the gap pressure corresponds to the target load value. By doing so, the gap pressure can be made to correspond to the target load value. The target load value is a load value when the gap amount is in an optimum state. Therefore, by controlling in this way, the load received by the machining means does not become excessive and safe operation is always possible.

  More specifically, the value measured by the gap pressure measurement unit is multiplied by a coefficient to convert it to a load value, and the feed operation of the machining means is controlled so that the calculation result converges to the target load value stored in the storage unit. In the present invention, it is preferable to have a control unit that performs such control.

  In the present invention, the air pressure sensor preferably detects the air pressure at a constant position in the circumferential direction of the spindle shaft portion. When the load value is constant and the spindle shaft portion is rotating, it is not necessary to use this embodiment as long as the gap amount is always constant at any location in the circumferential direction during one rotation of the spindle shaft portion. However, there is a case in which the gap amount is not constant in the circumferential direction and varies due to deformation of the spindle shaft portion or slight fluctuation of the rotation axis of the spindle shaft portion. Therefore, if the gap amount is always measured at a constant position in the circumferential direction, the change in the gap amount is not due to deformation or shaft runout of the spindle shaft portion, but relative movement of the spindle shaft portion with respect to the spindle housing. The air pressure can be accurately detected.

  Examples of the processing tool of the present invention include a grinding tool or a polishing tool having a processing surface parallel to a holding surface on which the holding means holds the workpiece.

  According to the present invention, the gap amount between the spindle shaft portion and the spindle housing, which is changed by the feeding operation of the machining means, is detected by the air pressure sensor, and the gap amount is controlled as an optimum target load value. It is possible to reliably and stably perform the feeding operation of the processing means. Further, since a load sensor is not required, accurate and uniform machining can be achieved, and cost can be reduced.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[1] Schematic Configuration of Processing Apparatus FIG. 1 shows a processing apparatus that uses a semiconductor wafer such as a silicon wafer (hereinafter abbreviated as a wafer) as a workpiece and grinds or polishes the back surface of the wafer. This processing apparatus 10 includes a rectangular parallelepiped base 11 having a horizontal upper surface. In FIG. 1, the longitudinal direction, the width direction, and the vertical direction of the base 11 are shown by the Y direction, the X direction, and the Z direction, respectively. At one end portion of the base 11 in the Y direction, a column 12 arranged in the X direction (here, left and right direction) is erected in a pair. A processing area 11A for grinding the wafer is provided on the base 11 on the column 12 side in the Y direction, and a wafer before processing is supplied to the processing area 11A on the side opposite to the column 12, and after processing. A detachable area 11B for collecting the wafer is provided.

  In the processing area 11A, a disk-shaped turntable 13 whose rotation axis is parallel to the Z direction and whose upper surface is horizontal is rotatably provided. The turntable 13 is rotated in the direction of arrow R by a rotation drive mechanism (not shown). A plurality of (in this case, three) disk-shaped chuck tables (holding means) 20 whose rotation axis is parallel to the Z direction and whose upper surface is horizontal are equidistantly spaced in the circumferential direction on the outer periphery of the turntable 13. It is arranged so that it can rotate freely.

  These chuck tables 20 are of a generally known vacuum chuck type and suck and hold a wafer placed on the upper surface. Each chuck table 20 is independently rotated or rotated in one direction or both directions by a rotation drive mechanism (not shown) provided in the turntable 13, and revolves when the turntable 13 rotates. It becomes a state.

  As shown in FIG. 1, in a state where two chuck tables 20 are arranged in the X direction on the column 12 side, a processing unit (processing means) 30 is disposed immediately above the chuck tables 20. Each chuck table 20 is positioned at three positions, that is, a processing position below each processing unit 30 and an attachment / detachment position closest to the attachment / detachment area 11B by rotation of the turntable 13.

  Each processing unit 30 is fixed to a slider 40 attached to the column 12 so as to be movable up and down. The slider 40 is slidably mounted on a guide rail 41 extending in the Z direction, and can be moved in the Z direction by a ball screw type feed mechanism 43 driven by a motor 42. Each processing unit 30 is moved up and down in the Z direction by the feed mechanism 43, and moves down to process the wafer by a feed operation that approaches the chuck table 20.

  In the center of the detachable area 11B, a two-bar link pickup robot 70 that moves up and down is installed. Around the pickup robot 70, a supply cassette 71, an alignment table 72, a supply arm 73, a recovery arm 74, a spinner type cleaning device 75, and a recovery cassette 76 are arranged counterclockwise as viewed from above. ing. The cassettes 71 and 76 accommodate a plurality of wafers in a horizontal posture and in a stacked state at a constant interval in the vertical direction, and are set at predetermined positions on the base 11.

  The wafer to be processed is first taken out from the supply cassette 71 by the pickup robot 70 and placed on the alignment table 72 to be determined at a certain position. Next, the wafer is picked up from the alignment table 72 by the supply arm 73 and placed on the chuck table 20 waiting at the attachment / detachment position with the back surface as the processing surface facing up. On the other hand, the wafer 1 on the chuck table 20 processed by the processing unit 30 and positioned at the attachment / detachment position is taken up by the recovery arm 74, transferred to the cleaning device 75, and washed and dried. The wafer 1 cleaned by the cleaning device 75 is transferred and accommodated in the collection cassette 76 by the pickup robot 70.

[2] Wafer as Workpiece (a) Wafer to be Grounded FIG. 2 shows a disk-shaped wafer whose back surface is ground and thinned by the processing apparatus 10. The wafer 1A has a thickness before processing of, for example, about 600 to 700 μm, and is thinned to a thickness of about 200 to 100 μm or about 50 μm by backside grinding. A plurality of rectangular semiconductor chips 3 are partitioned on the surface of the wafer 1A by grid-like division planned lines 2, and an electronic circuit (not shown) such as an IC or LSI is formed on the surface of the semiconductor chip 3. Has been.

  The plurality of semiconductor chips 3 are formed in a substantially circular device formation region 4 concentric with the wafer 1A. The device forming region 4 occupies most of the wafer 1A, and the outer peripheral portion of the wafer around the device forming region 4 is an annular outer peripheral region 5 in which the semiconductor chip 3 is not formed. A V-shaped notch 6 indicating the crystal orientation of the semiconductor is formed at a predetermined location on the peripheral surface of the wafer 1A. The wafer 1 </ b> A is finally cut and divided along the planned division line 2, and is divided into a plurality of semiconductor chips 3. In the back grinding of the wafer 1A, in addition to grinding the entire back surface, the region corresponding to the device formation region 4 may be ground and thinned to a target thickness to form a recess on the back surface.

  When the back surface of the wafer 1A is ground, for the purpose of protecting the electronic circuit, as shown in FIG. 2B, a protective tape 7 is attached to the surface on the side where the electronic circuit is formed. As the protective tape 7, for example, one having a configuration in which an adhesive of about 10 μm is applied to one side of a polyethylene or polyolefin sheet having a thickness of about 100 to 200 μm is used. The wafer 1 </ b> A is placed and held concentrically with the center of rotation of the chuck table 20 on the chuck table 20 at the attachment / detachment position of the processing apparatus 10.

(B) Wafer to be Polished FIG. 3 shows a wafer that is thinned by back surface grinding and whose ground back surface is polished by the processing apparatus 10. The wafer 1B is thinned to about 200 to 100 μm or about 50 μm as described above, and is the same as the wafer 1A shown in FIG. 2 except that it is thinned. That is, on the surface to which the protective tape 7 is attached, a plurality of semiconductor chips 3 on which electronic circuits are formed are partitioned by the division lines 2 and notches 6 are formed at predetermined locations on the peripheral surface. .

[3] Details of Processing Unit As shown in FIG. 4, the processing unit 30 is a cylindrical spindle housing 31 whose axial direction extends in the Z direction, and is coaxially and rotatably supported in the spindle housing 31. A spindle shaft portion 32, a motor 33 that is fixed to the upper end portion of the spindle housing 31 and rotationally drives the spindle shaft portion 32, and a disk-like flange 34 that is coaxially fixed to the lower end of the spindle shaft portion 32. ing. A working tool is detachably attached to the flange 34 by means such as screwing. Examples of the processing tool include a grinding tool for grinding the back surface of the wafer 1A shown in FIG. 2, and a polishing tool for polishing the back surface of the wafer 1B shown in FIG.

  FIG. 4 shows a state where the grinding tool 50 is grinding the back surface of the wafer 1 </ b> A shown in FIG. 2 by the processing unit 30 attached to the flange 34. In this case, as shown in FIG. 5, the region corresponding to the device formation region 5 is ground to form the recess 4A on the back surface, and the original thickness of the outer peripheral surplus region 5 remains around the recess 4A. As a result, an annular convex portion 5A protruding on the back surface is formed.

  As shown in FIG. 4, the grinding tool 50 is fixed to a lower end surface of a frame 51 having a disc shape and a lower conical shape, and a plurality of grindstones 52 arranged in an annular shape over the entire outer periphery of the lower end surface. It has been done. As the grindstone 52, for example, a vitreous sintered material called vitrified mixed with diamond abrasive grains and fired is used. As the grinding tool 50, a grinding tool 52 having a grinding outer diameter, that is, a diameter of the outer peripheral edge of the plurality of grinding wheels 52 is substantially equal to the radius of the wafer 1A is used. This corresponds to the device formation region 4 with the cutting edge of the grindstone 52 passing through the center of rotation of the wafer 1 and the inner peripheral edge of the outer peripheral surplus region 5 while leaving the thickness of the outer peripheral surplus region 5 when the back surface of the wafer 1A is ground. The dimension is set so that only the area to be ground can be ground to form the recess 4A.

  The back grinding of the wafer 1A is performed in at least two stages of rough grinding and finish grinding. In the processing apparatus 10, the upstream side in the transfer direction indicated by the arrow R of the chuck table 20 by the rotation of the turntable 13 ( The processing unit 30 on the back side in FIG. 1 is used for rough grinding, and the processing unit 30 on the downstream side is used for finish grinding. A grinding tool 50 including a grindstone 52 of, for example, # 280 to # 600 is attached to the flange 34 of the processing unit 30 for rough grinding, and the grindstone 52 is attached to the flange 34 of the processing unit 30 for finish grinding. For example, a grinding tool 50 including abrasive grains # 2000 to # 8000 is attached.

  In the ground wafer 1A, as shown in FIG. 5, grinding striations 9 having a shape in which a large number of arcs are radially drawn from the center remain on the bottom surface 4a of the recess 4A formed on the back surface. The grinding striation 9 is a trajectory of crushing processing by abrasive grains in the grindstone 52, and is a mechanical damage layer including microcracks and the like.

  FIG. 6 shows a state where the polishing tool 60 is polishing the entire back surface of the wafer 1 </ b> B shown in FIG. 3 by the processing unit 30 attached to the flange 34. In the polishing tool 60, a disk-shaped polishing pad 62 is fixed to the lower surface of a disk-shaped frame 61. The polishing pad 62 is formed by impregnating a base material such as a polishing cloth made of a non-woven fabric with a metal oxide polishing abrasive such as silica into a disk shape, and is fixed to the frame 61 by an adhesive means or the like. . The back surface of the wafer 1B is mirror-finished by polishing, and mechanical damage due to the grinding striations 9 as shown in FIG. 5 is removed, and the strength is improved.

  In the machining unit 30, the spindle shaft portion 32 is rotated by the motor 33, and the grinding tool 50 or the polishing tool 60 attached to the flange 34 is rotated, and the processing unit 30 is sent downward by the feeding mechanism 43 to rotate the grinding wheel 52 or the polishing wheel. By pressing the pad 62 against the back surface of the wafer, the back surface of the wafer is ground or polished. The lower surface that is the processing surface of the grinding tool 50 or the polishing tool 60 is parallel to the upper surface of the chuck table 20 on which the wafer is held. When grinding or polishing is performed, a predetermined grinding liquid and polishing liquid are supplied to the processed portion of the wafer as necessary.

Next, the bearing structure of the processing unit 30 according to the present invention will be described.
As shown in FIG. 7, the machining unit 30 employs an air bearing spindle structure that rotatably holds a spindle shaft portion 32 inserted into a spindle housing 31 with high-pressure air. FIG. 9 shows the details. As shown in FIG. 9, in the spindle housing 31, a bearing plate 313 is fixed to the lower end portion of the main housing body 311 through a ring 312. In the spindle shaft portion 32, a disk-shaped upper thrust plate 322 and a lower thrust plate 323 are fixed to a lower end portion of a main shaft portion main body 321 with a thrust collar 324 interposed therebetween. The flange 34 is fixed to the lower end surface of the lower thrust plate 323.

  The upper thrust plate 322 of the spindle shaft portion 32 is fitted with a gap between the housing body 311 and the bearing plate 313, and the bearing plate 313 of the spindle housing 31 has a gap between the upper and lower thrust plates 322 and 323. The spindle shaft portion 32 has a structure in which a thrust load is supported by fitting with a clearance.

  The bearing plate 313 of the spindle housing 31 has an air supply path 301 for supplying compressed high-pressure air to the upper and lower gaps 300a and 300b between the bearing plate 313 and the upper and lower thrust plates 322 and 323, and the gap between them. Air exhaust paths 302 for exhausting the air supplied to 300a and 300b are respectively formed. An opening 301 a of the air supply passage 301 and an opening 302 a of the air exhaust passage 302 are formed on the upper and lower end surfaces of the bearing plate 313.

  As shown in FIG. 8, the opening 301a of the air supply path 301 and the opening 302a of the air exhaust path 302 are respectively provided in the upper and lower sides (three in the illustrated example, but the number is not limited to this). They are formed at equal intervals in the circumferential direction and shifted in the radial direction at the same circumferential position. In this case, an opening 302 a of the air exhaust path 302 is formed on the outer peripheral side of the opening 301 a of the air supply path 301. In addition, one air supply path 301 is branched into each opening 301a, but the air exhaust path 302 is individually formed for each opening 302a.

  As shown in FIG. 9, an exhaust pipe 304 is connected to each air exhaust path 302, and the pressure of the air exhausted through the exhaust pipe 304 is detected by an air pressure sensor. A gap pressure measurement unit 401 for measuring based on the detection signal is connected. The air pressure measured by the gap pressure measuring unit 401 is equivalent to the air pressure of the gap 300 b facing the air exhaust side opening 302 a corresponding to the measuring unit 401. There are six gap pressure measuring units 401 corresponding to the three upper and lower air exhaust side openings 302 a in the circumferential direction, and the air pressures in the upper and lower gaps 300 a and 300 b are monitored by each gap pressure measuring unit 401. Is done.

  As a pressure sensor used in the gap pressure measuring unit 401, for example, MPS-R3SRC-GHA-D13 manufactured by Kuroda Pneumatics is preferably used. The air pressure detection signal measured by each gap pressure measurement unit 401 is supplied to the control unit 402. The control unit 402 controls the motor 42 of the feeding mechanism 43 via the drive unit 403. Further, the control unit 402 is connected to a storage unit 404 that stores predetermined information and receives the stored information.

[4] Processing Unit Control Operation by Control Unit Next, the operation of the processing unit 30 controlled by the control unit 402 will be described.
In the processing unit 30, compressed high-pressure air is pumped to the air supply path 301, so that the upper and lower gaps 300 a and 300 b are both vacated with the same gap amount (for example, about 20 μm) and rotated to the spindle housing 31. It is supported freely. Then, the processing unit 30 is lowered by the feed mechanism 43, and the processing tool such as the grinding tool 50 or the polishing tool 60 is pressed against the back surface of the wafer held on the chuck table 20, whereby the wafer is predetermined. Is processed.

  At the time of processing, the spindle housing 31 is lowered against the spindle shaft portion 32 which is pressed against the wafer and is fixed to the spindle shaft portion 32 in a fixed state, so that the spindle shaft portion 32 is relative to the spindle housing 31. Rises. Therefore, in the air bearing spindle, the upper gap 300a is larger than the original reference gap and the air pressure is lowered, whereas the lower gap 300b is smaller than the reference gap and the air pressure is increased.

  In actual operation, the pressure of air supplied from the air supply path 301 to the gaps 300a and 300b is, for example, about 0.5 MPa, and the exhaust pressure in this case is about 0.4 MPa. If the thrust load due to the pressing force of the spindle shaft portion 32 is about 10 N, the exhaust pressure changes by about 0.05 MPa (50 kPa) with respect to no load. Such fluctuation of the air pressure in the gap is measured by each gap pressure measuring unit 401. When the measured value shows an abnormal value, the control unit 402 controls the motor 42 via the driving unit 403 to send it. The feeding operation of the mechanism 43 is controlled. The abnormal value is, for example, a value exceeding a set threshold value, and the threshold value is stored in the storage unit 404.

  The measured value of the air pressure that is determined as an abnormal value by the control unit 402 may be the air pressure on either one of the upper and lower gaps 300a and 300b, or both. Alternatively, a more accurate air pressure may be obtained by averaging the difference between the upper and lower air pressures, that is, the amount of change. Furthermore, it is desirable that the measured values of the measurement points (air supply side opening 301a and air exhaust side opening 302a) arranged in the circumferential direction are respectively weighted and averaged.

  As a form of control of the feed operation, for example, there is a form in which the descent of the machining unit 30 is stopped and raised when the air pressure shows an abnormal value. At that time, for example, an alarm signal is displayed or sounded. May be. The storage unit 404 stores a load value received by the machining unit 30 at the maximum allowable gap as a target load value, and the control unit 402 determines that the load value based on the measurement value in the gap pressure measurement unit 401 is the target load. Feedback control may be performed so that the value converges. The load value here is converted by multiplying the value measured by the gap pressure measurement unit 401 by a coefficient. When such feedback control is performed, there is an advantage that processing can be performed without stopping the feeding operation of the processing unit 30.

  Note that the opposing surfaces of the bearing plate 313 and the upper and lower thrust plates 322 and 323 forming the upper and lower gaps 300a and 300b are not necessarily flat or inclined, so that the upper and lower gap amounts are increased. There may be variations in the circumferential direction that are not constant. This variation is also caused by the shaft shake of the spindle shaft portion 32. If there is such a variation, the air pressure differs in the circumferential direction, and control based on accurate air pressure measurement is not performed. Therefore, if the air pressure at a fixed position of the upper and lower thrust plates 322 and 323 of the rotating spindle shaft portion 32 is measured, the change in the gap amount is caused by deformation of the upper and lower thrust plates 322 and 323, shaft shake, or the like. It is not a thing, but it becomes a change of a regular gap amount, and the air pressure according to the gap amount can be measured accurately.

  For this purpose, the measurement timing may be made constant in consideration of the rotational speed of the spindle shaft portion 32. Specifically, for example, when the spindle shaft portion 32 rotates at 3600 rpm, the air is aired every 1/60 seconds. Measure the pressure. If it carries out like this, it will measure once per rotation and will always measure the air pressure of a fixed position.

  According to the present embodiment, the upper and lower gap amounts of the air bearing spindle that change with the feeding operation of the machining unit 30 are recognized by the change in the air pressure, and the feeding operation of the machining unit 30 is controlled. Can be reliably and stably performed. In addition, since it is not necessary to provide a load sensor on the spindle housing 31 or the chuck table 20, accurate and uniform machining can be achieved, and cost can be reduced.

[5] Form of processing unit that supports radial load The above embodiments are examples of an air bearing spindle that supports the thrust load of the spindle shaft portion 32, but the present invention supports the radial load. The present invention can also be applied to the form of an air bearing spindle.

  FIG. 10 shows such a configuration, in which the machining unit 30 is installed so as to be movable up and down in a state where the rotation shaft of the spindle shaft portion 32 is parallel to the upper surface of the chuck table 20. 80 is attached. The cutting edge of the cutting blade 80 is relatively thick, and the peripheral surface thereof grinds the back surface of the wafer (wafer 1B in FIG. 10) held on the chuck table 20.

  As shown in FIG. 11, the shaft portion main body 321 of the spindle shaft portion 32 of this embodiment has a thrust plate 325 in the vicinity of the tip, and the thrust plate 325 includes the housing main body 311 and the housing main body 311 of the spindle housing 31. And a bearing plate 313 fixed to the front end surface of the first through a thrust collar 312 with a gap. An air supply path 301 and an air exhaust path 302 are formed in the upper and lower portions of the thrust collar 312. The upper and lower openings 301 a and 302 a of the air supply passage 301 and the air exhaust passage 302 are located on the uppermost and lower sides on the inner peripheral surface of the thrust collar 312, and between the thrust collar 312 and the thrust plate 325 in that portion. It faces the upper and lower gaps 300a and 300b.

  As in the previous embodiment, an exhaust pipe 304 and a gap pressure measuring unit 401 are connected to each air exhaust path 302, and the air pressure in the upper and lower gaps 300a and 300b is monitored by these gap pressure measuring units 401. Further, similarly, each gap pressure measuring unit 401 is connected to a control unit 402 to which a motor driving unit 403 of the feed mechanism 43 and a storage unit 404 are connected.

  In this embodiment, the compressed high-pressure air is pumped to the air supply path 301 so that the annular gap between the thrust collar 312 and the thrust plate 325 is constant, and the spindle shaft portion 32 is connected to the spindle housing. 31 is rotatably supported. Then, the processing unit 30 is lowered by the feed mechanism 43 and the cutting blade 80 is pressed against the back surface of the wafer 1B held on the chuck table 20, whereby the wafer 1B is cut.

  At the time of this processing, the spindle housing 31 is lowered against the spindle shaft 32 that is pressed against the wafer 1B in the vertical direction with respect to the spindle shaft 32 that is fixed, so that the spindle shaft 32 moves against the spindle housing 31. Rise relatively. Accordingly, the upper gap 300a in the annular gap is reduced from the original reference gap to increase the air pressure, while the lower gap 300b is enlarged from the reference gap to lower the air pressure. Fluctuations in the air pressure in the gaps 300a and 300b are measured by the gap pressure measuring units 401. When the measured values indicate abnormal values, the control unit 402 controls the motor 42 via the driving unit 403, and the feed mechanism. The feeding operation of 43 is controlled in the same manner as in the above embodiment.

  In FIG. 11, an air exhaust passage and an exhaust pipe are provided near the tip of the spindle shaft portion 32. However, since the spindle shaft portion 32 is long, an air exhaust passage and an exhaust pipe are provided at least at both ends. In each case, the above-described configuration, that is, a configuration in which the air pressure in the gap is detected to control the feeding operation of the machining unit 30 may be provided.

[6] Form having an air bearing spindle on the chuck table side In each of the above embodiments, the air bearing spindle is provided on the machining unit 30 side. However, the present invention provides an air bearing spindle on the chuck table 20 side in the above embodiment. The present invention can also be applied to a form in which a bearing spindle is provided. The chuck table 20 shown in FIG. 10 has such a configuration, and the chuck table 20 is fixed to the upper end portion of the spindle shaft portion 22 that is rotatably supported by the table base 21. The spindle shaft portion 22 has upper and lower thrust plates 23 and 24 at an upper end portion, and a bearing plate 25 formed on the table base 21 is fitted between the thrust plates 23 and 24 with a gap therebetween.

  Also in this embodiment, similarly to the configuration shown in FIG. 9, an air supply path and an air exhaust path are provided in the bearing plate 25, and the upper and lower gaps between the upper and lower thrust plates 23 and 24 and the bearing plate 25 are gaps. The pressure is measured one by one by the pressure measuring unit, and the feeding operation of the machining unit 30 is controlled by the control unit. In this embodiment, when the wafer 1B is pressed by the cutting blade 80 of the processing unit 30, the chuck table 20 and the spindle shaft portion 22 are lowered, so that the upper gap is smaller than the original reference gap and the air pressure is reduced. On the contrary, the lower gap is larger than the reference gap and the air pressure is lowered.

  If the air pressure of the gap is detected in the air bearing spindle on the chuck table 20 side and the feed operation of the machining unit 30 is controlled as described above, the air pressure is not detected for the air bearing spindle on the machining unit 30 side. May be. However, more precise control is possible by detecting the air pressure in the gap of the air bearing spindle on both the chuck table 20 side and the processing unit 30 side and controlling the feed operation of the processing unit 30 based on the detected air pressure.

It is a perspective view of the processing apparatus which concerns on one Embodiment of this invention. It is the (a) perspective view and (b) side view of the wafer which are ground with the processing apparatus of one Embodiment. It is the (a) perspective view of the wafer ground with the processing device of one embodiment, and (b) the side view. It is the (a) perspective view of the state where the back surface of a wafer is ground and the crevice is formed in the processing unit which the processing device of one embodiment comprises, (b) The side view. FIG. 5A is a perspective view and FIG. 5B is a cross-sectional view of a wafer having a recess formed on the back surface by the processing unit of FIG. 4. It is the (a) perspective view in the state where the back surface of a wafer is ground with the processing unit which the processing device of one embodiment comprises, (b) side view. It is a side view which shows the air bearing spindle structure of the processing unit. It is a VIII-VIII arrow line view of FIG. It is sectional drawing which shows the detail of the air bearing spindle structure of FIG. FIG. 9 is a side view of a machining apparatus according to another embodiment of the present invention, in which an air bearing spindle structure is provided on each of a machining unit having a structure for supporting a radial load and a chuck table. It is sectional drawing which shows the detail of the air bearing spindle structure of the processing unit of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1A, 1B ... Semiconductor wafer 10 ... Processing apparatus 20 ... Chuck table (holding means)
30 ... Processing unit (processing means)
50 ... Grinding tools (processing tools)
60 ... Abrasive tool (processing tool)
DESCRIPTION OF SYMBOLS 31 ... Spindle housing 22, 32 ... Spindle shaft part 300a, 300b ... Gap 301 ... Air supply path 302 ... Air exhaust path 401 ... Gap pressure measurement part 402 ... Control part 404 ... Memory | storage part

Claims (5)

Holding means for holding the workpiece;
A processing device that holds a processing tool for processing the workpiece rotatably by an air bearing spindle, and has processing means for processing the workpiece by a feed operation approaching the holding means;
The air bearing spindle is
A spindle housing;
A spindle shaft portion rotatably inserted into the spindle housing and supporting the processing tool;
An air supply path formed in the spindle housing and configured to supply air to a gap between the spindle housing and the spindle shaft portion;
An air exhaust path formed in the spindle housing for exhausting air supplied to the gap;
Furthermore, the processing device comprises:
An air pressure sensor for detecting the pressure of air passing through the air exhaust path;
A gap pressure measurement unit that receives a detection signal of the air pressure sensor, measures the pressure of the gap based on the detection signal, and monitors the pressure of the gap;
A storage unit for storing a load value received by the processing means by a feeding operation as a predetermined target load value;
A processing apparatus comprising: the gap pressure measurement unit; and a control unit that controls the feeding operation of the processing unit based on information received from the storage unit. Holding means for holding the work piece rotatably by an air bearing spindle;
A processing device that rotatably holds a processing tool that processes the workpiece and that processes the workpiece by a feed operation that approaches the holding means;
The air bearing spindle is
A spindle housing;
A spindle shaft portion rotatably inserted into the spindle housing and supporting the holding means;
An air supply path formed in the spindle housing and configured to supply air to a gap between the spindle housing and the spindle shaft portion;
An air exhaust path formed in the spindle housing for exhausting air supplied to the gap;
Furthermore, the processing device comprises:
An air pressure sensor for detecting the pressure of air passing through the air exhaust path;
A gap pressure measurement unit that receives a detection signal of the air pressure sensor, measures the pressure of the gap based on the detection signal, and monitors the pressure of the gap;
A storage unit for storing a load value received by the processing means by a feeding operation as a predetermined target load value;
A processing apparatus comprising: the gap pressure measurement unit; and a control unit that controls the feeding operation of the processing unit based on information received from the storage unit.   The processing apparatus according to claim 1, wherein the processing tool is a grinding tool or a polishing tool having a processing surface parallel to a holding surface on which the holding unit holds the workpiece.   Control that multiplies the value measured by the gap pressure measurement unit by a coefficient to convert it into a load value, and controls the feed operation of the processing means so that the calculation result converges to the target load value stored in the storage unit The processing apparatus according to claim 1, further comprising a portion.   The processing apparatus according to claim 1, wherein the air pressure sensor detects air pressure at a constant position in a circumferential direction of the spindle shaft portion.

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