JP6489961B2 - Grinding equipment - Google Patents

Description

  The present invention relates to a grinding apparatus for grinding a wafer, and more particularly, to a grinding apparatus having a foreign matter removing mechanism for removing foreign matter attached to a holding surface of a chuck table.

  Grinding equipment used for grinding semiconductor wafers grinds the holding surface of the chuck table with a grinding wheel with the same diameter as the grinding wheel used for grinding, and then corrects the cone to a slight height before grinding the wafer. . This suppresses variations in the in-plane thickness of the ground wafer. In addition, if grinding debris adheres to the holding surface, the shape of the grinding debris is transferred to the wafer (dimple), resulting in variations in thickness. Clean by touching.

  TAIKO grinding is known to achieve both thinness and handling properties of semiconductor wafers (see, for example, Patent Document 1 and Patent Document 2). Even in the TAIKO grinding process, the holding surface is appropriately cleaned by a polishing tool.

JP 2007-19461 A JP 2008-60470 A

  In the grinding apparatus, the holding surface of the chuck table is formed in a conical shape having the center of rotation as the apex. However, in the grinding apparatus used for TAIKO grinding shown in Patent Document 1 and Patent Document 2, the conical shape of the holding surface is formed at a steeper angle than the grinding apparatus that grinds the entire back surface of the wafer. For this reason, in particular, in a grinding apparatus used for TAIKO grinding, the shape of the apex of the holding surface is easily changed by the polishing tool. Not only the grinding device used for TAIKO grinding, but the grinding device produces a poorly ground wafer in which the thickness of the wafer near the center of rotation becomes thicker than other parts when the top of the holding surface is cut. . For this reason, the grinding device is required to be able to quickly recognize the shape change of the apex of the holding surface, not limited to the grinding device used for TAIKO grinding.

  An object of the present invention is to provide a grinding apparatus that solves the above problems and can quickly recognize a change in shape of a holding surface.

  In order to solve the above-described problems and achieve the object, a grinding apparatus according to the present invention includes a chuck table that holds a wafer on a holding surface and is rotatably supported, and a grinding wheel that includes a grinding wheel is rotatably supported. Grinding means for grinding and thinning the back surface of the wafer held on the holding surface of the chuck table, and a foreign material for removing foreign matter adhering to the holding surface by bringing an abrasive tool into contact with the holding surface of the chuck table Removing means and confirmation means for measuring the thickness of the wafer held on the holding surface and confirming the shape change of the holding surface, and the holding surface of the chuck table is rotated before grinding the wafer. It is formed by a grinding wheel into a conical shape having an inclination with the center at the top, and the confirmation means oscillates a measurement wave that passes through the wafer from the back surface of the wafer and reflects it on the front and back surfaces of the wafer. Measuring means for measuring the thickness of the wafer held on the holding surface using a constant wave, and the thickness near the center of the wafer held and ground on the holding surface immediately after being formed into a conical shape on the holding surface. Storage means for measuring in a held state and storing the measured thickness as an initial value, and after storing the initial value, a thickness near the center of the wafer in a state where another wafer is ground and held on the holding surface When the difference between the measured value obtained by measuring and the initial value exceeds a predetermined amount, a comparison / determination unit that determines that there is a shape change of the holding surface is provided, and the shape change of the holding surface by the foreign matter removing unit It can be confirmed.

  Therefore, in the grinding apparatus of the present invention, since the confirmation means includes a measuring means for measuring the thickness of the wafer near the center of the holding surface, the shape change of the holding surface can be recognized quickly.

FIG. 1 is an external perspective view showing the configuration of the grinding apparatus according to the first embodiment. FIG. 2 is a perspective view of a wafer ground by the grinding apparatus according to the first embodiment. FIG. 3 is a perspective view of the wafer showing a state in which a protective tape is attached to the surface of the wafer shown in FIG. FIG. 4 is a perspective view showing a state where the wafer shown in FIG. 3 is ground. FIG. 5 is a partial cross-sectional view of a main part of the grinding apparatus shown in FIG. FIG. 6 is a partial cross-sectional view showing a state in which the measuring means of the grinding apparatus shown in FIG. 1 measures the thickness near the rotation center of the wafer held by the holding surface immediately after molding. FIG. 7 is a partial cross-sectional view showing a state in which the measuring unit of the grinding apparatus shown in FIG. 1 measures the thickness near the rotation center of another wafer. FIG. 8 is a flowchart showing an example of the machining operation of the grinding apparatus 1 shown in FIG. FIG. 9 is a partial cross-sectional view showing a state in which the measuring unit of the grinding apparatus according to the second embodiment measures the thickness near the rotation center of the wafer. FIG. 10 is a flowchart illustrating an example of a processing operation of the grinding apparatus according to the second embodiment.

  DESCRIPTION OF EMBODIMENTS Embodiments (embodiments) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited by the contents described in the following embodiments. The constituent elements described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the structures described below can be combined as appropriate. Various omissions, substitutions, or changes in the configuration can be made without departing from the scope of the present invention.

Embodiment 1
A grinding apparatus according to Embodiment 1 of the present invention will be described with reference to the drawings. 1 is an external perspective view showing a configuration of a grinding apparatus according to Embodiment 1, FIG. 2 is a perspective view of a wafer to be ground by the grinding apparatus according to Embodiment 1, and FIG. FIG. 4 is a perspective view of the wafer showing a state in which a protective tape is attached to the surface of the wafer shown, FIG. 4 is a perspective view showing a state where the wafer shown in FIG. 3 is ground, and FIG. It is a partial cross section figure of the principal part of the grinding apparatus shown by FIG.

  The grinding apparatus 1 according to the first embodiment is an apparatus for grinding (corresponding to processing) the wafer W (shown in FIG. 1) shown in FIG. Here, in the first embodiment, the wafer W to be processed is a disk-shaped semiconductor wafer or optical device wafer using silicon, sapphire, gallium nitride (GaN), or the like as a base material. As shown in FIG. 2, for example, the wafer W is divided into a plurality of regions by dividing lines L called streets formed in a lattice pattern on the surface WS, and the device D is formed in these divided regions. Yes. The wafer W includes a device region DR in which the device D is formed on the surface WS, and an outer peripheral surplus region GR that surrounds the device region DR. As shown in FIG. 3, the wafer W is attached to the protective tape T on the front surface WS on which the device D is formed, and the rear surface WR (corresponding to the processing surface) on the back side of the front surface WS is ground by the grinding wheel 23. The In the first embodiment, the wafer W is ground in a region corresponding to the device region DR on the back surface WR (a region overlapping in the thickness direction). As described above, the grinding apparatus 1 according to the first embodiment is an apparatus that performs TAIKO grinding of the wafer W.

  The grinding apparatus 1 grinds a region corresponding to the device region DR on the back surface WR of the wafer W, and forms a recess CD in a region corresponding to the device region DR on the back surface WR of the wafer W, as shown in FIG. The ring-shaped reinforcing portion RP including the outer peripheral surplus region GR is left on the outer peripheral side of the CD. The grinding apparatus 1 forms the concave portion CD in a region corresponding to the device region DR on the back surface WR of the wafer W, and the ring-shaped reinforcing portion RP including the outer peripheral surplus region GR is left on the outer peripheral side of the concave portion CD. This facilitates handling of the wafer W.

  As shown in FIG. 1, the grinding apparatus 1 is held by a chuck table 10 that holds a wafer W on a holding surface 10 a and is rotatably supported, a moving unit (not shown) that moves the chuck table 10, and a chuck table 10. Further, a grinding means 20 for grinding the wafer W, a grinding feed means 30, a foreign matter removing means 40 for removing foreign matter adhering to the holding surface 10a of the chuck table 10, and a confirmation means 50 are provided. As shown in FIG. 1, the grinding apparatus 1 includes a transfer robot 80, a temporary placement unit 90, two transfer units 95, a cleaning unit 85, and the like.

  The transport robot 80 takes out the unprocessed wafer W from the unprocessed material storage cassette 100a and supplies it to the temporary placement unit 90, and stores the ground wafer W from the cleaning means 85 into the processed product storage cassette 100b. Is. The transfer robot 80 includes a joint that allows the pick unit 81 that holds the wafer W to move in the X-axis direction parallel to the longitudinal direction of the grinding apparatus 1, the Z-axis direction orthogonal to the X-axis direction, and parallel to the vertical direction. The robot arm 82 includes a plurality of rotary joints that rotate around the Z axis. The unprocessed object storage cassette 100a and the processed object storage cassette 100b have the same configuration, and are installed at predetermined positions of the main body 2 of the grinding apparatus 1 to store a plurality of wafers W.

  In the temporary placement unit 90, the wafer W before grinding is placed by the transfer robot 80. One conveyance unit 95 rotates about the Z axis with respect to the apparatus main body 2 to place the wafer W before grinding on the temporary placement unit 90 on the chuck table 10 at the loading / unloading position. The other transport unit 95 transports the ground wafer W after grinding on the chuck table 10 at the carry-in / out position to the cleaning means 85 by rotating around the Z-axis with respect to the apparatus main body 2. The wafer W placed on the chuck table 10 at the carry-in / out position is moved to the grinding position below the grinding means 20 by the moving means and ground by the grinding means 20, and then moved to the carry-in / out position. The wafer W is transported to the cleaning unit 85 by the other transport unit 95, cleaned by the cleaning unit 85, and then stored in the processed product storage cassette 100b by the transport robot 80.

  The chuck table 10 is configured such that the protection tape T side of the wafer W is placed on the holding surface 10a and sucks and holds the wafer W placed on the holding surface 10a. The chuck table 10 has a disk shape in which a portion constituting the holding surface 10a is formed of porous ceramic or the like, and is connected to a vacuum suction source (not shown) via a vacuum suction path (not shown) and placed on the holding surface 10a. The wafer W is held by being sucked through the protective tape T. The chuck table 10 is provided so as to be movable in the X-axis direction parallel to the holding surface 10a by a moving means. The chuck table 10 is rotatably supported by a rotation driving unit (not shown), and can rotate the wafer W sucked and held by the rotation driving unit around a rotation axis passing through the center of the holding surface 10a. Note that the wafer W is carried in and out of the chuck table 10 at a carry-in / out position away from the grinding means 20. Further, the wafer W held at the grinding position below the grinding means 20 is ground on the chuck table 10. That is, the chuck table 10 is moved between the loading / unloading position and the grinding position by the moving means.

  Further, as shown in FIG. 5, the holding surface 10a of the chuck table 10 of the grinding apparatus 1 is gradually increased toward the outer peripheral portion PP with the rotation center RC as the apex before grinding the wafer W by the grinding means 20. It is formed into a conical shape having an inclination in a downward direction. 5 exaggerates the conical shape of the holding surface 10a of the chuck table 10. However, the inclination is so slight that it cannot be recognized with the naked eye. Since the grinding apparatus 1 of the first embodiment is a grinding apparatus 1 that performs so-called TAIKO grinding, the diameter of a grinding wheel for grinding a holding surface (not shown) that grinds the holding surface 10a is used to grind the entire back surface WR of the wafer W. It is smaller than the grinding wheel, and the conical shape of the holding surface 10a of the chuck table 10 is formed at a steeper angle than the grinding device that grinds the entire back surface WR of the wafer W. For this reason, in the grinding apparatus 1, the vicinity of the rotation center RC of the holding surface 10a is more easily scraped by the foreign matter removing means 40 than the grinding apparatus that grinds the entire back surface WR of the wafer W. When the holding surface 10a is formed by the grinding means 20, the rotation axis of the chuck table 10 is such that the outer edge of the grinding wheel of the grinding wheel for holding surface grinding contacts the outer peripheral portion PP from the rotation center RC of the holding surface 10a. And the rotation center RC of the holding surface 10a is positioned slightly above the outer peripheral portion PP of the holding surface 10a facing the rotation center RC with the outer peripheral portion PP in contact with the outer edge of the grinding wheel. Arranged slightly inclined with respect to the Z-axis direction.

  The grinding means 20 is rotatably supported by a grinding wheel 21 including a grinding wheel 23 that grinds the back surface WR of the wafer W before grinding held on the holding surface 10a of the chuck table 10 positioned at the grinding position. The wafer W is thinned by grinding the back surface WR of the wafer W held on the holding surface 10a. Further, before grinding the wafer W, the grinding means 20 uses the grinding wheel 21 for grinding the holding surface having the same diameter as that of the grinding wheel 21 for grinding the back surface WR of the wafer W to apex the rotation center RC of the holding surface 10a. The holding surface 10a is formed into a conical shape.

  The grinding means 20 includes a grinding water supply means (not shown) for supplying grinding water to the wafer W held on the chuck table 10 and a grinding wheel 21 (corresponding to a grinding member) that rotates at high speed around an axis parallel to the Z-axis direction. And a spindle unit 22 that rotates the grinding wheel 21 about its axis. The plurality of grinding wheels 23 included in the grinding wheel 21 are pressed against the back surface WR of the wafer W held on the chuck table 10 to grind the back surface WR of the wafer W. The grinding wheel 23 uses a metal bond, a resin bond, a vitrified bond, or the like as a bonding agent, and fixes abrasive grains such as diamond with one of these bonding agents. The diameter formed by the grinding wheel 23 disposed in an annular shape on the grinding wheel 21 is configured to be smaller than the diameter of the wafer W.

  The spindle unit 22 is mounted with a grinding wheel 21, and a spindle (not shown) that rotates the grinding wheel 21 around its axis and a movable base 25 that rotatably accommodates the spindle and is supported by the grinding feed means 30 are attached. And a spindle case 26.

  The grinding means 20 is processed and fed by the grinding feed means 30 while supplying grinding water from a grinding water supply means (not shown) while rotating the grinding wheel 21 around the Z axis, and the grinding wheel 23 is held on the chuck table 10. The wafer W is ground by being pressed against the back surface WR of the wafer W.

  The grinding means 20 is fed by grinding feed means 30 while supplying grinding water from a grinding water supply means (not shown) while rotating a grinding wheel for holding surface grinding around the Z axis, and chucks the grinding wheel. The holding surface 10 a is ground by being pressed against the holding surface 10 a of the table 10. The grinding means 20 grinds the holding surface 10a into a conical shape having the rotation center RC as a vertex.

  The grinding feed means 30 is for grinding and feeding the grinding means 20 to the holding surface 10 a of the chuck table 10. The grinding feed means 30 brings the grinding means 20 close to the wafer W held on the chuck table 10 and feeds the grinding means 20 by grinding. Further, the grinding feed means 30 moves the grinding means 20 away from the wafer W while keeping the grinding means 20 away from the wafer W held on the chuck table 10.

  The moving means is for moving the chuck table 10 relative to the grinding means 20 in the X-axis direction parallel to the holding surface 10a. In the first embodiment, the moving means moves the chuck table 10 in the X-axis direction parallel to the holding surface 10a over the carry-in / out position and the grinding position.

  The foreign matter removing means 40 is disposed between the chuck table 10 at the carry-in / out position and the grinding means 20. The foreign matter removing means 40 is for bringing the polishing tool 41 into contact with the holding surface 10a of the chuck table 10 positioned between the carry-in / out position and the grinding position, and removing foreign matter adhering to the holding surface 10a. .

  The foreign matter removing means 40 includes a polishing wheel 42 that rotates about an axis parallel to the Z-axis direction, and a spindle unit 43 that rotates the polishing wheel 42 about the axis. The polishing tool 41 included in the polishing wheel 42 is pressed against the holding surface 10a of the chuck table 10 to remove foreign matters attached to the holding surface 10a.

  The spindle unit 43 includes a spindle (not shown) to which the grinding wheel 42 is attached and rotates the grinding wheel 42 about its axis, and a spindle case 44 that rotatably accommodates the spindle and is supported by the foreign matter removing and feeding means 45. .

  The foreign matter removing means 40 is processed and fed by the foreign matter removing feed means 45 while rotating the polishing wheel 42 around the Z axis, and removes the foreign matter by pressing the polishing tool 41 against the holding surface 10 a of the chuck table 10.

  The foreign matter removing means 40 is supported on the apparatus main body 2 by a foreign matter removing and feeding means 45, a foreign matter removing and moving means 46 and a support frame 47. The support frame 47 is installed between the chuck table 10 at the loading / unloading position on the apparatus main body 2 and the grinding means 20. In the first embodiment, the support frame 47 is formed in a gate shape straddling the moving means. The foreign matter removing / moving means 46 is supported by the support frame 47 and moves the foreign matter removing means 40 in the Y axis direction perpendicular to the X axis direction and parallel to the width direction of the apparatus main body 2. The foreign matter removing and feeding means 45 is supported by the foreign matter removing and moving means 46 and is used to process and send the foreign matter removing means 40 to the holding surface 10 a of the chuck table 10. The foreign matter removing and feeding unit 45 moves the foreign matter removing and feeding unit 45 by processing the foreign matter removing unit 40 close to the holding surface 10a of the chuck table 10. Further, the foreign matter removal feeding means 45 moves the foreign matter removal means 40 away from the holding surface 10a.

  The confirmation means 50 is a means for measuring the thickness of the wafer W held on the holding surface 10a and checking the shape change of the holding surface 10a. The confirmation unit 50 includes a measurement unit 60 and a control unit 70.

  The measuring means 60 oscillates a measurement wave that passes through the wafer W from the back surface WR of the wafer W, and uses the measurement wave reflected by the front surface WS and the back surface WR of the wafer W, and the thickness of the wafer W held on the holding surface. Is to measure. The measuring unit 60 is disposed below the grinding unit 20 of the apparatus main body 2. As shown in FIG. 5, the measuring means 60 has a measuring position (shown in FIG. 6) in which the other end 61b faces the rotation center RC of the holding surface 10a of the chuck table 10 at the grinding position 1 with the one end 61a as the center. The other end 61b is rotatably provided over a retracted position (shown in FIG. 5) where the other end 61b is retracted from the holding surface 10a of the chuck table 10 at the grinding position, and the other end of the arm 61. And a sensor 62 facing the rotation center RC of the holding surface 10a of the chuck table 10 at the measurement position. When the arm portion 61 is positioned at the measurement position, the sensor 62 irradiates measurement light, which is a measurement wave, toward the holding surface 10a of the chuck table 10 holding the wafer W, and the back surface WR and the front surface WS of the wafer W. The thickness of the wafer W can be calculated by receiving the reflected light. In the present invention, the measuring means 60 is a spectroscopic interferometer that irradiates measurement light as a measurement wave from the sensor 62 and measures the phase difference of the reflected light, an infrared microscope that irradiates an infrared ray as a measurement wave and measures it according to the focal position, measurement It may be an ultrasonic measurement device that measures ultrasonic waves that are reflected by irradiating ultrasonic waves.

  The control means 70 controls the above-described components constituting the grinding apparatus 1 to cause the grinding apparatus 1 to perform grinding on the wafer W. The control means 70 is mainly composed of an arithmetic processing unit constituted by, for example, a CPU or the like and a microprocessor (not shown) provided with a ROM, a RAM, etc., and a display means 200 for displaying the state of the machining operation or an operator It is connected to an operation means (not shown) used when registering processing content information and the like.

  As illustrated in FIG. 1, the control unit 70 includes a storage unit 71, a comparison determination unit 72, and a notification unit 73. The storage means 71 is measured by the measuring means 60 in a state in which the thickness near the rotation center RC of the wafer W held and ground in the conical shape is held by the holding face 10a immediately after being formed is held by the holding face 10a. The measured thickness of the wafer W is stored as an initial value. The storage means 71 always stores the latest initial value.

  After the storage means 71 stores the initial value, the comparison determination means 72 is a state in which another wafer W is ground and held by the holding surface 10a and the thickness near the rotation center RC of the wafer W is held by the holding surface 10a. Then, the measuring means 60 measures, and the measured value of the measuring means 60 is compared with the initial value. The comparison determination unit 72 determines that the shape of the holding surface 10a has changed when the difference between the measured value and the initial value exceeds a predetermined amount. The predetermined amount is a value corresponding to the intersection of the devices D when the wafer W is divided into the devices D. If the predetermined amount is not exceeded, the dimensions of the device D are within tolerance, and if the predetermined amount is exceeded, the device D The dimension of exceeds the tolerance.

  The notification unit 73 is configured by at least one of a lighting unit, a display unit, or a speaker provided in the control unit 70. When the comparison determination unit 72 determines that the shape of the holding surface 10a has changed, the notification unit 73 is turned on. A display or notification sound is output to notify the operator that the shape of the holding surface 10a has changed.

  Next, the processing operation of the grinding apparatus 1 according to the first embodiment will be described with reference to the drawings. FIG. 6 is a partial cross-sectional view showing a state in which the measuring means of the grinding apparatus shown in FIG. 1 measures the thickness near the rotation center of the wafer held by the holding surface immediately after molding, and FIG. FIG. 8 is a partial cross-sectional view showing a state in which the measuring means of the grinding apparatus shown in FIG. 1 measures the thickness near the rotation center of another wafer, and FIG. 8 shows the processing of the grinding apparatus 1 shown in FIG. It is a flowchart which shows an example of operation | movement.

  In the machining operation, first, when the operator registers the machining content information in the control means 70 and the operator gives an instruction to start the machining operation, the grinding device 1 starts the machining operation. In the processing operation, the grinding device 1 positions the chuck table 10 below the foreign matter removing means 40 without holding the wafer W on the holding surface 10a every time a predetermined number of wafers W are ground. Is pressed against the holding surface 10a to remove foreign matter adhering to the holding surface 10a.

  First, in the holding surface machining operation, the control device 100 positions the chuck table 10 at the grinding position, positions the arm portion 61 of the measuring means 60 at the retracted position, and rotates the chuck table 10 around the axis while grinding the grinding means 20. The holding wheel grinding wheel is rotated against the holding surface 10a for a predetermined time around the axis. Thus, before grinding the wafer W, the control means 70 forms the holding surface 10a of the chuck table 10 into a conical shape having an inclination with the rotation center RC as the apex with a grinding wheel for holding surface grinding (step ST1). .

  The control means 70 moves the chuck table 10 to the loading / unloading position after separating the grinding means 20 from the chuck table 10. Thereafter, the grinding wheel for holding surface grinding may be replaced with a grinding wheel 21 for grinding the wafer W. Then, the control means 70 causes the transfer robot 80 to take out the unprocessed wafer W from the unprocessed article storage cassette 100a and supply it to the temporary placement unit 90, and places it on the temporary placement unit 90 on one transfer unit 95. The wafer W thus placed is placed on the holding surface 10a of the chuck table 10 at the loading / unloading position. The control means 70 sucks and holds the wafer W placed on the chuck table 10 and moves the chuck table 10 holding the wafer W to the grinding position. When the wafer W is sucked by the holding surface 10a of the chuck table 10, the wafer W is in close contact with the holding surface 10a through the protective tape T over the entire surface WS.

  The control means 70 feeds the grinding means 20 to the grinding feed means 30 while rotating the chuck table 10 and the grinding wheel 23. The control means 70, while supplying the grinding water to the wafer W, brings the grinding wheel 23 into contact with the end portion of the back surface WR including the rotation center RC of the back surface WR and close to the outer peripheral surplus region GR, thereby increasing the thickness of the wafer W. Grind until the thickness reaches a predetermined thickness (step ST2).

  When the grinding is completed, that is, when the thickness of the wafer W reaches a predetermined thickness, the control means 70 separates the grinding means 20 from the chuck table 10 and moves the arm portion 61 of the measuring means 60 as shown in FIG. Position at the measurement position. Then, the control means 70 irradiates the measurement light transmitted through the wafer W from the sensor 62 toward the rotation center RC of the chuck table 10 and receives the measurement light reflected by the front surface WS and the back surface WR of the wafer W. Then, the storage unit 71 of the control unit 70 measures the thickness near the center of the wafer W by the holding surface 10a based on the measurement result of the measuring unit 60, and stores the measured thickness as an initial value ( Step ST3).

  After storing the initial value, the control means 70 positions the arm portion 61 of the measurement means 60 in the retracted position, moves the chuck table 10 to the carry-in / out position, and cleans the wafer W that has been ground in the other transport unit 95 by the cleaning means 85. And the ground wafer W is cleaned by the cleaning means 85, and is then stored in the processed product storage cassette 100b by the transfer robot 80. Further, the control means 70 grinds another wafer W in the same manner as in step ST2 by causing the transfer robot 80 to take out another wafer W before grinding from the unprocessed article storage cassette 100a (step ST4). When the grinding of the predetermined number of wafers W is completed, the control unit 70 appropriately polishes the holding surface 10a by the foreign matter removing unit 40.

  When the grinding of another wafer W is completed, the control means 70 separates the grinding means 20 from the chuck table 10 and positions the arm portion 61 of the measurement means 60 at the measurement position as shown in FIG. Then, the control means 70 irradiates the measurement light transmitted through the wafer W from the sensor 62 toward the rotation center RC of the chuck table 10 and receives the measurement light reflected by the front surface WS and the back surface WR of the wafer W. Then, the control means 70 determines that the difference between the measured value obtained by measuring the thickness near the rotation center RC of another wafer W while being held by the holding surface 10a from the measurement result of the measuring means 60 and the initial value is a predetermined amount. It is determined whether or not there is a change in shape of the holding surface 10a (step ST5). As shown in FIG. 7, when the vicinity of the rotation center RC of the holding surface 10a is cut, the thickness near the rotation center RC of the wafer W after grinding becomes thicker than other portions. The grinding apparatus 1 requires about 10 seconds for the initial value storage (step ST3) and the comparison between the initial value and the measured value (step ST5).

  As shown in FIG. 7, the comparison / determination unit 72 of the control unit 70 determines that there is a change in the shape of the holding surface 10a when the difference between the measured value and the initial value exceeds a predetermined amount (step ST5: Yes). The notification means 73 informs the operator and returns to step ST1, stores the wafer W held on the chuck table 10 in the processed product storage cassette 100b, and then uses the grinding wheel for holding surface grinding to hold the holding surface 10a conically. Form into a shape (step ST1).

  When the difference between the measured value and the initial value does not exceed the predetermined amount, the comparison / determination unit 72 of the control unit 70 determines that there is no change in the shape of the holding surface 10a (step ST5: No). It is determined whether or not all the wafers W in the cassette 100a have been ground (step ST6). If the control means 70 determines that all the wafers W in the workpiece storage cassette 100a are not ground (step ST6: No), the control means 70 returns to step ST4, grinds another wafer W, and stores the workpieces. When it is determined that all the wafers W in the cassette 100a have been ground (step ST6: Yes), the processing operation is terminated. Thus, in the grinding apparatus 1, the comparison / determination unit 72 determines whether or not the difference between the measured value and the initial value exceeds a predetermined amount, whereby the shape change of the holding surface 10 a by the foreign matter removing unit 40 is performed. Can be confirmed.

  As described above, according to the grinding apparatus 1 according to the first embodiment, since the confirmation means 50 for measuring the thickness of the wafer W held on the holding surface 10a near the rotation center RC is provided, in particular, TAIKO grinding. It is possible to quickly recognize a shape change in the vicinity of the rotation center RC of the holding surface 10a that is likely to occur. For this reason, the grinding apparatus 1 can correct the shape of the holding surface 10a of the chuck table 10 without manufacturing a defective wafer W.

  In the grinding apparatus 1, the measuring unit 60 irradiates the measurement light from the back surface WR of the wafer W held on the holding surface 10 a, and measures the thickness of the rotation center RC of the wafer W. For this reason, since the grinding apparatus 1 does not directly measure the height near the rotation center RC of the holding surface 10a made of porous ceramics, it can accurately recognize the shape change near the rotation center RC of the holding surface 10a. it can. This is because the holding surface made of porous ceramics has a slight unevenness, and it is difficult to accurately measure the height directly. Thus, the grinding apparatus 1 accurately measures the shape change in the vicinity of the rotation center RC of the holding surface 10a by directly measuring the thickness variation in the surface of the wafer W, which is a problem due to the shape change of the holding surface 10a. Can be recognized.

  Since the grinding apparatus 1 measures the thickness of the wafer W near the rotation center RC immediately after grinding, the wafer W is maintained in a clean state by the grinding water immediately after grinding, and thus is affected by grinding debris. Therefore, the thickness of the wafer W can be measured accurately. Further, since the time required for storing the initial value (step ST3) and comparing the initial value with the measured value (step ST5) is about 10 seconds, the grinding apparatus 1 decreases the productivity of grinding the wafer W. This can be suppressed.

  Further, in the grinding apparatus 1, since the measuring means 60 measures the thickness of the rotation center RC of the wafer W from the back surface WR of the wafer W held on the holding surface 10a, in particular, the vicinity of the rotation center RC of the holding surface 10a is shaved. In easy TAIKO grinding, it is possible to recognize a shape change in the vicinity of the rotation center RC of the holding surface 10a, and to suppress the production of a defective wafer W.

[Embodiment 2]
A workpiece grinding method according to Embodiment 2 of the present invention will be described with reference to the drawings. FIG. 9 is a partial cross-sectional view showing a state in which the measuring unit of the grinding apparatus according to the second embodiment measures the thickness near the rotation center of the wafer, and FIG. 10 is a processing operation of the grinding apparatus according to the second embodiment. It is a flowchart which shows an example. 9 and 10, the same parts as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  In the grinding apparatus 1 according to the second embodiment, as shown in FIG. 9, the measuring unit 60 includes a sensor 62 provided at the other end portion 61 b of the arm portion 61 and facing the rotation center RC of the holding surface 10 a at the measurement position. The second sensor 63 provided in the arm portion 61 is provided closer to the one end portion 61a, for example, by about 10 mm than the sensor 62. In the grinding apparatus 1, the measuring unit 60 measures the thickness near the rotation center RC of the wafer W, and the second sensor 63 measures the thickness on the outer peripheral side of the rotation center RC of the wafer W. In the grinding apparatus 1, the comparison / determination unit 72 of the control unit 70 uses the measured value obtained by measuring the thickness near the rotation center RC of the wafer W measured by the sensor and the rotation center RC of the wafer W measured by the second sensor 63. Also, the measured value of the outer peripheral thickness is compared. When the difference between the measured value measured by the sensor 62 and the measured value measured by the second sensor 63 exceeds a predetermined amount, the grinding apparatus 1 changes the shape of the holding surface 10a. Judged to be present.

  Next, the processing operation of the grinding apparatus 1 according to the second embodiment will be described with reference to the drawings. In the machining operation, first, when the operator registers the machining content information in the control means 70 and the operator gives an instruction to start the machining operation, the grinding device 1 starts the machining operation. In the processing operation, before grinding the wafer W, the control device 100 forms the holding surface 10a of the chuck table 10 into a conical shape having an inclination with the rotation center RC as a vertex with the grinding wheel 21 (step ST1).

  The control means 70 brings the grinding wheel 23 into contact with the end portion of the back surface WR of the back surface WR including the rotation center RC and close to the outer peripheral surplus region GR, and grinds until the thickness of the wafer W reaches a predetermined thickness. (Step ST2). When the grinding is completed, that is, when the thickness of the wafer W reaches a predetermined thickness, the control means 70 positions the arm portion 61 of the measurement means 60 at the measurement position as shown in FIG. Then, the control means 70 irradiates the measurement light transmitted through the wafer W from the sensor 62 toward the rotation center RC of the chuck table 10 and receives the measurement light reflected by the front surface WS and the back surface WR of the wafer W. The control means 70 irradiates the measurement light transmitted through the wafer W from the second sensor 63 toward the outer peripheral side of the rotation center RC of the chuck table 10 and receives the measurement light reflected by the front surface WS and the back surface WR of the wafer W. To do. Then, the control means 70 measures the measured value of the thickness near the rotation center RC of the wafer W while being held by the holding surface 10a based on the measurement result of the measuring means 60, and the wafer W being held by the holding face 10a. It is determined whether or not the difference from the measured value obtained by measuring the thickness on the outer peripheral side of the rotation center RC exceeds a predetermined amount, that is, whether or not the shape of the holding surface 10a has changed (step ST5). In addition, the grinding apparatus 1 requires about 10 seconds for the comparison of measured values (step ST5).

  When the difference between the measured values exceeds a predetermined amount, the comparison determination unit 72 of the control unit 70 determines that there is a change in the shape of the holding surface 10a (step ST5: Yes), and notifies the operator by the notification unit 73. Returning to step ST1, after the wafer W held on the chuck table 10 is stored in the processed product storage cassette 100b, the holding surface 10a is formed into a conical shape by the grinding wheel 21 (step ST1).

  When the comparison / determination unit 72 of the control unit 70 determines that the shape of the holding surface 10a does not change when the difference between the measured values does not exceed the predetermined amount (step ST5: No), the comparison / determination unit 72 in the unprocessed object accommodation cassette 100a. It is determined whether or not all wafers W have been ground (step ST6). When the control means 70 determines that all the wafers W in the workpiece storage cassette 100a are not ground (step ST6: No), the control means 70 returns to step ST2, grinds another wafer W, and stores the workpieces. When it is determined that all the wafers W in the cassette 100a have been ground (step ST6: Yes), the processing operation is terminated. Thus, the grinding apparatus 1 can confirm the shape change of the holding surface 10a by the foreign material removing means 40 by determining whether or not the difference between the measured values exceeds a predetermined amount. it can.

  As described above, according to the grinding apparatus 1 according to the second embodiment, the check unit 50 for measuring the thickness of the wafer W held on the holding surface 10a near the rotation center RC is provided. It is possible to recognize a shape change in the vicinity of the rotation center RC of the holding surface 10a that easily occurs. For this reason, the grinding apparatus 1 can correct the shape of the holding surface 10a of the chuck table 10 without manufacturing a defective wafer W.

  In the grinding apparatus 1 according to the second embodiment, the sensor 62 measures the thickness near the rotation center RC of the wafer W, and the second sensor 63 measures the thickness on the outer peripheral side of the rotation center RC of the wafer W. . The grinding device 1 determines that there is a change in the shape of the holding surface 10a when the comparison determination unit 72 of the control unit 70 exceeds the predetermined amount. For this reason, since the grinding apparatus 1 does not need to measure and memorize | store an initial value after shape | molding the shape of the holding surface 10a, it can improve the processing efficiency of grinding.

  Thus, the confirmation unit 50 of the grinding apparatus 1 according to the second embodiment uses the measurement waves that oscillate from the back surface WR of the wafer W and are reflected by the front surface WS and the back surface WR of the wafer W. A measuring means 60 for measuring the thickness of the wafer W held by the holding surface 10a, and a measurement value obtained by measuring the thickness of the wafer W near the rotation center RC in a state where the wafer W is ground and held by the holding surface 10a. Comparison determining means for determining that there is a change in the shape of the holding surface 10a when the difference from the measured value of the thickness measured on the outer peripheral side of the rotation center RC of the wafer W held by the holding surface 10a exceeds a predetermined amount. 72, and the shape change of the holding surface 10a by the foreign matter removing means 40 can be confirmed. Further, the grinding device 1 moves the sensor 62 of the grinding device 1 according to the first embodiment by turning the arm portion 61, and the sensor 62 determines the thickness of the rotation center RC of the wafer W and the thickness on the outer peripheral side of the rotation center RC. You may measure with.

  The present invention is not limited to the above embodiment. That is, various modifications can be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Grinding device 10 Chuck table 10a Holding surface 20 Grinding means 21 Grinding wheel 23 Grinding wheel 40 Foreign matter removing means 41 Polishing tool 50 Confirming means 60 Measuring means 71 Storage means 72 Comparison judging means W Wafer WS Surface WR Back surface RC Rotation center

Claims (1)

A chuck table that holds a wafer on a holding surface and is rotatably supported, and a grinding wheel including a grinding wheel is rotatably supported and the back surface of the wafer held on the holding surface of the chuck table is ground and thinned. Grinding means for removing the foreign matter adhering to the holding surface by bringing a polishing tool into contact with the holding surface of the chuck table, and measuring the thickness of the holding surface by measuring the thickness of the wafer held on the holding surface. A confirmation means for confirming the shape change,
The holding surface of the chuck table is
Before grinding the wafer, it is formed with a grinding wheel into a conical shape with a slope centered on the rotation center,
The confirmation means is
A measuring means for measuring the thickness of the wafer held on the holding surface using the measurement waves oscillated from the back surface of the wafer and reflected from the front and back surfaces of the wafer, and a measurement wave that passes through the wafer;
Storage means for measuring the thickness near the center of the wafer held and ground by the holding surface immediately after being formed into a conical shape in a state of being held by the holding surface, and storing the measured thickness as an initial value;
After storing the initial value, if the difference between the measured value obtained by measuring the thickness near the center of the wafer with another wafer ground and held by the holding surface exceeds the predetermined amount, Comparing and determining means for determining that there is a shape change of the holding surface,
A grinding apparatus capable of confirming the shape change of the holding surface by the foreign matter removing means.

Images