JP2019075494A - Grinding method and grinding device of workpiece - Google Patents

Abstract

To prevent unintended grinding of a surface protective member stuck to a surface side of a workpiece by a grind stone in a grinding device.SOLUTION: A grinding method for a workpiece includes a step of covering a workpiece surface with a protective member, a step of holding the workpiece on a holding surface of a chuck table 30, a thickness measurement step of bringing a thickness measuring instrument 382 into contact with the surface of the workpiece opposite to the workpiece holding surface and measuring a thickness, and then calculating a variation from measured first thickness data and second thickness data measured upon elapsing arbitrary time from the moment in time when the first thickness data is measured, and a step of grinding a reverse face of the workpiece. In the thickness measurement step, if the calculated variation is less than a previously registered threshold level, a determination is made that the surface of the workpiece in contact with the thickness measuring instrument 382 is the reverse face of the workpiece and grinding is started, and if the calculated variation exceeds the previously registered threshold level, a determination is made that the surface of the workpiece in contact with the thickness measuring instrument 382 is a surface protective member and grinding is not started.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a method for grinding a plate-like workpiece such as a semiconductor wafer and a grinding apparatus for grinding the workpiece.

  The back surface of the workpiece with IC and LSI devices formed on multiple surfaces is ground and thinned to a predetermined thickness, and then divided into individual device chips by a dividing device such as a dicing device. Used in various electronic devices.

  A grinding apparatus (see Patent Document 1, for example) for grinding the back surface of a workpiece comprises a chuck table for holding the surface side of the workpiece to which a surface protection member is attached, and the workpiece held by the chuck table And a grinding means for rotatably supporting a grinding wheel for grinding the back surface of the workpiece, and the workpiece can be ground efficiently.

Patent No. 5025200 gazette

  However, in the grinding apparatus as described above, when the workpiece is held by the chuck table, the back surface side of the workpiece which is not covered by the surface protection member is accidentally attracted by the holding surface of the chuck table. There is. When the back side of the workpiece is absorbed by the chuck table, the grinding wheel grinds the surface protection member on the front side of the workpiece, and the current value of the motor that rotates the grinding wheel due to processing defects It may happen that the full-automatic operation of the grinding device is stopped. In such a case, it is necessary to dress (set up) the grinding wheel to return to a normal state, which leads to an increase in the downtime of the grinding apparatus.

  Therefore, in the grinding apparatus, there is a problem that the surface protection member stuck on the surface side of the workpiece by the grinding stone is not accidentally ground.

  The present invention for solving the above problems is a workpiece that has a surface on which a device is formed in a region partitioned by a plurality of planned dividing lines formed in a grid, and the back surface of the workpiece is ground with a grinding stone And a surface protection step of covering the surface of the workpiece with a surface protection member, and after performing the surface protection step, the workpiece can be rotated on a rotation axis whose axial direction is the vertical direction. After carrying out the holding step held by the holding surface of the chuck table and the holding step, the thickness measuring device is brought into contact with the surface opposite to the surface held by the chuck table of the workpiece to make the thickness of the workpiece A thickness measurement step of calculating the amount of change from the first thickness data measured and the second thickness data measured after an arbitrary time from the time of measuring the first thickness data, and the thickness Measurement And performing a grinding step of grinding the back surface of the workpiece while supplying grinding water with a grinding wheel rotating on a rotation axis orthogonal to the holding surface, and calculating the thickness in the thickness measurement step. If the amount of change is equal to or less than a pre-registered threshold value, it is determined that the surface of the workpiece to which the thickness measuring device is in contact is the back surface of the workpiece where the thickness measuring device hardly sinks. The grinding step is started, and if the calculated amount of change exceeds the pre-registered threshold value, the surface of the workpiece to which the thickness measuring device is in contact tends to cause the thickness measuring device to sink. It is a grinding method which judges that it is the surface protection member and does not start the grinding step.

  The surface protection member may be, for example, an adhesive tape.

  Further, according to the present invention for solving the above problems, there are provided a chuck table for holding a workpiece, a thickness measuring means for measuring the thickness of the workpiece held by the chuck table, and the chuck table And a grinding device for grinding the workpiece, wherein the chuck table is rotatable about a rotation axis having an axis in the vertical direction, and a surface protection member is attached on the holding surface. The workpiece is held, and the thickness measuring means measures the thickness by bringing the thickness measuring device into contact with the surface of the workpiece opposite to the surface held by the chuck table before starting the grinding of the workpiece. The grinding means grinds the back surface of the workpiece while supplying grinding water with a grinding wheel rotating on a rotation axis orthogonal to the holding surface of the chuck table, and the first thickness measured by the thickness measuring means Data and first thickness Calculation means for calculating the amount of change from the second thickness data measured after an arbitrary time has elapsed since the time the data was measured, and the amount of change calculated by the calculation means is equal to or less than a threshold previously registered And a control means for starting grinding and displaying an error if the amount of change exceeds the pre-registered threshold value and not for starting grinding. is there.

  The thickness measuring means is preferably used to measure the thickness of the workpiece before the start of grinding and to control the thickness of the workpiece after the start of grinding.

  In the thickness measurement of a workpiece by the thickness measurement means, when the measurement surface is a surface protection member having flexibility, the thickness of the workpiece is measured by the sinking of the thickness measurement device provided in the thickness measurement means into the surface protection member. The amount of change increases. On the other hand, when the measurement surface is a hard back surface which is the surface to be ground of the workpiece, the amount of change in thickness of the workpiece is small because the thickness measuring device provided in the thickness measuring means hardly sinks into the back surface. Therefore, in the grinding method according to the present invention, after performing the surface protection step of covering the surface of the workpiece with the surface protection member and the surface protection step, the workpiece can be rotated about the rotation axis whose axial direction is the vertical direction. After carrying out the holding step held by the holding surface of the chuck table and the holding step, the thickness measuring device is brought into contact with the surface opposite to the surface held by the chuck table of the workpiece to measure the thickness of the workpiece Measurement and thickness measurement steps of calculating the amount of change from the measured first thickness data and the second thickness data measured after the lapse of an arbitrary time from the time when the first thickness data was measured; And a grinding step of grinding the back surface of the workpiece while supplying grinding water with a grinding wheel rotating on a rotation axis orthogonal to the holding surface, and calculating the amount of change in the thickness measurement step. If it is equal to or less than the pre-registered threshold value, it is determined that the surface of the workpiece to which the thickness measuring device is in contact is the back surface of the workpiece with which the thickness measuring device hardly sinks and starts the grinding step If the amount of change exceeds the pre-registered threshold value, it is determined that the surface of the workpiece to which the thickness measuring device is in contact is a surface protection member that tends to cause the thickness measuring device to sink, and the grinding step is started. If the workpiece is sucked and held in the wrong state by the chuck table, that is, if the back surface, which is the surface to be ground of the workpiece, is adsorbed by the chuck table, the workpiece is not moved as it is. The grinding step is not performed, and the surface protection member is not ground to cause grinding defects.

  The grinding apparatus according to the present invention is the amount of change from the first thickness data measured by the thickness measuring means and the second thickness data measured after the lapse of an arbitrary time from the time when the first thickness data is measured. The grinding means is started if the amount of change calculated by the calculation means and the amount of change calculated by the calculation means is equal to or less than a threshold registered in advance, and an error is indicated if the amount of change exceeds the threshold registered in advance. By including control means for displaying and not starting grinding, the workpiece is sucked and held in an incorrect state by the chuck table, that is, the back surface of the workpiece to be ground is the chuck In the case where the surface protection member is absorbed by the table, the surface protection member is not ground as it is by the grinding means, and the grinding failure is not generated.

  The thickness measuring means of the grinding apparatus is used to measure the thickness of the workpiece before the start of grinding and is also used to control the thickness of the workpiece after the start of grinding, whereby the miniaturization of the grinding apparatus can be achieved, and It is possible to prevent an increase in the manufacturing cost of the grinding apparatus.

It is a perspective view showing an example of a grinding device. It is a perspective view which shows the state which has covered the surface of a to-be-processed object by the surface protection member. A cross-sectional view showing a state in which the second thickness measuring device is brought into contact with the back surface opposite to the front surface to which the surface protection member held by the chuck table of the workpiece is attached. It is. Sectional drawing which shows the state which is making the 2nd thickness measuring device contact the surface protection member stuck on the surface on the opposite side to the back side held by the chuck table of the workpiece, and to measure the thickness of the workpiece It is. A graph showing transition of the thickness of the workpiece when the thickness of the workpiece is measured by bringing the second thickness gauge into contact with the back surface, and contacting the second thickness gauge with the surface protection member It is a graph which shows transition of the thickness of a workpiece at the time of measuring thickness of a workpiece. It is sectional drawing which shows the state which is rough-grind by rough grinding means, while control of thickness is carried out of a to-be-processed object.

A grinding apparatus 3 according to the present invention shown in FIG. 1 is an apparatus for performing grinding on a workpiece W suctioned and held by a chuck table 30.
The workpiece W shown in FIG. 1 is, for example, a semiconductor wafer having a circular plate shape whose outer shape has silicon as a base material, and in FIG. A planned line S is formed, and devices D such as ICs are respectively formed in respective areas divided in a grid shape by the planned dividing line S. The back surface Wb opposite to the surface Wa of the workpiece W is a surface to be ground to be ground. The workpiece W may be made of gallium arsenide, sapphire, gallium nitride, silicon carbide or the like in addition to silicon, and its outer shape may not be circular but may be rectangular, for example.

  The front (−Y direction side) on the base 3A of the grinding apparatus 3 is an area where the workpiece W can be attached to and detached from the chuck table 30 by the robot 330 capable of transporting the workpiece W. The rear side (+ Y direction side) on 3A is held on the chuck table 30 by a rough grinding means 31 that performs rough grinding on the workpiece W or a finish grinding means 32 that performs finish grinding on the workpiece W It is an area where grinding of the workpiece W is performed.

  On the front side of the base 3A, a first cassette 331 for housing the workpiece W before grinding and a second cassette 332 for housing the ground workpiece W are disposed. In the vicinity of the first cassette 331 and the second cassette 332, the workpiece W before grinding is unloaded from the first cassette 331, and the ground workpiece W is loaded into the second cassette 332. A robot 330 having a function is disposed.

  In the movable area of the robot 330, alignment means 333 for aligning the workpiece W before processing to a predetermined position and cleaning means 334 for cleaning the ground workpiece W are disposed. The cleaning means 334 is, for example, a sheet-fed spinner cleaning device, and includes a spinner table that sucks and holds the ground workpiece W.

  A first transport means 335 is disposed in the vicinity of the alignment means 333, and a second transport means 336 is disposed in the vicinity of the cleaning means 334. The first transfer means 335 has a function of transferring the workpiece W before grinding placed on the alignment means 333 to any one of the chuck tables 30 shown in FIG. It has a function of conveying the ground workpiece W held on any one of the chuck tables 30 to the cleaning means 334.

  The turntable 34 is disposed on the rear side (+ Y direction side) of the first conveying means 335 on the base 3A, and for example, three chuck tables 30 are circumferentially arranged on the upper surface of the turntable 34. It is arranged at intervals. A rotating shaft (not shown) for rotating the turntable 34 is disposed at the center of the turntable 34. The turntable 34 can rotate on the base 3A about the rotating shaft. The chuck table 30 is configured to be positioned in the vicinity of the first conveying means 335 and the second conveying means 336 by the rotation of the turntable 34.

  The chuck table 30 is rotatably supported by the turntable 34. Further, a rotary shaft 30b whose axial direction is the vertical direction (Z-axis direction) is connected to the bottom surface side of the chuck table 30, and the rotary shaft 30b is rotated by a rotating means (not shown) such as a motor. The chuck table 30 is rotatable on the turntable 34 about a vertical rotation axis. The chuck table 30 has, for example, a suction portion 300 which has a circular outer shape and is made of a porous member or the like and holds the workpiece W by suction, and a frame 301 which supports the suction portion 300. The suction unit 300 is in communication with a suction source (not shown), and the suction force generated by suction by the suction source is transmitted to the holding surface 300 a which is the exposed surface of the suction unit 300, whereby the chuck table 30 holds the holding surface. The workpiece W is held by suction on 300 a.

  A column 3B and a column 3C are erected side by side on the rear side on the base 3A, and the workpiece W whose rough grinding means 31 is held by the chuck table 30 is provided on the side surface on the -Y direction side of the column 3B. The first grinding feed means 35 for grinding feed is provided for the workpiece W held by the chuck table 30 on the side of the column 3C on the -Y direction side with respect to the workpiece W held by the chuck table 30. A second grinding feed means 36 for grinding feed is provided.

  The first grinding and feeding means 35 includes a ball screw 350 having a vertical axial center, a pair of guide rails 351 disposed parallel to the ball screw 350, and a motor 352 connected to the ball screw 350 to rotate the ball screw 350. The elevating part 353 is guided by the guide rail 351 as the motor 352 rotates the ball screw 350. Is configured to move up and down. The elevating part 353 supports the rough grinding means 31, and the rough grinding means 31 is also raised and lowered by the elevation of the elevating part 353.

  The second grinding feed means 36 includes a ball screw 360 having an axis in the vertical direction, a pair of guide rails 361 disposed parallel to the ball screw 360, and a motor 362 coupled to the ball screw 360 and rotating the ball screw 360. The elevating part 363 is guided by the guide rail 361 as the motor 362 rotates the ball screw 360. Is configured to move up and down. The elevation unit 363 supports the finish grinding unit 32, and the finish grinding unit 32 is also elevated by the elevation of the elevation unit 363.

  The rough grinding means 31 has a rotating shaft 310 whose axial direction is a vertical direction (Z-axis direction) perpendicular to the holding surface 300 a of the chuck table 30, a housing 311 rotatably supporting the rotating shaft 310, and a rotating shaft 310. The motor includes a motor 312 which is driven to rotate, a mount 314 attached to the lower end of the rotary shaft 310, and a grinding wheel 313 detachably connected to the mount 314. On the bottom surface of the grinding wheel 313, a plurality of rough grinding stones 313a having a substantially rectangular parallelepiped shape are annularly disposed. The rough grinding stone 313a is formed, for example, by fixing diamond abrasive grains or the like by vitrified bonding or the like. In addition, the shape of the rough grinding stone 313a may be integrally formed in an annular shape. The rough grinding wheel 313a is, for example, a grinding wheel used for rough grinding, and is a grinding wheel in which the abrasive grains contained in the grinding wheel are relatively large.

  For example, a flow passage (not shown) communicating with the grinding water supply source and passing through the grinding water is formed in the rotation shaft 310 in the axial direction (Z-axis direction) of the rotation shaft 310. The passage is opened at the bottom surface of the grinding wheel 313 so that the grinding water can be jetted toward the rough grinding wheel 313a.

  The finish grinding unit 32 can perform finish grinding for enhancing flatness on the workpiece W thinned to a finish thickness or so by rough grinding. That is, the finish grinding means 32 further grinds the back surface Wb of the workpiece W ground by the rough grinding means 31 with the grinding wheel 313 having the finish grinding wheel 323a and rotatably mounted. The abrasive grains contained in the finish grinding wheel 323 a are abrasive grains having a smaller particle size than the abrasive grains contained in the rough grinding stone 313 a of the rough grinding means 31. The configuration other than the finish grinding wheel 323 a of the finish grinding unit 32 is the same as the configuration of the rough grinding unit 31.

  At positions adjacent to the rough grinding means 31 and the finish grinding means 32 in the state of being lowered to the grinding position, for example, a first thickness measuring means 38A and a second thickness measuring means for measuring the thickness of the workpiece W by contact. Thickness measuring means 38B are respectively provided. Since the first thickness measuring means 38A and the second thickness measuring means 38B have the same structure, only the first thickness measuring means 38A will be described below. The first thickness measuring means 38A is, for example, a pair of thickness measuring devices (height gauges), that is, a first thickness measuring device 381 for measuring the height position of the holding surface 300a of the chuck table 30; A second thickness measuring device 382 for measuring the height position of the surface (surface to be ground) opposite to the surface held by the chuck table 30 is provided.

The first thickness measuring device 381 and the second thickness measuring device 382 have contacts at their respective ends, which are vertically moved up and down to make contact with the respective measurement surfaces, and the contacts are, for example, gradually going downward. It is formed in the shape of a sharpened tip. The root side of the first thickness measuring device 381 (second thickness measuring device 382) is supported by a first support 383 (second support 384). The first support portion 383 (the second support portion 384) supports the first thickness measuring instrument 381 (the second thickness measuring instrument 382) so as to move up and down, and for example, a spring incorporated therein. By the generated pressure, the first thickness measuring device 381 (second thickness measuring device 382) can be pressed with an appropriate force against each measurement surface.
The first thickness measuring means 38A detects the height position of the upper surface of the frame body 301 serving as the reference surface by the first thickness measuring device 381, and the workpiece to be ground by the second thickness measuring device 382 The workpiece W is detected by detecting the height position of the surface to be ground of W, that is, the surface opposite to the surface held by the chuck table 30 of the workpiece W and calculating the difference between the detected values of the two. The thickness can be measured at any time before or during grinding.

  The grinding device 3 includes, for example, control means 9 for controlling the entire device. The control means 9 includes a CPU for performing arithmetic processing according to a control program, a ROM for storing control programs and the like, and a RAM for storing arithmetic results and other information and the like. 35 and a rotating means (not shown) for rotating the chuck table 30. Then, under the control of the control means 9, each of the grinding devices 3 such as the rotation operation of the chuck table 30 by the rotation means (not shown) and the grinding feed operation in the Z axis direction of the rough grinding means 31 by the first grinding feed means 35 The operation of the configuration is controlled.

  Below, each step in the case of grinding the to-be-processed object W shown in FIG. 1 using the grinding apparatus 3 which concerns on this invention is demonstrated.

(1) Surface Protection Step First, for example, a circular surface protection member T having substantially the same diameter as the workpiece W is attached to the surface Wa of the workpiece W, and the surface Wa is covered with the surface protection member T. Become protected. The surface protection member T is, for example, a pressure-sensitive adhesive tape including a base material layer made of a resin or the like having a certain degree of flexibility and an adhesive layer, but is not limited thereto. After the application, the resin may be cured by applying heat or irradiating ultraviolet light to form a protective member which has a certain degree of flexibility and covers the surface Wa of the workpiece W.

(2) Holding Step The turntable 34 shown in FIG. 1 rotates in the clockwise direction as viewed from the + Z-axis direction, and a certain chuck table 30 moves to the vicinity of the first conveying means 335. The robot 330 pulls out a single workpiece W with the surface protection member T attached thereto from the first cassette 331, and moves the workpiece W to the alignment unit 333. After the workpiece W is positioned at a predetermined position by the alignment unit 333, the first transport unit 335 transports the workpiece W on the alignment unit 333 onto the holding surface 300 a of the chuck table 30. Then, the suction force generated by a suction source (not shown) is transmitted to the holding surface 300 a, whereby the chuck table 30 sucks and holds the workpiece W.
Here, if the workpiece W is correctly conveyed to the chuck table 30 and suction-held, the surface of the workpiece W held by the chuck table 30 becomes the surface Wa covered by the surface protection member T, and the chuck table The back surface Wb opposite to the surface held at 30 is exposed upward.
On the other hand, the workpiece W may be transported to the chuck table 30 in an incorrect state and be held by suction. That is, the surface of the workpiece W held by the chuck table 30 is the back surface Wb, and the surface covered by the surface protection member T which is the surface opposite to the surface held by the chuck table 30 It may also occur that Wa is facing upward.

(3) Thickness Measurement Step When the workpiece W as described above is sucked and held in an incorrect state by the chuck table 30, grinding is started as it is to prevent generation of grinding defects. The grinding apparatus 1 according to the present invention carries out the thickness measurement step described below.
As shown in FIG. 1, as the turntable 34 rotates in the clockwise direction as viewed from the + Z-axis direction, the chuck table 30 holding the workpiece W moves below the first thickness measuring means 38A. Then, for example, the chuck table 30 is rotated around the rotation axis 30b at a predetermined rotation speed, and the thickness measurement of the workpiece W is started by the first thickness measurement means 38A. The thickness measurement of the workpiece W may be started while the chuck table 30 is not rotating.

FIG. 3 shows a case where the workpiece W is suctioned and held by the chuck table 30 in a correct state. Therefore, the first thickness measuring device 381 is pressed against the upper surface of the frame 301 serving as the reference surface of the rotating chuck table 30 with a predetermined pressing force, and the surface of the workpiece W held by the chuck table 30 The second thickness measuring device 382 is pressed with a predetermined pressing force against the back surface Wb of the surface opposite to a certain surface Wa.
On the other hand, FIG. 4 shows the case where the workpiece W is sucked and held by the chuck table 30 in an incorrect state. Therefore, the first thickness measuring device 381 is pressed against the upper surface of the frame 301 serving as the reference surface of the rotating chuck table 30 with a predetermined pressing force, and the surface of the workpiece W held by the chuck table 30 The second thickness measuring device 382 is pressed with a predetermined pressing force on the surface protection member T attached to the front surface Wa of the surface opposite to the back surface Wb.

In the case shown in FIG. 3, the height position of the upper surface of the frame 301 is measured by the first thickness measuring device 381, and the height position of the back surface Wb of the workpiece W is measured by the second thickness measuring device 382. The difference between the two measured values is calculated as the thickness of the workpiece W. Then, information on the calculated thickness of the workpiece W is, for example, transmitted to the control unit 9 and stored in the RAM.
The graph G1 shown in FIG. 5 shows the transition of the thickness of the workpiece W from the start of the thickness measurement of the workpiece W by the first thickness measuring means 38A shown in FIG. 3 to the time when an arbitrary time t1 has elapsed. It is an example of a graph. In FIG. 5, the vertical axis indicates the thickness of the workpiece W, and the horizontal axis indicates the elapsed time.

On the other hand, in the case shown in FIG. 4, the first thickness measuring device 381 measures the height position of the upper surface of the frame 301, and the second thickness measuring device 382 attaches it to the surface Wa of the workpiece W. The height position of the surface protection member T is measured, and the difference between the two measured values is calculated as the thickness of the workpiece W. Then, information on the calculated thickness of the workpiece W is, for example, transmitted to the control unit 9 and stored in the RAM.
The graph G2 shown in FIG. 5 shows the transition of the thickness of the workpiece W from the start of the thickness measurement of the workpiece W by the first thickness measuring means 38A shown in FIG. 4 to the time when an arbitrary time t1 has elapsed. It is an example of a graph.

Since the back surface Wb of the workpiece W is silicon having a certain degree of hardness, in the thickness measurement of the workpiece W by the first thickness measuring means 38A in FIG. Sinking to the back surface Wb of the As a result, the thickness of the workpiece W indicated by the difference between the measurement value of the first thickness measurement device 381 and the measurement value of the second thickness measurement device 382 changes so much as the graph G1 shown in FIG. Therefore, there is not much difference between the thickness M1 of the workpiece W at the start of the measurement and the thickness M2 of the workpiece W at the time when an arbitrary time t1 has elapsed from the start of the thickness measurement of the workpiece W.
On the other hand, since the surface protection member T is an adhesive tape made of resin or the like and provided with a certain degree of flexibility, in the thickness measurement of the workpiece W by the first thickness measurement means 38A in FIG. The depression of the surface protection member T at 382 is large. As a result, the thickness of the workpiece W indicated by the difference between the measured value of the first thickness measuring device 381 and the measured value of the second thickness measuring device 382 is a graph G1 and a graph G2 shown in FIG. Compared with the above, the thickness M1 of the workpiece W at the start of the measurement shown in graph G2 and the thickness M3 of the workpiece W at the time when an arbitrary time t1 has elapsed from the start of the thickness measurement of the workpiece W There is some difference between them.

The control means 9 includes, for example, the calculation means 90 shown in FIG. The calculating means 90 changes the first thickness data measured by the first thickness measuring means 38A and the second thickness data measured after an elapse of an arbitrary time from the time when the first thickness data is measured. Calculate the quantity. In the thickness measurement step shown in FIG. 3 in the present embodiment, the first thickness data is, for example, the thickness M1 of the workpiece W at the start of measurement shown in the graph G1 of FIG. The thickness data is the thickness M2 of the workpiece W when an arbitrary time t1 has elapsed from the start of the thickness measurement of the workpiece W shown in the graph G1. Then, the calculating means 90 calculates, for example, (M1-M2), which is the difference between the thickness M1 of the workpiece W and the thickness M2 of the workpiece W, as the change amount (difference amount) of the thickness of the workpiece W Do.
In the thickness measurement step in the case shown in FIG. 4 in the present embodiment, the first thickness data is, for example, the thickness M1 of the workpiece W at the start of the measurement shown in the graph G2, and the second thickness data Is a thickness M3 of the workpiece W at the time when an arbitrary time t1 has elapsed from the start of thickness measurement of the workpiece W shown in the graph G2. The calculating means 90 calculates, for example, (M1-M3), which is the difference between the thickness M1 of the workpiece W and the thickness M3 of the workpiece W, as the amount of change (difference amount) in the thickness of the workpiece W. Do.

  For example, in the ROM of the control means 9, the surface of the workpiece W in contact with the second thickness measurement device 382 is the back surface Wb of the workpiece W in which the second thickness measurement device 382 is unlikely to sink. In other words, the threshold Mc is registered to determine whether the surface of the workpiece W opposite to the surface held by the chuck table 30 is the back surface Wb, which is the surface to be ground. It is done. Then, the control means 9 determines that the change amount (the difference amount in the present embodiment) of the thickness of the workpiece W calculated by the calculation means 90 exceeds the threshold value Mc or is equal to or less than the threshold value Mc. Determine if there is. The amount of sinking of the second thickness measuring instrument 382 into the back surface Wb of the workpiece W or the surface protective member T differs depending on the type of the workpiece W and the type of the surface protection member T, so The threshold Mc is a value selected experimentally, empirically or theoretically corresponding to the type of the back surface Wb of the workpiece W and the surface protection member T.

In the case shown in FIG. 3, as shown in the graph G1 of FIG. 5, the change amount (M1-M) becomes a value smaller than the threshold value Mc. Is the back surface Wb of the workpiece W in which the second thickness measuring device 382 is unlikely to sink, that is, the workpiece W is held by suction with the chuck table 30 in a correct state It is determined that grinding may be started as it is.
In the case shown in FIG. 4, as shown in the graph G2 of FIG. 5, the change amount (M1-M3) becomes a value exceeding the threshold value Mc. The surface of the workpiece W in contact is the surface protection member T on which the second thickness measuring device 382 sinks, that is, the workpiece W is sucked and held by the chuck table 30 in the wrong state and remains as it is Judged that grinding should not be started.

  When it is determined that the control means 9 should not start grinding, the shift to the grinding step described later is stopped in the grinding device 3 under the control of the control means 9, and the workpiece W is ground It will not start processing. Further, the control means 9 notifies the operator of the judgment by, for example, emitting an alarm sound from a speaker or displaying an error on a monitor. For example, the workpiece W is corrected to a state in which the back surface Wb is exposed upward on the holding surface 300a of the chuck table 30 by the manual work of the operator notified of the determination, or the workpiece W is chucked It is removed from the table 30.

The thickness measurement step is not limited to the above embodiment, and may be performed, for example, as described below (hereinafter referred to as another embodiment of the thickness measurement step). In another embodiment of the thickness measurement step, the amount of change calculated by the calculation means 90 in the case shown in FIG. 3 is the slope (differential amount) of the tangent L1 of the graph G1 at an arbitrary time point t2 within the measurement time. That is, after an arbitrary time has elapsed from the time when the first thickness data measured by the first thickness measurement means 38A and the first thickness are measured after the start of thickness measurement, the calculation means 90 (after a slight time) The difference with the second thickness data measured in (4) is calculated, and the amount of change (the slope of the tangent L1) is calculated by differentiating the calculated difference. As the slope of the graph G1 at any two time points within the thickness measurement time (for example, when the measurement starts and t1 time elapses or t2 time elapses and t1 time elapses) without using the change amount as the slope of the tangent L1. It is also good.
Similarly, the amount of change calculated by the calculation means 90 in the case shown in FIG. 4 is the slope (differential amount) of the tangent L2 of the graph G2 at an arbitrary time point t2 within the measurement time. That is, after an arbitrary time has elapsed from the time when the first thickness data measured by the first thickness measurement means 38A and the first thickness are measured after the start of thickness measurement, the calculation means 90 (after a slight time) The difference with the second thickness data measured in (2) is calculated, and the amount of change (the slope of the tangent L2) is calculated by differentiating the calculated difference. As the slope of the graph G2 at any two time points within the thickness measurement time (for example, when the measurement starts and t1 time elapses or t2 time elapses and t1 time elapses) without making the change amount the slope of the tangent L2. It is also good.

  In the ROM of the control means 9, it is determined whether or not the surface of the workpiece W in contact with the second thickness measuring device 382 is the back surface Wb of the workpiece W in which the second thickness measuring device 382 hardly sinks. Or, in other words, a threshold value is registered to determine whether the surface of the workpiece W opposite to the surface held by the chuck table 30 is the back surface Wb, which is the surface to be ground. . Then, the control means 9 determines whether the calculated change amount (the differential amount in another embodiment) calculated by the calculation means 90 exceeds the threshold or is equal to or less than the threshold.

  In the case shown in FIG. 3, the inclination (change amount) of the tangent L1 of the graph G1 in FIG. 5 is smaller than, for example, the registered threshold, and the control means 9 makes contact with the second thickness measuring device 382 The surface of the workpiece W is the back surface Wb of the workpiece W in which the second thickness measuring device 382 is unlikely to sink, that is, the workpiece W is sucked and held by the chuck table 30 in the correct state. It is determined that grinding may be started. In the case shown in FIG. 4, the slope (change amount) of the tangent L2 of the graph G2 of FIG. 5 exceeds, for example, the registered threshold, and the control means 9 is in contact with the second thickness measuring device 382 The surface of the processed workpiece W is the surface protection member T where the second thickness measuring device 382 sinks, that is, the workpiece W is held by suction with the chuck table 30 in the wrong state and grinding is performed. Decide that it should not be started.

(4) Grinding step When any thickness measurement step is performed as described above, as a result, when it is determined that the control means 9 starts grinding the workpiece W, as shown in FIG. If it is determined that the workpiece W is suctioned and held by the chuck table 30 in the correct state, the main grinding step is performed.
As shown in FIG. 1, as the turntable 34 rotates in the clockwise direction as viewed from the + Z-axis direction, the chuck table 30 holding the workpiece W moves under the rough grinding means 31, and the grinding wheel Position alignment of 313 and the to-be-processed object W is made. For alignment, for example, as shown in FIG. 6, the rotation center of the grinding wheel 313 is shifted in the + X direction by a predetermined distance with respect to the rotation center of the workpiece W, and the rotation trajectory of the rough grinding stone 313a is the workpiece It is performed so as to pass through the rotation center of W.

  The grinding wheel 313 rotates as the rotation shaft 310 is rotationally driven. Further, the rough grinding means 313 is fed in the −Z direction by the first grinding feeding means 35 shown in FIG. 1 and the rough grinding stone 313 a of the rotating grinding wheel 313 abuts on the back surface Wb of the workpiece W Rough grinding is performed. Further, since the workpiece W held on the holding surface 300a is also rotated as the chuck table 30 is rotated, the entire back surface Wb of the workpiece W is ground. Further, grinding water is supplied to the contact portion between the rough grinding stone 313a and the workpiece W through a flow path (not shown) in the rotating shaft 310, and the contact portion is cooled and cleaned. In addition, during rough grinding of the workpiece W, the thickness of the workpiece W is measured by the first thickness measurement means 38A, and the workpiece W has a desired thickness (for example, the thickness before the finish thickness) Thickness control is performed as follows.

  The workpiece W ground to the front of the finish thickness by rough grinding is then ground to the finish thickness. After the rough grinding means 31 shown in FIG. 1 is separated from the workpiece W, the chuck table 30 is moved to the lower side of the finish grinding means 32 by the turntable 34 rotating clockwise as viewed from the + Z direction. Then, after the alignment between the grinding wheel 313 provided in the finish grinding unit 32 and the workpiece W is performed, the finish grinding unit 32 is fed in the −Z direction, and the finish grinding wheel 323 a that rotates is the workpiece W The workpiece W held on the holding surface 300a is rotated with the rotation of the chuck table 30, and the entire surface of the back surface Wb of the workpiece W is finish ground. . Further, grinding water is supplied to the contact portion between the finish grinding wheel 323 a and the workpiece W, and the contact portion is cooled and cleaned. Further, during rough grinding of the workpiece W, the thickness of the workpiece W is measured by the second thickness measurement means 38B, and thickness control is performed so that the workpiece W has a desired thickness (finish thickness). Be done.

  After the finish grinding means 32 is separated from the work W, the work piece W ground to the finish thickness and the flatness of the back surface Wb is enhanced, the turntable 34 rotates in a clockwise direction as viewed from the + Z direction. , To the vicinity of the second transport means 336. Then, the second transport means 336 transports the workpiece W on the chuck table 30 to the cleaning means 334. Then, after the workpiece W is cleaned by the cleaning means 334, the workpiece W is accommodated in the second cassette 332 by the robot 330.

  As described above, in the grinding method according to the present invention, after performing the surface protection step of covering the surface Wa of the workpiece W with the surface protection member T and the surface protection step, the axial direction of the workpiece W is vertical. After carrying out the holding step of holding the holding surface 300a of the chuck table 30 rotatable with a certain rotation shaft 30b and the holding step, the second side is the second surface of the workpiece W opposite to the surface held by the chuck table 30. And the thickness of the workpiece W measured, and the first thickness data measured and the second thickness data measured after an arbitrary time has elapsed from the time of measuring the first thickness data, and After performing the thickness measurement step of calculating the amount of change from the above and the thickness measurement step, the workpiece is supplied while the grinding water is supplied by the rough grinding stone 313a rotating on the rotation axis 310 orthogonal to the holding surface 300a. And, in the thickness measuring step, the surface of the workpiece W with which the second thickness measuring device 382 is in contact if the calculated amount of change is equal to or less than the previously registered threshold value. Is determined to be the back surface Wb of the workpiece W in which the second thickness measuring device 382 hardly sinks, and the grinding step is started, and if the calculated amount of change exceeds the previously registered threshold value, By judging that the surface of the workpiece W with which the second thickness measuring device 382 is in contact is the surface protection member T in which the second thickness measuring device 382 tends to sink, the grinding step is not started. If the workpiece W is suctioned and held in the wrong state by the chuck table 30, that is, if the back surface Wb, which is the surface to be ground of the workpiece W, is adsorbed by the chuck table 30, grinding is performed as it is. Step is carried out the surface protective member T that is eliminated that would not be ground generating grinding defects.

  As described above, in the grinding apparatus 3 according to the present invention, the first thickness data measured by the first thickness measuring means 38A and the first thickness data are measured after an arbitrary time has elapsed from the time when the first thickness data is measured. Calculation means 90 for calculating the amount of change from the thickness data of 2 and grinding is started if the amount of change calculated by calculation means 90 is equal to or less than a pre-registered threshold, and the amount of change is registered beforehand. When the workpiece W is suctioned and held in the wrong state by the chuck table 30 by providing the control means 9 that displays an error and does not start grinding when the threshold value is exceeded. That is, when the back surface Wb, which is the surface to be ground of the workpiece W, is adsorbed to the chuck table 30, the surface protection member T is ground by the rough grinding means 31 as it is to cause grinding defects. Bet is lost.

  The first thickness measurement means 38A of the grinding device 3 is used to measure the thickness of the workpiece W before the start of grinding, and is also used to control the thickness of the workpiece W after the start of grinding, thereby the grinding device 3 In addition, it is possible to prevent an increase in the manufacturing cost of the grinding apparatus 3.

The grinding method according to the present invention is not limited to the above embodiment, and the configuration of the grinding apparatus 3 shown in the attached drawings is not limited to this, and the effects of the present invention are exhibited. It can change suitably within the limits which can be done.
For example, the grinding device 3 in the present embodiment is not limited to the two-axis grinding device, and the grinding device may be a single-axis grinding device.
Also, for example, the first thickness measurement means 38A is not limited to the configuration including the first thickness measurement device 381 and the second thickness measurement device 382 as in this embodiment, and for example, the second thickness measurement Thickness of the workpiece W by one thickness measuring device as a configuration including a device 382, a carriage for holding the second thickness measuring device 382 so as to be vertically movable, and displacement detection means for detecting the position of the carriage. May be measured.

W: Workpiece Wa: Surface of Workpiece Wb: Back surface of Workpiece
T: surface protection member 3: grinding device 3A: base 3B, 3C: column 30: chuck table 300: suction portion 300a: holding surface 301: frame 31: rough grinding means 310: rotating shaft 311: housing 312: motor 313: Grinding wheel 313a: rough grinding wheel 32: finish grinding means 323a: finish grinding wheel 330: robot 331: first cassette 332: second cassette 333: alignment means 334: cleaning means 335: first conveying means 336: Second conveying means 34: Turn table 35: First grinding feeding means 350: Ball screw 351: Guide rail 352: Motor 353: Lifting part 36: Second grinding feeding means 360: Ball screw 361: Guide rail 362: Motor 363 : Lifting part 38A: First thickness measuring means 381: First See meter 382: second thickness gauge 38B: second thickness measuring means 9: Control means 90: calculation means

Claims (4)

A method of grinding a workpiece, comprising grinding a back surface of a workpiece having a surface on which devices are formed in regions partitioned by a plurality of planned dividing lines formed in a grid shape with a grinding stone,
A surface protection step of covering the surface of the workpiece with a surface protection member;
After performing the surface protection step, a holding step of holding the workpiece on a holding surface of a chuck table that is rotatable about a rotation axis whose axial direction is the vertical direction;
After carrying out the holding step, the thickness measuring device is brought into contact with the surface opposite to the surface held by the chuck table of the workpiece to measure the thickness of the workpiece, and the first thickness data measured A thickness measurement step of calculating an amount of change from the second thickness data measured after an arbitrary time has elapsed from the time of measuring the first thickness data;
And a grinding step of grinding the back surface of the workpiece while supplying grinding water with a grinding wheel rotating on a rotation axis orthogonal to the holding surface after performing the thickness measurement step.
In the thickness measurement step, if the calculated amount of change is equal to or less than a pre-registered threshold value, the surface of the workpiece to which the thickness measurement device is in contact is a workpiece on which the thickness measurement device is unlikely to sink. If it is judged that it is the back side of the object, the grinding step is started, and the calculated change amount exceeds the pre-registered threshold value, the surface of the workpiece to which the thickness measuring device contacts is the thickness A grinding method that does not start the grinding step, judging that the surface protection member is apt to cause sinking of a measuring instrument.   The grinding method according to claim 1, wherein the surface protection member is an adhesive tape. A chuck table for holding a workpiece, thickness measuring means for measuring the thickness of the workpiece held by the chuck table, and grinding means for grinding the workpiece held by the chuck table Grinding machine, and
The chuck table is rotatable about an axis of rotation having the vertical direction as an axial direction, and holds a workpiece to which a surface protection member is attached by a holding surface,
The thickness measuring means measures the thickness by bringing a thickness measuring device into contact with the surface of the workpiece opposite to the surface held by the chuck table before the start of grinding of the workpiece.
The grinding means grinds the back surface of the workpiece while supplying grinding water with a grinding wheel rotating on a rotation axis orthogonal to the holding surface of the chuck table.
Calculating means for calculating the amount of change from the first thickness data measured by the thickness measuring means and the second thickness data measured after an elapse of an arbitrary time from the time when the first thickness data is measured; Grinding is started if the amount of change calculated by the calculation means is equal to or less than a pre-registered threshold, and an error is displayed if the amount of change exceeds the pre-registered threshold. And c) a control means which does not start.   4. The grinding apparatus according to claim 3, wherein the thickness measuring means is used not only to measure the thickness of the workpiece before the start of grinding but also to control the thickness of the workpiece after the start of grinding.

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