JP7015139B2 - Grinding method and grinding equipment for workpieces - Google Patents

Description

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

A work piece on which devices such as ICs and LSIs are formed on a plurality of surfaces is ground on the back surface to be thinned to a predetermined thickness, and further divided into individual device chips by a dividing device such as a dicing device. Used for various electronic devices.

Grinding devices that grind the back surface of the workpiece (see, for example, Patent Document 1) include a chuck table that holds the surface side of the workpiece to which a surface protection member is attached and a chuck table that holds the workpiece on the chuck table. It is equipped with a grinding means that rotatably supports the grinding wheel that grinds the back surface of the work piece, and can efficiently grind the workpiece.

Japanese Patent No. 5025200

However, in the above-mentioned grinding apparatus, when the workpiece is held by the chuck table, the back surface side of the workpiece that is not covered with the surface protection member is erroneously adsorbed by the holding surface of the chuck table. There is. When the back side of the work piece is attracted by the chuck table, the grinding wheel grinds the surface protection member on the front side of the work piece, and the current value of the motor that rotates the grinding wheel due to processing defects is the allowable value. It may exceed the limit and the fully automatic operation of the grinding device may be stopped. In such a case, it is necessary to dress (dress) the grinding wheel to return it to a normal state, which leads to an increase in downtime of the grinding device.

Therefore, in the grinding apparatus, there is a problem that the surface protective member attached to the surface side of the workpiece is not erroneously ground by the grinding wheel.

In the present invention for solving the above problems, the present invention is to grind the back surface of a workpiece having a surface in which a device is formed in a region partitioned by a plurality of scheduled division lines formed in a grid pattern with a grinding wheel. In this grinding method, the surface of the workpiece is covered with a surface protection member to form a protected workpiece, and after the surface protection step is performed, the protected workpiece is used as an axis. A holding step of holding on a holding surface of a chuck table rotatable on a rotation axis whose direction is vertical, and a side opposite to the surface held by the chuck table of the protected workpiece after performing the holding step. The first thickness data obtained by bringing the thickness of the work piece into contact with the surface and measuring the thickness of the surface protection member covering the surface of the work piece is measured, and the first thickness data is measured. And the second thickness data obtained by combining the thickness of the work piece measured after an arbitrary time has elapsed from the time when the first thickness data was measured and the thickness of the surface protection member covering the surface of the work piece. After performing the thickness measurement step of calculating the amount of change from the above, the back surface of the workpiece is ground while supplying grinding water with a grinding wheel rotating on a rotation axis orthogonal to the holding surface. A grinding step is provided, and in the thickness measuring step, if the calculated change amount is equal to or less than a preset threshold value, the opposite surface of the protected workpiece to which the thickness measuring instrument is in contact is formed. If it is determined that the back surface of the workpiece is less likely to be subducted by the thickness measuring instrument, the grinding step is started, and the calculated change amount exceeds the preset threshold value, the thickness is determined. This is a grinding method in which it is determined that the opposite surface of the protected workpiece to which the measuring instrument is in contact is the surface protecting member in which the thickness measuring instrument is likely to sink, and the grinding step is not started.

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

Further, in the present invention for solving the above problems, the chuck table for holding the workpiece , the thickness measuring means for measuring the thickness of the workpiece held on the chuck table, and the chuck table are held. The chuck table is a grinding device provided with a grinding means for grinding the workpiece, and the chuck table is rotatable on a rotation axis having a vertical direction as an axial direction, and is a holding surface on the surface of the workpiece. A protected workpiece formed by attaching a protective member is held, and the thickness measuring means is a surface of the protected workpiece held by the chuck table before starting grinding of the protected workpiece. A thickness measuring instrument is brought into contact with the surface opposite to the surface to measure the thickness, and the grinding means is a grinding wheel that rotates on a rotation axis orthogonal to the holding surface of the chuck table to supply grinding water to the workpiece. The first thickness data obtained by grinding the back surface and combining the thickness of the workpiece measured by the thickness measuring means and the thickness of the surface protection member covering the surface of the workpiece before the start of grinding and the said . A second thickness data obtained by combining the thickness of the work piece measured after an arbitrary time has elapsed from the time when the first thickness data was measured and the thickness of the surface protection member covering the surface of the work piece. If the change amount calculated by the calculation means is equal to or less than the pre-registered threshold value, grinding is started, and the change amount is set to the pre-registered threshold value. It is a grinding device characterized by being provided with a control means for displaying an error and not starting grinding when the amount exceeds the limit.

The thickness measuring means is used for measuring the thickness of the work piece before the start of grinding and the thickness of the surface protection member covering the surface of the work piece, and is used for measuring the thickness after the start of grinding . It is preferable that it is also used for controlling the thickness of an object.

In the thickness measurement of the work piece by the thickness measuring means, when the measuring surface is a surface protection member having flexibility, the thickness of the work piece is increased by the sinking of the thickness measuring instrument provided in the thickness measuring means into the surface protection member. The amount of change is large. 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 the thickness of the workpiece is small because there is almost no sinking of the thickness measuring instrument provided in the thickness measuring means into the back surface. Therefore, in the grinding method according to the present invention, a surface protection step of covering the surface of the work piece with a surface protection member to form a protected work piece and a surface protection step are performed, and then the protected work piece is used as an axis. After performing the holding step of holding on the holding surface of the chuck table rotatable on the rotation axis whose direction is vertical, and the surface opposite to the surface held by the chuck table of the protected workpiece after performing the holding step. The first thickness data obtained by bringing the thickness of the work piece into contact with the thickness measuring device and the thickness of the surface protection member covering the surface of the work piece is measured, and the measured first thickness data and the first thickness are measured. The thickness for which the amount of change is calculated from the second thickness data obtained by combining the thickness of the work piece measured after an arbitrary time has elapsed from the time when the data was measured and the thickness of the surface protection member covering the surface of the work piece. The thickness measurement step includes a measurement step and a grinding step of grinding the back surface of the workpiece while supplying grinding water with a grinding wheel that rotates on a rotation axis orthogonal to the holding surface after performing the thickness measurement step. If the calculated amount of change is less than or equal to the pre-registered threshold value, the surface on the opposite side of the protected workpiece that the thickness measuring instrument is in contact with is the back surface of the workpiece that is unlikely to sink in the thickness measuring instrument. If it is determined that there is, the grinding step is started, and if the calculated change amount exceeds the pre-registered threshold value, the surface on the opposite side of the protected workpiece with which the thickness measuring instrument is in contact is subducted by the thickness measuring instrument. By not starting the grinding step because it is judged that the surface protection member is prone to the occurrence of When the back surface of the surface is attracted by the chuck table, the grinding step is performed as it is, and the surface protection member is not ground to cause a grinding defect.

The grinding apparatus according to the present invention holds a protected workpiece formed by attaching a surface protection member to the workpiece on a chuck table, and the workpiece measured by a thickness measuring means before starting grinding. The thickness of the work piece and the work piece measured after an arbitrary time has elapsed from the time when the first thickness data and the first thickness data, which are the sum of the thickness and the thickness of the surface protection member covering the surface of the work piece, are measured. The calculation means for calculating the change amount from the second thickness data including the thickness of the surface protection member covering the surface of the work piece, and the change amount calculated by the calculation means must be less than or equal to the preset threshold value registered in advance. For example, by providing a control means for starting grinding and displaying an error when the amount of change exceeds a pre-registered threshold and not starting grinding, the workpiece is subjected to a chuck table. If it is sucked and held in an erroneous state, that is, if the back surface of the work piece, which is the surface to be ground, is attracted to the chuck table, the surface protection member is ground by the grinding means as it is, and a grinding defect occurs. There is no need to let them.

The thickness measuring means of the grinding device is used to measure the thickness of the workpiece before the start of grinding and the thickness of the surface protection member covering the surface of the workpiece, and the thickness of the workpiece after the start of grinding. By being used for control, it is possible to reduce the size of the grinding device and prevent an increase in the manufacturing cost of the grinding device.

It is a perspective view which shows an example of a grinding apparatus. It is a perspective view which shows the state which the surface of a work piece is covered with a surface protection member. Cross-sectional view showing a state in which a second thickness measuring instrument 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 to measure the thickness of the workpiece. Is. A cross-sectional view showing a state in which a second thickness measuring instrument is brought into contact with a surface protection member attached to the surface opposite to the back surface held by the chuck table of the workpiece to measure the thickness of the workpiece. Is. A graph showing the transition of the thickness of the work piece when the thickness of the work piece is measured by contacting the second thickness measuring device with the back surface, and the surface protection member with the second thickness measuring device in contact with the cover. It is a graph which shows the transition of the thickness of the workpiece when the thickness of the workpiece is measured. It is sectional drawing which shows the state which the workpiece is roughly grinded by the rough grinding means while the thickness is controlled.

The grinding apparatus 3 according to the present invention shown in FIG. 1 is an apparatus for grinding a workpiece W sucked 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 having an outer shape made of silicon as a base material, and in FIG. 1, a plurality of divisions orthogonally different to each other on a surface Wa facing downward in FIG. A scheduled line S is formed, and a device D such as an IC is formed in each region partitioned in a grid pattern by the scheduled split line S. The back surface Wb on the opposite side of the surface Wa of the workpiece W is the 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 be formed in a rectangular shape, for example, instead of a circular shape.

The front surface (-Y direction side) of the grinding device 3 on the base 3A is a region where the workpiece W is 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 the rough grinding means 31 that performs rough grinding on the workpiece W or the finish grinding means 32 that performs finish grinding on the workpiece W. This is the area where the workpiece W is ground.

On the front side on the base 3A, a first cassette 331 accommodating the workpiece W before grinding and a second cassette 332 accommodating the workpiece W after grinding are arranged. In the vicinity of the first cassette 331 and the second cassette 332, the workpiece W before grinding is carried out from the first cassette 331, and the ground workpiece W is carried into the second cassette 332. A robot 330 having a function is arranged.

In the range of motion of the robot 330, an alignment means 333 for aligning the workpiece W before machining at a predetermined position and a cleaning means 334 for cleaning the ground workpiece W are arranged. The cleaning means 334 is, for example, a single-wafer type 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 transport means 335 has a function of transporting the workpiece W before grinding mounted on the alignment means 333 to any of the chuck tables 30 shown in FIG. 1, and the second transport means 336 has a function of transporting the workpiece W. It has a function of transporting the ground workpiece W held on any of the chuck tables 30 to the cleaning means 334.

A turntable 34 is disposed on the rear side (+ Y direction side) of the first transport means 335 on the base 3A, and for example, three chuck tables 30 are arranged in the circumferential direction on the upper surface of the turntable 34. They are arranged at intervals. A rotation axis (not shown) for rotating the turntable 34 is arranged at the center of the turntable 34, and the turntable 34 can be rotated on the base 3A about the rotation axis. Then, by rotating the turntable 34, one of the chuck tables 30 is positioned in the vicinity of the first transport means 335 and the second transport means 336.

The chuck table 30 is revolveably supported by the turntable 34. Further, a rotating 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 rotating shaft 30b is rotated by a rotating means (not shown) including a motor or the like. , The chuck table 30 can rotate around the rotation axis in the vertical direction on the turntable 34. The chuck table 30 has, for example, a circular outer shape, and includes a suction portion 300 which is made of a porous member or the like and sucks and holds the workpiece W, and a frame body 301 which supports the suction portion 300. The suction unit 300 communicates with a suction source (not shown), and the suction force generated by the suction source sucks is transmitted to the holding surface 300a, which is the exposed surface of the suction unit 300, so that the chuck table 30 has a holding surface. The workpiece W is sucked and held on 300a.

The column 3B and the column 3C are erected side by side on the rear side on the base 3A, and the workpiece W on which the rough grinding means 31 is held by the chuck table 30 on the side surface of the column 3B on the −Y direction side. A first grinding feed means 35 is disposed, and a finish grinding means 32 is provided on the side surface 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 is provided.

The first grinding feed means 35 includes a ball screw 350 having a vertical axis, a pair of guide rails 351 arranged in parallel with the ball screw 350, and a motor 352 connected to the ball screw 350 to rotate the ball screw 350. The internal nut is screwed into the ball screw 350, and the side portion is composed of an elevating portion 353 that is in sliding contact with the guide rail 351. As the motor 352 rotates the ball screw 350, the elevating portion 353 is guided to the guide rail 351. It is configured to move up and down. The elevating portion 353 supports the rough grinding means 31, and the elevating portion 353 also raises and lowers the rough grinding means 31.

The second grinding feed means 36 includes a ball screw 360 having a vertical axis, a pair of guide rails 361 arranged in parallel with the ball screw 360, and a motor 362 connected to the ball screw 360 to rotate the ball screw 360. The internal nut is screwed into the ball screw 360, and the side portion is composed of an elevating portion 363 that slides into contact with the guide rail 361. As the motor 362 rotates the ball screw 360, the elevating portion 363 is guided by the guide rail 361. It is configured to move up and down. The elevating portion 363 supports the finish grinding means 32, and the elevating portion 363 also raises and lowers the finish grinding means 32.

The rough grinding means 31 includes a rotating shaft 310 whose axial direction is perpendicular to the holding surface 300a of the chuck table 30 (Z-axis direction), a housing 311 that rotatably supports the rotating shaft 310, and a rotating shaft 310. It includes a rotary drive motor 312, 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 coarse grinding wheels 313a having a substantially rectangular parallelepiped shape are arranged in an annular shape. The rough grinding wheel 313a is formed by fixing diamond abrasive grains or the like with, for example, a vitrified bond or the like. The shape of the rough grinding wheel 313a may be integrally formed in an annular shape. The rough grinding wheel 313a is, for example, a grindstone used for rough grinding, and the grindstone contained in the grindstone is a relatively large grindstone.

For example, inside the rotating shaft 310, a flow path (not shown) that communicates with the grinding water supply source and serves as a passage for the grinding water is formed so as to penetrate in the axial direction (Z-axis direction) of the rotating shaft 310. The path is opened at the bottom surface of the grinding wheel 313 so that grinding water can be ejected toward the coarse grinding wheel 313a.

The finish grinding means 32 can perform finish grinding to improve the flatness of the workpiece W thinned to about the finish thickness 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 a grinding wheel 313 provided with a finish grinding wheel 323a and rotatably mounted. The abrasive grains contained in the finish grinding wheel 323a are abrasive grains having a smaller particle size than the abrasive grains contained in the coarse grinding wheel 313a of the rough grinding means 31. The configuration of the finish grinding means 32 other than the finish grinding wheel 323a is the same as the configuration of the rough grinding means 31.

At positions adjacent to the rough grinding means 31 and the finish grinding means 32 in a state of being lowered to the grinding position, for example, a first thickness measuring means 38A and a second thickness measuring means 38A for contactally measuring the thickness of the workpiece W. The thickness measuring means 38B and the thickness measuring means 38B are respectively arranged. 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 instruments (height gauges), that is, a first thickness measuring instrument 381 for measuring the height position of the holding surface 300a of the chuck table 30, and the workpiece W. It is provided with a second thickness measuring instrument 382 for measuring the height position of the surface (surface to be ground) opposite to the surface held by the chuck table 30.

The first thickness measuring instrument 381 and the second thickness measuring instrument 382 are provided with a contact at each tip thereof that moves up and down in the vertical direction and comes into contact with each measuring surface, and the contact gradually decreases downward, for example. It is formed in the shape of a sharp head that shrinks in diameter. The root side of the first thickness measuring instrument 381 (second thickness measuring instrument 382) is supported by the first support portion 383 (second support portion 384). The first support portion 383 (second support portion 384) supports the first thickness measuring instrument 381 (second thickness measuring instrument 382) so as to be able to move up and down, and for example, a spring built in the inside thereof. By the pressing force generated, the first thickness measuring instrument 381 (second thickness measuring instrument 382) can be pressed against each measuring surface with an appropriate force.
The first thickness measuring means 38A detects the height position of the upper surface of the frame body 301 serving as a reference surface by the first thickness measuring instrument 381, and the workpiece to be ground by the second thickness measuring instrument 382. By detecting the height position of the surface to be ground of W, that is, the surface of the workpiece W opposite to the surface held by the chuck table 30, and calculating the difference between the detected values of the two, the workpiece W is Thickness can be measured at any time before or during grinding.

The grinding device 3 includes, for example, a control means 9 that controls the entire device. The control means 9 includes a CPU that performs arithmetic processing according to a control program, a ROM that stores a control program, and a RAM that stores arithmetic results and other information. It is connected to a rotating means (not shown) for rotating the 35 and 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 behavior of the configuration is controlled.

Hereinafter, each step in the case of grinding the workpiece W shown in FIG. 1 by using the grinding apparatus 3 according to the present invention will be described.

(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. We will be in a protected state. The surface protective member T is, for example, an adhesive tape provided with a base material layer and an adhesive layer made of a resin or the like having a certain degree of flexibility, but the present invention is not limited to this, and a liquid resin is applied to the surface Wa. After coating, the resin may be cured by applying heat to the resin or irradiating it with ultraviolet rays to form a protective member having a certain degree of flexibility and covering the surface Wa of the workpiece W.

(2) Holding step The turntable 34 shown in FIG. 1 rotates clockwise when viewed from the + Z axis direction, and a certain chuck table 30 moves to the vicinity of the first transport means 335. The robot 330 pulls out a piece of workpiece W to which the surface protection member T is attached from the first cassette 331, and moves the workpiece W to the alignment means 333. After the workpiece W is positioned at a predetermined position in the alignment means 333, the first transport means 335 transports the workpiece W on the alignment means 333 onto the holding surface 300a of the chuck table 30. Then, the suction force generated by the suction source (not shown) is transmitted to the holding surface 300a, so that the chuck table 30 sucks and holds the workpiece W.
Here, if the workpiece W is correctly conveyed to the chuck table 30 and sucked and held, the surface of the workpiece W held by the chuck table 30 becomes the surface Wa covered with the surface protection member T, and the chuck table. The back surface Wb on the opposite side to the surface held by 30 is exposed upward.
On the other hand, there may be a case where the workpiece W is erroneously conveyed to the chuck table 30 and is sucked and held. That is, the surface of the workpiece W held by the chuck table 30 is the back surface Wb, and the surface covered with the surface protection member T which is the surface opposite to the surface held by the chuck table 30. It is possible that the Wa is facing upward.

(3) Thickness measurement step In order to prevent grinding failure from occurring because grinding is started as it is when the workpiece W as described above is sucked and held by the chuck table 30 in an erroneous state. , The grinding apparatus 1 according to the present invention carries out the thickness measuring step described below.
As shown in FIG. 1, by rotating the turntable 34 in the clockwise direction when viewed from the + Z axis direction, the chuck table 30 holding the workpiece W moves under the first thickness measuring means 38A. Then, for example, the chuck table 30 rotates around the rotation shaft 30b at a predetermined rotation speed, and the thickness measurement of the workpiece W is started by the first thickness measuring 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 sucked and held by the chuck table 30 in a correct state. Therefore, the first thickness measuring instrument 381 is pressed against the upper surface of the frame body 301 which is the reference surface of the rotating chuck table 30 with a predetermined pressing force, and is held by the chuck table 30 of the workpiece W. The second thickness measuring instrument 382 is pressed against the back surface Wb on the surface opposite to the front surface Wa with a predetermined pressing force.
On the other hand, FIG. 4 shows a case where the workpiece W is suction-held by the chuck table 30 in an erroneous state. Therefore, the first thickness measuring instrument 381 is pressed against the upper surface of the frame body 301 which is the reference surface of the rotating chuck table 30 with a predetermined pressing force, and is held by the chuck table 30 of the workpiece W. The second thickness measuring instrument 382 is pressed against the surface protection member T attached to the surface Wa on the surface opposite to the back surface Wb with a predetermined pressing force.

In the case shown in FIG. 3, the height position of the upper surface of the frame body 301 is measured by the first thickness measuring instrument 381, and the height position of the back surface Wb of the workpiece W is measured by the second thickness measuring instrument 382. Then, the difference between the measured values of the two is calculated as the thickness of the workpiece W. Then, the calculated information about the thickness of the workpiece W is transmitted to, for example, the control means 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. This is an example of a graph. In FIG. 5, the vertical axis shows the thickness of the workpiece W, and the horizontal axis shows the elapsed time.

On the other hand, in the case shown in FIG. 4, the height position of the upper surface of the frame body 301 is measured by the first thickness measuring instrument 381, and is attached to the surface Wa of the workpiece W by the second thickness measuring instrument 382. The height position of the surface protection member T is measured, and the difference between the measured values is calculated as the thickness of the workpiece W. Then, the calculated information about the thickness of the workpiece W is transmitted to, for example, the control means 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. This 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. 3, the workpiece W of the second thickness measuring instrument 382 is measured. The subduction to the back surface Wb is slight. As a result, the thickness of the workpiece W shown by the difference between the measured value of the first thickness measuring instrument 381 and the measured value of the second thickness measuring instrument 382 is changed so much as shown in the graph G1 shown in FIG. However, 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 having a certain degree of flexibility, in the thickness measurement of the workpiece W by the first thickness measuring means 38A in FIG. 4, the second thickness measuring device is used. The subduction of the 382 to the surface protection member T is large. As a result, the thickness of the workpiece W shown 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 the same as that of the graph G1 as shown in the graph G2 of FIG. The thickness M1 of the workpiece W at the start of measurement and the thickness M3 of the workpiece W at the time when an arbitrary time t1 elapses from the start of measurement of the thickness of the workpiece W shown in the graph G2. There is a certain difference between.

The control means 9 includes, for example, the calculation means 90 shown in FIG. The calculation means 90 changes from the first thickness data measured by the first thickness measuring means 38A and the second thickness data measured after an arbitrary time elapses from the time when the first thickness data is measured. Calculate the amount. In the thickness measurement step in the case 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 at the time 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 calculation 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 amount of change (difference amount) in 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 measurement shown in the graph G2, and the second thickness data. Is 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 shown in the graph G2. Then, the calculation means 90 calculates, for example, the difference (M1-M3) 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 with which the second thickness measuring instrument 382 is in contact is the back surface Wb of the workpiece W to which the second thickness measuring instrument 382 is unlikely to sink. Whether or not, in other words, the threshold value Mc for determining 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 is registered. Has been done. Then, in the control means 9, the amount of change in the thickness of the workpiece W calculated by the calculation means 90 (the difference amount in this embodiment) exceeds the threshold value Mc or is equal to or less than the threshold value Mc. Determine if there is. Since the amount of the second thickness measuring instrument 382 sinking into the back surface Wb or the surface protection member T of the workpiece W differs depending on the type of the workpiece W and the type of the surface protection member T, it is registered in advance. The threshold value Mc is an experimentally, empirically, or theoretically selected value 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 amount of change (M1-M) is smaller than the threshold value Mc, so that the control means 9 is the second thickness measuring instrument 382. The surface of the workpiece W that is in contact with the workpiece W is the back surface Wb of the workpiece W in which the second thickness measuring instrument 382 is unlikely to sink, that is, the workpiece W is suction-held by the chuck table 30 in the correct state. It is judged that the grinding may be started as it is.
In the case shown in FIG. 4, as shown in the graph G2 of FIG. 5, the amount of change (M1-M3) exceeds the threshold value Mc, so that the control means 9 is the second thickness measuring instrument 382. The surface of the workpiece W in contact is the surface protection member T in which the second thickness measuring instrument 382 is subducted, that is, the workpiece W is sucked and held by the chuck table 30 in an incorrect state as it is. Judge that grinding should not be started.

When the control means 9 determines that grinding should not be started, the transition to the grinding step described later in the grinding device 3 is stopped under the control of the control means 9, and the workpiece W is ground. Processing will not start. Further, the control means 9 notifies the operator of the determination by sounding an alarm sound from the speaker or displaying an error on the 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. Removed from the table 30.

The thickness measurement step is not limited to the above embodiment, and may be implemented 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 line L1 of the graph G1 at an arbitrary time point t2 within the measurement time. That is, the calculation means 90 is after an arbitrary time has elapsed (after a slight time has elapsed) from the time when the first thickness data measured by the first thickness measuring means 38A and the first thickness are measured after the start of the thickness measurement. The amount of change (slope of the tangent line L1) is calculated by calculating the difference from the second thickness data measured in 1 and further differentiating the calculated difference. It should be noted that the amount of change is not set as the slope of the tangent line L1, but as the slope of the graph G1 at any two time points within the thickness measurement time (for example, at the start of measurement and after t1 hour, or after t2 time and t1 hour). May be 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 line L2 of the graph G2 at an arbitrary time point t2 within the measurement time. That is, the calculation means 90 is after an arbitrary time has elapsed (after a slight time has elapsed) from the time when the first thickness data measured by the first thickness measuring means 38A and the first thickness are measured after the start of the thickness measurement. The amount of change (slope of the tangent line L2) is calculated by calculating the difference from the second thickness data measured in 1 and further differentiating the calculated difference. It should be noted that the amount of change is not set as the slope of the tangent line L2, but as the slope of the graph G2 at any two time points within the thickness measurement time (for example, at the start of measurement and after t1 hour, or after t2 time and t1 hour). May be good.

In the ROM of the control means 9, whether or not the surface of the workpiece W with which the second thickness measuring instrument 382 is in contact is the back surface Wb of the workpiece W to which the second thickness measuring instrument 382 is unlikely to sink. Or, in other words, a threshold value for determining 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, is registered. .. Then, the control means 9 determines whether the change amount (differential amount in another embodiment) calculated by the calculation means 90 exceeds the threshold value or is equal to or less than the threshold value.

In the case shown in FIG. 3, the slope (change amount) of the tangent line L1 of the graph G1 of FIG. 5 becomes smaller than, for example, a registered threshold value, and the control means 9 comes into contact with the second thickness measuring instrument 382. The surface of the workpiece W is the back surface Wb of the workpiece W where the sinking of the second thickness measuring instrument 382 is unlikely to occur, 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 line L2 of the graph G2 of FIG. 5 exceeds, for example, a registered threshold value, and the control means 9 is in contact with the second thickness measuring instrument 382. The surface of the workpiece W is a surface protection member T in which the second thickness measuring instrument 382 is subducted, that is, the workpiece W is sucked and held by the chuck table 30 in an incorrect state for grinding. Judge that it should not be started.

(4) Grinding step When any of the thickness measuring steps is carried out as described above and as a result, the control means 9 determines that the grinding of the workpiece W is started, that is, as shown in FIG. If it is determined that the workpiece W is suction-held by the chuck table 30 in the correct state, the main grinding step is performed.
As shown in FIG. 1, by rotating the turntable 34 in the clockwise direction when viewed from the + Z axis direction, the chuck table 30 holding the workpiece W moves to the bottom of the rough grinding means 31 and the grinding wheel. The alignment between the 313 and the workpiece W is performed. For alignment, for example, as shown in FIG. 6, the center of rotation of the grinding wheel 313 shifts in the + X direction by a predetermined distance with respect to the center of rotation of the work piece W, and the rotation trajectory of the coarse grinding wheel 313a is the work piece. It is performed so as to pass through the center of rotation of W.

The grinding wheel 313 rotates as the rotary shaft 310 is rotationally driven. Further, the rough grinding means 31 is fed in the −Z direction by the first grinding feed means 35 shown in FIG. 1, and the rough grinding wheel 313a of the rotating grinding wheel 313 comes into contact with the back surface Wb of the workpiece W. Rough grinding is performed. Further, as the chuck table 30 rotates, the workpiece W held on the holding surface 300a also rotates, so that the entire surface of the back surface Wb of the workpiece W is ground. Further, the grinding water is supplied to the contact portion between the coarse grinding wheel 313a and the workpiece W via a flow path (not shown) in the rotary shaft 310, and the contact portion is cooled and washed. Further, during the rough grinding of the workpiece W, the thickness of the workpiece W is measured by the first thickness measuring means 38A, and the workpiece W has a desired thickness (for example, a thickness before the finish thickness). The thickness is controlled so as to be.

The workpiece W ground to just before 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 turntable 34 rotates clockwise when viewed from the + Z direction, so that the chuck table 30 moves below the finish grinding means 32. Then, after the grinding wheel 313 provided in the finish grinding means 32 and the workpiece W are aligned, the finish grinding means 32 is sent in the −Z direction, and the rotating finish grinding wheel 323a is the workpiece W. As the chuck table 30 rotates, the workpiece W held on the holding surface 300a rotates to finish and grind the entire surface of the back surface Wb of the workpiece W. .. Further, the grinding water is supplied to the contact portion between the finish grinding wheel 323a and the workpiece W, and the contact portion is cooled and washed. Further, during the rough grinding of the workpiece W, the thickness of the workpiece W is measured by the second thickness measuring means 38B, and the thickness is controlled so that the workpiece W has a desired thickness (finishing thickness). Will be done.

In the workpiece W that has been ground to the finish thickness and the flatness of the back surface Wb has been improved, the turntable 34 rotates clockwise when viewed from the + Z direction after the finish grinding means 32 is separated from the workpiece W. Then, it moves 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, a surface protection step of covering the surface Wa of the workpiece W with the surface protection member T and a surface protection step are performed, and then the workpiece W is axially vertical. After performing the holding step of holding on the holding surface 300a of the chuck table 30 rotatable by a certain rotating shaft 30b and the holding step, the second surface of the workpiece W is on the surface opposite to the surface held by the chuck table 30. The thickness of the workpiece W is measured by contacting the thickness measuring device 382 of the above, and the measured first thickness data and the second thickness data measured after an arbitrary time elapses from the time when the first thickness data is measured. After performing the thickness measurement step and the thickness measurement step to calculate the amount of change from In the thickness measurement step, if the calculated change amount is equal to or less than the preset threshold value, the surface of the workpiece W with which the second thickness measuring instrument 382 is in contact is the second surface. If it is determined that the thickness measuring instrument 382 is the back surface Wb of the workpiece W in which subduction is unlikely to occur, the grinding step is started, and the calculated change amount exceeds the pre-registered threshold value, the second By determining that the surface of the workpiece W with which the thickness measuring instrument 382 is in contact is the surface protection member T in which the second thickness measuring instrument 382 is likely to sink, the grinding step is not started. When the object W is sucked and held by the chuck table 30 in an erroneous state, that is, when the back surface Wb which is the surface to be ground of the workpiece W is attracted by the chuck table 30, the grinding step is carried out as it is. Therefore, the surface protection member T is not ground and causes a grinding defect.

As described above, the grinding device 3 according to the present invention has the first thickness data measured by the first thickness measuring means 38A and the first thickness data measured after an arbitrary time has elapsed from the time when the first thickness data was measured. If the calculation means 90 for calculating the change amount from the thickness data of 2 and the change amount calculated by the calculation means 90 are equal to or less than the preset threshold value, grinding is started and the change amount is registered in advance. When the workpiece W is sucked and held in an erroneous state by the chuck table 30 by providing the control means 9 which 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 attracted to the chuck table 30, the rough grinding means 31 grinds the surface protection member T as it is, causing a grinding defect. Disappears.

The first thickness measuring means 38A of the grinding device 3 is used for measuring the thickness of the workpiece W before the start of grinding and also for controlling the thickness of the workpiece W after the start of grinding. It is possible to reduce the size of the grinding device 3 and prevent an increase in the manufacturing cost of the grinding device 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 effect of the present invention is exhibited. It can be changed as appropriate within the range that can be done.
For example, in the grinding device 3, the grinding means is not limited to the biaxial grinding device as in the present embodiment, and the grinding means may be a uniaxial grinding device.
Further, for example, the first thickness measuring means 38A is not limited to the configuration including the first thickness measuring device 381 and the second thickness measuring device 382 as in the present embodiment, and the first thickness measuring means 38A is not limited to, for example, the second thickness measuring device 38A. The thickness of the workpiece W is configured with one thickness measuring instrument as a configuration including a vessel 382, a carriage that movably holds the second thickness measuring instrument 382 in the vertical direction, and a displacement detecting means for detecting the position of the carriage. May be able to be measured.

W: Work piece Wa: Surface of work piece Wb: Back side of work piece
T: Surface protection member 3: Grinding device 3A: Base 3B, 3C: Column 30: Chuck table 300: Suction part 300a: Holding surface 301: Frame 31: Rough grinding means 310: Rotating shaft 311: Housing 312: Motor 313: Grinding wheel 313a: Rough grinding wheel 32: Finishing grinding wheel 323a: Finishing grinding wheel 330: Robot 331: First cassette 332: Second cassette 333: Alignment means 334: Cleaning means 335: First transport means 336: Second transport means 34: Turntable 35: First grinding feed means 350: Ball screw 351: Guide rail 352: Motor 353: Elevating part 36: Second grinding feed means 360: Ball screw 361: Guide rail 362: Motor 363 : Elevating part 38A: First thickness measuring means 381: First thickness measuring instrument 382: Second thickness measuring instrument 38B: Second thickness measuring means 9: Control means 90: Calculation means

Claims (4)

A method for grinding a work piece, which grinds the back surface of the work piece having a surface in which a device is formed in a region partitioned by a plurality of scheduled division lines formed in a grid pattern with a grinding wheel.
A surface protection step in which the surface of the work piece is covered with a surface protection member to form a protected work piece ,
After performing the surface protection step, a holding step of holding the protected workpiece on a holding surface of a chuck table rotatable on a rotation axis whose axial direction is vertical, and a holding step.
After performing the holding step, the thickness measuring instrument is brought into contact with the surface opposite to the surface held by the chuck table of the protected workpiece to cover the thickness of the workpiece and the surface of the workpiece. The first thickness data including the thickness of the surface protection member is measured, and the measured first thickness data and the first thickness data are measured after an arbitrary time has elapsed from the time when the first thickness data is measured . A thickness measurement step of calculating the amount of change from the second thickness data obtained by combining the thickness of the work piece and the thickness of the surface protection member covering the surface of the work piece .
After performing the thickness measuring step, a grinding step for 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 is provided.
In the thickness measuring step, if the calculated change amount is equal to or less than the threshold value registered in advance, the opposite surface of the protected workpiece to which the thickness measuring instrument is in contact is subducted by the thickness measuring instrument. If it is determined that the back surface of the workpiece is unlikely to occur, the grinding step is started, and if the calculated change amount exceeds the pre-registered threshold value, the protection that the thickness measuring instrument comes into contact with. A grinding method in which it is determined that the opposite surface of the finished workpiece is the surface protection member in which the thickness measuring instrument is likely to sink, and the grinding step is not started. The grinding method according to claim 1, wherein the surface protective member is an adhesive tape. A chuck table for holding the workpiece, a thickness measuring means for measuring the thickness of the workpiece held on the chuck table, and a grinding means for grinding the workpiece held on the chuck table. It is a equipped grinding device,
The chuck table is rotatable on a rotation axis having a vertical direction as an axial direction, and holds a protected workpiece formed by attaching a surface protection member to the workpiece on a holding surface.
The thickness measuring means measures the thickness of the protected workpiece by bringing the thickness measuring instrument into contact with the surface of the protected workpiece opposite to the surface held by the chuck table before starting grinding of the protected workpiece .
The grinding means grinds the back surface of the workpiece while supplying grinding water with a grinding wheel that rotates on a rotation axis orthogonal to the holding surface of the chuck table.
First thickness data and the first thickness data obtained by combining the thickness of the workpiece measured by the thickness measuring means and the thickness of the surface protection member covering the surface of the workpiece before the start of grinding . The amount of change is obtained from the second thickness data obtained by combining the thickness of the work piece measured after an arbitrary time has elapsed from the time when the value is measured and the thickness of the surface protection member covering the surface of the work piece. When the calculation means to be calculated and the change amount calculated by the calculation means are equal to or less than the pre-registered threshold value, grinding is started, and when the change amount exceeds the pre-registered threshold value. Is a grinding device characterized by being equipped with a control means that displays an error and does not start grinding. The thickness measuring means is used for measuring the thickness of the work piece before the start of grinding and the thickness of the surface protection member covering the surface of the work piece, and is used for measuring the thickness after the start of grinding . The grinding apparatus according to claim 3, wherein the grinding device is also used for controlling the thickness of an object.

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