JP4766993B2 - Method and apparatus for grinding plate-like workpiece - Google Patents

Description

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

  2. Description of the Related Art Conventionally, a grinding apparatus that rotates a semiconductor wafer while sucked and held on a chuck table and grinds the semiconductor wafer with a grinding wheel disposed on the lower surface of a rotating grinding wheel is known.

For example, Patent Document 1 discloses a semiconductor wafer grinding apparatus provided with an air bearing that supports a grinding wheel or a chuck table with an air bearing so as to provide cushioning and grinding so that silicon, which is a brittle material, is not damaged. It is disclosed. In this grinding apparatus, a thrust plate is arranged at a predetermined interval from a wheel mounter to which a grindstone is attached, so that the grinding wheel is not bent.
Japanese Patent Laid-Open No. 11-138432

  However, even if the grinding wheel is devised so as not to bend like the grinding device of Patent Document 1 above, the wafer and the grinding wheel are in a state of being supported with a gap between the air bearings. After the grinding wheel comes into contact with the wafer, grinding is not started until a grinding pressure is applied to the extent that the grinding is further performed.

  Even when the cutting is stopped, since the reaction force is received from the air bearing, when the grinding wheel is abruptly separated from the wafer, one grinding streak is finally formed at the place where the grinding wheel finally contacts the wafer. There is a problem that the finished surface accuracy is lowered.

  Therefore, conventionally, even when the cutting is stopped, the grinding wheel cannot be immediately separated from the wafer, but is gradually separated from the wafer so as not to generate grinding marks as much as possible, so that the grinding time becomes long. There was a problem.

  This invention is made | formed in view of this point, The place made into the objective is to shorten grinding time, without reducing the finished surface precision of a plate-shaped grinding | polishing thing.

  In order to achieve the above object, in the present invention, the grinding wheel when grinding is actually started presses the plate-shaped workpiece, the minimum pressure at which grinding is actually started is stored, and the grinding wheel is When the grinding pressure was reduced to the same value as the stored value in the step of separating from the plate-shaped workpiece, the grinding wheel was detached from the plate-shaped workpiece.

Specifically, in the first invention, on the premise of a method of grinding a plate-shaped workpiece,
The plate-like workpiece is sucked and held on a chuck table rotatably supported by the first air bearing, and has an annular grinding wheel for grinding the plate-like workpiece, and the second air bearing A preparatory step of arranging a grinding wheel rotatably supported on the grinding wheel so that the grinding wheel is placed on a rotation center of the chuck table;
A rough grinding step of rotating the chuck table, rotating the grinding wheel, bringing the grinding wheel close to and contacting the plate-shaped workpiece, cutting and grinding while pressing,
A pressure difference between a pair of chuck-side pressure ports provided in the first air bearing when the grinding wheel receives a predetermined grinding pressure and actually starts grinding the plate-shaped workpiece, or the second A storage step of measuring and storing a pressure difference between a pair of grinding wheel side pressure ports provided in the air bearing;
A final finishing step of stopping the cutting of the grinding wheel and releasing the bending accumulated in the grinding wheel and the chuck table;
In the final finishing step, when the measured pressure difference between the pair of chuck side pressure ports or the pressure difference between the pair of grinding wheel side pressure ports is reduced to the stored pressure difference, the grinding wheel is plate-shaped. And a detaching step for detaching from the object to be ground.

  That is, since the chuck table and the grinding wheel are rotatably supported by the first or second air bearing, respectively, the grinding wheel is cut during grinding so that the grinding pressure is applied from the grinding wheel to the plate-shaped workpiece. When loaded, the chuck table and grinding wheel tilt. At the stage where the grinding pressure is low, the grinding wheel merely slides on the surface of the plate-shaped workpiece, and grinding is not actually performed. And grinding is actually started when the grinding pressure rises to some extent, and the surface of the plate-like workpiece is removed. When the grinding wheel is suddenly moved away from the wafer when the cutting is stopped and the grinding pressure is lowered, a reaction force is received from the first or second air bearing. One grinding streak remains on the surface. However, according to the above configuration, by storing the pressure difference detected between the pair of chuck side pressure ports and the pair of grindstone side pressure ports when the grinding pressure increases and grinding is actually started, When the grinding wheel is removed while the grinding pressure is reduced in the final finishing process to stop the cutting of the grinding wheel and release the flexure accumulated on the grinding wheel and chuck table. Therefore, if the grinding wheel is removed from the plate-like workpiece after that, the grinding streak becomes less than the allowable level.

  In the second invention, the plate-shaped workpiece is a semiconductor wafer.

  According to the above configuration, a semiconductor wafer that is a brittle material and requires extremely high-precision finishing is ground without leaving a grinding streak.

In the third invention, a chuck table that is rotatably supported by the first air bearing and sucks and holds the plate-shaped workpiece;
A circular grinding wheel for grinding the plate-like workpiece, and a grinding wheel rotatably supported by a second air bearing;
A grinding apparatus in which the center of rotation of the chuck table and the center of rotation of the grinding wheel are offset so that the grinding wheel is placed on the center of rotation of the chuck table,
At least one pair of chuck-side pressure ports provided in the first air bearing, or
At least one pair of grinding wheel side pressure ports provided in the second air bearing;
Stores the pressure difference detected at the chuck side pressure port or the grindstone side pressure port when the grinding wheel receives a predetermined grinding pressure and starts to actually grind the plate-shaped workpiece, after stopping cutting, And a control means for detaching the grinding wheel when the pressure difference detected at the chuck side pressure port or the grindstone side pressure port decreases to the stored pressure difference.

  That is, since the chuck table and the grinding wheel are rotatably supported by the first or second air bearing, respectively, the grinding wheel is cut during grinding so that the grinding pressure is applied from the grinding wheel to the plate-shaped workpiece. When loaded, the chuck table and grinding wheel tilt. At the stage where the grinding pressure is low, the grinding wheel merely slides on the surface of the plate-shaped workpiece, and grinding is not actually performed. And grinding is actually started when the grinding pressure rises to some extent, and the surface of the plate-like workpiece is removed. When the grinding wheel is suddenly moved away from the wafer when the cutting is stopped and the grinding pressure is lowered, a reaction force is received from the first or second air bearing. One grinding streak remains on the surface. However, according to the above configuration, the control means stores the pressure difference detected at the pair of chuck-side pressure ports or the pair of grindstone-side pressure ports when the grinding pressure increases and grinding is actually started. Thus, in the final finishing process of stopping the cutting of the grinding wheel and releasing the flexure accumulated on the grinding wheel and chuck table, the grinding streak is allowed even if the grinding wheel is detached while reducing the grinding pressure Since the timing of the following becomes clear, if the grinding wheel is subsequently detached from the plate-shaped workpiece, the grinding striation becomes less than the allowable level.

In the fourth invention, the pair of chuck side pressure ports pass through the center of the chuck table in a plan view, and intersect the intersection of the outer peripheral ends of the grinding wheel and the plate-shaped workpiece and the rotation center of the chuck table. Arranged on a straight line substantially parallel to the connected reference straight line at an equal distance from the center,
The pair of grinding wheel side pressure ports are respectively arranged on a straight line that passes through the center of the grinding wheel in a plan view and is substantially perpendicular to the reference straight line with an equal distance from the center.

  According to the above configuration, since the pressure port is appropriately disposed with respect to the reference straight line, the inclination of the chuck table and the grinding wheel with respect to the reference straight line can be easily detected from the pressure difference. Thus, since the grinding pressure applied to the plate-like workpiece is estimated, the timing when the grinding streak is less than the allowable level even if the grinding wheel is removed is estimated.

  In the fifth invention, the plate-shaped workpiece is a semiconductor wafer.

  According to the above configuration, a semiconductor wafer that is a brittle material and requires extremely high-precision finishing is ground without leaving a grinding streak.

  As described above, according to the first and third inventions described above, the pressure of the pair of chuck-side pressure ports when the grinding wheel receives a predetermined grinding pressure and actually starts grinding the plate-shaped workpiece. By measuring the difference or the pressure difference between the pair of grinding wheel side pressure ports, the grinding pressure at which the grinding streak is less than or equal to the allowable level even if the grinding wheel is removed was memorized and measured in the final finishing step. After the pressure difference between the pair of chuck side pressure ports or the pressure difference between the pair of grinding wheel side pressure ports becomes smaller than the stored pressure difference, the grinding wheel is detached from the plate-shaped workpiece. For this reason, the grinding time can be shortened without reducing the finished surface accuracy of the plate-like ground material.

  According to the second and fifth aspects of the invention, the plate-like workpiece to be ground is made of a brittle material and is a semiconductor wafer that is required to have an extremely high precision finish. For this reason, the effect of this invention is exhibited notably.

  In the fourth aspect of the invention, the pressure port is appropriately arranged with respect to the reference straight line, the inclination of the chuck table and the grinding wheel with respect to the reference straight line is easily detected from the pressure difference, and the grinding pressure applied to the plate-like workpiece is determined. Estimated. For this reason, even when the grinding wheel is removed, it is possible to accurately estimate the timing at which the grinding striation is less than the allowable level, so that the grinding time can be made extremely efficient without degrading the finished surface accuracy of the plate-like grinding object. Can be shortened.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a grinding apparatus 1 according to an embodiment of the present invention. The grinding apparatus 1 includes a base 2 and a vertical wall portion 3 erected substantially vertically from the base 2. On the front side of the vertical wall portion 3, a pair of rails 4 are disposed substantially perpendicular to the base 2. A slide plate 5 is attached to the rail 4 so as to be slidable in the vertical direction. A propulsion unit 6 is provided from the slide plate 5 substantially vertically toward the vertical wall 3. The propulsion unit 6 is provided with a female screw.

  That is, a propulsion motor 7 is provided at the upper end of the vertical wall 3, and a propulsion screw (ball screw) is provided on the propulsion shaft 8 that is a drive shaft thereof. When the female screw of the propulsion unit 6 is fitted to the propulsion screw and the propulsion motor 7 is driven, the slide plate 5 can slide up and down.

  The grinding apparatus 1 includes a controller as a control means (not shown) and is configured to control the entire grinding apparatus 1.

  The base 2 is provided with a chuck table 10 for sucking and holding a semiconductor wafer 9 as a plate-like workpiece. That is, on the upper surface of the base 2, a base 11 having a through hole 11a in the center is disposed. A bearing housing 12 is disposed in the through hole 11 a of the base 11. A first air bearing 13 is disposed in the bearing housing 12, and the chuck table 10 is rotatably supported by the first air bearing 13.

  As shown in FIG. 2, the chuck table 10 has a conical surface 10a formed of a porous material having an inclined surface with an extremely small gradient with the rotation center X as a vertex. The chuck table 10 has a central shaft 10b extending downward, and an air hole 10c is provided at the center thereof. By sucking air from the air holes 10c, the semiconductor wafer 9 is sucked and held by sucking air from many holes of the conical surface 10a. On the opposite side of the conical surface 10a, a disc-shaped bottom 10d having a flat surface is formed.

  The first air bearing 13 has a surface made of a porous material such as carbon, and is generated by blowing pressurized gas supplied from a pressure source (not shown) from a small hole to the central shaft 10b and the bottom 10d of the chuck table 10. The chuck table 10 is rotatably supported by the static pressure.

  As shown in FIG. 1, the lower end portion of the central shaft 10 b of the chuck table 10 is coupled to the chuck rotation shaft 15 by a coupling 14 so as to be tiltable. The chuck rotating shaft 15 is provided with a chuck pulley 16 on the lower end side. A belt 17 fitted to the chuck side pulley 16 is driven by a chuck rotating motor 18.

  On the other hand, the slide plate 5 is provided with a grinding wheel rotating motor 20. The wheel rotating shaft 21 of the grindstone rotating motor 20 is rotatable in a state where it can be tilted with respect to the stator 22. As shown in FIG. 2, a central shaft 25 a of a grinding wheel 25 is connected to the wheel rotation shaft 21. The center axis 25a of the grinding wheel 25 has a disk portion 25b having a flat surface spread in a disk shape at a lower end portion, and a grindstone mounting portion 25c is provided below the center portion 25b. An annular grinding wheel 27 for grinding the wafer 9 is detachably attached to the lower end of the grinding wheel mounting portion 25c. For example, the grinding wheel 27 has a structure in which a diamond wheel is attached to an annular aluminum frame.

  A second air bearing 26 is provided on the inner surface on the lower end side of the grinding wheel rotating motor 20. The second air bearing 26 is also configured in the same manner as the first air bearing 13, and by the static pressure generated by blowing pressurized gas from the small hole to the central shaft 25a and the disc portion 25b of the grinding wheel 25, The grinding wheel 25 is rotatably supported.

  The rotation center X of the chuck table 10 and the rotation center Y of the grinding wheel 25 are offset so that the grinding wheel 27 is placed on the rotation center X of the chuck table 10.

  As shown in FIG. 1, the bearing housing 12 of the first air bearing 13 is configured so that the inclination angle of the contact surface of the wafer 9 with respect to the grinding wheel 27 can be adjusted. That is, the base 11 on the base 2 is provided with one ball-shaped tilt fulcrum 30 and a pair of ball screws 31 and 32.

  The ball screw 31 is fixed to the bearing housing 12 and is fitted to a ball screw nut 31a having an internal thread on the inner surface, and the ball screw nut 31a is moved up and down by driving a ball screw drive motor 31c via a speed reducer 31b. The ball screw drive motor 31c is composed of a servo motor or a stepping motor. The ball screw 32 has a similar structure.

  The positional relationship between the tilt fulcrum 30 and the pair of ball screws 31 and 32 will be specifically described with reference to FIG. A reference straight line Z is drawn by connecting the intersection C1 between the grinding wheel 27 and the outer periphery of the wafer 9 and the center point C2 of the chuck table 10 in plan view. A first ball screw 31 and a second ball screw 32 are arranged at a position substantially parallel to the reference straight line Z. The tilt fulcrum 30 is arranged so as to form an equilateral triangle with respect to the pair of ball screws 31 and 32. The center of this equilateral triangle coincides with the center of the chuck table 10. With this arrangement, the bearing housing 12 is supported at three points, and the chuck table 10 is configured to be tiltable with respect to the contact surface of the grinding wheel 27 with respect to the wafer 9.

A pair of chuck-side pressure ports 41 and 42 are provided at positions facing the center of the first air bearing 13 that is substantially parallel to the reference straight line Z. The pair of chuck side pressure ports 41 and 42 includes a first pressure port 41 and a second pressure port 42. As shown in FIG. 4, the first pressure port 41 detects the pressure P ₁ on the first ball screw 31 side between the surface of the first air bearing 13 and the bottom 10 d of the chuck table 10, and the second pressure port 42. Thus, the pressure P ₂ on the second ball screw 32 side is detected. That is, as shown in FIG. 5, during the grinding process, the chuck table 10 is tilted toward the second ball screw 32 due to the grinding load, so that there is a gap between the surface of the first air bearing 13 and the bottom 10d of the chuck table 10. As the pressure decreases, P ₂ increases (P ₂ > P ₁ ), and a pressure difference P _AC (P _AC = P ₂ −P ₁ ) occurs.

Similarly, a pair of grindstone-side pressure ports 43 and 44 are provided at positions facing the center of the second air bearing 26 that is substantially perpendicular to the reference straight line Z. The pair of grinding wheel side pressure ports 43 and 44 includes a third pressure port 43 and a fourth pressure port 44. As shown in FIG. 2, a pressure P ₃ opposite to the chuck table 10 between the surface of the second air bearing 26 and the disc portion 25 b is detected at the third pressure port 43, and at the fourth pressure port 44. The pressure P ₄ on the chuck table 10 side is detected. That is, during grinding, the grinding wheel 27 is tilted toward the chuck table 10 due to a grinding load, so the gap between the surface of the second air bearing 26 and the disk portion 25b is narrowed, and P ₄ is increased ( P ₄ > P ₃ ), and the pressure difference P _BW (P _BW = P ₄ −P ₃ ) is generated.

-Driving action-
Next, the operation of the grinding apparatus 1 according to this embodiment will be described.

(Teaching work)
The inclination of the chuck table 10 is adjusted in advance so that the shape of the wafer 9 can be ground to a target shape. The target shape is a shape finished to the required product thickness after grinding.

(Grinding work)
Next, the grinding operation will be described with reference to FIG. FIG. 6 shows the grinding power that is the power consumption of the grinding wheel rotating motor 20 and the gauge signal sent from the gauge (not shown) provided on the wafer.

  At the time of grinding, first, the wafer 9 is sucked and held on the chuck table 10, and the chuck rotating motor 18 is driven to rotate the chuck table 10.

  Next, in the preparation process, the grinding wheel rotating motor 20 is driven to rotate the grinding wheel 25, and the propulsion motor 7 is driven to rotate the grinding wheel 25 until the grinding wheel 27 is placed on the rotation center X of the chuck table 10. Lower. Then, since the chuck table 10 is mounted on the first air bearing 13 and the grinding wheel 25 is mounted on the second air bearing 26 with a gap therebetween, the chuck table 10 or the grinding wheel 25 is inclined. As a result, the grinding wheel 27 slides on the wafer 9 and causes crushing of the grinding wheel, and grinding does not start immediately.

Then, at P1, grinding is started when a load (minimum force when processing is actually started) is applied to the wafer 9 to some extent. At this time, the pressure difference P0 _Ac (P0 _Ac = P ₂ -P ₁ ) between the pair of chuck side pressure ports 41 and 42 during grinding or the pressure difference P0 _Bw (P0) between the pair of grindstone side pressure ports 43 and 44 _Bw = P ₄ −P ₃ ) is measured and stored in the controller (storage process).

  Next, the grinding wheel 25 is lowered to further apply a load, and the wafer 9 is ground. After P2, rough grinding is performed by lowering the grinding wheel 25 stably at a constant speed (rough grinding process). At this time, the grinding wheel 27 performs self-generated blades, and the wafer 9 is ground while the grinding wheel itself is being cut.

  Next, at P3, the lowering speed of the grinding wheel 25 is relaxed and the finishing process is performed.

  Next, in the final finishing process after P4, the cutting is stopped, and the bending accumulated between the grinding wheel 27 and the wafer 9 is released. In this final finishing step, the shape change speed is minimized and the final shape is determined. In the final finishing process, the gauge signal is flat because the probe is raised.

During this grinding, the pressure difference P _AC between the pair of chuck side pressure ports 41 and 42 or the pressure difference P _BW between the pair of grinding wheel side pressure ports 43 and 44 is measured. Then, the pressure difference P _AC or P _BW gradually decreases.

The pressure difference P _AC between the pair of chuck side pressure ports 41, 42 is equal to the stored pressure difference P0 _Ac , or the pressure difference between the pair of grindstone side pressure ports 43, 44 is stored. When it becomes equal to the above P0 _Bw , the propulsion motor 7 is driven at once, and the grinding wheel 27 is detached from the wafer 9 (detachment process).

-Effect of the embodiment-
Therefore, according to the grinding method and the grinding apparatus 1 according to the present embodiment, the pressure difference between the pair of chuck-side pressure ports 41 and 42 when the grinding wheel 27 receives a predetermined grinding pressure and actually starts grinding the wafer 9. By measuring the pressure difference P0 _Bw between P0 _Ac or the pair of grinding wheel side pressure ports 43, 44, the grinding wheel 27 starts to slide on the wafer 9, and even if the grinding wheel 27 is detached, the grinding streak is allowed. In the final finishing step, the grinding wheel 27 is moved after the measured pressure difference P _AC or P _BW becomes smaller than the stored pressure difference P 0 _Ac or P0 _Bw. It is separated from the wafer 9. For this reason, the grinding time can be shortened without reducing the finished surface accuracy of the wafer 9.

Further, the pressure ports 41 to 44 are appropriately arranged with respect to the reference straight line Z, and the inclination of the chuck table 10 and the grinding wheel 25 with respect to the reference straight line Z is easily detected from the pressure differences P _AC and P _BW , The applied grinding pressure is estimated. For this reason, even when the grinding wheel 27 is detached, the timing at which the grinding streak is less than the allowable level can be accurately estimated, so that the grinding time can be shortened very efficiently without reducing the finished surface accuracy of the wafer 9. can do.

(Other embodiments)
The present invention may be configured as follows with respect to the above embodiment.

  That is, in the above embodiment, the first air bearing 13 and the second air bearing 26 are provided with a pair of pressure ports 41 to 44, respectively, but the pair of pressure ports is the first air bearing 13 or the second air bearing 13. The air bearing 26 may be provided only on one side. Further, instead of one pair of pressure ports, two pairs of pressure ports may be provided with an interval of 90 degrees.

  Further, in the above embodiment, the grinding wheel 27 is detached from the wafer 9 after the pressure difference of the pressure port provided in the first air bearing 13 or the second air bearing 26 becomes smaller than the stored pressure difference. However, even if the grinding wheel 27 is detached from the wafer 9 after the pressure difference between the pressure ports provided in both the first air bearing 13 and the second air bearing 26 becomes smaller than the stored pressure difference, both. Good.

  In the above embodiment, the timing at which the grinding streak is less than or equal to the allowable level even if the grinding wheel 27 is detached is determined from the pressure, but the grinding power at that time may be used. In other words, the finishing power may be stored, and the process may be shifted to the separation process when the finishing power becomes equal.

  In addition, the above embodiment is an essentially preferable illustration, Comprising: It does not intend restrict | limiting the range of this invention, its application thing, or a use.

  As described above, the present invention is useful for a grinding apparatus and a grinding method for a plate-like workpiece such as a semiconductor wafer using an air bearing.

It is a side view which shows a grinding device concerning an embodiment of the present invention partially fractured. It is side sectional drawing which expands and shows a chuck table, a grinding wheel, and its periphery. It is a top view which shows the outline of the positional relationship of a chuck table, a grinding wheel, and its periphery. It is side sectional drawing which shows the inclination of the chuck table before a grinding stone hits. It is side sectional drawing which shows the inclination of a chuck table when the grinding wheel is hit. It is a graph which shows grinding electric power and a gauge signal.

Explanation of symbols

1 Grinding device 9 Wafer (plate-shaped workpiece)
DESCRIPTION OF SYMBOLS 10 Chuck table 13 1st air bearing 25 Grinding wheel 26 2nd air bearing 27 Grinding wheel 41 1st pressure port (chuck side pressure port)
42 Second pressure port (chuck side pressure port)
43 3rd pressure port (grinding wheel side pressure port)
44 4th pressure port (grinding wheel side pressure port)
Pressure difference Z reference line LW wheel spindle diameter P _AC pair of chuck side pair of chuck-side pressure port is the pressure difference P0 _Ac storage of the wheel-side pressure port of the pressure difference P _BW pair of pressure ports P0 is _Bw stored Pressure difference between a pair of grinding wheel side pressure ports

Claims (5)

In a method of grinding a plate-shaped workpiece,
The plate-like workpiece is sucked and held on a chuck table rotatably supported by the first air bearing, and has an annular grinding wheel for grinding the plate-like workpiece, and the second air bearing A preparatory step of arranging a grinding wheel rotatably supported on the grinding wheel so that the grinding wheel is placed on a rotation center of the chuck table;
A rough grinding step of rotating the chuck table, rotating the grinding wheel, bringing the grinding wheel close to and contacting the plate-shaped workpiece, cutting and grinding while pressing,
A pressure difference between a pair of chuck-side pressure ports provided in the first air bearing when the grinding wheel receives a predetermined grinding pressure and actually starts grinding the plate-shaped workpiece, or the second A storage step of measuring and storing a pressure difference between a pair of grinding wheel side pressure ports provided in the air bearing;
A final finishing step of stopping the cutting of the grinding wheel and releasing the bending accumulated in the grinding wheel and the chuck table;
In the final finishing step, when the measured pressure difference between the pair of chuck side pressure ports or the pressure difference between the pair of grinding wheel side pressure ports is reduced to the stored pressure difference, the grinding wheel is plate-shaped. A method for grinding a plate-like object to be ground, comprising a separation step of separating from the object to be ground. In the grinding method of the plate-shaped workpiece of Claim 1,
The plate-like object to be ground is a semiconductor wafer. A chuck table rotatably supported by the first air bearing and sucking and holding the plate-shaped workpiece;
A circular grinding wheel for grinding the plate-like workpiece, and a grinding wheel rotatably supported by a second air bearing;
A grinding apparatus in which the center of rotation of the chuck table and the center of rotation of the grinding wheel are offset so that the grinding wheel is placed on the center of rotation of the chuck table,
At least one pair of chuck-side pressure ports provided in the first air bearing, or
At least one pair of grinding wheel side pressure ports provided in the second air bearing;
Stores the pressure difference detected at the chuck side pressure port or the grindstone side pressure port when the grinding wheel receives a predetermined grinding pressure and starts to actually grind the plate-shaped workpiece, after stopping cutting, A grinding apparatus comprising: a control means for releasing the grinding wheel when a pressure difference detected at the chuck side pressure port or the grindstone side pressure port is reduced to the stored pressure difference. The grinding apparatus according to claim 3, wherein
The pair of chuck-side pressure ports pass through the center of the chuck table in plan view, and a reference straight line connecting the intersection of the outer peripheral ends of the grinding wheel and the plate-like workpiece and the rotation center of the chuck table. Arranged on a straight line substantially parallel to each other at an equal distance from the center,
The pair of grinding wheel side pressure ports are arranged on a straight line that passes through the center of the grinding wheel in a plan view and is substantially perpendicular to the reference straight line with an equal distance from the center. Grinding equipment. In the grinding device according to claim 3 or 4,
The plate-like object to be ground is a semiconductor wafer.

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