JP2017164837A - Grinding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grinding device that can reduce loads of a motor while preventing occurrence of backlash in grinding a wafer using the device.SOLUTION: The grinding device comprises grinding means 7 and means 5 for grinding/feeding the grinding means 7. The grind/feeding means 5 comprises: a ball screw 50; a rail 51 which guides the grinding means 7; a motor 52 which rotates the ball screw 50; a counter balance 59 which lifts up the grinding means 7; and a counter balance adjustment means 58. The adjustment means 58 adjusts the counter balance 59 when the grinding means 7 is fed in a descending direction, applies force for lifting up the grinding means 7 from the counter balance 59 to the grinding means 7 until a grinding grindstone 740 contacts a wafer, contacts a lower surface of a screw groove of the ball screw 50 with an upper surface of a screw groove of a nut 750 so as to eliminate backlash, and adjusts the counter balance 59 after the grinding grindstone 740 contacts the wafer, so as to weaken the force for lifting up the grinding means 7 to reduce loads of the motor 52.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a grinding apparatus that performs grinding by bringing a grinding wheel into contact with a wafer.

  A semiconductor wafer or the like is ground by a grinding machine to have a predetermined thickness, and then divided by a cutting machine or the like to form individual devices, which are used in various electronic devices. In a grinding apparatus used for such grinding, the grinding means provided with the grinding wheel is lowered with respect to the wafer held by the chuck table by the grinding feed means, and the rotating grinding wheel is brought into contact with the wafer and pressed. While grinding the wafer.

  The grinding means includes a spindle unit that rotates the grinding wheel and a holder that supports the spindle unit, and the total weight thereof is, for example, about 300 kg or more. The grinding feed means is composed of, for example, a ball screw, a guide rail, a motor, etc., but since a large load is applied to the grinding feed means due to the weight of the grinding means, a counter balance for reducing and canceling the load There is a grinding device provided with a mechanism called (for example, refer to patent documents 1).

JP 2006-303161 A

  The motor of the grinding feed means requires an output for raising the grinding means having a total weight of 300 kg or more. Further, in a grinding apparatus having a counter balance, when the grinding feed is performed in the downward direction, the backlash of the ball screw due to the grinding load (the rattling between the ball screw and the nut screwed to the ball screw) occurs. In order to prevent this, an upward force is applied to the grinding means by the counterbalance. That is, when performing grinding feed in the downward direction, the motor that rotates the ball screw is always rotating while receiving a load in the upward direction applied to the grinding means. Furthermore, when the grinding wheel comes into contact with the upper surface of the wafer and grinding starts, the motor is also applied with a force that pushes the grinding means upward from the wafer in addition to the upward force applied to the grinding means from the counter balance. Therefore, the load on the motor increases.

  Therefore, when a wafer is ground using a grinding apparatus having a counter balance, there is a problem of reducing the load applied to the motor while preventing the backlash of the ball screw from occurring due to the counter balance.

  The present invention for solving the above problems includes a chuck table for holding a wafer, a grinding means rotatably mounted with a grinding wheel having an annular grinding wheel for grinding the wafer held by the chuck table, A grinding apparatus comprising: a grinding feed means for grinding and feeding the grinding means in a vertical direction that is spaced apart from or approaching the chuck table; and the grinding feed means includes a ball screw that is screwed to a nut provided in the grinding means; A pair of guide rails arranged in parallel with the ball screw to guide the grinding means in the vertical direction, a motor for rotating the ball screw, and a counter balance for lifting the grinding means with a force corresponding to the weight of the grinding means; Counter balance adjusting means for adjusting a force for lifting the grinding means by the counter balance, and the counter balun The adjusting means adjusts the counter balance when the grinding means is fed in the downward direction until the grinding wheel of the grinding wheel comes into contact with the wafer held by the chuck table. Applying a force to lift the grinding means against the grinding means from the balance, the lower surface of the thread groove of the ball screw and the upper surface of the thread groove of the nut are brought into contact with each other via the ball, and the backlash is eliminated, and the grinding From the point of time when the grinding wheel of the wheel contacts the wafer held on the chuck table, the counter balance is adjusted, and a force for lifting the grinding means applied to the grinding means from the counter balance is increased. It is a grinding device that weakens and reduces the load on the motor.

  A grinding apparatus according to the present invention includes a chuck table for holding a wafer, a grinding means for rotatably mounting a grinding wheel having an annular grinding wheel for grinding the wafer held by the chuck table, and the grinding means as a chuck table. A grinding feed means for grinding and feeding in a vertical direction that is spaced apart from or approaching the grinding means, wherein the grinding feed means is disposed in parallel with the ball screw that is screwed into a nut provided in the grinding means, and the ball screw. A pair of guide rails for guiding the grinding means in the vertical direction, a motor for rotating the ball screw, a counter balance for lifting the grinding means with a force corresponding to the weight of the grinding means, and a counter for adjusting the force for lifting the grinding means by the counter balance A balance adjusting means, and the counter balance adjusting means is configured such that the grinding means descends. When the grinding balance is adjusted, the counter balance is adjusted and the grinding wheel of the grinding wheel is in contact with the wafer held on the chuck table by applying a force to lift the grinding means from the counter balance to the grinding means. From the point of time when the lower surface of the thread groove of the ball screw and the upper surface of the thread groove of the nut are brought into contact with each other through the ball to eliminate the backlash, the grinding wheel of the grinding wheel comes into contact with the wafer held on the chuck table. It is possible to reduce the power consumption of the motor that rotates the ball screw by adjusting the balance and reducing the load on the motor by weakening the force that lifts the grinding means applied to the grinding means from the counter balance. Become.

It is a typical side view showing an example of composition of a grinding device. It is a typical front view which shows an example of a structure of a grinding device. A graph showing the transition of the height position of the grinding means, the transition of the speed of the grinding means, the transition of the value of the force applied to the grinding means from the counter balance (pressure value), and the transition of the drive current value of the motor in the grinding feed means is there. It is a typical longitudinal section showing the state where a nut is screwed into a ball screw. It is a typical side view showing the state where a wafer is ground by a grinding device.

  A grinding apparatus 1 shown in FIG. 1 is an apparatus for grinding a wafer W held on a chuck table 30 by a grinding means 7. A column 11 is erected on the rear side (+ Y direction side) on the base 10 of the grinding apparatus 1, and the grinding means 7 is separated from the chuck table 30 on the side surface of the column 11 on the −Y direction side. Alternatively, a grinding feed means 5 for grinding and feeding in the approaching vertical direction is provided.

  The chuck table 30 disposed on the base 10 of the grinding apparatus 1 and holding the wafer W has, for example, a circular outer shape and is composed of a porous member or the like, and includes a suction unit 300 that sucks the wafer W and a suction unit 300. And a supporting frame 301. The suction unit 300 communicates with a suction source (not shown), and the suction force generated by the suction of the suction source is transmitted to the holding surface 300a that is the exposed surface of the suction unit 300, whereby the chuck table 30 is held on the holding surface. The wafer W is sucked and held on 300a. The chuck table 30 can be rotated about the Z axis as a rotation axis, and can be reciprocated on the base 10 in the Y axis direction by a Y axis direction feeding means (not shown).

  The grinding feed means 5 includes a ball screw 50 that is screwed into a nut 750 provided in the grinding means 7 and extends in the Z-axis direction, a pair of guide rails 51 that are arranged in parallel to the ball screw 50 and guide the grinding means 7 in the vertical direction, A motor 52 that rotates the ball screw 50, a counter balance 59 that lifts the grinding means 7 with a force according to the weight of the grinding means 7, and a counter balance adjustment means 58 that adjusts the force to lift the grinding means 7 by the counter balance 59. .

  The grinding means 7 for grinding the wafer W held on the chuck table 30 has a spindle 70 whose axial direction is a vertical direction (Z-axis direction), a spindle housing 71 that rotatably supports the spindle 70, and a spindle 70 that rotates. A spindle motor 72 for driving, an annular mount 73 connected to the lower end of the spindle 70, a grinding wheel 74 detachably connected to the lower surface of the mount 73, and a lifting holder 75 for holding the spindle housing 71 are provided. . The grinding means 7 has, for example, a total weight, that is, a self-weight value of about 300 kg.

  The grinding wheel 74 includes an annular wheel base 741 and a plurality of substantially rectangular parallelepiped grinding wheels 740 disposed in an annular shape on the bottom surface of the wheel base 741. The grinding wheel 740 is formed by, for example, diamond abrasive grains being hardened with a resin bond, a metal bond, or the like. In addition, the shape of the grinding stone 740 may be integrally formed in an annular shape. Inside the grinding means 7, a flow path (not shown) serving as a path for grinding water is formed, and an opening is provided on the bottom surface of the wheel base 741 so that the grinding water can be ejected toward the grinding wheel 740.

  On the side surface of the elevating holder 75, a nut 750 that is screwed into the ball screw 50 and a sliding portion 751 that slides on the guide rail 51 while being in sliding contact with the pair of guide rails 51 are disposed.

  The column 11 is provided with position recognition means 12 for recognizing the position of the grinding means 7. The position recognition unit 12 is, for example, a scale 120 that is fixed to the column 11 and extends along the moving direction (Z-axis direction) of the grinding unit 7, and a reading unit that reads position information (scale) displayed on the surface of the scale 120. 121. The reading unit 121 is, for example, an optical type that is fixed to the elevating holder 75, moves up and down together with the elevating holder 75, and reads the reflected light of the scale formed on the scale 120.

  The counterbalance 59 that cancels the weight of the grinding means 7 is composed of, for example, two air cylinders as shown in FIGS. 1 and 2, and a cylindrical case 590 having a bottom and a case disposed inside the cylinder case 590. It includes a piston 591 that slides inside, and a piston rod 592 that is inserted into the cylinder case 590 and has an upper end attached to the piston 591.

  The lower end side of each piston rod 592 is connected to the side surface of the lifting holder 75. Further, the upper end side of the cylinder case 590 is connected to a crane-like support arm 595 erected on the upper surface of the column 11. An air supply port 590a is formed through the side wall on the lower side of the cylinder case 590, and each air supply port 590a communicates with one air supply source 593 composed of a compressor or the like via a communication passage 593a. Yes. An electropneumatic regulator 594 is disposed on the communication path 593a, and the electropneumatic regulator 594 is in proportion to the electric signal sent from the counter balance adjusting means 58 to the pressure of air supplied into the cylinder case 590 ( The air supply amount) can be adjusted steplessly.

  The counter balance adjusting means 58 including at least a CPU and a storage element such as a memory is connected to the electropneumatic regulator 594, calculates the pressure value of air to be supplied into the cylinder case 590, and calculates the calculated air pressure. By outputting information (electrical signal) about the pressure value to the electropneumatic regulator 594, the force for lifting the grinding means 7 by the counter balance 59 is adjusted. Further, the counter balance adjusting means 58 has a force that lifts the grinding means 7 according to the weight of the grinding means 7 by the counter balance 59, that is, for example, a direction that can offset the own weight of 300 kg of the grinding means 7 is the + Z direction. Information on the force (air pressure of the electropneumatic regulator 594) is stored in advance.

  As shown in FIG. 1, the grinding apparatus 1 includes a pair of height gauges 19 that measure the thickness of the wafer W by a contact method. The pair of height gauges 19 includes a first height gauge 191 for measuring the height position of the holding surface 300 a of the chuck table 30, and a second height gauge 192 for measuring the height position of the ground surface Wa (upper surface) of the wafer W. The first height gauge 191 (second height gauge 192) includes a contact 191a (192a) that swings in the vertical direction at the tip thereof. The first height gauge 191 is set so that the tip of the contact 191a is in contact with the upper surface of the frame body 301 of the chuck table 30 that is not covered with the wafer W, and the second height gauge 192 is set so that the tip of the contact 192a is on the wafer W. It is set to be in contact with the surface to be ground Wa. In the pair of height gauges 19, the first height gauge 191 detects the height position of the upper surface of the frame 301 serving as a reference surface, and the second height gauge 192 detects the height of the surface Wa to be ground of the wafer W to be ground. The thickness position is detected, and by calculating the difference between the detected values, the thickness of the wafer W can be measured at any time during grinding.

  The operation of the grinding apparatus 1 when the wafer W is ground by the grinding apparatus 1 will be described below with reference to FIGS. 1 and 3 to 5.

  The wafer W shown in FIG. 1 is, for example, a semiconductor wafer having a circular outer shape, and a protective tape (not shown) is attached to the device surface Wb of the wafer W on which the device is formed. In grinding the wafer W, first, the wafer W is transported onto the chuck table 30 and the wafer W is placed on the holding surface 300a so that the ground surface Wa is on the upper side. Then, a suction force generated by a suction source (not shown) connected to the chuck table 30 is transmitted to the holding surface 300a, whereby the chuck table 30 sucks and holds the wafer W on the holding surface 300a.

  Next, the chuck table 30 holding the wafer W is moved in the + Y direction below the grinding means 7 by a Y-axis direction feeding means (not shown), and the grinding wheel 74 provided in the grinding means 7 and the wafer W are aligned. The Further, as the spindle motor 72 rotationally drives the spindle 70, the grinding wheel 74 also rotates.

  As shown in FIG. 3, the height position of the grinding means 7 during the grinding of the wafer W is lowered from the state positioned at the uppermost standby position to just before the grinding wheel 740 contacts the wafer W in the grinding preparation stage. To do. At this time, the lowering speed of the grinding means 7 is first accelerated and then decelerated through a constant speed movement.

  In the grinding preparation stage, when the motor 52 rotates the ball screw 50, the grinding means 7 is sent in the downward direction (−Z direction) by the grinding feeding means 5, and at the same time, the grinding means 7 is moved from the counter balance 59 to + Z. A lifting force is applied in the direction. That is, air is supplied from the air supply source 593 shown in FIG. 1, and the supplied air reaches the electropneumatic regulator 594 through the communication path 593a. An electrical signal is sent from the counter balance adjusting means 58 to the electropneumatic regulator 594 that has reached air, and the electropneumatic regulator 594 uses the supply pressure of air sent from the air supply source 593 based on this electrical signal. For example, air having a pressure that generates a force capable of canceling out the own weight 300 kg of the grinding means 7 is supplied into the cylinder case 590 from the air supply port 590a. Since the piston 591 is raised in the + Z direction by the air supplied into the cylinder case 590, a force is applied to the grinding means 7 to lift the grinding means 7 in the + Z direction that can offset its own weight of 300 kg.

  Here, the state where the ball screw 50 and the nut 750 are screwed together when the grinding means 7 is ground and fed in the downward direction will be described with reference to FIG. On the outer peripheral surface of the ball screw 50 extending in the Z-axis direction, a single thread groove 50a (male thread groove 50a) is formed in a spiral shape over the entire length. The nut 750 is attached to the outer peripheral side of the ball screw 50, and one screw groove 750a (female screw groove 750a) corresponding to the male screw groove 50a is formed on the inner peripheral surface thereof. Between the inner peripheral surface of the nut 750 and the outer peripheral surface of the ball screw 50, a plurality of balls B are spirally disposed so as to be in close contact with each other in order. That is, the space between the female screw groove 750a of the nut 750 and the male screw groove 50a of the ball screw 50 facing the nut is a ball passage, and the ball B rolls in this ball passage. A ball return 750 c for circulating the ball B is formed inside the nut 750, and one end of the ball return 750 c is open on the inner peripheral surface of the nut 750.

  When the motor 52 rotates the ball screw 50 and the ball screw 50 and the nut 750 rotate relatively, the nut 750 moves relative to the ball screw 50 in the −Z direction. By applying a force for lifting the grinding means 7 from the counter balance 59 shown in FIG. 1 to the grinding means 7, a force for lifting the grinding means 7 is also applied to the nut 750 of the grinding means 7 moving in the -Z direction. It is done. Then, the backlash can be eliminated by bringing the lower surface 50 b of the male screw groove 50 a of the ball screw 50 shown in FIG. 4 into contact with the upper surface 750 b of the female screw groove 750 a of the nut 750 via the ball B.

  As shown in FIG. 3, next to the grinding preparation stage, the lowering speed of the grinding means 7 is further reduced, and the air cutting stage until the grinding wheel 740 contacts the wafer W is entered. In the air cut stage, the grinding means 7 is continuously decelerated until the grinding wheel 740 actually contacts the wafer W.

  When the rotating grinding wheel 740 comes into contact with the wafer W at the grinding surface contact position, the process proceeds to a first grinding stage in which the lowering speed of the grinding means 7 is constant, and actual grinding is started as shown in FIG. Further, during grinding, as the chuck table 30 rotates, the wafer W held on the holding surface 300a also rotates, so that the grinding wheel 740 performs grinding of the entire surface to be ground Wa of the wafer W. .

  The counter balance adjusting means 58 adjusts the counter balance 59 from the time when the grinding wheel 740 of the grinding wheel 74 contacts the wafer W held on the chuck table 30, and adds the counter balance 59 to the grinding means 7. The load for lifting the grinding means 7 (shown as “pressure value” in FIG. 3) is weakened to reduce the load on the motor 52 shown in FIG. That is, when the grinding wheel 740 contacts the surface to be ground Wa of the wafer W, an electric signal for reducing the air pressure supplied into the cylinder case 590 from the counter balance adjusting means 58 to the electropneumatic regulator 594 is generated. Sent. The electropneumatic regulator 594 reduces the supply pressure of the air supplied to the cylinder case 590 to a predetermined pressure based on this electric signal. As the air supply pressure supplied to the cylinder case 590 is reduced, the piston 591 is lowered in the −Z direction, and the force for lifting the grinding means 7 in the + Z direction is also reduced.

  When the grinding means 7 is lowered, as shown in FIG. 3, the value of the drive current for driving the motor 52 (hereinafter referred to as “current value”) increases rapidly at first, and the power consumption of the motor 52 is increased. Becomes larger. Thereafter, the current value is constant until the grinding wheel 740 of the grinding wheel 74 contacts the wafer W held on the chuck table 30 at the grinding surface contact position. From the point of time when the grinding wheel 740 contacts the wafer W, the counter balance adjusting means 58 adjusts the counter balance 59 to weaken the force that lifts the grinding means 7 applied to the grinding means 7 from the counter balance 59. Therefore, the current value for driving the motor 52 is reduced, and the load on the motor 52 can be reduced. Further, during the grinding process, a vertical drag against the force with which the grinding wheel 740 is pressed is applied to the grinding wheel 740 from the surface Wa to be ground of the wafer W, so that the grinding means 7 applied to the grinding means 7 from the counter balance 59 is + Z Even if the force to lift in the direction decreases, the backlash is eliminated by bringing the lower surface 50b of the male screw groove 50a of the ball screw 50 shown in FIG. 4 into contact with the upper surface 750b of the female screw groove 750a of the nut 750 via the ball B. Meanwhile, the wafer W can be ground.

  In the present embodiment, for example, in the first grinding stage, the first height gauge 191 detects the height position of the upper surface of the frame body 301 serving as the reference surface, and the wafer to be ground by the second height gauge 192. When it is determined that the wafer W has been ground to a predetermined thickness by the pair of height gauges 19 by detecting the height position of the ground surface Wa of W and calculating the difference between the two detection values. The process proceeds to the second grinding stage by the grinding means 7.

  In the second grinding stage after the first grinding stage, the lowering speed of the grinding means 7 is further reduced. In this second grinding stage, in the first grinding stage, a damage layer is formed by pressing the grinding means 7 on the surface Wa to be ground of the wafer W. Therefore, the lowering speed of the grinding means 7 is further reduced. Grinding is carried out with the pressing of the grinding means 7 against the damaged layer slightly weakened. Then, the actual grinding is finished by the end of the second grinding stage.

  For example, the counter balance adjusting means 58 adjusts the counter balance 59 and is applied from the counter balance 59 to the grinding means 7 simultaneously with the transition from the first grinding stage to the second grinding stage. The force for lifting the grinding means 7 may be slightly increased. That is, in the second grinding stage, the grinding is performed by further reducing the lowering speed of the grinding means 7 so that the pressing of the grinding means 7 against the damaged layer is slightly weakened. The normal drag applied to the grinding wheel 740 is also reduced. Therefore, by slightly increasing the force for lifting the grinding means 7 applied from the counter balance 59 to the grinding means 7 by the decrease in the vertical drag applied to the grinding wheel 740 from the surface Wa of the wafer W, the ball screw The backlash can be eliminated by bringing the lower surface 50b of the 50 male screw grooves 50a into contact with the upper surface 750b of the female screw groove 750a of the nut 750 via the ball B.

  After the end of the second grinding stage, it becomes an escape cut stage for raising the grinding means 7. In the escape cut stage, the grinding means 7 starts to rise.

  After the end of the escape cut stage, it is an ascending and retracting stage in which the grinding means 7 is raised to return to the original position. In the ascending and retracting stage, the grinding means 7 is first accelerated, decelerated through a constant speed movement, and stopped.

  For example, the counter balance adjustment means 58 adjusts the counter balance 59 simultaneously with the start of the escape cut stage, and increases the pressure of the air supplied to the counter balance 59 to increase the pressure value, thereby increasing the grinding means 7. The current value is suppressed by reducing the load on the motor 52 as shown in FIG.

  The grinding device according to the present invention is not limited to the above embodiment, and the size and shape of each component of the cleaning device illustrated in the accompanying drawings are not limited thereto, and the present invention is not limited thereto. As long as the above effect can be exhibited, it can be changed as appropriate.

DESCRIPTION OF SYMBOLS 1: Grinding apparatus 10: Base 11: Column 12: Position recognition means 120: Scale 121: Reading part 30: Chuck table 300: Suction part 300a: Holding surface 301: Frame body 19: A pair of height gauges 191: First height gauge 192 : Second height gauge 191a, 192a: contact 5: grinding feed means 50: ball screw 50a: male screw groove 50b: bottom surface of male screw groove 51: pair of guide rails 52: motor 59: counter balance 590: cylinder case 590a: air Supply port
591: Piston 592: Piston rod 593: Air supply source 593a: Communication path 594: Electropneumatic regulator 58: Counter balance adjusting means 7: Grinding means 70: Spindle 71: Spindle housing
72: Spindle motor 73: Mount
74: Grinding wheel 740: Grinding wheel 740a: Grinding surface 741: Wheel base 75: Lifting holder 750: Nut 750a: Female thread groove 750b: Upper surface B of female thread groove B: Ball 751: Sliding part W: Wafer Wa: Wafer Surface to be ground Wb: Wafer device surface

Claims (1)

A chuck table for holding a wafer, a grinding means rotatably mounted with a grinding wheel having an annular grinding wheel for grinding a wafer held by the chuck table, and the grinding means spaced apart from the chuck table A grinding feed means for grinding and feeding in an approaching vertical direction,
The grinding feed means comprises:
A ball screw screwed into a nut provided in the grinding means, a pair of guide rails arranged in parallel with the ball screw to guide the grinding means in the vertical direction, a motor for rotating the ball screw, and the weight of the grinding means A counter balance that lifts the grinding means with a corresponding force; and a counter balance adjustment means that adjusts the force to lift the grinding means by the counter balance;
In the case where the counter balance adjusting means is ground and fed in the downward direction,
Until the counter balance is adjusted and the grinding wheel of the grinding wheel comes into contact with the wafer held by the chuck table, a force for lifting the grinding means from the counter balance to the grinding means is applied, The backlash is extinguished by contacting the lower surface of the thread groove of the ball screw and the upper surface of the thread groove of the nut via the ball,
When the grinding wheel of the grinding wheel comes into contact with the wafer held on the chuck table, the counter balance is adjusted, and the grinding means applied to the grinding means is lifted from the counter balance. A grinding device that reduces the load of the motor by weakening the force.

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