JP2018134717A - Grinding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable an operator to grasp when the rotational balance of a grinding wheel should be corrected to a normal balance in a grinding apparatus. SOLUTION: A table 3 for holding a waha, a grinding means 7 for rotatably mounting a grinding wheel 74 in which a grinding wheel 740 for grinding the waha is arranged in an annular shape, and a grinding means 7 in a direction approaching or separating from the table 3 The feeding means 5 and the control means 9 are provided, the grinding means 7 is provided with a measuring unit 8 for measuring the amount of vibration amplitude when the wheel 74 is rotated at a predetermined rotation speed, and the control means 9 is a table. When the wheel 74 is rotated at a predetermined rotation speed in a state where the wafer held by 3 and the grindstone 740 are not in contact with each other and the amplitude amount measured by the amplitude amount measuring unit 8 exceeds the preset amplitude amount value, the wheel 74 is used. The grinding device 1 includes a determination unit 90 for determining that the rotational balance of the wheel is unbalanced, and a notification unit 91 for notifying the operator that the rotation balance has become unbalanced by the determination of the determination unit 90. [Selection diagram] Fig. 1

Description

  The present invention relates to a grinding apparatus that rotates a grinding wheel to grind a wafer.

  A plate-like workpiece such as a semiconductor wafer is ground by a grinding machine having a rotating grinding wheel equipped with a grinding wheel and thinned to a predetermined thickness, and then divided into individual device chips by a cutting machine or the like. It is used for various electronic devices.

  In grinding, vibration is generated depending on the state of the grinding wheel. For example, when the workpiece is a wafer made of a hard material such as SiC or sapphire, vibration occurs because the grinding wheel does not easily bite against the ground surface of the wafer.

  Furthermore, even when the rotation balance of the grinding wheel is lost, vibration accompanying the rotation of the grinding wheel is generated, and this rotational vibration causes grinding spots on the surface to be ground of the wafer. One of the causes that the rotational balance of the grinding wheel is lost is the attachment of grinding waste generated by grinding to the grinding wheel. In order to prevent the grinding dust from adhering to the grinding wheel, there is a method of rotating the grinding wheel at a high speed and blowing the grinding waste together with the grinding water by centrifugal force. However, in order to reliably remove the grinding debris from the grinding wheel, it is not sufficient to use only the grinding water. Therefore, conventionally, for example, the grinding water for cleaning the grinding wheel in the configuration of the grinding device is separated from the grinding water by the grinding wheel. The problem of grinding scrap removal is being solved (see, for example, Patent Document 1).

JP 2013-141738 A

  However, constantly supplying cleaning water for cleaning the grinding wheel to the grinding wheel during the grinding process causes wasteful consumption of the cleaning water. On the other hand, if the consumption of cleaning water is constrained and the proper supply of cleaning water is neglected, for example, if grinding debris adheres to the mount on which the grinding wheel is mounted in addition to the grinding wheel, simply supplying the cleaning water will cause grinding. In some cases, the scrap cannot be removed and the generation of rotational vibration cannot be prevented. This is because even if the grinding debris adheres to the mount, it could be washed and removed with cleaning water before the grinding debris dried and solidified, but the cleaning water was not supplied at an appropriate timing. Occurs when it cannot be removed even with lumped washing water.

  Therefore, in the grinding machine, the timing at which the grinding wheel needs to be cleaned with the cleaning water, that is, the timing at which the rotation balance of the grinding wheel should be corrected from an unbalanced state to a normal balance can be detected so that the operator can grasp it. There is a problem of making it. And there exists a subject of preventing that grinding defects, such as generation | occurrence | production of the grinding spot which affects a device, arise.

  The present invention for solving the above-mentioned problems includes a chuck table for holding a wafer, a grinding means for rotatably mounting a grinding wheel in which a grinding wheel for grinding a wafer held by the chuck table is annularly arranged, and the grinding A grinding apparatus comprising a grinding feed means for grinding and feeding means in a direction approaching or separating from the chuck table, and a control means for controlling the apparatus, the grinding means including a grinding wheel at a predetermined rotational speed. An amplitude amount measuring unit for measuring an amplitude amount of vibration when rotated, and the control means is configured to rotate the grinding wheel at a predetermined rotational speed in a state where the wafer held by the chuck table and the grinding wheel are not in contact with each other. When the amplitude amount measured by the amplitude amount measuring unit exceeds the preset amplitude amount value, it is determined that the rotation balance of the grinding wheel has become unbalanced. A determination unit for a grinding apparatus and a notification unit that notifies that became unbalanced operator discretion of the determining unit.

  In the grinding apparatus according to the present invention, the grinding means includes an amplitude amount measuring unit that measures an amplitude amount of vibration when the grinding wheel is rotated at a predetermined rotation speed, and the control means includes a wafer held by the chuck table. If the amplitude measured by the amplitude measurement unit exceeds the preset amplitude value, the rotation balance of the grinding wheel is unbalanced. And a notifying unit for notifying the operator that an imbalance has occurred due to the determination by the determining unit. The operator can grasp the timing to correct the balance. As a result, for example, wasteful consumption of cleaning water can be suppressed, grinding can be prevented from being performed with a grinding wheel whose rotational balance is unbalanced, and occurrence of poor grinding of the wafer can be suppressed.

It is a perspective view which shows an example of a grinding device. A graph showing an example of changes in the amplitude amount measured by the amplitude amount measurement unit when the rotation balance of the grinding wheel is unbalanced, and a measurement by the amplitude amount measurement unit when the rotation balance of the grinding wheel is normal It is a graph which shows an example of a change of amplitude amount.

  A grinding apparatus 1 shown in FIG. 1 is an apparatus for grinding a wafer W held on a chuck table 3 by a grinding means 7. The front (−Y direction side) on the base 10 of the grinding apparatus 1 is an area where the wafer W is attached to and detached from the chuck table 3, and the rear (+ Y direction side) on the base 10 is grinding means. 7 is an area where the wafer W held on the chuck table 3 is ground.

  The chuck table 3 having a circular outer shape includes a suction portion 30 that is made of a porous member or the like and sucks the wafer W, and a frame body 31 that supports the suction portion 30. The suction part 30 of the chuck table 3 communicates with a suction source (not shown) including a compressor, a vacuum generator, and the like, and a suction force generated by suction of the suction source is a holding surface 30a that is an exposed surface of the suction part 30. The chuck table 3 can suck and hold the wafer W on the holding surface 30a. Further, the chuck table 3 can be rotated around the axis in the Z-axis direction while being surrounded from the periphery by the cover 39, and the Y-axis direction feeding means (not shown) disposed under the cover 39 allows the chuck table 3 to move over the base 10 on the Y-axis. It can be reciprocated in the axial direction.

  A column 11 is erected in the grinding region, and a grinding feed means 5 is provided on the side surface of the column 11 on the −Y direction side to feed the grinding means 7 in the vertical direction to be separated from or approach the chuck table 3. It is arranged. The grinding feed means 5 is connected to a ball screw 50 having a vertical (Z-axis direction) axis center, a pair of guide rails 51 arranged in parallel to the ball screw 50, and an upper end of the ball screw 50, and rotates the ball screw 50. And a lifting plate 53 whose inner nut is screwed to the ball screw 50 and whose side portion is in sliding contact with the guide rail 51. When the motor 52 rotates the ball screw 50, the lifting plate 53 is moved accordingly. Is guided by the guide rail 51 and reciprocates in the Z-axis direction, and the grinding means 7 fixed to the lifting plate 53 is ground and fed in the Z-axis direction.

  The grinding means 7 for grinding the wafer W held on the chuck table 3 includes a rotary shaft 70 whose axial direction is a vertical direction (Z-axis direction), a housing 71 that rotatably supports the rotary shaft 70, and a rotary shaft. A motor 72 that rotates the motor 70, an annular mount 73 connected to the lower end of the rotary shaft 70, a grinding wheel 74 that is detachably mounted on the lower surface of the mount 73, and a rotary shaft 70 supported by the housing 71. And a holder 75 fixed to the lifting plate 53 of the grinding feed means 5.

  The grinding wheel 74 includes a wheel base 741 and a plurality of grinding wheels 740 having a substantially rectangular parallelepiped shape arranged in an annular shape on the bottom surface of the wheel base 741. The grinding wheel 740 is formed by fixing diamond abrasive grains or the like with, for example, a resin bond or a metal bond. In addition, the shape of the grinding stone 740 may be integrally formed in an annular shape.

  Inside the rotary shaft 70, a flow path 70a that communicates with a grinding water supply source (not shown) and serves as a path for grinding water is provided so as to penetrate in the axial direction (Z-axis direction) of the rotary shaft 70. 70 a further passes through the mount 73 and is open so that grinding water can be jetted toward the grinding wheel 740 on the bottom surface of the wheel base 741.

  The grinding means 7 is provided with an amplitude measuring unit 8 that measures the amplitude of vibration when the grinding wheel 74 is rotated at a predetermined rotational speed. The predetermined rotation speed is, for example, the rotation speed of the grinding wheel 74 when the wafer W is actually ground.

In the example shown in FIG. 1, the arrangement location (measurement point) of the amplitude amount measuring unit 8 is on the motor 72, but is not limited to this, and the holder 75 that accommodates the rotating shaft 70 is not limited thereto. It may be disposed on the side surface or on the side surface of the housing 71. In other words, any portion of the grinding means 7 that does not rotate the amplitude amount measuring unit 8 with the rotation of the grinding wheel 74 may be used. Further, the distance between the grinding point (where the grinding wheel 740 and the wafer W are in contact), the support point at which the holder 75 supports the grinding spindle unit including the rotary shaft 70 and the housing 71, and the amplitude from the support point. It is preferable that the distance to the measurement point where the quantity measuring unit 8 is disposed is the same.
In this embodiment, the amplitude measuring unit 8 disposed on the motor 72 is, for example, a three-axis type acceleration sensor (model name: NP) manufactured by Ono Sokki Co., Ltd., which can detect vibrations in the X-axis, Y-axis, and Z-axis directions. -3572) is used. Note that the amplitude amount measuring unit 8 is not limited to an acceleration sensor.

  The grinding apparatus 1 includes a control unit 9 configured by a storage element such as a CPU and a memory to control the entire apparatus. The control means 9 is connected to the grinding feed means 5 and the grinding means 7 by wiring not shown, and the control means 9 performs the grinding feed operation of the grinding feed means 5 and the rotation operation of the grinding wheel 74 of the grinding means 7. Control is performed. Further, the control means 9 includes a determination unit 90 that determines when the rotation balance of the grinding wheel 74 is unbalanced, and a notification unit 91 that notifies the operator that the rotation is unbalanced by the determination of the determination unit 90. I have. The amplitude amount measuring unit 8 composed of an acceleration sensor follows the vibration generated with the rotation of the grinding wheel 74, measures the amplitude amount of the mechanical vibration, converts the measurement result into an electric signal, and sends it to the determining unit 90. Output.

  Hereinafter, the operation of the grinding apparatus 1 when grinding the wafer W held on the chuck table 3 by the grinding apparatus 1 shown in FIG. 1 will be described. The wafer W illustrated in FIG. 1 is, for example, a semiconductor wafer having a circular plate shape, and the back surface Wb of the wafer W is a surface to be ground on which grinding is performed. A surface Wa of the wafer W on which a device or the like is formed is protected by attaching a protective tape (not shown).

  First, in the attachment / detachment region, the wafer W is placed on the holding surface 30a of the chuck table 3 so that the back surface Wb is on the upper side. Then, the suction force generated by a suction source (not shown) is transmitted to the holding surface 30a, whereby the chuck table 3 sucks and holds the wafer W on the holding surface 30a.

  Next, the chuck table 3 holding the wafer W moves in the + Y direction from the attachment / detachment region to below the grinding means 7 in the grinding region. Further, the motor 72 rotationally drives the rotary shaft 70, and the grinding wheel 74 is also rotated accordingly. The grinding means 7 is fed in the −Z direction by the grinding feed means 5, and the rotating grinding wheel 740 comes into contact with the back surface Wb of the wafer W to perform grinding. During grinding, as the chuck table 3 rotates, the wafer W held on the holding surface 30a also rotates, so that the grinding wheel 740 grinds the entire back surface Wb of the wafer W. Further, the grinding water passing through the flow path 70a is supplied to the contact portion between the grinding wheel 740 and the wafer W, and the contact portion is cooled and washed.

  After grinding the wafer W to a desired thickness, the grinding means 7 is moved in the + Z direction by the grinding feed means 5 to move away from the wafer W, and the chuck table 3 is further moved in the −Y direction to attach / detach the region. Return to the original position. Next, another new wafer W before grinding is sucked and held on the chuck table 3, and grinding is performed in the same manner as described above.

  For example, when one or a plurality of wafers W are ground, grinding waste generated by grinding may adhere to the grinding wheel 74, and as a result, the gravity center of the grinding wheel 74 may be unevenly distributed. When the grinding wheel 74 in this state is rotated, the centrifugal force acting on the grinding wheel 74 is not balanced as a whole, and the rotational balance of the grinding wheel 74 is lost, so that the grinding wheel 74 vibrates mainly in the radial direction, for example. To do. Therefore, it is necessary to remove the adhering grinding dust by supplying cleaning water to the grinding wheel 74 or the like. The grinding apparatus 1 according to the present invention executes the operation described below under the control of the control means 9 in order to detect an appropriate cleaning timing with the cleaning water and allow the operator to recognize it.

For example, after grinding one or a plurality of wafers W and before grinding the next wafer W, the control means 9 is in a state where the wafer W held by the chuck table 3 and the grinding wheel 740 are not in contact with each other, for example, The grinding wheel 74 is rotated at a predetermined rotational speed (for example, a rotational speed of 2000 rpm) with the grinding means 7 in the upper limit position. In the present embodiment, the amplitude amount measuring unit 8 constituted by an acceleration sensor receives a vibration generated with the idling rotation of the grinding wheel 74 and vibrates the grinding wheel 74 (for example, the radial direction of the grinding wheel 74). The acceleration is measured and integrated twice to measure the displacement of the grinding wheel 74, that is, the amplitude. As described above, when the rotation speed (number of rotations) of the grinding wheel 74 is 2000 rpm, the amplitude amount measuring unit 8 measures the amplitude amount having a frequency of 33.3 Hz as shown in the graph of FIG. More realistically, the amplitude amount in the frequency band from 30 Hz to 40 Hz is measured. In FIG. 2, a graph G <b> 1 indicated by an alternate long and short dash line is a graph showing an example of a change in amplitude amount in each frequency band measured by the amplitude amount measuring unit 8 when the rotation balance of the grinding wheel 74 becomes unbalanced. In addition, a graph G2 indicated by a solid line is a graph showing an example of a change in amplitude amount in each frequency band measured by the amplitude amount measuring unit 8 when the rotation balance of the grinding wheel 74 is normal. Then, the amplitude measurement unit 8 transmits the measurement result of the measured amplitude of vibration of the grinding wheel 74 to the determination unit 90 of the control unit 9.
Note that when the rotational speed of the grinding wheel 74 is changed, the frequency band changes.

  In the determination unit 90, a value of an allowable amount of amplitude (allowable amount of amplitude) of the grinding wheel 74 that is rotating at a predetermined rotation speed is set in advance. An allowable value of this amplitude amount is 3 μm, for example. Then, the determination unit 90 determines whether the value of the amplitude amount of the vibration of the grinding wheel 74 sent from the amplitude amount measurement unit 8 exceeds the allowable value of the amplitude amount.

The amplitude value of the vibration of the grinding wheel 74 rotating at a rotational speed of 2000 rpm is equal to or less than the preset amplitude value shown in FIG. 2 (in this example, the allowable value of the amplitude at a frequency of 33.3 Hz). When the determination unit 90 determines, the next wafer W is ground in the same manner as the previous wafer W.
On the other hand, the value of the amplitude of vibration of the grinding wheel 74 rotating at a rotational speed of 2000 rpm is the value of the preset amplitude shown in FIG. 2 (in this example, the allowable value of the amplitude at a frequency of 33.3 Hz). When the determination unit 90 determines that the value has exceeded, the determination unit 90 further determines that the rotational balance of the grinding wheel 74 has become unbalanced due to, for example, adhesion of grinding scraps, and sends this determination to the notification unit 91. . The notification unit 91 notifies the operator of the determination result by displaying it as a warning on a monitor (not shown) or issuing a warning from the alarm.

  The operator who recognizes that the rotational balance of the grinding wheel 74 is unbalanced cleans the grinding wheel 74 before starting the grinding of the next wafer W, and brings the rotational balance of the grinding wheel 74 to a normal balance. Correct it.

  As described above, in the grinding apparatus 1 according to the present invention, the grinding means 7 includes the amplitude amount measuring unit 8 that measures the amplitude amount of vibration when the grinding wheel 74 is rotated at a predetermined rotational speed, and the control means. 9, the amplitude amount measured by the amplitude amount measuring unit 8 by rotating the grinding wheel 74 at a predetermined rotational speed while the wafer W held by the chuck table 3 is not in contact with the grinding wheel 740 is a preset amplitude amount. When the value exceeds the value, a determination unit 90 that determines that the rotational balance of the grinding wheel 74 has become unbalanced, and a notification unit 91 that notifies the operator that the balance has become unbalanced by the determination of the determination unit 90 are provided. Therefore, the operator can grasp the timing at which the rotation balance of the grinding wheel 74 should be corrected to a normal balance by washing the grinding wheel 74 or the like. As a result, for example, wasteful consumption of cleaning water can be suppressed, grinding can be prevented from being performed with the grinding wheel 74 having an unbalanced rotation balance, and occurrence of poor grinding of the wafer W can be suppressed. .

  The grinding device 1 according to the present invention is not limited to the above embodiment, and the configuration of the grinding device 1 illustrated in the accompanying drawings is not limited to this, and the effects of the present invention can be achieved. It can be appropriately changed within a range where it can be exhibited. For example, the rotation balance of the grinding wheel 74 may be unbalanced when grinding stones are chipped in addition to adhesion of grinding debris to the grinding wheel 74, and when the rotary shaft 70 is not an air bearing but a roller bearing. There is a bearing failure that occurs when it is rotatably supported by a mechanical bearing. The grinding apparatus 1 according to the present invention receives the notification from the notification unit 91 because the operator can grasp the timing at which the rotation balance of the grinding wheel 74 should be corrected to the normal balance by the notification from the notification unit 91. The operator can correct the rotational balance of the grinding wheel 74 to a normal balance by inspecting and repairing whether there is a bearing failure around the rotary shaft 70.

1: Grinding device 10: Base 11: Column 3: Chuck table 3: Holding part 30a: Holding surface 31: Frame body 39: Cover 5: Grinding feeding means 50: Ball screw 51: Guide rail 52: Motor 53: Lift plate
7: Grinding means 70: Rotating shaft 70a: Flow path 71: Housing 72: Motor 73: Mount 74: Grinding wheel 740: Grinding wheel 741: Wheel base 75: Holder 8 :: Amplitude measuring unit 9: Control means 90: Judgment part 91: Notification part

Claims (1)

A chuck table for holding a wafer, a grinding means for rotatably mounting a grinding wheel having an annular grinding wheel for grinding a wafer held by the chuck table, and a direction in which the grinding means approaches or separates from the chuck table A grinding apparatus comprising a grinding feed means for grinding and feeding to a control means for controlling the apparatus,
The grinding means includes an amplitude amount measuring unit that measures an amplitude amount of vibration when the grinding wheel is rotated at a predetermined rotation speed,
The control means rotates the grinding wheel at a predetermined rotational speed while the wafer held by the chuck table and the grinding wheel are not in contact with each other, and the amplitude amount measured by the amplitude amount measuring unit is a preset amplitude. A grinding apparatus comprising: a determination unit that determines that the rotational balance of the grinding wheel has become unbalanced when a quantity value is exceeded; and a notification unit that notifies an operator that the balance has become unbalanced by the determination by the determination unit.

Images