JP2009107084A - Grinding equipment - Google Patents

Abstract

To prevent damage to a wafer and a grinding apparatus when an abnormality occurs in a grinding wheel during grinding.
A grinding means 3 having a grinding wheel 34 for grinding a wafer W held on a chuck table 2, a processing feed means 4 for processing and feeding the grinding means 3 in a vertical direction, and a thickness of the wafer W are measured. In the grinding apparatus 1 having the thickness measuring unit 5, a thickness change rate calculating unit 60 that calculates a thickness change rate from the thickness of the wafer W measured by the thickness measuring unit 5, a processing feed rate and a thickness An abnormality determining unit 62 that determines whether there is an abnormality in the grinding wheel 34 from the relationship with the change speed is provided. When it is determined that there is an abnormality, the grinding feed is interrupted.
[Selection] Figure 1

Description

  The present invention relates to a grinding apparatus for grinding a wafer.

  A plurality of formed wafers in which a plurality of devices such as ICs, LSIs, etc. are partitioned by dividing lines are ground to have a predetermined thickness after being ground, and then divided into individual devices by a dicing machine. Used for equipment.

  A grinding apparatus used for grinding the back surface of a wafer is equipped with a grinding means configured such that a grinding wheel is connected to a spindle and the grinding wheel rotates. The grinding wheel has a grinding wheel fixed to the lower surface of a rotating base. It becomes the composition. Then, when the grinding means is processed and fed in a direction approaching the wafer, the rotating grinding wheel comes into contact with the wafer and grinding is performed. The grinding apparatus also includes means for measuring the thickness of the wafer being ground, and the wafer can be finished to a desired thickness by measuring the thickness while grinding the wafer (for example, Patent Document 1).

Japanese Patent Laid-Open No. 2005-21998

  However, even if clogging occurs in the grinding wheel that constitutes the grinding wheel or the grinding wheel is chipped, any abnormalities occur, and if the grinding means continues to be processed at the specified feed rate, it will be excessive for the wafer. There is a problem that there is a possibility of damaging the wafer or the grinding device by applying a large pressure or by causing a broken piece of the grindstone to enter between the grinding wheel and the wafer.

  Therefore, the problem to be solved by the present invention is to prevent wafer damage and grinding apparatus damage when an abnormality occurs in the grinding wheel during grinding.

  The present invention includes a chuck table for holding a wafer, a grinding means having a grinding wheel for grinding the wafer held on the chuck table, a processing feeding means for processing and feeding the grinding means in a direction perpendicular to the chuck table, The present invention relates to a grinding apparatus having a thickness measuring means for measuring the thickness of the wafer held on the chuck table, and controls the processing feeding means to hold the grinding means on the chuck table while feeding it at a predetermined feeding speed. A grinding control unit for grinding the wafer by bringing a grinding wheel into contact with the formed wafer, a thickness change rate calculating unit for calculating a thickness change rate from the thickness of the wafer measured by the thickness measuring means, and a processing feed rate The abnormality determination unit that determines whether there is an abnormality in the grinding wheel from the relationship between the thickness change speed and the thickness change rate, and the abnormality determination unit determines that the abnormality is abnormal Comprising abnormality monitoring means comprised of a suspend control unit interrupts the machining feed of the grinding means increases the grinding means when a.

  It is desirable that the abnormality determination unit determine that there is an abnormality when the difference or ratio between the machining feed rate and the thickness change rate is outside a preset allowable value range. Moreover, it is desirable to provide an abnormality notifying unit that informs the operator that the abnormality determining unit has determined that there is an abnormality.

  In the present invention, from the relationship between the processing feed speed of the grinding means and the thickness change speed, which is the speed at which the thickness changes due to the grinding of the wafer, it is determined whether or not the grinding is normally performed, If an error is detected, an abnormality monitoring unit is provided to interrupt grinding, so if there is an abnormality in the grinding wheel due to clogging or chipping in the grinding wheel that makes up the grinding wheel, grinding will occur. By interrupting, it is possible to prevent wafer damage and grinding apparatus damage.

  A grinding apparatus 1 shown in FIG. 1 includes a chuck table 2 for holding a wafer to be ground, a grinding means 3 for grinding a wafer held on the chuck table 2, and the grinding means 3 in a direction perpendicular to the chuck table 2. A processing feed means 4 for processing feed and a thickness measuring means 5 for measuring the thickness of the wafer held on the chuck table 2 are provided.

  The chuck table 2 can be rotated and moved in the horizontal direction, and can be moved directly below the grinding means 3.

  The grinding means 3 includes a spindle 30 having a vertical axis, a housing 31 that rotatably supports the spindle 30, a motor 32 that rotationally drives the spindle 30, and a wheel mount 33 formed at the lower end of the spindle 30. The grinding wheel 34 is mounted on the wheel mount 33 and grinds the wafer. The grinding wheel 34 is driven by the motor 32 to rotate. As shown in FIG. 2, the grinding wheel 34 is configured by a grinding grindstone 341 fixed in a ring shape on the lower surface of a ring-shaped base 340, and grinding water discharged downward is circulated through the base 340. A grinding water circulation hole 340 a and a screw hole 340 b for screwing to the wheel mount 33 are formed.

  1, the processing feed means 4 is connected to a ball screw 40 having a vertical axis, a pair of guide rails 41 arranged in parallel to the ball screw 40, and one end of the ball screw 40. The pulse motor 42 includes a pulse motor 42 that rotates the ball screw 40, and an elevating unit 43 that has a nut (not shown) inside and that is screwed into the ball screw 40 and whose side portion is in sliding contact with the guide rail 41. As the ball screw 40 is driven by the rotation, the elevating part 43 is guided by the guide rail 41 and moves up and down. Further, since the elevating part 43 supports the grinding means 3, the grinding means 3 also elevates as the elevating part 43 elevates.

  The thickness measuring means 5 is disposed in the vicinity of the chuck table 2 and can move in the horizontal direction together with the chuck table 2. In the illustrated example, the thickness measuring means 5 is of a type that obtains the thickness of the wafer from position information in the vertical direction of the stylus 50 that is movable in the vertical direction.

  A thickness change rate calculation unit 60 is electrically connected to the thickness measurement unit 5, and a measurement result in the thickness measurement unit 5 is sequentially transferred to the thickness change rate calculation unit 60. Then, the thickness change rate calculation unit 60 can obtain the change amount of the wafer thickness per unit time as the thickness change rate from the wafer thickness information transferred from the thickness measuring means 5. The thickness measuring means 5 is not limited to a stylus type.

  By supplying a pulse signal to the pulse motor 42 and controlling the machining feed means 4 to the pulse motor 42 of the machining feed means 4, the grinding means 3 is fed with a predetermined, eg 0.3 [μm / s] machining feed. A grinding control unit 61 that grinds the wafer by contacting the grinding wheel of the wafer by processing and feeding at a speed is electrically connected.

  An abnormality determination unit 62 is connected to the thickness change rate calculation unit 60 and the grinding control unit 61. The thickness change rate calculated by the thickness change rate calculation unit 60 is transferred to the abnormality determination unit 62, and the actual machining feed rate of the grinding means 3 is transferred from the grinding control unit 61. In the abnormality determination unit 62, an abnormality occurs in the grinding wheel 34 from the relationship between the thickness change rate transferred from the thickness change rate calculation unit 60 and the actual machining feed rate transferred from the grinding control unit 61. Determine whether or not. A specific method of determination will be described later.

  The abnormality determination unit 62 is connected to an interruption control unit 63 that interrupts machining feed and controls the interruption of grinding when the abnormality determination unit 62 determines an abnormality, and an abnormality notification unit 64 that notifies the operator of the abnormality. . The thickness change rate calculation unit 60, the grinding control unit 61, the abnormality determination unit 62, the interruption control unit 63, and the abnormality notification unit 64 constitute the abnormality monitoring unit 6.

  As shown in FIG. 3, for example, a plurality of devices D are formed on a surface W1 of a wafer W to be ground, which is partitioned by a division line S, and a protective tape for protecting the device D is formed on the surface W1. T is attached. Then, as shown in FIG. 4, the front and back are reversed, the protective tape T side is held by the chuck table 2, and the back surface W2 is exposed.

  Referring to FIG. 1, when the wafer W is held on the chuck table 2, the chuck table 2 moves horizontally to just below the grinding means 3. The chuck table 2 rotates at a rotational speed of, for example, 300 rpm, and the grinding wheel 34 is processed and fed by the processing feed means 4 while rotating at a rotational speed of 6000 rpm, and the rotating grinding wheel 341 contacts the wafer W. Then, the processing feed is controlled by the grinding control unit 61, and a pressing force is applied to the wafer W at a constant speed.

  During grinding performed in this manner, the thickness of the wafer W is constantly measured by the thickness measuring means 5 when the stylus 50 contacts the back surface of the wafer W as shown in FIG. . For example, the vertical position of the stylus 50 when the stylus 50 is in contact with the surface of the chuck table 2 is used as the origin, and the vertical position of the stylus 50 when it is in contact with the back surface W2 of the wafer W is obtained. Then, the displacement from the origin is calculated, and the displacement is set as the thickness H of the wafer. The thickness H may be a value obtained by subtracting the thickness of the protective tape T from the displacement from the origin at the vertical position of the stylus 50 when contacting the back surface W2 of the wafer W.

  During grinding, the grinding control unit 1 continues the processing feed, and the abnormality determination unit 62 sequentially calculates the relationship between the thickness change rate of the wafer W and the processing feed rate, for example, the speed ratio. The processing feed speed V1 of the grinding means 3 is input from, for example, the input unit 7 provided in advance on the front side of the apparatus and stored by the grinding control unit 61. On the other hand, the thickness change rate of the wafer W is calculated by the thickness change rate calculation unit 60 as the change amount per unit time of the thickness H of the wafer W (dH / dt = V2). The abnormality determination unit 62 stores in advance a speed ratio allowable value that is a threshold value when determining whether there is an abnormality. This allowable value can be input by the operator from the input unit 7.

  The abnormality determination unit 62 determines whether or not the calculated speed ratio (V2 / V1) is within a preset allowable value range (below the allowable value). For example, when 0.98 is stored as the allowable value, it is determined whether or not the relationship of (V2 / V1) ≦ 0.98 is established. When this relational expression is established, the grinding feed speed is too fast than the actual grinding amount per unit time. Therefore, the abnormality determination unit 62 determines that the grinding wheel 34 is abnormal, and accordingly Information is notified to the interruption control unit 63 and the abnormality notification unit 64. On the other hand, if the above relational expression is not satisfied, the machining feed is continued as it is without any abnormality and grinding is continued, and thereafter, the abnormality monitoring means 6 always monitors whether or not an abnormality occurs by the same method.

  The abnormality determination unit 62 calculates a speed difference between the machining feed speed V1 and the thickness change speed V2, and determines whether the grinding wheel 34 is abnormal depending on whether the calculated speed difference is within a preset allowable range. It can also be determined whether or not. In this case, for example, (V1−V2) is calculated, and when the value of (V1−V2) becomes larger than the allowable value stored in advance in the abnormality determination unit 62, it is determined that there is an abnormality in the grinding wheel 34. If the value of (V1-V2) is smaller than the allowable value, the grinding is continued with no abnormality.

  When the abnormality determination unit 62 determines that there is an abnormality, the interruption control unit 63 that has received the notification of the abnormality controls the pulse motor 42 to raise the grinding means 3 to interrupt the grinding. Further, the abnormality notifying unit 64 notifies the operator of the abnormality by sounding an alarm sound or the like. When the grinding wheel 341 of the grinding wheel 34 is clogged or the grinding wheel 341 is missing, it is considered that the processing feed speed of the grinding means 3 and the thickness change speed of the wafer W do not match. In such a case, grinding is interrupted and the grinding means 3 is raised, so that damage to the wafer and grinding apparatus can be prevented in advance. Furthermore, since the abnormality notifying unit 64 notifies the operator of the abnormality, the operator who knows the abnormality can replace the grinding wheel 34 or dress the grinding wheel 341.

It is a perspective view which shows an example of a grinding device. It is a perspective view which shows an example of a grinding wheel. It is a disassembled perspective view which shows a wafer and a protective tape. It is a perspective view which shows the state by which the protective tape was stuck on the surface of the wafer. It is a front view which shows the state which grinds the back surface of a wafer.

Explanation of symbols

1: Grinding device 2: Chuck table 3: Grinding device 30: Spindle 31: Housing 32: Motor 33: Wheel mount 34: Grinding wheel 340: Base 341: Grinding wheel 4: Work feed means 40: Ball screw 41: Guide rail 42 : Pulse motor 43: Elevating part 5: Thickness measuring means 50: Stylus 6: Abnormality monitoring means 60: Thickness change speed calculating part 61: Grinding control part 62: Abnormality judgment part 63: Interruption control part 64: Abnormality notification part

Claims (3)

A chuck table for holding the wafer, a grinding means having a grinding wheel for grinding the wafer held by the chuck table, a processing feed means for processing and feeding the grinding means in a direction perpendicular to the chuck table, A grinding apparatus comprising a thickness measuring means for measuring the thickness of the wafer held on the chuck table,
A grinding control unit for grinding the wafer by bringing the grinding wheel into contact with the wafer held on the chuck table while controlling the processing feeding means and processing and feeding the grinding means at a predetermined feeding speed;
A thickness change rate calculating unit for calculating a thickness change rate from the thickness of the wafer measured by the thickness measuring unit;
An abnormality determination unit that determines whether an abnormality has occurred in the grinding wheel from the relationship between the processing feed rate and the thickness change rate;
A grinding apparatus comprising an abnormality monitoring unit configured to include an interruption control unit that interrupts the processing feed of the grinding unit and raises the grinding unit when the abnormality determination unit determines that there is an abnormality.   The grinding apparatus according to claim 1, wherein the abnormality determination unit determines that there is an abnormality when a difference or ratio between the machining feed rate and the thickness change rate is outside a preset allowable value range. The grinding apparatus according to claim 1, further comprising an abnormality notifying unit that informs an operator that the abnormality determining unit has determined that an abnormality has occurred.

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