Grinding device

Abstract

To provide a grinding device that is configured to enable a leveling stone to contact a holding surface of a chuck table by proper pressure.SOLUTION: A grinding device comprises correcting means 56 in which an annular leveling stone 60 for correcting a holding surface of a chuck table 4 is attached to a rotary shaft 62a of a driving source 62 through a spring 66, and moving means 64 that makes the correcting means 56 approach and get away from the chuck table 4 to make the leveling stone 60 contact the holding surface of the chuck table 4. The control means rotates the chuck table 4 and also rotates the leveling stone 60; actuates the moving means 64 while detecting a load current value of a table driving source 12 or of the driving source 62; makes the leveling stone 60 contact the holding surface of the chuck table 4; and when the load current value reaches a proper value, makes the leveling stone 60 correct the holding surface of the chuck table 4 while keeping the load current value at the proper value.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a grinding apparatus including a rotatable chuck table for holding a wafer and equipped with a table drive source, grinding means equipped with a rotatable grinding wheel having grinding stones arranged in a ring shape for grinding the wafer held on the chuck table, and control means. [Background technology]

[0002] A wafer has a number of devices such as ICs and LSIs formed on its surface, separated by planned dividing lines. The back side of the wafer is ground by a grinding machine to form it to a specified thickness, and then the wafer is divided into individual device chips by a dicing machine. Each of the divided device chips is used in electrical equipment such as mobile phones and personal computers.

[0003] The grinding device includes a chuck table for holding the wafer, a grinding means having a rotatable grinding wheel with grinding stones arranged in a ring shape for grinding the wafer held on the chuck table, and a leveling stone for forcibly removing foreign matter such as grinding debris adhering to the holding surface of the chuck table, and is capable of grinding the wafer to a uniform thickness with high precision (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 01-205950 Summary of the Invention [Problem to be solved by the invention]

[0005] However, if the contact pressure of the leveling stone against the chuck table is too strong, uneven wear may occur on the holding surface of the chuck table, which may cause a problem that the wafer cannot be ground to a uniform thickness with high precision.

[0006] On the other hand, if the contact pressure of the leveling stone against the chuck table is too weak, it may not be possible to completely remove foreign matter such as grinding debris from the holding surface of the chuck table, which may result in dimples on the wafer due to the foreign matter remaining on the holding surface.

[0007] An object of the present invention is to provide a grinding device that can bring a leveling stone into contact with the holding surface of a chuck table with an appropriate pressure. [Means for solving the problem]

[0008] According to the present invention, there is provided the following grinding device that solves the above problems. "A grinding apparatus including a rotatable chuck table for holding a wafer and having a table drive source, a grinding means for rotatably including a grinding wheel having grinding stones arranged in an annular shape for grinding the wafer held on the chuck table, and a control means, a correction means for correcting the holding surface of the chuck table, the correction means being an annular leveling stone attached to a rotation shaft of a drive source via a spring, and a moving means for moving the correction means toward and away from the chuck table, so as to bring the leveling stone into contact with the holding surface of the chuck table, The control means rotates the chuck table and rotates the leveling stone, and while detecting the table drive source or the load current value of the drive source, operates the moving means to bring the leveling stone into contact with the holding surface of the chuck table, and when the load current value reaches an appropriate value, corrects the holding surface of the chuck table with the leveling stone while maintaining the appropriate value. Effect of the Invention

[0009] The grinding device of the present invention comprises: A grinding apparatus including: a rotatable chuck table for holding a wafer and having a table drive source; grinding means for rotatably including a grinding wheel having grinding stones arranged in an annular shape for grinding the wafer held on the chuck table; and control means, a correction means for correcting the holding surface of the chuck table, the correction means being an annular leveling stone attached to a rotation shaft of a drive source via a spring, and a moving means for moving the correction means toward and away from the chuck table, so as to bring the leveling stone into contact with the holding surface of the chuck table, The control means rotates the chuck table and also rotates the leveling stone, detecting the table drive source or the load current value of the drive source while operating the moving means to bring the leveling stone into contact with the holding surface of the chuck table, and when the load current value reaches an appropriate value, the leveling stone corrects the holding surface of the chuck table while maintaining the appropriate value, so that the leveling stone can be brought into contact with the holding surface of the chuck table with an appropriate pressure. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view of a grinding device according to the present invention. [Diagram 2] 2 is a perspective view of the chuck table and the chuck table cleaning mechanism shown in FIG. 1. [Diagram 3] FIG. 2 is a perspective view of the chuck table and the correcting means shown in FIG. [Figure 4] FIG. 2 is an exploded perspective view of the correction means shown in FIG. 1 . [Diagram 5] 2 is a perspective view showing a state in which a holding surface of the chuck table shown in FIG. 1 is being corrected; [Figure 6] FIG. 13 is a perspective view of a chuck table whose holding surface has been modified. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of a grinding device according to the present invention will be described with reference to the drawings.

[0012] (Grinding device 2) Referring to FIG. 1, the grinding apparatus generally designated by the reference symbol 2 includes a rotatable chuck table 4 for holding a wafer and equipped with a table drive source, grinding means 6 equipped with a rotatable grinding wheel having grinding stones arranged in a ring shape for grinding the wafer held on the chuck table 4, and control means 8.

[0013] (Chuck table 4) The chuck table 4 functions as a holding means for suction-holding an object to be ground such as a wafer. As shown in Figs. 2 and 3, a circular suction chuck 10 is disposed on the upper end of the chuck table 4. The suction chuck 10 is made of a porous material such as porous ceramics. The suction chuck 10 is connected to a suction means (not shown). In the chuck table 4, the suction means generates a suction force on the upper surface of the suction chuck 10, and the wafer placed on the upper surface of the suction chuck 10 is suction-held. In this manner, the upper surface of the suction chuck 10 serves as the holding surface of the chuck table 4.

[0014] The chuck table 4 is configured to be rotatable. As shown in Fig. 3, a rotation shaft 12a of a table driving source 12 is connected to the lower part of the chuck table 4. The table driving source 12 may be composed of a motor. The chuck table 4 is rotated by the table driving source 12 about an axis extending in the vertical direction.

[0015] The grinding apparatus 2 of this embodiment is provided with three chuck tables 4. As shown in Fig. 2, the three chuck tables 4 are attached to the peripheral side of the upper surface of a circular turntable 14 at equal intervals in the circumferential direction. The turntable 14 is rotatably supported on a base 16 of the grinding apparatus 2. The three chuck tables 4 are successively positioned at an attachment / detachment position A, a rough grinding position B, and a finish grinding position C by the rotation of the turntable 14.

[0016] (Grinding Means 6) The grinding means 6 is a means for grinding the wafer held on the chuck table 4. As shown in Fig. 1, the grinding means 6 of this embodiment includes a first grinding unit 6a, a second grinding unit 6b, a first grinding feed means 6c, and a second grinding feed means 6d.

[0017] The first grinding unit 6a roughly grinds a wafer positioned at the rough grinding position B. The first grinding unit 6a has a lift plate 20 supported so as to be movable up and down on a support wall 18 extending upward from an end (the rear end in FIG. 1) of the base 16, a protruding member 22 protruding from the lift plate 20, a spindle 24 supported by the protruding member 22 so as to be rotatable about an axis extending in the vertical direction, and a spindle motor 26 for rotating the spindle 24. A grinding wheel 28 is attached to the lower part of the spindle 24. A grinding stone 30a for roughly grinding a wafer positioned at the rough grinding position B is annularly arranged on the grinding wheel 28.

[0018] The second grinding unit 6b finish-grinds the wafer positioned at the finish grinding position C. The grinding wheel 30b of the second grinding unit 6b is a grinding wheel for finish grinding, and is made of abrasive grains smaller in size than the abrasive grains of the grinding wheel 30a (grinding wheel for rough grinding) of the first grinding unit 6a. The second grinding unit 6b may have the same configuration as the first grinding unit 6a except for the grinding wheel 30b, and therefore the same reference numerals as those of the first grinding unit 6a are used and the description thereof is omitted.

[0019] The first grinding feed means 6c feeds the first grinding unit 6a in the vertical direction for grinding, and brings the grinding wheel 30a rotated by the spindle motor 26 into contact with the wafer. The first grinding feed means 6c has a ball screw 32 extending in the vertical direction along one side of the support wall 18, and a motor 34 for rotating the ball screw 32. A nut portion (not shown) of the ball screw 32 is connected to the lift plate 20. The first grinding feed means 6c converts the rotational motion of the motor 34 into linear motion by the ball screw 32 and transmits it to the lift plate 20, and grinds and feeds the first grinding unit 6a in the vertical direction along a guide rail 18a attached to one side of the support wall 18.

[0020] The second grinding feed means 6d feeds the second grinding unit 6b in the vertical direction for grinding, and brings the grinding wheel 30b rotated by the spindle motor 26 into contact with the wafer. The second grinding feed means 6d may have the same configuration as the first grinding feed means 6c, and therefore the same reference numerals as those in the first grinding feed means 6c are used and a description thereof will be omitted.

[0021] (Control means 8) The control means 8 controls the operation of the grinding device 2. The control means 8 is electrically connected to each driving means, such as the table driving source 12 that rotates the chuck table 4 and the spindle motor 26 of the grinding means 6, and outputs an operation signal to each driving means. The control means 8 is also adapted to detect the load current value of each driving means. The control means 8 may be composed of a computer having a processor and a memory.

[0022] (Chuck table cleaning mechanism 36) 2, the grinding apparatus 2 of this embodiment is equipped with a chuck table cleaning mechanism 36 that cleans the chuck table 4 positioned at the attachment / detachment position A. The chuck table cleaning mechanism 36 includes a gate-shaped support member 38, a movable member 40 supported by the support member 38 so as to be movable in the Y-axis direction indicated by the arrow Y in Fig. 2, a Y-axis movement mechanism 42 that moves the movable member 40 in the Y-axis direction, and a cleaning liquid nozzle 44 that sprays cleaning liquid onto the chuck table 4 positioned at the attachment / detachment position A.

[0023] The support member 38 has a pair of posts 46 spaced apart in the Y-axis direction, and a beam 48 spanning between the upper ends of the pair of posts 46. The beam 48 extends along the Y-axis direction. The movable member 40 is supported by the beam 48 so as to be movable in the Y-axis direction.

[0024] The Y-axis movement mechanism 42 has a ball screw 50 arranged between the support columns 46, and a motor 52 that rotates the ball screw 50. The ball screw 50 extends parallel to the beam 48 (i.e., in the Y-axis direction). The movable member 40 is screw-coupled to this ball screw 50. The Y-axis movement mechanism 42 converts the rotational motion of the motor 52 into linear motion using the ball screw 50 and transmits it to the movable member 40, thereby moving the movable member 40 in the Y-axis direction.

[0025] A first housing 54a and a second housing 54b are attached to the movable member 40. The first and second housings 54a, 54b are disposed adjacent to each other in the Y-axis direction, and both are supported by the movable member 40 so as to be movable in the vertical direction. Correcting means 56 is provided in the first housing 54a, and brush means 58 is provided in the second housing 54b.

[0026] (Correction 56) The correcting means 56 breaks down and removes foreign matter (for example, thin grinding chips that have stuck like thorns into the upper surface gap of the suction chuck 10) attached to the holding surface of the chuck table 4, thereby correcting the holding surface of the chuck table 4 to a flat surface. Explained with reference to Figures 3 and 4, the correcting means 56 includes an annular leveling stone 60 and a drive source 62 that rotates the leveling stone 60.

[0027] (Leveling Stone 60) The leveling stone 60 destroys foreign matter adhering to the holding surface of the chuck table 4. The leveling stone 60 is made of a relatively hard material (for example, alumina ceramics). The hardness of the leveling stone 60 is slightly higher than the hardness of the holding surface of the chuck table 4. The diameter (outer diameter) of the annular leveling stone 60 may be approximately half the diameter of the suction chuck 10.

[0028] (Drive source 62) The driving source 62 is fixed to the first housing 54a and moves up and down together with the first housing 54a. The driving source 62 is disposed above the leveling stone 60. A rotating shaft 62a extending downward from the driving source 62 is fixed to a spring 66 disposed inside the leveling stone 60. That is, the rotating shaft 62a of the driving source 62 is attached to the leveling stone 60 via the spring 66. The spring 66 may be, for example, a leaf spring. As shown in FIG. 4, the spring 66 may be cross-shaped. The spring 66 is elastically deformable in the vertical direction. The driving source 62 rotates the leveling stone 60 via the spring 66 around the vertical direction as an axis. The driving source 62 may be a motor.

[0029] (Transportation 64) The first housing 54 a is also provided with a moving means 64 for moving the correction means 56 toward and away from the chuck table 4 and for bringing the leveling stone 60 into contact with the holding surface of the chuck table 4 .

[0030] The moving means 64 includes a screw gear 68 rotatably supported by the first housing 54a, and a motor 70 for rotating the screw gear 68. The screw gear 68 is engaged with a female-threaded straight gear (not shown) formed on the first housing 54a and extending in the vertical direction. The screw gear 68 is provided with a pulley 68a. A belt 72 is wound around the pulley 68a and a rotating shaft 70a of the motor 70. The moving means 64 moves the correcting means 56 toward and away from the chuck table 4 by rotating the screw gear 68 with the motor 70 to raise and lower the first housing 54a.

[0031] (Brush means 58) 2, the brush means 58 provided in the second housing 54b scrapes off foreign matter adhering to the holding surface of the chuck table 4 and cleans the holding surface of the chuck table 4. The brush means 58 may have the same configuration as the correcting means 56, except that a brush 74 is provided at the bottom. That is, the brush means 58 is provided with the brush 74 instead of the leveling stone 60 and the spring 66. The brush 74 of the brush means 58 is configured to be rotatable about an axis in the vertical direction, like the leveling stone 60 of the correcting means 56, and is also configured to be freely raised and lowered.

[0032] 1, in the grinding apparatus 2 of this embodiment, a cassette storage area 78 in which a cassette 76 capable of accommodating a plurality of wafers W is placed is provided on the upper surface of the base 16. The cassette storage area 78 has a first cassette storage area 78a in which a first cassette 76a containing a plurality of wafers W before grinding is placed, and a second cassette storage area 78b in which a second cassette 76b containing a plurality of wafers W after grinding is placed.

[0033] Furthermore, the grinding apparatus 2 of the illustrated embodiment is equipped with a loading / unloading means 80 for transporting the wafer W before grinding from the first cassette 76a and transporting the wafer W after grinding into the second cassette 76b, a centering table 82 for aligning the center of the wafer W before grinding transported by the loading / unloading means 80 to a predetermined position, a loading means 84 for transporting the wafer W after centering to the chuck table 4 positioned at the mounting / unloading position A, a cleaning means 86 for cleaning the wafer W after grinding, and a transporting means 88 for transporting the wafer W after grinding from the chuck table 4 positioned at the mounting / unloading position A to the cleaning means 86.

[0034] (Cleaning of holding surface) Next, the control executed by the control means 8 when cleaning the holding surface of the chuck table 4 in the above-mentioned grinding apparatus 2 will be described.

[0035] The control means 8 performs cleaning of the holding surface of the chuck table 4 positioned at the mounting / detaching position A. For this reason, when cleaning the holding surface, first, the brush means 58 is moved above the chuck table 4 positioned at the mounting / detaching position A. Next, the chuck table 4 and the brush 74 are rotated. Then, the rotated brush 74 is lowered to contact the holding surface of the chuck table 4. Furthermore, a cleaning liquid is supplied from the cleaning liquid nozzle 44 to the contact portion between the brush 74 and the chuck table 4. In this manner, the holding surface of the chuck table 4 is cleaned. Note that the cleaning effect may be enhanced by supplying a fluid (air, water, or a mixture) to the suction chuck 10 and ejecting the fluid from the upper surface of the suction chuck 10.

[0036] After cleaning with the brush means 58, the holding surface of the chuck table 4 is corrected by the correction means 56. Since foreign matter that cannot be completely removed by cleaning with the brush means 58 may remain on the holding surface, correction is performed by the correction means 56 to remove the remaining foreign matter. An example of the remaining foreign matter is thin grinding chips that have become thorn-like and stuck in the gaps on the upper surface of the suction chuck 10. If thin grinding chips stick into the upper surface of the suction chuck 10, it is difficult to remove them with the brush means 58.

[0037] When correcting the holding surface, first, the correcting means 56 is positioned above the chuck table 4 positioned at the attachment / detachment position A (see FIG. 3). At this time, the position of the correcting means 56 is adjusted so that the leveling stones 60 of the correcting means 56 overlap the outer periphery and center of the suction chuck 10. Since the chuck table 4 is rotated during correction, by adjusting the position of the correcting means 56 as described above, even if the diameter of the leveling stones 60 is about half the diameter of the suction chuck 10, the entire holding surface of the chuck table 4 (the upper surface of the suction chuck 10) can be corrected by the leveling stones 60.

[0038] Next, the control means 8 rotates the chuck table 4 positioned at the attachment / detachment position A by the table drive source 12. The rotation direction of the chuck table 4 may be the direction indicated by the arrow R1 in Fig. 3. The rotation speed of the chuck table 4 is, for example, about 300 rpm. Note that in Fig. 3, a foreign matter adhering to the holding surface of the chuck table 4 is indicated by the reference symbol 90.

[0039] Furthermore, the control means 8 rotates the leveling stone 60 of the correction means 56 by the drive source 62. The rotation direction of the leveling stone 60 may be the direction shown by the arrow R2 in Fig. 3. The rotation speed of the leveling stone 60 is, for example, about 100 rpm.

[0040] Next, as shown in FIG. 5, the control means 8 operates the moving means 64 to gradually lower the leveling stone 60. At this time, the control means 8 detects the load current value of the table driving source 12 of the chuck table 4 or the load current value of the driving source 62 of the correction means 56. Then, the control means 8 brings the leveling stone 60 into contact with the holding surface of the chuck table 4 to generate a pressing force, and gradually lowers the leveling stone 60 until the load current value of the table driving source 12 or the load current value of the driving source 62 reaches an appropriate value. Note that the appropriate value of the load current value of the table driving source 12 and the appropriate value of the load current value of the driving source 62 are different values. Both appropriate values ​​are registered in the control means 8 in advance. For example, a load current value of 0.4 mA corresponding to a pressing force of 5 N is registered as the appropriate value.

[0041] When the load current value of the table driving source 12 or the driving source 62 reaches the appropriate value, the control means 8 controls the operation of the moving means 64 so as to maintain the appropriate value. Specifically, when the load current value reaches the appropriate value, the operation of the moving means 64 is stopped. However, if the load current value becomes larger than the appropriate value by a predetermined value or more during the correction of the holding surface, the leveling stone 60 is raised by the moving means 64 until the load current value reaches the appropriate value. Conversely, if the load current value becomes smaller than the appropriate value by a predetermined value or more, the leveling stone 60 is lowered by the moving means 64 until the load current value reaches the appropriate value. In this way, the control means 8 controls the operation of the moving means 64 so as to maintain the load current value at the appropriate value while the holding surface is being corrected.

[0042] Then, the control means 8 corrects the holding surface of the chuck table 4 with the leveling stones 60 while maintaining the load current value at an appropriate value. When correcting the holding surface, a cleaning liquid is supplied to the portion to be corrected from the cleaning liquid nozzle 44. Also, a fluid (air, water, or a mixture) may be ejected from the upper surface of the suction chuck 10. In this way, as shown in FIG. 6, the foreign matter 90 adhering to the holding surface of the chuck table 4 is destroyed and removed, and the holding surface of the chuck table 4 can be corrected to a flat surface.

[0043] In this way, the control means 8 of the grinding device 2 corrects the holding surface of the chuck table 4 while maintaining the load current value of the table driving source 12 or the driving source 62 at an appropriate value. This allows the leveling stone 60 to come into contact with the holding surface of the chuck table 4 with an appropriate pressure. This prevents uneven wear from occurring on the holding surface of the chuck table 4 due to the correction, and allows the foreign matter 90 to be sufficiently removed from the holding surface of the chuck table 4. As a result, the grinding device 2 can grind the wafer W to a uniform thickness with high precision. [Explanation of symbols]

[0044] 2: Grinding device 4: Chuck table 6: Grinding means 8: Control means 12: Table drive source 28: Grinding wheel 30a: Grinding wheel for rough grinding 30b: Grinding wheel for finish grinding 56: Corrective measures 60: Leveling Stone 62: Power source 62a: Rotating shaft of driving source 64: Transportation 66: Spring 90: Foreign object W: Wafer

Claims

[Claim 1] A grinding apparatus including: a rotatable chuck table for holding a wafer and having a table drive source; grinding means for rotatably including a grinding wheel having grinding stones arranged in an annular shape for grinding the wafer held on the chuck table; and control means, a correction means for correcting the holding surface of the chuck table, the correction means being an annular leveling stone attached to a rotation shaft of a drive source via a spring, and a moving means for moving the correction means toward and away from the chuck table, so as to bring the leveling stone into contact with the holding surface of the chuck table, The control means rotates the chuck table and also rotates the leveling stone, and while detecting the load current value of the table drive source or the drive source, operates the moving means to bring the leveling stone into contact with the holding surface of the chuck table, and when the load current value reaches an appropriate value, the grinding device corrects the holding surface of the chuck table with the leveling stone while maintaining the appropriate value.

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