JP2014030883A - Grinding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grinding device capable of grinding a workpiece to a uniform finish thickness.SOLUTION: A grinding device is configured to grind a workpiece 11, and includes: grinding means 10 including a chuck table 46 having a conic holding surface 68a for holding the workpiece 11 and including a conic shaft of the holding surface 68a as a rotary shaft 46a, a spindle 21 driven to rotate, and a grinding wheel 24 mounted at a tip of the spindle 21, and grinding a grinding region of the workpiece 11, held on the chuck table 46, from the center to the outer periphery of the holding surface 68a; load current value detecting means of detecting a load current value of the spindle 21; tilt changing means of changing the tilt of the chuck table 46; and control means of controlling the tilt changing means based upon the load current value detected by the load current value detecting means.

Description

  The present invention relates to a grinding apparatus for grinding a workpiece such as a wafer.

  A semiconductor wafer in which a number of devices such as IC and LSI are formed on the surface, and each device is partitioned by a line to be divided (street), the back surface is ground by a grinding machine and processed to a predetermined thickness. A dividing line is cut by a dicing apparatus to be divided into individual devices, and the divided devices are used in various electric devices such as a mobile phone and a personal computer.

  A grinding apparatus for grinding the back surface of a wafer includes a chuck table that holds and rotates a wafer, and a grinding means that rotatably supports a grinding wheel provided with a grinding wheel for grinding the wafer held on the chuck table. In addition, a loading means for loading a wafer to be ground onto the chuck table and a loading means for unloading the ground wafer from the chuck table are provided, and the wafer can be processed to a desired thickness.

  The chuck table is formed in a conical shape having an inclined surface with an extremely small inclination with the center as an apex, and is rotated around the conical axis as a rotation axis. Further, the chuck table is supported by three points which are fixed at one point and movable at the other two points, so that the inclination of the conical holding surface of the chuck table can be adjusted.

  Furthermore, the chuck table is usually adjusted so that the rotation axis is slightly inclined from the vertical direction so that the inclined surface of the holding surface is parallel to the grinding surface of the grinding wheel, and the grinding wheel contacts the grinding surface of the workpiece. The grinding region to be performed is limited to a region from the rotation center of the workpiece to the outer periphery, and the grinding direction is a direction from the rotation center of the workpiece to the outer periphery.

JP-A-8-90376

  In in-feed grinding in which the wafer is ground while rotating, there is a difference in the work amount per unit time between the vicinity of the center of rotation and the vicinity of the outer periphery. As a general tendency, the machining load increases from the center of rotation to the outer periphery.

  For this reason, when the processing load increases, the grinding wheel that contacts the outer peripheral portion of the wafer slightly escapes and the amount of grinding in the thickness direction decreases. As a result, there is a problem that the thickness of the wafer after grinding increases in proportion to the distance from the center of rotation, and a uniform thickness cannot be obtained. In particular, this tendency becomes more prominent as the outer diameter of the wafer increases.

  This invention is made | formed in view of such a point, The place made into the objective is providing the grinding device which can grind a workpiece to uniform finish thickness.

  According to the present invention, there is provided a grinding apparatus for grinding a workpiece, the chuck table having a conical holding surface for holding the workpiece, the rotation axis of which is a conical axis of the holding surface, and a rotational drive. And a grinding means for grinding the workpiece held on the chuck table in a grinding region extending from the center of the holding surface to the outer periphery, and a grinding wheel attached to the tip of the spindle. Load current value detecting means for detecting the load current value of the spindle, inclination changing means for changing the inclination of the chuck table, and the inclination changing means based on the load current value detected by the load current value detecting means. And a control device for controlling the grinding device.

  According to the grinding apparatus of the present invention, since the tilt of the chuck table is controlled according to the load current value of the spindle that is processing the workpiece, the workpiece can be ground to a uniform thickness.

It is a schematic block diagram of the grinding device which can apply the principle of this invention. It is a partially broken perspective view which shows the chuck table support structure of this invention embodiment. It is a partially broken side view of the grinding apparatus shown in FIG. It is a schematic diagram which shows the support position of a flange. It is a partial cross section side view explaining escape of a grinding wheel. It is a partial cross section side view explaining the method of control by a control means.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a perspective view of a grinding apparatus 2 employing the chuck table support structure of the present invention. Reference numeral 4 denotes a base (housing) of the grinding apparatus 2, and two columns 6 a and 6 b are vertically provided behind the base 4. A pair of guide rails (only one is shown) 8 extending in the vertical direction is fixed to the column 6a.

  A rough grinding unit 10 is mounted along the pair of guide rails 8 so as to be movable in the vertical direction. The rough grinding unit 10 is attached to a moving base 12 whose housing 20 moves up and down along a pair of guide rails 8.

  The rough grinding unit 10 includes a housing 20, a spindle 21 (see FIG. 3) rotatably accommodated in the housing 20, a servo motor 22 that rotationally drives the spindle 21, and a plurality of fixed to the tip of the spindle 21. A grinding wheel 24 having a grinding wheel 26 for rough grinding is included.

  The rough grinding unit 10 includes a rough grinding unit feed mechanism 18 including a ball screw 14 and a pulse motor 16 that move the rough grinding unit 10 up and down along a pair of guide rails 8. When the pulse motor 16 is pulse-driven, the ball screw 14 rotates and the moving base 12 is moved in the vertical direction.

  A pair of guide rails (only one is shown) 19 extending in the vertical direction is also fixed to the other column 6b. A finish grinding unit 28 is mounted along the pair of guide rails 19 so as to be movable in the vertical direction.

  The finish grinding unit 28 is attached to a moving base (not shown) in which the housing 36 moves in the vertical direction along the pair of guide rails 19. The finish grinding unit 28 includes a housing 36, a spindle (not shown) rotatably accommodated in the housing 36, a servo motor 38 that rotationally drives the spindle, and a grinding wheel 42 for finish grinding fixed to the tip of the spindle. A grinding wheel 40 is included.

  The finish grinding unit 28 includes a finish grinding unit feed mechanism 34 including a ball screw 30 that moves the finish grinding unit 28 in the vertical direction along the pair of guide rails 19 and a pulse motor 32. When the pulse motor 32 is driven, the ball screw 30 rotates and the finish grinding unit 28 is moved in the vertical direction.

  The grinding apparatus 2 includes a turntable 44 disposed on the front side of the columns 6a and 6b. The turntable 44 is formed in a relatively large-diameter disk shape, and is rotated in a direction indicated by an arrow 45 by a rotation drive mechanism (not shown).

  On the turntable 44, three chuck tables 46 are arranged so as to be rotatable in a horizontal plane, spaced from each other by 120 ° in the circumferential direction. The chuck table 46 has a suction holding portion formed in a disk shape by a porous ceramic material, and sucks and holds the wafer placed on the holding surface of the suction holding portion by operating a vacuum suction means. A thickness gauge 48 measures the thickness of the wafer being ground.

  The three chuck tables 46 arranged on the turntable 44 are rotated in accordance with the turntable 44, so that the wafer loading / unloading area A, rough grinding area B, finish grinding area C, and wafer loading / unloading are performed. The region A is sequentially moved.

  In the front portion of the base 4, there are a first wafer cassette 50, a second wafer cassette 52, a wafer transfer robot 54, a positioning table 56 having a plurality of positioning pins 58, and a wafer carry-in mechanism (loading arm) 60. Also, a wafer carry-out mechanism (unloading arm) 62 and a spinner cleaning unit 63 are provided.

  A cleaning water spray nozzle 67 for cleaning the chuck table 46 is provided at the approximate center of the base 4. The cleaning water spray nozzle 67 sprays cleaning water toward the chuck table 46 in a state where the chuck table 46 is positioned in the wafer carry-in / carry-out region A.

  Referring to FIG. 2, a partially broken perspective view of the support structure for the chuck table 46 according to the embodiment is shown. FIG. 3 is a partially broken side view of the grinding apparatus shown in FIG. As shown in FIG. 2, the chuck table 46 includes a suction holding portion 68 formed in a disk shape from a porous ceramic material, and a metal frame 70 surrounding the suction holding portion 68. An annular flange 72 is formed integrally with the frame body 70. The chuck table 46 is connected to a motor 74 and is driven to rotate by the motor 74.

  As shown in FIG. 3, the turntable 44 includes a turntable base 44a and a turntable cover 44b, and the chuck table 46 projects upward from an opening 47 formed in the turntable cover 44b.

  The annular flange 72 is formed with three through holes that are 120 degrees apart from each other in the circumferential direction. A bolt 76 is inserted into one through hole formed in the flange 72, and the tip of the bolt 76 is engaged with an engaged member 78 fixed to the turntable base 44a. The bolt 76 and the engaged member 78 constitute a fixed support portion 80.

  A bolt 82 constituting the movable support portion 90 is inserted into another through hole formed in the annular flange 72, and a tip end portion of the bolt 82 is inserted into a through hole 83 formed in the turntable base 44a. Is engaged with one end of the. The rod 84 has a screw hole, and a screw 88 connected to the output shaft of the pulse motor 86 is screwed into the screw hole.

  The pulse motor 86 is fixed to the turntable base 44a by a bracket (not shown). When the pulse motor 86 is driven, the screw 88 is rotated and the bolt 82 constituting the movable support portion 90 is moved in the vertical direction. A movable support portion having the same configuration as that of the movable support portion 90 is disposed in another through hole portion of the annular flange 72.

  Referring to FIG. 3, the turntable base 44 a of the turntable 44 is mounted on the motor 92 and is rotated by the motor 92. The suction holding unit 68 of the chuck table 46 is connected to a negative pressure source via a tube 94, and a suction force is applied to the suction holding unit 68 by the negative pressure source.

  The pulse motor 86 is connected to the control means 100, and its driving is controlled by the control means 100. The servo motor 22 of the rough grinding unit 10 and the servo motor 38 of the finish grinding unit 28 are also connected to the control means 100, and their driving is controlled by the control means 100.

  Referring to FIG. 4, a schematic diagram of a support structure for the annular flange 72 of the chuck table 46 is shown. The annular flange 72 is supported at three points A, B, and C that are 120 degrees apart from each other in the circumferential direction. A corresponds to the fixed support portion 80, and B and C correspond to the movable support portion 90.

  Hereinafter, the operation of the grinding apparatus 2 of the present invention will be described. Since the operations of the rough grinding unit 10 and the finish grinding unit 28 are substantially the same, in the following description, the rough grinding unit 10 will be described as a representative.

  In the control of the grinding apparatus of the present invention, when the wafer 11 is ground under the same processing conditions, the load current value and the TTV (total thickness change) of the wafer 11 are acquired, and the wafer 11 is ground uniformly. A relationship between the drive current value and the amount by which the fine adjustment shaft (movable support portion) 90 is moved is obtained, and this relationship is stored in the memory 102 in advance. After storing such a relationship in the memory 102, rough grinding of the wafer 11 is performed.

  This rough grinding will be described with reference to FIG. The holding surface 68 a of the suction holding portion 68 of the chuck table 46 is formed in a conical shape whose central portion is slightly higher than the outer peripheral portion, and the conical axis of the holding surface 68 a coincides with the rotation axis 46 a of the chuck table 46. ing.

  Further, since the inclined surface (holding surface) 68 a of the chuck table 46 is adjusted to be parallel to the grinding wheel 26, the grinding region where the grinding wheel 26 contacts the grinding surface (back surface) of the wafer 11 is the wafer 11. The rotation direction is limited to the region from the rotation center 11a to the outer periphery 11b, and the grinding direction is the direction from the rotation center 11a to the outer periphery 11b of the wafer 11.

  In order to protect the device formed on the surface of the wafer 11, the surface protection tape 13 is adhered to the surface, and the surface protection tape 13 side is held by the suction holding portion 68 of the chuck table 46.

  In the rough grinding process of the wafer 11, as shown in FIG. 5, while rotating the chuck table 46 in the direction of arrow a at 300 rpm, for example, the rough grinding wheel 24 is rotated in the direction shown by arrow b at 6000 rpm, for example. The grinding wheel 24 is positioned so that the grinding wheel 26 passes through the rotation center 11a of the wafer 11 held on the wafer 11.

  Then, the rough grinding unit feed mechanism 18 is driven to grind the wafer 11 while feeding the rough grinding wheel 24 downward by a predetermined amount at a predetermined grinding feed speed. In the in-feed grinding in which the wafer 11 is ground while rotating, there is a difference in the work amount per unit time from the vicinity of the outer periphery near the center of rotation.

  As a general tendency, the machining load increases from the rotation center 11a to the outer periphery 11b, and the drive current value of the servo motor 22 increases. For this reason, when the machining load increases, the grinding wheel 24 pressed against the outer peripheral portion 11b of the wafer 11 slightly escapes in the direction of arrow A, and the grinding amount of the outer peripheral portion 11b of the wafer 11 decreases.

  In this embodiment, from the relationship between the drive current value stored in the memory 102 and the amount by which the movable support portion 90 is moved, the movable support portion 90 is finely adjusted to correct the amount of change in TTV. That is, when the drive current value of the servo motor 22 is increased, as shown in FIG. 6, the opposite side of the wafer 11 with which the grinding wheel 26 is in contact is slightly lowered in the direction of arrow B, and the central portion 11a of the wafer 11 is lowered. Adjust in the downward direction. By controlling in this way, the wafer 11 can be ground to a uniform thickness.

DESCRIPTION OF SYMBOLS 10 Rough grinding unit 11 Wafer 24 Rough grinding wheel 26 Rough grinding wheel 28 Finish grinding unit 49 Finish grinding wheel 42 Finish grinding wheel 44 Turntable 68 Suction holding part 68a Holding surface 80 Fixed support part 90 Movable support part

Claims (1)

A grinding device for grinding a workpiece,
A chuck table having a conical holding surface for holding a workpiece and having the conical axis of the holding surface as a rotation axis;
Grinding which has a spindle driven to rotate and a grinding wheel mounted on the tip of the spindle, and grinds a workpiece held on the chuck table in a grinding region extending from the center of the holding surface to the outer periphery. Means,
Load current value detecting means for detecting the load current value of the spindle;
Tilt changing means for changing the tilt of the chuck table;
Control means for controlling the slope changing means based on the load current value detected by the load current value detecting means;
A grinding apparatus comprising:

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