JP7592362B2 - Grinding Method - Google Patents

Description

The present invention relates to a grinding method.

Semiconductor device chips such as ICs (Integrated Circuits) and LSIs (Large Scale Integration) are essential components in various electronic devices such as mobile phones and personal computers. Such chips are manufactured, for example, by dividing a wafer on which a large number of semiconductor devices are formed into regions each containing an individual semiconductor device.

In recent years, wafers are often thinned before being divided in order to reduce the size and weight of chips. One method for thinning a wafer is to grind it using a grinding device that has a chuck table that holds the underside of the wafer by suction with a holding surface, and a grinding wheel that is provided above the chuck table and has multiple grinding stones that are arranged in a circular pattern.

In such grinding machines, workpieces such as wafers are often thinned by a grinding method also known as in-feed grinding, in which the chuck table and the grinding wheel are first rotated with the chuck table positioned below the grinding wheel.

Then, while the chuck table and grinding wheel are kept rotating, the chuck table and grinding wheel are moved relative to each other in the vertical direction so that the lower surfaces of the multiple grinding wheels come into contact with the upper surface of the workpiece. This causes the entire upper surface of the workpiece to be ground by the lower surfaces of the multiple grinding wheels. Furthermore, by continuing to move the chuck table and grinding wheel relative to each other in the vertical direction, a portion of the upper surface of the workpiece that has a predetermined thickness is ground away, thinning the workpiece.

In addition, such grinding devices may also thin the workpiece using a grinding method known as creep feed grinding (see, for example, Patent Document 1). In this grinding method, the chuck table and the grinding wheel are first separated horizontally, and the bottom surfaces of the multiple grinding stones are positioned lower than and higher than the top surface of the workpiece, and the grinding wheel is then rotated.

Then, while the grinding wheel is still rotating, the chuck table and the grinding wheel are moved relative to each other in the horizontal direction so that the outer surfaces of the multiple grinding wheels come into contact with the side of the workpiece. This causes the outer surfaces of the multiple grinding wheels to grind an end portion of the upper surface of the workpiece that has a predetermined thickness. Furthermore, by continuing to move the chuck table and the grinding wheel relative to each other in the horizontal direction, the entire area of the upper surface of the workpiece is ground, thinning the workpiece.

JP 2005-28550 A

When performing in-feed grinding in a grinding machine, as mentioned above, it is necessary to rotate the chuck table. Therefore, the chuck table is generally coupled to a rotatable spindle so as to rotate together with the spindle.

When creep feed grinding is performed with such a grinding device, larger vibrations occur in the chuck table compared to when in-feed grinding is performed. If the chuck table vibrates while the workpiece is being ground, there is a risk that large irregularities and cracks will form on the grinding surface of the workpiece being ground.

For this reason, known grinding machines that can be used for both in-feed grinding and creep feed grinding are generally provided with a mechanism for fixing the spindle connected to the chuck table (e.g., a mechanism for fixing the spindle using a screw or the like). However, such a mechanism complicates the structure of the grinding machine and may increase the manufacturing costs of the grinding machine.

In view of this, the object of the present invention is to provide a method capable of suppressing vibrations that occur in the chuck table during creep feed grinding without providing such a mechanism to the grinding device.

According to the present invention, there is provided a grinding method for grinding a workpiece using a grinding device comprising: a chuck table having a holding surface for holding a workpiece, a table base on which the chuck table is attached, a first spindle having a main body portion hanging down from the center of a lower part of the table base and a protrusion portion protruding outward from a side surface of the main body portion, a casing surrounding a side surface of the main body portion and having a communication passage provided therein that opens at a position facing a lower surface of the protrusion portion, a fluid supply source for supplying fluid to the communication passage, a second spindle having a lower end portion on which a grinding wheel having a plurality of grinding stones for grinding the workpiece is attached, a vertical direction movement mechanism for relatively moving the chuck table and the grinding wheel along a vertical direction, and a horizontal direction movement mechanism for relatively moving the chuck table and the grinding wheel along a horizontal direction perpendicular to the vertical direction, in-feed grinding in which the chuck table and the grinding wheel are moved relatively along the vertical direction while rotating the grinding wheel to grind the workpiece; and in-feed grinding in which the chuck table and the grinding wheel are moved relatively along the vertical direction while rotating the grinding wheel, with the chuck table and the grinding wheel spaced apart in the horizontal direction and the lower surfaces of the plurality of grinding wheels positioned lower than the upper surface of the workpiece and higher than the lower surface of the workpiece, and then the chuck table and the grinding wheel are moved relatively along the horizontal direction while rotating the grinding wheel to grind the workpiece. a separation step, when the creep-feed grinding is selected in the selection step, of supplying fluid from the fluid supply source to the communicating passage to separate the lower surface of the protrusion from the casing; and a contact step, when the creep-feed grinding is selected in the selection step, of contacting the lower surface of the protrusion with the casing without supplying fluid from the fluid supply source to the communicating passage.

In the present invention, when grinding a workpiece by creep feed grinding, the protruding portion of the spindle connected to the chuck table is brought into contact with the casing. In this case, when creep feed grinding is performed on a workpiece held by suction on the chuck table, the frictional force generated on the underside of the protruding portion of the spindle acts as resistance to the vibration of the chuck table. Therefore, in the present invention, vibrations generated in the chuck table during creep feed grinding are suppressed.

FIG. 1 is a perspective view illustrating an example of a grinding apparatus. FIG. 2 is a partially sectional side view that shows a schematic view of some of the components of an example of a grinding device. FIG. 3 is a flow chart that illustrates an example of a grinding method.

An embodiment of the present invention will be described with reference to the attached drawings. FIG. 1 is a perspective view showing a schematic example of a grinding device that can be used for both in-feed grinding and creep feed grinding. Note that the X-axis direction (front-back direction) and the Y-axis direction (left-right direction) shown in FIG. 1 are directions that are perpendicular to each other on a horizontal plane, and the Z-axis direction (up-down direction) is a direction (vertical direction) that is perpendicular to the X-axis and Y-axis directions.

The grinding device 2 shown in FIG. 1 has a base 4 that supports each component. An opening 4a having a longitudinal portion extending along the X-axis direction is formed on the upper surface of the base 4. A ball screw type X-axis direction movement mechanism (not shown) (horizontal direction movement mechanism) is disposed inside the opening 4a. The X-axis direction movement mechanism has a pair of guide rails (not shown) that extend along the X-axis direction.

An X-axis moving plate (not shown) is connected to the top of the pair of guide rails in a manner that allows it to slide along the pair of guide rails. A screw shaft (not shown) extending along the X-axis direction is disposed between the pair of guide rails. A motor (not shown) for rotating the screw shaft is connected to one end of the screw shaft.

A nut portion (not shown) that houses balls that roll on the surface of the rotating screw shaft is provided on the surface of the screw shaft where the helical grooves are formed, forming a ball screw. In other words, when the screw shaft rotates, the balls circulate inside the nut portion, causing the nut portion to move along the X-axis direction.

The nut is also fixed to the underside of the X-axis moving plate (not shown). Therefore, when the screw shaft is rotated by the motor, the X-axis moving plate moves along the X-axis direction together with the nut.

A table cover 6 is provided on the X-axis moving table. A chuck table 8 is also provided on the table cover 6. The chuck table 8 and other components will be described with reference to FIG. 2. FIG. 2 is a partially cross-sectional side view that shows a schematic view of some of the components of the grinding device 2 (such as the chuck table 8).

The chuck table 8 has a frame 10 made of, for example, a metal material such as stainless steel or ceramics. The frame 10 has a disk-shaped bottom wall and an annular side wall that extends upward from the outer periphery of the bottom wall. A recess 10a is defined on the upper surface of the frame 10 by the side wall.

A disk-shaped porous plate 12 made of ceramics is fixed in the recess 10a. The upper surface 12a of the porous plate 12 (the holding surface of the chuck table 8) may be configured in a shape equivalent to the side of a cone (cone-shaped), or may be configured flat. A disk-shaped table base 14 on which the chuck table 8 is replaceably mounted is provided below the chuck table 8.

The lower surface of the porous plate 12 is connected to a suction source (not shown) such as an ejector via, for example, a flow path (not shown) provided inside the frame 10 and the table base 14 and a valve (not shown). When the valve is opened while the suction source is operating, negative pressure is generated on the upper surface 12a of the porous plate 12 (the holding surface of the chuck table 8), making it possible to hold the workpiece by suction.

The upper part of the spindle (first spindle) 16 is fixed to the lower part of the table base 14. When the motor 26, which will be described later, is operated, the chuck table 8, table base 14, and spindle 16 rotate in the direction of arrow A shown in FIG. 2, with the axis of rotation being a straight line that passes through the center of the holding surface of the chuck table 8 and runs along the Z-axis direction or a direction slightly tilted from the Z-axis direction.

The spindle 16 has a cylindrical main body 16a that hangs down from the center of the lower part of the table base 14, and an annular protrusion 16b that protrudes outward from the side of the main body 16a. The spindle 16 is housed in a tubular casing 18 that is fixed to the X-axis moving plate via a support mechanism (not shown).

The inner circumferential surface of the casing 18 is provided with a recess 18a having a shape corresponding to the protrusion 16b. For example, the bottom surface of the recess 18a (a surface roughly parallel to the Z-axis direction, a surface extending vertically in FIG. 2) and the side surface of the protrusion 16b are concentric in plan view around the rotation axis of the chuck table 8 or the like. In this case, the diameter of the bottom surface of the recess 18a in plan view is slightly longer than the diameter of the side surface of the protrusion 16b in plan view.

The width of the bottom surface of the recess 18a in the direction along the rotation axis of the chuck table 8, etc. is wider than the width of the side surface of the protrusion 16b in this direction. The recess 18a surrounds the upper surface, side surface, and lower surface of the protrusion 16b.

The inner diameter of the inner peripheral surface of the casing 18 other than the recess 18a in plan view is slightly longer than the diameter of the main body portion 16a in plan view. This inner peripheral surface surrounds the side of the main body portion 16a. In addition, a protrusion 18b is provided on the outer peripheral surface of the casing 18.

Furthermore, a plurality of communication passages 18c are provided inside the casing 18. One end of each of the plurality of communication passages 18c opens at the protrusion 18b and is connected to a fluid supply source (not shown), for example, via a pipe (not shown) and a valve (not shown). This fluid supply source is capable of supplying a gas such as air or a liquid such as water to one end of each of the plurality of communication passages 18c.

The communication passages 18c branch off inside the casing 18, and the ends of the branched communication passages 18c open at positions facing the upper surface and the lower surface of the protruding portion 16b of the recess 18a. Therefore, when fluid is supplied from the fluid supply source to the multiple communication passages 18c, the fluid is supplied to the upper and lower surfaces of the protruding portion 16b.

When a fluid exceeding a predetermined pressure is supplied to the underside of the protrusion 16b, the underside of the protrusion 16b separates from the recess 18a. The fluid supplied to the upper and lower surfaces of the protrusion 16b passes through the gap between the spindle 16 and the casing 18 and is discharged to the outside of the grinding device 2.

On the other hand, when no fluid is supplied to the underside of the protrusion 16b, the underside of the protrusion 16b comes into contact with the casing 18 at the recess 18a due to the action of gravity. In this case, the spindle 16 is supported by the X-axis moving plate via the casing 18.

That is, in the spindle 16, when fluid exceeding a predetermined pressure is supplied from the fluid supply source to the multiple communication passages 18c, the lower surface of the protrusion 16b separates from the recess 18a of the casing 18, and when no fluid is supplied, the lower surface of the protrusion 16b comes into contact with the recess 18a of the casing 18.

A driven pulley 20 is fixed to the lower part of the main body 16a. The driven pulley 20 has a shaft 20a and flanges 20b provided on both the upper and lower ends of the shaft 20a. A belt 22, which is applied with a predetermined tension, is wound around the shaft 20a.

A transmission pulley 24 is provided near the driven pulley 20 and spaced apart from the driven pulley 20 in the horizontal direction. The belt 22 is also wound around the transmission pulley 24. One end of the transmission pulley 24 is connected to a motor 26. When the motor 26 operates, the transmission pulley 24 rotates in the direction of arrow B shown in FIG. 2, with a straight line along the Z-axis direction or a straight line slightly inclined from the Z-axis direction as the axis of rotation.

At this time, the frictional force between the transmission pulley 24 and the belt 22 also rotates the belt 22, and the frictional force between the belt 22 and the shaft 20a also rotates the driven pulley 20. As a result, the chuck table 8, the table base 14, and the spindle 16 rotate in the direction of the arrow A shown in FIG. 2.

Referring again to FIG. 1, other components of the grinding device 2 will be described. A bellows-shaped dustproof and drip-proof cover 28 that can expand and contract in the X-axis direction is provided in the opening 4a so as to sandwich the table cover 6. An operation panel 30 for inputting grinding conditions, etc. is provided near the front end of the opening 4a.

A rectangular parallelepiped support structure 32 extending upward is provided near the rear end of the opening 4a. A Z-axis direction movement mechanism (vertical direction movement mechanism) 34 is provided on the front side of the support structure 32 (i.e., the operation panel 30 side). The Z-axis direction movement mechanism 34 has a pair of Z-axis guide rails 36 extending along the Z-axis direction.

A Z-axis moving plate 38 is connected to the front side of the pair of Z-axis guide rails 36 in a manner that allows it to slide along the pair of Z-axis guide rails 36. A screw shaft 40 extending along the Z-axis direction is disposed between the pair of Z-axis guide rails 36. A motor 42 for rotating the screw shaft 40 is connected to one end of the screw shaft 40.

A nut portion (not shown) that accommodates balls that roll on the surface of the rotating screw shaft 40 is provided on the surface of the screw shaft 40 where the helical grooves are formed, forming a ball screw. In other words, when the screw shaft 40 rotates, the balls circulate inside the nut portion, causing the nut portion to move along the Z-axis direction.

The nut portion is also fixed to the back side of the Z-axis moving plate 38. Therefore, when the motor 42 rotates the screw shaft 40, the Z-axis moving plate 38 moves along the Z-axis direction together with the nut portion.

A support 44 is provided on the front side of the Z-axis moving plate 38. The support 44 supports a grinding unit 46. The grinding unit 46 has a cylindrical spindle housing 48 fixed to the support 44. A cylindrical spindle (second spindle) 50 extending along the Z-axis direction is partially housed in the spindle housing 48 in a rotatable state.

A motor 52 for rotating the spindle 50 is connected to the upper end of the spindle 50. The lower end of the spindle 50 is exposed from the spindle housing 48, and the upper part of a disk-shaped wheel mount 54 made of a metal material such as stainless steel is fixed to this lower end.

An annular grinding wheel 56 with a diameter roughly equal to that of the wheel mount 54 is attached to the bottom of the wheel mount 54. The grinding wheel 56 has an annular wheel base 58 made of a metal material such as stainless steel. A number of grinding stones 60 are fixed to the underside of the wheel base 58.

Each of the grinding wheels 60 is rectangular and arranged in a dispersed manner along the circumferential direction of the wheel base 58. Furthermore, a nozzle (not shown) is provided near or inside the grinding wheel 56 to supply a grinding fluid such as water to the grinding surface when grinding the workpiece.

In addition, in the grinding device 2, when the workpiece is ground by in-feed grinding, the lower surfaces of the multiple grinding wheels 60 mainly become the grinding surfaces that grind the workpiece, and when the workpiece is ground by creep feed grinding, the outer surfaces of the multiple grinding wheels 60 mainly become the grinding surfaces that grind the workpiece.

Therefore, a nozzle for supplying grinding fluid to the underside of the multiple grinding wheels 60 and a nozzle for supplying grinding fluid to the outer surfaces of the multiple grinding wheels 60 may be provided separately near or inside the grinding wheel 56.

When the motor 52 operates, the spindle 50, wheel mount 54, and grinding wheel 56 rotate around a straight line along the Z-axis direction or a direction slightly tilted from the Z-axis direction as the rotation axis.

Figure 3 is a flow chart showing an example of a grinding method for grinding a workpiece using the grinding device 2 shown in Figure 1. In this method, first, it is selected whether or not to grind the workpiece by creep feed grinding, that is, whether to grind the workpiece by in-feed grinding or creep feed grinding (selection step: S1).

When it is selected not to grind the workpiece by creep feed grinding, i.e., when it is selected to grind the workpiece by in-feed grinding (selection step (S1): NO), the spindle 16 (spindle fixed to the table base 14) for rotating the chuck table 8 is separated from the casing 18 (separation step: S11). Specifically, a fluid exceeding a predetermined pressure is supplied from a fluid supply source to one end of each of the multiple communication passages 18c of the casing 18.

Then, the workpiece is ground by in-feed grinding (grinding step: S12). This in-feed grinding is performed, for example, in the following order. First, the workpiece is suction-held on the chuck table 8. Specifically, after the workpiece is placed on the holding surface of the chuck table 8, the valve is opened while the suction source that communicates with the flow passage provided inside the frame 10 and table base 14 of the chuck table 8 via a valve is in operation.

Next, the chuck table 8 and the grinding wheel 56 are moved to predetermined positions. Specifically, the X-axis direction moving mechanism (not shown) and the Z-axis direction moving mechanism 34 are operated so that the chuck table 8 is positioned below the grinding wheel 56. As a result, any one of the multiple grinding stones 60 of the grinding wheel 56 is positioned, for example, directly above the center of the holding surface of the chuck table 8.

Next, the chuck table 8 and the grinding wheel 56 are rotated. Specifically, the motor 26 is operated to rotate the spindle 16, and the motor 52 is operated to rotate the spindle 50.

Next, the chuck table 8 and the grinding wheel 56 are moved relative to each other along the Z-axis direction to grind the workpiece. Specifically, the Z-axis movement mechanism 34 is operated so that the upper surface of the workpiece held by suction on the chuck table 8 comes into contact with the lower surfaces of the multiple grinding wheels 60.

As a result, the entire upper surface of the workpiece is ground by the undersides of the multiple grinding wheels 60. Furthermore, by continuing to operate the Z-axis movement mechanism 34, a portion of the upper surface of the workpiece that has a predetermined thickness is ground, thinning the workpiece.

In this in-feed grinding, the underside of the protruding portion 16b of the spindle 16 is separated from the casing 18 before the chuck table 8 is rotated. This allows the chuck table 8 to be rotated easily without large frictional forces being generated on the underside of the protruding portion 16b of the spindle 16 when the chuck table 8 is rotated.

On the other hand, if grinding the workpiece by creep feed grinding is selected (selection step (S1): YES), the spindle 16 (spindle fixed to the table base 14) for rotating the chuck table 8 is brought into contact with the casing 18 (contact step: S21). Specifically, the supply of fluid from the fluid supply source to one end of each of the multiple communication passages 18c of the casing 18 is stopped.

Then, the workpiece is ground by creep feed grinding (grinding step: S22). This creep feed grinding is performed, for example, in the following order. First, the workpiece is suction-held on the chuck table 8. Specifically, after the workpiece is placed on the holding surface of the chuck table 8, the valve is opened while the suction source that communicates with the flow path provided inside the frame 10 and table base 14 of the chuck table 8 via a valve is in operation.

Then, the chuck table 8 and the grinding wheel 56 are moved to a predetermined position. Specifically, the X-axis direction moving mechanism (not shown) and the Z-axis direction moving mechanism 34 are operated so that the chuck table 8 and the grinding wheel 56 are separated in the X-axis direction, and the bottom surfaces of the multiple grinding wheels 60 are lower than the top surface of the workpiece held by suction on the chuck table 8 and higher than the bottom surface of the workpiece.

Then, the grinding wheel 56 is rotated. Specifically, the motor 52 is operated to rotate the spindle 50. Next, the chuck table 8 and the grinding wheel 56 are moved relatively along the X-axis direction to grind the workpiece. Specifically, the X-axis movement mechanism (not shown) is operated so that the outer surface of the workpiece held by suction on the chuck table 8 comes into contact with the sides of the multiple grinding wheels 60.

As a result, the outer surfaces of the multiple grinding wheels 60 grind away the end of the workpiece on the top surface, which has a predetermined thickness. Furthermore, by continuing to operate the X-axis movement mechanism, the entire top surface of the workpiece is ground away, thinning the workpiece.

In this creep feed grinding, the underside of the protruding portion 16b of the spindle 16 is brought into contact with the casing 18 before the workpiece is ground. This creates resistance due to the frictional force generated on the underside of the protruding portion 16b of the spindle 16, suppressing vibrations that occur in the chuck table 8 when the workpiece is ground.

The structures and methods of the above-described embodiments can be modified as appropriate without departing from the scope of the present invention. For example, one end of each of the multiple communication passages 18c opening in the protruding portion 18b of the casing 18 may be connected to a suction source such as an ejector via a pipe (not shown) and a valve (not shown).

This suction source operates, for example, when the spindle 16 is brought into contact with the casing 18 (contact step (S21) shown in FIG. 3). In this case, the fluid in the gap between the spindle 16 and the casing 18 can be quickly evacuated. This can shorten the time required to grind the workpiece by creep feed grinding.

Alternatively, the suction source may operate when grinding the workpiece by creep feed grinding (grinding step (S22) shown in FIG. 3). In this case, creep feed grinding is performed with the spindle 16 sucked into the casing 18. This can further suppress vibrations that occur in the chuck table 8 when grinding the workpiece.

Furthermore, the suction source may operate during both the contacting step (S21) and the grinding step (S22) shown in FIG. 3.

2: Grinding device 4: Base (4a: Opening)
6: Table cover 8: Chuck table 10: Frame (10a: Recess)
12: Porous plate (12a: top surface)
14: Table base 16: Spindle (16a: Main body, 16b: Protrusion)
18: Casing (18a: recess, 18b: protrusion, 18c: communication passage)
20: driven pulley (20a: shaft, 20b: cylinder)
22: Belt 24: Transmission pulley 26: Motor 28: Dust-proof/water-proof cover 30: Operation panel 32: Support structure 34: Z-axis direction movement mechanism (vertical direction movement mechanism)
36: Z-axis guide rail 38: Z-axis moving plate 40: Screw shaft 42: Motor 44: Support 46: Grinding unit 48: Spindle housing 50: Spindle 52: Motor 54: Wheel mount 56: Grinding wheel 58: Wheel base 60: Grinding stone

Claims (1)

a chuck table having a holding surface for holding a workpiece;
a table base on which the chuck table is attached;
a first spindle having a main body portion depending down from the center of a lower portion of the table base and a protrusion portion protruding outwardly from a side surface of the main body portion;
a casing surrounding a side surface of the main body and having a communication passage therein that opens at a position facing a lower surface of the protruding portion;
a fluid supply source for supplying a fluid to the communication passage;
a second spindle having a lower end on which a grinding wheel having a plurality of grinding stones for grinding the workpiece is mounted;
a vertical movement mechanism for relatively moving the chuck table and the grinding wheel in a vertical direction;
a horizontal movement mechanism that relatively moves the chuck table and the grinding wheel along a horizontal direction perpendicular to the vertical direction;
A grinding method for grinding the workpiece using a grinding device comprising:
a selection step of selecting which method to use for grinding the workpiece: in-feed grinding, in which the chuck table and the grinding wheel are rotated with the chuck table positioned below the grinding wheel, and then the chuck table and the grinding wheel are moved relatively along the vertical direction while rotating the chuck table and the grinding wheel, to grind the workpiece; or creep-feed grinding, in which the chuck table and the grinding wheel are spaced apart in the horizontal direction and positioned so that the lower surfaces of the multiple grinding wheels are lower than and higher than the upper surface of the workpiece, and then the chuck table and the grinding wheel are moved relatively along the horizontal direction while rotating the grinding wheel, to grind the workpiece;
a separation step of supplying fluid from the fluid supply source to the communication passage to separate the lower surface of the protrusion from the casing when the in-feed grinding is selected in the selection step;
a contacting step of contacting a lower surface of the protrusion with the casing without supplying fluid from the fluid supply source to the communication passage when the creep feed grinding is selected in the selecting step;
A grinding method comprising:

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