CN116100385A

CN116100385A - Grinding method and grinding device for workpiece

Info

Publication number: CN116100385A
Application number: CN202111332058.2A
Authority: CN
Inventors: 山本敬祐
Original assignee: Disco Corp
Current assignee: Disco Corp
Priority date: 2021-11-11
Filing date: 2021-11-11
Publication date: 2023-05-12

Abstract

The invention provides a grinding method and a grinding device for a processed object, which can inhibit the generation of processing defects. The object to be processed is ground by a grinding device, which comprises: a holding table for holding a workpiece with a holding surface; and a grinding unit that grinds the workpiece held by the holding table with a grinding wheel having a plurality of grinding grindstone arranged in an annular shape, wherein the grinding method of the workpiece includes the steps of: a groove forming step of forming an arc-shaped groove having a depth less than a finished thickness in a workpiece by bringing a grinding wheel into contact with the workpiece to grind the workpiece while rotating the grinding wheel and without rotating a holding table; and a grinding step of bringing the grinding tool into contact with the surface side of the workpiece on which the groove is formed in a state in which the holding table and the grinding wheel are rotated, and grinding the workpiece until the thickness of the workpiece reaches the finished thickness.

Description

Grinding method and grinding device for workpiece

Technical Field

The present invention relates to a method of grinding a workpiece and a grinding apparatus for grinding a workpiece.

Background

In the device chip manufacturing process, wafers in which devices such as ICs (Integrated Circuit, integrated circuits) and LSIs (Large Scale Integration, large-scale integration) are formed in regions divided by a plurality of lines (streets) intersecting each other are used. The wafer is divided along a line to divide, thereby manufacturing a plurality of device chips each having a device. The device chip is mounted on various electronic devices such as a mobile phone and a personal computer.

In recent years, along with miniaturization of electronic devices, thinning of device chips has been demanded. Therefore, a method of thinning a wafer by performing grinding on a wafer before dicing is used. In grinding of a wafer, a grinding apparatus having a holding table for holding the wafer and a grinding unit for grinding the wafer is used.

A grinding wheel having a plurality of grinding tools arranged in a ring shape is installed in a grinding unit of a grinding device. The grinding tool is formed by fixing abrasive grains formed of diamond or the like with a bonding material. In a state in which the wafer is held by the holding table, the wafer is ground by bringing the grinding tool into contact with the wafer while rotating the holding table and the grinding wheel (see patent document 1).

Patent document 1: japanese patent laid-open No. 2009-90389

In the grinding process, abrasive grains protruding from the bonding material of the grinding tool contact the workpiece, thereby processing the workpiece. Therefore, in grinding the workpiece, it is preferable to maintain the state in which the abrasive grains protrude properly from the bonding material.

When the grinding tool collides with the workpiece, the abrasive grains are gradually released from the bonding material. However, when grinding processing is continued even after the removal of the abrasive grains, a phenomenon called spontaneous sharpening occurs: the binding material contacts with the workpiece to generate abrasion, so that new abrasive grains are exposed from the binding material. By this spontaneous sharpening, the state in which the abrasive grains protrude from the bond is maintained, and the grinding ability of the grinding tool is prevented from being lowered.

However, depending on the material of the workpiece and the state of the ground surface of the workpiece, the timing of the falling of the abrasive grains may be advanced. For example, when a thin film such as an oxide film is formed on a surface to be polished of a workpiece, abrasive grains are caught by the thin film, and the abrasive grains are easily separated. In such a case, a period from when the abrasive grains fall off to when the self-sharpening is completed (that is, a period during which the workpiece is ground in a state in which the grinding ability of the grinding tool is low) becomes long, and a processing failure is likely to occur in the workpiece.

Disclosure of Invention

The present invention has been made in view of the above-described problems, and an object thereof is to provide a grinding method and a grinding apparatus capable of suppressing occurrence of machining failure in a workpiece.

According to one aspect of the present invention, there is provided a method for grinding a workpiece, the workpiece being ground by a grinding apparatus including: a holding table for holding the workpiece with a holding surface; and a grinding unit that grinds the workpiece held by the holding table with a grinding wheel having a plurality of grinding grindstone arranged in a ring, wherein the grinding method of the workpiece includes the steps of: a groove forming step of grinding the workpiece by bringing the grinding tool into contact with the workpiece in a state in which the grinding wheel is rotated and the holding table is not rotated, and forming an arc-shaped groove having a depth of less than a finished thickness in the workpiece; and a grinding step of bringing the grinding tool into contact with the surface of the workpiece in which the groove is formed, while rotating the holding table and the grinding wheel, and grinding the workpiece until the thickness of the workpiece becomes the finished thickness.

In the groove forming step, it is preferable that the angle in the rotation direction of the holding table be set to a predetermined angle. In the groove forming step, it is preferable that the workpiece be ground in a state where the angle in the rotation direction of the holding table is different, and a plurality of grooves be formed in the workpiece.

In addition, according to another aspect of the present invention, there is provided a grinding apparatus including: a holding table for holding a workpiece with a holding surface; a grinding unit that grinds the workpiece held by the holding table with a grinding wheel having a plurality of grinding grindstones arranged in a ring shape; a grinding feed unit that relatively moves the holding table and the grinding unit in a direction perpendicular to the holding surface; and a control unit that controls the holding table, the grinding unit, and the grinding feed unit, wherein the control unit is capable of switching between a 1 st mode in which the grinding wheel is rotated and the holding table is not rotated, and a 2 nd mode in which the grinding tool is brought into contact with the workpiece by the grinding feed unit, thereby forming a groove having a depth of less than a finished thickness in the workpiece, and a 2 nd mode in which the grinding tool is brought into contact with a surface side of the workpiece on which the groove is formed by the grinding feed unit, with the holding table and the grinding wheel being rotated, thereby grinding the workpiece until the thickness of the workpiece becomes the finished thickness.

In addition, it is preferable that the control unit is capable of controlling the angle in the rotation direction of the holding table.

In the method and apparatus for grinding a workpiece according to one embodiment of the present invention, after forming an arc-shaped groove having a depth less than the finished thickness in the workpiece, a grinding wheel is brought into contact with the surface side of the workpiece where the groove is formed, and the workpiece is ground until the thickness of the workpiece reaches the finished thickness. Thus, when the workpiece is ground and thinned, the grinding wheel collides with the groove to promote spontaneous sharpening. As a result, the grinding ability of the grinding tool is maintained, and the occurrence of processing failure is suppressed.

Drawings

Fig. 1 is a perspective view showing a grinding apparatus.

Fig. 2 is a front view showing the grinding apparatus.

Fig. 3 (a) is a front view showing the grinding apparatus in the groove forming step, and fig. 3 (B) is a top view showing the holding table and the grinding wheel in the groove forming step.

Fig. 4 (a) is a plan view showing a workpiece in which grooves are formed, and fig. 4 (B) is a plan view showing a workpiece in which a plurality of grooves are formed.

Fig. 5 (a) is a front view showing a grinding apparatus in a grinding step, and fig. 5 (B) is a top view showing a holding table and a grinding wheel in the grinding step.

Fig. 6 is a cross-sectional view showing an enlarged portion of a workpiece to be ground by the grinding tool.

Fig. 7 is a plan view showing the workpiece after grinding.

Description of the reference numerals

11: a workpiece; 11a: front (1 st); 11b: back (2 nd); 11c: a groove; 11d: grinding marks (saw marks); 2: a grinding device; 4: a base station; 4a: an opening; 6: a conveying unit (conveying mechanism); 8a, 8b: a cartridge setting area; 10a, 10b: a case; 12: an alignment mechanism (alignment mechanism); 14: a conveying unit (conveying mechanism, loading arm); 16: a turntable; 18: a holding table (chuck table); 18a: a holding surface; 20: a rotation driving source; 22a, 22b: a support structure; 24a, 24b: a grinding feed unit (a moving unit, a moving mechanism); 26: a guide rail; 28: a moving plate; 30: a ball screw; 32: a pulse motor; 34a, 34b: a grinding unit; 36: a housing; 38: a main shaft; 40: a rotation driving source; 42: a mounting base; 44a, 44b: grinding the grinding wheel; 46: a base station; 48: grinding tool; 50: a thickness measurer; 52a, 52b: altimeter (altimeter); 54: a conveying unit (conveying mechanism, unloading arm); 56: a cleaning unit (cleaning mechanism); 58: a control unit (control section).

Detailed Description

An embodiment of the present invention will be described below with reference to the drawings. First, a configuration example of a grinding apparatus that can be used in the method for processing a workpiece according to the present embodiment will be described. Fig. 1 is a perspective view showing a grinding apparatus 2. In fig. 1, the X-axis direction (left-right direction, 1 st horizontal direction) and the Y-axis direction (front-rear direction, 2 nd horizontal direction) are directions perpendicular to each other. The Z-axis direction (vertical direction, height direction) is a direction perpendicular to the X-axis direction and the Y-axis direction.

The grinding device 2 includes a base 4 for supporting and housing each component constituting the grinding device 2. A rectangular opening 4a is provided on the upper surface side of the front end portion of the base 4, and a conveying unit (conveying means) 6 for conveying the workpiece 11 processed by the grinding device 2 is provided inside the opening 4a.

Cassette installation areas

8a and 8b are provided on both sides of the conveyance unit 6.

Cassettes

10a and 10b for storing the workpiece 11 are provided in the

cassette installation areas

8a and 8b, respectively. The cassette 10a accommodates a plurality of objects to be processed 11 (objects to be processed 11 before processing) to be processed by the grinding device 2. On the other hand, a plurality of objects to be processed 11 (processed objects 11) processed by the grinding device 2 are accommodated in the box 10b.

For example, the workpiece 11 is a silicon wafer formed in a disk shape, and has a front surface (1 st surface) 11a and a rear surface (2 nd surface) 11b that are substantially parallel to each other. The workpiece 11 is divided into a plurality of rectangular regions by a plurality of dividing lines (streets) arranged in a lattice shape so as to intersect with each other. Devices such as ICs and LSIs are formed on the front surface 11a side of the region divided by the lines to divide.

A plurality of device chips each having a device are manufactured by dividing the work 11 along a line to divide. In addition, when the workpiece 11 is thinned by grinding by the grinding device 2 in advance before the workpiece 11 is divided, a thinned device chip is obtained.

However, the type, material, size, shape, structure, and the like of the workpiece 11 are not limited. For example, the workpiece 11 may be a substrate made of a semiconductor (GaAs, inP, gaN, siC, etc.) other than silicon, glass, ceramic, resin, metal, or the like. The type, number, shape, structure, size, arrangement, and the like of the devices formed on the workpiece 11 are not limited, and the devices may not be formed on the workpiece 11.

An alignment mechanism (alignment mechanism) 12 is provided obliquely rearward of the opening 4a. The workpiece 11 stored in the cassette 10a is conveyed to the alignment mechanism 12 by the conveying unit 6. The alignment mechanism 12 is arranged to align the workpiece 11 at a predetermined position.

A conveying unit (conveying mechanism, loading arm) 14 that conveys the workpiece 11 is provided adjacent to the alignment mechanism 12. The conveying unit 14 has a suction pad for sucking and holding the upper surface side of the workpiece 11. The conveyance unit 14 holds the workpiece 11 aligned by the alignment mechanism 12 by the suction pad, and conveys the workpiece 11 rearward by rotating the suction pad.

A disc-shaped turntable 16 is provided behind the conveyance unit 14. A rotation driving source (not shown) such as a servo motor is connected to the turntable 16, and the rotation driving source rotates the turntable 16 about a rotation axis substantially parallel to the Z axis direction.

The turntable 16 is provided with a plurality of holding tables (chuck tables) 18 for holding the workpiece 11. Fig. 1 shows an example in which three holding tables 18 are arranged at substantially equal intervals along the circumferential direction of the turntable 16. The turntable 16 rotates counterclockwise (in the direction indicated by the arrow α) in plan view, and sequentially positions the holding tables 18 at the conveyance position a, the 1 st grinding position (rough grinding position) B, the 2 nd grinding position (finish grinding position) C, and the conveyance position a.

A rotation driving source 20 (see fig. 2) for rotating the holding table 18 is connected to each of the holding tables 18. For example, the rotation driving source 20 is a servo motor, and rotates the holding table 18 about a rotation axis substantially parallel to the Z-axis direction. The rotation driving source 20 includes a detector (encoder) that detects a rotation angle of an output shaft of the rotation driving source 20 (a rotation angle of the holding table 18).

A columnar support structure 22a is disposed behind the 1 st grinding position B, and a columnar support structure 22B is disposed behind the 2 nd grinding position C. A grinding feed unit (moving unit, moving mechanism) 24a is provided on the front surface side of the support structure 22a, and a grinding feed unit (moving unit, moving mechanism) 24b is provided on the front surface side of the support structure 22b.

The grinding

feed units

24a and 24b each have a pair of guide rails 26 arranged substantially parallel to the Z-axis direction. The plate-like moving plate 28 is attached to the pair of guide rails 26 in a slidable manner along the guide rails 26. A nut portion (not shown) is provided on the rear surface side (back surface side) of the moving plate 28, and a ball screw 30 disposed substantially parallel to the guide rail 26 is screwed into the nut portion. A pulse motor 32 is connected to an end of the ball screw 30. When the ball screw 30 is rotated by the pulse motor 32, the moving plate 28 moves in the Z-axis direction.

A grinding unit 34a for rough grinding of the workpiece 11 is fixed to the front surface side (front surface side) of the movable plate 28 included in the grinding feed unit 24 a. On the other hand, a grinding unit 34b for finish grinding the workpiece 11 is fixed to the front surface side (front surface side) of the movable plate 28 included in the grinding feed unit 24b. The grinding

feed units

24a, 24b relatively move the holding table 18 and the grinding

units

34a, 34b in a direction perpendicular to the holding surface 18a (see fig. 2) of the holding table 18 by lifting and lowering the grinding

units

34a, 34b.

The grinding

units

34a and 34b each have a hollow cylindrical housing 36. A cylindrical main shaft 38 (see fig. 2) disposed along the Z-axis direction is housed in the case 36. The front end portion (lower end side) of the spindle 38 is exposed from the housing 36. A rotation drive source 40 is coupled to a base end portion (upper end side) of the main shaft 38. For example, the rotation driving source 40 is a servo motor, and rotates the spindle 38 about a rotation axis substantially parallel to the Z-axis direction.

Fig. 2 is a front view showing the grinding device 2. Fig. 2 shows the holding table 18 and the grinding unit 34a disposed at the 1 st grinding position B.

The upper surface of the holding table 18 forms a holding surface 18a for holding the workpiece 11. The holding surface 18a is a flat surface substantially parallel to the X-axis direction and the Y-axis direction, and is formed in a circular shape corresponding to the shape of the workpiece 11, for example. The holding surface 18a is connected to a suction source (not shown) such as an ejector via a flow path (not shown) formed in the holding table 18, a valve (not shown), and the like. When a negative pressure of a suction source acts on the holding surface 18a in a state where the workpiece 11 is placed on the holding surface 18a, the workpiece 11 is sucked and held by the holding table 18.

A disk-shaped mount 42 made of metal or the like is fixed to the lower end portion of the main shaft 38 of the grinding unit 34a. A grinding wheel 44a for rough grinding is attached to the lower surface side of the mount 42. The grinding wheel 44a rotates about a rotation axis substantially parallel to the Z-axis direction by power transmitted from the rotation drive source 40 (see fig. 1) via the spindle 38 and the mount 42.

The grinding wheel 44a has an annular base 46, and the annular base 46 is made of metal such as aluminum or stainless steel and has substantially the same diameter as the mount 42. A plurality of rectangular parallelepiped grinding tools 48 are annularly arranged along the circumferential direction of the base 46 on the lower surface side of the base 46. For example, the grinding tool 48 is formed by fixing abrasive grains formed of diamond, cBN (cubic Boron Nitride ), or the like with a bonding material such as a metal bond, a resin bond, or a ceramic bond. However, the material, shape, structure, size, etc. of the grinding wheel 48 are not limited, and the number of grinding wheels 48 included in the grinding wheel 44a may be arbitrarily set.

The grinding unit 34b shown in fig. 1 is configured similarly to the grinding unit 34a. A grinding wheel 44b for finish grinding is attached to the lower surface side of the attachment seat 42 of the grinding unit 34b. The grinding wheel 44b is identical in structure to the grinding wheel 44a. However, the average particle size of the abrasive grains contained in the grinding wheel 48 of the grinding wheel 44b is smaller than the average particle size of the abrasive grains contained in the grinding wheel 48 of the grinding wheel 44a.

The grinding unit 34a grinds the workpiece 11 held by the holding table 18 positioned at the 1 st grinding position B with the grinding wheel 44a. Thereby, rough grinding is performed on the workpiece 11. The grinding unit 34b grinds the workpiece 11 held by the holding table 18 positioned at the 2 nd grinding position C with the grinding wheel 44b. Thereby, the workpiece 11 is subjected to finish grinding.

In addition, grinding fluid supply paths (not shown) for supplying a liquid (grinding fluid) such as pure water are provided in or near the grinding

units

34a and 34b, respectively. When grinding is performed on the workpiece 11, a grinding fluid is supplied to the workpiece 11 and the grinding tool 48.

A thickness measuring device 50 for measuring the thickness of the workpiece 11 held by the holding table 18 is provided near the holding table 18 positioned at the 1 st grinding position B and near the holding table 18 positioned at the 2 nd grinding position C. The thickness measuring device 50 includes a height measuring device (altimeter) 52a for measuring the height of the upper surface of the workpiece 11 held by the holding table 18, and a height measuring device (altimeter) 52b for measuring the height of the upper surface (holding surface 18 a) of the holding table 18. The thickness measuring device 50 calculates the thickness of the workpiece 11 from the difference between the values measured by the

height measuring devices

52a and 52b.

A conveying unit (conveying mechanism, unloading arm) 54 that conveys the workpiece 11 is provided adjacent to the conveying unit 14 in the X-axis direction. The conveying unit 54 has a suction pad for sucking and holding the upper surface side of the workpiece 11. The conveyance unit 54 holds the workpiece 11 held by the holding table 18 disposed at the conveyance position a with the suction pad, and conveys the workpiece 11 forward by rotating the suction pad.

A cleaning unit (cleaning mechanism) 56 that cleans the workpiece 11 conveyed by the conveying unit 54 is disposed on the front side of the conveying unit 54. The workpiece 11 cleaned by the cleaning unit 56 is conveyed by the conveying unit 6 and stored in the cassette 10b.

The grinding apparatus 2 further includes a control unit (control unit) 58, and the control unit (control unit) 58 is connected to the respective components (the conveying unit 6, the alignment mechanism 12, the conveying unit 14, the turntable 16, the holding table 18, the rotation driving source 20, the grinding

feed units

24a, 24b, the grinding

units

34a, 34b, the thickness measuring device 50, the conveying unit 54, the cleaning unit 56, and the like) constituting the grinding apparatus 2. The control unit 58 controls the operations of the constituent elements of the grinding apparatus 2.

For example, the control unit 58 is constituted by a computer, and the control unit 58 is constituted to include: a processing unit that performs processing such as computation necessary for the operation of the grinding device 2; and a storage unit that stores various information (data, programs, etc.) used in the processing by the processing unit. The processing unit includes a processor such as a CPU (Central Processing Unit ). The storage unit is configured to include various memories that function as a main storage device, an auxiliary storage device, and the like. The control unit 58 generates signals (control signals) for controlling the constituent elements of the grinding apparatus 2 by executing the programs stored in the storage unit.

Next, a specific example of a grinding method of the workpiece 11 by using the grinding device 2 will be described. Hereinafter, as an example, a case will be described in which the rear surface 11b side of the workpiece 11 is ground and the workpiece 11 is thinned until the thickness of the workpiece 11 becomes a predetermined thickness (finished thickness).

First, the workpiece 11 to be ground by the grinding device 2 is accommodated in the cassette 10a, and the cassette 10a is set in the cassette setting area 8a. The workpiece 11 is taken out of the cassette 10a by the conveying unit 6 and conveyed to the alignment mechanism 12, and the workpiece 11 is aligned by the alignment mechanism 12. Then, the workpiece 11 is conveyed from the alignment mechanism 12 to the holding table 18 disposed at the conveying position a by the conveying unit 14.

As shown in fig. 2, for example, the workpiece 11 is placed on the holding table 18 such that the front surface 11a faces the holding surface 18a and the rear surface 11b is exposed upward. When the negative pressure of the suction source acts on the holding surface 18a in this state, the workpiece 11 is sucked and held by the holding table 18. In the case where a device is formed on the front surface 11a side of the workpiece 11, a protective tape for protecting the device may be attached to the front surface 11a side of the workpiece 11 in advance. In this case, the workpiece 11 is sucked and held by the holding table 18 with the protective tape interposed therebetween.

Subsequently, the turntable 16 is rotated, and the holding table 18 holding the workpiece 11 is disposed at the 1 st grinding position B. The workpiece 11 held by the holding table 18 is ground by the grinding means 34a.

In the present embodiment, the workpiece 11 is first ground by the grinding means 34a, whereby an arc-shaped groove is formed in the workpiece 11 (groove forming step). Fig. 3 (a) is a front view showing the grinding device 2 in the groove forming step.

In the groove forming step, first, the rotation driving source 20 sets the rotation direction angle of the holding table 18 to a predetermined angle (for example, an initial angle (0 °). The grinding wheel 44a is rotated at a predetermined rotational speed by the rotation driving source 40 (see fig. 1) without rotating the holding table 18. At this time, the grinding wheel 48 of the grinding wheel 44a rotates so as to pass through a position overlapping the center of the workpiece 11. Then, the grinding wheel 44a is lowered (grinding fed) at a predetermined speed by the grinding feed unit 24a, and the rotating grinding wheel 48 is brought into contact with the rear surface 11b (ground surface) side of the workpiece 11.

When the grinding wheel 44a is lowered while bringing the grinding wheel 48 into contact with the rear surface 11b of the workpiece 11, the rear surface 11b of the workpiece 11 is ground by the grinding wheel 48. The lowering speed of the grinding wheel 44a is adjusted so that the grinding wheel 48 is pressed against the back surface 11b of the workpiece 11 with an appropriate force.

Fig. 3 (B) is a plan view showing the holding table 18 and the grinding wheel 44a in the groove forming step. When the grinding wheel 44a is rotated without rotating the holding table 18 to grind the workpiece 11, the workpiece 11 is ground along the locus of the rotating grinding wheel 48. As a result, an arc-shaped groove 11c is formed in the rear surface 11b side of the workpiece 11, and the groove 11c has the same width as the grinding wheel 48.

Fig. 4 (a) is a plan view showing the workpiece 11 in which the groove 11c is formed. The groove 11c is formed in an arc shape passing through the center from one end of the workpiece 11 to the other end. When the grinding amount (depth of the groove 11 c) of the workpiece 11 reaches a predetermined value, grinding of the workpiece 11 by the grinding wheel 44a is stopped. The groove 11c is formed to a depth not reaching the final thickness (finished thickness) of the workpiece 11 after grinding in a grinding step described later. For example, the depth of the groove 11c is set so that the difference between the finished thickness of the workpiece 11 and the thickness of the groove 11c is 20 μm or more.

In the groove forming step, a plurality of grooves 11c may be formed on the work 11. In this case, after the first groove 11c is formed, the holding table 18 is rotated by a predetermined angle by the rotation driving source 20, and the angle in the rotation direction of the holding table 18 is changed. The workpiece 11 is ground by the grinding tool 48, and a second arcuate groove 11c is formed in the rear surface 11b side of the workpiece 11. Then, the third and subsequent grooves 11c are formed in the same order.

Fig. 4 (B) is a plan view showing the workpiece 11 in which the plurality of grooves 11c are formed. For example, when the step of grinding the workpiece 11 with the grinding wheel 48 is repeated three times by rotating the holding table 18 by 90 ° after the first groove 11c is formed, four arcuate grooves 11c are formed on the rear surface 11B side of the workpiece 11 as shown in fig. 4 (B). In this way, the workpiece 11 is ground in a state where the angle in the rotation direction of the holding table 18 is different, whereby a plurality of grooves 11c are formed in the workpiece 11.

Next, the workpiece 11 is ground until the thickness of the workpiece 11 becomes the finished thickness (grinding step). Fig. 5 (a) is a front view showing the grinding apparatus 2 in the grinding step.

In the grinding step, the holding table 18 is rotated at a predetermined rotational speed by the rotational drive source 20 (see fig. 2), and the grinding wheel 44a is rotated at a predetermined rotational speed by the rotational drive source 40 (see fig. 1). At this time, the grinding wheel 48 of the grinding wheel 44a rotates so as to pass through a position overlapping the center of the workpiece 11. Then, the grinding wheel 44a is lowered (grinding fed) at a predetermined speed by the grinding feed unit 24a, and the rotating grinding wheel 48 is brought into contact with the surface side (rear surface 11b side) of the workpiece 11 where the groove 11c is formed.

Fig. 5 (B) is a top view showing the holding table 18 and the grinding wheel 44a in the grinding step. When the workpiece 11 is ground by rotating the holding table 18 and the grinding wheel 44a, the entire rear surface 11b side of the workpiece 11 is ground, and the workpiece 11 is thinned.

Fig. 6 is a cross-sectional view showing an enlarged portion of the workpiece 11 ground by the grinding tool 48. During grinding of the workpiece 11, the plurality of grinding tools 48 are brought into contact with each other from the outer peripheral edge of the workpiece 11 toward the center. When the rotating grinding wheel 48 passes through the groove 11c, the lower surface side of the grinding wheel 48 collides with the inner wall of the groove 11c, and abrasion of the bonding material of the grinding wheel 48 is likely to occur. As a result, spontaneous sharpening of the abrasive grains embedded in the inside of the bond material from the bond material is promoted, and the reduction in grinding ability of the grinding tool 48 is suppressed.

In particular, when a thin film such as an oxide film is formed on the rear surface 11b side of the workpiece 11, the grinding wheel 48 is easily caught by the thin film and is easily detached from the bonding material. However, since spontaneous sharpening of the grinding wheel 48 is promoted by the groove 11c as described above, the grinding ability of the grinding wheel 48 can be quickly restored.

When the workpiece 11 is ground until the thickness of the workpiece 11 reaches a predetermined thickness (finished thickness), the grinding of the workpiece 11 by the grinding wheel 44a is stopped. This completes the rough grinding of the workpiece 11. Fig. 7 is a plan view showing the workpiece 11 after grinding. On the rear surface 11b side of the workpiece 11 after grinding, grinding marks (saw marks) 11d formed radially from the center toward the outer periphery of the workpiece 11 remain. The grinding mark 11d is formed in a curved shape along the locus of the rotating grinding wheel 48.

In addition, during grinding of the workpiece 11 by the grinding wheel 44a, the thickness of the workpiece 11 is measured by the thickness gauge 50 (see fig. 1). The timing of stopping the grinding of the workpiece 11 by the grinding unit 34a is controlled based on the thickness of the workpiece 11 measured by the thickness measuring device 50.

Subsequently, the turntable 16 is rotated, and the holding table 18 holding the workpiece 11 is disposed at the 2 nd grinding position C. The workpiece 11 held by the holding table 18 positioned at the 2 nd grinding position C is ground by the grinding means 34b. Thereby, the workpiece 11 is finish-ground, and the grinding mark 11d (see fig. 7) formed on the rear surface 11b side of the workpiece 11 is removed.

The operations of the holding table 18 and the grinding unit 34b at the time of finish grinding are the same as those of the holding table 18 and the grinding unit 34a at the time of rough grinding. In addition, during grinding of the workpiece 11 by the grinding wheel 44b, the thickness of the workpiece 11 is measured by the thickness gauge 50.

In addition, the groove forming step and the grinding step described above may be performed during finish grinding. Specifically, first, the grinding wheel 48 is brought into contact with the workpiece 11 while the grinding wheel 44B is rotated without rotating the holding table 18, and the groove 11c is formed on the rear surface 11B side of the workpiece 11 (see fig. 3 a and 3B). Then, the grinding tool 48 is brought into contact with the workpiece 11 while the holding table 18 and the grinding wheel 44B are rotated, and the entire rear surface 11B side of the workpiece 11 is ground (see fig. 5 a and 5B). This promotes spontaneous sharpening of the grinding tool 48 even when finish grinding is performed on the workpiece 11.

Next, the turntable 16 is rotated, and the holding table 18 holding the workpiece 11 is disposed at the conveying position a. The processed object 11 is conveyed from the holding table 18 positioned at the conveying position a.

The workpiece 11 held by the holding table 18 positioned at the conveying position a is conveyed from the holding table 18 to the cleaning unit 56 by the conveying unit 54, and is cleaned. After the cleaning by the cleaning unit 56, the workpiece 11 is conveyed to the cassette 10b by the conveying unit 6.

As described above, the method for grinding a workpiece according to the present embodiment includes the steps of: a groove forming step of forming an arc-shaped groove 11c having a depth of less than the finished thickness in the workpiece 11; and a grinding step of bringing the grinding tool 48 into contact with the surface side of the workpiece 11 where the groove 11c is formed, and grinding the workpiece 11 until the thickness of the workpiece 11 becomes the finished thickness. Thus, when the workpiece 11 is thinned by grinding, the grinding wheel 48 collides with the groove 11c to promote spontaneous sharpening. As a result, the grinding ability of the grinding wheel 48 is maintained, and the occurrence of processing failure is suppressed.

The operations of the grinding device 2 in the groove forming step and the grinding step are controlled by the control unit 58. Specifically, in the groove forming step, the control unit 58 outputs a control signal to the rotation driving source 20 (see fig. 2 and the like), thereby setting the angle in the rotation direction of the holding table 18 to a predetermined angle, and then maintaining the holding table 18 in a stopped state (a state of not rotating). The control unit 58 outputs a control signal to the rotation driving source 40 of the grinding unit 34a, thereby rotating the grinding wheel 44a at a predetermined rotation speed.

The control unit 58 outputs a control signal to the pulse motor 32 of the grinding feed unit 24a to rotate the ball screw 30 at a predetermined speed. Thereby, the grinding unit 34a is lowered at a predetermined speed, the grinding wheel 48 is brought into contact with the workpiece 11, and the groove 11c is formed in the workpiece 11. That is, the control unit 58 outputs a control signal to the constituent elements of the grinding apparatus 2, thereby operating the grinding apparatus 2 in accordance with the mode (mode 1) for performing the groove forming step.

On the other hand, in the grinding step, the control unit 58 outputs a control signal to the rotation driving source 20 (see fig. 2 and the like), thereby rotating the holding table 18 at a predetermined rotation speed. The control unit 58 outputs a control signal to the rotation driving source 40 of the grinding unit 34a, thereby rotating the grinding wheel 44a at a predetermined rotation speed.

The control unit 58 outputs a control signal to the pulse motor 32 of the grinding feed unit 24a to rotate the ball screw 30 at a predetermined speed. As a result, the grinding unit 34a is lowered at a predetermined speed, and the grinding tool 48 is brought into contact with the workpiece 11, thereby grinding the entire rear surface 11b of the workpiece 11. That is, the control unit 58 outputs a control signal to the constituent elements of the grinding apparatus 2, thereby operating the grinding apparatus 2 in accordance with the mode (the 2 nd mode) for performing the grinding step.

As described above, after the holding table 18 holding the workpiece 11 is positioned at the 1 st grinding position B, the 1 st mode and the 2 nd mode are appropriately switched by the control unit 58, whereby the groove forming step and the grinding step are performed. The same applies to the operation of the control unit 58 when the groove forming step and the grinding step are performed by the grinding unit 34b.

When a plurality of grooves 11c are formed in the groove forming step (see fig. 4B), the control unit 58 outputs a control signal to the rotation driving source 20 (see fig. 2), thereby stopping the holding table 18 at a predetermined interval angle (for example, 90 ° interval). Then, the workpiece 11 is ground by the grinding means 34a with the angle of the holding table 18 being different, thereby forming grooves 11c.

The control unit 58 controls the angle of the holding table 18 based on a signal input from an encoder provided in the rotary drive source 20. Specifically, the encoder detects the rotation angle of the output shaft of the rotation driving source 20 and outputs the detected rotation angle to the control unit 58. Based on the detection result of the encoder, the control unit 58 calculates the rotation amount of the output shaft of the rotation driving source 20 required to stop the holding table 18 at a desired angle, and rotates the output shaft of the rotation driving source 20 by the rotation amount.

In addition, the structure, method, and the like of the above embodiment can be modified and implemented as appropriate without departing from the object scope of the present invention.

Claims

1. A method for grinding a workpiece by using a grinding device,

the grinding device comprises:

a holding table for holding the workpiece with a holding surface; and

a grinding unit for grinding the workpiece held by the holding table by using a grinding wheel having a plurality of grinding tools arranged in a ring shape,

it is characterized in that the method comprises the steps of,

the grinding method of the processed object comprises the following steps:

a groove forming step of grinding the workpiece by bringing the grinding tool into contact with the workpiece in a state in which the grinding wheel is rotated and the holding table is not rotated, and forming an arc-shaped groove having a depth of less than a finished thickness in the workpiece; and

and a grinding step of bringing the grinding tool into contact with the surface of the workpiece in which the groove is formed, while rotating the holding table and the grinding wheel, and grinding the workpiece until the thickness of the workpiece becomes the finished thickness.

2. The method for grinding an object to be processed according to claim 1, wherein,

in the groove forming step, the angle in the rotation direction of the holding table is set to a predetermined angle.

3. The method for grinding an object to be processed according to claim 1 or 2, characterized in that,

in the groove forming step, the workpiece is ground in a state where the angle in the rotation direction of the holding table is different, and a plurality of grooves are formed in the workpiece.

4. A grinding apparatus, comprising:

a holding table for holding a workpiece with a holding surface;

a grinding unit that grinds the workpiece held by the holding table with a grinding wheel having a plurality of grinding grindstones arranged in a ring shape;

a grinding feed unit that relatively moves the holding table and the grinding unit in a direction perpendicular to the holding surface; and

a control unit that controls the holding table, the grinding unit, and the grinding feed unit,

it is characterized in that the method comprises the steps of,

the control unit is capable of switching between a 1 st mode in which the grinding wheel is rotated and the holding table is not rotated, and a 2 nd mode in which the grinding tool is brought into contact with the workpiece by the grinding feed unit to thereby form a groove having a depth of less than a finished thickness in the workpiece, and a 2 nd mode in which the grinding tool is brought into contact with a surface side of the workpiece where the groove is formed by the grinding feed unit with the holding table and the grinding wheel rotated, and the workpiece is ground until the thickness of the workpiece becomes the finished thickness.

5. A grinding apparatus as defined in claim 4, wherein,

the control unit is capable of controlling an angle in a rotation direction of the holding table.