Method for machining workpiece

Abstract

To perform edge-trimming with high quality.SOLUTION: In the method for machining a workpiece, an outer periphery of the workpiece having a chamfered part on the outer periphery is cut to perform edge-trimming. The method comprises: a holding step of placing the workpiece on a holding surface of a chuck table having the holding surface and rotatable around a table rotary shaft intersecting the holding surface and holding the workpiece on the chuck table; and a cutting step of, after the holding step, making a cutting blade part of an annular cutting blade having the cutting blade part on the outer periphery cut in the chamfered part of the workpiece while rotating the cutting blade around a blade rotary shaft, and rotating the chuck table around the table rotary shaft once or more to cut the chamfered part of the workpiece by the cutting blade and partially remove the workpiece. In the cutting step, the table rotary shaft and the blade rotary shaft do not intersect each other while the cutting blade cuts the chamfered part of the workpiece.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a method for processing a workpiece, such as a semiconductor wafer, having a chamfered portion on its outer periphery, by cutting the outer periphery of the workpiece to perform edge trimming. [Background technology]

[0002] In the manufacturing process of device chips used in electronic devices such as mobile phones and personal computers, first, multiple intersecting division lines (streets) are set on the surface of a wafer made of a material such as a semiconductor. Then, devices such as ICs (Integrated Circuits) and LSIs (Large-scale Integrations) are formed in each area partitioned by the division lines. After that, the wafer is ground from the back side to thin it and divided along the division lines to form individual device chips.

[0003] A chamfered portion (also called a bevel portion) is formed on the outer periphery of the wafer on which the devices are formed in order to prevent chipping of the edge, etc. On the outer periphery of the wafer where the chamfered portion is formed, the cross-sectional shape of the wafer becomes an arc extending from the front surface to the back surface.

[0004] Here, when a wafer with a chamfered portion formed on its outer periphery is ground from the back side to thin it, a knife-edge shape (also called a sharp edge) consisting of the arc surface constituting the chamfer and the flat ground surface is formed on the outer periphery of the wafer, and the outer periphery of the wafer is likely to be chipped. Therefore, before grinding the wafer, an edge trimming process is performed in which an annular cutting blade is cut into the outer periphery of the wafer to remove at least a part of the chamfered portion (see Patent Documents 1 to 4). If the wafer is then ground, the knife-edge shape is not formed.

[0005] In general, when edge trimming is performed, the position of the wafer, which has a circular planar shape, is adjusted so that the axis of rotation of the cutting blade (blade rotation axis) is perpendicular to the tangent of the wafer at the outer peripheral position where the cutting blade cuts into the wafer. At this time, the center of the wafer is located on the blade rotation axis. Then, the edge trimming is performed by cutting the wafer with the cutting blade while rotating the wafer around this center. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2000-173961 A [Patent Document 2] JP 2004-207459 A [Patent Document 3] JP 2016-127098 A [Patent Document 4] JP 2020-40181 A Summary of the Invention [Problem to be solved by the invention]

[0007] When edge trimming is performed, a terrace surface parallel to the surface of the wafer and a steep wall surface rising from the inner periphery of the terrace surface are formed on the outer periphery of the wafer. In some cases, the terrace surface and the wall surface have uneven abrasive grain marks formed by the abrasive grains contained in the cutting edge of the cutting blade. In some cases, chipping occurs on the surface of the wafer.

[0008] When edge-trimmed wafers are ground, impacts can cause cracks to form from the abrasive grain marks or chipping, which can cause the cracks to progress inside the wafer, or fragments caused by the abrasive grain marks can detach from the wafer and reattach to the wafer. Furthermore, grinding debris generated when the wafer is ground can get into the abrasive grain marks and remain on the wafer. When these problems occur, the quality of the chips produced by dividing the wafer can decrease, or the amount of normal chips produced can decrease, resulting in a decrease in chip production efficiency.

[0009] The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for processing a workpiece, which is capable of performing edge trimming processing with high quality. [Means for solving the problem]

[0010] According to one aspect of the present invention, there is provided a method for processing a workpiece, which performs edge trimming by cutting an outer periphery of a workpiece having a chamfered portion on the outer periphery, comprising: a holding step of placing the workpiece on a holding surface of a chuck table which has a holding surface and can rotate about a table rotation axis which intersects the holding surface, and holding the workpiece with the chuck table; and a cutting step after the holding step, in which an annular cutting blade having a cutting edge portion on its outer periphery is rotated about the blade rotation axis while the cutting edge of the cutting blade is cut into the chamfered portion of the workpiece, and the chuck table is rotated about the table rotation axis by one or more rotations, thereby cutting the chamfered portion of the workpiece with the cutting blade to partially remove the workpiece, wherein in the cutting step, the table rotation axis and the blade rotation axis do not intersect while the cutting blade is cutting the chamfered portion of the workpiece.

[0011] Preferably, during the cutting step in which the cutting blade cuts the chamfered portion of the workpiece, the angle between the table rotation axis and the blade rotation axis in a plane parallel to the holding surface and including the center of the cutting edge of the cutting blade is greater than or equal to 5° and less than 175°. Effect of the Invention

[0012] In a method for processing a workpiece according to one aspect of the present invention, a cutting step is performed to rotate an annular cutting blade around a blade rotation axis while cutting the cutting edge of the cutting blade into a chamfered portion of the workpiece. Then, the chuck table is rotated around the table rotation axis by one or more revolutions, so that the cutting blade cuts the chamfered portion of the workpiece to partially remove the workpiece.

[0013] When performing conventional edge trimming, the table rotation axis and the blade rotation axis intersect while the cutting blade is cutting the chamfered portion of the workpiece. In this case, the direction of travel of the workpiece and the direction of travel of the cutting blade coincide at the point where the cutting blade cuts into the workpiece. Therefore, it is thought that abrasive marks are likely to remain on the workpiece.

[0014] In contrast, in the processing method according to one aspect of the present invention, in the cutting step, the table rotation axis and the blade rotation axis do not intersect while the cutting blade cuts the chamfered portion of the workpiece. In this case, at the point where the cutting blade of the cutting blade cuts into the workpiece, the moving direction of the workpiece and the moving direction of the cutting blade do not match. In this case, when the abrasive marks are formed on the workpiece, the abrasive marks are immediately polished and removed by the cutting blade, which is considered to improve the surface roughness.

[0015] In addition, the terrace surface and wall surface formed on the workpiece by the edge trimming process are connected by a curved surface (R-shape), which reinforces the terrace surface and wall surface and is thought to make cracks and chipping less likely to occur. This improves the quality of the chips manufactured by dividing the wafer, or increases the production volume of normal chips, thereby improving the chip manufacturing efficiency.

[0016] Therefore, according to one aspect of the present invention, there is provided a method for processing a workpiece that can perform edge trimming processing with high quality. [Brief description of the drawings]

[0017] [Figure 1] FIG. 2 is a perspective view illustrating a wafer. [Diagram 2] FIG. 2 is a perspective view showing a cutting device. [Diagram 3] FIG. 11 is a plan view showing a schematic positional relationship between a chuck table and a cutting unit when performing conventional edge trimming processing. [Figure 4] FIG. 1 is a side view showing a schematic diagram of a conventional edge trimming process. [Diagram 5] 11 is a plan view showing a schematic positional relationship between a chuck table and a cutting unit when a cutting step according to an example is performed; FIG. [Figure 6] FIG. 13 is a side view showing a schematic diagram of a cutting step according to an example. [Figure 7] FIG. 11 is a plan view illustrating a schematic positional relationship between the chuck table and the cutting unit during a cutting step according to another example. [Figure 8] FIG. 11 is a side view showing a schematic view of a cutting step according to another example. [Figure 9] FIG. 2 is a perspective view showing a grinding device. [Figure 10] FIG. 2 is a side view showing a schematic view of how a wafer is ground. [Figure 11] 3 is a flowchart showing the flow of each step of a method for machining a workpiece. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] An embodiment according to one aspect of the present invention will be described with reference to the accompanying drawings. First, a workpiece to be processed by a wafer processing method according to this embodiment will be described. FIG. 1 is a perspective view of the workpiece 1. The workpiece 1 is, for example, a disk-shaped wafer made of Si (silicon), SiC (silicon carbide), GaN (gallium nitride), GaAs (gallium arsenide), or other semiconductor material. The diameter of the workpiece 1 is about 6 inches to 12 inches, and the thickness is about 400 μm to 2000 μm. However, the diameter and thickness of the workpiece 1 are not limited to these values.

[0019] The front surface 1a of the workpiece 1 is partitioned by a plurality of planned division lines 3 that intersect with each other. Devices 5 such as ICs and LSIs are formed in each region partitioned by the planned division lines 3 on the front surface 1a of the workpiece 1. The region on the front surface 1a of the workpiece 1 in which the plurality of devices 5 are formed is a device formation region 7, and the surrounding region is a peripheral excess region 9. The workpiece 1 is ground from the back surface 1b side to be thinned, and the workpiece 1 is divided along the planned division lines 3 to form individual device chips.

[0020] In order to prevent chipping or cracking at the edge of the workpiece 1, a chamfered portion (see FIG. 4, etc.) is formed by cutting off the corners on the outer periphery 1c of the workpiece 1. The cross-sectional shape of the chamfered portion is, for example, an arc shape extending from the front surface 1a to the back surface 1b. In addition, a cutout called a notch 11 that indicates the crystal orientation of the material that constitutes the workpiece 1 is formed on the outer periphery 1c of the workpiece 1.

[0021] When the workpiece 1 with a chamfered portion formed on the outer periphery 1c is ground from the back surface 1b side to thin it, a knife-edge shape is formed on the cross section of the workpiece 1 at the outer periphery 1c by the chamfered portion and the ground surface. Therefore, chipping is likely to occur on the outer periphery 1c of the workpiece 1 that has been ground and thinned. Therefore, before grinding the workpiece 1, a process called edge trimming is performed on the workpiece 1, in which the outer periphery 1c of the workpiece 1 is cut to remove the chamfered portion. FIG. 2 is a perspective view showing a schematic diagram of the cutting device 2.

[0022] The workpiece 1 to be cut by the cutting device 2 is carried into the cutting device 2 in a state where it is integrated with, for example, an annular frame (not shown) having an opening with a diameter larger than that of the workpiece 1, and a tape (not shown) attached to the annular frame so as to close the opening of the annular frame. When the workpiece 1, the tape, and the annular frame are integrated to form a frame unit, the workpiece 1 can be easily handled. Note that the annular frame and the tape are omitted in each drawing.

[0023] Next, the cutting device 2 used for edge trimming will be described. The cutting device 2 has a base 4 that supports each component. An opening 4a is formed in the front corner of the base 4, and within this opening 4a, a cassette support table 8 that is raised and lowered by a lifting mechanism (not shown) is provided. On the upper surface of the cassette support table 8, a cassette 10 is mounted, which contains a plurality of workpieces 1 that each become part of a frame unit. For ease of explanation, only the outline of the cassette 10 is shown in FIG. 2.

[0024] A rectangular opening 4b is formed on the side of the cassette support base 8 so that its longitudinal direction is along the X-axis direction (front-rear direction, processing feed direction). A ball screw type X-axis moving mechanism (not shown), a table cover 14 that covers the upper part of the X-axis moving mechanism, and a bellows-shaped dust-proof and drip-proof cover 16 are arranged inside the opening 4b. The X-axis moving mechanism includes an X-axis moving table (not shown) covered by the table cover 14, and moves this X-axis moving table in the X-axis direction.

[0025] A chuck table 18 is disposed on the upper surface of the X-axis moving table so as to be exposed from the table cover 14. The chuck table 18 has a function of suction-holding the workpiece 1 placed on a holding surface 18a exposed upward. The chuck table 18 is connected to a rotation drive source (not shown) such as a motor, and rotates about a rotation axis roughly parallel to the Z-axis direction (vertical direction).

[0026] The chuck table 18 includes a porous member 18c having the same diameter as the workpiece 1, and a frame that covers the porous member 18c. A suction path (not shown) is formed inside the chuck table 18, one end of which is connected to a suction source (not shown) such as an ejector provided outside the chuck table 18. The other end of the suction path reaches the porous member 18c.

[0027] The upper surface of the porous member 18c is exposed on the holding surface 18a of the chuck table 18. The upper surface of the porous member 18c has the same diameter as the workpiece 1 and is formed approximately parallel to the X-axis and Y-axis directions. Furthermore, a plurality of clamps 18b for fixing an annular frame supporting the workpiece 1 are provided around the periphery of the chuck table 18.

[0028] When the workpiece 1 is held by the chuck table 18, first, the frame unit including the workpiece 1 is placed on the holding surface 18a of the chuck table 18. Then, the suction source is connected to the porous member 18c via the suction path, and negative pressure is applied to the workpiece 1 via the tape attached to the back surface 1b of the workpiece 1. The annular frame is fixed with the clamp 18b.

[0029] The cutting device 2 is provided with a transport unit (not shown) in an area adjacent to the opening 4b, which transports the workpiece 1 to the chuck table 18 and the like. A temporary placement mechanism for temporarily placing the workpiece 1 is provided in a position close to the side of the cassette support base 8. The temporary placement mechanism includes, for example, a pair of guide rails 12 that move toward and away from each other while maintaining a state parallel to the Y-axis direction (indexing feed direction). The pair of guide rails 12 sandwich the workpiece 1 pulled out of the cassette 10 by the transport unit along the X-axis direction, and align it to a predetermined position.

[0030] The workpiece 1 aligned in a predetermined position is lifted up by the transport unit and transported to the chuck table 18. At this time, the pair of guide rails 12 are separated from each other, and the workpiece 1 is passed between the pair of guide rails 12.

[0031] A first cutting unit 24a and a second cutting unit 24b that cut the workpiece 1 with an annular cutting blade are provided above the chuck table 18. A gate-shaped support part 20 for supporting the first cutting unit 24a and the second cutting unit 24b is disposed on the upper surface of the base 4 so as to straddle the opening 4b.

[0032] A first moving unit 22a that moves the first cutting unit 24a in the Y-axis direction and the Z-axis direction, and a second moving unit 22b that moves the second cutting unit 24b in the Y-axis direction and the Z-axis direction are provided on the upper front surface of the support part 20. The first moving unit 22a includes a Y-axis moving plate 28a, and the second moving unit 22b includes a Y-axis moving plate 28b. The two Y-axis moving plates 28a, 28b are slidably mounted on a pair of Y-axis guide rails 26 arranged on the front surface of the support part 20 along the Y-axis direction.

[0033] A nut portion (not shown) is provided on the back surface side (rear surface side) of the Y-axis moving plate 28a, and a Y-axis ball screw 30a that is generally parallel to the Y-axis guide rail 26 is screwed into this nut portion. In addition, a nut portion (not shown) is provided on the back surface side (rear surface side) of the Y-axis moving plate 28b, and a Y-axis ball screw 30b that is generally parallel to the Y-axis guide rail 26 is screwed into this nut portion.

[0034] A Y-axis pulse motor 32a is connected to one end of the Y-axis ball screw 30a. When the Y-axis ball screw 30a is rotated by the Y-axis pulse motor 32a, the Y-axis moving plate 28a moves in the Y-axis direction along the Y-axis guide rail 26. Furthermore, a Y-axis pulse motor (not shown) is connected to one end of the Y-axis ball screw 30b. When the Y-axis ball screw 30b is rotated by the Y-axis pulse motor, the Y-axis moving plate 28b moves in the Y-axis direction along the Y-axis guide rail 26.

[0035] A pair of Z-axis guide rails 34a are provided along the Z-axis direction on the surface (front surface) side of the Y-axis moving plate 28a, and a pair of Z-axis guide rails 34b are provided along the Z-axis direction on the surface (front surface) side of the Y-axis moving plate 28b. A Z-axis moving plate 36a is slidably attached to the pair of Z-axis guide rails 34a, and a Z-axis moving plate 36b is slidably attached to the pair of Z-axis guide rails 34b.

[0036] A nut portion (not shown) is provided on the back surface side (rear surface side) of the Z-axis moving plate 36a, and a Z-axis ball screw 38a provided along a direction generally parallel to the Z-axis guide rail 34a is screwed into the nut portion. A Z-axis pulse motor 40a is connected to one end of the Z-axis ball screw 38a, and the Z-axis moving plate 36a moves in the Z-axis direction along the Z-axis guide rail 34a by rotating the Z-axis ball screw 38a with the Z-axis pulse motor 40a.

[0037] A nut portion (not shown) is provided on the back surface side (rear surface side) of the Z-axis moving plate 36b, and a Z-axis ball screw 38b provided along a direction generally parallel to the Z-axis guide rail 34b is screwed into the nut portion. A Z-axis pulse motor 40b is connected to one end of the Z-axis ball screw 38b, and the Z-axis moving plate 36b moves in the Z-axis direction along the Z-axis guide rail 34b by rotating the Z-axis ball screw 38b with the Z-axis pulse motor 40b.

[0038] A first cutting unit 24a is provided below the Z-axis moving plate 36a. A camera unit 46a is provided adjacent to the first cutting unit 24a to capture images of the workpiece 1 held by suction on the chuck table 18. A second cutting unit 24b is provided below the Z-axis moving plate 36b. A camera unit 46b is provided adjacent to the second cutting unit 24b to capture images of the workpiece 1 held by suction on the chuck table 18.

[0039] The first moving unit 22a controls the positions of the first cutting unit 24a and the camera unit 46a in the Y-axis direction and the Z-axis direction, and the second moving unit 22b controls the positions of the second cutting unit 24b and the camera unit 46b in the Y-axis direction and the Z-axis direction. The positions of the first cutting unit 24a and the second cutting unit 24b are controlled independently of each other.

[0040] An opening 4c is formed at a position opposite to the opening 4b from the opening 4a. A cleaning unit 48 for cleaning the workpiece 1 is disposed in the opening 4c, and the workpiece 1 cut on the chuck table 18 is cleaned by the cleaning unit 48. The workpiece 1 cleaned by the cleaning unit 48 is stored in the cassette 10 again.

[0041] Here, the cutting units 24a and 24b will be further described. Figure 4 is a side view showing a schematic diagram of the cutting units 24a and 24b performing edge trimming processing by a conventional method. The edge trimming processing may be performed by either the first cutting unit 24a or the second cutting unit 24b. In the following figures, one cutting unit 24 is shown.

[0042] The cutting unit 24 includes a spindle 50 aligned along the Y-axis direction, and a spindle housing (not shown) that rotatably accommodates the base end side of the spindle 50. The spindle housing accommodates a rotation drive source (not shown) such as a motor connected to the spindle 50. An annular cutting blade 56 is fixed to the tip of the spindle 50 by a flange mechanism 52 and a fixing nut 54.

[0043] The cutting blade 56 is a cutting blade called a hub type, which has an annular base 58 made of a material such as aluminum and having an insertion hole formed in the center, and a cutting blade portion (grindstone portion) 60 fixed to the outer periphery of the base 58. However, the cutting blade 56 is not limited to the hub type.

[0044] The cutting blade portion (grindstone portion) 60 includes a countless number of abrasive grains and a bonding material (bond) that disperses and fixes the abrasive grains. For example, the abrasive grains are made of a material such as diamond or cubic boron nitride (cBN), and the bonding material is a nickel plating layer, a resin bond, a vitrified bond, a metal bond, or the like.

[0045] The blade thickness of the cutting blade 56 (the thickness of the cutting edge portion 60) is determined, for example, according to the width of the chamfered portion formed on the outer circumferential portion 1c of the workpiece 1. The blade thickness of the cutting blade 56 is preferably, for example, 0.5 mm or more and 5 mm or less. The diameter of the cutting blade 56 is preferably 49 mm or more and 59 mm or less. However, the blade thickness and diameter are not limited to these values.

[0046] When the rotary drive source is operated to rotate the spindle 50, the cutting blade 56 can be rotated, and when the rotating cutting blade 56 is caused to cut into the workpiece 1 held by suction on the chuck table 18, the workpiece 1 can be cut. At this time, cutting fluid such as pure water is sprayed onto the workpiece 1 and the cutting blade 56, and the cutting fluid removes machining chips and frictional heat generated by cutting.

[0047] Next, a grinding device that can be used to thin the workpiece 1 that has been edge-trimmed will be described. Fig. 9 is a perspective view that typically shows the grinding device 68, and Fig. 10 is a cross-sectional view that typically shows the workpiece 1 being ground by the grinding device 68. An opening 70a is provided on the upper surface of a base 70 of the grinding device 68. An X-axis moving table 74 is provided within the opening 70a, on whose upper surface a chuck table 72 that suction-holds the workpiece 1 is placed.

[0048] The X-axis moving table 74 can be moved in the X-axis direction by an X-axis moving mechanism (not shown). The X-axis moving table 74 is positioned at a loading / unloading area 76 where the workpiece 1 is loaded / unloaded on the chuck table 72 by the X-axis moving mechanism, and at a processing area 78 where the workpiece 1 sucked and held on the chuck table 72 is ground.

[0049] A porous member having an upper surface with the same diameter as the workpiece 1 is disposed on the upper surface of the chuck table 72, and the upper surface of the porous member serves as a holding surface 72a for holding the workpiece 1. The chuck table 72 is provided with an internal suction path (not shown) having one end connected to the porous member and the other end connected to a suction source (not shown). When the suction source is operated, negative pressure acts on the workpiece 1 placed on the holding surface 72a, and the workpiece 1 is sucked and held on the chuck table 72. The chuck table 72 can also rotate around an axis perpendicular to the holding surface 72a.

[0050] A grinding unit 80 that grinds the workpiece 1 is disposed above the machining area 78. A support part 82 is erected on the rear side of the base 70, and the grinding unit 80 is supported by this support part 82. A pair of Z-axis guide rails 84 extending in the Z-axis direction are provided on the front side of the support part 82, and a Z-axis moving plate 86 is slidably attached to each of the Z-axis guide rails 84.

[0051] A nut portion (not shown) is provided on the back surface side (rear surface side) of the Z-axis moving plate 86, and a Z-axis ball screw 88 parallel to the Z-axis guide rail 84 is screwed into this nut portion. A Z-axis pulse motor 90 is connected to one end of the Z-axis ball screw 88. When the Z-axis ball screw 88 is rotated by the Z-axis pulse motor 90, the Z-axis moving plate 86 moves in the Z-axis direction along the Z-axis guide rail 84.

[0052] A grinding unit 80 that grinds the workpiece 1 is fixed to the lower front side of the Z-axis moving plate 86. When the Z-axis moving plate 86 is moved in the Z-axis direction, the grinding unit 80 moves in the Z-axis direction.

[0053] The grinding unit 80 has a spindle 94 along the Z-axis direction, a spindle housing 92 that rotatably accommodates the upper end of the spindle 94, and a disk-shaped wheel mount 96 fixed to the lower end of the spindle 94. The spindle housing 92 accommodates a rotational drive source such as a motor that is connected to the upper end of the spindle 94 and rotates the spindle 94 about the Z-axis direction.

[0054] An annular grinding wheel 98 is fixed to the underside of the wheel mount 96. A grinding stone 100, in which abrasive grains made of diamond or the like are dispersed and fixed in a binder, is disposed in an annular shape on the underside of the grinding wheel 98.

[0055] When the spindle 94 is rotated to rotate the grinding wheel 98, the grinding wheel 100 rotates and moves on a circular orbit. Then, the grinding unit 80 is lowered to bring the rotating grinding wheel 100 into contact with the surface to be ground of the workpiece 1, thereby grinding the workpiece 1. The grinding device 68 has a thickness gauge (not shown) and proceeds with grinding while monitoring the thickness of the workpiece 1. When the thickness of the workpiece 1 reaches a predetermined finishing thickness, the lowering of the grinding unit 80 is stopped and grinding is completed.

[0056] When the workpiece 1 is ground with the grinding wheel 100, processing debris and frictional heat are generated from the workpiece 1 and the grinding wheel 100. The grinding device 68 is equipped with a grinding water supply nozzle (not shown), and while the workpiece 1 is being ground with the grinding wheel 100, grinding water such as pure water is supplied to the workpiece 1 and the like from the grinding water supply nozzle. The processing debris and frictional heat are removed by the grinding water.

[0057] When the workpiece 1 is ground and thinned by the grinding device 68, it is advisable to attach a protective member (not shown) to the surface 1a of the workpiece 1 in order to protect the surface 1a side of the workpiece 1. The protective member is a disk-shaped member having the same diameter as the workpiece 1, and is made of a material such as resin. More specifically, the protective member is a tape-shaped member including an adhesive layer that exerts an adhesive force on the workpiece 1, and a base layer that supports the adhesive layer.

[0058] When a protective member is attached to the front surface 1a of the workpiece 1, the front surface 1a does not come into direct contact with the chuck table 72 when the workpiece 1 is ground from the back surface 1b side. Therefore, no damage occurs to the front surface 1a of the workpiece 1. The workpiece 1 with the protective member attached to the front surface 1a side is placed on the chuck table 72 and held by suction to the chuck table 72.

[0059] When edge trimming is performed on a workpiece 1 such as a wafer, a terrace surface parallel to the surface 1a of the workpiece 1 and a steep wall surface rising from the inner periphery of the terrace surface are formed on the outer periphery 1c of the workpiece 1. The terrace surface and the wall surface may have uneven abrasive grain marks formed due to the abrasive grains contained in the cutting edge portion 60 of the cutting blade 56. In addition, chipping, which is a defect that occurs on the surface 1a of the workpiece 1, may occur near the wall surface.

[0060] A more detailed description will be given below. Fig. 4 is a side view showing a typical state in which a conventional edge trimming process is performed on a workpiece 1. Fig. 3 is a plan view showing a typical positional relationship between a chuck table 18 and a cutting blade 56 when a conventional edge trimming process is performed on a workpiece 1. For convenience of explanation, the workpiece 1, clamps 18b, etc. are omitted in Fig. 3.

[0061] In conventional edge trimming, the orientation of the cutting blade 56 is adjusted so that the tangent of the disk-shaped workpiece 1 is included in the rotation plane of the cutting edge portion 60 at the position where the cutting blade 56 cuts into the outer periphery 1c of the workpiece 1. In other words, the table rotation axis 18d, which is the rotation center of the chuck table 18, and the blade rotation axis 50a, which is the rotation center of the cutting blade 56, intersect. In other words, the tip of the spindle 50 of the cutting unit 24 is directed toward the center of the holding surface 18a.

[0062] During edge trimming, the chuck table 18 that holds the workpiece 1 by suction rotates around the table rotation axis 18d, and the cutting blade 56 rotates around the blade rotation axis 50a. Therefore, at the position where the cutting blade 60 of the cutting blade 56 cuts into the workpiece 1, the movement direction of the outer periphery 1c of the workpiece 1 and the movement direction of the cutting blade 60 coincide with each other. As a result, it is considered that uneven abrasive marks and chipping caused by the abrasive grains of the cutting blade 60 remain on the workpiece 1.

[0063] When grinding the workpiece 1 on which the edge trimming process has been performed and on which abrasive grain marks and the like have been formed, there are cases where impacts cause cracks to form from the abrasive grain marks and the cracks progress into the interior of the wafer, or the abrasive grain marks break into fragments and separate from the workpiece 1, which then reattach to the workpiece 1. Furthermore, there are cases where grinding debris generated when grinding the workpiece 1 gets into the abrasive grain marks and remains on the workpiece 1. When these problems occur, the quality of the chips manufactured by dividing the workpiece 1 decreases, or the amount of normal chips manufactured decreases, resulting in a decrease in the chip manufacturing efficiency.

[0064] Therefore, in the method for processing a workpiece according to this embodiment, edge trimming is performed in a manner that does not leave deep abrasive grain marks or the like on the terrace surface and wall surface formed on the workpiece 1. Hereinafter, the method for processing a workpiece according to this embodiment will be described.

[0065] The wafer processing method according to this embodiment relates to an edge trimming method for a workpiece 1 having a chamfered portion at an outer periphery 1c that extends from a front surface 1a to a back surface 1b. Fig. 11 is a flowchart showing the flow of each step of the wafer processing method according to this embodiment.

[0066] First, in the wafer processing method according to this embodiment, a holding step S10 is performed. In the holding step S10, the workpiece 1 is placed on the holding surface 18a of a chuck table 18 that has a holding surface 18a and can rotate around a table rotation axis 18d that intersects with the holding surface 18a, and the workpiece 1 is held by the chuck table 18.

[0067] The holding step S10 will be described in detail. In the holding step S10, first, the workpiece 1 is transported onto the holding surface 18a of the chuck table 18 of the cutting device 2 (see FIG. 2). If the workpiece 1 is integrated with a tape and an annular frame (not shown), the workpiece 1 is placed on the holding surface 18a via the tape. At this time, the front surface 1a opposite to the back surface 1b, which is the surface to be ground, of the workpiece 1 is directed upward, and the position of the workpiece 1 is adjusted so that the center of the workpiece 1 and the center of the holding surface 18a overlap.

[0068] Thereafter, the suction source of the chuck table 18 is operated to suction and hold the workpiece 1 on the chuck table 18. Furthermore, if the workpiece 1 is integrated with a tape and an annular frame, the annular frame is gripped by the clamps 18b.

[0069] In the method for processing the workpiece according to this embodiment, after the holding step S10, a cutting step S20 is performed in which the cutting blade 56 cuts the chamfered portion of the workpiece 1 to partially remove the workpiece 1. In other words, an edge trimming process is performed.

[0070] The cutting step S20 will be described in detail. In the cutting step S20, the cutting blade 56 having a circular cutting edge 60 on its outer periphery is rotated around the blade rotation axis 50a while the cutting edge 60 of the cutting blade 56 is cut into the chamfered portion of the workpiece 1. Also, the chuck table 18 is rotated around the table rotation axis 18d by one or more revolutions. As a result, the cutting blade 56 cuts the chamfered portion of the workpiece 1, thereby partially removing the workpiece 1.

[0071] The cutting step S20 will be described in more detail. First, the position of the cutting unit 24 is adjusted to position the cutting edge portion 60 of the cutting blade 56 near one end of the holding surface 18a of the chuck table 18. Then, the spindle 50 starts to rotate, and the cutting blade 56 is rotated around the blade rotation axis 50a at a rotation speed of about 30,000 revolutions per minute.

[0072] Next, the cutting blade 56 is lowered to a predetermined height position. Here, the predetermined height position is the height position of the cutting blade 56 when the lowest point of the cutting edge portion 60 of the cutting blade 56 is lower than the surface 1a of the workpiece 1 held by suction on the chuck table 18. More specifically, it is the height position of the cutting blade 56 when the lowest point of the cutting edge portion 60 is lower than the surface 1a of the workpiece 1 at a depth greater than the final finishing thickness of the workpiece 1 after grinding.

[0073] Specifically, the predetermined height position is the height position of the cutting blade 56 when the lowest point of the cutting edge portion 60 is at a height position lower than the front surface 1a of the workpiece 1 by 3 μm to 800 μm. In other words, the cutting depth of the cutting blade 56 in the edge trimming process is preferably 3 μm to 800 μm. However, the predetermined height position is not limited to this. The lowest point of the cutting edge portion 60 may reach a height position lower than the back surface 1b of the workpiece 1.

[0074] For example, the cutting blade 56 is lowered from above the incision position on the outer periphery 1c of the workpiece 1 toward the outer periphery 1c of the workpiece 1 and positioned at a predetermined height. At this time, when the cutting edge portion 60 of the rotating cutting blade 56 comes into contact with the workpiece 1, the workpiece 1 is cut.

[0075] Alternatively, the cutting blade 56 is lowered to a predetermined height position outside the outer periphery 1c of the workpiece 1. Thereafter, the chuck table 18 is moved in a direction parallel to the holding surface 18a, and the cutting edge portion 60 is moved to a cutting position in the outer periphery 1c of the workpiece 1. At this time, when the cutting edge portion 60 of the rotating cutting blade 56 comes into contact with the workpiece 1, the workpiece 1 is cut.

[0076] With the cutting blade 60 cutting into the cutting position of the outer periphery 1c of the workpiece 1, the chuck table 18 is rotated around the table rotation axis 18d by one or more revolutions. Then, the workpiece 1 is cut along the outer periphery 1c, and a part of the chamfered portion is removed. This performs edge trimming on the workpiece 1. Here, the rotation speed of the chuck table 18 may be any value between 0.1° per second and 180° per second.

[0077] In the method for processing a workpiece according to this embodiment, the table rotation axis 18d and the blade rotation axis 50a do not intersect while the cutting blade 56 cuts the chamfered portion of the workpiece 1 in the cutting step S20. Fig. 5 is a plan view showing a schematic positional relationship between the cutting unit 24 and the chuck table 18 when the cutting blade 56 cuts the chamfered portion. For convenience of explanation, the workpiece 1 is omitted in Fig. 5.

[0078] In conventional edge trimming processing, the table rotation axis 18d, which is generally aligned along the Z-axis direction, intersects with the blade rotation axis 50a, as shown in Fig. 3. On the other hand, in the cutting step S20 of the workpiece processing method according to this embodiment, the table rotation axis 18d does not intersect with the blade rotation axis 50a, as shown in Fig. 5.

[0079] Therefore, at the incision position of the cutting blade 60, the movement direction of the workpiece 1 and the movement direction of the cutting blade 60 do not match. In this case, since the workpiece 1 is rotating, the direction of the formed abrasive marks changes significantly with respect to the movement direction of the cutting blade 60 at the next moment. Therefore, even if abrasive marks are formed on the workpiece 1 by the abrasive grains exposed on the outer periphery of the cutting blade 60, the abrasive marks are immediately polished by the cutting blade 60, and the workpiece is flattened. As a result, it is considered that the abrasive marks become shallow or are removed from the workpiece 1.

[0080] Furthermore, when edge trimming processing is performed in a state where the table rotation axis 18d and the blade rotation axis 50a do not intersect, a terrace surface and a wall surface are formed near the outer periphery 1c of the workpiece 1, and a curved surface connecting the terrace surface and the wall surface is also formed.

[0081] Fig. 6 is a side view showing the chuck table 18 and the cutting unit 24 in the cutting step S20 according to one example. Fig. 6 includes a side view showing the workpiece 1. When the table rotation axis 18d and the blade rotation axis 50a do not intersect, a curved surface (R-shape) 17 reflecting the outer peripheral shape of the cutting edge portion 60 of the cutting blade 56 is formed between the terrace surface 13 and the wall surface 15. This curved surface 17 is considered to reinforce the terrace surface 13 and the wall surface 15, and it is considered that cracks and chipping are less likely to occur in the workpiece 1 on which the curved surface 17 is formed.

[0082] Therefore, when edge trimming is performed without intersecting table rotation axis 18d and blade rotation axis 50a, the quality of the chips finally produced by dividing workpiece 1 is improved, or the amount of normal chips produced is increased, i.e., the chip production efficiency is improved.

[0083] Here, the state in which the table rotation axis 18d and the blade rotation axis 50a do not intersect in the cutting step S20 will be further described from another perspective with reference to Fig. 5. First, a plane is assumed that is parallel to the holding surface 18a of the chuck table 18 and includes the center 62 of the cutting edge portion 60 of the cutting blade 56, and a straight line 64 is considered that connects the table rotation axis 18d and the center 62 of the cutting edge portion 60 of the cutting blade 56 on this plane.

[0084] Here, the center 62 of the cutting edge portion 60 of the cutting blade 56 refers to the center in each of the thickness direction, height direction, and front-rear direction of the cutting edge portion 60. In general, the center 62 of the cutting edge portion 60 is located in a through hole into which the spindle 50 is inserted, which passes through the cutting blade 56. The center 62 of the cutting edge portion 60 is a point on the blade rotation axis 50a, as shown in Figures 5 and 6, etc.

[0085] For comparison, a conventional edge trimming process will be described. As shown in Fig. 3, in the conventional edge trimming process, a straight line 64 connecting the table rotation axis 18d and the center 62 of the cutting edge portion 60 of the cutting blade 56 coincides with the blade rotation axis 50a. The angle between this straight line 64 and the blade rotation axis 50a is 0°.

[0086] 5, in the cutting step S20 of the workpiece processing method according to this embodiment, a straight line 64 connecting the table rotation axis 18d and the center 62 of the cutting edge portion 60 of the cutting blade 56 does not coincide with the blade rotation axis 50a. An angle 66 between this straight line 64 and the blade rotation axis 50a is not 0°.

[0087] The larger the angle 66 between the straight line 64 and the blade rotation axis 50a, the less likely abrasive marks will remain on the workpiece 1 during edge trimming, and the fewer cracks and the like formed in the workpiece 1 due to the abrasive marks. Furthermore, the larger the angle 66 between the straight line 64 and the blade rotation axis 50a, the larger the curved surface 17 connecting the terrace surface 13 and the wall surface 15 becomes.

[0088] Fig. 7 is a plan view showing a schematic positional relationship between the cutting unit 24 and the chuck table 18 when the cutting blade 56 cuts the chamfered portion. Fig. 7 shows a schematic positional relationship between the cutting unit 24 and the chuck table 18 in the cutting step S20 according to another example. Here, the angle 66 in Fig. 7 is larger than the angle 66 in Fig. 5. Note that the workpiece 1 is also omitted in Fig. 7 for ease of explanation.

[0089] 8 is a side view showing the chuck table 18 and the cutting unit 24 in the cutting step S20 according to another example. FIG. 8 includes a side view showing the workpiece 1. As can be understood by comparing FIG. 6 and FIG. 8, when the corner 66 becomes relatively large, the curved surface (R shape) 17 caused by the outer peripheral shape of the cutting edge portion 60 of the cutting blade 56 becomes larger. Therefore, when the corner 66 becomes large, the reinforcing effect provided by the curved surface 17 also becomes large.

[0090] Here, an experiment to confirm the relationship between the angle 66 formed by the straight line 64 and the blade rotation axis 50a, and the size of chipping occurring in the workpiece 1 during edge trimming will be described.

[0091] In this experiment, edge trimming was performed on a plurality of workpieces 1, each of which was a silicon wafer having a diameter of 300 mm, a thickness of approximately 780 μm, and a chamfered portion on the outer periphery 1c. In the edge trimming in this experiment, a cutting blade 56 having a cutting edge portion 60 with a thickness of 3 mm and a diameter of 58 mm was used. The rotation speed of the cutting blade 56 was approximately 30,000 revolutions per minute, and the rotation speed of the chuck table 18 was 3° per second. The cutting depth of the cutting blade 56 was 30 μm.

[0092] The edge trimming process performed on each workpiece 1 was performed under the same conditions except that the angle 66 between the straight line 64 and the blade rotation axis 50a was different. The edge trimming process was performed on each workpiece 1 with the angle 66 set to 0°, 1°, 2°, 3°, 5°, 10°, 45°, and 90°. Here, the edge trimming process performed with the angle 66 at 0° is a conventional edge trimming process performed for comparison.

[0093] Then, after performing edge trimming processing on each workpiece 1 under each condition, the end of the surface 1a of each workpiece 1 was observed and the size of the chipping formed was measured. As a result, when the angle 66 was 0°, the average chipping size was 11.5 μm, and similarly, when the angle 66 was 1°, it was 9.1 μm, when it was 2°, it was 5.4 μm, and when it was 3°, it was 4.4 μm. And, when the angle 66 was 5° or more, no significant chipping was formed on the workpiece 1. In other words, the average chipping size was 0.0 μm in all cases.

[0094] From the results of this experiment, it can be seen that when the angle 66 is greater than 0°, chipping of the workpiece 1 caused by the edge trimming process is reduced. In particular, it can be seen that when the angle 66 is 5° or more, chipping of significant size does not occur.

[0095] It is considered that when the angle 66 exceeds 90°, the tendency of chipping to occur until the angle 66 reaches 180° is consistent with the tendency of chipping to occur when the angle 66 reaches from 90° to 0°. This is because the manner in which the cutting edge portion 60 of the cutting blade 56 acts on the workpiece 1 is similar before and after the angle 66 reaches the boundary of 90°. In other words, it is considered that no significant chipping occurs in the edge trimming process until the angle 66 exceeds 175°, and the average size of chipping increases until the angle 66 reaches 180°.

[0096] Therefore, in a plane parallel to the holding surface 18a and including the center 62 of the cutting edge 60 of the cutting blade 56, it is preferable that the angle 66 formed by the straight line 64 connecting the table rotation axis 18d and the center 62 of the cutting edge 60 of the cutting blade 56 and the blade rotation axis 50a is not 0° or 180°. More preferably, the angle 66 is 5° or more and 175° or less.

[0097] When the cutting step S20 described above is carried out to perform edge trimming on the workpiece 1, abrasive marks and chipping are less likely to occur on the workpiece 1. Therefore, the quality of the chips formed by subsequently thinning and dividing the workpiece 1 is improved.

[0098] In the method for processing a plate-like object according to this embodiment, a grinding step S30 may be carried out next. Next, the grinding step S30 will be described. In the grinding step S30, the workpiece 1 is ground from the back surface 1b to reduce the thickness to a finishing thickness.

[0099] The grinding step S30 is performed by a grinding device 68 shown in Fig. 9. If tape is attached to the back surface 1b of the workpiece 1, the tape is peeled off from the workpiece 1. Also, a tape-like protective member (not shown) may be attached to the front surface 1a of the workpiece 1. In this case, the device 5 and the like formed on the front surface 1a of the workpiece 1 are protected.

[0100] In the grinding step S30, the front surface 1a of the workpiece 1 is faced downward, and the back surface 1b, which is to be ground, is faced upward. In this state, the workpiece 1 is placed on the holding surface 72a of the chuck table 72, and the workpiece 1 is suction-held by the chuck table 72. The chuck table 72 is moved to the processing area 78.

[0101] Next, the spindle 94 is rotated to rotate the grinding wheel 98, and the grinding wheel 100 is moved on the circular orbit. Then, the grinding unit 80 starts to descend, and the bottom surface of the moving grinding wheel 100 is brought into contact with the back surface 1b of the workpiece 1, thereby starting grinding of the workpiece 1. Fig. 10 is a cross-sectional view that typically shows the grinding step S30.

[0102] In the grinding step S30, the thickness of the workpiece 1 is monitored by a thickness measuring device (not shown), and when it is confirmed that the thickness of the workpiece 1 has reached the specified finishing thickness, the grinding unit 80 stops descending and ends grinding of the workpiece 1. Since no chamfer remains on the outer periphery 1c of the workpiece 1 after grinding, no knife-edge shape is created in the cross-sectional shape of the workpiece 1, and there is no risk of damage to the workpiece 1 due to the knife-edge shape.

[0103] After the grinding step S30 is performed, a dividing step S40 may be performed in which the workpiece 1 is divided along the planned dividing lines 3 to produce individual chips. For dividing the workpiece 1, for example, a cutting device 2 shown in Fig. 2 is used. In the dividing step S40, the workpiece 1 is cut along the planned dividing lines 3 with a cutting blade 56 to divide the workpiece 1.

[0104] As described above, in the method for processing a plate-like object according to this embodiment, the edge trimming process performed in the cutting step S20 suppresses the occurrence of abrasive marks and chipping on the workpiece 1. In other words, the edge trimming process can be performed with high quality. This improves the quality of the chips produced by dividing the workpiece 1, or increases the amount of normal chips produced, thereby improving the chip production efficiency.

[0105] The present invention is not limited to the above embodiment, and can be modified in various ways. For example, the above embodiment has been described with reference to the case where the terrace surface 13 and the wall surface 15 are formed on the outer periphery 1c of the workpiece 1 by the cutting step S20, as shown in FIG. However, one aspect of the present invention is not limited to this.

[0106] That is, in the cutting step S20, it is not necessary to form both the wall surface 15 and the terrace surface 13 on the workpiece 1, and only one of them may be formed, or neither may be formed. For example, in the cutting step S20 shown in Fig. 8, the wall surface 15 is not formed on the outer periphery 1c of the workpiece 1, and the curved surface 17 is connected to the surface 1a of the workpiece 1. Also, for example, in the cutting step S20, the terrace surface 13 is not formed on the outer periphery 1c of the workpiece 1, and the curved surface 17 is connected to the outer periphery of the workpiece 1.

[0107] Furthermore, in the cutting step S20, it is not necessary to clearly define the boundary between the curved surface 17 formed on the workpiece 1 and the wall surface 15 or the terrace surface 13. If the terrace surface 13 and the wall surface 15 are not directly connected but are connected via the curved surface 17, the curved surface 17 can reinforce the workpiece 1.

[0108] In the above embodiment, the position of the cutting blade 56 is not changed while the chuck table 18 rotates in the cutting step S20, but this aspect of the present invention is not limited to this. Also, the edge trimming process is performed over the entire circumference of the workpiece 1 by one rotation of the chuck table 18, but this aspect of the present invention is not limited to this.

[0109] For example, while the cutting blade 56 cuts into the outer periphery 1c of the workpiece 1, the cutting blade 56 may move parallel to the holding surface 18a so as to approach the center of the workpiece 1, and the chuck table 18 may rotate two or more times. In other words, the cutting blade 56 may cut gradually inward from the outer periphery 1c of the workpiece 1.

[0110] For example, in the cutting step S20, while the chuck table 18 is rotated by an amount of five revolutions, the cutting blade 56 is gradually cut into the workpiece 1 from the outer periphery 1c toward the center. When the edge trimming process is gradually performed in this manner, the amount of the workpiece 1 removed by the cutting edge portion 60 of the cutting blade 56 per unit time becomes relatively small, so that the load on the cutting edge portion 60 of the cutting blade 56 can be reduced.

[0111] In addition, the structures, methods, etc. according to the above-described embodiments can be modified as appropriate without departing from the scope of the object of the present invention. [Explanation of symbols]

[0112] 1 Workpiece 1a surface 1b back side 1c outer periphery 3. Planned division line 5 Devices 7 Device formation area 9 Surplus outer area 11 Notches 13 Terrace surface 15 Wall 17 Curved surface 2 Cutting equipment 4 Foundation 4a,4b,4c opening 8 Cassette Support Stand 10 Cassettes 12 Guide rail 14 Table Cover 16 Dust-proof / water-proof cover 18 Chuck table 18a Holding surface 18b Clamp 18c Porous material 18d Table rotation axis 20 Support part 22a, 22b Mobile unit 24, 24a, 24b Cutting unit 26 Y-axis guide rail 28a, 28b Y-axis moving plate 30a, 30b Y-axis ball screw 32a Y-axis pulse motor 34a, 34b Z-axis guide rail 36a, 36b Z-axis moving plate 38a, 38b Z-axis ball screw 40a, 40b Z-axis pulse motor 46a, 46b Camera unit 48 Cleaning Unit 50 Spindle 50a Blade Rotation Shaft 52 Flange mechanism 54 Fixing nut 56 Cutting Blade 58 Foundation 60 Cutting edge 62 center 66 angle 68 Grinding Equipment 70 Foundations 70a aperture 72 Chuck Table 72a Holding surface 74 X-axis moving table 76 Loading / unloading area 78 Processing area 80 Grinding Unit 82 Support part 84 Z-axis guide rail 86 Z-axis moving plate 88 Z-axis ball screw 90 Z-axis pulse motor 92 Spindle housing 94 Spindle 96 Wheel mount 98 Grinding Wheel 100 Grinding Wheel

Claims

1. A method for processing a workpiece, comprising the steps of: cutting an outer periphery of a workpiece having a chamfered portion on the outer periphery to perform edge trimming, the method comprising the steps of: a holding step of placing the workpiece on a holding surface of a chuck table which has a holding surface and is rotatable around a table rotation axis which intersects with the holding surface, and holding the workpiece with the chuck table; a cutting step in which, after the holding step, an annular cutting blade having a cutting edge portion on its outer periphery is rotated around a blade rotation axis while the cutting edge portion of the cutting blade is cut into the chamfered portion of the workpiece, and the chuck table is rotated around the table rotation axis by one or more revolutions, thereby cutting the chamfered portion of the workpiece with the cutting blade to partially remove the workpiece, The method for processing a workpiece, wherein in the cutting step, while the cutting blade is cutting the chamfered portion of the workpiece, the table rotation axis and the blade rotation axis do not intersect.

2. 2. The method for processing a workpiece according to claim 1, characterized in that, during the cutting step, when the cutting blade is used to cut the chamfered portion of the workpiece, an angle formed by a straight line connecting the table rotation axis and the center of the cutting edge portion of the cutting blade and the blade rotation axis in a plane parallel to the holding surface and including the center of the cutting edge portion of the cutting blade is 5° or more and 175° or less.

Images