JP2022130936A - Method for processing wafer - Google Patents

Abstract

To provide a method for processing a wafer capable of setting to zero or reducing the percentage of devices that are damaged by edge trimming and reducing the probability of a wafer breaking and/or the probability of a contamination source or a dust source being formed on a laminated wafer.SOLUTION: An outer edge portion of a wafer is processed with a width that varies in accordance with the spacing between a center of the wafer and a boundary between a device area on which a plurality of devices is formed and an outer surplus area surrounding the device area. In other words, the width of the outer edge portion to be removed by edge trimming of the wafer is set in accordance with the spacing between the boundary between the center of the wafer and the device area and the outer excess area .SELECTED DRAWING: Figure 3

Description

TECHNICAL FIELD The present invention relates to a method of processing a wafer having a device region in which a plurality of devices are formed and an outer peripheral marginal region surrounding the device region on its surface and having a chamfered outer peripheral edge.

Device chips such as ICs (Integrated Circuits) and LSIs (Large Scale Integration) are essential components in various electronic devices such as mobile phones and personal computers. Such chips are manufactured, for example, by forming a large number of devices on the surface of a wafer and then dividing the wafer into regions each including individual devices.

Wafers used for manufacturing chips are likely to break starting from chips formed at the outer peripheral edge. Therefore, in the chip manufacturing process, it is common to chamfer the outer peripheral edge of the wafer prior to various processes. Furthermore, in the chip manufacturing process, the wafer is often thinned by grinding the back side of the wafer prior to dividing the wafer for the purpose of miniaturizing the chips to be manufactured.

However, when the wafer is thinned by grinding the back side of the wafer whose outer peripheral edge is chamfered, the outer peripheral edge on the back side of the wafer becomes a sharp edge (knife edge). Stress concentrates on this outer peripheral edge, and chipping is likely to occur. Therefore, in the chip manufacturing process, prior to grinding the wafer, edge trimming is sometimes performed to remove part or all of the chamfered outer peripheral edge of the wafer (see, for example, Patent Documents 1 and 2). .

Such edge trimming is performed, for example, in the following order. First, the wafer is held by a holding table that has a holding surface for holding the wafer and is rotatable about a rotation axis that passes through the center of the holding surface. Then, while rotating the holding table, the processing point for edge trimming is positioned at a constant distance from the center of the holding surface, and the outer peripheral edge of the wafer is processed. This removes part or all of the chamfered outer peripheral edge from the wafer.

However, the wafer may be placed on the holding surface with its center offset from the center of the holding surface. If edge trimming is performed with the processing point positioned at a constant distance from the center of the holding surface in this state, the distance between the center of the wafer and the processing point varies. In view of this point, even when the center of the wafer and the center of the holding surface are displaced, a method of making the distance between the center of the wafer and the processing point of edge trimming constant has also been proposed (for example, Patent Document 3).

In this method, first, the positions of three points on the outer periphery of the wafer are measured, and the position of the center of the wafer is calculated based on the measured positions of the three points. Next, the amount of deviation between the center of the holding surface of the holding table and the center of the wafer is calculated. Next, the holding table is rotated so that the distance between the center of the wafer and the processing point is maintained constant, and the outer peripheral edge of the wafer is processed while changing the distance between the center of the holding surface and the processing point. do.

In addition, edge trimming is applied to wafers used for manufacturing chips of devices such as TSV (Through-Silicon Via) and BSI (Back Side Illumination) type CMOS (Complementary Metal Oxide Semiconductor) sensors. It may be implemented against (for example, see Patent Document 4).

Specifically, such a device is manufactured using two wafers bonded together (bonded wafer). An unbonded portion, in which the wafers are not sufficiently bonded to each other, is likely to be formed in the portion. Such an unbonded portion tends to accumulate dust and become a source of contamination or generation of dust. Therefore, edge trimming may be performed on at least one of the two wafers prior to bonding the two wafers together so that such sources of contamination or dust are not formed.

JP-A-2000-173961 JP 2006-108532 A JP-A-2006-93333 JP-A-10-242091

In order to reduce chip manufacturing costs, it is preferable to form as many devices as possible on the surface of the wafer. That is, the devices are preferably formed not only in the central area of the surface of the wafer but also in the area near the periphery of the wafer.

On the other hand, in order to prevent the wafer from cracking and/or not to form a source of contamination or dust in the bonded wafer as described above, sufficient edge trimming is required prior to grinding the back side of the wafer. preferably done. That is, edge trimming is preferably performed not only on the area near the outer periphery of the wafer, but also on a wide area extending to the inner area.

In view of these two conflicting demands, an object of the present invention is to eliminate or reduce the percentage of devices damaged by edge trimming, and to reduce the probability of wafer cracking and/or contamination sources or dust generation in bonded wafers. An object of the present invention is to provide a wafer processing method capable of reducing the probability that a source is formed.

According to the present invention, there is provided a method for processing a wafer having, on its surface, a device region in which a plurality of devices are formed and an outer peripheral surplus region surrounding the device region, the outer peripheral end being chamfered, the method comprising: a holding step of holding the wafer on a holding table that has a holding surface for holding the wafer and is rotatable on a rotation axis passing through the center of the holding surface; at least part of the plurality of devices and the outer periphery of the wafer; A boundary identifying step of identifying a boundary between the device region and the outer peripheral surplus region based on an image formed by imaging an area including the boundary while moving a processing point along the outer periphery of the holding surface By adjusting the distance between the center of the holding surface and the processing point according to the distance between the wafer and the center of the wafer, the width of the wafer varies according to the distance between the boundary and the center of the wafer. and a processing step of processing the outer peripheral edge.

Further, the processing step is preferably performed by cutting into the wafer with a cutting blade mounted on the tip of a rotatable spindle.

Alternatively, the processing step is preferably performed by irradiating the wafer with a laser beam of a wavelength that is absorbed by the wafer.

Alternatively, the processing step is formed inside the wafer by irradiating the wafer with the laser beam with the focal point of the laser beam having the wavelength that passes through the wafer positioned inside the wafer. It is preferably performed by breaking the wafer along the deteriorated layer.

In the present invention, the outer peripheral edge of the wafer is processed with a width that varies according to the distance between the center of the wafer and the boundary of the device region in which a plurality of devices are formed and the peripheral surplus region surrounding the device region. In other words, in the present invention, the width of the outer peripheral edge removed by edge trimming of the wafer is set according to the distance between the boundary of the device region and outer peripheral surplus region and the center of the wafer.

In short, if the distance between this boundary and the center of the wafer is long, edge trimming is performed to reduce this width. This can eliminate or reduce the percentage of devices damaged by edge trimming. Also, if the distance between this boundary and the center of the wafer is short, edge trimming is performed to widen this width. As a result, in the process after edge trimming, the probability that the wafer will crack and/or the probability that a contamination source or a dust source will form in the bonded wafer can be reduced.

FIG. 1 is a perspective view schematically showing an example of a processing device. FIG. 2A is a top view schematically showing an example of a wafer, and FIG. 2B is a cross-sectional view schematically showing an example of a wafer. FIG. 3 is a flow chart schematically showing an example of the processing method. FIG. 4 is a top view schematically showing an example of wafers placed on the holding table. FIG. 5A is a top view schematically showing an example of a wafer on which edge trimming is performed, and FIG. 5B is a cross-sectional view schematically showing an example of a wafer on which edge trimming is performed. It is a diagram. FIG. 6A is a top view schematically showing an example of a wafer on which edge trimming is performed, and FIG. 6B is a cross-sectional view schematically showing an example of a wafer on which edge trimming is performed. It is a diagram. FIG. 7A is a top view schematically showing an example of a wafer on which edge trimming has been performed, and FIG. 7B is a cross-sectional view schematically showing an example of a wafer on which edge trimming has been performed. It is a diagram. FIG. 8A is a top view schematically showing an example of a wafer on which edge trimming is performed, and FIG. 8B is a cross-sectional view schematically showing an example of a wafer on which edge trimming is performed. It is a diagram. FIG. 9A is a top view schematically showing an example of a wafer on which edge trimming is performed, and FIG. 9B is a cross-sectional view schematically showing an example of a wafer on which edge trimming is performed. It is a diagram. FIG. 10A is a top view schematically showing an example of a wafer subjected to edge trimming, and FIG. 10B is a cross-sectional view schematically showing an example of a wafer subjected to edge trimming. It is a diagram. FIG. 11A is a top view schematically showing an example of a wafer subjected to edge trimming, and FIG. 11B is a cross-sectional view schematically showing an example of a wafer subjected to edge trimming. It is a diagram. FIG. 12A is a top view schematically showing an example of an edge-trimmed wafer, and FIG. 12B is a side view schematically showing an example of an edge-trimmed wafer. FIG. 13 is a perspective view schematically showing an example of a laser irradiation device. FIG. 14 is a top view schematically showing an example of a wafer placed on the holding surface of the holding table with the center of the wafer shifted from the center of the holding surface of the holding table. FIG. 15 is a flow chart schematically showing another example of the processing method. FIG. 16 is a top view schematically showing an example of a wafer with the holding table shown in FIG. 14 rotated.

Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a perspective view schematically showing an example of a cutting device that serves as a processing device for processing a wafer. Note that the X-axis direction (front-rear direction) and the Y-axis direction (left-right direction) shown in FIG. It is a direction (vertical direction) orthogonal to the axial direction.

The cutting device 2 shown in FIG. 1 includes a base 4 that supports each component. The upper surface of the base 4 is formed with a rectangular opening 4a whose longitudinal direction is parallel to the X-axis direction. A flat plate-like cover 6 and a bellows-like cover 8 that expands and contracts as the cover 6 moves are provided in the opening 4a.

A holding table 10 is provided above the cover 6 . The holding table 10 has a disk-shaped porous plate 10a exposed upward. The upper surface of the porous plate 10a is generally parallel and serves as the holding surface of the holding table 10 that holds the wafer. An X-axis direction moving mechanism (not shown) is provided below the covers 6 and 8 to move the cover 6 and the holding table 10 along the X-axis direction.

FIG. 2A is a top view schematically showing an example of a wafer held on the holding surface of the holding table 10, and FIG. 2B is a cross-sectional view schematically showing this wafer. The wafer 11 shown in FIGS. 2A and 2B is made of a semiconductor material such as Si (silicon), SiC (silicon carbide), or GaN (gallium nitride).

A front surface 11a of the wafer 11 is partitioned into a plurality of regions by a plurality of planned dividing lines set in a grid pattern. Devices 13 such as ICs or LSIs are formed in each of the plurality of regions except for a portion of the region adjacent to the outer periphery of the wafer 11 . That is, the front surface 11a of the wafer 11 includes a device region 15a in which a plurality of devices 13 are formed, and an outer peripheral surplus region 15b surrounding the device region 15a.

Also, the outer peripheral edge of the wafer 11 is chamfered. That is, the side surface 11b of the wafer 11 is curved so as to protrude outward. Then, the back surface 11c of the wafer 11 is placed on the holding surface of the holding table 10 (upper surface of the porous plate 10a) directly or via a dicing tape (not shown).

A suction path (not shown) is formed inside the holding table 10 , one end of which is connected to a suction source (not shown) such as an ejector provided outside the holding table 10 . The other end of this suction path reaches the porous plate 10a. Therefore, when the suction source is operated while the wafer 11 is placed on the holding surface, the wafer 11 is held by the holding table 10 by suction.

Further, the holding table 10 is connected to a holding table rotation drive source (not shown) such as a motor. When this holding table rotation drive source is operated, the holding table 10 rotates around the rotation axis passing through the center of the holding surface and along the Z-axis direction.

A support structure 12 is provided in the vicinity of the opening 4 a on the top surface of the base 4 . The support structure 12 includes an upright portion 12a extending along the Z-axis direction from the upper surface of the base 4, and an arm extending along the Y-axis direction from the upper end of the upright portion 12a across the opening 4a. and a portion 12b. A Y-axis direction moving mechanism 14 is provided on the front side of the arm portion 12b.

The Y-axis movement mechanism 14 includes a pair of Y-axis guide rails 16 fixed to the front surface of the arm portion 12b and extending along the Y-axis direction. A Y-axis moving plate 18 is connected to the front side of the pair of Y-axis guide rails 16 so as to be slidable along the pair of Y-axis guide rails 16 .

A screw shaft 20 extending along the Y-axis direction is arranged between the pair of Y-axis guide rails 16 . A motor (not shown) for rotating the screw shaft 20 is connected to one end of the screw shaft 20 . A nut portion (not shown) that accommodates balls rolling on the surface of the rotating screw shaft 20 is provided on the surface of the screw shaft 20 on which the helical groove is formed, thereby forming a ball screw.

That is, when the screw shaft 20 rotates, the balls circulate in the nut portion and the nut portion moves along the Y-axis direction. Also, this nut portion is fixed to the rear surface side of the Y-axis moving plate 18 . Therefore, when the screw shaft 20 is rotated by a motor connected to one end of the screw shaft 20, the Y-axis moving plate 18 moves along the Y-axis direction together with the nut portion.

A Z-axis movement mechanism 22 is provided on the front side of the Y-axis movement plate 18 . The Z-axis movement mechanism 22 includes a pair of Z-axis guide rails 24 fixed to the front surface of the Y-axis movement plate 18 and extending along the Z-axis direction. A Z-axis movement plate 26 is connected to the front side of the pair of Z-axis guide rails 24 in a manner slidable along the pair of Z-axis guide rails 24 .

A screw shaft 28 extending along the Z-axis direction is arranged between the pair of Z-axis guide rails 24 . A motor 30 for rotating the screw shaft 28 is connected to one end of the screw shaft 28 . The helical grooved surface of the screw shaft 28 is provided with a nut portion (not shown) that accommodates balls rolling on the surface of the rotating screw shaft 28, thereby forming a ball screw.

That is, when the screw shaft 28 rotates, the balls circulate in the nut portion and the nut portion moves along the Z-axis direction. Also, this nut portion is fixed to the rear surface side of the Z-axis moving plate 26 . Therefore, when the screw shaft 28 is rotated by the motor 30, the Z-axis movement plate 26 moves along the Z-axis direction together with the nut portion.

A cutting unit 32 is fixed below the Z-axis moving plate 26 . The cutting unit 32 has a tubular spindle housing 34 whose longitudinal direction is parallel to the Y-axis direction. The spindle housing 34 accommodates a cylindrical spindle (not shown) whose longitudinal direction is parallel to the Y-axis direction. This spindle is rotatably supported by a spindle housing 34 .

The distal end of this spindle protrudes out of the spindle housing 34 and is fitted with a cutting blade 36 having an annular cutting edge. The base end of the spindle is connected to a rotary drive source (not shown) for cutting blades, such as a motor built in the spindle housing 34 . When this cutting blade rotary drive source is operated, the cutting blade 36 rotates along with the spindle along the Y-axis direction.

An imaging unit 38 fixed to the lower portion of the Z-axis moving plate 26 is provided at a position adjacent to the cutting unit 32 in the X-axis direction. The imaging unit 38 includes, for example, a light source such as an LED (Light Emitting Diode), an objective lens, and an imaging element such as a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor.

FIG. 3 is a flow chart schematically showing an example of a method for processing the wafer 11 in a processing device such as the cutting device 2. As shown in FIG. In this method, first, the wafer 11 is held by the holding table 10 (holding step: S1). For example, while the wafer 11 is placed on the holding surface of the holding table 10, a suction source connected to a suction path formed inside the holding table 10 is operated.

Next, the boundary between the device region 15a and the peripheral surplus region 15b of the wafer 11 is specified (boundary specifying step: S2). This identification is performed based on an image formed by imaging an area including the outer periphery of the wafer 11 and a portion of the plurality of devices 13 . Formation of this image is performed, for example, in the following order.

First, with the center of the field of view of the imaging unit 38 positioned slightly inside the outer periphery of the wafer 11 and the field of view including the outer periphery of the wafer 11 and at least one device 13, the imaging unit 38 An image of the wafer 11 is taken. Furthermore, after rotating the holding table 10 by operating the holding table rotation driving source so that the field of view of the imaging unit 38 partially overlaps before and after the holding table 10 rotates, the imaging unit 38 takes an image of the wafer 11 . . Further, the same processing is repeated multiple times until the holding table 10 rotates once.

This forms an image of the area including the outer periphery of the wafer 11 and a portion of the plurality of devices 13 . Then, the boundary between the device region 15a of the wafer 11 and the peripheral surplus region 15b is specified based on this image. For example, a polygonal line obtained by connecting the sides or points of the outermost device 13 among the plurality of devices 13 formed on the surface 11a of the wafer 11 is the boundary between the device region 15a and the peripheral surplus region 15b. identified as a boundary.

Next, the outer peripheral edge of the wafer 11 is processed with a width (processing width for edge trimming) that varies according to the distance between this boundary and the center of the wafer 11 (processing step: S3). In short, the processing width of edge trimming is set so that the longer the distance between the boundary and the center of the wafer 11, the narrower the width, and the narrower the distance between the boundary and the center of the wafer 11, the wider the width. This point will be described in detail with reference to FIG. 4 is a top view schematically showing the wafer 11 placed on the holding table 10. As shown in FIG.

A two-dot chain line A shown in FIG. 4 represents a concentric circle around the outer circumference of the wafer 11 whose radius is a length (reference length) obtained by subtracting a reference width (for example, 3 mm) for edge trimming from the radius of the wafer 11. The two-dot chain line A overlaps a part of the outermost device 13 among the plurality of devices 13 formed on the surface 11 a of the wafer 11 .

Specifically, the two-dot chain line A overlaps the devices 13d, 13j, 13k, etc., and does not overlap the devices 13a, 13b, 13c, 13e, 13f, 13g, 13h, 13i, 13l, etc. That is, the distance between the center of the wafer 11 and the boundary between the device region 15a near the devices 13d, 13j, 13k, and the like and the peripheral surplus region 15b is longer than the standard length.

When the interval is longer than the reference length in this way, the processing width for edge trimming is set narrower than the reference width. For example, the processing width is set narrower than the reference width for edge trimming within the maximum decrement value (for example, 0.5 mm). A dotted line B on the outside of the two-dot chain line A shown in FIG. 4 represents a concentric circle on the outer circumference of the wafer 11 whose radius is the length (maximum length) obtained by adding the maximum decrement value to the above reference length. .

Although this dotted line B overlaps the device 13j and the like, it does not overlap the devices 13d, 13k and the like. Therefore, by setting the processing width for edge trimming in this way, damage to the devices 13d, 13k and the like can be prevented. Although damage to the devices 13j and the like is unavoidable, edge trimming is performed with the minimum necessary processing width even in the vicinity of the devices 13j and the like, thereby suppressing an increase in the probability of cracking of the edge-trimmed wafer 11. .

Further, the distance between the boundary between the device region 15a near the devices 13a, 13b, 13c, 13e, 13f, 13g, 13h, 13i, 13l, etc. and the peripheral surplus region 15b and the center of the wafer 11 is the above reference length shorter than

In this way, when the interval is shorter than the reference length, the processing width for edge trimming is set wider than the reference width. For example, the processing width is set wider than the reference width for edge trimming within the maximum incremental value (for example, 0.5 mm). A dotted line C on the inside of the two-dot chain line A shown in FIG. 4 represents a concentric circle around the outer periphery of the wafer 11 whose radius is the length (shortest length) obtained by subtracting the maximum increment value from the reference length.

This dotted line C does not overlap the devices 13a, 13f, 13g, 13h, and the like. Therefore, the devices 13a, 13f, 13g, 13h, etc. are not damaged even if the processing width of the edge trimming is set to be wide. In addition, edge trimming is performed with a sufficient processing width in the vicinity of the devices 13a, 13f, 13g, 13h, etc., thereby reducing the probability that the edge-trimmed wafer 11 will crack.

Then, in the processing step (S3), edge trimming is performed while varying the processing width as described above. Specifically, this edge trimming is performed by moving the processing point along the outer circumference of the holding surface of the holding table 10 and adjusting the distance between the boundary between the device area 15a and the outer peripheral surplus area 15b and the center of the wafer 11. This is done by adjusting the distance between the center of the holding surface and the processing point. An example of such edge trimming will be described in detail with reference to FIGS. 5-11.

5 to 11A are top views schematically showing the wafer 11 on which edge trimming is performed, and FIGS. 5 to 11B are edge trimming performed. 2 is a cross-sectional view schematically showing a wafer 11; FIG. 5 to 11A schematically show the upper surface of the cutting blade 36 for convenience. 5 to 11B schematically show the side surface of the cutting blade 36 for convenience. As the cutting blade 36, a cutting blade having a width wider than the sum of the reference width for edge trimming and the maximum increment value is used.

When edge trimming the wafer 11, first, the cutting blade 36 is positioned directly above the region between the outer periphery of the wafer 11 and the device 13a. Specifically, the X-axis movement mechanism adjusts the position of the holding table 10 and the Y-axis movement mechanism 14 adjusts the position of the cutting unit 32 . At this time, the distance between the center of the wafer 11 and the area concerned is adjusted to be the shortest length described above (see FIGS. 5A and 5B).

Next, the cutting blade 36 is cut into the wafer 11 while rotating the cutting blade 36 by operating the rotary drive source for the cutting blade. For example, the Z-axis movement mechanism 22 lowers the cutting unit 32 so that the lowermost end of the cutting blade 36 is positioned lower than the front surface 11a of the wafer 11 and higher than the rear surface 11c. As a result, the portion where the cutting blade 36 and the chamfered outer peripheral edge of the wafer 11 come into contact becomes a processing point, and a portion of the wafer 11 at that portion is removed (FIGS. 6A and 6B). B)).

Next, while the cutting blade 36 is being rotated, the holding table rotation drive source rotates the holding table 10, and the Y-axis direction moving mechanism 14 moves the cutting unit 32 so that the cutting blade 36 is separated from the center of the wafer 11. position. For example, the Y-axis direction moving mechanism 14 moves the center of the wafer 11 and the cutting blade 36 at the timing when a straight line passing through the center of the wafer 11 and the farthest point of the device 13d from the center of the wafer 11 becomes parallel to the Y-axis direction. The cutting unit 32 is gradually separated from the center of the wafer 11 so that the distance from the lowest end becomes the maximum length described above (see FIGS. 7A and 7B).

Next, while rotating the cutting blade 36 and the holding table 10 , the Y-axis movement mechanism 14 adjusts the position of the cutting unit 32 so that the cutting blade 36 approaches the center of the wafer 11 . For example, the Y-axis direction moving mechanism 14 moves the center of the wafer 11 and the cutting blade 36 at the timing when a straight line passing through the center of the wafer 11 and the farthest point of the device 13f from the center of the wafer 11 becomes parallel to the Y-axis direction. The cutting unit 32 is gradually brought closer to the center of the wafer 11 so that the distance from the lowermost end becomes the shortest length described above (see FIGS. 8A and 8B).

Next, while rotating the cutting blade 36 and the holding table 10, the distance between the center of the wafer 11 and the cutting blade 36 is maintained. For example, the Y-axis direction moving mechanism 14 does not move the cutting unit 32 until a straight line passing through the center of the wafer 11 and the farthest point of the device 13h from the center of the wafer 11 becomes parallel to the Y-axis direction (see FIG. 9 ( A) and FIG. 9B).

Next, while rotating the cutting blade 36 and the holding table 10 , the Y-axis movement mechanism 14 adjusts the position of the cutting unit 32 so that the cutting blade 36 is separated from the center of the wafer 11 . For example, the Y-axis direction moving mechanism 14 moves the center of the wafer 11 and the cutting blade 36 at the timing when a straight line passing through the center of the wafer 11 and the farthest point of the device 13j from the center of the wafer 11 becomes parallel to the Y-axis direction. The cutting unit 32 is gradually separated from the center of the wafer 11 so that the distance from the lowest end becomes the maximum length described above (see FIGS. 10A and 10B).

Next, while rotating the cutting blade 36 and the holding table 10, the distance between the center of the wafer 11 and the cutting blade 36 is maintained. For example, the Y-axis movement mechanism 14 does not move the cutting unit 32 while the device 13j among the plurality of devices formed on the front surface 11a of the wafer 11 is the device closest to the edge trimming processing point.

Next, while rotating the cutting blade 36 and the holding table 10 , the Y-axis movement mechanism 14 adjusts the position of the cutting unit 32 so that the cutting blade 36 approaches the center of the wafer 11 . For example, the Y-axis direction moving mechanism 14 moves the center of the wafer 11 and the cutting blade 36 at the timing when a straight line passing through the farthest point of the device 13l from the center of the wafer 11 and the center of the wafer 11 becomes parallel to the Y-axis direction. The cutting unit 32 is gradually brought closer to the center of the wafer 11 so that the distance from the lowermost end becomes the above reference length (see FIGS. 11A and 11B).

Edge trimming of about 1/4 of the outer peripheral end portion of the wafer 11 is thus completed. Edge trimming of the remaining 3/4 of the outer peripheral edge of the wafer 11 is also performed in the same manner as described above. As a result, as shown in FIGS. 12(A) and 12(B), a wafer 11 having a step 11d formed at the outer peripheral edge by edge trimming is obtained.

12A is a top view schematically showing the wafer 11 after edge trimming, and FIG. 12B is a side view schematically showing the wafer 11 after edge trimming. For convenience, FIG. 12A also shows a dotted line B representing a concentric circle of the wafer whose radius is the longest length and a dotted line C representing a concentric circle of the wafer 11 whose radius is the shortest length.

In the method shown in FIG. 3, the width of the wafer 11 is varied according to the distance between the center of the wafer 11 and the boundary of the device region 15a in which the plurality of devices 13 are formed and the peripheral surplus region 15b surrounding the device region 15a. is processed. In other words, in this method, the width of the outer edge of the wafer 11 removed by edge trimming is set according to the distance between the center of the wafer 11 and the boundary between the device region 15a and the outer peripheral surplus region 15b.

In short, if the distance between this boundary and the center of the wafer 11 is long, edge trimming is performed so that this width becomes narrow. This can eliminate or reduce the percentage of devices damaged by edge trimming. Also, if the distance between this boundary and the center of the wafer 11 is short, edge trimming is performed so as to widen this width. As a result, in the process after the edge trimming, the probability that the wafer 11 will crack and/or the probability that a contamination source or a dust source will be formed in the bonded wafer using the wafer 11 can be reduced.

Note that the above-described method is one aspect of the present invention, and the method of the present invention is not limited to the above-described method. For example, in the processing step (S3) of the method described above, edge trimming is performed so as to leave a portion of the outer peripheral edge of the wafer 11 on the back surface 11c side. ), the entire outer peripheral edge of the wafer 11 may be removed.

In other words, in the processing step (S3) of the method of the present invention, the side surface perpendicular to the front surface 11a and the rear surface 11c of the wafer 11 is formed without forming the step 11d at the outer peripheral edge of the wafer 11. Edge trimming may be performed.

Such edge trimming is performed, for example, with the lowermost end of the cutting blade 36 positioned below the back surface 11c of the wafer 11, as described with reference to FIGS. It is done by machining the ends.

In this case, a dicing tape is preferably attached to the rear surface 11c side of the wafer 11. As shown in FIG. That is, it is preferable that edge trimming of the wafer 11 is performed while the wafer 11 is held on the holding table 10 via this dicing tape.

In addition, in the processing step (S3) of the method described above, the Z-axis direction moving mechanism 22 lowers the cutting unit 32 to cut the cutting blade 36 into the wafer 11, but the processing step of the method of the present invention is performed. In ( S<b>3 ), the cutting blade 36 may cut into the wafer 11 by moving the holding table 10 with the X-axis direction moving mechanism.

When performing edge trimming on the wafer 11 in this way, first, the X-axis direction moving mechanism moves the holding table 10 along the X-axis direction so that the cutting blade 36 is separated from the wafer 11 . Next, the Y-axis direction moving mechanism 14 moves the cutting unit 32 along the Y-axis direction so that the region between the outer periphery of the wafer 11 and the device 13a as seen from the cutting blade 36 is arranged in the X-axis direction.

At this time, the distance between the center of the wafer 11 and the area concerned is adjusted to be the shortest length described above. Next, the Z-axis movement mechanism 22 lowers the cutting unit 32 so that the lowest end of the cutting blade 36 is positioned at a position lower than the front surface 11a of the wafer 11 and higher than the rear surface 11c. Next, the cutting blade 36 is cut into the wafer 11 while rotating the cutting blade 36 by operating the rotary drive source for the cutting blade.

Specifically, the X-axis direction moving mechanism moves the holding table 10 along the X-axis direction until the lowermost end of the cutting blade 36 reaches the region between the outer periphery of the wafer 11 and the device 13a. After that, as described with reference to FIGS. 7 to 11 and the like, edge trimming is performed on the wafer 11 by processing the outer peripheral edge of the wafer 11 .

Further, in the processing step (S3) of the method described above, the wafer 11 was processed using the cutting blade 36, but in the processing step (S3) of the method of the present invention, the wafer 11 is processed using a laser beam. may be processed.

FIG. 13 is a perspective view schematically showing an example of a laser irradiation device that performs the processing step (S3) using a laser beam. The X-axis direction, Y-axis direction and Z-axis direction shown in FIG. 13 respectively correspond to the X-axis direction, Y-axis direction and Z-axis direction shown in FIG.

A laser irradiation device 40 shown in FIG. 13 has a holding table 42 . The holding table 42 has a disk-shaped porous plate 42a exposed upward. The upper surface of the porous plate 42a is generally parallel and serves as a holding surface of a holding table 42 that holds the wafer 11. As shown in FIG.

A suction path (not shown) having one end connected to a suction source (not shown) such as an ejector provided outside the holding table 42 is formed inside the holding table 42 . The other end of this suction path reaches the porous plate 42a. When the suction source is operated with the wafer 11 placed on the holding surface, the wafer 11 is held by the holding table 42 by suction.

Furthermore, the holding table 42 is connected to an X-axis movement mechanism (not shown) and a Y-axis movement mechanism (not shown). Then, when the X-axis direction moving mechanism and/or the Y-axis direction moving mechanism operate, the holding table 42 moves along the X-axis direction and/or the Y-axis direction.

Further, the holding table 42 is connected to a rotational drive source (not shown). When the rotary drive source is operated, the holding table 42 rotates around the rotation axis passing through the center of the holding surface and along the Z-axis direction. In the laser beam irradiation unit 44, the holding step (S1) shown in FIG. 3 is performed by holding the wafer 11 on the holding table 42. As shown in FIG.

A head 46 of a laser beam irradiation unit 44 is provided above the holding table 42 . The head 46 is provided at a tip (one end) of a connecting portion 48 extending along the Y-axis direction. The head 46 accommodates an optical system such as a condensing lens and a mirror, and the connecting portion 48 accommodates an optical system such as a mirror and/or a lens.

In addition, the other end of the connecting portion 48 is connected to a Z-axis movement mechanism (not shown). Then, when the Z-axis direction moving mechanism operates, the head 46 and the connecting portion 48 move along the Z-axis direction. The laser beam irradiation unit 44 has a laser oscillator (not shown) that generates a laser beam with a wavelength that is absorbed by the wafer 11 (eg, 365 nm) or a wavelength that is transmitted through the wafer 11 (eg, 1064 nm).

A laser oscillator has a laser medium such as Nd:YAG, for example. Then, when a laser beam is generated by the laser oscillator, the laser beam is irradiated directly below the head 46 via the optical system housed in the connecting portion 48 and the head 46 . Furthermore, an imaging unit 50 capable of imaging the holding surface side of the holding table 42 is provided on the side portion of the connecting portion 48 .

The imaging unit 50 has, for example, a light source such as an LED, an objective lens, and an imaging element such as a CCD image sensor or a CMOS image sensor. In addition, in the laser beam irradiation unit 44, the boundary identification step (S2) shown in FIG.

Then, in the laser beam irradiation unit 44, the processing step (S3) shown in FIG.

When using a laser beam having a wavelength that is absorbed by the wafer 11, for example, the processing step (S3) is performed in the following order. First, the wafer 11 is moved by the X-axis direction moving mechanism, the Y-axis direction moving mechanism, and the rotary drive source so that the head 46 of the laser beam irradiation unit 44 is positioned directly above the region between the outer periphery of the wafer 11 and the device 13a. Adjust the position of the holding table 10 to be held.

Next, the wafer 11 is irradiated with a laser beam having a wavelength that is absorbed by the wafer 11 . At this time, the laser beam is adjusted so that its width along the Y-axis direction is wider than the sum of the edge trimming reference width and the maximum increment value. Also, the distance between the center of the wafer 11 and the laser beam irradiated to the wafer 11 is adjusted to be the shortest length described above.

This causes ablation of the material forming the chamfered peripheral edge of the wafer 11 . That is, a portion of the wafer 11 irradiated with a laser beam having a wavelength that is absorbed by the wafer 11 becomes a processing point, and a portion of the wafer 11 at that portion is removed.

Next, as described with reference to FIGS. 7 to 11 and the like, while the Y-axis direction moving mechanism and the rotary drive source move the holding table 42, the laser beam irradiation unit 44 emits a laser beam of a wavelength that can be absorbed by the wafer 11. Irradiate the beam. As a result, as shown in FIGS. 12(A) and 12(B), a wafer 11 having a step 11d formed at the outer peripheral edge by edge trimming is obtained.

Further, when using a laser beam having a wavelength that passes through the wafer 11, the processing step (S3) is performed in the following order, for example. First, the wafer 11 is moved by the X-axis direction moving mechanism, the Y-axis direction moving mechanism, and the rotary drive source so that the head 46 of the laser beam irradiation unit 44 is positioned directly above the region between the outer periphery of the wafer 11 and the device 13a. Adjust the position of the holding table 10 to be held.

Next, the wafer 11 is irradiated with a laser beam having a wavelength that passes through the wafer 11 . At this time, the laser beam is adjusted so that its focal point is positioned inside the wafer 11 . Also, the distance between the center of the wafer 11 and the laser beam irradiated to the wafer 11 is adjusted to be the shortest length described above.

As a result, the structure of the material forming the chamfered outer edge of the wafer 11 is altered due to multiphoton absorption. That is, a portion of the wafer 11 irradiated with a laser beam having a wavelength that passes through the wafer 11 becomes a processing point, and an altered layer is formed on the wafer 11 at that portion.

Next, as described with reference to FIGS. 7 to 11 and the like, while the Y-axis direction moving mechanism and the rotary drive source move the holding table 42, the laser beam irradiation unit 44 emits a laser beam having a wavelength that passes through the wafer 11. to irradiate. As a result, a wafer 11 having an annular deteriorated layer formed inside the outer peripheral edge is obtained.

Next, by applying an external force to the wafer 11, the wafer 11 is broken along the annular altered layer. For example, by grinding the rear surface 11c side of the wafer 11, a crack develops in the thickness direction of the wafer 11 from the annular deteriorated layer, thereby separating the central portion of the wafer 11 from the chamfered outer peripheral edge portion. The result is an edge-trimmed wafer 11 .

The position of the processing point (position of the wafer irradiated with the laser beam) in the laser irradiation device 40 may be adjusted by adjusting the optical system housed in the laser beam irradiation unit 44 . That is, this adjustment of the processing point may be performed by adjusting the inclination of the mirror and/or the lens accommodated in the laser beam irradiation unit 44 .

Furthermore, in the holding step (S1) of the method of the present invention, the wafer 11 may be placed on the holding surface of the holding table 10 or 42 with the center of the wafer 11 shifted from the center of the holding surface. FIG. 14 is a top view schematically showing the wafer 11 placed on the holding surface in such a state. 14, the plurality of devices 13 formed on the wafer 11 are omitted for convenience.

14 can also be expressed as showing a coordinate plane (XY coordinate plane) parallel to the X-axis direction and the Y-axis direction, with the center of the holding surface of the holding table 10 or the holding table 42 as the origin O. . In FIG. 14, the center of the wafer 11 is located at a position shifted from the center (origin O) of the holding surface, that is, at coordinates (Xc, Yc) on the XY coordinate plane.

FIG. 15 shows an example of a method for processing the outer peripheral edge of the wafer 11 with a width that varies according to the distance between the center of the wafer 11 and the boundary between the device region 15a and the outer peripheral surplus region 15b. It is a flow chart which shows typically. In this method, first, the holding step (S1) is performed.

Next, the position of the center of the wafer 11 is calculated (center calculation step: S4). For example, the position of the center of the wafer 11 is calculated based on the positions of at least three points on the outer circumference of the wafer 11 . Specifically, when the coordinates of three points on the XY coordinate plane on the outer circumference of the wafer 11 are (X ₁ , Y ₁ ), (X ₂ , Y ₂ ) and (X ₃ , Y ₃ ), the wafer 11 The coordinates (Xc, Yc) on the XY coordinate plane of the center of are calculated by Equations 1 and 2 below.

The coordinates on the XY coordinate plane corresponding to the positions of at least three points on the outer circumference of the wafer 11 are based on an image formed by imaging an area including the outer circumference of the wafer 11 by the imaging unit 38 or the imaging unit 50, for example. identified by

Next, the positions of points on the outer periphery of the wafer 11 positioned on a straight line passing through the center of the holding surface (origin O) and the processing point are calculated (peripheral position calculation step: S5). In addition, in edge trimming using the cutting device 2 and the laser irradiation device 40 described above, this processing point is positioned in the Y-axis direction when viewed from the center of the holding surface.

Therefore, this straight line corresponds to the Y-axis of the XY coordinate plane shown in FIG. Further, when the center of the wafer 11 is located at coordinates (Xc, Yc) on the XY coordinate plane, the coordinates on the XY coordinate plane of a point on the outer periphery of this wafer 11 can be expressed as (0, Y ₀ ). Let φ be the angle formed by the X axis of the XY coordinate plane and a straight line passing through the center of the holding surface (origin O) and the center of the wafer 11 (coordinates (Xc, Yc)), and r be the radius of the wafer 11. Then, Y ₀ is calculated by Equation 3 below.

Furthermore, as described above, the holding table 10 or the holding table 42 rotates on the rotation axis along the direction (Z-axis direction) passing through the center of the holding surface (origin O) and perpendicular to the XY coordinate plane. For example, as shown in FIG. 16, when the holding table 10 or holding table 42 is rotated at a rotation angle θ, the coordinates of a point on the outer circumference of the wafer 11 on the XY coordinate plane are expressed as (0, y). can. Then, y is calculated by Equation 4 below.

Next, the above-described boundary identification step (S2) and processing step (S3) are performed. However, in the processing step (S3) of the method shown in FIG. , as well as the positions of points on the outer periphery of the wafer 11 positioned on a straight line passing through the center of the holding surface (origin O) and the processing point. Briefly, the distance between the center of the holding surface (origin O) and the machining point is adjusted according to the value of y, which is a function with the rotation angle θ of the holding table 10 or holding table 42 as a variable.

For example, as shown in FIGS. 6A and 6B, when performing edge trimming on the region between the outer periphery of the wafer 11 and the device 13a, the center of the holding surface (origin O) and the processing point is adjusted to a length obtained by subtracting the above reference width for edge trimming and the above maximum increment value from the value of y.

Further, as shown in FIGS. 7A and 7B, when performing edge trimming on the region between the outer periphery of the wafer 11 and the device 13d, the center of the holding surface (origin O) and the processing point is adjusted to be the length obtained by subtracting the above reference width for edge trimming from the value of y and adding the above maximum decrement value.

Further, as shown in FIGS. 11A and 11B, when performing edge trimming on the region between the outer periphery of the wafer 11 and the device 13l, the center of the holding surface (origin O) and the processing point is adjusted to be the length obtained by subtracting the above reference width for edge trimming from the value of y.

15, even if the center of the wafer 11 deviates from the center of the holding surface of the holding table 10 or the holding table 42, the boundary between the device region 15a and the peripheral surplus region 15b is The outer peripheral edge of the wafer 11 can be processed with a width that varies according to the distance from the center of the wafer 11 .

In the method shown in FIG. 15, the center calculation step (S4) and the outer circumference position calculation step (S5) may be performed after the boundary specifying step (S2). In this case, the image used to identify the boundary between the device area 15a and the outer peripheral surplus area 15b in the boundary identification step (S2) may also be used in the center calculation step (S4).

For example, after specifying the positions of three points on the outer periphery of the wafer 11 based on the image formed in the boundary specifying step (S2), the position of the center of the wafer 11 may be calculated based on the positions of these three points. good. In this case, it is preferable in that it is not necessary to perform new imaging in the center calculation step (S4).

In addition, the structure, method, and the like according to the above-described embodiments can be modified as appropriate without departing from the scope of the present invention.

2: cutting device 4: base (4a: opening)
6, 8: cover 10: holding table (10a: porous plate)
12: Support structure (12a: standing portion, 12b: arm portion)
14 : Y-axis direction movement mechanism 16 : Y-axis guide rail 18 : Y-axis movement plate 20 : Screw shaft 22 : Z-axis direction movement mechanism 24 : Z-axis guide rail 26 : Z-axis movement plate 28 : Screw shaft 30 : Motor 32 : Cutting unit 34 : Spindle housing 36 : Cutting blade 38 : Imaging unit 11 : Wafer (11a: front surface, 11b: side surface, 11c: back surface, 11d: step)
13: Device 13a to 13l: Device 15a: Device region 15b: Surplus peripheral region 40: Laser irradiation device 42: Holding table (42a: porous plate)
44: Laser beam irradiation unit 46: Head 48: Connecting part 50: Imaging unit

Claims (4)

A method for processing a wafer having a device region in which a plurality of devices are formed and an outer peripheral surplus region surrounding the device region on the surface thereof, and having a chamfered outer peripheral edge, comprising:
a holding step of holding the wafer on a holding table having a holding surface for holding the wafer and rotatable about a rotation axis passing through the center of the holding surface;
a boundary identifying step of identifying a boundary between the device region and the peripheral surplus region based on an image formed by imaging a region including at least part of the plurality of devices and the outer periphery of the wafer;
By adjusting the distance between the center of the holding surface and the processing point according to the distance between the boundary and the center of the wafer while moving the processing point along the outer periphery of the holding surface, the boundary and the processing point are adjusted. a processing step of processing the outer peripheral edge of the wafer with a width that varies according to the distance from the center of the wafer;
A wafer processing method comprising: 2. The method of processing a wafer according to claim 1, wherein said processing step is performed by cutting said wafer with a cutting blade attached to the tip of a rotatable spindle. 2. The method of processing a wafer according to claim 1, wherein said processing step is performed by irradiating said wafer with a laser beam having a wavelength that is absorbed by said wafer. The processing step includes irradiating the wafer with the laser beam in a state in which the focal point of the laser beam having a wavelength that passes through the wafer is positioned inside the wafer, thereby forming an altered layer inside the wafer. 2. The method of processing a wafer according to claim 1, wherein the processing is performed by breaking the wafer along.

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