Wafer Processing Method

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]

[0001] The present invention relates to a method for processing a wafer having, on its surface, a device region in which a plurality of devices are formed and a peripheral excess region surrounding the device region, and having a chamfered peripheral edge portion. [Background technology]

[0002] Device chips such as IC (Integrated Circuit) and LSI (Large Scale Integration) are essential components in various electronic devices such as mobile phones, personal computers, etc. 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 containing an individual device.

[0003] Wafers used in chip manufacturing are prone to cracking starting from chips formed on the outer periphery. Therefore, in the chip manufacturing process, the outer periphery of the wafer is generally chamfered prior to various processes. Furthermore, in the chip manufacturing process, the back side of the wafer is often ground to thin the wafer prior to division in order to miniaturize the chips to be manufactured.

[0004] However, when the back side of a wafer with a chamfered outer periphery is ground to thin the wafer, the outer periphery on the back side of the wafer becomes a sharp edge (knife edge). Stress is likely to concentrate on this outer periphery, leading to chipping. For this reason, in the chip manufacturing process, edge trimming is sometimes performed to remove part or all of the chamfered outer periphery of the wafer prior to grinding the wafer (see, for example, Patent Documents 1 and 2).

[0005] 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 passing through the center of the holding surface. Then, while rotating the holding table, the edge trimming processing point is positioned at a fixed distance from the center of the holding surface to process the outer peripheral edge of the wafer. As a result, a part or the whole of the chamfered outer peripheral edge is removed from the wafer.

[0006] However, the wafer may be placed on the holding surface with its center offset from the center of the holding surface. In this state, if edge trimming is performed by positioning the processing point at a fixed distance from the center of the holding surface, the distance between the center of the wafer and the processing point varies. In view of this, a method has been proposed for making the distance between the center of the wafer and the edge trimming processing point constant even when the center of the wafer is offset from the center of the holding surface (see, for example, Patent Document 3).

[0007] In this method, first, the positions of three points on the outer circumference of the wafer are measured, and the position of the wafer center is calculated based on the positions of the three measured 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 wafer center and the processing point is kept 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.

[0008] Edge trimming is also sometimes performed on wafers used in the manufacture of chips for devices such as through-silicon vias (TSVs) and back-side illumination (BSI) type complementary metal oxide semiconductor (CMOS) sensors (see, for example, Patent Document 4).

[0009] Specifically, such devices are manufactured using two bonded wafers (bonded wafers), but when the outer peripheral edge of each wafer is chamfered, an unbonded portion where the wafers are not sufficiently bonded to each other is likely to be formed at the outer peripheral edge of the wafer. Such an unbonded portion is likely to accumulate dust and become a source of contamination or dust generation. Therefore, in order to prevent such a source of contamination or dust generation from being formed, edge trimming is sometimes performed on at least one of the two wafers prior to bonding the two wafers. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] JP 2000-173961 A [Patent Document 2] JP 2006-108532 A [Patent Document 3] JP 2006-93333 A [Patent Document 4] Japanese Patent Application Publication No. 10-242091 Summary of the Invention [Problem to be solved by the invention]

[0011] In order to reduce the manufacturing cost of chips, it is preferable to form as many devices as possible on the surface of a wafer, that is, it is preferable to form devices not only in the central region of the surface of the wafer but also in the region near the periphery of the wafer.

[0012] On the other hand, in order to prevent the wafer from cracking as described above and / or to avoid the formation of a source of contamination or dust generation in the bonded wafer, it is preferable to perform edge trimming sufficiently before grinding the back side of the wafer, i.e., it is preferable to perform edge trimming not only on the region near the outer periphery of the wafer but also on a wide region extending to the inner region.

[0013] In view of these two conflicting demands, an object of the present invention is to provide a wafer processing method that can eliminate or reduce the proportion of devices damaged by edge trimming and reduce the probability of wafer cracking and / or the probability of formation of contamination or dust sources in bonded wafers. [Means for solving the problem]

[0014] The present invention One aspect of 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 a peripheral excess region surrounding the device region, and having a chamfered peripheral edge, the method including: 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 specifying step of specifying a boundary between the device region and the peripheral excess region based on an image formed by imaging an area including at least a portion of the plurality of devices and the outer periphery of the wafer; and a processing step of processing the outer periphery of the wafer with a width that varies depending on the distance between the boundary and the center of the wafer by moving a processing point along the outer periphery of the holding surface and adjusting the distance between the center of the holding surface and the processing point depending on the distance between the boundary and the center of the wafer. and in the processing step, the width is maintained at or above a predetermined length even if at least one of the plurality of devices is damaged. A method for processing a wafer is provided.

[0015] According to another aspect of 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 a peripheral excess region surrounding the device region, and having a chamfered peripheral edge, the method including: 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 a center of the holding surface; a boundary identifying step of identifying a boundary between the device region and the peripheral excess region based on an image formed by imaging an area including at least a portion of the plurality of devices and the outer periphery of the wafer; and a processing step of processing the outer periphery of the wafer with a width that varies depending on the distance between the boundary and the center of the wafer by moving a processing point along the outer periphery of the holding surface and adjusting the distance between the center of the holding surface and the processing point depending on the distance between the boundary and the center of the wafer. The processing step is performed by cutting the wafer with a cutting blade attached to the tip of a rotatable spindle. A method for processing a wafer is provided. .

[0016] moreover , In one aspect of the present invention, a wafer processing method includes: The processing step is preferably carried out by irradiating the wafer with a laser beam of a wavelength that is absorbed by the wafer.

[0017] or, In one aspect of the present invention, a wafer processing method includes:The processing step is preferably carried out by irradiating the wafer with a laser beam having a wavelength that transmits through the wafer, with the focal point of the laser beam positioned inside the wafer, and breaking the wafer along an altered layer formed inside the wafer. Effect of the Invention

[0018] In the present invention, the outer peripheral edge of the wafer is processed to a width that varies depending on 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 outer 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 depending on the distance between the center of the wafer and the boundary of the device region and the outer peripheral surplus region.

[0019] In short, if the distance between the boundary and the center of the wafer is long, edge trimming is performed to narrow this width. This can eliminate or reduce the percentage of devices damaged by edge trimming. Also, if the distance between the boundary and the center of the wafer is short, edge trimming is performed to widen this width. This can reduce the probability of the wafer cracking and / or the formation of contamination or dust sources in the bonded wafer in the process after edge trimming. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a perspective view illustrating an example of a processing apparatus. [Diagram 2] FIG. 2(A) is a top view that typically shows an example of a wafer, and FIG. 2(B) is a cross-sectional view that typically shows an example of a wafer. [Diagram 3] FIG. 3 is a flow chart illustrating an example of the processing method. [Figure 4] FIG. 4 is a top view diagrammatically illustrating an example of a wafer placed on a holding table. [Diagram 5]FIG. 5(A) is a top view that shows a schematic example of a wafer on which edge trimming has been performed, and FIG. 5(B) is a cross-sectional view that shows a schematic example of a wafer on which edge trimming has been performed. [Figure 6] FIG. 6(A) is a top view that shows a schematic example of a wafer on which edge trimming has been performed, and FIG. 6(B) is a cross-sectional view that shows a schematic example of a wafer on which edge trimming has been performed. [Figure 7] FIG. 7(A) is a top view that shows a schematic example of a wafer on which edge trimming has been performed, and FIG. 7(B) is a cross-sectional view that shows a schematic example of a wafer on which edge trimming has been performed. [Figure 8] FIG. 8(A) is a top view that shows a schematic example of a wafer on which edge trimming has been performed, and FIG. 8(B) is a cross-sectional view that shows a schematic example of a wafer on which edge trimming has been performed. [Figure 9] FIG. 9(A) is a top view that shows a schematic example of a wafer on which edge trimming has been performed, and FIG. 9(B) is a cross-sectional view that shows a schematic example of a wafer on which edge trimming has been performed. [Figure 10] FIG. 10(A) is a top view that shows a schematic example of an example of a wafer on which edge trimming has been performed, and FIG. 10(B) is a cross-sectional view that shows a schematic example of an example of a wafer on which edge trimming has been performed. [Figure 11] FIG. 11(A) is a top view that shows a schematic example of an example of a wafer on which edge trimming has been performed, and FIG. 11(B) is a cross-sectional view that shows a schematic example of an example of a wafer on which edge trimming has been performed. [Figure 12] FIG. 12(A) is a top view that shows a schematic example of an edge-trimmed wafer, and FIG. 12(B) is a side view that shows a schematic example of an edge-trimmed wafer. [Figure 13] FIG. 13 is a perspective view that illustrates an example of a laser irradiation device. [Figure 14]FIG. 14 is a top view that illustrates an example of a wafer placed on the holding surface of the holding table in a state in which the center of the wafer is shifted from the center of the holding surface. [Figure 15] FIG. 15 is a flow chart that illustrates another example of the processing method. [Figure 16] FIG. 16 is a top view that diagrammatically illustrates an example of the wafer in a state in which the holding table illustrated in FIG. 14 is rotated. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] An embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a perspective view showing a schematic example of a cutting device serving as a processing device for processing a wafer. Note that the X-axis direction (front-back direction) and the Y-axis direction (left-right direction) shown in Fig. 1 are directions perpendicular to each other on a horizontal plane, and the Z-axis direction (up-down direction) is a direction (vertical direction) perpendicular to the X-axis direction and the Y-axis direction.

[0022] The cutting device 2 shown in Fig. 1 includes a base 4 that supports each of the components. A rectangular opening 4a whose longitudinal direction is parallel to the X-axis direction is formed on the upper surface of the base 4. A flat cover 6 and a bellows-like cover 8 that expands and contracts as the cover 6 moves are provided within the opening 4a.

[0023] 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. In addition, an X-axis direction moving mechanism (not shown) that moves the cover 6 and holding table 10 along the X-axis direction is provided below the covers 6 and 8.

[0024] Fig. 2(A) is a top view showing an example of a wafer held on the holding surface of the holding table 10, and Fig. 2(B) is a cross-sectional view showing the wafer. The wafer 11 shown in Fig. 2(A) and Fig. 2(B) is made of a semiconductor material such as Si (silicon), SiC (silicon carbide) or GaN (gallium nitride).

[0025] The front surface 11a of the wafer 11 is divided into a plurality of regions by a plurality of planned dividing lines set in a lattice pattern. Devices 13 such as ICs or LSIs are formed in each of the plurality of regions, except for a portion of the region close 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 periphery surplus region 15b surrounding the device region 15a.

[0026] 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 be convex outward. The back surface 11c of the wafer 11 is placed on the holding surface (the upper surface of the porous plate 10a) of the holding table 10 directly or via a dicing tape (not shown).

[0027] 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 with the wafer 11 placed on the holding surface, the wafer 11 is sucked and held on the holding table 10.

[0028] Furthermore, the holding table 10 is connected to a rotation drive source for the holding table (not shown), such as a motor. When the rotation drive source for the holding table is operated, the holding table 10 rotates on a rotation axis that passes through the center of the holding surface and is aligned in the Z-axis direction.

[0029] A support structure 12 is provided near the opening 4a on the upper surface of the base 4. The support structure 12 includes an erected portion 12a extending along the Z-axis direction from the upper surface of the base 4, and an arm portion 12b extending along the Y-axis direction from the upper end of the erected portion 12a so as to cross the opening 4a. A Y-axis direction moving mechanism 14 is provided on the front side of the arm portion 12b.

[0030] The Y-axis direction moving mechanism 14 is fixed to the front surface of the arm portion 12b and includes a pair of Y-axis guide rails 16 extending along the Y-axis direction. A Y-axis moving plate 18 is connected to the front surface of the pair of Y-axis guide rails 16 in a manner that allows it to slide along the pair of Y-axis guide rails 16.

[0031] Further, a screw shaft 20 extending along the Y-axis direction is disposed 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) for accommodating balls that roll on the surface of the rotating screw shaft 20 is provided on the surface of the screw shaft 20 on which a spiral groove is formed, thereby forming a ball screw.

[0032] That is, when the screw shaft 20 rotates, the balls circulate inside the nut portion, and the nut portion moves along the Y-axis direction. 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.

[0033] A Z-axis direction moving mechanism 22 is provided on the front side of the Y-axis moving plate 18. The Z-axis direction moving mechanism 22 is fixed to the front side of the Y-axis moving plate 18 and includes a pair of Z-axis guide rails 24 extending along the Z-axis direction. A Z-axis moving plate 26 is connected to the front side of the pair of Z-axis guide rails 24 in a manner that allows it to slide along the pair of Z-axis guide rails 24.

[0034] Further, a screw shaft 28 extending along the Z-axis direction is disposed 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. A nut portion (not shown) for accommodating balls that roll on the surface of the rotating screw shaft 28 is provided on the surface of the screw shaft 28 on which a spiral groove is formed, thereby forming a ball screw.

[0035] That is, when the screw shaft 28 rotates, the balls circulate inside the nut portion, causing the nut portion to move along the Z-axis direction. 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 moving plate 26 moves along the Z-axis direction together with the nut portion.

[0036] A cutting unit 32 is fixed to the lower part of the Z-axis moving plate 26. The cutting unit 32 has a cylindrical spindle housing 34 whose longitudinal direction is parallel to the Y-axis direction. A columnar spindle (not shown) whose longitudinal direction is parallel to the Y-axis direction is accommodated in the spindle housing 34. This spindle is supported by the spindle housing 34 in a rotatable state.

[0037] The tip of the spindle protrudes outside the spindle housing 34, and a cutting blade 36 having an annular cutting edge is attached to this tip. The base end of the spindle is connected to a rotary drive source for the cutting blade (not shown), such as a motor, that is built into the spindle housing 34. When the rotary drive source for the cutting blade is operated, the cutting blade 36 rotates together with the spindle on a rotation axis along the Y-axis direction.

[0038] Furthermore, an imaging unit 38 is provided at a position adjacent to the cutting unit 32 in the X-axis direction and fixed to the lower part of the Z-axis moving plate 26. 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.

[0039] 3 is a flow chart that illustrates an example of a method for processing a wafer 11 in a processing device such as a cutting device 2. In this method, first, the wafer 11 is held by the holding table 10 (holding step: S1). For example, with the wafer 11 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.

[0040] Next, the boundary between the device region 15a and the peripheral surplus region 15b of the wafer 11 is identified (boundary identification step: S2). This identification is performed based on an image formed by imaging an area including the peripheral region of the wafer 11 and parts of the multiple devices 13. This image is formed, for example, in the following order.

[0041] First, the imaging unit 38 captures an image of the wafer 11 with the center of the field of view of the imaging unit 38 positioned slightly inside the outer periphery of the wafer 11 and with the outer periphery of the wafer 11 and at least one device 13 included in the field of view. Then, the holding table rotation drive source is operated to rotate the holding table 10 so that the fields of view of the imaging unit 38 overlap partially before and after the rotation of the holding table 10, and then the imaging unit 38 captures an image of the wafer 11. Furthermore, the same process is repeated multiple times until the holding table 10 makes one rotation.

[0042] This forms an image of an area including the periphery of the wafer 11 and parts of the multiple devices 13. Then, the boundary between the device area 15a and the peripheral surplus area 15b of the wafer 11 is identified based on this image. For example, a polygonal line obtained by connecting the sides or points of the device 13 located on the outermost side among the multiple devices 13 formed on the front surface 11a of the wafer 11 is identified as the boundary between the device area 15a and the peripheral surplus area 15b.

[0043] Next, the outer peripheral edge of the wafer 11 is processed with a width (edge ​​trimming processing width) that varies depending on the distance between this boundary and the center of the wafer 11 (processing step: S3). In short, the edge trimming processing width is set so that it is narrower if the distance between this boundary and the center of the wafer 11 is long, and is wider if the distance between this boundary and the center of the wafer 11 is short. This point will be described in detail with reference to FIG. 4. Note that FIG. 4 is a top view that typically shows the wafer 11 placed on the holding table 10.

[0044] 4 represents a concentric circle on the outer periphery of wafer 11, whose radius is a length (reference length) obtained by subtracting a reference width for edge trimming (e.g., 3 mm) from the radius of wafer 11. This two-dot chain line A overlaps with a part of device 13 located on the outermost side among multiple devices 13 formed on front surface 11a of wafer 11.

[0045] Specifically, this two-dot chain line A overlaps with devices 13d, 13j, 13k, etc., but does not overlap with devices 13a, 13b, 13c, 13e, 13f, 13g, 13h, 13i, 13l, etc. In other words, the distance between the boundary between device region 15a and peripheral surplus region 15b near devices 13d, 13j, 13k, etc. and the center of wafer 11 is longer than the above-mentioned reference length.

[0046] In this way, when the interval becomes longer than the above-mentioned reference length, the processing width of the edge trimming is set narrower than the reference width. For example, the processing width is set narrower than the reference width of the edge trimming by a maximum decrement value (e.g., 0.5 mm). Note that the dotted line B on the outside of the two-dot chain line A shown in Fig. 4 represents a concentric circle on the outer periphery of the wafer 11, whose radius is the length (maximum length) obtained by adding the above-mentioned reference length to the maximum decrement value.

[0047] This dotted line B overlaps with devices 13j etc., but does not overlap with devices 13d, 13k etc. Therefore, by setting the processing width of edge trimming in this manner, damage to devices 13d, 13k etc. is prevented. Also, although damage to devices 13j etc. is unavoidable, edge trimming is performed with the minimum necessary processing width even in the vicinity of devices 13j etc., thereby suppressing an increase in the probability that the edge-trimmed wafer 11 will crack.

[0048] In addition, 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 shorter than the above-mentioned reference length.

[0049] In this way, when the interval becomes shorter than the above-mentioned reference length, the processing width of the edge trimming is set wider than the reference width. For example, the processing width is set wider by up to the maximum increment value (e.g., 0.5 mm) from the reference width of the edge trimming. Note that the dotted line C inside the two-dot chain line A shown in Fig. 4 represents a concentric circle on the outer periphery of the wafer 11, whose radius is the length (shortest length) obtained by subtracting the maximum increment value from the above-mentioned reference length.

[0050] This dotted line C does not overlap with the devices 13a, 13f, 13g, 13h, etc. Therefore, even if the edge trimming width is set to be wide in this manner, the devices 13a, 13f, 13g, 13h, etc. will not be damaged. Furthermore, by performing edge trimming with a sufficient processing width near the devices 13a, 13f, 13g, 13h, etc., the likelihood of the edge-trimmed wafer 11 cracking is reduced.

[0051] 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 adjusting the distance between the center of the holding surface and the processing point according to the distance between the boundary between the device region 15a and the peripheral excess region 15b and the center of the wafer 11 while moving the processing point along the outer periphery of the holding surface of the holding table 10. An example of such edge trimming will be described in detail with reference to Figs. 5 to 11.

[0052] 5 to 11(A) are top views that typically show the wafer 11 on which edge trimming is being performed, and FIG. 5 to 11(B) are cross-sectional views that typically show the wafer 11 on which edge trimming is being performed. For convenience, FIG. 5 to 11(A) typically shows the top surface of the cutting blade 36. For convenience, FIG. 5 to 11(B) typically shows the side surface of the cutting blade 36. For this cutting blade 36, a cutting blade that is wider than the sum of the above-mentioned reference width for edge trimming and the above-mentioned maximum increment value is used.

[0053] When edge trimming is performed on the wafer 11, first, the cutting blade 36 is positioned directly above the area between the outer periphery of the wafer 11 and the device 13a. Specifically, the X-axis direction moving mechanism adjusts the position of the holding table 10, and the Y-axis direction moving 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 is adjusted to the shortest length described above (see FIGS. 5(A) and 5(B)).

[0054] Next, the cutting blade 36 is rotated by operating the rotary drive source for the cutting blade, while the cutting blade 36 is cut into the wafer 11. For example, the Z-axis direction moving mechanism 22 lowers the cutting unit 32 so that the bottom end of the cutting blade 36 is positioned lower than the front surface 11a of the wafer 11 and higher than the back surface 11c. As a result, the point where the cutting blade 36 comes into contact with the chamfered outer peripheral end of the wafer 11 becomes the processing point, and a part of the wafer 11 at that point is removed (see FIGS. 6(A) and 6(B)).

[0055] Next, while keeping the cutting blade 36 rotating, the holding table rotary drive source rotates the holding table 10, and the Y-axis direction moving mechanism 14 adjusts the position of the cutting unit 32 so that the cutting blade 36 moves away from the center of the wafer 11. For example, the Y-axis direction moving mechanism 14 gradually moves the cutting unit 32 away from the center of the wafer 11 so that the distance between the center of the wafer 11 and the bottom end of the cutting blade 36 becomes the maximum length at the timing when the straight line passing through the point of the device 13d farthest from the center of the wafer 11 and the center of the wafer 11 becomes parallel to the Y-axis direction (see FIGS. 7(A) and 7(B)).

[0056] Next, while rotating the cutting blade 36 and the holding table 10, the Y-axis direction moving 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 gradually moves the cutting unit 32 closer to the center of the wafer 11 so that the distance between the center of the wafer 11 and the bottom end of the cutting blade 36 becomes the above-mentioned shortest length at the timing when the straight line passing through the point of the device 13f farthest from the center of the wafer 11 and the center of the wafer 11 becomes parallel to the Y-axis direction (see FIGS. 8(A) and 8(B)).

[0057] 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 the straight line passing through the point of the device 13h farthest from the center of the wafer 11 and the center of the wafer 11 becomes parallel to the Y-axis direction (see FIGS. 9(A) and 9(B)).

[0058] Next, while rotating the cutting blade 36 and the holding table 10, the Y-axis direction moving mechanism 14 adjusts the position of the cutting unit 32 so that the cutting blade 36 moves away from the center of the wafer 11. For example, the Y-axis direction moving mechanism 14 gradually moves the cutting unit 32 away from the center of the wafer 11 so that the distance between the center of the wafer 11 and the bottom end of the cutting blade 36 becomes the longest length at the timing when the straight line passing through the point of the device 13j farthest from the center of the wafer 11 and the center of the wafer 11 becomes parallel to the Y-axis direction (see FIGS. 10(A) and 10(B)).

[0059] 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 while the device 13j among the multiple devices formed on the front surface 11a of the wafer 11 is the device closest to the edge trimming processing point.

[0060] Next, while rotating the cutting blade 36 and the holding table 10, the Y-axis direction moving 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 gradually moves the cutting unit 32 closer to the center of the wafer 11 so that the distance between the center of the wafer 11 and the bottom end of the cutting blade 36 becomes the above-mentioned reference length at the timing when the straight line passing through the point of the device 13l farthest from the center of the wafer 11 and the center of the wafer 11 becomes parallel to the Y-axis direction (see FIGS. 11(A) and 11(B)).

[0061] This completes edge trimming of approximately 1 / 4 of the outer periphery of the wafer 11. Edge trimming of the remaining approximately 3 / 4 of the outer periphery of the wafer 11 is also performed in the same manner as above. As a result, as shown in Figures 12(A) and 12(B), a wafer 11 is obtained in which a step 11d is formed on the outer periphery by edge trimming.

[0062] 12(A) is a top view that typically shows the wafer 11 after edge trimming, and FIG 12(B) is a side view that typically shows the wafer 11 after edge trimming. For convenience, FIG 12(A) also shows dotted lines B that represent concentric circles of the wafer having a radius equal to the maximum length, and dotted lines C that represent concentric circles of the wafer 11 having a radius equal to the minimum length.

[0063] 3, the outer peripheral edge of the wafer 11 is processed to a width that varies depending on the distance between the center of the wafer 11 and the boundary between the device region 15a, in which a plurality of devices 13 are formed, and the outer peripheral excess region 15b surrounding the device region 15a. In other words, in this method, the width of the outer peripheral edge removed by edge trimming of the wafer 11 is set depending on the distance between the center of the wafer 11 and the boundary between the device region 15a and the outer peripheral excess region 15b.

[0064] In short, if the distance between the boundary and the center of the wafer 11 is long, edge trimming is performed to narrow this width. This makes it possible to eliminate or reduce the proportion of devices damaged by edge trimming. Also, if the distance between the boundary and the center of the wafer 11 is short, edge trimming is performed to widen this width. This makes it possible to reduce the probability of the wafer 11 cracking in the process after edge trimming and / or the probability of a contamination source or dust source being formed in a bonded wafer formed using the wafer 11.

[0065] The above-mentioned method is one aspect of the present invention, and the method of the present invention is not limited to the above-mentioned method. For example, in the processing step (S3) of the above-mentioned method, edge trimming is performed so as to leave a part of the back surface 11c side of the outer peripheral edge of the wafer 11, but in the processing step (S3) of the method of the present invention, the entire outer peripheral edge of the wafer 11 may be removed.

[0066] That is, in the processing step (S3) of the method of the present invention, edge trimming may be performed so as to form a side surface that is perpendicular to the front surface 11a and back surface 11c of the wafer 11 without forming a step 11d at the outer peripheral edge of the wafer 11.

[0067] Such edge trimming is performed, for example, by processing the outer peripheral edge of the wafer 11 as described with reference to Figures 7 to 11, etc., with the lowest end of the cutting blade 36 positioned below the back surface 11c of the wafer 11.

[0068] In this case, it is preferable that a dicing tape is attached to the back surface 11c side of the wafer 11. In other words, it is preferable that the edge trimming of the wafer 11 is performed in a state in which the wafer 11 is held on the holding table 10 via the dicing tape.

[0069] In addition, in the processing step (S3) of the above-mentioned method, the Z-axis moving mechanism 22 lowers the cutting unit 32 to cause the cutting blade 36 to cut into the wafer 11, but in the processing step (S3) of the method of the present invention, the X-axis moving mechanism may move the holding table 10 to cause the cutting blade 36 to cut into the wafer 11.

[0070] When performing edge trimming on the wafer 11 in this manner, first, the X-axis direction moving mechanism moves the holding table 10 along the X-axis direction so that the cutting blade 36 moves away 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 area between the outer periphery of the wafer 11 and the device 13a is positioned in the X-axis direction as viewed from the cutting blade 36.

[0071] At this time, the distance between the center of the wafer 11 and the region is adjusted to the above-mentioned shortest length. Next, the Z-axis direction moving mechanism 22 lowers the cutting unit 32 so that the lowest end of the cutting blade 36 is positioned lower than the front surface 11a of the wafer 11 and higher than the back surface 11c of the wafer 11. Next, the cutting blade 36 is rotated by operating the cutting blade rotary drive source, and the cutting blade 36 is caused to cut into the wafer 11.

[0072] Specifically, the X-axis direction moving mechanism moves the holding table 10 along the X-axis direction until the bottom end of the cutting blade 36 reaches the region between the outer periphery of the wafer 11 and the device 13a. Thereafter, as described with reference to Figs. 7 to 11 etc., the outer periphery end of the wafer 11 is processed to perform edge trimming on the wafer 11.

[0073] In addition, in the processing step (S3) of the above-mentioned method, the wafer 11 is processed using a cutting blade 36, but in the processing step (S3) of the method of the present invention, the wafer 11 may be processed using a laser beam.

[0074] 13 is a perspective view showing a schematic example of a laser irradiation device that performs the processing step (S3) using a laser beam. Note that the X-axis direction, the Y-axis direction, and the Z-axis direction shown in FIG. 13 correspond to the X-axis direction, the Y-axis direction, and the Z-axis direction shown in FIG. 1, respectively.

[0075] 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 to the holding surface of the holding table 42 that holds the wafer 11.

[0076] A suction path (not shown) is formed inside the holding table 42, one end of which is connected to a suction source (not shown) such as an ejector provided outside 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 sucked and held on the holding table 42.

[0077] Furthermore, the holding table 42 is connected to an X-axis direction moving mechanism (not shown) and a Y-axis direction moving mechanism (not shown). When the X-axis direction moving mechanism and / or the Y-axis direction moving mechanism operates, the holding table 42 moves along the X-axis direction and / or the Y-axis direction.

[0078] The holding table 42 is connected to a rotary drive source (not shown). When the rotary drive source is operated, the holding table 42 rotates about a rotation axis that passes through the center of the holding surface and is aligned with the Z-axis direction. In the laser beam irradiation unit 44, the holding table 42 holds the wafer 11, thereby performing a holding step (S1) shown in FIG. 3.

[0079] A head 46 of the laser beam irradiation unit 44 is provided above the holding table 42. The head 46 is provided at the tip (one end) of a connecting portion 48 extending along the Y-axis direction. The head 46 houses an optical system such as a condenser lens and a mirror, and the connecting portion 48 houses an optical system such as a mirror and / or a lens.

[0080] The other end of the connecting part 48 is connected to a Z-axis direction moving mechanism (not shown). When the Z-axis direction moving mechanism operates, the head 46 and the connecting part 48 move along the Z-axis direction. The laser beam irradiation unit 44 has a laser oscillator (not shown) that generates a laser beam having a wavelength that is absorbed by the wafer 11 (e.g., 365 nm) or a wavelength that is transmitted through the wafer 11 (e.g., 1064 nm).

[0081] The laser oscillator has a laser medium such as Nd:YAG. When a laser beam is generated by the laser oscillator, the laser beam is irradiated directly below the head 46 via an 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 of the connecting portion 48.

[0082] The imaging unit 50 includes, 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, a boundary identification step (S2) shown in FIG. 3 is performed based on an image formed by imaging the wafer 11 by the imaging unit 50.

[0083] Then, in the laser beam irradiation unit 44, a processing step (S3) shown in FIG. 3 is performed using a laser beam having a wavelength that is absorbed by the wafer 11 or that is transmitted through the wafer 11.

[0084] When using a laser beam having a wavelength that is absorbed by the wafer 11, the processing step (S3) is performed, for example, in the following order: First, the X-axis direction moving mechanism, the Y-axis direction moving mechanism and the rotary drive source adjust the position of the holding table 10 that holds the wafer 11 so that the head 46 of the laser beam irradiation unit 44 is positioned directly above the area between the outer periphery of the wafer 11 and the device 13a.

[0085] Next, a laser beam having a wavelength absorbed by the wafer 11 is irradiated onto the wafer 11. At this time, the width of the laser beam along the Y-axis direction is adjusted to be wider than the sum of the above-mentioned reference width for edge trimming and the above-mentioned maximum increment value. Also, the distance between the center of the wafer 11 and the laser beam irradiated onto the wafer 11 is adjusted to be the above-mentioned shortest length.

[0086] This causes ablation of the material that constitutes the chamfered outer peripheral edge of the wafer 11. That is, the location of the wafer 11 that is irradiated with the laser beam having a wavelength that is absorbed by the wafer 11 becomes a processing point, and a part of the wafer 11 at that location is removed.

[0087] 7 to 11, the Y-axis direction moving mechanism and the rotary drive source move the holding table 42 while the laser beam irradiation unit 44 irradiates the wafer 11 with a laser beam having a wavelength that is absorbed by the wafer 11. As a result, as shown in Figures 12(A) and 12(B), a wafer 11 is obtained in which a step 11d is formed on the outer circumferential edge by edge trimming.

[0088] When using a laser beam having a wavelength that transmits through the wafer 11, the processing step (S3) is performed, for example, in the following order: First, the X-axis direction moving mechanism, the Y-axis direction moving mechanism, and the rotary drive source adjust the position of the holding table 10 that holds the wafer 11 so that the head 46 of the laser beam irradiation unit 44 is positioned directly above the area between the outer periphery of the wafer 11 and the device 13a.

[0089] Next, a laser beam having a wavelength that is transmitted through the wafer 11 is irradiated onto the wafer 11. At this time, the laser beam is adjusted so that its focal point is positioned inside the wafer 11. In addition, the distance between the center of the wafer 11 and the laser beam irradiated onto the wafer 11 is adjusted to be the shortest length described above.

[0090] As a result, the structure of the material that constitutes the chamfered outer peripheral edge of the wafer 11 is altered due to multiphoton absorption. That is, the portion of the wafer 11 that is irradiated with the laser beam having a wavelength that transmits through the wafer 11 becomes a processing point, and an altered layer is formed on the wafer 11 at that portion.

[0091] 7 to 11, the Y-axis direction moving mechanism and the rotary drive source move the holding table 42 while the laser beam irradiation unit 44 irradiates the wafer 11 with a laser beam having a wavelength that transmits the wafer 11. This results in a wafer 11 with a circular annular deteriorated layer formed inside the outer circumferential edge portion.

[0092] Next, an external force is applied to the wafer 11 to break the wafer 11 along the annular deteriorated layer. For example, by grinding the back surface 11c side of the wafer 11, a crack is caused to develop from the annular deteriorated layer in the thickness direction of the wafer 11, and the center part of the wafer 11 is separated from the chamfered outer peripheral edge part. As a result, an edge-trimmed wafer 11 is obtained.

[0093] The adjustment of the position of the processing point in the laser irradiation device 40 (the position of the wafer irradiated with the laser beam) may be performed by adjusting the optical system housed in the laser beam irradiation unit 44. That is, the adjustment of the processing point may be performed by adjusting the inclination of the mirror and / or lens housed in the laser beam irradiation unit 44.

[0094] Furthermore, in the holding step (S1) of the method of the present invention, the wafer 11 may be placed on the holding surface in a state where the center of the wafer 11 is shifted from the center of the holding surface of the holding table 10 or the holding table 42. Fig. 14 is a top view showing the wafer 11 placed on the holding surface in such a state. Note that, for convenience, a plurality of devices 13 formed on the wafer 11 are omitted in Fig. 14.

[0095] 14 can also be expressed as showing a coordinate plane (XY coordinate plane) parallel to the X-axis and Y-axis directions 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 placed at a position shifted from the center of the holding surface (origin O), that is, at the position of coordinates (Xc, Yc) on the XY coordinate plane.

[0096] 15 is a flow chart showing an example of a method for processing the outer peripheral edge of the wafer 11 in such a case with a width that varies depending on the distance between the boundary between the device region 15a and the outer peripheral excess region 15b and the center of the wafer 11. In this method, the above-mentioned holding step (S1) is first performed.

[0097] 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 periphery of the wafer 11. Specifically, when the coordinates of three points on the outer periphery of the wafer 11 on the XY coordinate plane are (X1, Y1), (X2, Y2), and (X3, Y3), the coordinates (Xc, Yc) of the center of the wafer 11 on the XY coordinate plane are calculated by the following formulas 1 and 2.

[0098]

number

[0099]

number

[0100] In addition, the coordinates on the XY coordinate plane corresponding to the positions of at least three points on the outer periphery of the wafer 11 are identified, for example, based on an image formed by imaging an area including the outer periphery of the wafer 11 using the imaging unit 38 or the imaging unit 50.

[0101] Next, the position of a point on the outer periphery of the wafer 11 located on a straight line passing through the center of the holding surface (origin O) and the processing point is calculated (outer periphery position calculation step: S5). In edge trimming using the above-mentioned cutting device 2 and laser irradiation device 40, this processing point is positioned in the Y-axis direction as viewed from the center of the holding surface.

[0102] Therefore, this line corresponds to the Y axis of the XY coordinate plane shown in Fig. 14. Furthermore, when the center of the wafer 11 is located at coordinates (Xc, Yc) on the XY coordinate plane, the coordinates of a point on the outer periphery of the wafer 11 on the XY coordinate plane can be expressed as (0, Y0). If the angle made by the X axis of the XY coordinate plane and a line passing through the center of the holding surface (origin O) and the center of the wafer 11 (coordinates (Xc, Yc)) is φ, and the radius of the wafer 11 is r, then Y0 can be calculated by the following Equation 3.

[0103]

number

[0104] Furthermore, as described above, the holding table 10 or the holding table 42 rotates on a rotation axis that passes through the center of the holding surface (origin O) and runs along a direction (Z-axis direction) perpendicular to the XY coordinate plane. For example, as shown in Fig. 16, when the holding table 10 or the holding table 42 is rotated by a rotation angle θ, the coordinates of a point on the outer periphery of the wafer 11 on the XY coordinate plane can be expressed as (0, y). Then, y is calculated by the following mathematical formula 4.

[0105]

number

[0106] Next, the above-mentioned boundary identification step (S2) and processing step (S3) are performed. However, in the processing step (S3) of the method shown in Fig. 15, the distance between the center (origin O) of the holding surface and the processing point is adjusted according to not only the distance between the boundary between the device region 15a and the peripheral excess region 15b and the center of the wafer 11, but also the position of a point on the outer periphery of the wafer 11 located on a straight line passing through the center (origin O) of the holding surface and the processing point. In short, the distance between the center (origin O) of the holding surface and the processing point is adjusted according to the value of y, which is a function with the rotation angle θ of the holding table 10 or the holding table 42 as a variable.

[0107] For example, as shown in Figures 6(A) and 6(B), when edge trimming is performed on the region between the outer periphery of the wafer 11 and the device 13a, the distance between the center of the holding surface (origin O) and the processing point is adjusted to be the length obtained by subtracting the above-mentioned edge trimming reference width and the above-mentioned maximum increment value from the value of y.

[0108] Furthermore, as shown in Figures 7(A) and 7(B), when edge trimming is performed on the region between the outer periphery of the wafer 11 and the device 13d, the distance between the center of the holding surface (origin O) and the processing point is adjusted to be the value of y minus the reference width for edge trimming described above and plus the maximum decrement value described above.

[0109] Furthermore, as shown in Figures 11(A) and 11(B), when edge trimming is performed on the region between the outer periphery of the wafer 11 and the device 13l, the distance between the center of the holding surface (origin O) and the processing point is adjusted to be the length obtained by subtracting the reference width for edge trimming described above from the value of y.

[0110] As a result, in the method shown in Figure 15, even if the center of the wafer 11 is shifted from the center of the holding surface of the holding table 10 or the holding table 42, the outer peripheral edge of the wafer 11 can be processed with a width that varies depending on the distance between the boundary between the device region 15a and the outer peripheral surplus region 15b and the center of the wafer 11.

[0111] 15, the center calculation step (S4) and the outer periphery position calculation step (S5) may be performed after the boundary identification step (S2). In this case, the image used to identify the boundary between the device area 15a and the outer periphery excess area 15b in the boundary identification step (S2) may be used in the center calculation step (S4).

[0112] For example, after identifying the positions of three points on the outer periphery of the wafer 11 based on the image formed in the boundary identifying step (S2), the position of the center of the wafer 11 may be calculated based on the positions of these three points. In this case, it is preferable because there is no need to newly capture an image in the center calculating step (S4).

[0113] In addition, the structures and methods according to the above-described embodiments can be modified as appropriate without departing from the scope of the present invention. [Explanation of symbols]

[0114] 2:Cutting device 4: Base (4a: opening) 6,8:Cover 10: Holding table (10a: Porous plate) 12: Support structure (12a: standing part, 12b: arm part) 14:Y-axis direction movement mechanism 16: Y-axis guide rail 18: Y-axis moving plate 20: Screw shaft 22:Z-axis direction movement mechanism 24: Z-axis guide rail 26: Z-axis moving 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~13l: Device 15a: Device area 15b: Surplus outer area 40: Laser irradiation device 42: Holding table (42a: Porous plate) 44: Laser beam irradiation unit 46: Head 48:Connection part 50: Imaging unit

Claims

1. A method for processing a wafer having a device region on a surface in which a plurality of devices are formed and a peripheral excess region surrounding the device region, the wafer having a chamfered peripheral edge portion, the method comprising the steps of: 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 a center of the holding surface; a boundary identifying step of identifying a boundary between the device region and the peripheral excess region based on an image formed by imaging an area including at least a portion of the plurality of devices and an outer periphery of the wafer; a processing step of processing the outer peripheral edge of the wafer with a width that varies according to the distance between the boundary and the center 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, A wafer processing method, wherein in the processing step, the width is maintained at or above a predetermined length even if at least one of the plurality of devices is damaged.

2. A method for processing a wafer having a surface including a device region in which a plurality of devices are formed and a peripheral excess region surrounding the device region, the peripheral edge of which is chamfered, 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 a center of the holding surface; a boundary identifying step of identifying a boundary between the device region and the peripheral excess region based on an image formed by imaging an area including at least a portion of the plurality of devices and an outer periphery of the wafer; a processing step of processing the outer peripheral edge of the wafer with a width that varies according to the distance between the boundary and the center 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, A wafer processing method, characterized in that the processing step is carried out by cutting the wafer with a cutting blade attached to the tip of a rotatable spindle.

3. 2. The method for processing a wafer according to claim 1, wherein the processing step is performed by irradiating the wafer with a laser beam having a wavelength that is absorbed by the wafer.

4. 2. The wafer processing method according to claim 1, wherein the processing step is performed by irradiating the wafer with a laser beam having a wavelength that transmits the wafer and positioning a focal point of the laser beam inside the wafer, thereby breaking the wafer along an altered layer formed inside the wafer.

Images