Improved wafer edge shape for processing thin wafers

Abstract

Semiconductor wafer comprising: a substrate (102) comprising: a front surface (104, 204, 304, 504), a rear surface (224, 314, 524) opposite the front surface (104, 204, 304, 504); and a peripheral edge (108, 208, 508) between the front surface (104, 204, 304, 504) and the back surface (224, 314, 524), wherein the peripheral edge (108, 208, 508) has a curved edge profile (110, 210, 310, 510) between an edge (106, 206, 306, 506) of the front surface (104, 204, 304, 504) and a side surface (222, 522) of the peripheral edge (108, 208, 508) of the semiconductor wafer, wherein the curved edge profile (110, 210, 310, 510) includes: a first convex curvature (216, 316, 516) which merges into the edge of the front surface (104, 204, 304, 504), and a concave curvature that merges into the first convex curvature (216, 316, 516), wherein a tangent to the edge profile (110, 210, 310, 510) at an inflection point between the first convex curvature (216, 316, 516) and the concave curvature is perpendicular to a plane coplanar with the front surface (104, 204, 304, 504) or meets the plane at a radial distance from a central portion of the front surface (104, 204, 304, 504) that is less than a perpendicular projection of the inflection point onto the plane.

Description

[0001] The present application relates to a wafer, in particular a wafer with a curved edge profile, and a method for producing such a wafer.

[0002] Semiconductor wafers, such as monocrystalline silicon wafers, are used to manufacture integrated circuits. The wafers are formed by cutting a cylindrical crystalline ingot into thin disc-shaped wafers. The rectangular edges of the cut wafers are rounded to reduce mechanical damage, such as edge chipping and cracking, that can occur during wafer handling. Rounding can be performed using a grinding process that uses a wafer edge grinding wheel. Since edge chipping and cracking can increase stress and facilitate the onset of wafer fracture or deformation during thermal processing, rounding will improve wafer yield. Typically, a larger edge rounding radius results in greater mechanical stability.

[0003] Wafers are available in sizes ranging from 25 millimeters (1 inch) to 300 millimeters (12 inches) and have corresponding thicknesses ranging from 300 micrometers to 800 micrometers. If the wafers require thinning during the manufacturing process, the stress-reducing benefit of the original rounding of the thick wafer edge will be lost if the final thickness value falls below the radius of the original edge rounding. For example, if 300-millimeter wafers have an edge rounding radius of 200 micrometers and are thinned to a final thickness of 100 micrometers or less, the resulting sharp wafer edges will become mechanically unstable during subsequent steps in the manufacturing process, leading to increased losses in wafer yield.

[0004] One approach that has been used is to round the edges of the wafer proportional to the expected target thickness of the wafer after thinning. However, wafers whose edges are rounded to radii of curvature that are relatively small compared to their original thickness will be more susceptible to mechanical damage during handling before they are thinned to their target thickness. This problem will worsen over time, as semiconductor industry roadmaps for target wafer thicknesses after thinning already call for thicknesses well below 100 micrometers. US 2009 / 0 325 382 A1 concerns the uneven deposition of material layers on a wafer, which is particularly problematic in the edge region. A bevel is therefore etched into a dielectric layer deposited on the wafer at the edge of the wafer to level the surface.The publication US 2008 / 0 044 984 A1 concerns the production of back-illuminated image sensors. A rectangular recess along the wafer edge is intended to reduce the risk of wafer breakage during a thinning process. The publication US 2012 / 0 241 916 A1 also addresses the question of how to prevent wafer breakage during a thinning process. For this purpose, the wafer edge is machined from the edge side. The publication US 2013 / 0 101 790 A1 concerns electronic-quality glass substrates and associated manufacturing methods. The publication US 2009 / 0 102 020 A1 concerns wafers and associated manufacturing methods.

[0005] One aspect provides a wafer according to claim 1, comprising a substrate having a front surface and a back surface. The wafer includes an edge between the front surface and the back surface. The edge has a curved edge profile between an edge of the front surface and a side surface of the edge of the wafer. The curved edge profile includes a first convex curvature that blends into the edge of the front surface.

[0006] In some embodiments, the curved edge profile includes a second convex curvature that transitions into the side surface. In some embodiments, the curved edge profile includes a concave intermediate curvature that transitions into the first convex curvature. In some embodiments, the concave intermediate curvature transitions into the second concave curvature.

[0007] In some embodiments, a minimum radius of curvature of the first convex curve is smaller than the minimum radius of curvature of the second convex curve. In some embodiments, the first convex curve and at least a portion of the intermediate concave curve have a positive gradient.

[0008] In some embodiments, the intermediate concave curvature merges into the first convex curvature at a first depth below a level of the front surface. In some embodiments, a minimum radius of curvature of the first convex curvature is less than or equal to the first depth. In some embodiments, the second convex curvature merges into the side surface at a second depth below the level of the front surface, and wherein the second depth is greater than the first depth. In some embodiments, the intermediate concave curvature merges into the second convex curvature at an intermediate depth below the level of the front surface, and wherein the intermediate depth is greater than the first depth and less than the second depth. In some embodiments, the first depth is less than or equal to 150 micrometers.

[0009] One aspect further provides a wafer according to claim 10, the substrate comprising a front surface and a back surface. The wafer includes a peripheral edge between the front surface and the back surface. The peripheral edge has a curved edge profile between an edge of the front surface and a side surface of the peripheral edge of the wafer. The curved edge profile includes a first convex curvature that merges into the edge of the front surface at a first radial distance from the side surface.

[0010] In some embodiments, the curved edge profile includes a second convex curvature that transitions into the side surface. The curved edge profile includes a concave curvature, also referred to herein as an intermediate concave curvature. In some embodiments, the intermediate concave curvature lies between the first convex curvature and the second convex curvature. In some embodiments, the intermediate concave curvature transitions into the first convex curvature at a second radial distance from the side surface.

[0011] In some embodiments, the concave intermediate curvature transitions into the second convex curvature at a third radial distance from the side surface. In some embodiments, the first radial distance is greater than the second radial distance, and the second radial distance is greater than the third radial distance.

[0012] In some embodiments, a minimum radius of curvature of the first convex curve is smaller than the minimum radius of curvature of the second convex curve. In some embodiments, the first convex curve and at least a portion of the intermediate concave curve have a positive gradient.

[0013] In some embodiments, the concave intermediate curvature transitions into the first convex curvature at a first depth below a level of the front surface. In some embodiments, a minimum radius of curvature of the first convex curvature is less than or equal to the first depth. In some embodiments, the second convex curvature transitions into the side surface at a second depth below the level of the front surface, and wherein the second depth is greater than the first depth. In some embodiments, the concave intermediate curvature transitions into the second convex curvature at an intermediate depth below the level of the front surface, and wherein the intermediate depth is greater than the first depth and less than the second depth.

[0014] One aspect further provides a method of forming a wafer according to claim 18 and comprises providing a wafer including a front surface, a back surface, and an edge between the front surface and the back surface. The method comprises forming a curved edge profile between an edge of the front surface and a side surface of the edge of the wafer. In some implementations, the curved edge profile includes a first convex curvature that blends into the edge of the front surface. In some implementations, the curved edge profile includes a second convex curvature that blends into the side surface. In some implementations, the curved edge profile includes a concave curvature, also referred to herein as an intermediate concave curvature, that blends into the first convex curvature. In some implementations, the intermediate concave curvature blends into the second convex curvature.

[0015] In some implementations, forming the curved edge profile comprises forming the edge of the wafer in a direction radial to the edge to form the first convex curvature, the second convex curvature, and the intermediate concave curvature. In some implementations, forming the curved edge profile comprises forming the edge of the wafer in a direction radial to the edge to form at least a portion of the first convex curvature and the second convex curvature. In some implementations, forming the curved edge profile comprises forming the edge of the wafer in a direction perpendicular to the front surface to form the intermediate concave curvature.

[0016] In some implementations, forming the curved edge profile comprises forming the first convex curvature with a minimum radius of curvature that is less than the minimum radius of curvature of the second convex curvature. In some implementations, forming the curved edge profile comprises forming the intermediate concave curvature such that it transitions into the first convex curvature at a first depth below a level of the front surface. In some implementations, forming the curved edge profile comprises forming the first convex curvature with a minimum radius of curvature that is less than or equal to the first depth. In some implementations, forming the curved edge profile comprises forming the second convex curvature such that it transitions into the side surface at a second depth below the level of the front surface, and wherein the second depth is greater than the first depth.In some implementations, forming the curved edge profile comprises forming the intermediate concave curvature such that it transitions to the second convex curvature at an intermediate depth below the level of the front surface, and wherein the intermediate depth is greater than the first depth and less than the second depth.

[0017] According to one embodiment of a wafer, the wafer includes a front surface, a back surface, and an edge between the front surface and the back surface with a curved edge profile between an edge of the front surface and a side surface of the edge of the wafer. The edge profile includes a first convex curvature that transitions into the edge of the front surface and a concave curvature that transitions into the first convex curvature. In some embodiments, a tangent to the edge profile at an inflection point between the first convex curvature and the concave curvature is perpendicular to a plane coplanar with the front surface.In some embodiments, a tangent to the edge profile meets the plane at an inflection point between the first convex curvature and the concave curvature at a radial distance from a central portion of the front surface that is less than a normal projection of the inflection point onto a plane coplanar with the front surface.

[0018] According to one embodiment of a wafer, the wafer includes a front surface, a back surface, and a peripheral edge between the front surface and the back surface, having a curved edge profile between an edge of the front surface and a side surface of the peripheral edge of the wafer. The edge profile includes a first convex curvature that transitions into the edge of the front surface at a first radial distance from the side surface. The edge profile includes a concave curvature, also referred to herein as an intermediate concave curvature, that transitions into the first convex curvature. In some embodiments, a tangent to the edge profile at an inflection point between the first convex curvature and the concave curvature is perpendicular to a plane coplanar with the front surface.In some embodiments, a tangent to the edge profile meets the plane at an inflection point between the first convex curvature and the concave curvature at a radial distance from a central portion of the front surface that is less than a normal projection of the inflection point onto a plane coplanar with the front surface.

[0019] According to one embodiment of a method of forming a wafer, the method comprises providing a wafer including a front surface, a back surface, and an edge between the front surface and the back surface, and forming a curved edge profile between an edge of the front surface and a side surface of the edge of the wafer. The curved edge profile includes a first convex curvature that transitions into the edge of the front surface, a second convex curvature that transitions into the side surface, and a concave curvature, also referred to herein as an intermediate concave curvature, that transitions into the first convex curvature and the second convex curvature.

[0020] The independent claims define the invention in various aspects. The dependent claims set out embodiments according to the invention in various aspects.

[0021] Those skilled in the art will recognize additional features and advantages upon reading the following detailed description and examining the accompanying drawings.

[0022] First, the drawings are briefly described. The elements of the drawings are not necessarily to scale. Like reference numerals indicate corresponding similar parts. The features of the various illustrated embodiments may be combined unless mutually exclusive. Embodiments are illustrated in the drawings and set forth in the following description.

[0023] Fig. Figure 1 illustrates a top view of one embodiment of a wafer having a curved edge profile.

[0024] Fig. Figure 2 illustrates a cross-sectional view of one embodiment of a wafer having a curved edge profile.

[0025] Fig. 2A illustrates a cross-sectional view of an embodiment of the Fig. 2 illustrated wafers.

[0026] Fig. Figure 3 illustrates a cross-sectional view of one embodiment of a wafer that has been thinned.

[0027] Fig. 4 illustrates a cross-sectional view of the embodiment of the Fig. 2 and Fig. 2A illustrated curved edge profile.

[0028] Fig. Figure 5 illustrates a cross-sectional view of one embodiment of a wafer having a curved edge profile.

[0029] Fig. 5A illustrates a cross-sectional view of an embodiment of the Fig. 5 illustrated wafers.

[0030] Fig. Figure 6 illustrates a cross-sectional view of the embodiment of the Fig. 5 and Fig. 5A illustrated curved edge profile.

[0031] Fig. 7 illustrates a flowchart of one embodiment of a method for forming a wafer having a curved edge profile.

[0032] Next, embodiments are described in detail.

[0033] Fig. 1 illustrates a top view of one embodiment of a wafer at 100. A cross-sectional view of the wafer 100 is shown in Fig. 2, Fig. 2A, Fig. 5 and Fig. 5A, where Fig. 2, Fig. 2A, Fig. 5 and Fig. 5A to a dashed line in Fig. 1. In the illustrated embodiment, wafer 100 includes a substrate 102. In one embodiment, substrate 102 is a silicon (Si) substrate. In other embodiments, substrate 102 may be formed from other suitable materials, including, but not limited to, silicon germanium (SiGe), silicon-on-insulator (SOI), silicon carbide (SiC), gallium arsenide (GaAs), and gallium nitride (GaN).

[0034] In the illustrated embodiment, the wafer 100 includes a front surface 104 having an edge 106. The wafer 100 further includes an edge 108 located between the front surface 104 and the back surface (not shown, except Fig. 2). In the illustrated embodiment, the edge 108 is a peripheral edge 108. In other embodiments, the edge 108 may have other suitable shapes. In the illustrated embodiment, the edge 108 includes a curved edge profile 110 between the edge 106 of the front surface 104 and a side surface (not shown, except Fig. 2) from edge 108.

[0035] Fig. 2 illustrates at 200 a cross-sectional view of an embodiment of a Fig. 1. The wafer 200 includes a front surface 204, a back surface 224, and an edge 208 located between the front surface 204 and the back surface 224. The edge 208 includes a curved edge profile 210 between the edge 206 of the front surface 204 and a side surface 222 of the edge 208. The edge profile 210 includes a first convex curvature 216 that blends into the edge 206 of the front surface 204, a second convex curvature 220 that blends into the side surface 222, and an intermediate concave curvature 218 that blends into the first convex curvature 216 and the second convex curvature 220.

[0036] Fig. 2 illustrates an embodiment of wafer 200 before wafer thinning has been performed. The dashed line at 214 illustrates a final wafer thickness after wafer 200 has been thinned, and substrate portion 212 illustrates the portion of substrate 102 remaining after thinning. After thinning, substrate portion 212 of wafer 200 includes front surface 204 and a first convex curvature 216 that merges into edge 206 of front surface 204. The dashed line at 214 corresponds to back surface 314 of wafer 300 (assuming Fig. 3).

[0037] Fig. 2A illustrates at 200A a cross-sectional view of an embodiment of the Fig. 2. In this embodiment, wafer 200 is an SOI wafer including a buried oxide layer 230. Buried oxide layer 230 is below front surface 204 and above dashed line 214. In other embodiments, buried oxide layer 230 may be below dashed line 214.

[0038] Fig. 3 illustrates a cross-sectional view of one embodiment of a wafer 300 that has been thinned. In one embodiment, wafer 300 corresponds to wafer 200 after wafer 200 has been thinned. In one embodiment, wafer 300 corresponds to wafer 500 after wafer 500 has been thinned (refer to Fig. 5). In the illustrated embodiment, wafer 300 includes a substrate portion 312 and has a front surface 304, a back surface 314, and an edge 308 located between front surface 304 and back surface 314. After thinning, edge profile 310 of edge 308 includes a first convex curvature 316. In various embodiments, first convex curvature 316 has a radius of curvature that continuously changes between high values at endpoints where first convex curvature 316 meets edge 306 and meets back surface 314, and a minimum value reached between edge 306 and back surface 314. In one embodiment, first convex curvature 316 has a radius of curvature that does not change.In other embodiments, the first convex curvature 316 has a radius of curvature that varies between one or more high values and one or more low values.

[0039] Fig. 4 illustrates at 400 a cross-sectional view of the embodiment of the Fig. 2 and Fig. 2A. The edge 208 includes a curved edge profile 210 between the edge 206 of the front surface 204 and the side surface 222 of the edge 208. The edge profile 210 includes a first convex curve 216 that blends into the edge 206 of the front surface 204, a second convex curve 220 that blends into the side surface 222, and an intermediate concave curve 218 that blends into the first convex curve 216 and the second convex curve 220. A radial direction 460 illustrates a direction that is radial to the peripheral edge 208. A perpendicular direction 462 illustrates a direction that is perpendicular to the front surface 204.

[0040] In the illustrated embodiment, the first convex curvature 216 has a first endpoint 432 at a first depth 440 below a level of the front surface 204. In one embodiment, at least a portion of the intermediate concave curvature 218 is below the first depth 440. In one embodiment, the first depth 440 is less than or equal to 150 micrometers. In one embodiment, the first depth 440 is less than or equal to 100 micrometers. In one embodiment, the first depth 440 is less than or equal to 50 micrometers. In other embodiments, the first depth 440 may have other suitable values.

[0041] In the illustrated embodiment, the second convex curvature 220 merges into the side surface 222 at a second endpoint 438, which is at a second depth 444 below the level of the front surface 204. The second depth 444 is greater than the first depth 440. The intermediate concave curvature 218 merges into the second convex curvature 220 at an intermediate endpoint 436, which is at an intermediate depth 442 below the level of the front surface 204. In the illustrated embodiment, the intermediate depth 442 is greater than the first depth 440 and less than the second depth 444. In other embodiments, the intermediate depth 442 may be less than the first depth 440.

[0042] In the illustrated embodiment, the first convex curve 216 meets the edge 206 of the front surface 204 at a first radial distance 426 from the side surface 222 of the peripheral edge 208. The first endpoint 432 is located at a second radial distance 430 from the side surface 222. An intermediate endpoint 436 is located at a third radial distance 434 from the side surface 222. In the illustrated embodiment, the first radial distance 426 is greater than the second radial distance 430, and the second radial distance 430 is greater than the third radial distance 434. In other embodiments, the first radial distance 426, the second radial distance 430, and the third radial distance 434 may have other suitable relationships.

[0043] In the illustrated embodiment, the first convex curve 216 has a radius of curvature, which is illustrated by the radius arrow 446. This radius of curvature is positive because the center of the radius of curvature, which is illustrated by the radius arrow 446, is located within the wafer 200 or within the substrate 102 of the wafer 200. In various embodiments, the first convex curve 216 has a radius of curvature that continuously changes from high values at the edge 206 and the first endpoint 432 to a low value or minimum value at a point between the edge 206 and the first endpoint 432. In one embodiment, the minimum value occurs at a midpoint between the edge 206 and the first endpoint 432 and is determined by the position of the radius arrow 446 in Fig. 4. In one embodiment, a minimum radius of curvature of the first convex curve 216 is less than or equal to the first depth 440. In other embodiments, a minimum radius of curvature of the first convex curve 216 is greater than the first depth 440. In some embodiments, the first convex curve 216 has a radius of curvature that does not change. In other embodiments, the first convex curve 216 has a radius of curvature that changes between one or more high values and one or more low values.

[0044] In the illustrated embodiment, the second convex curve 220 has a radius of curvature, which is illustrated by the radius arrow 450. This radius of curvature is positive because the center of the radius of curvature, which is illustrated by the radius arrow 450, is located within the wafer 200 or within the substrate 102 of the wafer 200. In various embodiments, the second convex curve 220 has a radius of curvature that continuously changes from high values at the intermediate endpoint 436 and the second endpoint 438 to a low value or minimum value at a point between the intermediate endpoint 436 and the second endpoint 438. In one embodiment, the minimum value occurs at a midpoint between the intermediate endpoint 436 and the second endpoint 438 and is determined by the position of the radius arrow 450 in Fig. 4. In other embodiments, the second convex curve 220 has a radius of curvature that does not change. In other embodiments, the second convex curve 220 has a radius of curvature that changes between one or more high values and one or more low values. In the illustrated embodiment, a minimum radius of curvature 446 of the first convex curve 216 is smaller than the minimum radius of curvature 450 of the second convex curve 220.

[0045] In the illustrated embodiment, the concave intermediate curvature 218 has a radius of curvature, illustrated by the radius arrow 448. This radius of curvature is negative because the center of the radius of curvature, illustrated by the radius arrow 448, is located outside the wafer 200 or outside the substrate 102 of the wafer 200. In various embodiments, the concave intermediate curvature 218 has a radius of curvature that continuously changes from high values at the first endpoint 432 and the intermediate endpoint 436 to a low value or minimum value at a point between the first endpoint 432 and the intermediate endpoint 436. In one embodiment, the minimum value occurs at a midpoint between the first endpoint 432 and the intermediate endpoint 436 and is indicated by the position of the radius arrow 448 in Fig. 4. In other embodiments, the concave intermediate curvature 218 has a radius of curvature that does not change. In other embodiments, the concave intermediate curvature 218 has a radius of curvature that changes between one or more high values and one or more low values.

[0046] In the illustrated embodiment, the concave intermediate curvature 218 transitions into the first convex curvature 216 at the first endpoint 432. Thus, the first endpoint 432 is an inflection point between the first convex curvature 216 and the concave intermediate curvature 218. In some implementations, a tangent 432a to the edge profile 210 at the inflection point is perpendicular to a plane 204a coplanar with the front surface 204. In one embodiment, the first convex curvature 216 and at least a portion 452 of the concave intermediate curvature 218 have a positive gradient. The portion 452 is the portion of the concave intermediate curvature 218 that transitions into the first convex curvature 216. The gradient is defined as the ratio of the change in the vertical direction 454 to the change in the radial direction 460 for the part 452 of the concave intermediate curvature 218 and for the first convex curvature 216.

[0047] Fig. 5 illustrates at 500 a cross-sectional view of an embodiment of the Fig. 1. The wafer 500 includes a front surface 504, a back surface 524, and an edge 508 located between the front surface 504 and the back surface 524. The edge 508 includes a curved edge profile 510 between the edge 506 of the front surface 504 and a side surface 522 of the edge 508. The edge profile 510 includes a first convex curvature 516 that blends into the edge 506 of the front surface 504, a second convex curvature 520 that blends into the side surface 522, and an intermediate concave curvature 518 that blends into the first convex curvature 516 and the second convex curvature 520.

[0048] Fig. 5 illustrates an embodiment of wafer 500 before wafer thinning has been performed. The dashed line at 514 illustrates a final wafer thickness after wafer 500 has been thinned, and substrate portion 512 illustrates the portion of substrate 102 remaining after thinning. After thinning, substrate portion 512 of wafer 500 includes front surface 504 and a first convex curvature 516 that merges into edge 506 of front surface 504. The dashed line at 514 corresponds to a back surface of wafer 500 after thinning (see also Fig. 3).

[0049] Fig. 5A illustrates at 500A a cross-sectional view of an embodiment of the Fig. 5. In this embodiment, wafer 500 is an SOI wafer including a buried oxide layer 530. Buried oxide layer 530 is below front surface 504 and above dashed line 514. In other embodiments, buried oxide layer 530 may be below dashed line 514.

[0050] Fig. 6 illustrates at 600 a cross-sectional view of the embodiment of the Fig. 5 and Fig. 5A. The edge 508 includes a curved edge profile 510 between the edge 506 of the front surface 504 and the side surface 522 of the edge 508. The edge profile 510 includes a first convex curve 516 that transitions into the edge 506 of the front surface 504, a second convex curve 520 that transitions into the side surface 522, and an intermediate concave curve 518 that transitions into the first convex curve 516 and the second convex curve 520. A radial direction 660 illustrates a direction that is radial to the peripheral edge 508. A perpendicular direction 662 illustrates a direction that is perpendicular to the front surface 504.

[0051] In the illustrated embodiment, the first convex curvature 516 has a first endpoint 632 at a first depth 640 below a level of the front surface 504. In one embodiment, at least a portion of the intermediate concave curvature 518 is below the first depth 640. In one embodiment, the first depth 640 is less than or equal to 150 micrometers. In one embodiment, the first depth 640 is less than or equal to 100 micrometers. In one embodiment, the first depth 640 is less than or equal to 50 micrometers. In other embodiments, the first depth 640 may have other suitable values.

[0052] In the illustrated embodiment, the second convex curvature 520 merges into the side surface 522 at a second endpoint 638, which is at a second depth 644 below the level of the front surface 504. The second depth 644 is greater than the first depth 640. The intermediate concave curvature 518 merges into the second convex curvature 520 at an intermediate endpoint 636, which is at an intermediate depth 642 below the level of the front surface 504. In the illustrated embodiment, the intermediate depth 642 is greater than the first depth 640 and less than the second depth 644. In other embodiments, the intermediate depth 642 may be less than the first depth 640.

[0053] In the illustrated embodiment, the first convex curve 516 meets the edge 506 of the front surface 504 at a first radial distance 626 from the side surface 522 of the peripheral edge 508. The first endpoint 632 is located at a second radial distance 630 from the side surface 522. An intermediate endpoint 636 is located at a third radial distance 634 from the side surface 522. In the illustrated embodiments, the first radial distance 626 is greater than the second radial distance 630, and the second radial distance 630 is greater than the third radial distance 634. In other embodiments, the first radial distance 626, the second radial distance 630, and the third radial distance 634 may have other suitable relationships.

[0054] In the illustrated embodiment, the first convex curve 516 has a radius of curvature, which is illustrated by the radius arrow 646. This radius of curvature is positive because the center of the radius of curvature, which is illustrated by the radius arrow 646, is located within the wafer 500 or within the substrate 102 of the wafer 500. In various embodiments, the first convex curve 516 has a radius of curvature that continuously changes from high values at the edge 506 and the first endpoint 632 to a low value or minimum value at a point between the edge 506 and the first endpoint 632. In one embodiment, the minimum value occurs at a midpoint between the edge 506 and the first endpoint 632 and is indicated by the position of the radius arrow 646 in Fig. 6. In one embodiment, a minimum radius of curvature of the first convex curve 516 is less than or equal to the first depth 640. In other embodiments, a minimum radius of curvature of the first convex curve 516 is greater than the first depth 640. In some embodiments, the first convex curve 516 has a radius of curvature that does not change. In other embodiments, the first convex curve 516 has a radius of curvature that changes between one or more high values and one or more low values.

[0055] In the illustrated embodiment, the second convex curve 520 has a radius of curvature, which is illustrated by the radius arrow 650. This radius of curvature is positive because the center of the radius of curvature, which is illustrated by the radius arrow 650, is located within the wafer 500 or within the substrate 102 of the wafer 500. In various embodiments, the second convex curve 520 has a radius of curvature that continuously changes from high values at the intermediate endpoint 636 and the second endpoint 638 to a low value or minimum value at a point between the intermediate endpoint 636 and the second endpoint 638. In one embodiment, the minimum value occurs at a midpoint between the intermediate endpoint 636 and the second endpoint 638 and is indicated by the position of the radius arrow 650 in Fig. 6. In other embodiments, the second convex curve 520 has a radius of curvature that does not change. In other embodiments, the second convex curve 520 has a radius of curvature that changes between one or more high values and one or more low values. In the illustrated embodiment, a minimum radius of curvature 646 of the first convex curve 516 is smaller than the minimum radius of curvature 650 of the second convex curve 520.

[0056] In the illustrated embodiment, the concave intermediate curvature 518 has a radius of curvature, illustrated by the radius arrow 648. This radius of curvature is negative because the center of the radius of curvature, illustrated by the radius arrow 648, is located outside the wafer 500 or outside the substrate 102 of the wafer 500. In various embodiments, the concave intermediate curvature 518 has a radius of curvature that continuously changes from high values at the first endpoint 632 and the intermediate endpoint 636 to a low value or minimum value at a point between the first endpoint 632 and the intermediate endpoint 636. In one embodiment, the minimum value occurs at a midpoint between the first endpoint 632 and the intermediate endpoint 636 and is indicated by the position of the radius arrow 648 in Fig. 6. In other embodiments, the concave intermediate curvature 518 has a radius of curvature that does not change. In other embodiments, the concave intermediate curvature 518 has a radius of curvature that changes between one or more high values and one or more low values.

[0057] In the illustrated embodiment, the concave intermediate curvature 518 transitions into the first convex curvature 516 at the first endpoint 632. Thus, the first endpoint 632 is an inflection point between the first convex curvature 516 and the concave intermediate curvature 518. In some implementations, a tangent 632a to the edge profile 510 at the inflection point is perpendicular to a plane 504a coplanar with the front surface 504. In one embodiment, the first convex curvature 516 and at least a portion 652 of the concave intermediate curvature 518 have a positive gradient. The portion 652 is the portion of the concave intermediate curvature 518 that transitions into the first convex curvature 516. The gradient is defined as the ratio of the change in the vertical direction 654 to the change in the radial direction 660 for the part 652 of the concave intermediate curvature 518 and for the first convex curvature 616.

[0058] Regarding the curvature of the curved edge profile, although in the examples discussed above, particularly with reference to Fig. 4 and Fig. 6, the tangent to the inflection point between the first convex curvature and the concave intermediate curvature is perpendicular to a plane with the front surface, the curved edge profile is, in some implementations (not shown), such that the first convex curvature does not bend sufficiently far down from the front surface for a tangent to the endpoint of the first convex curvature, i.e., the inflection point between the first convex curvature and the concave intermediate curvature, to be perpendicular to the plane with the front surface. In such an embodiment, a perpendicular projection of the inflection point onto the plane with the front surface lies farther from a center or central portion of the front surface than a point at which the tangent to the endpoint or the inflection point meets the plane with the front surface.

[0059] Fig.7 illustrates a flowchart of one embodiment of a method for forming a wafer having a curved edge profile. The method is illustrated at 700. At 702, a wafer 200 is provided, including a front surface 204, a back surface 224, and an edge 208 between the front surface 204 and the back surface 224. At 704, a curved edge profile 210 is formed between an edge 206 of the front surface 204 and a side surface 222 of the edge 208 of the wafer 200. The curved edge profile 210 includes a first convex curvature 216 that transitions into the edge 206 of the front surface 204, a second convex curvature 220 that transitions into the side surface 222, and a concave intermediate curvature 218 that transitions into the first convex curvature 216 and the second convex curvature 220.

[0060] In one embodiment, forming the curved edge profile 210 includes forming the first convex curve 216 with a minimum radius of curvature 446 that is less than the minimum radius of curvature 450 of the second convex curve 220. In one embodiment, forming the curved edge profile 210 includes forming the first convex curve 216 with a first endpoint 432 located at a first depth 440 below a level of the front surface 204. In one embodiment, forming the curved edge profile 210 includes forming the first convex curve 216 with a minimum radius of curvature that is less than or equal to the first depth 440. In another embodiment, the minimum radius of curvature of the first convex curve 216 is greater than the first depth 440. In one embodiment, the first depth 440 is less than or equal to 150 micrometers.In one embodiment, the first depth 440 is less than or equal to 100 micrometers. In one embodiment, the first depth 440 is less than or equal to 50 micrometers. In other embodiments, the first depth 440 may have other suitable values.

[0061] In one embodiment, forming the curved edge profile 210 includes forming a second convex curve 220 to transition into the side surface 222 at a second depth 444 below the level of the front surface 204. In this embodiment, the second depth 444 is greater than the first depth 440. In one embodiment, forming the curved edge profile 210 includes forming the intermediate concave curve 218 to transition into the second convex curve 220 at an intermediate depth 442 below the level of the front surface 204. In this embodiment, the intermediate depth 442 is greater than the first depth 440 and is less than the second depth 444.

[0062] In one embodiment, forming the curved edge profile 210 includes forming the edge 208 of the wafer 200 in the radial direction 460 to form the convex curvature 216, the convex curvature 220, and the intermediate curvature 218. In this embodiment, the radial direction 460 includes directions having angular deviations from the radial direction 460 ranging up to and including 30°. In some embodiments, forming the curved edge profile 210 includes driving a material removal tool from above the front surface 204 into the front surface 204. For example, in one embodiment, forming the curved edge profile 210 may include, or be achieved by, a grinding process using a wafer edge grinding wheel. In one embodiment, the edge grinding wheel has a surface shape that is an inverse of the curved edge profile 210.In one embodiment, forming the curved edge profile 210 may include, or be achieved by, using a laser to remove material from the wafer 200, directing the wafer toward the front surface 204 either perpendicular to the front surface 204 or at an obtuse angle to the front surface 204 from above the front surface 204, i.e., outward toward the front surface 204. In one embodiment, the edge 208 of the wafer 200 may be formed in a perpendicular direction 462 to form the convex curvature 216, the convex curvature 220, and the intermediate concave curvature 218. In this embodiment, the perpendicular direction 462 includes directions having angular deviations from the perpendicular direction 462 ranging up to and including 30°.

[0063] In one embodiment, forming the curved edge profile 210 includes forming the edge 208 of the wafer 200 in the radial direction 460 to form at least a portion of the convex curvature 216 and the convex curvature 220, and forming the edge 208 of the wafer 200 in the perpendicular direction 462 to form the intermediate concave curvature 218. In this embodiment, the radial direction 460 includes directions having angular deviations from the radial direction 460 that range up to and including 30°. In this embodiment, the perpendicular direction 462 includes directions having angular deviations from the perpendicular direction 462 that range up to and including 30°. In some embodiments, forming the curved edge profile 210 includes driving a material removal tool from above the front surface 204 into the front surface 204.For example, in various embodiments, forming the curved edge profile 210 may include, or be achieved by, a grinding process using a wafer edge grinding wheel applied in the radial direction 460, in the perpendicular direction 462, or in both the radial direction 460 and the perpendicular direction 462. In one embodiment, the edge grinding wheel has a surface shape that is an inverse of the curved edge profile 210. In other embodiments, the convex curvature 216, the convex curvature 220, and the intermediate concave curvature 218 may be formed sequentially or individually in the radial direction 460, in the perpendicular direction 462, or in both the radial direction 460 and the perpendicular direction 462.

[0064] In other embodiments, the curved edge profile 210 may be formed using other suitable approaches. In one embodiment, forming the curved edge profile 210 may include or be achieved by using a laser to remove material from the wafer 200, directing the wafer toward the front surface 204 either perpendicular to the front surface 204 or at an obtuse angle to the front surface 204 from above the front surface 204, i.e., directing it outward toward the front surface 204.

[0065] In one embodiment, forming the curved edge profile 510 includes forming the edge 508 of the wafer 500 in the radial direction 660 to form the convex curvature 516, the convex curvature 520, and the intermediate curvature 518. In this embodiment, the radial direction 660 includes directions having angular deviations from the radial direction 660 ranging up to and including 30°. In some embodiments, forming the curved edge profile 510 includes driving a material removal tool from above the front surface 504 into the front surface 504. For example, in one embodiment, forming the curved edge profile 510 may include, or be achieved by, a grinding process using a wafer edge grinding wheel. In one embodiment, the edge grinding wheel has a surface shape that is an inverse of the curved edge profile 510.In one embodiment, the edge 508 of the wafer 500 may be formed in a perpendicular direction 662 to form the convex curvature 516, the convex curvature 520, and the concave intermediate curvature 518. In this embodiment, the perpendicular direction 662 includes directions having angular deviations from the perpendicular direction 662 ranging up to and including 30°.

[0066] In one embodiment, forming the curved edge profile 510 includes forming the edge 508 of the wafer 500 in the radial direction 660 to form at least a portion of the convex curvature 516 and the convex curvature 520, and forming the edge 508 of the wafer 500 in the perpendicular direction 662 to form the intermediate concave curvature 518. In this embodiment, the radial direction 660 includes directions having angular deviations from the radial direction 660 that range up to and including 30°. In this embodiment, the perpendicular direction 662 includes directions having angular deviations from the perpendicular direction 662 that range up to and including 30°. In some embodiments, forming the curved edge profile 510 includes driving a material removal tool from above the front surface 504 into the front surface 504.For example, in various embodiments, forming the curved edge profile 510 may include, or be achieved by, a grinding process using a wafer edge grinding wheel applied in the radial direction 660, in the perpendicular direction 662, or in both the radial direction 660 and the perpendicular direction 662. In one embodiment, the edge grinding wheel has a surface shape that is an inverse of the curved edge profile 510. In other embodiments, the convex curvature 516, the convex curvature 520, and the intermediate concave curvature 518 may be formed sequentially or individually in the radial direction 660, in the perpendicular direction 662, or in both the radial direction 660 and the perpendicular direction 662.

[0067] In other embodiments, the curved edge profile 510 may be formed using other suitable approaches. In one embodiment, forming the curved edge profile 510 may include or be achieved by using a laser to remove material from the wafer 500, directing the wafer toward the front surface 504 either perpendicular to the front surface 504 or at an obtuse angle to the front surface 504 from above the front surface 504, i.e., directing it outward toward the front surface 504.

[0068] Spatially relative terms such as "under," "beneath," "lower," "above," "upper," and the like are used for convenience of description to describe the positioning of one element relative to a second element. These terms are intended to encompass various orientations of the device in addition to those depicted in the figures. Further, terms such as "first," "second," and the like are also used to describe various elements, regions, sections, etc., and again, these are not intended to be limiting. Throughout the description, like terms refer to similar elements.

[0069] As used herein, the terms "comprising," "containing," "include," "comprise," and the like are open-ended terms that indicate the presence of the specified elements or features, but do not preclude additional elements or features. The articles "a," "an," and "the" are intended to include both the plural and singular, unless the context clearly indicates otherwise.

Claims

[1] Semiconductor wafer comprising: a substrate (102) comprising: a front surface (104, 204, 304, 504), a rear surface (224, 314, 524) opposite the front surface (104, 204, 304, 504); and a peripheral edge (108, 208, 508) between the front surface (104, 204, 304, 504) and the back surface (224, 314, 524), wherein the peripheral edge (108, 208, 508) has a curved edge profile (110, 210, 310, 510) between an edge (106, 206, 306, 506) of the front surface (104, 204, 304, 504) and a side surface (222, 522) of the peripheral edge (108, 208, 508) of the semiconductor wafer, wherein the curved edge profile (110, 210, 310, 510) includes: a first convex curvature (216, 316, 516) which merges into the edge of the front surface (104, 204, 304, 504), and a concave curvature that merges into the first convex curvature (216, 316, 516), wherein a tangent to the edge profile (110, 210, 310, 510) at an inflection point between the first convex curvature (216, 316, 516) and the concave curvature is perpendicular to a plane coplanar with the front surface (104, 204, 304, 504) or meets the plane at a radial distance from a central portion of the front surface (104, 204, 304, 504) that is less than a perpendicular projection of the inflection point onto the plane. [2] The semiconductor wafer of claim 1, wherein the first convex curvature (216, 316, 516) and at least a portion of the concave curvature have a positive gradient. [3] The semiconductor wafer of claim 1 or 2, wherein the concave curvature transitions into the first convex curvature (216, 316, 516) at a first depth below a level of the front surface (104, 204, 304, 504). [4] The semiconductor wafer of claim 3, wherein a minimum radius of curvature of the first convex curvature (216, 316, 516) is less than or equal to the first depth. [5] The semiconductor wafer of any one of claims 1 to 4, wherein the curved edge profile (110, 210, 310, 510) includes a second convex curvature (220, 520) that merges into the side surface (222, 522), and wherein the concave curvature lies between the first convex curvature (216, 316, 516) and the second convex curvature (220, 520). [6] The semiconductor wafer of claim 5, wherein a minimum radius of curvature of the first convex curvature (216, 316, 516) is smaller than the minimum radius of curvature of the second convex curvature (220, 520). [7] The semiconductor wafer of claim 5 or 6, wherein the second convex curvature (220, 520) merges into the side surface (222, 522) at a second depth below the level of the front surface (104, 204, 304, 504), and wherein the second depth is greater than the first depth. [8] The semiconductor wafer of claim 7, wherein the concave curvature merges into the second convex curvature (220, 520) at an intermediate depth below the level of the front surface (104, 204, 304, 504), and wherein the intermediate depth is greater than the first depth and less than the second depth. [9] The semiconductor wafer of any one of claims 3 to 8, wherein the first depth is less than or equal to 150 micrometers. [10] Semiconductor wafer comprising: a substrate (102) comprising: a front surface (104, 204, 304, 504), a rear surface (224, 314, 524) opposite the front surface (104, 204, 304, 504); and a peripheral edge (108, 208, 508) between the front surface (104, 204, 304, 504) and the back surface (224, 314, 524), the peripheral edge (108, 208, 508) having a curved edge profile (110, 210, 310, 510) between an edge (106, 206, 306, 506) of the front surface (104, 204, 304, 504) and a side surface (222, 522) of the peripheral edge (108, 208, 508) of the semiconductor wafer, the curved edge profile (110, 210, 310, 510) including: a first convex curvature (216, 316, 516) which merges into the edge of the front surface (104, 204, 304, 504) at a first radial distance from the side surface (222, 522), and a concave curvature that merges into the first convex curvature (216, 316, 516), wherein a tangent to the edge profile (110, 210, 310, 510) at an inflection point between the first convex curvature (216, 316, 516) and the concave curvature is perpendicular to a plane coplanar with the front surface (104, 204, 304, 504) or meets the plane at a radial distance from a central portion of the front surface (104, 204, 304, 504) that is less than a perpendicular projection of the inflection point onto the plane. [11] The semiconductor wafer of claim 10, wherein the first convex curvature (216, 316, 516) and at least a portion of the concave curvature have a positive gradient. [12] The semiconductor wafer of any one of claims 10 to 11, wherein the concave curvature transitions into the first convex curvature (216, 316, 516) at a first depth below a level of the front surface (104, 204, 304, 504). [13] The semiconductor wafer of claim 12, wherein a minimum radius of curvature of the first convex curvature (216, 316, 516) is less than or equal to the first depth. [14] The semiconductor wafer of any one of claims 10 to 13, wherein the curved edge profile (110, 210, 310, 510) includes a second convex curvature (220, 520) that merges into the side surface (222, 522), and wherein the concave curvature lies between the first convex curvature (216, 316, 516) and the second convex curvature (220, 520). [15] The semiconductor wafer of claim 14, wherein a minimum radius of curvature of the first convex curvature (216, 316, 516) is smaller than the minimum radius of curvature of the second convex curvature (220, 520). [16] The semiconductor wafer of claim 15, wherein the second convex curvature (220, 520) merges into the side surface (222, 522) at a second depth below the level of the front surface (104, 204, 304, 504), and wherein the second depth is greater than the first depth. [17] The semiconductor wafer of claim 16, wherein the concave curvature merges into the second convex curvature (220, 520) at an intermediate depth below the level of the front surface (104, 204, 304, 504), and wherein the intermediate depth is greater than the first depth and less than the second depth. [18] A method of forming a semiconductor wafer, comprising the steps of: Providing a semiconductor wafer comprising a substrate (102) having a front surface (104, 204, 304, 504), a back surface (224, 314, 524) opposite the front surface (104, 204, 304, 504), and a peripheral edge (108, 208, 508) between the front surface (104, 204, 304, 504) and the back surface (224, 314, 524); Driving a material removal tool from above the front surface (104, 204, 304, 504) into the front surface (104, 204, 304, 504); and Forming a curved edge profile (110, 210, 310, 510) between an edge (106, 206, 306, 506) of the front surface (104, 204, 304, 504) and a side surface (222, 522) of the peripheral edge (108, 208, 508) of the semiconductor wafer, wherein the curved edge profile (110, 210, 310, 510) includes a first convex curvature (216, 316, 516) that merges into the edge of the front surface (104, 204, 304, 504) and a concave curvature that merges into the first convex curvature (216, 316, 516), wherein a tangent to the edge profile (110, 210, 310, 510) at an inflection point between the first convex curvature (216, 316, 516) and the concave curvature is perpendicular to a plane coplanar with the front surface (104, 204, 304, 504) or meets the plane at a radial distance from a central portion of the front surface (104, 204, 304, 504) that is less than a perpendicular projection of the inflection point onto the plane. [19] The method of claim 18, wherein forming the curved edge profile (110, 210, 310, 510) includes forming a second convex curvature (220, 520) that merges into the side surface (222, 522), the concave curvature being intermediate between the first convex curvature (216, 316, 516) and the second convex curvature (220, 520). [20] The method of claim 19, wherein forming the curved edge profile (110, 210, 310, 510) comprises forming the first convex curve (216, 316, 516) with a minimum radius of curvature that is smaller than the minimum radius of curvature of the second convex curve (220, 520). [21] The method of claim 19 or 20, wherein forming the curved edge profile (110, 210, 310, 510) comprises forming the concave curvature such that it transitions into the first convex curvature (216, 316, 516) at a first depth below a level of the front surface (104, 204, 304, 504). [22] The method of claim 21, wherein forming the curved edge profile (110, 210, 310, 510) comprises forming the first convex curvature (216, 316, 516) with a minimum radius of curvature less than or equal to the first depth. [23] The method of claim 21 or 22, wherein forming the curved edge profile (110, 210, 310, 510) comprises forming the second convex curvature (220, 520) such that it merges into the side surface (222, 522) at a second depth below the level of the front surface (104, 204, 304, 504), and wherein the second depth is greater than the first depth.

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