US20090044831A1 - Wafer edge cleaning - Google Patents

Abstract

In a first aspect, a method of cleaning an edge of a wafer is provided. The method comprises providing an edge cleaning roller having a first inclined frictional surface for cleaning an edge corner of a wafer rotating within a first plane; and causing the edge cleaning roller to rotate within a second plane at an angle to the first plane while the inclined frictional surface contacts and cleans the edge corner. Numerous other aspects are provided.

Description

• This application is a division of, and claims priority to, U.S. Non-Provisional patent application Ser. No. 10/976,011, filed Oct. 28, 2004, and titled “WAFER EDGE CLEANING” (Attorney Docket No. 8186), which claims priority to U.S. Provisional Application Ser. No. 60/514,938, filed Oct. 28, 2003 and titled “WAFER EDGE CLEANING” (Attorney Docket No. 8186/L). Both of these patent applications are incorporated by reference herein in their entirety for all purposes.
FIELD OF THE INVENTION
• The present invention relates generally to cleaning thin disks, such as semiconductor wafers, compact disks, glass substrates and the like. More particularly, the invention relates to scrubbing devices for simultaneously scrubbing the entire surface of a thin disk, including the edges thereof.
BACKGROUND OF THE INVENTION
• To manufacture a thin disk such as a semiconductor wafer, an elongated billet of semiconductor material is cut into very thin slices or disks, about 2 mm in thickness. The slices or wafers of semiconductor material are then lapped and polished by a process that applies an abrasive slurry to the wafer's surfaces. After polishing, slurry residue conventionally is cleaned or scrubbed from wafer surfaces via a mechanical scrubbing device, such as a device which employs polyvinyl acetate (PVA) brushes, brushes made from other porous or sponge-like material, or brushes having bristles made from nylon or similar materials. Although these conventional cleaning devices remove a substantial portion of the slurry residue which adheres to wafer edges, slurry particles nonetheless may remain and produce defects during subsequent processing.
• A conventional PVA brush scrubber is shown in the side elevational view ofFIG. 1. Theconventional scrubber11, shown inFIG. 1, comprises a pair ofPVA brushes13a,13b, aplatform15 for supporting a wafer W, and a mechanism (not shown) for rotating the pair ofPVA brushes13a,13b. Theplatform15 comprises a plurality of rollers17a-cfor both supporting and rotating the wafer W.
• Preferably, the pair ofPVA brushes13a,13bare positioned to extend beyond the edge of the wafer W, so as to facilitate cleaning the wafer's edge. However, research shows that slurry induced defects still occur, and are caused by slurry residue remaining along the edges of the wafer despite cleaning with apparatuses such as that described above. Specifically, subsequent processing has been found to redistribute slurry residue from the wafer edges to the front of the wafer, causing defects.
• A number of devices have been developed to improve wafer edge cleaning. One such device is shown in the side elevational view ofFIG. 2. The edge-cleaning scrubber19, shown inFIG. 2, includes a pair ofrollers17b,17cadapted to support and rotate the wafer W, and further includes an edge-cleaning roller21 that fits over the edge of the wafer W for cleaning the edge as the wafer rotates. Although the edge-cleaning roller21 addresses the need to clean slurry residue from wafer edges, it can be subject to quick wear, such wear typically being concentrated at locations where it contacts the wafer W.
• FIGS. 3A-3C illustrate details related to how the edge-cleaning roller21 of the edge-cleaning scrubber19 ofFIG. 2 cleans the edge of the wafer W. Referring to the side elevational view ofFIG. 3A, which shows the wafer W above the edge-cleaning roller21, the edge-cleaning roller21 ofFIG. 2 is shown in contact with the wafer W. Specifically, opposing first and secondinclined surfaces23,25 of the edge-cleaning roller21 are in contact with respective opposite first andsecond edge corners27,29 of the edge of the wafer W. For example, either or both of the first andsecond edge corners27,29 may comprise a bevel so as to form, e.g., a truncated frustoconical edge surface (not separately shown) which may be placed in surface-to-surface contact with the first and secondinclined surfaces23,25 of theedge cleaning roller21.
• Referring to the side elevational view ofFIG. 3B, in which the wafer W is shown in phantom across the edge-cleaning roller21, the wafer W rotates in anominal rotation plane31, as does the edge-cleaning roller21. By “nominal rotation plane” is meant that plane within which the wafer W is expected to rotate based on the specific arrangement of rollers (e.g., therollers17b,17c) used to support, drive and guide the wafer W within the edge-cleaningscrubber19 ofFIG. 2. Further, it may be seen that contact betweeninclined surfaces23,25 of the edge-cleaning roller21 and the first andsecond edge corners27,29 of the wafer W takes place along respective first andsecond contact areas33,35 on theinclined surfaces23,25.
• Referring to the cross-sectional view of the edge-cleaning roller21 shown inFIG. 3C, corresponding tosection3C-3C as shown onFIG. 3B, thefirst contact area33 on the firstinclined surface23 translates to a ring-shaped wear sector37 on the firstinclined surface23, typically relatively narrow, which performs the edge-cleaning function and is subject to friction-induced wear over time. Conversely, the remaining portions of the firstinclined surface23 may not typically contact the wafer W during edge cleaning, and therefore may not be subject to such friction-induced wear.
• Other rollers that may rotate in a common plane with a wafer W while contacting a portion of the wafer edge, but that perform additional or separate functions such as rotating the wafer W (e.g., drive rollers, such as the spinning mechanism17a-cofFIG. 1) or guiding the rotating wafer W so as to limit or prevent tilting of the same (e.g., idling guide rollers (not separately shown)), are typically also subject to rapid wear where contact is made with the wafer W. The cost of maintaining proper operation of such parts and/or conducting frequent replacement of the same can mount quickly.
• Accordingly the field of wafer cleaning requires methods and apparatus for effectively performing one or more of the functions of cleaning, supporting, driving and guiding both the flat surfaces and the edge surfaces of a semiconductor wafer, preferably so as to reduce the cost and/or frequency of replacement due to frictional wear from wafer contact.
SUMMARY OF THE INVENTION
• The present invention addresses the need for a more effective edge cleaner by providing a number of different roller embodiments that are adapted for wafer edge cleaning. Specifically:
• • (1) for cleaning the edge bevel of a wafer, an edge cleaning roller is adapted to rotate within a plane that is at an angle to a first plane in which the wafer is supported and rotated;
  • (2) for cleaning the circumferential edge of a wafer, an edge cleaning roller is provided with a flat-bottomed channel having a frictional surface along the channel's bottom; and/or
  • (3) for cleaning an edge region of a major surface of a wafer, an edge cleaning roller is provided with a straight-walled channel having a frictional surface along at least one of the straight walls thereof.
• In a first aspect of the invention, an apparatus for cleaning a thin disk is provided. The apparatus includes (1) a plurality of support rollers adapted to support an edge of the thin disk as the thin disk rotates within a first plane; and (2) an edge-cleaning roller adapted to rotate within a second plane oriented at a first non-zero angle to the first plane, so as to contact an edge bevel of the thin disk while so rotating.
• In a second aspect of the invention, a support roller is provided for supporting a vertically rotating wafer. The support roller includes (1) a guide portion, for receiving an edge of a wafer, having an inclined surface comprising a low-friction material and adapted to allow the wafer edge to slide thereagainst; and (2) an edge-trap portion for retaining the edge of the wafer and having a transverse surface comprising a high-friction material and adapted, when in communication with the edge of the wafer, to resist sliding thereagainst.
• In a third aspect of the invention, a side-contact roller is provided for contacting one or more major surfaces of a rotating wafer. The side-contacting roller includes (1) a guide portion, for receiving an edge of a wafer, having an inclined surface comprising a low-friction material and adapted to allow the wafer edge to slide thereagainst; and (2) an edge-trap portion for retaining the edge of the wafer and having a planar surface comprising a high-friction material and adapted, when in communication with a major surface of the wafer, to resist sliding thereagainst. Numerous other aspects, as are methods in accordance with these and other aspects of the invention.
• Other features and aspects of the present invention will become more fully apparent from the following detailed description, the appended claims and the accompanying drawings.
BRIEF DESCRIPTION OF THE FIGURES
• FIG. 1 is a side elevational view of a conventional PVA brush scrubber.
• FIG. 2 is a side elevational view of a conventional scrubber comprising a conventional edge-cleaning roller for improving wafer edge cleaning.
• FIG. 3A is a side elevational view of the edge-cleaning roller ofFIG. 2, shown cleaning the edge corners of the wafer W.
• FIG. 3B is another side elevational view of the edge-cleaning roller ofFIG. 2, shown contacting the wafer W along contact areas on respective inclined surfaces of the edge-cleaning roller.
• FIG. 3C is a cross-sectional view, corresponding to view3C-3C ofFIG. 2, of the edge-cleaning roller ofFIG. 2 showing a relatively narrow wear sector on an inclined surface of the edge-cleaning roller where contact is made with an edge corner of the wafer W.
• FIG. 4 is a side elevational view of an inventive edge-cleaning roller, shown contacting edge corners of the wafer W and in an inventive angled orientation to a plane of rotation of the wafer W.
• FIG. 5A is a view, corresponding to view5A-5A ofFIG. 4, of a major surface of the wafer W showing separate radial locations at which the inventive edge-cleaning roller ofFIG. 4 contacts respective edge corners of the wafer W.
• FIG. 5B is a cross-sectional view, corresponding to view5B-5B ofFIG. 4, of the inventive edge-cleaning roller ofFIG. 4 showing a relatively wide wear sector on an inclined surface of the edge-cleaning roller where contact is made with an edge corner of the wafer W.
• FIG. 6A is a side elevational view of an inventive edge-cleaning support roller, shown in contact with a cylindrical edge surface of the wafer W.
• FIG. 6B is an exploded assembly perspective view of an edge-cleaning support roller that is a particular embodiment of the inventive edge-cleaning support roller ofFIG. 6A.
• FIG. 7A is a side elevational view of an inventive edge-cleaning side-contact roller, shown engaging the edge of the wafer W.
• FIG. 7B is a cross-sectional view of an edge-cleaning side-contact roller that is a particular embodiment of the inventive edge-cleaning side-contact roller ofFIG. 7A.
• FIG. 8 is a side elevational view of an inventive edge-cleaning roller, shown contacting edge corners of the wafer W and in another inventive angled orientation to a plane of rotation of the wafer W.
• FIG. 9 is a side elevational view of two inventive edge-cleaning rollers ofFIG. 8, shown contacting edge corners of the wafer W and in opposite inventive angled orientations to a plane of rotation of the wafer W.
DETAILED DESCRIPTIONEdge Cleaning Roller
• FIG. 4 is an side elevational view of an inventive edge-cleaningroller101 in which the wafer W is shown in phantom across the edge-cleaningroller101, the edge-cleaningroller101 being adapted to contact edge surfaces (e.g., edge bevels as described above with reference toFIG. 3A) of the wafer W for cleaning. Where, as described above, the wafer W is supported and driven so as to rotate and remain within thenominal rotation plane31 of the wafer W (rotation and support means for the same not being shown), the edge-cleaningroller101 may be inventively oriented relative to the wafer W so as to form afirst angle103, thefirst angle103 being that angle which is described between thenominal rotation plane31 of the wafer W and arotation plane105 within which the edge-cleaningroller101 is disposed and is adapted to rotate.
• As shown inFIG. 4, therotation plane105 of the edge-cleaningroller101 may be oriented relative to thenominal rotation plane31 of the wafer W such that, in forming thefirst angle103, the rotation planes intersect along a line (not separately shown) generally extending radially outward from the center of rotation of the wafer W. Other relative orientations are possible, such as a relative orientation between the rotation planes whereby the planes intersect along a line generally extending tangentially to the wafer W, as is illustrated inFIGS. 8 and 9 and as will be described later.
• Referring again toFIG. 4, the edge-cleaningroller101 may comprise opposing first and secondinclined surfaces107,109 which contact the respective opposite first andsecond edge corners27,29 (FIG. 3A) of the edge of the wafer W. By contrast to the pattern of contact between the wafer W and the edge-cleaningroller21 as shown above inFIGS. 3A and 3B, e.g., in which both the first and thesecond edge corners27,29 of the wafer W are contacted by the edge-cleaningroller21 at substantially the same radial location along the perimeter of the wafer W, the inventive angled orientation of the edge-cleaningroller101 relative to the wafer W shown inFIG. 4 may result in divergent radial contact locations along the perimeter of the wafer W. For example, as shown in the planar view of a major surface of the wafer W shown inFIG. 5A (corresponding to theview5A-5A ofFIG. 4), contact between the first inclined surface107 (FIG. 4) of the edge-cleaningroller101 and thefirst edge corner27 of the wafer W may occur at a firstradial location111 along the perimeter of the wafer W, contact between the second inclined surface109 (FIG. 4) of the edge-cleaningroller101 and thesecond edge corner29 of the wafer W may occur at a secondradial location113 along the perimeter of the wafer W, and asecond angle115 separates the firstradial location111 and the secondradial location113.
• Referring again toFIG. 4, the inventive angled orientation of the edge-cleaningroller101 relative to the wafer W may result in a longer useful life for the edge-cleaningroller101. For example, where inFIGS. 3A and 3C it is shown that coplanar orientation between the respective rotation planes of the edge-cleaningroller21 and the wafer W may result, as mentioned above, in a relatively narrow ring-shapedwear sector37 on the firstinclined surface23 of the edge-cleaningroller21, the inventive angled orientation ofFIG. 4 may increase wear sector width, thus distributing the edge-cleaning function over larger contact areas (see121,FIG. 5B) on the inclined surfaces of the edge-cleaningroller101. The inventive angled orientation ofFIG. 4 therefore may increase the wafer's edge cleaning duty cycle and may extend the useful life of theroller101.
• FIG. 5B, which is a cross-sectional view of the edge-cleaningroller101 taken along asection5B-5B ofFIG. 4, illustrates the above-described feature. Referring toFIG. 5B, contact between the firstinclined surface107 of the edge-cleaningroller101 and the edge of the wafer W (shown in phantom) at the first edge corner27 (FIG. 3A) of the wafer W takes place along afirst contact area117 on the firstinclined surface107, and a ring-shapedwear sector119 on the secondinclined surface109 may be produced thereby (e.g., by virtue of the rotation of the edge-cleaning roller101) having acharacteristic width121.
• As shown inFIG. 5B, thefirst contact area117 tends to extend not only laterally across the slope of the firstinclined surface107, e.g., similarly to thefirst contact area33 ofFIG. 3C, but also up the slope of the firstinclined surface107, e.g., in contrast to thefirst contact area33 ofFIG. 3C. It may readily be seen, therefore, that thewidth121 of the ring-shapedwear sector119 on the firstinclined surface109 of the edge-cleaningroller101 may be proportionately greater than a corresponding dimension (not separately shown) of thewear sector37 on the firstinclined surface23 of the edge-cleaningroller21 ofFIGS. 3A-3C. Given a greater wear sector width, it follows that the area of the firstinclined surface107 subjected to friction-induced wear during wafer edge cleaning (i.e., the wear sector area) will be proportionately greater.
• Assuming the degree of edge cleanliness required by the process remains the same, providing a greater area for the ring-shapedwear sector119 as described above can reduce the edge-cleaning burden per unit area of the wear sector, which may result in a longer useful life for the edge-cleaningroller101. For example, given a larger portion of the firstinclined surface107 of the edge-cleaningroller101 is being used to clean thefirst edge corner27 of the wafer W, edge cleaning may be more efficient, thus allowing, e.g., the length of time that the firstinclined surface107 is applied to thefirst edge corner27 of the wafer W to be decreased, or the contact pressure between the same to be reduced, while still producing the required degree of wafer edge cleanliness. Those possessing skill in the art will recognize that the same dynamic exists between the second edge corner29 (FIG.3A) of the wafer W and the second inclined surface109 (FIG. 4) of the edge-cleaningroller101, resulting in a similar beneficial broadening of a corresponding wear sector (not separately shown), and the same benefits as to part life.
• Those possessing skill in the art will also recognize that additional flexibilities may be obtained by dividing edge-cleaning contact between the edge-cleaningroller101 and the wafer W between radially spaced-apart locations on the edge of the wafer W, e.g., as shown inFIG. 5A. For example, in some embodiments of the edge-cleaningroller101, a third angle123 (seeFIG. 4) described between the firstinclined surface107 and the secondinclined surface109 may be provided that is wider than is typical for edge-cleaning rollers, e.g., so as to more readily facilitate rotation of therotation plane105 of the edge-cleaningroller101 relative to thenominal rotation plane31 of the wafer W. Nevertheless, despite the widerthird angle123, the respective effective angles of contact (not shown) between the firstinclined surface107 and the secondinclined surface109 relative to thenominal rotation plane31 of the wafer (e.g., as measured along the slope of the firstinclined surface107 normal to the direction along which thescrubber117 extends, and along the slope of the secondinclined surface109 in a corresponding direction) may be controlled so as to be equivalent to those of typical edge-cleaning rollers.
• Alternatively, if it is desired to increase the wafer's edge cleaning “duty cycle”, e.g., that angular fraction of the wafer's perimeter which is in contact with theinclined surfaces107,109 of the edge-cleaningroller101 at any given time, or if it is desired to increase the size of an area of edge-cleaning contact on one or more edge surfaces of the wafer W, the same angles of contact may be reduced below that which is typical, in effect narrowing the angular gap between theinclined surfaces107,109 of the edge-cleaningroller101 and the major surfaces of the wafer W. This may be accomplished without undue risk of causing the edge of the wafer to become wedged between the inclined surfaces of the edge-cleaningroller101 and the rotation of the wafer W to become impeded thereby, e.g., since an angular space exists in the form of thesecond angle115 between the first and secondradial locations111,113 (FIG. 5A) along the perimeter of the wafer W at which contact with theinclined surfaces107,109 of the edge-cleaningroller101 takes place.
• Many different angles may be specified for thethird angle123. For example, applicants observe that an angle of 70 degrees, ±10 degrees, produces a good result.
• The edge-cleaningroller101 may further include a normal surface125 (FIG. 4), e.g., cylindrical in shape, and occupying a space between the inclined surfaces of the edge-cleaningroller101. Such a space may be introduced so as to facilitate the rotation of the edge-cleaningroller101 relative to thenominal rotation plane31 of the wafer W. Although many different widths may be specified for such a space, including widths of up to 10 mm or more, applicants observe that a dimension of 2 mm, ±1 mm produces a good result. In addition, thenormal surface125 in that space may or may not be disposed directly adjacent to the inclined surfaces. For example, thenormal surface125 may comprise a bottom surface of a channel disposed in a space between the inclined surfaces (see, e.g.,FIG. 4).
• In some modes of use of the edge-cleaningroller101, thenormal surface125 is spaced apart from a cylindrical edge surface39 (FIG. 3A) of the wafer W while the firstinclined surface107 and the secondinclined surface109 of the edge-cleaningroller101 clean theedge corners27,29 of the wafer W. In other modes of use of the edge-cleaningroller101, thenormal surface125 may be caused to contact and/or support and/or clean thecylindrical edge surface39 of the wafer W.
• In addition, applicants observe that beneficial edge cleaning may be provided where thefirst angle103 described between therotation plane105, within which the edge-cleaningroller101 is disposed, and the nominal rotation plane31 (FIG. 3B) of the wafer W, ranges from 10-30 degrees. Optionally, therefore, thefirst angle103 may be set at 15 degrees, which applicants observe produces a good result.
• Values of (1) a width of the space between the firstinclined surface107 and the secondinclined surface109, (2) thethird angle123, and (3) thefirst angle103 may be established/selected via an iterative, coordinated design process, so as to produce the desired interaction between the edge-cleaningroller101 and the wafer W. Alternatively, selection of such values may be performed automatically based on the desired result. Respective values of 3 mm, 50 degrees, and 20 degrees for those three values provide a good result.
• Furthermore, if desired, a slight torque may be introduced, e.g., to increase a frictional cleaning pressure between theinclined surfaces107,109 of the edge-cleaningroller101 and theedge corners27,29 (FIG. 3A) of the wafer W. In some embodiments, such a torque serves to increase an area of the edge of the wafer W to be cleaned by the edge-cleaningroller101, without undue risk of the wafer's edge being pinched between the inclined surfaces of the edge-cleaningroller101 and thus without wafer rotation tending to be inhibited thereby.
• In operation, the wafer W may be inserted between the firstinclined surface107 and the secondinclined surface109 of the edge-cleaningroller101, placed in contact with same, e.g., according to the pattern ofFIG. 5A, and rotated in the nominal rotation plane31 (FIG. 3B). For example, the wafer may be inserted between the firstinclined surface107 and the secondinclined surface109 of the edge-cleaningroller101 with therotation plane105 of the edge-cleaningroller101 preliminarily in a coplanar relationship with thenominal rotation plane31 of the wafer W, and the edge-cleaningroller101 may thereafter be rotated to achieve the desiredfirst angle103. Alternatively, thefirst angle103 may be established prior to the wafer W being introduced to the edge-cleaningroller101.
• As mentioned above, the edge-cleaningroller101 may be utilized in a mode in which contact with the wafer W is restricted to the firstinclined surface107 and the secondinclined surface109. Alternatively, and as also mentioned above, thecylindrical edge surface39 of the wafer W may also be made to contact a normal surface125 (FIG. 4) of the edge-cleaningroller101 at one or more times, e.g., either before or during wafer edge cleaning, or before or during rotation of the edge-cleaningroller101.
• Where sliding contact is intended between the edge-cleaningroller101 and the wafer W, the surfaces of the edge-cleaningroller101 involved may be adapted so as to further improve cleaning through greater friction. For example, such surfaces may comprise polyurethane, or some other suitable frictional material.
• Additionally, edge surfaces of the wafer W and frictional surfaces of the edge-cleaningroller101 may be caused to rotate at different velocities so as to enhance sliding contact. For example, the speed of rotation of the edge-cleaningroller101 may be controlled via a separate motor, e.g., so as to cause thenormal surface125 to rotate at a different velocity than the cylindrical edge surface of the wafer W it contacts. Also for example, the speed of the edge-cleaningroller101 may be selectively retarded (e.g., with a brake) if the wafer W itself is used to drive the edge-cleaningroller101.
• Where theedge corners27,29 (FIG. 3A) of the wafer W comprise edge bevels, the first and secondinclined surfaces107,109 of the edge-cleaningroller101 may be angled and disposed so as to increase an area of the edge bevels of the wafer W contacted/cleaned by the inclined surfaces. For example, the effective angles described between the inclined surfaces along the areas of contact described above and thenominal rotation plane31 of the wafer W can be controlled so as to maximize contact with the edge bevels.
Additional Edge-Cleaning Rollers
• FIGS. 6A,6B,7A and7B illustrate additional rollers adapted to achieve frictional contact with the edge of the wafer W, e.g., for purposes of driving or supporting the wafer W, and/or for preventing tilting thereof during rotation. It will be understood, also, that where the rollers ofFIGS. 6A-B and7A-B achieve frictional contact with the edge of the wafer W, edge cleaning of the wafer may also take place, such that the rollers may also be denominated edge-cleaning rollers, e.g., either by design, or by virtue of how they are used in conjunction with a wafer edge.
• Unlike the edge-cleaningroller101 of FIGS.4 and5A-B, which is adapted to achieve frictional contact with edge corners (or edge bevels)27,29 (FIG. 3A) of the wafer W, the rollers ofFIGS. 6A-B and7B are adapted to achieve frictional contact with edge surfaces of the wafer W that may be adjacent to theedge corners27,29. For example, the roller ofFIGS. 6A-B is adapted to achieve frictional contact with the cylindrical edge surface39 (FIG. 3A) between theedge corners27,29, and the roller ofFIGS. 7A-B is adapted to achieve frictional contact with one or both of a first edge-adjacent region41 (FIG. 3A) of a first major surface43 (FIG. 3A) of the wafer W, and a second edge-adjacent region45 (FIG. 3A) of a secondmajor surface47 of the wafer W (FIG. 3A). Additionally, the rollers ofFIGS. 6A-B and7A-B may comprise easily replaceable frictional components adapted to bear the greater portion of friction-induced wear where such frictional contact between the rollers and the wafer W is intended to occur. Such frictional components may be of low cost relative to other components of the rollers, and may assist in reducing and/or minimizing the cost of maintaining the rollers at a proper performance level, given that a certain level of wear may be anticipated and planned for.
Edge-Cleaning Support Roller
• FIG. 6A is a side elevational view of aninventive support roller601, shown adjacent to a wafer W and in contact with thecylindrical edge surface39 of the wafer W. Thesupport roller601 comprises a cylindricalfrictional surface603, e.g., comprising polyurethane or some other suitable frictional material, adapted to achieve frictional contact with the cylindrical edge surface39 (FIG. 3A) of the wafer W, as shown inFIG. 6A. Thesupport roller601 is adapted, via such frictional contact, to support and/or rotate the wafer W.
• In operation, the edge of the wafer W may be introduced between first and second guide surfaces605,607 of thesupport roller601, which may comprise low-friction, low-wear material such as virgin PTFE to encourage sliding communication with the edge of the wafer W down the slopes of the guide surfaces605,607 toward the cylindricalfrictional surface603. Once frictional contact is established between the cylindricalfrictional surface603 of thesupport roller601 and thecylindrical edge surface39 of the wafer W, thesupport roller601 may be used to rotatably support and/or drive the wafer W. As described above, the cylindricalfrictional surface603 of thesupport roller601 may also be used to clean the wafer W'scylindrical edge surface39, e.g., via rubbing contact caused by unmatched speeds of rotation.
• FIG. 6B illustrates a particular embodiment of thesupport roller601 ofFIG. 6A (support roller601a), shown in an exploded assembly perspective view. As shown inFIG. 6B, the cylindricalfrictional surface603 of thesupport roller601amay comprise a portion of afriction disk609, which may be of a simple, low-cost design adapted to minimize cost of replacement.
• Thesupport roller601amay further comprise amain body611, of which thesecond guide surface607 may comprise a part, and anend portion613, of which thefirst guide surface605 may comprise a part. Thefriction disk609 may be adapted to fit between themain body611 and theend portion613, and the assembly may be adapted to be secured such that thefriction disk609 rotates along with themain body611 and theend portion613.
• Thesupport roller601amay still further comprise a channel615 (FIG. 6A) comprising first andsecond sides617,619 (FIG. 6A) for retaining the edge of the wafer during rotational support thereof (e.g., by forming an “edge-trap” for retaining the edge of the wafer that includes the frictional surface603 (FIG. 6B)). In the embodiment ofFIG. 6A, thefrictional surface603 may form a transverse frictional surface that is adapted to contact the edge of the wafer and resist sliding thereagainst. Thechannel615 may be straight, i.e., thefirst side617 and thesecond side619 of thechannel615 may be arranged so as not to form a V, unlike the firstinclined surface23 and the secondinclined surface25 of the edge-cleaningroller21 ofFIG. 3A. Additionally, an offset may be established between thefirst side617 and thesecond side619 of thechannel615 that is sufficiently large to permit insertion of the edge of the wafer W, which may have, for example, a nominal thickness of 0.030 inches, and yet is sufficiently small so as to prevent tilt in the wafer W during rotation of the same, e.g., via low-friction contact between thefirst side617 of thechannel615 and the first edge-adjacent region41 (FIG. 3A) of the wafer W and/or between thesecond side619 of thechannel615 and the second edge-adjacent region45 (FIG. 3A) of the wafer W.
Edge-Cleaning Side-Contact Roller
• FIG. 7A is a side elevational view of an inventive side-contact roller701, shown adjacent to a wafer W. The side-contact roller701 comprises a first frictionalplanar surface703, e.g., comprising polyurethane or some other suitable frictional material, adapted to achieve frictional contact with the first edge-adjacent region41 (FIG. 3A) of the wafer W. The side-contact roller701 may additionally comprise a second frictionalplanar surface705, similar to the first frictionalplanar surface703, and adapted to achieve frictional contact with the second edge-adjacent region45 (FIG. 3A) of the wafer W. The first frictionalplanar surface703 and the second frictionalplanar surface705 may comprise sides of astraight channel707, e.g., similar to that described above with reference toFIG. 6B, such that the edge of the wafer W may be accommodated between the channel sides, and tilt in the wafer W may be prevented. The side-contact roller701 is adapted to rotate the wafer W via frictional contact between the frictional planar surfaces of the side-contact roller701 and the edge-adjacent regions of the major surfaces of the wafers.
• In operation, the edge of the wafer W may be introduced between first and second guide surfaces709,711 of the side-contact roller701, which may comprise a low-friction, low-wear material such as virgin PTFE to encourage sliding communication with the edge of the wafer W down the slopes of the guide surfaces709,711 toward thechannel707 of the side-contact roller701. Once the edge of the wafer W has been inserted into thechannel707, e.g., between the first frictionalplanar surface703 and the second frictionalplanar surface705, avertical gap713 may be maintained between the cylindrical edge surface39 (FIG. 3A) of the wafer W and a corresponding portion of the side-contact roller701 to restrict contact between the side-contact roller701 and the wafer W to the frictional “side” contact described above (i.e., at the edge-adjacent regions of the wafer's major surfaces), which frictional contact may be employed to drive the wafer W. Specifically, the wafer W may be vertically supported by other rollers (not shown) that prevent the wafer W from fully descending into thechannel707. As described above, the first frictionalplanar surface703 and the second frictionalplanar surface705 of the side-contact roller701 may also be used to clean the edge-adjacent regions of the wafer's major surfaces, e.g., via rubbing contact.FIG. 7B illustrates a particular embodiment of the side-contact roller701 ofFIG. 7A (side-contact roller701a), shown in a cross-sectional view. As shown inFIG. 7B, the first frictionalplanar surface703 of the side-contact roller701amay comprise a portion of afirst friction ring715, which may be of a simple low-cost design adapted to minimize cost of replacement. Also, as shown inFIG. 7B, if the side-contact roller701aincludes a second frictionalplanar surface705, the second frictionalplanar surface705 may comprise a portion of a similarsecond friction ring717.
• The side-contact roller701amay further comprise ahub719, afirst guide ring721 mounted on thehub719 of which thefirst guide surface709 may comprise a part, and asecond guide ring723 mounted on thehub719 of which thesecond guide surface711 may comprise a part. Thefirst friction ring715 and thesecond friction ring717 may also be mounted on thehub719, e.g., between thefirst guide ring721 and thesecond guide ring723 as shown. An assembly may be formed thereby in which all components rotate in unison.
Wafer Cleaning Apparatus Including the Above Inventive Rollers
• One or more edge-cleaning rollers of FIGS.4 and5A-B, and one or more of the frictional rollers ofFIGS. 6A-B and7A-B may be incorporated within a wafer cleaning apparatus (not separately shown) utilizing scrubber brushes to clean major surfaces of a wafer in a manner similar to that of the scrubber mechanism ofFIG. 2. Such a mechanism can take many forms and/or perform many functions, including:
• • (1) comprising separate drive motors for the edge cleaning roller and the other frictional rollers, e.g., so as to facilitate an angled plane of rotation for the edge-cleaning roller;
  • (2) comprising a toggle enabling the edge-cleaning roller to switch between a mode in which it either lags behind or exceeds the speed of rotation of the wafer edge so as to slide against the wafer edge when in contact with it, and a mode in which it matches the wafer edge speed and therefore does not slide thereagainst when contacting the same;
  • (3) allowing the angle between the plane of rotation of the edge-cleaning roller and the plane of rotation of the wafer to be selectively varied;
  • (4) permitting the edge cleaning roller to toggle between speed-matching and speed-lagging or speed-exceeding modes while other frictional rollers remain in a speed-matching mode;
  • (5) the toggle of (2) above comprising a clutch that engages for speed-exceeding or speed-lagging and disengages for speed matching; and/or
  • (6) the toggle of (2) above comprising a friction brake that engages for speed-lagging and disengages for speed matching.
    Other configurations are also permissible.
• The foregoing description discloses only exemplary embodiments of the invention. Modifications of the above disclosed apparatus and methods which fall within the scope of the invention will be readily apparent to those of ordinary skill in the art. For instance, according to one or more embodiments, such as shown inFIG. 8, anedge cleaning roller801 may be provided having a plane ofrotation803 at an inventive angled orientation to the plane ofrotation805 of the wafer W, e.g., as described by anangle807, such that the plane ofrotation803 of theroller801 intersects the plane ofrotation805 of the wafer W along a line (not separately shown) extending generally tangentially to the wafer W (e.g., as opposed to extending generally radially from the center of the wafer W as in the embodiment ofFIG. 4). Such an arrangement permits the creation of multiple wear sectors on a single inclined surface of theroller801 by permitting removal, inversion, and reinstallation of thesame roller801 midway through a useful life that may be twice that of a conventionally oriented roller. This may be possible, for example and as is apparent fromFIG. 8, since each edge corner tends to produce a wear sector at a unique location along the slope of a given inclined surface of theroller801, such that inversion and reinstallation of the roller exposes unworn or “fresh” friction surfaces to each of the edge corners. In other embodiments, such as shown inFIG. 9, multiple edge-cleaningrollers801 may be inventively oriented at one of two preferably equal and opposite angles to the plane of rotation of the wafer W, e.g., for balancing of out-of-plane forces imparted to the wafer W by the angled rollers.
• Finally, it should be understood that the inventive edge cleaning rollers described herein are each independently inventive, and may be employed in apparatuses other than those adapted to scrub a wafer's major surface.
• Further, as will be apparent to those of ordinary skill in the art, the inventive rollers may be employed to clean the edge of a wafer supported in any orientation (e.g., horizontal, vertical, etc.). Thus the inventive edge cleaning rollers may be advantageously employed in a vertically-oriented scrubber such as that disclosed in U.S. Pat. No. 6,575,177, the entire disclosure of which is incorporated herein by this reference.
• Accordingly, while the present invention has been disclosed in connection with exemplary embodiments thereof, it should be understood that other embodiments may fall within the spirit and scope of the invention, as defined by the following claims.

Claims (20)

1. A method of cleaning an edge of a wafer, the method comprising:

providing an edge cleaning roller having a first inclined frictional surface for cleaning an edge corner of a wafer rotating within a first plane; and

causing the edge cleaning roller to rotate within a second plane at an angle to the first plane while the inclined frictional surface contacts and cleans the edge corner.

2. The method ofclaim 1, wherein causing the edge cleaning roller to rotate within a second plane at an angle to the first plane while the inclined frictional surface contacts and cleans the edge corner comprises:

orienting the second plane at an angle to the first plane such that a line formed by an intersection between the first and the second planes is disposed perpendicular to a line drawn tangent to the edge of the wafer.

3. The method ofclaim 1, wherein causing the edge cleaning roller to rotate within a second plane at an angle to the first plane while the inclined frictional surface contacts and cleans the edge corner comprises:

orienting the second plane at an angle to the first plane such that a line formed by an intersection between the first and the second planes is disposed parallel to a line drawn tangent to the edge of the wafer.

4. The method ofclaim 1, wherein the angle is sufficiently large such that an area of contact on the edge cleaning roller between an abrasive material of the edge cleaning roller and the edge of the wafer is greater than would be the case if the second plane were oriented at an angle of zero relative to the first plane.

5. The method ofclaim 1, wherein the angle is at least ten degrees.

6. The method ofclaim 5, wherein the angle is thirty degrees or less.

7. The method of1 further comprising:

rotating the edge cleaning roller and the edge of the wafer at different velocities to enhance sliding contact.

8. The method ofclaim 1 further comprising:

rotating the edge cleaning roller at the same speed as the edge of the wafer.

9. The method ofclaim 1 further comprising:

introducing torque between the first inclined surface of the edge cleaning roller and the edge corner of the wafer.

10. A method of cleaning an edge of a wafer, the method comprising:

providing a roller for cleaning an edge of a wafer rotating within a first plane; and

causing the roller to rotate within a second plane at an angle to the first plane such that the roller cleans the edge of the wafer.

11. The method ofclaim 10 further comprising:

inserting the wafer between a first and second inclined surface of the roller for cleaning the wafer edge prior to causing the roller to rotate.

12. The method ofclaim 11 further comprising:

contacting the wafer edge with the roller.

13. The method ofclaim 12 wherein an abrasive side of the roller contacts the wafer edge.

14. The method ofclaim 12 further comprising:

contacting the wafer edge with the first and second inclined surfaces of the roller.

15. The method ofclaim 12 further comprising:

contacting a cylindrical surface of the wafer with a normal surface of the roller.

16. The method ofclaim 10 further comprising:

rotating the roller in the first plane before causing the roller to rotate within the second plane at the angle to the first.

17. The method of10 further comprising:

rotating the roller and the edge of the wafer at different velocities to enhance sliding contact.

18. The method ofclaim 10 further comprising:

rotating the roller at the same speed as the edge of the wafer.

19. The method ofclaim 14 further comprising:

introducing torque between the first and second inclined surfaces of the edge cleaning roller and the edge of the wafer.

20. The method ofclaim 10 wherein:

the angle is at least ten degrees and less than thirty degrees.

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