Patent Application
20060030242
The present invention relates generally to shaped polishing pads for beveling microfeature workpiece edges, along with associated systems and methods.
Microfeature workpieces (e.g., round wafers) are typically provided to microfeature device manufacturers with beveled edges. A variety of techniques are used to bevel the edges, including applying plasma jets to the workpiece, running a polishing tape along the edges, and contacting the edges with a conical abrasive surface. During the course of processing, layers of materials are built up on the microfeature workpiece and then planarized using mechanical and chemical-mechanical planarization and polishing processes (collectively “CMP”). As a result of these processes, the initially beveled edges of the microfeature workpiece also receive deposits, which can reduce or eliminate the beveled shape of these edges. During subsequent planarization operations, these edges can be a source for defects. In particular, the deposited layers at and near the edge of the workpiece may tend to peel or delaminate, causing defects in the edge region of the microfeature workpiece. Defects in the edge region can migrate to other portions of the microfeature workpiece during subsequent processing steps, so that the defects are not necessarily limited to only the peripheral region of the workpiece. Furthermore, particles released from the edge region can cause scratch defects at the parts of the workpiece as the particles are dragged across the workpiece surface during processing.
One proposed solution to the foregoing problem is to use the same beveling tools that initially bevel the edges of the workpiece to also bevel the workpiece at selected points during microfeature device fabrication.
One drawback with the foregoing approach is that the tool 10, while effective for beveling workpiece edges, can be expensive. In particular, the tool can be expensive to acquire and, because it occupies a relatively large amount of clean-room floor space, can be expensive to own and maintain. Furthermore, the risk of damage to microfeature workpieces as they are shuttled back and forth between an edge bevel tool 10 and a CMP tool can further increase the overall cost of using such a tool.
The present invention is directed toward systems and methods for beveling microfeature workpiece edges. A system in accordance with one aspect of the invention is configured to remove material from a microfeature workpiece having a first face, a second face facing opposite from the first face, an edge surface between the first and second faces, and an edge at a juncture between the edge surface and one of the first and second faces. The system can include a carrier positioned to carry the microfeature workpiece with the first and second faces generally normal to an axis. The system can further include a first polishing pad having a support surface and a polishing surface facing generally away from the support surface. The polishing surface can have a first shape, with at least one portion oriented at an acute angle relative to the axis and the support surface to remove material from the edge of the microfeature workpiece. A polishing pad support is positioned to carry the first polishing pad proximate to the carrier with the polishing surface facing toward the carrier. The polishing pad support can be configured to carry a second polishing pad in lieu of the first, the second polishing pad having a polishing surface with a second shape different than the first shape. The second shape can be configured to remove material from the first face of the microfeature workpiece while the microfeature workpiece rotates about the axis.
In a particular embodiment, the first polishing pad can have a generally circular planform shape, and the at least one portion of the pad can form a rim that extends circumferentially around at least part of the pad. In another embodiment, the at least one portion of the pad can include first and second portions facing at least partially toward each other, and a third portion (between the first and second portions) oriented generally normal to the axis.
A system in accordance with another aspect of the invention can include a carrier positioned to carry the microfeature workpiece with the first and second faces generally normal to an axis, a polishing pad support positioned proximate to the carrier, and a compliant polishing pad carried by the polishing pad support. The polishing pad can include a support surface facing toward the polishing pad support, and a polishing surface facing generally away from the support surface. The polishing surface can have at least one portion oriented at an acute angle relative to the axis and non-parallel to the support surface to remove material from the edge of the microfeature workpiece.
A system in accordance with yet another aspect of the invention includes a carrier positioned to carry a microfeature workpiece with the first face at a polishing plane. The system can further include a first polishing pad support, and a first polishing pad carried by the first polishing pad support. The first polishing pad can have a first polishing surface oriented generally parallel to the polishing plane. The system can further include a second polishing pad support carrying a second polishing pad. The second polishing pad can have a second polishing surface that is non-parallel to the polishing plane.
A method in accordance with yet another aspect of the invention includes positioning a microfeature workpiece at a processing tool, contacting the edge of the microfeature workpiece with a polishing surface of a polishing pad while the polishing surface is non-parallel to the first face of the workpiece, and removing material from the edge of the microfeature workpiece by rotating at least one of the microfeature workpiece and the polishing pad relative to the other about an axis generally normal to the first face of the workpiece while the edge contacts the polishing surface. The method can further include removing material from the first face of the workpiece without removing the workpiece from the processing tool.
As used herein, the terms “microfeature workpiece” and “workpiece” refer to substrates on and/or in which microfeature devices are integrally formed. Typical microfeature devices include microfeature circuits or components, thin-film recording heads, data storage elements, microfluidic devices, and other products. Micromachines and micromechanical devices are included within this definition because they are manufactured using much of the same technology that is used in the fabrication of integrated circuits. The substrates can be semiconductive pieces (e.g., doped silicon wafers and gallium arsenide wafers), nonconductive pieces (e.g., various ceramic substrates) or conductive pieces. In some cases, the workpieces are generally round, and in other cases the workpieces have other shapes, including rectilinear shapes. Several embodiments of systems and methods for removing material from the edges of microfeature workpieces are described below. A person skilled in the relevant art will understand, however, that the invention may have additional embodiments, and that the invention may be practiced without several of the details of the embodiments described below with reference to
The system 200 can include the polishing pad 220 carried on the polishing pad support 240, with an optional underpad 241 positioned between the polishing pad 220 and the pad support 240. A drive assembly 242 can rotate the pad support 240 and the polishing pad 220 (as indicated by arrow A). The drive assembly 242 can also reciprocate the pad support 240 and the polishing pad 220 (as indicated by arrow B). A polishing liquid 230 can be disposed on the polishing pad 220, and the polishing pad 220 (with or without the polishing liquid 230) can form a polishing medium 231 for removing material from the microfeature workpiece 250.
The microfeature workpiece 250 can include a first face 251, a second face 252 facing generally opposite from the first face 251, and an edge surface 253 between the first face 251 and the second face 252. The edge surface 253 can form one edge 254 at its juncture with the first face 251 and another edge 254 at its juncture with the second face 252. The edges 254 are shown as sharp 900 corners in
The microfeature workpiece 250 can be supported relative to the polishing pad 220 with a carrier 260. Accordingly, the carrier 260 can include a carrier head 261 and, optionally, a resilient pad 264 that supports the workpiece 250 relative to the polishing pad 220. The carrier 260 can include a carrier actuator assembly 262 that translates the carrier head 261 and the workpiece 250 (as indicated by arrow C) and/or rotates the carrier head 261 and the workpiece 250 (as indicated by arrow D). The carrier head 261 can include a vacuum chuck or other arrangement for releasably holding the microfeature workpiece 250. An optional and independently actuatable retainer ring 263 can prevent the microfeature workpiece 250 from slipping out from under the carrier head 261. The relative movement between the polishing pad 220 and the workpiece 250 chemically and/or chemically-mechanically removes material from the workpiece 250 during polishing and/or planarization, as described in greater detail below.
The polishing pad 220 can include a support surface 221 that directly engages a corresponding interface surface 243 of the pad support 240, or engages an underpad 241 positioned between the pad support 240 and the polishing pad 220. Accordingly, the support surface 221 faces generally toward the pad support 240. The polishing pad 220 can further include a polishing surface 224 facing generally opposite from the support surface 221. Some or all of the polishing surface 224 can be inclined at an acute angle X relative to the first face 251 of the microfeature, workpiece 250. Accordingly, these portions of the polishing surface 224 can also be oriented at an acute angle Y relative to an axis E that extends generally normal to the first and second faces 251, 252. As a result, these portions of the polishing surface 224 can be positioned to bevel the edge 254 between the first face 251 and the edge surface 253.
In a particular embodiment, the polishing surface 224 can include a first portion 222 that extends circumferentially around a peripheral region of the polishing pad 220 to form a rim 225. The polishing surface 224 can also include a second portion 223 disposed annularly inwardly from the first portion 222 to form a generally conical, central surface. The carrier 260 can support the microfeature workpiece 250 so that the edge 254 contacts both the first portion 222 and the second portion 223. As the carrier 260 and/or the pad support 240 rotate relative to each other, the first and second portions 222, 223 of the polishing surface 224 contact and bevel the edge 254 by removing material from the edge 254. When the carrier 261 includes a retainer ring 263, the retainer ring 263 can be elevated or removed so as not to interfere with the bevel process. Accordingly, the forces holding the microfeature workpiece 250 to the carrier head 261 can be strong enough to withstand the transverse force (e.g., directed out of the plane of
In a particular aspect of an embodiment shown in
The operator can control the force applied to the workpiece 250 (as well as the orientation of the workpiece 250) to assist in selectively removing material from either the edge 254 or the first face 251. For example, when the microfeature workpiece 250 is positioned against the rim 325, the downforce applied to the workpiece 250 can be reduced so as to reduce or eliminate the amount of material removed from the first face 251 while material is being removed from the edge 254. In a particular aspect of this embodiment, the gripping force applied to the workpiece 250 by the carrier 260 can be sufficient to allow the carrier 260 to force the edge 254 of the workpiece 250 laterally outwardly against the rim 325, without applying a significant downforce on the workpiece 250, and without causing the workpiece 250 to slip out from under the carrier head 261. In some embodiments, the retainer ring 263 described above with reference to
In a further particular embodiment, the carrier 260 can lift the workpiece 250 above the third portion 326 of the polishing surface 324, while engaging the workpiece edge 254 with the polishing pad rim 325, thereby ensuring that material is not removed from the first face 251 while material is being removed from the edge 254. An advantage of arrangements that limit or eliminate the amount of material removed from the first face 251 while material is being removed from the edge 254 is that the likelihood for damaging the first face 251 with material removed from the edge 254 can be reduced or eliminated.
In other arrangements, the composition of the polishing pad 320 (and in particular, the polishing surface 324) can be controlled to selectively remove material from the workpiece edge 254 more quickly than from the first face 251. For example, the first and second portions 322, 323 can be formed from constituents that have a higher material removal rate than do constituents of the third portion 326. In particular arrangements, the first and second portions 322, 323 can have a higher abrasiveness and/or hardness than the third portion 326, and in other arrangements, other attributes of the polishing surface 324 can be selected to produce different polishing rates.
In the embodiments described above with reference to
In the embodiments described above with reference to
Polishing pads configured in accordance with any of the embodiments described above with reference to
The first station 612a can include a first polishing pad support 640a carrying a first polishing pad 620a having a configuration generally similar to the polishing pad 220 described above with reference to
After material has been removed from the edge 254 of the microfeature workpiece 250, the robot 615 can transfer the microfeature workpiece 250 to the second station 612b where material can be removed from the first face 251, for example, using conventional CMP techniques. Accordingly, the second station 612b can include a second pad support 640b having a generally flat polishing pad 620b with a generally flat polishing surface 624b configured to remove material from the first face 251.
An advantage of the system 600 describe above with reference to
The polishing pads described above with reference to
The system 700 can also have a plurality of rollers to guide, position and hold the polishing pad 720 over the top panel 721. The rollers can include a supply roller 747, first and second idler rollers 744a and 744b, first and second guide rollers 745a and 745b, and a take-up roller 746. The supply roller 747 carries an unused or preoperative portion of the polishing pad 720, and the take-up roller 746 carries a used or post-operative portion of the polishing 720. Additionally, the first idler roller 744a and the first guide roller 745a can stretch the polishing pad 720 over the top panel 741 to hold the polishing pad 720 stationary during operation. A motor (not shown) drives at least one of the supply roller 747 and the take-up roller 746 to sequentially advance the polishing pad 720 across the top-panel 741. Accordingly, clean pre-operative sections of the polishing pad 720 may be quickly substituted for used sections to provide a consistent surface for polishing the microfeature workpiece 250.
The system 700 can also have a carrier assembly 760 that controls and protects the microfeature workpiece 250 during polishing. The carrier assembly 760 can include a head 761 to pick up, hold and release the microfeature workpiece 250 at appropriate stages of the polishing process. The carrier assembly 760 can also have a support gantry 765 carrying a drive assembly 770 that can translate along the gantry 765. The drive assembly 770 can have an actuator 762, a drive shaft 767 coupled to the actuator 762, and an arm 768 projecting from the drive shaft 767. The arm 768 carries the head 761 via a terminal shaft 769 such that the drive assembly 770 orbits the head 761 about an axis G-G (as indicated by arrow R1). The terminal shaft 769 may also rotate the head 761 about its central axis H-H (as indicated by arrow R2).
From the foregoing, it will be appreciated that specific embodiments of the invention have been described herein for purposes of illustration, but that various modifications may be made without deviating from the spirit and scope of the invention. For example, features described above in the context of particular embodiments of the invention can be combined or eliminated in other embodiments. Accordingly, the invention is not limited except as by the appended claims.
