Patent Application
20100099339
1. Field of the Invention
Embodiments of the present invention generally relate to polishing a substrate, such as a semiconductor wafer.
2. Description of the Related Art
In the fabrication of integrated circuits and other electronic devices on substrates, multiple layers of conductive, semiconductive, and dielectric materials are deposited on or removed from a feature side, i.e., a deposit receiving surface, of a substrate. As layers of materials are sequentially deposited and removed, the feature side of the substrate may become non-planar and require planarization and/or polishing. Planarization and polishing are procedures where previously deposited material is removed from the feature side of the substrate to form a generally even, planar or level surface. The procedures are useful in removing undesired surface topography and surface defects, such as rough surfaces, agglomerated materials, crystal lattice damage, and scratches. The procedures are also useful in forming features on a substrate by removing excess deposited material used to fill the features and to provide an even or level surface for subsequent deposition and processing.
Chemical mechanical polishing is one process commonly used in the manufacture of high-density integrated circuits to planarize or polish a layer of material deposited on a semiconductor wafer by moving the feature side of the substrate in contact with a polishing pad while in the presence of a polishing fluid. Material is removed from the feature side of the substrate that is in contact with the polishing surface through a combination of chemical and mechanical activity.
Periodic conditioning of the polishing surface is required to maintain a consistent roughness and/or a generally flat profile across the polishing surface. The conditioning is typically performed using a rotating conditioning disk that is swept across and urged against the polishing surface. Conditioning of the peripheral or edge region of the pad creates challenges to global roughness and/or global flatness of the polishing surface.
Therefore, there is a need for a method and apparatus that facilitates equalized conditioning of the polishing surface.
A method and apparatus for providing a substantially uniform pressure to a polishing surface from a conditioning element is provided. In one embodiment, an apparatus for extending a peripheral edge of a polishing pad is described. The apparatus includes a base having a platen coupled to an upper surface thereof, a polishing pad coupled to an upper surface of the platen, the polishing pad having a polishing surface, a support member coupled to the base adjacent a peripheral edge of the polishing pad, and a bearing material coupled to an upper surface of the support member, the bearing material having an upper surface that is coplanar with the polishing surface of the polishing pad.
In another embodiment, an apparatus for extending a peripheral edge of a polishing pad is described. The apparatus includes a base having a platen rotatably coupled to an upper surface thereof, a polishing pad coupled to an upper surface of the platen, the polishing pad having a polishing surface, a support member coupled to the base adjacent a peripheral edge of the polishing pad, the support member being adjustable relative to the polishing surface of the polishing pad, and a bearing material coupled to an upper surface of the support member.
In another embodiment, a method for conditioning a peripheral edge of a circular polishing pad is described. The method includes urging a conditioning disk against a polishing surface of a rotating polishing pad, moving the conditioning disk across the polishing surface in a sweep pattern that includes at least a portion of the conditioning disk extending over a peripheral edge of the polishing surface, and maintaining a substantially uniform pressure to the polishing surface from the conditioning disk across the sweep pattern.
So that the manner in which the above-recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation.
For example, the first processing station 102 may be configured to perform an electrochemical mechanical planarization (ECMP) process, while the second processing station 103 and the third processing station 106 may perform a conventional chemical mechanical polishing (CMP) process. It is to be understood that the invention is not limited to this configuration and that any or all of the stations 102, 103, and 106 may be adapted to use an ECMP process to remove various layers deposited on the substrate. Alternatively, the processing module 105 may include two stations that are adapted to perform an ECMP process while another station may perform a CMP process. In one embodiment of a process, a substrate having feature definitions formed therein and filled with a barrier layer and then a conductive material disposed over the barrier layer may have the conductive material removed. The removal can be in two steps in the first and second processing stations 102, 103, by a CMP process, with the barrier layer processed in the third station 106 by a third CMP process to form a planarized surface on the substrate.
The embodiment described in system 100 includes a base 108 that supports the processing stations 102, 103 and 106, a transfer station 110, and a carousel 112. A plurality of conditioning devices 182 are shown coupled to the base 108 and are movable in the direction indicated by arrow 109 in order to selectively place the conditioning device 182 over each of the processing stations 102, 103, and 106. The transfer station 110 generally facilitates transfer of substrates 114 to and from the system 100 via a loading robot 116. The loading robot 116 typically transfers substrates 114 between the transfer station 110 and an interface 120 that may include a cleaning module 122, a metrology device 104 and one or more substrate storage cassettes 118.
The transfer station 110 comprises an input buffer station 124, an output buffer station 126, a transfer robot 132, and a load cup assembly 128. The loading robot 116 places the substrate 114 onto the input buffer station 124. The transfer robot 132 has two gripper assemblies, each having pneumatic gripper fingers that hold the substrate 114 by the substrate's edge. The transfer robot 132 lifts the substrate 114 from the input buffer station 124 and rotates the gripper and substrate 114 to position the substrate 114 over the load cup assembly 128, and then places the substrate 114 down onto the load cup assembly 128.
The carousel 112 supports a plurality of carrier heads 190, each of which retains one substrate 114 during processing. The carousel 112 moves the carrier heads 190 between the transfer station 110 and processing stations 102, 103 and 106. The carousel 112 is centrally disposed on the base 108 and includes a plurality of arms 138. Each arm 138 supports one of the carrier heads 190. Two of the arms 138 depicted in
The carrier head 190 retains the substrate 114 while the substrate 114 is disposed in the processing stations 102, 103, 106, which allows the substrate 114 to be sequentially processed by moving the substrate between stations while being retained in the same carrier head 190.
To facilitate control of the processing system 100 and processes performed thereon, a controller 140 comprising a central processing unit (CPU) 142, memory 144 and support circuits 146 is connected to the processing system 100. The CPU 142 may be one of any form of computer processor that can be used in an industrial setting for controlling pressures and various drives disposed on the system 100. The memory 144 is connected to the CPU 142. The memory 144, or computer-readable medium, may be one or more of readily available memory such as random access memory (RAM), read only memory (ROM), floppy disk, hard disk, or any other form of digital storage, local or remote. The support circuits 146 are connected to the CPU 142 for supporting the processor in a conventional manner. These circuits include cache, power supplies, clock circuits, input/output circuitry, subsystems, and the like.
Power to operate the processing system 100 and/or the controller 140 is provided by a power supply 150. Illustratively, the power supply 150 is shown connected to multiple components of the processing system 100, including the transfer station 110, the interface 120, the loading robot 116 and the controller 140.
The conditioning device 182 generally includes a conditioner carrier 212 coupled to the head assembly 202, which is coupled to a support member 204 by an arm 206. The support member 204 is disposed through the base 108 of the processing station 106. Bearings are provided between the base 108 and the support member 204 to facilitate rotation of the support member 204 about a centerline B relative to the base 108. An actuator (not shown) may be coupled between the base 108 and the support member 204 to control the rotational orientation of the support member 204 about the centerline B and laterally position the head assembly 202 relative to the processing station 106. The support member 204 may house drive components to selectively rotate the conditioning element 208 relative to the polishing pad 226 about a centerline C. The support member 204 may also provide fluid conduits to control the vertical position of one of the conditioner carrier 212 or the head assembly 202.
A conditioning element 208 is coupled to the bottom surface of the conditioner carrier 212. The conditioner carrier 212 is coupled to the head assembly 202 and may be selectively pressed against the platen 230 while rotating about centerline C to condition the polishing material 228. Likewise, the platen 230 with the polishing pad 226 thereon rotates relative to the base 108 about a centerline D. The conditioning element 208 may be urged toward the polishing material 228 at a pressure or downforce between about 0.1 pound-force to about 20 pound-force. The conditioning element 208 may be an abrasive disc, such as a diamond or ceramic material, that is configured to abrade and enhance the polishing material 228. Alternatively, the conditioning element 208 may be a brush-type conditioning disk, such as a disk having nylon bristles. The conditioning element 208 is adapted to be easily replaced to provide a new or different disk as desired by the user.
In one embodiment, the polishing material 228 of the polishing pad 226 is a commercially available pad material, such as polymer based pad materials typically utilized in CMP. The polymer material may be a polyurethane, a polycarbonate, fluoropolymers, PTFE, PTFA, polyphenylene sulfide (PPS), or combinations thereof. The pad material may further comprise open or closed cell foamed polymers, elastomers, felt, impregnated felt, plastics, and like materials compatible with the processing chemistries. In another embodiment, the pad material is a felt material impregnated with a porous coating.
Generally, the polishing pad 226 comprises a processing surface 125 which includes a nap that may include microscopic pore structures. The nap and/or pore structures effect material removal from the feature side of the substrate. Attributes such as polishing compound retention, polishing or removal activity, and material and fluid transportation affect the removal rate. In order to facilitate optimal removal of material from the substrate, the processing surface 125 must be roughened and/or fully and evenly open to provide a relatively high and stable removal rate. The roughened processing surface 125 facilitates removal by enhancing pad surface wetability and dispersing polishing compounds, such as, for example, abrasive particles supplied from the polishing compound.
In
Other factors may contribute to the uneven or non-uniform conditioning of the zones 305, 310. For example, as the conditioning element 208 moves over the edge 315, the conditioning element 208 may tilt as it is unsupported over the edge 315. The tilt of the conditioning element 208 may promote greater roughening of the processing surface 125 in the peripheral zone 310.
In one embodiment, the polishing pad 226 is circular and includes a diameter of between about 24 inches to about 52 inches. The inner zone 305 may be defined as a central radial region of the processing surface 125 including a geometric center of the polishing pad 226 up to the peripheral zone 310. The peripheral zone 310 may be defined as the edge region of the processing surface 125. If a circular conditioning element 208 is used, the peripheral zone 310 includes a length that is substantially equal to a radius of the conditioning element 208. For example, if a circular conditioning element 208 having a diameter of about 4.0 inches to about 5.0 inches is used, then the length of the peripheral zone 310 is about 2.0 inches to about 2.5 inches.
Embodiments described herein provide a method and apparatus to provide uniform pressure to a polishing pad 226 from a conditioning element 208 and therefore counter the effect of non-uniform conditioning across the processing surface 125 of the polishing pad 226. In one embodiment, the downforce of the conditioning element 208 may be varied to include a lower downforce when the conditioning element 208 is at or near the edge 315 of the polishing pad 226. In this embodiment, the conditioning head assembly 202 (
One or both of the polishing pad extension 505 and the support member 510 is selectively fixed or adjustable relative to the polishing pad 226. In one embodiment, the support member 510 and the polishing pad extension 505 may be adjusted vertically (Z direction) and horizontally (X and/or Y direction) relative to the horizontal plane of the processing surface and/or the edge 315 and then fixed relative to the polishing pad 226. In one embodiment, the support member is coupled to the base 108 of the processing station. In one aspect, the polishing pad extension 505 includes or is coupled to a drive system 605 adapted to adjust the position of the edge extension 526 at least in the X direction and Z direction. A small gap between the peripheral edge 315 of the polishing pad 226 may be provided to allow for rotational movement of the polishing pad 226 without interference from the polishing pad extension 505.
In one embodiment, the drive system 605 includes an actuator 610 adapted to move the polishing pad extension 505 laterally (X and/or Y direction) and/or vertically (Z direction) relative to the polishing pad 226 and/or platen 230. In one embodiment, the actuator 610 is a pneumatic motor with a brake adapted to move the polishing pad extension 505 laterally and/or vertically relative to the polishing pad 226 and/or platen 230. The actuator 610 may be coupled to a drive platform 615 that may in turn be coupled to the base 108 by fasteners that may be loosened to adjust the drive platform 615 relative to the base 108, which moves the polishing pad extension 505 relative to the polishing pad 226 and/or platen 230. In another embodiment, lateral adjustment of the polishing pad extension 505 is provided by one or more fasteners, such as set screws or bolts, either concentrically or eccentrically. Additionally or alternatively, the actuator 610 may be a hydraulic cylinder, a lead screw, among other mechanical or electromechanical drives.
When a new polishing pad 226 is installed on the platen 230, the height of the processing surface 525 of the polishing pad extension 505 may be matched with the height of the processing surface 125 of the polishing pad 226. Depending on the wear rate of either of the processing surfaces 525 and 125, the height of the processing surface 525 may be readjusted. The height of the processing surface 525 may be determined by a straight edge or gauge relative to the height of the processing surface 125 of the polishing pad 226. In one embodiment, the height is determined by the lower surface of the conditioning element 208 (not shown in this Figure).
The inventors performed tests using a polishing pad extension 505 using an edge extension 526 made of a material that was identical to the material of the polishing pad 226. It was found that the processing surface 525 of the edge extension 505 wears at the same rate as the processing surface 125 of the polishing pad 226. Thus, the polishing pad extension 505 may be replaced during polishing pad replacement without readjustment during processing.
The embodiments described herein provide a method and apparatus for counteracting conditioning effects that may be detrimental to a polishing pad. The method and apparatus as described herein promotes a longer pad lifetime and facilitates a greater usable are of a polishing pad.
While the foregoing is directed to embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof.
