1. Field of the Invention
Embodiments of the present invention relate to a method and apparatus for cleaning a substrate after chemical mechanical planarizing (CMP).
2. Background of the Invention
In the process of fabricating modern semiconductor integrated circuits (ICs), it is often necessary to planarize surfaces prior to depositing subsequent layers to ensure accurate formation of photoresist masks and to maintain stack tolerances. One method for planarizing a layer during IC fabrication is chemical mechanical planarizing (CMP). In general, CMP involves the relative movement of the substrate held in a polishing head against a polishing material to remove surface irregularities from the substrate. In a CMP process, the polishing material is wetted with a polishing fluid that may contain at least one of an abrasive or chemical polishing composition. This process may be electrically assisted to electrochemically planarize conductive material on the substrate.
Planarizing hard materials such as oxides typically requires that the polishing fluid or the polishing material itself include abrasives. As the abrasives often cling or are become partially embedded in the layer of material being polished, the substrate is processed on a buffing module to remove the abrasives from the polished layer. The buffing module removes the abrasives and polishing fluid used during the CMP process by moving the substrate which is still retained in the polishing head against a buffing material in the presence of deionized water or chemical solutions. The buffing module is substantially identical to the CMP module except for the polishing fluids utilized and the material on which the substrate is processed.
Once buffed, the substrate is transferred to a series of cleaning modules that further remove any remaining abrasive particles and/or other contaminants that cling to the substrate after the planarizing and buffing process before they can harden on the substrate and create defects. The cleaning modules may include, for example, a megasonic cleaner, a scrubber or scrubbers, and a dryer. The cleaning modules that support the substrates in a vertical orientation are especially advantageous, as they also utilize gravity to enhance removal of particles during the cleaning process, and are also typically more compact.
Although present CMP processes have been shown to be robust and reliable systems, the configuration of the system equipment requires the buffing module to utilize critical space which could alternatively be utilized for additional CMP modules. However, certain polishing fluids, for example those using cerium oxide, are particularly difficult to remove and conventionally require processing the substrate in buffing module before being transferred to the cleaning module as conventional cleaning modules have not demonstrated the ability to satisfactorily remove abrasive particles from oxide surfaces that have not been buffed prior to cleaning.
Therefore, there is a need in the art for an improved CMP process and cleaning module.
A method and apparatus for cleaning a substrate are provided. In one embodiment, a particle cleaning module is provided that includes a substrate holder and a pad holder disposed in a housing, and an actuator operable to move the pad holder relative to the substrate holder. The substrate holder is configured to retain and rotate a substrate in a substantially vertical orientation. The pad holder has a pad retaining surface that faces the substrate holder in a parallel and spaced apart relation. The pad holder is rotatable on an axis parallel to an axis on which the substrate holder rotates. The actuator is operable to move the pad holder relative to the substrate holder as to change a distance defined between the first axis and the second axis.
In another embodiment, a method for cleaning a substrate is provided that includes spinning a substrate disposed in a vertical orientation, providing a cleaning fluid to a surface of the spinning substrate, pressing a pad against the spinning substrate, and scanning the pad across the substrate.
So that the manner in which the above recited embodiments of the invention are obtained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof, which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of the 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, wherever possible, to designate identical elements that are common to the Figures. Additionally, elements of one embodiment may be advantageously adapted for utilization in other embodiments described herein.
Embodiments of the present invention relate to a method and apparatus for cleaning a substrate after chemical mechanical planarizing (CMP). The apparatus, described below as a particle cleaning module, advantageously allows for increase utilization and throughput of the CMP system, while reducing the amount and cost of consumables needed to effectively clean a substrate as further described below.
In addition to the cleaning system 116, the exemplary CMP system 100 generally includes a factory interface 102, a loading robot 104, and a planarizing module 106. The loading robot 104 is disposed proximate the factory interface 102 and the planarizing module 106 to facilitate the transfer of substrates 122 therebetween.
A controller 108 is provided to facilitate control and integration of the modules of the CMP system 100. The controller 108 comprises a central processing unit (CPU) 110, a memory 112 and support circuits 114. The controller 108 is coupled to the various components of the CMP system 100 to facilitate control of, for example, the planarizing cleaning and transfer processes.
The factory interface 102 generally includes an interface robot 120 and one or more substrate cassettes 118. The interface robot 120 is employed to transfer substrates 122 between the substrate cassettes 118, the cleaning system 116 and an input module 124. The input module 124 is positioned to facilitate transfer of substrates 122 between the planarizing module 106 and the factory interface 102 as will be further described below.
Optionally, polished substrates exiting the cleaning system 116 may be tested in a metrology system 180 disposed in the factory interface 102. The metrology system 180 may include an optical measuring device, such as the NovaScan 420, available from Nova Measuring Instruments, Inc. located in Sunnyvale, Calif. The metrology system 180 may include a buffer station (not shown) for facilitating entry and egress of substrates from the optical measuring device or other metrology device. One such suitable buffer is described in U.S. Pat. No. 6,244,931, issued Jun. 12, 2001 to Pinson, et al., which is hereby incorporated by reference in its entirety.
The planarizing module 106 includes at least one CMP station. It is contemplated that the CMP station maybe configured as an electrochemical mechanical planarizing station. In the embodiment depicted in
The exemplary planarizing module 106 also includes a transfer station 136 and a carousel 134 that are disposed on an upper or first side 138 of a machine base 140. In one embodiment, the transfer station 136 includes an input buffer station 142, an output buffer station 144, a transfer robot 146 and a load cup assembly 148. The loading robot 104 is configured to retrieve substrates from the input module 124 and transfer the substrates to the input buffer station 142. The loading robot 104 is also utilized to return polished substrates from the output buffer station 144 to the input module 124, from where the polished substrates are then advanced through the cleaning system 116 prior to being returned to the cassettes 118 coupled to the factory interface 102 by the interface robot 120. The transfer robot 146 is utilized to move substrates between the buffer stations 142, 144 and the load cup assembly 148.
In one embodiment, the transfer robot 146 includes two gripper assemblies, each having pneumatic gripper fingers that hold the substrate by the substrate's edge. The transfer robot 146 may simultaneously transfer a substrate to be processed from the input buffer station 142 to the load cup assembly 148 while transferring a processed substrate from the load cup assembly 148 to the output buffer station 144. An example of a transfer station that may be used to advantage is described in U.S. Pat. No. 6,156,124, issued Dec. 5, 2000 to Tobin, which is herein incorporated by reference in its entirety.
The carousel 134 is centrally disposed on the base 140. The carousel 134 typically includes a plurality of arms 150, each supporting a polishing head 152. Two of the arms 150 depicted in
The cleaning system 116 removes polishing debris, abrasives and/or polishing fluid from the polished substrates that remains after polishing. The cleaning system 116 includes a plurality of cleaning modules 160, a substrate handler 166, a dryer 162 and an output module 156. The substrate handler 166 retrieves a processed substrate 122 returning from the planarizing module 106 from the input module 124 and transfers the substrate 122 through the plurality of cleaning modules 160 and dryer 162. The dryer 162 dries substrates exiting the cleaning system 116 and facilitates substrate transfer between the cleaning system 116 and the factory interface 102 by the interface robot 120. The dryer 162 may be a spin-rinse-dryer or other suitable dryer. One example of a suitable dryer 162 may be found as part of the MESA™ or Desica® Substrate Cleaners, both available from Applied Materials, Inc., of Santa Clara, Calif.
In the embodiment depicted in
In operation, the CMP system 100 is initiated with the substrate 122 being transferred from one of the cassettes 118 to the input module 124 by the interface robot 120. The loading robot 104 then moves the substrate from the input module 124 to the transfer station 136 of the planarizing module 106. The substrate 122 is loaded into the polishing head 152 moved over and polished against the polishing pad 126 while in a horizontal orientation. Once the substrate is polished, polishing substrates 122 are returned to the transfer station 136 from where the robot 104 may transfer the substrate 122 from the planarizing module 106 to the input module 124 while rotating the substrate to a vertical orientation. The substrate handler 166 then retrieves the substrate from the input module 124 transfers the substrate through the cleaning modules 160 of the cleaning system 116. Each of the modules 160 is adapted to support a substrate in a vertical orientation throughout the cleaning process. Once cleaned, the cleaned substrate 122 is to the output module 156. The cleaned substrate 122 is returned to one of the cassettes 118 by the interface robot 120 while returning the cleaned substrate 122 to a horizontal orientation. Optionally, the interface robot 120 may transfer the cleaned substrate to the metrology system 180 prior to the substrate's return to the cassette 118.
Although any suitable substrate handler may be utilized, the substrate handler 166 depicted in
In the embodiment depicted in
The mounting plate 204 is coupled to the carriage first 202. The mounting plate 204 includes at least two parallel tracks 216A-B along which the positions of the grippers 174, 176 are independently actuated along a second and third axes of motion A2, A3. The second and third axes of motion A2, A3 are oriented perpendicular to the first axis A1 and are parallel to the Y-axis.
The substrate receiver 310 has a substrate receiving slot 332 facing upwards parallel to the Y-axis. The receiving slot 332 is sized to accept the perimeter of the substrate 122, thereby allowing the one of the grippers 174, 176 of the substrate handler 166 to place the substrate 122 in the receiving slot 322 in a substantially vertical orientation. The substrate receiver 310 is coupled to an Z-Y actuator 311. The Z-Y actuator 311 may be actuated to move the substrate receiver 310 upwards in the Y-axis to align a centerline of the substrate 122 disposed in the substrate receiver 310 with a centerline of the substrate rotation assembly 304. Once the centerline of the substrate 122 is aligned with the centerline of the substrate rotation assembly 304, the Z-Y actuator 311 may be actuated to move the substrate receiver 310 in the Z-axis to contact the substrate 122 against the substrate rotation assembly 304, which then actuates to chuck the substrate 122 to the substrate rotation assembly 304. After the substrate 122 has been chucked to the substrate rotation assembly 304, the Z-Y actuator 311 may be actuated to move the substrate receiver 310 in the Y-axis clear of the substrate 122 and the substrate rotation assembly 304 so that the substrate 122 held by the substrate rotation assembly 304 may be rotated without contacting the substrate receiver 310.
The substrate rotation assembly 304 is disposed in the housing 302 and includes a substrate holder 314 coupled to a substrate rotation mechanism 316. The substrate holder 314 may be an electrostatic chuck, a vacuum chuck, a mechanical gripper or any other suitable mechanism for securely holding the substrate 122 while the substrate is rotated during processing within the particle cleaning module 182.
The substrate holder 314 is coupled to the substrate rotation mechanism 316 by a first shaft 323 that extends through a hole 324 formed through the housing 302. The hole 324 may optionally include sealing members 326 to provide a seal between the first shaft 323 and the housing 302. The substrate holder 314 is controllably rotated by the substrate rotation mechanism 316. The substrate rotation mechanism 316 may be an electrical motor, an air motor, or any other motor suitable for rotating the substrate holder 314 and substrate 122 chucked thereto. The substrate rotation mechanism 316 is coupled to the controller 108. In operation, the substrate rotation mechanism 316 rotates the first shaft 323, which rotates the substrate holder 314 and the substrate 122 secured thereto. In one embodiment the substrate rotation mechanism 316 rotates the substrate holder 314 (and substrate 122) at a rate of at least 500 revolutions per minute (rpm).
The pad actuation assembly 306 includes a pad rotation mechanism 336, a pad cleaning head 338, and a lateral actuator mechanism 342. The pad cleaning head 338 is located in the internal volume 312 of the housing 302 and includes a pad holder 334 that holds a pad 344 and a fluid delivery nozzle 350. The fluid delivery nozzle 350 is coupled to a fluid delivery source 382 that provides deionized water, a chemical solution or any other suitable fluid to the pad 344 during cleaning the substrate 122. The lid 330 may be moved to a position that closes the opening 308 of the housing 302 above the fluid delivery nozzle 350 to prevent fluids from being spun out of the housing 302 during processing.
A centerline of the pad holder 334 may be aligned with the centerline of the substrate holder 314. The pad holder 334 (and pad 344) has a diameter much less than that of the substrate 122, for example at least less than half the diameter of the substrate or even as much as less than about one eighth the diameter of the substrate. In one embodiment, the pad holder 334 (and pad 344) may have a diameter of less than about 25 mm. The pad holder 334 may holds the pad 344 utilizing clamps, vacuum, adhesive or other suitable technique that allows for the pad 344 to periodically be replaced as the pad 344 becomes worn after cleaning a number of substrates 122.
The pad 344 may be fabricated from a polymer material, such as porous rubber, polyurethane and the like, for example, a POLYTEXT™ pad available from Rodel. Inc. of Newark, Del. In one embodiment, the pad holder 334 may be used to a hold a brush or any other suitable cleaning device. The pad holder 334 is coupled to the pad rotation mechanism 336 by a second shaft 346. The second shaft 346 is oriented parallel to the Z-axis and extends from the internal volume 312 through an elongated slit formed through the housing 302 to the pad rotation mechanism 336. The pad rotation mechanism 336 may be an electrical motor, an air motor, or any other suitable motor for rotating the pad holder 334 and pad 344 against the substrate. The pad rotation mechanism 336 is coupled to the controller 108. In one embodiment, the pad rotation mechanism 336 rotates the pad holder 334 (and pad 344) at a rate of at least about 1000 rpm.
The pad rotation mechanism 336 is coupled to bracket 354 by an axial actuator 340. The axial actuator 340 is coupled to the controller 108 or other suitable controller and is operable to move the pad holder 334 along the Z-axis to move the pad 344 against and clear of the substrate 122 held by the substrate holder 314. The axial actuator 340 may be a pancake cylinder, linear actuator or any other suitable mechanism for moving the pad holder 334 in a direction parallel to the Z-axis. In operation, after the substrate holder 314 is in contact with and holding the substrate, the axial actuator 340 drives the pad holder 334 in a z-direction to make contact with the substrate.
The bracket 354 is coupled to a base 362 by the lateral actuator mechanism 342 by a carriage 356 and rail 358 that allows the pad cleaning head 338 to move laterally in a direction parallel to the X-axis, as depicted in
Scanning the polymer pad 344 across the substrate 122 in the particle cleaning module 182 has effectively demonstrated the ability to effectively remove particles, such as abrasives from the polishing fluid, from the surface of the substrate 122. Accordingly, the need for a dedicated buffing station on the polishing module is substantially eliminated.
Referring back to
Substrate transfer begins after cleaning and moving the pad holder 334 and pad 344 in the pocket 504 by having the substrate receiver 310 move upward in a direction parallel to the Y-axis to engage the substrate 122 in the receiving slot 332. Once the substrate is disposed in the substrate receiving slot 332, the substrate holder 314 releases the substrate 122 by turning off the vacuum provided by the vacuum source 380, and optionally providing a gas through the apertures 402 of the substrate holder 314 to separate the substrate from the substrate holder 314. The substrate receiver 310 with the substrate 122 disposed in the receiving slot 332 is then moved laterally away from the substrate holder 314 in a direction parallel to the Z-axis to clear the substrate 122 from the substrate holder 314. One of the grippers 174, 176 of the robot 168 retrieves the substrate 122 from the substrate receiver 310 and removes the substrate 122 from the housing 302. An optional top spray bar 364 and bottom spray bar 366 are positioned across the internal volume 312 and may spray the substrate 122 with deionized water or any other suitable fluid to clean the substrate 122 as the substrate 122 is removed from the particle cleaning module 182 by the robot 168. At least one of the spray bars 364, 366 may be utilized to wet the substrate 122 prior to chucking against the substrate receiver 310 to remove particles that may potentially scratch the backside of the substrate and/or to improve chucking by the substrate receiver 310. The spray bars 364, 366 may be coupled to different fluid sources 388, 390 so that different fluids may be provided to each of the spray bars 364, 366, or both spray bars 364, 366 may be coupled to a single fluid delivery source.
Referring back to the planarizing module 106 of
Furthermore, the particle cleaning module 182 effectively cleans the substrate and decreases the loading of particulate on the brushes of the first brush module 164B and second brush module 164C. Therefore, the lifespan of the brushes in the first brush module 164B and second brush module 164C are advantageously increased. Thus, the particle cleaning module removes particularly difficult to remove polishing fluids without requiring a buffing station in the polishing module and simultaneously frees the second and or third station for additional CMP stations to increase throughput of the planarizing system.
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
This application claims priority to U.S. Patent Application Ser. No. 61/590,034, filed on Jan. 24, 2012, which is incorporated by reference in its entirety.
Number | Date | Country | |
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61590034 | Jan 2012 | US |