Patent Application
20070212976
1. Field of the Invention
Embodiments of the invention generally relate to a polishing media assembly for use in a chemical mechanical polishing system.
2. Background of Invention
In semiconductor wafer processing, the use of chemical mechanical planarization, or CMP, has gained favor due to the enhanced ability to increase device density on a semiconductor workpiece, or substrate, such as a wafer. As the demand for planarization of layers formed on wafers in semiconductor fabrication increases, the requirement for greater system (i.e., process tool) throughput with less wafer damage and enhanced wafer planarization has also increased.
CMP systems generally include a polishing head and a polishing material disposed on a platen. A substrate retained in the polishing head is pressed against the polishing material and moved relative to the polishing material in the presence of a polishing fluid. Abrasives, typically contained in the polishing fluid and/or polishing material, remove material from the surface of the substrate synergistically with the chemical activity provided by the polishing fluid.
Conventional polishing material is generally comprised of a foamed polymer, such as polyurethane. Conventional polishing materials are generally available in the form of circular pads or in a linear form, such as a web or belt. The web or belt is periodically advanced over the course of polishing a number of substrates as the polishing surface of the web is consumed by the polishing process. Alternatively, the web or belt may be continuously advanced or moved back and forth during processing.
Polishing materials generally wear during polishing, causing the surface of the polishing material to lose the ability to adequately retain polishing fluid during the polishing process, resulting in a non-uniform distribution of polishing fluid across the polishing material. A non-uniform distribution of polishing fluid may result in variations of removal rates across the substrate surface and inhibit uniform polishing of a substrate surface. To maintain uniform polishing results, the polishing material is periodically conditioned, cleaned, or advanced across the platen after polishing one or more substrates, thereby refreshing the portion of the polishing surface in contact with substrate during processing to maintain good processing results.
As the polishing material may be removed from the polishing system before fully consumed, or reused after an interruption in processing, it is critical to preserve the historical information regarding the prior use of the polishing material in order to prevent substrate damage and defect generation. For example, it may be undesirable to utilize polishing material that was used to polish one material, such as conductive material, for later used to polish another material, such as an insulating material. Furthermore, it may be undesirable to use different polishing fluids on the same polishing material to prevent cross-talk between polishing fluids, which may lead to undesired polishing results. Additionally, information regarding the number of times that a polishing material has been utilized and/or conditioned is critical to prevent the start of a polishing process without enough material life or length remaining to complete substrate polishing process. Moreover, as the polishing material may be transferred between tools, it would be advantageous for information associated with the polishing material to remain with the polishing material.
Therefore, there is a need for polishing material which can communicate with a processing system.
Embodiments of the invention generally include a smart polishing media assembly having a memory device, a polishing system in communication with the smart polishing media assembly, and methods for using the same. In one embodiment, the smart polishing media assembly includes a polishing material and a memory device coupled to the polishing material.
In another embodiment, the apparatus includes a polishing station, a polishing material disposed in the polishing station, a memory device coupled to the polishing material, and a computer based controller adapted to communicate with the memory device.
In yet another embodiment, the method for using a smart polishing media assembly includes reading information from a memory device coupled to a polishing media disposed in a polishing station, and polishing a substrate placed in contact with the polishing material. In other embodiment, historical processing information may be written to the memory device.
So that the manner in which the above recited features of the present invention are attained 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 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 and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.
It is to be noted, however, that the appended drawings illustrate only exemplary 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.
The invention will be described below in reference to a planarizing process and a polishing material that can be performed on a chemical mechanical polishing system, such as a REFLEXION® CMP System available from Applied Materials, Inc., located in Santa Clara, Calif. Although the polishing process and composition described herein is illustrated utilizing the REFLEXION® CMP System, any system enabling chemical mechanical polishing and/or electrochemical mechanical processing using the methods or polishing material described herein can be used to advantage.
A computer based controller 190 is connected to the polishing system 100 for instructing the system to perform one or more processing steps on the system, such as polishing a substrate or transferring a substrate in the polishing system 100. In one embodiment, the invention may be implemented as a computer program-product for use with a computer system or computer based controller 190. The programs defining the functions of an embodiment can be provided to a computer via a variety of signal-bearing media and/or computer readable media, which include but are not limited to, (i) information permanently stored on non-writable storage media (e.g., read-only memory devices within a computer such as read only CD-ROM disks readable by a CD-ROM or DVD drive; (ii) alterable information stored on a writable storage media (e.g., floppy disks within diskette drive or hard-disk drive); or (iii) information conveyed to a computer by communications medium, such as through a computer or telephone network, including wireless communication. Such signal-bearing media, when carrying computer-readable instructions that direct the functions of the invention, represent alternative embodiments of the present invention.
The factory interface 102 generally includes a cleaning module 116 and one or more substrate cassettes 118. An interface robot 120 is employed to transfer substrates 122 between the substrate cassettes 118, the cleaning module 116 and an input module 124. The input module 124 is positioned to facilitate transfer of substrates 122 between the polishing module 106 and the factory interface 102 by the loading robot 104. For example, unpolished substrates 122 retrieved from the cassettes 118 by the interface robot 120 may be transferred to the input module 124 where the substrates 122 may be accessed by the loading robot 104 while polished substrates 122 returning from the polishing module 106 may be placed in the input module 124 by the loading robot 104. Polished substrates 122 are typically passed from the input module 124 through the cleaning module 116 before the factory interface robot 120 returns the cleaned substrates 122 to the cassettes 118. An example of such a factory interface 102 that may be used to advantage is disclosed in U.S. Pat. No. 6,361,422, issued Mar. 26, 2002, which is hereby incorporated by reference.
The loading robot 104 is generally positioned proximate the factory interface 102 and the polishing module 106 such that the range of motion provided by the robot 104 facilitates transfer of the substrates 122 therebetween. An example of a loading robot 104 is a 4-Link robot, manufactured by Kensington Laboratories, Inc., located in Richmond, Calif.
The exemplary loading robot 104 has an articulated arm 126 having a rotary actuator 128 at its distal end. An edge contact gripper 130 is coupled to the rotary actuator 128. The rotary actuator 128 permits the substrate 122 secured by the gripper 130 to be oriented in either a vertical or a horizontal orientation without contacting the feature side of the substrate 122 and possibly causing scratching or damage to the exposed features. Additionally, the edge contact gripper 130 securely holds the substrate 122 during transfer, thus decreasing the probability that the substrate 122 will become disengaged. Optionally, other types of grippers, such as electrostatic grippers, vacuum grippers and mechanical clamps, may be substituted.
The polishing module 106 may be any suitable device for planarizing a substrate on a polishing material, including those that use polishing pads, polishing belts, polishing webs, or a combination thereof. Other systems that benefit from the systems include moving a substrate relative a polishing surface in a rotational, linearly or in other motion within a plane. As noted above, the polishing modules may be utilized in an electrochemical mechanical polishing system in which a substrate is processed by electrochemical dissolution concurrently with mechanical polishing. One such electrochemical mechanical process is described in U.S. patent application Ser. No. 10/941,060 filed Sep. 14, 2004, which is hereby incorporated by reference.
The exemplary polishing module 106 has a transfer station 136, a plurality of polishing stations 132 and a carousel 134 disposed on an upper or first side 138 of a machine base 140. In one embodiment, the transfer station 136 comprises at least an input buffer station 142, an output buffer station 144, a transfer robot 146, and a load cup assembly 148. The loading robot 104 places the substrate 122 onto the input buffer station 142. The transfer robot 146 has two gripper assemblies, each having pneumatic gripper fingers that grab the substrate 122 by the substrate's edge. The transfer robot 146 lifts the substrate 122 from the input buffer station 142 and rotates the gripper and substrate 122 to position the substrate 122 over the load cup assembly 148, then places the substrate 122 down onto the load cup assembly 148. 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, which is hereby incorporated by reference.
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 assembly 152. Two of the arms 150 depicted in
Generally, a planarization process is performed at each polishing station 132. The planarization process may be a chemical mechanical planarization process, an electrochemical mechanical planarization process or other planarization process employing a pad or a web of polishing material to process a substrate thereon. A conditioning device 182 is disposed on the base 140 adjacent each polishing station 132. The conditioning device 182 periodically conditions the polishing surface 131 to maintain uniform polishing results.
In one embodiment, the polishing head 204 includes a housing 214 having an extending lip 216 that defines a center recess 218 in which is disposed a bladder 220. The bladder 220 may be comprised of an elastomeric material or thermoplastic elastomer such as ethylene propylene, silicone and HYTREL™ polymer. The bladder 220 is coupled to a fluid source (not shown) such that the bladder 220 may be controllably inflated or deflated. The bladder 220, when in contact with the substrate 122, retains the substrate 122 within the polishing head 204 by deflating, thus creating a vacuum between the substrate 122 and the bladder 220. A retaining ring 224 circumscribes the polishing head 204 to retain the substrate 122 below the polishing head 204 while polishing. In another embodiment, the polishing head 204 is a TITAN HEAD™ substrate carrier manufactured by Applied Materials, Inc., Santa Clara, Calif.
The polishing station 132 generally includes a platen 230 that supports a polishing material 252. The platen 230 is typically comprised of aluminum. The platen 230 is supported above the base 140 by a bearing 238 so that the platen 230 may rotate in relation to the base 140. An area of the base 140 circumscribed by the bearing 238 is open and provides a conduit for the electrical, mechanical, pneumatic, control signals and connections communicating with the platen 230.
Conventional bearings, rotary unions and slip rings (not shown) are provided such that electrical, mechanical, pneumatic, control signals and connections may be coupled between the base 140 and the rotating platen 230. The platen 230 is typically coupled to a motor 232 that provides the rotational motion to the platen 230.
A polishing material 252 is disposed on the platen 230 and defines the polishing surface 131. The polishing material 252 may be in the form of a pad, a belt or a web. The polishing surface 131 of the polishing material 252 may be a dielectric or conductive material. The polishing material 252 may include grooves, embossments, texturing and/or perforations. In the embodiment depicted in
The platen 230 has an upper portion 236 that supports the polishing material 252. A top surface 260 of the platen 230 contains a center recess 276 extending into the top portion 236. The top portion 236 may optionally include a plurality of passages 244 disposed adjacent to the recess 276. The passages 244 are coupled to a fluid source (not shown). Fluid flowing through the passages 244 may be used to control the temperature of the platen 230 and the polishing material 252 disposed thereon. The polishing material 252 may be releasably fixed by adhesives, vacuum, mechanical clamps or by other holding methods to the platen 230.
A process fluid delivery system 290 may be disposed adjacent the platen 230. The process fluid delivery system 290 includes a nozzle or outlet 286 coupled to an process fluid source 292. The outlet 286 flows process fluid, such as electrolyte, from the process fluid source 292 onto the surface of the polishing material 252. Alternatively, it is contemplated that the process fluid may be delivered from other portion of the system, such as through the platen 230 and the polishing material 252.
A sub-pad 278 and a sub-plate 280 are disposed in the center recess 276. The sub-pad 278 is typically a polymeric material, such as polycarbonate or foamed polyurethane. Generally, the hardness or durometer of the sub-pad may be chosen to produce a particular polishing result. The sub-pad 278 generally maintains the polishing material 252 parallel to the plane of the substrate 122 held in the polishing head 204 and promotes global planarization of the substrate 122. The sub-plate 280 is positioned between the sub-pad 278 and the bottom of the recess 276 such that the upper surface of the sub-pad 278 is coplanar with the top surface 260 of the platen 230.
Both the sub-pad 278 and the sub-plate 280 optionally contain a plurality of apertures (not shown). A vacuum port 284 is provided in the recess 276 and is coupled to an external pump 282. When a vacuum is drawn through the vacuum port 284, the air removed between the polishing material 252 and the sub-pad 278 causes the polishing material 252 to be firmly secured to the sub-pad 278 during polishing. One example of such polishing material retention system is disclosed in U.S. Pat. No. 6,491,570, which is hereby incorporated by reference.
Optionally, to assist in releasing the polishing material 252 from the sub-pad 278 and platen 230 prior to advancing the polishing material 252, surface tension caused by fluid that may be disposed between the sub-pad 278 and the polishing material 252, a blast of fluid may be provided through the vacuum port 284 or other port (not shown) into the recess 276 by the pump 282 (or other source). The fluid within the recess 276 moves through the apertures (not shown) disposed in the sub-pad 278 and sub-plate 280 and lifts the polishing material 252 from the sub-pad 278 and the top surface 260 of the platen 230. The polishing material 252 rides upon the cushion of fluid such that it may be freely indexed across the platen 230.
In one embodiment, the polishing material 252 is part of a polishing media assembly 274. The polishing media assembly 274 includes a memory device 298 for providing information relating to the polishing material 252. In the embodiment depicted in
The supply roll 240 is removably coupled to the platen 230 to facilitate loading another supply roll containing different polishing material. The supply roll 240 may be replaced once the polishing material 252 is consumed over the course of polishing a number of substrates or for other reasons. The supply roll 240 is coupled to a slip clutch 250 or similar device that prevents the polishing material 252 from inadvertently unwinding from the supply roll 240. After processing, the polishing material 252 may be rewound on the supply roll 240 for removal from the polishing station 132.
The memory device 298 is utilized to store information relating to the polishing material 252. In one embodiment, the memory device 298 is a read/writable chip. Information that may be written to, and/or read from the memory device 298 includes polishing material type, unused or remaining length, conditioning information, historical use information, thickness, diameter, unique identification code and the like. Conditioning information may include the number of times the material has been conditioned, which portions of the material has been conditioned, the type of conditioner used (i.e., brush, diamond, etc.), conditioning downforce, conditioner, RPM, conditioner sweep information, conditioning and fluids used and among others. Historical use information may include the numbers of substrate being polished, the polishing fluid used thereon, type of materials polished on the substrate, polishing recipes used (platen/head RPM), head sweep and substrate downforce, and among others. In another embodiment, the memory device 298 is a computer writeable and readable chip that can be remotely read and/or written by a computer based controller, such as the controller 190 described in
The take-up roll 248 generally is removably coupled to the platen 230 to facilitate removal of used polishing material 252 that is wound thereon. The take-up roll 248 is coupled to a tensioning device 262 that keeps the polishing material 252 taunt between the supply roll 240 and take-up roll 248.
The polishing material 252 is advanced between the supply roll 240 and take-up roll 248 by a driver 266. In one embodiment, the driver 266 comprises a drive roller 268 and an idler 270 that pinches the polishing material 252 therebetween. The drive roller 268 generally is coupled to the platen 230. The drive roller 268 is connected to a controlled motor such as a stepper and an encoder 294 (as shown in phantom). The encoder 294 detects a metric indicative of the length of polishing material advanced across the driver roller 268 that corresponds to an amount of linear displacement of the polishing material across the platen 230. The encoder 294 may be a rotary encoder, a proximity sensor, an optical sensor, a linear displacement transducer or other sensor for detecting a length of polishing material as the polishing material 252 advances. Alternatively, the encoder 294 may be positioned to detect rotation of the rollers 242, 246 having a polishing material running thereover to determine the amount of polishing material advanced.
The driver 266 enables a predetermined length of polishing material to be pulled off the supply roll 240 by drive roller 268 as the drive roller 256 is controllably rotated. The predetermined length is usually about 1 inch or less, such as about ¼ inch indexing between substrates. A corresponding length of polishing material is wound on the take-up roll 248 as the polishing material 252 is advanced across the platen 230. The roll of polishing material 252 is about 100 feet in length, which allows for about 5000 or more substrates to be polished as compared to prior art polishing pads which often have to be replaced after 600 to 1000 substrates are polished.
A sensor 288 for detecting the diameter of the polishing material wound on the take-up roll 248 is typically coupled to the platen 230. The sensor 288 detects the surface of the polishing material such that as the polishing material advances, a chance in the diameter of the polishing material disposed the take-up roll 248 may be detected. It is contemplated that other types of sensors may be utilized to provide and detect different information as needed. The sensor 288 may also provide surface texture information, such as roughness, porosity, glazing, contamination, compressibility, and hardness, among others.
In one embodiment, the sensors 288, 294 may provide the controller 190 with signals that are resolved to indicate the usage, the amount of linear displacement, and condition of the polishing material 252 in the system, thereby allowing the controller to dynamically write and update information in the memory device 298. The updated and rewritten information in the memory device 298 allows the controller 190 to obtain the latest performance and condition of the polishing material 252, thus enhancing the process control and consumable material management. The signals between the controller 190 and memory device 298 may be provided by radio frequency transmission, optical communication, wireless transmission, hard wire or any other suitable means.
FIGS. 3A-B depict end and side views of one embodiment of the supply roll 240 of the polishing media assembly 274. In the embodiment depicted in
The memory device 298 provides information relating to the polishing material 252 to the controller 190. As the memory device 298 being installed with the polishing media assembly 274 in the polishing system 100, the computer based controller 190 may sense the memory device 298 and read the information contained in the memory device 298, thereby allowing the system 100 to determine suitable parameters corresponding to the installed polishing media assembly 274. In one embodiment, the controller 190 may remotely detect and/or sense the memory device 298 by radio transmission, optical communication, wireless transmission, or other suitable methods. Alteratively, a connector may be provided on the platen 230 or polishing station 132 to facilitate communication with the controller 190 through wires.
Thus, the present invention provides a memory device coupled to a polishing material to provide information associated with the polishing material. Moreover, the memory device advantageously facilitates efficient management of the polishing material by dynamically communicating with a computer based controller in a polishing system, thereby enhancing a better control of the polishing performance, polishing material maintenance and process cost.
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.
