JP2013532588A - Real-time monitoring of retaining ring thickness and life - Google Patents

Abstract

  A method and apparatus for monitoring the condition of the surface of the retaining ring located on the carrier head of the polishing module is described. In one embodiment, an apparatus is provided. The apparatus includes a travel path between at least one polishing station for polishing the substrate when the substrate is held by the carrier head and a transfer station for transferring the substrate to and from the carrier head having a retaining ring. And a sensor disposed in the path of movement of the carrier head and operable to provide a metric indicative of the state of the retaining ring.

Description

  Embodiments described herein relate generally to a polishing system for polishing a substrate such as a semiconductor substrate. More particularly, embodiments of the present invention relate to methods and apparatus for monitoring components of a polishing system.

  Chemical mechanical polishing (CMP) is one process commonly used to planarize or polish a layer of material deposited on a substrate in the manufacture of high density integrated circuits. The substrate can be held on a carrier head that is provided in a polishing station of a polishing system and controllably presses the substrate against a movable polishing pad. CMP is effectively used by contacting the feature side of the substrate and the polishing pad and moving the substrate relative to the polishing pad while the polishing fluid is present. Material is removed by a combination of chemical and mechanical action from the feature side of the substrate in contact with the polishing surface.

  The carrier head generally includes a retaining ring that surrounds the substrate and can facilitate holding the substrate on the carrier head. One or more surfaces of the retaining ring generally contact the polishing pad during polishing. Although the retaining ring is adapted to withstand the polishing of multiple substrates, the surface in contact with the polishing pad is subject to wear and requires periodic replacement of the retaining ring. Therefore, inspection of the retaining ring is necessary to monitor wear and determine replacement time intervals.

  Conventional inspection methods are time consuming, require personnel to physically handle the components of the station, and require the polishing system to be shut down. Furthermore, conventional methods may require partial disassembly of the polishing station and removal of the carrier head from the station, thereby exposing other components in the system to contamination.

  Therefore, there is a need for a method and apparatus that facilitates monitoring of the retaining ring without requiring physical retaining ring handling or polishing system shutdown.

  The present invention generally provides a method and apparatus that facilitates monitoring of a retaining ring in a polishing system to determine the condition of the retaining ring and / or to evaluate the life of the retaining ring. In one embodiment, an apparatus is provided. The apparatus includes a travel path between at least one polishing station for polishing the substrate when the substrate is held by the carrier head and a transfer station for transferring the substrate to and from the carrier head having a retaining ring. And a sensor disposed in the path of movement of the carrier head and operable to provide a metric indicative of the state of the retaining ring.

  In another embodiment, a transfer station disposed in the polishing module is provided for transferring a substrate between the substrate transfer device and the at least one carrier head. The transfer station is disposed on the body and indicates a state of the retaining ring, and a load cup assembly having a body sized to receive the substrate and at least a portion of the retaining ring coupled to the at least one carrier head. A sensor operable to provide a metric, the substrate includes a first radius, and the sensor is positioned on the body with a second radius greater than the first radius.

  In another embodiment, a method for monitoring at least one surface of a retaining ring coupled to a carrier head is provided. The method includes moving the carrier head proximate to a sensor device disposed in the polishing module, delivering energy from the sensor device toward the retaining ring, and receiving energy reflected from the retaining ring. Determining the state of the retaining ring based on the received energy.

  In another embodiment, a method for monitoring at least one surface of a retaining ring coupled to a carrier head is provided. The method includes moving the carrier head proximate to a load cup assembly disposed in the polishing module, wherein the sensor device is disposed in the body of the load cup assembly, and the retaining ring is in line of sight of the sensor device. At some point, the method includes delivering energy from the sensor device toward the surface of the retaining ring, receiving energy reflected from the surface, and determining a thickness of the retaining ring based on the received energy. .

  In another embodiment, a method for monitoring at least one surface of a retaining ring coupled to a carrier head is provided. The method includes moving a carrier head proximate to a load cup assembly disposed in the polishing module, wherein the sensor device is disposed in a body of the load cup assembly, rinsing the retaining ring, retaining ring Is in the line of sight of the sensor device, delivering energy from the sensor device towards the surface of the retaining ring, receiving energy reflected from the surface, and thickness of the retaining ring based on the received energy Determining.

  In another embodiment, an apparatus is provided. The apparatus includes a travel path between at least one polishing station for polishing the substrate when the substrate is held by the carrier head and a transfer station for transferring the substrate to and from the carrier head having a retaining ring. And a sensor disposed in the path of movement of the carrier head and operable to provide a metric indicative of the state of the retaining ring.

  In another embodiment, a transfer station disposed in the polishing module is provided for transferring a substrate between the substrate transfer device and the at least one carrier head. The transfer station is disposed on the body and indicates a state of the retaining ring, and a load cup assembly having a body sized to receive the substrate and at least a portion of the retaining ring coupled to the at least one carrier head. A sensor operable to provide a metric, the substrate includes a first radius, and the sensor is positioned on the body with a second radius greater than the first radius.

  In order that the foregoing features of the invention may be more fully understood, a more detailed description of the invention, briefly summarized above, may be had by reference to embodiments, some of which may be It is shown in the accompanying drawings. However, the attached drawings show only typical embodiments of the present invention, and thus should not be considered as limiting the scope of the present invention, and the present invention allows other equally effective embodiments. Note that you can.

1 is a plan view of one embodiment of a polishing system. FIG. 2 is a partial cross-sectional view of one embodiment of a transfer station that can be utilized in the polishing system of FIG. 1. FIG. 2 is a schematic cross-sectional view of another embodiment of a transfer station that can be utilized in the polishing system of FIG. 1. FIG. 2 is a schematic cross-sectional view of another embodiment of a transfer station that can be utilized in the polishing system of FIG. 1. A is a partial plan view of one embodiment of a retaining ring and B is a schematic cross-sectional view of another embodiment of a transfer station that can be utilized in the polishing system of FIG. FIG. 2 is a schematic cross-sectional view of another embodiment of a transfer station that can be utilized in the polishing system of FIG. 1. 2 is a flow diagram illustrating one embodiment of a method.

  For ease of understanding, identical reference numerals are used where possible to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be advantageously utilized in other embodiments without special description.

  The present invention generally provides a method and apparatus that facilitates monitoring of a retaining ring in a polishing system to determine retaining ring wear and / or to assess retaining ring life. An on-tool monitoring device is described that monitors the retaining ring without requiring physical handling of the retaining ring or shutting down of the polishing system. In addition, data from the monitoring device can be provided to the controller and used to coordinate subsequent polishing processes.

  FIG. 1 is a plan view of a polishing system 100 having a polishing module 105 and a substrate transfer device and suitable for electrochemical mechanical polishing and / or chemical mechanical polishing. The polishing module 105 includes a first polishing station 110A, a second polishing station 110B, and a third polishing station 110C disposed in an environmentally controlled housing 115. A substrate transfer device, such as carousel 125, moves the substrate between polishing stations 110A, 110B, and 110C. Any of the polishing stations 110A, 110B, 110C can perform a planarization or polishing process to remove material from the feature side of the substrate to form a planar surface on the feature side. Module 105 is available from Applied Materials, Inc., located in Santa Clara, California. One of the larger polishing systems such as REFLEXION®, REFLEXION® LK, REFLEXION® LK ECMP ™, MIRRA MESA®, and REFLEXION GT ™ polishing system available from Other polishing systems can be used. Use other types of polishing pads, belts, indexable web-type pads, or combinations thereof, and those that move the substrate relative to the polishing surface in a rotating, linear, or other plane motion Other polishing modules including may still be adapted to benefit from the embodiments described herein.

  In one embodiment, each of the polishing stations of 110A-110C of the polishing module 105 is configured to perform a conventional chemical mechanical polishing (CMP) process. Alternatively, the first polishing station 110A can be adapted to perform an electrochemical mechanical planarization (ECMP) process, while the second polishing station 110B and the third polishing station 110C perform a CMP process. Can do. In one embodiment of the process, a substrate having a feature profile formed in the substrate and covered with a barrier layer and a conductive material disposed on the barrier layer is provided by the first and second polishing stations 110A. , 110B, having conductive material removed by the CMP process in two stages, along with a barrier layer processed by the third CMP process at the third station 110C to form a planarized surface on the substrate. Can do.

  In one embodiment, system 100 includes a module base 118 that supports polishing stations 110A, 110B, and 110C, a transfer station 120, and a carousel 125. Each of the polishing stations 110A, 110B, and 110C includes a polishing fluid delivery arm 128 that is adapted to supply polishing fluid to the polishing surface 175 during the polishing process. A plurality of adjustment devices 130 are shown coupled to the module base 118 and are movable in direction A to selectively position the adjustment devices 130 for each of the polishing stations 110A, 110B, and 110C. Transfer station 120 generally facilitates transfer of substrate 135 to and from system 100 via wet robot 140. The wet robot 140 generally transfers substrates 135 between the transfer station 120 and a factory interface (not shown), which may include a cleaning module, a metrology device, and one or more substrate storage cassettes. it can. The transfer station 120 includes a first buffer station 145, a second buffer station 150, a transfer robot 155, and a load cup assembly 160. The transfer robot 155 transfers the substrate between the first buffer station 145, the second buffer station 150, and the load cup assembly 160. Load cup assembly 160 includes a monitoring device 162 coupled to the controller.

  The carousel 125 includes a plurality of arms 170, and each arm 170 supports carrier heads 165A to 165D. Carrier heads 165C and 165D and portions of the two arms 170 are shown in phantom so that the polishing surface 175 of transfer station 120 and polishing station 110C can be seen. The polishing surface 175 comprises the upper surface of the pad assembly disposed on a rotatable platen (not shown in this view). Each of the carrier heads 165A-165D includes an actuator 168. The carousel 125 moves the carrier heads 165A-165D between the transfer station 120 and the polishing stations 110A, 110B, and 110C, and the actuator 168 is adapted to move the carrier heads 165A-165D relative to the carousel 125. The The carousel 125 can be indexed so that the carrier heads 165A-165D can be moved between the polishing stations 110A, 110B, 110C and the transfer station 120 in a sequence defined by the user. Each of the carrier heads 165A-165D holds one substrate 135 at the polishing station 110A-110C during the polishing process. Other polishing modules, such as the REFLEXION GT ™ polishing system that includes more than one carrier head per polishing station, can also be adapted to benefit from the embodiments described herein. Each of the carrier heads 165 </ b> A to 165 </ b> D is movable on the longitudinal axis of each arm 170. The polished substrate 135 can be transferred from each carrier head 165A-165D at the transfer station 120. Further, the unpolished substrate 135 can be transferred to each of the carrier heads 165A-165D at the transfer station 120. As shown in connection with the carrier head 165D, the carrier head 165D is movable along the longitudinal axis of the arm 170 in a movement path 164 indicated by a broken line, whereby the carrier head 165D is loaded with the load cup. The assembly 160 can be accessed to facilitate substrate transfer.

  In one embodiment, the carousel 125 is continuously advanced in a counterclockwise direction (direction B) to move the carrier heads 165A-165D over the polishing stations 110A-110C and the transfer station 120. During processing, three of the four carrier heads 165A-165D have substrates held therein and are placed on the polishing stations 110A, 110B, 110C on which the polishing process takes place. . The substrate 135 is continuously processed by moving the substrate between stations while being held by the same carrier heads 165A to 165D. In one example, the three carrier heads 165A-165C include a substrate and press the substrate 135 toward the polishing surface 175 of the polishing stations 110A, 110B, and 110C. During polishing, the carrier heads 165A-165C including the substrate are rotated clockwise (direction C) while the polishing surface 175 is rotated counterclockwise (direction D).

  Since three carrier heads, shown as carrier heads 165A-165C in this example, are utilized at stations 110A-110C, carrier head 165D is adjacent to transfer station 120 where the substrate transfer process takes place. The carrier head 165D can be deactivated for a period of time because the three carrier heads 165A-165C are performing a polishing process. During this period, the carrier head 165D is prepared at the transfer station 120 for use at the polishing station 110A for the next cycle. The carrier head 165D travels along the travel path 164 and can be very close to the transfer station 120. While the carrier head 165D is in the transfer station 120, the carrier head 165D can remove the polished substrate 135, be cleaned, and receive a new unpolished substrate 135 for the polishing process at the polishing station 110A. In one embodiment, the carrier head 165D is inspected using a monitoring device 162 located at the transfer station 120.

  The polished surface 175 is roughened to facilitate mechanical removal of material from the substrate 135. The polishing surface 175 of the polishing pad can be a polymeric material, and the polymeric material can be exclusively dielectric to facilitate removal of material from the substrate 135 during the polishing process. Alternatively, the polishing surface 175 of the polishing pad can be at least partially conductive to facilitate electrochemical dissolution of material from the substrate in an electrochemical mechanical polishing (ECMP) process. Suitable polymeric materials that can be used include polyurethane, polycarbonate, fluoropolymer, PTFE, PTFA, polyphenylene sulfide (PPS), or combinations thereof, and other abrasive materials used in polishing substrate surfaces. . In one embodiment, the polishing surface 175 of the polishing pad comprises a polymeric material, such as an open or closed pore polyurethane material commonly used in the manufacture of polishing pads useful in semiconductor substrate polishing. In another embodiment, the polishing surface 175 of the polishing pad can include a fixed abrasive. A polishing fluid is generally supplied to the polishing surface 175 of the polishing pad during polishing. The polishing fluid can be a slurry or electrolyte fluid depending on the polishing process and the type of polishing pad used.

  FIG. 2 is a partial cross-sectional view of one embodiment of the transfer station 120 of FIG. As previously described, the transfer station 120 includes a load cup assembly 160 adjacent to the first buffer station 145. The first buffer station 145 may be an input or output buffer station configured to support the substrate 135. The transfer robot 155 transfers the substrate 135 between the first buffer station 145 and the load cup assembly 160 that facilitates transferring the substrate to the carrier head 165D.

  In one embodiment, the first buffer station 145 supports the polished substrate 135 such that the wet robotic robot 140 (FIG. 1) transfers the substrate 135 to the factory interface for subsequent polishing and / or storage. To be able to. In another embodiment, the first buffer station 145 supports the unpolished substrate 135 so that the carrier head 165D can receive the substrate 135 for polishing at the polishing station 110A. In one embodiment, the transfer robot 155 transfers the substrate 135 between the first buffer station 145 and the load cup assembly 160 and the carrier head 165D moves the substrate 135 as shown in phantom in FIG. Configured to be able to receive.

  The carrier head 165D is coupled to the shaft 200, which is coupled to a motor 215 configured to move the carrier head 165D laterally in a linear motion (X and / or Y direction) relative to the arm 170. . The carrier head 165D further includes an actuator or motor 210 to raise or lower the carrier head 165D in the Z direction relative to the arm 170. The carrier head 165D is further coupled to a rotary actuator or motor 220 that is adapted to rotate the carrier head 165D about an axis of rotation relative to the arm 170. Motors 210, 215, and 220 disposed on carrier head 165D are further configured to move carrier head 165D relative to polishing surface 175 (FIG. 1) of the polishing pad. In one embodiment, the motors 210, 215, and 220 rotate the carrier head 165D relative to the rotating polishing surface 175, and the substrate held on the carrier head 165D relative to the polishing surface 175 of the polishing pad during processing. It is comprised so that downward force may be given so that 135 may be pressed. The structure and operation of the carrier head 165D shown in FIG. 2 is representative of the carrier heads 165A-165C of FIG. 1, and the carrier heads 165A-165C are not further described for the sake of brevity.

  The carrier head 165D includes a body 225 surrounded by a retaining ring 230. The carrier head 165D further includes one or more bladders 235A, 235B adjacent to the flexible membrane 240. The flexible membrane 240 contacts the back side of the substrate 135 when the substrate 135 is held by the carrier head 165D. The bladders 235A and 235B are coupled to a first variable pressure source 245A that selectively supplies fluid to the bladders 235A and 235B to apply force to the flexible membrane 240. In one embodiment, bladder 235A applies a force to the outer zone of flexible membrane 240, while bladder 235B applies a force to the central zone of flexible membrane 240. The force applied to the flexible membrane 240 from the bladders 235A and 235B is transmitted to a portion of the substrate 135 and may be used to press the portion of the substrate 135 toward the polishing surface of the polishing pad (not shown). it can. The first variable pressure source 245A is configured to independently supply fluid to each of the bladders 235A and 235B to control the force on the individual regions of the substrate 135 by the flexible membrane 240. Further, a vacuum port (not shown) can be provided in the carrier head 135, the back side of the substrate 135 can be sucked, and the substrate 135 can be easily held by the carrier head 165D. Examples of carrier heads 165D that can be used include Applied Materials, Inc. of Santa Clara, California. TITAN HEAD ™, TITAN CONTROL ™, and TITAN PROFILER ™ carrier heads available from:

  In one embodiment, retaining ring 230 is coupled to body 225 by actuator 232. The actuator 232 is controlled by the second variable pressure source 245B. The second variable pressure source 245B supplies or removes fluid from the actuator 232, thereby moving the retaining ring 230 at least in the Z direction relative to the body 225 of the carrier head 165D. The second variable pressure source 245B is adapted to perform the Z-direction movement of the retaining ring 230 independently of the movement provided by the motor 210. The second variable pressure source 245B can move the holding ring 230 by applying a negative pressure or a positive pressure to the actuator 232 and / or the holding ring 230. In one aspect, pressure is applied to the retaining ring 230 to force the retaining ring 230 toward the polishing surface 175 (FIG. 1) of the polishing pad (not shown) during the polishing process. Each of the first variable pressure source 245A and the second variable pressure source 245B is coupled to a controller to facilitate execution of a polishing strategy that automatically controls the pressure on the zone of the substrate 135 during the polishing process. Can do.

  The retaining ring 230 contacts the polishing surface 175 during the polishing process. The retaining ring 230 further facilitates transport of polishing fluid to the polishing surface 175 and can generate heat by friction from contact with the polishing surface 175. Fluid transport and generated heat can be utilized to benefit during the polishing process. Due to contact with the polishing surface 175, the retaining ring 230 wears. Wear on the surface of the retaining ring 230 will affect the polishing process, and the retaining ring 230 will eventually require replacement. Accordingly, the thickness of the retaining ring 230 must be periodically evaluated to determine wear and replacement time intervals.

  In one embodiment, the surface of the retaining ring 230 is monitored with a monitoring device 162 disposed on the load cup assembly 160. When the carrier head 165D is adjacent to the load cup assembly 160, the surface of the retaining ring 230 can be sensed and data representing wear of the retaining ring 230 can be sent to the controller. The controller can communicate with the monitor and display data to the user. Data from the monitoring device 162 is used to predict and / or confirm the state of the retaining ring 230 and the state of the retaining ring 230 is utilized to determine the life and replacement of the retaining ring 230. In one embodiment, the data indicates the thickness of the retaining ring 230. Alternatively or additionally, the controller can be a system controller, and the system controller can analyze the data and implement corrective actions in the process strategy to compensate for wear of the retaining ring 230 in the polishing process. Thus, the data from the monitoring device 162 can be used to determine the life and replacement of the retaining ring 230 and can further be used as a control knob to adjust the polishing process. In addition, in systems having a number of carrier rings with retaining rings, data from the monitor device 162 is utilized to adjust the individual retaining ring process strategy independently of other retaining rings on other carrier heads of the system. can do. For example, individual retaining rings can wear at different rates, so the process strategy of one retaining ring on one carrier head may be adjusted, while other processes on other retaining rings on the remaining carrier head Strategies may remain the same.

  FIG. 3 is a schematic cross-sectional view of another embodiment of a transfer station 120 that may be utilized with the polishing system 100 of FIG. The transfer station 120 includes a load cup assembly 160 and the carrier head 165D is positioned adjacent to the load cup assembly 160. In this embodiment, the load cup assembly 160 is configured as a cleaning station 300 adapted to clean the carrier head 165D when the carrier head 165D is not utilized for polishing at the polishing stations 110A-110C of FIG. The

  In one embodiment, the load cup assembly 160 includes a body 305 having a reference cone or ring 307 that is coupled to a base 309. Ring 307 and base 309 can be moved relative to module base 118 by first actuator 310A. The main body 305 can be moved in at least a linear direction (Z direction) with respect to the module base 118 by using the first actuator 310A. The load cup assembly 160 further includes a pedestal 320 adapted to support the substrate 135 (shown in phantom). The pedestal 320 is coupled to a second actuator 310B adapted to raise and lower the support surface 321 of the pedestal 320. The second actuator 310B facilitates transfer of the substrate 135 to or from the carrier head 165D by moving the support surface 321 in the Z direction relative to the body 305.

  The body 305 further includes a plurality of nozzles 315 that are utilized to clean the carrier head 165D when the substrate is not on the pedestal 320. Nozzle 315 is in fluid communication with pressurized fluid supply 330. Pressurized fluid supply 330 includes a fluid, such as deionized water, which is provided through nozzle 315 to clean carrier head 165D. In one embodiment, the support surface 321 of the pedestal 320 is configured as a ring having a number of open areas so that the cleaning fluid from the nozzle 315 strikes the carrier head 165D. The cleaning fluid cleans polishing liquid and other debris from the polishing process that may be held on the carrier head 165D. The cleaning station 300 further includes an opening 325 formed in the base 309 that is adapted as a waste tube to selectively remove fluid and polishing debris moved from the carrier head 165D.

  In this embodiment, the cleaning station 300 includes a monitoring device 162 that includes a sensor 335 coupled to a controller. Sensor 335 is adapted to measure the thickness T of retaining ring 230. In one embodiment, sensor 335 is an ultrasonic sensor. The sensor 335 can be coupled to or embedded within the body 305 for transmitting and receiving sound waves. The sound wave is transmitted to the controller, and a metric indicating the thickness T of the retaining ring 230 is generated. In one embodiment, the retaining ring 230 comprises two annular portions such as an upper portion 355A and a lower portion 355B. In one embodiment, the upper portion 355A and the lower portion 355B can include a material that is chemically inert in a CMP process, such as a metallic material, a ceramic material, or a plastic material. In one embodiment, the lower portion 355B comprises a plastic, such as polyphenylene sulfide (PPS), polyetheretherketone (PEEK), a carbon-containing PEEK material, a TEFLON®-containing PEEK material, or a composite material. The upper portion 355A can include a material that is more rigid or dense than the lower portion 355B. In one embodiment, the upper portion 355A includes stainless steel, aluminum, molybdenum, or a ceramic material.

  In one example of operation, sensor 335 is attached to active surface 340 of land area 345 of body 305. Land area 345 can be defined as the area of the bottom surface of ring 307, and lower portion 355 B of retaining ring 230 contacts the surface of ring 307. The active surface 340 can directly face the surface of the ring 307 in the land area 345 where the retaining ring 230 is located. In one embodiment, sound waves are transmitted to or through the lower portion 355B of the retaining ring 230 and reflected from the upper portion 355A. The reflected signal is sent to the controller and used to determine the thickness T of the lower portion 355B of the retaining ring 230. Changes in thickness T over time indicate wear of retaining ring 230.

  FIG. 4 is a schematic cross-sectional view of another embodiment of a transfer station 120 that may be utilized with the polishing system 100 of FIG. In this embodiment, the load cup assembly 160 is configured as a cleaning station 400 that may be substantially similar to the embodiment shown in FIG. Elements of transfer station 120 that are similar to transfer station 120 of FIG. 3 are not repeated for the sake of brevity.

  In this embodiment, the monitoring device 162 includes a sensor 335 that is an eddy current sensor adapted to measure the thickness T of the lower portion 355B. In this embodiment, the contact surface 405 of the lower portion 355B contacts the active surface 340 of the ring 307. In other embodiments, the sensor 335 can be utilized when the retaining ring 230 is separated from the ring 307. In one aspect, a sensor 335 adapted as an eddy current sensor can be utilized to measure displacement between the active surface 340 and the contact surface 405 of the upper portion 355A of the retaining ring 230. The displacement corresponds to a change in the thickness of at least the lower portion 355B of the retaining ring 230. The displacement can be determined when the lower portion 355B of the retaining ring 230 contacts the active surface 340 or when the lower portion 355B is held at a certain distance from the active surface 340.

  FIG. 5A is a partial plan view of one embodiment of a retaining ring 230 having one or more grooves 500. Each of the one or more grooves 500 is formed in the retaining ring 230 at a desired depth between the contact surface 405 of the retaining ring 230 and the bottom 505 of the groove 500. Each of the grooves 500 disposed in the retaining ring 230 can be utilized to facilitate polishing by enhancing the transport of polishing fluid during the polishing process.

  FIG. 5B is a schematic cross-sectional view of another embodiment of a transfer station 120 that may be utilized with the polishing system 100 of FIG. 1 and the retaining ring 230 shown in FIG. 5A. The retaining ring 230 includes one or more grooves 500 having a depth D ′ defined by the contact surface 405 and the bottom 505. A change in the depth D ′ of the groove 500 corresponds to a change in the thickness of the retaining ring 230. In one embodiment, sensor 335 can be coupled to ring 307 or embedded therein. Sensor 335 can be an optical sensor, an eddy current sensor, an ultrasonic sensor, or other suitable sensing device. In one embodiment, sensor 335 is an ultrasonic sensor configured to transmit and receive sound waves indicated as signal 510 that strikes contact surface 405. The sound wave is sent to the controller, whether it senses that the retaining ring 230 is dry or wet, and determines the depth D ′ of the groove 500 and thus the thickness of the retaining ring 230. A metric is generated that indicates. Accordingly, the depth of the groove 500 is measured between the contact surface 405 and the bottom 505 to determine wear without physical contact between the retaining ring 230 and other portions of the load cup assembly 160. The carrier head 165D can rotate at a predetermined rotational speed and perform sensing at a number of locations on the retaining ring 230. In this way, a large number of grooves 500 can be monitored. Alternatively, the carrier head 165D is stationary and can sense a single groove 500. In another embodiment, a controlled air or liquid column can be utilized to surround signal 510 and control the interface between retaining ring 230 and sensor 335. For example, a bubbler (not shown) can be utilized to form a cylindrical air column that surrounds the path of signal 510.

In one embodiment, the position of the monitor device 162 is outside the area of the substrate 135, thereby preventing unintentional sensing of the substrate 135 or a portion of the unintended carrier head 165D. For example, the substrate 135 includes a first radius R ₁ in the case of a circular substrate. In one embodiment, the first radius R ₁ includes a radius of about 100 mm for a 200 mm diameter substrate. In another embodiment, the first radius R ₁ includes a radius of about 150 mm for a 300 mm diameter substrate. In one embodiment, the monitoring device 162 is positioned with a _second radius R ₂ that is larger than or outside the first radius R ₁ . Second radius _{R 2,} in the substrate of 200mm may be greater than about 100mm, such as about 120mm to about 105mm from the center line C '. In another example, the second radius R ₂ can be greater than about 150 mm, such as about 155 mm to about 170 mm from the center line C ′ for a 300 mm substrate. Center line C ′ may be the geometric center of load cup assembly 160 and / or the center of carrier head 165D. Thus, this positioning of the monitor device 162 prevents unintentional sensing of the substrate 135 or a portion of the untargeted carrier head 165D.

  FIG. 6 is a schematic cross-sectional view of another embodiment of a transfer station 120 that may be utilized with the polishing system 100 of FIG. In this embodiment, the load cup assembly 160 is similar to the embodiment shown in FIGS. Elements of transfer station 120 that are similar to transfer station 120 of FIGS. 3-5 are not repeated for the sake of brevity. In one embodiment, retaining ring 230 includes one or more grooves 500 similar to the embodiment of retaining ring 230 of FIG.

  In this embodiment, the monitor device 162 includes a sensor 335 that is an ultrasonic sensor, although an optical sensor, eddy current sensor, or other suitable sensing device may be utilized. In one embodiment, sensor 335 can be utilized when retaining ring 230 is within the line of sight or field of view of sensor 335. In other embodiments, the sensor 335 can be utilized when the retaining ring 230 is at least partially disposed on the load cup assembly 160. In one aspect, sensor 335 includes a tubular conduit 600 disposed adjacent to sensor 335. Tubular conduit 600 is coupled to a fluid source 605 that supplies a fluid, such as deionized water, to surround the signal path of sensor 335. The fluid is utilized to eliminate uncontrolled air that can affect the signal from sensor 335. In one embodiment, the contact surface 405 of the retaining ring 230 contacts the active surface 340 of the ring 307 directly. In another embodiment, the tubular conduit 600 is coupled to an actuator 610 that can cause the tubular conduit 600 to move in and out of the active surface 340 of the ring 307. Tubular conduit 600 can be actuated to a position near contact surface 405 of retaining ring 230 toward contact surface 405 as indicated by phantom lines when carrier head 165D is not in contact with ring 307. Tubular conduit 600 may include at least a portion of sensor 335, at least a portion of sensor 335 being moved by tubular conduit 600 toward contact surface 405 of retaining ring 230. Actuator 610 can further retract tubular conduit 600 when sensor 335 is not needed.

  FIG. 7 is a flow diagram illustrating one embodiment of method 700. At 705, the carrier head 165 </ b> D having the retaining ring 230 is moved to the vicinity of the monitor device 162. In one embodiment, the monitoring device 162 is disposed on the load cup assembly 160 in the polishing module 105. In other embodiments, the monitoring device 162 can be adjacent to the transfer station 120, in the path of travel of the carrier head 165 D adjacent to the transfer station 120, or in other locations on the polishing module 105. The monitoring device 162 includes a sensor 335 and energy is delivered from the sensor 335 as indicated at 710. The energy can be ultrasound, light waves, or a magnetic or magnetic signal. At 715, the energy reflected from retaining ring 230 is received at sensor 335. The reflected energy can be from one or more inner or outer surfaces of the retaining ring 230. At 720, the state of the retaining ring is determined based on the received energy. The reflected signal is provided to the controller to determine the condition of the retaining ring 230, for example, the thickness of the retaining ring 230 or a portion thereof, or the depth of the groove 500 in the retaining ring 230 that may be related to the thickness of the retaining ring 230. A metric can be obtained. This data can be used to determine adjustment of the retaining ring 230 replacement time interval and / or subsequent polishing process variables.

  The embodiments described herein provide a method and apparatus for monitoring the condition of the surface of a retaining ring 230 disposed on a carrier head of a polishing station, such as the carrier heads 165A-165D described herein. provide. A monitoring device 162 is described that can be mounted on-tool and in one embodiment can sense the condition of the retaining ring 230 during the polishing cycle. The sensing of the retaining ring 230 can be set by the user at a predefined time interval as part of routine monitoring or at a time interval selected based on user preferences. Data from the monitoring device 162 is provided to a controller that can be used to monitor the wear of the retaining ring 230, determine the life of the retaining ring 230, and / or determine the replacement time interval of the retaining ring 230. The In one aspect, data from the monitoring device 162 can be used to predict the life of the retaining ring 230 and facilitate replacement of the retaining ring 230 at a practical lifetime limit. In another aspect, data from the monitoring device 162 can be used to predict life and aid in convenient replacement time intervals even when the retaining ring 230 is not fully worn.

  Embodiments of monitoring device 162 as described herein minimize or eliminate physical handling and / or mechanical contact with carrier heads 165A-165D and retaining ring 230. For example, a mechanical measurement device such as a caliper requires contact with the retaining ring 230. Contact with the mechanical measurement device can damage the retaining ring 230 during measurement, and as a result, the polishing surface 175 can be damaged during processing. Measurements can be made in the tool without having to shut down the polishing system. Furthermore, it is not necessary for the retaining ring 230 to be completely dried for measurement. The monitoring device 162 is mounted on-tool so that the environment is confined to the environmentally controlled housing 115 (FIG. 1). Accordingly, the monitoring device 162 as described herein provides for the monitoring of the retaining ring 230 with potentially less damage due to handling or contact with the carrier heads 165A-165D and / or destruction of the environment of the polishing module 105. To do. This method and apparatus further eliminates or minimizes visual inspection, which can be time consuming and inaccurate. In addition, the polishing system does not require a shutdown to measure and / or observe the retaining ring 230, thereby maximizing throughput.

  Further, the wear data of the retaining ring 230 can be used as a control variable during the polishing process. For example, if the retaining ring 230 includes a groove 500 and the groove 500 exhibits a predetermined amount of wear, one or more polishing parameters may be adjusted to compensate for any retaining ring 230 thickness effect with respect to polishing uniformity. can do. In one example, polishing parameters such as the rotational speed and downward force of the carrier heads 165A-165D are adjusted to account for the cause of wear of the retaining ring 230 and to simulate the polishing effect of the retaining ring 230 with less wear. be able to. In one aspect, the rotational speed of the carrier heads 165A-165D facilitates transport of the polishing fluid and accelerates to generate heat on the polishing surface 175 that is substantially equivalent to the effect of the low wear retaining ring 230. can do.

  In another example, wear data of the retaining ring 230 can be utilized to minimize in-wafer non-uniformity over the life of the retaining ring 230. The wear data of the retaining ring 230 can be utilized in an automated process control system coupled to a multi-zone carrier head bladder 235A and 235B, such as the carrier head 165D shown in FIG. Further, the automatic processing control system can be in communication with the actuator 232 of the carrier head 165D shown in FIG. In one aspect, the pressure applied to the outer zone (bladder 235A) and / or applied to the retaining ring 230 by the actuator 232 can vary as the thickness of the retaining ring 230 changes. Changes to the pressure applied to the substrate by the bladders 235A and 235B and / or the pressure applied to the retaining ring 230 can be made in real time based on the thickness data of the retaining ring 230. Accordingly, the removal rate, removal profile, and / or topography of the substrate being polished can be controlled by manipulating polishing parameters based on the wear of the retaining ring 230. Furthermore, since the polishing parameters can be adjusted for each of the carrier heads 165A to 165D, fluctuations between the carrier heads can be minimized.

  The embodiments described herein provide a method and apparatus that facilitates monitoring of the retaining ring in the polishing system to determine the state of the retaining ring and / or to evaluate the life of the retaining ring. In one embodiment, an apparatus is provided. The apparatus includes a travel path between at least one polishing station for polishing the substrate when the substrate is held by the carrier head and a transfer station for transferring the substrate to and from the carrier head having a retaining ring. And a sensor disposed in the path of movement of the carrier head and operable to provide a metric indicative of the state of the retaining ring.

  In another embodiment, a transfer station disposed in the polishing module is provided for transferring a substrate between the substrate transfer device and the at least one carrier head. The transfer station is disposed on the body and indicates a state of the retaining ring, and a load cup assembly having a body sized to receive the substrate and at least a portion of the retaining ring coupled to the at least one carrier head. A sensor operable to provide a metric, the substrate includes a first radius, and the sensor is positioned on the body with a second radius greater than the first radius.

  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.

Claims (15)

In a movement path between at least one polishing station for polishing the substrate when the substrate is held on a carrier head and a transfer station for transferring the substrate to and from the carrier head having a holding ring A movable carrier head;
A sensor disposed in the travel path of the carrier head and operable to provide a metric indicative of a state of the retaining ring.   The apparatus of claim 1, wherein the sensor is an ultrasonic sensor.   The apparatus of claim 1, wherein the sensor is an eddy current sensor.   The apparatus of claim 1, wherein the sensor is an optical sensor.   The sensor includes a plurality of waveguides disposed in the body of the transfer station and positioned to direct light toward the holding ring when the retaining ring is aligned with the body of the transfer station. The apparatus according to claim 4.   The apparatus of claim 4, wherein the sensor comprises a transmitter and a receiver.   The apparatus of claim 1, wherein the transfer station comprises one or more nozzles in fluid communication with a water source.   The apparatus of claim 2, wherein the transfer station comprises a body shaped to contain a fluid.   The apparatus of claim 7, wherein the substrate includes a first radius and the sensor is positioned at a second radius that is greater than the first radius. A method of monitoring at least one surface of a retaining ring coupled to a carrier head, comprising:
Moving the carrier head in the vicinity of the sensor device disposed in the polishing module;
Delivering energy from the sensor device toward the retaining ring;
Receiving energy reflected from the retaining ring;
Determining the state of the retaining ring based on the received energy.   The method of claim 10, wherein the transmitted and received energy is sound waves.   The method of claim 10, wherein the transmitted and received energy is an optical signal.   The method of claim 10, wherein the transmitted and received energy is a magnetic field.   The method of claim 10, wherein the energy is delivered and received by a liquid.   The method of claim 10, further comprising moving the carrier head proximate to a load cup assembly disposed in the polishing module, wherein the sensor device is disposed in a body of the load cup assembly. .

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