Patent Publication Number: US-7914363-B2

Title: Smart conditioner rinse station

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This patent application is a continuation of U.S. patent application Ser. No. 11/741,609, filed Apr. 27, 2007 now U.S. Pat. No. 7,611,400, which is a continuation of U.S. patent application Ser. No. 11/273,766 filed Nov. 14, 2005, and issued as U.S. Pat. No. 7,210,981, which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Embodiments of the present invention generally relate to a chemical mechanical polishing system. In particular, embodiments of the present invention relate to a method and apparatus for monitoring a polishing surface conditioning mechanism of a chemical mechanical polishing system. 
     2. Description of the Related Art 
     Chemical mechanical polishing is one process commonly used in the manufacture of high-density integrated circuits. Chemical mechanical polishing is utilized to planarize a layer of material deposited on a semiconductor substrate by moving the substrate in contact with a polishing surface while in the presence of a polishing fluid. Material is removed from the surface of the substrate that is in contact with the polishing surface through a combination of chemical and mechanical activity. 
     In order to achieve desirable polishing results, the polishing surface must be periodically dressed, or conditioned. One type of conditioning process, typically performed on the polyurethane polishing pads traditionally utilized in chemical mechanical polishing, is configured to restore the fluid retention characteristics of the polishing surface and to remove embedded material from the polishing surface. Another type of conditioning process, typically performed on fixed abrasive polishing materials, is configured to expose abrasive elements disposed within structures comprising the abrasive polishing material, while removing asperities from the upper surface of the polishing material and leveling the structures comprising the polishing surface to a uniform height. 
     In one embodiment, a polishing surface conditioner includes a replaceable conditioning element, such as a diamond disk, coupled to a conditioning head that is movable over the polishing surface. The conditioning element is lowered into contact with the polishing surface while being rotated. The conditioning head is generally swept across the rotating polishing surface to allow the conditioning element to condition a predefined area of the polishing surface. 
     Conventional conditioners commonly utilize diaphragms within the conditioning head to control the elevation of the conditioning element. A cavity behind the diaphragm is generally pressurized to lower the conditioning element and press it against the polishing surface of the polishing pad during conditioning. Upon completion of conditioning, the cavity is vented, allowing the conditioning element to retract, typically assisted by an upward spring bias. 
     The pressurization and the venting of the cavity causes the diaphragm to repeatedly stretch and relax. In addition, the raising and lowering of the conditioning element further applies stress to the diaphragm. However, the elastomeric diaphragm, like all other elastomeric materials have a finite life. Without repair or replacement, the eventual deterioration of the diaphragm leads to poor conditioning. To prevent the inevitable deterioration, the diaphragm is typically replaced on a set interval, for example after a preselected number of conditioning cycles. However, the conventional method is inefficient. Sometimes, the diaphragm will be replaced while it is still in good condition, causing unnecessary downtime and increasing costs. At other times, a diaphragm in poor condition is not replaced soon enough, causing poor conditioning of the pad. 
     Therefore, there is a need for a method and apparatus for monitoring pad conditioning mechanisms. 
     SUMMARY OF THE INVENTION 
     A method and apparatus for monitoring polishing pad conditioning mechanisms is provided. In one embodiment, an apparatus is provided for monitoring a conditioner that includes a sensor arranged to detect a performance attribute of a conditioning element when the conditioning element is not engaged with a processing pad. Performance attributes may include at least one of downforce, power transmission or condition of the conditioning surface, among other attributes that may affect conditioning performance. 
     In another embodiment, a semiconductor substrate polishing system includes a rinse station, a polishing surface, a conditioning element, and a conditioning mechanism. The conditioning mechanism selectively positions the conditioning element over the polishing surface and over the rinse station. At least one sensor is provided and is configured to detect a first position and a second position of the conditioning element when disposed over the rinse station. 
     In another embodiment, a semiconductor substrate polishing system having a polishing surface and a conditioning mechanism that is movable between a conditioning position disposed over the polishing surface and a non-conditioning position to the side of the polishing surface. The conditioning mechanism has a conditioning element for conditioning the polishing surface. A sensor is provided and is configured to detect a performance attribute of the conditioning element while in the non-conditioning position. 
     In another aspect of the invention, a method for characterizing a conditioning mechanism is provided. In one embodiment the method includes sensing a metric of a performance attribute of the conditioning mechanism and determining from the sensed metric is within a process window. 
     In another embodiment, a method for characterizing a component of a conditioning mechanism includes actuating a conditioning element of the conditioning mechanism to move between a first position and a second position. Next, the time required to actuate the conditioning element between the first position and the second position is analyzed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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. 
         FIG. 1  is a top view of an illustrative polishing system having one embodiment of a rinse station for a conditioning mechanism; 
         FIG. 2  is a sectional side view of one embodiment of the conditioning mechanism and rinse station of  FIG. 1 ; 
         FIGS. 3A and 3B  respectively depict a side and top view of one embodiment of a rinse station; 
         FIGS. 4A ,  4 B and  4 C depict methods of use of the rinse station; and 
         FIG. 5  is a chart depicting sensor timings for the rinse station. 
     
    
    
     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 from one embodiment may be beneficially incorporated in other embodiments without further recitation. 
     DETAILED DESCRIPTION 
       FIG. 1  is a top view of an illustrative polishing system  100  having one embodiment of a rinse station  135  of the present invention. The polishing system  100  generally includes a factory interface  104 , a cleaner  106  and a polisher  108 . Two polishing systems that may be adapted to benefit from the invention is a REFLEXION® chemical mechanical polishing system and the REFLEXION LK Ecmp™, both available from Applied Materials, Inc., located in Santa Clara, Calif. Another polishing system that may be adapted to benefit from the invention is described in U.S. Pat. No. 6,244,935, issued Jun. 12, 2001, to Birang, et al., entitled, “Apparatus and Methods for Chemical Mechanical Polishing with an Advanceable Polishing Sheet,” which is incorporated by reference in its entirety. 
     A controller  160  is provided to facilitate control and integration of the system  100 . The controller  160  typically comprises a central processing unit (CPU), memory, and support circuits (not shown). The controller  160  is coupled to the various components of the system  100  to facilitate control of, for example, the planarizing, cleaning, and transfer processes. 
     In one embodiment, the factory interface  104  includes a first, or interface, robot  110  adapted to transfer substrates from one or more substrate storage cassettes  112  to a first transfer station  114 . A second robot  116  is positioned between the factory interface  104  and the polisher  108  and is configured to transfer substrates between the first transfer station  114  of the factory interface  104  and a second transfer station  118  disposed on the polisher  108 . The cleaner  106  is typically disposed in or adjacent to the factory interface  104  and is adapted to clean and dry substrates returning from the polisher  108  before being returned to the substrate storage cassettes  112  by the interface robot  110 . 
     The polisher  108  includes at least one polishing station  126  and a transfer device  120  disposed on a base  140 . In the embodiment depicted in  FIG. 1 , the polisher  108  includes three polishing stations  126 , each having a platen  130  that supports a polishing material  128  on which the substrate is processed. 
     The transfer device  120  supports at least one polishing head  124  that retains the substrate during processing. In the embodiment depicted in  FIG. 1 , the transfer device  120  is a carousel supporting one polishing head  124  on each of four arms  122 . One arm  122  of the transfer devices is cutaway to show the second transfer station  118 . The transfer device  120  facilitates moving substrates retained in each polishing head  124  between the second transfer station  118  and the polishing stations  126  where substrates are processed. The polishing head  124  is configured to retain a substrate while polishing. The polishing head  124  is coupled to a transport mechanism that is configured to move the substrate retained in the polishing head  124  between the transfer station  118  and the polishing stations  126 . One polishing head that may be adapted to benefit from the invention is a TITAN HEAD™ substrate carrier, available from Applied Materials, Inc. 
     The second transfer station  118  includes a load cup  142 , an input buffer  144 , an output buffer  146  and a transfer station robot  148 . The input buffer  144  accepts a substrate being transferred to the polisher  108  from the second robot  116 . The transfer station robot  148  transfers the substrate from the input buffer  144  to the load cup  142 . The load cup  142  transfers the substrate vertically to the polishing head  124 , which retains the substrate during processing. Polished substrates are transferred from the polishing head  124  to the load cup  142 , and then moved by the transfer station robot  148  to the output buffer  146 . From the output buffer  146 , polished substrates are transferred to the first transfer station  114  by the second robot  116  and then transferred through the cleaner  106 . One second transfer station that may be adapted to benefit from the invention is described in U.S. Pat. No. 6,156,124, issued Dec. 5, 2000 to Tobin, entitled, “Wafer Transfer Station for a Chemical Mechanical Polisher,” which is incorporated by reference in its entirety. 
     A polishing fluid delivery system  102  includes at least one polishing fluid supply  150  coupled to at least one polishing fluid delivery arm assembly  152 . Generally, each polishing station  126  is equipped with a respective delivery arm assembly  152  positioned proximate to a respective platen  130  to provide polishing fluid thereto during polishing. In the embodiment depicted in  FIG. 1 , the three polishing stations  126  each have one delivery arm assembly  152  associated therewith. 
     The platen  130  of each polishing station  126  supports a polishing material  128 . During processing, the substrate is held against the polishing material  128  by the polishing head  124  in the presence of polishing fluid provided by the delivery system  102 . The platen  130  rotates to provide at least a portion of the polishing motion imparted between the substrate and the polishing material  128 . Alternatively, the polishing motion may be imparted by moving at least one of the polishing head  124  or polishing material  128  in a linear, orbital, random, rotary or other motion. 
     The polishing material  128  may be comprised of a foamed polymer, such as polyurethane, a conductive material, a fixed abrasive material or combinations thereof. Fixed abrasive material generally includes a plurality of abrasive elements disposed on a flexible backing. In one embodiment, the abrasive elements are comprised of geometric shapes formed from abrasive particles suspended in a polymer binder. The polishing material  128  may be in either pad or web form. 
     A conditioning mechanism  134  is disposed proximate each polishing station  126  and is adapted to dress or condition the polishing material  128  disposed on each platen  130 . Each conditioning mechanism  134  is adapted to move between a position clear of the polishing material  128  and platen  130  as shown in  FIG. 1 , and a conditioning position over the polishing material  128 . In the conditioning position, the conditioning mechanism  134  is actuated to engage the polishing material  128  and works the surface of the polishing material  128  to a state that produces desirable polishing results. In the position clear of the polishing material  128  and the platen  130 , the conditioning mechanism  134  is positioned to engage with the rinse station  135 . 
       FIG. 2  is a sectional view of one embodiment of the conditioning mechanism  134  engaged within the rinse station  135 . The conditioning mechanism  134  generally includes a head assembly  202  coupled to a support member  204  by an arm  206 . The support member  204  is disposed through the base  140  of the polisher  108 . Bearings  212  are provided between the base  140  and the support member  204  to facilitate rotation of the support member  204 . An actuator  210  is coupled between the base  140  and the support member  204  to control the rotational orientation of the support member  204 . The actuator  210 , such as a pneumatic cylinder, servo motor, motorized ball screw, harmonic drive or other motion control device that is adapted to control the rotational orientation of the support member  204 , allows the arm  206  extending from to the support member  204  to be rotated about the support member  204 , thus laterally positioning the head assembly  202  relative to the polishing station  126 . A conditioning element  208  is coupled to the bottom of the head assembly  202  and may be selectively pressed against the platen  130  to condition the polishing material  128 . 
     The elevation of the conditioning element  208  is generally controlled by pressurizing an expandable cavity  290  partially bounded by a diaphragm  240  disposed in head assembly  202 . A spring  242  disposed in the head assembly  202  provides an upward bias that assists in the retraction of the conditioning element  208  when the cavity  290  behind the diaphragm  240  is vented or evacuated. Examples of conditioning mechanisms suitable for use with the present invention are described in U.S. patent application Ser. No. 10/411,752, filed Apr. 10, 2003 by Lischka, et al., entitled “Conditioner Mechanism for Chemical Mechanical Polishing,” and U.S. Pat. No. 6,572,446, issued Jun. 3, 2003 to Osterheld, et al., entitled “Chemical Mechanical Polishing Pad Conditioning Element with Discrete Points and Compliant Membrane,” each of which are hereby incorporated by reference. Although the conditioning head assembly  202  depicted in  FIG. 2  shows a rolling diaphragm  240  and a spring  242 , it is contemplated that conditioning head assemblies  202  utilizing other actuating mechanisms, such as full diaphragms, belts, springs, actuators, and the like, may be characterized in the rinse station  135 , as further discussed below. Moreover, it is contemplated that teachings disclosed herein may be utilized to characterize components in other processing equipment, for example, the diaphragms and/or bladders in the polishing head  124 , or other components subject to wear over its service life. 
     The support member  204  houses a drive shaft  214  that couples a motor  216 , disposed below the base  140 , to a pulley  218  disposed adjacent a first end  220  of the arm  206 . A belt  222  is disposed in the arm  206  and operably couples the pulley  218  and the head assembly  202 , thereby allowing the motor  216  to selectively rotate the conditioning element  208 . The belt  222  is contemplated as any member adapted to transfer rotational motion between the motor  216  and the head assembly  202 . 
     A control fluid conduit  224  from a fluid control system  226  is routed through the support member  204  and arm  206 , and is coupled to the head assembly  202 . The fluid control system  226  includes a gas supply and various control devices (i.e., valves, regulators, and the like) that facilitate the application and/or removal of fluid pressure to the cavity  290  of the head assembly  202 . In one embodiment, the fluid control system  226  provides air or nitrogen to control the elevation of the conditioning element  208  relative to the platen  130  (or base  140 ), and to control the pressure applied by the conditioning element  208  against the polishing material  128  during conditioning (e.g., down force of the conditioning head). 
     The conditioning element  208  is moved to the rinse station  135  when not in use. The rinse station  135  generally includes a body  230 , one or more sensors  250 , and a rinse nozzle  234 . In one embodiment, the body  230  is held in position above the base  140  by a support  238 . The body  230  may be coupled directly to the support  238 . Alternatively, the body  230  may be coupled to the support  238  through a mounting plate  232 . Having the body  230  raised above the base  140  facilitates drainage of fluids and removal of other debris as the conditioning element  208  is rinsed as described further below. 
     The one or more sensors  250  are provided to detect a metric of conditioner performance. Some metrics of conditioner performance that may be sensed include conditioner downforce, attributes of the conditioning surface, power transmission (such as for conditioner rotation), seal and diaphragm performance and rinse fluid flow, among others. In one embodiment, sensors  250  are configured to sense the position of the conditioning element  208  at multiple predefined positions of extension with respect to the head assembly  202 . The sensors  250  may be positioned anywhere suitable for detecting the position of the conditioning element  208  at the predefined locations. Alternatively, one or more of the sensors  250  may be located in a position remote from the rinse station  135 . For example, one or more sensors  250  may be positioned in or on the head assembly  202 , the arm  206 , the base  140 , or other location suitable for sensing the position of the conditioning element  208  with respect to the head assembly  202 . In the embodiment depicted in  FIG. 2 , at least one sensor  250  is coupled to the body  230 . 
     The rinse nozzle  234  provides a cleaning fluid from a fluid source  236  to rinse, or clean, the working surface of the conditioning element  208 . The nozzle  234  is positioned to effectively rinse the conditioning element  208  and/or other components of the head assembly  202 . In one embodiment, the rinse nozzle  234  is disposed to the mounting plate  232 . 
       FIGS. 3A and 3B  respectively depict side and top views of one embodiment of the rinse station  135 . The body  230  of the rinse station  135  includes an arm  302  and a bracket  306 . The arm  302  may be coupled to the mounting plate  232  in any suitable manner, for example, by a plurality of screws (not shown). The arm  302  includes a contoured inner edge  330  and a ledge  304 . The inner edge  330  is contoured to allow clearance of the conditioning element  208  when engaged with the rinse station  135  (as depicted in  FIG. 2 ). The ledge  304  provides a hard stop for the conditioning element  208  when lowered into the rinse station  135 . Thus, when the conditioning element  208  is positioned in the rinse station  135 , the conditioning element  208  is disposed proximate the inner edge  330  of the arm  302  and may contact the ledge  304  when lowered. The ledge  304  is typically contoured to allow the conditioning element  208  to be rinsed by the rinse arm  234  (i.e., the ledge  304  is cut away to expose substantially all of the bottom of the conditioning element  208 . 
     Optionally, one of the sensors  250  for characterizing conditioner performance may be a sensor  390  disposed in the ledge  304  suitable for detecting a metric of conditioning downforce. Thus, as the conditioning element  208  is actuated against the ledge  304 , the sensor  390  may provide the controller with a metric indicative of downforce which may be compared with an expected value or a process window. If the sensed downforce is outside of the process window and/or a value different than an expedited value, the controller may flag the event, notify the operator or interrupt processing operations. The data provided by the sensor  390  may also be used to trend performance to predict or monitor service life. Moreover, the downforce sensor  390  will allow the detection of seal and/or diaphragm leaks, pressure supply draft and the like by providing data that enables the detection of force changes over time. 
     Optionally, instead of providing characterizing information directly to the controller  160 , a dedicated PLC  292  or other computing device may monitor the sensors  250 . The PLC  292  may have an output coupled to the controller  160  to flag potential conditioner performance issues that have been identified as triggers for the controller to halt and/or alter conditioning and/or substrate process. 
     Also depicted in the embodiment of  FIG. 2  are one or more sensors  250  that include a first sensor  312  disposed on the inner edge  330  of the arm  302 , and a second sensor  316  is coupled to a bottom surface of the arm  302 . The sensors  250  may comprise any suitable sensor for detecting the position of the conditioning element  208 . In one embodiment, the first sensor  312  is a break-through sensor configured to transmit and receive a beam of light (as indicated by dashed line  314 ) for sensing when an interposing object (i.e., the conditioning element  208 ) is positioned therebetween. 
     In one embodiment, the second sensor  316  is a proximity sensor positioned beneath a portion  318  of the ledge  304 . The proximity sensor, or second sensor  316 , detects when the conditioning element  208  is disposed within a predefined distance from or on the portion  318  of the ledge  304 . 
     The sensors  312 ,  316  are generally coupled to the PLC  292  or other device suitable for recording the data obtained by the sensors such as a strip chart recorder or memory module. By detecting the position of the conditioning element  208  at various locations in the rinse station  135 , a plurality of characterizations of the conditioning mechanism  134  may be advantageously performed, as described in more detail below. 
     The bracket  306  is adjustably coupled to the arm  302  in any suitable manner, for example, by a screw or bolt (not shown) disposed through an elongated slot  310 . The adjustment of the bracket  306  allows alignment of a support ledge  308  formed in the bracket  306  with the ledge  304  of the arm  302 , thereby providing an extended support area for the conditioning element  208  of the head assembly  202  when positioned in the rinse station  135 . The extended support area prevents uneven forces from being applied to the components of the head assembly  202  when the conditioning element  208  is lowered and pressed against the ledge  304 . 
     In another embodiment, the sensor  390  may be configured to provide a metric indicative of a surface condition of the conditioning element  208 . For example, the sensor  390  may be a roughness sensor for monitoring the surface condition of the conditioning element. In another example, the sensor  390  may be a camera for visually monitoring the surface condition of the conditioning element  208 . It is contemplated that images from the surface of the conditioning element  208  may be electronically analyzed to determine the state of the condition, such as missing diamond or abrasives, and the like. It is also contemplated that the sensor  390  may be configured to provide a metric indicative of the cut rate the conditioning element  208 . 
     The rinse nozzle  234  is positioned to supply a stream of rinsing and/or cleaning fluid to the bottom surface of the conditioning element  208  and/or head assembly  202 . In one embodiment, the rinse nozzle  234  is coupled to the mounting plate  232  in a suitable manner, such as by threaded engagement. The configuration and position of the nozzle  234  is selected to direct the flow of fluid to a desired location on the conditioning element  208  when the head assembly  202  is disposed in the rinse station  135 . The nozzle  234  is coupled to the fluid source  236 . It is contemplated that the rinse nozzle  234  may alternatively be coupled to different components of the polishing system  100 , such as the base  140 , so long as it is disposed in a position suitable for delivering a stream of rinsing and/or cleaning fluid to the conditioning element  208  and/or head assembly  202 . 
     Optionally, additional nozzles may be formed in the member  320  or other location in the rinse station  135  and coupled to the fluid source  236 . For example, in the embodiment depicted in  FIGS. 3A and 3B , a second nozzle  324  is formed in the mounting plate  232  and is positioned to spray rinsing and/or cleaning fluid along the periphery of the conditioning element  208  and/or the head assembly  202 . 
     In one embodiment, one of the sensors  250  for characterizing the conditioner may be positioned to detect the flow of cleaning fluid into the rinse station  135 . For example, in the embodiment depicted in  FIG. 3B , a sensor  322 , such as a flow sensor, may be interfaced with the conduits providing fluid to the nozzle  234  and configured to provide a metric of flow in the rinse station  135 , thereby providing the PLC  292  an indication whether the conditioning element  208  is being rinsed as expected. 
     In yet another embodiment, one of the sensors  250  for characterizing the conditioner may be positioned to detect the rotational motion of the conditioning element. For example, in the embodiment depicted in  FIG. 2B , a sensor  252 , such as a rotary sensor, may be interfaced with the belt  222  and/or head assembly  202  or other component and configured to provide a metric indicative of the rotation of the conditioning element  208 , thereby providing the PLC  292  an indication that the conditioning element  208  rotating in a predetermined manner. 
     In operation, the conditioning mechanism  134  is rotated to place the head assembly  202  and conditioning element  208  above the rinse station  135 . A cleaning fluid may be supplied from the nozzles  322  and  324  to remove any debris disposed on the surface of the conditioning element  208  and/or head assembly  202  (for example, polishing slurries, particulate matter, and the like). 
     The conditioning element  208  may further be lowered into contact with the ledges  304 ,  308  of the rinse station  135  via pressurization of the cavity  290  (depicted in  FIG. 2 ). As the conditioning element  208  is lowered, the PLC  292  records data corresponding to when the first sensor  312  detects the position of the conditioning element  208  (e.g., when the beam  314  is broken). The PLC  292  further records data corresponding to when the conditioning element  208  contacts the ledge  304 , as detected by the second sensor  316 . 
     By comparing the data recorded when the conditioning element  208  passes the first sensor  312  and the second sensor  316 , a time to move the conditioning element  208  downwards between a known distance (i.e., between the sensors  312 ,  316 ) may be obtained. The time may be compared to a predefined amount of time or the time may be charted over a period of multiple cycles to monitor trends in the time to actuate the conditioning element  208  downwards. 
     Characterization of the conditioning elements movement relative the rinse station  135  may also be obtained by utilizing one or more parameters such as time between commencing the heat movement conditioning elements (i.e., the pressurization of the cavity  290 ), cavity pressure and/or rate of change at different elevations and the like. Additionally, the bottom surface of the conditioner may be monitored for cleanliness, damage and/or for wear. Furthermore, operational aspects of the conditioner, such as downforce, rotational speed, cut rate and cleanliness, which may be compared to a process window so that the conditioner may be recleaned or surface prior to conditioning the polishing surface, thereby preventing process abnormalities. 
     For example,  FIG. 4A  depicts a method  400  for monitoring a conditioning mechanism, described with reference to the apparatus depicted in FIGS.  2  and  3 A-B. The method  400  begins at step  402 , where the conditioning element  208  is lowered into the rinse station  135  by pressurizing the cavity  290 . The method continues at step  404 , where the time required to lower the conditioning element  208  into within a predetermined distance of the ledge  304  is recorded. The recorded time may be the time between commencement of cavity pressurization and sensor trigger. 
     In one embodiment, step  404  includes substep  406 , where a timer begins counting when the first sensor  312  senses the conditioning element  208  (e.g., when the conditioning element  208  breaks the beam of light  314  between the emitter and receiver pair of the first sensor  312 ). At substep  408 , the timer stops counting when the second sensor  316  detects the conditioning element  208  on the ledge  304 . Alternatively, a start time may be recorded in step  406  and a stop time recorded in step  408 , with the time required to lower the conditioning element  208  calculated by subtracting the start time from the stop time. 
     In other embodiments, the sensors  312 ,  316  may detect alternate positions of the conditioning element  208 . For example, the sensors  312 ,  316  or the method may be configured to record the time required to raise the head assembly  202 . Alternatively or in addition, the sensor  252  may be utilized to detect the rotation of the conditioning element  208 . By recording a time required to raise, lower, or rotate the conditioning element  208 , the condition of the diaphragm, springs, or other components of the head assembly  202  of the conditioning mechanism  134  may be monitored. 
     In another example,  FIG. 4B  depicts a method  410  for monitoring a conditioning mechanism, described with reference to the apparatus depicted in FIGS.  2  and  3 A-B. The method  410  begins at step  412 , when the time required to lower the conditioning element  208  is stored, for example, in a database. Next, at step  414 , the time required to lower the conditioning element  208  is analyzed. The time required to lower the conditioning element  208  may be analyzed in many different ways. For example, at substep  416 , the time required to lower the head assembly may be charted over a plurality of cycles in order to determine or monitor trends in the variation of the time required to lower the conditioning element  208 . Alternatively or in combination, substep  418  may be utilized to compare the time required to lower the conditioning element  208  to a preselected threshold value. 
     Next, at step  420 , a course of action is decided upon based on the analysis of step  414 . For example, at step  422 , a decision may be made to repair or replace the diaphragm  240  of the head assembly  202 . Alternatively, the analysis may indicate that the diaphragm  240  is still in acceptable condition and may be continued to be used, as depicted in substep  424 . The decision made in step  420  may be made in a variety of ways. 
     For example, in embodiments where the time required to lower the conditioning element  208  is charted over a plurality of cycles, as in substep  416 , the decision may be made based upon changes in the slope of the charted curve, which may indicate a more rapid deterioration in the condition of the diaphragm  240 . Alternatively, before substep  418  is used, a preselected threshold value may be utilized in comparison to the time required to lower the conditioning element  208 , such that if the time required to lower the conditioning element  208  exceeds the threshold value, it is indicative of the deterioration of the diaphragm  240  to the point where its replacement is required. 
     It is contemplated that step  412  and substep  416  of the method  410  may be omitted. For example, the method  410  may comprise merely comparing the time required to lower the conditioning element  208  to a preselected threshold value, as in substep  418 , without the need for reference to previous values and thus, the need to store the time required to lower the conditioning element  208 , or to chart the time over a plurality of cycles. 
       FIG. 4C  is a flow diagram of another method  440  for monitoring a conditioning mechanism. The method  440  begins at step  442  by detecting a metric indicative of a characteristic of the conditioning mechanism  134 . The metric may be provided to the controller  160  and/or PLC  292  tasked with monitoring conditioner function and/or performance from one or more of the sensors as described above. At step  444 , the metric and/or information derived from the sensor is analyzed. The analysis may include determining if the characteristic is within a processing window, determining if maintenance is required, determining a wear rate of a component, determining an arrival of a need for maintenance based an a wear rate, determining if the conditioning element  208  needs replacement, determining if power transmission parts (e.g., belts, bearing, etc.) need service, should be re-cleaned determining if the conditioning element  208  should be re-cleaned, determining if the cleaning of the conditioning element is operating within specification, and determining if conditioning operations need to be suspended or modified. It is contemplated that many other performance/conditioner health indicators may be monitored. At step  446 , if the analysis indicates that the sensed metric is out of specification or outside a process window, corrective action is taken at step  448 . Examples of corrective action include flagging a need for maintenance and/or component replacement, adjusting downforce pressure, adjusting rotational speed, adjusting a pad conditioning routine for a change in conditioner cut-rate, unclogging a fluid line, re-cleaning the conditioning element, predicting a need for future maintenance, and flagging potential conditioning abnormalities, among others. If, at step  446 , the analysis indicates that performance is within specification, then the method returns to step  442  to continuing to monitoring the conditioning mechanism  134 . 
       FIG. 5  depicts a graph of sensor timings showing additional variables that may be monitored, recorded, charted, and the like to further characterize critical components of the conditioning mechanism  134 .  FIG. 5  depicts the digital states, i.e., “on” or “off,” (along an axis  502 ) over time (along an axis  504 ) for the first sensor (line  506 ), second sensor (line  508 ), and the pressure command (line  510 ). 
     The pressure command is the instruction to pressurize or exhaust the diaphragm  240  to raise or lower the conditioning element  208 . The graph arbitrarily starts with the conditioning element  208  lowered and disposed against the ledge  304 . At time  520 , the state of the pressure command is switched from off to on, correlating with a command to raise the conditioning element  208 . At time  522 , the state of the second sensor  316  changes from on to off, indicating that the conditioning element  208  has begun to rise and is no longer on the ledge  304 . At time  524 , the state of the first sensor  312  changes from off to on, indicating that the conditioning element  208  has passed the first sensor  312 . 
     The time period between the change in state of the pressure command and the change in state of the second sensor  316  is labeled T 1 . T 1  is indicative of the amount of time it takes between the issuance of the command to raise the conditioning element  208  and the lift off of the conditioning element  208  from the ledge  304 . The time period between the change in state of the pressure command and the change in state of the first sensor  312  is labeled T 2 . T 2  is indicative of the amount of time it takes between the issuance of the command to raise the conditioning element  208  and the arrival of the conditioning element  208  at an upper position proximate the first sensor  312 . The time difference between T 2  and T 1  is indicative of the amount of time actually required for the conditioning element  208  to travel between the lower position on the ledge  304  and the upper position proximate the first sensor  312 . 
     At time  526 , the state of the pressure command is switched from on to off, correlating with a command to lower the conditioning element  208 . At time  528 , the state of the first sensor  312  changes from on to off, indicating that the conditioning element  208  has begun to descend and is no longer proximate the first sensor  312 . At time  530 , the state of the second sensor  316  changes from off to on, indicating that the conditioning element  208  has contacted the ledge  304 . 
     The time period between the change in state of the pressure command and the change in state of the first sensor  312  is labeled T 3 . T 3  is indicative of the amount of time it takes between the issuance of the command to lower the conditioning element  208  and the descent of the conditioning element  208  from the position proximate the first sensor  312 . The time period between the change in state of the pressure command and the change in state of the second sensor  316  is labeled T 4 . T 4  is indicative of the amount of time it takes between the issuance of the command to lower the conditioning element  208  and the arrival of the conditioning element  208  on the ledge  304 . The time difference between T 4  and T 3  is indicative of the amount of time actually required for the conditioning element  208  to travel between the upper position proximate the first sensor  312  and the lower position on the ledge  304 . 
     Any one or a combination of these time periods may be monitored and/or charted over time as described above with respect to  FIGS. 4A and 4B  in order to determine whether the diaphragm  240  requires repair or replacement. Alternatively, other motions may be monitored, such as the rotation of the head assembly  202 , in order to characterize the condition of the desired critical components. 
     Thus, methods and apparatus for monitoring a conditioning mechanism are provided. In one embodiment a smart rinse station is provided to clean the conditioning mechanism when not in use and to characterize critical components of the conditioning mechanism, such as a diaphragm, springs, and the like. The conditioning mechanism may be characterized over time to detect trends or in comparison to preselected threshold values in order to detect deterioration in the performance of the conditioning mechanism and to prevent poor conditioning. Although the above apparatus and methods are described with respect to a conditioning mechanism, it is contemplated that the above teachings may be modified for use in monitoring and characterizing critical components in other systems as well. 
     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.