Abstract: A polishing apparatus comprises a polishing tool, a substrate holding member, and a sensor for detecting a failure of a substrate to be polished.

Abstract: For use with a chemical mechanical polishing apparatus for polishing a semiconductor wafer having a platen, a polishing pad and a wafer carrier, an optical closed-loop control system. In one embodiment, the system includes a plurality of optical probes impacting a corresponding probe window and rigidly mountable through the platen. The system also includes a flash lamp configured to provide light to each of the plurality of optical probes and minimize an exposure time of the light onto the semiconductor wafer, a spectrograph configured to spatially image light received by each of the plurality of optical probes to a common charge-coupled device and produce real-time spectral reflectometry data therefrom. The system further includes a control subsystem configured to analyze the real-time spectral reflectometry data and determine at least one wafer state parameter therefrom, and cause the polishing to be adjusted based upon the at least one wafer state parameter.

Abstract: A method of in situ control for finishing semiconductor wafers to improve cost of ownership is discussed. A method to use business calculations combined with physical measurements to improve control is discussed. The use of lubricating layer control in the operative finishing interface is discussed. Use of business calculations to change the cost of finishing semiconductor wafers is discussed. The method aids control of differential lubricating films and improved differential finishing of semiconductor wafers. The method aids cost of manufacture forecasting. The method can help manage and/or reduce cost of manufacture for pre-ramp-up, ramp-up, and commercial manufacture of the workpieces. The method can aid cost of manufacture forecasting for pre-ramp-up, ramp-up, and commercial manufacture of the workpieces. The method can aid process control for pre-ramp-up, ramp-up, and commercial manufacture of workpieces. Activity based accounting can be preferred for some applications.

Abstract: Planarizing machines, planarizing pads, and methods for planarizing or endpointing mechanical and/or chemical-mechanical planarization of microelectronic substrates. One particular embodiment is a planarizing machine that controls the movement of a planarizing pad along a pad travel path to provide optical analysis of a substrate assembly during a planarizing cycle. The planarizing machine can include a table having an optical opening at an illumination site in a planarizing zone and a light source aligned with the illumination site to direct a light beam through the optical opening in the table. The planarizing machine can further include a planarizing pad and a pad advancing mechanism. The planarizing pad has a planarizing medium and at least one optically transmissive window along the pad travel path. The pad advancing mechanism has an actuator system coupled to the pad and a position monitor coupled to the actuator system.

Abstract: A polishing apparatus is used for polishing a substrate such as a semiconductor wafer, and has a sensor capable of continuously detecting the thickness of an electrically conductive layer. The polishing apparatus includes a polishing table having a polishing surface, and a top ring for holding and pressing the substrate against the polishing surface to polish the surface of the substrate. A sensor such as an eddy-current sensor is disposed below the polishing surface of the polishing table for measuring the thickness of a conductive layer formed on the surface of the substrate.

Abstract: A grinding wheel system includes a grinding wheel with at least one embedded sensor. The system also includes an adapter disk containing electronics that process signals produced by each embedded sensor and that transmits sensor information to a data processing platform for further processing of the transmitted information.

Abstract: A lens grinding processing apparatus of the present invention has lens rotating shafts 23 and 24 for holding an eyeglass lens ML, a lens retaining members (300, 320) fixed respectively to opposed end sections of the lens rotating shafts 23 and 24 capable of slanting adjustably, a drilling device (drilling processing device 200) for drilling a hole for a point frame into the slanted eyeglass lens ML, and a grinding stone (grinding stone 35, chamfering stones 224, 225) for grinding and processing a circumferential part of the eyeglass lens ML.

Abstract: A workpiece W and a grinding wheel G are relatively moved in Z and X-axis directions perpendicular to each other, the rotational axis of the grinding wheel is inclined relative to the X-axis, and the grinding wheel is composed of a taper section Ga having a generating line parallel to the Z-axis and a spherical section Gb connecting with the generating line at the maximum diameter portion of the taper section Ga. While performing a cam profile generating motion, the grinding wheel is controlled to perform a plunge grinding feed toward the workpiece in the X-axis direction to effect a plunge grinding on the cam of the workpiece and then, while performing the cam profile generating motion, is controlled to perform a traverse grinding feed in the Z-axis direction to effect a traverse grinding on the cam.

Abstract: A CMP system accurately measures eccentric forces applied to carriers for wafer or polishing pad conditioning pucks. An initial coaxial relationship between wafer axis of rotation and a carrier axis is maintained during application of the eccentric force, such that a sensor may measure the eccentric forces. Such initial coaxial relationship is maintained by a linear bearing assembly mounted between the carrier and the sensor. The linear bearing assembly is provided as an array of separate linear bearing assemblies, and may be assembled with a retainer ring in conjunction with a motor for moving the ring relative to the wafer mounted on the carrier so that an exposed surface of the wafer and a surface of the retainer ring to be engaged by the polishing pad are coplanar during the polishing operation.

Abstract: A balancing method and apparatus is used for dynamically balancing an out of balance condition in a rotating body caused by resistance forces acting tangentially to the body. A device having a rotatable component and automatic or dynamic balancing includes a housing, a shaft rotatably mounted in the housing, the shaft supporting the component near one end of the shaft, at least one counterweight fixedly mounted on the shaft and at least one automatically adjusting balancer mounted on the shaft. The automatically adjusting balancer includes one or more compensating masses contained to move about a path relative to the shaft to compensate for variable imbalanced forces acting on the component.

Abstract: Methods and apparatuses for analyzing and controlling performance parameters in planarization of microelectronic substrates. In one embodiment, a planarizing machine for mechanical or chemical-mechanical planarization includes a table, a planarizing pad on the table, a carrier assembly, and an array of force sensors embedded in at least one of the planarizing pad, a sub-pad under the planarizing pad, or the table. The force sensor array can include shear and/or normal force sensors, and can be configured in a grid pattern, concentric pattern, radial pattern, or a combination thereof.

Abstract: Planarizing machines for accurately planarizing microelectronic workpieces. Several embodiments of the planarizing machines produce a planar surface at a desired endpoint in the microelectronic workpieces by (a) quickly reducing variances on the surface of the workpiece using a planarizing medium that removes topographical features but has a low polishing rate on planar surfaces; and (b) subsequently planarizing the wafer on a planarizing medium that has a higher polishing rate on planar surfaces than the first polishing medium.

Abstract: A chemical mechanical polishing apparatus and method can use an eddy current monitoring system and an optical monitoring system. Signals from the monitoring systems can be combined on an output line and extracted by a computer. A thickness of a polishing pad can be calculated. The eddy current monitoring system and optical monitoring system can measure substantially the same location on the substrate.

Abstract: A retaining ring for chemical mechanical polishing (CMP) apparatus comprising a body of the retaining ring, and a single trigger cavity, or a plurality of trigger cavities. Each trigger cavity formed inside the body of the retaining ring is filed with gas or fluid, and is configured to indicate that thickness of the retaining ring is less than or equal to a predetermined thickness threshold.

Abstract: The invention is directed to chemical-mechanical polishing pads comprising a transparent window. In one embodiment, the transparent window comprises an inorganic material and an organic material, wherein the inorganic material comprises about 20 wt. % or more of the transparent window. In another embodiment, the transparent window comprises an inorganic material and an organic material, wherein the inorganic material is dispersed throughout the organic material and has a dimension of about 5 to 1000 nm, and wherein the transparent window has a total light transmittance of about 30% or more at at least one wavelength in the range of about 200 to 10,000 nm. In yet another embodiment, the transparent window comprises an inorganic/organic hybrid sol-gel material. In an additional embodiment, the transparent window comprises a polymer resin and a clarifying material, wherein the transparent window has a total light transmittance that is substantially higher than a window comprising only the polymeric resin.

Abstract: In a system and a method according to the present invention, a sensor signal, such as a motor current signal, from a drive assembly of a pad conditioning system is used to control a CMP system to compensate for a change in the conditions of consumables, thereby enhancing process stability.

Abstract: A polishing apparatus for polishing a substrate comprises a polishing table having a polishing surface, and a substrate holding apparatus for holding a substrate to be polished and pressing the substrate against the polishing surface. The substrate holding apparatus comprises a vertically movable top ring body for holding a substrate, and a fluid supply source for supplying a fluid under a positive pressure or a negative pressure to a hermetically sealed chamber which is defined in the top ring body so as to control pressure under which the substrate is pressed against the polishing surface. The substrate holding apparatus further comprises a measuring device disposed in a fluid passage interconnecting the hermetically sealed chamber and the fluid supply source for measuring a flow rate of the fluid in the fluid passage.

Abstract: A magnetorheological fluid delivery system includes a mixing and tempering vessel. Fluid is admitted to the vessel via a plurality of tangential ports, creating a mixing of the fluid in the vessel and promoting homogeneity. Fluid may be reconstituted in the vessel by metered addition of carrier fluid. A fixed-speed centrifugal pump disposed in the vessel pressurizes the system. Fluid is pumped through a magnetic-induction flowmeter and a magnetic flow control valve having solenoid windings whereby MR fluid is magnetically stiffened to restrict flow. A closed-loop feedback control system connects the output of the flowmeter to performance of the valve. A nozzle having a slot-shaped bore dispenses MR fluid for re-use in the work zone.

Abstract: An apparatus (10) for checking the diameter of an eccentric pin (8?) of a small-size shaft (8), for example a shaft for compressors, includes a support (16), a first arm (19) rotating with respect to the support (16), a second arm (22) rotating with respect to the first, a Vee-shaped reference device (28) carried by the second arm, a measuring device (25,26,24,37,38) associated with the reference device, limiting devices (29,29?,30,30?) for limiting the rotations of the arms and thrust means (33) for keeping the reference device in contact with the pin in the course of the checking. A hydraulic actuator (13) displaces the apparatus (10) from a rest condition to a checking condition, in which the reference device (28) is in contact with the pin (8?) to be checked, and vice versa.

Abstract: A method and apparatus for comparing the flow rate through an orifice within a master part with the orifice within a workpiece by subjecting each orifice to an identical fluid at an identical temperature, under an identical pressure, and comparing the downstream pressures of the fluid exiting these orifices when the upstream pressure is constant or comparing the upstream pressure when the downstream pressure is constant. For purely measurement purposes, the fluid may be a non-abrasive media, however, in the event the workpiece orifice must be machined, it is possible to introduce a flowable abrasive media, and pass this media through the orifices until the desired pressure difference is achieved. With additional flow characteristics of the master part, it is also possible to calculate the flow rate through the workpiece orifice using only the pressure differential at the exits of the workpiece and the master part.

Abstract: A flatness of a substrate is determined to achieve a desired flatness of a mask blank by predicting the variation in flatness resulting from a film stress of a thin film formed on the substrate. The flatness is adjusted by measuring the flatness of the substrate as a measured flatness, selecting a load type with reference to the measured flatness, and polishing the substrate under pressure distribution specified by the load type. A principal surface of the substrate has a flatness greater than 0 ?m and not greater than 0.25 ?m. A polishing apparatus includes a rotatable surface table, a polishing pad formed thereon, abrasive supplying means for supplying an abrasive to the polishing pad, substrate holding means, and substrate pressing means for pressing the substrate. The substrate pressing means has a plurality of pressing members for individually and desirably pressing a plurality of divided regions of the substrate surface.

Abstract: A fabricating system. A processing tool executes a film removal process on a wafer using a chemical mechanism. A metrology tool monitors surface characteristics of the wafer to obtain a measured film thickness thereof before and after a first removal process, wherein the first removal process lasts a first processing duration. The controller, coupled to the processing and metrology tools, determines whether the difference between the measured film thickness and a preset film thickness exceeds a preset value, and determines a second processing duration of a second removal process according to the measured and preset film thickness and the first processing duration.

Abstract: A speed adjuster is provided in a belt-disc sander for controlling the rotating speed of a motor of the belt-disc sander. A speed adjust knob is disposed outside the belt-disc sander. The speed adjuster has a control circuit, a current sensor, a drive circuit, and a converter. The current sensor detects the motor current and feeds back to the control circuit, which controls the frequency variation of a SPWM signal of the drive circuit in response to the input of the speed adjust knob. The converter transforms the square wave voltage into an AC voltage for driving the motor. The desired rotating speed can be adjusted through the speed adjust knob. The control circuit will compare the present rotating speed of the motor with the set rotating speed to determine whether the present rotating speed conforms to the set one for correcting the rotating speed of the motor.

Abstract: A lens shape data processing apparatus and a lens grinding machine having the same apparatus in which the lens shape data reading out and the layout setting work for another spectacle lens can be conducted during the lens edge measurement or the grinding process is provided.

Abstract: A saw cutting pattern is dynamically established for a semiconductor dicing saw based on detection of the saw blade contacting a wafer or a portion of a wafer. The dynamic cutting pattern may terminate cuts if the saw blade no longer contacts the wafer or a portion of a wafer. Thus, irregular shaped wafers may be cut without requiring that an entire predefined cutting pattern be carried out and/or without previously mapping the shape of the wafer or portion of a wafer. A map of the wafer or a portion of a wafer may also be generated based on the detection of the saw blade contacting the wafer during a first cutting pass and may be used during a second cutting pass.

Abstract: A chemical mechanical polishing (CMP) apparatus and method for polishing semiconductor wafers utilizes multiple wafer carriers that are transferred to different positions about a polishing pad to polish at least one semiconductor wafer while another semiconductor wafer is being loaded onto or unloaded from one of the wafer carriers. The different positions include multiple polishing positions and one or more loading/unloading positions. In some embodiments, the CMP apparatus is configured such that a semiconductor wafer is polished at a loading/unloading position. The CMP apparatus may also be configured to continuously polish one or more semiconductor wafers while the wafer carriers are being transferred to different positions. Thus, the CMP apparatus can continuously process the semiconductor wafers without significant idle periods. Consequently, in these embodiments, the efficiency of the CMP apparatus is significantly increased.

Abstract: A sensing apparatus for detecting a processing endpoint of a multi-layer semiconductor wafer includes a light source to emit light against a surface of the semiconductor wafer, a color sensor to sense a reflection color from the surface of the semiconductor wafer in response to the incident light and to generate a sensor signal, and a decision circuit coupled to the color sensor and configured to decide whether the wafer processing endpoint has been reached based at least in part on the sensor signal. In another embodiment, a sensing apparatus is coupled to a movable structure to position the sensing apparatus to sense the surface of the semiconductor wafer.

Abstract: Improperly mounted wafer saw blades can damage wafers cut or diced with the blades. Embodiments of this invention employ sensors to measure a distance to the blade to help indicate if the blade is improperly mounted. In one method of the invention, a the distance to the blade face is measured as the blade is rotated and a variance in this measured distance is determined. If the variance is no greater than a predetermined maximum, the blade may be used to cut the wafer. In one apparatus of the invention, a wafer saw include a blade and a sensor. The sensor is adapted to monitor a distance to a face of the rotating blade. A processor coupled to the sensor may indicate if the distance to the face of the blade as it rotates deviates too far from a baseline position of the blade face.

Abstract: A method of predicting the lapping property of a charged lapping plate uses samples with a known lap surface. The samples are lapped on the plate and a non-invasive sensor is used to determine the lapping rate under a fixed load and rotation speed. The total frictional force of the samples is measured during the lapping to calculate the friction and Preston coefficients of the plate. The samples are held in place while the plate rotates and the sensor measures the distance to the plate. The plate rotates for a specific time so that adequate removal of the pad material has occurred. The lapping rate is determined from a change in the gap distance over a time interval. The lapping rate and friction are then assessed to determine if the plate is lapping worthy.

Abstract: An apparatus and method are provided for detecting wear in substrate retainers used for chemical mechanical planarization processes. A substrate retainer is provided that is adapted to enable a sensor to detect when the wear edge of the retainer has worn to a critical wear threshold so that the retainer may be replaced prior to failure.

Abstract: A computer-implemented method for process control in chemical mechanical polishing in which an initial pre-polishing thickness of a substrate is measured at a metrology station, a parameter of an endpoint algorithm is determined from the initial thickness of the substrate, a substrates is polished at a polishing station, and polishing stops when an endpoint criterion is detected using the endpoint algorithm.

Abstract: A reliable, inexpensive “back side” thinning process and apparatus therefor, capable of globally thinning an integrated circuit die to a target thickness of 10 microns, and maintaining a yield of at least 80%, for chip repair and/or failure analysis of the packaged die. The flip-chip packaged die is exposed at its backside and mounted on a lapping machine with the backside exposed. The thickness of the die is measured at at least five locations on the die. The lapping machine grinds the exposed surface of the die to a thickness somewhat greater than the target thickness. The exposed surface of the die is polished. The thickness of the die is again measured optically with high accuracy. Based on the thickness data collected, appropriate machine operating parameters for further grinding and polishing of the exposed surface are determined. Further grinding and polishing are performed. These steps are repeated until the target thickness is reached.

Abstract: A method and apparatus for pre-conditioning a polishing pad for use in chemical mechanical planarization of semiconductor wafers is described. The apparatus includes a pre-conditioning member having a smooth surface. The method includes providing a pre-conditioning member having a smooth surface, pressing the pre-conditioning member against the polishing pad while moving the polishing pad, and flattening the surface of the polishing pad until a polishing pad flatness is achieved that may be used to achieve a desired semiconductor wafer planarity.

Abstract: The grindstone is configured so that at least the surface of each abrasive grain is colored differently from the surface of a base.

Abstract: An in-situ technique for the acoustic emission monitoring of burnish heads while they are cleaning or burnishing magnetic media is described. The burnishing process is monitored and controlled to identify interaction or contact between the head and media due to, for example, burnish head damage, substrate curvature problems, and lube pick-up problems. A piezoelectric sensor is mounted on the burnish arm that holds the burnish heads. When head-disk interaction occurs, stress waves travel through the head to the sensor and an amplified signal is gathered in a tester database as an acoustic emission. Abnormal conditions will trigger an unusual emission that is detected to trigger an alert.

Abstract: A magnetoresistive read head has read head layers that are shaped to form an air bearing surface and a sensor stripe cavity with an open side at the air bearing surface. A sensor stripe is deposited in the sensor stripe cavity. The sensor stripe has a front surface that is set back from the air bearing surface to define an encapsulation cavity extending from the front surface to the air bearing surface. An encapsulation layer is deposited in the encapsulation cavity. The encapsulation layer encapsulates the front surface.

Abstract: Methods and systems for generating a two-dimensional map of a characteristic at relative or absolute locations of measurement spots on a specimen during polishing are provided. One method includes scanning a specimen with a measurement device during polishing to generate output signals at measurement spots on the specimen. The method may also include determining a characteristic of polishing at the measurement spots from the output signals. In addition, the method may include determining relative or absolute locations of the measurement spots on the specimen. The method may further include generating a two-dimensional map of the characteristic at the relative or absolute locations of the measurement spots on the specimen. In some embodiments, the relative locations of the measurement spots may be determined from a representative scan path of the measurement device and an average spacing between starting points on individual scans.

Abstract: When a forming a bevel on a lens, the value of the bevel curve is calculated based on the value of the curve of the concave face, a reference axis of the bevel curve is determined to be in the same direction as the curvature of the concave face, a reference position on the peripheral edge of the lens in the first portion having the minimum thickness is determined based on the thickness of the first portion, a correction for the initial reference axis of the bevel curve is obtained, an angle of inclination from the direction of the initial reference axis of the bevel curve is obtained based on the correction and the locus of the bevel is determined based on the value of the bevel curve, the reference position and the angle of inclination.

Abstract: A measuring apparatus includes a heating unit for applying heat to a first point within a workpiece or on a surface of a workpiece and propagating the heat to a second point within the workpiece or on the surface of the workpiece. The measuring apparatus further includes a measuring unit for measuring a displacement of the surface of the workpiece at the second point to which the heat has been propagated, and an analyzing unit for analyzing a structure of the workpiece based on the displacement measured by the measuring unit in consideration of a distance between the first point and the second point.

Abstract: In a wafer polishing apparatus which polishes a wafer surface or in a wafer cleaner, there are provided a transfer and cleaning chamber which shuts off a wafer from the outside air and an inert gas supply device which fills an inert gas into the transfer and cleaning chamber. Thus, there are provided a polishing apparatus, a cleaner, a cleaning method and a wafer evacuation program which can prevent the oxidation and modification of a wafer surface in each step, such as the polishing step of a wafer, the transfer step after polishing, the cleaning step after polishing, the drying step after polishing, the inspection step after polishing, and the storage step after polishing.

Abstract: A method of determining the endpoint of a planarizing process is disclosed. An endpoint detection signal is selectively sampled from at least one predetermined location within a planarizing region defined on a planarizing web. Planarization is stopped when the endpoint criterion based on the endpoint detection signal is detected.

Abstract: A method of determining the condition of a grinding wheel is provided to avoid over use or premature changing of the grinding wheel in a grinding machine, such as for crankshaft or camshaft grinding. The grinding machine has a motor which drives a grinding spindle carrying an abrasive coated hub acting as a grinding wheel. Sensors detect the level of grinding force and motor torque required to grind a workpiece into a desired shape. The information is relayed to a controller, which averages and compares the grinding force and torque information to force and torque limits to determine the condition of the wheel. In addition, the controller compares grinding force and motor torque over a series of grinds to determine the level of increase between grinds to further determine the condition of the grinding wheel. If the level of increase exceeds an increase limit, the controller actuates a fault signal to stop the grinding machine indicating that the wheel is near the end of its life cycle.

Abstract: Polishing pads, planarizing machines and methods for mechanical and/or chemical-mechanical planarization of microelectronic-device substrate assemblies. The polishing pads, for example, can be web-format pads, and the planarizing machines can be web-format machines. In a typical application, the web-format machines have a pad advancing mechanism and stationary table with a first dimension extending along a pad travel path, a second dimension transverse to the first dimension, and an illumination site from which a laser beam can emanate from the table. The pad advancing mechanism moves the pad along the pad travel path to replace worn portions of the pad with fresh portions. In one embodiment of the invention, a web-format polishing pad includes a planarizing medium and an optical pass-through system having a plurality of view sites through which a light beam can pass through the pad.

Abstract: The present invention relates to a polishing apparatus for polishing a workpiece such as a semiconductor wafer. The polishing apparatus has a processing section including a polishing section (1) for polishing a semiconductor wafer (6) and a cleaning section (10) for cleaning a polished semiconductor wafer, a receiving section (40) for supplying a semiconductor wafer (6) to be polished to the processing section and receiving a polished semiconductor wafer (6), and a cleaning chamber (20) disposed between the processing section and the receiving section and defined by partitions (102, 103) with shutters (22, 24) which separate the processing section and the receiving section from each other.

Abstract: A system and method of measuring a metallic layer on a substrate within a multi-step substrate process includes modifying a metallic layer on the substrate such as forming a metallic layer or removing at least a portion of the metallic layer. At least one sensor is positioned a predetermined distance from the surface of the substrate. The surface of the substrate is mapped to determine a uniformity of the metallic layer on the surface of the substrate.

Abstract: The present invention relates to methods and apparatus that allow for chemical mechanical polishing using a flexible pad and variable fluid flow for variable polishing.

Abstract: A fixture includes a fixing member attached to a grinding machine (10), a guiding shaft (37) attached to the fixing member and a clamp (38). The clamp defines a pair of holes (381, 382) in opposite ends thereof, for movably receiving the guiding shaft and an indicator (20) therein respectively. When the shaft and indicator are loosened from the holes of the clamp respectively, the clamp is rotated about the guiding shaft toward a workpiece (19) on the grinding machine, and the indicator is adjusted with respect to the workpiece, for measuring of the workpiece.

Abstract: An apparatus and method for chemical mechanical polishing are disclosed. An example apparatus for use with a chemical mechanical polishing (CMP) process includes a polishing part configured to perform a CMP process to a polishing endpoint for a polishing target deposited on a substrate, a cleaning part configured to clean the substrate, and a resistance measurement part configured to measure a sheet resistance of the substrate. The example apparatus also includes a CMP control part configured to determine based on the sheet resistance whether a residual target exists, to estimate re-polishing time, and to control the polishing part to perform a re-polishing process if the residual target exists.

Abstract: An automated lapping system is provided for lapping a work product using a robot. Because the robot can apply continuous consistent pressure that far exceeds the capabilities of a human operator, lapping and polishing evolutions take a fraction of the time taken by a human operator. The system includes a robot having one or more lapping end effectors and a control component that controls the robot to lap the work product. The control component includes a processor, a user interface coupled to the processor, a communication component that receives final work product dimensions, and a positioning component that detects a lapping zone on the work product and sends the detected lapping zone to the control component. The control component controls the robot based on the sent lapping zone and received work product dimensions.

Abstract: A device for predicting the lapping property of a charged lapping plate uses samples with a known lap surface. The samples are lapped on the plate and a non-invasive sensor is used to determine the lapping rate under a fixed load and rotation speed. The total frictional force of the samples is measured during the lapping to calculate the friction and Preston coefficients of the plate. The samples are held in place while the plate rotates and the sensor measures the distance to the plate. The plate rotates for a specific time so that adequate removal of the pad material has occurred. The lapping rate is determined from a change in the gap distance over a time interval. The lapping rate and friction are then assessed to determine if the plate is lapping worthy.