Abstract: In one embodiment, a semiconductor substrate (38) is uniformly polished using a polishing pad (16) that has a first polishing region (26), a second polishing region (28), and a third polishing region (30). The semiconductor substrate (38) is aligned to the polishing pad (16), such that the center of the semiconductor substrate (38) overlies the second polishing region (28), and the edge of the semiconductor substrate overlies the first polishing region (26) and the third polishing region (30). During polishing, the semiconductor substrate (38) is not radially oscillated over the surface of the polishing pad, and as a result a more uniform polishing rate is achieved across the semiconductor substrate (38). This allows the semiconductor substrate (38) to be uniformly polished from center to edge, and increases die yield because die located on the semiconductor substrate (38) are not over polished.

Abstract: Polishing machines and methods for mechanical and/or chemical-mechanical polishing of microfeature workpieces are disclosed herein. In one embodiment, a machine includes a table having a support surface, an under-pad carried by the support surface, and a workpiece carrier assembly over the table. The under-pad has a cavity and the carrier assembly is configured to carry a microfeature workpiece. The machine further includes a magnetic field source configured to generate a magnetic field in the cavity and a magnetorheological fluid in the cavity. The magnetorheological fluid changes viscosity within the cavity under the influence of the magnetic field source. It is emphasized that this Abstract is provided to comply with the rules requiring an abstract. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. 37 C.F.R §172 (b).

Abstract: An improved pad and process for polishing metal damascene structures on a semiconductor wafer. The process includes the steps of pressing the wafer against the surface of a polymer sheet in combination with an aqueous-based liquid that optionally contains sub-micron particles and providing a means for relative motion of wafer and polishing pad under pressure so that the moving pressurized contact results in planar removal of the surface of said wafer, wherein the polishing pad has a low elastic recovery when said load is removed, so that the mechanical response of the sheet is largely anelastic. The improved pad is characterized by a high energy dissipation coupled with a high pad stiffness. The pad exhibits a stable morphology that can be reproduced easily and consistently. The pad surface resists glazing, thereby requiring less frequent and less aggressive conditioning.

Abstract: A lapping machine operable with a lap wheel for lapping gold jewelry and adapted to collect gold dust produced by the lapping machine, includes: (a) a base, (b) an electric motor mounted to the base, the electric motor having a rotatable output shaft extending upward and adapted to be coupled to the lap wheel which is situated above the electric motor and rotates about the axis of the output shaft, with a gold dust debris space defined as the area surrounding the lap wheel and extending from below the lap wheel downward and surrounding at least part of the output shaft, (c) a shroud comprising rear and opposite side parts that surround the rear and opposite sides of the gold dust debris space respectively, thus leaving the front of the gold dust debris space open and accessible, the shroud including a continuous front wall and a continuous rear wall spaced radially outward of the front wall, with air flow passages defined between the front and rear walls of the rear and side parts, the front walls of the side

Abstract: A polishing pad for a chemical mechanical polishing apparatus. The polishing pad includes a plurality of concentric circular grooves. The polishing pad may include multiple regions with grooves of different widths and spacings.

Abstract: A lapping plate has photolithographically defined patterns that are electroplated to produce lands with well-defined channels. By choosing a particular geometry, the retention force is significantly reduced over prior art options, while still retaining a high land area fraction. In some versions, the material is electroplated onto sufficiently thin substrates to allow conformation to a curved vacuum chuck. This configuration provides a very large reduction in retraction force when compared to smooth, flat lapping plates. In addition, the substrate used to form the lapping plate has reduced thickness, and a vacuum chuck is used to pull the thin, flat lapping plate against it to define the curvature. This allows the lapping plate to be charged by a flat charging ring. The substrate used is typically glass and has been sputter-metallized on both sides. The resist is then patterned, leaving an exposed pattern in the metallization on both sides.

Abstract: An abrasive ground fabric which is a composite ground fabric comprising a fiber substrate and a elastic polymer filled in the fiber substrate, wherein (1) the fiber substrate is composed of bundles, each consisting of 20 to 3,000 fine fibers, and (2) the average diameter (D1) of fine fibers existent in a center portion from the center of the cross section perpendicular to a lengthwise direction of each bundle to ½ of the radius of each bundle is 0.3 to 10 &mgr;m, the average diameter (D2) of fine fibers existent in a peripheral portion from ½ of the radius to the end of each bundle is 0.05 to 1 &mgr;m, and the D1/D2 ratio is 1.5 or more. According to the present invention, the abrasive ground fabric is suitably used for the texturing of a substrate in the production of a magnetic recording medium, particularly a hard disk, enables high-accuracy surface finish and has excellent strength.

Abstract: A polishing pad useful for chemical mechanical planarization has a polishing layer for planarizing substrates. The polishing layer comprises a radius that extends from a center of the polishing layer to an outer perimeter of the polishing layer; one or more continuous grooves formed in the polishing layer and extending inward from the outer perimeter of the polishing layer; and a circumference fraction grooved (CF). The CF occurs in the area extending from the outer perimeter of the polishing layer a majority distance to the center of the polishing layer; and CF is that portion of circumference at a given radius lying across the one or more continuous grooves divided by full circumference at the given radius. The CF remains within 25% of its average value as a function of the polishing layer radius.

Abstract: Provided is a method for manufacturing a fixed abrasive material suitable for use in CMP planarization pads from an aqueous polymer dispersion that also includes abrasive particles that involves frothing the polymer dispersion, applying the froth to a substrate, mold or carrier and curing the froth to form a fixed abrasive material having an open cell structure containing between about 5 and 85 wt % abrasive particles and a dry density of about 350 kg/m3 to 1200 kg/m3.

Abstract: A sanding disc particularly useful for smoothing drywall. The sanding disc includes a circular abrasive disc having an abrasive surface, and a circular foam disc smaller in diameter than the abrasive disc which is co-axially adhered to the surface of the abrasive disc opposite its abrasive surface. The abrasive disc has a circular central portion along which the surface defined by the abrasive is generally planar, and has an annular peripheral portion extending from its central portion to its peripheral surface along which its surface defined by the abrasive is generally cylindrically convex to position the peripheral surface of the abrasive disc in a plane passing through the foam disc.

Abstract: One polishing media for chemical mechanical planarization includes an underlayer and a plurality of pressure sensors provided on the underlayer. At least some of the pressure sensors have a pad asperity provided thereon. The pressure sensors may be micro electromechanical systems (MEMS) pressure transducers or MEMS thermal actuators that monitor at least one of localized strain and temperature variation. Another polishing media includes a plurality of chemical sensors. Yet another polishing media includes pressure sensors, chemical sensors, and piezoelectric elements. Based upon the sensory outputs received from adjacent sensors, the piezoelectric elements provide active control to the process input by, for example, inducing localized vibration to modify the spatial removal behavior, inducing localized electric fields, or inducing localized heating/cooling elements.

Abstract: Of the type designed to be attached to the propeller-shaped bases or heads of a concrete grinder, to enhance the grinding effect of said propeller-shaped bases after the latter are used without disks, it is shaped like a cross, with four equal arms which are equiangularly distributed, in the shape of an isosceles trapezoid, each of which has a curved-convex end (1), forming part of the imaginary circumferential outline corresponding to the theoretical disk, and curved-concave side edges (2-2′), which are joined to each other without a break in continuity between adjoining arms and which define a deep concave indentation (3), whose path is circumferential and whose radius appreciably coincides with the theoretical radius of the disk, so that a pair of disks may be used in a concrete grinder with two heads, working on the same plane without touching each other, by means of offsetting them angularly from each other by 45°.

Abstract: The invention provides a polishing system that comprises a liquid carrier, an alkali metal ion, hydroxide ions, and a polishing pad and/or an abrasive. The abrasive can be dispersed in the liquid carrier of the polishing system or bound to the polishing pad. The alkali metal ion can be any univalent group I metal ion and is present in the polishing system at a concentration of about 0.05 M or more. Hydroxide ions are present in a sufficient amount to provide the system with a pH of about 9 or more. The liquid carrier of the polishing system can be any suitable polar solvent, such as water. The invention further provides a polishing method that involves polishing a portion of a substrate with the polishing system beginning about 6 hours or less after the polishing system is prepared.

Abstract: Embodiments of the invention include methods and apparatus for electrodialytic polishing of various layers formed on semiconductor substrates. In certain embodiments the use of electrodialytic processes in conjunction with chemical mechanical forces to achieve a copper interconnect with a desired level of planarity and process performance. In certain embodiments electrodialytic polishing uses an electrodialytic polish pad, which is an active pad which has copper binding groups provided in its core structure and has an added capability of allowing electrical conductivity. An electrodialytic polish pad allows transfer of cations or anions through a membrane in the presence of an electric field and into a cathodic electrolyte. Under the influence of an electric field the electrodialytic polish pad and/or electrodialytic pads are continuously refreshed to bind cations.

Abstract: A backing plate for an abrasive flap wheel has a sunk inner part and an outer flange. The sunk inner part has a hub which is provided with a location hole having an internal thread. The internal thread serves to fasten the backing wheel to the threaded shaft of a driving machine.

Abstract: A polishing pad (for example, polishing pad 305) for use in planarization of a semiconductor wafer (for example, semiconductor wafer 420), the polishing pad 305 featuring a plurality of different polishing surfaces, depending upon the direction of the movement of the polishing pad 305. The polishing pad 305 may take the form of a polishing disc or a polishing belt. The planarization of the semiconductor wafer 420 can then take place at a fewer number of polishing stations, thereby reducing the amount of time needed and reducing the probability of damage to the semiconductor wafer 420.

Abstract: An abrasive molding composed of a mass of inorganic particles, said mass having pores intervening among the inorganic particles, which molding has abrasive area to be placed in frictional contact with an article to be abraded, and non-abrasive area on a abrading surface of the abrasive molding. The abrasive area has exposed pores having a diameter of not larger than 1 &mgr;m, the total area of said exposed pores having a diameter of not larger than 1 &mgr;m occupying below 15% of the total area of abrasive area, and the non-abrasive area occupies 20% to 60% of the sum of the abrasive area and the non-abrasive area.

Abstract: A polishing pad includes a polishing layer and an adhesive layer. An adhesive bottom surface of the adhesive layer has an air transmitting pathway to collect air that is expelled from under the adhesive bottom surface, which avoids entrapment of air under the adhesive bottom surface.

Abstract: A superabrasive wheel (100, 200) for mirror finishing includes an annular base plate (120, 220) having an annular end surface (121, 221) and a plurality of superabrasive members (110, 210), each having a peripheral end surface (111), arranged along the periphery of the annular base plate (120, 220) at intervals from each other in a circumferential direction and fixed onto the end surface (121, 221) of the base plate (120, 220). Each of the superabrasive members (110, 210) has a flat plate shape, and is so arranged that the peripheral end surface (111) is substantially parallel to the rotary shaft of the superabrasive wheel (100, 200). A surface (113) defined by the thickness of the flat plate shape of each superabrasive member (110, 210) is fixed onto the end surface (121, 221) of the base plate (120, 220). In the superabrasive members (110, 210), superabrasive grains are bonded by a binder of a vitrified bond.

Abstract: A processing tool is used to carry out a fixed-abrasive grinding process on a surface of a silicon work-piece. The processing tool includes abrasive grains made up silica grains. A primary average grain size of the silica grains is desirably 0.8 nm to 10 &mgr;m.

Abstract: The present invention relates to a polishing pad for the chemical mechanical polishing (CMP). According to the present invention, there is provided a chemical mechanical polishing pad for polishing a semiconductor wafer with chemicals containing predetermined components supplied between the semiconductor wafer and the polishing pad, comprising a base layer; and an abrasive layer which contains polishing abrasives capsulated with a material soluble in the chemicals and is formed to have a constant thickness on the top surface of the base layer. The capsulated polishing abrasives become free abrasives in the chemicals supplied upon polishing, and take part in the polishing. Capsulating the polishing abrasives can be performed by granulization or spraying. According to the polishing pad of the present invention, planarization polishing can be performed as whole. In addition, since a small amount of chemicals are used, it is advantageous in the economic and environmental aspects.

Abstract: A polishing pad for a chemical mechanical polishing apparatus. The polishing pad includes a plurality of concentric circular grooves. The polishing pad may include multiple regions with grooves of different widths and spacings.

Abstract: A manufactured chemical mechanical polishing pad is annealed after manufacture to improve its operating characteristics. Annealing can stabilize the operational properties of the pad, such as coefficient of thermal expansion and compressibility. In one embodiment, annealing partially or fully completes a curing process that was incomplete after the pad was manufactured.

Abstract: An abrasive article that includes a fixed abrasive element having a plurality of abrasive particles, a resilient element, and a plurality of rigid segments disposed between the fixed abrasive element and the resilient element.

Abstract: Rotary saw blades (1, 17, 18) for use on a power saw are disclosed for cutting and sanding materials simultaneously. The rotary blades have abrasive sanding means (10, 11) affixed to each face of the blade to accomplish the sanding process. The abrasive means may take the form of donut-shaped abrasive pieces (10) affixed radially inward of blade cutting teeth (3) on each face of the blade or a plurality of abrasive pieces or disks (11) attached to various locations on both faces of the blade. The plurality of abrasive pieces may consist of different grades of sand paper with the heavier grades of paper being radially nearest the teeth and finer grades inward so that the material when cut may be gradually sanded and polished as the cutting occurs. One embodiment provides rotary blades (17, 18) with recessed areas (12, 15) for fixing thicker pieces of adhesive means or for use when the kerf width (9) of the blade teeth (3) is less.

Abstract: The invention provides a method and an apparatus that prevent the accumulation of copper ions during CMP of copper lines by performing the CMP process at low temperatures and by maintaining this low temperature during the CMP process by adding a slurry that functions as a corrosion inhibitor.

Abstract: A method of chemically modifying a wafer suited for fabrication of semiconductor devices includes a) contacting a surface of wafer with an article that includes a plurality of unit cells repeating across the surface of the article, the individual unit cells including at least a portion of a three-dimensional structure and being characterized by a unit cell parameter as follows: [[V1−Vs]/Aas]/{square root over (A)}uc>5 where V1 is the volume defined by the area of the unit cell and the height of the structure of the unit cell, Vs is the volume of the structure of the unit cell, Aas is the apparent contact area of the structure of the unit cell, and Auc is the area of the unit cell, and b) moving at least one of the wafer and the article relative to each other in the presence of a polishing composition that is chemically reactive with a surface of the wafer and capable of either enhancing or inhibiting the rate of removal of at least a portion of the surface of the wafer.

Abstract: A polishing pad for polishing glass and the like has a working layer with a plurality of polishing grains, an attaching layer with which the polishing pad is attachable to a polishing head of a power tool, and a connection layer which connects the working layer, with the attaching layer, and the connection layer is composed of vulcanizable material, which is vulcanized at certain temperature and under certain pressure and thereby connects the working layer with the attaching layer.

Abstract: A polishing system can have a rotatable platen, a polishing pad secured to the platen, a carrier head to hold a substrate against the polishing pad, and an eddy current monitoring system including a coil or ferromagnetic body that extends at least partially through the polishing pad. A polishing pad can have a polishing layer and a coil or ferromagnetic body secured to the polishing layer. Recesses can be formed in a transparent window in the polishing pad.

Abstract: A chemical mechanical polishing system is provided having one more polishing stations. The polishing stations include a platen and pad mounted to an upper surface of the platen. The upper surface of the platen is patterned to define a raised area and a recessed area. The raised area provides a rigid mounting surface for the pad and the recessed area provides the pad a desired degree of flexibility and compliance of the pad when brought into contact with a substrate.

Abstract: Methods and apparatuses for planarizing a microelectronic substrate. In one aspect of the invention, a first portion of an energy-sensitive, non-sacrificial planarizing pad material is exposed to a selected energy without exposing a second portion of the material to the selected energy source. The planarizing pad material is exposed to a solvent to remove material from one of the first or second portions of the planarizing pad material at a faster rate than removing material from the other of the first and second portions. The process forms a plurality of recesses directly in the surface of the planarizing pad which are configured to support a planarizing liquid proximate to the surface of the planarizing pad material during planarization of the microelectronic substrate. Alternatively, the process can form a mold having protrusions that are pressed into the planarizing pad to define the recesses in the pad.

Abstract: An abrasive wheel to grind or cut a variety of materials comprising a core part fixed to a tool transmitting motive power and long tips and short tips alternately attached on the base surface of a shank around the core part. The tips are arranged to cover the base surface with space therebetween at predetermined intervals along the circumference of the shank.

Abstract: A sanding disc particularly useful for smoothing drywall. The sanding disc includes a circular abrasive disc having an abrasive surface, and a circular foam disc smaller in diameter than the abrasive disc which is co-axially adhered to the surface of the abrasive disc opposite its abrasive surface. The abrasive disc has a circular central portion along which the surface defined by the abrasive is generally planar, and has an annular peripheral portion extending from its central portion to its peripheral surface along which its surface defined by the abrasive is generally cylindrically convex to position the peripheral surface of the abrasive disc in a plane passing through the foam disc.

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: The present invention is floor conditioning system. The floor conditioning system improves the ease of use as compared to currently available sanding or polishing devices. Thereby, allowing the unsophisticated do-it-yourselfers to use a floor conditioning system. The floor conditioning system provides a random rotating orbital action which greatly improves the ability to control a floor conditioning system as well as providing a much nicer job of conditioning a floor. The floor conditioning system includes a main housing, wheel assembly, a handle assembly, a motor, a belt cover, a belt, a dust recovery system and orbital head assemblies.

Abstract: A stacked polishing pad includes an upper polishing layer and a lower sub-layer having major faces which are in contact with each other. The polishing layer is substantially impermeable to liquid while the sub-layer is liquid absorbent. The sub-layer has an outer peripheral edge which is sealed to prevent absorption of liquid into the sub-layer through the outer peripheral edge. When the stacked polishing pad is mounted on a platen of a polishing machine, the sub-layer has no exposed surface which can absorb liquid.

Abstract: The abrasive flap wheel (1) has a backing plate (2) which comprises a sunk inner part (3) and an outer flange (4). The sunk inner part (3) has a hub (7) which projects toward the front side (3a), i.e. toward the side of the abrasive flaps, and is provided with a location hole (8) and an internal thread (9). The internal thread (9) serves to fasten the abrasive flap wheel to a corresponding driving machine.

Abstract: A polishing pad for a chemical mechanical polishing apparatus. The polishing pad includes a plurality of concentric circular grooves. The polishing pad may include multiple regions with grooves of different widths and spacings.

Abstract: A workpiece is pinched from above and below by polishing pads attached to the inner surfaces of a pair of upper and lower rotary platens. A slurry is dropped between the workpiece and the polishing pads to polish the workpiece. The polishing pad is comprised of a base layer, and a sheet-shaped nap layer, which is laminated on the base layer and is made of a soft plastic foam. The nap layer is formed of closed pores, whose surface is covered with non-foaming skin layers and which involves pores (air bubble) in the nap layer without opening the pores in the surface. The polishing pad is used in combination with a colloidal slurry whose abrasive grains are colloidal silica in order to polish a surface of the workpiece.

Abstract: Grinding wheels are fabricated with outwardly extending circular peripheral rims having a continuous rim surface to which separate abrasive pieces, preferably of a superabrasive such as CBN, are secured by suitable adhesive. The superabrasive pieces are preferably circular and of a diameter corresponding to the width of the rim and are secured to the rim surface so as to either be adjacent and touch one another or to be spaced one from the other around the circle of the rim surface so that a predetermined amount but not all of the rim surface is covered with abrasive pieces. That rim surface coverage optimize grinding efficiency while providing space for fluid flow for purposes of cooling and carrying away particles from the grinding process.

Abstract: The invention is directed to a base-pad for placement under a polishing pad for use with a polishing fluid during a polishing operation, the base-pad having a layer with vertical elongated pores that absorb polishing fluid and that confine absorbed polishing fluid from transport laterally in the base-pad. Micropores in the layer are impermeable to the polishing fluid and permeable to gasses.

Abstract: A chemical-mechanical polishing system which is particularly well suited for use in the manufacture of semiconductor devices or the like. The invention is directed to a polishing pad composition comprising a high modulus phase component and a low modulus phase component. The multi-phase polishing pads are very efficient and effective in providing high performance polishing along an entire polishing surface interface.

Abstract: A polishing system includes a polishing tool having a platen, a polishing pad, and a controller. The platen is adapted to have the polishing pad attached thereto. The polishing pad includes a polishing surface and a back surface that is opposite the polishing surface. At least one sender electrode and at least one response electrode is disposed in the polishing pad. The controller is coupled to the polishing tool. A method includes polishing a conductive process layer of a wafer using a polishing pad of a polishing tool having at least one sender electrode and at least one response electrode disposed therein. A signal is provided to the at least one sender electrode. The signal provided to the at least one sender electrode is monitored with at least one of a group of the at least one response electrode, the at least one response electrode communicating with the at least one sender electrode through the conductive process layer of the wafer.

Abstract: An improved CMP polishing member having a plurality of protrusions with an outer surface, the outer surface of the protrusions defining a polishing surface of the CMP pad adapted to polish or planarize an exposed surface of a semiconductor wafer. A plurality of cavities are interposed between the protrusions and the cavities have a hydrophilic surface so as to attract wetting solution to thereby enhance retention of the wetting solution adjacent the polishing interface between the surface of the semiconductor wafer and the polishing surface of the polishing pad. In one embodiment, the protrusions are comprised of a fixed abrasive material, such that the polishing pad is a fixed abrasive polishing pad. In one embodiment, the cavities between the protrusions are coated with a hydrophilic material so as to retain wetting solution immediately adjacent the exposed surfaces of the fixed abrasive protrusion.

Abstract: The invention provides a method and an apparatus that prevent the accumulation of copper ions during CMP of copper lines by performing the CMP process at low temperatures and by maintaining this low temperature during the CMP process by adding a slurry that functions as a corrosion inhibitor.

Abstract: Abrasive filaments including plastic abrasive particles interspersed in a thermoplastic matrix. The abrasive filaments can comprise monofilaments, coextruded core/sheath filaments, and coated preformed cores. Also disclosed are abrasive brush constructions using a plurality of such abrasive filaments mounted on a suitable substrate, and unitary injection molded abrasive brushes. Also disclosed are methods of making such filaments and brushes, and method of using such brushes.

Abstract: The invention concerns a grinding spindle, comprising a spindle housing and two coaxial shafts which are driven by a drive motor. A concentric grinding disk is fixed to each of said shafts. The shafts can be moved in an axial direction in relation to each other with a lifting or lowering movement in order to engage one grinding disk or the other. The inner shaft is connected to the drive motor as a main shaft (1), the outer shaft (8) is coupled to said main shaft (1) by a carrier device (10). In addition, a bush (4) is coaxially semimounted on the spindle housing (3), the outer shaft (8) is pivotably mounted on the bush (4) with a pivot bearing (9), and the bush (4) is provided with an actuator (13) which executes the lifting or lowering movement.

Abstract: There is provided a conductive grinding wheel 10 rotating centering on a vertical shaft center and including a horizontal working surface 10a, and the grinding wheel comprises a conductive base member 11 formed of an integrally molded flat plate, and a plurality of fan-shaped segments 12 detachably attached to the base member to entirely constitute the annular working surface. Each segment comprises a base metal 12a directly attached to the base member and a grinding wheel part 12b formed on the surface of the base metal. Moreover, the grinding wheel part comprises a recessed groove 14 for partitioning the working surface into a plurality of working areas 13, and an electrolytic fluid supply hole 15 for directly supplying the electrolytic fluid to the respective working areas, so that the electrolytic fluid is supplied to the respective electrolytic fluid supply holes through the base member.

Abstract: A patterned polishing pad adapted for use in a wafer polishing machine. The patterned polishing pad has a polishing surface adapted to contact frictionally a semiconductor wafer being polished in a chemical mechanical polishing machine. The polishing surface has a first region and a second region. The first region is adapted to contact frictionally the wafer and achieve a first process effect. The second region is adapted to contact frictionally the wafer and achieve a second process effect. The surface of the second region extends a predetermined protrusion amount above the polishing surface with respect to the surface of the first region.

Abstract: A polishing pad is provided, having its face shaped to produce controlled nonuniform removal of material from a workpiece. Non-uniformity is produced as a function of distance from the pad's rotational axis (the working radius). The pad face is configured with both raised, contact regions and voided, non-contact regions such that arcuate abrasive contact varies nonuniformly as a function of distance from the pad's rotational axis. Void density at any distance may be produced by several techniques such as varying void size as a function of working radius or varying the number of voids per unit area as a function of working radius. Either technique produces variation in voided area per total unit area for rings of pad surface concentric with the rotational axis having infintesimally small width.