Patent Publication Number: US-2020282506-A1

Title: Spiral and concentric movement designed for cmp location specific polish (lsp)

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15/891,722 filed Feb. 8, 2018, which claims priority to U.S. Provisional Patent Application Ser. No. 62/467,672 filed Mar. 6, 2017. Each of the aforementioned applications is herein incorporated in its entirety. 
    
    
     BACKGROUND 
     Field 
     Embodiments of the present disclosure generally relate to methods for polishing a substrate, such as a semiconductor wafer, and more particularly, to methods for polishing specific locations or regions of a substrate in an electronic device fabrication process. 
     Description of the Related Art 
     Chemical mechanical polishing (CMP) is a process which is commonly used in the manufacture of high-density integrated circuits to planarize or polish a layer of material deposited on a substrate, by contacting the material layer to be planarized with a polishing pad and moving the substrate, and hence the material layer surface, with respect to the polishing pad in the presence of a polishing fluid such as a slurry. In a typical polishing process, the substrate is retained in a carrier head that presses the backside of the substrate toward the polishing pad. Material is removed across the material layer surface in contact with the polishing pad through a combination of chemical and mechanical activity. The carrier head may contain multiple individually controlled pressure regions that apply differential pressure to different annular regions of the substrate. For example, if greater material removal is desired at the peripheral region of the substrate as compared to the desired material removal at the center of the substrate, the carrier head will apply more pressure to the peripheral region of the substrate. However, the stiffness of the substrate tends to redistribute the pressure applied to local regions of the substrate by the carrier head such that the pressure applied to the substrate may be spread or smoothed generally across the entire substrate. The smoothing effect makes local pressure application, for local material removal, difficult if not impossible. 
     Two common applications of CMP are planarization of a bulk film, for example pre-metal dielectric layer (PMD) or interlayer dielectric layer (ILD) polishing, where underlying features create recesses and protrusions in the layer surface, and shallow trench isolation (STI) and interlayer metal interconnect polishing, where polishing is used to remove a portion of a via, contact or trench fill material from the exposed surface (field) of the layer having the feature. For example, in interlayer metal interconnect polishing, a conductor, such as tungsten (W) which was deposited in openings in a dielectric film layer is also deposited on the field surface thereof, and the tungsten on the field must be removed therefrom before a next layer of metal or dielectric material can be formed thereover. 
     After CMP, typically one or more substrates, from a batch or a lot of substrates, are measured or inspected for conformance with process objectives and device specifications. If a substrate film is too thick following some CMP operations (i.e. PMD or ILD), or has a residual undesirable film remaining on the field surface of the substrate, (known as inadequate clearing following a CMP operation such as post metal interconnect or STI polishing), the substrate will typically be returned to the conventional CMP polisher for further polishing. However, post-CMP, the film thickness, and film removal rate, of a substrate may be non-uniform thereacross as a degree of non-uniform material removal across the substrate is inherent in most conventional CMP processes. Thus, reworking of a substrate where the polished layer is too thick or has an undesired residual film thereon may result in film that is too thin at some locations or locations that are over-polished during the rework operation. 
     In addition to over-polish resulting in a film thickness that is too thin, over-polishing may result in undesirable dishing of the upper surface of a film material in recessed features such as vias, contacts and lines, and/or erosion of the planer surface in areas with high feature density. In addition, over-exposure of a metal such as tungsten (W) to the a metal CMP slurry can result in chemical conversion of the metal by the slurry and thus coring, where the metal fill material no longer adheres to the side wall and base of the opening which it fills, and it pulls away during polishing. 
     Therefore, there is a need for a method that facilitates removal of materials from specific locations of the substrate with process performance comparable or superior to that of conventional CMP. 
     SUMMARY 
     Embodiments herein generally relate to methods for providing a planarized substrate surface, or a substrate wherein an overburden material is fully cleared from the field surface without dishing of the material filling a hole, or trench, by polishing specific desired locations on a substrate, such as a semiconductor wafer. 
     In one embodiment, a method of polishing a substrate includes positioning a polishing pad on a substrate at a first radius of the substrate, the polishing pad supported by a support arm and having a contact portion surface area less than a surface area of the substrate and polishing the substrate at the first radius using a first polishing recipe. The first polishing recipe comprises a first polishing dwell time, a first polishing downforce, and a first polishing speed. The method further includes moving the support arm using a positioning motion so that the polishing pad traverses from the first radius to a second radius on the substrate and polishing the substrate at the second radius using a second polishing recipe. The second polishing recipe comprises a second polishing dwell time, a second polishing downforce, and a second polishing speed. 
     In another embodiment, a method of polishing a substrate urging a polishing pad supported by a first end of a support arm against a surface of a substrate, the polishing pad having a contact portion surface area less than a surface area of the substrate, polishing a first area surface of the substrate, smaller than the surface of the substrate, using a first polishing recipe. The first polishing recipe comprises a first polishing dwell time, a first polishing downforce, and a first polishing speed. The method further includes simultaneously moving the substrate and the support arm so that the polishing pad traverses from a first area surface of the substrate to a second area surface of the substrate smaller than the surface of the substrate and polishing the second area surface of the substrate using a second polishing recipe. The second polishing recipe comprises a second polishing dwell time, a second polishing downforce, and a second polishing speed. 
     In another embodiment, a method of polishing a substrate includes urging a polishing pad supported by a support arm against a surface of a substrate, the polishing pad having a contact portion surface area less than a surface area of the substrate, simultaneously rotating a chuck that has the substrate secured thereon and moving the support arm so that the polishing pad traverses to each radius of a plurality of radii of the surface of the substrate, and polishing the surface of the substrate using a plurality of polishing recipes, each the plurality of polishing recipes corresponding to each of the plurality of radii. Each of the plurality of polishing recipes comprises a polishing dwell time, a polishing downforce, and a polishing speed. 
     In another embodiment, a residual film thickness profile is determined based on manual or automated inspection techniques and polishing recipes are generated based on the residual film thickness profile. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, 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 disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments. 
         FIG. 1A  is a top perspective view of an LSP module according to one embodiment. 
         FIG. 1B  is a schematic cross-sectional view of the LSP module of  FIG. 1A . 
         FIG. 2  is a schematic cross-sectional view of a polishing head according to one embodiment. 
         FIG. 3  is a schematic cross-sectional view of a polishing pad assembly according to one embodiment. 
         FIG. 4A  is a schematic sectional view of an eccentric member disposed in a polishing head according to one embodiment. 
         FIG. 4B  depicts a polishing motion in accordance with the embodiment of the polishing head depicted in  FIG. 4A . 
         FIG. 5A  is schematic sectional view of another eccentric member disposed in a polishing head according to another embodiment. 
         FIG. 5B  depicts the polishing motion in accordance with the embodiment of the polishing head depicted in  FIG. 5A . 
         FIG. 6  is an schematic isometric cross-sectional view of an LSP module according to another embodiment. 
         FIG. 7  is a schematic plan view of a LSP module showing various motion modes of a polishing pad assembly on a substrate, according to one embodiment. 
         FIG. 8  is a schematic plan view of a LSP module showing another embodiment of various motion modes of the polishing pad assembly. 
         FIGS. 9A-9C  are illustrations showing polishing paths that produced on a substrate, according to some embodiments. 
         FIG. 10  is a flow diagram of a method for polishing a substrate, according to one embodiment. 
     
    
    
     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 disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation thereof with respect to the other embodiment(s). 
     DETAILED DESCRIPTION 
     The present disclosure provides a method of polishing a film layer on a substrate using a module particularly suited for location specific polishing (LSP) on the substrate during a fabrication process. The method includes the generation of a thickness correction profile for a film layer on the substrate and the generation of a polishing recipe, or series of polishing recipes, based on the thickness correction profile. In some embodiments, the method may be employed before or after a conventional CMP operation. When the method is used before a conventional CMP operation, in one aspect it is used to selectively remove film layer material, by polishing portions of the exposed film layer, to correct for the existing non-uniform film thickness thereof, and/or to selectively remove film layer material, by polishing portions of the exposed film layer, in anticipation of non-uniform removal of portions of the film layer material during conventional CMP. When the method is used after a conventional CMP operation it is used to correct under-polishing of the film layer surface, or portions of the surface, i.e., inadequate material removal (aka “rework”). Likewise, the equipment and methods herein can be used to correct planarity of a substrate, such as a semiconductor wafer, before processing thereof to form an integrated circuit therewith. 
     A non-uniform film thickness of a material layer, or the presence of a residual film on the field, following CMP may be a function of film thickness non-uniformity of the film layer before polishing and/or non-uniform material removal during CMP. Material removal non-uniformity is influenced by a number of factors, such as variations in the CMP consumables including the polishing pad structure, the pad surface, substrate retaining rings, pad conditioners, the polishing slurry, polishing process parameters, and substrate properties. The properties of consumables vary from consumable part to part, lot to lot, and manufacturer to manufacturer. Additionally, the effect of the consumable on polishing changes over the lifetime of the consumable. Variations in process parameters which affect resulting film thickness uniformity, and the presence of undesirable residual film on the substrate (inadequate clearing), include deviations in: down force on a substrate, platen and carrier speeds, conditioning forces, platen temperature, and fluid flowrates. Variations in the substrates which effect polishing performance include film layer material properties, film layer level on a multi-level interconnect structure, and/or device size and feature density. 
     Conventional quality control and in-process monitoring methods are used to reduce incoming consumable and process parameter variation. Changes in material removal non-uniformity profiles across consumable lifetimes and/or due to substrate properties are unavoidable but generally predictable. For conventional CMP systems, configured to polish circular substrates, material removal profiles can often be described with reference to a radial distance from the center of the substrate. Generally, a material removal profile along a diameter of substrate will mirror itself if divided at the center of the substrate. This means that the remaining film thickness, or the presence of a residual film in a particular location on a substrate, is largely dependent on the radius of the location from the center of the substrate and will generally be similar when measured at circumferential locations on the substrate at that same radius. 
     Monitoring of film thickness or the presence of residual films on production substrates may be done using stand alone, in-line, and in-situ metrology systems as well as post-CMP optical inspection (manual or automated). Measurements and/or inspections may be made before, after, or during conventional CMP, or a combination thereof. For some dielectric film layers, such as pre-metal dielectric layers (PMD) and inter-layer dielectric layers (ILD), post-CMP film thickness, and film thickness uniformity, may be monitored on production substrates for statistical process control (SPC) purposes as well as to ensure compliance with device design specifications. 
     PMD and ILD post-CMP film thickness is commonly monitored using in-line or stand-alone optical metrology systems. Generally, a specified number of measurements are taken on each substrate, or on a sample number of substrates within a substrate lot (batch of substrates of the same device). Each film thickness measurement is commonly taken within a die or at a dedicated measurement site in a scribe line between dies. The number of measurements, and the corresponding locations, are generally standardized across most or all operations in a semiconductor manufacturing facility including an electrical test operation at the end of a production line which takes electrical measurements of test structures also located in the scribe lines. Matching of measurements taken inline during production with measurements taken at electrical test facilitates SPC and trouble-shooting of the production line, however, these standardized measurement sites may not be ideal for determining a correction profile for use with LSP. One option for determining a correction profile is to take additional measurements across the production substrate beyond the standardized measurements described above. 
     Metrology throughput and capacity concerns are a factor in how many additional measurements are taken and whether they are taken within a die or at dedicated measurement sites within the scribe lines. The metrology tool may have device pattern recognition capabilities so that the thickness measurement result commonly determines thickness for only the film layer of concern, i.e., the layer just polished, and does not include the thicknesses of underlying layers. Device manufacturers with a changing range of device products, such as foundries, commonly use the dedicated measurement sites in the scribe lines to facilitate automated metrology recipe creation. However, there are fewer dedicated measurement sites on a substrate than there are die, so a correction profile based on these measurement sites may not reflect deviations in film thickness between the measurement sites. Deviations in film thickness between measurement sites may be predicted based on the measurements taken and the process conditions under which the substrate was polished using conventional CMP. 
     Post CMP monitoring of metal and/or STI properties is done to ensure that metal or STI films are removed from the surface of the substrate but remain in recessed features, such as lines, vias, trenches, or other recesses therein. The presence of residual film is typically the result of under-polishing. Incomplete removal of this film may result in device failure due to shorting (metal CMP) or incomplete transistor formation (STI). Monitoring includes post-CMP thickness measurements of the residual film (i.e. eddy current testing, or optical metrology, for metal and optical metrology for STI) or other optical inspection techniques. Manual optical inspection may comprise a 1× visual inspection of all substrates for residual films and/or a manual inspection under magnification. Automated optical inspection is commonly performed using inline or standalone inspection systems, such as bright field and/or dark field inspection systems. 
     In some embodiments, film thickness measurements and/or residual film inspection results may be uploaded to a facility automation system where determinations of film layer correction profiles may be made. The facility automation system will generate a polishing recipe based on the correction profile, or may select a polishing recipe based on a known film thickness profile related to the polished film layer, and will then download the correction polishing recipe to the LSP module. 
     In other embodiments, systems suited for polishing specific locations of a substrate can use information from thickness measurements and/or optical inspections to create a correction profile for a particular substrate. The correction profile is one of a film thickness correction profile and a residual film thickness profile. Predicted post CMP film layer profiles based on consumable lifetime and/or substrate properties, as well as a radial material removal profile of a conventional CMP process and tool, are also useful to improve the accuracy of the correction profile. Polishing recipes based on the correction profile can then be generated for use on the LSP modules disclosed herein, or on any apparatus suitable for selectively polishing discrete portions of a substrate. The polishing recipes may be generated by the LSP module, by a facility automation system, or by some other system. Polishing recipes may be optimized to reduce total correction time using rotational and radial motions of the LSP module. 
     As will be appreciated by one of ordinary skill in the art, aspects of the present disclosure may be embodied as a system, method, computer program product, or a combination thereof. Accordingly, aspects of the present disclosure may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may be referred to herein as a “circuit,” “module” or “system.” Furthermore, aspects of the present disclosure may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon. 
     Any combination of one or more computer readable medium(s) may be utilized for storing a program product which, when executed, is configured to perform a method for polishing a substrate. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium would include the following: a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. 
     A computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, radio, or any suitable combination thereof. A computer readable signal medium may be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. 
     Program code embodied on a computer readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing. Computer program code may be written in any one or more programming languages. The program code may execute entirely on the user&#39;s computer, partly on the user&#39;s computer, as a stand-alone software package, partly on the user&#39;s computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user&#39;s computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). 
     The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational activities to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. 
       FIG. 1A  is a schematic perspective view of an LSP module  100  used to practice the methods described herein.  FIG. 1B  is a schematic cross-sectional view of the LSP module  100  shown in  FIG. 1A . The LSP module  100  includes a base  105  supporting a chuck  110 , which rotatably supports a substrate  115  thereon. In the embodiment shown, the chuck  110  is configured as a vacuum chuck, although other substrate securing devices, such as electrostatic, adhesive or clamp based chucks, may be employed. The chuck  110  is coupled to a drive device  120 , such as a motor or rotating actuator, providing at least a rotational movement of the chuck  110  about axis A (oriented in the Z direction). The rotational speed of the chuck is desirably between about 0.1 rpm and about 100 rpm, such as between about 3 rpm and 90 rpm. 
     The substrate  115  is disposed on the chuck  110  in a “face-up” orientation such that a feature (device) side of the substrate  115  faces a polishing pad assembly  125  located thereover. The polishing pad assembly  125  is used to polish or remove material from a specific location of the substrate  115 , before or after polishing of the substrate in a conventional CMP system. 
     The polishing pad assembly  125  is coupled to a polishing head  145  which is, in turn, coupled to a support arm  130  that moves the polishing pad assembly  125  relative to the surface layer of the substrate  115 . The support arm  130  is coupled to an actuator system  135 . The actuator system  135  herein includes a motor  137  coupled to a support arm shaft  133  which provides rotational motion to the support arm  130  around an axis B. Other embodiments, not shown, may use more than one polishing pad assembly  125 , support arm  130 , and actuator system  135 . 
     In one embodiment, a fluid applicator  155  is rotatably coupled to the base  105 . The fluid applicator  155  includes one or more nozzles  143  to deliver fluids from a fluid source  140  to the surface layer of the substrate  115 . The one or more nozzles  143  are selectively positionable over the surface of the substrate  115  by swinging the nozzles  143  of the fluid applicator  155  about a vertical axis C. The fluids delivered through the nozzles  143  facilitate polishing and/or cleaning of the substrate  115  and include a polishing fluid such as a slurry, a buffing fluid, de-ionized water, a cleaning solution, a combination thereof, or other fluids. The base  105  is configured as a basin to collect polishing fluid and/or DIW that has flowed off of the edges of the substrate  115 . In another embodiment, the fluid from the fluid source  140  is applied to the substrate through the polishing head. The fluid source  140  may also provide gases to the polishing head, such as clean dry air (CDA) or nitrogen. 
     Generally, the LSP module  100  includes a system controller  190  configured to control the automated aspects of the LSP module  100 . The system controller  190  facilitates the control and automation of the overall LSP module  100  and includes a central processing unit (CPU) (not shown), memory (not shown), and support circuits (or I/O) (not shown). The CPU may be one of any form of computer processors that are used in industrial settings for controlling various processes and hardware (e.g., actuators, fluid delivery hardware, etc.) and monitoring the system processes (e.g., substrate position, process time, detector signal, etc.). The memory is connected to the CPU, and is one or more of a readily available memory, such as random access memory (RAM), read only memory (ROM), floppy disk, hard disk, or any other form of digital storage, local or remote. Software instructions and data are coded and stored within the memory for instructing the CPU to perform one or more polishing process related activities. The support circuits are also connected to the CPU to support the processor in a conventional manner. The support circuits include cache, power supplies, clock circuits, input/output circuitry, subsystems, and the like. A program (or computer instructions) readable by the system controller  190  determines which tasks are performable by the various components in the LSP module  100 . Preferably, the program is software readable by the system controller  190 , which includes code to generate and store at least substrate positional information, the sequence of movement of the various controlled components, coordinate the movement of various components in the LSP module  100  (e.g., the support arm  130 , the polishing pad assembly  125  and the movement of the substrate  115 ) and any combination thereof. Alternatively, the control of the polishing apparatus can be embodied in a remote controller, computer or other control system, such as a fab wide control system. 
     In some embodiments, the system controller  190  obtains measurement data or other information concerning the substrate  115  from a metrology station, a factory interface, FAB host controllers, or other devices, and stores the data for determining the correction profile or the residual film profile for the substrate  115 . In some embodiments, the system controller  190  stores and executes programs to determine polishing recipe parameters such as polishing dwell time, polishing down force, and polishing speed required for each radius of the substrate  115 . The data is stored as formulas, graphs, tables, discrete points, or by other suitable methodology. 
     In some embodiments, a metrology device  165  (shown in  FIG. 1A ) is coupled to the base  105 . The metrology device  165  is used to provide an in-situ metric of polishing progress by measuring a metal or dielectric film thickness on the substrate  115  during polishing, or detect residual film on the field surface using optical inspection techniques, such as bright field/dark field techniques. The metrology device  165  is one of an eddy current sensor, an optical sensor, or other sensing device useful to determine metal or dielectric film thickness or the presence of a residual film on the field surface. In other embodiments, ex-situ metrology feedback is used to determine post-polishing film layer parameters such as location of thick/thin areas of deposition or residual films on the wafer, and thus the motion recipe for the chuck  110 , support arm  130  and polishing pad assembly  125 , polishing dwell time, as well as the downforce or pressure of the LSP. Ex-situ feedback can also be used to determine the final profile of the polished film. In situ metrology can be used to optimize polishing by monitoring progress of the parameters determined by ex-situ metrology. 
       FIG. 2  is a schematic cross-sectional view of one version of a polishing head  200  used to practice the methods described herein. Herein, polishing head  200  is used as the polishing head  145  shown in  FIGS. 1A-1B . Polishing head  200  comprises a polishing head housing  205  movably coupled to a support  215  by one or more posts  220  and one or more post couplings  223 . The posts  220  and the post couplings  223  maintain a parallel relationship between the support  215  and the polishing head housing  205  and prevent the polishing head housing  205  from rotating relative to the support  215 , while allowing for limited lateral motion, such as an orbital motion or an oscillating motion, of the polishing head housing  205  relative to the support  215 . In some embodiments, the posts  220  are made of a plastic material, such as nylon. The polishing head housing  205  comprises an upper housing  203  and a lower housing  207 . The lower housing  207  is made of a polymer material, such as polyurethane, PET (polyethylene terephthalate), or other suitable polymers having sufficient hardness and/or strength such as polyether ketone (PEEK) or polyphenylene sulfide (PPS). These materials have sufficient structural strength to maintain their shape under typical CMP process conditions, and are chemically and physically resistant to known CMP fluids and abrasives. 
     A flexible membrane  235  is movably disposed between the upper housing  203  and the lower housing  207 . The flexible membrane  235  and the upper housing  203  define a housing volume  225 . The fluid source  140  is fluidly coupled to a gas inlet  280  disposed through the upper housing  203 . The fluid source  140  provides a pressurized gas, such as CDA or nitrogen, into housing volume  225 . The polishing pad assembly  125  is coupled to the flexible membrane  235  so that the polishing pad assembly  125  protrudes from an opening in the lower housing  207 . In operation, the pressurized gas is introduced to the housing volume  225  through the gas inlet  280 . The pressurized gas urges the polishing pad assembly  125  against the uppermost layer surface of an underlying substrate (not shown) with a polishing downforce. The polishing downforce of the polishing pad assembly  125  against the surface of the substrate is adjusted by changing the pressure of the gas with in the housing. A pressure controller (not shown) regulates the gas pressure within the housing volume  225  so that the polishing downforce on the polishing pad assembly remains constant through an axial rotation of the polishing head housing  205  relative to the support  215  that results with some embodiments disclosed herein. 
     In this embodiment, lateral movement of the polishing head housing  205  relative to the support  215  is provided by a shaft  250  coupled to a polishing head motor  240 , which rotates the shaft  250  about a vertical axis E. The shaft  250  is coupled to an eccentric member  255 , and the eccentric member  255  is rotatably coupled to a bearing  245 . The bearing  245  is coupled to the upper housing  203  by a bearing cap  230 . An eccentric member housing volume  288  is defined by an inner wall  260  and the bearing cap  230  within which the bearing  245  is piloted, the inner wall  260  surrounding shaft axis E, but offset therefrom. During a polishing operation, the shaft  250  rotates the eccentric member  255  and the eccentric member  255  contacts the inner wall  260  within the eccentric member housing volume  288 . The contact of the eccentric member  255  with the inner wall  260  causes the polishing head housing  205  to move laterally and orbitally around axis E relative to the support  215  in a polishing motion. The posts  220  support the polishing head housing  205  below the support  215  and follow the motion of the housing, while limiting the lateral travel of the polishing head housing  205 . The polishing motion has a polishing motion radius R of between about 0.5 mm and about 5 mm, such as about +1-1 mm, from the vertical axis E. Herein, the polishing speed is controlled by the rotational speed of the shaft  250 . The rotational speed of the shaft  250  is desirably maintained between about 1,000 rpm and about 5,000 rpm. 
     In another embodiment, the shaft  250  is directly coupled to the polishing head housing  205  and the posts  220  are removed. Here, shaft  250  rotates the polishing head housing  205  relative to the support arm  130 . This embodiment may be used to create a rotational polishing motion of the polishing pad assembly relative to the substrate if the vertical axis of the polishing pad assembly is vertical axis E. In another embodiment, the shaft  250  is directly coupled to the polishing head housing  205 , the posts  220  are removed, and the center axis F of the polishing pad assembly  125  is offset from vertical axis E so that the rotation of the shaft  250  creates an orbital motion of the polishing pad assembly  125  at a radius R from the vertical axis E (an orbital polishing motion). 
       FIG. 3  is a schematic cross-sectional view of the polishing pad assembly  125  and flexible membrane  235  useful to practice the methods described herein. The polishing pad assembly  125  comprises a contact portion  300  and a support portion  305 . The contact portion  300  may be a conventional polishing pad material, such as commercially available polishing pad material, for example polymer based pad materials typically utilized in CMP processes. The polymer material includes a polyurethane, a polycarbonate, fluoropolymers, polytetrafluoroethylene (PTFE), polyphenylene sulfide (PPS), or combinations thereof. In some embodiments, the contact portion  300  comprises open or closed cell foamed polymers, elastomers, felt, impregnated felt, plastics, and like materials compatible with the CMP processing chemistries. In some embodiments, the contact portion  300  comprises a polishing pad material available from DOW® that is sold under the tradename IC1010™. 
     The support portion  305  is a polymer material, such as high density polyurethane, polyethylene, a material sold under the tradename DELRIN®, PEEK, or another suitable polymer having sufficient hardness. The contact portion  300  is coupled to the support portion  305  by an adhesive  325 , such as a pressure sensitive adhesive, epoxy, or other suitable adhesive. 
     The polishing pad assembly is adhered to the flexible membrane  235  by the adhesive  325 . In some embodiments, the support portion  305  of the polishing pad assembly  125  is disposed in a recess  310  formed in the flexible membrane  235 . In some embodiments, the material used for the flexible membrane  235  has a hardness of between about 55 Shore A and about 65 Shore A. The flexible membrane has a thickness T of between about 1.45 mm to about 1.55 mm and a height H of between about 4.2 mm to about 4.5 mm. The contact surface  327  of the polishing pad assembly  125  has a surface area smaller than the surface area of the uppermost layer of the substrate, such as having an area less than about 5%, less than about 1%, or less than about 0.1% of the surface area of the uppermost layer of the substrate. For example, for a circular shaped contact surface  327 , the diameter D of the polishing pad assembly  125  is about 5 mm, which is an area of about 0.03% of the uppermost surface layer area of a 300 mm diameter substrate. However, in other embodiments, the contact surface  327  may have a different shape and/or a different size. 
       FIG. 4A  is a schematic sectional view of one embodiment of the eccentric member  255  disposed in the eccentric member housing volume  288 .  FIG. 4B  illustrates the path of the orbital polishing motion of the contact surface  327  provided by the embodiment shown in  FIG. 4A . In this embodiment, the inner wall  260  forms a circle around an axis F, which herein is also the center of contact surface  327  and which is offset from axis E. Herein, the inner wall  260  is in the shape of a circle and has a radius that is less than a radius formed by eccentric member  255  as it rotates about vertical axis E. As the shaft  250  rotates the eccentric member  255 , the eccentric member  255  pushes against the inner wall  260  causing the contact surface  327  to move in an orbital polishing motion relative to the vertical axis E. Herein, the contact surface  327  of the polishing pad assembly  125  is circular and is centered about center axis F, but in other embodiments it may be a different shape.  FIG. 4B  shows four different positions of center axis F and contact surface  327  as the eccentric member  255  makes one revolution about vertical axis E. The distance between the vertical axis E and the center axis F determines the polishing motion radius R of the contact surface  327 . In other embodiments, the polishing motion radius R can be increased by increasing the distance between vertical axis E and the center of the contact surface  327 . 
       FIG. 5A  is a schematic sectional view of another embodiment of the eccentric member  255  disposed in the eccentric member housing volume  288 .  FIG. 5B  illustrates an oscillating polishing motion, provided to the contact surface  327 , by the embodiment shown in  FIG. 5A . In this embodiment, the inner wall  260  is irregularly shaped, as the eccentric member  255  pushes against the inner wall  260  at the two opposite locations that have a radius smaller than the radius formed by the eccentric member  255  it causes the contact surface  327  to move in an oscillating polishing motion.  FIG. 5B  shows two different positions of center axis F and contact surface  327  as the eccentric member  255  makes one revolution about vertical axis E. 
       FIG. 6  is a schematic side cross-sectional view of an embodiment of a LSP module  600  used to practice the methods described herein. The LSP module  600  includes the chuck  110  coupled to a vacuum source. The chuck  110  comprises a substrate receiving surface  605  with a plurality of openings (not shown) in fluid communication with the vacuum source to secure a substrate (not shown) thereon. A drive device  120  rotates the chuck  110  around a center vertical axis. The polishing head  145  is coupled to the support arm  130 . The polishing head  145  has the structure thereof shown and described with respect to  FIG. 1  and the operations described with respect to  FIGS. 2 to 5B . 
     The support arm  130  is movably mounted on the base  105  through an actuator assembly  660 . The actuator assembly  660  includes a first actuator  625 A and a second actuator  625 B. The actuator assembly  660  moves the support arm  130  vertically (Z direction) and laterally (X direction, and thus along the radial direction of the substrate). The first actuator  625 A is used to move the support arm  130  (with the respective polishing head  145 ) vertically (Z direction) the second actuator  625 B is used to move the support arm  130  (with the respective polishing head  145 ) laterally (X direction), and a third actuator  625 C is used to move the support arm  130  (with the respective polishing head  145 ) in a sweep direction (theta direction). The first actuator  625 A may also be used to provide a controllable downforce that urges the polishing head towards the substrate receiving surface  605 . Other embodiments, not shown, may use more than one polishing pad assembly  125 , support arm  130 , actuator assembly  660 , and third actuator  625 C. 
     The actuator assembly  660  includes a linear movement mechanism  627 , such as a lead screw mechanism, a slide mechanism the position of which is controlled by an actuator, or ball screw coupled to the second actuator  625 B. Likewise, the first actuators  625 A is a linear movement device such as a lead screw mechanism, a slide mechanism the position of which is controlled by an actuator, a ball screw coupled to the support shaft  642 , or a cylinder slide mechanism that moves the support arm  130  vertically. The actuator assembly  660  also includes an actuator support arm  635 , first actuator  625 A and the linear movement mechanism  627 . A dynamic seal  640  may be disposed about a support shaft  642  that may be part of the first actuator  625 A. The dynamic seal  640  may be a labyrinth seal that is coupled between the support shaft  642  and the base  105 . The third actuator  625 C includes a motor coupled to the support arm  130  that provides a rotational motion to the support arm  130  around an axis G. 
     The support shaft  642  is disposed in an opening  644  formed in the base  105 , which allows the support arm  130  to move laterally as a result of axial movement of the actuator assembly  660 . The opening  644  is sized to allow sufficient lateral movement of the support shaft  642  such that the support arm  130  and polishing head  145  mounted thereon can move from a perimeter  646  of the substrate receiving surface  605  to the center thereof. Additionally, the opening  644  is sized to allow sufficient lateral movement of the support shaft  642  such that the end  648  of the support arm  130  can be located outwardly of the chuck perimeter  650  of the chuck  110 . Thus, when the polishing head  145  is moved outwardly to clear the chuck perimeter  650 , a substrate can be transferred onto or off of the substrate receiving surface  605  without interference form the polishing head  145 . The substrate may be transferred by a robot arm or end effector to or from a conventional polishing station before or after a conventional global CMP process. 
       FIG. 7  is a schematic plan view of the motion paradigm of the polishing pad assembly  125  and the substrate in an LSP module  700 , showing the positioning of the polishing pad assembly  125  relative to a rotating substrate  115  as described herein. The LSP module  700  may be similar to the LSP modules  100  and  600  shown in  FIGS. 1 and 6 . 
     A polishing pad assembly  125  is supported by the support arm  130  of  FIG. 6 . As shown in  FIG. 7 , the support arm  130  moves the polishing pad assembly  125  in one of, or a combination of, a radial direction  705  and a sweep direction  715  (theta direction). The rotary motion of the substrate  115 , in rotational direction  720  (theta direction), sweeps discrete portions of the substrate  115  under the polishing pad assembly  125 . The combined motions of the substrate  115  and the multiple degrees of freedom of motion of the polishing pad assembly  125  facilitate greater control and accuracy for polishing the substrate  115 . For example, the combined motions can create an oscillation mode along direction  705  and a circular polishing path. Along the polishing path  715  may, a lateral or random vibration of the polishing pad assembly is provided during polishing of the uppermost layer of the substrate. 
       FIG. 8  is a schematic plan view of the motion paradigm of an LSP module  800  showing various movements of the polishing pad assembly  125  with respect to the uppermost layer surface of a substrate  115 , caused by movement of both the polishing pad assembly and rotation of the substrate  115  during polishing. The LSP module  800  shown in  FIG. 8  may be similar to the LSP module  100  and  600  shown in  FIGS. 1 and 6 . 
     In one embodiment, the substrate  115  (mounted on the chuck  110  (shown in  FIGS. 1A-B  and  6 ) moves in rotational direction  720 . The rotational direction  720  can be a back and forth motion (e.g., clockwise and counterclockwise, or vice versa) or a continuous motion in the same direction, clockwise or counterclockwise. The polishing pad assembly  125  is mounted on the support arm  130  and can move on the sweep direction  710  facilitated by the support arm  130  moving about an axis B. While the support arm  130  moves about the axis B in order to move the polishing pad assembly  125  in the sweep direction  710 , the polishing pad assembly  125  is moved in a desired way to create a polish path  715 . In addition, while the support arm  130  moves about the axis B, and the polishing pad assembly  125  is moved in direction  715 , the substrate  115  is moved in the rotational direction  720 . In some embodiments, the system controller  190  is configured to coordinate the motion of the support arm  130  and the substrate  115  by controlling the actuators coupled to each. The rotational direction  720  may form an arc or circular shaped path. 
     The movement of the substrate  115  in the rotational direction  720  has an angular speed that is equivalent to an average rotational speed of between about 0.1 revolutions per minute (rpm) and about 100 rpm in some embodiments. The movement of the support arm  130  in the sweep direction  710  has an angular speed that is equivalent to an average rotational speed of between about 0.1 rpm and about 100 rpm in some embodiments. The movement of the polishing pad assembly  125  in the circular polishing motion  715  has a rotational speed of between about 100 rpm and about 5000 rpm, while the center of the pad is at an offset position from the center of rotation by a distance between about 0.5 mm and about 30 mm, in some embodiments. In some embodiments, a polishing downforce on the polishing pad assembly  125  is provided by a pressurized gas provided to a housing volume  225  of the polishing head  200 . The polishing downforce provided to the polishing pad assembly  125  is equivalent to a desirable pressure between about 0.1 psig and about 50 psig. 
       FIG. 9A  is an illustration showing a polishing path of the polishing pad assembly  125 , according to one embodiment disclosed herein, that may be produced on the substrate  115  using the motion modes shown in  FIGS. 7 and 8 . In this embodiment, the polishing path  905  is a spiral path starting where the polishing pad assembly  125  is urged against the substrate  115  at a beginning location  910  on the substrate and ending at an ending location  915  on the substrate. The polishing pad assembly  125  is urged against the substrate at the beginning location  910  using a first polishing recipe, the first polishing recipe comprising a polishing dwell time, a polishing downforce, and a polishing speed. As the polishing pad assembly traverses from the beginning location  910  to the ending location  915  it polishes a plurality of intermediate locations using one of a plurality of polishing recipes that correspond to each of the intermediate locations. The polishing downforce on the polishing pad assembly  125  is relieved between the intermediate locations so that the polishing pad assembly is pulled up from the surface of the substrate. In other embodiments the beginning location can be radially outward from the ending location so that the polishing pad assembly travels radially inward towards the center of the substrate. The width of the polishing path  905  is determined by the width of the contact surface area of the polishing pad and the radius of the orbital polishing motion. The polishing path  905  may or may not overlap itself as it traverses from the beginning location  910  to the ending location  915 .  FIG. 9B  is an illustration showing an area polished on the substrate between the beginning location  910  and the ending location  915  that comprises an annular shaped ring, according to another embodiment.  FIG. 9C  shows one or more polishing paths  905 , according to another embodiment. In this embodiment the polishing paths  905  resemble annular rings and a beginning and end of the polishing path may be at a same start stop location  930 . The polishing path  905  may be repeated at different radii from the center of the substrate  115  so that the area polished  920  resembles an annular ring. The polishing paths  905  may or may not overlap as they extend radially outwardly. 
       FIG. 10  is a flow diagram of a method for polishing a substrate, according to embodiments described herein. The method provides shorter correction polishing times by minimizing travel distance and travel time between each correction location on the substrate. For example, a substrate requiring material thickness correction of between about 20 Å and 200 Å or about 80 Å may be processed in less than about 10 minutes. It is also believed that the methods described herein improve within die range (WIDR) uniformity and result in improved step height polishing performance comparable to conventional CMP. 
     In one embodiment, the method  1000  begins at activity  1010  with measuring of the film thickness of a substrate. Measurements may be taken at specified locations on the substrate. In some embodiments, the specified locations may correspond to locations used throughout a device fabrication facility for SPC purposes, for example, at the locations corresponding to a standardized 17 point map for a 300 mm substrate. Each film measurement may be taken within a device die or may be taken at a dedicated measurement site in a scribe line between the die. 
     The method continues at activity  1020  with determining of a film thickness correction profile for the substrate. Determining the film thickness correction profile is based on the measurements taken in activity  1010  and/or a material removal profile for the substrate based on conventional CMP polishing of the substrate before or after the method disclosed herein. The material removal profile is used to determine a correction profile between the measurement sites of activity  1010 . The material removal profile is calculated from predictive modeling or determined using empirical data. 
     The method continues at activity  1030  with determining a plurality of polishing recipes for the substrate. Each of the plurality of recipes corresponds to a specific area of the substrate, such as an annular ring at a specified radius from a center of the substrate. Each of the plurality of recipes comprises at least one of a polishing downforce, a polishing dwell time, and a polishing motion speed. The polishing downforce is provided by the support arm, by the polishing head, or by another method. The polishing dwell time determines how long a polishing pad or polishing pad assembly remains in a location and how fast it traverses from one location to another. Polishing dwell time comprises the relative velocity of the rotating substrate support chuck, the substrate secured thereon, and the positioning motion of a support arm coupled to the polishing head. Polishing dwell time can be increased by reducing the rotational speed of the chuck, by reducing the rotational speed of the arm, or by a combination of both. Polishing speed comprises the rotational speed of a shaft deposed within the polishing head. Determining the polishing recipe commonly includes determining the polishing downforce, polishing dwell time, and polishing speed to remove a desired thickness of film as determined by the film thickness correction profile. 
     The method continues at activity  1040  with positioning a polishing pad or a polishing pad assembly at a first radius on the substrate. The first radius is determined from the film thickness correction profile. The polishing pad assembly is positioned by moving the support arm using a positioning motion, by moving the substrate, or by the combination thereof. The positioning motion is provided by rotating the support arm about an axis vertically disposed through a second end of the support arm or by moving the support arm laterally in an X direction, a Y direction, or a combination thereof. The substrate is moved by rotating the substrate support chuck or by moving the chuck laterally in an X direction, a Y direction, or a combination thereof. 
     The method continues at activity  1050  with polishing at a first radius of the substrate using a polishing recipe for the first radius. In some embodiments, polishing the substrate comprises a polishing motion of the polishing pad or polishing pad assembly, such as an orbital motion, an arcuate motion, a circular motion, an oscillating motion, a rotational motion of the polishing head, or a combination thereof. In other embodiments, the polishing motion is provided by the support arm. 
     The method continues at activity  1060  with moving the chuck, which has the substrate secured thereon, and at activity  1070  with moving the support arm using the positioning motion so the polishing pad assembly traverses from the first radius on the substrate to a second radius on the substrate. In some embodiments, the first radius is less than the second radius so that the polishing pad moves towards the edge of the substrate as it traverses from the first location to the second location. In other embodiments, the first radius is more than the second radius so the polishing pad assembly moves towards the center of the substrate as it traverses from the first location to the second location. 
     The method continues at activity  1080  with polishing the substrate at the second radius using a polishing recipe for the second radius. 
     In some embodiments, the relative motion of the chuck and the positioning motion of the support arm are combined to cause the polishing pad assembly to traverse a spiral shaped polishing path across the surface of the substrate between the first radius and the second radius. In some embodiments, the spiral shaped path does reach the center of the substrate, thus forming an annular ring about the center of the substrate. 
     In other embodiments, the method begins with inspecting a substrate for a residual film and determining a residual film thickness profile, followed by carrying out the activities of  FIG. 10  to polish the upper surface layer of the substrate and selectively remove the residual film. In embodiments that only use an optical inspection technique to inspect for residual metal film, thickness measurements are not available. In those embodiments, a material removal profile is used to determine a residual film thickness profile from the radial location and surface coverage of the residual metal film 
     The method described above may be used before or after conventional CMP. Benefits of the method include developing highly accurate correction profiles, and corresponding polishing recipes, without increasing the number of measurements needed on a substrate. Polishing recipes based on a radial distance from the center of the substrate minimize total processing time and maximize substrate throughput. 
     While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.