Abstract:
An apparatus capable of assisting in controlling an electrolyte flow and an electric field distribution used for processing a substrate is provided. It includes a rigid member having a top surface of a predetermined shape and a bottom surface. The rigid member contains a plurality of channels, each forming a passage from the top surface to the bottom surface, and each allowing the electrolyte and electric field flow therethrough. A pad is attached to the rigid member via a fastener. The pad also allows for electrolyte and electric field flow therethrough to the substrate.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a highly versatile apparatus for depositing, removing, modifying, or polishing a material on a workpiece, such as a substrate. More particularly, the present invention is directed to various pad designs and structures for depositing, removing, modifying and/or polishing a material on a suitable substrate.  
           [0003]    2. Description of Related Art  
           [0004]    There are numerous processing steps in the fabrication of high performance integrated circuits (ICs), packages, magnetic film heads, thin film display units, and the like. One important step is to deposit, remove, or planarize a conductive or insulative material on a workpiece, such as a semiconductor substrate. Deposition of conductive materials such as copper, gold, nickel, rhodium, and their various alloys may be performed, for example, by electrodeposition.  
           [0005]    In inlaid metal technology, a workpiece, such as a substrate  10  shown in FIG. 1 a , may consist of various topographical features such as channels  14  and vias  12  etched in a suitable dielectric material  16 . The surface of the etched dielectric material  16  is generally coated with a suitable adhesion/barrier film layer  18 . Over the barrier layer  18 , a suitable plating base layer  20 , often called a “seed layer”, is deposited. A conductive layer  20  is then applied over the plating base layer to fill, and preferably over-fill, the vias  12  and channels  14  etched in the dielectric material  16 .  
           [0006]    The conductive material may be, for example, Cu deposited by way of a chamber-type device  100  (generally shown in FIG. 1 b ) . The chamber device  100  includes a deposition chamber  102 , which contains an anode  104  and electrolyte  106 . The anode  104  may be attached to the bottom of the chamber  102 .  
           [0007]    A holder  108  holds the workpiece, such as the substrate  10 . For a detailed description of the holder, reference can be made to the assignee&#39;s co-pending application Ser. No. 09/472,523, entitled “Work Piece Carrier Head For Plating and Polishing” filed Dec. 27, 1999, the specification of which is incorporated by reference herein as non-essential matter.  
           [0008]    For the deposition process, the substrate  10  is typically immersed in the electrolyte  106  with the aid of the holder  108 , which also provides a way of electrically contacting the substrate  10 . By applying a potential difference between the anode  104  and the substrate  10  (i.e., the cathode), materials may be deposited on or removed from the substrate. For example, when the anode is more positive than the substrate, copper may be deposited on the substrate  10 . If the anode is more negative than the substrate, however, copper may be etched or removed from the substrate. To aid electrolyte agitation and enhance mass transfer, the substrate holder  108  may include a rotatable shaft  112  such that the substrate holder  108  and the substrate  10  can be rotated. The substrate  10  is typically spaced apart from the anode  104  at a distance of at least about 10 mm; this distance may, however, be as great as about 300 mm. The surface of the substrate  10  may contain topographic features, such as the vias  12  and channels  14  illustrated in FIG. 1 a . After performing material deposition to fill the various features/cavities using electrolyte containing leveling additives, a variation in the thickness of the deposited conductive material  22  inevitably occurs over the surface of the substrate. This variation in thickness is termed “overburden” and is shown in FIG. 1 c  with reference to portions  22   a  and  22   b.    
           [0009]    After depositing the conductive material  22  on the top surface of the substrate  10 , the substrate  10  is typically transferred to a chemical mechanical polishing (CMP) apparatus in order to polish, planarize, or both polish and planarize the same surface. FIG. 2 a  illustrates one possible version of a conventional CMP apparatus  200  used to polish/planarize the substrate  10  and/or electrically isolate the deposited conductive material within the particular features located thereon. The substrate holder  208 , which may be similar to the holder  108  described above, holds and positions the substrate  10  in close proximity to a belt-shaped CMP pad  214 . The belt-shaped pad  214  is adapted to rotate in an endless loop fashion about rollers  216 . The polishing/planarizing process occurs when the rollers  216  rotate and the pad  214  is moved with a circular motion while making contact with the surface of the substrate  10 . A conventional slurry may also be applied to the pad  214  while the substrate  10  is being polished. The substrate surface after polishing is shown in FIG. 2 b.    
           [0010]    The conventional method for depositing a conductive material produces large variations in material overburden across the substrate as shown in FIG. 1 c . The conventional CMP of this large overburden causes defects on the substrate  10  such as dishing  22   c  and dielectric erosion  16   c  also shown in FIG. 1 c . It also is responsible for low substrate processing throughput, which is a major source of manufacturing yield loss.  
         SUMMARY OF THE INVENTION  
         [0011]    There is therefore needed an apparatus that can reduce the time needed during the planarization phase of the fabrication process, and that can simplify the planarization phase itself. In other words, a more efficient and effective method and apparatus for depositing a conductive material on a substrate is needed. Various pad designs and structures are disclosed herein that can be used for depositing conductive material with a very uniform material overburden on a surface of a substrate.  
           [0012]    It is an object of the present invention to provide a method and apparatus for performing any of depositing, removing, polishing, and/or modifying operations on conductive material, which is to be applied to or has been applied on a substrate.  
           [0013]    It is another object of the present invention to provide a method and apparatus for depositing a conductive material with minimum material overburden.  
           [0014]    It is still another object of the invention to provide a method and apparatus for depositing a conductive material with a uniform material overburden across the surface of a substrate.  
           [0015]    It is a further object of the invention to provide a method and apparatus for depositing material on a substrate in an efficient and cost-effective manner.  
           [0016]    It is still a further object of this invention to provide various pad designs and structures for depositing a conductive material on a substrate.  
           [0017]    It is yet another object of this invention to provide a method for mounting a pad having channels, holes or grooves for depositing a conductive material on a substrate.  
           [0018]    It is a further object of this invention to provide a method and apparatus to mount a pad to be used for depositing a material on a surface.  
           [0019]    It is yet another object of the invention to provide a method and pad to control the uniformity of a deposited material on a substrate.  
           [0020]    These and other objects of the present invention are obtained by providing a method and apparatus for simultaneously plating and polishing a conductive material on a substrate. The substrate (or cathode in the deposition process) is disposed in close proximity to a rotating member having a pad material attached thereto. The pad is interposed between the substrate (cathode) and the anode. Upon applying an electrical current or potential between the substrate and the anode in the presence of a suitable electrolyte, the conductive material may be removed or deposited on the cathode.  
           [0021]    In a preferred embodiment, the conductive material may be selectively deposited in the cavities of topographical features on the substrate surface, while the pad material minimizes or prevents material depositions in regions above the cavities.  
           [0022]    The nature, design, fabrication and mounting of the pad material used in this invention advantageously allow for the modification of material removal from, or the deposition of a high quality conductive material on, a substrate surface.  
           [0023]    Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]    [0024]FIG. 1 a  is a partial cross-sectional view of a substrate having various material layers disposed thereon;  
         [0025]    [0025]FIG. 1 b  is a simplified illustration of a conventional deposition chamber for depositing a conductive material on a substrate;  
         [0026]    [0026]FIG. 1 c  is a partial cross-sectional view illustrating a variation in material overburden across the substrate after material deposition;  
         [0027]    [0027]FIG. 2 a  is a simplified illustration of a conventional CMP apparatus for polishing a substrate surface;  
         [0028]    [0028]FIG. 2 b  is-a partial cross-sectional view of a substrate after the conventional CMP process;  
         [0029]    [0029]FIG. 2 c  is a partial cross-sectional view, similar to FIG. 1 c , but showing a conductive layer having a uniform overburden across the substrate surface after deposition in a plating and polishing apparatus according to the invention;  
         [0030]    [0030]FIG. 3 a  illustrates an apparatus in accordance with a first preferred embodiment of the present invention;  
         [0031]    [0031]FIG. 3 b  is an enlarged view of the anode component of the apparatus shown in FIG. 3 a;    
         [0032]    [0032]FIG. 3 c  illustrates another embodiment of the anode component using a non-conducting, non-porous adhesive material;  
         [0033]    [0033]FIG. 4 a  illustrates an apparatus in accordance with a second preferred embodiment of the present invention;  
         [0034]    [0034]FIG. 4 b  illustrates an apparatus in accordance with a third preferred embodiment of the present invention;  
         [0035]    [0035]FIGS. 5 a - 5   m  schematically illustrate preferred embodiments of various plating and polishing pads using PSA adhesives, as well as PSA adhesive arrangements, for attaching a pad to a pad support member of the anode component;  
         [0036]    [0036]FIGS. 6 a - 6   h  each depict top and cross sectional schematic views of the plating and polishing pads having channels, holes, slits and/or grooves in accordance with the preferred embodiments of the present invention;  
         [0037]    [0037]FIGS. 7 a - 7   f  illustrate yet additional cross-sectional views of the plating and polishing pads having channels, holes, slits and/or grooves in accordance with the preferred embodiments of the present invention;  
         [0038]    [0038]FIG. 8 illustrates an apparatus in accordance with a fourth preferred embodiment of the present invention;  
         [0039]    [0039]FIGS. 9 a - 9   f  are top views of additional preferred embodiments of the plating and polishing pads according to the present invention;  
         [0040]    [0040]FIG. 10 is a partial cross-sectional view of a plating and polishing pad arranged over a pad support member in accordance with the present invention;  
         [0041]    [0041]FIG. 11 is an enlarged partial top-plan view of the structure according to FIG. 10;  
         [0042]    [0042]FIG. 12 is a schematic top-plan view of another embodiment of the plating and polishing pads according to the present invention;  
         [0043]    [0043]FIG. 13 is a schematic top-plan view of another embodiment of the plating and polishing pads according to the present invention;  
         [0044]    [0044]FIG. 14 is a schematic top-plan view of yet another embodiment of the plating and polishing pads according to the present invention; and  
         [0045]    [0045]FIG. 15 is a schematic top-plan view of still yet another embodiment of the plating and polishing pads according to the present invention 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0046]    The present invention will now be described in detail. Various refinements in and modifications of the various embodiments are possible based on the principles and teachings herein.  
         [0047]    The present invention can be used to deposit and/or remove materials on any substrate, such as a wafer, flat panel, magnetic film head, integrated circuit, package, semiconductor device or chip, or any other device or workpiece of interest. For purposes of this description, the terms “substrate” and “workpiece” can be used interchangeably. Further, the specific parameters referred to herein, such as materials, dimensions, thicknesses, and the like, are intended to be explanatory rather than limiting.  
         [0048]    [0048]FIG. 3 a  illustrates an apparatus  300  in accordance with the first preferred embodiment of the present invention. A substrate holder  308  having a rotatable shaft  312  holds and positions the substrate  10  in a manner similar to that described above. The substrate holder  308  can move up, down, and about the z-axis, as well as translate along the x- or y-axes. It has the ability to control the pressure at which the substrate  10  is pushed against a pad  330 . However, unlike known processes, both deposition and removal steps are performed using the apparatus illustrated in FIG. 3 a , which includes a novel cathode-pad-anode arrangement. For further details on this overall apparatus for performing both deposition and removal steps, reference can be made to assignee&#39;s co-pending U.S. application Ser. No. 09/201,929, filed Dec. 1, 1998 and titled “Method and Apparatus for Electrochemical Mechanical Deposition”, the specification of which is incorporated by reference herein as non-essential matter.  
         [0049]    In FIG. 3 a , an anode component, generally indicated at  322 , includes a bottom portion  322   a , which may be a soluble or inert anode material, attached to an anode holder or housing  322   b  by known methods. A stiff upper pad support member  320  is attached or secured to the anode holder  322   a . Electrically isolating the anode holder  322   b  from the stiff pad support member  320  is an insulating spacer  322   c.    
         [0050]    The pad support member  320  is secured to the anode holder  322   b  with screws in a manner such that they are both electrically isolated from one another. An electrolyte or solution chamber  322   e  is therefore formed between anode bottom portion  322   a  and the pad support member  320 . The gap  322   f  separates the anode bottom portion  322   a  from the pad support member  320 . Small channels  324  are formed in the pad support member  320  for fluid solutions to communicate between the chamber  322   e  to the substrate  10 . A polishing pad material  330  is attached above the pad support member  320 . The polish pad material  330  may contain two or more distinct types of channels. Channels  330   a  are provided for the fluids to communicate between the chamber  322   e  and the substrate  10 , and channels  330 b for mostly an electric field to communicate between the anode bottom portion  322   a , via the electrolyte chamber  322   e  and pad support member  330 , and the substrate  10 . The combination of channels (sometimes referred to as holes) are used to manipulate the electrolyte fluid flow and electric field distribution over the substrate  10  to control the nature of the material deposited on the substrate, in particular the uniformity of the deposit on the substrate.  
         [0051]    The pad material  330  is secured to the pad support member  320  with the aid of a fastener, such as an adhesive material  332 . The entire anode bottom portion-pad support member-pad assembly  322  is housed in another chamber  334 , in which electrolytes emanating from interface  334   b  between the substrate  10  and a surface of the pad material  330   b  accumulate. This accumulated electrolyte solution may be pumped into a reservoir system for reclaimation and reuse, or may just simply be discarded.  
         [0052]    It is further noted that electrical contact with the anode bottom portion  322   a  may occur directly or via the anode housing  322   b , while another electrical contact of opposite polarity is made to the substrate  10 . Thus, electrical contact need not be made to the pad support member  320 .  
         [0053]    By way of example, the anode housing  322   b  may be formed of soluble polymeric material such as PVDP, polypropylene, PTFE, and/or other materials that are essentially inert to the electrolyte fluids used in the reaction. However, it is most preferred that the anode housing  322   b  be made of titanium, stainless steel, graphite, and the like. The anode housing may also be coated with a very thin layer of platinum or palladium. The anode material itself may be an inert type of anode such as graphite, platinized metals, such as Pt/Ti and the like. In some inert anode applications, for simplification, the inner wall of the anode housing  322   b  may serve as the anode.  
         [0054]    In other applications, a soluble anode  322   a  may be housed in the anode housing  322   a . The soluble anode  322   a  may be formed by materials such as Cu, phosphorized Cu, Ni, gold, At, Ag, Cd, Rh and/or various other alloy electrode materials. The insulating sealing spacer  322   c  may be made of a polymeric material or a combination of polymeric/metallic and/or polymeric/ceramic materials. It is only essential that the electrolyte or fluids used in the reaction do not degrade the spacer  322   c , and/or that the spacer  322   c  does not adversely affect the designed qualities of the metal deposited on the substrate  10 . Additionally, the method of securing the pad support member  320  via the insulating spacer  322   c  must not electrically short the anode  322   a  to the pad support member  320 .  
         [0055]    The pad support member  320  is preferably fabricated from a stiff material with a very specific modulus, such as aluminum titanium and the like. Stainless steel may also be used. The pad support member material must not interact in an adverse manner with the deposition fluids so as to affect the material deposited on the substrate. The thickness of the pad support member  320  is such that the member behaves as if it has an infinite stiffness relative to itself (weight) and with respect to the applied polishing load. Additionally, the pad support member  320  may be coated with a very thin layer of platinum or palladium, e.g. about up to 500 Å, to enhance the adhesion of the pad material  330  and also to enhance the electric field dispersion.  
         [0056]    The anode housing  322   b  of FIG. 3 a  has at least one channel for fluid entry (not shown) such that the electrolyte fluid can fill the chamber  322   e  formed by the gap  322   f . The electrolytes then pass through the small channels or holes  324 ,  324   b  in the pad support member  320  and through the channels or holes  330   a  in the pad material  330  to a surface of the substrate  10 . The fluid exits the substrate surface as indicated at  334   b  and returns to the bottom of the outer chamber housing  334 , where it is drained via drain opening  334   c.    
         [0057]    Referring back to the channels or holes formed in the pad material  330 , more than one type of channel/hole with respect to the pad support member  320  or the anode  322   a  may be provided. For example, a first family of channels  330   a  (or holes, cavities, etc.) can be designed and positioned for fluid and electric field transfer from the electrolyte chamber  322   e  to the substrate. Hence, the channels  330   a  may be disposed directly on, or adjacent to, channels  324   b  formed in the pad support member  320  as shown in FIG. 3 a . Another family of holes or channels  330   b  are positioned with respect to the pad support member  320  (e.g., with the aid of the adhesive sheet  332 ), such that the electric field predominately communicates from the anode chamber  322   e  to the substrate  10  through these channels. Other channels may also be designed into the pad material  330  to enhance fluid shearing, mass transfer, and the like, at the substrate surface.  
         [0058]    [0058]FIG. 3 b  is an enlarged view of the anode component of FIG. 3 a  showing a configuration of channels in the pad material  330 . Here, the broken arrows indicate channels  330   b  designed for mostly electric field communication, while the solid arrows indicate channels  330   a  designed for mostly fluid communication. Thus, as shown by the solid/broken arrows, portions of the channels in the pad material  320  allow both the fluid and the electric field to communicate from the anode chamber  332   e  to the substrate. Other portions of the pad material predominantly allow the electric field to communicate as opposed to the electrolyte fluid.  
         [0059]    Combination of these families of channels  330   a ,  330   b  and placement of adhesive sheets  332  are used to control electrolyte and electric field distribution on the substrate  10 , and thus control the nature of the material deposited. More particularly, the uniformity of the deposited material can be controlled during plating or plating/polishing operations.  
         [0060]    In FIGS. 3 a  and  3   b , the anode-pad support member-pad material is depicted as being stationary. In fact, the combined unit may rotate and also translate in both lateral directions, similar to that of the substrate holder  308 .  
         [0061]    Referring back to the channels  324  arranged in the pad support member  320  and the channels  330   a  and  330   b  in the pad material  330 , these channels may have any shape, such as square, rectangular, etc., however, it is preferred that they be cylindrical in shape. The diameter of the channels may range from about 0.01 to 8 mm, preferably between about 0.03 to 6 mm.  
         [0062]    The number of channels in the pad support member  320  may range between about 1 to at least 1000, but preferably between about 10 to 800, depending on the dimensions of the pad support member. These channels may be distributed across the lateral dimensions of the pad support member in any profile that enhances fluid and electric field transfer through the channels. For instance, the channels may be spaced apart by about 0.5 to 50 mm, but preferably between about 1 to 20 mm. Also, the channels need not all be uniform, but may have varying dimensions and diameters.  
         [0063]    The channels  330   a  and  330   b  in the pad material  330  may be similar to those on the pad support member  320 . However, channels  330   b  are positioned in the pad material  330  so as to land on the pad support member away from channels  324 , or at least separated from channels  324  via an insulating or adhesive sheet material  332   x  (see FIG. 3 c ). As a result, fluids passing through channels  324  cannot communicate directly with channels  330   b . In this manner, the electrolytes flowing in channels  330   a  originate directly from channels  324  in the pad support member, while any fluids in channels  330   b  emanate from the fluids discharged from the channels  330   a . Besides the channels in the pad material, the dimensions of the pad material, e.g. the pad diameter, may also be smaller than-that of the substrate.  
         [0064]    Another embodiment of the invention is illustrated in FIG. 4. Here, a chamber, generally indicated at  405 , includes a lower chamber housing  404  and an upper chamber housing  407 . Arranged  411  in or on the lower chamber housing  404  are an anode  406 , which may be soluble or insoluble, electrolyte inlets  408  and  410 , and drains  412 ,  414 . The anode  406  may be stationary or may rotate. For rotating anodes, a top surface of the anode  406  may include shaped impellers to enhance fluid transfer and communication between the lower chamber and the upper chamber. The lower chamber housing  404  may also contain an anode holder (such as holder  322   b  of FIG. 3 a ) with particulate filtering arrangements.  
         [0065]    The entire chamber housing  404 ,  407  may be made of a polymeric material such as PVDF, or titanium, but preferably from stainless steel coated with a polymeric film such as PVDF, Teflon or other inert materials that do not adversely affect the performance of the electrolyte or deposited material.  
         [0066]    The lower chamber is separated from the upper chamber by an electrolyte filled space or gap  419  (when the tool is operational). The electrolyte gap  419  may vary in size from about 0.5 to 30 mm, but preferably between about 1 to 20 mm. This electrolyte gap  419  may serve as a mixing zone for electrolytes before entering the pad support member  420 . This is important in the deposition of laminate films, where metals of different composition are deposited. Thus, for example, one type of electrolyte may be injected via electrolyte inlet  408 , while a second electrolyte may be injected intermittently or at a different flow rate into the electrolyte gap  419  from the electrolyte inlet  410 . For example, one electrolyte may be injected at a flow rate of about 0.2 to 8 L/min through the electrolyte inlet  408 , while a second fluid may be injected intermittently or continuously through electrolyte inlet  410  at a rate ranging from about 2 cc to 20000 cc/min. A portion of the electrolyte mixing may occur within the electrolyte gap  419 . The balance of the mixing may occur within the pad support member  420 , or within the pad material itself and in the area between the pad material  430  and the substrate  10 .  
         [0067]    Separating the lower chamber from the upper chamber is the pad support member  420  (shown as part of the lower chamber in FIG. 4). The pad support member  420  is essentially a plate with openings or channels  424  allowing the electric field and electrolyte fluid or fluids to communicate between the lower chamber and the upper chamber. The channels  424  in the pad support member  420  can be of any shape. If they are cylindrical, their diameter may range from about 0.5 to 5 mm, and the spacing between the various channel openings may range from about less than 1 to greater than 4 times their diameter, but preferably between about 1 and 4 times. Also, the channels themselves in the pad support member  420  may vary in diameter. The range of variation in diameter preferably need not exceed 3 times that of the smallest channel opening. The pad support member  420  may be fabricated from a polymeric material, but preferably from titanium or stainless steel, a ceramic material, a high performance composite material, or some combination of the above materials. It is preferred than the pad support member  420  be coated with a very thin layer of Pt or palladium. The material preferably should not, however, degrade the performance of the electrolyte, degrade the deposited material on the substrate, or cause the pad material to react with the electrolyte.  
         [0068]    Also, the pad support member  420  should be sufficiently stiff to minimize its deformation or deflection during material deposition and planarization pressures. In addition, the mount for the pad support member should be designed to minimize deformation or deflection of the pad support member  420 . Thus, stiffeners (not shown) may be used as appropriate, on the lower surface of the pad support member  420  (surface facing the anode  406 ). It should be noted that the substrate holder  440  of FIG. 4 can move in the indicated x, y, and z directions, as well as rotate about the z-axis. The substrate holder  440  has the ability to control the pressure at which the substrate  10  is pushed against the pad  430 .  
         [0069]    The pad  430  is attached to the top surface of the pad support member  420  which faces the substrate  10 . The pad material preferably may contain fixed abrasives. The pad  430  has channels  432  of various shapes and forms. Their distribution on the pad  430  also varies depending on the functions to be carried out. In the present invention, the channels  432  in the pad  430  are designed to influence several important process parameters. These channels  432  determine the distribution of the electrolyte fluid or fluids over the surface of substrate  10 . The channels  432  also shape the electric field between the anode  406  and the substrate  10 . Proper choice of the pad material and the distribution of channel openings  432  on the pad  430 , as well as the channels  424  in the pad support member  420  (or the top anode portion  320  of FIG. 3 b ) allow the inventive apparatus to be used for many different tasks. These include depositing super planar metal layers over a topological surface of the substrate, depositing a material in a conventional way but with better properties, removing material by wet etch or electro-etch, or planarizing an already deposited material.  
         [0070]    The pad  430  may be attached to the pad support member  420  of FIG. 4 (or the top anode portion  320  of FIG. 3B) by a series of fine screws (not shown) that are recessed well into the pad material. Alternatively, the pad  430  may be attached to the pad support member  420  with a pressure sensitive adhesive (PSA). Regardless of the nature of the pad attachment, the materials used must be inert in the electrolyte and not degrade the electrolyte or the deposited material. As discussed previously, it is preferable that the pad support member  420 , which is disposed above the anode  406 , be stationary; however, it may also be designed to vibrate or otherwise move with up/down, translational and/or rotational movements. It should also be noted that in FIG. 4, the pad support member  420  does not form a part of the anode, and is not selectively rendered anodic with respect to the substrate. It&#39;s potential may be allowed to float.  
         [0071]    A third embodiment of the invention illustrated in FIG. 4 b  likewise includes a substrate holder  440  and substrate  10  as described earlier. The pad material  430  is arranged below the substrate  10  and is secured to the pad support member  420  via adhesive sheets  432 . Like the pad material  430 , the pad support member  420  also has its own fluid channels as described above. Electrolyte deposition solution E is fed into the pad support member  420  through a shaft  450  or other valving mechanism. Uniquely in this arrangement, the original flow volume of electrolyte E splits its flow into an anode compartment  452  (flow E 1 ) and directly to the substrate. The portion that is fed to the anode compartment  452  (or the anolyte) is further split into two portions. A major portion of this solution flows through a filter  454  (flow E 4 ) to the substrate by passing through the channels of the pad support member  420  and pad  430 . The other minor portion E 2  of the solution in the anode compartment  452  is allowed to leak out in a controlled manner at the uppermost corners of the anode chamber  452 . This controlled fluid leak E 2  allows air bubbles to escape and prevents their accumulation over the anode  406 . It also allows for the selective loss of anode sludge material in the case of soluble anode materials like CuP, where thick anode sludge may affect metal deposit uniformity. Thus, in this arrangement, the volume of electrolyte E 1  at any given time discharged into the anode chamber  452  is such that 
           E   1 = E   2 + E   4 , 
         [0072]    where E 2  is the allowed controlled leakage volume to help purge bubbles and anode fines, and the balance E 4  is the portion filtered through filter  454  and migrated to the substrate surface via the pad support member channels and pad channels.  
         [0073]    In a preferred embodiment, the amount of solution E 2  allowed to leak ranges between about 0.1 to 20%, but preferably between about 1 to 10% of the total electrolyte flow E 1 . Also, it is preferred that the volume E 4  of the electrolyte discharged into the anode chamber to minimize concentration polarization ranges between about 10 to 40%, but preferably between about 15 to 30% of the volume flow. Thus, the orifices in the shaft  450  discharging E 1  into the anode chamber  452  may be chosen accordingly.  
         [0074]    In FIG. 4 b , the anode  406  resides or is secured in anode housing  460 . A clearance gap  93  separates the anode housing  460  from portions of the pad support chamber adjacent to it. This clearance gap  93  is configured to allow for the controlled electrolyte leak E 2  in this region as described earlier. Besides the clearance gap, tiny holes (not shown), typically less than 0.5 mm in diameter, may be drilled around the top of the anode housing  460  to supplement the clearance gap to manage the controlled leak. One or more large ports may also be secured to this region to control the leak solution volume E 2 .  
         [0075]    The electrolyte E 3  emanating from the substrate and the controlled leakage solution E 2  may drain through a drain opening  462  at the bottom of the anode chamber  405 . These solutions are typically drained to a reservoir for process filtering, and then recycled back to the deposition chamber. Also in FIG. 4 b , as described earlier, the pad support member  420  may rotate. In this configuration, the anode housing  460  remains stationary. Electrolyte solution injected into the anode chamber  405  from a stationary or rotating pad support member causes excellent agitation of the electrolyte in the anode chamber  405 . The rotation of the pad support member  420  may range from about 3 to 400 rpm, but preferably between about 5 to 300 rpm.  
         [0076]    Referring again to FIG. 4 a , an example involving copper deposition will be described. A suitable copper plating solution is circulated from a reservoir through the lower chamber  404  from electrolyte inlet  408 . The anode  406  may rotate to help the expulsion of flow of the electrolyte from the lower chamber  404  to the upper chamber  407  via the channels  424  in the pad support member  422  and the channels  432  in the pad material  430 . Electrolyte flow may range between about 50 ml/min to about 12 L/min, but preferably between about 100 ml/min to 6 L/min depending on the size of the substrate  10 . The larger the substrate size, the higher the flow rate. As the fluids emanate through and wetten the pad  430 , the substrate  10  is lowered to rotate, glide or hydroplane on the surface of the wet pad  430 .  
         [0077]    The anode and cathode may be energized after a brief moment of wetting the substrate. The current density to the cathode may range between about 1 to 50 mA/cm 2 , but preferably between about 5 to 45 mA/cm 2 .  
         [0078]    For example, the substrate may be plated at a current density of about 10 to 25 mA/cm 2  for 20 to 70% of the deposition time at a pressure of about 0 to 0.5 psi, and at a higher pressure for the 30 to 80% balance of the deposition time. The pressure on the substrate may increase from 0 to 0.5 psi mentioned above to 0.5 to 3 psi. The electrolyte flow may also be varied within the intervals. Also during the deposition, the carrier head may make continuous or intermittent contact with the stationary pad or rotating pad. The substrate and the anode may rotate between about 2 to 250 rpm, but preferably between about 5 to 200 rpm. Also, lateral movement of the substrate relative to the pad may occur during the deposition process. The speed of the lateral motion ranged between about 0.5 to 15 mm/second.  
         [0079]    The lateral motion is programmed such that the substrate, while rotating, comes to rest momentarily at various points, or during any stage of its motion. In addition, the rotation of the substrate may be varied in such a manner that, for instance, the substrate is rotated at only about 60 to 85% of normal when the substrate is at one end of a smaller anode/pad than when the centers of the substrate and anode coincide.  
         [0080]    Also, the pressure on the substrate is varied depending on the later position of the substrate relative to the pad. Thus, for a given pad design, the combination of various lateral motions, substrate rotation, substrate pressure and electrolyte flow rate may be used to control the uniformity of the deposited material. The deposited material may be either uniform or thinner at the edge or center of the substrate. Using the above process, a superplanar metal deposit may be readily obtained when copper or any other metal is deposited over structures of the type shown in FIG. 1 a . A resulting superplanar deposition structure is shown in FIG. 2 c  , in which the material overburden across the substrate is nearly independent of the width of the features on the substrate. This contrasts with deposited material structures from conventional metal deposition systems as shown in FIG. 1 c.    
         [0081]    The apparatus of FIGS. 4 a  and  4   b  can also be used for etching. Using a shaped pad in which only a small quadrant or rectangular area is accessible to the electrolyte and the electric field, the substrate may be electro-polished or electro-etched in a very controlled manner. The difficulty with electro-etching using a standard pad is that because electric current flows from the substrate&#39;s edge towards its center, the material removal rate is higher closer to the electrical contacts. Hence, by making the channel openings arranged closer to the contacts smaller in diameter and fewer in number than those towards the center of the pad, the rate of metal removal by wet etch, electro-etching or polish may be rendered uniform from the center to the edge of the substrate, or may be dynamically controlled.  
         [0082]    The invention therefore describes an apparatus allowing for the deposition/removal of material on a substrate or workpiece surface while the surface is in static or dynamic contact with another surface. The other surface need not be the anode. The workpiece surface may be abrasive or non-abrasive in nature. It is essential, however, that the material of the other surface transmit fluid or electrolytes between an anode and a workpiece, as well as allow magnetic, electric or electromagnetic fields to communicate between the anode and the workpiece. In some portions, the pad contact material allows only the electric, magnetic or electromagnetic fields to communicate with the workpiece.  
         [0083]    Besides the choice of the pad material, the design and placement of the adhesive material  332  or  332   x  (in FIG. 3 b  and FIG. 3 c ) between the pad material  330  and the pad support member  320  may be used to control the electrolyte solution flow rate, electrolyte flow pattern, and the distribution of electromagnetic fields or electric fields. As illustrated in FIG. 3 c , for example, a continuous circular non-porous and non-conducting adhesive material  332   x  may be attached to the pad material  330  or pad support member  320  to block some selected flow channels  324   b  and  330   b . The presence of the blocking adhesive layer  332   x  redistributes the local electric field and electrolyte flow to the adjacent channels  324  and  330   a . On the other hand, if the adhesive material is conductive, it selectively blocks the electrolyte flow through the channels  324   b  and  330   b , while permitting the electric field flow. Some channels may therefore be designed to allow both the electrolyte and electric field to communicate between the anode and substrate, while other channels may selectively allow only the electric or magnetic field to communicate. The interplay between the electrolyte and electric/magnetic field flow through these channels controls the material deposition on the substrate, especially the uniformity of the deposit.  
         [0084]    In other embodiments, the adhesive material may be a conducting porous material. Also, a conducting adhesive material may be combined with a non-conducting adhesive to attach a pad to the surface of interest. The adhesive material may also be porous or transparent to electric fields, magnetic fields, and even the electrolyte.  
         [0085]    In yet other embodiments, the pad material and the adhesive material may selectively diffuse certain ions, e.g. cationst while preventing the diffusion of other ions. The criteria for selectivity may be by charge type, charge size, ion size, ratio of ion charge to ion size, and the like.  
         [0086]    In yet other embodiments, the pad  330  can be-attached/bonded to the support member  320  using any of the following alternative methods described herein. It is noted that methods other than those described herein can be implemented without departing from the principle teachings provided herein.  
         [0087]    [0087]FIGS. 5 a - 5   m  illustrate views of various plating and polishing pads having PSA adhesives attached thereto in accordance with preferred embodiments of the present invention, as well as PSA adhesives allowing the pad attachment to the top anode portion (or pad support member).  
         [0088]    [0088]FIG. 5 a  is a bottom view of a continuous circular adhesive  541  attached/bonded to the bottom of the pad  530   a . This prevents the electrolyte solution from leaking from the edge of the anode. Again, the adhesive  541  may be conducting or non-conducting, as well as porous or non-porous as described above. The width (shaded portion) of the circular adhesive  541  is generally between about 2 to 10 mm, depending on the size and shape of the pad  530   a.    
         [0089]    In FIG. 5 b , smaller strips of adhesives  542  are provided in addition to the continuous circular adhesive  541  attached to the bottom of the pad  530   b  as in FIG. 5 a . The smaller strips  542  are attached to the bottom of the pad  530   b  providing additional bonding between the pad  530   b  and the top anode plate. The smaller adhesive strips  542  have widths that are between about 1 to 5 mm and lengths between about 5 to 50 mm, and may have circular, rectangular, or square shapes. Preferably, the width is between about {fraction (1/50)} to ⅓ the length of the adhesive strips  542 . Moreover, although only three adhesive strips  542  are illustrated in FIG. 5 b , more or less can be used.  
         [0090]    In the embodiment of FIG. 5 c , discontinuous adhesive strip portions  544  are arranged about the periphery of the pad  530   c . The adhesive strips  544  are spaced apart at regular intervals of, for example, about ¼ to 2 times the length of the strips. Smaller adhesive strips  546  (similar to adhesive strips  542 ) may be used to provide additional bonding between the pad  530   c  and the top anode portion. This design can be used to increase the deposited metal thickness at the substrate&#39;s edge.  
         [0091]    In the embodiment of FIG. 5 d , multiple triangular shaped adhesives  548  are attached/bonded to the periphery of the pad  530   d . Alternatively, multiple circular shaped adhesives  549  can be attached to the periphery and central areas of the pad  530   e  as illustrated in FIG. 5 e . The circular shaped adhesives  549  can have a diameter between about 0.5 to 8 mm.  
         [0092]    [0092]FIG. 5 f  illustrates another embodiment in which adhesive strips  560  are secured over the anode between the channel openings, in addition to circularly arranged adhesive strips  541 .  
         [0093]    Similar PSA adhesive films are used to attach the pad to either the anode portion or the pad support member. Besides strips, a continuous perforated adhesive material sheet or ply  562  may be used as shown in FIG. 5 g . Here, the perforation holes  564  correspond more or less to the channel openings  532  in the pad  530 .  
         [0094]    As illustrated in FIG. 5 h , multiple pads may be laminated together, such as pad material  530   h  with subpad material  566 , using an adhesive spray or sheet  568 . In an alternate embodiment to the adhesive sheet  568  laminating the pad and subpad, FIGS. 5 i - 5   k  show an oversized continuous adhesive sheet material  570  used to attach the pad assembly to the anode portion (pad support member). The diameter of the adhesive sheet  570  is larger than that of the sub-pad  566  beneath it. The pad assembly is secured to the anode portion as shown in FIG. 5 k  using the overlapping portion(s)  570   p  of the sheet  570 .  
         [0095]    This presents a very practical method to assemble and secure the pad to an anode surface. The edges of the anode are fully sealed to prevent any undesirable fluid leakage. Thus, all the electrolyte emanates from the top of the pad in a controlled manner.  
         [0096]    The channels in the subpad need not align directly with those in the pad material above it. Often, it is advantageous to slightly displace the channels in both pads relative to each other, such that the solution does not spray out of the pad but, rather, oozes or migrates out of the pad.  
         [0097]    In another embodiment shown in FIG. 5 l , the subpad material is a napped polypropylene, polycarbonate or polyurethane type of fabric or material. The use of a fabric material  574  diffuses the flow of electrolyte such that the electrolyte migrates uniformly and evenly from the surface of the pad  530   l.    
         [0098]    The choice of the subpad material should allow the electric field to migrate freely through it with minimum resistance. In this way, the electric field distribution is determined by the channels/holes in the pad only. Also, the subpad material and the pad material may be laminated to form more than two layers to obtain optimum material deposition and removal characteristics.  
         [0099]    The entire pad structure or pad assembly may be shaped, such as by varying in thickness from its center to the edge. Thus, the pad assembly may be about 3-25% thicker in regions closer to the center than regions closer to the edge. These lateral variations in pad thickness may be necessary to overcome any substantial difference between material net deposition rates across the surface of the pad.  
         [0100]    Examples of shaped pads are shown in FIGS. 5 m   1 - 5   m   4 . In FIGS. 5 m   1  and  5   m   2 , these shapes are obtained by contouring the pads  530   ml  and  530   m   2 . In FIGS. 5 m   3  and  5   m   4 , pads are internally shaped by adding adhesive plys  580  and  582 , respectively. For example, a circular PSA type material  580  with its diameter about 20 to 70% smaller than the diameters of the top and sub pads may be inserted therebetween. Multiple layers having similar or different designs may be used to achieve the desired net material deposition uniformity across a substrate. In other applications, the subpad may not be necessary, thus the shaping ply may be bonded directly on top of the anode or pad support member.  
         [0101]    Adhesives other than those illustrated herein can be used to attach/bond the pad to the top anode portion (pad support member). These other adhesives may also be shaped in various configurations and in combinations of various shapes described herein so long as they are sufficient to provide a strong bond between the pad and the top anode portion (pad support member), while not degrading the deposited material on the substrate.  
         [0102]    As mentioned above, the shape, type, and placement of the adhesives on the pad is important in order to control the uniformity of the deposited material on the substrate. In certain embodiments, a combination of conductive and non-conductive adhesives may be used to obtain a desired level of uniformity. Further, depending on the type, shape, and placement of the adhesives in relation to the pad and the top anode portion or pad support member, the electrolyte solution and electric field distribution across the substrate can also be controlled. For example, when discontinuous sections of adhesives are used, portions of the electrolyte solution may emanate from regions between the adhesives to the pad. Then, the adhesive sheets are used as a fluid or electric field shield or deflector.  
         [0103]    Each of the pads described herein may include abrasive or non-abrasive materials. The pad thicknesses may range from about 0.2 to 20 mm, but preferably between about 0.4 to 10 mm. It is also desirable that the pads  330  be made of a material such as polyurethane, kevlar, glass fibers, ceramic fibers, polycarbonate, polyimide, electomerized epoxy and PVDF, polysulfone or other suitable materials or material combinations.  
         [0104]    One of the most important attributes of the pad material is that it does not degrade, contaminate or adversely affect the performance of the electrolyte solution. The pad material may be reinforced with hard abrasive particles. The abrasive particles may be titanium nitride, silicon carbide, cubic boron nitride, alumina, zirconia, diamond, ceria, hard ceramic powders, or hard metallic powders. Again, regardless of the type of abrasive particles used, the abrasive particles should not adversely affect the performance of the electrolyte solution, be dissolved by the electrolyte solution, or degrade the electrical and mechanical properties of the deposited metal layer.  
         [0105]    The size of the abrasive particles should be less than approximately  5000  nm, preferably between about 3 to 1000 nm, and most preferably between about 4 to 50 nm. The particle loading or volume fraction in the pad may range from about 5 to 75%, but most preferably range from about 5 to 60% for optimum performance.  
         [0106]    The abrasive content of the pad material may be varied radially from the center of the pad to the edge of the pad. For example, particle loading may be about 30-40% in the center and in regions around the center of the pad, and may be gradually reduced to about 5 to 15% at the periphery of the pad material. This gradation in particle distribution within the pad promotes uniform material removal across the pad, such that material removal by the pad is almost independent of the location of the pad. By way of example, for a nominal pad rotating at 100 rpm, the removal rate is expected to be lowest at the center of the rotating polishing pad, while it may be highest close to the periphery of the pad where the pad velocity with respect to the substrate is highest. Similarly, high abrasive loading in the pad material is expected to produced higher material removal rate. Thus, the abrasive loading in a pad may vary so as to effect equivalent removal rates radially across the pad material despite the velocity differences.  
         [0107]    Each of FIGS. 6 a - 6   h  illustrate top and cross sectional views of plating and polishing pads having one or more of channels, holes, slits and/or grooves in accordance with the preferred embodiments of the present invention. FIG. 6 a  illustrates a pad  630   a  having cylindrical channels  650 . The channels  650  extend fully through the pad  630   a  from its top surface to bottom surface as illustrated in the cross sectional view.  
         [0108]    In the embodiment of FIG. 6 b , the pad  630   b  includes polygonal-shaped channels  652 . Here, again, the polygonal channels  652  extend through the pad  630   b  from the top surface to the bottom surface. In certain embodiments, the channel openings  652  cover up to 65% of the pad&#39;s surface.  
         [0109]    [0109]FIG. 6 c  illustrates grooves/slits  654  formed on the top surface of the pad  630   c.  The grooves  654  are shaped to provide a high level of agitation and fluid dynamics on top of the pad near the surface of the substrate, which is difficult to obtain using conventional deposition methods. The groove dimensions can have about 0.5-2 mm depth, and be spaced apart from each other by about 2-15 mm. The grooves can be formed on the pad  630   c  in only one direction as shown in FIG. 6 c , or grooves  656  can be formed in multiple directions as shown in FIG. 6 d.    
         [0110]    In yet other embodiments, the plating and polishing pad may include both through channels and grooves. For example, FIGS. 6 e  and  6   f  illustrate top and cross sectional views of pads  630   e ,  630   f  having both. In FIG. 6 e , grooves  658  extend transversely with respect to one another on the top surface of the pad  630   e . In addition, channels  660  extend through the pad from the top surface to the bottom surface at locations so as not to intersect with the grooves. The channels  660  may have various cross-sectional shapes, such as the circular shape illustrated in FIG. 6 e , as well as other configurations such as a polygon, rectangle, square, or combinations thereof. In an alternative embodiment shown in FIG. 6 f , the grooves  662  extend horizontally and vertically, similar to those in FIG. 6 e , but the channels  664  are arranged to intersect the grooves  662 .  
         [0111]    In alternative embodiments, radial V-shaped grooves may be formed on the top surface of the pad. For example, FIG. 6 g  illustrates multiple substantially radially extending grooves  666  formed on the pad  630   g . FIG. 6 h  illustrates multiple V-shaped grooves formed on the pad  630   h . These grooves are shaped to enhance fluid transfer and agitation between the substrate and anode or second surface.  
         [0112]    In other instances, the grooves may be wedge-shaped with lips to enhance fluid shear and for continuous injection of the electrolyte solution toward the surface of the substrate. FIGS. 7 a - 7   f  are additional cross-sectional views of pads having both channels and grooves/slits in accordance with further preferred embodiments of the invention.  
         [0113]    In FIG. 7 a , grooves  770  intersect the channels  772  and are shaped such that the electrolyte solution is channeled to the substrate in a manner providing optimal fluid dynamics. The side walls  774  of the grooves  770  are inclined at an angle of between about 0 to 50 degrees with respect to a vertical plane. In other embodiments, such as one shown in FIG. 7 b , certain groove side walls  778 ,  776  may be angled 90 degrees with respect to a horizontal plane.  
         [0114]    In other embodiments of the present invention, narrow channels and grooves/slits may be used to enhance electrolyte solution flow to the substrate. Examples of various constructions are illustrated in FIGS. 7 c - 7   f . The width of the channels may range from about ⅛ to 3 times the thickness of the pad, and the depth may range from about 4 to 60 times the width of the particular channel. The spacing of the channels may range from about 5 to 50 times their width. The more channels/grooves that are present on the pad, the more vigorously the electrolyte solution is applied to the substrate. Thus, it is important to provide an appropriate number of channels/grooves in the pad such that there is a balance between the deposition and polishing rates. For example, forming channels that are closer than 3 mm apart from each other may lead to premature wear and tear on the pad. The channels need not extend perpendicular to the plane of the pad as shown in FIGS. 7 c  and  7   d . The channels can be inclined relative to a vertical plane at an angle from about 0 to 85 degrees, but preferably from about 15 to 80 degrees, as shown in FIGS. 7 e  and  7   f.    
         [0115]    A third embodiment of the apparatus according to the invention is shown in FIG. 8. Here, the plating and polishing pad  880  is shaped so as to be attached to the top anode portion (pad support member)  820  at its flanges  882  via a suitable arrangement such as a ring  884 . In this case, adhesive sheets may still be used to attach the pad  880  to the pad support member  820 . However, adhesive and non-adhesive sheets may still be used to shape and control electrolyte flow and electric field distribution.  
         [0116]    As discussed earlier, the apparatus using a shaped pad can perform electro-etching or workpiece surface modification. In this case, channels/holes/openings/slits or the like may be placed on the pad in substantially linear and non-linear fashion as shown in FIGS. 9 a  through  9   f . FIG. 9 a  depicts two linear arrays of holes  900 ,  901  punched in a pad material  930 . Both single or multiple arrays may be used. Moreover, for multiple linear arrays, it is beneficial if the holes are slightly staggered with respect to each other. In FIG. 9 b , the array of holes  903  originates around the center of the pad and extends only in one radial direction as opposed to diametrically across the pad, while in FIG. 9 c , a pie shaped geometric segmental array  904  of holes in disclosed.  
         [0117]    Other embodiments preferably use a slit fabricated into a pad such as by punching or cutting, as illustrated in FIGS. 9 d  to  9   f . In FIG. 9 d , a single slit  906  is shown, however, multiple slits may also be used. The slits may be segmented, forming a discontinuous array of slits. In addition to a radial slit  908  depicted in FIG. 9 e , a segmental radial slit  910  may also be fabricated into a pad  930  for electro-etching or surface modification applications. Here, the angle θ between the chord of the slit may range from about 0 to 250 degrees, but most preferably range from about 0 to 180 degrees.  
         [0118]    During electro-etching applications, the substrate is at a more positive potential than the anode. It is essential that the electrolyte and the electric field communicate to the substrate through the channels/holes/openings/slits, etc. in the pad material. During the etching removal process, either the anode carrying the pad or the substrate may be stationary, while the other component, disposed in close proximity, may rotate. The rotation of the substrate depends on the current density applied thereto. Thus, the material of interest may be completely removed in ½ to one full rotation of the substrate. At lower current densities, several rotations of the substrate around the anode may be needed. Also, only portions of the material on the substrate may be removed. In some applications the substrate may come into contact with the pad during the process operation. The combination of the electrolyte and mechanical work of the pad on the substrate may be used to modify the surface of the substrate.  
         [0119]    Returning to the material removal or deposition process, the linear or non-linear openings in the non-porous pad allow electric field distribution only through the openings. As the substrate or the pad is slowly rotated, the openings sweep over the substrate surface to be processed. The regions or portions of the substrate directly across from the openings in the pad are therefore plated in the case of deposition, etched in the case of substrate electro-removal (etch or polish), or just oxidized and then dissolved in the electrolyte with or without the mechanical actions of the pad. The openings can have various shapes. However, for uniform material removal or deposition/surface modifications, it is important that the pad and/or the substrate be rotated, such that all portions of the substrate surface are exposed to the electric field for some period of time.  
         [0120]    In certain preferred embodiments of the invention, the channel openings (orifices or perforations) in the pad support member  320  (anode portion) and the orifices in the pad material  330  arranged directly above can be of different dimensions. For example, FIG. 10 is a partial cross-section of the pad support member  320  and pad material  330  in which the diameter of the channel  10   a  in the pad support member  320  is less than the diameter of the channel lob in the pad material  330 . While FIG. 10 illustrates a concentric arrangement between the channels  10   a  and  10   b , this need not be the case. A top-plan view of the partial cross-section of FIG. 10 is shown in FIG. 11.  
         [0121]    The surface of the pad support member  320  (anode portion) arranged between the pad support member  320  and the pad material  330  as shown in FIGS. 10 and 11 may be used to control the uniformity of the metal deposited on the substrate. For example, the diameter of the channel loa in the pad support member  320  may range between about 0.3 to 1.5 mm, while the diameter of the channel  10   b  and the pad material  330  may range between about 1.7 to 7 mm. The portion  10   c  of the surface of the pad support member between the two channel openings  10   a  and  10   b , are regions where the electric field and the electrolyte are exposed to the substrate. By contrast, pad material regions  10   d  act as an insulating shield with respect to the substrate. Depending on the shaping of the channel openings in the pad material and the pad support member, the pad material may serve as both an anode and cathode shield. This is because it is in contact with both the anode and cathode simultaneously during material processing. The shield may selectively filter the electrolyte fluid, the electric field or the magnetic field in different proportions. This selective filtration of the deposition parameters is used to control the uniformity of the deposited/removed material, as well as the mechanical, electrical and magnetic properties of the process with respect to the surface of the material or substrate. Also, the net amount of material deposited on the substrate or removed from the substrate is further enhanced by the presence of abrasive material in the pad material, especially in the surface of the pad material.  
         [0122]    In a preferred embodiment, portions of the pad material in contact with the substrate act as insulators, however, in other embodiments, magnetic materials may be incorporated or laminated within the pad material. The incorporation of a magnetic material within the pad material may be used to filter or shield magnetic field communications through the material during the deposition of a magnetic film on the workpiece.  
         [0123]    Besides using circular or cylindrical channels or orifices in the various components, other geometries or combinations of geometries may be used. It is found particularly helpful to use slits and circular or cylindrical openings in the pad material to control local uniformity. FIG. 12, for example, is a top view of a pad in which a number of slits  120  are used near the edge of the pad material to increase the thickness of the material deposited at and/or near the edge of the substrate. The slits may be incorporated into pads with circular channels  121  designed to tune or tailor the local uniformities of the material deposits on the substrate or the removed materials from the substrate. FIG. 13 is an example in which an outwardly increasing diametrical hole size is used to increase the thickness of deposited material at and/or near the edge of the substrate.  
         [0124]    In certain material removal applications, it is often preferred that the material removal process proceed from at or near the center of the workpiece and decrease outwardly towards the periphery. In this case, it is especially advantageous that the larger sized channels in the pad material be arranged at or close to the center of the pad material as shown in FIGS. 14 and 15. In this case, the smaller holes in the pad material reside close to the periphery of the pad material. Also, the diameter or size of the holes may be graded, such that the diameter decreases from the center of the pad towards the edge or periphery of the pad.  
         [0125]    In yet another embodiment, the diameter or size of the pad material or the pad support member (or even the anode) may be smaller than the size of the substrate. For example, the diameter of the pad may be about 40% to 70% of the substrate. During material deposition, in the case when the anode and pad is preferentially arranged to one side of the chamber relative to the substrate, excessive material deposits may be observed on the portion of the substrate that continuously overlaps with the anode or pad material. This excess local deposit is a major source of deposit non-uniformity. This poor deposit uniformity is drastically reduced by shaping the pad material in such a manner that fewer and smaller holes or perforations are fabricated around the center of the pad, especially in the region of continuous overlap between the pad and the substrate. While large perforations may be fabricated away from the region of overlap and towards the periphery of the pad as shown in FIG. 13.  
         [0126]    The above-described channel or perforation distribution selectively enhances more electrolyte and electric field communication towards the larger openings in the pad, thus increasing metal deposition to this region.  
         [0127]    In the previous descriptions, numerous specific details are set forth, such as specific materials, structures, chemicals, processes, etc., in order to provide a thorough understanding of the present invention. However, as one having ordinary skill in the art recognizes, the present invention can be practiced without resorting to the details or specific embodiments set forth.  
         [0128]    The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.