Methods and systems for controlling current in electrochemical processing of microelectronic workpieces

Abstract

A method and system for electrolytically processing a microelectronic workpiece. In one embodiment, the method includes contacting the workpiece with an electrolytic fluid, positioning one or more electrodes in electrical communication with the workpiece, directing an electrical current through the electrolytic fluid from the electrodes to the workpiece or vice versa, and actively changing a distribution of the current at the workpiece during the process. For example, the current can be changed such that a current ratio of at least one electrical current to the sum of the electrical currents shifts from a first current ratio value to a second current ratio value. Accordingly, the current applied to the workpiece can be adjusted to achieve a target shape for a conductive layer on the workpiece, or to account for temporally and/or spatially varying characteristics of the electrolytic process.

I/We claim:  
     
         1 . A method for electrolytically processing a microelectronic workpiece, comprising: 
 contacting the microelectronic workpiece with an electrolytic fluid;    positioning at least one electrode in electrical communication with the electrolytic fluid;    directing at least one electrical current through the at least one electrode to produce a first current distribution in the electrolytic fluid; and    actively changing the first current distribution to produce a second current distribution in the electrolytic fluid while the microelectronic workpiece is in contact with the electrolytic fluid, the second current distribution being different than the first current distribution.    
     
     
         2 . The method of  claim 1  wherein the at least one electrode is one of a plurality of electrodes and wherein directing at least one electrical current includes directing a plurality of currents through the plurality of electrodes.  
     
     
         3 . The method of  claim 1  wherein directing at least one electrical current includes directing a plurality of electrical currents through a plurality of electrodes with a current ratio of the at least one of the electrical current to a sum of all of the electrical currents having a first current ratio value, and wherein actively changing the first current distribution includes directing the plurality of electrical currents through the plurality of electrodes with the current ratio having a second current ratio value.  
     
     
         4 . The method of  claim 1  wherein the microelectronic workpiece has an exposed layer of conductive material that is initially generally uniformly thick from a central region of the microelectronic workpiece to a peripheral region of the microelectronic workpiece, and wherein the method further comprises adding conductive material to the layer to increase a thickness of the layer at the central region by a first amount and increase the thickness of the layer at the peripheral region by a second amount greater than the first amount.  
     
     
         5 . The method of  claim 1  wherein the microelectronic workpiece has an exposed layer of conductive material that is initially generally uniformly thick from a central region of the microelectronic workpiece to a peripheral region of the microelectronic workpiece, and wherein the method further comprises adding conductive material to the layer to increase a thickness of the layer at the central region by a first amount and increase the thickness of the layer at the peripheral region by a second amount less than the first amount.  
     
     
         6 . The method of  claim 1  wherein the microelectronic workpiece has an exposed layer of conductive material that initially has a thickness with a first uniformity, and wherein the method further comprises adding conductive material to the layer to increase a thickness of the layer and increase a uniformity of the thickness from the first uniformity to a second uniformity.  
     
     
         7 . The method of  claim 1  wherein the microelectronic workpiece has a layer of conductive material, the layer having topographical features, and wherein the method further comprises directing the at least one electrical current to produce the first current distribution while the topographical features are being filled with conductive material, and directing the at least one electrical current to produce the second current distribution while conductive material is applied to the filled topographical features.  
     
     
         8 . The method of  claim 1  wherein current density is equivalent to current per unit area of the microelectronic workpiece, and wherein the method further comprises providing to a first portion of the microelectronic workpiece current at a first current density and providing to a second portion of the microelectronic workpiece current at a second current density, the first current density being at least approximately the same as the second current density, the first and second current densities being at least approximately equal to each other before and after actively changing the first current distribution.  
     
     
         9 . The method of  claim 1  wherein current density is equivalent to current per unit area of the microelectronic workpiece, and wherein the method further comprises: 
 filling features on the surface of the microelectronic workpiece by applying a negative potential to the microelectronic workpiece while directing the electrical currents through the plurality of electrodes; and  
 building a layer of conductive material on the microelectronic workpiece after the features have been filled by applying a negative potential to the microelectronic workpiece, wherein a current density distribution across a surface of the microelectronic workpiece is approximately the same while filling the features and while building the layer of conductive material.  
 
     
     
         10 . The method of  claim 1 , wherein current density is equivalent to current per unit area of the microelectronic workpiece, and wherein the method further comprises: 
 filling features on the surface of the microelectronic workpiece by providing to the microelectronic workpiece current at an approximately constant current density over the surface of the microelectronic workpiece; and    applying current to the microelectronic workpiece at a spatially varying current density to form a conductive layer having a selected shape.    
     
     
         11 . The method of  claim 1 , wherein current density is equivalent to current per unit area of the microelectronic workpiece, and wherein the method further comprises: 
 filling features on the surface of the microelectronic workpiece by providing to the microelectronic workpiece current at an approximately constant current density over the surface of the microelectronic workpiece; and    applying current to the microelectronic workpiece at a spatially varying current density to form a conductive layer having a generally concave profile, a generally convex profile or a generally flat profile.    
     
     
         12 . The method of  claim 1  wherein current density is equivalent to current per unit area of the microelectronic workpiece, and wherein directing at least one electrical current includes providing a first electrical current to an inner portion of the microelectronic workpiece at a first current density that is at least approximately constant with time, and providing a second electrical current to an outer portion of the microelectronic workpiece at a second current density that is at least approximately constant with time and that is at least approximately the same as the first current density.  
     
     
         13 . The method of  claim 1 , further comprising positioning a shield adjacent to the least one electrode while the microelectronic workpiece contacts the electrolytic fluid, and wherein actively changing the first current distribution includes changing a configuration and/or relative position of the shield while the first microelectronic workpiece is in contact with the electrolytic fluid.  
     
     
         14 . A method for electrolytically processing a microelectronic workpiece, comprising: 
 contacting the microelectronic workpiece with an electrolytic fluid;    positioning a plurality of electrodes in electrical communication with the electrolytic fluid;    directing a plurality of electrical currents through the plurality of electrodes with a current ratio of at least one of the electrical currents to a sum of all of the electrical currents having a first current ratio value; and    directing the plurality of electrical currents through the plurality of electrodes with the current ratio having a second current ratio value.    
     
     
         15 . The method of  claim 14  wherein the plurality of electrodes includes four electrodes, and wherein the method further comprises changing a current passing through each of the four electrodes while the electrodes are in fluid and electrical communication with the microelectronic workpiece.  
     
     
         16 . The method of  claim 14  wherein the microelectronic workpiece has an exposed layer of conductive material that is initially generally uniformly thick from a central region of the microelectronic workpiece to a peripheral region of the microelectronic workpiece, and wherein the method further comprises adding conductive material to the layer to increase a thickness of the layer at the central region by a first amount and increase the thickness of the layer at the peripheral region by a second amount greater than the first amount.  
     
     
         17 . The method of  claim 14  wherein the microelectronic workpiece has an exposed layer of conductive material that is initially generally uniformly thick from a central region of the microelectronic workpiece to a peripheral region of the microelectronic workpiece, and wherein the method further comprises adding conductive material to the layer to increase a thickness of the layer at the central region by a first amount and increase the thickness of the layer at the peripheral region by a second amount less than the first amount.  
     
     
         18 . The method of  claim 14  wherein the microelectronic workpiece has an exposed layer of conductive material that initially has a thickness with a first uniformity, and wherein the method further comprises adding conductive material to the layer to increase a thickness of the layer and increase a uniformity of the thickness from the first uniformity to a second uniformity.  
     
     
         19 . The method of  claim 14  wherein the microelectronic workpiece has a layer of conductive material, the layer having topographical features, further comprising selecting the current ratio to have the first current ratio value while the topographical features are being filled with conductive material, and selecting the current ratio to have the second current ratio value while conductive material is applied to the filled topographical features, the first current ratio value being different than the second current ratio value.  
     
     
         20 . The method of  claim 14  wherein directing the plurality of electrical currents with the current ratio having a second current ratio value includes changing the current ratio while the microelectronic workpiece is in electrical communication with the plurality of electrodes.  
     
     
         21 . The method of  claim 14  wherein current density is equivalent to current per unit area of the microelectronic workpiece, and wherein the method further comprises providing to a first portion of the microelectronic workpiece current at a first current density and providing to a second portion of the microelectronic workpiece current at a second current density, the first current density being at least approximately the same as the second current density.  
     
     
         22 . The method of  claim 14  wherein current density is equivalent to current per unit area of the microelectronic workpiece, and wherein the method further comprises: 
 filling features on a surface of the microelectronic workpiece by applying a negative potential to the microelectronic workpiece while directing the electrical currents through the plurality of electrodes; and  
 building a layer of conductive material on the microelectronic workpiece after the features have been filled by applying a negative potential to the microelectronic workpiece, wherein a current density distribution across a surface of the microelectronic workpiece is approximately the same while filling the features and while building the layer of conductive material.  
 
     
     
         23 . The method of  claim 14 , wherein current density is equivalent to current per unit area of the microelectronic workpiece, and wherein the method further comprises: 
 filling features on a surface of the microelectronic workpiece by providing to the microelectronic workpiece current at an approximately constant current density over the surface of the microelectronic workpiece; and    applying current to the microelectronic workpiece at a spatially varying current density to form a conductive layer having a selected shape.    
     
     
         24 . The method of  claim 14 , wherein current density is equivalent to current per unit area of the microelectronic workpiece, and wherein the method further comprises: 
 filling features on a surface of the microelectronic workpiece by providing to the microelectronic workpiece current at an approximately constant current density over the surface of the microelectronic workpiece; and    applying current to the microelectronic workpiece at a spatially varying current density to form a conductive layer having a generally concave profile, a generally convex profile or a generally flat profile.    
     
     
         25 . The method of  claim 14  wherein current density is equivalent to current per unit area of the microelectronic workpiece, and wherein directing a plurality of electrical currents includes providing a first electrical current to an inner portion of the microelectronic workpiece at a first current density that is at least approximately constant with time, and providing a second electrical current to an outer portion of the microelectronic workpiece at a second current density that is at least approximately constant with time and that is at least approximately the same as the first current density.  
     
     
         26 . The method of  claim 14 , further comprising changing the current ratio in a generally monotonic, incremental manner between the first current ratio value and the second current ratio value.  
     
     
         27 . The method of  claim 14  wherein the plurality of electrodes includes a first electrode in electrical communication with a first portion of the microelectronic workpiece and a second electrode in electrical communication with a second portion of the microelectronic workpiece positioned outwardly from the first portion, and wherein the method further comprises decreasing an electrical current applied to the first electrode relative to an electrical current applied to the second electrode and/or increasing an electrical current applied to the second electrode relative to an electrical current applied to the first electrode.  
     
     
         28 . The method of  claim 14 , further comprising applying a copper material to the microelectronic workpiece in an electrolytic deposition process.  
     
     
         29 . The method of  claim 14 , further comprising applying to the microelectronic workpiece at least one of a metal and a metal alloy in an electrolytic deposition process.  
     
     
         30 . The method of  claim 14  wherein the plurality of electrodes function as anodes and wherein the microelectronic workpiece functions as a cathode, and wherein the method further comprises adding electrically conductive material to the microelectronic workpiece.  
     
     
         31 . The method of  claim 14  wherein the plurality of electrodes function as cathodes and wherein the microelectronic workpiece functions as an anode, and wherein the method further comprises removing electrically conductive material from the microelectronic workpiece.  
     
     
         32 . The method of  claim 14  wherein directing the electrical currents through the electrolytic fluid includes directing the electrical currents through an electrolytic fluid having a conductivity of from about 5 mS/cm to about 500 mS/cm.  
     
     
         33 . The method of  claim 14  wherein the microelectronic workpiece is a first microelectronic workpiece, and wherein the method further comprises changing a conductivity of the electrolytic fluid after contacting the first microelectronic workpiece with the electrolytic fluid and before contacting a second microelectronic workpiece with the electrolytic fluid.  
     
     
         34 . The method of  claim 14  wherein the microelectronic workpiece is a first microelectronic workpiece, and wherein the method further comprises: 
 positioning a shield adjacent to at least one of the electrodes while the first microelectronic workpiece contacts the electrolytic fluid; and  
 changing a configuration and/or relative position of the shield after contacting the first microelectronic workpiece with the electrolytic fluid and before contacting a second microelectronic workpiece with the electrolytic fluid.  
 
     
     
         35 . The method of  claim 14  wherein the sum of the electrical currents remains constant as the current ratio changes.  
     
     
         36 . The method of  claim 14  wherein the sum of the electrical currents changes as the current ratio changes.  
     
     
         37 . A method for electrolytically processing a microelectronic workpiece, comprising: 
 contacting the microelectronic workpiece with an electrolytic fluid;    positioning a plurality of electrodes and electrical communication with the electrolytic fluid, the plurality of electrodes including a first electrode and a second electrode;    directing a first electrical current through the first electrode and a first portion of the microelectronic workpiece;    directing a second electrical current through the second electrode and a second portion of the microelectronic workpiece while the first electrical current is directed through the first electrode and the first portion of the microelectronic workpiece, wherein a first current ratio of the first electrical current to a sum of the first and second electrical currents has a first value, and wherein a second current ratio of the second electrical current to a sum of the first and second electrical currents has a second value;    changing the first current ratio from the first value to a third value and directing the first electrical current at the third value; and    changing the second current ratio from the second value to a fourth value and directing the second electrical current at the fourth value.    
     
     
         38 . The method of  claim 37  wherein the microelectronic workpiece has a layer of conductive material, the layer having topographical features, and wherein changing the first current ratio includes selecting the first current ratio to have the first value while the topographical features are being filled with conductive material, and selecting the first current ratio to have the third value while conductive material is applied to the filled topographical features, the first value being different than the third value.  
     
     
         39 . The method of  claim 37 , further comprising: 
 directing a fifth electrical current through the electrolytic fluid between a third electrode and a third portion of the microelectronic workpiece while directing the first and second electrical currents; and    directing a sixth electrical current through the electrolytic fluid between a fourth electrode and a fourth portion of the microelectronic workpiece while directing the first and second electrical currents.    
     
     
         40 . The method of  claim 37  wherein current density is equivalent to current per unit area of the microelectronic workpiece, and wherein the method further comprises providing to the first portion of the microelectronic workpiece current at a first current density and providing to the second portion of the microelectronic workpiece current at a second density, the first current density being at least approximately the same as the second current density.  
     
     
         41 . The method of  claim 37  wherein the second portion of the microelectronic workpiece is positioned outwardly from the first portion of the microelectronic workpiece, and wherein changing the first current ratio includes decreasing an electrical current applied to the first electrode relative to an electrical current applied to the second electrode and/or increasing an electrical current applied to the second electrode relative to an electrical current applied to the first electrode.  
     
     
         42 . The method of  claim 37  wherein directing the first electrical current through the electrolytic fluid includes directing the first electrical current through an electrolytic solution having a conductivity of from about 5 mS/cm to about 500 mS/cm.  
     
     
         43 . The method of  claim 37  wherein directing the first electrical current through the electrolytic fluid includes directing the first electrical current through an electrolytic fluid having a conductivity of about 5 mS/cm or less to about 500 mS or more.  
     
     
         44 . A method for electrolytically processing a microelectronic workpiece, comprising: 
 contacting a surface of the microelectronic workpiece with an electrolytic fluid;    positioning a plurality of electrodes in electrical communication with the microelectronic workpiece, the plurality of electrodes including at least a first electrode and a second electrode;    directing a first electrical current through the electrolytic fluid between the first electrode and a first portion of the microelectronic workpiece;    directing a second electrical current through the electrolytic fluid between the second electrode and a second portion of the microelectronic workpiece while the first electrical current is directed between the first electrode and the first portion of the microelectronic workpiece;    varying the first and second electrical currents as a function of time while directing the first and second electrical currents and while the microelectronic workpiece contacts the electrolytic fluid;    while the first electrical current varies with time, providing the first electrical current at a current density per unit area of the microelectronic workpiece that varies by less than about 10% of a 3σ value over the surface of the microelectronic workpiece; and    while the second electrical current varies with time, providing the second electrical current at a current density per unit area of the microelectronic workpiece that varies by less than about 10% of a 3σ value over the surface of the microelectronic workpiece.    
     
     
         45 . The method of  claim 44  wherein providing the first electrical current includes providing the first electrical current at a current density per unit area of the microelectronic workpiece that varies by less than about 5% of a 3σ value over the surface of the microelectronic workpiece, and wherein providing the second electrical current includes providing the second electrical current at a current density per unit area of the microelectronic workpiece that varies by less than about 5% of a 3σ value over the surface of the microelectronic workpiece.  
     
     
         46 . The method of  claim 44  wherein the second portion of the microelectronic workpiece is disposed outwardly from the first portion, and wherein varying the first electrical current as a function of time includes changing a ratio of the first electrical current to a sum of the first and second electrical currents, further wherein varying the second electrical current as a function of time includes changing a ratio of the second current to a sum of the first and second electrical currents.  
     
     
         47 . The method of  claim 44  wherein varying the first and second electrical currents as a function of time includes temporally changing a ratio of the first electrical current to a sum of electrical currents passing through all electrodes in fluid and electrical communication with the microelectronic workpiece and temporally changing a ratio of the second electrical current to the sum electrical currents passing through all electrodes in fluid and electrical communication with the microelectronic workpiece.  
     
     
         48 . The method of  claim 44  wherein the microelectronic workpiece has a layer of conductive material, the layer having topographical features, the layer having a thickness that is different at an inner portion of the microelectronic workpiece than at an outer portion of the microelectronic workpiece, and wherein varying the first and second electrical currents as a function of time includes selecting a ratio of the first electrical current to a first sum of all electrical currents passing through the microelectronic workpiece to have a first value while the topographical features are being filled with conductive material, and selecting a ratio of the first electrical current to a second sum of all electrical currents passing through the microelectronic workpiece to have a second value while conductive material is applied to the filled topographical features, the first value being different than the second value.  
     
     
         49 . The method of  claim 44  wherein varying the first and second electrical currents as a function of time includes applying to the first electrode a current at a first value while filling features on a surface of the microelectronic workpiece, and applying to the first electrode a current at a second value while building a layer of conductive material on the microelectronic workpiece after the features have been filled.  
     
     
         50 . The method of  claim 44 , further comprising: 
 directing a third electrical current through the electrolytic fluid between a third electrode and a third portion of the microelectronic workpiece;    directing a fourth electrical current through the electrolytic fluid between a fourth electrode and a fourth portion of the microelectronic workpiece; and    varying the third and fourth electrical currents as a function of time while directing the third and fourth electrical currents and while the microelectronic workpiece contacts the electrolytic fluid.    
     
     
         51 . The method of  claim 44  wherein the first and second portions of the microelectronic workpiece are disposed outwardly from a third and fourth portion of the microelectronic workpiece, and wherein a third electrode is positioned in fluid and electrical communication with the third portion, further wherein a fourth electrode is positioned in fluid and electrical communication with the fourth portion, and wherein the method further comprises providing to the first and second portions of the microelectronic workpiece current at a first current per unit area of the microelectronic workpiece and providing to the fourth portion of the microelectronic workpiece current at a second current per unit area of the microelectronic workpiece, the first current per unit area being at least approximately constant while the first and second electrodes are in electrical communication with the microelectronic workpiece, the second current per unit area temporally varying while the fourth electrode is in electrical communication with the microelectronic workpiece.  
     
     
         52 . The method of  claim 44 , further comprising: 
 filling features on a surface of the microelectronic workpiece by applying a negative potential to the microelectronic workpiece while directing the first and second currents; and    building a layer of conductive material on the microelectronic workpiece after the features have been filled by applying a negative potential to the microelectronic workpiece while directing the first and second currents, wherein a current per unit area of the of the microelectronic workpiece is approximately the same while filling the features and while building the layer of conductive material.    
     
     
         53 . The method of  claim 44  wherein directing the first electrical current through the electrolytic fluid includes directing the first electrical current through an electrolytic solution having a conductivity of about 5 mS/cm to about 500 mS/cm.  
     
     
         54 . A method for electrolytically processing a microelectronic workpiece, comprising: 
 contacting a surface of the microelectronic workpiece with an electrolytic fluid;    positioning a plurality of electrodes in electrical communication with the microelectronic workpiece, the plurality of electrodes including at least a first electrode and a second electrode;    directing a first electrical current through the electrolytic fluid between a first electrode and a first portion of the microelectronic workpiece;    directing a second electrical current through the electrolytic fluid between a second electrode and a second portion of the microelectronic workpiece while the first electrical current is directed between the first electrode and the first portion of the microelectronic workpiece;    applying the first electrical current at a first value while filling features of the microelectronic workpiece with conductive material, then applying the first electrical current at a second value different than the first value while applying conductive material to the filled features; and    applying the second electrical current at a first value while filling features of the microelectronic workpiece with conductive material, then applying the second electrical current at a second value while applying conductive material to the filled features, wherein a ratio of the first value of the first current to a sum of the first values of the first and second currents is different than a ratio of the second value of the first current to a sum of the second values of the first and second currents.    
     
     
         55 . The method of  claim 54 , further comprising changing a ratio of the first electrical current to the sum of the first and second electrical currents as a function of time and changing a ratio of the second electrical current to the sum of the first and second electrical currents as a function of time.  
     
     
         56 . The method of  claim 54  wherein the first electrode is in electrical communication with a first portion of the microelectronic workpiece and the second electrode is in electrical communication with a second portion of the microelectronic workpiece positioned outwardly from the first portion, and wherein the method further comprises decreasing an electrical current applied to the first electrode relative to an electrical current applied to the second electrode and/or increasing an electrical current applied to the second electrode relative to an electrical current applied to the first electrode.  
     
     
         57 . The method of  claim 54  wherein directing the first electrical current through the electrolytic fluid includes directing the first electrical current through an electrolytic solution having a conductivity of from about 5 mS/cm to about 500 mS/cm.  
     
     
         58 . The method of  claim 54  wherein directing the first electrical current through the electrolytic fluid includes directing the first electrical current through an electrolytic fluid having a conductivity of about 5 mS/cm or less to about 500 mS/cm or more.  
     
     
         59 . A method for electrolytically processing a microelectronic workpiece, comprising: 
 contacting the microelectronic workpiece with an electrolytic fluid, the microelectronic workpiece having an inner region, an outer region disposed outwardly from the inner region, and a conductive layer disposed on the inner region and the outer region;    removing conductive material from the conductive layer in the outer region cover zero or non-zero; and    after removing conductive material from the conductive layer in the outer region, simultaneously adding conductive material to the conductive layer in both the outer region and the inner region.    
     
     
         60 . The method of  claim 59  wherein removing conductive material from the conductive layer in the outer region includes removing conductive material at a first rate, and wherein the method further comprises removing conductive material from the conductive layer in the inner region at a second rate less than the first rate.  
     
     
         61 . The method of  claim 59 , further comprising adding conductive material to the conductive layer in the inner region and the outer region prior to removing conductive material from the conductive layer.  
     
     
         62 . The method of  claim 59 , further comprising positioning first and second electrodes in electrical communication with the microelectronic workpiece, the first electrode being disposed inwardly from the second electrode, and wherein removing conductive material in the outer region while adding conductive material to the conductive layer in the inner region includes removing material to the second electrode and adding conductive material from the first electrode.  
     
     
         63 . The method of  claim 59  wherein simultaneously adding conductive material to the conductive layer in both the outer region and the inner region includes directing a first current through the electrolytic fluid between a first electrode and the inner region and directing a second current through the electrolytic fluid between a second electrode and the outer region.  
     
     
         64 . The method of  claim 59  wherein simultaneously adding conductive material to the conductive layer in both the outer region and the inner region includes directing a first current through the electrolytic fluid between a first electrode and the inner region, directing a second current through the electrolytic fluid between a second electrode and the outer region, and varying the first and second currents over time while the microelectronic workpiece contacts the electrolytic fluid.  
     
     
         65 . A method for electrolytically processing a microelectronic workpiece, comprising: 
 contacting the microelectronic workpiece with an electrolytic fluid, the microelectronic workpiece having an inner region, an outer region disposed outwardly from the inner region, and a conductive layer disposed on the inner region and the outer region;    directing conductive material from a first electrode toward the microelectronic workpiece;    attracting to a second electrode spaced apart from the first electrode and the microelectronic workpiece at least a portion of the conductive material in the electrolytic fluid that would otherwise attach to the microelectronic workpiece;    while attracting at least a portion of the conductive material to the second electrode, adding at least a portion of the conductive material to the conductive layer in at least the inner region;    changing a current applied to the first electrode as a function of time; and    after attracting at least a portion of the conductive material to the second electrode, simultaneously adding conductive material to the conductive layer in both the outer region and the inner region.    
     
     
         66 . The method of  claim 65  wherein attracting to the second electrode at least a portion of the conductive material includes changing a rate at which at least a portion of the conductive material is attracted to the second electrode.  
     
     
         67 . The method of  claim 65  wherein simultaneously adding conductive material to the conductive layer in both the outer region and the inner region includes directing a first current through the electrolytic fluid between a first electrode and the inner region, directing a second current through the electrolytic fluid between a second electrode and the outer region, and varying the first and second currents over time while the microelectronic workpiece contacts the electrolytic fluid.  
     
     
         68 . The method of  claim 65  wherein simultaneously adding conductive material in both the outer region and the inner region includes applying a first electrical current to the first electrode and applying a second electrical current to the second electrode, and wherein changing a current applied to the first electrode includes changing a ratio of the first electrical current to a sum of the first and second electrical currents as a function of time.  
     
     
         69 . A method for electrolytically processing a microelectronic workpiece, comprising: 
 contacting a surface of a microelectronic workpiece with an electrolytic fluid;    directing a plurality of electrical currents from a corresponding plurality of electrodes through the electrolytic fluid and to a corresponding plurality of portions of the microelectronic workpiece;    for each electrical current, varying a ratio of the electrical current to a sum of electrical currents applied to the microelectronic workpiece; and    for each portion of the microelectronic workpiece at any point in time, maintaining a current density per unit area of the microelectronic workpiece at approximately the same value while the microelectronic workpiece contacts the electrolytic fluid.    
     
     
         70 . The method of  claim 69 , further comprising maintaining approximately the same current density per unit area of the microelectronic workpiece while features are being filled and while the conductive material is applied to the filled features.  
     
     
         71 . A system for electrolytically processing a microelectronic workpiece, comprising: 
 a processing station having a vessel configured to carry an electrolytic fluid, the processing station further having at least one contact and at least one electrode configured to be in electrical communication with the microelectronic workpiece to produce a first current distribution at a surface of the microelectronic workpiece; and    a device operatively coupled to the processing station to actively change the first current distribution and produce a second current distribution at the surface of the microelectronic workpiece while the microelectronic workpiece is in contact with the electrolytic fluid, the second current distribution being different than the first current distribution.    
     
     
         72 . The system of  claim 71  wherein the at least one electrode is one of a plurality of electrodes and wherein the device includes a controller having a computer operable medium with contents capable of: 
 directing a plurality of electrical currents through the plurality of electrodes, with a current ratio of at least one of the electrical currents to a sum of all of the electrical currents having a first current ratio value; and  
 changing the current ratio from the first current ratio value to a second current ratio value and directing the at least one electrical current at the second current ratio value through one of the electrodes.  
 
     
     
         73 . The system of  claim 71  wherein the microelectronic workpiece has a layer of conductive material, the layer having topographical features, and wherein the at least one electrode is one of a plurality of electrodes, further wherein the at least one electrode is one of a plurality of electrodes and wherein the device includes a controller having a computer operable medium with contents capable of: 
 directing a plurality of electrical currents through the plurality of electrodes, with a current ratio of at least one of the electrical currents to a sum of all of the electrical currents having a first current ratio value; and  
 changing the current ratio from the first current ratio value to a second current ratio value and directing the at least one electrical current at the second current ratio value through one of the electrodes with the current ratio of the at least one electrical current having the first value while the topographical features are being filled with conductive material, and having the second value while conductive material is applied to the filled topographical features, the first value being different than the second value.  
 
     
     
         74 . A system for electrolytically processing a microelectronic workpiece, comprising: 
 a processing station having a vessel configured to carry an electrolytic fluid, the processing station further having at least one contact and a plurality of electrodes, all configured to be in electrical communication with the microelectronic workpiece; and    a controller having a computer operable medium with contents capable of: 
 directing a plurality of electrical currents through the plurality of electrodes, with a current ratio of at least one of the electrical currents to a sum of all of the electrical currents having a first current ratio value; and  
 changing the current ratio from the first current ratio value to a second current ratio value and directing the at least one electrical current at the second current ratio value through one of the electrodes.  
   
     
     
         75 . The system of  claim 74  wherein the plurality of electrodes includes four electrodes, and wherein the computer operable medium has contents capable of changing a current passing through each of the four electrodes while the electrodes are in electrical communication with the microelectronic workpiece.  
     
     
         76 . The system of  claim 74  wherein the microelectronic workpiece has a layer of conductive material, the layer having topographical features, and wherein the computer operable medium has contents capable of directing the electrical currents with the current ratio of the at least one electrical current having the first value while the topographical features are being filled with conductive material, and having the second value while conductive material is applied to the filled topographical features, the first value being different than the second value.  
     
     
         77 . The system of  claim 74  wherein the computer operable medium is capable of changing the current ratio in a generally monotonic, incremental manner between the first current ratio value and the second current ratio value.  
     
     
         78 . The system of  claim 74  wherein computer operable medium is capable of maintaining the sum of the electrical currents constant as the current ratio changes.  
     
     
         79 . The system of  claim 74  wherein the computer readable medium is capable of changing the sum of the electrical currents as the current ratio changes.  
     
     
         80 . The system of  claim 74  wherein the computer readable medium is capable of directing the plurality of electrical currents to fill features on a surface of the microelectronic workpiece by providing to the microelectronic workpiece current at an approximately constant current density over the surface of the microelectronic workpiece and apply current to the microelectronic workpiece at a spatially varying current density to form a conductive layer having a selected shape.  
     
     
         81 . A system for electrolytically processing a microelectronic workpiece, comprising: 
 a processing station having a vessel configured to carry an electrolytic fluid, the processing station further having at least one contact and a plurality of electrodes, all configured to be in electrical communication with the microelectronic workpiece; and    a controller having a computer operable medium with contents capable of: 
 directing a first electrical current through first electrode and a first portion of the microelectronic workpiece;  
 directing a second electrical current through the second electrode and a second portion of the microelectronic workpiece while the first electrical current is directed through the first electrode and the first portion of the microelectronic workpiece, wherein a first current ratio of the first electrical current to a sum of the first and second electrical currents has a first value, and wherein a second current ratio of the second electrical current to a sum of the first and second electrical currents has a second value;  
 changing the first current ratio from the first value to a third value and directing the first electrical current at the third value; and  
 changing the second current ratio from the second value to a fourth value and directing the second electrical current at the fourth value.  
   
     
     
         82 . The system of  claim 81  wherein the microelectronic workpiece has a layer of conductive material, the layer having topographical features, and wherein the computer operable medium is capable of directing current with the first current ratio having the first value while the topographical features are being filled with conductive material, and having the third value while conductive material is applied to the filled topographical features, the first value being different than the third value.  
     
     
         83 . The system of  claim 81  wherein current density is equivalent to current per unit area of the microelectronic workpiece, and wherein the computer operable medium is capable of providing to the first portion of the microelectronic workpiece current at a first current density and providing to the second portion of the microelectronic workpiece current at a second density, the first current density being at least approximately the same as the second current density.  
     
     
         84 . The system of  claim 81  wherein the second portion of the microelectronic workpiece is positioned outwardly from the first portion of the microelectronic workpiece, and wherein the computer operable medium is capable of decreasing an electrical current applied to the first electrode relative to an electrical current applied to the second electrode and/or increasing an electrical current applied to the second electrode relative to an electrical current applied to the first electrode.  
     
     
         85 . A system for electrolytically processing a microelectronic workpiece, comprising: 
 a processing station having a vessel configured to carry an electrolytic fluid, the processing station further having at least one contact and a plurality of electrodes, all configured to be in electrical communication with the microelectronic workpiece, the plurality of electrodes including at least a first electrode and a second electrode; and    a controller having a computer operable medium with contents capable of: 
 directing a first electrical current through the electrolytic fluid between the first electrode and a first portion of the microelectronic workpiece;  
 directing a second electrical current through the electrolytic fluid between the second electrode and a second portion of the microelectronic workpiece while the first electrical current is directed between the first electrode and the first portion of the microelectronic workpiece;  
 varying the first and second electrical currents as a function of time while directing the first and second electrical currents and while the microelectronic workpiece contacts the electrolytic fluid;  
 while the first electrical current varies with time, providing the first electrical current at a current density per unit area of the microelectronic workpiece that varies by less than about 10% of a 3σ value over the surface of the microelectronic workpiece; and  
 while the second electrical current varies with time, providing the second electrical current at a current density per unit area of the microelectronic workpiece that varies by less than about 10% of a 3σ value over the surface of the microelectronic workpiece.  
   
     
     
         86 . The system of  claim 85  wherein the second portion of the microelectronic workpiece is disposed outwardly from the first portion, and wherein the computer operable medium is capable of changing a ratio of the first electrical current to a sum of the first and second electrical currents, and changing a ratio of the second current to a sum of the first and second electrical currents.  
     
     
         87 . The system of  claim 85  wherein the computer operable medium is capable of directing to the first electrode a current at a first value while features on a surface of the microelectronic workpiece are being filled, and directing to the first electrode a current at a second value while a layer of conductive material is built on the microelectronic workpiece after the features have been filled.  
     
     
         88 . A system for electrolytically processing a microelectronic workpiece, comprising: 
 a processing station having a vessel configured to carry an electrolytic fluid, the processing station further having at least one contact and a plurality of electrodes, all configured to be in electrical communication with the microelectronic workpiece; and    a controller having a computer operable medium with contents capable of: 
 directing a first electrical current through the electrolytic fluid from one of a first electrode and a first portion of the microelectronic workpiece to the other;  
 directing a second electrical current through the electrolytic fluid from one of a second electrode and a second portion of the microelectronic workpiece to the other while the first electrical current is directed between the first electrode and the first portion of the microelectronic workpiece;  
 directing the first electrical current at a first value while filling features of the microelectronic workpiece with conductive material, then applying the first electrical current at a second value different than the first value while applying conductive material to the filled features; and  
 directing the second electrical current at a first value while filling features of the microelectronic workpiece with conductive material, then applying the second electrical current at a second value while applying conductive material to the filled features, wherein a ratio of the first value of the first current to a sum of the first values of the first and second currents is different than a ratio of the second value of the first current to a sum of the second values of the first and second currents.  
   
     
     
         89 . The system of  claim 88  wherein the computer operable medium is capable of changing a ratio of the first electrical current to the sum of the first and second electrical currents as a function of time and changing a ratio of the second electrical current to the sum of the first and second electrical currents as a function of time.  
     
     
         90 . A system for electrolytically processing a microelectronic workpiece, comprising: 
 a processing station having a vessel configured to carry an electrolytic fluid, the processing station further having at least one contact and a plurality of electrodes, all configured to be in electrical communication with the microelectronic workpiece; and    a controller having a computer operable medium with contents capable of: 
 directing first electrical currents through at least one of the plurality of electrodes to remove conductive material from an outer region of a conductive layer of the microelectronic workpiece; and  
 after removing conductive material from the conductive layer in the outer region, directing second electrical currents through at least one of the plurality of electrodes to simultaneously add conductive material to the conductive layer in both the outer region and the inner region of the conductive layer.  
   
     
     
         91 . The system of  claim 90  wherein the computer operable medium is capable of directing currents for simultaneously adding conductive material to the conductive layer in both the outer region and the inner region by directing a first current through the electrolytic fluid between a first electrode and the inner region and directing a second current through the electrolytic fluid between a second electrode and the outer region.  
     
     
         92 . The system of  claim 90  wherein the computer operable medium is capable of directing currents for simultaneously adding conductive material to the conductive layer in both the outer region and the inner region by directing a first current through the electrolytic fluid between a first electrode and the inner region, directing a second current through the electrolytic fluid between a second electrode and the outer region, and varying the first and second currents over time while the microelectronic workpiece contacts the electrolytic fluid.  
     
     
         93 . A system for electrolytically processing a microelectronic workpiece, comprising: 
 a processing station having a vessel configured to carry an electrolytic fluid, the processing station further having at least one contact and a plurality of electrodes configured to carry a plurality of electrical currents, wherein the at least one contact and the plurality of electrodes are configured to be in electrical communication with the microelectronic workpiece; and    a controller having a computer operable medium with contents capable of: 
 for each electrical current, varying a ratio of the electrical current to a sum of electrical currents applied to the microelectronic workpiece; and  
 for each portion of the microelectronic workpiece at any point in time, maintaining a current density per unit area of the microelectronic workpiece at approximately the same value while the microelectronic workpiece contacts the electrolytic fluid.  
   
     
     
         94 . The system of  claim 93  wherein the computer operable medium is capable of directing currents for maintaining approximately the same current density per unit area of the microelectronic workpiece while features are being filled and while the conductive material is applied to the filled features.