Abstract:
A fluid processing cell for depositing a conductive layer onto a substrate is provided. The cell includes a catholyte solution fluid volume positioned to receive a substrate for plating, a first anolyte solution fluid volume at least partially ionically separated from the catholyte solution fluid volume, an anode assembly positioned in the first anolyte solution fluid volume, a second anolyte solution fluid volume, the second anolyte solution fluid volume being electrically isolated from the first anode solution fluid volume and at least partially in ionic communication with the cathode solution fluid volume, and a cathode counter electrode positioned in the second anolyte solution volume.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     Embodiments of the invention generally relate to an electrochemical plating cell.  
         [0003]     2. Description of the Related Art  
         [0004]     Metallization of sub 100 nanometer sized features is a foundational technology for present and future generations of integrated circuit manufacturing processes. However, metallization of sub 100 nanometer features presents several challenges to conventional metallization apparatuses and techniques. For example, conventional metallization techniques for integrated circuit applications generally include depositing a conductive seed layer onto surfaces that are to be metallized, and then electrochemically plating a conductive layer onto the seed layer to metallize and fill the features. The seed layer is often deposited by a physical vapor deposition (PVD) process and generally has a thickness of between about 300 Å and about 700 Å. However, seed layer deposition becomes increasingly difficult with sub 100 nanometer features, as the opening at the top of the features tends to close off from field or horizontal surface deposition before the sidewalls or vertical surfaces of the features are adequately metallized by the seed layer. This closure of the opening of the feature inhibits subsequent processes from metallizing or filling the main body of the feature with the desired conductive material.  
         [0005]     Deposition of the thin seed layer required for sub 100 nanometer features also presents challenges with respect to the continuity or resistance of the thin seed layer. More particularly, since the thickness of the conductive seed layer is directly proportional to the resistance of the layer, the decreasing thicknesses of seed layers in sub 100 nanometer features results in a substantially higher seed layer resistance. This increased resistance is known to cause an edge high plating condition, i.e., thicker plating near the edge of the substrate as a result of the decreased electric field near the center of the substrate from the high seed layer resistance.  
         [0006]     Another challenge in metallization of sub 100 nanometer features is the metallization or feature filling process that is conducted after the seed layer is deposited. Metallization of integrated circuit devices is generally conducted with an electrochemical plating process, however, the small size of the feature opening and high aspect ratio of the feature body makes it very difficult to obtain continuous bottom up fill of the main body of the feature without closing the opening of the feature and preventing subsequent plating in the feature, thus generating an unfilled void or pocket in the feature.  
         [0007]     Therefore, there is a need for an apparatus and method for metallizing sub 100 nanometer integrated circuit devices and minimizing edge high plating effects that result from thin seed layers.  
       SUMMARY OF THE INVENTION  
       [0008]     Embodiments of the invention provide an electrochemical plating cell configured to metallize sub 100 nanometer features on integrated circuit devices. The plating cell includes a fluid basin having an anolyte solution compartment and a catholyte solution compartment, an ionic membrane positioned between the anolyte solution compartment and the catholyte solution compartment, an anode positioned in the anolyte solution compartment, and a cathode electrode positioned to electrically contact and support a substrate for processing in the fluid basin. The anolyte compartment is divided into a first and second anolyte compartments, such that the anode is positioned in the first compartment and a counter electrode is positioned in the second compartment. The first and second compartments both have an anolyte fluid flow therethrough, however, the first and second compartments are electrically isolated from each other.  
         [0009]     Embodiments of the invention may further provide an electrochemical plating cell having a fluid container having an ionic membrane positioned across the fluid container, the ionic membrane being positioned to fluidly separate a catholyte volume from a first anolyte volume in the fluid container. The plating cell further includes an anode assembly positioned in fluid communication with the first anolyte volume, a cathode substrate support member positioned to support a substrate at least partially in the catholyte volume for a plating process, a counter electrode positioned in fluid communication with a second anolyte volume, the second anolyte volume being electrically isolated from the first anolyte volume, and a vent member positioned in fluid communication with the catholyte volume, the vent member being in ionic communication with the second anolyte volume.  
         [0010]     Embodiments of the invention may further provide a fluid processing cell for depositing a conductive layer onto a substrate. The cell generally includes a catholyte solution fluid volume positioned to receive a substrate for plating, a first anolyte solution fluid volume at least partially ionically separated from the catholyte solution fluid volume, an anode assembly positioned in the first anolyte solution fluid volume, a second anolyte solution fluid volume, the second anolyte solution fluid volume being electrically isolated from the first anode solution fluid volume and at least partially in ionic communication with the cathode solution fluid volume, and a cathode counter electrode positioned in the second anolyte solution volume.  
         [0011]     Embodiments of the invention may further provide an electrochemical plating cell having a fluid basin having an ionic membrane positioned across a middle portion of the basin, the ionic membrane separating the fluid basin into an upper catholyte volume and a lower anolyte volume, an anode assembly positioned in the lower anolyte volume, and a cathode substrate support member removably positioned in the catholyte volume. The plating cell further includes a counter electrode positioned in an isolated anolyte volume, the isolated anolyte volume being positioned below the ionic membrane and not in direct electrical communication with the lower anolyte volume, and a counter electrode vent positioned in an upper portion of the fluid basin at a position proximate an edge of a substrate being plated in the fluid basin, the counter electrode vent being in electrical communication with the counter electrode via a fluid conduit.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.  
         [0013]      FIG. 1  illustrates a sectional view of an exemplary electrochemical plating cell and head assembly of the invention.  
         [0014]      FIG. 2A  illustrates a schematic sectional view of an exemplary electrode and membrane configuration of the invention.  
         [0015]      FIG. 2B  illustrates a horizontal section of the exemplary plating cell showing the anolyte fluid flow patterns.  
         [0016]      FIG. 3  illustrates another sectional view of the plating cell of the invention.  
         [0017]      FIG. 4  illustrates a detailed sectional view of the fluid delivery conduits of the plating cell of the invention.  
         [0018]      FIG. 5  illustrates a detailed sectional view of the fluid return conduits of the plating cell of the invention.  
         [0019]      FIG. 6  illustrates a sectional view of the plating cell of the invention and representative electrical flux lines that are generated during plating operations.  
         [0020]      FIGS. 7   a - 7   e  illustrate exemplary anode configurations that may be used in the plating cell of the invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0021]     The present invention is directed to a plating cell configured to support metallization processes for sub 100 nanometer integrated circuits. The plating cell generally includes a partitioned fluid basin, i.e., the fluid volume in the plating cell fluid basin is separated into a catholyte solution volume and an anolyte solution volume. An example of this type of separation of a plating cell into an anolyte volume and a catholyte volume may be found in commonly assigned U.S. patent application Ser. No. 10/627,336, filed Jul. 24, 2003 entitled “Electrochemical Processing Cell”, which is hereby incorporated by reference in its entirety. The anolyte volume of the plating cell includes at least one anode electrode and at least one counter electrode, however, the counter electrode is positioned and configured to be electrically isolated from the anode electrode.  
         [0022]      FIG. 1  illustrates a simplified sectional view of an exemplary plating cell  100  and head assembly  102  of the invention in a processing position.  FIG. 3  illustrates another sectional view of plating cell  100  of the invention without the head assembly  102 . Plating cell  100  includes a head assembly  102  configured to support a substrate for plating operations in a plating cell fluid basin  108 . The head assembly  102  generally includes a thrust plate member  104  and a cathode contact ring member  106 . Thrust plate  104  and contact ring  106 , which will be further discussed herein, are generally configured to support and electrically bias a substrate for electrochemical processing in plating cell  100 . Fluid basin  108  is configured to confine an inner fluid volume  110  and to receive a substrate for plating in the fluid volume  110 . Fluid basin  108  also includes an overflow weir  109  (a contiguous uppermost fluid overflow point) that spills into an outer collection volume  112  that circumscribes weir  109 . Collection volume  112  operates to drain overflow plating solution from the inner volume  110  such that the plating solution may be recirculated back to inner volume  110 . Fluid basin  108  optionally includes a fluid diffusion member  114  positioned across the inner volume  110  at a position below where the substrate  118  being plated is positioned. The fluid diffusion member  114  generally operates to dampen fluid flow variations in the direction of the substrate  118 , as well as operating to provide a resistive element in the plating bath between the anode and the substrate. A more thorough description of the diffusion member and other plating cell components and operational characteristics may be found in commonly assigned U.S. Pat. No. 6,261,433 and commonly assigned U.S. Pat. No. 6,585,876, both of which are hereby incorporated by reference in their entireties.  
         [0023]     Fluid basin  108  further includes a membrane  116  positioned across the fluid basin  108  at a position below where the diffusion member  114  may be positioned, if used. Membrane  116  is generally an ionic membrane, and more particularly, a cationic membrane, that is generally configured to prevent fluid passage therethrough, while allowing ions, such as copper ions, to travel through the membrane  116  toward substrate  118 . As such, membrane  116  generally operates to separate a catholyte volume  119  of the plating cell  100  from an anolyte volume  120  of the plating cell  100 , wherein the catholyte volume  119  is generally defined as the fluid volume between the membrane  116  and the substrate  118 , and the anolyte volume  120  is defined as the fluid volume below the membrane  116  adjacent the anode. A more thorough description of the membrane  116  and the separation of the anolyte from the catholyte may be found in commonly assigned U.S. patent application Ser. No. 10/627,336, filed Jul. 24, 2003 entitled “Electrochemical Processing Cell”, which is hereby incorporated by reference in its entirety.  
         [0024]     The anolyte volume  120  generally contains an anode assembly  122  that includes at least one electrically conductive member positioned in contact with the anolyte solution flowing through the anolyte volume  120 . The conductive member may be manufactured from a soluble material, such as copper, or from an insoluble material, such as platinum or another noble metal, etc. A counter electrode assembly  124 , which is generally positioned radially outward of the perimeter of anode assembly  122 , may also be manufactured from either a soluble or an insoluble material, such as copper, platinum, etc.  
         [0025]     Although anode assembly  122  and the counter electrode  124  are generally positioned such that both assemblies  122 ,  124  are in communication with an anolyte solution, the respective assemblies  122 ,  124  are also positioned and configured such that the anode assembly  122  is electrically isolated from the counter electrode  124 . More particularly, an electrically insulating spacer  126  is generally positioned between anode assembly  122  and counter electrode  124 . Further, the anolyte solution fluid flow that is in fluid contact with the anode assembly  122  is not the same anolyte fluid flow that is in fluid contact with the counter electrode  124 , as will be further discussed herein with respect to  FIG. 4 . Anode assembly  122  is in electrical communication with an anodic terminal of a power supply (not shown). The cathodic terminal of the same power supply is generally in electrical communication with the contact ring  106 , which is configured to electrically contact the substrate  118  and the counter electrode  124 . However, although only one power supply is discussed herein with respect to supplying the cathodic bias, it is understood that more than one independently controlled power supply may be used without departing from the scope of the invention.  
         [0026]     A plating solution, also termed a catholyte, is supplied to the catholyte volume  119  by a fluid supply conduits  133   a ,  133   b  which is in fluid communication with a catholyte solution tank (not shown). The catholyte solution generally includes several constituents, including, for example, water, copper sulfate, halide ions, and one or more of a plurality plating additives (levelers, suppressors, accelerators, etc.). The catholyte solution supplied by conduits  133   a ,  133   b  overflows the weir  109  and is collected by collection volume  112 . The anolyte solution is supplied to anolyte volume  120  by an anolyte supply conduit  131   a  and drained from anolyte volume  120  by an anolyte drain conduit  131   b  positioned on an opposing side from the supply conduit  131   a . The positioning of the supply and drain conduits  131   a ,  131   b  generates directional flow of the anolyte across the upper surface of the anode  122 , as described in commonly assigned U.S. patent application Ser. No. 10/268,284, filed Oct. 9, 2002 entitled “Electrochemical Processing Cell”, which is hereby incorporated by reference in its entirety.  
         [0027]     Plating cell  100  also includes a second anolyte fluid inlet  132   a  and a second anolyte fluid drain  132   b . The second anolyte fluid inlet  132   a  is configured to supply an anolyte solution to the volume  135  surrounding the counter electrode  124 , while not fluidly or electrically communicating with the main anolyte volume  120  contained in the volume adjacent the anode  122  and supplied by conduits  131   a ,  131   b  as illustrated in  FIG. 2   a . Volume  135  is fluidly bound by membrane  116  on the upper side thereof. The fluid boundary is generally a result of the lack of fluid permeability of membrane  116 , combined with positioning two seals  136  adjacent electrode  124 , and more particularly, between the partition  126  and membrane  116 , and between the cell body portion  127  outward of electrode  124  and membrane  116 . The positioning of the two seals  136 , which may generally be circular o-ring-type seals, operates to channel the flow of anolyte supplied by conduit  132   a  around volume  135  to drain conduit  132   b . As such, the anolyte supplied by conduit  132   a  generally flows through the volume  135  above the counter electrode  124  in a semicircular pattern, as illustrated by arrows “A” in  FIG. 2   b . As such, the anolyte fluid circulated through the volume  135  is collected by the second anolyte drain conduit  132   b  on the opposing side of the cell from which the anolyte was supplied by conduit  131   a . Alternatively, the anolyte supplied to the anolyte compartment  120  generally flows directly across the anode  122 , as illustrated by arrows “B” in  FIG. 2   b , and is collected by conduit  131   b . The fluid flows indicated by arrows “A” and “B” both occur below the membrane  116 . Flow “A” occurs between seals  136 , and flow “B” occurs across the top of the anode  122  radially inward of the inner seal  136 .  
         [0028]     Although the membrane  116  provides a fluid barrier that prevents the anolyte solution from fluidly transferring therethrough, membrane  116  allows for ionic transfer, and more particularly, for positive ionic transfer. As such, although the anolyte cannot permeate membrane  116 , ions such as copper and hydrogen ions may transfer through the membrane  116  into vent conduit  140 , which contains catholyte. Thus, the combination of the volume  135  above the electrode  124  and the catholyte in vent conduit  140  generates an electrical path for current to travel from the cathode contact ring (the substrate)  106  to the counter electrode  124 .  
         [0029]      FIG. 2   a  illustrates the flux lines generated near the anode  122  and the counter electrode  124  during a plating process. The electrical flux immediately above the anode  122  is represented by the arrows labeled “C”. The flux above the anode  122  may be controlled by applying a different electrical power to the respective anode segments  122   a ,  122   b , and  122   c . Anode segments  122   a ,  122   b ,  122   c  may be concentric, symmetric, or any other configuration depending upon the desired flux.  FIGS. 7   a - 7   e  illustrate exemplary anode configurations that may be used in embodiments of the invention, wherein the anode segments  1 ,  2 , and  3  are denoted. It is understood that each of segments  1 ,  2 , and  3  of the respective anode arrangements may be individually powered to control and/or optimize plating parameters. Returning to  FIG. 2   a , the anode segments  122   a ,  122   b ,  122   c  may also be individually powered and are not limited to any particular number, i.e., there may be between 1 and about 10 or more anode segments in a plating cell. With regard to independently powering anode segments, anode segment  122   a  illustrated in  FIG. 2   a  has more power applied thereto than anode segment  122   b . This is evident from the density of the flux lines “C” originating from segment  122   a  is greater than those originating from anode segment  122   b , thus indicating the less power is being applied to segment  122   b.    
         [0030]      FIG. 4  illustrates an enlarged sectional view of the electrode and membrane configuration of the plating cell of  FIGS. 1 and 3  on the fluid supply side of the plating cell. More particularly, arrows “F” indicate the anolyte fluid flow path for the anolyte solution that is flowing over the upper surface of anode  122 . The anolyte fluid flow indicated by arrows “F” is generally supplied to conduit  131   a  and directed to flow across the upper surface of anode  122  in the flow direction generally indicated by arrows “B” in  FIG. 2   b . This fluid flow is generally perpendicular to any slots or elongated apertures formed into anode  122  for the purpose of receiving anode sludge or other dense fluids that may form on the anode surface during plating operations.  
         [0031]     Arrows “G” in  FIG. 4  indicate the anolyte ion flow path for the anolyte solution that is flowing over the counter electrode  124 , which also generally corresponds with the fluid flow indicated by arrows “A” in  FIG. 2   b . As such, the anolyte ion flow “G” is generally supplied to volume  135  by conduit  132   a , which generates a semicircular flow of fluid over the top of the counter electrode  124 , below membrane  116 , and between seals  136 .  
         [0032]     Arrows “E” indicate the fluid flow path for the catholyte solution that is supplied to the catholyte volume  119  of plating cell  100 . The catholyte solution flows upward through conduit  132   a , then generally horizontally across at least a portion of the upper surface of membrane  116 , and then upward to an opening, i.e., vent conduit  140 , that communicates with the catholyte region  119 . The flow of the catholyte over the upper surface of the membrane is generally configured to be at a position that overlaps the volume  135  above the counter electrode  124 , which provides a current path between the catholyte and the counter electrode  124  via transmission through membrane  116 . This current path generally travels from the cathode contact ring  106  through vent  140  via the catholyte solution residing therein, through membrane  116 , and through the anolyte residing in volume  135  to the counter electrode  124 , as indicated by arrows “H” in  FIG. 6 .  
         [0033]      FIG. 5  illustrates an enlarged sectional view of the electrode and membrane configuration of the plating cell of  FIGS. 1 and 3  on the fluid drain side of the plating cell. Arrows “J” illustrate the flow direction for the anolyte being removed from the anode chamber  120  adjacent the anode  122 . The anolyte drain conduit  131   b  is positioned to drain anolyte from the anode chamber  120  in a direction that is generally perpendicular to slots formed in the anode  122 , as illustrated by arrows “B” in  FIG. 2   b . Arrows “K” illustrate the flow direction of the anolyte solution over the counter electrode  124 . The anolyte flowing over counter electrode  124  is removed from the volume  135  above the electrode  124  at a point that facilitates the semicircular flow pattern illustrated by arrows “A” in  FIG. 2   b . Arrows “L” illustrate the catholyte flow direction for the catholyte traveling through supply conduits  131   a ,  131   b  to supply fresh catholyte to the catholyte chamber  119 . Arrows “M” illustrate the flow direction of the anolyte being drained from volume  135  above the counter electrode  124 .  
         [0034]     In operation, counter electrode  124  is used in combination with anode member  122 , which may be one of the segmented anodes illustrated in  FIGS. 7   a - 7   e  or variations thereof, to control the electrical flux across the surface of the substrate  118  being plated. More particularly, counter electrode  124 , which is also in electrical communication with a power supply (not shown) is used to selectively reduce the electric flux near the edge of the substrate  118  to prevent edge high plating. Counter electrode  124  reduces the electric flux near the edge of the substrate by supplying an additional cathodic flux source to the area proximate the edge or perimeter of the substrate  118 . Counter electrode  124  supplies the additional flux, which is illustrated by arrows “H” in  FIG. 6 , to the area proximate the edge or perimeter of the substrate by electrically communicating with the cathode volume  119  via vent  140 . Vent  140 , which is generally an annular vent that circumscribes the perimeter of the substrate, is positioned to conduct flux from the counter electrode  124  to the catholyte volume  119  in a manner that reduces the quantity of flux generated by the substrate/cathode near the perimeter of the substrate. More particularly, the combination of vent  140  and counter electrode  124  being cathodically biased essentially operates to flood the perimeter of the substrate with a flux source, which prevents the anode from conducting flux directly to the perimeter edge of the substrate where vent  140  is supplying flux. As such, the electrical flux originating on the substrate  118  is increased near the center of the substrate  118 , as illustrated by arrows “C” in  FIG. 6 , while reducing the electrical flux at the substrate surface near the perimeter of the substrate  118 , as the flux represented by arrows “H” has essentially displaced the flux originating near the perimeter of the substrate  118 .  
         [0035]     This reduction in the flux near the perimeter of the substrate, which may be controlled by the cathodic bias applied to the counter electrode  124 , generally operates to reduce edge or perimeter high plating characteristics of conventional plating cells. More particularly, the counter electrode  124  operates as a cathodic source near the edge of the substrate  118  via the flux traveling from counter electrode  124  through vent  140  to the anode assembly  122 , and therefore, reduces the flux near the edge of the substrate. This reduced flux has been shown to reduce the plating near the perimeter of the substrate.  
         [0036]     While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, wherein the scope is determined by the claims that follow.