Abstract:
A method and apparatus for plating a metal onto a substrate. The apparatus generally The apparatus generally includes a substrate support member configured to support a substrate during a plating process, a cathode clamp ring detachably positioned to circumscribe a perimeter of the substrate and a movable anode assembly disposed above the substrate, wherein the anode assembly is movable in a direction generally perpendicular the substrate. The apparatus generally further includes a fluid inlet formed through the anode assembly, the fluid inlet being configured to supply a plating solution to the processing area sufficient to electrically connect the anode assembly to the substrate. The method generally includes supplying a plating solution to a processing chamber, the processing chamber being defined by a movable anode assembly disposed above the substrate and a cathode clamp ring detachably positioned to circumscribe the perimeter of the substrate, wherein the plating solution is supplied at a rate sufficient to electrically connect the anode assembly to the substrate and plating a metal from the plating solution onto the substrate.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    Embodiments of the present invention generally relate to deposition of a metal layer onto a substrate. More particularly, the embodiments of the present invention relate to electroplating a metal layer onto a substrate.  
           [0003]    2. Description of the Related Art  
           [0004]    Metallization for sub-quarter micron sized features is a foundational technology for present and future generations of integrated circuit manufacturing processes. In devices such as ultra large scale integration-type devices, i.e., devices having integrated circuits with more than a million logic gates, the multilevel interconnects that lie at the heart of these devices are generally formed by filling high aspect ratio interconnect features with a conductive material, such as copper or aluminum. Conventionally, deposition techniques such as chemical vapor deposition (CVD) and physical vapor deposition (PVD) have been used to fill these interconnect features. However, as interconnect sizes decrease and aspect ratios increase, void-free interconnect feature fill via conventional metallization techniques becomes increasingly difficult. As a result thereof, plating techniques, such as electrochemical plating (ECP) and electroless plating, for example, have emerged as viable processes for filling sub-quarter micron sized high aspect ratio interconnect features in integrated circuit manufacturing processes.  
           [0005]    In an ECP process sub-quarter micron sized high aspect ratio features formed on a substrate surface may be efficiently filled with a conductive material, such as copper, for example. ECP plating processes are generally two stage processes, wherein a seed layer is first formed over the surface features of the substrate, and then the surface features of the substrate are exposed to an electrolyte solution while an electrical bias is simultaneously applied between the substrate and an anode positioned within the electrolyte solution. The electrolyte solution is generally rich in ions to be plated onto the surface of the substrate. Therefore, the application of the electrical bias causes these ions to be urged out of the electrolyte solution and to be plated as a metal on the seed layer. The plated metal, which may be copper, for example, grows in thickness and forms a copper layer that fills the features formed on the substrate surface.  
           [0006]    Present designs of cells for electroplating a metal on semiconductor substrates are generally based on a fountain plater type configuration. FIG. 1 illustrates a cross sectional view of a simplified exemplary fountain plater. Generally, the fountain plater  10  includes an electrolyte container  12  having a top opening, a substrate holder  14  disposed above the electrolyte container  12 , an anode  16  disposed at a bottom portion of the electrolyte container  12 , and a cathode  20  contacting the substrate  18 . The cathode  20  includes a plurality of contact pins distributed about the peripheral portion of the substrate  18  to provide an electrical bias to the substrate surface. The semiconductor substrate  18  is generally positioned a fixed distance above the electrolyte container  12 , and the electrolyte generally impinges perpendicularly on the substrate plating surface. Because of the possible dispersion effects of the electrical current at the exposed edges of the substrate  18  and the possible non-uniform flow of the electrolyte, the fountain plater  10  may provide non-uniform current distribution, particularly at the region near the edges and at the center of the substrate  18 , which may result in non-uniform plating on the substrate. The electrolyte flow uniformity at the center of the substrate  18  can be improved by rotating the substrate  18 . However, the plating uniformity still may deteriorate as the boundaries or edges of the substrate are approached.  
           [0007]    Therefore, there remains a need for a reliable, consistent copper electroplating technique to deposit and form copper layers on semiconductor substrates having nanometer-sized, high aspect ratio features. There is also a need for a face-up electroplating system that allows fast substrate processing and increases throughput with a small volume of plating solution. Furthermore, there is a need for an apparatus for delivering a uniform electrical power distribution to a substrate surface and a need for an electroplating system that provides uniform deposition on the substrate surface.  
         SUMMARY OF THE INVENTION  
         [0008]    Embodiments of the invention generally include an apparatus for plating a metal onto a substrate surface. The apparatus generally includes a substrate support member configured to support a substrate during a plating process, a cathode clamp ring detachably positioned to circumscribe a perimeter of the substrate and a movable anode assembly disposed above the substrate, wherein the anode assembly is movable in a direction generally perpendicular the substrate. The apparatus generally further includes a fluid inlet formed through the anode assembly, the fluid inlet being configured to supply a plating solution to the processing area sufficient to electrically connect the anode assembly to the substrate.  
           [0009]    Embodiments of the invention further include a method for plating a metal onto a substrate. The method generally includes supplying a plating solution to a processing chamber, the processing chamber being defined by a movable anode assembly disposed above the substrate and a cathode clamp ring detachably positioned to circumscribe the perimeter of the substrate, wherein the plating solution is supplied at a rate sufficient to electrically connect the anode assembly to the substrate and plating a metal from the plating solution onto the substrate. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    So that the manner in which the above recited features of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof 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.  
         [0011]    [0011]FIG. 1 (Prior Art) illustrates a cross-sectional view of an exemplary fountain plater.  
         [0012]    [0012]FIG. 2 illustrates a cross-sectional view of an exemplary plating cell.  
         [0013]    [0013]FIG. 3 illustrates a cross-sectional view of an exemplary anode assembly.  
         [0014]    [0014]FIG. 4 illustrates a cross-sectional view of another anode assembly.  
         [0015]    [0015]FIG. 5 illustrates a cross-sectional view of another anode assembly. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0016]    [0016]FIG. 2 illustrates a cross-sectional view of an exemplary plating cell  100  with a substrate  116  in a processing position. The plating cell  100  generally includes an enclosure  126  having a substrate support member  102  and an anode assembly  104 . The substrate support member  102  generally includes a conductive base plate  130  providing a cathode connection to a cathode clamp ring  108 . The substrate support member  102  is generally disposed in a bottom portion of the enclosure  126 . The anode assembly  104 , discussed in further detail below, is electrically connected to a power supply  106  via an electrical line  128 . The plating cell  102  may further include a vacuum chuck to secure the substrate  116  onto a substrate supporting surface  132  on the substrate support member  102  during processing.  
         [0017]    In the loading position, the cathode clamp ring  108 , which may be supported by an annular catch cup  110 , is generally disposed in a middle portion of the plating cell  100  between the substrate support member  102  and the anode assembly  104 . The cathode clamp ring  108  is positioned in the plating cell  100  such that the movement of the substrate support member  102  from a load/transfer position (not shown), to the processing position lifts the cathode clamp ring  108  slightly off the catch cup  110 . The load/transfer position is discussed in detail in U.S. Pat. No. 6,416,647, filed on Apr. 19, 1999, which is hereby incorporated by reference.  
         [0018]    The cathode clamp ring  108  preferably includes an outer portion having a downwardly sloping surface  166  that overlaps an inner terminus  168  of the catch cup  110  to assist the plating solution flow into the catch cup  110 . The inner terminus  168  includes a ridge  170  corresponding to a recess  172  on the bottom surface  174  of the cathode clamp ring  108 . The ridge  170  supports the cathode clamp ring  108  when the substrate support member  102  is not engaged in a deposition position. When the substrate support member  102  is engaged in the deposition position, the cathode clamp ring  108  is lifted from the ridge  170  and is supported on the substrate deposition surface  176 .  
         [0019]    The electrical power is delivered by the cathode clamp ring  108  to the substrate deposition surface  176  through a contact portion  178  of the cathode clamp ring  108 . To provide electrical power to the cathode clamp ring  108 , one or more cathode contacts  180  are fixedly secured to a bottom surface  146  of the conductive base plate  130  of the substrate support member  102  and extend radially outward to electrically contact a bottom surface  174  of the cathode clamp ring  108 . Upon rotation, the electrical power is conducted through the rotating shaft  134  to the conductive base plate  130 , then through one or more cathode contacts  180  secured onto the conductive base plate  130 , and then to a bottom surface  174  of the cathode clamp ring  108 . Alternatively, the cathode clamp ring  108  is fixedly connected to the power supply  106  through connection wires (not shown).  
         [0020]    The rotating shaft  134  extends through a lift pin platform  136  having a plurality of lift pins  138  disposed thereon. A lift platform actuator  142  moves the lift pin platform  136  vertically to lift and lower a substrate  116  for transfer into and out of the plating cell  100 . A flexible bellow  144 , preferably made of polyethylene, is disposed around each lift pin  138 , to provide a splash seal against plating solutions, rinsing solutions, and other processing chemicals. The flexible bellow  144  is attached from a top surface of the lift pin platform  136  to a bottom surface of the conductive base plate  146  of the substrate support member  102 . The flexible bellow  144  compresses when the lift pin platform  136  is elevated by the lift platform actuator  142  and stretches when the lift pin platform  136  is resting on a platform ridge  148 . Each flexible bellow  144  also maintains a seal when subjected to a slight side load, such as when the substrate support member  102  rotationally accelerates or decelerates.  
         [0021]    To prevent plating solutions, rinsing solutions, and other process chemicals from contacting components disposed in the central portion of the plating cell  100 , such as the lift platform actuator  142  and the shaft sleeve  150 , a splash guard  152  is generally attached to an outer portion of a lower surface of the lift pin platform  136 . The splashguard  152  includes a cylindrical downward extension that is disposed radially outward of an upwardly extending inner container wall  154 . The inner container wall  154  is a cylindrical upward extension from the enclosure bottom  156  of the plating cell  100  that holds the process solutions to be pumped out of the system through a solution outlet  114 .  
         [0022]    To provide rotational movement to the substrate support member  102 , a rotary actuator  158  is disposed on an actuator platform  160  and connected to the rotating shaft  134 . The rotary actuator  158  rotates the rotating shaft  134  freely within the shaft sleeve  150 . During deposition, the rotary actuator  158  rotates or oscillates the substrate support member  102  about a central axis through the rotating shaft  134 . Generally, the rotary actuator  158  rotates the support member  102  at between about 10 revolutions or cycles per minute to about 50 RPM or cycles per minute. The rotation or oscillation of the substrate support member  102  provides uniform exposure of the plating solution to the substrate deposition surface  176  promoting uniform metal deposition. In the alternative, the anode assembly  104  may be rotated. Deposition uniformity is further promoted by continuous cathode electrical contact provided by the cathode clamp ring  108 . The cathode clamp ring  108  operates to distribute a uniform current density across the substrate deposition surface  176 .  
         [0023]    To move the substrate support member  102  vertically, a vertical actuator  162  extends and retracts a shaft  164  connected to the actuator platform  160 . The vertical actuator  162  is disposed outside of the cell  100  on the cell bottom  156 , and the shaft  164  extends through the cell bottom  156  and is attached to a bottom surface of the actuator platform  160 . These actuators may be fluid cylinders, screw-type actuators, or any other actuator capable of producing longitudinal movements. In addition, a substrate transfer actuator  122  vertically adjusts the anode assembly  104  to set an anode assembly  104  to substrate  116  distance. The distance may be from about 2 mm to about 20 mm. The anode assembly  104  may be sized to recess within the contact ring  108  upon vertical adjustment, e.g., during plating, so that the anode assembly  104  is in electrical contact with the plating solution. In addition, plating solution may flow through the anode assembly  104  to provide additional plating solution or to provide movement within the existing plating solution. Alternatively, the anode assembly  104  may be sized to rest upon the contact ring  108  upon vertical adjustment. When the anode assembly  104  rests upon the contact ring  108 , an insulator may be utilized to separate the anode assembly  104  and the contact ring  108 .  
         [0024]    The cell  100  additionally includes a sidewall  124  having a slit  118  formed therein for receiving and discharging a substrate  116 , e.g., loading and transferring the substrate  116 . The plurality of lift pins  136  extends through vertical bores in the substrate support member  102  and lifts the substrate  116  above a robot blade (not shown). The robot blade then retracts out of the cell  100  and the slit valve  120  closes the slit opening  118 . Once the substrate  116  is in the processing position, a plating solution pump (not shown), which is connected to a plating solution inlet  112 , pumps plating solution from a plating solution reservoir (not shown) into the plating cell  100 . Generally, a plating solution outlet  114  is connected to a plating solution drain (not shown) formed in the catch cup  110  to return the plating solution back to the plating solution reservoir to be re-circulated to the plating cell  100 .  
         [0025]    The plating solution fills a processing area defined by the substrate  116 , i.e., the processing area bottom, and the contact ring  108 , i.e., the sidewalls. Therefore, the volume of the processing area and the resulting volume of the plating solution utilized are dependent upon the size of the substrate  116  and the height of the contact ring  108 . In addition, the volume is dependent upon the distance of the anode assembly  104  from the substrate  116 . Generally the anode assembly  104  is from about 2 mm to about 20 mm from the substrate  116 . Preferably, the anode assembly  104  is from about 2 mm to about 10 mm from the substrate  116 .  
         [0026]    [0026]FIG. 3 illustrates a cross-sectional view of an exemplary anode assembly  200 . The anode assembly  200  may be used in the plating cell  100  described above, or another plating cell capable of processing semiconductor substrates in the face-up position. The anode assembly  200  and the substrate  116  and clamp ring  108  define a cell chamber  208 , e.g., a processing area. The cell chamber  208  generally has a volume of from about 0.5 L to about 1.9 L.  
         [0027]    The anode assembly  200  generally includes an anode plate  202  and a hood  204 . The anode plate  202  generally has a circular cross-section. The anode plate  202  preferably includes a consumable metal that can dissolve in the electroplating solution to provide the metal particles to be deposited onto the substrate deposition surface. The hood  204 , which is electrically insulated from the anode plate  202 , depends from the outer periphery of the anode plate  202  and may be made of anodic material, which is the same or different from the material of the anode plate  202 . For example, the anode plate  202  may be formed of a mesh material. Alternatively, the anode plate  202  and hood  204  are each made of consumable metal particles encased in a fluid permeable membrane such as a porous ceramic plate. An alternative to the consumable anode plate is a non-consumable anode plate that is perforated or porous for passage of the electroplating solution therethrough. However, when a non-consumable anode plate is used, the electroplating solution requires a metal particle supply to continually replenish the metal particles to be deposited in the process.  
         [0028]    As described above, the contact ring  108  is in electrical communication with the cathode terminal of a power supply (not shown). The power source discussed in reference to FIG. 2 generally includes controls for varying the voltage and polarity of the anode plate  202  and the hood  204 . For example, to ensure plating in a central portion of the substrate, the hood  204  may be electrically isolated to prevent ions from plating on the hood  204 .  
         [0029]    The hood  204  generally is secured to the anode plate  202  by an insulating ring  206 . The hood  204  is sized to substantially cover the substrate  116  and the clamp ring  108  from the outer edges of the anode plate  202  extending downward towards the substrate  116 .  
         [0030]    The flow of electrolyte through the processing chamber  208  is controlled by the size of an annular opening  210 , e.g., the distance between the hood  204  and the clamp ring  108 . The annular opening  210  is sized in relation to the electrolyte flow rate to maintain the electrolyte in the chamber  208  at a predetermined level during the plating process. Generally, the flow of plating solution continues during plating to retain electrical contact between the anode plate  202  and the substrate  116 . In addition, the flow of electrolyte into the processing chamber  208  is generally equal to the flow of electrolyte out of the processing chamber through the annular opening  210  and the consumption of electrolyte due to plating on the substrate. Generally, the processing chamber  208  is full of electrolyte throughout plating to maintain an electrical connection between the anode and the substrate.  
         [0031]    In operation, the plating cell provides a small volume (electrolyte volume) processing chamber  208  that may be used for copper electrochemical plating processes, for example. A substrate  116  is first immersed into a plating solution contained within the processing chamber  208 . Once the substrate is immersed in the plating solution, which generally contains copper sulfate, chlorine, and one or more of a plurality of plating additives (levelers, suppressors, accelerators, etc.) configured to control plating parameters, an electrical plating bias is applied between a seed layer on the substrate and the anode  202  positioned above the substrate  116 . The electrical plating bias generally operates to cause metal ions in the plating solution to deposit on the cathodic substrate surface  116 . The plating solution is continually circulated through the processing chamber  208  via fluid inlets and outlets.  
         [0032]    [0032]FIG. 4 illustrates a cross-sectional view of another anode assembly  300 . The embodiment shown in FIG. 3 includes the same components as the embodiment shown in FIG. 2, except that the anode plate  304  does not include a hood. Thus, the cell chamber  302  is defined by the downwardly facing surface of the anode plate  304 , the upwardly facing surface of the substrate  116 , and the clamp ring  108 , e.g., the clamp ring  108  operates as sidewalls for the chamber  302 , thereby defining the volume of the chamber  302 . The distance of the anode plate  304  from the substrate  116  is generally minimized. For example, the distance may be from about 2 mm to about 20 mm, resulting in a small chamber volume. Alternatively, the distance may be from about 2 mm to about 10 mm. The precise volume of the chamber is determined by the vertical actuator setting.  
         [0033]    [0033]FIG. 5 illustrates yet another embodiment of an anode assembly  400 . The anode assembly  400  includes an anode plate  402 . The anode plate  402  generally includes a plurality of annular anode segments that are separated by insulators  404 . The insulators  404  may be annular spaces, plastic rings, or other means capable of insulating the anode segments from one another. The individual anode segments allow selective plating operation by providing individual voltage control for each anode segment. Selective operation provides control over the flow of cations adhering and flowing to the cathode/substrate  116 , thereby resulting in uniform plating upon the substrate  116 . Although the anode assembly  400  may be used alone, the anode assembly  400  may also be used in conjunction with either of the embodiments illustrated in FIGS. 2 and 3.  
         [0034]    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, and the scope thereof is determined by the claims that follow.