Patent Publication Number: US-11655556-B2

Title: Flow assisted dynamic seal for high-convection, continuous-rotation plating

Description:
CLAIM OF PRIORITY 
     This application is a continuation application under 35 U.S.C. 120 of prior U.S. patent application Ser. No. 16/044,412, filed Jul. 24, 2018, which claims priority under 35 U.S.C. 119(e) to U.S. Provisional Patent Application No. 62/636,818, filed Feb. 28, 2018. The disclosure of each above-identified patent application and provisional patent application is incorporated herein by reference in its entirety for all purposes. 
    
    
     BACKGROUND 
     1. Field of the Disclosure 
     The present disclosure relates to semiconductor device fabrication. 
     2. Description of the Related Art 
     Some semiconductor device fabrication processes include electroplating of a material onto a semiconductor wafer. The electroplating can be done in an electroplating cell in which the wafer, with an electrically conductive seed layer present thereon, is positioned so that the wafer is in physical contact with multiple electrical contacts. The wafer surface on which the seed layer is deposited is exposed to a bath of electroplating solution. An anode containing the metal to be plated onto the wafer is disposed within the bath of the electroplating solution. The anode is electrically connected to a positive terminal of a direct current (DC) power supply. Through the multiple electrical contacts, the wafer is electrically connected to a negative terminal of the DC power supply. The DC power supply is operated to supply DC current to the anode, which oxidizes and dissolves atoms of the anode into the bath of electroplating solution. The wafer functions as the cathode of the electroplating cell, such that negative charge on the wafer reduces the atoms liberated from the anode that are present in the electroplating solution at the surface of the wafer and causes plating of the atoms from the anode onto the wafer. How the wafer is exposed to a flow of the electroplating solution affects how the wafer is exposed to the atoms liberated from the anode within the electroplating solution and thereby affects how the atoms plate onto the wafer. It is within this context that the present disclosure arises. 
     SUMMARY 
     In an example embodiment, an apparatus for electroplating a semiconductor wafer is disclosed. The apparatus includes an insert member configured to circumscribe a processing region. The insert member has a top surface. A portion of the top surface of the insert member has an upward slope that slopes upward from a peripheral area of the top surface of the insert member toward the processing region. The apparatus also includes a seal member that has an annular-disk shape. The seal member is positioned on the top surface of the insert member. The seal member is flexible such that an outer radial portion of the seal member conforms to the upward slope of the top surface of the insert member and such that an inner radial portion of the seal member projects inward toward the processing region. 
     In an example embodiment, a sealing device for an electroplating apparatus for semiconductor wafer fabrication is disclosed. The sealing device includes an annular-disk-shaped structure configured for installation on a top surface of an insert member of the electroplating apparatus. The annular-disk-shaped structure has flexibility to physically conform to a contour of the top surface of the insert member, such that an outer radial portion of the annular-disk-shaped structure conforms to an upward slope of the top surface of the insert member, and such that an inner radial portion of the annular-disk-shaped structure projects inward from the top surface of the insert member, when the annular-disk-shaped structure is installed on the top surface of the insert member. 
     In an example embodiment, a method is disclosed for electroplating a semiconductor wafer. The method includes having an electroplating apparatus that includes an insert member configured to circumscribe a processing region. The insert member has a top surface. A portion of the top surface of the insert member has an upward slope that slopes upward from a peripheral area of the top surface of the insert member toward the processing region. The electroplating apparatus also includes a seal member having an annular-disk shape. The seal member is positioned on the top surface of the insert member. The seal member is flexible such that an outer radial portion of the seal member conforms to the upward slope of the top surface of the insert member and such that an inner radial portion of the seal member projects toward the processing region. The electroplating apparatus also includes a cup member having an annular shape. The cup member has a bottom surface that includes an outer radial portion configured to form a liquid seal with a top surface of the inner radial portion of the seal member, when the cup member is substantially centered over the seal member and moved downward to contact the seal member. The method also includes moving the cup member downward to form the liquid seal between the outer radial portion of the bottom surface of the cup member and the top surface of the inner radial portion of the seal member. The method also includes flowing electroplating solution through the processing region. A portion of the electroplating solution flows against a bottom surface of the inner radial portion of the seal member and presses the seal member against the cup member to assist with maintaining the liquid seal between the outer radial portion of the bottom surface of the cup member and the top surface of the inner radial portion of the seal member. 
     In an example embodiment, an insert member for a sealing mechanism within an electroplating apparatus for semiconductor wafer fabrication is disclosed. The insert member includes a structural member configured to circumscribe a processing region within the electroplating apparatus. The structural member has a top surface. A portion of the top surface of the structural member has an upward slope that slopes upward from a peripheral area of the top surface of the structural member toward the processing region. The top surface of the structural member is configured to receive and support a seal member having an annular-disk shape with an inner radial portion of the seal member projecting inward toward the processing region. The structural member has sufficient rigidity to cause an outer radial portion of the seal member to conform to the upward slope of the top surface of the insert member when the inner radial portion of the seal member is pushed downward. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1 A  shows a generalized diagram of a vertical cross-section of an electroplating apparatus for electroplating a wafer, in accordance with some embodiments. 
         FIG.  1 B  shows the diagram of  FIG.  1 A  with the cone member moved downward to interface with the wafer, so as press the peripheral downward facing region of the wafer against a sealing surface of the lip seal member, in accordance with some embodiments. 
         FIG.  2 A  shows a top view of the finger contacts, in accordance with some embodiments. 
         FIG.  2 B  shows a vertical cross-section view, “View A-A” as referenced in  FIG.  2 A , through one of the finger contacts, in accordance with some embodiments. 
         FIG.  3    shows a vertical cross-section of the cup member positioned near the insert member, in accordance with some embodiments. 
         FIG.  4    shows a vertical cross-section of a cup member positioned near an insert member, with a flow-assisted dynamic seal disposed to seal a gap between the cup member and the insert member, in accordance with some embodiments. 
         FIG.  5 A  shows a vertical cross-section of the interface between the cup member and the seal member just as the outer radial portion of the bottom surface of the cup member is brought into contact with the inner radial portion of the seal member, in accordance with some embodiments. 
         FIG.  5 B  shows the vertical cross-section of the interface between the cup member and the seal member of  FIG.  5 A  as the cup member is lowered further relative to the insert member, in accordance with some embodiments. 
         FIG.  5 C  shows the vertical cross-section of the interface between the cup member and the seal member of  FIG.  5 B  as the cup member is lowered further relative to the insert member to a plating position, in accordance with some embodiments. 
         FIG.  6    shows a top isometric view of the insert member, with the seal member and clamp ring installed on the insert member, in accordance with some embodiments. 
         FIG.  7    shows another top isometric view of the insert member, with the seal member and clamp ring installed on the insert member, in accordance with some embodiments. 
         FIG.  8    shows a vertical cross-section view of the seal member positioned to seal/close the gap between the cup member and the insert member when the cup member is lowered to the plating position, in accordance with some embodiments. 
         FIG.  9    shows a bottom isometric view of the cup member, in accordance with some embodiments. 
         FIG.  10 A  shows another vertical cross-section view of the seal member positioned to seal/close the gap between the cup member and the insert member when the cup member is lowered to the plating position, in accordance with some embodiments. 
         FIG.  10 B  shows a top isometric view of the seal member, in accordance with some embodiments. 
         FIG.  11 A  shows a vertical cross-section of the cup member positioned near the insert member, with the seal member disposed to seal the gap between the cup member and the insert member, and with a backing member positioned below the seal member, in accordance with some embodiments. 
         FIG.  11 B  shows a top isometric view of the backing member, in accordance with some embodiments. 
         FIG.  12    shows a flowchart of a method for electroplating a semiconductor wafer, in accordance with some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, numerous specific details are set forth in order to provide an understanding of embodiments of the present disclosure. It will be apparent, however, to one skilled in the art that embodiments the present disclosure may be practiced without some or all of these specific details. In other instances, well known process operations have not been described in detail in order not to unnecessarily obscure the present disclosure. 
       FIG.  1 A  shows a generalized diagram of a vertical cross-section of an electroplating apparatus  100  for electroplating a wafer  109 , in accordance with some embodiments. In an example embodiment, the term wafer as used herein refers to a semiconductor wafer. Also, in various embodiments, the wafer as referred to herein may vary in form, shape, and/or size. For example, in some embodiments, the wafer as referred to herein may correspond to a 200 mm (millimeters) semiconductor wafer, a 300 mm semiconductor wafer, or a 450 mm semiconductor wafer. 
     The electroplating apparatus  100  includes a cup member  101  and a cone member  103 . The electroplating apparatus  100  also includes a lip seal component  105  configured to engage with a top of the cup member  101 . A number of finger contacts  107  are disposed on top of the lip seal component  105 . The finger contacts  107  are arranged in a circular configuration to provide substantially uniform support to a peripheral edge region of the wafer  109  to be processed. 
       FIG.  2 A  shows a top view of the finger contacts  107 , in accordance with some embodiments.  FIG.  2 B  shows a vertical cross-section view, “View A-A” as referenced in  FIG.  2 A , through one of the finger contacts  107 , in accordance with some embodiments. As shown in  FIG.  2 A  the number of finger contacts  107  are integrally formed in connection with a ring-shaped conductive strip  107 A, e.g., metallic strip. Both the finger contacts  107  and the conductive strip  107 A are electrically conductive. It should be understood that in various embodiments, the finger contacts  107  and the conductive strip  107 A can be formed from any electrically conductive material that provides sufficient electrical conduction for performance of the electroplating process and that has sufficient mechanical properties for supporting the wafer  109  during the electroplating process and that is chemically compatible with the environment and materials to which it is exposed during the electroplating process. 
     As shown in  FIGS.  2 B and  1 A , the finger contact  107  is shaped so as to bend down following an upper contour of the top of the lip seal member  105 . And, an interior end section  107 B of the finger contact  107 , relative to the circumferential configuration of the conductive strip  107 A, is turned upward to provide a support surface  107 C for the wafer  109 . More specifically, during the electroplating process, the wafer  109  is positioned on the support surfaces  107 C of the finger contacts  107 , with the surface of the wafer  109  that is to be electroplated facing downward toward a processing region  102  so as to physically contact the support surfaces  107 C of the finger contacts  107 . 
     The cone member  103  is attached to a shaft  111  that is configured to move up and down relative to the cup member  101 , as indicated by arrow  111 A. During the electroplating process, the cone member  103  is moved downward to interface with the wafer  109  and press the wafer  109  onto the support surfaces  107 C of the finger contacts  107 , so as to flex the interior end sections  107 B of the finger contacts  107  downward toward the lip seal member  105 , and so as to press the peripheral downward facing region of the wafer  109  against a sealing surface  105 A of the lip seal member  105 .  FIG.  1 B  shows the diagram of  FIG.  1 A  with the cone member  103  moved downward to interface with the wafer  109 , as indicated by arrow  111 B, so as press the peripheral downward facing region of the wafer  109  against a sealing surface  105 A of the lip seal member  105 , in accordance with some embodiments. In the plating position, the cup member  101  is positioned proximate to an insert member  116 , such that a gap  119  is present between the cup member  101  and the insert member  116  to allow for rotation of the cup member  101  and wafer  109 , as indicated by arrows  120 . 
     A bath volume  113  for containing an electroplating solution is provided below the wafer  109 . When the wafer  109  is pressed against the sealing surface  105 A of the lip seal member  105  by the downward force exerted by the cone  103 , a seal is formed between the wafer  109  and the sealing surface  105 A so that electroplating solution will not get past the contact location between the wafer  109  and the sealing surface  105 A of the lip seal member  105 , thereby keeping electroplating solution away from the finger contacts  107 . 
     The electroplating apparatus  100  also includes a bus bar  115  disposed to physically contact the conductive strip  107 A, thereby establishing an electrical connection between the bus bar  115  and the finger contacts  107 . The bus bar is formed of a solid piece of metal for improvement in azimuthal electroplating uniformity about a periphery of the wafer  109 . 
     The bath volume  113  includes an anode member  117 . In some embodiments, the anode member  117  is formed of copper. However, in other embodiments, the anode member  117  can be formed of other electrically conductive materials suitable for the particular electroplating process that is being performed. In some embodiments, a membrane  118  is disposed within the bath volume  113  to physically separate an anodic region below the membrane  118  from a cathodic region above the membrane  118 . The membrane  118  is configured to prevent bulk communication of electroplating solution (electrolyte) between the anodic region and the cathodic region, while allowing for ionic communication between the anodic region and the cathodic region. In some embodiments, the membrane  118  is an ion selective membrane. A channeled ionic resistive plate (CIRP)  114  is positioned between the wafer  109  and the anode member  117 . The CIRP  114  includes channels to allow electroplating solution from the bath volume  113  to flow upward into the processing region  102  and to the surface of the wafer  109 . These channels within the CIRP  114  are shown in  FIG.  6   . 
     During the electroplating process, a positive terminal of a direct current power supply is electrically connected to the anode member  117 , and a negative terminal of the direct current power supply is electrically connected to the bus bar  115 . In this manner an electrical current flow path is established from the anode member  117  through the electroplating solution to the surface of the wafer  109  exposed to the electroplating solution, and from the surface of the wafer  109  to the finger contacts  107 , and from the finger contacts  107  to the bus bar  115 . Typically, prior to the electroplating process, a conductive seed layer is formed on the surface of the wafer  109  to be plated, thereby providing initial electrical conductivity across the wafer  109 . Then, as material deposits/grows on the wafer  109  during the electroplating process, the deposited material contributes to the electrical conductivity across the wafer  109 . 
       FIG.  3    shows a vertical cross-section of the cup member  101  positioned near the insert member  116 . The cup member  101  (holding the wafer  109  face-down) is placed in close proximity though slightly above the top side of the insert member  116  to allow rotation of the cup member  101  and wafer  109  during plating. In the configuration of  FIG.  3   , the gap  119  between the cup member  101  and the insert member  116  is unsealed. Electroplating solution (provided from under/within the CIRP  114 ) is provided as a high velocity cross-flow between the CIRP  114  and wafer  109 , with the goal of providing fresh supply of electroplating solution deep into the wafer&#39;s features. Because of the large pressure generated by the cross-flow of electroplating solution, a portion of the flow leaks out of the gap  119  between the cup member  101  and insert member  116 . This loss of electroplating solution reduces the quantity and velocity of the cross-flow of electroplating solution that contacts the wafer  109  surface. Fluidic models have indicated that up to 30% of the cross-flow of electroplating solution can be lost through the gap  119  between the cup member  101  and the insert member  116 . This loss of electroplating solution reduces metal ion supply deep within through-resist features, thereby reducing the plating throughput while also degrading on-wafer performance. However, in the configuration of  FIG.  3   , the gap  119  between the cup member  101  and the insert member  116  is maintained to enable rotation of the cup member  101  (and wafer  109 ) relative to the insert member  116 . 
     A modified version of the configuration of  FIG.  3    can include a rubber seal  121  (e.g., Viton rubber seal) disposed between the cup member  101  and the insert member  116  to reduce the cross-flow leakage of electroplating solution through the gap  119 . In various embodiments, the rubber seal  121  can be attached either to the cup member  101  or to the top side of the insert member  116 . When the rubber seal  121  is compressed tightly between the cup member  101  and the insert member  116 , cross-flow electroplating solution is stopped from leaking out through the gap  119  around the cup member  101 . However, the rubber seal  121  approach can have some limitations. For example, the rubber seal  121  may only be effective at stopping electroplating solution flow leakage when the rubber seal  121  is firmly compressed between the cup member  101  and the insert member  116 . In this firmly compressed state, the cup member  101  (and wafer  109 ) cannot be rotated relative to the insert member  116  in a continuous manner while plating without damaging the cup member  101  and/or rubber seal  121 . Because plating without rotation of the wafer  109  can result in large feature tilt (poor within-feature (WiF) uniformity control) and can also lead to poor coplanarity/within-die (WiD) uniformity control (depending on the wafer  109  layout), rotation of the wafer  109  can be necessary to achieve acceptable plating performance. Also, the rubber seal  121  between the cup member  101  and the insert member  116  is a soft material that can have a short operational lifetime under high friction conditions. Additionally, the rubber seal  121  between the cup member  101  and the insert member  116  can be highly susceptible to failure from rubber seal  121  aging/wear or improper setup. For example, as the rubber seal  121  becomes stretched, soft, and/or damaged with age/wear, the rubber seal  121  may no longer resist flow/pressure of the electroplating solution even when compressed to a proper plating gap. The plating gap is the distance between the cup member  101  and the insert member  116 . Also, if the plating gap is set too high, the rubber seal  121  may not make firm contact with both the cup member  101  and the insert member  116  due to the rubber seal  121  having an inherently small effective range of seal. 
       FIG.  4    shows a vertical cross-section of a cup member  401  (modified relative to cup member  101 ) positioned near an insert member  403  (modified relative to insert member  116 ) with a flow-assisted dynamic seal  405  disposed to seal a gap  407  between the cup member  401  and the insert member  403 , in accordance with some embodiments. The flow-assisted dynamic seal  405  is referred to hereafter as a seal member  405 . The seal member  405  is a robust seal that eliminates cross-flow leakage of electroplating solution through the gap  407  between the cup member  401  and the insert member  403 , so as to maximize convection of electroplating solution at the wafer  109  surface to enable high throughput plating and uniform deposition. 
     In some embodiments, the seal member  405  has an annular-disk shape. In these embodiments, when viewed from above or below, the seal member  405  has a substantially annular shape defined by a uniform inner diameter and by an outer periphery. In some embodiments, the outer periphery of the seal member  405  can vary in shape as a function of azimuthal position around the outer periphery of the seal member  405 . For example, in some embodiments, the outer periphery of the seal member  405  can include a number of spaced apart outward radial projections in which holes are formed through the seal member  405  for fastener insertion. 
     The seal member  405  is positioned on the top surface of the insert member  403 . The insert member  403  is configured to circumscribe the processing region  102 . A portion  403 A of the top surface of the insert member  403  has an upward slope that slopes upward from a peripheral area  403 B of the top surface of the insert member  403  toward the processing region  102 , and to an apex  403 C of the top surface of the insert member  403 . The seal member  405  is flexible such that an outer radial portion  405 A of the seal member  405  conforms to the upward slope of the portion  403 A of the top surface of the insert member  405 , and such that an inner radial portion  405 B of the seal member  405  projects inward toward the processing region  102 . 
     In some embodiments, the inner radial portion  405 B of the seal member  405  projects toward the processing region  102  at an upward angle relative to horizontal when the seal member  405  is positioned on the top surface of the insert member  403 . In some embodiments, the inner radial portion  405 B of the seal member  405  projects inward toward the processing region  102  from the apex  403 C of the top surface of the insert member  405 . And, the inner radial portion  405 B of the seal member  405  is configured to flex downward about the apex  403 C of the top surface of the insert member  403  when a downward force is applied to a top surface of the inner radial portion  405 B of the seal member  405 . 
     The leakage path that the seal member  405  stops is the small but significant gap  407  between the cup member  401  (which holds the wafer  109  facing downward toward the processing region  102 ) and a top side of the insert member  403 . The insert member  403  is attached to the CIRP  114  that separates the wafer  109  from the anode  117 . The seal member  405  is attached to the top side of the insert member  403  (as opposed to being attached to the cup member  401 ) using a clamp ring  409 . The top side of the insert member  403  is formed to slant upward toward the processing region  102 , which forces the seal member  405  to arc upward when the seal member  405  is clamped down to the top side of the insert member  403  by the clamp ring  409 . In some embodiments, the clamp ring  409  is configured to hold the seal member  405  against the top surface of the insert member  403  at a location radially outside of the upward slope of the top surface of the insert member  403 . For example, in the example configuration of  FIG.  4   , the clamp ring  409  is configured to hold the seal member  405  against the top surface of the insert member  403  at the peripheral area  403 B located radially outside of the upward slope of the portion  403 A of the top surface of the insert member  403 . In some embodiments, the clamp ring  409  is bolted to the insert member  403  through the seal member  405 . However, it should be understood that in other embodiments, the clamp ring  409  can be secured to the insert member  403  in other ways, such as by exterior c-clamps or other tightening/fastening devices, so long as the clamp ring  409  functions to pull the seal member  405  downward toward the top surface of the insert member  403  such that the seal member  405  assumes a vertical cross-sectional shape that conforms to the contour of the top surface of the insert member  403 . 
     The cup member  401  has an annular shape so as to circumscribe the processing region  102 . The cup member  401  has a bottom surface that includes an outer radial portion  411  configured to form a liquid seal with the top surface of the inner radial portion  405 B of the seal member  405  when the cup member  401  is substantially centered over the seal member  405  and moved downward to contact the seal member  405 . In some embodiments, the outer radial portion  411  of the bottom surface of the cup member  401  is part of a notch region formed at the bottom perimeter of the cup member  401  to provide a location where the seal member  405  can press against the cup member  401  in a substantially uniform manner about the periphery of the cup member  101  to firmly block electroplating solution leak paths through the gap  407 . In some embodiments, the outer radial portion  411  of the bottom surface of the cup member  401  has a substantially horizontal orientation when the cup member  401  is substantially centered over the seal member  405  and moved downward to contact the seal member  405 . It should be understood that the top surface of the inner radial portion  405 B of the seal member  405  presses firmly against outer radial portion  411  of the bottom surface of the cup member  401 , when the cup member  401  is lowered into plating position, i.e., when the cup member  401  is lowered relative to the insert member  403  to a position at which the inner radial portion  405 B of the seal member  405  is contacted and pressed downward by the outer radial portion  411  of the bottom surface of the cup member  401 . 
     The slanted design of the top side of the insert member  403  serves to pre-load the seal member  405 , such that the inner radial portion  405 B of the seal member  405  arcs upward to make contact with the cup member  401  when the cup member  401  is lowered into plating position. In some embodiments, the cup member  401  is configured to rotate relative to the seal member  405  when the cup member  401  is substantially centered over the seal member  405  and moved downward to contact the seal member  405 , such that the outer radial portion  411  of the bottom surface of the cup member  401  is configured to slide on the top surface of the inner radial portion  405 B of the seal member  405  while maintaining the liquid seal with the top surface of the inner radial portion  405 B of the seal member  405 . 
     The seal member  405  is made of a durable and low-friction/slippery material to enable rotation of the cup member  401  relative to the seal member  405 . The cup member  401  can be continuously rotated while in contact with the seal member  405  to provide for continuous rotation of the wafer  109  (i.e., in a dynamic fashion) without damaging the seal member  405  and/or the cup member  401 , even at cup member  401 /wafer  109  rotation rates up to 200 rpm (revolutions per minute). In some embodiments, the seal member  405  is formed of polytetrafluoroethylene (PTFE). For example, in some embodiments, the seal member  405  is made of TEFLON™, which is a form of PTFE. When the seal member  405  is formed of PTFE, the top surface of the inner radial portion  405 B of the seal member  405  is durable and has a low coefficient of friction so that the cup member  401  can rotate against the seal member  405  without damaging either the cup member  401  or the seal member  405 . In some embodiments, the seal member  405  is formed of a material other than PTFE. For example, in some embodiments, the seal member  405  is formed of a low friction, high wear resistance polymer, such as polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polyamideimide (PAI), or ultra-high-molecular-weight polyethylene (UHMW), among others. 
     In some embodiments, the seal member  405  can be formed of an elastomer mixture, so long as the seal member  405  has sufficient durability and a sufficiently low coefficient of friction to enable rotation of the cup member  401  against the seal member  405  without damaging either the cup member  401  or the seal member  405 . In some embodiments, the seal member  405  can be formed of an elastomer mixture that includes a low friction additive that reduces the coefficient of friction of the seal member  405 . For example, in some embodiments, the low friction additive is one or more of polytetrafluoroethylene, molybdenum disulfide, and graphite. In some embodiments, the seal member  405  has a coefficient of friction less than about 0.5. In some embodiments, the seal member has a coefficient of friction less than about 0.1. 
     The seal member  405  is referred to as a “flow-assisted dynamic seal” because a pressure of the electroplating solution flow underneath the cup member  401  is used to enhance the sealing ability of the seal member  405  by pressing the inner radial portion  405 B of the seal member  405  more firmly against the cup member  401 . It should be appreciated that in contrast to the above-mentioned rubber seal  121  disposed between the cup member  101  and the insert member  116 , which can leak when the electroplating solution flow pushes against the rubber seal  121 , the configuration of the seal member  405  uses the pressure of the electroplating solution flow underneath the cup member  401  to enhance the sealing ability of the seal member  405  by pressing the inner radial portion  405 B of the seal member  405  more firmly against the outer radial portion  411  of the bottom surface of the cup member  401 . Additionally, another advantage of the seal member  405  relative to the rubber seal  121  is that that the seal member  405  conforms to misalignments between the cup member  401  and the insert member  116 . In contrast to the seal member  405 , the rubber seal  121  has low compression and imperfect parallelism between the cup member  401  and the insert member  116 , which results in varying compression and corresponding sealing performance along the sealing interface provided by the rubber seal  121 . Relative to the rubber seal  121 , the seal member  405  provides much higher compression without application of significantly higher force. This means that the performance of the seal member  405  is maintained over a larger range of operating conditions. 
     Use of the seal member  405  provides for optimal plating conditions by enabling: 1) high electroplating solution cross-flow across the wafer  109  due to minimized electroplating solution flow leaks, and 2) continuous rotation of the cup member  401 /wafer  109 . These optimal plating conditions of minimized electroplating solution flow leakage and continuous cup member  401 /wafer  109  rotation, together yield high wafer  109  processing throughput and excellent WiF and WiD. Also, the seal member  405  is flexible and effective over a wide setup range. That is, the seal member  405  has a large effective range. More specifically, the seal member  405  is able to eliminate electroplating solution flow losses through the gap  407 , even if the plating gap (distance between the cup member  401  and the insert member  403 ) is varied over several millimeters. The large effective range of the seal member  405  is achieved through the flexibility and the pre-loaded, upward-arcing design of the seal member  405 . The large effective range of the seal member  405  enables a high process-window and high margin-for-error in terms of hardware installation and setup reproducibility. The large effective range of the seal member  405  also enables edge tuning the wafer  109  performance (e.g., feature height distribution) by intentionally varying the plating gap. Also, the plating gap adjustability afforded by the seal member  405 , while maintaining the sealed state between the cup member  401  and the insert member  403 , enables processing of multiple product types. Even under various loads and/or plating gap setup heights, the seal member  405  is able to effectively block electroplating solution flow losses through the gap  407  over a wide range due to its flexibility and pre-loaded, upward arcing design. 
       FIG.  5 A  shows a vertical cross-section of the interface between the cup member  401  and the seal member  405  just as the outer radial portion  411  of the bottom surface of the cup member  401  is brought into contact with the inner radial portion  405 B of the seal member  405 , in accordance with some embodiments. The contact between the cup member  401  and the seal member  405  in  FIG.  5 A  may be sufficient to seal the gap  407  between the cup member  401  and the insert member  403 .  FIG.  5 B  shows the vertical cross-section of the interface between the cup member  401  and the seal member  405  of  FIG.  5 A  as the cup member  401  is lowered further relative to the insert member  403 , in accordance with some embodiments. As the seal member  405  presses against the outer radial portion  411  of the bottom surface of the cup member  401 , the seal member  405  can flex to ensure a tight seal against the cup member  401 . In the configuration of  FIG.  5 B , the cup member  401  makes moderate contact with the seal member  405 .  FIG.  5 C  shows the vertical cross-section of the interface between the cup member  401  and the seal member  405  of  FIG.  5 B  as the cup member  401  is lowered further relative to the insert member  403  to a plating position, in accordance with some embodiments. At the plating position, the seal member  405  presses against the outer radial portion  411  of the bottom surface of the cup member  401 , and the seal member  405  flexes to contact an area within the outer radial portion  411  of the bottom surface of the cup member  401  to ensure a substantially liquid-tight seal against the cup member  401 . In the configuration of  FIG.  5 C , the cup member  401  makes extensive contact with the seal member  405 . 
       FIG.  6    shows a top isometric view of the insert member  403  with the seal member  405  and clamp ring  409  installed on the insert member  403 , in accordance with some embodiments.  FIG.  7    shows another top isometric view of the insert member  403  with the seal member  405  and clamp ring  409  installed on the insert member  403 , in accordance with some embodiments. 
       FIG.  8    shows a vertical cross-section view of the seal member  405  positioned to seal/close the gap  407  between the cup member  401  and the insert member  403  when the cup member  401  is lowered to the plating position, in accordance with some embodiments.  FIG.  9    shows a bottom isometric view of the cup member  401 , in accordance with some embodiments. The outer radial portion  411  of the bottom surface of the cup member  401  is shown in  FIG.  9   . 
       FIG.  10 A  shows another vertical cross-section view of the seal member  405  positioned to seal/close the gap  407  between the cup member  401  and the insert member  403  when the cup member  401  is lowered to the plating position, in accordance with some embodiments.  FIG.  10 B  shows a top isometric view of the seal member  405 , in accordance with some embodiments. 
       FIG.  11 A  shows a vertical cross-section of the cup member  401  positioned near the insert member  403  with the seal member  405  disposed to seal the gap  407  between the cup member  401  and the insert member  403 , and with a backing member  1101  positioned below the seal member  405 , in accordance with some embodiments. The backing member  1101  can also be referred to as an “energizer.”  FIG.  11 B  shows a top isometric view of the backing member  1101 , in accordance with some embodiments. The backing member  1101  is disposed between the seal member  405  and the top surface of the insert member  403 . More specifically, the backing member  1101  is positioned between the seal member  405  and the top side of the insert member  403 , and is clamped to the insert member  403  in conjunction with clamping of the seal member  405  to the insert member  403  using the clamp ring  409 . In some embodiments, the backing member  1101  has a shape that is substantially equivalent to the annular-disk shape of the seal member  405 . In some embodiments, the clamp ring  409  is configured to hold both the seal member  405  and the backing member  1101  against the top surface of the insert member  403  at a location radially outside of the upward slope of the top surface of the insert member  403 . In some embodiments, the clamp ring  409  is bolted to the top surface of the insert member  403  through both the seal member  405  and the backing member  1101 . 
     The backing member  1101  is a support material disposed as a backing underneath the seal member  405  to increase a pressure applied by the seal member  405  against the cup member  401  and to extend the operational lifetime of the seal member  405 . The backing member  1101  is configured to apply a resistive upward force through the seal member  405  when a downward force is applied to a top surface of the inner radial portion  405 B of the seal member  405 . Also, the backing member  1101  is configured to prevent a flow of electroplating solution against a bottom surface of the inner radial portion  405 B of the seal member  405 . In some embodiments, the backing member  1101  is formed of spring stainless steel. However, in other embodiments, the backing member  1101  can be formed of other materials that provide adequate mechanical, chemical, and thermal performance. The backing member  1101  can extend the operational lifetime of the seal member  405  by reducing the susceptibility of the seal member  405  to creasing. The backing member  1101  can also serve as a scaffolding for the seal member  405  in the event that the seal member  405  gradually creeps or deforms over time. When the backing member  1101  is formed of spring stainless steel, or similar material, the backing member  1101  can be thermally treated to retain its integrity and resist deformation. 
     It should be understood a sealing device is disclosed herein for an electroplating apparatus for semiconductor wafer fabrication. The sealing device includes the seal member  405  defined as an annular-disk-shaped structure configured for installation on the top surface of the insert member  403  of the electroplating apparatus. The annular-disk-shaped structure (seal member  405 ) has flexibility to physically conform to the contour of the top surface of the insert member  403  such that the outer radial portion  405 A of the annular-disk-shaped structure (seal member  405 ) conforms to the upward slope of the top surface of the insert member  403 , and such that the inner radial portion  405 B of the annular-disk-shaped structure (seal member  405 ) projects inward toward the processing region when the annular-disk-shaped structure (seal member  405 ) is installed on the top surface of the insert member  403 . 
       FIG.  12    shows a flowchart of a method for electroplating a semiconductor wafer, in accordance with some embodiments. The method includes an operation  1201  for having an electroplating apparatus that includes the insert member  403  configured to circumscribe the processing region  102 . The top surface of the insert member  403  includes the portion  403 A has the upward slope that slopes upward from the peripheral area  403 B of the top surface of the insert member  403  toward the processing region  102 . The electroplating apparatus also includes the seal member  405  having the annular-disk shape. The seal member  405  is positioned on the top surface of the insert member  403 . The seal member  405  is flexible such that the outer radial portion  405 A of the seal member  405  conforms to the upward slope of the top surface of the insert member  403 , and such that the inner radial portion  405 B of the seal member  405  projects toward the processing region  102 . The electroplating apparatus also includes the cup member  401  having an annular shape. The cup member  401  has the bottom surface that includes the outer radial portion  411  configured to form the liquid seal with the top surface of the inner radial portion  405 B of the seal member  405  when the cup member  401  is substantially centered over the seal member  405  and moved downward to contact the seal member  405 . 
     The method also includes an operation  1203  for moving the cup member  401  downward to form the liquid seal between the outer radial portion  411  of the bottom surface of the cup member  401  and the top surface of the inner radial portion  405 B of the seal member  405 . The method also includes an operation  1205  for flowing electroplating solution through the processing region  102 . In the operation  1205 , a portion of the electroplating solution flows against the bottom surface of the inner radial portion  405 B of the seal member  405  and presses the seal member  405  against the cup member  401  to assist with maintaining the liquid seal between the outer radial portion  411  of the bottom surface of the cup member  401  and the top surface of the inner radial portion  405 B of the seal member  405 . The method also includes an optional operation  1207  for rotating the cup member  401  relative to both the insert member  403  and the seal member  405 , such that the outer radial portion  411  of the bottom surface of the cup member  401  slides on the top surface of the inner radial portion  405 B of the seal member  405  while maintaining the liquid seal between the outer radial portion  411  of the bottom surface of the cup member  401  and the top surface of the inner radial portion  405 B of the seal member  405 . 
     It should be appreciated that the seal member  405  disclosed herein, along with the cup member  401  and the insert member  403 , reduces and/or prevents electroplating solution leakage through the gap  407  between the cup member  401  and the insert member  403 , and therefore provides improved electroplating solution cross-flow and improved electroplating solution convection within features on the wafer  109 . This improved electroplating solution cross-flow and convection corresponds to improved plating performance on the wafer  109 , such as improved WiF uniformity and skirting reduction. The improved electroplating solution convection also enables better ion transport to feature bottoms on the wafer  109 , which can enable higher plating rates and increase overall wafer  109  fabrication throughput. 
     The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure. 
     Although the foregoing disclosure has been presented in some detail for purposes of clarity of understanding, it will be apparent that certain changes and modifications can be practiced within the scope of the embodiments disclosed herein. Accordingly, the present embodiments are to be considered as illustrative and not restrictive, and the disclosure is not to be limited to the details given herein, but may be modified within the scope and equivalents of the described embodiments.