System and method for solder bump plating

Abstract

The present invention relates to a system single-metal plating, a system for binary-metal plating, and a system for solder-bump plating. The solder-bump plating system comprises a single-metal plating system for plating a preconditioned substrate to form a single-metal plated substrate; and a binary-metal plating system for plating the single-metal plated substrate. In a preferred implementation, the solder-bump plating system of the present invention is configured to single-metal plate a preconditioned substrate using a first plating solution to provide a single-plated substrate; to single-metal plate the single-plated substrate using a second plating solution to provide a double-plated substrate; and to binary-metal plate the double-plated substrate using a third plating solution to provide a solder-bump plated substrate. A novel apparatus for use in plating a substrate comprises an electrically conductive holder comprising a handle portion having at least one electrical contact and a holder portion having at least one flexible electrical contact.

1 . A system of binary-metal plating comprising:
 a solution comprising a material source of metal ions of two or more metals;   an anode and a cathode immersed in the solution, thereby forming a circuit;   a preconditioned substrate electrically connected to the cathode;   a current source connected to the anode and cathode for applying a high current density to the circuit; and   a means for agitating the solution, wherein application of the high current density and the agitating means to the solution causes metal ions in the solution to be reduced and to become uniformly deposited onto the substrate.   
     
     
         2 . The system of  claim 1 , wherein the material source of metal ions comprises tin and lead ions. 
     
     
         3 . The system of  claim 2 , wherein the material source of metal ions are substantially in a composition ratio of 63% tin ions and 37% lead ions. 
     
     
         4 . The system of  claim 1 , wherein the preconditioned substrate comprises one of an integrated circuit, a semiconductor chip, and a wafer. 
     
     
         5 . The system of  claim 1 , wherein high current density is within a range of greater than 10 mA/cm 2  to 3,000 mA/cm 2 . 
     
     
         6 . The system of  claim 1 , wherein the cathode comprises:
 an electrically conductive holder having at least one electrical contact; and   a cover.   
     
     
         7 . The system of  claim 1 , wherein the current source comprises a power supply configured to deliver at least one of direct current (DC), pulsed-DC, and reversed-pulsed DC. 
     
     
         8 . The system of  claim 1 , wherein the agitation means comprises an electrically controlled magnetic stirrer. 
     
     
         9 . The system of  claim 1 , further comprising an instrument configured to measure at lease one of plating thickness and plating uniformity. 
     
     
         10 . A method of binary-metal plating comprising:
 providing a solution comprising a material source of metal ions of two or more metals;   immersing an anode and a cathode into the solution, thereby forming a circuit;   electrically connecting a preconditioned substrate to the cathode;   applying a high current density to the circuit while agitating the solution, thereby causing metal ions in the solution to be reduced and to become uniformly deposited onto the substrate.   
     
     
         11 . The method of  claim 10 , wherein the material source of metal ions comprises tin and lead ions. 
     
     
         12 . The method of  claim 10 , wherein the cathode comprises:
 an electrically conductive holder having at least one electrical contact; and   a cover.   
     
     
         13 . The method of  claim 10 , wherein high current density is within a range of greater than 10 mA/cm 2  to 3,000 mA/cm 2 . 
     
     
         14 . The method of  claim 10 , wherein the agitating step is performed via an electrically controlled magnetic stirrer. 
     
     
         15 . The method of  claim 10 , wherein the steps of the method are performed at room temperature. 
     
     
         16 . A method of solder bump plating comprising:
 single-metal plating a preconditioned substrate to form a single-metal plated substrate;   and binary-metal plating the single-metal plated substrate.   
     
     
         17 . The method of  claim 16 , wherein the single-metal plating step comprises:
 providing a single-metal plating solution comprising a material source of metal ions of a single metal;   immersing a first anode and a cathode into the single-metal plating solution, thereby forming a first circuit;   electrically connecting a preconditioned substrate to the cathode; and   applying a low current density to the first circuit, thereby causing metal ions in the solution to be reduced and to become uniformly deposited onto the substrate; and wherein the binary-metal plating step comprises:   providing a binary-metal solution comprising a material source of metal ions of two or more metals;   immersing a second anode and the cathode into the binary-metal plating solution, thereby forming a second circuit;   applying a high current density to the second circuit while agitating the binary-metal plating solution, thereby causing metal ions in the binary-metal plating solution to be reduced and to become uniformly deposited onto the substrate.   
     
     
         18 . The method of  claim 17 , further comprising:
 single-metal plating the preconditioned substrate one or more times using one or more single-metal plating solutions prior to the binary-metal plating step.   
     
     
         19 . The method of  claim 18 , further comprising:
 single-metal plating the preconditioned substrate using a first single-metal plating solution, thereby forming a single-metal plated substrate;   single-metal plating the single-metal plated substrate using a second single-metal plating solution, thereby forming a double-metal plated substrate; and   binary-metal plating the double-metal plated substrate.   
     
     
         20 . The method of  claim 19  further comprising:
 removing one or more preconditioning layers from the binary-metal plated substrate.   
     
     
         21 . The method of  claim 20  further comprising:
 reflowing the binary-metal plated substrate.   
     
     
         22 . The method of  claim 21 , wherein the first single-metal plating solution comprises copper ions. 
     
     
         23 . The method of  claim 21 , wherein second single-metal plating solution comprises nickel ions. 
     
     
         24 . The method of  claim 21 , wherein high current density is within a range of greater than 10 mA/cm 2  to 3,000 mA/cm 2 . 
     
     
         25 . The method of  claim 21 , wherein low current density is within a range of greater than 9 mA/cm 2  to 10 mA/cm 2 . 
     
     
         26 . The method of  claim 21 , wherein the cathode comprises:
 an electrically conductive holder having at least one electrical contact; and   a cover.   
     
     
         27 . The method of  claims 21 , wherein binary-metal plating solution is agitated via an electrically controlled magnetic stirrer. 
     
     
         28 . The method of  claim 21 , wherein the steps of the method are performed at room temperature. 
     
     
         29 . A system for solder bump plating comprising:
 a first plating solution comprising a material source of metal ions of a first single metal;   a first anode immersed in the first solution;   a preconditioned substrate electrically connected to a cathode;   a second plating solution comprising a material source of metal ions of a second single metal;   a second anode immersed in the second solution;   a third plating solution comprising a material source of metal ions of two or more metals;   a third anode immersed in the third solution;   a means for applying a current density to the first, second, and third plating solutions; and   a means for agitating the third solution,   wherein the cathode and substrate are immersed in the first plating solution, thereby forming a first circuit to which a low current density is applied for causing metal ions in the first plating solution to be reduced and to become uniformly deposited onto the substrate forming a first plating layer thereon;   wherein the cathode and substrate are immersed in the second plating solution, thereby forming a second circuit to which a low current density is applied for causing metal ions of the second plating solution to be reduced and to become uniformly deposited onto the first plating layer thereby forming a second plating layer thereon; and   wherein the cathode and substrate are immersed in the third plating solution, thereby forming a third circuit to which a high current is applied, together with agitation from the agitating means, thereby causing metal ions in the third solution to be reduced and to become uniformly deposited onto the second plating layer thereby forming a third plating layer thereon.   
     
     
         30 . The system of  claim 29 , wherein the cathode comprises:
 an electrically conductive holder having at least one electrical contact; and   a cover.   
     
     
         31 . The system of  claims 29 , wherein means for agitating the third plating solution comprises an electrically controlled magnetic stirrer.