Method and system for depositing alloy composition

Abstract

Electric potential, current density, and deposition rate are controlled to deposit metal alloys, such as tin based solder alloys or magnetic alloys, with minimal variations in the weight ratios of alloying metals at different locations within the deposited metal alloy feature. Alternative embodiments include processes that form metal alloy features wherein the variation in weight ratio of alloying metals within the feature is not necessarily minimized, but is controlled to provide a desired variation.

1 . A method of forming a metal alloy feature comprising:
 providing a microfeature workpiece that includes a metal feature within a recess;   providing an electroplating bath in contact with an electrode;   contacting the microfeature workpiece with the electroplating bath;   applying an electric potential between the metal feature and the electrode and producing a first current density;   depositing metal alloy having a first weight ratio of alloying metals within the recessed feature;   adjusting the electric potential to change the first current density to a second current density;   depositing metal alloy having a second weight ratio of alloying metals within the recessed feature;   adjusting the electric potential to change the second current density to a third current density; and   depositing metal alloy having a third weight ratio of alloying metals within the recessed feature.   
     
     
         2 . The method of  claim 1 , wherein the second current density is greater than the first current density. 
     
     
         3 . The method of  claim 1 , wherein the third current density is greater than the second current density. 
     
     
         4 . The method of  claim 1 , wherein the weight ratio of alloying metals in at least two of the first composition, the second composition, and the third composition are substantially the same. 
     
     
         5 . The method of  claim 1 , wherein the weight ratio of alloying metals in the first composition, the second composition and the third composition are not substantially the same. 
     
     
         6 . The method of  claim 1 , wherein the metal alloy is a solder alloy. 
     
     
         7 . The method of  claim 6 , wherein the solder alloy comprises metals selected from lead, tin, silver, and copper. 
     
     
         8 . The method of  claim 1 , wherein the metal alloy is a non-solder alloy. 
     
     
         9 . The method of  claim 1 , further comprising:
 filling the recessed feature with the metal alloy; and   depositing the metal alloy over the filled recessed feature.   
     
     
         10 . The method of  claim 9 , where the step of depositing metal alloy over the filled recessed feature is carried out at a fourth current density, the fourth current density being less than the third current density. 
     
     
         11 . The method of  claim 10 , wherein the step of depositing metal alloy over the filled recessed feature is carried out at a fourth current density, the fourth current density being greater than the third current density. 
     
     
         12 . A tool for forming a metal alloy feature comprising:
 a reactor for receiving a microfeature workpiece that includes a metal feature within a recess and contacting the microfeature workpiece and an electrode with an electroplating bath; and   a power source for applying a first electric potential, second electric potential, and third electric potential between the metal feature and the electrode, the first electric potential producing a first current density, the first current density causing a metal alloy having a first weight ratio of alloying metals to be deposited within the recessed feature, the second electric potential producing a second current density, the second current density causing a metal alloy having a second weight ratio of alloying metals to be deposited within the recessed feature, and the third electric potential producing a third current density, the third current density causing a metal alloy having a third weight ratio of alloying metals to be deposited within the recessed feature.   
     
     
         13 . A method of forming a metal alloy feature comprising:
 providing a microfeature workpiece that includes a metal feature within a recess;   providing an electroplating bath in contact with an electrode;   contacting the microfeature workpiece with the electroplating bath;   applying an electric potential between the metal feature and the electrode and producing a first current density;   depositing metal alloy having a first weight ratio of alloying metals;   adjusting the first current density to a second current density as the recessed feature is filled; and   continuing to deposit metal alloy having a weight ratio of alloying metals that is substantially similar to the first weight ratio.   
     
     
         14 . The method of  claim 13 , further comprising:
 adjusting the second current density to a third current density as the recessed feature is filled; and   continuing to deposit metal alloy having a weight ratio of alloying metals that is substantially similar to the first weight ratio.   
     
     
         15 . A method of forming a metal alloy feature comprising:
 providing a microfeature workpiece that includes a metal feature within a recess;   providing an electroplating bath in contact with an electrode;   contacting the microfeature workpiece with the electroplating bath;   applying an electric potential between the metal feature and the electrode and producing a first current density;   depositing metal alloy having a first weight ratio of alloying metals; and   controlling the variation of the weight ratio of the alloying metals in the deposited metal alloy from the first weight ratio by adjusting the current density as the recessed feature is filled.