Via filling method

Abstract

A process for via filling is provided, wherein after flash plating, a PPR current is applied for a cycle of 1 to 50 msec positive electrolysis time and 0.2 to 5 msec reverse electrolysis time until an F/R ratio representing the ratio of positive electrolysis current density to reverse electrolysis current density is at least 1/0.2 and less than 1/1.

What is claimed is:  
     
         1 . A process for filling a via with a metal comprising the steps of flash plating and then applying a PPR current for a cycle of 1 to 50 msec positive electrolysis time and 0.2 to 5 msec reverse electrolysis time such that a F/R ratio representing a ratio of positive electrolysis current density to reverse electrolysis current density is from 1/0.2 to 1/1.  
     
     
         2 . The process of  claim 1 , wherein the flash plating is performed by direct-current electrolysis.  
     
     
         3 . The process of  claim 1 , wherein the flash plating is performed under conditions of applying a PPR current for a cycle of 1 to 50 msec positive electrolysis time and 0.2 to 5 msec reverse electrolysis time until an F/R ratio is 1/1 to 1/10.  
     
     
         4 . The process of  claim 1 , wherein the flash plating is performed by pulse electrolysis.  
     
     
         5 . The process of  claim 1 , wherein the PPR current is applied for a cycle of 1 to 50 msec positive electrolysis time, 0.2 to 5 msec reverse electrolysis time, and 0.1 to 20 msec rest time.  
     
     
         6 . The process of  claim 1 , wherein the metal used for filling is copper.  
     
     
         7 . The process of  claim 1 , wherein the via filling is performed using a metal plating bath containing a grain refiner.  
     
     
         8 . The process of  claim 1 , wherein the via filling is performed using a metal plating bath containing a surface active agent.  
     
     
         9 . A printed circuit board containing a via filled by the process of  claim 1 .  
     
     
         10 . A wafer containing a via filled by the process of  claim 1.