Patent ID: 6309528
Filing Date: 2001-10-30
Classification: C25D,H05K,Y10S,Y10T

Abstract:
A method for depositing a continuous layer of a metal onto a substrate having both hydrodynamically inaccessible recesses and hydrodynamically accessible recesses on its surface comprisingimmersing as an electrode an electrically conductive substrate having a generally smooth surface having both at least one hydrodynamically inaccessible recess and at least one hydrodynamically accessible recess in said surface in an electroplating bath containing ions of a metal to be deposited onto said surface,immersing a counter electrode in said plating bath,in a first electroplating step, passing a first modulated reversing electric current between said electrodes, whereinsaid first modulated reversing electric current comprises first cathodic pulses and first anodic pulses,said first cathodic pulses have a duty cycle less than about 50% and said first anodic pulses have a duty cycle greater than about 50%,the charge transfer ratio of said first cathodic pulses to said first anodic pulses is greater than one, andthe frequency of said first pulses ranges from about 10 Hertz to about 12000 Hertz; andin a second electroplating step, passing a second modulated reversing electric current between said electrodes, whereinsaid second modulated reversing electric current comprises second cathodic pulses and second anodic pulses,said second cathodic pulses have a duty cycle greater than about 50% and said second anodic pulses have a duty cycle less than about 50%,the charge transfer ratio of said second cathodic pulses to said second anodic pulses is greater than one, andthe frequency of said second pulses ranges from about 10 Hertz to about 5000 Hertz.