Patent ID: 6652727
Filing Date: 2003-11-25
Classification: C25D,H05K

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 comprising,immersing, as an electrode, an electrically conductive substrate having a generally smooth surface having 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, said electroplating bath being substantially devoid of at least one additive selected from the group consisting of levelers and brighteners; immersing a counterelectrode in said plating bath; preferentially depositing metal into said hydrodynamically isolated recesses by passing a first modulated reversing electric current between said electrodes, wherein said first modulated reversing electric current comprises a first pulse train of first cathodic pulses and first anodic pulses, with respect to said electrically conductive substrate, the charge transfer ratio of said first cathodic pulses to said first anodic pulses is greater than one, said first cathodic pulses have an on-time ranging from about 0.83 microseconds to about 200 milliseconds, and said first anodic pulses have an on-time greater than the on-time of said first cathodic pulses and ranging from about 42 microseconds to about 198 milliseconds; and preferentially depositing metal into said hydrodynamically accessible recesses by passing a second modulated reversing electric current between said electrodes, wherein said second modulated reversing electric current comprises a second pulse train of second cathodic pulses and second anodic pulses, the charge transfer ratio of said second cathodic pulses to said second anodic pulses is greater than one, said second cathodic pulses have an on-time ranging from about 0.12 milliseconds to about 198 milliseconds, said second anodic pulses have an on-time shorter the on-time of said second cathodic pulses and ranging from about 2 microseconds to about 60 milliseconds.