Patent ID: 6863793

Claim:
A method for depositing a continuous layer of a metal onto a substrate having small recesses in its surface comprising: immersing an electrically conductive substrate having a generally smooth surface having small recesses therein 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 member selected from the group consisting of levelers and brighteners, immersing a counter electrode in said plating bath, passing an electric current between said electrodes, wherein said electric current is a modulated reversing electric current comprising pulses that are cathodic with respect to said substrate and pulses that are anodic with respect to said substrate, the charge transfer ratio of said cathodic pulses to said anodic pulses is greater than one, and the on-time of said first cathodic pulses ranges from about 0.83 microseconds to about 50 milliseconds and the on-time of said first anodic pulses is greater than the on-time of said cathodic pulses and ranges from about 42 microseconds to about 99 milliseconds, in a second electroplating step, passing a second modulated reversing electric current between said electrodes, wherein said 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, and the frequency of said second pulses ranges from about 10 Hertz to about 5000 Hertz.