Pulse sequence for plating on thin seed layers

A method of controlling plating of copper interconnects on a semiconductor wafer, the method comprising:

• (a) immersing a plating surface of the wafer in plating bath comprising a copper salt and a suppressor while applying a cathodic current to the wafer in the range of about 1.5 to 20 mA/cm2 during substantially the entire immersion of the plating surface;
• (b) within less than about 1000 ms of completing the immersion in (a), applying a cathodic current pulse to the wafer, the pulse having a magnitude of at least about 20 mA/cm2 for a duration of about 20 to 1000 ms;
• and
• (c) within less than about 1000 ms of completing the optional current pulse in (b), conducting bottom up copper fill with a baseline current density of about 1 to 20 mA/cm2 and a plurality of micropulses having a magnitude of about 10 to 40 mA/cm2 above the baseline current density, the micropulses having a duration of about 1 to 495 ms, a time interval between micropulses being about 50 to 500 ms, wherein the magnitude of each micropulse, the duration of each micropulse, or the time interval between any two micropulses is stochastic.

An electroplating apparatus comprising:

• one or more electroplating chambers;
• one or more robots capable of transferring semiconductor wafers;
• and
• a power supply with an associated controller for executing a set of instructions, the set of instructions comprising instructions for:
• applying a fixed cathodic potential to a wafer during immersion;
• removing the fixed cathodic potential upon an indication that the wafer is fully immersed in a plating bath;
• applying a high current pulse within less than about 1000 ms after removing the fixed cathodic potential, the high current pulse having a magnitude of at least about 20 mA/cm2 for a duration of about 20 to 1000 ms;
• and
• transitioning to a current appropriate for bottom up fill.