A study is undertaken to determine the effect of low (10gL) and high (100gL) acid conditions on superconformal copper electroplating. The suppressor used is the surfactant P-104 at 200ppm, with the accelerator bis(3-sulfopropyl)-disulfide (SPS) at a concentration of 535ppm. High acid open circuit potential and polarization curves are shifted approximately 30mV from low acid, both with and without P-104; Tafel slopes are the same at 100mV/decade. P-104 displays the same suppression strength in both electrolytes. Patterned 100nm trenches show that the rate of high and low acid filling is essentially the same at low SPS concentration (5ppm). As SPS increases, high acid filling is improved; the effect in low acid is inverse, albeit not as strong. As suppression strength is the same in high and low acids, the dependence on SPS during filling is attributed to acceleration, which involves an interaction between suppressor and accelerator molecules.

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