Real Time Observation by Atomic Force Microscopy of Spontaneous Recrystallization at Room Temperature in Electrodeposited Copper Metallization

Room temperature recrystallization of electrodeposited copper metallization was observed in real time by in situ atomic force microscopy. The films examined were 31 nm thick and were deposited galvanostatically from a stirred CuSO 4 bath containing 0.05 mol dm − 3 CuSO 4 and 1 mol dm − 3 H 2 SO 4 , both with and without 1.3 × 10 − 4 mol dm − 3 thiourea, typically at 0.8 mA cm − 2 . Substrates were polished bulk gold or sputter-coated copper films on TaN on silicon. An induction period was observed before the onset of recrystallization, and subsequently, grain growth occurred. The nucleated grains appeared to be significantly smaller than the existing grains and this may have important implications for surface reactivity and the stability and evolution of microstructure. Surface roughness measurements were correlated with recrystallization.