Self-limiting deposition of copper from copper beta-diketonates and plasma electrons

Copper metallic films are essential components in semiconductor devices. In this study, copper films were deposited by a pulsed electron chemical vapor deposition (e-CVD) process using free electrons from a plasma discharge as reducing agents, with copper beta-diketonates, Cu(hfac)2 and Cu(acac)2 as the copper source. The mass gain per deposition cycle monitored by a quartz crystal microbalance (QCM) sensor revealed a self-limiting deposition process, suggesting that the process is an electron atomic layer deposition (e-ALD) process. X-ray photoelectron spectroscopy (XPS) shows that the films are contaminated by carbon, oxygen, and when Cu(hfac)2 was used, also fluorine. Optical emission spectroscopy (OES) suggests that this is caused by redeposition of precursor fragments from plasma volume decomposition of precursor molecules desorbing during the plasma step.