Self-limiting deposition of copper from copper <i>beta</i> -diketonates and plasma electrons

We studied deposition of copper films by a pulsed electron chemical vapor deposition 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, as monitored by a quartz crystal microbalance sensor, suggests that pulsing allows us to access a process window with a self-limiting deposition process. X-ray photoelectron spectroscopy shows that the films are not metallic copper and that they are contaminated by carbon, oxygen, and when Cu(hfac)2 was used, also fluorine. We speculate that the surface chemistry involves electron stimulated desorption reactions. Optical emission spectroscopy suggests redeposition of precursor fragments from plasma volume decomposition of precursor molecules desorbing during the plasma step. This redeposition limits the control of the surface chemistry during the plasma step of the deposition cycle.