Applying Lessons Learned from An Etching Lab: The Role of O Atoms In PECVD
Colin A. Wolden, Colorado School of Mines, 1500 Illinois, Golden, CO 80401
I was fortunate to spend the final 18 months of my PhD working in the Sawin laboratory. In this talk I will briefly recount that experience and illustrate the vital impact it had on the evolution of my own research in developing plasma-assisted technologies for the deposition of electronic oxides and thin film photovoltaics. My experience in the Sawin laboratory led directly to our development of high vacuum plasma-assisted chemical vapor deposition, which was used for the synthesis of semi-conducting zinc oxide. A modification of this approach was used for the plasma-assisted co-evaporation copper chalcopyrite photovoltaic absorbers. In studies of metal oxide synthesis by standard PECVD our work has focused on the dominant role of O atoms in controlling the gas-phase chemistry. This work lead to the development of low frequency pulsed PECVD as a high rate alternative to ALD for self-limiting deposition (~ 1 Å/pulse) of metal oxides. We describe the deposition process and highlight critical aspects of reaction design and operation, using examples from several material systems. With cycle times < 1 s, net rates > 30 nm/min were obtained by pulsed PECVD while retaining high quality and digital control.