Cost-effective systems for atomic layer deposition

Herein, we describe the design and testing of two different home-built atomic layer deposition (ALD) systems for the growth of thin films with sub-monolayer control over film thickness. The first reactor is a horizontally aligned hot-walled reactor with a vacuum purging system. The second reactor is a vertically aligned cold-walled reactor with a quartz crystal microbalance (QCM) and a vacuum purging system. This latter reactor was also built to be capable of the addition of liquid- or solution-phase precursors, including the addition of a solution-based precursor containing nanoparticles. Each system cost less than $10,000, and they were used to deposit aluminum oxide thin films using trimethylaluminum and water/isopropyl alcohol as coreactants. Whereas the horizontal hot-walled system was able to deposit alumina thin films at a growth rate of 1.2-1.4 Å/cycle, the more sophisticated vertically aligned reactor deposited films at 0.95-1.1 Å/cycle, which is comparable to commercial systems costing 100,000 or more. Most importantly, both systems were fabricated entirely by M.S. and undergraduate students at Central Michigan University.