Report on the Database of Etchant-material Pairs for Self-correcting AS-ALD
This research focuses on developing a self-correcting method for AS-ALD, with the ultimate aim to generate a vapor-based process in which defects that arise during AS-ALD can be removed by a vapor etch step and eventually move toward a SAM-free process. The first step of the research is the construction of a database of etchant-material pairs intended to help in the selection of etchants for the AS-ALD process. This report describes the etching capability of several solvents and dilute acid/base solutions. Commonly used solvents such as acetone, ethanol, methanol and isopropyl alcohol, as well as acids and bases, were investigated in solution phase. It is found that the use of dilute acids and bases such as nitric acid and potassium hydroxide can be used to slowly etch metal oxide materials deposited by ALD. These slow etch rates combined with differential nucleation rates between various substrate surfaces may be exploited to improve selectivity in AS-ALD by incorporating cyclical etch-back steps to remove defects.