Area selective atomic layer deposition (ALD) of titanium dioxide using polymer films as masking layers has been investigated. A number of factors which must be considered while designing a successful area selective ALD process have been determined and are briefly discussed. Reactivity of the polymer with the ALD precursor species, diffusion of ALD precursors through the polymer mask, and remnant precursor content in the masking film during ALD cycling are key factors. This article investigates the effect of different precursor chemistries in view of the above mentioned factors. Titanium tetrachloride and titanium isopropoxide have been used as two different metal precursors in conjunction with poly(methyl methacrylate) films as photodefinable masking layers. Processing problems arising from factors such as diffusion of precursors through the masking layer can be solved through careful choice of ALD precursors. (c) 2006 American Vacuum Society.