Film Uniformity in Atomic Layer Deposition

The sources of non‐uniformity in thin films produced using atomic layer deposition (ALD) have been investigated by reviewing the mechanical hardware of ALD reactors, precursors, and the by‐products of surface reactions. The most common causes of non‐uniformity are overlapping pulses, thermal self‐decomposition of precursors, and non‐uniform gas distribution. Less studied, however, are the consequences of downstream surface reactions of gaseous by‐products. In particular, titanium nitride films have been found to be significantly less uniform than those of transition metal oxides deposited from metal halides. The influence of reaction by‐products on the TiN film growth has been studied by comparing the deposition in the cross‐flow and showerhead style reactors. Finally, the sources of non‐uniformity in plasma enhanced (PE) ALD are illustrated by studying the TiN deposition process.