Optimization of Plasma Characteristics in Plasma-Assisted Atomic Layer Deposition: Effect on Film Structure and Process Enhancement Prospects

摘要

Atomic layer deposition (ALD) has demonstrated its potential to fabricate barrier and modification layers on polymer substrates. It can provide very high performance in applications such as flexible electronics and flexible packaging. The optimization of cycle steps represents a challenge in low temperature ALD required for polymers. One way to increase the process efficiency is to assist the process by plasma. Plasma is used to generate radicals to increase the reaction rates but can also be used to increase the desorption of by-products and adsorbed precursors. Both the gas generating the plasma and the plasma exposure time play a crucial role in the film growth mechanism, the interaction between plasma and polymer surface, film structure, and consequently the performance of the deposited film. In this paper we report the growth characteristics of metal oxide films on various polymer substrates. When the gas used for purging and in generating the plasma was pure argon, the film adhesion on PMMA substrate became insufficient. Satisfactory adhesion was achieved with a nitrogen-argon mixture with low plasma power and with relatively short plasma exposure time. Plasma-assistance can also be used to control the film structure. Using TDMAT precursor for TiO_2 film growth produced nitrogen doping of the film, which may improve its photocatalytic activity.