Selective deposition of Ta2O5 by adding plasma etching super-cycles in plasma enhanced atomic layer deposition steps

Abstract

In this paper, a new route for a selective deposition of thin oxide by atomic layer deposition is discussed. The proposed process is using super cycles made of an additional plasma etching step in a standard plasma enhanced atomic layer deposition (PEALD) process. This allows the selective growth of a thin oxide on a metal substrate without a specific surface deactivation by means of self assembled monolayer. It is shown that adding a small amount of NF3 etching gas to an oxygen plasma gas every eight cycles of the PEALD process helps to fully remove the Ta2O5 layer on Si and/or SiO2 surface while keeping few nanometers of Ta2O5 on the TiN substrate. NF3 addition is also used to increase the incubation time before Ta2O5 growth on Si or SiO2 substrate. In this way, a selective deposition of Ta2O5 on the TiN substrate is obtained with properties (density, leakage current…) similar to the ones obtained in a conventional PEALD mode. Hence, the authors demonstrate that a future for selective deposition could be a process using both PEALD and atomic layer etching.