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

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.