Advanced Metal Thin Film Nucleation During Atomic Layer Deposition

North Carolina State University, Raleigh NC

Investigators

Abstract

Thin film electronic materials formed by atomic layer deposition (ALD) are now well ingrained in semiconductor device manufacturing, and they are emerging as important materials for encapsulation of organic light-emitting displays and lighting, flexible and wearable electronics, and photovoltaics, batteries, supercapacitors and other renewable energy conversion and storage devices. While commercial ALD is well developed for metal oxides, there is a strong and growing need for new approaches for metal ALD. Relatively few options are currently available due to lack of effective vapor-phase reducing agents and ALD-compatible metal precursors that provide sufficient volatility and self-limiting surface reaction capacity to satisfy ALD reaction requirements. Beyond understanding steady-state metal ALD reactions, there is a critical need to attain a more detailed understanding of metal ALD nucleation, including defining elementary reactions during growth initiation. In particular, substrate selective ALD is becoming an acute challenge for the semiconductor industry to achieve advanced sub-10 nm feature patterning. This project addresses these challenges by combining first-principles modeling with in-situ analysis of ALD nucleation and growth using novel metal precursors and reducing agents to develop new models and insights into elementary surface reactions important for advanced thin film reaction engineering design. The research project aims at exploring newly available metal precursors and metal reducing agents to expand fundamental understanding of low temperature thermally-driven reaction mechanisms on a range of substrate surfaces. The fundamental understanding of vapor/surface chemical reaction mechanisms developed by combined experiment/first-principles modeling approach may lead to new nanoscale elemental metal, semimetal and metalloid thin films by thermal atomic layer deposition (ALD). The combination of novel precursors and reducing agents combined with insights gained from modeling will be used to understand substrate-dependent nucleation. In-situ reaction analysis will improve ALD-nucleation models and provide pathways for improved selective area ALD. There is a plan to explore nucleation reversibility in ALD, including emerging thermal atomic layer etching (ALE) processes. Adapting a strategy from CVD to coupling deposition and etching, new ALE processes could refine significantly expand selective ALD capabilities. The proposed approach is unique because of the choice of novel materials to study, new modeling approaches, and unique combinations of in-situ atomic-scale surface reaction characterization tools.