Thermal Atomic Layer Deposition of Silicon Carbonitride: A Density Functional Theory Study

Abstract

Silicon carbonitride (SiCN) films have received considerable attention due to their lower dielectric constant and better etch selectivity than silicon nitride (SiN) films [1]. Therefore, SiCN is replacing SiN in a variety of applications, such as dielectric barriers for copper interconnects or sidewall spacers for self-aligned contacts. SiCN films have been mainly prepared by plasma-enhanced chemical vapor deposition (PECVD) or plasma-enhanced atomic layer deposition (PEALD). However, plasma-based deposition techniques suffer from poor film quality and lack of conformability on high-aspect-ratio patterns. Thermal atomic layer deposition at high process temperatures can deposit high-quality thin films with excellent conformality. However, no studies have been published on thermal ALD in SiCN, while there are a few reports on PEALD in SiCN. In this work, we studied the thermal ALD process of SiCN by alternating exposures to a carbon-containing silicon precursor and NH3 and compared it with the thermal ALD of SiN processes using carbon-free precursors. Density functional theory (DFT) calculations were used to model and simulate the continuous ligand exchange reactions between the silicon precursor and the substrate surface. The carbon incorporation in the growing film when using carbon-containing precursors was predicted by DFT, which is in good agreement with the experimental observations. Acknowledgments This work was supported by Hansol Chemical Co., Ltd.