Friday, May 7, 2021
12:20 PM - 12:40 PM (EDT)
Insight into Molecular Layer Deposition Initiation and Transition to Steady Growth by Systematic Adjustment of Polyurea Precursor Structure
Rachel Nye - North Carolina State University

*Rachel Nye, Siyao Wang, Gregory Parsons, North Carolina State University, Raleigh, NC
Molecular layer deposited (MLD) thin films enjoy a wide range of properties that are tunable simply via precursor selection, making them useful in next-generation microelectronics, energy storage, and resists. Accordingly, new precursors with advanced functionality and structure are constantly explored. However, even subtle differences in precursor structure can significantly alter growth in ways that are not fully understood. We deposit a series of polymers with systematically increasing flexibility from ethylenediamine, 1,6-hexanediamine, p-phenylene diisocyanate (PDIC), and 1,6-hexamethylene diisocyanate (HDIC), introduced to MLD for the first time herein. Mass spectrometry and FTIR measurements demonstrate HDIC as a highly flexible alternative to the standard PDIC monomer with improved thermal stability. In situ ellipsometry reveals a nonlinear growth rate corresponding to a transition in active site density between substrate and deposited polymer. The extent of this transition depends on both polymer flexibility and temperature, where the largest changes in growth rate occur for flexible polymers deposited at low temperatures. This growth transition is accurately described with a simple decay model, facilitating control over film thickness critical to applications such as area selective deposition. This novel precursor provides flexible tuning capabilities (e.g. volume expanding coatings for battery electrodes), while providing important insight on growth initiation.

Session Type
Atomic Layer Processing