Molecular dynamics insights into flowable chemical vapor deposition: Gap-fill mechanisms and transport properties

Continued downscaling of three-dimensional semiconductor devices demands dielectric deposition methods capable of void-free filling in highly confined features. Flowable chemical vapor deposition addresses this challenge through a transient liquidlike infiltration stage followed by curing, yet the molecular origins of precursor transport and wetting in the precure regime remain poorly understood. Here, classical molecular dynamics simulations are used to investigate tetraethoxysilane (TEOS) and TEOS-based siloxane liquids as representative model precursors for flowable oxide deposition. Focusing on the precure, transport-dominated state, we quantify how viscosity, surface tension, wetting behavior, and region-resolved substrate interactions govern infiltration in hydroxylated SiO2 trench geometries. Increasing silane substitution systematically raises viscosity and surface tension, reduces flowability, and delays gap filling. Contact-angle analysis and force decomposition further show that substrate interactions promote sidewall-dominated infiltration, whereas weaker driving in the trench interior contributes to transient center voiding. These results establish molecularly grounded precure transport and wetting boundary conditions for subsequent cure modeling. This work establishes a quantitative, precursor-dependent framework that directly links molecular-scale interactions to gap-fill kinetics in flowable systems.