Ab Initio Study of Confined HF Etching Mechanism on SiO2
Advancements in semiconductor manufacturing has relied heavily upon increasing the density of features in integrated circuits which necessitates decreasing feature size. This involves controlled etching within features of a critical dimension (CD) <5 nm. Recent studies have found departures in etching rates from their blanket rates within such confined dimensions vary based on wall identity (Si, SiN), solvent (vapor, water, ethylene glycol, & isopropyl alcohol), and etchant identity (HF,[HF2]-). To probe the origins of these changes in etch rate (ER), density functional theory (DFT) is an ideal tool to probe the reaction mechanisms within these nanoconfined features. Through analyzing the electronic structure underpinning these etching reactions, we can investigate how confinement and solvent identity affect the etching reaction within CD<5 nm.
Dilute hydrofluoric acid (dHF) is used to etch SiO2 in semiconductor processing to remove layers from the wafer surface wherein a variety of deposition processes are used to construct integrated circuitry. For wet etch, both single wafer and batch processing rely upon the uniform etching of all features across the wafer surface via the following reaction in dry etch, SiO2+6HF→H2SiF6+2H2O, and the following reaction in wet etch applications, SiO2+3HF2-+3H+→H2SiF6+2H2O. Using DFT, we can analyze changes reaction mechanisms in a variety of confined environments. From these calculations we can extract relevant values such as activation energy, Ea, and thermodynamic favorability of the reaction, ΔErxn. These values can aid in predicting the etching behavior under various confined environments.
BIOGRAPHY
Tyler "TJ" Duncan is a Research Scientist in Tokyo Electron's Surface Preparation R&D team focusing on using density functional theory (DFT) to investigate reaction mechanisms within nanoconfined dimensions. He graduated from The University of Texas at Austin in August 2025 with a PhD in Chemical Engineering focused on evaluating ion selectivity of artificial channels using computational chemistry under his advisor, Dr. Venkat Ganesan. TJ attended The University of Kansas for undergraduate studies in Chemical Engineering where he researched novel Nb-doped catalysts under Dr. Ward H. Thompson as well as studying cello performance with the KU School of Music. TJ is most excited to collaborate with experimentalists to help understand nanoscale phenomena.