Influence Of O(P-3)/O-2 Flux On The Atomic Layer Deposition Of B2o3 Using Trimethyl Borate At Room Temperature

Oxygen plasma is crucial to many atomic layer deposition (ALD) processes, and O(P-3) radicals play a significant role in terms of reactivity and surface modification. In situ X-ray photoelectron spectroscopy (XPS), residual gas analysis mass spectrometry (RGA-MS), and ab initio molecular dynamics (AIMD) simulations were used to study the free-radical-assisted ALD of boron oxide (B2O3) films on Si(100) using trimethyl borate [B(OCH3)(3)] and mixed O(P-3)/O-2 effluents at room temperature at varying levels of O(P-3)/O-2 flux to the surface. Under these conditions, no reaction with pure O-2 was observed. The XPS results show that at low O(P-3)/O-2 flux, a complete removal of alkyl ligands is observed and C-free B2O3 is achieved, with CO2 and H2O as the main reaction products. At higher O(P-3)/O-2 fluxes, the formation of a stable oxidized C surface layer is observed with some C incorporation into the growing B2O3 film. In both flux regimes, the B2O3 film thickness increased linearly with the number of cycles, consistent with an ALD process. AIMD simulations of O(P-3) collisions with B(OCH3)(3) indicate a multistep ligand removal mechanism initiated by hydrogen abstraction at a threshold O(P-3) energy of similar to 0.1 eV, consistent with RGA-MS results. In contrast, C oxidation and incorporation in the high-flux regime result from O-2 termination of the O(P-3)-induced C radical sites. This work demonstrates that the purity of B2O3 films, efficiency of ligand removal, and surface reaction products can be flux-dependent.