Coupling interfacial chemistry and temperature for anisotropy-enhanced sidewall evolution in silicon dioxide wet etching

Abstract

Silicon dioxide (SiO2) microstructures are widely employed in photonic and microelectronic devices. However, achieving well-controlled device profiles typically relies on costly dry-etching tools and complex fabrication workflows. Wet etching of SiO2 in hydrofluoric acid (HF), while attractive for its simplicity and scalability, is commonly regarded as inherently isotropic, limiting sidewall control. This work demonstrates that pronounced and continuously tunable anisotropy can be achieved using a buffered oxide etch (BOE)-based wet etching strategy. By systematically modulating etchant chemistry, surfactant-assisted interfacial transport, and etching temperature, anisotropic selectivity is engineered at a relatively high etch rate while maintaining smooth and uniform profiles, without relying on high-cost fabrication methods. In particular, reducing the etching temperature leads to a reduction in the sidewall angle of 33% and an increase in the vertical-to-lateral etch-rate ratio of 16%. These results establish BOE-based wet etching as a simple, scalable, and cost-effective approach for near-anisotropic SiO2 microfabrication with improved profile fidelity.