Research on etching high aspect ratio microchannels by active oxide layer reset

In deep silicon etching processes employing oxide hard masks, the quality and controllability of the oxide layer are critical determinants of etch accuracy and surface purity. Conventional methods utilizing native or deposited oxides often suffer from inconsistent etch rates and unpredictable impurity incorporation due to poorly controlled initial film conditions. This paper presents a novel process integration strategy involving a "BOE clean+thermal oxidation+HMDS"sequence. By actively stripping the uncontrolled native oxide layer from commercial silicon wafers and subsequently performing a controlled thermal oxidation at 900 °C to grow a precise 1 μm oxide film, we achieve an engineered hard mask with superior uniformity and purity. Immediate HMDS treatment and photolithography following oxidation prevent uncontrolled reoxidation, ensuring interface stability. This approach enables precise regulation of etch critical dimensions and effective minimization of contamination, demonstrating significant improvements in process reliability for high-aspect-ratio MEMS fabrication.