Atmospheric Gas-Phase Catalyst Etching of SiO₂ for Deep Microfabrication Using HF Gas and Patterned Photoresist

Micro/nanoscale structure fabrication is an important process for designing miniaturized devices. Recently, three-dimensional (3D) integrated circuits using SiO₂ via-holes interlayer filling by copper have attracted attention to extend the lifetime of Moore's law. However, the fabrication of vertical and smooth-sidewall via-hole structures on SiO₂ has not been achieved using the conventional dry etching method due to the limitation of the selective etching ratio of SiO₂ and hard mask materials. In this study, we developed a unique method for the deep anisotropic dry etching of SiO₂ using atmospheric gas-phase HF and a patterned photoresist. The hydroxyl groups in the photoresist catalyzed the HF gas-phase dry etching of SiO₂ at high-temperature conditions. Therefore, fabrication of vertical with smooth-sidewall deep microstructures was demonstrated in the photoresist-covered area on SiO₂ at a processing rate of 1.3 μm/min, which is 2-3 times faster than the conventional dry etching method. Additionally, the chemical reaction pathway in the photoresist-covered area on SiO₂ with HF gas was revealed via density functional theory (DFT) calculations. This simple and high-speed microfabrication process will expand the commercial application scope of next-generation microfabricated SiO₂-based devices.