An HF-Free Etching of SiO2 for Soft Lithography

We show that inorganic fluorides, such as NaF and NH
₄
F, can etch SiO
₂
in the presence of HCl vapor resulting in a negative tone pattern transfer to a SiO
₂
substrate. Using a polydimethylsiloxane stamp, we demonstrate high-quality one-step pattern transfer to a SiO
₂
substrate. Compared with traditional HF vapor etching and buffered oxide etching methods, the current approach avoids direct handling of HF and, therefore, significantly reduces the associated safety risks. Our results suggest that fluoride etching could be a general purpose pattern transfer technique for soft lithography of SiO
₂
substrates.