http://www.microchemicals.com/technical_information/hf_etching.pdf
Etching of SiO2, Quartz, and Glasses with HF
Hydrofluoric acid is the only etchant which attacks amorphous SiO2, quartz, or glasses at
significant high etch rate.
However, HF is not only a strong corrosive, but also highly toxic towards higher concentrations:
Local effects include tissue destruction and necrosis, deaths have been reported from
concentrated acid burns to as little as 2.5 % body surface area. Besides personal protective
equipment, it’s recommended not to handle higher concentrations of HF than required, and
use ready-diluted mixtures instead of making own dilutions. We supply HF in a concentration
of 1, 10, and 50% as well as buffered HF (BOE 7 : 1) in semiconductor-quality (VLSI).