Borosilicate glass typically contains materials that are not etched by
BOE alone. The following paper discusses removing these residues with
HCL,

A fast prototyping process for fabrication of microfluidic systems on
soda-lime glass
Che-Hsin Lin et al 2001 J. Micromech. Microeng. 11 726-732

Roger Shile

-----Original Message-----

Dear all,

We have been trying to understand the chemistry during the HF wet-etch
on borosilicate glass. It turns out the different combination of acid
(HCL, H3PO4) with HF results different etch rate. We believe the
impurity inside the glass caused this change of etch rate. But not sure
the exact chemical reaction happened in this process. Any one have any
suggestions or refer me to some reference papers?

Appreciate the help.

Michael