----- Original Message -----
 > Did anybody of you tried etching glass 7740 wafer? I want to etch it
through
> and the thickness of the wafer is 0.5mm. Can I use HF to etch it? what
kind
> of PR or film can be used to be etching mask? And how long will it take?
> Thank you in advance.
>
> Best regards,
> Lanzy

For Pyrex 7740, we measured an etch rate of 43 nm/min in 5:1 BHF.
Concentrated HF will be a lot faster and more suitable for your deep 500 um
etch.

Photoresist is not etched by HF solutions, but will peel off when the HF
concentration is high.
I suggest using a metal mask of ~10 nm Cr and 100 nm of Au.

    --Kirt Williams, Ph.D.   consultant