Aluminum mask with SF6-CHF3 combination should be OK for 10um deep RIE.

Edward Sebesta  wrote:

Aluminum is fairly impervious to CF4. AlF3 isn't volatile at all. So you
could us it or Al2O3. You should avoid heat and do the deposition cold
so the Al won't react with your quartz.

I would look down the periodic table for other metals with involitle
fluorides.

I am not sure why you don't use resist for this. If you are in a SiO2
etch mode, with no O2 added, and maybe a little H2 or CHF3, the resist
should be fairly resistant, though I am not sure it would be good for 10
microns.