Hi Marlene

As Parijat says, the conditions should be very similar to thermal oxide.
Basically, all you need is fluorine based chemistry (CF4, CHF3, SF6 or
similar).  This is compatible with open load systems, so most basic plasma
etch systems should be OK.  You might want to add either an inert gas such
as Ar (e.g. CHF3/Ar) or something to control the F/CF ratio (either H2 or
O2, depending on the other gases you are using).  This ratio affects the
selectivity to silicon (which may not matter for you) and to resist, which
is probably more significant.  Increasing power will increase your quartz
etch rate, but will take the resist off faster.  Keep the substrate cool to
achieve good resist survival.  Alternatively, you could use metal masking
(such as aluminium) which has much higher selectivity.
ICP or ECR will give you higher ion densities, and hence higher etch rates.

Martin