Dear everybody: I am use the unaxis-Nextral 860L equipment to etch 6-8um sio2 film now with the recipe:O2 10sccm,CHF3 80sccm,He 10sccm,rf power 250watt, UHF power 1800watt, pressure 22mtorr.but found the selectivity is very poor whatever the mask material is Aluminium!"Titanium or a-si.how to etch this sample with CHF3,can you give me some good advice.Thanking you in advance regards. Li-bing Zhou