Hi,

I'm trying to use SiO2 as etching mask on GaAs, so I use ebeam evaporator to
deposit a thin layer (3000A) SiO2 on it. The deposition rate is 10A/s, and very
stable. But when I dip that sample in AZ400K developer, some part of SiO2 lift
off from the substrate. The substrate is very clean, because when I took it out
from a growth chamber (we're using MBE to grow structures on GaAs substrate), I
immediately put it into evaporator chamber.

So does anyone have such experience and can give me some suggestion on the
following questions?

1) Is this ebeam evaporation of SiO2 totally unsuitable for etching mask
purpose?
2) Do I need special treatment on GaAs surface prior to loading it into
evaporator?
3) Do I need post deposition treatment, like thermal curing at, for example,
400C?

Thanks a lot

Lion