Hello Friends,

I was wondering if there are some silicon-dioxide which will not etch in
BHF(31°C).

I was etching the buried oxide of an SOI  which has the device layer DRIE'ed and
i experienced this suprising effect whereby some of the oxide is somewhat
resistant to the BHF. most of the oxide is etched but on some parts, there is
still oxide which seems to be resistant to the BHF. There has not been any high
temperature oven  process either......so i cant explain this effect.
Has anybody experienced this effect and possible explanation why some
silicon-dioxide will not etch in BHF.

thanks in advance.
Nimo