It is possible that you had an effect of material diffusion or re-deposition
during the DRIE process, which would make the oxide more resistant to BHF.

Elina


> On Jul 19, 2010, at 2:29 PM, antwi nimo wrote:
>
>  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
>>

Elina Kasman

Process Development Engineer, R&D
Engis Corporation
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