Suresh,
According to my tables (Williams and Muller, JMEMS V.5#4), LPCVD SiN only
etches at about 5nm/min in 49% HF. Since the annealing step is making your
PECVD SiN more like LPCVD, you may just need to let it etch a little bit
longer. Maybe 30 minutes, maybe longer. SiN can't become proof to HF,
right? So, it's just a matter of time.



Jesse Fowler
  UCLA/MAE Dept., 420 Westwood Plaza, Room 37-129, ENGR IV
  Los Angeles, CA 90095-1597 | (310)825-3977
"We did our best but God didn't want to give us any goals."
 -- Saudi Arabian goalkeeper Mohammed Al-Deayea (World Cup 2002)

On Tue, 25 Jun 2002, Suresh Uppal wrote:

> Dear All,
>
> I wonder if someone has a solution to my problem..
>
> I have a Ge substrate on which 200 nm SiO2 and top of that 200 nm SIN film was
> deposited ( PECVD). After annealing at high temperatures,  HF etch does not
> get rid of the deposited nitride layer though it does uniformly before
> annealing. I have tried etching for more than 15 min in HF (48 %).
>
> Any suggestion. Please send email directly at [email protected]
>
> Regards,
> suresh
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