Hi all,

i have some silicon wafers coated with 100nm LPCVD silicon nitide.
I need to patter the silicon nitride. I realized photolitograhy and
immersed the wafer in BHF. Usually removal of silicon nitride takes about
4 hours, but this time after 7 hours silicon nitride was still present.
I removed photoresist and immersed the wafer in concentrated HF. I can see
that the color of silicon nitride slowly changes with time, so probably
there is some etching, but after 1 hour silicon nitride was still
present!!

After that i immersed in the same HF a second wafers coated with 100nm
LPCVD silicon nitide (this second wafer is coming from another source).
Silicon nitride was removed in some minutes.

Where could be the problem with the silicon nitride on the first wafer ??

Best regards,
Andrea


> Hi,
>
> We are looking at transferring a pattern using standard photoresist such
> as shipley into an underlying (50nm) Cr layer. Does anybody know any
> tricks for wet chrome etching, which will prevent the strong undercutting?
> What else does anyone recommend looking at to limit this undercutting?
>
> Best wishes, Paul