etching SiN on Pt?

[Yves Acremann]

Hi

We need to etch SiN on a Pt layer using MRC. Is there a process which is 
reasonabely selective?
Our SiN layer is 100nm thick, masked by 10nm Pt and sitting on 20nm Pt. 
Does anyone have some
experience? Are there other masking materials you recommend?

We also want to etch 10nm SiN layers with the MRC, masked by 340nm PMMA. 
Does anyone know if the etch rate for PMMA compared to SiN allows to do that?

Thanks
Yves