I am trying to define narrow Cu lines on wafer, a few microns wide.
Cu was sputtered and I need to deposite PECVD nitride to seal Cu lines,
since Cu is easy to oxidize, I sputtered TiW cap on Cu film. Then use PR
as mask, I sequencially wet etched TiW and Cu. The problem is TiW
adhesion to Cu not very good and has large stress, if Cu is side etched
under TiW, then TiW will pop up from Cu lines.
Should I use some other metal instead of TiW?
If I don't use metal cap layer, how can I deposite nitride without
oxidize Cu?
Thanks.