Barc shaping for improved fabrication of dual damascene integrated circuit features

Abstract

Method, materials and structures are described for the fabrication of dual damascene features in integrated circuits. In via-first dual damascene fabrication, a bottom-antireflective-coating ('BARC') is commonly deposited into the via and field regions surrounding the via,. Subsequent trench etch with conventional etching chemistries typically results in isolated regions of BARC,, surrounded by 'fencing' material,, at the bottom of the via. Such fencing hinders conformal coating with barrier/adhesion layers and can reduce device yield. The present invention relates to the formation of a BARC plug,, partially filling the via and having a convex upper surface,, prior to etching the trench. Such a BARC structure is shown to lead to etching without the formation of fencing and a clean dual damascene structure for subsequent coating. A directional, anisotropic etching of BARC, and more particularly, an ammonia plasma etch, is one convenient method of removing BARC and forming the desired convex upper surface.