Sn-Ag Compatible Selective Ti Etch in Cu RDL Fabrication and 3D IC Integration

Selective Titanium (Ti) etch chemistries have been developed to provide enabling Ti removal up to $0.2\mu \mathrm{m}$ thickness with good Cu, Sn-Ag and TEOS compatibility. They are alkaline oxidizing compositions with unique etch promoters. Their applications in Cu RDL and 2.5D/3D integrations have been demonstrated. Etch mechanisms and substrate compatibility are also discussed.