Tantalum Pentoxide Gate Dielectrics Formed by Tantalum Oxidation

Abstract

ABSTRACTTantalum pentoxide (Ta2O5) films were formed by oxidizing thin tantalum (Ta) films on bare and NO-nitrided silicon substrates. The 43-400 Å thick Ta films were deposited using physical vapor deposition (PVD) and oxidized using O2 for 2-60 min at 550-800 C in a furnace or single wafer tool. Uniform and stoichiometric Ta2O5 films were successfully produced as determined from XRD, AES depth profiling, XTEM, and ellipsometric analysis. The nitridation pretreatment was found to minimize the interfacial Ta-Si reactions which occur during the oxidation. Well-behaved CV and IV curves were obtained from mercury probe measurements. No CV hysteresis was observed. An equivalent oxide thickness of 38 Å and a leakage current of 7×10−9 A/cm2 at +1V were obtained for a 120 Å thick Ta2O5 film on a 15 Å interfacial SiO2 layer.