Electrical properties of high-pressure reactive sputtered thin hafnium oxide high-kgate dielectrics

Thin films of hafnium oxide have been deposited by the high-pressure reactive sputtering (HPRS) system. In this growth system the deposition pressure is around 1 mbar, three orders of magnitude higher than in the conventional ones, assuring that both reflected and sputtered particles reach the substrate with a low energy. The amorphous or polycrystalline structure is modified by adjusting the ratio of oxygen to argon of the sputtering gas. The electrical characteristics of both polycrystalline and amorphous films are compared. In all cases, the leakage current can be fitted to Poole–Frenkel emission. Amorphous films show the best characteristics in terms of capacitance–voltage behaviour, leakage current and interfacial state density, with conductance and flat-band voltage transients almost negligible.