Effects of O 2 thermal annealing on the properties of CVD Ta 2O 5 thin films

Abstract

Tantalum pentoxide (Ta 2O 5) thin film with an initial thickness of 10.5 nm was deposited onto p-type silicon substrate by chemical vapor deposition (CVD), and subsequently annealed in O 2 ambience at 500 to 800 °C for 30 min. It was found that with proper thermal treatment, we could reduce the leakage current down to 6.4×10 −8 A cm −2 at 3 V, although, the effective oxide thickness will also increase from 2.42 to 3.50 nm. Higher annealing temperatures will result in a rougher sample surface and higher leakage current due to Ta 2O 5 crystallization. Before the crystallization of the Ta 2O 5 film, the leakage current was dominated by the Poole–Frenkel emission mechanism. For the crystalline Ta 2O 5 film, the conduction mechanism at low electric field was not obvious and could be affected by the formation of the grain boundary in the Ta 2O 5 film.