Low Effective SiO2 Thickness and Low Leakage Current Ta2O5 Capacitors Based on Tantalum Tetraethoxide Dimethylamino-Ethoxide Precursor

Abstract

Tantalum pentoxide (Ta2O5) films have been chemically deposited at low pressure on heavily phosphorous doped poly silicon using oxygen and a metal organic precursor, tantalum tetraethoxide dimethylamino-ethoxide Ta(OC2H5)4(OC2H4N(CH3)2), (TATDMAE). Good conformality of Ta2O5 films was seen. Hydrocarbon contamination was reduced by way of the annealing processes. The capacitance and the leakage current of the patterned capacitors were measured. Continuous improvements based on the crystallization and the reduction of hydrocarbon contamination were achieved by reducing the effective SiO2 thickness (teff, or the equivalent SiO2 thickness), and teff∼30.6 Å on average was achieved for 100-Å-thick Ta2O5 films. Crystallization occurs at 800°C or above upon application of rapid thermal processing (RTP) in the N2 ambient. During crystallization, hydrocarbon contaminations are out-diffused, which leaves dangling bonds in the as-deposited Ta2O5 films. To reduce the dangling bonds, the films were continuously processed by means of RTP in an O2 or N2O ambient. The leakage current was measured and plotted. The I–V plot shows the non-symmetric structure, namely metal–insulator–silicon (MIS), and the leakage current at 1.0 V achieves 1.190×10-9 A/cm2.