Effects of postannealing on the electrical properties of Ta2O5 thin films deposited on TiN/T

The effects of postannealing on the structural and leakage current characte ristics of Ta2O5 thin films deposited on a TiN/Ti bottom electrode by chemi cal-vapor deposition at 350 degreesC were investigated. The Ta2O5 film of 5 0 nm thickness shows an amorphous phase and smooth surface morphology after annealing in N2O plasma at 350 degreesC, but the film treated with rapid t hermal annealing in nitrogen (RTN) at 750 degreesC prior to N2O plasma anne aling at 350 degreesC has an orthorhombic structure and rugged surface morp hology. In addition, the TiSi phase also appears in the specimen of RTN-tre ated Ta2O5 film. Moreover, the residual carbon can be effectively eliminate d and the oxygen deficiency can be well compensated by the N2O plasma annea ling for both amorphous and crystalline Ta2O5 films. The I-V relation of th e amorphous Ta2O5 films is asymmetric with respect to the biasing polarity, which indicates that the leakage current is primarily dominated by the Sch ottky emission. On the other hand, the crystalline Ta2O5 film has a symmetr ical I-V relation, suggesting that the non-Ohmic leakage in the crystalline Ta2O5 film is related to the Poole-Frenkel effect. The barrier heights Phi (B) for the non-Ohmic leakage in the amorphous and crystalline Ta2O5 films , as evaluated from the temperature dependence of the I-V relation, are 0.5 2 and 0.82 eV, respectively. (C) 2000 American Institute of Physics. [S0021 -8979(00)02601-9].