Evaluation and Comparison of Novel Precursors for Atomic Layer Deposition of Nb2O5Thin Films

Atomic layer deposition (ALD) of Nb2O5 thin films was studied using three novel precursors, namely, tBuN═Nb(NEt2)3, tBuN═Nb(NMeEt)3, and tamylN═Nb(OtBu)3. These precursors are liquid at room temperature, present good volatility, and are reactive toward both water and ozone as the oxygen sources. The deposition temperature was varied from 150 to 375 °C. ALD-type saturative growth modes were confirmed at 275 °C for tBuN═Nb(NEt2)3 and tBuN═Nb(NMeEt)3 together with both oxygen sources. Constant growth rate was observed between a temperature regions of 150 and 325 °C. By contrast, amylN═Nb(OtBu)3 exhibited limited thermal stability and thus a saturative growth mode was not achieved. All films were amorphous in the as-deposited state and crystallized between 525–575 °C, regardless of the applied precursor and oxygen source. Time-of-flight elastic recoil detection analysis (TOF-ERDA) demonstrated the high purity of the films. Atomic force microscopy (AFM) revealed that the films were smooth and uniform. The films exhibited promising dielectric characteristics with permittivity values up to 60.