Abstract
The C-V characteristics of Au/Ta2O5/p-Si capacitors were studied. The Ta2O5 films were deposited by plasma-enhanced chemical vaporized deposition. Two Ta2O5 thicknesses, 14.4 nm and 9.2 nm were used in this experiment. The oxide charge and interface-trapped charge density were characterized. Constant voltage stress test was performed and the resulting DVFB shift was used to measure electron and hole trapping. The magnitude of the flat-band voltage shift began to increase significantly when the stress field was larger than a particular onset electric field Eonset. This onset electric field was also correlated with the orientation of the C-V hysteresis curves. In summary, the oxide charges and interface-trapped charge density of the metal-Ta2O5-silicon capacitors are characterized. The flat-band voltage shift due to constant voltage stress is measured. A critical onset electric field is observed. This phenomenon is explained by the enhanced electric field in the silicon substrate due to the large dielectric constant of Ta2O5, which in turn gives a higher impact ionization generation rate. To avoid excess hole impact ionization, the applied gate voltage for capacitors and MOSFET with Ta2O5 oxide should be limited below the critical value defined by this critical onset electric field.