Abstract
AbstractConventional SONOS (polysilicon-oxide-nitride-oxide-silicon) non-volatile memory devices use silicon nitride as the charge storage layer. In this work, metal－high-k dielectric－high-k dielectric－oxide－silicon (MHHOS) capacitors and transistors were fabricated using Ta2O5 as the charge storage layer and Y2O3, La2O3 as the blocking oxide layers. Both Al/Y2O3/Ta2O5/SiO2/Si and Al/La2O3/Ta2O5/SiO2/Si capacitors achieve retention time longer than 10 years. In addition, the conduction mechanism under positive bias for Al/SiO2/Ta2O5/SiO2/Si capacitors was studied. With Ta2O5 as the charge storage layer, the dominating conduction mechanism at 495 K with the electric field lower than 0.3 MV/cm is Poole-Frenkel emission. With SiO2 as the blocking layer, the dominating conduction mechanism at the electric field of 0.5 MV/cm < E < 1 MV/cm and in the temperature range from 448 K to 495 K is Schottky emission. The dominating conduction mechanism with the electric field above 1 MV/cm and at the temperature lower than 58 K is Fowler-Nodheim tunneling.The programming and erase times of the Al/Y2O3/Ta2O5/SiO2/Si and the Al/Y2O3/Ta2O5/SiO2/Si transistors are characterized. With a programming stress pulse voltage of 6 V, the threshold voltage shift of more than 0.5 V for both structures are achieved in 10 ns. With a erase stress pulse voltage of -8 V, the erase times of the Al/Y2O3/Ta2O5/SiO2/Si and Al/La2O3/Ta2O5/SiO2/Si transistors are 10μs and 1μs, respectively. The retention properties of MHHOS transistors were also characterized. The Al/Y2O3/Ta2O5/SiO2/Si transistor can keep a ΔVth window of 0.89 V for 10 years. The corresponding number for the Al/La2O3/Ta2O5/SiO2/Si transistor is 0.83 V for 10 years.