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We report the fabrication of completely CMOS-compatible ferroelectric field-effect transistors (FETs) by stabilization of a ferroelectric phase in 10-nm-thin Si:HfO2. The program and erase operation of this metal-ferroelectric-insulator-silicon FET (MFIS) with poly-Si/TiN/Si:HfO2/SiO2/Si gate stack is compared to the transient switching behavior of a TiN-based metal-ferroelectric-metal (MFM) capacitor. Polarization reversal in the MFM capacitor follows a characteristic time and field dependence for ferroelectric domain switching, leading to a higher switching speed with increasing applied field. Similar observations were made for the material when implemented into an MFIS structure. Nonvolatile switching was observed down to 20-ns pulsewidth, yielding a memory window (MW) of 1.2 V. Further increase in gate bias or pulsewidth led to charge injection and degradation of the MW. Retention measurements for up to 106 s suggest a retention of more than ten years.
Date of Publication: Feb. 2012