Ferroelectric deep trench capacitors based on Al:HfO2 for 3D nonvolatile memory applications

Aiming for future nonvolatile memory applications the fabrication and electrical characterization of 3-dimensional trench capacitors based on ferroelectric HfO ₂ is reported. It will be shown that the ferroelectric properties of Al-doped HfO ₂ ultrathin films are preserved when integrated into 3-dimensional geometries. The Al:HfO ₂ thin films were deposited by ALD and electrical data were collected on trench capacitor arrays with a trench count up to 100k. Stable ferroelectric switching behavior was observed for all trench arrays fabricated and only minimal remanent polarization loss with increasing 3-dimensional area gain was observed. In addition these arrays were found to withstand 2 *10 ⁹ endurance cycles at saturated hysteresis loops. With these report the 3D capability of ferroelectric HfO ₂ is confirmed and for the first time a feasible solution for the vertical integration of ferroelectric 1T/1C as well as 1T memories is presented.