CeO2 Doping of Hf0.5Zr0.5O2 Thin Films for High Endurance Ferroelectric Memories

Ferroelectric switching is demonstrated in CeO2-doped Hf0.5Zr0.5O2 (HZCO) thin films with application in back-end-of-line compatible embedded memories. At low cerium oxide doping concentrations (2.0-5.6 mol%), the ferroelectric orthorhombic phase is stabilized after annealing at temperatures below 400 degrees C. HZCO ferroelectrics show reliable switching characteristics beyond 10(11) cycles in TiN/HZCO/TiN capacitors, several orders of magnitude greater than identically processed Hf0.5Zr0.5O2 (HZO) capacitors, without sacrificing polarization and retention. Internal photoemission and photoconductivity experiments show that CeO2-doping introduces in-gap states in HZCO that are nearly aligned with TiN Fermi level, facilitating electron injection through these states. The enhanced average bulk conduction, which may lead to more uniform thermal dissipation in the HZCO films, delays irreversible degradation via breakdown that leads to device failure after repeated programming cycles.