Dependence of Reliability of Ferroelectric HfZrOx on Epitaxial SiGe Film with Various Ge Content

TiN/ferroelectric-HfZrOx (HZO)/epi-SiGe (MFS) structure was employed as the platform to investigate the dependence of Ge content on reliability performance and the mechanism behind it. As compared to Si counterpart, HZO on Si0.56Ge0.44 exhibits not only enhanced remnant polarization (Pr) by 58 % but much improved reliability in terms of negligible Pr degradation up to 109 cycles under ±4 V/100k Hz bipolar AC stress, desirable retention at pristine and cycled state up to 104 sec, and smaller imprint effect against time at 85 °C. The Ge content-dependent reliability performance is mainly due to the thinner sub-oxide interfacial layer (IL) with better quality since it is too thin to trap charges while less vulnerable to defect generation due to stronger bonding (fewer Vo). IL with higher κ value is also helpful to suppress E-field across it, beneficial to enhance reliability. The results suggest that as the technology advances into SiGe platform, it is more viable for MFS-based memory as the reliability issues for Si will be greatly mitigated.