Enhanced Reliability of Ferroelectric HfZrO x on Semiconductor by Using Epitaxial SiGe as Substrate

Abstract

As compared with Si as the substrate, ferroelectric (FE) HfZrO x with orthorhombic phase on Si0.56Ge0.44 substrate was found to demonstrate improved FE characteristics. Through the incorporation of Ge into the silicon substrate, remanent polarization ( ${P}_{r}$ ) can be further enhanced by 58% magnitude to $15~\mu \text{C}$ /cm2. Moreover, devices on Si0.56Ge0.44 show significant reliability enhancement in terms of negligible ${P}_{r}$ degradation up to 107 cycles under ±4 MV/cm with 10-kHz bipolar stress and desirable retention up to 104 s arising from smaller imprint effect against time at 85°C. The major role of Ge introduction into the substrate is to suppress the formation of the interfacial layer (IL) between HfZrO x /substrate and further reinforce the quality of the IL. The suboxide IL of the enhanced quality can be explained by the fact that it is too thin to trap charges while less vulnerable to defect generation due to stronger bonding with fewer oxygen vacancies. The results suggest that as the technology advances from Si into SiGe platform, HfZrO x -based devices possess more reliable ferroelectricity for metal–FE–semiconductor (MFS) gate-stack for the next-generation FeFET.