Quasi-Single-Grain Pb(Zr,Ti)O 3 on Poly-Si TFT for Highly Reliable Nonvolatile Memory Device

Quasi-single-grained Pb(Zr,Ti)O 3 (PZT) was successfully grown for the gate dielectric of a poly-Si thin-film transistor (TFT) in a metal-ferroelectric-insulator-semiconductor memory structure. The quasi-single-grained PZT was obtained by controlling the artificial nucleation formed by Pt dot arrays and was enlarged by the nucleated PZT seeds until it covers the poly-Si channel. The single-grained diameter size was 40 μm with a (100) dominated texture. The poly-Si memory device with the single-grained PZT showed excellent ferroelectric, electrical, and reliability properties compared with the poly-Si memory device with poly-grained PZT. Moreover, eliminating the grain boundary in a PZT film showed the fatigue and retention characteristics with only 1.1% after 10¹³ cycles and 22% after 1 month.