Fabrication and Properties of $hbox{Pt}/hbox{Bi}_{3.15}hbox{Nd}_{0.85} hbox{Ti}_{3}hbox{O}_{12}/breakhbox{HfO}_{2}/hbox{Si}$ Structure for Ferroelectric DRAM (FEDRAM) FET

摘要

Metal-ferroelectric-insulator-semiconductor (MFIS) capacitors with 400-nm-thick Bi3.15Nd0.85Ti3O12 (BNdT) ferroelectric film and 4-nm-thick hafnium oxide (HfO2) layer on silicon substrate have been fabricated and characterized. It is demonstrated that the Pt/Bi3.15Nd0.85Ti3O12/ HfO2/Si structure exhibits a large memory window of around 1.12 V at an operation voltage of 3.5 V. Moreover, the MFIS memory structure suffers only 10% degradation in the memory window after 1010 switching cycles. The retention time is 100 s, which is enough for ferroelectric DRAM field-effect-transistor application. The excellent performance is attributed to the formation of well-crystallized BNdT perovskite thin film on top of the HfO2 buffer layer, which serves as a good seed layer for BNdT crystallization, making the proposed Pt/Bi3.15Nd0.85Ti3O12/ HfO2/Si suitable for high-performance ferroelectric memories.