Ferroelectricity in Al-doped HfO2 on highly doped si substrate

Lei Bai Xin Liu,Xin Liu,Jiale Mao,Yonghong Cheng

doi:10.1109/ceidp.2017.8257486

Abstract

Novel hafnium oxide (HfO 2 )-based ferroelectrics reveal high scalability and integratability with semiconductors and are regarded to be satisfying substitutes for traditional perovskite-based ferroelectrics used in nonvolatile ferroelectric random access memories. In this work, the influence of annealing atmosphere and temperature on structural and electrical properties of Al-doped HfO 2 are investigated, and the underlying ferroelectric phase transition phenomena are deeply discussed. P-V and I-V characteristics of samples annealed at 700°C show typical ferroelectric hysteresis loop and dual current peaks at the voltage of about 6V, while samples annealed at 900°C show almost linear polarization. The sample annealed at 700°C for 30s in N 2 possesses the largest switching current and remanent polarization value (2Pr=25.40μC/cm 2 ) compared to the one in O 2 . TEM studies reveal that the deposited Al:HfO 2 thin films show good uniformity and high crystallinity whatever the annealing temperature and atmosphere were adopted. The orthorhombic non-centrosymmetric phase induced during the rapid thermal annealing (RTA) process is proposed to be responsible for the ferroelectricity in HfO 2 . X-ray diffraction (GI-XRD) results indicate that the monoclinic phase fraction promoted with the increase of annealing temperature. Annealing temperature and atmosphere exhibit conspicuous influence on the ferroelectric phase transition, which lead to different proportion of ferroelectric phase and different remanent polarization in Al:HfO 2 thin films.

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