Improved ferroelectric properties of CMOS back-end-of-line compatible Hf0.5Zr0.5O2 thin films by introducing dielectric layers
Changfan Ju, Binjian Zeng, Z.-F. Luo, Zhibin Yang, Puqi Hao, Luocheng Liao, Qijun Yang, Qiangxiang Peng, Shuaizhi Zheng, Yichun Zhou, Min Liao
Abstract
Hf0.5Zr0.5O2 (HZO) ferroelectric thin films have gained significant attention for the development of next-generation ferroelectric memories by complementary-metal-oxide semiconductor (CMOS) back-end-of-line (BEOL) processing, due to their relatively low crystallization temperature. However, it remains challenging to achieve excellent ferroelectric properties with post deposition annealing (PDA) process at a BEOL compatible temperature. Along these lines, in this work, it is demonstrated that the ferroelectricity of 15-nm-thick HZO thin film prepared by PDA process at 400 °C can be improved to varying degrees, via depositing 2-nm-thick dielectric layers of Al2O3, HfO2, or ZrO2 at either the bottom or the top of the film. Notably, the HZO thin film with the top-Al2O3 layer exhibits remarkable ferroelectric properties, which are independent of the thickness of HZO. The 6-nm-thick HZO thin film shows a total remanent polarization (2Pr) of 31 μC/cm2 under an operating voltage of 2.5 V. These results represent a significant advancement in the fabrication of high-performance, BEOL compatible ferroelectric memories, as compared to previously reported state-of-the-art works.