Device engineering strategy of Zr-doped Hfo_x ferroelectric memory for unconventional computing applications

This study reports the device design strategy of ferroelectric memory based on Zr doped HfOx for memory and neuromorphic computing systems. It has been believed that polarization switching occurs due to the transformation in the HfOx layer to a specific crystalline phase through high temperature annealing. Considering the essentially required fabrication process, ferroelectric memory available in various configurations may be thermally stable or need to be demonstrated at as low a temperature as possible. Therefore, in this paper, device design and engineering strategies to improve the polarization switching are addressed. First, the experimental results show that a high pressure annealing technique not only significantly lowers the temperature required for phase transition in the HfOx layer to550 ^oC, but also enhances the crystallinity. On the other hand, in a situation where the polarization is utilized to adjust the carrier density of the transistor channel, thermally stabilized ferroelectricity at high temperatures is preferred. A trilayer structure in which thin Al2O3 layer is introduced to improve instability is also discussed.