Optimized annealing conditions to enhance stability of polarization in sputtered HfZrOx layers for non-volatile memory applications

Abstract

In this paper, we report stable polarization switching in metal-HfZrOx (HZO)-metal capacitors when pulses are repeatedly applied from the initial state. By examining various process parameters including annealing method, annealing temperature, and annealing time, we investigated the optimal conditions for realizing ferroelectricity in HZO layers deposited by sputtering systems. More specifically, we examined how polarization behaviors evolved as a function of annealing temperatures. Our results showed that annealing HZO capped by a top electrode, when annealing temperature was higher than 850 degrees C, drives the transformation to large quantities of orthorhombic phases, and enables constant remnant polarization without the fluctuations caused by wake-up and fatigue. We continued to observe stable polarization up to 10(8) cycles with a pulse width of 5 mu s.