Enhanced Endurance and Imprint Properties in Hf_0.5Zr_0.5O_2−δ Ferroelectric Capacitors by Tailoring the Oxygen Vacancy

Abstract

HfO 2 -based ferroelectric thin films are promising in both memory and logic devices owing to their compatibility with complementary metal-oxide-semiconductor platforms and excellent thickness scalability. However, the fatigue and imprint effect are the main concerns, hindering the device's applications. In this work, we comprehensively investigate the impact of oxygen vacancies on the reliability of Hf 0.5 Zr 0.5 O 2−δ (HZO) ferroelectric capacitors. The oxygen vacancy concentration was tailored by varying the exposure time of the H 2 O precursor and oxygen plasma during atomic layer deposition. By decreasing the oxygen vacancy concentration to 1.9%, the endurance is enhanced owing to the suppression of defect migration under field cycling. In addition, a milder imprint with coercive field shift of below 0.6 MV/cm under 120 °C is obtained, benefiting from the alleviation of the built-in field at the ferroelectric/metal interfaces. The fabricated HZO capacitors with considerable remnant polarization show superior reliability compared with the reported ones.

On the relationship between imprint and reliability in Hf0.5Zr0.5O2 based ferroelectric random access memory

“…6(a), with the number of cycles increases, HZO FE capacitors exhibit three states: 1) Waking-up state-the polarization of HZO devices increases with cycling operation due to the redistribution of oxygen vacancies or the transformation of tetragonal phases into orthogonal phases [13,14] ; 2) Wakedup state-The polarization of FE devices remains relatively sta-ble as the number of cycles increases; 3) Fatigue state-Stress gradually accumulates, generating oxygen vacancies at grain boundaries, leading to a decrease in polarization and an increase in leakage [15,16] . Typically, imprint measurements were conducted by using waked-up FE devices [17,18] . However, the measurement of imprint for HZO capacitors during the waking-up and fatigue states has not been evaluated yet.…”