Multi-Step Chemical Solution Deposition-Annealing Process Toward Wake-Up Free Ferroelectricity in Y:HfO2 Films

Abstract

Ferroelectricity in HfO2 thin films can be utilized for fast, power-efficient, and highly scalable non-volatile memories. However, the required wake-up process for inducing ferroelectricity/ achieving higher polarization is one of the major hurdles that hinder HfO2-based thin films from developing reliable electronic devices. The wake-up effect is believed to originate from i) phase transformation from non-ferroelectric to ferroelectric, ii) movement of defect entities (mainly oxygen vacancy defects) near the film-electrode interface, and iii) heterogeneity of the electrode interfaces. In the present study, an experimental strategy is designed to overcome these sources of the wake-up process. A multi-step deposition and annealing process is carried out to induce wake-up-free ferroelectricity in Yttrium doped HfO2 (Y:HfO2) thin film directly grown on Si-substrate. Furnace annealing is utilized instead of the standard rapid thermal annealing process to reduce the oxygen deficiencies and stimulate the direct growth of the polar Y:HfO2. The oxygen-vacancy-related defects are found to be the dominating source of wake-up effect in Y-doped HfO2 films. The step-wise deposition and annealing in the oxygen atmosphere facilitate direct growth of the polar phase, reduce the oxygen vacancies, and induce wake-up-free ferroelectricity in Y:HfO2.