Enhanced Ferroelectricity Achieved in Sub-6-nm Hf 0.5 Zr 0.5 O 2 Films by Using WO x Inserted W Electrodes

HfO2-based ferroelectric thin films have attracted a deal of interest due to its potential in industry. However, achieving high performance in sub-6-nm films is challenging due to pronounced interface effects. This work demonstrates that WOxinserted in W bottom electrode can effectively suppress the “dead layer”, and subsequently reduce the oxygen vacancies in Hf0.5Zr0.5O2(HZO) film without sacrificing the required stress and surface energy for high proportion of ferroelectric phase. The optimized 5-nm-thick HZO film exhibits a 20.9% increase in 2Pr(51.4 μ C/cm2under 2.0 V), a 22.3% reduction in 2Ecand a over 40% decrease in leakage current. Furthermore, excellent endurance characteristics (no significantPrdegradation over 109cycles under ±2.5-4.0 MV/cm @100 kHz) and film uniformity (yield > 95%) are achieved. This approach is expected to be effective for 4 nm and 3 nm HZO ferroelectric thin films, offering valuable insights for the scaling of high-performance ferroelectric devices.