Characteristics of ZrO_2/Al_2O_3 Bilayer Film for Gate Dielectric Applications Deposited by Atomic Layer Deposition Method

摘要

ZrO_2/Al_2O_3 bilayer structure was investigated as one of potential replacements for SiO_2 gate dielectric. Al_2O_3 and ZrO_2 films were also examined and showed stoichiometric characteristics with negligible chlorine and carbon impurities. Al_2O_3 film exhibited an amorphous structure without interlayer formation while ZrO_2 film showed a randomly oriented polycrystalline structure with amorphous phase of interlayer. ZrO_2/Al_2O_3 bilayer film exhibited no interfacial layer between Si substrate and Al_2O_3 layers. The flat band voltage and hysteresis of ZrO_2/Al_2O_3 bilayer film were 0.8 V and 150 mV, respectively, with folly reversible hysteresis. The measured leakage current of ZrO_2/Al_2O_3 bilayer film was 1.2E-6 A/cm~2 with EOT value of 1.4 nm. ZrO_2/Al_2O_3 bilayer film showed significantly enhanced gate oxide properties compared to those of the individual Al_2O_3 and ZrO_2 films.