Scaling of gate dielectric on Ge substrate

Scaling of Hf-based and Zr-based gate dielectric stack on Ge is investigated. Effects of dielectric thickness and thermal budget on the MOS device characteristics are studied. Tradeoff among effective oxide thickness (EOT), leakage current density (J _G ), interface state density (D _it ), and hysteresis are observed and discussed. With the same HfO ₂ and ZrO ₂ thickness, the ZrO ₂ samples exhibit lower D _it and smaller hysteresis but slightly higher J _G . The crystallized ZrO ₂ exhibits the best J _G -EOT performance. However, as the EOT becomes thinner than 0.8 nm, it is hard to lower D _it to 1×10 ¹² eV ^-1 cm ^-2 . According to these results, novel techniques for Ge surface passivation and ZrO ₂ crystallization are required.