Low-Leakage Tetragonal ZrO2 (EOT < 1 nm) With In Situ Plasma Interfacial Passivation on Germanium

Abstract

We successfully fabricated gate stacks (ZrO2/GeOx/Ge) with a subnanometer equivalent oxide thickness (EOT) and low-leakage current on n-/p-Ge through plasma-enhanced atomic layer deposition (ALD). A 0.78-nm-thick GeOx was formed through plasma oxidation (i.e., in situ plasma interfacial passivation, followed by 3.48-nm-thick ZrO2 growth in the same ALD reactor). A subnanometer EOT of similar to 0.9 nm was achieved with a relatively high dielectric constant (roughly 30) of tetragonal-phase ZrO2. The gate leakage was similar to 1 x 10(-4) A/cm(2) at V-FB - 1 V, and roughly 5 x 10(-5) A/cm(2) at V-FB + 1 V on p-and n-type Ge, respectively. Our ZrO2 stabilized in the tetragonal phase, when the post-deposition annealing temperature, was higher than 500 degrees C. Therefore, the proposed scheme is simple and effective for use in pursuing an ultralow EOT gate dielectric on Ge.