Low-Leakage Tetragonal ZrO<sub>2</sub> (EOT < 1 nm) With <italic>In Situ</italic> Plasma Interfacial Passivation on Germanium

Abstract

We successfully fabricated gate stacks (ZrO2/GeO x /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 GeO x 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 $\sim 0.9$ nm was achieved with a relatively high dielectric constant (roughly 30) of tetragonal-phase ZrO2. The gate leakage was $\sim 1 \times 10^{-4}$ A/cm2 at $\text{V}_{\mathrm {\mathbf {FB}}} - 1$ V, and roughly $5 \times 10^{-5}$ A/cm2 at $\text{V}_{\mathrm {\mathbf {FB}}} + 1$ 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 °C. Therefore, the proposed scheme is simple and effective for use in pursuing an ultralow EOT gate dielectric on Ge.