Effect of Yttrium Treatment on Germanium-Oxide-Based Interfacial Layer of Ge P-Channel Metal–Oxide–Semiconductor Field-Effect Transistor Fabricated Through in Situ Plasma-Enhanced Atomic Layer Deposition

This study investigated the effect of yttrium (Y) treatment on a germanium (Ge)-oxide-based interfacial layer (IL) through in situ plasma-enhanced atomic layer deposition (PEALD). Time-of-flight secondary-ion mass spectrometry revealed that the surface reaction and deposition could be successfully performed with a Y precursor, and X-ray photoelectron spectroscopy (XPS) revealed that Y treatment on an IL can suppress GeO $_{\text{x}}$ volatilization. A metal–oxide–semiconductor capacitor gate-stack with a Y-GeO $_{\text{x}}$ IL has a low leakage current density (2.1 $\times$ 10 $^{-\text{5}}$ A/cm $^{\text{2}}$ ) and a low interface trap density (approximately 5.5 $\times$ 10 $^{\text{11}}$ eV $^{-\text{1}}$ cm $^{-\text{2}}$ ) under optimized temperatures. Moreover, the Ge P-channel metal–oxide–semiconductor field-effect transistor (P-MOSFET) containing a gate-stack with a Y-treated Ge-oxide-based IL exhibited a high I $_{\biosc{on}}$ / I $_{\biosc{off}}$ ratio and low OFF-state current. Therefore, applying the proposed Y treatment on the IL of a Ge P-MOSFET can help achieve a subnanometer equivalent oxide thickness (EOT) and an extremely low gate leakage current.