Interface-engineered high-mobility high-κ/Ge pMOSFETs with 1-nm equivalent oxide thickness

Abstract

High-κ/germanium (Ge) interfaces are significantly improved through a new interface engineering scheme of using both effective pregate surface GeO2 passivation and postgate dielectric (postgate) treatment incorporating fluorine (F) into a high-κ/Ge gate stack. Capacitance-voltage (C-V) characteristics are significantly improved with minimum density of interface states (Dit of 2 × 1011 cm-2 · eV-1 for Ge MOS capacitors. A hole mobility up to 396 cm2/V · s is achieved for Ge p-metal-oxide-semiconductor field-effect transistors (pMOSFETs) with equivalent oxide thickness that is ∼10 Å and gate leakage current density that is less than 10-3A/cm2 at Vt ± 1 V. A high drain current of 37.8 μA/μm at Vg - Vt= Vd = -1.2 V is presented for a channel length of 10 μm. The Ge MOSFET interface properties are further investigated using the variable-rise-and-fall-time charge-pumping method. Over three times Dit reduction in both upper and lower halves of the Ge bandgap is observed with F incorporation, which is consistent with the observation that frequency-dependent flat voltage shift is much less for samples with F incorporation in the C-V characteristics of Ge MOS capacitors. © 2009 IEEE.