Alternate lanthanum oxide/silicon oxynitride-based gate stack performance enhancement due to ultrathin oxynitride interfacial layer for CMOS applications

Abstract

Metal–insulator–semiconductor (MIS)-based Pt/La2O3/SiOXNY/p-Si/Pt structures are fabricated using ultrathin silicon oxynitride (SiOXNY ~ 4 nm) interfacial layer underneath of lanthanum (III) oxide (La2O3 ~ 7.8 nm) with Pt as gate electrode for CMOS applications. Capacitance–voltage (C–V) characteristics of Pt/La2O3/SiOXNY/p-Si/Pt at 500 kHz showed a positive gate bias threshold voltage (Vth) shift of ~ 0.43 V (~ 43.8%) and flat-band (Vfb) shift of ~ 1.24 V (~ 42.3%) as compared to Pt/La2O3/p-Si/Pt MIS structures, attributing to the reduction in effective positive oxide charges at La2O3/SiOXNY/Si gate stack. Likewise, conductance–voltage (G–V) characteristics show ~ 0.56 (~ 44.4%) reduction in FWHM for Pt/La2O3/SiOXNY/p-Si/Pt as compared to Pt/La2O3/p-Si/Pt MIS structures revealing the reduction in interface states at La2O3/SiOXNY/Si interface. There is a considerable reduction of effective oxide charge concentration (Neff) ~ 3.99 × 1010 cm−2 by (~ 15.2%) and ~ 56.8% lower gate leakage current density ~ 4.47 × 10−7 A/cm2 (|J|–V) at − 1 V for SiOXNY based MIS structures w.r.t its counterpart. Capacitance–time (C–t) characteristics, constant voltage stress (CVS) and temperature measurements for C–V and |J|–V demonstrate the considerable retention ~ 12 years, electrical improvement and reliability of MIS structures. The depth profile analysis X-ray photoelectron spectroscopy (XPS) for SiOXNY/Si gate stack clearly reveals that less nitrogen concentration in bulk than SiOXNY/Si interface. Atomic force microscopy (AFM) micrographs of La2O3/Si and SiOXNY/Si showed the significantly lesser r.m.s roughness of ~ 1.11 ± 0.39 nm and ~ 0.97 ± 0.11 nm, respectively. Thus, the ultrathin SiOXNY interfacial layer underneath of La2O3 demonstrates a significantly improved electrical performance and prelude the gate stack strong potential for reliable CMOS logic devices and integrated circuits.