Characterization of ultrathin gate dielectrics formed by in-situ steam generation with nitrogen postprocessing

We examined ultrathin films produced by in-situ steam generation (ISSG), ISSG with NO anneal, ISSG with remote plasma nitridation (RPN), and rapid thermal oxidation (RTO). Capacitance-voltage measurements performed on these films indicated an equivalent oxide thickness (EOT) in the range of 1.6–2.5 nm. The nitrogen postprocessing made it possible to achieve thinner EOTs while keeping theleakage current density below 10⁻² A/cm² at V_g=−1.5 V. Total x-ray fluorescence (TXRF) analysis on the films yielded a transition metal concentration less than 5×10¹⁰ atoms/cm². Atomic force microscopy (AFM) measurements yielded microroughness values of 0.18–0.2 nm, which were conformal to the starting material surface microroughness. High-resolution transmission electron microscopy (HRTEM) images showed physical thicknesses ranging from 2.0–3.0 nm, which were used, in conjunction with the EOTs, to calculate effective dielectric constants for the films. Low energy (500 eV) secondary ion mass spectrometry (SIMS) measurements performed on the ISSG + NO and ISSG + RPN films showed sharply different [N] profiles.