Growth and characterization of titanium silicate nanofilms for gate oxide applications

Abstract

Atomic layer chemical vapor deposition (ALCVD) of titanium silicate nanofilms using a precursor combination of tetrakis-diethylamido-titanium (Ti(N(C2H5)(2))(4)) and tetra-n-butyl-orthosilicate (Si(O-n Bu)(4)) was studied for high dielectric gate oxides. ALCVD temperature window in our study was 170-210 degrees C with a growth rate of 0.8 angstrom/cycle. We investigated the effects of deposition conditions, such as deposition temperature, pulse time of precursor and purge injection, on the titanium silicate nanofilm growth. The saturated composition of Ti/(Ti + Si) ratio was 0.6 and impurity concentrations were less than 1 atomic %. Dielectric constant (k) of the as-deposited titanium silicate film was similar to 10.5. Hysteresis in capacitance-voltage (C-V) measurements was less than 0.35 V before and after annealing. The leakage current density of the as-deposited and 400 degrees C annealed film was 1.4 x 10(-4) A/cm(2), 4.2 x 10(-4) A/cm(2), respectively, at a bias of -1 V.