Modification of band alignments and optimization of electrical properties of InGaZnO MOS capacitors with high-k HfOxNy gate dielectrics

Abstract

High-k HfOxNy and HfO2 have been applied to amorphous InGaZnO (a-IGZO) metal–oxide–semiconductor (MOS) capacitors as high-k gate dielectrics by using radio-frequency sputtering at room temperature. Effects of nitrogen incorporation on the optical band gap, band alignment and electrical properties of HfOxNy/IGZO/Si gate stacks have been systematically investigated by spectroscopic ellipsometry (SE), UV–vis spectroscopy, x-ray photoemission spectroscopy (XPS) and electrical measurements. Experimental results have confirmed the successful incorporation of nitrogen into HfO2 films and reduction in band gap with the incorporation of nitrogen for HfOxNy thin films. Reduction in valence band offset and increase in conduction band offset have been observed for HfOxNy/IGZO gate stack. Electrical properties measurements for a-IGZO MOS capacitors based on HfOxNy gate dielectrics have indicated that nitrogen incorporation leads to the improved interface quality, increased dielectric constant, reduced hysteresis voltage, and decreased leakage current density. Meanwhile, the leakage current mechanism under gate injection for MOS capacitors based on HfO2 and HfOxNy high-k gate dielectrics has been investigated systematically.