Increased Mobility in Enhancement Mode 4H-SiC MOSFET Using a Thin SiO₂/ Al₂O₃Gate Stack

Abstract

A field effect mobility of 125 cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\textsf {2}}/\text{V}\cdot \text{s}$ </tex-math></inline-formula> and a subthreshold slope of 130 mV/dec were obtained in enhancement mode 4H-SiC MOSFETs with a channel length of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2~\mu \text{m}$ </tex-math></inline-formula> . The fabricated devices utilized a gate stack comprising a 0.7 nm thin thermal SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , thereby reducing defects following oxidation, and a 40 nm thick Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> formed by atomic layer deposition. A high mobility was maintained over a wide gate voltage range and resulted in increases of up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$120\times $ </tex-math></inline-formula> in drain current for the same gate overdrive voltage compared to MOSFETs having a thicker thermal SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> gate stack with the same effective oxide thickness fabricated alongside. Nitridation is not included in either MOSFET process.