High-temperature low-damage gate recess technique and ozone-assisted ALD-grown Al<inf>2</inf>O<inf>3</inf> gate dielectric for high-performance normally-off GaN MIS-HEMTs

Abstract

A high-temperature (180 °C) gate recess technique featuring low damage and in-situ self-clean capability, in combination with O 3 -assisted atomic-layer-deposition (ALD) of Al 2 O 3 gate dielectric, is developed for fabrication of high performance normally-off AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs), which exhibit a threshold voltage of +1.6 V, a pulsed drive current of 1.1 A/mm, and low dynamic ON-resistance under hard-switching operation. Chlorine-based dry-etching residues (e.g. AlCl 3 and GaCl 3 ) are significantly reduced by increasing the wafer temperature during the gate recess to their characteristic desorption temperature, while defective bonds like Al-O-H and positive fixed charges in ALD-Al 2 O 3 are significantly suppressed by substitution of H 2 O with O 3 precursor.