Impact of Post-Deposition Anneal on ALD Al2O3/etched GaN Interface in Gate-First MOSc-HEMT Process Flow

International audienceIn this work, we investigate the impact of Post-Deposition Anneal (PDA) of Atomic-Layer Deposited (ALD) Al2O3 on etched GaN for MOS-channel High Electron Mobility Transistors (MOSc-HEMTs) Gate-First process flow using C-V measurements carried out on MOS capacitors (MOSCAPs). For PDA up to 500°C, a reduction of the flat-band voltage hysteresis (ΔVFB) is reported and explained by the reduction of Ga-O bonds and O-H groups observed by Hard X-Ray Photoelectron Spectroscopy (HAXPES) analysis, the latter being confirmed by Fourier Transform Infrared Spectroscopy (FTIR). For a 600°C PDA, Grazing Incidence XRD (GIXRD) analysis shows a small crystallized κ-Al2O3 signal on etched GaN, which is absent for asgrown GaN. This beginning of crystallization could explain the degradation in ΔVFB and breakdown field for PDA above 500°C observed on MOSCAPs after the Gate-First process flow overall thermal budget