Thermal stability of ALD-grown SiO2 and Al2O3 on (010) β-Ga2O3 substrates

Abstract

Ultra-wide band gap semiconductors like β-Ga2O3 undergo different high temperature processes during device fabrication. In addition, devices made with β-Ga2O3 are also promising for high temperature applications. Therefore, it is very important to study thermal stability of materials and devices, as high temperatures are known to change the integrity of the dielectric and cause diffusion of atoms across different interfaces within the device. In this article, we study the thermal stability of SiO2 and Al2O3 formed using plasma-enhanced atomic layer deposition (PEALD) on (010) Sn-doped β-Ga2O3. Our study reveals that MOSCAPs made with SiO2 maintains a breakdown strength (EBD) of > 10 MV/cm at temperatures up to 900 °C, while maintaining low leakage current at oxide electric fields Eox ≤ 5 MV/cm. In comparison, devices made with Al2O3 shows high leakage current (often starting at Eox ~ 2.5 MV/cm) and interfacial/bulk crystallization (starting at 600°C). Interface trap density (NIT) probed using multi-frequency and UV-assisted C-V measurements shows ≤ 10¹² cm² for Al2O3 and higher values for SiO2 This is the first demonstration of better thermal stability for ALD SiO2 compared to Al2O3 formed on (010) β-Ga2O3 substrates.