Effect of fabrication processes before atomic layer deposition on β-Ga2O3/HfO2/Cr/Au metal–oxide–semiconductor capacitors

Abstract

As β-Ga2O3 becomes a popular semiconductor material for high-power electronic devices, researchers are presenting innovative device structures and fabrication processes to achieve high performance and enhanced reliability of these devices. In many cases, these fabrication processes involve the formation of mesas, trenches, and other structures by plasma etching of β-Ga2O3 with Cl2 and/or BCl3. This paper looks at the effects of photoresist patterning and BCl3 plasma etching prior to atomic layer deposition of HfO2 dielectric to form metal–oxide–semiconductor capacitors. The β-Ga2O3/HfO2 interface is critical for controlling device characteristics such as flat-band voltage and maximum capacitance under accumulation and can be greatly affected by roughness and chemical residues. Capacitance-voltage data and atomic force microscope (AFM) scans indicate that photoresist and BCl3 residues are not adequately removed with acetone/IPA/DIW cleaning but are removed using piranha (H2O2/H2SO4) cleaning before deposition of the dielectric.