GaAs Corrosion Under Ohmic Contacts by Electrochemical Oxidation in HBT Device Fabrication
Hong Shen, Lam Luu-Henderson, Sheila O’Neil, Shiban Tiku, tom Grayson, and Ravi Ramanathan
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Keywords: GaAs Ohmic Contact, Electrochemical, Corrosion
This paper presents a comprehensive study of GaAs corrosion happening adjacent to ohmic contact metal, often caused by GaAs degradation and subsequent electrochemical oxidation of the semiconductor material in wet chemical solutions. GaAs surface degradation, induced by chemical cleaning processes, ion-bombardment from dry etch processes and thin film deposition processes such as PVD and CVD, makes GaAs prone to electrochemical attacks. Ohmic contact metals put on these damaged surfaces will accelerate electrochemical reaction of GaAs, resulting in GaAs corrosion and poor device performances, if the chemicals used in these processes are not carefully chosen or the sequence of these process steps are not carefully designed. Processes to minimize GaAs corrosion are also discussed.