Aluminium Thin Film Surface Modification via Low-Pressure and Atmospheric-Pressure Argon Plasma Exposure

Hydrophilicity of the aluminium thin film's surface is one of the imperative surface characteristics needed for metal pad bonding process in microelectronic circuitries. In this paper, we present a study on the influence of argon plasma exposure on the surface properties of sputter-deposited aluminium thin film layer. The exposure of aluminium thin film layer in argon plasma at atmospheric pressure and low pressure are carried out and compared. The water contact angle and surface topology of the aluminium's surface are inspected. The aluminium-gold metal-metal ohmic contact resistance and the aluminium thin film sheet resistivity are measured. Argon plasma has modified the originally hydrophobic aluminium's surface into hydrophilic profile, which may be related to its increase of surface energy. Higher/smaller thin film surface roughness has been measured from the low-pressure/atmospheric-pressure argon plasma exposure that produces thin film with higher (9.64 omega)/smaller (6.78 omega) contact resistivity compared to the unexposed aluminium thin film layer (7.85 omega). The argon plasma exposure treatment on the aluminium thin film has generally improved its surface properties, inducing hydrophilicity surface profile for the aluminium metal pad. The conducted treatment at the atmospheric pressure level specifically helps to reduce the surface roughness and increase the thin film layer conductivity.