The influence of surface oxide films on hardness and thermosonic wire bonding of Al bondpads

Using indentation tests, bond tests and electron microscopy methods, the influence of oxide films on Al bondpad surfaces on hardness and bonding properties was investigated. It is shown that the bond quality is distinctively decreased if the oxide film thickness is larger than about 30 nm. The presence of such films causes also a hardness increase which can be detected by current indentation test methods. Therefore, indentation tests can be applied during the quality control of bondpad metallizations prior to wire bonding.