Effects of plasma cleaning on the reliability of wire bonding

The yield of wire bonding predominantly depends on the surface characteristics of wire bond pads. The contamination on bond pads may result in low ball shear/wire pull strength and poor strength uniformity. Therefore, it is essential to remove the contaminants from the bond pad surface prior to wire bonding. In the present study, the effects of plasma cleaning on the reliability of wire bonding are investigated. Two types of plasma cleaning with various processing parameters are studied. Besides, specimens without plasma cleaning are also investigated for benchmarking. In addition to the comparison of contact angle, both ball shear and wire pull tests are performed to evaluate the effects of plasma cleaning. From the experimental data, it is observed that the plasma cleaning with proper parameter tuning can improve the contact angle characteristics and the reliability of wire bonding. However, a certain type of plasma cleaning may reduce the ball shear strength. Further analytical inspection is conducted on the bond pad surface. Detailed composition characterization is performed to confirm the findings of the present study.