Effect of Atmospheric-Pressure Plasma Treatment on the Joint Strength between Au Flip Chip Bumps and Cu-Finished Si Wafer Substrates Bonded Using Ultrasonic Energy

Abstract

This study investigated the effects of the conditions of atmospheric-pressure plasma (APP) treatment on the ultrasonic bonding property of Ail flip chip bumps on Cu-finished silicon substrates. The substrate underwent the de-ionized (DI)-water spreading test and a surface analysis using Auger electron spectroscopy (AES) after plasma treatment had been performed for various treatment times from 0.3 s to 18 s with three different gases: N-2, N-2+O-2 and N-2+H-2. The treatment conditions greatly affected the spreading angle and the joint strength. The gases containing 02 and H-2 were effective in improving the wettability of the substrate and the bondability between the All bump and the Cu substrate, respectively.