In Situ Investigation Of Precise High Strength Micro Assembly Using Au-Si Eutectic Bonding

Abstract

Au-Si eutectic bonding for assembling microelements into complex, three-dimensional microsysterns has been investigated. Si microelements and substrates are coated with Au and bonding is made by beat treatment above the eutectic temperature. Microelements are manipulated and subsequently bonded in an SEM. Bond strengths as high as 245 MPa have been achieved. Previously encountered problems with variations in bond strengths and misalignments during the process, have been examined. Mechanisms for misalignments, such as mechanical and thermal instabilities in combination with morphological changes in the liquid interface, have been identified during in situ monitoring. Based on these observations, submicrometer precision has been attained, using a high load during bonding.