Low Temperature Cu/Pd Diffusion Bonding Development and Applying Cu-Pd Bonding on Thin-Gan Led Packaging Process(2/3)

Three-dimensional integrated circuit (3D IC) has been considered as the key process for the next generation semiconductor technology. Also, wafer-to-wafer bonding technology also has advantages on thin-GaN vertical LED because of (1) uniform current spreading and (2) high emitting area. Therefore, wafer-to-wafer technology would be an important technology in the future.For 3D IC package and wafer to wafer bonding technology, solid/solid metal bonding has demonstrated to be a suitable process in low temperature. The solid diffusional bonding has many merits, such as, (1) no formation of intermetallic compounds (IMC) at the bonding interface, (2) Avoid the residual stress produced by CTE mismatch in high temperature process. In this proposal, we will develop Cu/Pd bonding. Importantly, an applied external stress can enhance the bonding interface and reduce the bonding temperature. Therefore, we propose three-year project focusing on developing a low-temperature Cu/Pd bonding process below 150°C. The entire three-years project breaks down to the following two main items: (1) Under an external stress, the inter-diffusion barrier energy of Cu/Pd inter-diffuse in different preferred orientation and the different grain size of the electroplating copper layer. (2) Fabricate verticalthin-GaN LED by lower bonding temperature Cu/Pd bonding process.