Thermal Conductivity Enhancement of Benzocyclobutene With Carbon Nanotubes for Adhesive Bonding in 3-D Integration

Thermal management is one of the critical challenges in 3-D integration. The intermediate bonding interfaces between two chips, such as silicon dioxide and polymer adhesives, are the major source of internal thermal resistance in 3-D integrated circuits, leading to thermal issues such as high temperature spots and larger temperature gradients. This paper reports an approach to reduce the thermal resistance of a common bonding adhesive benzocyclobutene (BCB) by loading carbon nanotubes (CNTs) to improve the thermal conductivity. By exploiting the aromatic property of BCB, an ultrasonication-assisted noncovalent dispersion method is developed to disseminate CNTs with different concentrations into BCB. Thanks to the high thermal conduction ability of CNTs, the thermal conductivity of BCB is improved as much as 20% by loading 1.5 wt% CNTs. The surface temperature of bonded chips during heating are measured to evaluate the dynamic heat transfer ability, and a 13% improvement is achieved for BCB-CNT composites. The bonding strength of pure BCB and BCB-CNT composites are tested and the results show that CNTs is beneficial to improving the bonding strength.