Reliability of interfacial adhesion in a multi-level copper/low-k interconnect structure

As the electronics industry continues its efforts in miniaturizing the integrated circuit (IC), an IC chip with copper/low-k stacked back end of line (BEoL) structures has been developed for reducing RC delay in order to obtain high-speed signal communication. However, its reliability might become a concern due to the considerably lower adhesive strength as well as greater coefficient of thermal expansion (CTE) of the low-k materials. In this paper, the four-point bending technique is used to quantify the adhesion energy (GC). The global local finite element method, including the specified boundary condition (SBC) method and the multi-point constrain (MPC) method, is validated by the four-point bending experiment and is employed as a bridge to estimate the impact from package level to the deep sub-micron BEoL structure of the plastic ball grid array (PBGA) package. A crack driving force of 1.8 J/m2 acting on the BEoL structure is obtained when the curing process of the moulding compound is performed.