A numerical method for efficient failure modelling of three-dimensional bond pad structures

Thermo-mechanical reliability issues are major bottlenecks in the development of future microelectronic components. This is caused by the following technology and business trends: (1) increasing miniaturization, (2) introduction of new materials, (3) shorter time-to-market, (4) increasing design complexity and decreasing design margins, (5) shortened development and qualification times, (5) gap between technology and fundamental knowledge development [1]. It is now well established that for future CMOS-technologies (CMOS065 and beyond), low-k dielectric materials will be integrated in the back-end structures [2]. However, bad thermal and mechanical integrity as well as weak interfacial adhesion result in major thermo-mechanical reliability issues. Especially the forces resulting from packaging related processes such as dicing, wire bonding, bumping and molding are critical and can easily induce cracking, delamination and chipping of the IC back-end structure when no appropriate development is performed [3]. The scope of this paper is on the development of numerical models that are able to predict the failure sensitivity of complex three-dimensional microelectronic components while taking into account the details at the local scale (i.e., the back-end structure) by means of a multi-scale method. The damage sensitivity is calculated by means of an enhanced version of the previously introduced area release energy (ARE) criterion. This enhancement results in an efficient and accurate prediction of the energy release rate (ERR) at a selected bimaterial interface in any location. Moreover, due to the two-scale approach, local details of the structure are readily taken into account. In order to evaluate the efficiency and accuracy of the proposed method, several two-dimensional and three-dimensional benchmarks will be simulated. Finally, the failure sensitivity of a three-dimensional back-end structure during a wire pull test is evaluated.