Gold Wire Bonding Induced Peeling in Cu/Low-k Interconnects: 3D Simulation and Correlations

Fine and ultra‐fine pitch wire bonding: challenges and solutions

“…The industry is replacing SiO 2 with a low‐ k dielectric and the Al conductor with Cu (Hoofman et al , 2005), because of many advantages (Wang et al , 2005; Hsia, 2006; Yazdani, 2006). This also brings new challenges to wire bonding (Degryse et al , 2005; Tagami et al , 2005; Viswanath et al , 2005; Zhao, 2005; Chhun et al , 2006; Dang et al , 2006; Gottfried et al , 2006; Huang et al , 2006; Kim et al , 2006; Leduc et al , 2006; Yeh et al , 2006; Fiori et al , 2007c; Inoue et al , 2007; Kregting et al , 2007; van der Sluis et al , 2007a, b; van Driel, 2007; van Gils et al , 2007; van Hal et al , 2007; Srikanth et al , 2008).…”

“…Finite element analysis (FEA) is a useful tool to investigate processes (Sun and Zhong, 2002; Luan et al , 2003; Tee et al , 2003a; Zhong and Yip, 2003; Tee et al , 2004; Tee and Zhong, 2004a, b; MacKerle, 2005). There is increasing research on applying FEA to wire‐bonded packages (Chen, K.M., et al , 2006; Ishiko et al , 2006; Saiki et al , 2006; Fiori et al , 2007a, b; Viswanath et al , 2007; Chen et al , 2008; Gao et al , 2008; He et al , 2008).…”

Wire bonding of low‐k devices

“…A stiffer capping redistributes the deformation over a larger area, leading to a smaller local deformation in the metal layer at the bond edge, and the stress peak decreases Degryse et al (2005) Low-k materials need longer bond time to overcome the energy loss Tan et al (2005) Stiffer wires require higher USG power than a softer wire to achieve equivalent ball sizes and ball shear Soft 4 N wire needs lower USG power and is suitable for bonding of low-k devices The low-k material type is the most effective determinant for the pad deformation Viswanath et al (2005) Smaller copper pad thickness and wire diameter lead to a higher pad deformation Viswanath et al (2007) Thicker copper deposition reduces the pad cupping and leads to better bonding and reduction of cratering problems Decreasing low-k modulus leads to stress increases in the Cu/low-k structure and pad sinking Increasing the cap metallization thickness results in a better Cu/low-k structural behavior and minimises cratering problems The ultrasonic energy transfer of a capillary with a small radius transition is higher than that of a capillary with a sharp transition, resulting in satisfactory ball shear, size and height, and stitch pull Goh and Zhong (2006) A capillary with a smaller chamfer angle, a larger inner chamfer and a larger chamfer diameter can increase the percentage of the IMC in the bond interface, eliminating metal pad peeling and ball lift failures Peeling defects can be reduced by squashing FABs using initial force and bonding force just before bonding starts Kim et al (2006) A larger squashed area can distribute and reduce the stress originated by power onto the bond pads Initial force larger than bonding force is effective to reduce defects The pull force increases with increased bond force Yeh et al (2006) Peeling failure rates significantly depend on wire types used and their respective bonding parameters Fiori et al (2007) Increasing the contact area of the wire to the narrow-pitched pad is effective Inoue et al (2007) 630 mm 2 or the bonding force was above 8 gf. No failure was detected during the reliability tests.…”

“…et al , 2006a). The 3D multi‐scale simulations of wire bonding and wire pull testing with wire bonding trials have found that the peeling failure rates significantly depend on the wire types used and their respective bonding parameters (Fiori et al , 2007).…”