Electromigration Behavior and Mechanical Properties of the Whole Preferred Orientation Intermetallic Compound Interconnects for 3D Packaging

The preferred orientation full intermetallic compound (IMC) interconnects were fabricated using the current driven bonding (CDB) method. The electromigration behavior and mechanical properties of the (001) Cu/IMC(30 µm Cu6Sn5)/Cu interconnects under a current density of 2.0×10^4 A/cm2 at 150 °C and 180 °C were investigated. The Cu/Cu6Sn5/Cu IMC interconnects exhibited an excellent electromigration resistance, since there was no obvious damage after aging at 150 °C and 180 °C for 200 h, and even after electromigration under 2.0×10^4 A/cm2 at 150 °C and 180 °C for 200 h. The microstructural evolution of the Cu/Cu6Sn5/Cu IMC interconnects undergoing aging and electromigration was mainly the growth of interfacial Cu3Sn and formation of Kirkendall voids in Cu3Sn. Electromigration significantly accelerated the growth of interfacial Cu3Sn IMCs compared with aging, and there was no obvious "polarity effect" for the growth of interfacial Cu3Sn IMCs undergoing electromigration. The Cu/Cu6Sn5/Cu IMC interconnects had a high mechanical reliability even undergoing high temperature aging and high current stressing (electromigration). The average tensile strength of full IMC interconnects remained unchanged, i.e., 82.0 MPa and 81.8 MPa, even after aging at 150 °C for 300 h and electromigration (2.0×10^4 A/cm2) at 150 °C for 300 h, respectively, which were similar to that of the as-soldered state (86.7 MPa). However, the microstructural degradation of traditional Sn-3.0Ag-0.5Cu solder interconnects undergoing electromigration was greatly serious, and the Sn-3.0Ag-0.5Cu solder interconnects failed even after electromigration at 150 oC for less than 100 h. The present work is expected to provide a guidance for the promising application of the preferred orientation full IMC interconnects in 3D integrated circuits packaging.