Discussion of Supercritical CO2 Copper Electroplating Parameters for Applications in TSV Chip

• Main Authors: Wei-Hong Lai, 賴威宏
• Other Authors: Ho-Chiao Chuang
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/4sjamh

碩士 === 國立臺北科技大學 === 機電整合研究所 === 102 === This study uses supercritical electroplating for the filling of Though Silicon Vias (TSV) in chips for applications in 3D IC structures, which differs from wires that can only be connected in a 2D plain; the structure in a 3D IC has the advantage that the range of connections that can be done is increased, because the area can be added by multiple layers, therefore reducing the cost and decreasing packaging space, volume and weight, etc. In this study we cut the silicon wafer into chips, and the TSV holes are etched by method of ICP RIE (Inductively Coupled Plasma Reactive Ion Etching), the pressure and current density fabrication parameters of the supercritical carbon dioxide are studied, and how the change of these parameters affects the filling of the TSV copper pillar and its resistance is discussed; the final supercritical electroplating results are compared to traditional electroplating techniques. The hermeticity of the TSV copper pillar is analyzed by performing a Helium leaking test on the TSV to check if the filling is satisfactory, and the analysis of electric properties is an important point of this study; for this purpose, the resistance at both horizontal ends of the TSV is measured, and next a high current (10 Amperes) is passed in the same manner to determine if the TSV is capable of withstanding a high current without burnout. Finally, the chip is cut at cross-section to observe the filling of the TSV copper pillars under supercritical electroplating to check for voids, and the fabrication time required for supercritical electroplating and traditional electroplating techniques is compared. The supercritical electroplating fabrication method in the present study has no added any surfactant to aid the electroplating/filling of TSV holes, but relies only on the special properties of the supercritical state to reach the desired goal, the final result of the analysis is that the best electroplating parameters for pressure and current density are 2000 psi and 3 ASD, respectively; the electroplating quality is the best observed and can resist a high current of 10 amperes, and the shortest time for the sc-CO2 electroplating is 3 hours.