Copper Electrodeposition for 3D Integration

Two dimensional (2D) integration has been the traditional approach for IC integration. Increasing demands for providing electronic devices with superior performance and functionality in more efficient and compact packages has driven the semiconductor industry to develop more advanced packaging technologies. Three-dimensional (3D) approaches address both miniaturization and integration required for advanced and portable electronic products. Vertical integration proved to be essential in achieving a greater integration flexibility of disparate technologies, resulting in a general trend of transition from 2D to 3D integration in the industry. 3D chip integration using through silicon via (TSV) copper is considered one of the most advanced technologies among all different types of 3D packaging technologies. Copper electrodeposition is one of technologies that enable the formation of TSV structures. Because of its well-known application for copper damascene interconnects, it was believed that its transfer to filling TSV vias would be easily adopted. However, as any new technology at its beginning, there are several challenges that need to be addressed and resolved before becoming a fully mature technology. This paper will address the TSV rill processes using copper electrodeposition, the advantages as well as difficulties associated with this technology and approaches taken to overcome them. The effect of wafer design on process, including necessary process optimization that is required for achieving void-free filling will be discussed.