CMP for Copper TSV Applications

Abstract

AbstractThrough-silicon via (TSV) 3-D packaging and integration present many new opportunities and challenges for metals CMP applications. For front-side TSV polishing, challenges include the removal of large amounts of copper overburden, dishing control during copper clearing steps, and removal of large amounts of barrier metal and dielectric layers while still maintaining control over topography and defectivity. Additionally, the choice of barrier material can have significant impact on polishing in terms of the mechanical reliability regarding adhesion between the barrier metal and underlying dielectric layers. This paper will address many of these challenges with an emphasis on innovative technologies for superior process and endpoint controls, such as real-time profile control for thick copper films up to 6μm or more in thickness and automatic endpoint controls for barrier removal and dielectric stopping. The paper will also discuss some salient challenges for back-side TSV polishing, including the handling and polishing of bonded wafer pairs and strategies to minimize handling and polishing damage to the potentially fragile thinned device wafer. Additionally, the development of slurries with highly tunable copper-to-dielectric selectivity will be critical for enabling a wide range of final topographies, depending on requirements for subsequent bonding steps.