Enabling Reliability of 3D TSV Advanced Packages with Nonconductive, Pre-Applied Underfill Film Materials

Abstract

Consumer and industry demand for high-performance computing, networking and graphics processing are pushing the limits of semiconductor packaging technology to support high-density integration, greater functionality and more complex device architectures in increasingly smaller form factors. To address these requirements, the packaging community is incorporating advanced packaging technologies such as 3D stacking of IC chips, vertically connected by through silicon vias (TSVs). Advanced memory manufacturers are already integrating 3D TSV-based chip stacking processes using thermal compression bonding (TCB) to develop the next-generation of memory devices for high bandwidth applications. These dense packaging architectures require materials that enable robust wafer processing and deliver long-term package reliability. Moreover, for die thicknesses less than $100 \mu \mathrm{m}$, existing non-conductive paste (NCP) materials pose several challenges for thermal compression bonding due to potential die top and bonding tool contamination. Packaging specialists have moved toward the use of non-conductive film (NCF) for die structures – including TSV and Cu pillars – where more controlled flow, precise fillet formation and contamination prevention are essential.In this paper, the latest-generation of NCF materials and corresponding film lamination, base tape removal, die singulation, and thermal compression bonding process will be discussed. The new NCF formulation provides rapid curing kinetics to enable shorter bonding times and, therefore, higher UPH by delivering a three-second bonding profile, as well as feasibility for a two-second bonding profile. Combined with the embedded flux system and flow properties optimization, curing kinetics optimization, the novel NCF material achieves proper solder joint formation, no material entrapment, and void-free filling. Bonding force study of this NCF material was carried out on a die to substrate test vehicle to find out the optimal bonding force. And the reliability testing results will also be discussed. Based on the study outcomes, the new NCF material is expected to show excellent performance for thermal compression bonding for 3D chip-stacking applications.