14nm Chip Package Interaction (CPI) Technology Development

Abstract

Abstract This paper presents the 14 nm chip and package interaction (CPI) challenges and development by using 140 um minimum pitch with SnAg bump in flip chip BGA package. We evaluated 14 nm back-end-of-line (BEOL) film strength/structure / adhesion with large die size of 21×21 mm2 and optimized bumping technology by passing all the CPI reliability tests (QTC, Precon, UBHAST, TCJ, MSV, and HTS) with following the JEDEC standard. We also evaluated assembly with different bump foot print at 140um bump pitch with SnAg bump, and no assembly issues were encountered. Crack stop plays very critical role in defending the crack propagation into the die active area. In our development, we observed reliability failure with severe test condition TCG (−45°C to 125°C), but passed TCJ (0°C to 100°C) with single wall crack stop on the large die size. With increasing crack stop width which enhanced the mechanical strength of crack stop, both TCG and TCJ passed. So it is strongly recommended to use wider crack stop for large dies to eliminate any failures.