Reliability Investigations of Advanced Photosensitive Polymer based RDL Processes Protected by Inorganic Capping Layers

In this work, a 35 nm thin inorganic ALD-deposited capping layer is integrated into a polymer-based redistribution layer (RDL) technology with the primary objective of developing a thin barrier to prevent copper oxidation. Owing to their density, uniformity and defect free characteristics, ALD layers are established permeation barriers. Nevertheless, polymer-based RDL technologies require lower deposition temperatures resulting in higher defect densities and enhanced susceptibility to moisture.The primary objective of enhanced reliability is demonstrated through electrical measurements. After extensive reliability testing, 100 % yield is achieved. FIB cross sections confirm the absence of oxidation on the copper lines after more than 2000 hours of high temperature storage at 150 °C. Likewise, the capping layer is unaffected by thermal-cycling and corrosion stress tests.