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 demon-strated 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
$150\ {}^{\circ}\mathrm{C}$
. Likewise, the capping layer is unaffected by thermal-cycling and corrosion stress tests.