Self Assembled Monolayer for thin film capacitors on printed circuit boards

Abstract:
Nowadays the integration of passive components in printed circuit boards (PCB) and especially of capacitors has become a crucial aspect in the advance of miniaturized electronic circuits. In this article we report a novel method for integrated capacitors in which the pre-processing of the substrate includes only a standard surface cleaning, avoiding complex roughness reduction. For the realization of embedded capacitors with an integration level up to 15 times higher than state of the art (10pF/mm²), we present a dielectric consisting of two layers: a self-assembling monolayer (SAM) and a polymer layer. The thickness of SAM is less than 3nm, whereas the thickness of the spin coated polymer layer was chosen between 200nm and 500nm. We demonstrated the integration of capacitors with integration densities between 10pF/mm² and 150pF/mm². The achieved yield was >93% for all processed substrates. The achievable level of the integration density is however not the only aspect of interest in the present work: the electrical properties of the capacitors embedded in PCB, like for example loss factor or leakage current, are directly comparable to those of standard SMD capacitors.