Hybrid Method for Metallization of Glass Interposers

Abstract

Glass has gained interest as a material for interposer technology due to its low/adjustable thermal expansion coefficient, low cost, good dimensional stability and availability in large panels compared to silicon substrates. However, the metallization of glass constitutes a major challenge owing to the notoriously poor adhesion between glass and metals. In this work, strategies for improving the adhesion to the glass surface and for providing at the same time continuous coating of through glass holes (TGHs) are explored. As result, a hybrid approach for glass metallization based on sputtering of a thin Ti-Cu layer and subsequent coating by electroless Ni deposition is introduced and developed. The proposed approach takes advantage of the good adhesion of very thin sputtered films on glass surfaces and combines this with the ability of electroless plating to bridge center regions of high aspect TGHs that are inaccessible to metallization by sputtering. Robust layers deposited by the hybrid method, shown to continuously coat the surface and TGHs, allow for further Cu elctrodeposition on the way to final circuitry. Approaches explored for seeding, coating and further metallization are described in detail. Results of cross-section analysis, optical microscopy, and SEM are also presented.