Methods of forming blind wafer interconnects

Abstract

Methods for forming blind wafer interconnects (BWIs) from the back side of a previously thinned substrate structure such as a semiconductor wafer to the underside of a bond pad on its active surface includes the formation of a blind hole from the back side, application of a passivating layer therein, anisotropically etching to remove passivation material from the blind hole bottom, blanket-depositing at least one conductive layer within the blind hole and over the back side, blanket-depositing a resist in the blind hole and over the back side, planarizing the back side to remove resist and the at least one conductive layer, removing resist from the blind hole, and filling the blind hole with solder or other conductive material or a dielectric material. Variations in the methods include formation of a conductive pad adjacent the back side surface, disposition of a solder ball or other conductive structure on the BWI, or forming an end thereof in the form of an extended slug protruding from the back side (for ball-less attachment) as the outer terminus of the BWI.