Self‐Aligning Metallic Vertical Interconnect Access Formation through Microlensing Gas Phase Electrodeposition controlling Airgap and Morphology

Abstract This publication reports self‐aligning metallic via microlensing gas phase electrodeposition formation. Key operational parameters to fabricate vertical ruthenium and rhodium interconnects (via) with a diameter of 100 nm are discussed. Moreover, airgaps are implemented during the deposition process, which utilizes spark discharge to generate a flux of charged nanoparticles. An inert gas flow transports the nanoparticles through a reactor chamber close to the target substrate. The substrate uses a pre‐patterned resist with openings to a silicon/silicon dioxide/metal stack to direct the deposition of the nanoparticles to form localized self‐aligning vertical interconnects. Five process parameters were identified, which impact the morphology and conductance of the resulting interconnects: spark discharge power, gas flow rate, microlens via dimensions, substrate surface potential, and in situ flash lamp power. This parameter set enables a controlled adjustment of the via interconnect morphology and its minimum feature size. Gas flow rate in combination with spark discharge power contribute significantly to the morphology of the interconnect. Spark power and microlens via dimensions have the largest influence on the surface potential of the insulating resist cover, which enables a localized microlensing gas phase electrodeposition of a via with a controlled ratio between conducting diameter and airgap.