The present disclosure, in some embodiments, relates to a multi-dimensional integrated chip structure. The structure includes a first interconnect layer within a first dielectric structure on a first substrate, and a second interconnect layer within a second dielectric structure on a second substrate. A bonding structure is between the first dielectric structure and the second substrate. An inter-tier interconnect structure extends through the second substrate and between a top of the first interconnect layer and a bottom of the second interconnect layer. The inter-tier interconnect structure includes a first region having substantially vertical sidewalls extending through the second substrate and a second region below the first region and having tapered sidewalls surrounded by the bonding structure.