Stacked substrate structure with inter-tier interconnection

A method of forming a multi-dimensional integrated chip structure, comprising:

• forming one or more semiconductor devices within a first substrate;
• forming a first plurality of metal interconnect layers within a first dielectric structure along a front-side of the first substrate;
• forming a first dielectric bonding layer on a top surface of the first dielectric structure;
• forming one or more image sensing elements within a second substrate;
• forming one or more second metal interconnect layers within one or more dielectric layers arranged along a front-side of the second substrate;
• forming a second dielectric bonding layer along a back-side of the second substrate;
• bonding the first dielectric bonding layer to the second dielectric bonding layer;
• forming an inter-tier interconnect structure configured to electrically couple the one or more semiconductor devices and the one or more image sensing elements;
• and
• wherein the inter-tier interconnect structure comprises a first segment having substantially vertical sidewalls, a second segment having a width that increases as a distance from the second substrate increases, and a third segment separated from the first segment by the second segment and having a width that increases as a distance from the first substrate increases.

A multi-dimensional integrated chip structure, comprising:

• a first plurality of metal interconnect layers arranged within a first dielectric structure over a first substrate;
• a second plurality of metal interconnect layers arranged within a second dielectric structure over a second substrate;
• a bonding structure arranged between the first dielectric structure and the second substrate;
• an inter-tier interconnect structure extending between one of the first plurality of metal interconnect layers and one of the second plurality of metal interconnect layers and through the bonding structure and the second substrate, wherein the inter-tier interconnect structure comprises a plurality of different segments that respectively have sidewalls with different sidewall angles;
• and
• wherein the plurality of different segments comprise a first region extending through the second substrate and a second region surrounded by the bonding structure, the second region contacting a bottom surface of the first region at locations laterally offset from sidewalls of the first region by non-zero distances.