US Patent 11551969 Integrated circuit structure with backside interconnection structure having air gap

An integrated circuit (IC) structure includes a transistor, a front-side interconnection structure, a backside via, and a backside interconnection structure. The transistor includes a source/drain epitaxial structure. The front-side interconnection structure is on a front-side of the transistor. The backside via is connected to the source/drain epitaxial structure of the transistor. The backside interconnection structure is connected to the backside via and includes a conductive feature, a dielectric layer, and a spacer structure. The conductive feature is connected to the backside via. The dielectric layer laterally surrounds the conductive feature. The spacer structure is between the conductive feature and the dielectric layer and has an air gap.