Layer-by-layer formation of through-substrate via

A method, comprising:

• forming a plurality of interconnect layers of an interconnect structure over a first side of a substrate, wherein a first region of the interconnect structure is formed to be aligned vertically with electrical circuitry disposed within the substrate, and wherein a second region of the interconnect structure is formed to be unaligned vertically with the electrical circuitry;
• etching the substrate from a second side of the substrate opposite the first side, wherein the etching forms an opening in a portion of the substrate that is aligned vertically with, but narrower than, the second region of the interconnect structure;
• and
• depositing a conductive material into the opening, wherein the conductive material deposited into the opening forms a first segment of a through-substrate via (TSV), and wherein the second region of the interconnect structure forms a second segment of the TSV.

A method, comprising:

• forming a plurality of transistors over a first side of a substrate;
• forming, over the first side of the substrate, a multi-layer interconnect structure that includes a plurality of metal layers interconnected together by a plurality of vias, wherein a first region of the multi-layer interconnect structure is formed over the transistors, and wherein a second region of the multi-layer interconnect structure is laterally separated from the first region by a non-conductive material;
• reducing, after the multi-layer interconnect structure has been formed, a thickness of the substrate;
• etching after the thickness of the substrate has been reduced, an opening from a second side of the substrate toward the first side, wherein the opening is etched until a portion of the multi-layer interconnect structure in the second region is exposed;
• and
• filling the opening with a conductive material , wherein a through-substrate via (TSV) is formed collectively by the conductive material and the second region of the multi-layer interconnect structure.