Systems and methods for forming die sets with die-to-die routing and metallic seals

Stitched die structures, and methods for interconnecting die are described. In an embodiment, a stitched die structure includes a semiconductor substrate that includes a first die area of a first die and a second die area of a second die separate from the first die area. A back-end-of-the-line (BEOL) build-up structure spans over the first die area and the second die area, and includes a first metallic seal directly over a first peripheral area of the first die area, a second metallic seal directly over a second peripheral area of the second die area, and a die-to-die routing extending through the first metallic seal and the second metallic seal to electrically connect the first die to the second die.