The main process or implementation flavours for through-silicon vias (TSVs). Via-first TSVs are fabricated before the active layers (front-end-of-line, FEOL); via-middle TSVs are fabricated after the FEOL but before the metal layers (back-end-of-line, BEOL); via-last TSVs are fabricated after (or during) the BEOL process.
Own work
Jknechtel