Method for forming through silicon via with wafer backside protection

Semiconductor devices with through silicon vias (TSVs) are formed without copper contamination. Embodiments include exposing a passivation layer surrounding a bottom portion of a TSV in a silicon substrate, forming a silicon composite layer over the exposed passivation layer and over a bottom surface of the silicon substrate, forming a hardmask layer over the silicon composite layer and over the bottom surface of the silicon substrate, removing a section of the silicon composite layer around the bottom portion of the TSV using the hardmask layer as a mask, re-exposing the passivation layer, and removing the hardmask layer and the re-exposed passivation layer to expose a contact for the bottom portion of the TSV.