> When semiconductors were being researched at Bell Labs in the 1940s, mysterious component failures were eventually traced to researchers who had touched copper door knobs; the tiny number of copper atoms that migrated from the door to the workers hands was enough to ruin their work material.

Copper is incredibly destructive when it's in the wrong part of the fab. It's such a problem that most manufacturers typically separate it across physical cleanroom boundaries and use things like skybridges to move the wafers from one to the other. Once a lot touches the copper area, there's no coming back. It's basically a zombie virus.