Characterization of waferstepper and process related front- to backwafer overlay errors in bulk micro machining using electrical overlay test structures

To validate the Front- To Backwafer Alignment (FTBA) calibration and to investigate process related overlay errors, electrical overlay test structures are used that requires FTBA [1]. Anisotropic KOH etch through the wafer is applied to transfer the backwafer pattern to the frontwafer. Consequently, the crystal orientation introduces an overlay...