Mark Scan Parameter Setup
Setting up alignment mark detection is a multi-stage process.
1) First, one finds the video setting levels that give a detectable mark scan signal from the alignment mark.
2) Next, one adjust other geometric and signal-processing parameters so that the system software can find an alignment mark reliably and repeatbly.
3) Finally, one defines expected mark positions and other necessary parameters in one or both alignment routines, SETWFR or CHIPAL.
The initial setup can be done on a chip without resist - the presence of resist usually has almost affect on mark parameter definitions, and without resist, you can scan wherever and as much as necessary to get a functional mark definition and setup.