Patent ID: 7790480

Claim:
A method of determining relative swing curve amplitudes for a plurality of wafer processes comprising the steps of: coating a first wafer with a first photo resist having a first thickness in accordance with a first process; coating a second wafer with a second photo resist having a second thickness in accordance with a second process, the second photo resist for providing different a top antireflective coating at an actinic wavelength; exposing the first coated wafer to the actinic wavelength; exposing the second coated wafer to the actinic wavelength; sensing a first reflectance of the first photo resist within a predetermined range of the actinic wavelength to determine first peak height data and first valley data; sensing a second reflectance of the second photo resist within a predetermined range of the actinic wavelength to determine second peak height data and second valley data; and determining a value relating to critical dimension (CD) as a function of the first peak height data, the first valley data, the second peak height data and the second valley data.