A method to monitor the state of polarization incident on a photomask in
projection printing is presented. The method includes a series of
phase-shifting mask patterns that take advantage of high NA effects to
create a signal dependent on only one incident polarization component.
The patterns include in two embodiments a Radial Phase Grating (RPG) and
Proximity Effect Polarization Analyzers (PEPA). A test reticle design
includes multiple polarimeters with an array of pinholes on the backside
of the photomask. This technique is able to monitor any arbitrary
illumination scheme for a particular tool.