Meeting the demands of the lithography mask manufacturing industry moving toward 45nm and 32nm node for in-die
phase metrology on phase shifting masks, Zeiss is currently developing an optical phase measurement tool (PhameTM),
providing the capability of extending process control from large CD test features to in-die phase shifting features with
high spatial resolution.
In collaboration with Intel, the necessity of designing this optical metrology tool according to the optical setup of a
lithographic exposure tool (scanner) has been researched to be fundamental for the acquisition of phase information
generated from features the size of the used wavelength. Main cause is the dependence of the image phase of a scanner
on polarization and the angle of incidence of the illumination light due to rigorous effects, and on the imaging NA of
the scanner due to the loss of phase information in the imaging pupil.
The resulting scanner phase in the image plane only coincides with the etch-depth equivalent phase for large test
features, exceeding the size of the in-die feature by an order of magnitude.
In this paper we introduce the PhameTM phase metrology tool, using a 193nm light source with the optical capability of
phase measurement at scanner NA up to the equivalent of a NA1.6 immersion scanner, under varying, scanner relevant
angle of incidence for EAPSMs and CPLs, and with the possibility of polarizing the illuminating light. New options for
phase shifting mask process control on in-die features will be outlined with first measurement results.