Extreme ultraviolet (EUV) holographic metrology for lithography applications

In this thesis, various holographic metrology systems are presented to address a number of the key technological issues facing EUV lithography. These issues include characterization of optical system performance, characterization of illuminator coherence properties, and detection and characterization of EUV mask-blank defects.; The holographic techniques presented here are all based on the previously described EUV phase-shifting point diffraction interferometer (PS/PDI). PS/PDI can be viewed as a special case of a holographic metrology tool where a Fourier-transform hologram of the optical system point-spread function is recorded. Here this point of view is further developed laying the foundation for all subsequent holographic metrologies described in this thesis.; A critical issue for the PS/PDI is its accuracy, which is ultimately limited by the quality of the pinhole-diffracted illumination and reference beams.; A holographic aerial image monitoring system has been developed through modification of the PS/PDI. The system, based on lensless Fourier-transform holography, provides 100-mn-resolution aerial image monitoring at EUV wavelengths and uses synchrotron-based illumination. The holographic system is used to characterize the imaging performance of an EUV 10×-Schwarzschild objective. Various object patterns, including phase-shift-enhanced objects, have been studied.; Another important EUV metrology is the ability to characterize illumination coherence properties. The holographic aerial image monitoring system developed here is also well suited to the coherence metrology task. The capabilities of this method are demonstrated through the coherence characterization of two EUV synchrotron-based illuminators. Moreover, the effect of certain beamline parameters on coherence is characterized.; Another crucial component to EUV lithography is the multilayer reflective mask. Perhaps the biggest challenge for EUV mask technology is that of defect control. Because defects in the mask can be transferred to the wafer, it is crucial to have a defect free mask. The concept of holographic metrology can also be applied to the microscopic characterization of EUV multilayer-mask-blank defects. The holographic method is of particular interest because few other methods exist that can quantify both the phase and amplitude of sub-micron sized defects on EUV mask blanks. As a proof of principle, a holographic defect characterization tool is developed and demonstrated using programmed defects in transmission masks. (Abstract shortened by UMI.)...