Characterization of extreme ultraviolet lithography mask defects by actinic inspection with broadband extreme ultraviolet illumination

We present our study on actinic detection of defects on extreme ultraviolet (EUV) lithography mask blanks with broadband EUV illumination from a synchrotron light source. A mirror blank was substituted for the monochromator grating in the synchrotron beamline. This increases the spectral bandwidth that is taken from the broadband synchrotron beam by 1 order of magnitude, leading to a commensurate increase in the total available flux. The detection sensitivity of this actinic inspection system is able to reach approximately 20 nn in equivalent defect size. This has been determined through cross correlation experiments done with commercial visible-light inspection tools. Experimental results also show that this broadband EUV inspection system has a capability of detecting phase defects with 5 nm surface height. (C) 2002 American Vacuum Society.