Multilayer Measurements with the Calibration and Standards Beamline at the
Advanced Light Source 

J. H. Underwood and E. M. Gullikson

Center for X-ray Optics, Lawrence Berkeley Laboratory, University of
California, Berkeley CA 94720

This beamline has been in operation since February 1995 for the
characterization of optical elements (mirrors, gratings, multilayers,
detectors, etc.)  in the energy range 50-1000 eV.  Although it was designed
primarily for precision reflectometry of multilayer reflecting optics for EUV
projection lithography, it has capabilities for a wide range of measurements.
The optics consist of a monochromator, a reflectometer, and refocusing mirrors
to provide a small spot on the sample.  The monochromator is a very compact
entrance slitless, varied line spacing plane grating design in which the
mechanically ruled grating operates in the converging light from a spherical
mirror working at high demagnification.  Aberrations of the mirror are
corrected by the line spacing variation, so that the spectral resolving power
is limited by the ALS source size to about 7000.  Wavelength is scanned by
simple rotation of the grating with a fixed exit slit.  The reflectometer has
the capability of positioning the sample to 10 microns, with an angular
precision of .002 deg.  LABVIEW (TM) based software provides a convenient
interface to the user.  The reflectometer is separated from the beamline by a
differential pump, and can be pumped down in 1/2 hour.  A separate order
suppressor reduces contamination by higher grating orders to a low level.
Results are shown which demonstrate the performance and operational
convenience of the beamline.