Patent ID: 7075649

Claim:
A spectroscopic ellipsometer system comprising: a source of polychromatic electromagnetic radiation; a polarizer which is fixed in position during data acquisition; a stage for supporting a sample system; an analyzer which is fixed in position during data acquisition; and a multi-element spectroscopic detector system; said spectroscopic ellipsometer system further comprising at least one means for discretely, sequentially, modifying a Polarization state of a beam of electromagnetic radiation Provided by said source of polychromatic electromagnetic radiation through a plurality of polarization states, said means for discretely, sequentially, modifying a polarization state of a beam of electromagnetic radiation provided by said source of polychromatic electromagnetic radiation through a plurality of polarization state being present at at least one location selected from the group consisting of: between said polarizer and said stage for supporting a sample system; and between said stage for supporting a sample system and said analyzer; and positioned so that said beam of electromagnetic radiation transmits therethrough in use; in which said at least one means for discretely, sequentially, modifying a polarization state of a beam of electromagnetic radiation provided by said source of polychromatic electromagnetic radiation through a plurality of polarization states, involves at least one rotatable compensator that changes the phase angle between orthogonal components of said electromagnetic beam of radiation provided by said source of polychromatic electromagnetic radiation; in which said at least one rotatable compensator comprises at least two per se. zero-order waveplates (MOA) and (MOB), said per se. zero-order waveplates (MOA) and (MOB) having their respective fast axes rotated to a position offset from zero or ninety degrees with respect to one another, with a nominal value being forty-five degrees.