Patent ID: 7298480

Claim:
A broadband ellipsometer/polarimeter system for analysing a sample ( 8 ) comprising: an illumination source ( 5 ) emitting a polychromatic light beam ( 12 ), a polarisation state generator (PSG) ( 6 ) including a fixed linear polarizer ( 13 ) and a substantially achromatic retarder ( 21 ) mounted on a rotating holder ( 14 ), said light beam ( 12 ) passing through said PSG ( 6 ), a sample holder ( 3 ), on which the sample ( 8 ) can be mounted, the light beam ( 12 ) being focused on the sample ( 8 ), a polarisation state analyser (PSA) ( 10 ) including a fixed linear polarizer ( 20 ) and a substantially achromatic retarder ( 22 ) mounted on a rotating holder ( 19 ), the beam going through said PSA ( 10 ), after being transmitted, reflected or scattered by the sample ( 8 ), a primary detection system ( 11 ) measuring the intensity of the light beam transmitted through said PSA ( 10 ) at each wavelength, optics to collimate the beam into the PSG ( 6 ) and into the PSA ( 10 ) and to focus the beam into the sample surface, wherein, said linear polarizer ( 20 ) and said substantially achromatic retarder ( 22 ) in the PSA ( 10 ) are identical to the linear polarizer ( 13 ) and the substantially achromatic retarder ( 21 ) of the PSG ( 6 ) and inverted according to the sense of propagation of the light, said rotating holders ( 14 , 19 ) run in a stepper mode allowing a set of only four selected orientation angles for the retarders ( 21 , 22 ), said set of four selected orientation angles being optimized in order to maintain the condition numbers of the modulation and analysis matrices associated respectively with the PSG ( 6 ) and the PSA ( 10 ) over 0.2.