Broadband ellipsometer / polarimeter system

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.