Method and apparatus for ellipsometric metrology for a sample contained in a chamber or the like

An ellipsometric metrology apparatus for a sample contained in a chamber, comprising:

• a light source outside the chamber for producing an illuminating beam;
• a polarising device outside the chamber for polarising the illuminating beam;
• a window of selected dimensions and features disposed in a plane substantially parallel to the sample surface and at least partly closing the chamber;
• a first directing device for directing the polarised illuminating beam on to an area of the sample along a first optical path extending from the polarising device to the area of the sample through the window, the first optical path forming a predetermined oblique angle of incidence relative to the sample surface;
• a polarisation analysing device outside the chamber;
• a second directing device for directing the reflected beam resulting from the illumination of the sample by the illuminating beam on to the analysing device along a second optical path extending from the sample towards the analysing device through the window, the reflected beam being symmetrical to the illuminating beam relative to a normal to the sample surface;
• a detecting device for detecting the output beam transmitted by the analysing device in order to supply an output signal;
• processing means for processing the output signal in order to determine the changes in stage of polarisation in phase and in amplitude caused by the reflection on the area of the sample;
• and j) means for calibration comprising:
• 1) means for carrying out a first ellipsometric measurement on a predetermined sample, according to first experimental conditions without a window,
• 2) means for effecting a second ellipsometric measurement on the same sample as that in step 1) according to second experimental conditions similar to the first experimental conditions, but through the window,
• 3) means for determining from the first and second ellipsometric measurements the effect resulting from the window on the relationship of the tangent Ψ amplitudes of the perpendicular and parallel polarisations of the reflected beam in order to deduce therefrom a correction factor, and
• 4) means for processing according to step i) for deducing a correction factor.

A box capable of containing a sample and being intended to be associated with a metrology apparatus, comprising:

• an upper face with a window of selected dimensions and features disposed in a plane substantially parallel to a sample surface and closing the box;
• a light source outside the chamber in order to produce an illuminating beam;
• a polarising device outside the chamber in order to polarise the illuminating beam;
• a first directing device for directing the polarised illuminating beam on to an area of the sample along a first optical path extending from the polarising device to the area of the sample through the window, the first optical path forming a predetermined oblique angle of incidence relative to the sample surface;
• a polarisation analysing device outside the chamber;
• a second directing device for directing the reflected beam resulting from the illumination of the sample by the illuminating beam on to the analysing device along a second optical path extending from the sample towards the analysing device through the window, the reflected beam being symmetrical to the illuminating beam relative to a normal to the sample surface;
• a detection device for detecting the output beam transmitted by the analysing device in order to form an output signal;
• processing means for processing the output signal in order to determine the changes in stage of polarisation in phase and in amplitude caused by the reflection on the area of the sample;
• and
• j) means for calibration comprising:
• 1) means for carrying out a first ellipsometric measurement on a predetermined sample, according to first experimental conditions without a window,
• 2) means for effecting a second ellipsometric measurement on the same sample as that in step 1) according to second experimental conditions similar to the first experimental conditions, but through the window,
• 3) means for determining from the first and second ellipsometric measurements the effect resulting from the window on the relationship of the tangent Ψ amplitudes of the perpendicular and parallel polarisations of the reflected beam in order to deduce therefrom a correction factor, and
• 4) means for processing according to step i) for deducing a correction factor.