Differential Polarisation Imaging and Imaging Precision Ellipsometry

A method for imaging ellipsometry comprising:

• generating a laser beam;
• rastering the laser beam in a first direction and rastering the laser beam in a second direction to generate a rastered laser beam of linearly polarised light, wherein the first direction is perpendicular to the second direction;
• and
• directing the rastered laser beam of linearly polarised light onto a surface of a sample to reflect elliptically polarised light off the surface of the sample for imaging ellipsometry of the sample.

An imaging ellipsometry system for generating a polarisation image in response to elliptically polarised light reflected off a surface of a sample, the system comprising:

• an illumination system generating linearly polarised light and directing the linearly polarised light onto the surface of the sample;
• a quarter wavelength retarder converting reflected elliptically polarised light into linearly polarised light having a direction of polarisation rotated by an angle proportional to an ellipticity of the reflected light;
• a polarisation modulator generating an oscillating component of an intensity of the reflected light, wherein a difference between intensities of the reflected light during a first half-period of the oscillation and during a second half-period of the oscillation depends on a direction of polarisation of light passing through the retarder;
• an imaging device imaging an illuminated area of the surface of the sample using reflected light;
• a synchronising circuit coupled to the imaging device and the polarisation modulator and synchronising imaging of the reflected linear polarised light with oscillations of the polarisation modulator to image first and second array images;
• and
• a computer coupled to the imaging device for differential imaging processing of the first and second array images to generate a polarisation image comprising a plurality of pixels, wherein a value of each of the plurality of pixels of the polarisation image is proportional to the ellipticity of the reflected light.

An imaging ellipsometry system for generating a polarisation image in response to linear polarised light reflected off a surface of a sample, the system comprising:

• a laser for generating a laser beam;
• and
• a laser beam rastering device rastering the laser beam in a first direction and rastering the laser beam in a second direction to generate a rastered laser beam of linear polarised light, wherein the first direction is perpendicular to the second direction,
• wherein the laser beam rastering device further directs the rastered laser beam of linear polarised light onto a surface of a sample to reflect elliptically polarised light off the surface of the sample for imaging ellipsometry of the sample.