Lateral shearing interferometry for surface profile measurement of pattern wafers

A system comprising:

• a light source configured to generate illumination, wherein the illumination is directed to a sample along an illumination path and lands on a surface of the sample at an angle of incidence, wherein the angle of incidence is at grazing incidence, wherein the illumination reflects from the sample as reflected light encoding a surface profile of the surface in a phase of the reflected light, wherein the surface profile includes an edge roll-off of an edge of the sample;
• a stage configured to support the sample;
• a lateral shearing interferometer comprising:
• a grating, wherein the reflected light is directed from the sample to the grating along an imaging path, wherein the grating diffracts the reflected light as diffracted light;
• and
• a detector, wherein the diffracted light is directed from the grating to the detector along the imaging path, wherein the detector is configured to generate images of the diffracted light;
• and
• a controller, wherein the controller comprises one or more processors and memory, wherein the one or more processors are configured to execute program instructions maintained on the memory causing the controller to:
• receive the images from the detector;
• and
• measure the surface profile and the edge roll-off by reconstructing the phase of the reflected light from the images.