Imaging ellipsometer system utilizing a tunable acoustic gradient lens

A computer implemented method for operating an imaging ellipsometer system, the computer implemented method comprising:

• under control of one or more computing systems configured with executable instructions,
• operating a light source as part of an ellipsometer illumination configuration of an imaging ellipsometer system to provide source light along an illumination path that is directed toward a workpiece, wherein a polarizer is included as part of the illumination configuration and is located along the illumination path and polarizes the source light from the illumination source that is directed toward the workpiece, wherein the source light is reflected from the workpiece as workpiece light which travels along an imaging optical path toward a camera, and a compensator is located along at least one of the illumination path or the imaging optical path and elliptically polarizes at least one of source light along the illumination path or workpiece light along the imaging optical path;
• operating a tunable acoustic gradient index of refraction (“TAG”) lens of a lens configuration that is located along the imaging optical path, including controlling the TAG lens to provide a modulation of a focus position of the imaging ellipsometer system at or near a resonant frequency of operation of the TAG lens, wherein an analyzer is located along the imaging optical path and receives the workpiece light that is transmitted through the TAG lens;
• operating a camera that receives the workpiece light that is transmitted along the imaging optical path through the TAG lens and the analyzer during an image exposure to provide a corresponding camera image;
• and
• based at least in part on a characteristic of the workpiece light, determining at least one of a refraction index or a thickness of one or more layers of the workpiece that are proximate to the surface of the workpiece.

A imaging ellipsometer system, comprising:

• a lens configuration that is located along an imaging optical path, wherein the lens configuration is configured to receive workpiece light that is reflected from a workpiece, for which the workpiece light corresponds to reflected source light that is provided along an illumination path toward the workpiece by an ellipsometer illumination configuration, the lens configuration comprising:
• an objective lens that inputs workpiece light that is reflected from the workpiece and transmits the workpiece light along the imaging optical path;
• and
• a tunable acoustic gradient index of refraction (“TAG”) lens that is located along the imaging optical path and is controlled to provide a modulation of a focus position of the imaging ellipsometer system;
• an analyzer that is located along the imaging optical path;
• and
• a camera that receives workpiece light that is transmitted along the imaging optical path through the TAG lens and the analyzer during an image exposure and provides a corresponding camera image.