Transmission shear grating in checkerboard configuration for EUV wavefront sensor

A wavefront measurement system comprising:

• a source of electromagnetic radiation;
• an imaging system that focuses the electromagnetic radiation at an object plane;
• a first grating positioned on a reticle stage that generates a diffraction pattern at a focal plane;
• a projection optical system that projects an image of the first grating onto the focal plane;
• a second grating positioned on a wafer stage that receives a diffracted image of the first grating;
• and
• a detector positioned on the wafer stage in the focal plane that receives the image of a pupil of the projection optical system through the second grating.

A system for EUV photolithography comprising:

• an EUV source emitting EUV radiation;
• an imaging system that uniformly illuminates an object plane with the EUV radiation;
• a reticle stage for mounting a reticle in an object plane;
• a first grating positioned on a reticle stage that generates a diffraction pattern at a focal plane;
• a projection optical system that optically conjugates the focal plane and the object plane;
• a wafer stage;
• a second grating in the focal plane and positioned on the wafer stage;
• and
• a detector positioned on the wafer stage that receives multiple images of a pupil of the projection optical system through the second grating.

A method of measuring a wavefront of an optical system comprising:

• generating electromagnetic radiation at a source;
• directing the electromagnetic radiation at an object plane of the optical system;
• positioning a first grating in an optical path of the optical system that generates conditioning a diffraction pattern at a focal plane of the optical system;
• conjugating the focal plane and the object plane;
• positioning a detector below the focal plane and a second grating at the focal plane;
• receiving multiple images of a pupil of the projection optical system through the second grating;
• and
• calculating wavefront parameters from the image.