Compact NIR Imaging Module for Photolithography Source Metrology

This team employed novel imaging and optomechanical architectures – including off-axis aspheres, freeforms and non-rotationally symmetric surfaces – in order to match or improve the optical performance of existing Near-Infrared Imager (NIRIM) designs while significantly reducing the overall volume.

ASML develops extreme ultraviolet (EUV) lithography light sources used in the manufacture of semiconductor chips. EUV generation takes place inside a large diameter – greater than 1.5 meter – chamber by vaporizing/ionizing small liquid tin droplets at high repetition rates using a powerful carbon dioxide laser. The vaporized/ionized tin droplets produce EUV radiation, which is collected by a mirror and focused into a lithographic scanner. The scanning system exposes lithographic patterns on semiconductor wafers using the EUV light. The function of the Compact NIRIM is to monitor the size, position, spatial stability and form factor of the stream of tin droplets as they traverse through its field of view.

Due to the extremely high cost, lead time and complexity of manufacturing custom optics, the team was only responsible for designing the optical system, its optomechanical mounts and enclosure dimensions within relevant software.