US Patent 7394535 Optical metrology using a photonic nanojet

An inspection area on a semiconductor wafer can be examined using a photonic nanojet. The photonic nanojet, an optical intensity pattern induced at a shadow-side surface of a dielectric microsphere, is generated. The inspection area is scanned with the photonic nanojet. A measurement is obtained of the retroreflected light from the dielectric microsphere as the photonic nanojet scans the inspection area. The existence of a structure in the inspection area is determined with the obtained measurement of the retroreflected light.