Grating Pitch Measurement Beyond the Diffraction Limit with Modified Laser Diffractometry

The demand for accurate measurements of nanostructures is increasing for the microprocesses and nanotechnology used in the semiconductor industry. In this study, we present an improved method for measuring gratings with a pitch size lower than one-half of the laser wavelength by using a modified laser diffractometer (LD). In experiments, the modified LD with a 633 nm laser is used to measure a grating with a 288 nm pitch size. This result is compared with results measured by both a metrological atomic force microscope and the traditional LD with a 543 nm laser. The validity of this method is demonstrated. The difference between the pitch size of 288 nm obtained by these three methods is approximately 0.17 nm.