Optical scatterometry evaluation of groove depth in lamellar silicon grating structures

A simple nondestructive method of measuring groove depth in lamellar gratin gs is presented. The method is based on processing scatterometry data for a wavelength much smaller than the grating pitch using formulas derived by m eans of scalar diffraction theory. The method has structural and optical li mitations that are specified. The intensities of the 0th and +/- 1st orders reflected from silicon grating samples irradiated by a He-Ne laser, as fun ctions of the incident angle, are measured and processed to determine the g roove depths. The diffraction efficiencies calculated using the thus determ ined groove depths by means of rigorous diffraction theory agree with the e xperimental data. For the examples studied in this paper the uncertainty in the determined groove depths is as small as 10 nm. (C) 2001 Society of Pho to-Optical Instrumentation Engineers.