Optical scatterometry evaluation of groove depth in lamellar silicon grating structures

Shlomo HavaMark AuslenderBen-Gurion University of the NegevDepartment of Electrical and ComputerEngineeringPOB 653Beer-Sheva 84105, IsraelE-mail: marka@ee.bgu.ac.ilAbstract. A simple nondestructive method of measuring groove depthin lamellar gratings is presented. The method is based on processingscatterometry data for a wavelength much smaller than the grating pitchusing formulas derived by means of scalar diffraction theory. The methodhas structural and optical limitations that are specified. The intensities ofthe 0th and 61st orders reflected from silicon grating samples irradiatedby a He-Ne laser, as functions of the incident angle, are measured andprocessed to determine the groove depths. The diffraction efficienciescalculated using the thus determined groove depths by means of rigor-ous diffraction theory agree with the experimental data. For the ex-amples studied in this paper the uncertainty in the determined groovedepths is as small as 10 nm.

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