EUV scatterometer with multiple orders of high-harmonic generation

Scatterometry is an optical metrology technique designed for analyzing the changes of light intensity in a device. This technique is widely used for the wafer metrology of nanostructured surfaces in the semiconductor industry. There are two scatterometric approaches: angle-resolved and spectroscopic scatterometer.1, 2 Angle-resolved scatterometry involves single-wavelength readings at various angles, and measure both zeroth-order and first order diffractions. Spectroscopic systems work at a fixed angle of incidence but in broadband wavelengths range in the visible or UV, and measure only the zeroth-order diffraction. In contrast to angle-resolved and spectroscopic scatterometries, the proposed extreme ultraviolet (EUV) scatterometer is designed to measure the intensity of non-zero-order diffractions at a fixed incident angle and at multiple laser-like wavelengths. The short wavelengths of EUV, which give rise of several diffraction orders of scattering from nanoscale grating features. The well-separated higher-order diffraction beams are more informative than the zero-order diffraction beam, coupled with a very efficient rigorous coupled-wave analysis (RCWA), can achieve a detailed reconstruction of the profile of nanoscale periodic gratings. In this paper, however, describes the use of yet two more methods for breaking correlations and increasing sensitivity—include the use of non-zeroth order (m = + 1 and m = −1) diffracted light and polychromatic wavelengths of high harmonic generation (HHG). For many structures, this flexibility significantly increases parameter sensitivity and reduces parameter correlation.