Reflective small angle electron scattering to characterize nanostructures on opaque substrates

Abstract

Features sizes in integrated circuits (ICs) are often at the scale of 10 nm and are ever shrinking. ICs appearing in today’s computers and hand held devices are perhaps the most prominent examples. These smaller feature sizes demand equivalent advances in fast and accurate dimensional metrology for both development and manufacturing. Techniques in use and continuing to be developed include X-ray based techniques, optical scattering and of course the electron and scanning probe microscopy techniques. Each of these techniques have their advantages and limitations. Here the use of small angle electron beam scattering measurements in a reflection mode (RSAES) to characterize the dimensions and the shape of nanostructures on flat and opaque substrates is demonstrated using both experimental and theoretical evidence. In RSAES, focused electrons are scattered at angles smaller than 1° with the assistance of electron optics typically used in transmission electron microscopy. A proof-of-concept experiment is combined with rigorous electron reflection simulations to demonstrate the efficiency and accuracy of RSAES as a method of non-destructive measurement of shapes of features less than 10 nm in size on flat and opaque substrates.

Electron reflectometry for measuring nanostructures on opaque substrates

“…see Ref. 5 on RSAES. Existing and new dimensional measurement techniques continue to be modified and further developed.…”

“…2 also shows a simulated electron probability density during reflection with small azimuthal rotation. Wave functions were simulated using the previous method 5,13,14 but now implemented in Python. 15 Electrons have wavelength, λ e = 9.94 pm (accelerating voltage = 15 kV), and the grating and substrate have a mean inner potential for Si 16 U = (−12.1 -i2.23) eV.…”