Optimized trapezoid FIB sample preparation method for dielectric nanocharacterization

Abstract

A novel FIB sample preparation for advanced BEOL, FEOL and beyond CMOS dielectric reliability is presented. The simultaneous milling of the two sides of the lamella with trapezoidal dual milling patterns results in a thin (~30 nm) TEM sample with minimum implantation and damage. The resulting geometry is strain-symmetrized and free from curtain effect. The optimum crystal quality is assessed by Auger and EDX spectrometry, equal orientation fringes, strain mapping and quantitative analysis of HRTEM images. The complex dielectric permittivity of advanced dielectric stacks is properly mapped by energy loss spectroscopy only when this preparation method is used. The nanostructure and conduction properties of a nanofilament inside hafnia are henceforward measured, which provide a direct insight into the physics of resistive memory (ReRAM) cells or high-K gate dielectric defectivity at the nanometric scale.