Methods of determining an amount and/or a thickness of residual material in a via based on LL-BSE images of the material are disclosed. Embodiments include etching a plurality of vias through at least one material layer on a wafer; loading the wafer with predetermined measurement parameters in a CD-SEM; acquiring an image of each via of interest using LL-BSE imaging; quantifying grey level values of the images; characterizing residuals of the at least one material layer in each via based on the grey level values; determining an etching success rate based on the characterizing of the residuals; adjusting the etching based on the determining of the etching success rate; and repeating the steps of acquiring, quantifying, characterizing, determining, and adjusting until a desired etching success rate is achieved.