1. A method comprising: etching a plurality of vias through a material layer on a wafer; loading the wafer with predetermined measurement parameters in a critical dimension scanning electron microscope (CD-SEM); acquiring an image of each via of interest using Low Loss Back Scattered Electron (LL-BSE) imaging; quantifying grey level values of each image; determining a residual amount of the material layer in each via based on the grey level values; determining an etching success rate across the wafer inline based on the determining of the amount of each material layer covering each via; and adjusting the etching based on the determining of the etching success rate.