Method and a system for characterising structures through a substrate

A method for characterizing structures etched in a substrate, such as a wafer, wherein a bottom of the structures is embedded in the substrate opposite to the structure etched in the top side of the substrate, the substrate having a top side in which the structures are etched and a bottom side opposite to the top side, the method comprising the following steps:

• illuminating a bottom of at least one structure etched on the top side of the substrate with an illumination beam transmitting through the substrate issued from a light source arranged at the bottom side of the substrate and emitting light with a wavelength adapted to be transmitted through the bottom side of the substrate;
• acquiring, with an imaging device positioned on the bottom side of said substrate, at least one image of a bottom of said at least one structure through the substrate;
• and
• measuring at least one data, called lateral data, relating to a lateral dimension of the bottom of said at least one structure from the at least one acquired image.