Multi layer structures are widely used in micro electronics devices and visualisation of their sub surface layers is important to understand the nature and properties of these devices. One of the more common methods of sub surface imaging is ion beam milling, in which sections of the overlaying material are removed to reveal sub surface details. Some disadvantages of this technique are that the equipment required is expensive and the technique is destructive. Another technique is to image a device at different accelerating voltages and determine at which voltage a particular feature is first detected. A major disadvantage of this technique is that the underlying layers are always observed partially obscured by the overlaying material. The development of a non destructive technique for three dimensional characterisation of electronic, physical, compositional and/or topological properties of these structures could be useful.

One such technique is micro tomography using the backscattered electron (BSE) signal in the scanning electron microscope SEM [1].