Patent ID: 7312448

Claim:
A method for generating three dimensional tomographic image data of a sample with a scanning electron microscope, the method comprising the steps of: a) providing on a surface of the sample, two longitudinally extending marks having a distance between respective sections of said longitudinally extending marks whereby said distance is varying in a selected direction of said surface; b) removing a slice from said sample by a beam of charged particles scanning across said sample in a direction perpendicular to said selected direction; c) scanning said sample by a primary electron beam, said primary electron beam having a direction of propagation not perpendicular to said selected direction, and recording image data by detecting electrons emitted by said sample and storing said image data as a set of image data; d) repeating said step b) and said step c) for a plurality of times and generating a plurality of sets of image data; and, e) analyzing said stored image data to identify said respective sections of said longitudinally extending marks in each set of image data and calculate a thickness of said slice from said distance of said respective sections of said longitudinally extending marks in said respective set of image data.