Field mapping of focused ion beam prepared semiconductor devices by off-axis and dark field electron holography

Off-axis electron holography is a unique technique in that it can be used to provide maps of the electrostatic potentials and strain in semiconductor specimens with nm-scale resolution. In this paper, we show that if sufficient care is taken, focused ion beam milling can be used to prepare electrically tested devices from a precise location on a wafer for studies of their electrostatic and strain fields as well as their structure and composition. We have compared the physical properties of several devices with process simulations and electrical test results which were measured over a time period of several months. We believe that electron holography can now be used to measure the positions of the electrical junctions and also quantitative values of the strain in an industrial environment.