Semiconductor Dopant Profiling by Off-Axis Electron Holography

Abstract Two-dimensional dopant profiling continues to be a topic of great interest and importance to the semiconductor industry. Off-axis electron holography provides access to the phase of the electron wavefront that has traversed a sample, and it thus enables voltage contrast to be visualized. The technique was used by McCartney et al. (1994) to observe the potential distribution across Si/Si p-n junctions [1], and it was later also used by Rau et al. (1999) to map the two-dimensional electrostatic potential in deep-submicron transistor structures [2]. in this paper, we have used electron holography and a known test structure to demonstrate that accurate voltage profiles can be extracted under carefully controlled sample preparation conditions. Carrier information can be obtained using a simulation program. Experimental factors that affect quantitative measurement are also discussed. The sample studied was a test structure fabricated at IBM for comparison of various profiling methods [3]. Both p-n junctions and p-p+ regions were available for study.