Sheet resistance corrections for spreading resistance ultrashallow profiling

Abstract

Carrier profiles of ultrashallow structures obtained from raw spreading resistance probe (SRP) data frequently display artifacts related to sheet resistance values which are higher than those measured by the four point probe. Furthermore, the SRP raw data may already display a substantial resistance increase while the probes are still stepping over the original polished surface as they approach the bevel edge. It can be shown that these artifacts are related to the surface damage due to the beveling procedure. Carrier and electrically active dopant profiles can in principle be corrected for this damage either by introducing a depth dependent mobility function allowing for a reduced mobility near the surface or by introducing surface states and Fermi level pinning into the calculations. Both approaches will be discussed in relation to Poisson based calculations since carrier spilling is not negligible for these structures. The surface states approach fits best the currently available data.