Incremental sheet resistance and spreading resistance: A comparison

Abstract

Spreading resistance measurements are widely used to obtain carrier depth profiles in shallow silicon diffused layers. The transformation of the raw spreading resistance data into concentration data relies on the calibration of the system against standards of known resistivity. This procedure implies that, for a given carrier concentration, the analyzed sample and the standards have the same carrier mobility. However, this hypothesis is not verified when other carrier scattering centers, in addition to those active in a perfect silicon single crystal (lattice and ionized impurities), are present in the sample. In this case spreading resistance cannot give the correct carrier concentration and an independent measurement of carrier mobility must be performed. In addition, uniform standards are not easily available at the very high doping levels used, for instance, for the source and drain diffusion of complementary metal–oxide semiconductor devices, or for the emitter diffusion in bipolar devices. In this paper we compare the results obtained with incremental sheet resistance and sheet Hall coefficient, secondary ion mass spectrometry, and spreading resistance measurements on samples implanted with BF2 at high fluence and annealed at low temperatures, and on high fluence arsenic implanted layers. Rapid thermal annealed samples, implanted with As, As and P, and BF2 have been also studied, due to the present interest in this low thermal budget method for dopant activation.