Cross-sectional nano-spreading resistance profiling

Abstract

The nano-spreading resistance profiling (nano-SRP) method has been developed and improved such that it can now be used as an accurate tool for quantitative two-dimensional carrier profiling. Instrumental improvements include the use of batch-fabricated, conducting diamond-coated silicon probes, and a low-noise logarithmic current amplifier. The spatial resolution (10 nm), the dynamic range (1014–1020 atoms/cm3), and the sensitivity (1014 atoms/cm3) of the nano-SRP technique are illustrated by profiling a wide range of state-of-the-art device structures. Two-dimensional measurements of the carrier distribution inside fully processed metal–oxide–semiconductor transistors with gate lengths varying from 2 μm down to 0.25 μm illustrate the strength of the technique to map present and future devices. The nano-SRP method currently has sufficient resolution to demonstrate the small asymmetry in the source/drain profiles from transistors in which the sample was not rotated during the 7° implant. The electrical transistor characteristics confirm the nano-SRP results. As another example, the lateral diffusion of arsenic and phosphorus profiles is studied as a function of implantation conditions. All results are compared with conventional one-dimensional techniques (SRP and secondary ion mass spectroscopy).