Low weight spreading resistance profiling of ultrashallow dopant profiles

Abstract

The application of the conventional spreading resistance profiling (SRP) method on ultrashallow profiles is endangered by the phenomenon of pressure enhanced carrier spilling which results in false dopant and carrier profile differences, the need for large correction factors, and the presence of surfaces states on the bevel. Furthermore, the tedious preparation of the conventional SRP probes requires a lot of expertise. In this work, it is shown that some of these limitations can be resolved by the application of the nano-SRP technique on beveled samples. The use of a single conductive diamond-coated silicon tip mounted on an atomic force microscope (AFM) maintains the strong points of SRP while eliminating the need for probe conditioning. Contact sizes for nano-SRP are a factor of one hundred smaller than in conventional SRP. The small contact size combined with small probe movements allows for considerably larger bevel angles and provides a geometrical resolution as small as 0.5 nm. The smaller contact, i.e., 20–50 nm in diameter, reduces the SRP correction factor by a factor of 20. The much smaller pressure interaction volume reduces the pressure enhanced carrier spilling component. As a consequence, the application of the so-called zero field Poisson contact model becomes more feasible.