Two-dimensional dopant profiling of a 60 nm gate length nMOSFET using scanning capacitance microscopy

It is now possible using scanning capacitance microscopy to directly obtain a two-dimensional profile of the doping in MOSFETs with gate lengths greater than 60 nm. We have accomplished this using highly doped, ultrasharp silicon cantilevers with a tip diameter of less than 10 nm. These tips provide images with very little voltage dependence (over a 1-2 V range), and improved resolution (<20 nm). The observed carrier density profiles correspond closely to die simulations of the dopant distribution and indicate that a straightforward interpretation of die image derived for ultra-sharp silicon tips is possible, in contrast to previous work on metal tips which manifested a dramatic voltage dependence and >30-50 nm resolution.