Two-dimensional characterization of carrier concentration in metal-oxide-semiconductor field-effect transistors with the use of scanning tunneling microscopy

An evaluation technique for two-dimensional (2D) carrier profiles in metal-oxide-semiconductor field-effect transistors (MOSFETs) is presented that is based on the use of scanning tunneling microscopy (STM). First, the procedure of STM-based carrier profiling method is presented. Sample preparation that enables accurate carrier measurements is described. It is shown that STM has both the spatial resolution and sensitivity of tunneling current to carrier concentration enough to evaluate the carrier profile in an aggressively scaled device. The conversion method from obtained images into carrier profiles is described. Next, the STM-based technique is used to evaluate two-dimensional carrier profiles in the extension regions of 70 nm n -MOSFETs. The dependence of 2D carrier profiles in the extension regions where arsenic is implanted at an energy of 3 keV on the implantation dose and annealing temperature is investigated. STM is a powerful tool for the efficient development of scaled Si devices.