Accurate profiling of PN junction carrier concentration by scanning nonlinear dielectric microscopy (SNDM)

We used scanning nonlinear dielectric microscopy (SNDM) to diagnose doping integrity in a transistor. Non-linear capacitance (dC/dV) profiling and pinpoint capacitance-voltage analysis were implemented by SNDM and the results clearly discriminated a depletion layer in a n⁺/p junction and tailing of the carrier distribution due to out-diffusion of dopants. The carrier state analysis was applied to n⁺/p/n⁺ transistor-channel structures formed with different process parameters. An increase in the n⁺ activation temperature from 800 to 950°C caused narrowing of the p-type region in the channel. A decrease in the substrate doping concentration from 10¹⁸ to 10¹⁷ cm^-3 caused depletion of the entire channel when the gate length was less than 200 nm.