Doping integrity diagnostics of planar transistor channel structures by scanning nonlinear dielectric microscopy

Abstract

The integrity of doping in transistor structures was diagnosed using scanning nonlinear dielectric microscopy (SNDM). Nonlinear capacitance profiling and pinpoint capacitance-voltage analysis were done through SNDM, and the results clearly discriminated between a depletion layer and a tailing of carrier distribution due to outdiffusion of dopants in an n+∕p junction. This analysis was applied to n+∕p∕n+ and p+∕n∕p+ transistor channel structures formed with different process parameters. An increase in the n+ activation temperature from 800to950°C caused a narrowing of the p-type region in the n+∕p∕n+ structure. A decrease in the substrate doping concentration from 2×1018to2×1017cm−3 caused a depletion of the entire channel when the gate length was less than 200nm. The influence of channel depletion was proven to be more severe in p+∕n∕p+ transistor channel structures because boron had higher diffusivity than arsenic.