Application of the deconvolution of AFM profiles to the Etch/AFM method for measuring 2-D dopant concentrations in sub-100nm deep junction n+/p silicon MOSFETs

The Etch/AFM method with tip size deconvolution has been used to obtain 2-D dopant concentration profiles from sub-100nm deep junction n⁺/p silicon MOSFET test structures. Polished cross-section bulk specimens were dopant selectivity etched with 0.5% HF / 99.5% HNO₃. 2-D etching depth profiles were obtained for individual source/drain regions using an AFM and a 55nm tip radius. The 2-D etching profiles were deconvoluted with respect to the tip size and shape in directions perpendicular and parallel to the wafer surface, converted to 2-D etch rate profiles and then to 2-D dopant concentration profiles using an independently obtained calibration curve. These 2-D dopant profiles indicated a vertical junction depth X^j of ~75nm and a lateral junction distance X_lj underneath the gate edge of ~17nm. These results are compared with corresponding results obtained from the same MOSFET structures by the analogous Etch/TEM method.