Origin of characteristic variability in metal-oxide-semiconductor field-effect transistors revealed by three-dimensional atom imaging

The greater variability in the electrical properties of n-type metal-oxide-semiconductor field-effect transistors (MOSFETs) compared with those of p-type MOSFETs poses problems for scaling of silicon based large-scale integration technology. We have elucidated the origin of the variability difference between n- and p-type transistors by using laser-assisted atom probe tomography to directly count the number of discrete atoms in local regions. We found that ion implantation and activation annealing for source/drain extension fabrication enhances anomalous dopant fluctuations of boron atoms in n-MOSFET channel regions, interpreted by fast migration of boron atoms.