Capture Cross Section of Electric-Stress-Induced Interface States in (100) Si Metal/Oxide/Semiconductor Capacitors

The capture cross section of interface states induced by Fowler-Nordheim tunneling electron injection in (100) n- and p-Si metal/oxide/semiconductor (MOS) capacitors has been measured as a function of interface-state density by means of the ac conductance method. In n-Si MOS capacitors two interface states are generated in the upper half of the Si gap, while in p-Si MOS capacitors only one interface state is observed in the lower half of the gap. The capture cross section for electrons (upper half of the gap) and for holes (lower half of the gap) tends to decrease when the interface-state densities exceed about 1.5×10¹¹ cm^-2eV^-1. This behavior is explained by taking the occurrence of additional tunneling to defect states in the oxide into account. Moreover, the difference in the slopes of the descending characteristics of electron and hole capture cross sections is used to estimate the effective-mass ratio of an electron and a hole in the SiO₂ gap.