Determination of interface and bulk-trap states of IGFET’s using deep-level transient spectroscopy

Abstract

A transient capacitance technique for measuring the interface states and bulk traps in IGFET’s is described. When the source and drain are biased properly, IGFET’s may be pulsed from deep depletion to accumulation. The change of surface potential and the space-charge region as a result of the pulsing affects the occupation of the interface states and bulk traps in the band gap. The capacitance transient when the pulse is restored represents the emission of majority carriers, and from this transient the interface-state and bulk-trap energies may be determined. Similarly, the emission transient of minority carriers may also be measured in terms of the gate capacitance transient by pulsing the source and drain to invert the surface. Au-implanted IGFET’s were used as an example to demonstrate the technique. In addition to the gold levels in silicon, other defect levels were observed. These may be complexes of gold with other impurities and defects.