Observation of interfacial electrostatic field‐induced changes in the silicon dielectric function using spectroscopic ellipsometry

This work investigates the capability of spectroscopic ellip-sometry to measure charge trapping centers in thin dielectric films. Specific interfacial electrostatic fields, induced by electrons injected into charge trapping states at the interface, have been identified that directly affect the underlying silicon substrate critical points. The effect of a field-induced change in the silicon fundamental absorption edge due to different processing conditions affecting the oxygen vacancy defects at the interface is presented. Measuring the field-induced change in the silicon dielectric function between a sample with a 2 nm HfO 2 film as-deposited and the same sample after a 1000 °C anneal in an N 2 ambient reveals that a stronger interfacial field is present for the as-deposited HfO 2 film. These results are consistent with the understanding that high temperature anneals work well to passivate oxygen vacancy defects at the silicon/HfO 2 interface. Finally, we compare our results with Second Harmonic Generation where specific resonant features are identifiable with electric field enhancements at the same interface.