Charge transport in thick SiO2-based dielectric layers

Charge transport in thick (≥ 1 μm) SiO₂-based dielectric layers was investigated by means of I(U) measurements. Investigations were carried out on thermally grown field oxide (FOX) as well as on TEOS and BPSG. Gate oxide layers (GOX) were measured as reference. C(U) measurements were performed for the determination of charges in the oxide. To determine the electrical parameters of the layers, the model from Chen and Wu[1] was developed further. The model takes into account tunnelling, capture and emission processes, impact ionization, recombination, interface states and ohmic currents.

The I(U) characteristics for all dielectrics examined can be described with the aid of the model. The FOX parameters correspond to those of GOX. The parameters of TEOS and BPSG fluctuate strongly with the process parameters. After high-temperature annealing and from measurement of the examined parameters, the insulation properties of TEOS and BPSG were found to be at least as good as those of FOX.