Iron contamination in silicon and its impact on ultrathin gate oxide integrity.

摘要

Contamination, defect control and monitoring are major concerns in advanced integrated circuit production. Contaminants can be deliberately introduced to increase the speed of bipolar devices, even at the cost of increased leakage current. Metallic contamination makes a device more sensitive to degradation as device dimensions keep shrinking. The degradation of silicon/silicon dioxide (Si/SiO₂) interfaces and of SiO₂ layers is a critical issue for metal-oxide semiconductor field effect transistors (MOSFETs). Metallic contaminants generally degrade thermally grown oxides and also lead to enhanced leakage currents. Leakage currents also degrade refresh times in dynamic random access memories (DRAMs). To understand measurement techniques and the behavior of ultra-thin oxides with and without metal contamination, this researcher proposes an alternative characterization solution to the traditional constant voltage-time and constant current-time measurements.; Iron-contaminated oxides of metal-oxide semiconductor (MOS) devices were investigated to study gate oxide integrity (GOI) degradation dependence on oxide thickness for oxide thicknesses ranging from 3 nm to 5 nm and iron densities from 4 × 1010 cm−3 to 1.4 × 1012 cm−3. In contrast to other publications, this study shows that oxides as thin as 3 nm show gate oxide integrity degradation, especially for the higher iron densities. But even for the low iron density, this researcher observed GOI degradation for all oxides.