Time‐of‐flight secondary ion mass spectroscopic characterization of the nitrogen profile of shallow gate oxynitride thermally grown on a silicon substrate

Abstract

Silicon oxynitride has been used as a shallow gate oxide material for microelectronics and its thickness has been reduced over the years to only a few tens of angstroms due to device size scaling. The nitride distribution and density characteristic in the gate oxide thus becomes imperative for the devices. The shallow depth profiling capability using time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) has huge potential for the nitrogen characterization of the shallow gate oxide film. In this article, both positive and negative spectra of TOF‐SIMS on silicon oxynitride have been extensively studied and it was found that the silicon nitride clusters SixN− (x = 1–4) are able to represent the nitrogen profiles because their ion yields are high enough, especially for the low‐level nitride doping in the oxide, which is formed by the annealing of nitric oxide on SiO2/Si. The gate oxide thickness measured by the TOF‐SIMS profiling method using 18O or CsO profile calibration was found to correlate very well with transmission electron microscope measurement. The nitrogen concentration in the gate oxide measured using the TOF‐SIMS method was consistent with the results obtained using the dynamic SIMS method, which is currently applied to relatively thicker oxynitride films. Copyright © 2012 John Wiley & Sons, Ltd.

Optimization of the depth resolution for profiling SiO2/SiC interfaces by dual‐beam TOF‐SIMS combined with etching

“…Moreover, it can also be mentioned that among the advantages of TOF‐SIMS are its capabilities of conducting small‐area analyses because of its higher lateral resolution or qualification analyses by taking advantage of the TOF mass analyzer; the aforementioned options are available for applications. Actually, TOF‐SIMS depth profiling methods for stacked layer samples such as SiON/Si, high‐k film/Si, and Al electrode/SiC have previously been reported. In this study, an analytical method to optimize the depth resolution to below the sub‐nm level will be presented; the method is focused on profiling the (55‐65 nm thick) SiO 2 /SiC interface by dual‐beam TOF‐SIMS.…”

“…Actually, TOF-SIMS depth profiling methods for stacked layer samples such as SiON/Si, [11][12][13] high-k film/Si, 14 and Al electrode/SiC 15 have previously been reported. In this study, an analytical method to optimize the depth resolution to below the sub-nm level will be presented; the method is focused on profiling the (55-65 nm thick) SiO 2 /SiC interface by dual-beam TOF-SIMS.…”