AVS 47th International Symposium
    Material Characterization Monday Sessions
       Session MC-MoM

Paper MC-MoM2
Analysis of Ultra-thin Oxynitride Layers by TOF-SIMS

Monday, October 2, 2000, 8:40 am, Room 207

Session: Depth Profiling
Presenter: E. Niehuis, ION-TOF GmbH, Germany
Authors: E. Niehuis, ION-TOF GmbH, Germany
T. Grehl, ION-TOF GmbH, Germany
R. Möllers, ION-TOF GmbH, Germany
O. Brox, University of Münster, Germany
Correspondent: Click to Email
The analysis of very thin oxynitride layers with a thickness below 3 nm becomes increasingly important. Methods are needed to determine the layer thickness, the nitrogen content and the nitrogen distribution in a quantitative manner. The film thickness can be measured with high reproducibility by Ellipsometry, but the SiO@sub 2@/Si interface properties and contamination layers can influence the accuracy. The total N content for very thin films can be quantified using XPS. However, no analytical technique can give the quantitative N distribution with sufficiently high depth resolution and sensitivity. SIMS depth profiling using Cs primary ions in the energy range of 500-1000 eV has been used extensively to study oxynitrides. However, the transient width in this energy range is still above 3 nm. In order to reduce it below the thickness of the film, very low energies of 100-300 eV and/or high impact angles are required. The low sputter yield in this energy regime leads to extremely high Cs surface concentration and to significant sputter rate changes in the transient regime. We have investigated the capabilities of Cs depth profiling at very low energies using TOF-SIMS depth profiling in the dual beam mode. A Cs beam with an energy below 300 eV has been used for the erosion while the center of the sputter crater is analysed with a high energy Ga beam. We have used a new Cs-Xe co-sputtering method to control the Cs surface concentration and keep it in the optimum range for the formation of MCs@super +@ cluster ions. The achievable depth resolution, the sensitivity for nitrogen and the accuracy of the thickness measurement will be discussed in detail.