AVS 45th International Symposium
    Applied Surface Science Division Thursday Sessions
       Session AS-ThA

Paper AS-ThA10
Coincidence Counting in Highly Charged Ion Based Time-of-Flight Secondary Ion Mass Spectrometry

Thursday, November 5, 1998, 5:00 pm, Room 307

Session: SIMS - Depth Profiling and Molecular Surface Analysis
Presenter: A.V. Hamza, Lawrence Livermore National Laboratory
Authors: A.V. Hamza, Lawrence Livermore National Laboratory
T. Schenkel, Lawrence Livermore National Laboratory
A.V. Barnes, Lawrence Livermore National Laboratory
D.H. Schneider, Lawrence Livermore National Laboratory
Correspondent: Click to Email
The high (>1) secondary ion yield per incident primary ion, which is produced when slow, highly charged ions impinge on a surface, affords the collection of time-of-flight secondary ion mass spectra in coincidence mode. In coincidence mode a spectrum may be acquired in which a particular secondary ion is required for each recorded primary ion event. Primary ion events that do not exhibit the required secondary ion are discarded. Since the primary highly charged ion induces the emission of secondary ions from a localized area of ~20 nm, the coincidence measurement insures that secondary ion emission be from within 20 nm of the coincident secondary ion emission. Hence localized (20nm scale) chemical information is obtained. An example of the power of this technique with highly charged ions is presented for a tungsten/SiO@sub 2@ patterned silicon sample wafer. Details of the wafer processing steps can be discerned from the coincidence spectra. By this coincidence method trace impurities can be associated with tungsten features. This work was performed under the auspices of the U. S. Department of Energy at Lawrence Livermore National Laboratory under contract number W-7405-ENG-48.