Matrix effect-free depth profiling of multilayered Si/Ti with laser-SNMS

Abstract

In order to reveal matrix effect at surface and interfacial regions, we have measured the depth profiles of multilayered Si/Ti by secondary ion mass spectrometry (SIMS) and resonance-enhanced multiphoton ionization sputtered neutral mass spectrometry (REMPI-SNMS) using Ar+ beam as primary ion beam. Titanium profile of SIMS was strongly influenced with matrix effect in comparison to silicon one. Especially in the Si/Ti interfacial regions, the Ti+ yield of SIMS was enhanced, whereas the Ti neutral yield of SNMS was proportional to the actual Ti in-depth concentration profile. By means of the XPS measurement, we confirmed the existence of the TiSi2 at these regions. Useful yield of Ti+ sputtered from a TiSi2 sample was about five times larger than that sputtered from a Ti sample which is caused by the difference of chemical state in Ti and TiSi2 bulk. This difference could be interpretable by using the electron tunneling model. On the other hand, useful yield of Ti neutral sputtered from Ti sample was same as that from TiSi2 one. In conclusion, the distribution of the fraction of secondary ion species relating with Ti, such as Ti+, TiO+, TiSi+, etc., was only varied with the change of chemical state in the sample, which caused the matrix effect for the SIMS measurement. We consider the results of both SIMS and SNMS measurements give us the significant knowledge about the mechanism of the matrix effect for depth profile measurement.