Matrix and element dependences of useful yield in Si and SiO2 matrices using laser-ionization sputtered neutral mass spectrometry

The element and/or material dependence of the useful yield in laser-ionization sputtered neutral mass spectrometry (SNMS) using a high-photon-flux laser was investigated. Useful yields obtained from Si, B, As, and O in Si and SiO2 matrices using both secondary ion mass spectrometry (SIMS) and SNMS were compared, and the possibility of the accurate analysis of impurities in multilayers was investigated in terms of tunnel ionization. The behavior of atoms released from the surface by ion bombardment was calculated, and it was considered that the flying speed of sputtered atoms depends on the mass and that this causes the elemental difference in the fractions of laser-irradiated atoms. In the case of SNMS, excluding O, whose ionization probability is considered to be much lower than for the other elements, the useful yields of Si, B, and As are within 1 order of magnitude in both the Si and SiO2 matrices, and the difference between the matrices for each element is within a factor of two. These differences are much smaller than in the result of SIMS. It was confirmed that the distribution of B in a SiO2/Si stacked layer can be analyzed more accurately by SNMS than by SIMS. SNMS with a high-photon-density laser is considered to be effective for the analysis of more than one element in multilayers.