Static time-of-flight secondary ion mass spectrometry analysis of microelectronics related substrates using a polyatomic ion source

Recent time-of-flight secondary ion mass spectrometry studies using primary ion cluster sources such as Aun+, SF5+, Bin+ or C60+ have shown the great advantages in terms of secondary ion yield enhancement and ion formation efficiency of polyatomic ion sources as compared to monoatomic ion sources like the commonly used Ga+. In this work, the effective gains provided by such a source in the static ToF-SIMS analysis of microelectronics devices were investigated. Firstly, the influence of the number of atoms in the primary cluster ion on secondary ion formation was studied for physically adsorbed di-isononyl phthalate (DNP) (plasticizer) and perfluoropolyether (PFPE). A drastic increase in secondary ion formation efficiency and a much lower detection limit were observed when using a polyatomic primary ion. Moreover, the yield of the higher mass species was much enhanced indicating a lower degree of fragmentation that can be explained by the fact that the primary ion energy is spread out more widely, or that there is a lower energy per incoming ion. Secondly, the influence of the number of Bi atoms in the Bin primary ion on the information depth was studied using reference thermally grown silicon oxide samples. The information depth provided by a Bin cluster was shown to be lowered when the number of atoms in the aggregate was increased.