Secondary ion mass spectrometry of organic thin films using metal-cluster-complex ion source

Tetrairidium dodecacarbonyl, Ir-4(CO)(12), is a metal cluster complex that has a molecular weight of 1104.9. Using a metal-cluster-complex ion source, secondary ion mass spectrometry (SIMS) of poly(methyl methacrylate) (PMMA) thin films on silicon substrates was performed with a quadrupole mass spectrometer. The secondary ion intensity of PMMA bombarded with Ir-4(CO)(7)(+) ions was investigated in the beam energy ranging from 3 to 10keV at an incident angle of 45 degrees. For comparison, bombardment with oxygen ions, O-2(+), was also tested. It was confirmed that the use of Ir-4(CO)(7)(+) ions enhanced secondary ion intensity by at least one order of magnitude compared with that Of O-2(+) ions. Experimental results also showed that secondary ion intensity increased with beam energy; particularly, high-mass secondary ion intensity markedly increased.