DEVELOPMENT OF A LASER MICROPROBE FOURIER-TRANSFORM MASS-SPECTROMETER WITH EXTERNAL ION-SOURCE

Laser microprobe mass spectrometry (LMMS) employs focused laser-beam irradiation of solids and subsequent mass analysis of the ions produced. The technique is suitable for the local analysis of inorganic and organic constituents with a spatial resolution in the micrometer range. The Fourier transform mass spectrometer (FTMS) is an analyser of choice for LMMS because high mass resolution and accurate mass determination can be routinely achieved at adequate sensitivity. This paper describes the first LMMS instrument using FTMS with an external ion source. The design considerations and the experimental performance are described with respect to such analytical parameters as spatial resolution and sensitivity. A comparison between time-of-flight mass spectrometry and FT-LMMS for diagnostic analysis of organic molecules is interpreted in terms of the ion formation processes. Finally, the analysis of a selected integrated circuit evidences the feasibility of local analysis with 2 spatial resolution of 5 mum.