SURFACE-ANALYSIS OF DIELECTRIC FILMS BY TIME-OF-FLIGHT SECONDARY ION MASS-SPECTROMETRY

A simple time-of-flight-secondary ion mass spectrometry (TOF-SIMS) system has been built, which is designed around a time-of-flight analyser of the Poschenrieder type (164-degrees electrostatic sector). High transmission and parallel detection of several ion species in the single ion counting mode allows operation of the instrument with a very low primary ion dose. This extends analysis well into the static regime with high sensitivity and with negligible surface damage. The problems of charging of insulating samples can be reduced to negligible levels by a decrease of the primary dose. Preliminary experiments on BPSiO2 (BPSG-films) coated silicon wafer samples with a resistivity of the deposit of 10(12)-10(13)-OMEGA cm have been carried out. The poorly conducting surface has been successfully analysed without further means of charge composition using a primary pulse dose below 10(4) ions.