OPTIMIZED TIME-OF-FLIGHT SECONDARY-ION MASS-SPECTROSCOPY DEPTH PROFILING WITH A DUAL-BEAM TECHNIQUE

High resolution depth profiling has been performed in a time-of-flight secondary ion mass spectroscopy (TOF-SIMS) instrument equipped with i ndependent ion sources for sputtering (crater formation) and for SIMS analysis. In this dual beam mode a low energy sputter gun (Cs or any g as ion) allows a free selection of optimum sputter conditions with reg ard to depth resolution and matrix optimization. For secondary ion gen eration an independent high energy ion beam, optimized with regard to focussing and secondary ion yield (Ga or gas ion source) is applied. F or different sputter gases (Ar, Xe, O-2, and SF6), energies (0.3-2 keV ) and angles of incidence a systematic investigation of B layers in Si and GaAlAs multilayers has been carried out. Decay lengths of 0.53 nm were achieved for low energy sputtering of B layers in Si with 0.6 ke V SF5+. In this dual beam mode the depth profiling performance of TOF- SIMS exceeds that of state of the art quadrupole and magnetic sector f ield instruments in several fields of application, important in partic ular in microelectronics. (C) 1997 American Vacuum Society.