Microarea analysis of iron and phosphorus by resonance photoionization sputtered neutral mass spectrometry

A resonance-multiphoton-ionization sputtered neutral mass spectrometry (SNMS) instrument for submicron microarea analysis was developed. The laser system for producing resonance ionization in this SNMS consists of two yttrium aluminum garnet (YAG) lasers and three dye lasers. A combination of these laser beams, which makes available a maximum of four colors from the dye lasers and YAG lasers, can be simultaneously focused above a sample. The primary-ion-beam optical system, which uses a liquid-metal ion source, was developed specifically for this instrument. This system provides an ion-beam current density of more than 8 A/cm2 at a beam diameter of about 30 nm. The depth profile of iron in a submicrometer microarea on a silicon wafer was obtained at a useful yield of about 5%, and the lateral profile of phosphorus in a rectangle area about 1400x500 nm2 was obtained at useful yield of about 0.2%