SECONDARY ION MASS-SPECTROMETRY ANALYSIS STRATEGY FOR SHALLOW JUNCTIONS ON TEST AND PRODUCT SILICON-WAFERS

The ability to pattern silicon with sub-micron linewidths has resulted in the need to measure junction depths less than 100 mm. Analysis of shallow junctions using secondary ion mass spectrometry (SIMS) is complicated by distortions due to primary ion beam mixing, the equilibration zone required for the primary species, and surface roughness. Abrupt dopant profiles can be obtained with low energy primary beams. The pre-equilibrium region can be moved with deposition of a silicon overlayer, and topography effects can be reduced by sample rotation during bombardment. SIMS cannot provide part-per-million to part-per-billion detectability for present feature sizes. Imaging depth profiles and SIMS test areas designed into the grid regions between chips assist in the analysis of production wafers.