Ultra shallow secondary ion mass spectrometry

Following the increasingly stringent requirements in the characterization of sub-micron IC devices, a good understanding of the various factors affecting ultra shallow depth profiling in secondary ion mass spectrometry (SIMS) has become crucial. Achieving high depth resolution (of the order of 1 nm) is critical in the semiconductor industry today, and various methods have been developed to optimize depth resolution. In this paper, we discuss ultra shallow SIMS depth profiling of B and Ge delta-doped Si samples using low energy (e.g. 500 eV) O/sub 2//sup +/ primary beams. The relationship between depth resolution of the delta layers and surface topography measured by atomic force microscopy (AFM) is studied. The effects of oxygen flooding and sample rotation, used to suppress surface roughening, are also investigated. The various factors that limit the depth resolution in ultra shallow SIMS depth profiling are discussed.