QUANTITATIVE-ANALYSIS OF IMPURITIES IN SIMOX SAMPLES USING SECONDARY ION MASS-SPECTROMETRY

Silicon films produced by the SIMOX process (separation by implanted oxygen) must be annealed at high temperature to remove the crystal damage introduced during implantation of the high oxygen dose. Different annealing gases, temperatures and times have been investigated. In such processes, various impurities present in the high-temperature ceramic furnace tube, as well as annealing gas species, may be incorporated into the samples. Secondary ion mass spectrometry (SIMS) is used as a quantitative tool to analyze the diffusion the diffusion of tube components and gases into annealed SIMOX samples. Samples prepared for this investigation were annealed in nitrogen and argon at temperatures ranging from 1250 to 1350-degrees-C. We found that most impurities are present at low levels and are generally trapped in the surface oxide that is grown during the anneal. SIMS analyses of SIMOX samples annealed in nitrogen showed that nitrogen tends to collect in both the surface oxide and buried oxide layers, piling up at the oxide/silicon interfaces.