(Invited) Metallic Impurity Control in Silicon Processing

The performances of a few techniques for the analysis of metal contamination in silicon are reviewed. The chemical dissolution of a polysilicon gettering layer associated to ICP-MS (Inductively Coupled Plasma - Mass Spectroscopy) analysis, TXRF (Total Reflection X-Ray Fliuorescence) Recombination lifetime measurement techniques, DLTS (Deep Level Transient Spectroscopy) and micro-photoluminescence analyses are compared. A few case studies are discussed to test the ability of these techniques in detecting contaminants with different properties as silicon impurities. The results reported in this paper show that it is not possible to define a unique recipe that can be applied in all cases. Different approaches are required depending, on one hand, on the contaminant diffusivity and solubility, and, on the other hand, on the process step to be monitored. Finally, we show that the device itself can be a sensitive monitor of metal contamination.