Techniques for Improving SIMS Depth Resolution: C[sub 60]+] Primary Ions and Backside Depth Profile Analysis
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We are evaluating methods to improve depth resolution for SIMS analyses of semiconductors. Two methods that show promise are: (1) backside depth profile analysis and (2) the use of cluster primary ion beams. Backside analysis improves depth resolution by eliminating sample-induced artifacts caused by sputtering through processing layers on the front side of the wafer. Mechanical backside sample preparation however, also introduces artifacts. The most troublesome artifact is inclined (non-planar) polishing. Using a combination of both secondary ion image depth profiling and image analysis techniques, the effects of inclined polishing are minimized. A Buckminsterfullerene C 60+ primary ion source has been interfaced to a magnetic sector SIMS instrument for the purpose of depth profile analysis. Application of this source to NIST SRM 2135a (nickel/ chromium multilayer depth profile standard) demonstrated that all layers of this standard were completely resolved. Initial applications of C60+ to silicon have produced some unexpected results that are not completely understood at this time. Research is underway to evaluate the application of C60+ primary ions to silicon semiconductors and other materials of interest. 2005 American Institute of Physics.
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CHARACTERIZATION AND METROLOGY FOR ULSI TECHNOLOGY 2005