Silicon Self-Interstitial Cluster Formation and Dissolution in SOI
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Silicon Self-Interstitial Cluster Formation and Dissolution in SOI A. Saavedra, J. Frazer , D. Wrigley , K. Jones Department of Materials Science and Engineering, University of Florida, Gainesville, FL I. Avci, S. Earles, M. Law Department of Electrical and Computer Engineering, University of Florida, Gainesville, FL E. Jones IBM Research Division, T.J. Watson Research Center, Yorktown Heights, NY Abstract Silicon-on-insulator (SOI) is a promising alternative to bulk silicon as ultra shallow junction depths have begun to shrink below 50 nm. This study examined the effect of the SOI surface silicon/buried oxide interface on {311} defect evolution after Si+ ion implantation. SOI wafers were produced such that the surface silicon thickness varied from 300Å to 1600Å. Non-amorphizing Si+ implants at 5 and 20 keV with a dose of 2x1014 cm-2 were performed into SOITEC SOI wafers. Furnace anneals were done at 750°C from 5 minutes to 4 hours and quantitative transmission electron microscopy (QTEM) was used to study the implant damage evolution. At 5 keV, the dissolution behavior of the SOI was very similar to that of the bulk. However, the extended defects in the 300 Å SOI did not nucleate the same as those observed in the bulk or thicker SOI. Similar results were seen at 20 keV for the 700 Å SOI, but a slight decrease in the concentration of trapped interstitials was observed due to interface recombination as a result of the increased projected range of the implant. It is concluded that the surface Si/BOX interface does not significantly affect recombination of interstitials trapped in extended defects unless the interstitial profile is close to or truncates the interface. However, the interface does appear to affect the stability of zig-zag {311} defects and dislocation loops in thin SOI at lower implant energies. Introduction While the advantages of silicon-on-insulator (SOI) over bulk silicon have been well documented over the years, only recently has it begun to make its way into mainstream CMOS technology.1 In order to scale SOI devices in the future, significant research must be done to understand the diffusion processes that make SOI different from bulk Si. Transient enhanced diffusion (TED) is exhibited by numerous dopants and is one of the main issues affecting ultra shallow junction formation.2 One of the sources of TED are extended defects such as {311} defects and dislocation loops, which regulate the release of excess interstitials.3 It is via these interstitials that many dopants, most notably B and P, diffuse throughout the silicon lattice.4 Thus, in order to understand TED in SOI, it is imperative to discern the role of the surface Si/buried oxide (BOX) interface on the evolution of extended defects. The current study has attempted to understand this role by
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viewing the evolution of extended defects created by Si+ ion implantation using quantitative transmission electron microscopy (QTEM). A few studies have been aimed at trying to understand how the surface Si/BOX interface affects dopant diffusion
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