Silicon Self-Interstitial Cluster Formation and Dissolution in SOI

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.

Comparison of {311} Defect Evolution in SIMOX and Bonded SOI Materials

“…The excess oxygen could theoretically serve as traps for interstitials, thus affecting dopant diffusion and interstitial recombination. The current study extends from previous studies 10,11 by investigating the dependence of point defect populations on the type of surface silicon/BOX interface ͑e.g., SIMOX or SOITEC͒, as well as proximity to the interface. This is accomplished by monitoring trapped interstitials within extended defects ͑e.g., ͕311͖ defects and dislocation loops͒.…”

“…A reduction in the initial trapped interstitial concentration has been previously observed for dose losses as low as 6%. 10,11 The previous experiments also showed that an enhancement in the decay rate was not observed without more than a 13% dose loss. The instability of the ͕311͖ defect compared to the dislocation loop is the likely cause of these observations.…”

“…Comparison of the decay of the trapped interstitial population between SOI and bulk silicon agrees well with previous experiments. 10,11 For ion and interstitial profiles confined to the surface silicon layer, little difference is seen between SOI and bulk. However, no measurable decrease in the initial trapped interstitial concentration is observed in the 750 Å SOI despite a 10% dose loss at 30 keV.…”

Influence of the surface Si/buried oxide interface on extended defect evolution in silicon-on-insulator scaled to 300 Å

“…The surface silicon layer of the SOI wafers was thinned using oxidation and etching from 1600 Å down to 670-688 and 299-305 Å, respectively. Figures 3 and 4 show the PTEM micrographs and QTEM data, respectively, from Saavedra et al 3 for the 5 keV samples. The wafers were then implanted with 28 Si ϩ ions at energies ranging from 5 to 40 keV and a constant dose of 2ϫ10 14 cm Ϫ2 .…”

“…These include the elimination of latch up, improved radiation hardness, low-power consumption, and higher operating temperatures. 3 Dopant diffusion in SOI has previously been shown to be quite different from that of bulk silicon. 2 In order to scale SOI devices in the future, the diffusion phenomena that take place must be understood so that process simulators can be updated.…”