Secondary defect formation in bonded silicon-on-insulator after boron implantation

Abstract

Silicon-on-insulator (SOI) has proven to be a viable alternative to traditional bulk silicon for fabrication of complementary metal–oxide–semiconductor devices. However, a number of unusual phenomena with regards to diffusion and segregation of dopants in SOI have yet to be explained. In the present study, SOITEC wafers were thinned to 700 and 1600 Å using oxidation and etching. Ion implantation was performed into SOI and bulk silicon wafers using B+11 ions at 6.5 and 19 keV with a dose of 3×1014 cm−2. Thermal processing occurred in a furnace at 750 °C for times ranging from 5 min to 8 h under an inert ambient. Using quantitative transmission electron microscopy it was observed that the concentration of trapped interstitials and density of {311} defects was significantly reduced in SOI compared to the bulk. Hall effect was used to monitor the activation process of boron in SOI and bulk silicon. Significantly less activation was observed in SOI compared to the bulk and was dependent on the surface silicon thickness. For the first time, a decrease in the trapped interstitial concentration is observed in SOI even with minimal dose loss to the buried oxide. It is hypothesized that the formation of boron–interstitial clusters may be more pronounced in SOI, leading to a reduction in the trapped interstitial population and {311} defect density.

Evolution of end-of-range defects in silicon-on-insulator substrates

“…The possible effect of the Si top layer/BOX interface acting as a sink, for example, has been confirmed by some already published experimental analysis [2,5], and ruled out by others [3,7].…”

“…It is commonly accepted [2,3,[5][6][7] that the density and size of EOR defects decreases when passing from Bulk Silicon to SOI but different arguments are used in the literature to explain this reduction. The possible effect of the Si top layer/BOX interface acting as a sink, for example, has been confirmed by some already published experimental analysis [2,5], and ruled out by others [3,7].…”

Structural Characterization of Arsenic Implanted SOI

“…It has been shown that the dopants behavior and extended defects formation depend on the top Si film thickness in SOI [11][12][13] , but up to now, a deep understanding about the mechanism of atomic transport and dopant activation in SOI substrates lacks. In this work, we discuss silicon crystal structural characteristics and electrical activation of As implanted in SOI layers with different thicknesses, considering the amorphization depth reached by dopant implantation and the crystal recovery process via thermal treatment, whether it returns to single crystal structure or becomes poly-crystalline.…”

Electrical activation of arsenic implanted in silicon on insulator (SOI)

“…It has been shown that the dopants' behaviour and extended defects formation depend on the top Si film thickness in SOI [11][12][13]. Until now, there has been a lack of deep understanding about the mechanism of atomic transport and dopant activation in SOI substrates.…”