Abstract
The effects of oxygen-inserted (OI) layers and a low-temperature-deposited oxide (LTO) capping layer on rapid thermal activation of ultrashallow implanted boron, phosphorus, and arsenic atoms in silicon (Si) are investigated using sheet resistance (Rsh) measurements, secondary ion mass spectrometry analyses, and technology computer-aided design simulations. The experimental findings suggest that the electrical activation of dopants in Si is not significantly affected by the presence of OI layers so that they can be effective for achieving lower Rsh along with shallower junction depth, thanks to reduced dopant loss and diffusion during thermal annealing. On the other hand, an LTO capping layer is found to result in larger Rsh associated with the lower peak active dopant concentration as a result of dopant segregation and/or reduced uphill diffusion. The presence of OI layers is found to mitigate these detrimental effects.
Highlights
Planar bulk-silicon metal-oxide-semiconductor field-effect transistors with sub-50 nm gate lengths must have ultrashallow source and drain (S/D) extension regions to adequately suppress short-channel effects.1,2 To achieve low parasitic S/D resistance, the active dopant concentration in the heavily doped S/D extension regions must be high
A recent study of ultrashallow junction (USJ) formation via ion implantation followed by rapid thermal annealing (RTA) showed that the incorporation of partial monolayers of oxygen into crystalline silicon is effective for impeding interstitial-assisted dopant diffusion, resulting in shallower junction depth (XJ) and reduced dopant loss
Sheet resistance (Rsh) measurements together with technology computer-aided design (TCAD) simulations are used to determine the effect of OI layers on dopant activation in USJ regions
Summary
Planar bulk-silicon (bulk-Si) metal-oxide-semiconductor field-effect transistors with sub-50 nm gate lengths must have ultrashallow (sub-25 nm) source and drain (S/D) extension regions to adequately suppress short-channel effects. To achieve low parasitic S/D resistance, the active dopant concentration in the heavily doped S/D extension regions must be high. To achieve low parasitic S/D resistance, the active dopant concentration in the heavily doped S/D extension regions must be high. A recent study of ultrashallow junction (USJ) formation via ion implantation followed by rapid thermal annealing (RTA) showed that the incorporation of partial monolayers of oxygen into crystalline silicon is effective for impeding interstitial-assisted dopant diffusion, resulting in shallower junction depth (XJ) and reduced dopant loss.. Since that study involved only secondary ion mass spectroscopy (SIMS) analyses, the impact of the oxygen-inserted (OI) layers on dopant activation could not be ascertained. Sheet resistance (Rsh) measurements together with technology computer-aided design (TCAD) simulations are used to determine the effect of OI layers on dopant activation in USJ regions. The effect of a low-temperature-deposited oxide (LTO) capping layer on dopant activation in USJs is investigated
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