J.A. Sharp

Deactivation of ultrashallow boron implants in preamorphized silicon after nonmelt laser annealing with multiple scans

Electrical activation and redistribution of 500eV boron implants in preamorphized silicon after nonmelt laser annealing at 1150°C and isochronal rapid thermal postannealing are reported. Under the thermal conditions used for a nonmelt laser at 1150°C, a substantial residue of end-of-range defects remained after one laser scan but these were mainly dissolved within ten scans. The authors find dramatic boron deactivation and transient enhanced diffusion after postannealing the one-scan samples, but very little in the five- and ten-scan samples. The results show that end-of-range defect removal during nonmelt laser annealing is an achievable method for the stabilization of highly activated boron profiles in preamorphized silicon.

Diffusion and activation of ultrashallow B implants in silicon on insulator: End-of-range defect dissolution and the buried Si∕SiO2 interface

The fabrication of preamorphized p-type ultrashallow junctions in silicon-on-insulator (SOI) has been investigated. Electrical and structural measurements after annealing show that boron deactivation and transient enhanced diffusion are reduced in SOI compared to bulk wafers. The reduction is strongest when the end-of-range defects of the preamorphizing implant are located deep within the silicon overlayer of the SOI silicon substrate. Results reveal a very substantial increase in the dissolution rate of the end-of-range defect band. A key player in this effect is the buried Si∕SiO2 interface, which acts as an efficient sink for interstitials competing with the silicon surface.

Formal verification of Tokeneer behaviours modelled in fUML using CSP

Much research work has been done on formalizing UML diagrams, but less has focused on using this formalization to analyze the dynamic behaviours between formalized components. In this paper we propose using a subset of fUML (Foundational Subset for Executable UML) as a semi-formal language, and formalizing it to the process algebraic specification language CSP, to make use of FDR as a model checker. Our formalization includes modelling the asynchronous communication framework used within fUML. This allows different interpretations of the communications model to be evaluated. To illustrate the approach, we use the modelling of the Tokeneer ID Station specifications into fUML, and formalize them in CSP to check if the model is deadlock free.

Effect of buried Si/SiO2 interface on dopant and defect evolution in preamorphizing implant ultrashallow junction

P-type ultrashallow junctions are widely fabricated using Ge preamorphization prior to ultralow-energy boron implantation. However, for future technology nodes, issues arise when bulk silicon is supplanted by silicon-on-insulator (SOI). An understanding of the effect of the buried Si∕SiO2 interface on defect evolution, electrical activation, and diffusion is needed in order to optimize the preamorphization technique. In the present study, boron has been implanted in germanium preamorphized silicon and SOI wafers with different preamorphizing implant conditions. Subsequent to implantation an isothermal annealing study of the samples was carried out. Electrical and structural properties were measured by Hall-effect and secondary-ion-mass spectroscopy techniques. The results show a variety of interesting effects. For the case where the Ge preamorphization end-of-range defects are close to the buried oxide interface, there is less dopant deactivation and less transient-enhanced diffusion, due to a lower inter...

Deactivation of Ultra Shallow B and BF2 Profiles After Non-melt Laser Annealing

Ultra-shallow B and BF2 implants in silicon pre-amorphised with Ge have been activated using a scanning non-melt laser. The implants were activated either by using 1 or 10 laser scans. Isochronal 60s post-laser annealing between 700-1000oC were then undertaken to study the deactivation and reactivation of the B. Both B and BF2 samples were implanted with a dose of 1x10 15 B cm -2 at an effective energy of 500eV. The presence of F from the BF2 implants, which is superimposed over the boron profile increases the sheet resistance of the initial fabricated junction (from 600-700 ohms/sq from B implants only to 750-1100 ohms/sq for BF2 implants). Fluorine also changes the deactivation and reactivation behaviour of the boron during the postanneals by increasing the amount of deactivation of the boron.

Interaction of the end of range defect band with the upper buried oxide interface for B and BF2 implants in Si and silicon on insulator with and without preamorphizing implant

The International Roadmap for Semiconductors requires ultrashallow, highly activated, abrupt dopant profiles in the source/drain extension regions, for technology nodes beyond 45nm. The authors contrast B and BF2 implants in Si and silicon on insulator (SOI) substrates with and without a preamorphizing implant (PAI). The objective of the study is to compare between Si and SOI substrates, PAI and non-PAI condition, and B and BF2 implants. The results show the absence of the “reverse annealing effect” in BF2 implants, which is observed in B implants. The presence of F appears to impede the formation of boron interstitial clusters, which is shown in the case of B implant. The BF2 implants follow a similar trend for SOI and Si with and without PAI.

Deactivation of low energy Boron Implants into Pre‐amorphised Si after Non‐Melt Laser Annealing with Multiple Scans

Activation/deactivation of 500eV B implants in pre‐amorphised Si after non‐melt laser annealing with multiple scans at 1150°C and isochronal rapid thermal post‐annealing has been investigated. Under the thermal conditions used for non‐melt laser at 1150°C, a substantial residue of end‐of‐range defects remained after 1 laser scan, evidenced by end‐of‐range defect decoration by B atoms after 700°C post‐annealing and by transient enhanced diffusion after 800°C post‐annealing. Dramatic boron deactivation is also observed after post‐annealing the 1‐scan samples. Most of these features were not present in samples receiving 5 or 10 laser scans, indicating that the end‐of‐range defects had been stabilised or dissolved within 5 and 10 scans. The results show that the detrimental effects of end‐of‐range defects can be removed during non‐melt laser annealing and is therefore an achievable method for stabilisation of highly activated B profiles in pre‐amorphised Si.