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The formation of ultra-shallow junctions (USJs) for future integrated circuit technologies requires preamorphization and high dose boron doping to achieve high activation levels and abrupt profiles. To achieve the challenging targets set out in the semiconductor roadmap, it is crucial to reach a much better understanding of the basic physical processes taking place during USJ processing. In this paper we review current understanding of dopant-defect interactions during thermal processing of device structures – interactions which are at the heart of the dopant diffusion and activation anomalies seen in USJs. First, we recall the formation and thermal evolution of End of Range (EOR) defects upon annealing of preamorphized implants (PAI). It is shown that various types of extended defect can be formed: clusters, {113} defects and dislocation loops. During annealing, these defects exchange Si interstitial atoms and evolve following an Ostwald ripening mechanism. We review progress in developing models based on these concepts, which can accurately predict EOR defect evolution and interstitial transport between the defect layer and the surface. Based on this physically based defect modelling approach, combined with fully coupled multi-stream modelling of dopant diffusion, one can perform highly predictive simulations of boron diffusion and de/re-activation in Ge-PAI boron USJs. Agreement between simulations and experimental data is found over a wide range of experimental conditions, clearly indicating that the driving mechanism that degrades boron junction depth and activation is the dissolution of the interstitial defect band. Finally, we briefly outline some promising methods, such as co-implants and/or vacancy engineering, for further down-scaling of source-drain resistance and junction depth.

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The fabrication of preamorphized p-type ultrashallow junctions in silicon-on-insulator ͑SOI͒ 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/ SiO 2 interface, which acts as an efficient sink for interstitials competing with the silicon surface. © 2006 American Institute of Physics. ͓DOI: 10.1063/1.2240257͔ Formation of highly activated, ultrashallow, and abrupt profiles is a key requirement for the next generation of complementary metal oxide semiconductor ͑CMOS͒ devices, particularly for source-drain extensions.1 For p-type ͑boron͒ dopant implants, a promising method of increasing junction abruptness is to use Ge preamorphizing implants ͑PAI͒ prior to ultralow energy B implantation. Advantages of this method are a reduction in B channeling and an increase in B electrical activation due to the solid-phase-epitaxial ͑SPE͒ regrowth process. 2 SPE regrowth of the amorphized silicon does not remove interstitial defects located at depths greater than the initial amorphous/crystalline ͑a / c͒ interface. Excess interstitial atoms in this region agglomerate into "end-of-range" ͑EOR͒ defects situated just below the former a / c interface. During higher temperature annealing these defects undergo a series of transitions from self-interstitial clusters to ͕113͖ defects to dislocation loops depending on the initial PAI and subsequent conditions.3 These defects dissolve during annealing and the silicon self-interstitials so released migrate to nearby sinks such as the silicon surface.3 Transient enhanced diffusion and B electrical deactivation result from the interstitials that diffuse towards the silicon surface during annealing. 3,4 In the absence of sinks within the silicon, all of the released interstitials diffuse towards the surface. Thus they either end up reacting with B atoms in the implant or migrating unscathed through the B-doped layer to the silicon surface-the former being the more probable event in the case of highdose B implants.One possible method to reduce the number of interstitials that migrate to the B implanted region is to provide an efficient alternative sink for the interstitials. In this letter we investigate whether the buried oxide interface of the silicon top layer in silicon on insulator ͑SOI͒ may function in this way. This question is of considerable importance as SOI emerges as a candidate technology for future CMOS applications. 5Experiments were performed on n-type ͗100͘ Czochralski silicon wafers with a resistivity of ϳ10-25 ⍀ cm and on SOI wafers with a 145-nm-thick buried oxide and a 55-nm-thick p-type Si overlayer. Silicon and Soitec© SOI wafers were i...

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A new technique for measuring the temporal transfer function of optical fibers is described. The method consists of placing the fiber under test in one arm of a Mach-Zehnder interferometer excited by a broadband source. The temporal impulse response is obtained from a holographic reconstruction. The method requires only short lengths of single-mode or multimode fibers (less than 1 m). We have measured a dispersion of 0.3 nsec/km.nm at 0.59 microm with a single-mode fiber, in good agreement with theory. The arrival times of the various modes of multimode fibers are resolved.

In a modern, generalized version of Young’s two-slit experiment, it is shown that two separate pulsed lasers can generate visually observable, transient interference fringes of high contrast under the simple and obvious condition that the temporal and spectral structures of the interfering pulses overlap. In a second experiment, a picosecond streak camera allows the observation of spatio-temporal interference fringes between two waves having different frequencies.

The evolution of {113} defects as a function of time and depth within Si implant-generated defect profiles has been investigated by transmission electron microscopy. Two cases are considered: one in which the {113} defects evolve into dislocation loops, and the other, at lower dose and energy, in which the {113} defects grow in size and finally dissolve. The study shows that dissolution occurs preferentially at the near-surface side of the defect band, indicating that the silicon surface is the principal sink for interstitials in this system. The results provide a critical test of the ability of physical models to simulate defect evolution and transient enhanced diffusion.