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Title: The effect of excimer laser pretreatment on diffusion and activation of boron implanted in silicon

Abstract

We have investigated the effect of excimer laser annealing (ELA) on transient enhanced diffusion (TED) and activation of boron implanted in Si during subsequent rapid thermal annealing (RTA). It is observed that ELA with partial melting of the implanted region causes reduction of TED in the region that remains solid during ELA, where the diffusion length of boron is reduced by a factor of {approx}4 as compared to the as-implanted sample. This is attributed to several mechanisms such as liquid-state annealing of a fraction of the implantation induced defects, introduction of excess vacancies during ELA, and solid-state annealing of the defects beyond the maximum melting depth by the heat wave propagating into the Si wafer. The ELA pretreatment provides a substantially improved electrical activation of boron during subsequent RTA.

Authors:
; ; ; ; ; ; ; ;  [1];  [2];  [3];  [3]
  1. Department of Physics, Physical Electronics, University of Oslo, P.O. Box 1048 Blindern, N-0316 Oslo (Norway)
  2. (Sweden)
  3. (Italy)
Publication Date:
OSTI Identifier:
20706455
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 87; Journal Issue: 19; Other Information: DOI: 10.1063/1.2126144; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ANNEALING; BORON; CRYSTALS; DIFFUSION; DIFFUSION LENGTH; EXCIMER LASERS; ION IMPLANTATION; MELTING; SEMICONDUCTOR MATERIALS; SILICON; VACANCIES

Citation Formats

Monakhov, E.V., Svensson, B.G., Linnarsson, M.K., La Magna, A., Italia, M., Privitera, V., Fortunato, G., Cuscuna, M., Mariucci, L., Royal Institute of Technology, Lab of Materials and Semiconductor Physics, P.O. Box Electrum 229, SE-164 40 Kista, CNR-IMM Sezione Catania, Stradale Primosole 50, 95121 Catania, and IFN-CNR, Via Cineto Romano 42, 00156 Rome. The effect of excimer laser pretreatment on diffusion and activation of boron implanted in silicon. United States: N. p., 2005. Web. doi:10.1063/1.2126144.
Monakhov, E.V., Svensson, B.G., Linnarsson, M.K., La Magna, A., Italia, M., Privitera, V., Fortunato, G., Cuscuna, M., Mariucci, L., Royal Institute of Technology, Lab of Materials and Semiconductor Physics, P.O. Box Electrum 229, SE-164 40 Kista, CNR-IMM Sezione Catania, Stradale Primosole 50, 95121 Catania, & IFN-CNR, Via Cineto Romano 42, 00156 Rome. The effect of excimer laser pretreatment on diffusion and activation of boron implanted in silicon. United States. doi:10.1063/1.2126144.
Monakhov, E.V., Svensson, B.G., Linnarsson, M.K., La Magna, A., Italia, M., Privitera, V., Fortunato, G., Cuscuna, M., Mariucci, L., Royal Institute of Technology, Lab of Materials and Semiconductor Physics, P.O. Box Electrum 229, SE-164 40 Kista, CNR-IMM Sezione Catania, Stradale Primosole 50, 95121 Catania, and IFN-CNR, Via Cineto Romano 42, 00156 Rome. Mon . "The effect of excimer laser pretreatment on diffusion and activation of boron implanted in silicon". United States. doi:10.1063/1.2126144.
@article{osti_20706455,
title = {The effect of excimer laser pretreatment on diffusion and activation of boron implanted in silicon},
author = {Monakhov, E.V. and Svensson, B.G. and Linnarsson, M.K. and La Magna, A. and Italia, M. and Privitera, V. and Fortunato, G. and Cuscuna, M. and Mariucci, L. and Royal Institute of Technology, Lab of Materials and Semiconductor Physics, P.O. Box Electrum 229, SE-164 40 Kista and CNR-IMM Sezione Catania, Stradale Primosole 50, 95121 Catania and IFN-CNR, Via Cineto Romano 42, 00156 Rome},
abstractNote = {We have investigated the effect of excimer laser annealing (ELA) on transient enhanced diffusion (TED) and activation of boron implanted in Si during subsequent rapid thermal annealing (RTA). It is observed that ELA with partial melting of the implanted region causes reduction of TED in the region that remains solid during ELA, where the diffusion length of boron is reduced by a factor of {approx}4 as compared to the as-implanted sample. This is attributed to several mechanisms such as liquid-state annealing of a fraction of the implantation induced defects, introduction of excess vacancies during ELA, and solid-state annealing of the defects beyond the maximum melting depth by the heat wave propagating into the Si wafer. The ELA pretreatment provides a substantially improved electrical activation of boron during subsequent RTA.},
doi = {10.1063/1.2126144},
journal = {Applied Physics Letters},
number = 19,
volume = 87,
place = {United States},
year = {Mon Nov 07 00:00:00 EST 2005},
month = {Mon Nov 07 00:00:00 EST 2005}
}
  • The activation process induced by excimer laser annealing (ELA) has been investigated in 10 keV B-implanted samples. It is found that for energy densities inducing melt depths of the order or larger of the implanted region the junction depth is controlled by the melt depth, with activation approaching 100% and box-shaped carrier density distributions with abrupt junction profile. For energy densities inducing a melting shallower than the implanted region, two different activation mechanisms have been identified: the first occurring in the molten region and leading to complete B activation; the second occurring in the region immediately below the molten zonemore » and leading to thermal activation of B, induced by the heat wave propagating into the Si wafer. This last process is characterized by an activation energy of 5 eV and is not accompanied by B diffusion. As a consequence, a deep tail of active B is produced, preventing the possibility to form abrupt and ultrashallow junctions. These results suggest that for the formation of ultrashallow junctions it is essential to combine ELA with ultralow energy ion implantation.« less
  • The advantage of pulsed excimer lasers for semiconductor processing are reviewed. Studies of XeCl excimer laser annealing with pulses of 25 and 70 nsec duration and energy densities in the range from 0.5-3.0 J/cm/sup 2/ are discussed. The annealing characteristics are described in terms of the results of melt depth, dopant profile spreading, and electrical properties (sheet resistivity, diode characteristics) measurements. Solar cells with efficiencies as high as 16.7% Am1 have been fabricated using glow discharge implantation and XeCl laser annealing.
  • Diffusion of co-implanted carbon (C) and boron (B) in silicon (Si) and its effect on excess Si self-interstitials (I's) after annealing at 800 and 1000 deg. C were investigated by means of secondary ion mass spectrometry. The experimental results showed that C diffusion was not significant at 800 and 1000 deg. C but later became visible for longer annealing times at 1000 deg. C. B diffusion was reduced by the presence of C when no significant C diffusion was observed, but it was enhanced when C diffusion was observed. These results indicate that all implanted C atoms form immobile CImore » clusters with excess I in the amount of implanted C and that these CI clusters are stable and trap I to reduce B diffusion. On the contrary, CI clusters are dissolved to emit I for longer annealing times at 1000 deg. C and both B and C diffusion are enhanced. Diffusion simulation based on these models fits the experimental profiles of B and C.« less
  • Rapid processing and reduced end-of-range diffusion result from susceptor-assisted microwave (MW) annealing, making this technique an efficient processing alternative for electrically activating dopants within ion-implanted semiconductors. Sheet resistance and Hall measurements provide evidence of electrical activation. Susceptor-assisted MW annealing, of ion-implanted Si, enables more effective dopant activation and at lower temperatures than required for rapid thermal annealing (RTA). Raman spectroscopy and ion channeling analyses are used to monitor the extent of ion implantation damage and recrystallization. The presence and behavior of extended defects are monitored by cross-section transmission electron microscopy. Phosphorus implanted Si samples experience effective electrical activation upon MWmore » annealing. On the other hand, when boron implanted Si is MW annealed, the growth of extended defects results in reduced crystalline quality that hinders the electrical activation process. Further comparison of dopant diffusion resulting from MW annealing and rapid thermal annealing is performed using secondary ion mass spectroscopy. MW annealed ion implanted samples show less end-of-range diffusion when compared to RTA samples. In particular, MW annealed P{sup +} implanted samples achieve no visible diffusion and equivalent electrical activation at a lower temperature and with a shorter time-duration of annealing compared to RTA. In this study, the peak temperature attained during annealing does not depend on the dopant species or dose, for susceptor-assisted MW annealing of ion-implanted Si.« less
  • A pulsed ultraviolet excimer laser (XeCl, 308 nm wavelength, 40 nsec FWHM pulse duration) has been successfully used for laser annealing of both boron- and arsenic-implanted silicon. TEM, SIMS, and sheet electrical measurements are used to characterize specimens. C-V and I-V measurements demonstrate that near-ideal p-n junctions are formed (diode perfection factor A = 1.2). Electrical activation of implanted ions by single laser pulses is essentially complete for energy densities E/sub l/ greater than or equal to 1.4 J/cm/sup 2/, far below the threshold for substantial surface damage --4.5 J/cm/sup 2/. Melting model calculations are in good agreement with observedmore » thresholds for dopant redistribution and for epitaxial regrowth. Changes in annealing behavior resulting from multiple (1,2,5) laser pulses are also reported. Finally, the authors demonstrate the use of scanned overlapping excimer laser pulses for fabrication of large area (2 cm/sup 2/) solar cells with good performance characteristics. In contrast to pulsed ruby laser annealing, high open circuit voltages can be obtained without the use of substrate heating.« less