An explanation of transient-enhanced diffusion and electrical activation of boron in crystalline silicon during postimplantation annealing

Author(s):  
H.U. Jäger
1997 ◽  
Vol 469 ◽  
Author(s):  
N. E. B. Cowern ◽  
E. J. H. Collart ◽  
J. Politiek ◽  
P. H. L. Bancken ◽  
J. G. M. Van Berkum ◽  
...  

ABSTRACTLow energy implantation is currently the most promising option for shallow junction formation in the next generations of silicon CMOS technology. Of the dopants that have to be implanted, boron is the most problematic because of its low stopping power (large penetration depth) and its tendency to undergo transient enhanced diffusion and clustering during thermal activation. This paper reports recent advances in our understanding of low energy B implants in crystalline silicon. In general, satisfactory source-drain junction depths and sheet resistances are achievable down to 0.18 micron CMOS technology without the need for implantation of molecular species such as BF2. With the help of defect engineering it may be possible to reach smaller device dimensions. However, there are some major surprises in the physical mechanisms involved in implant profile formation, transient enhanced diffusion and electrical activation of these implants, which may influence further progress with this technology. Some initial attempts to understand and model these effects will be described.


1999 ◽  
Vol 568 ◽  
Author(s):  
E. Napolitani ◽  
A. Carnera ◽  
V. Privitera ◽  
A. La Magna ◽  
E. Schroer ◽  
...  

ABSTRACTWe investigated the atomic transport properties and electrical activation of boron in crystalline epitaxial silicon after ultra-low energy ion implantation (0.25–1 keV) and rapid thermal annealing (750–1100 °C). A wide range of implant doses was investigated (3×1012-1×105/cm2). A fast Transient Enhanced Diffusion (TED) pulse is observed involving the tail of the implanted Boron, the profile displacement being dependent on the implant dose. The excess of interstitials able to promote enhanced diffusion of implanted boron occurs, provided the implant dose is high enough to generate a significant total number of point defects. The Boron diffusion following the fast initial TED pulse can be described by the equilibrium diffusion equations.The electrical activation of ultra-shallow implants is hard to achieve, due to the high concentration of dopant and point defects confined in a very shallow layer that significantly contributes to the formation of clusters and complex defects. Provided a correct combination of annealing temperatures and times for these ultra-shallow implants is chosen, however, a sheet resistance 500 Δ/square with a junction depth below 0.1μm can be obtained, which has a noteworthy technological relevance for the future generations of semiconductor devices.


2000 ◽  
Vol 610 ◽  
Author(s):  
E. Napolitani ◽  
A. Carnera ◽  
V. Privitera ◽  
E. Schroer ◽  
G. Mannino ◽  
...  

AbstractThe transient enhanced diffusion (TED) during activation annealing of ultra low energy implanted boron (0.5 keV & 1 keV, 1×1013/cm2 & 1×1014/cm2) in silicon is investigated in detail. Annealing in the temperature range from 450°C to 750°C is either performed directly after implantation or after the removal of a surface layer before annealing. The kinetics revealed two regimes of enhanced diffusion ruled by different decay constants and different activation energies. The dependence of these two processes on implantation energy and annealing temperature is described and explained from the microscopical point of view. The annealings performed after surface layer removal, revealed that the defects responsible for the faster diffusion are located deeper than the defects responsible for the slower process.


2005 ◽  
Vol 864 ◽  
Author(s):  
Scott A. Harrison ◽  
Thomas F. Edgar ◽  
Gyeong S. Hwang

AbstractIn recent years, experimental studies [1-3] have suggested that Si interstitials may play a role in facilitating As transient enhanced diffusion during pn junction formation in silicon. These studies contradict conventional models that assume vacancy-mediated As diffusion. Using density functional theory calculations within the generalized gradient approximation, we have examined the structure, stability, and diffusion of the neutral As-Sii pair. We find the lowest energy structure is comprised of an As and Sii atom pair that is aligned in the [110] direction while sharing a lattice site. We have calculated the binding energy as well as diffusion pathways and barriers for the neutral As-Sii pair. Our results suggest that the neutral As-Sii pair has a binding energy relative to neutral Sii and neutral As of 0.63 eV. We also find an overall diffusion activation energy of 3.3 eV, which is similar to experimental observations for As diffusion and preVious calculations for As-vacancy complex diffusion. These results clearly support that interstitials can contribute significantly to As transient enhanced diffusion, especially in regions where interstitials exist in excess. In addition, interstitial-mediated arsenic diffusion suggests that interstitials may also play a role in arsenic agglomeration.


1997 ◽  
Vol 469 ◽  
Author(s):  
V. C. Venezia ◽  
T. E. Haynes ◽  
A. Agarwal ◽  
H. -J. Gossmann ◽  
D. J. Eaglesham

ABSTRACTThe diffusion of Sb and B markers has been studied in vacancy supersaturations produced by MeV Si implantation in float zone (FZ) silicon and bonded etch-back silicon-on-insulator (BESOI) substrates. MeV Si implantation produces a vacancy supersaturated near-surface region and an interstitial-rich region at the projected ion range. Transient enhanced diffusion (TED) of Sb in the near surface layer was observed as a result of a 2 MeV Si+, 1×1016/cm2, implant. A 4× larger TED of Sb was observed in BESOI than in FZ silicon, demonstrating that the vacancy supersaturation persists longer in BESOI than in FZ. B markers in samples with MeV Si implant showed a factor of 10× smaller diffusion relative to markers without the MeV Si+ implant. This data demonstrates that a 2 MeV Si+ implant injects vacancies into the near surface region.


1998 ◽  
Vol 532 ◽  
Author(s):  
M. Kase ◽  
Y Kikuchi ◽  
H. Niwa ◽  
T. Kimura

ABSTRACTThis paper describes ultra shallow junction formation using 0.5 keV B+/BF2+ implantation, which has the advantage of a reduced channeling tail and no transient enhanced diffusion. In the case of l × 1014 cm−2, 0.5 keV BF2 implantation a junction depth of 19 nm is achieved after RTA at 950°C.


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