Dopant diffusion in amorphous silicon

2004 ◽  
Vol 810 ◽  
Author(s):  
R. Duffy ◽  
V.C. Venezia ◽  
A. Heringa ◽  
M.J.P. Hopstaken ◽  
G.C.J. Maas ◽  
...  
Keyword(s):  
Low Temperature ◽  
Ion Implantation ◽  
Amorphous Silicon ◽  
Amorphous Region ◽  
Boron Diffusion ◽  
Diffusion Characteristic ◽  
High Concentration ◽  
Isochronal Anneal ◽  
High Concentrations ◽  
Boron Diffusivity

ABSTRACTIn this work we investigate the diffusion of high-concentration ultrashallow boron, fluorine, phosphorus, and arsenic profiles in amorphous silicon. We demonstrate that boron diffuses at high concentrations in amorphous silicon during low-temperature thermal annealing. Isothermal and isochronal anneal sequences indicate that there is an initial transient enhancement of diffusion. We have observed this transient diffusion characteristic both in amorphous silicon preamorphized by germanium ion implantation and also in amorphous silicon preamorphized by silicon ion implantation. We also show that the boron diffusivity in the amorphous region is similar with and without fluorine, and that the lack of diffusion for low-concentration boron profiles indicates that boron diffusion in amorphous silicon is driven by high concentrations. Ultrashallow high-concentration fluorine profiles diffuse quite rapidly in amorphous silicon, and like boron, undergo a definite transient enhancement. In contrast, ultrashallow high- concentration phosphorus and arsenic profiles did not significantly diffuse in our experiments.

Ultra-Shallow Junctions for the 65nm Node Based on Defect and Stress Engineering

2005 ◽  
Vol 864 ◽  
Author(s):  
Victor Moroz ◽  
Majeed Foad ◽  
Houda Graoui ◽  
Faran Nouri ◽  
Dipu Pramanik ◽  
...  
Keyword(s):  
Stress Gradient ◽  
Process Window ◽  
Boron Diffusion ◽  
High Concentration ◽  
Stress Effects ◽  
Ion Channeling ◽  
Rapid Temperature ◽  
Ultra Shallow Junctions ◽  
High Concentrations ◽  
Non Equilibrium

AbstractThe co-implantation of germanium, carbon, and boron with the optimum implant energies and doses makes it possible to create p+/n junctions with the sheet resistance of less than 600 Ohm/square and the slope of less than 3 nm/decade. The narrow process window is based on careful engineering of the amorphization, point defects, and stresses and includes standard 1050°C spike annealing. The germanium pre-amorphization suppresses the ion channeling for the subsequent boron implant. The tensile stress induced by the substitutional carbon atoms and the compressive stress induced by the substitutional germanium atoms slow down boron diffusion and help to make the junctions shallower. The stress gradient in the transition region from the strained carbon and germanium doped layers to the relaxed silicon underneath creates an uphill boron flux that makes the junction slope steeper.The optimum amount of carbon is placed in between the implanted boron and the implant damage, which is located below the amorphized layer. During the annealing, the carbon atoms capture silicon interstitials that are coming from the implant damage and form carbon-interstitial clusters. The analysis demonstrates that it is possible to capture over 95% of the interstitials this way before they have a chance to reach boron-doped layer. This completely suppresses the transient-enhanced boron diffusion (TED) and drastically reduces the amount of boron that is deactivated in boron-interstitial clusters (BICs). In fact, the point defect engineering with an optimized carbon profile allows to remove all non-equilibrium silicon interstitials that are generated by the following three sources: the implant damage below the amorphized layer, the rapid temperature ramp down, and the interstitials generated by boron at high concentrations (due to the effect known as boron-enhanced diffusion (BED)).The latter effect leads to significant increase of the apparent boron activation level beyond the well-characterized solid-state solubility level. We explain this effect as a reduction in formation of BICs due to the lack of interstitial supersaturation. In carbon-free silicon, high concentration boron is always accompanied by the non-equilibrium interstitials, coming from either the implant damage or the BICs even if boron is introduced into silicon by pre-deposition instead of the implantation. Extensive experiments and theoretical analysis based on simulation of the interaction of Ge, C, I, and B atoms, as well as the stress effects, point to the optimized process flow that improves the shape and parameters of the p+/n USJs.

Effect of Fluorine on the Diffusion of Boron in Amorphous Silicon

2002 ◽  
Vol 717 ◽  
Author(s):  
J. M. Jacques ◽  
L. S. Robertson ◽  
K. S. Jones ◽  
Joe Bennett
Keyword(s):  
Amorphous Silicon ◽  
Boron Concentration ◽  
Solid Phase ◽  
Amorphous Layer ◽  
Boron Diffusion ◽  
Enhanced Diffusion ◽  
Diffusion Characteristics ◽  
Junction Formation ◽  
Amorphous Surface ◽  
Boron Diffusivity

AbstractFluorine and boron co-implantation within amorphous silicon has been studied in order to meet the process challenges regarding p+ ultra-shallow junction formation. Previous experiments have shown that fluorine can reduce boron TED (Transient Enhanced Diffusion), enhance boron solubility and reduce sheet resistance. In this study, boron diffusion characteristics prior to solid phase epitaxial regrowth (SPER) of the amorphous layer in the presence of fluorine are addressed. Samples were pre-amorphized with Si+ at a dose of 1x1015 ions/cm2 and energy of 70 keV, leading to a deep continuous amorphous surface of approximately 1500 Å. After pre-amorphization, B+ was implanted at a dose of 1x1015 ions/cm2 and energy of 500 eV, while F+ was implanted at a dose of 2x1015 ions/cm2 and energies ranging from 3 keV to 9 keV. Subsequent furnace anneals for the F+ implant energy of 6 keV were conducted at 550°C, for times ranging from 5 minutes to 260 minutes. During annealing, the boron in samples co-implanted with fluorine exhibited significant enhanced diffusion within amorphous silicon. After recrystallization, the boron diffusivity was dramatically reduced. Boron in samples with no fluorine did not diffuse during SPER. Prior to annealing, SIMS profiles demonstrated that boron concentration tails broadened with increasing fluorine implant energy. Enhanced dopant motion in as-implanted samples is presumably attributed to implant knock-on or recoil effects.

Diffusion of Fluorine at High Concentration in Silicon: Experiments and Models

2004 ◽  
Vol 810 ◽  
Author(s):  
Robert R. Robison ◽  
Antonio F. Saavedra ◽  
Mark E. Law
Keyword(s):  
Time Dependence ◽  
Amorphous Silicon ◽  
Depth Profiling ◽  
Amorphous Region ◽  
High Concentration ◽  
Conventional Furnace

ABSTRACTWe have developed a model for high concentration fluorine diffusion and fluorine diffusion in amorphous silicon. In this context, we define high concentration fluorine to mean fluorine doses above the threshold of amorphization for implantation into silicon, which is approximately 1×1015/cm2 dose. We pre-amorphized with silicon to create a continuous amorphous region, and samples were subsequently implanted with the fluorine conditions of 16keV at 2×1015cm−2 dose, 30keV at 2×1014 cm−2 dose, or 16keV at 8×1015cm−2 dose. Samples were annealed by either conventional furnace or RTA with an N2 ambient for various times at temperatures of 550-750 °C. SIMS was used for depth profiling, and TEM images were also taken of the samples to check for defects and amorphous depth. We then created the model for the data by extending the fluorine model presented in our previous work, and it models the profile motion and the time dependence well. The model is also still capable of describing our previous work and fits it very well.

Low-Resistivity Amorphous Silicon for Contacts Using Low-Temperature Rapid Thermal Annealing

1992 ◽  
Vol 258 ◽  
Author(s):  
Lynnita Knoch ◽  
Gordon Tam ◽  
N. David Theodore ◽  
Ron Pennell
Keyword(s):  
Low Temperature ◽  
Ion Implantation ◽  
Grain Boundaries ◽  
Amorphous Silicon ◽  
Sheet Resistance ◽  
Rapid Thermal Annealing ◽  
Thermal Budget ◽  
Temperature Rapid Thermal Annealing ◽  
Low Thermal Budget ◽  
Polycrystalline Deposition

ABSTRACTFabrication of SiGe heterojunction bipolar transistors (HBTs) requires a low thermal budget to avoid relaxation of the strained SiGe base layer. Ion implantation is one of the most widely used techniques to achieve contacts. However, due to thermal budget constraints, low temperature rapid thermal annealing (RTA) cycles to activate these implants are insufficient to anneal out all of the implant damage. Polysilicon contacts provide an alternative to ion implantation, but are typically annealed at high temperatures (>950°C) to achieve low sheet resistivity. In this study, amorphous silicon and polycrystalline silicon films were implanted with boron, arsenic, or phosphorus and RTA'd at temperatures from 800°C to 950°C and compared to single crystal silicon with identical implants and RTA cycles. The films were characterized using four-point probe, Hall measurements, TEM (transmission electron microscopy), and SIMS (secondary-ion mass-spectrometry). TEM analysis shows that the amorphous deposition produces larger grains upon RTA due to more rapid grain growth than the polycrystalline deposition. The sheet resistance for the amorphous deposited films is much lower than that of the polycrystalline deposition for all implant conditions. Activations of the implants indicate that the arsenic and phosphorus segregate to the grain boundaries, while the boron does not. The segregation is more significant for the polycrystalline films than for the amorphous films and can be explained by the grain boundary area. For contacts to the SiGe HBT, which requires a low thermal budget, an amorphous deposited silicon film is advantageous over a polycrystalline film at low annealing temperatures because it has lower sheet resistance, less segregation to the grain boundaries, and produces larger grains.

Magnetic Cooperative Phenomenon with Unpaired sp-Electrons System by MBE Low-Temperature Growth

2019 ◽  
Vol 290 ◽  
pp. 336-341
Author(s):  
Mohd Ambri Mohamed ◽  
Burhanuddin Yeop Majlis
Keyword(s):  
Low Temperature ◽  
Low Temperatures ◽  
Molecular Beam ◽  
Electronic Devices ◽  
High Concentration ◽  
Temperature Growth ◽  
Cooperative Phenomenon ◽  
High Concentrations ◽  
Cooperative Transition ◽  
Synthesis Of Materials

We present a new possibility of crystal growth as synthesis of materials containing high concentrations of unpaired sp electrons by growth of Be doped Gallium Arsenides at low temperatures of 200-3000C using Molecular Beam Epitaxy (MBE) and investigate a possibility of applications of magnetotransport properties based on these unpaired sp-electrons to spintronics devices.The present study using high concentration of unpaired sp-electrons by the growth of Beryllium-doped GaAs layers at low temperatures resulted in a cooperative transition of localized spins at low temperature and also affected the mechasnism of tranport properties of the sample from hopping conduction to valence band conduction.This attempts will give rise to a possibility of adding new functions to existing electronic devices.

Diffusion of Boron in Germanium and Si1-xGex (x>50%) alloys Suresh Uppal

2003 ◽  
Vol 765 ◽  
Author(s):  
A.F.W. Willoughby ◽  
J.M. Bonar ◽  
N.E.B. Cowern ◽  
R.J.H. Morris ◽  
M. Bollani
Keyword(s):  
Ion Implantation ◽  
Entire Range ◽  
Boron Diffusion ◽  
Furnace Annealing ◽  
Germanium Content ◽  
Pairing Model ◽  
Boron Diffusivity

AbstractBoron diffusion in germanium and relaxed Si1-xGex alloys with Ge content x>50% is reported. Relaxed SiGe layers were grown by LEPECVD and boron was introduced using ion implantation. Samples were given equal thermal budgets using furnace annealing. Diffusivity values of boron have been extracted. The results confirm that diffusion of boron in germanium is indeed slower than that reported in literature. The diffusivity of boron was found to increase gradually for x>50% at 900°C but the increase is not substantial. We found that pairing model is not sufficient to explain boron diffusivity behavior in SiGe alloys over the entire range of germanium content. The results suggest that an interstitial mediation of boron diffusion in germanium should be considered.

The Toxicity of Castor Beans and its Treatment with Doxycycline in Local Rabbits

2018 ◽  
Vol 9 (2) ◽  
Author(s):  
Nael Mohammed Sarheed ◽  
Osamah Faisal Kokas ◽  
Doaa Abd Alabas Muhammed Ridh
Keyword(s):  
Castor Bean ◽  
The Body ◽  
Control Group ◽  
High Concentration ◽  
Biochemical Tests ◽  
Doxycycline Treatment ◽  
High Concentrations ◽  
Physiological Tests ◽  
Animal House ◽  
Physiological And Biochemical

The plant of castor is widely spread in the Iraqi land, and characterized with containing ricin toxin, which has a very serious effects, and because the seeds of this plant scattered in the agricultural soil and rivers water, which increases the exposure of humans and animals to these beans. Objective: This experiment was designed to study the effect of high concentration of castor bean powder in some physiological and biochemical parameters and changes in some tissues of the body, as well as trying to use doxycycline to reduce the effects of ingestion of these seeds. Materials and Methods: In the experiment, 24 local rabbits were raised and fed in the Animal House of the Faculty of Medicine / Al-Muthanna University, then divided into four groups and treated for three weeks (21 days), Control group: treated with normal saline solution (0.9) orally throughout the experiment, G1: was treated orally with a concentration of 25 mg / kg of castor bean powder daily during the experiment, G2 : orally treated 25 mg / kg of castor bean and 25 mg / kg of doxycycline, G3: orally treated 25 mg / kg of castor powder with 50 mg / kg of doxycycline daily throughout the trial period. Results: The results of the experiment showed significant changes (P less than 0.05) in all physiological and biochemical blood tests when compared with control group. There was a significant decrease in PCV, Hb, RBC, T.protein and body weights, while demonstrated a significant increase in WBC, Urea, Creatinine, ALT, AST and ALP, with distortions in liver and kidney of animals that treated with Castor beans. In contrast, the treatment with doxycycline and caster beans showed significant improvement reflected by a normal proportion in physiological tests and biochemical tests with improvement in the tissues when compared to control group. Conclusions: It can be concluded from this study that castor bean has high toxic and pathogenic effects that may be dangerous to the life of the organism. Therefore, it is advisable to be cautious of these pills and avoid exposure to them, also recommended to take high concentrations of doxycycline treatment when infected with castor bean poisoning.

The Effects of Shock Vancomycin Concentrations on the Formation of Heteroresistance in Staphylococcus aureus

2020 ◽  
Vol 65 (9-10) ◽  
pp. 3-7
Author(s):  
V. V. Gostev ◽  
Yu. V. Sopova ◽  
O. S. Kalinogorskaya ◽  
M. E. Velizhanina ◽  
I. V. Lazareva ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
In Vitro Selection ◽  
Methicillin Resistant Staphylococcus Aureus ◽  
High Concentration ◽  
Short Term ◽  
High Concentrations ◽  
Selection Of ◽  
Selection Of Resistance ◽  
Test Cultures

Glycopeptides are the basis of the treatment of infections caused by MRSA (Methicillin-Resistant Staphylococcus aureus). Previously, it was demonstrated that antibiotic tolerant phenotypes are formed during selection of resistance under the influence of high concentrations of antibiotics. The present study uses a similar in vitro selection model with vancomycin. Clinical isolates of MRSA belonging to genetic lines ST8 and ST239, as well as the MSSA (ATCC29213) strain, were included in the experiment. Test isolates were incubated for five hours in a medium with a high concentration of vancomycin (50 μg/ml). Test cultures were grown on the medium without antibiotic for 18 hours after each exposure. A total of ten exposure cycles were performed. Vancomycin was characterized by bacteriostatic action; the proportion of surviving cells after exposure was 70–100%. After selection, there was a slight increase in the MIC to vancomycin (MIC 2 μg/ml), teicoplanin (MIC 1.5–3 μg/ml) and daptomycin (MIC 0.25–2 μg/ml). According to the results of PAP analysis, all strains showed an increase in the area under curve depending on the concentration of vancomycin after selection, while a heteroresistant phenotype (with PAP/AUC 0.9) was detected in three isolates. All isolates showed walK mutations (T188S, D235N, E261V, V380I, and G223D). Exposure to short-term shock concentrations of vancomycin promotes the formation of heteroresistance in both MRSA and MSSA. Formation of VISA phenotypes is possible during therapy with vancomycin.

Growth responses of periphyton and chironomids exposed to biologically treated bleached kraft pulp mill effluent

1997 ◽  
Vol 35 (2-3) ◽  
pp. 339-345 ◽  
Author(s):  
M. G. Dubé ◽  
J. M. Culp
Keyword(s):  
Kraft Pulp ◽  
Pulp Mill ◽  
Pulp Mill Effluent ◽  
Growth Responses ◽  
High Concentration ◽  
Wood Extractives ◽  
Kraft Pulp Mill ◽  
Bleached Kraft Pulp ◽  
Low Levels ◽  
High Concentrations

Experiments were conducted in artificial streams to determine the effects of increasing concentrations of biologically treated bleached kraft pulp mill effluent (BKPME) on periphyton and chironomid growth in the Thompson River, British Columbia. Periphyton growth, as determined by increases in chlorophyll a, was significantly stimulated at all effluent concentrations tested (0.25%, 0.5%, 1.0%, 5.0% and, 10.0%). Chironomid growth (individual weight) was also significantly stimulated at low effluent concentrations (≤1.0%). At higher concentrations (5.0% and 10.0%), chironomid growth was inhibited relative to the 1.0% treatment streams. Increases in growth were attributed to the effects of nutrient and organic enrichment from BKPME. The effluent contained high concentrations of phosphorus and appears to be an important source of carbon for benthic insects grazing on the biofilm. In high concentration effluent streams, chironomid growth decreased despite low levels of typical pulp mill contaminants. This suggests that other compounds in the effluent, such as wood extractives, may be inhibiting chironomid growth. These results support findings of field monitoring studies conducted in the Thompson River where changes in periphyton and chironomid abundance occurred downstream of the bleached kraft pulp mill.

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