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.

Enhanced Boron Diffusion in Amorphous Silicon

2004 ◽  
Vol 810 ◽  
Author(s):  
J.M. Jacques ◽  
N. Burbure ◽  
K.S. Jones ◽  
M.E. Law ◽  
L.S. Robertson ◽  
...  
Keyword(s):  
Amorphous Silicon ◽  
Room Temperature ◽  
Solid Phase ◽  
Amorphous Layer ◽  
Boron Diffusion ◽  
Cross Sectional ◽  
Enhanced Diffusion ◽  
Transmission Electron ◽  
Variable Angle Spectroscopic Ellipsometry ◽  
Secondary Ion

ABSTRACTIn prior works, we demonstrated the phenomenon of fluorine-enhanced boron diffusion within self-amorphized silicon. Present studies address the process dependencies of low temperature boron motion within ion implanted materials utilizing a germanium amorphization. Silicon wafers were preamorphized with either 60 keV or 80 keV Ge+ at a dose of 1×1015 atoms/cm2. Subsequent 500 eV, 1×1015 atoms/cm211B+ implants, as well as 6 keV F+ implants with doses ranging from 1×1014 atoms/cm2 to 5×1015 atoms/cm2 were also done. Furnace anneals were conducted at 550°C for 10 minutes under an inert N2 ambient. Secondary Ion Mass Spectroscopy (SIMS) was utilized to characterize the occurrence of boron diffusion within amorphous silicon at room temperature, as well as during the Solid Phase Epitaxial Regrowth (SPER) process. Amorphous layer depths were verified through Cross-Sectional Transmission Electron Microscopy (XTEM) and Variable Angle Spectroscopic Ellipsometry (VASE). Boron motion within as-implanted samples is observed at fluorine concentrations greater than 1×1020 atoms/cm3. The magnitude of the boron motion scales with increasing fluorine dose and concentration. During the initial stages of SPER, boron was observed to diffuse irrespective of the co-implanted fluorine dose. Fluorine enhanced diffusion at room temperature does not appear to follow the same process as the enhanced diffusion observed during the regrowth process.

Formation of Shallow P+ Junctions Using Two-Step Anneals

1984 ◽  
Vol 35 ◽  
Author(s):  
C.I. Drowley ◽  
J. Adkisson ◽  
D. Peters ◽  
S.-Y. Chiang
Keyword(s):  
Amorphous Silicon ◽  
Silicon Layer ◽  
Amorphous Layer ◽  
Single Step ◽  
Step Process ◽  
Enhanced Diffusion ◽  
Isothermal Anneal

ABSTRACTShallow (0.15-0.2 μm deep) p+ junctions have been formed using boron implanted into silicon which was pre-amorphized using a silicon implant. The implants were annealed using a two-step process; initially the wafers were furnace annealed at 600 °C for 100 min., followed by a rapid isothermal anneal (RIA) at 950-1100 °C for 10 sec. For comparison, some wafers were only given a single-step rapid isothermal anneal at 950-1100 °C for 10 sec. The shallowest junctions were formed when the amorphous silicon layer was deeper than the boron implant, because of the suppression of channelling. When the amorphous/crystalline interface was shallower than the tail of the boron implant, some channeling occurred. This channeling tail exhibited an enhanced diffusion during the single-step RIA which was reduced significantly by the two-step anneal. When the amorphous layer was deeper than the boron implant, the single-step and two-step anneals gave identical results.

Junction Depth Reduction of ion Implanted Boron in Silicon Through Fluorine ion Implantation

2000 ◽  
Vol 610 ◽  
Author(s):  
L. S. Robertson ◽  
P. N. Warnes ◽  
K. S. Jones ◽  
S. K. Earles ◽  
M. E. Law ◽  
...  
Keyword(s):  
Ion Implantation ◽  
Secondary Ion Mass Spectrometry ◽  
Chemical Species ◽  
Amorphous Layer ◽  
Experimental Conditions ◽  
Enhanced Diffusion ◽  
Transient Enhanced Diffusion ◽  
Transmission Electron ◽  
Species Effect ◽  
Boron Diffusivity

AbstractThe interaction between boron and excess silicon interstitials caused by ion implantation hinders the formation of ultra-shallow, low resistivity junctions. Previous studies have shown that fluorine reduces boron transient enhanced diffusion, however it is unclear whether this observed phenomenon is due to the fluorine interacting with the boron atoms or silicon self-interstitials. Amorphization of a n-type Czochralski wafer was achieved with a 70 keV Si+ implantation at a dose of 1×1015/cm2. The Si+ implant produced a 1500Å deep amorphous layer, which was then implanted with 1.12 keV 1×1015/cm2 B+. The samples were then implanted with a dose of 2×1015/cm2F+ at various energies ranging from 2 keV to 36 keV. Ellipsometry measurements showed no increase in the amorphous layer thickness from either the boron or fluorine implants. The experimental conditions allowed the chemical species effect to be studied independent of the implant damage caused by the fluorine implant. Post-implantation anneals were performed in a tube furnace at 750° C. Secondary ion mass spectrometry was used to monitor the dopant diffusion after annealing. Transmission electron microscopy (TEM) was used to study the end-of-range defect evolution. The addition of fluorine reduces the boron transient enhanced diffusion for all fluorine energies. It was observed that both the magnitude of the boron diffusivity and the concentration gradient of the boron profile vary as a function of fluorine energy.

Damage removal following low energy ion implantation

1988 ◽  
Vol 46 ◽  
pp. 906-907
Author(s):  
Edward R. Myers
Keyword(s):  
Ion Implantation ◽  
Large Scale ◽  
Solid Phase ◽  
Semiconductor Industry ◽  
Amorphous Layer ◽  
Light Ions ◽  
Large Scale Integration ◽  
Amorphous Surface ◽  
Scale Integration ◽  
Spatial Locations

Ion implantation has become the most common method of doping in the semiconductor industry. Precise concentration profiles with exact spatial locations are achievable. However, direct implantation of the desired dopant does not always meet the stringent size requirements of ultra large scale integration (ULSI). Implantation of light ions, such as boron, tend to channel down open crystallographic orientations in crystalline substrates resulting in enhanced ion penetration and an extended doping tail. Channeling can be prevented by creation of an amorphous surface layer prior to the dopant implant. The amorphous layer can be created by implanting heavy isoelectronic ions, such as Ge+, or by implanting molecular dopant ions like BF2. Solid phase epitaxial (SPE) regrowth restores the crystallinity of the amorphous layer and activates the dopant. However, the ion implantation process damages the crystalline material adjacent to the amorphous- crystalline (a/c) interface.

Defects Induced by Helium Implantation: Impact on Boron Diffusivity

2005 ◽  
Vol 864 ◽  
Author(s):  
F. Cayrel ◽  
D. Alquier ◽  
C. Dubois ◽  
R. Jerisian
Keyword(s):  
Defect Density ◽  
Defect Layer ◽  
High Dose ◽  
Boron Diffusion ◽  
Enhanced Diffusion ◽  
Helium Implantation ◽  
Buried Layer ◽  
Boron Diffusivity ◽  
Induced Defects ◽  
Metallic Impurities

AbstractHigh dose helium implantation followed by a suitable thermal treatment induces defects such as cavities and dislocations. Gettering efficiency of this technique for metallic impurities has been widely proved. Nevertheless, dopants, as well as point defects, interact with this defect layer. Due to the presence of vacancy type defects after helium implantation, boron diffusion can be largely influenced by such a buried layer. In this paper, we study the influence of helium induced defects on boron diffusion. The boron diffusion in presence of these defects has been analyzed as a function of different parameters such as distance between boron profile and defect layer and defect density. Our results demonstrate that the major impact known as boron enhanced diffusion can be partially or completely suppressed depending on parameters of experiments. Moreover, these results clarify the interaction of boron with extended He-induced defects.

Transient Enhanced Diffusion of Dopants in Preamorphised Si Layers

1996 ◽  
Vol 438 ◽  
Author(s):  
A. Claverie ◽  
C. Bonafos ◽  
M. Omri ◽  
B. De Mauduit ◽  
G. Ben Assayag ◽  
...  
Keyword(s):  
Ostwald Ripening ◽  
Dislocation Loops ◽  
Boron Diffusion ◽  
Enhanced Diffusion ◽  
Transient Enhanced Diffusion ◽  
Interstitial Atoms ◽  
Extrinsic Dislocation ◽  
The Mean ◽  
Boron Diffusivity ◽  
Shed Light

AbstractTransient Enhanced Diffusion (TED) of dopants in Si is the consequence of the evolution, upon annealing, of a large supersaturation of Si self-interstitial atoms left after ion bombardment. In the case of amorphizing implants, this supersaturation is located just beneath the c/a interface and evolves through the nucleation and growth of End-Of-Range (EOR) defects.For this reason, we discuss here the relation between TED and EOR defects. Modelling of the behavior of these defects upon annealing allows one to understand why and how they affect dopant diffusion. This is possible through the development of the Ostwald ripening theory applied to extrinsic dislocation loops. This theory is shown to be readily able to quantitatively describe the evolution of the defect population (density, size) upon annealing and gives access to the variations of the mean supersaturation of Si self-interstitial atoms between the loops and responsible for TED. This initial supersaturation is, before annealing, at least 5 decades larger than the equilibrium value and exponentially decays with time upon annealing with activation energies that are the same than the ones observed for TED. It is shown that this time decay is precisely at the origin of the transient enhancement of boron diffusivity through the interstitial component of boron diffusion. Side experiments shed light on the effect of the proximity of a free surface on the thermal behavior of EOR defects and allow us to quantitatively describe the space and time evolutions of boron diffusivity upon annealing of preamorphised Si layers.

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.

Post-Oxidation Enhanced Diffusion of Low-Energy Implanted Boron in Ultra-Shallow P+/N Junctions Formation

2000 ◽  
Vol 610 ◽  
Author(s):  
D. Lenoble ◽  
A. Halimaoui ◽  
A. Grouillet
Keyword(s):  
Experimental Data ◽  
Simple Model ◽  
Reflection Coefficient ◽  
Mirror Effect ◽  
Low Energy ◽  
Boron Diffusion ◽  
Enhanced Diffusion ◽  
Boron Diffusivity ◽  
First Time

AbstractIn this paper, we report for the first time the effect of sacrificial oxide (sacox) on the boron diffusion in ultra-shallow P+/N junctions. It is shown that the boron diffusivity is enhanced when low energy implantations are performed through sacrificial oxide. The various experimental data lead to conclude that the Post-Oxidation Enhanced Diffusion (POED) is due to a « mirror effect » seen by the Si interstitials incoming into the sacox layer. POED occurs even for sacox as thin as 1.5 nm. From a simple model, the reflection coefficient is estimated to be about 100 % for a 2.5 nm-thick sacox.

Quantitative Measurement of Reduction of Boron Diffusion by Substitutional Carbon Incorporation

1998 ◽  
Vol 527 ◽  
Author(s):  
M. S. Carroll ◽  
L. D. Lanzerotti ◽  
J. C. Sturm
Keyword(s):  
Quantitative Measurement ◽  
Device Modeling ◽  
Electrical Characteristics ◽  
Boron Diffusion ◽  
Carbon Incorporation ◽  
Combined Process ◽  
Enhanced Diffusion ◽  
Interstitial Concentration ◽  
Transient Enhanced Diffusion ◽  
Boron Diffusivity

ABSTRACTRecently, the suppression of boron diffusion due to both thermal and transient enhanced diffusion (TED) has been demonstrated through the incorporation of 0.5% substitutional carbon in the base of Si/SiGe/Si heterojunction transistor's (HBT)[1,2]. Because the devices are sensitive to diffusion on a scale less than that we can detect with SIMS, in this paper combined process and device modeling (TMA TSUPREM4 and MEDICI) are used to relate observed electrical characteristics (collector saturation currents and Early voltages) of the HBT's to boron diffusion, with a sensitivity of 20-30Å. Boron diffusivity in the SiGeC base is ~8 times slower than that of the boron diffusivity in the SiGe base without implant damage (no TED). In the case of ion implant damage in an overlying layer to cause TED the excess interstitial concentration due to ion implant damage is reduced by approximately 99% through incorporation of 0.5% substitutional carbon in the HBT SiGe bases. This demonstrates that carbon incorporation acts as an effective sink for interstitials.

Modeling and Experiments of Boron Diffusion During Sub-Millisecond Non-Melt Laser Annealing in Silicon

2006 ◽  
Vol 912 ◽  
Author(s):  
Taiji Noda ◽  
Susan Felch ◽  
Vijay Parihar ◽  
Christa Vrancken ◽  
Tom Janssens ◽  
...  
Keyword(s):  
Laser Annealing ◽  
Secondary Ion Mass Spectrometry ◽  
Kinetic Monte Carlo ◽  
Amorphous Layer ◽  
Dislocation Loops ◽  
Boron Diffusion ◽  
Transmission Electron ◽  
Defect Evolution ◽  
Evolution Behavior ◽  
Boron Diffusivity

AbstractBoron diffusion and defect evolution during sub-millisecond (ms) laser annealing with partial SPER are investigated using secondary ion mass spectrometry and transmission electron microscopy. Boron diffusivity enhancement in amorphous-Si is observed during partial SPER at 550 °C. It is shown that boron diffusion during the laser annealing process is a 2-step diffusion (SPER + Laser). The depth of the amorphous layer affects the dopant activation behavior. During sub-ms laser annealing, end-of-range defects are formed and show an evolution behavior. {311} defects cannot completely transfer to dislocation loops after 1300 °C laser annealing. It is considered that the thermal budget of sub-ms laser is too small for full defect evolution. Atomistic diffusion modeling using a kinetic Monte Carlo method can explain the defect behavior during laser annealing.

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