Enhanced Boron Diffusion in Amorphous Silicon

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.

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Effect of Fluorine on the Diffusion of Boron in Amorphous Silicon

MRS Proceedings ◽

10.1557/proc-717-c4.6 ◽

2002 ◽

Vol 717 ◽

Cited By ~ 13

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.

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Boron Diffusion in Fluorine Preamorphized Silicon During Rapid Thermal Annealing

MRS Proceedings ◽

10.1557/proc-303-253 ◽

1993 ◽

Vol 303 ◽

Cited By ~ 1

Author(s):

H. Kinoshita ◽

T. H. Huang ◽

D. L. Kwong ◽

P. E. Bakeman

Keyword(s):

Thermal Annealing ◽

Rapid Thermal Annealing ◽

Annealed Sample ◽

Transmission Electron Micrograph ◽

Boron Diffusion ◽

Cross Sectional ◽

Dopant Activation ◽

Enhanced Diffusion ◽

Transmission Electron ◽

Secondary Ion

ABSTRACTThe effect of fluorine preamorphization on boron diffusion and activation during rapid thermal annealing (RTA) has been investigated. Compared with low energy B or BF2 implant into crystalline Si, F preamorphization suppressed the transient enhanced diffusion of B and increased dopant activation. Results show that the tail diffusion was absent, and thus the junction depth of the RTA annealed sample was established by the as-implanted B profile. Secondary ion mass spectroscopy and cross-sectional transmission electron micrograph results show F accumulation near the surface and at end-of-range defects. The interaction of F with defects is believed to reduce the B diffusion during RTA.

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Ohmic Contact Formation Mechanism in the Ge/Pd/N-GaAs System

MRS Proceedings ◽

10.1557/proc-148-163 ◽

1989 ◽

Vol 148 ◽

Cited By ~ 20

Author(s):

E.D. Marshall ◽

S.S. Lau ◽

C.J. Palmstrøm ◽

T. Sands ◽

C.L. Schwartz ◽

...

Keyword(s):

Electron Microscopy ◽

Mass Spectrometry ◽

Secondary Ion Mass Spectrometry ◽

Solid Phase ◽

Cross Sectional ◽

Ohmic Behavior ◽

Transmission Electron ◽

Solid Phase Regrowth ◽

Ohmic Contact Formation ◽

Secondary Ion

ABSTRACTAnnealed Ge/Pd/n-GaAs samples utilizing substrates with superlattice marker layers have been analyzed using high resolution backside secondary ion mass spectrometry and cross-sectional transmission electron microscopy. Interfacial compositional and microstructural changes have been correlated with changes in contact resistivity. The onset of good ohmic behavior is correlated with the decomposition of an intermediate epitaxial Pd4(GaAs,Ge2) phase and solid-phase regrowth of Ge-incorporated GaAs followed by growth of a thin Ge epitaxial layer.

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Temperature Dependence of Damage in Boron-Implanted Silicon

MRS Proceedings ◽

10.1557/proc-147-85 ◽

1989 ◽

Vol 147 ◽

Cited By ~ 6

Author(s):

G. Ottaviani ◽

F. Nava ◽

R. Tonini ◽

S. Frabboni ◽

G. F. Cerofolini ◽

...

Keyword(s):

Room Temperature ◽

Amorphous Layer ◽

Systematic Investigation ◽

Vacuum Furnace ◽

Cross Sectional ◽

Ion Channeling ◽

Projected Range ◽

Transmission Electron ◽

Boron Implantation ◽

Residual Damage

AbstractWe have performed a systematic investigation of boron implantation at 30 keV into <100> n-type silicon in the 77 –300 K temperature range and mostly at 9×1015 cm−2 fluence. The analyses have been performed with ion channeling and cross sectional transmission electron microscopy both in as-implanted samples and in samples annealed in vacuum furnace at 500 °C and 850 °C for 30 min. We confirm the impossibility of amorphization at room temperature and the presence of residual damage mainly located at the boron projected range. On the contrary, a continuous amorphous layer can be obtained for implants at 77 K and 193 K; the thickness of the implanted layer is increased by lowering the temperature, at the same time the amorphous-crystalline interface becomes sharper. Sheet resistance measurements performed after isochronal annealing shows an apparent reverse annealing of the dopant only in the sample implanted at 273 K. The striking differences between light and heavy ions observed at room temperature implantation disappears at 77 K and full recovery with no residual damage of the amorphous layer is observed.

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Growth of Epitaxial CoSi2/Si Multilayers

MRS Proceedings ◽

10.1557/proc-77-351 ◽

1986 ◽

Vol 77 ◽

Author(s):

B. D. Runt ◽

N. Lewis ◽

L. J. Schotalter ◽

E. L. Hall ◽

L. G. Turner

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Room Temperature ◽

Solid Phase ◽

Multilayer Structures ◽

Solid Phase Epitaxy ◽

Cross Sectional ◽

Temperature Growth ◽

Transmission Electron

ABSTRACTEpitaxial CoSi2/Si multilayers have been grown on Si(111) substrates with up to four bilayers of suicide and Si. To our knowledge, these are the first reported epitaxial metal-semiconductor multilayer structures. The growth of these heterostructures is complicated by pinhole formation in the suicide layers and by nonuniform growth of Si over the suicide films, but these problems can be controlled through nse of proper growth techniques. CoSi2 pinhole formation has been significantly reduced by utilizing a novel solid phase epitaxy technique in which room-temperature-deposited Co/Si bilayers are annealed to 600–650δC to form the suicide layers. Islanding in the Si layers is minimized by depositing a thin (<100Å) Si layer at room temperature with subsequent high temperature growth of the remainder of the Si. Cross-sectional transmission electron microscopy studies demonstrate that these growth procedures dramatically improve the continuity and quality of the CoSi. and Si multilayers.

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Implant Damage in AlGaAs Based Superlattices and Alloys at 77K

MRS Proceedings ◽

10.1557/proc-147-285 ◽

1989 ◽

Vol 147 ◽

Cited By ~ 5

Author(s):

E. A. Dobisz ◽

H. Dietrich ◽

A. W. McCormick ◽

J. P. Harbison

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Layer Thickness ◽

Room Temperature ◽

Amorphous Layer ◽

Current Work ◽

Cross Sectional ◽

Bulk Gaas ◽

Transmission Electron ◽

Extensive Damage

AbstractPreviously, it was shown that superlattices implanted with Si at 77K, exhibited more extensive damage and uniform compositional mixing upon subsequent annealing than samples implanted at room temperature.[l,2] The current work focuses on the damage in samples implanted with Si at 77K. The study shows that for a given dose, the amount of damage depends upon the layer thickness and the composition. Specimens of bulk GaAs, Al 3Ga. 7As, 7.5 nm GaAs -10 nm Al. 3Ga. 7As superlattice (SL1), 5.5 nm GaAs −3.5 nm AlAs superlattice (SL2), and 8.0 nm GaAs −8.0 nm AlAs superlat-tice (SL3) were implanted at 77K with 100 KeV Si, with doses ranging from 3 × 1013 cm−2 to 1 × 1015 cm−2. The samples were examined by ion channelling and cross sectional transmission electron microscopy (TEM). At 77K and a dose of 1 × 1014 cm−2, the GaAs and SLi showed an amorphous layer, while no damage peak was observed in SL2. The 77K amorphization thresholds of the Al 3Ga. 7As alloy, SL2, and SL3 were 2.5 × 1014 cm−2, 4 × 1014 cm−2, and 1 × 1015 cm−2 respectively. The sharpness of the amorphization threshold varied with the material.

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Formation of β-FeSi2, by thermal annealing of Fe-implanted (001) Si

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100149878 ◽

1993 ◽

Vol 51 ◽

pp. 808-809

Author(s):

X.W. Lin ◽

Z. Liliental-Weber ◽

J. Washburn ◽

J. Desimoni ◽

H. Bernas

Keyword(s):

Thermal Annealing ◽

Room Temperature ◽

Solid Phase ◽

Ion Beam ◽

High Resolution Electron Microscopy ◽

Optoelectronic Device ◽

Amorphous Layer ◽

Cross Sectional ◽

Resolution Electron ◽

Device Technology

Epitaxy of semiconducting β-FeSi2 on Si is of interest for optoelectronic device technology, because of its direct bandgap of ≈0.9 eV. Several techniques, including solid phase epitaxy (SPE) and ion beam synthesis, have been successfully used to grow β-FeSi2 on either Si (001) or (111) wafers. In this paper, we report the epitaxial formation of β-FeSi2 upon thermal annealing of an Fe-Si amorphous layer formed by ion implantation.Si (001) wafers were first implanted at room temperature with 50-keV Fe+ ions to a dose of 0.5 - 1×1016 cm−2, corresponding to a peak Fe concentration of cp ≈ 2 - 4 at.%, and subsequently annealed at 320, 520, and 900°C, in order to induce SPE of the implanted amorphous layer. Cross-sectional high-resolution electron microscopy (HREM) was used for structural characterization.We find that the implanted surface layer ( ≈100 nm thick) remains amorphous for samples annealed at 320°C for as long as 3.2 h, whereas annealing above 520°C results in SPE of Si, along with precipitation of β-FeSi2.

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Thin Ni Silicide Formation by Low Temperature-Induced Metal Atom Reaction with Ion Implanted Amorphous Silicon

MRS Proceedings ◽

10.1557/proc-279-237 ◽

1992 ◽

Vol 279 ◽

Cited By ~ 1

Author(s):

Yu.N. Erokhin ◽

B. K. Patnaik ◽

S. Pramanick ◽

F. Hong ◽

C. W. White ◽

...

Keyword(s):

Amorphous Silicon ◽

Rutherford Backscattering Spectrometry ◽

Silicon Layer ◽

Amorphous Layer ◽

Vacuum Furnace ◽

Silicide Formation ◽

Cross Sectional ◽

Silicon Area ◽

Transmission Electron ◽

Silicide Growth

ABSTRACTWe have extended our recent work [1,2] on buried suicide formation by Ni diffusion into a buried amorphous silicon layer to the case where silicide formation is at lower temperatures on silicon substrates which have been preamorphized. The reaction of metal atoms from a 12 nm Ni film evaporated on top of a 65 nm thick surface amorphous layer formed by 35 keV Si+ ion implantation has been investigated at temperature ≤400 °C. Rutherford Backscattering Spectrometry (RBS) with channeling, cross-sectional transmission electron microscopy (XTEM), X-ray diffraction and four-point-probe measurements were used to determine the structure, interfacial morphology, composition and resistivity of the silicide films. It has been found that an increased rate of silicidation occurs for amorphous silicon with respect to crystalline areas permitting a selective control of the silicon area to be contacted during silicide growth. Vacuum furnace annealing at 360 °C for 8 hours followed by an additional step at 400 °C for one hour produces a continuos NiSi2 layer with a resistivity 44 μΩ cm.

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The Role of Ion Mass on End-of-Range Damage in Shallow Preamorphizing Silicon

MRS Proceedings ◽

10.1557/proc-669-j3.6 ◽

2001 ◽

Vol 669 ◽

Author(s):

Mark H. Clark ◽

Kevin S. Jones ◽

Tony E. Haynes ◽

Charles J. Barbour ◽

Kenneth G. Minor ◽

...

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Secondary Ion Mass Spectrometry ◽

Amorphous Layer ◽

Cross Sectional ◽

Plan View ◽

Enhanced Diffusion ◽

Transmission Electron ◽

Marker Layer ◽

Process Simulator

ABSTRACTPreamorphization is commonly used to form shallow junction in silicon CMOS devices. The purposeof this experiment was to study the effect of the preamorphizing species' mass on the interstitial concentration at the end-of-range (EOR). Isovalent species of Si, Ge, Sn and Pb were compared. Silicon wafers with a buried boron marker layer (4700 Å deep) were amorphized using implants of 22 keV 28Si+, 32 keV73Ge+, 40 keV 119Sn+ or 45 keV 207Pb+, which resulted in similar amorphous layer depths. All species were implanted at a dose of 5×1014 /cm2. Cross-sectional transmission electron microscopy (XTEM) was used tomeasure amorphous layer depths (approximately 400 Å). Post-implantation anneals were performed at 750 °C for 15 minutes. Plan-view transmission electron microscopy (PTEM) was used to observe and quantify the EOR defect population upon annealing. Secondary ion mass spectrometry (SIMS) was used to monitor the transient enhanced diffusion (TED) of the buried boron marker layer resulting from the EOR damage introduced by the amorphizing implants. Based upon the SIMS results Florida Object Oriented Process Simulator (FLOOPS) calculated the resulting time average diffusivity enhancements. Results showed that increasing the ion mass over a significant range (28 to 207 AMU) not only affects the quantity and type of damage that occurs at the EOR, but results in a reduced diffusivity enhancement.

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Effects of Concurrent Co or Ti Silicidation on Transient Diffusion and End-of-Range Damage in Phosphorus Implanted Silicon

MRS Proceedings ◽

10.1557/proc-262-701 ◽

1992 ◽

Vol 262 ◽

Cited By ~ 1

Author(s):

J.W. Honeycutt ◽

J. Ravi ◽

G. A. Rozgonyi

Keyword(s):

Secondary Ion Mass Spectrometry ◽

Complete Removal ◽

Dislocation Loops ◽

Enhanced Diffusion ◽

Depth Profiles ◽

Enhanced Dissolution ◽

Implantation Damage ◽

Transmission Electron ◽

Defect Behavior ◽

Secondary Ion

ABSTRACTThe effects of Ti and Co silicidation on P+ ion implantation damage in Si have been investigated. After silicidation of unannealed 40 keV, 2×1015 cm-2 P+ implanted junctions by rapid thermal annealing at 900°C for 10–300 seconds, secondary ion mass spectrometry depth profiles of phosphorus in suicided and non-silicided junctions were compared. While non-silicided and TiSi2 suicided junctions exhibited equal amounts of transient enhanced diffusion behavior, the junction depths under COSi2 were significantly shallower. End-of-range interstitial dislocation loops in the same suicided and non-silicided junctions were studied by planview transmission electron microscopy. The loops were found to be stable after 900°C, 5 minute annealing in non-silicided material, and their formation was only slightly effected by TiSi2 or COSi2 silicidation. However, enhanced dissolution of the loops was observed under both TiSi2 and COSi2, with essentially complete removal of the defects under COSi2 after 5 minutes at 900°C. The observed diffusion and defect behavior strongly suggest that implantation damage induced excess interstitial concentrations are significantly reduced by the formation and presence of COSi2, and to a lesser extent by TiSi2. The observed time-dependent defect removal under the suicide films suggests that vacancy injection and/or interstitial absorption by the suicide film continues long after the suicide chemical reaction is complete.

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