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Nicole Herbots

Arizona State University, Physics, Faculty Member

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N. Herbots received her engineering physics PhD from the Catholic University of Louvain. After joining Oak Ridge National Lab in the Solid State Division, she became IBM Prof. of Electronic Materials at MIT in 1987 and joined Arizona State University Physics in 1991 to create the Ion Beam Analysis for Materials (IBeAM) user facility at ASU
Supervisors: SiO2 Innovates and MicroDrop Diagnostics, Boards of Advisors, Dr. Eric J. Culbertson, MD, GS, P. D. Glass, RN, Surveyor, Alan Carey, Global Business, LM Puglisi, IT and N. Herbots PhD thesis advisor, was Prof. Dr. Fernand VAN de WIELE, professeur ordinaire à la Faculté des sciences appliquées ;
Phone: 480-965-3561 (department office, email is better)
Address: Arizona State University
Department of Physics,
PO Box 85287-1504
Tempe AZ 85287

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Papers by Nicole Herbots

Ross Bennett Interview for AAAS 2013 Poster Partici...for Biology and Society”

Semiconductor-based heterostructure formation using low energy ion beams: Ion beam deposition (IBD) & combined ion and molecular beam deposition (CIMD)

AIP Conference Proceedings, 1988

In our previous work, we investigated the use of ion beam deposition (IBD) to grow epitaxial film... more In our previous work, we investigated the use of ion beam deposition (IBD) to grow epitaxial films at tempe~'atures lowe~ than those used in thermal processing (less than 500~ Presently, we have applied IBD to the growth of dense (6.4 x 1022 atom/era 3) silicon dioxide thin films at 400~ Through these experiments we have found several clues to the microscopic processes leading to the formation of thin fdm phases by low energy ions. Using Monte-Carlo simulations, we have found that low energy atomic collision cascades in silicon have unique feaua'es such as a high probability of relocation events that refill vacancies as they are created. Our results show that the combination of a low defect density in low energy collision cascades with the high mobility of inten'stitials in covalent materials can be used to athermally generate atomic displacements that can lead to onJering. These displacements can lead to epitaxial ordering at subsu'ate temperatures below the minimum temperature necessa~ for molecular beam epitaxy (550~ It can also lead to the formation of high quality silicon dioxide at temperatures well below that of thermal oxidation in silicon (i.e. < 850~ A growth model which we derived from these observations provides a fundamental understanding of how atomic collisions can be used to induce epitsxy or compound formation at low temperatures. Applications of low eaergy ion beams to the fabrication of arfficially structured materials at temperatures below which thermal decomposition and diffusivity become negligible have been explored using the insights gained from our model. This has led to the conception of a technique combining ion and molecular beam deposition (CIMD). We show that such a combination resolves the limitations of molecular beam epitaxy (MBE) and ion beam deposition (IBD) when either is used alone.

Low-temperature epitaxy of Si and Ge by direct ion beam deposition

Journal of Vacuum Science & Technology A, 1987

Amorphous, polycrystaHine, and epitaxial thin films of Si and Ge have been grown by ion beam depo... more Amorphous, polycrystaHine, and epitaxial thin films of Si and Ge have been grown by ion beam deposition (IBD) under ultrahigh-vacuum conditions. lBD involves the direct deposition ofions onto single-crystal substrates from mass-and energy-analyzed beams with energies of 10 to 200 eV. The IBD films were characterized by Rutherford back scattering, ion channeling, crosssection transmission electron microscopy, and x-ray diffraction. The effects of substrate temperature, ion energy, and substrate cleaning were studied. Differences in the formation of epitaxial thin films on pand n-type 8i substrates were observed with n. Si showing better epitaxy at low temperatures. Epitaxial overlayers which showed good minimum yields by ion channeling (3%-4%) have been produced at temperatures as low as 375°C for Ge on Ge(lOO) and 8i on Si(lOO).

AAAS 2012-BennettKennett.pdf”

Methods for Wafer Bonding, and for nucleating Bonding Nanophases. N. Herbots, R.J. Culbertson, J. D. Bradley, M. A. Hart, D.A. Sell, S.F. Whaley . 2012 . United States Patent Office Patent Application Publication . Pub. No 13/259,278, PCT/US2010/033301. May 31, 2012 . 15 pages

FIELD OF THE INVENTION This invention relates to methods for bonding substrates, and in particula... more FIELD OF THE INVENTION This invention relates to methods for bonding substrates, and in particular, bonding of semiconductor and/or semiconductor oxide and nitride wafers. BACKGROUND OF THE INVENTION The long-term reliability of multicomponent devices such as bio-sensors and solar cells is at least in part determined by the robustness of the bonding methods used to hold the devices together. Typically, epoxy bonding methods are used to prepare such devices, but suffer from the limitations of limited longevity (10 years) as well as poor thermal matching between components which can lead to internal stresses and ultimately bonding failure. Implantable bio-sensor devices need to be hermetically sealed in a saline environment such as a human or an animal body for the lifetime of the implant. As many biosensors and solar cells are typically based on silica wafers (boro-silicate, alpha-quartz, etc.) and Si(100) wafers, there exists a need in the art for improved methods for bonding the sa...

Imaging of Buried Si and Si:Ge Surface Structure Under Amorphous Ge Films by Plan View Transmission Electron Microscopy

MRS Proceedings, 1994

ABSTRACTReal space plan-view Transmission Electron Microscopy (TEM) of the interfacial structure ... more ABSTRACTReal space plan-view Transmission Electron Microscopy (TEM) of the interfacial structure at the amorphous-Ge / Si (111) interface is presented. Ge is deposited at between room temperature and 150°C on either a 5×5 or 7×7 reconstructed surface. Conventional Plan-view TEM analysis reveals microstructural details such as surface steps, reconstruction phase shift boundaries and the reconstruction itself buried under the amorphous film, features which have previously been seen only as clean surfaces in UHV. Also imaged are small regions where Ge grows epitaxially on the Si surface above room temperature. These are seen to appear preferentially at steps and phase shift boundaries.

International Committee Program Committee

Ion Beam Analysis of Wet NanoBonding™ of SitoSiO2 and SiO2toSilica for singledevice sensing electronics using Atomic Force Microscopy & Three Liquids Contact Angle Analysis to Correlate Components of the Surface Free Energy to Topography and Composition

Methods for Wafer Bonding and for Nucleating Bonding Nanophases Using Wet and Steam Pressurization

We claim: 1. A method for bonding substrates comprising contacting a first bonding surface of a f... more We claim: 1. A method for bonding substrates comprising contacting a first bonding surface of a first substrate with a second bonding surface of a second substrate to form an assembly in an atmosphere comprising steam and oxygen, under suitable conditions to form a bonding layer between the first surface and the second surface;; and optionally compressing the assembly, wherein the first bonding surface comprises a polarized surface layer;; the second bonding surface comprises a hydrophilic surface layer;; and the first bonding surface and the second bonding surface are different. 2. The method of claim 1, wherein the compressing is at a pressure between about 1 atm and about 1.1 atm. 3. The method of claim 1, wherein the compressing is at a temperature less than about 200° C. 4. The method of claim 1, wherein the compressing is at a temperature between about 25° C. and about 200° C. 5. The method of claim 1, wherein the first substrate and the second substrate each independently comprises

Beam Solid Interactions: Fundamentals and Applications Symp. ed M Nastasi, LR Harriott, N Herbots and RS Averback (Pittsburgh, PA: Materials Research Society)

In our previous work, we investigated the use of ion beam deposition (IBD) to grow epitaxial film... more In our previous work, we investigated the use of ion beam deposition (IBD) to grow epitaxial films at tempe~'atures lowe~ than those used in thermal processing (less than 500~ Presently, we have applied IBD to the growth of dense (6.4 x 1022 atom/era 3) silicon dioxide thin films at 400~ Through these experiments we have found several clues to the microscopic processes leading to the formation of thin fdm phases by low energy ions. Using Monte-Carlo simulations, we have found that low energy atomic collision cascades in silicon have unique feaua'es such as a high probability of relocation events that refill vacancies as they are created. Our results show that the combination of a low defect density in low energy collision cascades with the high mobility of inten'stitials in covalent materials can be used to athermally generate atomic displacements that can lead to onJering. These displacements can lead to epitaxial ordering at subsu'ate temperatures below the minimum temperature necessa~ for molecular beam epitaxy (550~ It can also lead to the formation of high quality silicon dioxide at temperatures well below that of thermal oxidation in silicon (i.e. < 850~ A growth model which we derived from these observations provides a fundamental understanding of how atomic collisions can be used to induce epitsxy or compound formation at low temperatures. Applications of low eaergy ion beams to the fabrication of arfficially structured materials at temperatures below which thermal decomposition and diffusivity become negligible have been explored using the insights gained from our model. This has led to the conception of a technique combining ion and molecular beam deposition (CIMD). We show that such a combination resolves the limitations of molecular beam epitaxy (MBE) and ion beam deposition (IBD) when either is used alone.

Beam Solid Interactions: Fundamentals and Applications, MRS Symposium Proceedings

In our previous work, we investigated the use of ion beam deposition (IBD) to grow epitaxial film... more In our previous work, we investigated the use of ion beam deposition (IBD) to grow epitaxial films at tempe~'atures lowe~ than those used in thermal processing (less than 500~ Presently, we have applied IBD to the growth of dense (6.4 x 1022 atom/era 3) silicon dioxide thin films at 400~ Through these experiments we have found several clues to the microscopic processes leading to the formation of thin fdm phases by low energy ions. Using Monte-Carlo simulations, we have found that low energy atomic collision cascades in silicon have unique feaua'es such as a high probability of relocation events that refill vacancies as they are created. Our results show that the combination of a low defect density in low energy collision cascades with the high mobility of inten'stitials in covalent materials can be used to athermally generate atomic displacements that can lead to onJering. These displacements can lead to epitaxial ordering at subsu'ate temperatures below the minimum temperature necessa~ for molecular beam epitaxy (550~ It can also lead to the formation of high quality silicon dioxide at temperatures well below that of thermal oxidation in silicon (i.e. < 850~ A growth model which we derived from these observations provides a fundamental understanding of how atomic collisions can be used to induce epitsxy or compound formation at low temperatures. Applications of low eaergy ion beams to the fabrication of arfficially structured materials at temperatures below which thermal decomposition and diffusivity become negligible have been explored using the insights gained from our model. This has led to the conception of a technique combining ion and molecular beam deposition (CIMD). We show that such a combination resolves the limitations of molecular beam epitaxy (MBE) and ion beam deposition (IBD) when either is used alone.

Integrated Processinyg of Silicided Shallow Junctions using Rapid Thermal Annealing Prior to Dopant Activation

A method for producing shallow silicided diodes for MOS devices (with junction depths of about 0.... more A method for producing shallow silicided diodes for MOS devices (with junction depths of about 0.1 gm), by implanting after forming the silicide layer was investigated. The key to this integrated process is the use of rapid thermal annealing (RTA) to activate the dopants in the silicon, so that there is very little thermal broadening of the implant distribution. Self-aligned titanium silicide (TiSi 2) films with thicknesses ranging from 40 to 80 nm were grown by RTA of sputter deposited titanium films on silicon substrates. After forming the TiSi 2 , arsenic and boron were implanted. A second RTA step was used after implantation to activate these dopants. It was found that implanting either dopant caused a sharp increase in the sheet resistivity of the TiSi 2. The resistivity can be easily restored to its original value (about 18 pfl-cm) by a post implant RTA anneal. RBS analysis showed that arsenic diffuses rapidly in the TiSi 2 during RTA at temperatures as low as 600 0 C. SIMS data indicated that boron was not mobile up to temperatures of 900°C, possibly because it forms a compound with the titanium which precipitates in the TiSi 2. Coalescence of TiSi 2 occurs during post implant furnace annealing, leading to an increase in the sheet resistivity. The amount of coalescence depends on the film thickness, but not on whether or not the film had been subject to implantation. Spreading resistance profiling data showed that both arsenic and boron diffused into the TiSi 2 during furnace annealing, reducing the surface concentrations of dopant at the TiSi 2 /Si interface. Both N+/P and P+/N diodes formed by this technique exhibited low leakage currents after the second RTA anneal. This is attributed to removal of the implant damage by the RTA. In summary, the second RTA serves the dual purpose of removing implant damage in the TiSi 2 and creating the shallow junction by dopant activation.

A New 3D Multistring Code to Identify Compound Oxide Nanophase With Ion Channeling

MRS …, 2007

Topics in solid phase epitaxy: Strain, structure and geometry

Materials Science and Engineering: R: Reports, 1996

The effects of some experimental parameters on the solid-phase crystallization of amorphous films... more The effects of some experimental parameters on the solid-phase crystallization of amorphous films on single crystals, a process known as Solid Phase Epitaxy (SPE), are examined. Results from a large community of researchers concerning SPE of alloys and compounds, strained films, films in constrained geometries and films with unusual amorphous/crystal interfaces are reviewed. Our present understanding of mechanisms involved in SPE is given, and the implications of the wide range of experimental results are discussed.

Comparative study of low energy ion beam oxidation of Si(100), Ge/Si(100) and

Materials Science and Engineering: B, 1992

... Abstract. Low energy ion beam oxidation (IBO) of Si(100) and germanium and Si 1−x Ge x grown ... more

Atomic collisions, elastic recombination, and thermal diffusion during thin-film growth from low-energy ion beams

Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 1991

Low-energy (< 1 keV) ions are used in a variety of thin-film techniques. When low-energy ions ... more Low-energy (< 1 keV) ions are used in a variety of thin-film techniques. When low-energy ions are used during growth, the atomic mobility is athermally enhanced. This can lead to a significant lowering of the temperature necessary to induce epitaxial growth and chemical reactions. Athermal enhancement of atomic mobility in semiconductors can be described below the temperature for plastic deformation ( T = 540°C in Si) by classifying the mechanisms involved into three categories according to their respective timescale: collisions, elastic recombination, and thermal diffusion. A quantitative model can then be derived to predict the conditions of temperature, dose rate, and energy to obtain thin film growth, epitaxial growth, and oxidation in techniques such as ion beam deposition (IBD), and ion beam oxidation (IBO). Using computer simulations, the dynamics of defect generation and redistribution, and the resulting thin-film growth rate can be investigated. Energies below 200 eV are...

Heteroepitaxial properties of Si[sub 1−x−y]Ge[sub x]C[sub y] on Si(100) grown by combined ion- and molecular-beam deposition

Journal of Applied Physics, 1997

The heteroepitaxial growth of the new ternary, group-IV, semiconductor material, Si 1xy Ge x C y ... more The heteroepitaxial growth of the new ternary, group-IV, semiconductor material, Si 1xy Ge x C y on Si100, has been investigated. The epitaxial quality of Si 1xy Ge x C y is found to be inferior to that of Si 1x Ge x with similar Si/Ge concentration ratio, grown under identical conditions, and the quality deteriorates with increasing C fraction. Also, the surface roughness, as studied by tapping mode atomic force microscopy, increases with increasing C fraction as well as with increasing Ge fraction, suggesting a transition from Frank-van der Merwe to Stranski-Krastanov type growth. We suggest that the very large mismatch between the average bond length in the Si 1xy Ge x C y material, as determined by Vegard's law, and the equilibrium Si-C bond length, weakens the Si-C bonds and reduces the elastic range of the material, thus lowering the barrier for dislocation and stacking fault formation. The change in elasticity may also be responsible for the change in growth morphology, either directly by a lowered barrier for island formation or indirectly through the formation of defects. A decrease in Ge incorporation in the Si 1xy Ge x C y films with increasing C incorporation suggests a repulsive Ge-C interaction. Moreover, we observe a C-rich, Ge-deficient precursor phase to SiC precipitates at a growth temperature of 560°C, whereas at 450°C no such phase can be observed. The temperature dependence of the precursor formation is consistent with C bulk diffusion. Infrared absorption measurements cannot be used to detect the precursor phase. Finally, the onset of epitaxial breakdown is discussed and an accurate and independent determination of the C fraction and its substitutionality is emphasized.

Topics in solid phase epitaxy: Strain, structure and geometry

Materials Science and Engineering: R: Reports, 1996

The effects of some experimental parameters on the solid-phase crystallization of amorphous films... more The effects of some experimental parameters on the solid-phase crystallization of amorphous films on single crystals, a process known as Solid Phase Epitaxy (SPE), are examined. Results from a large community of researchers concerning SPE of alloys and compounds, strained films, films in constrained geometries and films with unusual amorphous/crystal interfaces are reviewed. Our present understanding of mechanisms involved in SPE is given, and the implications of the wide range of experimental results are discussed.

Infrared spectroscopic analysis of an ordered Si/SiO2 interface

Applied Physics Letters, 2004

Infrared spectroscopy is used to compare the Si/SiO 2 interfaces created by thermal oxidation of ... more Infrared spectroscopy is used to compare the Si/SiO 2 interfaces created by thermal oxidation of a standard Si͑100͒ substrate and of an ordered, ͑1ϫ1͒ Si͑100͒ substrate. The thermal oxides ͑approximately 25 Å͒ examined in this study are etched in dilute hydrofluoric acid and the resulting films analyzed spectroscopically. The behavior of the dominant optical phonon modes as a function of film thickness provides strong evidence that the ordered Si͑100͒ substrate provides a template for an Si/SiO 2 interface with a higher degree of homogeneity in the Si-O bonding environment of the intervening substoichiometric SiO x layer than does the standard Si͑100͒ substrate.

Ion beam induced oxidation of silicon

Applied Physics Letters, 1988

ABSTRACT A new physical phenomenon causing oxidation of silicon has been observed. The phenomenon... more ABSTRACT A new physical phenomenon causing oxidation of silicon has been observed. The phenomenon is controlled by the impact of an energetic ion beam on a clean silicon target exposed to low‐pressure oxygen. An oxide layer of 50–100 Å can be formed at room temperature by properly choosing the oxidation conditions. The growth was studied in situ by measuring the ion‐induced secondary electron yield. A strong dependence on oxygen pressure and target temperature was observed. By studying the oxide with x‐ray photoelectron spectroscopy, it was concluded that the film formed is stoichiometric SiO 2 . A discussion on possible growth mechanisms is carried out in terms of ion energy deposition.

Ross Bennett Interview for AAAS 2013 Poster Partici...for Biology and Society”

Semiconductor-based heterostructure formation using low energy ion beams: Ion beam deposition (IBD) & combined ion and molecular beam deposition (CIMD)

AIP Conference Proceedings, 1988

In our previous work, we investigated the use of ion beam deposition (IBD) to grow epitaxial film... more In our previous work, we investigated the use of ion beam deposition (IBD) to grow epitaxial films at tempe~'atures lowe~ than those used in thermal processing (less than 500~ Presently, we have applied IBD to the growth of dense (6.4 x 1022 atom/era 3) silicon dioxide thin films at 400~ Through these experiments we have found several clues to the microscopic processes leading to the formation of thin fdm phases by low energy ions. Using Monte-Carlo simulations, we have found that low energy atomic collision cascades in silicon have unique feaua'es such as a high probability of relocation events that refill vacancies as they are created. Our results show that the combination of a low defect density in low energy collision cascades with the high mobility of inten'stitials in covalent materials can be used to athermally generate atomic displacements that can lead to onJering. These displacements can lead to epitaxial ordering at subsu'ate temperatures below the minimum temperature necessa~ for molecular beam epitaxy (550~ It can also lead to the formation of high quality silicon dioxide at temperatures well below that of thermal oxidation in silicon (i.e. < 850~ A growth model which we derived from these observations provides a fundamental understanding of how atomic collisions can be used to induce epitsxy or compound formation at low temperatures. Applications of low eaergy ion beams to the fabrication of arfficially structured materials at temperatures below which thermal decomposition and diffusivity become negligible have been explored using the insights gained from our model. This has led to the conception of a technique combining ion and molecular beam deposition (CIMD). We show that such a combination resolves the limitations of molecular beam epitaxy (MBE) and ion beam deposition (IBD) when either is used alone.

Low-temperature epitaxy of Si and Ge by direct ion beam deposition

Journal of Vacuum Science & Technology A, 1987

Amorphous, polycrystaHine, and epitaxial thin films of Si and Ge have been grown by ion beam depo... more Amorphous, polycrystaHine, and epitaxial thin films of Si and Ge have been grown by ion beam deposition (IBD) under ultrahigh-vacuum conditions. lBD involves the direct deposition ofions onto single-crystal substrates from mass-and energy-analyzed beams with energies of 10 to 200 eV. The IBD films were characterized by Rutherford back scattering, ion channeling, crosssection transmission electron microscopy, and x-ray diffraction. The effects of substrate temperature, ion energy, and substrate cleaning were studied. Differences in the formation of epitaxial thin films on pand n-type 8i substrates were observed with n. Si showing better epitaxy at low temperatures. Epitaxial overlayers which showed good minimum yields by ion channeling (3%-4%) have been produced at temperatures as low as 375°C for Ge on Ge(lOO) and 8i on Si(lOO).

AAAS 2012-BennettKennett.pdf”

Methods for Wafer Bonding, and for nucleating Bonding Nanophases. N. Herbots, R.J. Culbertson, J. D. Bradley, M. A. Hart, D.A. Sell, S.F. Whaley . 2012 . United States Patent Office Patent Application Publication . Pub. No 13/259,278, PCT/US2010/033301. May 31, 2012 . 15 pages

FIELD OF THE INVENTION This invention relates to methods for bonding substrates, and in particula... more FIELD OF THE INVENTION This invention relates to methods for bonding substrates, and in particular, bonding of semiconductor and/or semiconductor oxide and nitride wafers. BACKGROUND OF THE INVENTION The long-term reliability of multicomponent devices such as bio-sensors and solar cells is at least in part determined by the robustness of the bonding methods used to hold the devices together. Typically, epoxy bonding methods are used to prepare such devices, but suffer from the limitations of limited longevity (10 years) as well as poor thermal matching between components which can lead to internal stresses and ultimately bonding failure. Implantable bio-sensor devices need to be hermetically sealed in a saline environment such as a human or an animal body for the lifetime of the implant. As many biosensors and solar cells are typically based on silica wafers (boro-silicate, alpha-quartz, etc.) and Si(100) wafers, there exists a need in the art for improved methods for bonding the sa...

Imaging of Buried Si and Si:Ge Surface Structure Under Amorphous Ge Films by Plan View Transmission Electron Microscopy

MRS Proceedings, 1994

ABSTRACTReal space plan-view Transmission Electron Microscopy (TEM) of the interfacial structure ... more ABSTRACTReal space plan-view Transmission Electron Microscopy (TEM) of the interfacial structure at the amorphous-Ge / Si (111) interface is presented. Ge is deposited at between room temperature and 150°C on either a 5×5 or 7×7 reconstructed surface. Conventional Plan-view TEM analysis reveals microstructural details such as surface steps, reconstruction phase shift boundaries and the reconstruction itself buried under the amorphous film, features which have previously been seen only as clean surfaces in UHV. Also imaged are small regions where Ge grows epitaxially on the Si surface above room temperature. These are seen to appear preferentially at steps and phase shift boundaries.

International Committee Program Committee

Ion Beam Analysis of Wet NanoBonding™ of SitoSiO2 and SiO2toSilica for singledevice sensing electronics using Atomic Force Microscopy & Three Liquids Contact Angle Analysis to Correlate Components of the Surface Free Energy to Topography and Composition

Methods for Wafer Bonding and for Nucleating Bonding Nanophases Using Wet and Steam Pressurization

We claim: 1. A method for bonding substrates comprising contacting a first bonding surface of a f... more We claim: 1. A method for bonding substrates comprising contacting a first bonding surface of a first substrate with a second bonding surface of a second substrate to form an assembly in an atmosphere comprising steam and oxygen, under suitable conditions to form a bonding layer between the first surface and the second surface;; and optionally compressing the assembly, wherein the first bonding surface comprises a polarized surface layer;; the second bonding surface comprises a hydrophilic surface layer;; and the first bonding surface and the second bonding surface are different. 2. The method of claim 1, wherein the compressing is at a pressure between about 1 atm and about 1.1 atm. 3. The method of claim 1, wherein the compressing is at a temperature less than about 200° C. 4. The method of claim 1, wherein the compressing is at a temperature between about 25° C. and about 200° C. 5. The method of claim 1, wherein the first substrate and the second substrate each independently comprises

Beam Solid Interactions: Fundamentals and Applications Symp. ed M Nastasi, LR Harriott, N Herbots and RS Averback (Pittsburgh, PA: Materials Research Society)

In our previous work, we investigated the use of ion beam deposition (IBD) to grow epitaxial film... more In our previous work, we investigated the use of ion beam deposition (IBD) to grow epitaxial films at tempe~'atures lowe~ than those used in thermal processing (less than 500~ Presently, we have applied IBD to the growth of dense (6.4 x 1022 atom/era 3) silicon dioxide thin films at 400~ Through these experiments we have found several clues to the microscopic processes leading to the formation of thin fdm phases by low energy ions. Using Monte-Carlo simulations, we have found that low energy atomic collision cascades in silicon have unique feaua'es such as a high probability of relocation events that refill vacancies as they are created. Our results show that the combination of a low defect density in low energy collision cascades with the high mobility of inten'stitials in covalent materials can be used to athermally generate atomic displacements that can lead to onJering. These displacements can lead to epitaxial ordering at subsu'ate temperatures below the minimum temperature necessa~ for molecular beam epitaxy (550~ It can also lead to the formation of high quality silicon dioxide at temperatures well below that of thermal oxidation in silicon (i.e. < 850~ A growth model which we derived from these observations provides a fundamental understanding of how atomic collisions can be used to induce epitsxy or compound formation at low temperatures. Applications of low eaergy ion beams to the fabrication of arfficially structured materials at temperatures below which thermal decomposition and diffusivity become negligible have been explored using the insights gained from our model. This has led to the conception of a technique combining ion and molecular beam deposition (CIMD). We show that such a combination resolves the limitations of molecular beam epitaxy (MBE) and ion beam deposition (IBD) when either is used alone.

Beam Solid Interactions: Fundamentals and Applications, MRS Symposium Proceedings

In our previous work, we investigated the use of ion beam deposition (IBD) to grow epitaxial film... more In our previous work, we investigated the use of ion beam deposition (IBD) to grow epitaxial films at tempe~'atures lowe~ than those used in thermal processing (less than 500~ Presently, we have applied IBD to the growth of dense (6.4 x 1022 atom/era 3) silicon dioxide thin films at 400~ Through these experiments we have found several clues to the microscopic processes leading to the formation of thin fdm phases by low energy ions. Using Monte-Carlo simulations, we have found that low energy atomic collision cascades in silicon have unique feaua'es such as a high probability of relocation events that refill vacancies as they are created. Our results show that the combination of a low defect density in low energy collision cascades with the high mobility of inten'stitials in covalent materials can be used to athermally generate atomic displacements that can lead to onJering. These displacements can lead to epitaxial ordering at subsu'ate temperatures below the minimum temperature necessa~ for molecular beam epitaxy (550~ It can also lead to the formation of high quality silicon dioxide at temperatures well below that of thermal oxidation in silicon (i.e. < 850~ A growth model which we derived from these observations provides a fundamental understanding of how atomic collisions can be used to induce epitsxy or compound formation at low temperatures. Applications of low eaergy ion beams to the fabrication of arfficially structured materials at temperatures below which thermal decomposition and diffusivity become negligible have been explored using the insights gained from our model. This has led to the conception of a technique combining ion and molecular beam deposition (CIMD). We show that such a combination resolves the limitations of molecular beam epitaxy (MBE) and ion beam deposition (IBD) when either is used alone.

Integrated Processinyg of Silicided Shallow Junctions using Rapid Thermal Annealing Prior to Dopant Activation

A method for producing shallow silicided diodes for MOS devices (with junction depths of about 0.... more A method for producing shallow silicided diodes for MOS devices (with junction depths of about 0.1 gm), by implanting after forming the silicide layer was investigated. The key to this integrated process is the use of rapid thermal annealing (RTA) to activate the dopants in the silicon, so that there is very little thermal broadening of the implant distribution. Self-aligned titanium silicide (TiSi 2) films with thicknesses ranging from 40 to 80 nm were grown by RTA of sputter deposited titanium films on silicon substrates. After forming the TiSi 2 , arsenic and boron were implanted. A second RTA step was used after implantation to activate these dopants. It was found that implanting either dopant caused a sharp increase in the sheet resistivity of the TiSi 2. The resistivity can be easily restored to its original value (about 18 pfl-cm) by a post implant RTA anneal. RBS analysis showed that arsenic diffuses rapidly in the TiSi 2 during RTA at temperatures as low as 600 0 C. SIMS data indicated that boron was not mobile up to temperatures of 900°C, possibly because it forms a compound with the titanium which precipitates in the TiSi 2. Coalescence of TiSi 2 occurs during post implant furnace annealing, leading to an increase in the sheet resistivity. The amount of coalescence depends on the film thickness, but not on whether or not the film had been subject to implantation. Spreading resistance profiling data showed that both arsenic and boron diffused into the TiSi 2 during furnace annealing, reducing the surface concentrations of dopant at the TiSi 2 /Si interface. Both N+/P and P+/N diodes formed by this technique exhibited low leakage currents after the second RTA anneal. This is attributed to removal of the implant damage by the RTA. In summary, the second RTA serves the dual purpose of removing implant damage in the TiSi 2 and creating the shallow junction by dopant activation.

A New 3D Multistring Code to Identify Compound Oxide Nanophase With Ion Channeling

MRS …, 2007

Topics in solid phase epitaxy: Strain, structure and geometry

Materials Science and Engineering: R: Reports, 1996

The effects of some experimental parameters on the solid-phase crystallization of amorphous films... more The effects of some experimental parameters on the solid-phase crystallization of amorphous films on single crystals, a process known as Solid Phase Epitaxy (SPE), are examined. Results from a large community of researchers concerning SPE of alloys and compounds, strained films, films in constrained geometries and films with unusual amorphous/crystal interfaces are reviewed. Our present understanding of mechanisms involved in SPE is given, and the implications of the wide range of experimental results are discussed.

Comparative study of low energy ion beam oxidation of Si(100), Ge/Si(100) and

Materials Science and Engineering: B, 1992

... Abstract. Low energy ion beam oxidation (IBO) of Si(100) and germanium and Si 1−x Ge x grown ... more

Atomic collisions, elastic recombination, and thermal diffusion during thin-film growth from low-energy ion beams

Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 1991

Low-energy (< 1 keV) ions are used in a variety of thin-film techniques. When low-energy ions ... more Low-energy (< 1 keV) ions are used in a variety of thin-film techniques. When low-energy ions are used during growth, the atomic mobility is athermally enhanced. This can lead to a significant lowering of the temperature necessary to induce epitaxial growth and chemical reactions. Athermal enhancement of atomic mobility in semiconductors can be described below the temperature for plastic deformation ( T = 540°C in Si) by classifying the mechanisms involved into three categories according to their respective timescale: collisions, elastic recombination, and thermal diffusion. A quantitative model can then be derived to predict the conditions of temperature, dose rate, and energy to obtain thin film growth, epitaxial growth, and oxidation in techniques such as ion beam deposition (IBD), and ion beam oxidation (IBO). Using computer simulations, the dynamics of defect generation and redistribution, and the resulting thin-film growth rate can be investigated. Energies below 200 eV are...

Heteroepitaxial properties of Si[sub 1−x−y]Ge[sub x]C[sub y] on Si(100) grown by combined ion- and molecular-beam deposition

Journal of Applied Physics, 1997

The heteroepitaxial growth of the new ternary, group-IV, semiconductor material, Si 1xy Ge x C y ... more The heteroepitaxial growth of the new ternary, group-IV, semiconductor material, Si 1xy Ge x C y on Si100, has been investigated. The epitaxial quality of Si 1xy Ge x C y is found to be inferior to that of Si 1x Ge x with similar Si/Ge concentration ratio, grown under identical conditions, and the quality deteriorates with increasing C fraction. Also, the surface roughness, as studied by tapping mode atomic force microscopy, increases with increasing C fraction as well as with increasing Ge fraction, suggesting a transition from Frank-van der Merwe to Stranski-Krastanov type growth. We suggest that the very large mismatch between the average bond length in the Si 1xy Ge x C y material, as determined by Vegard's law, and the equilibrium Si-C bond length, weakens the Si-C bonds and reduces the elastic range of the material, thus lowering the barrier for dislocation and stacking fault formation. The change in elasticity may also be responsible for the change in growth morphology, either directly by a lowered barrier for island formation or indirectly through the formation of defects. A decrease in Ge incorporation in the Si 1xy Ge x C y films with increasing C incorporation suggests a repulsive Ge-C interaction. Moreover, we observe a C-rich, Ge-deficient precursor phase to SiC precipitates at a growth temperature of 560°C, whereas at 450°C no such phase can be observed. The temperature dependence of the precursor formation is consistent with C bulk diffusion. Infrared absorption measurements cannot be used to detect the precursor phase. Finally, the onset of epitaxial breakdown is discussed and an accurate and independent determination of the C fraction and its substitutionality is emphasized.

Topics in solid phase epitaxy: Strain, structure and geometry

Materials Science and Engineering: R: Reports, 1996

The effects of some experimental parameters on the solid-phase crystallization of amorphous films... more The effects of some experimental parameters on the solid-phase crystallization of amorphous films on single crystals, a process known as Solid Phase Epitaxy (SPE), are examined. Results from a large community of researchers concerning SPE of alloys and compounds, strained films, films in constrained geometries and films with unusual amorphous/crystal interfaces are reviewed. Our present understanding of mechanisms involved in SPE is given, and the implications of the wide range of experimental results are discussed.

Infrared spectroscopic analysis of an ordered Si/SiO2 interface

Applied Physics Letters, 2004

Infrared spectroscopy is used to compare the Si/SiO 2 interfaces created by thermal oxidation of ... more Infrared spectroscopy is used to compare the Si/SiO 2 interfaces created by thermal oxidation of a standard Si͑100͒ substrate and of an ordered, ͑1ϫ1͒ Si͑100͒ substrate. The thermal oxides ͑approximately 25 Å͒ examined in this study are etched in dilute hydrofluoric acid and the resulting films analyzed spectroscopically. The behavior of the dominant optical phonon modes as a function of film thickness provides strong evidence that the ordered Si͑100͒ substrate provides a template for an Si/SiO 2 interface with a higher degree of homogeneity in the Si-O bonding environment of the intervening substoichiometric SiO x layer than does the standard Si͑100͒ substrate.

Ion beam induced oxidation of silicon

Applied Physics Letters, 1988

ABSTRACT A new physical phenomenon causing oxidation of silicon has been observed. The phenomenon... more ABSTRACT A new physical phenomenon causing oxidation of silicon has been observed. The phenomenon is controlled by the impact of an energetic ion beam on a clean silicon target exposed to low‐pressure oxygen. An oxide layer of 50–100 Å can be formed at room temperature by properly choosing the oxidation conditions. The growth was studied in situ by measuring the ion‐induced secondary electron yield. A strong dependence on oxygen pressure and target temperature was observed. By studying the oxide with x‐ray photoelectron spectroscopy, it was concluded that the film formed is stoichiometric SiO 2 . A discussion on possible growth mechanisms is carried out in terms of ion energy deposition.

A New Epitaxial Silicon Dioxide 2-D Nanophase nucleated on OH-(1x1) Silicon(100) for MOS technology Identified Via 3.05 MeV Ion Channeling & Blocking and a New 3-D Multristring Code.

Ion Beam Analysis (IBA) using 4He+ ion channeling combined with Nuclear Resonance Analysis (NRA) ... more Ion Beam Analysis (IBA) using 4He+ ion channeling combined with Nuclear Resonance Analysis (NRA) and 3DMultiString computer simulations detect order in silicon dioxide (SiO2) nucleated on (1×1) Si(100) via the Herbots-Atluri clean (U.S. patent 6,613,677) in air at 300 K. Alignment of the SiO2 to Si(100) is also supported by 10 keV Reflection High Energy Electron Diffraction (RHEED). Infrared spectroscopy of ordered oxides exhibit a constant, well-defined frequency of optical absorption across a 1 nm thickness in the interfacial region near Si, supporting the presence of a well defined bond-length and stoichiometry as detected by IBA and RHEED. Comparison between HRTEM and ellipsometry measurements show that the HRTEM thickness is significantly lower, by 30%, when compared to the thickness measured by ellipsometry, indicating a change in optical properties. In this work IBA is combined with 3DMultiString to identify a new heteroepitaxial nanophase of tetragonally distorted β-cristobalite SiO2 (annotated β-c SiO2) extending to a critical thickness of 2 nm from the (1×1) Si (100)/β-c SiO2 interface to the β-c SiO2 /amorphous SiO2 interface (annotated β-c SiO2/a-SiO2). 3DMultiString simulations of IBA data taken on the newly identified β-c SiO2/(1×1) Si(100) interphase includes channeling along the three <100>, <110>, and <111> axes of Si (100) in combination 16O(α, α)16O 3.045 MeV NRA to measure oxygen areal densities corresponding to nm-thick films. In this manner, the critical thickness of the new heteroepitaxial β-c SiO2 nanophase can be established as a function of oxygen coverage.

Nanoscience, Materials Physics & Biophysics in Research and Education: Synthesis of New Materials Molecule-by-molecule in Two-dimensional Nanophases & Interphases, Nanotechnology For Creating An Artificial Pancreas & Improving Interocular Implants for Curing Cataracts

Our most recent research and technology disclosures are at the boundary of condensed matter physi... more Our most recent research and technology disclosures are at the boundary of condensed matter physics, biology and medical electronics, such as integrating single device medical implants (artificial pancreas) with Nano-Bonding™ and controlling hydro-affinity & pepto-affinity of inter-ocular lenses (IOL), laparoscope lenses and other human device implants with VitreOx™ & ProteinKnox™ (Patents pending).
We research & model synthesis of new semiconductor nano-phases such as sub-nanometer ordered silicon oxides (US Patent 7,851,365 granted on 12/12/10 ) & SiGeO2 (US patent 5,124,421). Our methods include CIMD (US Patent 4,800,200) & new low temperature techniques such as the Herbots-Atluri process (US patent 6,613,677, granted 9/2/03) to produce either templates for (hetero) epitaxy in our clean-room laboratory, "nano-stacks" of ultrathin films to create high performance gate oxides, peroskvites and photovoltaic surfaces