Abrasive jet micro-machining (AJM), in which abrasive particles are accelerated by air and directed toward a target, has been used to make components for micro-electro-mechanical (MEMS) and micro-fluidic capillary electrophoresis devices. One of the disadvantages of AJM is that the compressed air jet used to propel the erodent particles diverges significantly after the nozzle exit, increasing the size of the blast zone and the width of the smallest channel or hole that can be machined without the use of a patterned erosion-resistant mask that defines the micro-feature edges. Abrasive slurry jet micro-machining (ASJM) is similar to AJM except that pressurized water, instead of air, is used to accelerate the suspended abrasive particles such as garnet or alumina (Al2O3). In both AJM and ASJM, the material removal occurs by erosion. However, for the same jet dimension and low speed, slurry jets have a much lower divergence angle than air jets, allowing for the micro-machining of small features without the use of patterned masks.
In metallurgy, cladding refers to the bonding together of dissimilar metals, normally achieved by extruding two or more metals through a die or pressing sheets together under high pressure. Timely detection of delamination that occurs occasionally during the cladding processes is very important for the industry. This paper presents an EMAT system based on ultrasonic guided wave techniques. The analysis of a three-layer, brass/copper/brass product is also presented including dispersion curves, and interaction of ultrasonic guided wave with delamination defects. The authors observed a cyclic behavior of guided wave propagation with the increase of defect size. An explanation is introduced and proved with finite element analysis. The results presented in this paper will have a very significant impact on understanding of delamination detection in multilayered composite structures including adhesive bonded structures.
Residual stresses in diamond coatings grown on WC-Co substrate have been investigated by
X-ray diffraction (XRD) method. Nano-diamond coatings were deposited by microwave
plasma-enhanced chemical vapor deposition technique (MP-CVD). To measure residual stress,
we tried different peak selection and instrument setting mode (χ mode and ω mode). For getting
reliable residual stress value, sin2ψ-method with omega-tilting mode (χ=0) was employed. The
(311) plane of CVD diamond was used with tilting angle (ψ) from -40 to 40 degrees. A
compressive stress of 1.65GPa was obtained by linear fitting the mean d-spacing values of
positive and negative tilting. The occurrence of “ψ-splitting” demonstrates the existence of
non-zero shear stress normal to the surface.
Abrasive jet micro-machining (AJM), in which abrasive particles are accelerated by air and directed toward a target, has been used to make components for micro-electro-mechanical (MEMS) and micro-fluidic capillary electrophoresis devices. One of the disadvantages of AJM is that the compressed air jet used to propel the erodent particles diverges significantly after the nozzle exit, increasing the size of the blast zone and the width of the smallest channel or hole that can be machined without the use of a patterned erosion-resistant mask that defines the micro-feature edges. Abrasive slurry jet micro-machining (ASJM) is similar to AJM except that pressurized water, instead of air, is used to accelerate the suspended abrasive particles such as garnet or alumina (Al2O3). In both AJM and ASJM, the material removal occurs by erosion. However, for the same jet dimension and low speed, slurry jets have a much lower divergence angle than air jets, allowing for the micro-machining of small features without the use of patterned masks.
In metallurgy, cladding refers to the bonding together of dissimilar metals, normally achieved by extruding two or more metals through a die or pressing sheets together under high pressure. Timely detection of delamination that occurs occasionally during the cladding processes is very important for the industry. This paper presents an EMAT system based on ultrasonic guided wave techniques. The analysis of a three-layer, brass/copper/brass product is also presented including dispersion curves, and interaction of ultrasonic guided wave with delamination defects. The authors observed a cyclic behavior of guided wave propagation with the increase of defect size. An explanation is introduced and proved with finite element analysis. The results presented in this paper will have a very significant impact on understanding of delamination detection in multilayered composite structures including adhesive bonded structures.
Residual stresses in diamond coatings grown on WC-Co substrate have been investigated by
X-ray diffraction (XRD) method. Nano-diamond coatings were deposited by microwave
plasma-enhanced chemical vapor deposition technique (MP-CVD). To measure residual stress,
we tried different peak selection and instrument setting mode (χ mode and ω mode). For getting
reliable residual stress value, sin2ψ-method with omega-tilting mode (χ=0) was employed. The
(311) plane of CVD diamond was used with tilting angle (ψ) from -40 to 40 degrees. A
compressive stress of 1.65GPa was obtained by linear fitting the mean d-spacing values of
positive and negative tilting. The occurrence of “ψ-splitting” demonstrates the existence of
non-zero shear stress normal to the surface.
Concentrated dispersion & emulsion stability and instability analysis.
Formulation and quality control of
• emulsions
• suspensions
• foams
The TurbiScan MA 2000 is designed as a formulation and a product
stability control tool. The early stage detection allows to quickly correct
formulations and to shorten ageing tests.
The kinetic analysis visualisation is the only way to document stability studies in an easy to interpret format. Providing information about the mechanisms involved in a destabilisation, the TurbiScan MA 2000 allows to fully understand these physical processes and to apply the proper correction to the formulation.
Further informations there : http://www.formulaction.com/stability-turbiscan-classic.html
We conducted molecular dynamics simulations to investigate the atomistic edge crack vacancy interactions in graphene. We demonstrate that the crack tip stress field of an existing crack in graphene can be effectively tailored (reduced by over 50% or increased by over 70%) by the strategic placement of atomic vacancies of varied shapes, locations, and orientations near its tip. The crack vacancy interactions result in a remarkable improvement (over 65%) in the fracture strength of graphene. Moreover, at reduced stiffness of graphene, due to a distribution of atomic vacancies, a drastic difference (~60%) was observed between the fracture strengths of two principal crack configurations (i.e. armchair and zigzag). Our numerical simulations provide a remarkable insight into the applicability of the well-established continuum models of crack microdefect interactions for the corresponding atomic scale problems. Furthermore, we demonstrate that the presence of atomic vacancies in close proximity to the crack tip leads to a multiple stage crack growth and, more interestingly, the propagating cracks can be completely healed even under a significantly high applied tensile stress level (~5 GPa). Our numerical experiments offer a substantial contribution to the existing literature on the fracture behavior of two dimensional nanomaterials.
Nano Scale Surface Characterization of Poly Ethyleneterephthalate Silicon Rub...ijtsrd
Atomic force microscopy has been used to investigated the surface properties of different materials, in this paper it is used to measure the surface roughness and surface adhesive force of three different membrane samples Poly ethyleneterephthalate PET , Silicon Rubber SR and PET SRcopolymers. This analytical method allows images representing the topography and adhesive force Phase image of the surface to be captured simultaneously at a molecular nanometer resolution. The distribution of hydrophilic polar groups and the surface roughness on the investigated surfaces ofthese membrane samples influences the subsequent processing of polymeric membrane manufacture as well as their performance. From the results a clear distinction was observed between the three samples in both images the topography surface roughness images and adhesive force images. Promising result were obtained for the PET SRcopolymer samples to be a good candidate in membrane separation applications. This study may also help to explain the differences in membrane performances and efficiency during applications in the separation process. Dr. Abduelmaged Abduallah | Dr. Kamal M. Sassi | Dr. Mustafa T. Yagub "Nano-Scale Surface Characterization of Poly (Ethyleneterephthalate) - Silicon Rubber Copolymers using Atomic Force Microscopy" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-5 | Issue-4 , June 2021, URL: https://www.ijtsrd.compapers/ijtsrd43688.pdf Paper URL: https://www.ijtsrd.comengineering/chemical-engineering/43688/nanoscale-surface-characterization-of-poly--ethyleneterephthalate--silicon-rubber-copolymers-using-atomic-force-microscopy/dr-abduelmaged-abduallah
Abstract: A terahertz sub-surface scanner is introduced that utilizes reflection mode non-contact
interrogation of surfaces and interior layers of composite substrates with resolution of ~1 nm. Quantitative
measurements are done by implementing a modified Beer-Lambert’s law.
Amorphous-nano-crystalline silicon composite thin films (a-nc-Si:H) samples were synthesized by
Plasma Enhanced Chemical Vapor Deposition technique. The measurement of DC conductivities was
accomplished using Dielectric spectroscopy (Impedance Spectroscopy) in wide frequency and temperature range.
In analysis of impedance data, two approaches were tested: the Debye type equivalent circuit with two parallel R
and CPEs (constant phase elements) and modified one, with tree parallel R and CPEs including crystal grain
boundary effects. It was found that the later better fits to experimental results properly describes crystal grains
dielectric effect and hydrogen concentration indicating presence of strain. The amorphous matrix showed larger
resistance and lower capacity than nano-crystal phase. Also it was found that composite silicon thin film cannot
be properly described by equivalent circuit only with resistors and constant phase elements in serial relation
Abstract
Terahertz sub-surface imaging offers an effective solution for surface and 3D imaging because of minimal
sample preparation requirements and its ability to “see” below the surface. Another important property is the ability
to inspect on a layer-by layer basis via a non-contact route, non-destructive route. Terahertz 3D imager designed
at Applied Research and Photonics (Harrisburg, PA) has been used to demonstrate reconstructive imaging with a
resolution of less than a nanometer. Gridding with inverse distance to power equations has been described for 3D
image formation. A continuous wave terahertz source derived from dendrimer dipole excitation has been used for
reflection mode scanning in the three orthogonal directions. Both 2D and 3D images are generated for the analysis
of silver iodide quantum dots’ size parameter. Layer by layer image analysis has been outlined. Graphical analysis
was used for particle size and layer thickness determinations. The demonstrated results of quantum dot particle
size checks well with those determined by TEM micrograph and powder X-ray diffraction analysis. The reported
non-contact measurement system is expected to be useful for characterizing 2D and 3D naomaterials as well as for process development and/or quality inspection at the production line.
Concentrated dispersion & emulsion stability and instability analysis.
Formulation and quality control of
• emulsions
• suspensions
• foams
The TurbiScan MA 2000 is designed as a formulation and a product
stability control tool. The early stage detection allows to quickly correct
formulations and to shorten ageing tests.
The kinetic analysis visualisation is the only way to document stability studies in an easy to interpret format. Providing information about the mechanisms involved in a destabilisation, the TurbiScan MA 2000 allows to fully understand these physical processes and to apply the proper correction to the formulation.
Further informations there : http://www.formulaction.com/stability-turbiscan-classic.html
We conducted molecular dynamics simulations to investigate the atomistic edge crack vacancy interactions in graphene. We demonstrate that the crack tip stress field of an existing crack in graphene can be effectively tailored (reduced by over 50% or increased by over 70%) by the strategic placement of atomic vacancies of varied shapes, locations, and orientations near its tip. The crack vacancy interactions result in a remarkable improvement (over 65%) in the fracture strength of graphene. Moreover, at reduced stiffness of graphene, due to a distribution of atomic vacancies, a drastic difference (~60%) was observed between the fracture strengths of two principal crack configurations (i.e. armchair and zigzag). Our numerical simulations provide a remarkable insight into the applicability of the well-established continuum models of crack microdefect interactions for the corresponding atomic scale problems. Furthermore, we demonstrate that the presence of atomic vacancies in close proximity to the crack tip leads to a multiple stage crack growth and, more interestingly, the propagating cracks can be completely healed even under a significantly high applied tensile stress level (~5 GPa). Our numerical experiments offer a substantial contribution to the existing literature on the fracture behavior of two dimensional nanomaterials.
Nano Scale Surface Characterization of Poly Ethyleneterephthalate Silicon Rub...ijtsrd
Atomic force microscopy has been used to investigated the surface properties of different materials, in this paper it is used to measure the surface roughness and surface adhesive force of three different membrane samples Poly ethyleneterephthalate PET , Silicon Rubber SR and PET SRcopolymers. This analytical method allows images representing the topography and adhesive force Phase image of the surface to be captured simultaneously at a molecular nanometer resolution. The distribution of hydrophilic polar groups and the surface roughness on the investigated surfaces ofthese membrane samples influences the subsequent processing of polymeric membrane manufacture as well as their performance. From the results a clear distinction was observed between the three samples in both images the topography surface roughness images and adhesive force images. Promising result were obtained for the PET SRcopolymer samples to be a good candidate in membrane separation applications. This study may also help to explain the differences in membrane performances and efficiency during applications in the separation process. Dr. Abduelmaged Abduallah | Dr. Kamal M. Sassi | Dr. Mustafa T. Yagub "Nano-Scale Surface Characterization of Poly (Ethyleneterephthalate) - Silicon Rubber Copolymers using Atomic Force Microscopy" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-5 | Issue-4 , June 2021, URL: https://www.ijtsrd.compapers/ijtsrd43688.pdf Paper URL: https://www.ijtsrd.comengineering/chemical-engineering/43688/nanoscale-surface-characterization-of-poly--ethyleneterephthalate--silicon-rubber-copolymers-using-atomic-force-microscopy/dr-abduelmaged-abduallah
Abstract: A terahertz sub-surface scanner is introduced that utilizes reflection mode non-contact
interrogation of surfaces and interior layers of composite substrates with resolution of ~1 nm. Quantitative
measurements are done by implementing a modified Beer-Lambert’s law.
Amorphous-nano-crystalline silicon composite thin films (a-nc-Si:H) samples were synthesized by
Plasma Enhanced Chemical Vapor Deposition technique. The measurement of DC conductivities was
accomplished using Dielectric spectroscopy (Impedance Spectroscopy) in wide frequency and temperature range.
In analysis of impedance data, two approaches were tested: the Debye type equivalent circuit with two parallel R
and CPEs (constant phase elements) and modified one, with tree parallel R and CPEs including crystal grain
boundary effects. It was found that the later better fits to experimental results properly describes crystal grains
dielectric effect and hydrogen concentration indicating presence of strain. The amorphous matrix showed larger
resistance and lower capacity than nano-crystal phase. Also it was found that composite silicon thin film cannot
be properly described by equivalent circuit only with resistors and constant phase elements in serial relation
Abstract
Terahertz sub-surface imaging offers an effective solution for surface and 3D imaging because of minimal
sample preparation requirements and its ability to “see” below the surface. Another important property is the ability
to inspect on a layer-by layer basis via a non-contact route, non-destructive route. Terahertz 3D imager designed
at Applied Research and Photonics (Harrisburg, PA) has been used to demonstrate reconstructive imaging with a
resolution of less than a nanometer. Gridding with inverse distance to power equations has been described for 3D
image formation. A continuous wave terahertz source derived from dendrimer dipole excitation has been used for
reflection mode scanning in the three orthogonal directions. Both 2D and 3D images are generated for the analysis
of silver iodide quantum dots’ size parameter. Layer by layer image analysis has been outlined. Graphical analysis
was used for particle size and layer thickness determinations. The demonstrated results of quantum dot particle
size checks well with those determined by TEM micrograph and powder X-ray diffraction analysis. The reported
non-contact measurement system is expected to be useful for characterizing 2D and 3D naomaterials as well as for process development and/or quality inspection at the production line.
Abstract
Terahertz spectral analysis has been conducted on epitaxially grown semiconductor structures. Epitaxially grown semiconductors are important for microelectronic and optoelectronic devices and also for integrated circuits
fabricated using semiconductors. In this paper, we report results of terahertz time-domain spectroscopy of grown
SiGe layers on Ge buffer and separately a Ge buffer that was grown on a Si <001> wafer. In particular, evolution of
the time-domain spectra as a function of thickness of both samples was investigated by the terahertz pump-probe
technique. Representative spectra were analyzed to determine the respective layers’ spectral signatures. It was found that the spectroscopic analysis uniquely identified different layers by characteristic absorbance peaks. In addition, terahertz imaging was conducted in a non-destructive, non-contact mode for detecting lattice stacking fault and dislocations. Sub-surface imaging of grown SiGe layers on Ge buffer and that of the Ge buffer grown on a Si wafer reveals interesting lattice features in both samples. A comparison with TEM images of the samples exhibits that the terahertz image reproduces the dimensions found from TEM images within the experimental error limits. In particular, 3D images of both samples were generated by the terahertz reconstructive technique. The images were analyzed by graphical means to determine the respective layer thicknesses. Thus, this technique offers a versatile tool for both semiconductor research and in-line inspections.
This review article describes the fundamental principles of atomic force spectroscopy (AFS) and how this technique became a useful tool to investigate adhesion forces. AFS is a technique derived from atomic force microscopy (AFM) and can determine, at every location of the sample
surface, the dependence of the interaction on the probe–sample distance. AFS provides valuable information, at the nano-scale, such as, for example: (i) how the magnitude of the adhesion force depends on long- and short-range interactions and (ii) the tip–sample contact area. An overview about the theory and experiments with local force spectroscopy, force imaging spectroscopy, chemical
force microscopy and colloidal probe technique is presented. The many applications of the AFS technique for probing surface interactions open up new possibilities to evaluate adhesion, an important characteristic of materials.
MODELING STUDY OF LASER BEAM SCATTERING BY DEFECTS ON SEMICONDUCTOR WAFERSjmicro
Accurate modeling of light scattering from nanometer scale defects on Silicon wafersiscritical for enabling
increasingly shrinking semiconductor technology nodes of the future. Yet, such modeling of defect
scattering remains unsolved since existing modeling techniques fail to account for complex defect and
wafer geometries. Here, we present results of laser beam scattering from spherical and ellipsoidal
particles located on the surface of a silicon wafer. A commercially available electromagnetic field solver
(HFSS) was deployed on a multiprocessor cluster to obtain results with previously unknown accuracy
down to light scattering intensity of -170 dB. We compute three dimensional scattering patterns of silicon
nanospheres located on a semiconductor wafer for both perpendicular and parallel polarization and show
the effect of sphere size on scattering. We further computer scattering patterns of nanometer scale
ellipsoidal particles having different orientation angles and unveil the effects of ellipsoidal orientation on
scattering.
MODELING STUDY OF LASER BEAM SCATTERING BY DEFECTS ON SEMICONDUCTOR WAFERSjmicro
Accurate modeling of light scattering from nanometer scale defects on Silicon wafersiscritical for enabling
increasingly shrinking semiconductor technology nodes of the future. Yet, such modeling of defect
scattering remains unsolved since existing modeling techniques fail to account for complex defect and
wafer geometries. Here, we present results of laser beam scattering from spherical and ellipsoidal
particles located on the surface of a silicon wafer. A commercially available electromagnetic field solver
(HFSS) was deployed on a multiprocessor cluster to obtain results with previously unknown accuracy
down to light scattering intensity of -170 dB. We compute three dimensional scattering patterns of silicon
nanospheres located on a semiconductor wafer for both perpendicular and parallel polarization and show
the effect of sphere size on scattering. We further computer scattering patterns of nanometer scale
ellipsoidal particles having different orientation angles and unveil the effects of ellipsoidal orientation on
scattering.
Terahertz (T-ray) techniques for measuring, profiling, and mapping of semiconductor features and doping concentration of via a T-ray volume imaging route, deep-level spectroscopy, and empirical modeling; and application thereof for semiconductor doping concentration thickness profiling and surface mapping for both undoped and doped semiconductors.
This paper outlines the basic technology and economic model of the core silicon technology. Silicon is the second most abundant element on the earth’s crust but there is no specific deposit or mine for silicon.
The only source for silicon is “sand” that the earth has an abundant supply. Here we outline the basic steps of manufacturing silicon ingot and wafers. It is projected that, once produced, these products will gain immediate market access, thus creating economic activities in a reasonably short period of time. The three initial products that could stem from the basic silicon ingot are silicon wafers, for both semiconductor and solar cell applications, and optical fiber for communication. This report focuses on the essential silicon
technology to produce silicon ingot, and silicon wafer, as the first step. Finally, the historic data available for the silicon wafer consumption per year have been modeled with the well-known Bass diffusion model.
It was found that with modified parameters, the Bass model fits the historic data well and the same model allows a projection for a few years in the future. This projected economic activities, therefore, encourages a social transformation towards a technological self-sufficiency.
Keywords: Silicon technology; Bass diffusion model; Silicon wafer consumption; Social transformation;
Technological self-sufficiency
DOI: 10.31031/NRS.2022.11.000760
Abstracts and Bios of the Chief Guest, Guest of Honor, distinguished Speakers and Panelists of the 2021 AABEA-FOBANA joint Seminar in Washington DC, November 27 and 28, 2021.
Lattice dilation of metallic nickel film deposited by plasma-spraying on a ceramic layer that is also prepared by plasma-spraying, has been investigated by high resolution terahertz imaging and sequential zooming of the images to quantify the lattice parameter by graphical analysis. A metallic nickel sample
was first imaged, and its measured lattice constant was found to be in agreement with the known value.
Subsequently, four additional samples containing plasma-sprayed nickel film have also been imaged via an identical procedure. The lattice images of all samples were used for graphical analysis and quantification of the respective lattice parameters. Four samples, viz., 77, 81, 129 and 111 have been analyzed and their lattice dilation was investigated. It was found that the lattice distance (d) of these samples is in the order as, d77 < d81 < d129 < d111 and higher than the value of metallic nickel. Unit cell volume and density were also calculated for each sample from the measured lattice parameter. The density was found in the decreasing order for the 4 samples; i.e., ρρρ ρ77 > ρ81 > ρ129 > ρ111 and the density values are significantly lower than the value for nickel. To our knowledge, this is the first direct evidence of the lattice dilation of plasma-sprayed metallic nickel measured via the terahertz lattice imaging, without requiring an electron microscope. Thus, the results presented herein establish an exciting extension of camera-less, reconstructive terahertz imaging technique that produces such a clear lattice image of nickel and allows to quantify the lattice parameter. The technique, however, is a general one, applicable to any material.
Abstract— This paper demonstrates overcoming of the Abbe diffraction limit (ADL) on image resolution. Here, terahertz multispectral reconstructive imaging has been described and used for analyzing nanometer size metal lines fabricated on a silicon wafer. It has also been demonstrated that while overcoming the ADL is a required condition, it is not sufficient to achieve sub-nanometer image resolution with longer wavelengths. A nanoscanning technology has been developed that exploits the modified Beer-Lambert’s law for creating a measured reflectance data matrix and utilizes the ‘inverse distance to power equation’ algorithm for achieving 3D, sub-nanometer image resolution. The nano-lines images reported herein, were compared to SEM images. The terahertz images of 70 nm lines agreed well with the TEM images. The 14 nm lines by SEM were determined to be ~15 nm. Thus, the wavelength dependent Abbe diffraction limit on image resolution has been overcome. Layer-by-layer analysis has been demonstrated where 3D images are analyzed on any of the three orthogonal planes. Images of grains on the metal lines have also been analyzed. Unlike electron microscopes, where the samples must be in the vacuum chamber and must be thin enough for electron beam transparency, terahertz imaging is non-destructive, non-contact technique without laborious sample preparation.
Abstract:
This paper demonstrates overcoming of the Abbe diffraction limit (ADL) on image resolution. Here, terahertz multispectral reconstructive imaging has been described and used for analyzing nanometer size metal lines fabricated on a silicon wafer. It has also been demonstrated that while overcoming the ADL is a required condition, it is not sufficient to achieve sub-nanometer image resolution with longer wavelengths. A nanoscanning technology has been developed that exploits the modified Beer-Lambert’s law for creating a measured reflectance data matrix and utilizes the ‘inverse distance to power equation’ algorithm for achieving 3D, sub-nanometer image resolution. The nano-lines images reported herein, were compared to SEM images. The terahertz images of 70 nm lines agreed well with the TEM images. The 14 nm lines by SEM were determined to be 15 nm. Thus, the wavelength dependent Abbe diffraction limit on image resolution has been overcome. Layer-by-layer analysis has been demonstrated where 3D images are analyzed on any of the three orthogonal planes. Images of grains on the metal lines have also been analyzed. Unlike electron microscopes, where the samples must be in the vacuum chamber and must be thin enough for electron beam transparency, terahertz imaging is non-destructive, non-contact technique without laborious sample preparation.
Two critical nanoscale design parameters (CNDPs); namely, surface chemistry and interior compositions of poly(amidoamine) (PAMAM) dendrimers were systematically engineered to produce unique hyperpolarizable, electro-optical substrates. These electro-optically active dendritic films were demonstrated to produce high quality, continuous wave terahertz radiation when exposed to a suitable pump laser that could be used for spectrometry and molecular imaging. These dendrimer based dipole excitation (DDE) terahertz sources were used to construct a working spectrometer suitable for many practical applications including THz imaging and analysis of encapsulated hydrogen species in fullerenes.
Abstract: Non-destructive terahertz reflection interferometry offers many advantages for sub-surface inspection such as interrogation of hidden defects and measurement of layers’ thicknesses. Here, we describe a terahertz reflection interferometry (TRI) technique for non-contact measurement of paint panels where the paint is comprised of different layers of primer, basecoat, topcoat and clearcoat. Terahertz interferograms were generated by reflection from different layers of paints on a metallic substrate. These interferograms’ peak spacing arising from the delay-time response of respective layers, allow one to model the thicknesses of the constituent layers. Interferograms generated at different incident angles show that the interferograms are more pronounced at certain angles than others. This “optimum” angle is also a function of different paint and substrate combinations. An automated angular scanning algorithm helps visualizing the evolution of the interferograms as a function of incident angle and also enables the identification of optimum reflection angle for a given paint-substrate combination. Additionally, scanning at different points on a substrate reveals that there are observable variations from one point to another of the same sample over its entire surface area. This ability may be used as a quality control tool for in-situ inspection in a production line.
Electro-optic Dendrimer is used to generate milliwatts of terahertz power by difference frequency
method. A terahertz time-domain spectrometer (THz-TDS) has been designed around this source that
exhibits wide broadband terahertz range, 0.1 to 35 THz. Examples of molecular characterization are discussed
for three common explosives and the vibrational states of Fullerenes. The explosives’ spectra are
unique for each explosive that allow detection and identification of the species. The Fullerenes C60 and
H2@C60 also exhibit distinctively different spectra and absorbance states indicating that the THz-TDS is
suitable for probing increased number of vibrational states expected from molecular vibrations.
2011 Elsevier B.V. All rights reserved.
http://thz-pacifichem.blogspot.com/
Call for Abstracts
Advances in Terahertz Spectroscopy and Imaging (#413)
THE INTERNATIONAL CHEMICAL CONGRESS OF
PACIFIC BASIN SOCIETIES
Honolulu, Hawaii, USA DECEMBER 15 - 20, 2015
Dear Colleague:
It is our great pleasure to announce a symposium on “Advances in Terahertz Spectroscopy and Imaging” at the Pacifichem 2015 in Hawaii. Please see the link above for details. Contributions are solicited addressing subjects from all walks of terahertz applications. As an emerging area of science and technology, terahertz applications, such as spectroscopy, reflectometry and imaging, have the potential for addressing some of the critical problems of the 21st century. As indicated by increased attendance and number of papers in the past, the proposed symposium will fill a gap in the technical program by attracting the terahertz spectroscopy and related communities from all over the world. While there are other spectroscopic techniques, terahertz technology provides unique information that is not available from the predecessors. Therefore, this symposium solicits papers on the advances of terahertz applications in crucial matters such as: biomedical research, early detection of skin cancer, transdermal drug delivery, biopharmaceuticals, materials for energy, conservation and forensic science, security & screening, geology and minerals, semiconductors and any other relevant areas. This symposium will present an opportunity for the exchange of knowledge in a global forum, including results and discussions of current and breakthrough terahertz techniques and their applications. Papers, including spectroscopic, reflectometry and imaging techniques on the above mentioned areas and other terahertz applications in solving important problems are welcome. Formal abstracts submission will be open from January 1 – April 3, 2015. See this link for details of submission: http://www.pacifichem.org/congress-details/abstracts/
Sincerely yours,
Anis Rahman (USA): a.rahman@arphotonics.net
Choonho Kim (S Korea): chkim1202@gmail.com
Wolfgang Jaeger (Canada): wolfgang.jaeger@ualberta.ca
Sing Kiong Nguang (New Zealand): sk.nguang@auckland.ac.nz
Yacov Shamash (USA): yacovshamash@yahoo.com
Terahertz dynamic scanning reflectometry (TDSR) was used for measuring layered materials’ deformation kinetics
spectra. Multi-layered materials are used for protective devices such as helmet and body armor. An in-situ measurement of deformation profile and other dynamic characteristics is important when such material is subjected to ballistic impacts. Current instrumentation is limited in their abilities to provide sub-surface information in a non-destructive fashion. A high sensitivity TDSR has been used to measure dynamic surface deformation characteristics in real-time (in-situ) and also at post deformation (ex-situ). Real-time ballistic deformation kinetics was captured with a high speed measurement system. The kinetics spectra was used to compute a number of crucial parameters such as deformation
length and its propagation profile, the relaxation position, and the macroscopic vibration profile. In addition, the loss of mass due to impact was quantified for accurate determination of the trauma causing energy. For non-metallic substrates, a transmitted beam was used to calibrate mass loss, a priori, of the laminate layers due to impact. Deformation kinetics information may then be used to formulate trauma diagnosis conditions from blunt hit via the Sturdivan criterion [1].
The basic difference in the proposed approach is that here diagnostic criteria are inferred by measuring the helmet itself; no need to draw blood or any biopsy from the patient.
The Art of the Pitch: WordPress Relationships and SalesLaura Byrne
Clients don’t know what they don’t know. What web solutions are right for them? How does WordPress come into the picture? How do you make sure you understand scope and timeline? What do you do if sometime changes?
All these questions and more will be explored as we talk about matching clients’ needs with what your agency offers without pulling teeth or pulling your hair out. Practical tips, and strategies for successful relationship building that leads to closing the deal.
UiPath Test Automation using UiPath Test Suite series, part 3DianaGray10
Welcome to UiPath Test Automation using UiPath Test Suite series part 3. In this session, we will cover desktop automation along with UI automation.
Topics covered:
UI automation Introduction,
UI automation Sample
Desktop automation flow
Pradeep Chinnala, Senior Consultant Automation Developer @WonderBotz and UiPath MVP
Deepak Rai, Automation Practice Lead, Boundaryless Group and UiPath MVP
Key Trends Shaping the Future of Infrastructure.pdfCheryl Hung
Keynote at DIGIT West Expo, Glasgow on 29 May 2024.
Cheryl Hung, ochery.com
Sr Director, Infrastructure Ecosystem, Arm.
The key trends across hardware, cloud and open-source; exploring how these areas are likely to mature and develop over the short and long-term, and then considering how organisations can position themselves to adapt and thrive.
"Impact of front-end architecture on development cost", Viktor TurskyiFwdays
I have heard many times that architecture is not important for the front-end. Also, many times I have seen how developers implement features on the front-end just following the standard rules for a framework and think that this is enough to successfully launch the project, and then the project fails. How to prevent this and what approach to choose? I have launched dozens of complex projects and during the talk we will analyze which approaches have worked for me and which have not.
Slack (or Teams) Automation for Bonterra Impact Management (fka Social Soluti...Jeffrey Haguewood
Sidekick Solutions uses Bonterra Impact Management (fka Social Solutions Apricot) and automation solutions to integrate data for business workflows.
We believe integration and automation are essential to user experience and the promise of efficient work through technology. Automation is the critical ingredient to realizing that full vision. We develop integration products and services for Bonterra Case Management software to support the deployment of automations for a variety of use cases.
This video focuses on the notifications, alerts, and approval requests using Slack for Bonterra Impact Management. The solutions covered in this webinar can also be deployed for Microsoft Teams.
Interested in deploying notification automations for Bonterra Impact Management? Contact us at sales@sidekicksolutionsllc.com to discuss next steps.
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Dev Dives: Train smarter, not harder – active learning and UiPath LLMs for do...UiPathCommunity
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👩🏫 Lenka Dulovicova, Product Program Manager, UiPath
Dev Dives: Train smarter, not harder – active learning and UiPath LLMs for do...
Asmc2014 5.8
1. Effective testing for wafer reject minimization
by terahertz analysis and sub-surface imaging
Anis Rahman and Aunik K. Rahman
Applied Research & Photonics
470 Friendship Road, Suite 10
Harrisburg, PA 17111, USA
a.rahman@arphotonics.net
Abstract— This paper outlines applications of terahertz
spectrometry, terahertz reflectometry and sub-surface imaging
for effective characterization of various aspects of semiconductor
wafer testing. Exemplary results of scanning a wafer have been
analyzed for defect determination. Additionally, terahertz
reflectometry for controlling wafer polishing for planarization
has been exemplified via high precision thickness monitoring.
Application of terahertz spectrometry for identifying self-
assembled monolayer (SAM) on a wafer is also outlined with
example. The technique may be extended to other substrates
transparent to terahertz radiation. Characterizing different SAM
coated silicon wafers for identifying two different SAM species
has been discussed. The Fourier transform absorbance spectra
of both SAM specimens reveals several distinguishable
absorbance peaks that may be used as signatures of the
respective SAMs. The SAM having 18 carbon chain exhibits
higher absorbance than that of the SAM comprised of 8 carbon
chain. This is consistent with the higher molecular weight of the
former.
Keywords—Terahertz spectrometry; Terahertz reflectometry;
Terahertz scanner; sub-surface imaging; wafer defect analysis;
Wafer thickness monitoring; Self-assembled monolayer on wafer
I. INTRODUCTION
Terahertz spectrometry [1] and reflectometry [2] offers an
effective solution for wafer reject minimization by means of
sub-surface, nano scale, 3D imaging, via a non-destructive and
non-contact route. A terahertz sub-surface 3D imager (Applied
Research & Photonics) has been used for the current
investigations. Simultaneous reflection and transmission
measurements allow inspection of semiconductor wafers
during fab processes (in-situ) as well as for post-fab characteri-
zations (ex-situ). The intensity of the reflected terahertz beam
is proportional to the specific features (layers) of the specimen
under test. Therefore, measured intensity may be modeled in
terms of suitable physical parameters such as refractive index,
density, dielectric constant, etc., via a modified Beer-Lambert’s
law. For a given wafer, all material parameters remain
unchanged during measurements, because, terahertz radiation
is non-ionizing and does not perturb the intrinsic properties.
Thus, the reflectance, is proportional to the variations in
materials at the point where the beam is incident. As such, the
reflectance is dependent on the spatial and angular coordinates:
( ) A 3D reconstructed image generated from
reflectance, therefore, will yield the characteristic features
(patterns) on the substrate. Another advantage of the terahertz
scanner is that silicon and other semiconductor wafers are
transparent at these wavelengths. Therefore, scanning may be
done across the thickness of a wafer for inspecting internal
layers. So, if there is a hole or void on the substrate or in any of
the sub-surface layers, that will be identifiable from both
reflected and transmitted intensities. Based on the above
principle, a signature of a given defect may be established. Any
defect such as, inclusions, cracks, non-uniformity, or
particulate foreign material can be detected and identified by
this technique. Moreover, defect size may be estimated from
either a 2-D scan, or 3-D scanned reconstructed imaging. The
terahertz nano-scanner deploys a non-contact measurement
system with an adjustable stand-off distance. The sample space
is adjustable to accommodate required sample size. A rotary
axis enables examination of a wafer (or other sample) from
different viewing angles. This is important because cracks or
other non-uniformities might not be along a straight line-of-
sight. Thus an angular scan enables viewing hidden features. In
addition, with the advent of the angular axis, one can scan
cylindrical objects in a conformal fashion.
Another important issue for the semiconductor wafers is the
requirement of planarization as the fabrication process
progresses with layer by layer deposition and patterning.
Chemical and mechanical polishing (CMP) used for wafer
planarization requires just sufficient material to be removed,
but too much removal can result in failure/rejection of the
wafer. As such precise thickness control, on the order of
nanometers, is required for lowering the reject rate. Terahertz
transmission and/or reflection measurements can be used for
monitoring the CMP process. Here, we report a technique for
controlling the polishing process based on given thickness
criterion. The removal of material from the wafer surface is a
complex function of the polishing slurry, spin speed and
duration, among other factors. However, a straightforward
2. method that minimizes monitoring of individual variables is
the direct measurement of the thickness of the wafer, from
which the mass of the removed material may also be
calculated. In this technique a terahertz beam is reflected off of
the polishing surface while a transmission measurement may
also be carried out simultaneously. A requirement of this
technique is a rigorous calibration of the material removal as a
function of polishing conditions while all physical parameters
essentially remain fixed. This process reduces the number of
control variables to a single parameter, i.e., reflected (and/or
transmitted) power vs. thickness removed.
Additionally, semiconductor wafers’ surface needs to be
modified for different chemistry in preparation of processes
such as patterning of waveguides or CMOS process with
different functionalities. Common surface modification
involves making a wafer hydrophilic or if it is already
hydrophilic then converting it to hydrophobic. This is uniquely
done by various self-assembled monolayers (SAMs). However,
it is difficult to characterize the SAMs with common laboratory
instruments (e.g., UV/Vis, Raman or FTIR), because, SAMs
being only one molecule thick layer, physical characterization
between different SAMs applied on wafer surfaces is
challenging. Terahertz spectroscopy offers an advent of
characterizing the molecular systems – even with minimal
structural and mass differences – owing to its ultra-high
sensitivity stemmed from the fact that terahertz photons
interact with the entire molecule as opposed to a bond or a
charge states as used by its predecessors.
In the followings, exemplary results of wafer scans have
been analyzed for defect determination. Additionally, terahertz
reflectometry for wafer polishing has been exemplified with
data. Finally, application of terahertz spectrometry for
identifying self-assembled monolayer (SAM) on a wafer is also
outlined with example.
II. EXPERIMENTAL
Fig. 1 displays a schematic diagram of the terahertz nano-
scanner. Here the wafer is mounted on a rotary stage which is
mounted on a XYZ stage. The measurement system comprises
of an electro-optic dendrimer based continuous wave (CW)
terahertz source and a matching detection system that was
described elsewhere [3]. All positioning stages are automated;
the linear stages have a resolution of ~25 nm. As shown in Fig.
1, this design is based on normal incidence of the terahertz
beam to the target. In case of normal incidence, the incident
beam is the sum of the reflected, transmitted, absorbed and
scattered intensities. Assuming the material properties remain
unchanged during measurement, the reflectance will be
proportional to the material characteristics. Ordinarily, the
Beer-Lambert’s law is used to determine the concentration, C,
of a solute in a solvent from absorbance data: A= εlC, where l
is the path length and is the extinction coefficient (or molar
absorptivity). Since the reflectance, R, is material dependent, a
modified Beer-Lambert’s law may be stated as,
( ) ( ) ( ) ( ), (1)
where, the reflectance is coordinate dependent because the
materials on a wafer is position dependent, which in turn
causes variation in the path length, ( ), and consequently
variation in the coefficient ( ) . It is notable that, the
coefficient ( ) may be used for modeling desired material
parameters such as density, dielectric constant, refractive
index, etc. Obviously, this modeling gives the effective value
of the chosen parameter as opposed to the complex quantity.
Mapping of R(r) yields a 3D visualization of the specimen. Fig.
2 shows a 3D surface plot of a wafer where different features
are depicted by different colors and their sizes are as indicated
by the coordinates of the axes.
III. RESULTS AND DISCUSSION
A. Wafer inspection
Fig. 3 shows a pattern of adjacent dies on a wafer revealed
by a 1D scan. Fig. 3 also shows that adjacent layers are
detectable by their unique reflected intensity. A high resolution
scan thus clearly shows the start, the end, and intricate pattern
for each die on a wafer (Fig. 3 lower plot). The repetitive
pattern from high resolution scan serves as a distinguishing
Figure 1. Schematic representation of the nano-scanner.
Fig. 2. A 3D image of a wafer area.
3. metric for good dies from the bad ones. Since the scans are in
exact coordinates, one can inspect the patterns closely for their
irregularity and/or defect conditions. Once a defect position is
identified, insight from process parameters may be used to
Fig. 3. High resolution scan pattern from two different segments of a
wafer. Both top and bottom segment clearly show the start, end,
and intricate pattern for each die.
Fig. 4. Reproducibility of the traces. Slight mismatch is due to the
course resolution of the stage.
deduce the actual nature of the defect. Fig. 4 shows the
reproducibility of the measurements. Fig. 5 shows a
reconstructed sub-surface image of an area; a comparison of
such images between a good and a bad area will reveal the
exact position and layer of the defect.
Fig. 5. Reconstructed 3D representation of problem area. A series of
1-D scan in the X-direction was made at different heights to
reconstruct the 3-D profile. Some small features are visible.
B. Wafer polishing
In order to demonstrate the resolution of mass removal of a
silicon wafer by polishing, a piece of Si-wafer was gradually
polished by hand on an 800-grit sand paper. The wafer was
weighed after each polish by a lab microbalance, mounted on
the THz spectrometer (Fig. 6) and transmitted power (in
counts) vs. the removed mass was recorded. Fig. 7 shows that
as the mass is removed by polishing, the transmitted power
increases successively for each polish, indicating that
transmitted power is an inverse function of removed mass.
The results were used for computing the corresponding
thickness from known area and density of the wafer. Fig. 8
shows the computed thickness vs. the change in measured
power. The slope of Fig. 8 indicates that for each nanometer
thickness removed, the counts difference is 8.15 million. The
noise floor of the detection system is ~ ± 5103
counts. Thus,
the uncertainly in the thickness data of Fig. 8 is < ± 10 pm.
Therefore, it is demonstrated that THz transmission
measurement can be used for high precision thickness
monitoring of wafer’s planarization process. Thus, a control
system operated by this monitoring system is expected to
maintain high level of uniformity of the CMP process.
However, the actual CMP process involves use of polishing
slurry and other chemicals. Therefore, the performance of this
system must be determined via calibration for an actual CMP
system. In addition, different calibration will be necessary for
different slurry and polishing protocol combinations.
C. Self-assembled monolayers on wafer
Self-assembled monolayers (SAMs) were fabricated on
double side polished silicon wafers [4]. Two different SAMs
have been used. (1): n-Octadecyltrichlorosilane (abbreviated
as C-18), Mw = 387.93 g/mol; and (2): 7-OCT-1-
Enyltrichlorosilane (abbreviated as C-8); Mw = 245.65 g/mol.
The experimental setup was described elsewhere [1]. As
received SAM coated wafers were mounted on the
spectrometer with similar arrangement as shown in Fig. 6.
Terahertz time-domain spectra were acquired with the
TeraSpectra front end [5]. Fig. 9 shows the comparison of
time-domain signals of the two samples. The SAM C-8,
having lower number of carbons, exhibit higher transmission
4. Fig. 6. A piece of Si-wafer mounted on a fixture for polishing
experiment and analysis by THz spectrometry. The mount
ensures positioning of the wafer at the same place after every
polish.
Fig. 7. Transmitted power (counts) increases as a function of
removed mass of wafer by polishing.
compared to the SAM C-18. The Fourier transform
absorbance spectra of both specimens are shown in Fig. 10.
Here also the C-18 SAM-wafer exhibits higher absorbance
than that of C-8 SAM-wafer; consistent with the higher Mw of
C-18. Fig. 11 shows a close-up of Fig. 10 where several peaks
are identified by their frequency that may be used as
distinguishing features between the two SAMs. The
absorbance of C-18 SAM is always higher than that of C-8
SAM; this observation is consistent with C-18’s higher Mw.
The spectra shows clear identifying characteristics between
the two SAM species (see Fig. 11).
Fig. 8. Computed cumulative layer thickness removed vs THz
transmitted power (counts). The data is fitted by y = 8.15x,
where x is in millions.
IV. SUMMARY AND CONCLUSIONS
In summary, a terahertz scanner has been used to detect
defects in a semiconductor wafer. A high resolution scan
clearly shows the start, the end, and intricate patterns for each
die on a wafer. Since the scan is in scale in all three
dimensions, the defect position may be pin pointed. Terahertz
reconstructed imaging allows visual inspection of wafers both
on the surface and also the layers under the surface in a non-
destructive fashion. All measurements are done by non-contact
means. It is also demonstrated that terahertz transmission
measurements may be used with high precision for monitoring
and controlling wafer CMP process. The technique may be
extended to other substrates transparent to terahertz radiation.
We also demonstrate that terahertz spectroscopy can be
effectively used to identify different SAM coated silicon
wafers for the SAM species. Two SAMs used here are 8 and
18 carbons long, respectively. The C-18 SAM-wafer exhibits
higher absorbance than C-8. This is assigned to the higher
molecular weight of C-18. The Fourier transform absorbance
spectra of both specimens also exhibits higher absorbance for
C-18 than that of C-8 SAM-wafer. This is also consistent with
the higher Mw of C-18. Thus the terahertz system of the
present study offers a reasonable and accurate solution for
different aspects of wafer inspection, thereby aiding to reduce
the wafer rejects during fabrication.
Si wafer
5. Fig. 9. Temporal signal of silicon wafer coated with two different
SAM. C8 having 8 carbon chain has a higher transmission
compared to C18, an 18 carbon chain molecule.
Fig. 10. The absorbance spectra of two SAMs on silicon wafer.
Several peaks may be identified for characteristic differences
between the two SAM species.
REFERENCES
[1] Rahman, Anis., Dendrimer Based Terahertz Time-Domain Spectroscopy
and Applications in Molecular Characterization. Journal of Molecular
Structure, 2011. 1006: p. 59-65.
[2] A. Rahman, S. Frenchek, B. Kilfoyle, L. Patterkine, A. K. Rahman, and
B. Michiniak-Kohn, “Diffusion kinetics and permeation concentration of
human stratum corneum,” Drug Development & Delivery, May 2012,
pp. 43–49.
[3] A. Rahman and A. K. Rahman, “Wide Range Broadband Terahertz
Emission From High (2) Dendrimer,” in Terahertz Technology and
Applications V, edited by Laurence P. Sadwick, Créidhe M. O'Sullivan,
Proc. SPIE Vol. 8261, 82610H (2012).
[4] “Investigation of self-assembled monolayers on silicon wafer by
terahertz spectrometry,” white paper:
http://arphotonics.net/THzSpectraSAMonSiliconWafer.pdf.
[5] http://arphotonics.net/TeraSpectraBrochure_spec_2011_.pdf
Fig. 11. The absorbance spectra of both SAMs (same as Fig. 10,
but X-axis truncated to 20 THz). Several peaks may be
identified for characteristic differences between the two
SAM species.