2017 5th International Workshop on Low Temperature Bonding for 3D Integration (LTB-3D), 2017
We report direct bonding of liquid crystal polymer and copper film for electrochemical sensing fo... more We report direct bonding of liquid crystal polymer and copper film for electrochemical sensing for the first time. A peel strength of 683 g/cm was observed indicating strong adhesion. X-ray photoelectron and electrochemical impedance spectroscopies were used to characterize the sensing electrodes.
Copper (Cu) film bonded with polymer substrates offers better dimensional stability than that of ... more Copper (Cu) film bonded with polymer substrates offers better dimensional stability than that of deposited Cu especially in humid environment. However, poor adhesion is an issue in both cases. In this paper, we demonstrate a two-step, low temperature direct bonding technique for liquid crystal polymer (LCP) and copper (Cu) using oxygen plasma. The bonded interface showed high peel strength. This strong adhesion is due to the interdiffusion of Cu and carbon atoms into LCP and Cu film respectively. These phenomena resulted in three-dimensional metal clusters of Cu atoms and islands at the LCP/Cu interface, which gradually diffuse into the LCP. Interfacial elemental analysis reveals an intermediate oxide layer formation due to Cu 2 O and C=O.
Wearable sensors are of interest for several application areas, most importantly for their potent... more Wearable sensors are of interest for several application areas, most importantly for their potential to allow for the design of personal continuous health monitoring systems. For wearable sensors, flexibility is required and imperceptibility is desired. Wearable sensors must be robust to strain, motion, and environmental exposure. A number of different strategies have been utilized to achieve flexibility, imperceptibility, and robustness. All of these approaches require the integration of materials having a range of chemical, mechanical, and thermal properties. We have given a concise review of the range of materials that must be incorporated in wearable sensors regardless of the strategies adopted to achieve wearability. We first describe recent advances in the range of wearable sensing materials and their processing requirements and then discuss the potential routes to the integration of these heterogeneous materials.
Journal of Materials Science: Materials in Electronics, 2019
State of the art of cobalt germanide contacts to semiconductor devices is reviewed in this articl... more State of the art of cobalt germanide contacts to semiconductor devices is reviewed in this article. First, evolution of contacts is covered from the dawn of the transistor to present day. The history of contact has three stages: (a) elemental metals as direct contacts to the semiconductor with focus on aluminum, (b) self-aligned silicide contacts, and, recently, (c) the paradigm shift that emphasizes the interface contact resistivity. The second section outlines the current role of germanium in the semiconductor industry and the reasons cobalt germanide is an ideal contact material to germanium and silicon germanium semiconductor devices. Fundamental physical properties of cobalt germanides are presented next. Models for phase formation sequence are, then, detailed. This is followed by a comprehensive survey of the experimental results of formation of cobalt germanides. Those results are discussed and reconciled. Factors affecting the resulting phases and their quality are identified and some optimum choices for the experimental parameters are pointed based on the survey. After that, electrical properties of the contact are discussed. The role of germanium crystal orientation in ohmic and Schottky properties of the contact is analyzed. Fermi level pinning (FLP) plays a role mainly on metal/(100) n-type Ge interfaces. The role of FLP is minimal on p-type Ge and other crystalline orientations. Schottky barrier heights (SBH's) for cobalt and cobalt germanide contacts reported in the literature are surveyed. Mechanisms of FLP and methods adopted by the industry to depin the fermi level at the interface are outlined. The electrical properties section is concluded with a subsection that focuses on the effect of the crystallinity of the contact material on its electrical behavior. Crystalline cobalt germanides are expected to have lower interface resistivities compared to those calculated based on the SBH survey. The role of heat during Co deposition to obtain epitaxial germanides is pointed. Finally, current challenges and future trends of cobalt germanide contacts are summarized.
The first systematic study for the first phase to form during cobalt germanidation was conducted.... more The first systematic study for the first phase to form during cobalt germanidation was conducted. Hexagonal b-Co 5 Ge 3 was the first phase to form in case of cobalt germanidation on (100) Ge. This phase formed at a temperature as low as 227 C. Monoclinic CoGe was experimentally shown to be the second phase to form at the same temperature. Our results are contrary to the previous reports suggesting monoclinic CoGe to be the first phase to form. This is mainly due to the experimental setup that was designed to detect all forming phases: in-situ XRD monitoring at constant low temperature long time anneals of 24-48 h. We also report for the first time that both b-Co 5 Ge 3 and monoclinic CoGe phases that formed during cobalt germanidation were highly ordered partial epitaxial crystal orientations.
We propose a complete model for the oxidation of silicon-germanium. Our model is capable of predi... more We propose a complete model for the oxidation of silicon-germanium. Our model is capable of predicting, as a function of time, the oxide thickness, the profile of the silicon in the underlying alloy, and the profile of germanium in the oxide. The parameters of the model vary with temperature, alloy composition and oxidizing ambient. The model shows excellent agreement with published results, with the model parameters following trends consistent with the physical phenomena hypothesized.
*Geoff Norman served as the representative for the Faculty of Health Sciences in the initial meet... more *Geoff Norman served as the representative for the Faculty of Health Sciences in the initial meetings of
Transient Enhanced Diffusion (TED) in silicon has been extensively investigated recently as resea... more Transient Enhanced Diffusion (TED) in silicon has been extensively investigated recently as researchers have gained more insight into the dopant-defect kinetics that are responsible for this phenomenon which is important for the fabrication of semiconductor devices. In gallium arsenide technology transient diffusion is also an important phenomenon as thermal budgets for real processes decrease and diffusion during sample growth becomes more important. To fully characterize dopant diffusion in gallium arsenide, an understanding must be developed of the dominant atomistic processes for a given dopant as well as the sources of transient effects under a given set of experimental conditions. The process simulator, SUPREM-IV.GS, was expanded to include the Frank-Turnbull diffusion mechanism and this model was used to fit experimental data on the diffusion of grown-in magnesium in gallium arsenide. Theoretical, experimental and simulation results were obtained to understand transient diffusivities in grown-in and implanted samples. In implanted samples, implant damage is responsible for enhancing the effective diffusivity of interstitial dopants at short times. "Uphill diffusion" and segregation to the surface occur, particularly for high dose shallow implants. These phenomena may be understood by modeling the evolution of point defect populations and properly accounting for the increased dopant solubility in the near surface region which is likely to occur as a result of the excess vacancies created in the near surface region during ion implantation, the formation of a separate phase containing the dopant or the difference in bonding and crystal structure between the interface region and the bulk. Experiments were performed to illustrate these phenomena and simulations used to show the validity of this model. In grown-in samples, transient diffusivities were explained by modeling the increase in point defect populations from their equilibrium levels at the growth temperature to achieve equilibrium at the anneal temperature. Experiments and simulations have been carried out to understand the effect of annealing under an oxide cap which is responsible for the injection of Ga vacancies and to probe the effect of defect recombination at, and diffusion from, the surface.
Low Temperature Bonding for 3D Integration (LTB-3D), 2017 5th International Workshop on, 2017
We report direct bonding of liquid crystal polymer and copper film for electrochemical sensing fo... more We report direct bonding of liquid crystal polymer and copper film for electrochemical sensing for the first time. A peel strength of 683 g/cm was observed indicating strong adhesion. X-ray photoelectron and electrochemical impedance spectroscopies were used to characterize the sensing electrodes.
ABSTRACT ▪ Abstract Transient diffusion is an increasingly important phenomenon as thermal budget... more ABSTRACT ▪ Abstract Transient diffusion is an increasingly important phenomenon as thermal budgets for real processes decrease and diffusion during sample growth becomes more important. To fully characterize dopant diffusion in gallium arsenide, an understanding must be developed of the dominant atomistic processes for a given dopant, as well as the sources of transient effects under a given set of experimental conditions. Theoretical, experimental, and simulation results were obtained to understand transient diffusivities of beryllium and silicon in grown-in and implanted samples. In implanted samples, by understanding implant damage and modeling the evolution of point defect populations, the observed transient effects can be explained. Such phenomena cannot account for the time-dependent diffusivity observed when the dopant is introduced during molecular beam epitaxial growth. Transient diffusivities for grown-in beryllium were investigated and explained by modeling the evolution of point defect populations as t...
Interstitials can recombine at an oxide/silicon interface. Previous experimental work produces co... more Interstitials can recombine at an oxide/silicon interface. Previous experimental work produces contradictory results. Transient enhanced diffusion experiments suggest a nearly infinite surface recombination rate, while oxidation enhanced diffusion suggests a much weaker recombination rate. A di-interstitial mechanism is investigated, and analytic solutions are developed. This is compared to the more commonly used interstitial mechanism. The di-interstitial mechanism can account for most of the discrepancy in the data.
ABSTRACT An analytical kinetic model has been developed within this framework to describe the gro... more ABSTRACT An analytical kinetic model has been developed within this framework to describe the growth of ternary III-V semiconductor nanowires. The key to apply the model is to divide the ternary system into two separate binary systems and model each binary system separately. The model is used to describe the growth of InGaP nanowires. The growth conditions were varied among several samples, and the model was able to predict the temperature and growth rate behaviors. The model predicts the axial and radial elemental distribution along the nanowires and the dependence of the elemental distribution on the nanowire's diameter size for all growth rates. The model reveals the limitations of In incorporation into the nanowires for high temperatures or low growth rates and the effects of the group-V elements on the In incorporation.
Canadian Conference on Electrical and Computer Engineering, 2005., 2005
ABSTRACT We have used the process simulator ISE-FLOOPS to implement a model describing the diffus... more ABSTRACT We have used the process simulator ISE-FLOOPS to implement a model describing the diffusion behaviors of boron and carbon in silicon and silicon germanium. The model has been tested against a wide range of sample structures and experimental conditions in published work, and proven to successfully simulate all common phenomena involving boron and carbon in SiGe systems. In particular, we consider the reduction of transient enhanced diffusion of boron due to localized carbon concentrations in SiGeC. The model takes into account carbon diffusion according to both the kickout and Frank-Turnbull mechanisms for diffusion, the effect of boron-interstitial clusters, {311} defects, and interstitial capture by substitutional carbon.
ABSTRACT Silicon-Germanium (SiGe) has become increasingly attractive to semiconductor manufacture... more ABSTRACT Silicon-Germanium (SiGe) has become increasingly attractive to semiconductor manufacturers over the last decade for use in high performance devices. In order to produce thin layers of device grade SiGe with low concentrations of point defects and well-...
Inexpensive, easy-to-process, light-weight polymer-based materials that are biocompatible, mechan... more Inexpensive, easy-to-process, light-weight polymer-based materials that are biocompatible, mechanically flexible, and optically transparent have emerged as alternatives to metals and ceramics in the packaging of implantable sensors. These materials have been used to package components such as microelectrode arrays, telemetric coils and structural membranes. Polymers are also being used for the encapsulations and coatings of the implants. The devices and packages require fine-pitch, low-loss, and highly-conductive paths on mechanically and chemically reliable polymer films. In this review, several polymers used for implantation and related integration technologies are identified. We give an overview of novel applications of polymers in implantable sensor packages, and identify future directions for their application. Polymers exhibit high moisture absorption rate, high-frequency electrical loss, and low mechanical stability. These properties are aggravated when polymers are used for in vivo applications. Also, the integration of polymers with polymers/metals at high bonding temperatures and pressures may degrade their properties and interfaces. Furthermore, adhesive bonding and physical/chemical deposition methods for the integration may introduce non-hermetic, permeable, optically opaque, and poorly conductive interfaces. Thus, creating polymer-based high-density and small-dimension structures are critical for packaging. To address these issues, polymers with improved characteristics as well as integration techniques using low bonding temperature and pressure are indispensable. Liquid crystal polymer (LCP) and surface activated bonding (SAB) technologies meet these requirements. SAB technologies enable nanoscaled polymer-polymer/metal bonding to realize reliable, miniaturized, and high-performance packages for implantable sensors. This article is meant to serve as a reference for future research in the emerging field of implantable sensors by critically assessing the specific merits and drawbacks of several material-process combinations.
2017 5th International Workshop on Low Temperature Bonding for 3D Integration (LTB-3D), 2017
We report direct bonding of liquid crystal polymer and copper film for electrochemical sensing fo... more We report direct bonding of liquid crystal polymer and copper film for electrochemical sensing for the first time. A peel strength of 683 g/cm was observed indicating strong adhesion. X-ray photoelectron and electrochemical impedance spectroscopies were used to characterize the sensing electrodes.
Copper (Cu) film bonded with polymer substrates offers better dimensional stability than that of ... more Copper (Cu) film bonded with polymer substrates offers better dimensional stability than that of deposited Cu especially in humid environment. However, poor adhesion is an issue in both cases. In this paper, we demonstrate a two-step, low temperature direct bonding technique for liquid crystal polymer (LCP) and copper (Cu) using oxygen plasma. The bonded interface showed high peel strength. This strong adhesion is due to the interdiffusion of Cu and carbon atoms into LCP and Cu film respectively. These phenomena resulted in three-dimensional metal clusters of Cu atoms and islands at the LCP/Cu interface, which gradually diffuse into the LCP. Interfacial elemental analysis reveals an intermediate oxide layer formation due to Cu 2 O and C=O.
Wearable sensors are of interest for several application areas, most importantly for their potent... more Wearable sensors are of interest for several application areas, most importantly for their potential to allow for the design of personal continuous health monitoring systems. For wearable sensors, flexibility is required and imperceptibility is desired. Wearable sensors must be robust to strain, motion, and environmental exposure. A number of different strategies have been utilized to achieve flexibility, imperceptibility, and robustness. All of these approaches require the integration of materials having a range of chemical, mechanical, and thermal properties. We have given a concise review of the range of materials that must be incorporated in wearable sensors regardless of the strategies adopted to achieve wearability. We first describe recent advances in the range of wearable sensing materials and their processing requirements and then discuss the potential routes to the integration of these heterogeneous materials.
Journal of Materials Science: Materials in Electronics, 2019
State of the art of cobalt germanide contacts to semiconductor devices is reviewed in this articl... more State of the art of cobalt germanide contacts to semiconductor devices is reviewed in this article. First, evolution of contacts is covered from the dawn of the transistor to present day. The history of contact has three stages: (a) elemental metals as direct contacts to the semiconductor with focus on aluminum, (b) self-aligned silicide contacts, and, recently, (c) the paradigm shift that emphasizes the interface contact resistivity. The second section outlines the current role of germanium in the semiconductor industry and the reasons cobalt germanide is an ideal contact material to germanium and silicon germanium semiconductor devices. Fundamental physical properties of cobalt germanides are presented next. Models for phase formation sequence are, then, detailed. This is followed by a comprehensive survey of the experimental results of formation of cobalt germanides. Those results are discussed and reconciled. Factors affecting the resulting phases and their quality are identified and some optimum choices for the experimental parameters are pointed based on the survey. After that, electrical properties of the contact are discussed. The role of germanium crystal orientation in ohmic and Schottky properties of the contact is analyzed. Fermi level pinning (FLP) plays a role mainly on metal/(100) n-type Ge interfaces. The role of FLP is minimal on p-type Ge and other crystalline orientations. Schottky barrier heights (SBH's) for cobalt and cobalt germanide contacts reported in the literature are surveyed. Mechanisms of FLP and methods adopted by the industry to depin the fermi level at the interface are outlined. The electrical properties section is concluded with a subsection that focuses on the effect of the crystallinity of the contact material on its electrical behavior. Crystalline cobalt germanides are expected to have lower interface resistivities compared to those calculated based on the SBH survey. The role of heat during Co deposition to obtain epitaxial germanides is pointed. Finally, current challenges and future trends of cobalt germanide contacts are summarized.
The first systematic study for the first phase to form during cobalt germanidation was conducted.... more The first systematic study for the first phase to form during cobalt germanidation was conducted. Hexagonal b-Co 5 Ge 3 was the first phase to form in case of cobalt germanidation on (100) Ge. This phase formed at a temperature as low as 227 C. Monoclinic CoGe was experimentally shown to be the second phase to form at the same temperature. Our results are contrary to the previous reports suggesting monoclinic CoGe to be the first phase to form. This is mainly due to the experimental setup that was designed to detect all forming phases: in-situ XRD monitoring at constant low temperature long time anneals of 24-48 h. We also report for the first time that both b-Co 5 Ge 3 and monoclinic CoGe phases that formed during cobalt germanidation were highly ordered partial epitaxial crystal orientations.
We propose a complete model for the oxidation of silicon-germanium. Our model is capable of predi... more We propose a complete model for the oxidation of silicon-germanium. Our model is capable of predicting, as a function of time, the oxide thickness, the profile of the silicon in the underlying alloy, and the profile of germanium in the oxide. The parameters of the model vary with temperature, alloy composition and oxidizing ambient. The model shows excellent agreement with published results, with the model parameters following trends consistent with the physical phenomena hypothesized.
*Geoff Norman served as the representative for the Faculty of Health Sciences in the initial meet... more *Geoff Norman served as the representative for the Faculty of Health Sciences in the initial meetings of
Transient Enhanced Diffusion (TED) in silicon has been extensively investigated recently as resea... more Transient Enhanced Diffusion (TED) in silicon has been extensively investigated recently as researchers have gained more insight into the dopant-defect kinetics that are responsible for this phenomenon which is important for the fabrication of semiconductor devices. In gallium arsenide technology transient diffusion is also an important phenomenon as thermal budgets for real processes decrease and diffusion during sample growth becomes more important. To fully characterize dopant diffusion in gallium arsenide, an understanding must be developed of the dominant atomistic processes for a given dopant as well as the sources of transient effects under a given set of experimental conditions. The process simulator, SUPREM-IV.GS, was expanded to include the Frank-Turnbull diffusion mechanism and this model was used to fit experimental data on the diffusion of grown-in magnesium in gallium arsenide. Theoretical, experimental and simulation results were obtained to understand transient diffusivities in grown-in and implanted samples. In implanted samples, implant damage is responsible for enhancing the effective diffusivity of interstitial dopants at short times. "Uphill diffusion" and segregation to the surface occur, particularly for high dose shallow implants. These phenomena may be understood by modeling the evolution of point defect populations and properly accounting for the increased dopant solubility in the near surface region which is likely to occur as a result of the excess vacancies created in the near surface region during ion implantation, the formation of a separate phase containing the dopant or the difference in bonding and crystal structure between the interface region and the bulk. Experiments were performed to illustrate these phenomena and simulations used to show the validity of this model. In grown-in samples, transient diffusivities were explained by modeling the increase in point defect populations from their equilibrium levels at the growth temperature to achieve equilibrium at the anneal temperature. Experiments and simulations have been carried out to understand the effect of annealing under an oxide cap which is responsible for the injection of Ga vacancies and to probe the effect of defect recombination at, and diffusion from, the surface.
Low Temperature Bonding for 3D Integration (LTB-3D), 2017 5th International Workshop on, 2017
We report direct bonding of liquid crystal polymer and copper film for electrochemical sensing fo... more We report direct bonding of liquid crystal polymer and copper film for electrochemical sensing for the first time. A peel strength of 683 g/cm was observed indicating strong adhesion. X-ray photoelectron and electrochemical impedance spectroscopies were used to characterize the sensing electrodes.
ABSTRACT ▪ Abstract Transient diffusion is an increasingly important phenomenon as thermal budget... more ABSTRACT ▪ Abstract Transient diffusion is an increasingly important phenomenon as thermal budgets for real processes decrease and diffusion during sample growth becomes more important. To fully characterize dopant diffusion in gallium arsenide, an understanding must be developed of the dominant atomistic processes for a given dopant, as well as the sources of transient effects under a given set of experimental conditions. Theoretical, experimental, and simulation results were obtained to understand transient diffusivities of beryllium and silicon in grown-in and implanted samples. In implanted samples, by understanding implant damage and modeling the evolution of point defect populations, the observed transient effects can be explained. Such phenomena cannot account for the time-dependent diffusivity observed when the dopant is introduced during molecular beam epitaxial growth. Transient diffusivities for grown-in beryllium were investigated and explained by modeling the evolution of point defect populations as t...
Interstitials can recombine at an oxide/silicon interface. Previous experimental work produces co... more Interstitials can recombine at an oxide/silicon interface. Previous experimental work produces contradictory results. Transient enhanced diffusion experiments suggest a nearly infinite surface recombination rate, while oxidation enhanced diffusion suggests a much weaker recombination rate. A di-interstitial mechanism is investigated, and analytic solutions are developed. This is compared to the more commonly used interstitial mechanism. The di-interstitial mechanism can account for most of the discrepancy in the data.
ABSTRACT An analytical kinetic model has been developed within this framework to describe the gro... more ABSTRACT An analytical kinetic model has been developed within this framework to describe the growth of ternary III-V semiconductor nanowires. The key to apply the model is to divide the ternary system into two separate binary systems and model each binary system separately. The model is used to describe the growth of InGaP nanowires. The growth conditions were varied among several samples, and the model was able to predict the temperature and growth rate behaviors. The model predicts the axial and radial elemental distribution along the nanowires and the dependence of the elemental distribution on the nanowire's diameter size for all growth rates. The model reveals the limitations of In incorporation into the nanowires for high temperatures or low growth rates and the effects of the group-V elements on the In incorporation.
Canadian Conference on Electrical and Computer Engineering, 2005., 2005
ABSTRACT We have used the process simulator ISE-FLOOPS to implement a model describing the diffus... more ABSTRACT We have used the process simulator ISE-FLOOPS to implement a model describing the diffusion behaviors of boron and carbon in silicon and silicon germanium. The model has been tested against a wide range of sample structures and experimental conditions in published work, and proven to successfully simulate all common phenomena involving boron and carbon in SiGe systems. In particular, we consider the reduction of transient enhanced diffusion of boron due to localized carbon concentrations in SiGeC. The model takes into account carbon diffusion according to both the kickout and Frank-Turnbull mechanisms for diffusion, the effect of boron-interstitial clusters, {311} defects, and interstitial capture by substitutional carbon.
ABSTRACT Silicon-Germanium (SiGe) has become increasingly attractive to semiconductor manufacture... more ABSTRACT Silicon-Germanium (SiGe) has become increasingly attractive to semiconductor manufacturers over the last decade for use in high performance devices. In order to produce thin layers of device grade SiGe with low concentrations of point defects and well-...
Inexpensive, easy-to-process, light-weight polymer-based materials that are biocompatible, mechan... more Inexpensive, easy-to-process, light-weight polymer-based materials that are biocompatible, mechanically flexible, and optically transparent have emerged as alternatives to metals and ceramics in the packaging of implantable sensors. These materials have been used to package components such as microelectrode arrays, telemetric coils and structural membranes. Polymers are also being used for the encapsulations and coatings of the implants. The devices and packages require fine-pitch, low-loss, and highly-conductive paths on mechanically and chemically reliable polymer films. In this review, several polymers used for implantation and related integration technologies are identified. We give an overview of novel applications of polymers in implantable sensor packages, and identify future directions for their application. Polymers exhibit high moisture absorption rate, high-frequency electrical loss, and low mechanical stability. These properties are aggravated when polymers are used for in vivo applications. Also, the integration of polymers with polymers/metals at high bonding temperatures and pressures may degrade their properties and interfaces. Furthermore, adhesive bonding and physical/chemical deposition methods for the integration may introduce non-hermetic, permeable, optically opaque, and poorly conductive interfaces. Thus, creating polymer-based high-density and small-dimension structures are critical for packaging. To address these issues, polymers with improved characteristics as well as integration techniques using low bonding temperature and pressure are indispensable. Liquid crystal polymer (LCP) and surface activated bonding (SAB) technologies meet these requirements. SAB technologies enable nanoscaled polymer-polymer/metal bonding to realize reliable, miniaturized, and high-performance packages for implantable sensors. This article is meant to serve as a reference for future research in the emerging field of implantable sensors by critically assessing the specific merits and drawbacks of several material-process combinations.
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Papers by Yaser Haddara