The organic Methylsilsesquioxane (MSQ) exhibits low dielectric constant and is an important and p... more The organic Methylsilsesquioxane (MSQ) exhibits low dielectric constant and is an important and promising material to reduce the capacitive coupling between metal layers in semiconductor integrated circuits. However, MSQ has lower film density and therefore more porous than the traditional SiO2 film and could pose reliability issues. The aim of this paper is to study the effect of post deposition annealing of Copper and Aluminium using evaporation method. Electrical characterisation employing high-frequency C-V and bias-temperature stress (BTS) were employed to study the effect of MOS capacitor (MOSC) structures annealed at different temperatures. The results showed that the leakage current of MOSC with Aluminium and Copper gate increases as the annealing temperatures increases. In addition, MOSC with Aluminium gate has greater reliability compared to MOSC with Copper gate when subject to BTS. However, the leakage current of MOSC with Aluminium gate is much greatly affected by the operating temperature. These concerns need to be addressed and overcome to ensure that MSQ can be a viable interlayer dielectric (ILD) for integrated circuits (IC).
Polymers are commonly found to have low mechanical properties e.g. low stiffness and low strength... more Polymers are commonly found to have low mechanical properties e.g. low stiffness and low strength. To improve the mechanical properties of polymers, various types of fillers are added. These fillers can be either micro or nano sized, however nano sized fillers are found to have more profound effect on improving the mechanical properties compared to micro sized fillers. In this research, we have analysed the mechanical behaviour of the silica reinforced nanocomposites printed by using a new 5 axis photopolymer extrusion 3D printing technique. The printer has 3 translational axis and 2 rotational axis which enables it to print free standing objects. Since this is a new technique and in order to characterise the mechanical properties of the nanocomposites manufactured using this new technique, we carried out experimental and numerical analyses. We added nano sized silica filler to enhance the properties of 3D printed photopolymer. Different concentrations of the filler were added and their effects on mechanical properties were studied by conducting uniaxial tensile tests. We observed improvement in mechanical properties by the addition of nano sized filler. In order to observe the tensile strength, dog-bone samples using new photopolymer extrusion printing were prepared. A viscoelastic model was developed and stress relaxation tests were conducted on photopolymer in order to calibrate the viscoelastic parameters. The developed computational model of nano reinforced polymer composite takes into account the nanostructure and dispersion of nanoparticles. Hyper and viscoelastic phenomena was employed to validate and analyse the stress-strain relationship of 8%, 9% and 10% filler concentrations. In order to represent the nanostructure, a 3D representative volume element (RVE) was utilized and subsequent simulations were ran in commercial finite element package ABAQUS. Results acquired in this study could lead to better understanding of the mechanical characterisation of the nanoparticle reinforced composite, manufactured using the new photopolymer extrusion 5-axis 3D printing technique.
The bandgap phenomenon in metamaterials has attracted much research interest for controlling stru... more The bandgap phenomenon in metamaterials has attracted much research interest for controlling structural vibrations. To tailor the bandgap for applications in a specific frequency range, analytical tools for bandgap bound estimations are critically important. This work presents a generic theoretical approach for fast estimation of the bandgap bounds. Starting from the lattice metamaterial systems, we develop the procedure and provide the analytical bound expressions based on a hypothesis of extreme points in the band structure of metamaterial systems. The proposed approach for the lattice system is verified by the results of transmittance analysis. Subsequently, to explore the fidelity of the proposed approach on continuous metamaterial systems, three typical metamaterial beams (metabeams) have been investigated: a metabeam with mechanical local resonators, a piezoelectric metabeam with shunt resonant circuits, and a hybrid metabeam. Finite element analysis is performed to verify the theoretical expressions of bandgap bounds derived using the proposed approach. With the verified bound expressions, bandgap tailoring and optimization are further investigated. In summary, the developed theoretical approach is generic and offers a promising technique for bandgap estimation of metamaterial systems integrated with various types of resonators.
Piezoelectric metamaterials with shunt resonant circuits have been extensively investigated for t... more Piezoelectric metamaterials with shunt resonant circuits have been extensively investigated for their tunability in bandgaps. However, the vibration attenuation ability induced by the electromechanical coupling is generally weaker than that of mechanical metamaterials, limiting their applications in engineering practice. This research presents a non-uniform piezoelectric metamaterial beam with shunt circuit parameters optimized by an adaptive genetic algorithm (AGA) for tailoring the vibration attenuation zone. First, the non-uniform piezoelectric metamaterial beam is modeled for transmittance analysis and verified by the finite element method. By simultaneously tuning the resonance frequencies and the resistance of the shunt circuits, it is conceptually demonstrated that the attenuation zone can be broadened, and the undesired localized vibration modes can be mitigated. Subsequently, two optimization strategies are proposed respectively for two typical vibration scenarios. The inductances and the load resistance in the shunt circuits constitute the set of design variables and are optimized by the AGA. Dedicated case studies are carried out, and the results show that the objective-oriented circuitry parameters can greatly enrich the design freedom, and tailor the transmittance profile according to a given vibration spectra. As compared to the conventional uniform and the graded piezoelectric metamaterial beams, the proposed design provides superior vibration attenuation performance and demonstrates a promising approach for tailoring piezoelectric metamaterials systems.
With the evolution of additive manufacturing, there is an increasing demand to produce high stren... more With the evolution of additive manufacturing, there is an increasing demand to produce high strength and stiffness polymers. Photopolymers are very commonly used in Stereo lithography (SLA) and Fused Deposition Modelling (FDM) processes but their application is limited due to their low strength and stiffness values. Nano sized fibers or particles are generally embedded in the polymer matrix to enhance their properties. In this study, we have studied the effect of fumed nano sized silica filler on the elastic and viscoelastic properties of the photopolymer.
Journal of Intelligent Material Systems and Structures, Jan 29, 2018
A flexure frame mechanism is a device historically used to amplify the displacement of an actuato... more A flexure frame mechanism is a device historically used to amplify the displacement of an actuator with limited travel, such as a piezoelectric stack actuator. Conversely, these mechanisms may be used as a generator to amplify the force applied to piezoelectric transducers. This in turn can greatly increase the harvested power. Previous studies have used a variety of methods to analyse the amplification factor of a flexure frame mechanism operating as an actuator in displacement mode, as opposed to a generator in force amplification mode. The effects on the performance of such a device when operating in force amplification mode are not as well understood. In this study, an analysis of the force amplification of a flexure frame mechanism is conducted. A model of the force amplification factor based on the material properties and geometry of the device is developed for use as an optimisation and design tool. The analytical findings are compared against finite element analysis simulation and experimental results for validation. The effect of the stiffness of the central piezoelectric stack and the maximum stresses developed in the frame are determined to be critical parameters in determining the effectiveness of the mechanism as an energy harvester.
Semiconductor physics, quantum electronics & optoelectronics, Dec 11, 2003
Spin-on Methylsilsesquioxane (MSQ) exhibits low dielectric constant and is an important and promi... more Spin-on Methylsilsesquioxane (MSQ) exhibits low dielectric constant and is an important and promising material to reduce parasitic capacitive coupling between metal layers in semiconductor integrated circuits. However, MSQ has lower film density and therefore more porous than the traditional silicon dioxide (SiO 2) film and could pose reliability issues. This paper is an extension to previous paper [1], which reported that evaporated copper (Cu) onto spin-on MSQ has high leakage current and provides two alternative models with the aid of energy band diagrams to describe the effect of evaporated Cu onto spin-on MSQ using Metal Oxide Semiconductor capacitor (MOSC) structure.
The organic Methylsilsesquioxane (MSQ) exhibits low dielectric constant and is an important and p... more The organic Methylsilsesquioxane (MSQ) exhibits low dielectric constant and is an important and promising material to reduce the capacitive coupling between metal layers in semiconductor integrated circuits. However, MSQ has lower film density and therefore more porous than the traditional SiO2 film and could pose reliability issues. The aim of this paper is to study the effect of post deposition annealing of Copper and Aluminium using evaporation method. Electrical characterisation employing high-frequency C-V and bias-temperature stress (BTS) were employed to study the effect of MOS capacitor (MOSC) structures annealed at different temperatures. The results showed that the leakage current of MOSC with Aluminium and Copper gate increases as the annealing temperatures increases. In addition, MOSC with Aluminium gate has greater reliability compared to MOSC with Copper gate when subject to BTS. However, the leakage current of MOSC with Aluminium gate is much greatly affected by the operating temperature. These concerns need to be addressed and overcome to ensure that MSQ can be a viable interlayer dielectric (ILD) for integrated circuits (IC).
Polymers are commonly found to have low mechanical properties e.g. low stiffness and low strength... more Polymers are commonly found to have low mechanical properties e.g. low stiffness and low strength. To improve the mechanical properties of polymers, various types of fillers are added. These fillers can be either micro or nano sized, however nano sized fillers are found to have more profound effect on improving the mechanical properties compared to micro sized fillers. In this research, we have analysed the mechanical behaviour of the silica reinforced nanocomposites printed by using a new 5 axis photopolymer extrusion 3D printing technique. The printer has 3 translational axis and 2 rotational axis which enables it to print free standing objects. Since this is a new technique and in order to characterise the mechanical properties of the nanocomposites manufactured using this new technique, we carried out experimental and numerical analyses. We added nano sized silica filler to enhance the properties of 3D printed photopolymer. Different concentrations of the filler were added and their effects on mechanical properties were studied by conducting uniaxial tensile tests. We observed improvement in mechanical properties by the addition of nano sized filler. In order to observe the tensile strength, dog-bone samples using new photopolymer extrusion printing were prepared. A viscoelastic model was developed and stress relaxation tests were conducted on photopolymer in order to calibrate the viscoelastic parameters. The developed computational model of nano reinforced polymer composite takes into account the nanostructure and dispersion of nanoparticles. Hyper and viscoelastic phenomena was employed to validate and analyse the stress-strain relationship of 8%, 9% and 10% filler concentrations. In order to represent the nanostructure, a 3D representative volume element (RVE) was utilized and subsequent simulations were ran in commercial finite element package ABAQUS. Results acquired in this study could lead to better understanding of the mechanical characterisation of the nanoparticle reinforced composite, manufactured using the new photopolymer extrusion 5-axis 3D printing technique.
The bandgap phenomenon in metamaterials has attracted much research interest for controlling stru... more The bandgap phenomenon in metamaterials has attracted much research interest for controlling structural vibrations. To tailor the bandgap for applications in a specific frequency range, analytical tools for bandgap bound estimations are critically important. This work presents a generic theoretical approach for fast estimation of the bandgap bounds. Starting from the lattice metamaterial systems, we develop the procedure and provide the analytical bound expressions based on a hypothesis of extreme points in the band structure of metamaterial systems. The proposed approach for the lattice system is verified by the results of transmittance analysis. Subsequently, to explore the fidelity of the proposed approach on continuous metamaterial systems, three typical metamaterial beams (metabeams) have been investigated: a metabeam with mechanical local resonators, a piezoelectric metabeam with shunt resonant circuits, and a hybrid metabeam. Finite element analysis is performed to verify the theoretical expressions of bandgap bounds derived using the proposed approach. With the verified bound expressions, bandgap tailoring and optimization are further investigated. In summary, the developed theoretical approach is generic and offers a promising technique for bandgap estimation of metamaterial systems integrated with various types of resonators.
Piezoelectric metamaterials with shunt resonant circuits have been extensively investigated for t... more Piezoelectric metamaterials with shunt resonant circuits have been extensively investigated for their tunability in bandgaps. However, the vibration attenuation ability induced by the electromechanical coupling is generally weaker than that of mechanical metamaterials, limiting their applications in engineering practice. This research presents a non-uniform piezoelectric metamaterial beam with shunt circuit parameters optimized by an adaptive genetic algorithm (AGA) for tailoring the vibration attenuation zone. First, the non-uniform piezoelectric metamaterial beam is modeled for transmittance analysis and verified by the finite element method. By simultaneously tuning the resonance frequencies and the resistance of the shunt circuits, it is conceptually demonstrated that the attenuation zone can be broadened, and the undesired localized vibration modes can be mitigated. Subsequently, two optimization strategies are proposed respectively for two typical vibration scenarios. The inductances and the load resistance in the shunt circuits constitute the set of design variables and are optimized by the AGA. Dedicated case studies are carried out, and the results show that the objective-oriented circuitry parameters can greatly enrich the design freedom, and tailor the transmittance profile according to a given vibration spectra. As compared to the conventional uniform and the graded piezoelectric metamaterial beams, the proposed design provides superior vibration attenuation performance and demonstrates a promising approach for tailoring piezoelectric metamaterials systems.
With the evolution of additive manufacturing, there is an increasing demand to produce high stren... more With the evolution of additive manufacturing, there is an increasing demand to produce high strength and stiffness polymers. Photopolymers are very commonly used in Stereo lithography (SLA) and Fused Deposition Modelling (FDM) processes but their application is limited due to their low strength and stiffness values. Nano sized fibers or particles are generally embedded in the polymer matrix to enhance their properties. In this study, we have studied the effect of fumed nano sized silica filler on the elastic and viscoelastic properties of the photopolymer.
Journal of Intelligent Material Systems and Structures, Jan 29, 2018
A flexure frame mechanism is a device historically used to amplify the displacement of an actuato... more A flexure frame mechanism is a device historically used to amplify the displacement of an actuator with limited travel, such as a piezoelectric stack actuator. Conversely, these mechanisms may be used as a generator to amplify the force applied to piezoelectric transducers. This in turn can greatly increase the harvested power. Previous studies have used a variety of methods to analyse the amplification factor of a flexure frame mechanism operating as an actuator in displacement mode, as opposed to a generator in force amplification mode. The effects on the performance of such a device when operating in force amplification mode are not as well understood. In this study, an analysis of the force amplification of a flexure frame mechanism is conducted. A model of the force amplification factor based on the material properties and geometry of the device is developed for use as an optimisation and design tool. The analytical findings are compared against finite element analysis simulation and experimental results for validation. The effect of the stiffness of the central piezoelectric stack and the maximum stresses developed in the frame are determined to be critical parameters in determining the effectiveness of the mechanism as an energy harvester.
Semiconductor physics, quantum electronics & optoelectronics, Dec 11, 2003
Spin-on Methylsilsesquioxane (MSQ) exhibits low dielectric constant and is an important and promi... more Spin-on Methylsilsesquioxane (MSQ) exhibits low dielectric constant and is an important and promising material to reduce parasitic capacitive coupling between metal layers in semiconductor integrated circuits. However, MSQ has lower film density and therefore more porous than the traditional silicon dioxide (SiO 2) film and could pose reliability issues. This paper is an extension to previous paper [1], which reported that evaporated copper (Cu) onto spin-on MSQ has high leakage current and provides two alternative models with the aid of energy band diagrams to describe the effect of evaporated Cu onto spin-on MSQ using Metal Oxide Semiconductor capacitor (MOSC) structure.
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