Metal Cap Research Articles

Enabling Effective Work Function Tuning by RF-PVD Metal Oxide on High-k Gate Dielectric

RF-PVD was investigated as a metal oxide cap deposition process to tune the effective work function in a gate first flow for high-k metal gate stacks. Samples with an aluminum oxide cap layer showed a large flat band voltage shift at minimal equivalent oxide thickness increase by about 0.1 nm. It was confirmed that RF-PVD induced no additional charge damage. Extended RF-PVD process runs also promised a robust process for high-k metal gate device manufacturing.

Crystallinity of CoSi2 nanolayer grown by refractory metal interlayer and cap layer methods

Epitaxial formation of CoSi2 nanolayer by solid state reaction of Co-Si in refractory metal intermediate-layer and cap-layer systems was investigated. Thin films of Ta and W, as the refractory metal intermediate or cap layers of the Co film, were deposited on Si(100) substrate and then heat-treated. The both interlayers resulted in formation of epitaxial CoSi2 with (100) crystallographic orientation at 900°C. However, in the Ta intermediated system, the grown CoSi2 layer was thermally unstable at 1000°C, unlike the W system with a stable silicide layer. We found that use of W cap-layer cannot yield an epitaxial CoSi2 phase. But, a Ta cap-layer resulted in formation of epitaxial CoSi2(100) layer even in a lower temperature (800°C). Again, in the presence of Ta, the grown CoSi2 layer was thermally unstable at 900°C.

Biomimetic Composite-Metal Hip Resurfacing Implant

Hip resurfacing technique is a conservative arthroplasty used in the young patient in which the femoral head is reshaped to accept metal cap with small guide stem. In the present investigation, a hybrid composite-metal resurfacing implant is proposed. The cup is made of carbon fiber/polyamide 12 (CF/PA12) covered with a thin layer of cobalt chrome (Co-Cr). Finite element (FE) method was applied to analyze and compare the biomechanical performances of the hybrid hip resurfacing (HHR) and the conventional Birmingham (BHR). Results of the finite element analysis showed that the composite implant leads to an increase in stresses in the cancellous bone by more than 15% than BHR, indicating a lower potential for stress shielding and bone fracture and higher potential for bone apposition with the HHR.

Atopy Patch Test for the Diagnosis of Food Protein-Induced Enterocolitis Syndrome

Fogg MI, Brown-Whitehorn TA, Pawlowski NA, Spergel JM. Pediatr Allergy Immunol. 2006;17:351–355 PURPOSE OF THE STUDY. This prospective study was undertaken to determine if the atopy patch test (APT) is able to predict the results of the oral food challenge (OFC) for food protein–induced enterocolitis syndrome (FPIES). The APT involves placement of food in a Finn chamber (metal cap) left on the skin for 48 hours and evaluated for rash in the subsequent days after removal. STUDY POPULATION. Nineteen patients aged 5 to 30 months who had suspected FPIES on the basis of clinical history. METHODS. The infants underwent APT to the suspected foods. After APT was performed, the subjects underwent OFC to determine if FPIES was present. The results of APT and OFC were compared and used to calculate sensitivity and specificity of the APT. RESULTS. APT predicted the results of OFCs in 28 of 33 instances. There were 16 cases of FPIES confirmed by OFCs. In all 16 cases of FPIES, the APT result was positive to the suspected food. However, the APT was positive in 5 instances in which the OFC result was negative. All 12 patients with a negative APT result had a negative OFC result to the suspected food. CONCLUSIONS. APT seems to be a promising diagnostic tool for the diagnosis of FPIES. REVIEWER COMMENTS. FPIES is a non–immunoglobulin E (IgE)-mediated food allergy in which affected infants develop gastrointestinal symptoms hours after ingestion of the offending food. Current allergy skin and serum tests are not useful for diagnosing this disorder, because they test for food-specific IgE levels that are often negative in FPIES. A diagnostic OFC is the gold standard. The role for APT in diagnosing other non–IgE-mediated food hypersensitivities has been investigated. The results of this study suggest that APT may have some utility in guiding the diagnosis and management of FPIES.

Effects of experimental occlusal hypofunction, and its recovery, on mandibular bone mineral density in rats

The aim of this investigation was to examine the effects of experimental occlusal hypofunction, and recovery, on mandibular bone mineral density (BMD) using peripheral quantitative computed tomography. A metal cap was inserted between the upper and lower incisors of 40 male Wistar rats (aged 6 weeks) to prevent the molars from biting. The rats were divided into two equal groups: 'hypofunction' and 'recovery' animals. In addition, there was a third group comprising 20 control animals. The recovery animals were anaesthetized at 4 weeks in order to remove the metal cap using pliers. The rats were killed under deep anaesthesia, after which the mandibles were immediately removed and fixed in 10 per cent neutral formalin. After 2, 4, 6, and 8 weeks, BMD was measured in the cancellous and cortical bone in the first molar region. Data were analysed using one-way analysis of variance. At 6 and 8 weeks, in the hypofunction group, cancellous bone density decreased on the buccal and lingual sides, at the bifurcation of the root and at the root apex. In the recovery group, the density on the buccal and lingual sides had recovered to the normal levels, compared with the control group. However, density of the bifurcation of the root and the root apex recovered by only 30 and 50 per cent, respectively. At 6 and 8 weeks, cortical bone density in the hypofunction group had reduced in the lingual basal and lingual middle cortical bone areas. Cortical bone density in the lingual basal and lingual areas recovered to control group levels at 6 weeks. Recovery of occlusal hypofunction may restore decreased BMD of both cancellous and cortical bone.

Displacement amplification and electric characteristics of modified rectangular cymbal transducers using electroactive materials

Three typical electroactive materials were used as the drive elements for a cymbal transducer. The included materials were hard and soft lead zirconate titanate (PZT) piezoelectric ceramics and single crystal lead magnesium niobate–lead titanate (PMNT). Finite element analysis was used to calculate the displacement of the transducer under dc voltage. The displacement of the PMNT based cymbal transducer is much larger than that of the PZT based cymbal transducer. The electric performance of the cymbal transducers was also measured. The effects of material properties and the size of the metal caps on the displacement of the cymbal transducer are discussed.

Converse magnetoelectric effect in three-phase composites of piezoceramic, metal cap, and magnet

We report experimentally and theoretically the converse magnetoelectric (CME) effect in a three-phase piezoceramic-metal-cap-magnet composite made by sandwiching a thickness-polarized Pb(ZrxTi1−x)O3 (PZT) disk between two truncated conical brass caps and two thickness-magnetized SmCo disks. The reported CME effect originates from the product of the converse piezoelectric effect in the PZT disk, the mechanical transformation/amplification effect in the brass caps, and the magnetic induction effect in the SmCo disks. The composite exhibits a large CME coefficient (αB) in excess of 2mG∕V with a flat response in the broad frequency range of 0.1–100kHz. The measured magnetic flux density shows an extremely linear relationship to the applied voltage with amplitude varying from 10to100V over a wide range of detection distance of 0.7–6.5mm. This electromechanomagnetically coupled effect enables applications of the composite in coil-free magnetic flux control devices, featuring smaller Joule heating loss, wider operational bandwidth, and greater property-tailorable flexibility compared to conventional electromagnet-based devices.

In vitro study of reduction of stress transferred onto tissues around implants using a resilient material in maxillary implant overdentures.

The purpose of this in vitro study was to investigate the effect of hardness on the reduction of stress transferred to tissues around implants using a resilient material applied to the female parts of the ball attachment in maxillary implant overdentures. A cast chrome-cobalt framework was mounted onto a maxillary acrylic edentulous model, which contained two implants and four strain gauges attached to the implant. Ball abutments were screwed into the implant. One abutment was connected to a dedicated metal cap embedded in the housing, while the others were connected to resilient test materials with four different hardnesses. Loads were applied using a universal testing machine with a magnitude of 50 N. The sums of the absolute values recorded from the four strain gauges were used for stress evaluation. The measured strains were analyzed statistically using two-way ANOVA and multiple comparisons. A resilient material with hardness 90 exhibited strains that did not differ significantly from the control. In contrast, the other resilient materials showed significantly reduced strains under all conditions. In this limited study, application of resilient silicone materials with approximate hardness 80 to the female parts of ball attachments significantly reduced the stress on the tissues around the implant.

Enabling Damascene Solutions for 45 nm Beyond

ABSTRACTThere are several technology developments, which should have been completed in CN 65 nm (Commercial node) device development, but passed over to CN 45 nm device development. Seven items relating with damascene process, especially connecting with planarization process, are nominated and introduced herein including new advent technologies as enabling solutions for CN 45 nm. First one is low-down-force planarization. Although there are several planarization technologies such as CMP (Chemical Mechanical Polisher), ECMP (Electrical Chemical Mechanical Polisher), ECP (Electrical Chemical Polisher), CE (Chemical Etching) and those combination technologies, it is not decided which is the best one and how low down force is optimized taking into account of CoC (Cost of Consumable) issues. In this report, all planarization technologies are explained using ‘General Principle governing all planarization technologies’, and allowable down force is suggested through stress analysis and fracture toughness analysis. Second one is direct polish on ULK. There may be two approaches. One is to adopt CMP hard mask which dielectric constant would not be changed by direct polish. In this case, non-uniformity of CMP in this hard mask is important. Second is to polish directly on ULK, which dielectric constant would be changed by CMP, then restoration technology should be discussed at a same time. Third one is Ru liner application. When is this technology required? Deposition for Ru seed and polishing of Ru integration are reported. Forth one is watermark free drying of ULK. Vacuum drying and IPA drying (Rotagoni) which is necessary for hydrophobic surfaces are reported. Fifth one is cleaning technologies for less than 45 nm FM. After CN 45 nm, it is difficult to distinguish several defects such as scratches or FM. In this case, soft cleaning methods such as non-contact cleaning would be required. Cavitation jet as one of non-contact type cleanings is reported with its cleaning results. Sixth one is Co-W cap process. Electro-less metal cap technology in order to enhance EM is reported. CMP after Co-W deposition may be useful in order to clean cap surfaces. Seventh one is starting material such as nanotopography and roll off which would affect on CMP performances.

Analysis of a hybrid composite/metal bolted connection subjected to flexural loading

Abstract This paper presents the structural response of hybrid composite/metal bolted joints using an experimental investigation and finite element analysis. The primary motivation for this work is to provide alternatives to conventional hull construction techniques using modular hybrid construction methods. The main objective is to implement a watertight hybrid connection concept that provides access using removable panels on a ship hull. The hybrid joint developed is used to connect fiberglass reinforced composite panels to a metal sub-structure. An experimental study was conducted to quantify the performance of various hybrid joints with various geometries, loaded in flexure. The test results show that, for resisting bending loads, joints with metal cap plates can be made stronger and rotationally stiffer than standard bolted joints, while also mitigating opening of the joint, thereby improving the ability to seal the connection for watertight integrity. Local shell and detailed solid finite element analyses of the connections are presented. Simplified shell finite element models were developed for implementation into global models of the structure and good correlation with the test results was observed with respect to connection stiffness. Nonlinear response of the connection was predicted using detailed plane strain contact models to capture the three-dimensional effects. The results of this study were used to select a connection geometry, which was subsequently incorporated into the hydrostatic testing of a full-scale four-panel assembly.

“PIEZO-BOW”—HIGH DISPLACEMENT AND HIGH BLOCKING FORCE ACTUATOR

ABSTRACT Bending type actuators providing high displacement (∼1 mm) with low blocking force (∼0.5 N) and the stack actuators providing low displacement (∼1 μm) with high blocking force (∼1 kN) represent the extreme ends of the current piezoelectric actuation technology. In the intermediate range there is deficiency of the actuator designs that provide high displacement with high blocking force in the frequency range of few kilohertz. This study addresses this issue and describes an actuator design “Piezo-Bow” which exhibits high displacement with high blocking force at low frequencies. The structure consist of a piezoelectric bar poled along the length with metal caps attached to the two major faces of the bar bounded by steel blocks. The piezoelectric bar is multilayered for operating at low voltages. The dimensions of the structure were optimized by FEM simulation in order to realize the resonance frequency near 2 kHz. It was observed that by changing the actuator parameters, cavity depth and cap thickness the resonance frequency can be shifted to desired frequency range. Based on the FEM analysis the optimized actuator design was fabricated. A PZT based composition corresponding to 0.98Pb(Zr0.52Ti0.48)O3+0.01Nb2O5+ 0.01PbO was synthesized to fabricate the active actuation component. The fabricated actuator was characterized for impedance, piezoelectric constant and displacement. The experimental results were found to be consistent with the FEM analysis.

An Electromagnetic Compressive Force by Cell Exciter Stimulates Chondrogenic Differentiation of Bone Marrow–Derived Mesenchymal Stem Cells

In this study, we present a biological micro-electromechanical system and its application to the chondrogenic differentiation of rabbit bone marrow-derived mesenchymal stem cells (MSCs). Actuated by an electromagnetic force, the micro cell exciter was designed to deliver a cyclic compressive load (CCL) with various magnitudes. Two major parts in the system are an actuator and a cartridge-type chamber. The former has a permanent magnet and coil, and the latter is equipped with 7 sample dishes and 7 metal caps. Mixed with a 2.4% alginate solution, the alginate/MSC layers were positioned in the sample dishes; the caps contained chondrogenic defined medium without transforming growth factor-beta (TGF-beta). Once powered, the actuator coil-derived electromagnetic force pulled the metal caps down, compressing the samples. The cyclic load was given at 1-Hz frequency for 10 min twice a day. Samples in the dishes without a cap served as a control. The samples were analyzed at 3, 5, and 7 days after stimulation for cell viability, biochemical assays, histologic features, immunohistochemistry, and gene expression of the chondrogenic markers. Applied to the alginate/MSC layer, the CCL system enhanced the synthesis of cartilage-specific matrix proteins and the chondrogenic markers, such as aggrecan, type II collagen, and Sox9. We found that the micromechanically exerted CCL by the cell exciter was very effective in enhancing the chondrogenic differentiation of MSCs, even without using exogenous TGF-beta.

Self-aligned metal capping layers for copper interconnects using electroless plating

Self-aligned metal capping layers formed by electroless plating, such as CoWP and NiMoP, are being investigated for a number of Cu interconnect technologies. One application is for high performance logic chips at the 45 nm node and below. The main motivation for using these capping layers is to improve electromigration lifetime, and a dielectric cap is typically used in addition to the metal cap. An improvement in electromigration lifetime of over 100X is observed with a CoWP cap, and the lifetime is independent of the direction of electron flow for dual damascene structures. A different application is for CMOS image sensors using 0.18 μm technology. For this application, the self-aligned metal cap replaces the dielectric cap, resulting in improved optical performance of the image sensor. The uniformity of the CoWP is critical for this application; if there are thin regions in the capping layer, the Cu will be exposed to the etch or strip chemistry, and via yield and reliability will be poor. For both applications the main issue with using selective capping layers is loss of selectivity, which results in high leakage currents between the metal lines. Interestingly, the leakage can actually be lower for a stand-alone CoWP cap compared to a stand-alone SiN cap, presumably due to damage associated with the SiN deposition.

Modeling of Piezoelectric Energy Harvesting Using Cymbal Transducers

This study reports the experimental and analytical results on a piezoelectric cymbal with 29 mm diameter and 1 mm thickness operating under force of 70 N in the frequency range of 10–200 Hz. It was found that the generated power increases with the frequency and around 100 mW can be harvested at frequency of 200 Hz across a 200 kΩ resistor. Power generation from the cymbal transducer was modeled by using the theory developed for the Belleville spring. The calculated results were found to be in good agreement with the experimental results. The results indicate that the metal–ceramic composite transducer “CYMBAL” is the most promising structure for harvesting the electric energy from automobile engine vibrations. The metal cap enhances the endurance of the ceramic to sustain high loads along with stress amplification.

Effect of passivation on stress relaxation in electroplated copper films

The present study investigated the effect of passivation on the kinetics of interfacial mass transport by measuring stress relaxation in electroplated Cu films with four different cap layers: SiN, SiC, SiCN, and a Co metal cap. Stress curves measured under thermal cycling showed different behaviors for the unpassivated and passivated Cu films, but were essentially indifferent for the films passivated with different cap layers. On the other hand, stress relaxation measured under an isothermal condition revealed clearly the effect of passivation, indicating that interface diffusion controls the kinetics of stress relaxation. The relaxation rates in the passivated Cu films were found to decrease in the order of SiC, SiCN, SiN, and metal caps. This correlates well with previous studies on the relationship between interfacial adhesion and electromigration. A kinetic model based on coupling of interface and grain-boundary diffusion was used to deduce the interface diffusivities and the corresponding activation energies.

Investigation of the Dynamics of Microend Milling—Part I: Model Development

Abstract In microend milling, due to the comparable size of the edge radius to chip thickness, chip formation mechanisms are different. Also, the design of microend mills with features of a large shank, taper, and reduced diameter at the cutting edges introduces additional dynamics and faults or errors at the cutting edges. A dynamic microend milling cutting force and vibration model has been developed to investigate the microend milling dynamics caused by the unique mechanisms of chip formation as well as the unique microend mill design and its associated fault system. The chip thickness model has been developed considering the elastic-plastic nature in the ploughing process. A slip-line field modeling approach is taken for a cutting force model development that accounts for variations in the effective rake angle and dead metal cap. The process fault parameters associated with microend mills have been defined and their effects on chip load have been derived. Finally, a dynamic model has been developed considering the effects of both the unique microend mill design and fault system and factors that become significant at high spindle speeds including rotary inertia and gyroscopic moments.

What a Hot Comb Can Tell Us about History: Material Culture and the Classroom

The object being passed around the classroom attracts the keen interest of my students. Long and thin, it spans almost ten inches from end to end but measures just over an inch at its fat test. The head of the object, which is about three and a quarter inches long, is made of gold colored metal. One side of the head is solid and rounded, and the other has thirty-three thin metal spikes that stick out about three-quarters of an inch and taper to a sharp point. They are even and orderly, each spaced precisely one-sixteenth of an inch apart from the next. The metal head rests snugly on a one-inch metal pole, also gold colored, which itself fits into a silver metal cap. The cap is rounded on top, curves in around the short pole, and fits tightly against a black laminated wood shaft. The rounded shaft

Relationship between masticatory function and internal structure of the mandible based on computed tomography findings

The purposes of this study were to investigate bone mineral density as a part of bone construction in human skulls and to examine the relationship between dentofacial morphology and masticatory function by using computed tomography (CT) findings. Changes in bone mineral density in the mandible because of loss of masticatory function were tested in rats by experimentally producing an environment that inhibited mastication by the molars. Data for the human study were obtained from 27 modern male Japanese skulls (mean age, 28 years) from the University of Tokyo. Cortical bone thickness (CBT) and CT value (CV) were measured by each CT scan of the first and molars. For the animal study, a metal cap was inserted between the maxillary and mandibular incisors to prevent the molars from biting in 6-week-old male Wistar rats. The rats were killed after 2, 4, or 6 weeks, and bone mineral density was measured in cancellous and cortical bone equivalent to the first molar region by using peripheral quantitative computed tomography. In the human skull study, significant negative correlations were observed between CV in the regions of the buccal side of the second molar and the angle between the Frankfort horizontal and mandibular planes. Significant negative correlations were also observed between the gonial angle and CV in the buccal and basal sides. In the animal study, cancellous bone mineral density began to decline 4 weeks after the start of the experiment in the masticatory hypofunction group compared with the control group. By week 6, cancellous bone density had declined by 11.6% on the buccal side, 16.7% on the lingual side, 12.3% at the bifurcation of the root, and 38.1% at the root apex. Cortical bone density declined by 8% to 12% on the lingual side. The results support our hypothesis that a functional adaptive response by the mandible to mechanical stress resulting from mastication occurs not only in the muscle insertion area, but also in mandibular alveolar bone in the molar region.

Thermal resistance analysis and validation of flip chip PBGA packages

This work proposes a finite element numerical methodology to predict the thermal resistance of both flip chip-plastic ball grid array (FC-PBGA) with a bare die and FC-PBGA with a metal cap. The 3D finite element model was initially constructed to simulate the thermal resistance of FC-PBGA. A thermal resistance experiment was performed to verify the FEM results, following the construction of specimens of FC-PBGA with a bare die and with an aluminum cap, using six-layered substrate. The verified finite element model was employed to determine the thermal resistance of FC-PBGA with a copper cap using four-layered and six-layered substrates. Experimental results demonstrated that FC-PBGA with a metal cap improves thermal performance by 35% over with a bare die. FC-PBGA with a copper cap slightly improves thermal performance from 2% to 2.8% over that of FC-PBGA with an aluminum cap. The thermal resistance of FC-PBGA with a four-layered substrate is reduced by 4.0% to 5.9% from that of FC-PBGA with a six-layered substrate, since the four-layered substrate contains less metal. The finite element numerical results negligibly differ from the experimental results by 6% to 8.1%. A finite element numerical methodology is here proposed to predict the thermal resistance of FC-PBGA. The methodology is effective in researching and developing new products or improving existing packages.

O16 Organoleptic assessment of pure odour compounds representative of the metabolic end‐products of oral microbes

We have measured various production rates of volatile compounds in tongue scrape cell suspensions, oral biofilm models and the oral cavity in situ and wish to relate these to equivalent levels of oral malodour as assessed by the human nose.Objectives To assess the relationship between measured concentrations of pure odourants and resultant organoleptic scores (using a defined 0–5 score).Methods Seven odour judges, all with experience of organoleptic assessment, were used in this study for all experiments carried out at a single site (UWE, Bristol). A wide range of pure odourants were prepared at a range of concentrations (from a stock of 0.1 M) and were dispensed as 12 ml volumes into ‘universal’ bottles (24 ml capacity) leaving a headspace of 12 ml. The bottles were secured with rubber‐lined metal caps, labelled with a randomized code and were presented to the odour judges for assessment using the Rosenberg 0–5 scale. The volatile sulphur compounds (H2S and CH3SH) were presented as gases with dilutions being prepared through a dynamic gas flow rig (using oxygen free nitrogen as the diluent) and presented to the odour judges at a flow rate of 200 ml min−1. Group means of determinations for each odourant were plotted against log10 of the concentration. Linear regression analysis was used to measure the gradient, 95% CI, and the scatter of the points around the gradient (R2 value).Results Organoleptic scores were proportional to the log10 concentration of odourant. Detection thresholds (expressed as mol dm‐3) were skatole (7.2 × 10−13) < methyl mercaptan (1.0 × 10−11) < trimethylamine (1.8 × 10−11) < butyrate (2.3 × 10−10) < hydrogen sulphide (6.4 × 10−10) < putrescine (9.1 × 10−10) < dimethyldisulphide (5.9 × 10−8). Hydrogen sulphide showed highest olfactory power whilst putrescine was the lowest.Conclusions The olfactory response is exponential in nature. For any single compound, its contribution to malodour depends on: odour (olfactory) power, threshold (of detection) and volatility in addition to the concentration. It is now possible to relate production rates of VC's in models to typical levels of oral malodour perceived by the human nose.