Glass-ceramic Substrates Research Articles

Microstructure and Mechanical Properties of a Glass-ceramic Bond Coated TBC System

BaO–MgO–SiO2 based glass-ceramics was used as bond coat between 8wt. % yttria stabilized zirconia (8YSZ) top coat and nickel based superalloy substrate of a thermal barrier coating (TBC) system. The glass-ceramic bonded TBC system was characterized in terms of microstructure and mechanical properties (e.g. nanohardness, Young's modulus). The nanohardness and Young's modulus values of 8YSZ top coat, glass-ceramic bond coat and substrate of the TBC system were lower on the cross- section than those obtained on its plan-section.

Circuit and Physical Design of the zEnterprise™ EC12 Microprocessor Chips and Multi-Chip Module

This work describes the circuit and physical design implementation of the processor chip (CP), level-4 cache chip (SC), and the multi-chip module at the heart of the EC12 system. The chips were implemented in IBM's high-performance 32nm high-k/metal-gate SOI technology. The CP chip contains 6 super-scalar, out-of-order processor cores, running at 5.5 GHz, while the SC chip contains 192 MB of eDRAM cache. Six CP chips and two SC chips are mounted on a high-performance glass-ceramic substrate, which provides high-bandwidth, low-latency interconnections. Various aspects of the design are explored in detail, with most of the focus on the CP chip, including the circuit design implementation, clocking, thermal modeling, reliability, frequency tuning, and comparison to the previous design in 45nm technology.

Influence of sputtering atmosphere on hopping conductance in granular nanocomposite (FeCoZr)x(Al2O3)1−x films

The present paper investigates conductivity σ for a wide temperature range of 2K<T<300K in the nanocomposite (FeCoZr)x(Al2O3)1−x films (1–6μm thicknesses, 0.30<x<1.00) which were sputtered on glass–ceramic substrates from the compound target in vacuum chamber filled with Ar (set 1 films) or Ar+O2 gas mixture (set 2 films). TEM and HRTEM images revealed that granular films of set 1 containing nanosized crystalline metallic bcc α-FeCo-based nanoparticles embedded in the amorphous Al2O3 matrix. In case of Ar+O atmosphere of deposited α-FeCo-based crystalline “cores” with stabilized sizes were covered with an amorphous FeCo-based oxide “shells”. The σ(T) dependences were found to be in agreement with this phase structure. They show transition of the set 1 films σ(T) curves with x from tunneling (hopping) behavior below the percolation threshold x<xC≈0.46 to metallic one for x>xC. Moreover, as opposed to such behavior, for the set 2 films hopping mechanism of σ(T) was revealed far beyond xC due to the formation of semiconducting FeCo-based oxide “shells” separating electrically contacting FeCoZr cores.

Microstructural and Wear Behavior Characterization of Porous Layers Produced by Pulsed Laser Irradiation in Glass-Ceramics Substrates.

In this work, wear behavior and microstructural characterization of porous layers produced in glass-ceramic substrates by pulsed laser irradiation in the nanosecond range are studied under unidirectional sliding conditions against AISI316 and corundum counterbodies. Depending on the optical configuration of the laser beam and on the working parameters, the local temperature and pressure applied over the interaction zone can generate a porous glass-ceramic layer. Material transference from the ball to the porous glass-ceramic layer was observed in the wear tests carried out against the AISI316 ball counterface whereas, in the case of the corundum ball, the wear volume loss was concentrated in the porous layer. Wear rate and friction coefficient presented higher values than expected for dense glass-ceramics.

Negative differential resistance in magnetic tunnel junction systems

We study the electrophysical properties of the Fe/MgO/Fe magnetic tunnel junctions (MTJ) with impurities. Sample structures are fabricated on top of fine‐crystalline glass–ceramic substrates by e‐beam evaporation in a relatively low vacuum (∼10−4 Torr). The influence of the first magnetic layer fabrication conditions on the degradation of the MTJ is explained by the interlayer diffusion. Various models of electrophysical processes in MTJ on polycrystalline substrates are discussed. The current–voltage (I–V) characteristics of the fabricated structures are found to exhibit a region with negative differential resistance, similar to the one in tunneling diodes. We explain this phenomenon by the formation of excitons in the MgO layer modified by the conductive impurity atoms and their diffusion. The obtained results will be useful in the development of MRAM devices containing MTJs and tunneling diodes.

Creep rupture of the joint of a solid oxide fuel cell glass–ceramic sealant with metallic interconnect

Creep properties of sandwich joint specimens made of a newly developed BaO–B2O3–Al2O3–SiO2 glass–ceramic sealant (GC-9) and a ferritic-stainless-steel interconnect (Crofer 22 H) for planar solid oxide fuel cells (pSOFCs) are investigated at 800 °C under constant shear and tensile loadings. The creep rupture time of Crofer 22 H/GC-9/Crofer 22 H joint specimens is increased with a decrease in applied load for both shear and tensile loading modes. The given metal/sealant/metal joint has a greater degradation of joint strength at 800 °C under prolonged, constant tensile loading as compared to shear loading. The tensile creep strength at a rupture time of 1000 h is about 9% of the average tensile joint strength, while the shear creep strength at 1000 h is about 23% of the average shear joint strength. Failure patterns of both shear and tensile joint specimens are similar regardless of the creep rupture time. In general, creep cracks initiate at the interface between the (Cr,Mn)3O4 spinel layer and the BaCrO4 chromate layer, penetrate through the BaCrO4 layer, and propagate along the interface between the chromate layer and glass–ceramic substrate until final fracture. Final, fast fracture occasionally takes place within the glass–ceramic layer.

Thin-film solar cells on perlite glass-ceramic substrates

For the first time, thin-film CIGS solar cells have been fabricated by co-evaporation on specially developed non-conducting perlite (an aluminum potassium sodium silicate natural mineral of volcanic origin) glass-ceramic substrates to develop a fully integrated photovoltaic and building element. Such glass-ceramic material can meet the physical requirements to solar cells substrates as well as the cost goals. The preliminary data presented show that CIGS solar cells deposited on ceramic substrates can exhibit efficiency higher than 10%.

Structure and magnetoresistance of a Ni79.7Fe14.0Co2.8Zr2.0Cu1.5 thin film

The structure and magnetoresistance R of thin films based on Ni80Fe20 permalloy doped with Co, Zr, and Cu have been examined by X-ray diffraction analysis and resistance measurement. The films have been obtained by ion plasma sputtering on oxidized silicon, fused quartz, and glass ceramic cold substrates. It has been shown that the structure of a film in the initial state is a mixture of solid solutions based on two phases: Ni(fcc) particles with a size of L ≈ 8 nm and (Zr0.67Ni0.22O0.11)γ particles with a size of L ≈ 12 nm. The R(H) dependences on the strength and direction of the magnetic field H have been obtained at room temperature for film samples in the initial state and after isothermal annealing at 653 K for 1 h. According to R(H) dependences and X-ray diffraction analysis, films in the initial state are assumingly in a superparamagnetic state, whereas they exhibit ferromagnetic properties after isothermal annealing.

Overview on Developed Functional Plasma Sprayed Coatings on Glass and Glass Ceramic Substrates

For diverse applications in optical, electronic and consumer industries, the use of glass and glass ceramics as substrates for functional coatings is becoming of outstanding interest in order to develop advanced composites. Atmospheric Plasma Spraying (APS) is an adequate technology for the deposition of a wide variety of materials on glasses. Glass and glass ceramics are characterised by their specific thermo physical properties like low or even negative CTE, low heat conductivity and high dimensional stability. Consequently, modified production processes in comparison to the established coating operations on metal surfaces are required regarding the substrate activation methods or a more accurate heat transfer guidance to the substrate by optimized robot trajectories. This paper aims to give an overview of the investigations carried out at the IMTCCC for the development of plasma sprayed layer composites on borosilicate glass and glass ceramic substrates.

Self-organization of copper nanosystems under Volmer–Weber conditions during quasi-equilibrium condensation

Copper nanosystems were obtained by means of magnetron sputtering and further deposition of extremely weak vapour fluxes onto glass ceramic substrates and KCl cleaved facets. The increased pressure (∼10Pa) of highly purified argon, low discharge powers (∼24W) of the magnetron sputterer, as well as relatively high growth surface temperature (∼653K) have been used during the technological process. The mechanisms of structure formation on different substrates were analysed by SEM, TEM and electron and x-ray diffraction. To explain the self-organization of low-dimensional systems we developed a mathematical model of mass transfer of sputtered substance within the space between the magnetron sputterer and substrate. On the basis of experimental and modelling studies it was found that Ostwald ripening of Cu nanocrystal systems is possible to realize on KCl (001) cleaved facets under conditions of critically low supersaturations and at increased concentration of nucleation sites.

Processing of Foturan® glass ceramic substrates for micro-solid oxide fuel cells

Abstract The microfabrication of Foturan ® glass ceramic as a potential substrate material for micro-solid oxide fuel cells (micro-SOFC) was investigated. Foturan ® was etched in 10% aqueous hydrofluoric (HF) acid solution at 25 °C with a linear rate of 22 ± 1.7 μm/min to create structures with an aspect ratio of 1:1 in 500 μm-thick Foturan ® substrates for micro-SOFCs. The concentration of the HF etchant was found to influence the etching rate, whereas the UV-exposure time creating nuclei in the glass for subsequent crystallization of the amorphous Foturan ® material had no significant influence on the etching rates. The surface roughness of the crystallized Foturan ® was determined by the crystallite size in the order of 10–15 μm. Free-standing micro-SOFC membranes consisting of a thin film Pt cathode, an yttria-stabilized-zirconia electrolyte and a Pt anode were released by HF etching of the Foturan ® substrate. An open-circuit voltage of 0.57 V and a maximum power density of 209 mW/cm 2 at 550 °C were achieved.

Conditions of hydrochemical synthesis, composition, and structure of tellurium films

Conditions of the hydrochemical synthesis of thin tellurium fi lms by reduction of an aqueous solution of tellurous acid with hydrazine were determined. The redox potentials of tellurous acid and hydrazine and their difference in relation to pH of the medium and concentration of tellurite ions were calculated. The kinetics of tellurium layer growth on glass-ceramic substrates and the structure, composition, and morphology of the layers were studied.

Mechanical characterization of glass–ceramics substrate with embedded microstructure

One of the biggest challenge in the microfluidic channel fabrication in glass–ceramics or so called low temperature co-fired ceramics (LTCC) is the elimination of channel deformation during lamination. In this paper the expected deformation of the substrate and the sacrificial layer (starch powder and 3D printed UV polymerized material) during the lamination process of microfluidic structure fabrication is described. The choice of sacrificial volume material (SVM) plays an important role in channel deformation. Two types of SVM were investigated considering the width of the channel and the applicability. Uniaxial compression and Jenike shear test was used to obtain the mechanical parameters of starch SVM. To determine the stress–strain characteristics of LTCC uniaxial compression experiment was conducted. The shape of the laminated LTCC containing embedded channel was modeled by finite element method using the mechanical parameters obtained by the measurements. A design rule is given considering the channel width and the choice of SVM based on the simulation results.

Impedance spectra of thin permalloy films with a nanoisland structure

The behavior of the impedance spectra of island permalloy films prepared through vacuum evaporation onto optically polished glass-ceramic substrates has been investigated in the frequency range from 0.0001 to 100 MHz. A resistor-capacitor model of the films has been developed and the model parameters, for which there is a good agreement with experimental data on the frequency dependences of the real and imaginary components of the impedance, have been determined. The specific features in the behavior of the electrical and physical characteristics with variations in the thickness of the sample and the gap between the measuring electrodes have been investigated. It has been found that the relative permittivity of the films under investigation reaches values ɛ ∼ 107–108. The structural relaxation times have been calculated.

Electromigration Reliability of Glass Ceramic Multilayer Substrate with Various Surface Finishes

The process speed of high-end servers and supercomputers are steadily increasing. As a result, the backbone of the high speed processing, such as high-end LSI (flip-chip type), and associated substrate circuits is also becoming more dense and miniaturized, while supporting higher current densities. However, recent studies indicate that the higher current density triggers an electromigration (EM) at the solder bumps connecting the under bump metallurgy (UBM) of the flip-chip pad (e.g. Ni) and substrate pads (e.g. Ni/Au). This electromigration leads to voids within the solder joints, which may result in an open circuit. As of result, the life-cycle of the packaged devices is shortened. Thus solution to the EM issue is critical. To respond to such concerns, we have studied the mechanism of the void development, by closely examining differences in diffusion rate among the connective metals - within the pads and the solders. We have mitigated the EM occurrence by reducing the differences in diffusion rate by utilizing high purity Cu for the substrate metallization pads, Cu exhibits a diffusion rate similar to Sn used in solder bumps. Also, solder wettability was improved by utilizing a solder on pad (SOP) construction. As of result we were able to successfully demonstrate an improved life-cycle of the flip-chip solder joints, while accommodating a higher current density. Furthermore, a glass ceramic substrate was used for our study. Since this particular glass ceramic substrate has a coefficient of thermal expansion of 11.8ppm/K, there is an improvement in 1st and 2nd level reliabilities associated with thermal stress from device heat generation. At the same time, it possesses a dielectric constant of 5.8, which is conductive with superior electrical performance (high speed and high frequency). Thus, this glass ceramic substrate is capable of supporting increases in current density, while sustaining high reliability.

Long-term stability of Ag and Cu thin films on glass, LTCC and alumina substrates

Silver (Ag) and copper (Cu) are regarded as advanced material for metallization systems in microelectronic devices because of their high electrical conductivity and enhanced electromigration resistance. Typically, organic circuit boards as well as ceramic and glass–ceramic substrates use galvanic deposited Cu films or screen-printed metallization for this purpose. When applying the latter approach, however, the lateral resolution in the μm-region being required e.g. for novel high frequency applications can not be guaranteed. Hence, sputter deposition is envisaged for the realization of thin film metallization systems. The reliability of 300 nm thick Cu and Ag thin films is comparatively investigated under accelerated aging conditions, utilizing a test structure which consists of parallel lines stressed with current densities up to 2.5 × 106 A cm−² at temperatures up to 300°C on Si/SiO2, glass, LTCC (low temperature co-fired ceramics) and alumina substrates. To detect the degradation via the temporal characteristics of the current signal a constant voltage is applied according to the overall resistance of the test structure. Knowing the mean time to failure (MTF) and the activation energy at elevated temperatures conclusions on the migration mechanism can be drawn. Whereas on LTCC substrates the activation energy Ea is about 0.75 eV for both Ag and Cu thin films, the higher activation energies of about Ea ~ 1 eV measured for Cu on glass and alumina indicate a suppression of back diffusion especially at enhanced temperature levels. This effect is predominantly caused by a stable oxide layer which is formed at high temperatures and which acts as passivation layer. Therefore, the overall electromigration resistance is lower compared to Ag.

Bonding quality of contemporary dental cements to sandblasted esthetic crown copings*

To evaluate the shear bond strength of current luting cements to sandblasted crown-coping substrates. Specimens of nickel-chromium, pressable glass ceramic, and zirconia crown-coping substrates were sandblasted in three groups (n = 30 each) with 50 (group 1), 110 (group 2), and 250 μm (group 3) alumina particles at a pressure of 250 kPa. Cylinders of glass ionomer, universal resin, and self-adhesive resin cements were then built up on the sandblasted substrate surfaces of each group (n = 10). All bonded specimens were stressed to evaluate the cement-substrate shear bond strength. Both the mode and incidence of bond failure were also considered. No difference was noticed between all test groups in terms of cement-substrate bond strength. In comparison to self-adhesive type, the universal resin cement provided lower bond strengths to both metal and glass-ceramic substrates in group 1. The self-adhesive resin cement provided the highest bond strengths to the zirconia substrates in groups 2 and 3. The adhesive type of bond failure was common in the metal and zirconia substrates in all groups. Cement-substrate bonding quality is not affected by the size of sandblasting particles. Resin cements bond better to different coping substrates. Self-adhesive resin cement is the best choice to bond zirconia-based substrates.

High-aspect-ratio MEMS deformable mirrors for next-generation telescopes

The next generation of extremely large telescopes (ELTs) that will be built on a scale of 30–50 meters in diameter necessarily require an increased ability to correct wavefront errors. Currently, wavefront correction is achieved through the use of a deformable mirror (DM). The degree and amount of correction depends on amechanical displacement of segments of themirror (stroke), and the number of actuators in the mirror surface (order). An effective ELTwill require a high-stroke (10microns) and high-order (100X100 actuators) mirror, a costly prospect using current technology.1 Lowering the cost while improving the performance of DMs is possible using microelectromechanical systems (MEMS) technology. However, current surface machining processes used to fabricate MEMS deformable mirrors, such as the Sandia ultra-planar multilevel MEMS technology (SUMMiT) and MEMSCAP’s PolyMUMPS process, limit a DM’s stroke due to the use of thin-film sacrificial layers (which are dissolved away after the etching process to free up micromechanical components in the actuators).2, 3 Commercially available surface micromachined MEMS mirrors are limited in stroke to approximately 5.5 microns, about half of the stroke required by ELTs. A high aspect ratio fabrication process capable of depositing thick layers will allow the DM’s to provide both high-stroke and highorder corrections, thus bypassing the need for a complex dual woofer (high stroke, low order)/tweeter (high order, low stroke) DM configuration.4 In our work, we tested different actuator designs with a bonded faceplate constructed using the LIGA (German acronym for lithography, electroplating, and molding) process, enabling multilayer fabrication of MEMS devices.5 Various types of high-stroke gold actuators consisting of folded springs with Figure 1. Diagram showing the final release of the monolithic fabricated structure created using our technique. The gap for the Xbeam electrostatic actuators is 20 microns, enabling a mirror stroke of 10 microns. WMS-15: specific glass-ceramic substrate. Not to scale.

Densification Mechanism of the Low Temperature Co-Fired Glass-Ceramic Substrate

In this paper, application of multilayered circuit substrates has been studied, the glass ceramic (50%Al2O3-50%glass) with low temperature co-fired and good performance as the raw material was used, by means of calculating the apparent activation energy of densification in the experiment and observing the SEM images of glass ceramic substrate section, the densification mechanism of glass ceramic substrate sintering is analyzed.

Diffusivity of silver ions in the low temperature co-fired ceramic (LTCC) substrates

Diffusion of silver inner-electrode occurred during sintering of commercial low temperature co-fired glass ceramic substrate made the dielectric surface become light yellow. The samples added with silicon oxide (SiO2) powder, however, maintained white color. Silicon-oxide powder was used to modified the sintering behavior and inhibit the silver ions diffusion for the LTCC ceramics. The alumina particles in the LTCC substrates could be regarded as the diffusion barrier of silver ions. The activation energy for silver ions diffusion in the LTCC substrates was 101 kJ/mol. When 5 wt% SiO2 powder was added into the LTCC substrate, the diffusion activation energy of silver ions became 145 kJ/mol. At sintering temperature of 1180 K, the diffusion coefficient of silver ion in the LTCC ceramic substrates with and without additional SiO2 were 8.88 × 10−13 cm2/s and 1.08 × 10−12 cm2/s, respectively.