By combining ion track technology with ordinary low-resolution printed circuitboard lithography it is possible at low cost to create high aspect ratios via connectors, as solid plugs or consisting of bundles of sub-micron connector wires at a small total cross-section.

Ion track enabled microwave circuits in flexible printed circuit boards are suggested to be used in applications like inductors, ferromagnetic resonance microwave filters, circulators and magnetoresistive sensors. In this paper we demonstrate this technology with integrated printed circuitboard devices in two different flexible polyimide-based foils (Espandex and Kapton HN), using the ultra-high-density vias and the sub-micron wires.

Dielectric permittivity (εr) of BaTiO3(BTO) powders was determined by measuring εr of slurries prepared from BTO powder and propylene carbonate as dispersion medium, followed by analyzing with a finite element methods (FEM). The εr of powders depended on their characters such as tetragonality (c/a ratio), density, particle size and specific surface area. In order to extract the effect of each character, a statistical analysis was carried out to represent the εr of powders with an empirical formula, where the c/a ratio, density and particle size were used as parameters. A fairly good agreement between observed data and those expected from the formula was obtained and the contribution of each character to the εr could be determined.

A precision measurement technique for measuring complex dielectric permittivity in the 118 – 178 GHz frequency range is described. The combination of a high-quality Fabry-Perot resonator, excited by a free-running BWO (backward wave oscillator), combined with the processing capability of a sensitive receiver based on the Tektronix 2782 spectrum analyzer, using the WM782 (F-G) harmonic mixer, yields a very sensitive measurement technique.

The development of techniques for measuring extremely low losses in dielectric materials has been driven primarily by the requirements of the fusion energy research program. The heating of a plasma to the temperatures required for fusion is expected to require the delivery of megawatts of RF power through vacuum windows into the plasma vessel. A material with very low loss as well as excellent thermal and mechanical properties must be utilized to avoid a catastrophic window failure.

The relevant loss mechanisms and measured results for several candidate materials are discussed

Barium Strontium Titanate (BST) thin films have been deposited on (100)-oriented MgO substrate by combining preparation of initial layer by Pulsed Laser Deposition and main layer by Metal-Organic-Decomposition method. Films with an initial layer of 20, 30 and 40 nm thickness and final thickness of 400, 650 and 800 nm have been obtained. Physical and dielectric properties of the BST thin films have been characterized from the viewpoint of frequency-agile micro and millimeter wave circuit applications. The results reveal that Ba0.6Sr0.4TiO3 thin films have a good crystallinity with characteristic orientation that is affected by the deposition conditions of the initial layer. Interdigital capacitor with a gap of 10 μm has been characterized and the dielectric loss and tunability are as low as 0.002 to 0.004 and 12%, respectively, at frequency of 1 MHz for the applied voltage from -/+40V to +/-40V. At microwave frequencies, classical coplanar waveguide lines formed on BST/(100)MgO were investigated. A differential phase shift of 18 degree was obtained at 20 GHz with insertion loss of about −2 dB at 60 V for Au/Cr interconnection. Finally, a 3-stage LC-ladder-type phase shifter with variable capacitors of BST thin film has been fabricated considering the experimental results obtained for the coplanar waveguide lines and a maximum phase shift of 40 degrees is obtained at 20 GHz at 60 V.

Die-on-wafer and wafer-level three-dimensional (3D) integrations of heterogeneous IC technologies are briefly described, emphasizing a specific 3D hyper-integration platform using dielectric adhesive wafer bonding and Cu damascene inter-wafer interconnects to provide a perspective on wafer-level 3D technology processing. Wafer-level 3D partitioning of high Q passive components, analog-to-digital (A/D) converters, RF transceivers, digital processors, and memory is discussed for high-performance RF-microwave-millimeter applications, especially where high manufacturing quantities are anticipated. Design and simulation results of 3D heterogeneous integration are presented. This 3D technology is applicable to smart wireless terminals, millimeter phased array radars, and smart imagers.

(001) oriented (Ba, Sr)TiO3 (BST) thin films were deposited on MgO (001) single crystal substrates by the pulsed laser deposition method. Structural properties of BST films were investigated using X-ray diffractometer. Coplanar waveguide (CPW) device based on BST/MgO layer structure was fabricated by dc sputtering deposition, photolithography and etching process. To study the geometrical factor dependent microwave performance of the CPW phase shifter based on (001) oriented BST film, the CPW devices having various gap and width were fabricated. The microwave dielectric properties of BST CPW phase shifter devices were examined by calculating the scattering parameter obtained using a HP 8510C vector network analyzer with the frequency range 0.5 ∼ 20 GHz at room temperature under the dc bias field of 0 ∼ 40V. The measured return loss and insertion loss at 10 GHz with no dc bias were about -12 ∼ -4 dB and -14 ∼ -3 dB, respectively, which mainly depended on the impedances of the CPW transmission lines. The measured differential phase shift values were about 20 ° ∼ 140 ° at 10 GHz with 40 V dc bias variations, which depended on the gap size.

Ba0.60Sr0.40TiO3 thin films were deposited on orthorhombic <100> oriented NdGaO3 substrates by pulsed-laser deposition. Film thickness ranged from 25 nm to 1200 nm. X-ray pole figures have shown consistent <110> textured films with good alignement to the substrate. X-ray strain analysis indicates up to 0.5% compressive strain along the (001) direction, and weaker tensile strain along (-110). Dislocation densities, as computed from strain data, were found to be in the range 5–6×105 cm-1 along both directions. The critical thickness for dislocation formation along (001) and (-110) were found to be 5 and 7 nm, respectively. Permittivity and tunability were investigated using interdigitated capacitors in the 45 MHz-20 GHz range. Dielectric properties and tunability in the <110> oriented films exhibited strong strain and directional properties. Tunability up to 54% was observed at moderate field levels (∼ 5 kV/mm).

This paper reports on a novel low temperature sputter deposition of AlN on an Al substrate, yielding films with stresses and crystalline orientation comparable to those of films deposited on Pt. The study focuses on the importance of the initial film growth step on both the stress and crystalline orientation of the film. The AlN layer is deposited using Pulsed DC (250 kHz, 90% duty cycle) magnetron reactive sputtering (93% N2, 7% Ar) using an Al target. The substrates are 150mm Si wafers with an aluminum seed layer (100 nm). The thickness of the AlN films is ≈2.5μm with uniformity across the wafer of 0.4%. The films were deposited in 4 passes of 0.625μm each to avoid overheating of the substrate. The influence of the substrate bias (0 V, 80 V and 120V) and argon pre-sputtering of the aluminum substrate been investigated. The film stress, and to a smaller extent the crystalline orientation, were mainly driven by the properties of the film deposited during the first pass. The bias is useful at the beginning of the film growth for stress control. This study suggests that it is beneficial not to use bias during the entire film deposition. With this approach, it was possible to deposit c-axis oriented AlN layers on Al with a FWHM of the rocking curve of 1.63° and low stress (<300MPa).

For the millimeter-wave dielectrics, forsterite-based ceramics were produced. Stoichiometric forsterite ceramics (Mg2SiO4) shows porous microstructure and very low Q*f values, which is not suitable for dielectrics in the microwave and millimeter-wave bands. The small addition (0.025 mol%) of Ta2O5 instead of SiO2 enhanced the sinterability of forsterite ceramics. The sintering temperature was reduced more than 150°C by the addition of Ta2O5. The density was greatly increased by Ta2O5 addition. The dielectric constant and Q*f of 0.025 mol% Ta2O5 modified forsterite sintered at 1500°C was 7.3 and 150, 000, respectively in microwave band (8–11GHz). The dielectric constant and Q*f of the same sample measured at 55GHz was 6.7 and 179, 000, respectively. Further addition of Ta2O5 decreases the sintering temperature.

The US Army is actively pursuing technologies to enable transformation goals of a lighter, faster, more potent force via affordable, electronically scanned phased array antennas (ESA's) that will provide the means for achieving a high data rate with beyond-line-of-sight, mobile communications. In order to transition this technology to Army applications, it is important that the cost of each device be decreased from current technology. Traditionally, paraelectric, active thin films of magnesium doped barium strontium titanate, have been deposited on expensive ceramic (MgO, LaAlO3, SrTiO3, Al2O3) substrates, and compositionally designed for tunable microwave applications. By integrating an active, thin film material with a large area, low cost, microwave friendly substrate, the cost could be significantly reduced. While Si is not a suitable substrate for microwave applications, a low cost, microwave friendly, buffer layer on silicon would be.

A high performance Ta2O5 thin film, passive, buffer layer on Si substrates has been successfully designed, fabricated, characterized, and optimized via metalorganic solution decomposition technique. The optimized Ta2O5 based thin film exhibited suitable microwave material properties, including an enhanced dielectric constant (εr = 45.6), low dielectric loss (tan δ=0.006), low leakage current, high film resistivity (ρ=1012 Ω-cm at E=1 MV/cm), excellent temperature stability (temperature coefficient of capacitance of 52 ppm/°C), and outstanding bias stability of capacitance (∼1.41% at 1 MV/cm). The permittivity and dissipation factor, also of extreme importance, exhibited minimal dielectric dispersion with frequency. The dielectric passive buffer layer film was typified by a uniform dense microstructure with minimal defects, and a smooth, nano-scale fine grain, crack and pinhole free surface morphology. At elevated processing temperature, there was negligible elemental interdiffusion at the interface between the substrate and buffer layer as verified by Rutherford Backscatter Spectroscopy and Auger Spectroscopy, ensuring long-term reliability of the heterostructure.

By developing a passive, thin film material that is microwave friendly, we have demonstrated the direct integration of paraelectric active thin films with silicon substrates. This should allow phase shifter materials technology to be implemented across a wide spectrum of Army and commercial applications, specifically, affordable, mobile phased array antenna systems for a variety of DoD applications.

Embedding passives into printed wiring boards have numerous advantages that show up in different segments of the market. For example, the ability to locate decoupling capacitors within a couple hundred microns of semiconductor I/Os greatly improves response time and signal integrity leading to product performance improvements. One crucial need, however, is high capacitance density. High capacitance density can only be readily achieved by ceramic technology. Therefore, the focus of this work has been the development of ceramic thick-film capacitor technology that can be used to bury high capacitance density components within an organic substrate. This allows high value decoupling capacitors to be buried for chip packaging or related applications in spaces available within any layer of the substrate.

The dielectric paste is based on doped barium titanate composition and works together with a cofired copper electrode paste. The capacitor system is designed to be screen printed on copper foil in the locations desired in the circuit and fired in nitrogen at 900°C to form the ceramic components. Following this, the foil is laminated, component face down, to the organic laminate using standard prepreg and the inner layer etched to reveal the components in an organic matrix. The system has a dielectric constant of approximately 3000 and achieves a capacitance density of ∼1.5 nF/mm2. In the following sections, issues that we encountered when making embedded capacitors with this first generation system are presented.

High dielectric constant, perovskite-structure materials, such as barium strontium titanate (BST), have been widely investigated for use in GHz LSI decoupling capacitor applications. In addition to modifying deposition process parameters, such as increasing deposition temperature, doping may be a viable way to increase permittivity and tunability in BST thin films without increasing the thermal budget. In this research, the effects of Y dopants on the dielectric behavior of RF-sputtered BST thin films have been systematically investigated. The BST thin films were deposited using ceramic targets with different compositions of yttrium oxide dopant. With Y-doping concentration of ∼ 1.3 at.%, the permittivity at around zero electrical fields can be increased by more than 70% compared to nominally undoped BST thin films produced under the same deposition conditions. Based on x-ray diffraction strain analysis and inductively-coupled plasma composition measurements, the correlations among the dopant composition, BST film elastic strain and dielectric behavior have been systematically studied.

In acoustic devices such as film bulk acoustic resonators (FBAR), it is most essential to accurately determine the thin-film sound velocities in situ. In this work, we analyzed the microstructure properties of the zirconia thin films deposited by RF magnetron reactive sputtering with various oxygen partial pressures, and measured the longitudinal film velocity with picosecond ultrasonic technique. The picosecond ultrasonic waves were produced by irradiating the testing samples with an ultrafast laser pulse generated by a self-made mode-locked Ti: Sapphire laser, and detected by a delayed probe laser pulse. The acoustic velocities of the thin films were next determined from the echo times of the ultrasonic waves. To derive more accurate and reliable velocity, three different reflective layers were employed so that the echo shapes and intensities of ultrasonic wave can be compared. It was found in this work that the thin film velocities we measured were less than the bulk value, which can be calculated from Young's modulus and the density. Meanwhile, with the measurement results, it is also found that the measured acoustic velocity and the microstructure of films have strong dependence on the growth conditions. Consequently, accurate thin film velocity will be obtained for an SMR designer through better controlling on deposition conditions during manufacturing process.

Perovskite ferroelectric thin films in the paraelectric state exhibit outstanding dielectric properties, even at high frequencies (>1 GHz). The tunable dielectric constant of ferroelectric thin films can be used to design frequency and phase agile components. High dielectric constant thin film ferroelectric materials in the paraelectric state have received enormous attention due to their feasibility in applications such as decoupling capacitors and tunable microwave capacitors; the latter application has been fueled by the recent explosion in wireless and satellite communications. This paper reportsBa0.96Ca 0.04Ti0.84Zr0.16O3 (BCTZ) thin films that were deposited on Pt electrodes using radio frequency magnetron sputtering at a low (450 °C) substrate temperature. Sputtered thin film BCTZ at low substrate temperature is compatible with conventional integrated circuit technology. The structural characterization of the deposited films was performed by x-ray diffraction. The electrical characterization of the films was achieved by capacitance-voltage, current-voltage, and S-parameter (via vector network analyzer) measurements. In addition, the effect of post annealing on the deposited films was investigated. A detailed understanding of both their processing and material properties is discussed for successful implementation in high frequency applications.

BaTiO3/SrTiO3, BaTiO3/BaZrO3, and SrZrO3/SrTiO3 artificial superlattices were fabricated on SrTiO3 substrates by the molecular beam epitaxy (MBE) process. The stacking periodicity of each layer was varied from 1 unit cell to 40 unit cells, and the total thickness was fixed at 80 unit cells. In-situ reflection high-energy electron diffraction (RHEED) and x-ray diffraction (XRD) clearly shows the formation of the superlattice structure. Their lattice parameters obtained from the reciprocal space mapping measurement indicated that the lattice distortion was dependent on the stacking periodicity. The capacitance and the complex admittance of the superlattices were measured with interdigital electrodes by an impedance analyzer up to 110 MHz. It was found that the dielectric permittivity changed with the superlattice periodicity. The Q-V measurement results showed clear hysteresis curves and this suggested that ferroelectricity was induced into the SrZrO3/SrTiO3 superlattices despite a combination between paraelectrics/paraelectrics.

We report on recent developments in microwave applications and understanding of thin Ba50Sr50TiO3 films. Most of our recent efforts have focused on developing low loss, wide band phase shifters from X-band (8.4 GHz) to Ka-Band (26.5 GHz) for scanning reflectarray antennas. Attempts to reduce tanδ by Mn-doping Ba50Sr50TiO3 films are briefly discussed. We have demonstrated a hybrid device at X-band that produces in excess of 300 degrees of phase shift with about 3.5 dB insertion loss and greater that 10% bandwidth. Preliminary results are presented here. The effects of mild (600 rad Si) proton radiation on device performance will also be discussed. Preliminary results on optical phase shifters will be included.

La-Ni-O films were deposited at deposition temperature ranging from 250 to 540°C by rf magnetron sputter deposition. The effects of deposition temperature and the following heat-treatment condition on the constituent phases and characteristics of LaNiO3 films were investigated. LaNiO3 phase was obtained at the deposition temperature of 250 and 360°C, while La-rich phase of La2NiO4 was appeared above 540°C. Crystalline phases of resultant films after the following heat-treatment strongly depended on the partial pressure of oxygen gas in ambience, i.e., in case of the heat-treatment at 800°C, diffraction peaks originated from LaNiO3 phase disappeared on XRD patterns in pure nitrogen gas ambience, while impurity peaks of NiO appeared in oxygen-excess (>50%) ambience. As a result, LaNiO3 films with high crystallinity and the same lattice parameter as the bulk one were obtained in the deposition at 360°C followed by the heat-treatment at 700°C in air.

In this paper, recent advancements related to a novel approach for fabricating low cost capacitive radio frequency microelectromechanical (RF MEMS) switches using directly photodefinable high dielectric constant metal oxides are discussed. In this approach, a radiation sensitive metal-organic precursor is deposited via spin coating and converted patternwise to a metal oxide using exposure to ultraviolet light. The feasibility of this approach has previously been demonstrated by fabricating bridge-type and cantilever-type RF MEMS switches. These early experiments showed that the photopatterned oxides displayed dielectric breakdown strengths that were insufficient for reliable operation of MEMS switches which required actuation voltages on the order of 20 V to 30 V. Recent work has focused on developing advanced processes based on the photodefinable metal-organic approach that can produce oxides with higher dielectric breakdown strengths and higher dielectric constants. A variety of post-patterning processes, including thermal baking and oxygen plasma annealing, were investigated and the impact of such processing on the resulting dielectric properties are discussed in this paper. It is shown that a combination of thermal annealing and oxygen plasma treatment can substantially improve the dielectric breakdown strength of the metal oxides produced using the photosensitive metal-organic process.

We used the Advanced Photon Source (APS) at Argonne National Laboratory to perform fast (ps range) time-resolved diffraction measurements of the dynamic characteristics in BaTiO3 films subjected to strong high-frequency electric fields. The time-dependent lattice response measured at frequencies between 6.5 MHz and 1.3 GHz revealed damped domain movements with attenuation time rapidly increasing with electric field frequency, v. We found that at frequencies higher than ν ∼ 600 MHz the domain motions in BaTiO3 films become heavily damped, information that may be important to future device operation. A minimum attenuation time, τ ∼ 330 ps, measured at ν = 1.3 GHz was limited by the time constant of the electrical circuit.

In universal relaxation, a material's complex dielectric susceptibility follows a fractional power law f1-n where 0 < n < 1 over multiple decades of frequency. In a variety of materials, including Ba0.5Sr0.5Ti03, dielectric relaxation has been observed to follow this universal relaxation model with values of n close to 1. In this work we have shown that the universal relaxation model can be used to calculate dielectric loss even when n is very close to 1. Our calculated Q-factors agree with measured values at 1 MHz; this agreement suggests that this technique may be used for higher frequencies where network analyzer measurements and electrode parasitics complicate Q-factor determination.