Parthasarathi Chakraborti

Tunable and Miniaturized RF Components with Nanocomposite and Nanolayered Dielectrics

Nanocomposite and nanolayered dielectrics provide new avenues to enhance the performance of RF and power components. They enable engineering of properties such as permeability, permittivity, frequency-and temperature-stability, and tunability, along with low loss, to miniaturize next-generation multiband RF modules that require higher functional density and improved performance. This paper demonstrates two such advances in nanodielectrics: 1.) Magnetic nanocomposites for miniaturization of antennas, metamaterials and other RF components, 2.) Nanolayered stack dielectrics for tunable RF components with temperature- and frequency-stability and low loss. The materials design, synthesis, processing and characterization to demonstrate the superior properties are presented.

Novel Nanostructured Passives for RF and Power Applications: Nanopackaging with Passive Components

Miniaturization of passive components, while mounting them close to the active devices to form ultrathin high-performance power and RF modules, is a key enabler for next-generation multifunctional miniaturized systems. Traditional microscale materials do not lead to adequate enhancement in volumetric densities to miniaturize passive components as thin films or thin integrated passive devices. With these materials, component miniaturization also degrades performance metrics such as quality factor, leakage current, tolerance, and stability. Nanomaterials such as nanocomposite dielectrics and magneto-dielectrics, nanostructured electrodes, and the resulting thin-film components have the potential to address this challenge. This chapter describes the key opportunities in nanomaterials and nanostructures for power and RF passive components. The first part of this chapter describes the role of nanostructured materials for high-density capacitors and inductors in power modules. The second part of the chapter describes application of nanoscale materials as nanocomposite dielectrics and magneto-dielectrics with stable and high permeability and permittivity for miniaturized RF modules.

High-density capacitors with conformal high-k dielectrics on etched-metal foils

This paper describes the fabrication and characterization of high-density capacitors using etched-metal foils as high-surface area electrodes. High permittivity films were conformally-formed over the metal foils using an anodization reaction. The approach was demonstrated with two material systems, viz., etched aluminum foils and porous titanium foils. Both the metal anodizations were carried out with aqueous solution of citric acid as electrolytes. The electrical properties of the etched-foil capacitor were measured using a sulfuric acid solution as the top contact. The high surface area electrodes yielded very high capacitance densities of 35-40 μF/cm2.

Coaxial through-package-vias (TPVs) for enhancing power integrity in 3D double-side glass interposers

Double-sided 3D glass interposers and packages, with through package vias (TPV) at the same pitch as TSVs in Si, have been proposed to achieve high bandwidth between logic and memory with benefits in cost, process complexity, testability and thermal over 3D IC stacks with TSV. However, such a 3D interposer introduces power distribution network (PDN) challenges due to increased power delivery path length and plane resonances. This paper investigates the use of coaxial through-package-vias (TPVs) with high dielectric constant liners as an effective method to deliver clean power within a 3D glass package, and provides design and fabrication guidelines to achieve the PDN target impedance. The Coaxial TPV structure is simulated using electromagnetic (EM) solvers and a simplified equivalent circuit model to study via impedance and parasitics. Test vehicles with anodized tantalum oxide capacitors were fabricated in ultra-thin, 100μm thick glass interposers to demonstrate process feasibility, with a capacitance density of 5 nF/mm2. Self-impedance (Z11) of a 3D glass interposer containing the coaxial TPVs was analyzed with variations in (a) Via location, (b) Number of coaxial vias, and (c) Via capacitance and stack-up, to provide optimal PDN design guidelines. Based on the above parameters, the added decoupling vias achieved more than 30% impedance suppression over multiple resonance frequencies between 0.5-6 GHz, providing an effective and flexible PDN design method for double-side 3D glass interposers.

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High-k barium strontium titanate (BST) thin films were deposited onto glass substrates to demonstrate integrated capacitors for power supply in high-speed digital packages. Ferroelectric BST films were sputter deposited onto solution-derived lanthanum nickel oxide (LNO) electrodes. Zirconium oxide was studied for the first time as a barrier between glass and LNO electrodes to prevent electrode (LNO) interdiffusion into the glass substrate. The LNO and BST films were annealed in an oxygen-rich atmosphere at 650°C. A capacitance density of 20-30 nF/mm2 was obtained at an operating voltage of 3 V. Leakage currents of 1-10 nA/nF were measured up to 3 V. These properties demonstrate the potential for low-cost high-k thin-film decoupling capacitors in 2-D, 2.5-D, and 3-D glass interposers. A process to integrate and test such capacitors on glass substrates using sequential dielectric and electrode patterning is also demonstrated.

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This paper describes ultrathin tantalum-based high volumetric-density power capacitors with low leakage properties for 1-10-MHz frequency applications. Nano dielectrics with low-defect density were grown on nanoporous tantalum anodes using the self-limiting anodization process. The fundamental mechanisms that govern the film growth and quality were investigated to provide anodization process guidelines. Conducting polymer nanoparticles were used as the cathodes. Complete filling of conducting polymer was achieved by the optimization of conducting polymer application process. Energy dispersive spectroscopy and structural SEM studies were performed to investigate the morphology and structure of the tantalum pentoxide films. The fabricated capacitor showed 0.6-0.8 μF/mm2 of capacitance density in the 1-10-MHz range, in substrate compatible ultrathin (<;75 μm) form factors. This is the highest volumetric density reported for such thin-film capacitors in a megahertz frequency range.

Thin-Film Capacitors With Conducting Oxide Electrodes on Glass Substrates for Power-Supply Applications

This paper describes an innovative scheme for integrating thinfilm tantalum (Ta) capacitors on active silicon substrates, an approach that can serve as a roadmap for the potential integration of ultra-thin high density capacitors in near future. The paper describes a new 3D concept for ultra-miniaturized, multi-functional and relatively low-cost power converter modules. The scheme consists of planar tantalum (Ta) capacitors by forming Ta2O5 (30-120 nm thick) dielectric and attaching directly to active or passive Si substrates using ultra-loss dielectrics (Zeon, ZS-100). Capacitors attached directly on Si allow for shorter interconnection length (<; 10μm) yielding lower parasitics in loop inductance and planar resistance. Reducing these parasitics results in higher switching frequency (>100 MHz) with fewer Ta capacitors on active Si. The paper focuses on capacitor fabrication of ultra-thin Ta foils (<; 5μm) and their integration on ultra-thin active Si for lowering the parasitics. Consequently, electrical characterization of the above capacitors demonstrates the fundamental electrical superiority of the 3D integrated Ta capacitors.

Ultrathin, Substrate-Integrated, and Self-Healing Nanocapacitors With Low-Leakage Currents and High-Operating Frequencies

This paper demonstrates 3D functional modules that are ultra-miniaturized, high-performance and low-cost, based on an innovative 3D Integrated Passive and Active Component (3D IPAC) concept [1]. The 3D IPAC concept utilizes an ultra-thin (30-100 microns) and ultra-low-loss glass substrate, low-cost through-package-vias (TPVs) and double-side redistribution layers (RDL) for assembly of both active and passive components. In this concept, both active and passive components are integrated on both sides of the glass substrate, either as thinfilms or as discretely fabricated and assembled components, separated by only about 50-100 microns in interconnection length. This paper specifically addresses the power functional modules with passive components by integrating ultra-thin high-density capacitors on one side and power-supply inductors on the other side. The first part of the paper describes the electrical modeling and design of power inductors and capacitors in 3D IPAC structure. The second section describes the fabrication for both the building block L and C components and the assembly of integrated modules. The last section presents the electrical characterization. The paper, thus, provides a first demonstration of a novel power module platform for double-side thin active and passive component integration for power module applications.

Demonstration of ultra-thin tantalum capacitors on silicon substrates for high-frequency and high-efficiency power applications

This paper investigates the role of electrode–dielectric interactions, and barrier materials on leakage current, breakdown voltage, yield and reliability of thinfilm (Ba,Sr)TiO3 capacitors on silicon and glass substrates. The first part of the paper investigates the electrode–dielectric interactions with sputtered Cu and Ni electrodes to identify the mechanisms that lead to high leakage current and low yield. The second part of the paper presents lanthanum nickel oxide as a viable solution to overcome the problems with sputtered Cu and Ni electrodes. A combination of low leakage current, high yield and capacitance densities was achieved with the oxide electrode systems.

Ultra-thin and ultra-small 3D double-side glass power modules with advanced inductors and capacitors

This paper explores silicon nanowire technology for ultrathin high-density capacitors, supercapacitors and batteries. Development of such thin power components on glass or silicon will allow integration with other passive components as well as actives such as decoupling capacitors close to locic Ics to form 3D integrated passive and active devices (3D IPACs) that could then be surface-assembled onto glass packages leading to ultrathin self-powered modules or subsystems. Thinfilm integration of power components and passives on ultrathin glass 3D IPD substrates also leads to highly-efficient power distribution for miniaturized and high-performance electronic systems. The first part of the paper presents an analytical model to highlight the benefits of nanowire electrode-based high-density capacitors in capacitance density and operating frequency. The second part of the paper describes nanowire synthesis and a novel fabrication process for nanowire-electrode capacitors, and their characterization. Results indicate that nanowires enable a major breakthrough in thinfilm capacitors with ultrahigh volumetric capacitance densities of about 100 μF /mm3, 10X higher than all current capacitor technologies including trench, MLCC and tantalum capacitors.