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Author

Rao Tummala

Other affiliations: Qualcomm, IBM, AVX Corporation  ...read more
Bio: Rao Tummala is an academic researcher from Georgia Institute of Technology. The author has contributed to research in topics: Interposer & Capacitor. The author has an hindex of 43, co-authored 623 publications receiving 11663 citations. Previous affiliations of Rao Tummala include Qualcomm & IBM.


Papers
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Journal ArticleDOI
TL;DR: In this article, a comparison of the liquid-based photo-imageable dielectric (PID) and dry-film (DDF) materials in terms of interconnect path losses that are critical in mm-wave frequency bands is presented.
Abstract: Heterogeneous package integration and chiplet approaches are the key technology to enable next-generation high performance small form-factor packages for emerging applications. Millimeter-wave packaging for fifth-generation and upcoming sixth-generation platforms also need to meet the high-density low signal-loss interconnect specifications utilizing advanced conductor and dielectric materials. This article presents the comparison of the liquid-based photoimageable dielectric (PID) and dry-film dielectric materials in terms of interconnect path losses that are critical in mm-wave frequency bands. The conductor loss being more dominant in the frequency bands and in thinner dielectric structures, we assess daisy chains and microstrip lines on 15-μm dielectric by measuring the S-parameters to quantify the impact of the surface roughness at around 28 GHz. Measured results from the daisy chain and microstrip line structures exhibit that the smooth surface of the liquid-based PID (3 nm) leads to 8%–32% lower signal loss in the dB scale than the 325-nm rough dry-film dielectric. The study provides comprehensive experimental results that the different material forms with various surface roughness largely impact the package-level interconnect loss.

7 citations

Proceedings ArticleDOI
30 Jul 2012
TL;DR: In this article, the fabrication and characterization of high-density capacitors using etched metal foils as high-surface area electrodes was described. Butts et al. showed that the high surface area electrodes yielded very high capacitance densities of 35-40 μF/cm2.
Abstract: 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.

7 citations

Proceedings ArticleDOI
27 May 2014
TL;DR: In this paper, the authors describe the first demonstration of 10 μm diameter interlayer vias in low-moisture uptake and low surface roughness dry film polymer dielectric for multi-layered re-distribution layer (RDL) structures to achieve 50 μm bump pitch in high density organic and glass interposers.
Abstract: This paper describes the first demonstration of 10 μm diameter interlayer vias in low-moisture uptake and low surface-roughness dry film polymer dielectric for multi-layered re-distribution layer (RDL) structures to achieve 50 μm bump pitch in high density organic and glass interposers. A new series of polymer dry films, ZS-100, at 10 μm thickness were deposited on thin and low CTE organic or glass cores using double-sided vacuum lamination processes. The ultra-small vias were fabricated by 248nm KrF excimer laser drilling, followed by electroless and electrolytic copper plating. Fully-filled via structures were successfully fabricated without any chemical-mechanical polishing. The processes demonstrated in this paper achieve much finer bump pitch than current organic packages, and can be scaled to large panels leading to lower cost than previous work in fine pitch Si interposers using back-end of line (BEOL) wafer processes.

7 citations

Proceedings ArticleDOI
25 Jun 2007
TL;DR: This paper will highlight the performance of DuPont's planar embedded capacitor laminates in organic packages to provide I/O decoupling for active circuits.
Abstract: Embedded passives are gaining in importance due to the reduction in size of consumer electronic products. Embedded passives are gradually replacing discretes due to the miniaturization of electronic products. Integration of these passives within the package increases the real estate for active components. This would increase the functionality of the system. Among the passives, capacitors pose the biggest challenge due to the large capacitance required for decoupling high performance circuits. This paper will highlight the performance of DuPont's planar embedded capacitor laminates in organic packages to provide I/O decoupling for active circuits.

7 citations

Proceedings ArticleDOI
29 Oct 2001
TL;DR: In this paper, a method for extracting the frequency dependent characteristic impedance of transmission lines from Time Domain Reflectometry (TDR) measurements using an Open, Short, Load, and Shortline calibration was proposed.
Abstract: This paper discusses a method for extracting the frequency dependent characteristic impedance of transmission lines from Time Domain Reflectometry (TDR) measurements using an Open, Short, Load, and Shortline calibration. The frequency dependent behavior of transmission lines was successfully captured using this method. Two types of transmission lines were measured using this method namely, thick metal transmission lines in Printed Wiring Board (PWB) and thin transmission lines in MCM-L technology.

7 citations


Cited by
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Journal ArticleDOI

[...]

08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

Journal ArticleDOI
TL;DR: Shape-memory polymers as discussed by the authors are an emerging class of active polymers that can change their shape in a predefined way from shape A to shape B when exposed to an appropriate stimulus.

1,575 citations

Journal ArticleDOI
14 Feb 2008-Nature
TL;DR: This work establishes a methodology for scavenging light-wind energy and body-movement energy using fabrics and presents a simple, low-cost approach that converts low-frequency vibration/friction energy into electricity using piezoelectric zinc oxide nanowires grown radially around textile fibres.
Abstract: Nanodevices don't use much energy, and if the little they do need can be scavenged from vibrations associated with foot steps, heart beats, noises and air flow, a whole range of applications in personal electronics, sensing and defence technologies opens up. Energy gathering of that type requires a technology that works at low frequency range (below 10 Hz), ideally based on soft, flexible materials. A group working at Georgia Institute of Technology has now come up with a system that converts low-frequency vibration/friction energy into electricity using piezoelectric zinc oxide nanowires grown radially around textile fibres. By entangling two fibres and brushing their associated nanowires together, mechanical energy is converted into electricity via a coupled piezoelectric-semiconductor process. This work shows a potential method for creating fabrics which scavenge energy from light winds and body movement. A self-powering nanosystem that harvests its operating energy from the environment is an attractive proposition for sensing, personal electronics and defence technologies1. This is in principle feasible for nanodevices owing to their extremely low power consumption2,3,4,5. Solar, thermal and mechanical (wind, friction, body movement) energies are common and may be scavenged from the environment, but the type of energy source to be chosen has to be decided on the basis of specific applications. Military sensing/surveillance node placement, for example, may involve difficult-to-reach locations, may need to be hidden, and may be in environments that are dusty, rainy, dark and/or in deep forest. In a moving vehicle or aeroplane, harvesting energy from a rotating tyre or wind blowing on the body is a possible choice to power wireless devices implanted in the surface of the vehicle. Nanowire nanogenerators built on hard substrates were demonstrated for harvesting local mechanical energy produced by high-frequency ultrasonic waves6,7. To harvest the energy from vibration or disturbance originating from footsteps, heartbeats, ambient noise and air flow, it is important to explore innovative technologies that work at low frequencies (such as <10 Hz) and that are based on flexible soft materials. Here we present a simple, low-cost approach that converts low-frequency vibration/friction energy into electricity using piezoelectric zinc oxide nanowires grown radially around textile fibres. By entangling two fibres and brushing the nanowires rooted on them with respect to each other, mechanical energy is converted into electricity owing to a coupled piezoelectric–semiconductor process8,9. This work establishes a methodology for scavenging light-wind energy and body-movement energy using fabrics.

1,473 citations

Journal ArticleDOI
TL;DR: This work demonstrates the vertical and lateral integration of ZnO nanowires into arrays that are capable of producing sufficient power to operate real devices and uses the vertically integrated nanogenerator to power a nanowire pH sensor and a Nanowire UV sensor, thus demonstrating a self-powered system composed entirely of nanowiring.
Abstract: The lateral and vertical integration of ZnO piezoelectric nanowires allows for voltage and power outputs sufficient to power nanowire-based sensors.

1,465 citations

Journal ArticleDOI
TL;DR: In this paper, the authors focus on the important role and challenges of high-k polymer-matrix composites (PMC) in new technologies and discuss potential applications of highk PMC.

1,412 citations