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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, the authors measured through glass via (TGV) noise coupling and the effectiveness of shielding structures in a glass interposer, and the proposed shielding structures include the variation of signal TGV pitches and the number of grounded shield TGVs, ground pads, and guard rings.
Abstract: In this article, we first measured through glass via (TGV) noise coupling and the effectiveness of shielding structures in a glass interposer. To analyze the noise coupling between signal TGVs, an open-ended structure is adopted. Glass interposer test vehicles were fabricated to verify the noise coupling between signal TGVs. With these test vehicles, noise transfer functions between signal TGVs were measured. Based on these measurement results and the equivalent circuit model, the noise coupling between signal TGVs was analyzed. To suppress this TGV noise coupling, shielding structures for the TGV noise coupling were proposed and verified. The proposed shielding structures include the variation of signal TGV pitches and the number of grounded shield TGVs, ground pads, and guard rings, respectively. The effectiveness of the proposed shielding structures was verified up to 20 GHz in frequency-domain measurements. Using the proposed shielding structures, the noise transfer function decreased by 9.4 dB at 5 GHz. Also, the effectiveness of the proposed guard ring structure was verified by a time-domain coupling noise simulation with clock signals at frequencies of 1 GHz. The proposed guard ring successfully suppressed the clock noise coupling between signal TGVs by 60.5% and 69.2% when a signal TGV pitchis 300 and 900 $\mu {\text{m}}$ , respectively.

4 citations

Journal ArticleDOI
TL;DR: In this paper, the modeling, development, and demonstration of glass interposer technology with singlemode waveguides (SMWGs) for high-bandwidth communications and embedded trenches for ultrafine copper traces for high speed electronics is presented.
Abstract: This article presents the modeling, development, and demonstration of glass interposer technology with single-mode waveguides (SMWGs) for high-bandwidth communications and embedded trenches for ultrafine copper traces for high-speed electronics. Glass as the substrate for the integration of photonics and electronics exhibits a unique combination of superior properties over silicon, laminates, and polymers. In conjunction with the advantages of glass, shape control of photoimageable dielectric lines during development and cure was developed and optimized. Single-mode polymer waveguides on glass were fabricated and characterized. Sample preparation methods and their impact on the sample edge quality and coupling loss will also be discussed in this article. Overall, this article presents the successful process development and demonstration of 3- $\mu \text{m}$ embedded trenches in the dielectric film for ultrafine copper traces and 2- $\mu \text{m}$ microvias for interlayer interconnects.

4 citations

Proceedings ArticleDOI
18 Aug 2016
TL;DR: In this paper, a silicon-integrated, thin-film, high-density tantalum capacitors for integrated power modules are presented, which achieve stable capacitance densities of more than 0.3 µF/mm2 with leakage of less than 1 µA/µF at 3 V. The capacitors are integrated directly above the active silicon, enabling shorter interconnection path with lower system parasitics.
Abstract: This paper demonstrates silicon-integrated, thinfilm, high-density tantalum capacitors for integrated power modules. The capacitors in form-factors of less than 75µm showed stable capacitance densities of more than 0.3 µF/mm2 with leakage of less than 0.1 µA/µF at 3 V. To the best of authors' knowledge, this is the highest capacitance density reported till date at the mentioned form-factors. Furthermore, these capacitors are integrated directly above the active silicon, enabling shorter interconnection path with lower system parasitics, leading to higher switching frequencies and lower losses. These ultra-miniaturized, substrate-compatible tantalum capacitors, thus, address the strategic need for highly-efficient, ultra-miniaturized power modules.

4 citations

Proceedings ArticleDOI
18 Nov 2008
TL;DR: In this article, the authors demonstrate the use of electromagnetic band gap (EBG) structures for isolation between multiple plane pairs along the vertical direction and show good isolation in the stop bands of the EBGs.
Abstract: This paper for the first time demonstrates the use of electromagnetic band gap (EBG) structures for isolation between multiple plane pairs along the vertical direction. Planar EBG structures have been applied for the suppression of vertical noise coupling in the GHz range of frequencies. Simulation and measurement results showing good isolation in the stop bands of the EBGs are presented.

4 citations

Proceedings ArticleDOI
25 Jun 2007
TL;DR: In this article, the surface treatment of copper and dielectric in multilayer wiring is proposed for fine line and space fabrication and a novel copper adhesion process and its operating parameters are presented.
Abstract: System-on-package (SOP) is a highly integrated systems packaging technology for convergent computing, communication, consumer, and bio-electronic functions in a single package or module. SOP aims to miniaturize systems by the integration of system-level components at microscale in the short term and nanoscale in the future. A key challenge for active and passive component integration is the demand for additional fine pitch wiring in the substrate for interconnecting these thin film embedded components. This adds to the already escalating need for high wiring density substrates driven by transistor density on the IC (Moore's Law). This paper addresses a critical process technology for SOP/microprocessor ultra-high density organic build-up substrates, namely, surface treatment of copper and dielectric in multilayer wiring. This process is critical for the challenges of processing and maintaining signal integrity at lines and spaces below 12 mum. A complete description of fine line and space fabrication and a novel copper adhesion process and its operating parameters are presented. We demonstrate this process with superior bonding strength through accelerated reliability testing. Results are shown not only state-of-the-art build-up films but also for high-performance substrates and prepregs in comparison to more traditional copper roughening treatment methods.

4 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