25 research outputs found
Enhanced Adhesion Between Electroless Copper and Advanced Substrates
In this work, adhesion between electrolessly deposited copper and dielectric materials for use in microelectronic devices is investigated. The microelectronics industry requires continuous advances due to ever-evolving technology and the corresponding need for higher density substrates with smaller features. At the same time, adhesion must be maintained in order to preserve package reliability and mechanical performance. In order to meet these requirements two approaches were taken: smoothing the surface of traditional epoxy dielectric materials while maintaining adhesion, and increasing adhesion on advanced dielectric materials through chemical bonding and mechanical anchoring.
It was found that NH3 plasma treatments can be effective for increasing both catalyst adsorption and adhesion across a range of materials. This adhesion is achieved through increased nitrogen content on the polymer surface, specifically N=C. This nitrogen interacts with the palladium catalyst particles to form chemical anchors between the polymer surface and the electroless copper layer without the need for roughness. Chemical bonding alone, however, did not enable sufficient adhesion but needed to be supplemented with mechanical anchoring. Traditional epoxy materials were treated with a swell and etch process to roughen the surface and create mechanical anchoring. This same process was found to be ineffective when used on advanced dielectric materials. In order to create controlled roughness on these surfaces a novel method was developed that utilized blends of traditional epoxy with the advanced materials. Finally, combined treatments of surface roughening followed by plasma treatments were utilized to create optimum interfaces between traditional or advanced dielectric materials and electroless copper. In these systems adhesion was measured over 0.5 N/mm with root-mean-square surface roughness as low as 15 nm. In addition, the individual contributions of chemical bonding and mechanical anchoring were identified.
The plasma treatment conditions used in these experiments contributed up to 0.25 N/mm to adhesion through purely chemical bonding with minimal roughness generation. Mechanical anchoring accounted for the remainder of adhesion, 0.2-0.8 N/mm depending on the level of roughness created on the surface. Thus, optimized surfaces with very low surface roughness and adequate adhesion were achieved by sequential combination of roughness formation and chemical modifications.Ph.D.Committee Chair: Kohl, Paul; Committee Co-Chair: Bidstrup Allen, Sue Ann; Committee Member: Hess, Dennis; Committee Member: Nair, Sankar; Committee Member: Qu, Jianmi
Controlling trapping potentials and stray electric fields in a microfabricated ion trap through design and compensation
Recent advances in quantum information processing with trapped ions have
demonstrated the need for new ion trap architectures capable of holding and
manipulating chains of many (>10) ions. Here we present the design and detailed
characterization of a new linear trap, microfabricated with scalable
complementary metal-oxide-semiconductor (CMOS) techniques, that is well-suited
to this challenge. Forty-four individually controlled DC electrodes provide the
many degrees of freedom required to construct anharmonic potential wells,
shuttle ions, merge and split ion chains, precisely tune secular mode
frequencies, and adjust the orientation of trap axes. Microfabricated
capacitors on DC electrodes suppress radio-frequency pickup and excess
micromotion, while a top-level ground layer simplifies modeling of electric
fields and protects trap structures underneath. A localized aperture in the
substrate provides access to the trapping region from an oven below, permitting
deterministic loading of particular isotopic/elemental sequences via
species-selective photoionization. The shapes of the aperture and
radio-frequency electrodes are optimized to minimize perturbation of the
trapping pseudopotential. Laboratory experiments verify simulated potentials
and characterize trapping lifetimes, stray electric fields, and ion heating
rates, while measurement and cancellation of spatially-varying stray electric
fields permits the formation of nearly-equally spaced ion chains.Comment: 17 pages (including references), 7 figure
The James Webb Space Telescope Mission
Twenty-six years ago a small committee report, building on earlier studies,
expounded a compelling and poetic vision for the future of astronomy, calling
for an infrared-optimized space telescope with an aperture of at least .
With the support of their governments in the US, Europe, and Canada, 20,000
people realized that vision as the James Webb Space Telescope. A
generation of astronomers will celebrate their accomplishments for the life of
the mission, potentially as long as 20 years, and beyond. This report and the
scientific discoveries that follow are extended thank-you notes to the 20,000
team members. The telescope is working perfectly, with much better image
quality than expected. In this and accompanying papers, we give a brief
history, describe the observatory, outline its objectives and current observing
program, and discuss the inventions and people who made it possible. We cite
detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space
Telescope Overview, 29 pages, 4 figure
Identification of a female sex pheromone in Carcinus maenas
Despite major progress in our understanding of animal signaling systems, the identification of chemical signals in aquatic organisms is still in its infancy. Exemplary for this is the lack of structural knowledge of crustacean sex pheromones despite their initial description in crabs almost 40 yr ago. We hypothesized that species in which the reproductive event is linked to a short window of mating opportunities centered around the time of ecdysis would be ideal to purify and identify such a cue. Here we present the first identification of a crustacean sex pheromone, the female signal produced by the green crab Carcinus maenas from both conditioned seawater and female urine. We used a bioassay-driven purification scheme combined with a candidate approach focusing on excreted compounds that changed through the course of the female molt cycle. Uridine diphosphate (UDP), a nucleotide accumulated from UDP-N-acetylglucosamine during chitin biosynthesis, is the major component of the female crab pheromone and induced all key characteristics of male sexual behavior in bioassays (i.e. pre- and post-copulatory guarding of the female and initiation of mating) at a threshold of 10(-5) M UDP in seawater. The identification of a nucleotide pheromone in crustaceans will enable future studies on signal specificity, biological function, biosynthesis, reception, and evolution as well as focus its potential use in pest control and aquaculture, thus allowing for a major expansion of crustacean chemical and behavioral ecology research that was hindered by the lack of structural knowledge
A Novel Missense Mutation 224G>T (R75M) in SRY Coding Region Interferes with Nuclear Import and Results in 46, XY Complete Gonadal Dysgenesis
REL, encoding a member of the NF-κB family of transcription factors, is a newly defined risk locus for rheumatoid arthritis
We conducted a genome-wide association study of rheumatoid arthritis in 2,418 cases and 4,504 controls from North America and identified an association at the REL locus, encoding c-Rel, on chromosome 2p13 (rs13031237, P = 6.01 x 10(-10)). Replication in independent case-control datasets comprising 2,604 cases and 2,882 controls confirmed this association, yielding an allelic OR = 1.25 (P = 3.08 x 10(-14)) for marker rs13031237 and an allelic OR = 1.21 (P = 2.60 x 10(-11)) for marker rs13017599 in the combined dataset. The combined dataset also provides definitive support for associations at both CTLA4 (rs231735; OR = 0.85; P = 6.25 x 10(-9)) and BLK (rs2736340; OR = 1.19; P = 5.69 x 10(-9)). c-Rel is an NF-kappaB family member with distinct functional properties in hematopoietic cells, and its association with rheumatoid arthritis suggests disease pathways that involve other recently identified rheumatoid arthritis susceptibility genes including CD40, TRAF1, TNFAIP3 and PRKCQ
IRF7: activation, regulation, modification and function
Interferon regulatory factor 7 (IRF7) was originally identified in the context of Epstein–Barr virus (EBV) infection, and has since emerged as the crucial regulator of type I interferons (IFNs) against pathogenic infections, which activate IRF7 by triggering signaling cascades from pathogen recognition receptors (PRRs) that recognize pathogenic nucleic acids. Moreover, IRF7 is a multifunctional transcription factor, underscored by the fact that it is associated with EBV latency, in which IRF7 is induced as well as activated by the EBV principal oncoprotein latent membrane protein-1 (LMP1). Aberrant production of type I IFNs is associated with many types of diseases such as cancers and autoimmune disorders. Thus, tight regulation of IRF7 expression and activity is imperative in dictating appropriate type I IFN production for normal IFN-mediated physiological functions. Posttranslational modifications have important roles in regulation of IRF7 activity, exemplified by phosphorylation, which is indicative of its activation. Furthermore, mounting evidence has shed light on the importance of regulatory ubiquitination in activation of IRF7. Albeit these exciting findings have been made in the past decade since its discovery, many questions related to IRF7 remain to be addressed