Validation of Thermal Resistance Extracted From Measurements on Stripe Geometry SiGe HBTs

International audienceIn this article, we present a straightforward methodology to validate the consistency of thermal resistance (RTH) measurements for a set of stripe geometry silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs). The proposed approach is based on the behavior of frequency-dependent thermal impedance (ZTH) of HBTs. The key advantage of this method is its simplicity and ease of applicability because it requires no additional measurements than the conventional approaches to extract the electrothermal parameters. First, we provide a physics-based formulation to extract ZTH as a function of RTH. As a next step, we propose different normalization methods for ZTH in stripe emitter SiGe HBTs to validate the RTH used in our ZTH formulation. Finally, we substantiate our validation technique across stripe emitter SiGe HBTs having different emitter dimensions corresponding to STMicroelectronics B55 technology

SiGe HBTs Optimization for Wireless Power Amplifier Applications

This paper deals with SiGe HBTs optimization for power amplifier applications dedicated to wireless communications. In this work, we investigate the fT-BVCEO tradeoff by various collector optimization schemes such as epilayer thickness and dopant concentration, and SIC and CAP characteristics. Furthermore, a new trapezoidal base Germanium (Ge) profile is proposed. Thanks to this profile, precise control of Ge content at the metallurgical emitter-base junction is obtained. Gain stability is obtained for a wide range of temperatures through tuning the emitter-base junction Ge percent. Finally, a comprehensive investigation of Ge introduction into the collector (backside Ge profile) is conducted in order to improve the fT values at high injection levels

Measurement issues of on-Silicon de- embedding test structures in the Sub-THz range

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On wafer small signal characterization beyond 100 GHz for compact model assessment

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Outcome of Poor-Grade Subarachnoid Hemorrhage as Determined by Biomarkers of Glucose Cerebral Metabolism

Purpose: The aim of this study was to determine if the measurement of blood biomarkers of glucose cerebral metabolism, performed with retrograde jugular catheter, could predict the outcome of poor-grade aneurysmal subarachnoid hemorrhage (aSAH) patients. Methods: This study was conducted in 68 poor-grade aSAH patients. A total of 4,024 blood samples obtained from jugular and radial catheters were analyzed for glucose, lactate, and oxygen content every 8h for 10±0.5days. Metabolic ratio (MR) and lactate-oxygen index (LOI) were obtained by ratios using arterio-jugular differences. Functional outcome was evaluated at 12months with the Glasgow Outcome Scale. Results: Outcome was unfavorable in 40 patients. In this group of patients, the MR was significantly lower (p<0.0001) and the LOI was significantly higher (p=0.0001) than in the group with favorable outcome. The MR cutoff value, below which the patients are likely to have an unfavorable outcome, was determined to be 3.35. More interestingly, the data obtained in this study demonstrated that the patients achieving an unfavorable outcome were distinguished from those with a favorable outcome by having at least three events of MR inferior to 3.35 (sensitivity=90%, specificity=82.1%). Moreover, in patients who developed cerebral vasospasm, we observed a significant decrease in the MR. Conclusion: Our data provide additional support to the view that the MR is a reliable marker for predicting the outcome of poor-grade aSAH patients. Prospective studies are needed to confirm its value in multimodal monitorin

Anatomy of the inferior orbital fissure: Implications for endoscopic cranial base surgery

Considering many approaches to the skull base confront the inferior orbital fissure (IOF) or sphenomaxillary fissure, the authors examine this anatomy as an important endoscopic surgical landmark. In morphometric analyses of 50 adult human dry skulls from both sexes, we divided the length of the IOF into three segments (anterolateral, middle, posteromedial). Hemotoxylin- and eosin-stained sections were analyzed. Dissections were performed using transnasal endoscopy in four formalin-fixed cadaveric cranial specimens (eight sides); three endoscopic approaches to the IOF were performed.IOF length ranged from 25 to 35 mm (mean 29 mm). Length/width of the individual anterolateral, middle, and posteromedial segments averaged 6.46/5, 4.95/3.2, and 17.6/ 2.4 mm, respectively. Smooth muscle within the IOF had a consistent elationship with several important anatomical landmarks. The maxillary introstomy,total ethmoidectomy approach allowed access to the posteromedial segment of the fissure. The endoscopic modified, medial maxillectomy approach allowed access to the middle and posterior-medial segment. The Caldwell-Luc approach allowed complete exposure of the IOF. The IOF serves as an important anatomic landmark during endonasal endoscopic approaches to the skull base and orbit. Each of the three segments provides a characteristic endoscopic corridor, unique to the orbit and different fossas surrounding the fissure.Fil: de Battista, Juan Carlos. University of Cincinnati; Estados Unidos. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Anatomia Normal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Zimmer, Lee A.. University of Cincinnati; Estados UnidosFil: Theodosopoulos, Philip V.. University of Cincinnati; Estados UnidosFil: Froelich, Sebastien C.. University of Cincinnati; Estados UnidosFil: Keller, Jeffrey T.. University of Cincinnati; Estados Unidos. Mayfield Clinic; Estados Unido

Second Preimage Attacks on Dithered Hash Functions

The goal of this paper is to analyze the security of dithered variants of the Merkle-Damgard mode of operation that use a third input to indicate the position of a block in the message to be hashed. These modes of operation for hash functions have been proposed to avoid some structural weaknesses of the Merkle-Damgard paradigm, e.g. that second preimages can be constructed in much less than $2^n$ work, as pointed out by Kelsey and Schneier. Among the modes of operation that use such a third input are Rivest\u27s dithered hashing and Biham and Dunkelman\u27s HAIFA proposal. We propose several new second preimage attacks on the Merkle-Damgard mode of operation, which can also attack Rivest\u27s dithered hash with almost the same complexity. When applied to Shoup\u27s UOWHF, these attacks can be shown to be optimal since their complexity matches Shoup\u27s security bound

S-Parameter Measurement and EM Simulation of Electronic Devices towards THz frequency range

In this paper, we present on-wafer S-parameter measurement of silicon-based devices up to 500 GHz and EM simulation analysis up to 750GHz. The EM simulation is carried out with RF probe models and without RF probe model (intrinsic EM simulation) up to 750 GHz. To understand difference between EM simulation predictions with and without RF probe model in frequency range 500-750 GHz, electric field distributions in the DUTs are analysed

BEOL Thermal Resistance Extraction in SiGe HBTs

A prior estimate of the impact of thermal resistance from the back-end-of-line (BEOL) metallization layers is crucial for an accurate circuit design and thermally aware device design. This paper presents a robust technique to extract the thermal resistance component originating from the BEOL metal layers in silicon germanium heterojunction bipolar transistors (SiGe HBTs). The proposed technique is first tested on data generated using analytical equations and later validated with 3D TCAD simulation. The results clearly show that the exact contribution of the BEOL to the overall thermal resistance is captured in the proposed approach. Finally, we verified the method using measured data obtained from fabricated SiGe HBT structures using Infineon B11HFC technology. The extracted parameters show reasonable accuracy and consistency across different emitter dimensions and BEOL configurations

Degradation of cellular mir-27 by a novel, highly abundant viral transcript is important for efficient virus replication in vivo.

Cytomegaloviruses express large amounts of viral miRNAs during lytic infection, yet, they only modestly alter the cellular miRNA profile. The most prominent alteration upon lytic murine cytomegalovirus (MCMV) infection is the rapid degradation of the cellular miR-27a and miR-27b. Here, we report that this regulation is mediated by the ∼1.7 kb spliced and highly abundant MCMV m169 transcript. Specificity to miR-27a/b is mediated by a single, apparently optimized, miRNA binding site located in its 3'-UTR. This site is easily and efficiently retargeted to other cellular and viral miRNAs by target site replacement. Expression of the 3'-UTR of m169 by an adenoviral vector was sufficient to mediate its function, indicating that no other viral factors are essential in this process. Degradation of miR-27a/b was found to be accompanied by 3'-tailing and -trimming. Despite its dramatic effect on miRNA stability, we found this interaction to be mutual, indicating potential regulation of m169 by miR-27a/b. Most interestingly, three mutant viruses no longer able to target miR-27a/b, either due to miRNA target site disruption or target site replacement, showed significant attenuation in multiple organs as early as 4 days post infection, indicating that degradation of miR-27a/b is important for efficient MCMV replication in vivo