Long term noise measurements and median time to failure test for the characterization of electromigration in metal lines

The high sensitivity, which can be obtained by means of noise measurements, is especially useful for the characterization of the early stages of the electromigration phenomenon. In addition, with the noise being strictly dependent on the sample microstructure, it is obvious to expect that it can be used for monitoring the different stages of the degradation process. In this paper, the results obtained by performing noise measurements during lifetime tests are presented, with the aim of investigating the evolution of the electromigration noise during the entire life of the sample. Conventional Median Time to Failure (MTF) tests have been performed on samples belonging to the same set. One of the aims of this work is to investigate the possibility of establishing a new failure criterion based on noise measurement capable of providing, in a shorter time, the same type of information normally obtained from MTF tests.     

A Fluorescent Silver(I) Carbene Complex with Anticancer Properties: Synthesis,Characterization, and Biological Studies

The silver(I) N-heterocyclic carbene (NHC) complex bis(1-(anthracen-9-ylmethyl)-3-ethylimidazol-2-ylidene) silver chloride ([Ag(EIA)₂]Cl), bearing two anthracenyl fluorescent probes, has been synthesized and characterized. [Ag(EIA)₂]Cl is stable in organic solvents and under physiological conditions, and shows potent cytotoxic effects in vitro toward human SH-SY5Y neuroblastoma cells. The interactions of [Ag(EIA)₂]Cl with a few model biological targets have been studied as well as its ability to be internalized in cells. The in vitro anticancer activity is apparently related to the level of drug internalization. Notably, [Ag(EIA)₂]Cl does not react with a few model proteins, but is capable of binding the C-terminal dodecapeptide of thioredoxin reductase hTrxR(488–499) and to strongly inhibit the activity of this enzyme. Binding occurs through an unconventional process leading to covalent binding of one or two carbene ligands to the C-terminal dodecapeptide with concomitant release of the silver cation. To the best of our knowledge, this mode of interaction is reported here for the first time for Ag(NHC)₂ complexes.     

Fusion of range camera and photogrammetry: a systematic procedure for improving 3-D models metric accuracy

The generation of three-dimensional (3-D) digital models produced by optical technologies in some cases involves metric errors. This happens when small high-resolution 3-D images are assembled together in order to model a large object. In some applications, as for example 3-D modeling of Cultural Heritage, the problem of metric accuracy is a major issue and no methods are currently available for enhancing it. The authors present a procedure by which the metric reliability of the 3-D model, obtained through iterative alignments of many range maps, can be guaranteed to a known acceptable level. The goal is the integration of the 3-D range camera system with a close range digital photogrammetry technique. The basic idea is to generate a global coordinate system determined by the digital photogrammetric procedure, measuring the spatial coordinates of optical targets placed around the object to be modeled. Such coordinates, set as reference points, allow the proper rigid motion of few key range maps, including a portion of the targets, in the global reference system defined by photogrammetry. The other 3-D images are normally aligned around these locked images with usual iterative algorithms. Experimental results on an anthropomorphic test object, comparing the conventional and the proposed alignment method, are finally reported.     

Comments on the utilization of noise measurements for the characterization of electromigration in metal lines

Some of the problems connected with the characterization of electromigration by means of noise measurements are discussed in this paper. Some specific criticisms moved in the past toward the interpretation of the experimental data are also addressed. In particular, the question of the interpretation of the 1/ƒ² noise component is discussed. Finally, a set of rules are given which should be followed, both in the choice of the instrumentation and in performing the measurements, in order to obtain meaningful and reliable results.     

Ultralow-noise PC-Based measurement system for the characterizationof the metallizations of integrated circuits

The design, realization, and test of a multichannel ultralow-noise data acquisition system are described in this paper. The instrument, controlled by a personal computer (PC), has been specifically designed for performing low-frequency noise measurements on interconnect lines of an integrated circuits. A specifically designed ultralow-noise preamplifier has been realized and an optical link has been used for connecting the front-end of the instrument with the PC in order to minimize the effects of electromagnetic interferences. An overall background noise some orders of magnitude below that of preexisting instrumentation has been obtained. In particular, the power spectral density of the equivalent input voltage noise was 1.5, 3, 10 nV/(Hz)^1/2 at 1, 0.1, and 0.01 Hz, respectively     

Ultralow-noise programmable voltage source

To avoid introducing additional noise sources while making low-frequency noise measurements, batteries are normally used instead of electronic power supplies. This paper presents an alternative solution by describing the design, construction, and testing of an ultralow-noise voltage source. Such a power supply can be computer controlled and has a typical noise level two orders of magnitude below that of similar commercial instruments. Some typical values of the spectral density of the voltage fluctuations at its output are: (10^-12, 10^-15, 10^-16) V²/Hz at (0.01, 0.1, and 1) Hz, respectively. These noise performances are almost independent of the supplied current, with a degradation of less than 3 dB up to 400 mA. A special algorithm for digital-to-analog conversion, using passive devices with 1% tolerance, ensures a resolution of 2.5 mV and an accuracy better than ±1.5 mV over the entire output range from 0 to 8 V     

Enhanced sensitivity cross-correlation method for voltage noise measurements

Ultralow noise measurements often require the application of signal processing and correction techniques to go beyond the noise performances of front-end amplifiers. In this paper, a new method for the voltage noise measurement is proposed, which allows, at least in principle, the complete elimination of the noise introduced by the amplifiers used for the measurements. This is obtained by resorting to the conventional cross-correlation technique for the elimination of the contribution of the equivalent input voltage noise of the amplifiers and by using a new three-step-measurement procedure that exploits different amplifier-configuration measurements in order to subtract the contribution of the equivalent input current noise of the amplifiers.     

On the Calibration of DA Converters Based on $R/beta R$ Ladder Networks

In this paper, we discuss the possibility of realizing high-accuracy digital-analog(DA) converters by exploiting the properties of R/betaR (beta > 2) ladder networks. Extensive simulations demonstrate that, if a proper value of beta is chosen, high accuracy can be obtained by resorting to a very simple self-calibration algorithm. This is true, even in the case of large tolerance values for the resistors that make up the ladder network. Such a result may allow the design of a high-accuracy very low cost converter. The effect of the offset of the comparator needed for the self-calibration algorithm is also discussed.     

A New Circuit Topology for the Realization of Very Low-Noise Wide-Bandwidth Transimpedance Amplifier

In this paper, after discussing some important limitations of the most common circuital configuration that is used for the realization of very low-noise transimpedance amplifiers, we propose and analyze a new circuit topology which allows us to obtain significant advantages as far as equivalent input current noise and bandwidth (BW) are concerned. We present a simple circuit implementation of the new transimpedance amplifier, together with the results of its noise characterization. The comparison between these measurements and those obtained on a conventional transimpedance amplifier with the same transimpedance gain has confirmed that the proposed approach allows us to obtain a lower background noise and a larger BW for the same transimpedance gain.