The recent development of bright X-ray sources, reliable X-ray focusing optics, large X-ray detectors and X-ray data modelling and processing, have improved X-ray techniques to the point where many are being introduced in MOS transistor manufacturing lines as new metrology methods. The fundamental X-ray physical properties, such as their small wavelength and their weak interaction with solid-state matter satisfy basic in-line metrology requirements: non-destructiveness, speed, accuracy, reliability and long-term stability. The capability of X-ray based metrology methods to monitor critical 65 and 45 nm processes such as ion implant, nitrided SiO2 gate dielectrics, NiSi, Cu/porous low-κ interconnects and MIM capacitors is highlighted in this paper. 


An infrared heat reflecting multilayer thin film filter comprising alternate layers of ZrO2 and SiO2 has been modeled and prepared on a BK7 glass substrate using RF-magnetron sputtering. Initially, the individual films of the used materials have been characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) for structural and surface quality prior to the deposition of multilayer structure. Spectral analysis showed that the filter has an average transmission of greater than 90% in 450 to 700 nm range and less than 2% in 700-1100 nm band fulfilling the design requirements. The XRD study of multilayer structure showed few peaks of ZrO2 along with a solitary peak for SiO2 indicating some crystallinity for ZrO2 layers in the structure. Hardness analysis showed that the initial phase of the indentation is predominantly ductile with gradual transition in behaviour from ductile to brittle with increased penetration. Interface analysis of multilayered structure was carried out by Rutherford back scattering using Tandem 5 MeV ion accelerator, showed that interfaces formed in the multilayer structure are sharp and no substantial evidence of interlayer diffusion or mixing at the interfaces.


Plasma nitriding of aluminium in a 50 Hz pulsed-dc glow discharge is studied for different ion-current densities (2.0-5.0 mA cm-2) by keeping the corresponding discharge parameters such as treatment time, chamber pressure, substrate temperature and gas composition same. The treated samples are analysed for changes induced in surface properties using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and Vickers's micro-hardness testing. XRD showed the downshift in the original diffraction peak corresponding to (111) plane reflection along with the emergence of new diffraction peak corresponding to (220) plane reflection, confirming the N-diffusion into existing Al-lattice and formation of AlN compound. Surface hardness is significantly improved which might be attributed to the diffusion of nitrogen and compound layer formation.

Various thermoplastic and thermo-set based polymers, blended with acetylene carbon blacks and graphite fillers to form electrically conductive polymers, were investigated to determine the switching mechanism under high power short-circuit fault conditions. Presently, a positive temperature coefficient (PTC) effect is the accepted switching mechanism for low power overcurrent devices. However, for high power, distribution level devices, this mechanism has been assumed to be the same under high fault conditions. This work proposes another possible switching mechanism responsible for a steep change in resistance under high power faults. The proposed mechanism of resistance change comes, not from the PTC change in the material, but rather from the vaporization of the conducting polymer contact areas at the polymer/electrode interface. A comparison between low power polypropylene based devices with a positive temperature coefficient (PTC) effect (thermal expansion of the polymer bulk) and high power devices was done to support this theory. A model was developed along with numerous short-circuit tests to support this theory. Modifications with e-beam irradiation were made to alter the PTC characteristics of thermoplastics but had little effect on high fault short-circuit switching. Also, numerous short-circuit testing on thermo-set based materials without any PTC transition still switched under high fault currents. These all supported the proposed theory that switching, under high fault currents, was from vaporization of the contact areas at the polymer surface rather than thermal expansion in the bulk of the conductive polymer as previously accepted.

Conductive ceramics have widespread use in many industrial applications. One important application for such materials is electrical contact technology. Over the last few years, a new class of nanocomposite ceramic thin film materials has been developed with contact coatings as one key objective. This family of materials has proven to combine the favorable contact properties of metals, such as low electrical and thermal resistivity, and high ductility, with those of ceramics such as low friction and wear rate, high chemical integrity and good high-temperature properties. Furthermore, it is also found that the tribological properties of such materials can be tailored by alloying thus creating a triboactive system. The technology is now industrialized, and a practical example of a contact system utilizing a nanocomposite coating for improved performance is given.

Fretting remains a major cause of connector failure and can impair reliability in complex systems like automotive applications. Tin is particularly previous to fretting phenomena; we report here the first results of an analysis of tin and lubricated tin contacts, based on the analysis of the friction or slip regimes and the electrical behaviour. Lubricant properties are analysed in terms of friction behaviour and the effect of a special additive is examined.

The presented study deals with the influence of the contacts materials on the evolution of the arc in low voltage circuit breakers. The commutation from the mobile contact onto the electrode is especially investigated in order to improve the breaking device performances. Hence, to preserve the qualities of the contact, the arc must leave this area as soon as possible. To undertake this study, several diagnostics are implemented. A measuring device is composed of magnetic induction sensors located outside the chamber. It allows the determination of the position and the volume of the arc during the breaking. Optical (ultra-speed camera) and electrical measurements are also performed with the technical support of Schneider Electric. Different current values (assumed peak current of 3 kA, 8 kA and 12 kA) and different natures of materials composing the electrical contacts have been tested. Copper contacts, different contacts on silver base obtained with different processes have been used. Experimental results show the influence of these various parameters on the arc volume and on the transfer of the arc towards the quenching chamber. Indeed, different dynamic behaviors are observed during the current transfer phase.

The formation of intermetallic compounds (IMC) and its effects at the interface between different metals has always been of interest for the electronics industry, contacts manufacturers and users. The purpose of this work is primarily to develop an in situ technique of thermally aging metallic samples within the vacuum chamber of a scanning electron microscope (SEM). This setup enables ongoing observation of the formation and growth of intermetallic compounds within the chamber. Due to the amount of data available in literature, copper-tin specimens were chosen as a basis to validate the technique. Once the samples were thermally aged, energy dispersive X-ray (EDX) analyses as well as electron backscattered diffraction (EBSD) were done on the surfaces. Ex situ nano-indentation measurements were also performed on the IMC. Results have shown that the IMC formation can be observed while aging within a SEM chamber.


High copper alloys were required by the industry to improve mechanical and electrical contact resistance for connecting device. This work addresses the electrical contact resistance law versus force in the range (1–100 N) for sphere/plan shapes. The designed samples are submitted to indentation (static contact) and insertion (sliding contact). Experimental power law of contact resistance versus forces was obtained where the law parameters are well related to electrical resistivity, Young modulus, yield stress... Previous analytical relationship Rc=f(Fc) in the literature and finite element simulation code are used to discuss the origin and the validity of such practical power law. Nevertheless the analytic expression are found unsatisfactory, the numerical model gives some agreement with this previous experimental law. However better convergence between numerical and experimental data was obtained in indentation when the surface topography is considered. The obtained results are a useful tool to evolve compromise between the electrical and mechanical aspects for a high loading contact. The main statement is that numerical model including the real topography and roughness is robust so it can be used in different contact shape and complex design for contact resistance evaluation. Finally, depending on the hardness and the resistivity, these uncoated materials were found to act on fretting apparitions and its level.


The precise characterization of the local microstructure situation is a precondition to investigate and to understand the degradation phenomena occurring in electrical contact materials, because the microstructure is the unique and authentic monitor of the whole materials experience. However, it could not be fully exploited so far due to the lack of adequate characterization techniques. The recently developed FIB-nanotomography may solve this problem. It is based on the automatic serial sectioning by a focused ion beam (FIB) of the volume of interest at the nanoscale and offers an optimum resolution in x-y-z directions. For imaging all well established contrast information of the scanning electron microscopy (chemistry, phase composition, grain structure, texture, stress and strain) is available. After imaging, a detailed 3D image analysis enables the comprehensive quantitative evaluation of local microstructure degradation effects. This work gives an overview of these new possibilities using the example of a Ag/SnO2 contact material in its initial state and after switch operations.

Since electromagnetic (EM) noise resulting from an arc discharge disturbs other electric devices, parameters on electromagnetic compatibility, as well as lifetime and reliability, are important properties for electrical contacts. To clarify the characteristics and the mechanism of the generation of the EM noise, the current noise up to GHz band frequency generated by slowly breaking contacts with external direct current (dc) magnetic field, up to 40 mT, was investigated experimentally using Ag and AgSnO2 material. To reveal the characteristics as pure clean surface contact operation, the arc only at the operation of the first contact break was measured. Firstly, the effect of the external dc magnetic field on the duration and voltage fluctuation of the breaking arc of AgSnO2 material, which has relatively longer arc duration, was quantified. The experimental results on AgSnO2 material newly revealed that although applying external dc magnetic field is effective in reduction of duration of gaseous phase in arc discharge, higher variation of contact voltage in the gaseous phase which results in high frequency noise is caused. Secondly, the effect of the external dc magnetic field on the breaking arc of Ag was measured. It was found that larger current noise arises, when the contact voltage is rapidly varied at the arc discharge. There are two kinds of rapid changes, which cause high-frequency EMC problem, in the voltage waveform. One is at extinction of arc discharge. Other kind is short-duration arc (short-arc) before the ignition of the continuous metallic arc. Especially, we focused on the characteristics of the short-arc at the initial of the opening of the contact for clarifying the high frequency EMC problem. It was demonstrated that the spectrum of current noise in the case of “B = 30 mT” is smaller than that in the case of “B = 0 mT”. In addition, duration and fluctuation of short-arc is suppressed by the dc magnetic field. These results are basic and useful finding to know not only the noise generation in the contact-breaking phenomena but also the material dependency for EMC problems.

Due to ongoing miniaturization in electronics, connector contact designs have to follow the same trends. The prediction of the mechanical and electrical performance of low force connector contacts becomes increasingly important. This paper shows a new approach for modeling elastic plastic contact between two multi-layered non-conforming rough bodies subjected to pressure and shear traction. Three main considerations will be presented: realistic surface simulations, numerical simulation of contact interfaces, and constriction resistance calculations. (i) Since measured three dimensional (3D) digitized surface data is not always available, having the ability to numerically simulate “realistic” rough surface topographies is of great importance. It will be shown how realistic engineered surfaces can be modeled using five scale independent parameters: RMS roughness, x/y correlation length, kurtosis and skew. (ii) A numerical algorithm has been developed which calculates the stresses and deformations generated in a contact system with up to three different layers per contact partner. The mechanical properties of each individual contact layer are incorporated into the calculation. This numerical algorithm is based on Papkovich-Neuber Potentials, both multi grid and conjugate gradient methods are used, and the plastic deformation of the individual contact points (a-spots) can be interpolated using different material hardening behaviors. (iii) Once the contact interface a-spot distribution is simulated, the constriction resistance of the true contact area can then be calculated. The voltage drop within the contacting bodies is interpolated by iteratively solving the Laplace equation. The electrical properties of all the individual contact layers as well as the interaction between the individual a-spots are taken into account. A validation of these simulation algorithms will be shown using a hard Au/Ni/CuSn6 contact system. The results show excellent agreement between measured and simulated contact resistance results over a normal force range from 1 cN up to 250 cN. The algorithms have been implemented with an “easy to use” Windows software interface called “First Contact”. The software also incorporates a material database that when used together with a surface modeler, allows for the fast calculation and 3D visualization of all mechanical and electrical contact characteristics. 


The arc behavior in an arrangement of parallel arc rails with a splitter plate in between has been investigated experimentally and in numerical computations. Thereby, the arc is simulated by coupling finite-volume modeling for the gasdynamics and finite-elements modeling for the electromagnetics. The formation of arc roots on the splitter plate can be described by a thin layer of elements with a current-density dependent specific resistance. The simulations were extended to model the experimental arrangement exactly. Additionally, net emission coefficients and radiation heat conductivity of air plasma instead of a simplified T4 net emission of a black body were used to model the radiative cooling of the arc. The results of the arc voltage, the arc movement and the splitting process have been compared to measurements and high speed movies of the arc and yield good correlation. Moreover, the simulations allow good insight into the temperature distribution of the arc and the movement of the pressure waves caused at the arc ignition.