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Abstract

This paper deals with the development of a micro-interconnection technology suitable for the elaboration of RF-NEMS (Nano-ElectroMechanical Systems) varactors. It aims to present an extension of RF MEMS concept into nano-scale domain by using multi-walled carbon nanotubes (MWCNT) as movable part instead of micrometric membranes into reconfigurable passive circuits for microwave applications. For such a study, horizontal configuration of the NEMS varactors has been chosen and is commented. The technology is established to fulfill several constraints, technological and microwave ones. As far as technological requirements are concerned, specific attentions and tests have been carried out to satisfy: " Possible and later industrialization. No e-beam technique has been selected for RF NEMS varactor elaboration. Lateral MWCNT growth performed on a Ni catalyst layer, sandwiched between two SiO2 layers, showed feasibility of suspended MWCNT beam. " High thermal budget, induced by the MWCNT growth by CVD (Chemical Vapor Deposition), at least to 600°C. All the dielectric and metallic layers, required to interlink the nano world with the micrometric measurements one, have been studied accordingly. Consequently, the order of the technological steps has been identified. About microwave and actuation specifications (targeted close to 25V), the minimization of losses and actuation voltage implies large layer's thicknesses compared to the CNT diameter. Several specific technological issues are presented in this paper, taking care of both technological and microwave compatibility to go toward RF NEMS varactor's elaboration.

Mots-Clés / Keywords

MWCNT; RF MEMS; Varactors; Microwave;

Mots-Clés / Keywords

Electrochemical processes; Magnetic devices; DC-DC power conversion;

Abstract

A vertical N-channel 150-200 V FLYMOSFET concept has been applied on silicon: its P-buried layer introduced in the N2 epitaxial region, called "P floating island", is the key factor for superior performance. A particular physical characterisation technique, scanning capacitance microscopy, is used on a power device to establish 2D and 3D island representation and to go beyond 1D information given by spreading resistance profiling. Experiments including four different boron implantations of P floating islands and two different spacings of the basic cell are conducted, because the form and the concentration of the floating islands and, moreover, the spacing between them directly impact the electrical performance. Concerning the electrical study, FLYMOSFET measurements show good "specific on-resistance/breakdown voltage" (RON.S- BVdss) trade-offs, better than the conventional VDMOSFETs, and UIS ruggedness as good as superjunction MOSFETs.

Mots-Clés / Keywords

Power MOSFET; Floating Islands; FLYMOS; Superjunction; Breakdown voltage; Specific On-resistance; Spreding resistance profiling (SRP); Scanning capacitance microscopy (SCM); 2D/3D physical characterization;

Abstract

For applications such as computers, cellular telephones and Microsystems, it is essential to reduce the size and the weight of electronic devices. More particularly, this evolution implies the miniaturization of high effi ciency on-chip dc-dc converters providing low voltage to the various ICs. Therefore, fabrication of magnetic components dedicated to power conversion becomes necessary. To miniaturize inductors, the micromachining techniques provide solutions based on low-temperature process compatible with active part of the converter. The proposed inductor topology is based on a spiral-type structure which consists in a copper conductor sandwiched between two CoNiFe (60%- 15%-25%) layers shielding the magnetic fl ux of the inductor winding. Considering a 1-5 MHz operating switching frequency, a laminated core has been investigated in order to reduce eddy-current induced in the core. We have made several investigations on the electroplating baths parameters by changing temperature, pH and current density values in order to obtain optimum magnetic properties (Bsat=2.3T, low Hc, ¼r=250, resistivity>30 ¼Ohm.cm). These proprieties are measured by SQUID and the composition is analyzed using quantitative energy dispersive X-ray analysis. Research reported in this paper is an example relative to the microinductors fabrication for micropower applications. It shows the feasibility of a spiral inductor structure with a laminated core adequate for a high frequency switching operation. The fi nal paper will describe with more details the characterizations of a ten turns prototype exhibiting a 1¼H inductance value.

Mots-Clés / Keywords

Integrated inductors; Spiral; Electroplating; CoNiFe; CMP; DC-DC converters;

Mots-Clés / Keywords

High aspect ratio; DRIE; TMA; IPA; Scalloping;

Abstract

The electrical and optical properties of the ZnO layers and of the ITO/ZnO bilayers are investigated. We show that a ZnO layer of about 120 nm is the best compromise to obtain simultaneously a high transmittance and conductivity. Moreover an X-ray diffraction analysis underscores that an amorphous ITO deposited on a polycrystalline ZnO could change into a polycrystalline ITO. The modifications of the ITO layer by a preliminary deposition of a 120 nm thick ZnO underlayer enables us to decrease the threshold voltage of organic light emitting diodes.

Mots-Clés / Keywords

ITO/ZnO bilayer; Electrical properties; X-ray diffraction; OLEDs; Polycrystalline ZnO films;

Résumé

Cette étude se propose d'explorer les mécanismes de chargement de diélectriques qui apparaissent dans les actionneurs MEMS électrostatiques et qui aujourd'hui sont les principales limitations à leurs industrialisations. De nombreux travaux ont montré les méthodes de tests qui pouvant être utilisées pour mettre en évidence les mécanismes de chargement responsables du phénomène de collage. L'objectif de ce travail est d'étudier les mécanismes de chargement de diélectriques pour des films réalisés à partir de conditions expérimentales différentes afin de proposer une amélioration de la fiabilité des actionneurs électrostatiques vis-à-vis des mécanismes de dégradation