The impact of Cubic Silicon Carbide (3C-SiC) transition layer on breakdown voltage and frequency performance of GaN high electron mobility transistors is investigated. A combination of distinct material and device characterizations techniques, including Raman spectroscopy, coplanar waveguides, electrical measurements, and Technology Computer-Aided Design (TCAD) simulations, are adopted to inspect the role of the 3C-SiC interlayer. Raman spectra reveal a good quality of the 3C-SiC layer, similar to the mono-crystalline 3C-SiC spectra. A relatively low transmission loss of ∼0.16 dB/mm at 40 GHz is measured for the device with 3C-SiC layer, rather than 2.1 dB/mm for the device without 3C-SiC. In addition, a soft breakdown voltage around 1530 V at 1 μA/mm is achieved, which is three times larger compared with that of the conventional device. The failure mechanism, related to carrier injection at the nucleation layer, is not observed in the structure with the 3C-SiC layer. Instead, TCAD simulations disclose a substantial improvement of the buffer/substrate interface through the suppression of an interface current path.

A cost-effective fabrication process is developed to improve the power performance of AlGaN/GaN High Electron Mobility Transistors (HEMTs). This process uses nitrogen ion (N+) implantation to form multiple parallel nanoribbons on AlGaN/GaN heterostructures, with a thin buffer layer (AlGaN/GaN NR-HEMTs). The stopping and range of ions in matter simulations of the N+ implantation combined with measured current-field characteristics reveal a good electrical isolation beneath the two-dimensional electron gas, resulting in substantial increase in the breakdown field of the NR-HEMTs, when compared to conventional AlGaN/GaN HEMTs. The fabricated AlGaN/GaN NR-HEMTs performed (i) an ON/OFF current ratio more than two orders of magnitude larger and (ii) a buffer leakage current more than one order of magnitude weaker than that of the conventional AlGaN/GaN HEMTs. The on-resistance, RON, and series resistance, RS, of AlGaN/GaN NR-HEMTs are both reduced by one order of magnitude when compared to those of the conventional AlGaN/GaN HEMTs. These have boosted the drive current density by up to 435%. Furthermore, we have found that the architecture of the AlGaN/GaN NR-HEMTs reduces the destructive impact of electron traps in the device. An optimized AlGaN/GaN NR-HEMT exhibited a better electrostatic integrity, a subthreshold slope of ∼210 mV/dec instead of 730 mV/dec for a conventional GaN HEMT. A higher linearity in the transconductance, gm, of NR-HEMTs is observed, twice of that of a conventional GaN HEMT. These results demonstrate the great interest of developed process technology of NR-HEMTs for high-power switching applications.

A new parametric and cost-effective technique is developed to decouple the mechanisms behind current degradation in AlGaN/GaN high-electron mobility transistors (HEMTs) under a normal device operation: self-heating and charge trapping. Our unique approach investigates charge trapping using both source ( ${I}_{\text {S}}$ ) and drain ( ${I}_{\text {D}}$ ) transient currents for the first time. Two types of charge-trapping mechanisms are identified: 1) bulk charge trapping occurring on a timescale of less than 1 ms and 2) surface charge trapping with a time constant larger than a millisecond. Through monitoring the difference between ${I}_{\text {S}}$ and ${I}_{\text {D}}$ , a bulk charge-trapping time constant is found to be independent of both drain ( ${V}_{\text {DS}}$ ) and gate ( ${V}_{\text {GS}}$ ) biases. Surface charge trapping is found to have a much greater impact on slow degradation than bulk trapping and self-heating. At a short timescale (<1 ms), the RF performance is mainly restricted by both bulk charge-trapping and self-heating effects. However, at a longer time (>1 ms), the dynamic ON-resistance degradation is predominantly limited by surface charge trapping.

The source/drain and gate induced charge trapping within an AlGaN/GaN high electron mobility transistor is studied, under normal device operation, by excluding self-heating effects, for the first time. Through direct measurement of current transients of both source and drain terminals, a characterisation technique has been developed to: (i) analyse the transient current degradations from mu s to seconds, and (ii) evaluate the drain and gate induced charge trapping mechanisms. Two degradation mechanisms of current are observed: bulk trapping at a short time (<1ms); and surface trapping and redistribution (>1ms). The bulk charge trapping is found to occur during both ON and OFF states of the device when V-DS>0V; where its trapping time constant is independent of bias conditions. In addition, the time constant of the slower current degradation is found to be mainly dependent on surface trapping and redistribution, not by the second heat transient.

An integrated Terahertz Mach-Zehnder interferometer is presented in order to perform difierential measurements in a chip. Both simulation and experiment are performed for validating the interferometer structure. Destructive interference peaks are observed, and destructive frequencies are predicted by a mathematical model with a good agreement. The structure is then used to characterize dielectric constant of materials. Simulation results enable to quantify the device sensitivity. An experimental validation is given with the characterization of a thermosensitive polymer (Cyclotene BCB) in the sub-THz frequency band. Perspectives to increase investigated frequencies are discussed.

Summary form only given. Plasma polymerization, so called remote plasma enhanced chemical vapour deposition (RPECVD) has been increasingly used in microsystems field. Plasma polymers served primarily as supports for electronic sensors or carriers for biomolecules and cell attachment. This work describes the first use of plasma thin film deposition for the easy, fast and reduced cost fabrication of microfluidic channels. A new method named "plasma polymerization on a micropatterned surface" (PPMS) is presented. First, micropatterns representing the desired channels were designed on a silicon wafer, either by lithography of a sacrificial photoresist or by plasma etching of the Si substrate. Then, the patterned substrate was introduced into the reaction chamber of a home-made microwave (2.45 GHz) plasma reactor. The organosilicon monomer 1,1,3,3,tetramethyldisiloxane was used as the precursor to synthetize and deposit a polymer organosilicon film by a remote afterglow PECVD. The deposited polymer is used as the structural material of the microfluidic network. Unlike conventional plasma deposition methods, PPMS process occurs at moderate temperatures and allows the deposition of a wide range of thicknesses (10 nm-500 mum), with 14 nm/s growth rate. Our method enables a rapid creation of capillarity-driven flow systems with channels width ranging from 4 to 700 mum without pillars. Channels are characterized and successfully tested. Capillary forces draw water, as well as aqueous solution into the channel from the inlet reservoir to the outlet one with the initial velocity of 4.4 cm/s. In addition, PPMS easily and softly allows the building of transparent microfluidic networks directly on processed electronic components.

Single-cell analysis is a very important field of research and is currently at the frontier of physical and biological sciences. Understanding how the phenotype of a single-cell arises from its genotype is a complex topic. Currently, the prevailing paradigm to analyze cellular functions is the study of biochemical interactions using fluorescence based imaging systems. However, the elimination of the labelling process is highly desirable to improve the accuracy of the analysis. Living cells are electromagnetic units; in as much they use electric mechanisms to control and regulate dynamic processes involved in inter alia signal transduction, metabolism, proliferation and differentiation. Recent developments in micro- and nanofabrication technologies are offering great opportunities for the analysis of single cells; the combination of micro fluidic environments, nano electrodes/wires and ultra wide band electromagnetic engineering will soon make possible the investigation of local (submicrometer scale) dynamic processes integrating several events at different time scales. In the paper, we present recent approaches which aim at investigating singlecells with the help of MEMS and NEMS (Micro and Nano Electro Mechanical Systems) and ultra wide band (DC-THz) electromagnetic characterization techniques.

By performing dielectric spectroscopy across a wide spectrum of frequencies (DC-THz), single-cell analysis could be performed without labeling process. That is why we are developing different micro structures, either planar/3D electrodes or transmission lines, and microfluidic devices using BIOMEMS technologies. In our devices, silicon or glass substrates are combined with polymeric materials and gold patterns. For low frequency (LF) applications, PDMS has been chosen while for high frequency (HF) structures, the PPTMDSO is preferred. We are designing the devices thanks to modeling and simulation using either COMSOL (LF) or CST (HF) softwares. Different designs have already been fabricated and are presented in this paper. Finally, we have performed single cell measurements for the low frequency range (< 10 MHz) and the next step will focuse on high frequency measurements.

We propose a new technology for high throughput bioMEMS based on a mixed technology polymer on silicon. This technology is compatible with microelectronic processes, the electromagnetic propagation, the microfluidic circulation and the biological solutions. We use a new process and a new polymer deposited by a "cold" plasma technique. We can use it for a surface functionalization or for the encapsulation with plasma assisted wafer bonding

perfmitng dielectric spectroscopy across awidespectrum offrequencies (DC-TH), single-cel1 analysis could be performed with outlabeling proc ess. That isy wearedeveloping diffrent microstmrctures, either plan ar/3Dlectrodes or transmission Imes, andmicrofuildic devices usigBIOMEMStechnologies. Inourdevices, silicon orglass substrates are combimed with polymeric materials andgoldpatems. Forlowfrequeny (LF)Vpplictions, PDMShasbeenchosen while fbrhighfrequency (i)structures, thePPTWMSOisprefered. We aredesigning thedevices thankis tomodelimg and simulation using either COMSOL(LE)orCST([F) softwares. Differnt designs havealread beenfabricated andare presented inthis paper. Finally, wehaveperbrmned single cell measurements fbrthelowfreqenc range (c10MHz)and thenexstep will focuse onhigh frequency measurements.

In this letter, the microwave and noise performance of SiGe heterojunction bipolar transistors (HBTs) has been characterized when cooling down the temperature. It was found that SiGe HBTs (fabricated in the framework of BiCMOS process) exhibit a maximum oscillation frequency f(max) of about 292 GHz at 78 K, which represents an increase of about 30% with the value measured at room temperature. The noise performance has also been characterized at cryogenic temperatures, using an original de-embedding approach. Then, using the Hawkin's noise model in conjunction with an accurate small signal equivalent extraction, the four noise parameters have been estimated. The noise figure with a 50 Omega source impedance was measured to be equal to 1.5 dB at 40 GHz at 78 K, which is one of the lowest value reported for BiCMOS SiGe HBT in the millimeter-wave range.

We investigate a possible fabrication of microfluidic MEMS dedicated to the THz spectroscopy in a mixing technology based on silicon substrate coated with a thick layer of polymer. This layer is useful for the microfluidic circulation and the electromagnetic propagation. We use an original deposition process realized by RPECVD (remote plasma enhanced vapor deposition), called also "cold plasma". We obtain layers up to 110 /spl mu/m without any cracks. We have measured the dielectric characteristics of this new type of polymer up to 220 GHz with a vectorial network analyzer and between 0.1 to 1.2 THz in the time domain with an electro-optic technique. This technology is now ready and allows realizing a mass production compatible with disposable bioMEMS.

A methodology to perform accurate on-wafer high-frequency noise measurements at cryogenic temperatures (77K) is presented. In this work, the distribution of the temperature along probes and cables at low temperatures is carefully taken into account in the de-embedding process using a 3-D thermal modelling software (®ANSYS) and thermal measurements. Cables and probes are modelled in ®ADS software using a distributed RLCG network associated to this temperature distribution. The validity of this model has been checked by measuring the noise power of a 50 Ω on-wafer resistance placed at several low temperatures. Finally, we apply this technique to the noise characterization of sub-100 nm gate's length MM-HEMT at 77K and 173K.

This work consist in an accurate estimation of the available noise power of the accesses of our cryogenic probe station in order to estimate precisely the on wafer Noise Figure or Noise Power of devices under cryogenic temperatures (until 78K). These available noise powers are estimated using a transmission line approach based on a consequent RLCG network associated to the temperatures distributions of the electrical accesses of the bench. These temperatures distributions along probes and cables during a measurement performed at low temperatures are obtained using a 3-D thermal modeling software (ANSYS) associated to thermal measurements and are carefully taking into account in our distribution network. This modeling has been validate by the measurement of the available noise power of a 50 Ω on-wafer resistance placed at several low temperatures (78K, 123K and 173K). This de-embedding approach is finally applied to the noise characterization of 100 nm gate??s length MM-HEMT at 77K and 173K.

Biosensors allow investigating complex media with many applications in biology, environment and food processing. But new constraints in terms of sensitivity, real-time measurement and life time lead to new designs. Microfluidic and microsystems technologies can bring interesting solutions. We present here a new technological method for the microfabrication of such biosensors, called bioMEMS, based on the deposition of a polymer on a silicon substrate by "cold" RPECVD. Moreover, this structure is well suitable for the deposition of planar waveguide up to the THz frequencies. We try to develop a transduction function based on the dielectric spectroscopy of biomolecules and we present some experimental results obtained up to 220GHz with an on-wafer vectorial network analyzer..

An important activity is developed today in the field of biosensors and biochips. These sensors are used essentially in the detection and/or characterization of biological or chemical entities in complex media. The aim of this paper is the development of a new type of biosensors combining microfluidic components and millimeter or sub-millimeter wave (or THz or FIR) spectroscopy tools. Today, many different microsystems in the field of biology are realized in all polymers or in silicon with a bounding of silicon or glass. We have selected to deposit a Plasma Polymerized TetraMethylDiSiloxane (PPTMDS) on a silicon wafer. A new technological process based on cold remote nitrogen plasma allows us to obtain 50-80μm thick layers with a rigid texture and a very good link with silicon. This technological process is now well defined and is compatible with a classical microelectronic process for the deposition of the metallic planar waveguides. For the first time, measurements using an-in-house vectorial network analyzer (VNA) 140-220GHz are reported. Fairly good results have been obtained from impedance and propagation characteristics. These measurements allow us to determine the PPTMDS permittivity in this bandwidth. Thanks to this knowledge, we have designed a matched coplanar waveguide where a water droplet is deposited. An inversion model has been developed to retrieve the water permittivity and will be broadened to biological entities.

The use of terahertz waves is a promising approach for the characterization of the informative molecular assembly and its evolution inside biological cell membranes. In this way we propose a new microprobe which combines microfluidic and microwave structures for measurements in the 140-220 GHz band. This structure, based on a thinned microstrip line, includes an excellent coplanar to microstrip transition in the full band, necessary for the on-wafer vectorial network analyser (VNA) measurements and the future temporal measurement up to 1.5 THz.