PECVD silicon carbide: A structural material for surface micromachined devices

Electrical Engineering, Mathematics and Computer Scienc

Genetic diversity of Vietnamese domestic chicken populations as decision-making support for conservation strategies

The aims of this study were to assess the genetic diversity of 17 populations of Vietnamese local chickens (VNN) and one Red Jungle Fowl population, together with six chicken populations of Chinese origin (CNO), and to provide priorities supporting the conservation of genetic resources using 20 microsatellites. Consequently, the VNN populations exhibited a higher diversity than did CNO populations in terms of number of alleles but showed a slightly lower observed heterozygosity. The VNN populations showed in total seven private alleles, whereas no CNO private alleles were found. The expected heterozygosity of 0.576 in the VNN populations was higher than the observed heterozygosity of 0.490, leading to heterozygote deficiency within populations. This issue could be partly explained by the Wahlund effect due to fragmentation of several populations between chicken flocks. Molecular analysis of variance showed that most of genetic variation was found within VNN populations. The Bayesian clustering analysis showed that VNN and CNO chickens were separated into two distinct groups with little evidence for gene flow between them. Among the 24 populations, 13 were successfully assigned to their own cluster, whereas the structuring was not clear for the remaining 11 chicken populations. The contributions of 24 populations to the total genetic diversity were mostly consistent across two approaches, taking into account the within- and between-populations genetic diversity and allelic richness. The black H'mong, Lien Minh, Luong Phuong and Red Jungle Fowl were ranked with the highest priorities for conservation according to Caballero and Toro's and Petit's approaches. In conclusion, a national strategy needs to be set up for Vietnamese chicken populations, with three main components: conservation of high-priority breeds, within-breed management with animal exchanges between flocks to avoid Wahlund effect and monitoring of inbreeding rate

Fast response thermal linear motor with reduced power consumption

AbstractThis paper presents the principle, fabrication and characterization of a fast response Thermal Linear Motor (TLM) havingreduced heat loss (and thus power consumption) without reduction in mechanical output power. Our double wedge shaped, aluminum TLM is 12 μm and 6 μm wide at the edges respectively center and 400 μm long. Theory and measurements show that this TLM has up to 20% more mechanical output power for the same electrical input power compared to a simple rectangular beam TLM. The TLM is the crucial driving element for our Hard Disk Drive (HDD) thermal micro actuator. The actuator uses two of the here presented TLMs to accurately move the HDD head up to several micrometers

Residue-free plasma etching of polyimide coatings for small pitch vias with improved step coverage

The authors have found that patterning polyimide coatings containing organosilane adhesion promoter using pure oxygen plasma resulted in a thin silicon-rich residue layer. They show in this paper that adding small amounts of fluorine-containing gas to the etching gas mixture is necessary in order to achieve residue-free polyimide plasma etching. They report residue-free plasma etching of polyimide coatings with both isotropic and anisotropic profiles, using either metal or oxide hard masks. These etching methods are however not sufficient for the fabrication of high density metal filled vias in 10??m thick polyimide coatings. In order to improve the metal step coverage over the vias while keeping the pitch as small as possible, the authors have developed a two-step etching recipe combining both isotropic and anisotropic profiles, resulting in wine-glass shaped vias.MicroelectronicsElectrical Engineering, Mathematics and Computer Scienc

A porous SiC ammonia sensor

When used as the dielectric in a capacitive sensing arrangement, porous SiC has been found to be extremely sensitive to the presence of ammonia (NH3) gas. The exact sensing method is still not clear, but NH3 levels as low as 0.5 ppm could be detected. We report the fabrication and preliminary characterisation of NH3 sensors based on porous SiC and Al electrodes. SiC is a very durable material and should be good for sensors in harsh environments. So far, the only NH3 sensors using SiC have been FET based, and the SiC was not porous. In our devices, SiC was deposited by PECVD on standard p-type single-crystal Si and was then made porous by electrochemical etching in 73% HF using anodisation current densities of 1–50 mA/cm2. Preliminary data is given for our devices response to NH3 in the range 0–10 ppm NH3 in dry N2 carrier gas

Polarization-insensitive PECVD SiC waveguides for photonic sensing

Planar silicon carbide (SiC) waveguides are proposed for fabrication on a silicon substrate with a oxide isolation layer. Using post deposition annealing it is possible to achieve low Polarization-Dependent Loss (PDL) within optical SiC waveguides fabricated using a low temperature deposition technique. Those waveguides have been successfully used in power splitters and cantilivers. These first devices open the way for photonic sensing in harsh environment using SiC.Electronic Instrumentation LaboratoryElectrical Engineering, Mathematics and Computer Scienc

Influence of seed layer on crystallinity and orientation of pulsed — DC sputtered AlN thin-films for piezoelectric actuators

Aluminum Nitride thin films with the desired properties for piezoelectric actuators are grown by pulsed DC sputtering on Si (100) substrates coated with different seed layers (Al/1%Si, Mo, Ti). The influence of sputtering parameters and the seed layers on crystallinity and orientation of the AlN films is investigated. Raman spectroscopy measurements are performed and the results are analyzed to identify the optimal deposition conditions. The high-cc axis orientation of AlN thin films obtained with Ti as a seed layer was confirmed by X-ray diffraction. It appears that seed layers of 200 nm Ti are a valid alternative to Molybdenum or Platinum for IC compatible piezoelectric actuators fabrication.MicroelectronicsElectrical Engineering, Mathematics and Computer Scienc

Robust Wafer-Level Thin-Film Encapsulation (Packaging) of Microstructures (MEMS) using Low Stress PECVD Silicon Carbide

This paper presents a new low-cost, CMOS-compatible and robust wafer-level encapsulation technique developed using a stress-optimised PECVD SiC as the capping and sealing material, imparting harsh environment capability. This technique has been applied for the fabrication and encapsulation of a wide variety of surface- and thin-SOI microstructures that included microcavities, a RF switch and various accelerometers. Advantages of our technique are its versatility, smaller footprint, reduced chip thickness and process complexity, post-CMOS batch processing capability and added functionality due to the possibility of integrating additional electrodes for MEMS. Besides fabrication details, this work also discusses design aspects and demonstrates the encapsulation results. Encapsulation of structural area as large as 955 x 827 µm^2 has been successfully achieved.Microelectronics & Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc