Design and coupled-effect simulations of CMOS micro gas-sensors built on SOI thin membranes

This paper describes coupled-effect simulations of smart micro gas-sensors based on standard BiCMOS technology. The smart sensor features very low power consumption, high sensitivity and potential low fabrication cost achieved through full CMOS integration. For the first time the micro heaters are made of active CMOS elements (i.e. MOSFET transistors) and embedded in a thin SOI membrane consisting of Si and SiO2 thin layers. Micro gas-sensors such as chemoresistive, microcalorimeteric and Pd/polymer gate FET sensors can be made using this technology. Full numerical analyses including 3D electro-thermo-mechanical simulations, in particular stress and deflection studies on the SOI membranes are presented. The transducer circuit design and the post-CMOS fabrication process, which includes single sided back-etching, are also reported.

Design and simulations of SOI CMOS micro-hotplate gas sensors

This paper describes a new generation of integrated solid-state gas-sensors embedded in SOI micro-hotplates. The micro-hotplates lie on a SOI membrane and consist of MOSFET heaters that elevate the operating temperature, through self-heating, of a gas sensitive material. These sensors are fully compatible with SOI CMOS or BiCMOS technologies, offer ultra-low power consumption (under 100 mW), high sensitivity, low noise, low unit cost, reproducibility and reliability through the use of on-chip integration. In addition, the new integrated sensors offer a nearly uniform temperature distribution over the active area at its operating temperatures at up to about 300-350°C. This makes SOI-based gas-sensing devices particularly attractive for use in handheld battery-operated gas monitors. This paper reports on the design of a chemo-resistive gas sensor and proposes for the first time an intelligent SOI membrane microcalorimeter using active micro-FET heaters and temperature sensors. A comprehensive set of numerical and analogue simulations is also presented including complex 2D and 3D electro-thermal numerical analyses. © 2001 Elsevier Science B.V. All rights reserved.

Micro-Scale Gas Flows

了解微尺度气体流动特点是微机电系统设计和优化的基础.有关的研究可以上溯到20世纪初Knudsen的平面槽道流动质量流量的测量和Millikan的小球阻力系数的测量,实验结果揭示了稀薄气体效应即尺度效应对气体运动的重要影响.由于流动特征长度很小,微尺度气流经常处于滑流区甚至过渡领域,流动的相似参数为Knudsen数和Mach数.因此可以考虑利用相似准则,通过增大几何尺寸、减小压力的途径,解决微机电系统实验观测遇到的困难.为解决直接模拟MonteCarlo方法分析微机电系统中低速稀薄气流遇到的统计涨落困难,我们提出了信息保存法(IP),该方法能够有效克服统计散布,并已成功用于多种微尺度气流.

Fourier Transform Method for Measuring the Micro Amplitu of Water Surface Waves

采用一种非接触的光学方法傅立叶变换莫尔法(Fourier transform method),结合数字图像处理技术,对微幅振荡的水表面波的振幅进行测量.它是对全场中每一个像素点进行测量,比接触测量法具有更高的灵敏度.它为微幅水表面波振幅的测量提供了一种手段.通过将计算机生成的周期性光栅图像经投影机直接投影到被测物体的参考平面,经CCD摄像头、图像板捕捉存储形成数字化的光栅图像,利用傅立叶变换莫尔法处理光栅图像,从而获得包含有水表面波的振幅的相位信息,再经适当的几何变换获得振幅信息.我们在垂直振荡装置上进行了不同激励频率和不同振幅的表面波的振幅测量.

Numerical Simulation on the Micro-Scale Bending Induced by Pulsed Laser Beam

利用自行研制的含热传导、冲击动力学大、变形有限元程序,模拟了小尺寸梁在脉冲激光加热条件下的变形过程。在此基础上,利用商用程序模拟了冷却及残余应力的产生,研究了激光参数（强度及分布）等对于微弯曲的影响。数值模拟结果与文献中的实验观察相吻合。

Characteristics of Gas Flow Within a Micro Diffuser/Nozzle Pump

英文摘要: The gas flow characteristics for various shapes of micro diffuser/nozzles have been experimentally investigated. The micro diffuser/nozzles with the lengths of 70 mu m, 90 mu m, 125 mu m and the taper angles of 7 degrees, 10 degrees, 14 degrees are designed and fabricated based on silicon micromachining technology for optimizing and comparing. The flat-wall diffuser/nozzle is 40 mu m x 5 mu m in depth and width. An experimental setup is designed to measure the gas flow rates under controlled temperature and pressure condition. Optimized values for the taper angle and the length of the diffuser/nozzle are experimentally obtained.

Characterisation of ultrafast micro-structuring of alumina (Al 2O3)

Alumina ceramic, Al2O3, presents a challenge to laser micro-structuring due to its neglible linear absorption coefficient in the optical region coupled with its physical properties such as extremely high melting point and high thermal conductivity. In this work, we demonstrate clean micro-structuring of alumina using NIR (λ=775 nm) ultrafast optical pulses with 180 fs duration at 1kHz repetition rate. Sub-picosecond pulses can minimise thermal effects along with collateral damage when processing conditions are optimised, consequently, observed edge quality is excellent in this regime. We present results of changing micro-structure and morphology during ultrafast processing along with measured ablation rates and characteristics of developing surface relief. Initial crystalline phase (alpha Al2O3) is unaltered by femtosecond processing. Multi-pulse ablation threshold fluence Fth, ∼ 1.1 Jcm-2 and at low fluence ∼ 3 Jcm -2, independent of machined depth, there appears to remain a ∼ 2 μm thick rapidly re-melted layer. On the other hand, micro-structuring at high fluence F ∼ 21 Jcm-2 shows no evidence of melting and the machined surface is covered with a fine layer of debris, loosely attached. The nature of debris produced by femtosecond ablation has been investigated and consists mainly of alumina nanoparticles with diameters from 20 nm to 1 micron with average diameter ∼ 300 nm. Electron diffraction shows these particles to be essentially single crystal in nature. By developing a holographic technique, we have demonstrated periodic micrometer level structuring on polished samples of this extremely hard material.

Thermodynamics of the displacive mechanism of alpha(1) transformation in a beta

Thermodynamics of the displacive mechanism of plate-shaped phase alpha(1) was analyzed in beta'Cu-Zn alloys. It was proposed that the displacive transformation of the alpha(1) plate took place in the solute-depleted region formed in the parent phase during the incubation period. The thermodynamic analysis indicated that the driving force of alpha(1) transformation, Delta G, increased with the reduction of x(d), the solute concentration of the depleted region. And, Delta G could overcome-the transformation barrier with solute depletion to a certain degree. In addition, x(d) was higher than the equilibrium concentration in the phase diagram. Therefore, the shear formation of alpha(1) plate in the solute-depleted region was thermodynamically supported.

Size Effects in Micro-bending Deformation of MEMS Devices Based on the Discrete Dislocation Theory

In the present research, the discrete dislocation theory is used to analyze the size effect phenomena for the MEMS devices undergoing micro-bending load. A consistent result with the experimental one in literature is obtained. In order to check the effectiveness to use the discrete dislocation theory in predicting the size effect, both the basic version theory and the updated one are adopted simultaneously. The normalized stress-strain relations of the material are obtained for different plate thickness or for different obstacle density. The prediction results are compared with experimental results.

ZnO film based surface acoustic wave micro-pump

In this study, a micro-pump unit based on surface acoustic wave (SAW) on piezoelectric ZnO film is designed and fabricated as a micro-fluidic device. It employs a mechanical wave, which is generated electrically using an aluminum interdigital transducer (IDT), and propagates on the surface of the ZnO film. The ZnO film was used in this study because it has a high electromechanical coefficient and an excellent bonding with various substrate materials, in particular silicon. The sputtering parameters for ZnO film deposition have been optimized, and the ZnO films with different thickness from 1 micron to 5.5 microns were prepared. The film properties have been characterized using different methods, such as scanning electron microscopy, X-ray diffraction and atomic force microscopy. Aluminum IDT with a finger width and spacing of 8 microns was patterned on the ZnO film using a lift-off process. The frequency generated was measured using a network analyzer, and it varies from 130 MHz to 180 MHz as a function of film thickness. A signal generator was used to generate the frequency with a power amplifier to amplify the signal, which was then applied to aluminum IDT to generate the surface acoustic wave. If a liquid droplet exists on the surface carrying the acoustic wave, the energy and the momentum of the SAW will be coupled into the fluid, causing the liquid to vibrate and move on film surface. The strength of this movement is determined by the applied voltage and frequency. The volume of the liquid drop loaded on the SAW device in this study is of several hundreds of nanoliters. The movement of the liquid inside the droplet and also on the ZnO film surface can be demonstrated. The performance of ZnO SAW device was characterized as a function of film thickness. © 2007 IOP Publishing Ltd.

Size Effect and Geometrical Effect of Solids in Micro-Indentation Test

Micro-indentation tests at scales of the order of sub-micron show that the measured hardness increases strongly with decreasing indent depth or indent size, which is frequently referred to as the size effect. At the same time, at micron or sub-micron scale, another effect, which is referred to as the geometrical size effects such as crystal grain size effect, thin film thickness effect, etc., also influences the measured material hardness. However, the trends are at odds with the size-independence implied by the conventional elastic-plastic theory. In the present research, the strain gradient plasticity theory (Fleck and Hutchinson) is used to model the composition effects (size effect and geometrical effect) for polycrystal material and metal thin film/ceramic substrate systems when materials undergo micro-indenting. The phenomena of the "pile-up" and "sink-in" appeared in the indentation test for the polycrystal materials are also discussed. Meanwhile, the micro-indentation experiments for the polycrystal Al and for the Ti/Si_3N_4 thin film/substrate system are carried out. By comparing the theoretical predictions with experimental measurements, the values and the variation trends of the micro-scale parameter included in the strain gradient plasticity theory are predicted.

Efecto de aplicaciones de NPK sobre el crecimiento, desarrollo y rendimiento agroindustrial de la caña de azucar (Saccharum sp híbrido) variedad C87-51 en caña planta en el IBZ-CASUR S.A., Potosí, Rivas

El presente estudio se realizó en áreas de la finca "San Fernando" perteneciente al Ingenio Benjamin Zeledón (IBZ) de la Compañía Azucarera del Sur (CASUR, S.A.) ubicado en Potosí, departamento de Rivas (11005' LN y 86001' LO, a 70 msnm) con el objetivo de contribuir al incremento del rendimiento agroindustrial de la caña de azúcar se evaluaron el efecto de niveles de NPK: Nitrógeno (0, 80, 120 y 160 kg ha-1), Fósforo (0 y 60 kg ha-1) y Potasio (0, 60, 90 y 120 kg ha-1) sobre el crecimiento, desarrollo y rendimiento agroindustrial de la variedad C87-51. Los 32 tratamientos fueron distribuidos en un diseño de Bloques Completamente al Azar (BCA) con arreglo en Parcelas Subdivididas con tres réplicas. Se inició y estableció en la segunda semana de abril del 2003 y se cosechó en marzo del 2004. A los resultados de campo se les aplicó un análisis de varianza (ANDEVA) y separación de medias (Tukey ∞=0.05) sobre 13 variables cuantitativas. Asimismo, se utilizó un modelo estadístico de tendencia (lineal, cuadrática y cúbica) en el rendimiento agroindustrial para evaluar los niveles de N y K, y modelos de regresión múltiple en rendimiento. Se otuvieron efecto significativo en las variables de desarrollo y rendimiento, en el caso del P su efecto no fue significativo en el rendimiento. El mayor rendimiento agroindustrial se alcanzó en la combinación de 160–0–120 (9.34 Ton ha-1) y 160–60–120 (9.42 Ton ha-1), y presentó significancia estadística para una respuesta lineal y cúbica en N; para el caso del K la respuesta a los tres modelos establecidos fue significativa, pero con mayor significancia estadística la función lineal. La relación del rendimiento industrial a partir de rendimiento agrícola fue significativa con un ajuste cuadrático determinada por un R2 de 0.8671.

Micro-systems for Optical Protein-Chip

Protein-Chip as micro-assays for the determination of protein interaction, the analysis, the identification and the purification of proteins has large potential applications. The Optical Protein-Chip is able to detect the multi-interaction of proteins and multi-bio-activities of molecules directly and simultaneously with no labeling. The chip is a small matrix on solid substrate containing multi-micro-area prepared by microfabrication with photolithography or soft lithography for surface patterning, and processed with surface modification which includes the physical, chemical, and bio-chemical modifications, etc. The ligand immobilization, such as protein immobilization, especially the oriented immobilization with low steric hindrance and high bio-specific binding activity between ligand and receptor is used to form a sensing surface. Each area of the pattern is corresponding to only one bioactivity. The interval between the areas is non-bioactive and optically extinctive. The affinity between proteins is used to realize non-labeling microassays for the determination of protein identification and protein interaction. The sampling of the chip is non-disturbing, performed with imaging ellipsometry and image processing on a database of proteins.

Evaluación de dosis de fertilización nitrogenada y densidad de siembra sobre el rendimiento del cultivo de repollo (Brassica oleraceae, var capitata L.) híbrido Izalco

Se realizó un estudio en la Finca San Bernardo, Municipio de Nandasmo – Masaya en el período del 21 d e Agosto al 21 de Diciembre de 2004. S e probaron tres dosis de fertilización nitrogenada siendo estas 75 kg/ha, 150kg/ha, 225 kg/ha, un testigo de 0 nitrógeno y dos densidades de siembra con 28571 y 22222 plantas /ha. El experimento consistió en una bifact orial con diseño de bloques completos al azar, evaluando los siguientes parámetros: diámetro polar, diámetro ecuatorial, peso fresco, número de cabezas formadas, rendimiento, calidad y rentabilidad del repollo. Los datos obtenidos se sometieron al análisis de varianza y a la prueba de Tukey al 1% y a un análisis económico de presupuesto parcial. Se observó la tendencia de obtener mayor diámetro polar, diámetro ecuatorial, rendimiento, beneficio bruto y beneficio neto con dosis de 150 kilogramos de nitrógeno por hectárea y densidad de siembra de 28571 plantas por hectárea. De igual forma se obtuvo el mayor peso fresco con dosis de 150 kilogramos de nitrógeno por hectárea y densidad de siembra de 22222 plantas y el mayor n ú mero de cabezas formadas se obtuvo c on dosis de 225 kilogramos de nitrógeno y densidad de 28571 plantas. Los tratamientos sometidos al análisis de retorno marginal superaron la tasa mínima de retorno de 150%. La mayor tasa de retorno marginal se obtuvo con dosis de 75 kilogramos de nitrógeno y densidad de siembra con 22222 plantas.

Characterization of the Fracture Work for Ductile Film Undergoing the Micro-Scratch

The interface adhesion strength (or interface toughness) of a thin film/substrate system is often assessed by the micro-scratch test. For a brittle film material, the interface adhesion strength is easily obtained through measuring the scratch driving forces. However, to measure the interface adhesion strength (or interface toughness) for a metal thin film material (the ductile material) by the microscratch test is very difficult, because intense plastic deformation is involved and the problem is a three-dimensional elastic-plastic one. In the present research, using a double-cohesive zone model, the failure characteristics of the thin film/substrate system can be described and further simulated. For a steady-state scratching process, a three-dimensional elastic-plastic finite element method based on the double cohesive zone model is developed and adopted, and the steady-state fracture work of the total system is calculated. The parameter relations between the horizontal driving forces (or energy release rate of the scratching process) and the separation strength of thin film/substrate interface, and the material shear strength, as well as the material parameters are developed. Furthermore, a scratch experiment for the Al/Si film/substrate system is carried out and the failure mechanisms are explored. Finally, the prediction results are applied to a scratch experiment for the Pt/NiO material system given in the literature.