基于压电基片微液滴间隙式驱动研究

连续的声辐射力驱动方式难以在平面内精确操控微流体,报道了单步驱动微流体及其在平面中位置确定的方法.在128°-YX LiNbO3上制作中心频率27.7 MHz叉指换能器组,经方波调制的载波信号加到叉指换能器激发间隙性声表面波,以单步驱动其声路径上的微液滴.垂直方向叉指换能器组确定微液滴平面上位置.采用水和0.1 g/mL的NaCl溶液进行间隙性驱动实验,结果表明,在载波强度达到一定幅度时,微液滴运动速度随调制信号频率增大而减少;当调制信号频率一定时,声路径上微液滴运动速度随载波幅度增大而增大.     

太阳电池超细栅电极喷印控制系统设计与实现

针对传统丝网印刷技术制造太阳电池金属化栅极容易造成基材破损,且制造的栅极精度和高宽比很难提高的问题,采用喷墨技术直接将纳米银墨水打印到太阳电池基材上实现栅极金属化,并设计实现了太阳电池栅极喷印样机系统．样机系统通过USB模块实现高速数据通信;两组动态随机存储器（SDRAM）内存模块构成乒乓操作,实现不间断打印;喷印控制模块采用现场可编程门阵列（FPGA）产生喷头复杂时序波形和压电驱动波形．基于流体体积法建立了微液滴喷射模型,研究了微滴喷射机制及压电驱动波形幅值对微液滴尺寸、速度一致性的影响,并进行实验验证．通过优化喷印分辨率和在线固化温度进行系统测试,结果表明,多晶硅硅片固化温度80 ℃条件下,随着喷印层数的增加,栅极高度线性增加,喷印一层大约增高0.5 μm,栅极宽度基本维持在35～40 μm,打印层数60～80层时,形成三维形貌均匀的具有高“高宽比”的栅极．     

64×64元IRFPACMOS读出电路的研制

64×64元IRFPACMOS读出电路是为红外探测器配套使用的数据处理芯片,用于对红外探测器产生的信号进行积分采样并且串行输出.为提高灵敏度及改善信号质量,取样电路的源跟随器的两个NMOSFET采用了零开启电压;并且采用了双采样结构,用来减小噪声的影响.芯片的数字模块与模拟模块间用电源和电线进行了良好的隔离,减小了相互间的影响.电路工作电压10V,芯片面积5.6×7.9mm2.本文简述了电路功能,重点介绍了该电路的制造工艺,分析了工艺中的重点,即电路采用P型(100)单晶硅衬底、N阱CMOS双层多晶硅双阈值工艺.双层多晶硅用来制作芯片内的电容.第一层多晶硅仅用作电容下极板,第二层多晶硅作电容的上极板、栅和部分连线,为了保证电容值及击穿电压,双层多晶间的介质采用二氧化硅和氮化硅复合层介质等.     

碳纤维温度传感器的感温机理及其应用研究

针对连续流光寻址电位传感器微分析系统样品溶液消耗量大的问题,本文提出了一种液滴型光寻址电位传感器微流控芯片系统。该液滴芯片以电渗微泵驱动微流体,通过电渗流动将样品溶液引流至微流路内,形成单个样品液滴。研究了样品液滴I/t特性曲线,当样品液滴流经检测点时,光电流突然升高至0.1 μA左右,当样品液滴流出检测点时,光电流降至最小。研究了不同pH值、体积均为1 μL样品液滴的I/V特性曲线,得出光寻址电位传感器的灵敏度为45.9 mV/pH;其它条件不变,改变微流路深度,获得不同pH值体积均为200 nL的样品液滴的I/V特性曲线,得出光寻址电位传感器的灵敏度为47.5 mV/pH。结果表明,可以通过减小流路深度将所需测试样品的体积减少至200 nL。该液滴型光寻址电位传感器微分析系统有望应用于微量化学/生物样品的分析。     

声表面波驱动微流体研究

报道了在128°旋转Y切割X传播方向的LiNbO3基片上研制了微流体驱动器件。RF信号经功率放大器放大后馈入叉指换能器,由它激发的声表面波驱动微流体。为减少由于声波辐射引起微流体温度上升,提出了间接微流体驱动方法,即通过声表面波驱动中间微粒,再由此驱动目标微流体。实验表明:声表面波驱动微流体所需的RF信号功率决定于微流体体积和粘性;采用间接方法驱动1μL50%甘油水液滴,在10V的RF信号持续5min下其温度变化仅0.5℃,而相同条件下直接驱动该液滴,其温度上升12.6℃。     

中国微米纳米-微纳结构对电容式柔性压力传感器性能影响的研究

设计制备出三明治结构的电容式柔性压力传感器,并对其性能进行研究.该传感器以银纳米线为电极材料,聚二甲基硅氧烷(PDMS)为柔性衬底,同时采用毛面玻璃和光面玻璃分别作为柔性衬底的制备模板,制备出微纳结构和平面结构的PDMS薄膜.然后采用喷涂法制备AgNWs/PDMS复合电极,以另外一层PDMS为介电层,将两电极面对面封装,得到电容式柔性压力传感器,最后系统研究了传感器的电极微纳结构对器件性能的影响.本文研究表明,具有微纳结构的AgNWs/PDMS复合薄膜传感器的灵敏度为1.0 kPa-1,而平面结构的AgNWs/PDMS复合薄膜传感器的灵敏度为0.6 kPa-1,由此可知具有微纳结构的柔性衬底能够显著提高器件的灵敏度.     

微陀螺仪敏感芯片的选择性电铸技术研究

介绍了一种新的MEMS器件敏感芯片的制备技术———选择性电铸技术。以金为检测电极、铜为牺牲层、正胶作为电铸胎膜,在牺牲层上经过数次电铸形成MEMS器件敏感芯片的各组成部分,腐蚀掉牺牲层后便得到了所需的敏感芯片。以微机械陀螺仪敏感芯片的制备为例,介绍了选择性电铸技术的工艺流程,进行了工艺流片,所制备的微机械陀螺仪敏感芯片结构完整、侧壁陡直、表面平整。该技术在电容式微加速度计及微机械陀螺仪等多种MEMS器件敏感芯片的制作中有广泛的应用前景。     

集成微流体测控芯片的研制

设计、研制了集成有微泵、微沟道、微流量传感器、温度传感器的微流体测控芯片.采用有限元软件ANSYS模拟分析了将其作为冷却芯片时微沟道的散热作用,分析确定了芯片上各元件的结构.该集成芯片为硅-玻璃结构,在硅片上,利用ICP法刻蚀无阀微泵泵体和微沟道;在7740玻璃片上,以溅射、剥离法制作微流量和温度传感器;图形精确对准后硅/玻璃以静电键合方法封接.无阀微泵采用压电元件驱动.测试结果表明:集成芯片具有冷却功能,循环水的流速最大可达25.4mm/s.     

新型双并联电渗微泵的制备与测试

设计了一个双并联电渗驱动泵,它由三条并联的主通道和叉指型电极两部分组成,其中每条主通道由若干个与电渗流形成方向成45°角的沟槽并联构成。通过选用ITO载玻片作为芯片基底并获得其最佳工艺参数,制作了带电极的PDMS-玻璃微流控芯片。最后对制作的电渗微泵进行测试,通过记录一段时间内单个主通道泵输送液体的体积,得出单个主通道的流速与微泵总流速。实验发现在5V内,微泵泵送液体的能力随着电压的增加而增大,微泵流速可以达到正常人体眼球房水生成速度,该结构在未来房水引流器件制作方面具有潜在的应用价值。     

基于微电极的交流电热效应粒子驱动理论与仿真分析

交流电热效应对实现微流体的驱动和微流体中粒子的操控具有便捷高效等优势。采用对称、非对称平面电极、对称双面电极及螺旋叉指电极，利用有限元方法对其电场、温度场、流场和粒子浓度场进行了强耦合仿真计算，并分析了所施加电压和电导率对局部流速及温度梯度的影响。进而，比较了不同几何类型叉指电极在相同激励下对微流体的驱动能力。结果表明，在只改变电压或电导率的情况下，电压与局部流速及温度梯度的平方成正比，电导率与局部流速及温度梯度呈线性关系；在相同激励下，四种叉指电极的局部流速和温度梯度大小依次为非对称电极、对称电极、双面电极和螺旋电极。实现了对多种典型几何形式微电极的交流电热效应仿真分析，可为优化利用该效应及相关的生物传感器设计提供参考。     

Porous polycrystalline silicon: a new material for MEMS

A new technique for the fabrication of thin patterned layers of porous polycrystalline silicon (polysilicon) and surface micromachined structures is presented. First, a multilayer structure of polysilicon between two layers of low-stress silicon nitride is prepared on a wafer of silicon. Electrochemical anodization with an external cathode takes place in an RF solution. A window in the outer nitride layer provides contact between the polysilicon and the HF solution; the polysilicon layer contacts the substrate through openings in the lower silicon nitride layer (remote from the upper windows). Porous polysilicon growth in the lateral direction is found at rates as high as 15 μm min^-1 in 12M (25%, wgt) HF to be controlled by surface-reaction kinetics. A change in morphology occurs when either the anodic potential is raised or the HF concentration is decreased, causing the polysilicon to be electropolished. The etch front advances proportionally to the square root of time as expected for a mass-transport-controlled process. Similar behavior is observed in HF anodic reactions of single-crystal silicon. Dissolution of the polysilicon layer is confirmed using profilometry and scanning electron microscopy. Enclosed cavities (chambers surrounded by porous plugs) are formed by alternating between pore formation and uniform dissolution. Porous polysilicon also forms over a broad-area layer of polycrystalline silicon that has been deposited without overcoating the silicon wafer with a thin film of silicon nitride. The resulting porous layer may be useful for gas-absorption purposes in ultrasonic sensors     

Micro-electro-mechanical systems fast fabrication by selective thick polysilicon growth in epitaxial reactor

A thick layer selective polysilicon growth technique has been developed for micro-electro-mechanical systems (MEMS) fabrication. It allows fast MEMS fabrication without using silicon on insulator wafers or deep ICPRIE etching. The fabrication technique is based on two main steps: a first seed layer of polysilicon is deposited and patterned; the second step consists in the selective growth of this layer in an epitaxial reactor. The first part of this work is devoted to the optimisation of growth parameters. Afterwards, this technique is applied for fabrication of different kinds of actuators, involving films several microns thick with good mechanical properties such as a low mechanical stress and a low roughness of the polysilicon film surface. Furthermore, thermal actuator prototypes were fabricated by using this technique;showing good mechanical properties and high reliability.     

Horizontal buried channels in monocrystalline silicon

A thick layer selective polysilicon growth technique has been developed for micro-electro-mechanical systems (MEMS) fabrication. It allows fast MEMS fabrication without using silicon on insulator wafers or deep ICPRIE etching. The fabrication technique is based on two main steps: a first seed layer of polysilicon is deposited and patterned; the second step consists in the selective growth of this layer in an epitaxial reactor. The first part of this work is devoted to the optimisation of growth parameters. Afterwards, this technique is applied for fabrication of different kinds of actuators, involving films several microns thick with good mechanical properties such as a low mechanical stress and a low roughness of the polysilicon film surface. Furthermore, thermal actuator prototypes were fabricated by using this technique;showing good mechanical properties and high reliability.

     

High aspect-ratio combined poly and single-crystal silicon (HARPSS)MEMS technology

This paper presents a single-wafer high aspect-ratio micromachining technology capable of simultaneously producing tens to hundreds of micrometers thick electrically isolated poly and single-crystal silicon microstructures. High aspect-ratio polysilicon structures are created by refilling hundreds of micrometers deep trenches with polysilicon deposited over a sacrificial oxide layer. Thick single-crystal silicon structures are released from the substrate through the front side of the wafer by means of a combined directional and isotropic silicon dry etch and are protected on the sides by refilled trenches. This process is capable of producing electrically isolated polysilicon and silicon electrodes as tall as the main body structure with various size capacitive air gaps ranging from submicrometer to tens of micrometers. Using bent-beam strain sensors, residual stress in 80-μm-thick 4-μm-wide trench-refilled vertical polysilicon beams fabricated in this technology has been measured to be virtually zero. 300-μm-long 80-μm-thick polysilicon clamped-clamped beam micromechanical resonators have shown quality factors as high as 85 000 in vacuum. The all-silicon feature of this technology improves long-term stability and temperature sensitivity, while fabrication of large-area vertical pickoff electrodes with submicrometer gap spacing will increase the sensitivity of micro-electromechanical devices by orders of magnitude     

A self-aligned fabrication method of dual comb drive using multilayers SOI process for optical MEMS applications

A novel method for fabricating a self-aligned electrostatic dual comb drive using a multi-layer SOI process is developed. The present method utilizes four aligned masks, greatly simplify the existing SOI-MEMS fabrication methods in manufacturing optical MEMS devices. Here, the actuating structure consists of fixed combs and moving combs that are composed of single crystal silicon, nitride and polysilicon. One mask is used to provide a deep etching to etch polysilicon, nitride and single crystal silicon respectively. The nitride separates polysilicon and single crystal silicon and provides an additional dielectric for the purpose of producing bi- directional motion upon applying electrostatic forces. A dual comb drive actuator with optical structures was fabricated with the developed process. The actuator is capable of motion 250 nm downward and 480 nm upward with 30 V applied voltage at 4 kHz frequency. The dynamic characteristics of the first and the second resonant frequency of the dual comb-drive actuator are 10.5 kHz and 23 kHz respectively. Experimental results indicated that the measured data agreed well with simulation results using the ANSOFT Maxwell^® 2D field simulator, ANSYS^® and Coventor Ware^®.     

Integrated polysilicon and DRIE bulk silicon micromachining for anelectrostatic torsional actuator

This paper presents a fabrication process that integrates polysilicon surface micromachining and deep reactive ion etching (DRIE) bulk silicon micromachining. The process takes advantage of the design flexibility of polysilicon surface micromachining and the deep silicon structures possible with DRIE. As a demonstration, a torsional actuator driven by a combdrive moving in the out-of-plane direction, consisting of polysilicon fingers and bulk silicon fingers, has been fabricated. The integrated process allows the combdrive to be integrated with any structure made by polysilicon surface micromachining     

Microfabrication of submicron nozzles in silicon nitride

A novel microfabrication process is described for obtaining nanometer apertures in highly cusped nozzle-like structures fabricated in silicon nitride, having apex angles of up to a few degrees. The process is based on a sacrificial etch technology using single-crystal silicon as the mold and silicon nitride as the material for the nozzle. The nitride coating on the apex of the pyramid shaped mold is selectively etched off using a polymer layer as the etch mask, which leaves the tip of the silicon mold protruding from the masked nitride, thus defining the aperture of the nozzles. The silicon mold is then removed in an alkaline etchant, which leaves the freestanding nozzles. The process is applicable to fabrication of similar structures in a variety of other materials such as silicon dioxide, boron-doped silicon, polysilicon, and refractory and noble metals. The main requirement is the preferential etchability of the mold with respect to material for the nozzles     

Design and fabrication of a novel microfluidic nanoprobe

The design and fabrication of a novel microfluidic nanoprobe system are presented. The nanoprobe consists of cantilevered ultrasharp volcano-like tips, with microfluidic capabilities consisting of microchannels connected to an on-chip reservoir. The chip possesses additional connection capabilities to a remote reservoir. The fabrication uses standard surface micromachining techniques and materials. Bulk micromachining is employed for chip release. The microchannels are fabricated in silicon nitride by a new methodology, based on edge underetching of a sacrificial layer, bird's beak oxidation for mechanically closing the edges, and deposition of a sealing layer. The design and integration of various elements of the system and their fabrication are discussed. The system is conceived mainly to work as a "nanofountain pen", i.e., a continuously writing upgrade of the dip-pen nanolithography approach. Moreover, the new chip shows a much larger applicability area in fields such as electrochemical nanoprobes, nanoprobe-based etching, build-up tools for nanofabrication, or a probe for materials interactive analysis. Preliminary tests for writing and imaging with the new device were performed. These tests illustrate the capabilities of the new device and demonstrate possible directions for improvement.     

Sub-Micro-Gravity In-Plane Accelerometers With Reduced Capacitive Gaps and Extra Seismic Mass

This paper presents a robust fabrication technique for manufacturing ultrasensitive micromechanical capacitive accelerometers in thick silicon-on-insulator substrates. The inertial mass of the sensor is significantly increased by keeping the full thickness of the handle layer attached to the top layer proof mass. High-aspect-ratio capacitive sense gaps are fabricated by depositing a layer of polysilicon on the sidewalls of low aspect- ratio trenches etched in silicon. Using this method, requirements on trench etching are relaxed, whereas the performance is preserved through the gap reduction technique. Therefore, this process flow can potentially enable accelerometers with capacitive gap aspect-ratio values of greater than 40:1, not easily realizable using conventional dry etching equipment. Also, no wet-etching step is involved in this process which in turn facilitates the fabrication of very sensitive motion sensors that utilize very compliant mechanical structures. Sub-micro-gravity in-plane accelerometers are fabricated and tested with measured sensitivity of 35 pF/g, bias instability of 8 mug, and footprint of <0.5 cm².     

Microfabrication using one-step LPCVD porous polysilicon films

A simple, one-step LPCVD process was recently reported to allow the repeatable fabrication of polycrystalline silicon (polysilicon) thin films containing through-pores measuring 10-50 nm in diameter, as-deposited, with no additional processing steps required. This paper describes methods for using this one-step porous polysilicon material to quickly and easily fabricate structures of interest to MEMS designers. Among the structures presented are hermetically sealed diaphragms, hollow tube and shell structures, substrate-aligned membranes over one square centimeter in area ("supermembranes"), and permeable fluidic microchannels on silicon and quartz substrates.