微热板气体传感器低功耗工作模式研究

微热板气体传感器大多采用金属氧化物半导体气敏材料,通常需要工作在200～500℃的温度下才能获得良好的气敏特性.采用传统的直流电压加热模式时需要消耗数十毫瓦的功耗用于维持工作温度.必须进一步减小气体传感器的功耗,才能使之适用于微型无线传感网等对功耗要求苛刻的应用领域.研究了脉冲电压加热工作模式下微热板气体传感器对(20...     

微热板阵列式集成气体传感器的芯片电路设计

针对加热测温一体化集成微热板阵列气体传感器的需要,以微热板加热性能测试参数为依据,提出了一种基于微热板气体传感器阵列的单片集成方案。该方案包括由四个微热板构成的传感器阵列,加热驱动单元和信号采集单元。采用Hspice软件对加热驱动电路和信号采集电路进行设计,并进行了芯片电路系统的仿真。仿真结果表明实现了微热板的独立控温和信号的采集,验证了该方案的可行性和正确性。     

微气体传感器结构设计和优化

设计了一种新型微气体传感器的电极结构,这种共平面型电极结构消除了加热器产生的磁场对测量信号的干扰。利用铂作为电极材料,SiO2作为隔热层,利用有限元软件分析优化,当SiO2,Si的厚度分别为50,250μm,加热电极的宽度、信号电极的宽度和间距分别为150,15,60μm时,传感器获得的中心温度较高且比较均匀的中心温度分布,有利于传感器整体性能的提高。     

一种AlN基陶瓷微热板NO2气体传感器研究

针对传统硅基微热板半导体气体传感器存在的热稳定性差,工艺复杂等难点,采用良好热导特性的AlN陶瓷为衬底,利用柔性机械剥离工艺和半导体材料In2O3/Nb2O5/Pt厚膜工艺制备了NO2微热板气体传感器.传感器中间加热区周围采用热隔离结构设计,降低了加热区温度分布梯度,提高了温度效率.利用ANSYS有限元工具进行了热结构仿真分析和响应测试分析,验证了热隔离结构设计的合理性.气敏测试分析表明,传感器在不同加热功率条件下,对5×10-6~100×10-6的NO2气体都具有良好的气敏响应特性,经对比分析,在功率150 mW~200 mW时稳定性最佳,且响应速率小于60 s,恢复时间在100 s左右,可实现5×10-6~100×10-6浓度的NO2气体良好检测功能.     

AlN陶瓷微热板MEMS传感器阵列设计与工艺实现

针对陶瓷基微热板MEMS器件难以微加工,器件表面加热Pt膜使用普通正性光刻胶难以实现光刻剥离的工艺难点问题,提出了激光微加工和柔性机械剥离相结合的微加工方法。以AlN陶瓷为衬底基片,采用激光微加工技术实现热隔离刻蚀体加工,刻蚀梁宽可达0.2 mm。采用柔性机械剥离工艺制备方法解决普通正性光刻胶形成倒梯形凹槽Pt膜难实现图形化问题,可在复杂表面特性的陶瓷基衬底上实现Pt膜剥离线宽10μm。同时利用有限元法进行传感器阵列设计和热结构仿真,验证设计工艺的可行性。     

基于MEMS工艺的NO2气体传感器研制

设计了一种基于微机电系统(MEMS)工艺的以氧化钨(WO3)为敏感材料的微结构气体传感器,并从半导体理论解释了WO3对二氧化氮(NO2)的敏感机理.气体传感器芯片尺寸为1.3mm ×1.3mm,微热板的有效面积为0.4mm ×0.4 mm.实验结果表明:设计的气体传感器对NO2气体表现出良好的响应,在最佳工作温度下(140℃)功耗为23 mW,最低检测限达50×10-9,响应时间为60 s,恢复时间为180 s.     

MEMS低功耗氧化锌气体传感器的设计

本文介绍了一种基于MEMS技术的ZnO气体传感器的设计与制备方案。该传感器采用磁控溅射技术制备掺杂碳纳米管的ZnO薄膜气敏材料,利用干法刻蚀技术形成硅中空膜片,并在膜片上形成Pt环形加热电阻作为微型加热装置。该传感器具有低温敏感、低功耗和小型化等特性。     

基于MEMS的微热板结构仿真优化研究

金属氧化物半导体气敏传感器是气体传感器领域研究的热点内容,而微热板作为金属氧化物半导体气体传感器的重要组成部分之一,对微热板结构及稳态热特性的研究至关重要.为了研究不同结构参数对微热板性能的影响,为微热板的设计优化提供指导,基于微机电系统(MEMS)工艺技术,设计了一种悬浮式结构微热板,对微热板支撑层和隔离层的材料组成...     

微热板中微纳空气间隙传热特性研究

在微热板(MHP)的应用过程中,其本身的热特性是影响器件性能的重要因素之一,同时加热电极和衬底之间的气体间隙传热是影响MHP热特性的一个关键因素.采用标准CMOS工艺和简单的post-CMOS工艺,设计制作了一种具有550 nm空气间隙的MHP,在热稳态下利用MHP的自加热效应测得了空气间隙的传热热导,结果表明:截面积为35 μm ×35 μm、厚550 nm的空气间隙的热导为6.74 ×10-5W/K,MHP的整体热导为7.51 ×10-5W/K,可见在MHP热耗散中,空气间隙传热占主导地位.     

基于悬浮薄膜堆叠式结构的微气体传感器设计

本文基于MEMS工艺所设计的气体传感器,克服了以往同类传感器响应时间长,读取数据量小,功耗大等缺点。由于温度作为气体传感器的一个重要工作条件,其敏感薄膜上温度的均衡度直接影响气体传感器的工作性能。该传感器采用悬浮薄膜式堆叠结构,堆叠层主要包含硅基底、隔离层、加热电极、绝缘层以及敏感薄膜。这样的结构设计是为了形成热隔离真空腔,真空环境可以有效降低温度瞬变对敏感薄膜的影响。利用ANSYS软件建立该结构建模,并对其进行温度仿真后发现该结构符合预期的理论分析,其响应时间缩短,拾取的数据量大幅增加,同时功耗有效降低。     

微加热板式半导体微气压传感器的测试

组建了一套用于半导体微气压传感器的测试系统。该系统主要由真空装置和信号采集系统两部分组成。该系统为半导体微气压传感器的研制提供了实验平台,利用该系统对一种微加热板式传感器的微气压特性进行了实验测试及分析。     

ZnO薄膜紫外探测器的研制

利用射频磁控溅射技术在SiO2/n-Si衬底上制备了ZnO薄膜,并在薄膜上制作了Ag-ZnO肖特基二极管和Ag-ZnO-Ag肖特基MSM叉指结构的紫外探测器。所制备的ZnO薄膜具有良好的c轴择优取向,表面平整,在可见光范围具有较高的透射率,吸收边在370 nm附近;所制作的肖特基二极管显示了良好的整流特性,有效势垒高度约为0.65 eV;所制作的MSM紫外探测器在5 V偏压下漏电流为3.3×10-8A,在紫外波段有较高的响应度,光响应度峰值在365 nm附近。     

SnO2基薄膜气体传感器制作与敏感性测试

在现有的粉末烧结型SnO2基气敏传感器基础上研制了薄膜型SnO2基气体传感器,以抛光的丽热石英玻璃为基片,真空磁控溅射50～70nm厚度的SnO2薄膜,在SnO2薄膜上分别溅射不连续的ZnO、Al2O3、CeO2、InO2等薄膜,传感器背面溅射30μm的Ni80Cr20电阳合金作为传感器加热电阻,用薄膜热电偶测量传感器工作温度。测试了不同的复合瞑对传感器灵敏度和选择性的影响,并对传感器的吸附与解吸速度进行了测试,薄嗅传感器达到相同灵敏度所需的工作温度比粉末烧结型传感器下降100～150℃,吸附解吸速度比粉末烧结型快。     

直流反应磁控溅射WO3薄膜气敏特性研究

用直流反应磁控溅射法制成纳米结构的WO3薄膜气敏传感器,通过XRD,SEM和XPS对该薄膜的晶体结构和化学成分进行分析,研究了不同基片上制备的WO3薄膜的氨敏特性与薄膜厚度、退火温度的关系.实验得到的薄膜粒径大小约30-50 nm,结果表明:在未抛光的三氧化二铝基片上沉积厚度为40 nm的WO3薄膜,经过400℃退火,在体积分数为5×10-5 NH3中的灵敏度达到300,而且气体选择性好,响应-恢复时间短,可以作为理想的氨敏元件.     

Ethanol gas sensor based on Al-doped ZnO nanomaterial with many gas diffusing channels

ZnO nanomaterial with multi-microstructures is synthesized by using normal pressure thermal evaporation and then doped with different Al₂O₃ contents by grinding in an agate mortar. The as-prepared Al-doped ZnO nanomaterials are characterized by X-ray diffraction and scanning electron microscopy. The characterization results show that all the compounds are wurtzite with hexagonal structure and are well crystallized. Channels/connecting holes arising from many kinds of ZnO microstructures are abundant. Both annealing and Al₂O₃-doping contributes to an increase in the quasi-one-dimensional and tri-dimensional microstructures. The as-prepared Al-doped ZnO nanomaterials show excellent gas responses to ethanol. The sensing mechanism of the ZnO-based nanomaterials with multi-microstructures is further analyzed by using the Effective Specific Surface Model. Excellent sensitivity (200) companied with short response time (8 s) and recovery time (10 s) to 3000 ppm ethanol is obtained with a ZnO-based sensor with 2 at.% Al₂O₃ at the operating temperature of 290 °C after the sensor is annealed at 500 °C.     

Love wave hydrogen sensors based on ZnO nanorod film/36°YX-LiTaO3 substrate structures operated at room temperature

Love wave hydrogen sensors based on ZnO nanorod layers deposited on 36°YX-LiTaO₃ substrates have been studied. The ZnO nanorod layers are prepared by two steps: first, the seed layers, as well the guiding layers of the Love wave devices, are deposited by RF magnetron sputtering; second, the nanostructural layers, as well the sensing layers of the sensors, are grown by hydrothermal synthesis. Two kinds of ZnO layers have been analyzed by XRD, SEM and XPS. The XRD shows that both ZnO layers have (0 0 2) oriented wurtzite structures. The SEM results reveal that the morphologies of the deposited ZnO seed layers are continuous and compact, while the hydrothermal treated layers are with nanorods almost perpendicular to the substrate surfaces. Finally, the hydrogen sensing responses of the Love wave sensors activated by Pt catalysts are measured for various concentrations of hydrogen in synthetic air at room temperature. The results show that the sensors have high sensitivity and repeatability as the nanorod layers are optimized, such as the frequency shift 8 kHz toward 0.04% of H₂ in synthetic air is obtained while the height of the nanorod layer is about 2.1 μm and the central frequency of the sensor is about 125.5 MHz. The XPS analyses of the sensitive layers show that there are oxygen vacancies in the layers, so the oxygen vacancy model is used to explain the hydrogen sensing mechanism of the Love wave sensors.     

Selective NH3 gas sensor based on Langmuir-Blodgett polypyrrole film

Polypyrrole thin films have been deposited onto a glass substrate by the Langmuir-Blodgett technique to fabricate a selective ammonia (NH₃) gas sensor. The d.c. electrical resistance of the sensing elements is found to exhibit a specific increase upon exposure to different gases such as NH₃, CO, CH₄, H₂ in N₂ and pure O₂. The polypyrrole thin-film detector shows a considerable increase of resistance when exposed to NH₃ in N₂, and negligible response when exposed to comparable concentrations of interfering gases such as CO, CH₄, H₂ in N₂ and pure O₂. The calibration curve for NH₃ in N₂ at room temperature is measured in the concentration range from 0.01 to 1%. The relative change of the electrical resistance is about 10% for the lower detectable limit of 100 ppm of NH₃ in N₂. The sensitivity of the Langmuir-Blodgett polypyrrole towards ammonia is considerably higher than that of the electrochemical polypyrrole. The fast rise time and the high sensitivity of the detector are reported as a function of number of the polypyrrole layers. Long-term aging tests of the selective NH₃ gas sensor are performed.