UFPA器件的新型微桥结构设计及其有限元分析

提出一种应用于非致冷红外焦平面(UFPA)器件的U形三层微桥结构,其单元尺寸为25μm×25μm、占空比高达90%、支撑稳固且响应率高。采用有限元分析法对其进行力、热分析,并与雷神公司报导的微桥结构[1]进行比较,证明其具有稳定的力学支撑和良好的热性能;引入经典光学膜系分析方法,在8~14μm波段内获得80%以上平均红外吸收率。     

512×512像素PtSi肖特基势垒红外图像传感器

已经研制了具有电视质量标准的红外图像传感器,该传感器可在3～5μm红外波段区热成像,陈列尺寸为外512×512像素,器件采用PtSi肖特基势垒光电探测器。为了获得大的占空系数,应用了电荷扫描器件(CSD)结构。该像素由两层多晶硅和两层铝构成,并具有最小设计基准为2μm。像素尺寸和占空系数分别为26×20μm~2和30％。采用金属薄膜和光腔结构改善了器件的灵敏度,势垒高度为0.22eV时,相应的截止波长约为5.6μm。器件以标准电视帧频工作。借助于微粒噪声探测器,在300K时该器件噪声被限制在f/1.5光学范围内,器件的温度差分辨能力约为0.11K。使用该器件已经制作了典型的红外电视摄像机,并获得了高质量的红外图像。     

非晶硅微测辐射热计热学和光学分析

通过理论计算得到了桥腿长度和宽度与热导和桥面温升之间的线性关系,辐射功率和桥面温升之间的线性关系,并利用ANSYS软件对线性关系进行模拟验证.根据光学导纳矩阵法,利用MatLab软件模拟微测辐射热计对红外线的吸收率,结果表明微测辐射热计对8～13μm波段红外有很好的吸收率.分析结果为微测辐射热计的研制提供了可靠依据.     

有聚酰亚胺绝热层的新型非制冷红外探测器

提出了一种基于聚酰亚胺绝热层的新型非制冷红外探测器结构.该结构具有工艺简单、成本低廉、成品率高等优点.利用底部反射金属层可以提高红外吸收率;底层金属和有源层间的隔离层不仅可以减小器件热导,还可以和上层材料层构成三明治红外吸收结构,进一步改善红外吸收效果.对制备工艺进行了简单介绍,器件性能测试结果表明,该新结构探测器虽然和空腔结构探测器的探测率相当,但在工艺制备及成品率方面要优异得多.     

以Si3N4作增透膜的Si基Ge量子点探测器的研究

设计并制作了以Si3N4作增透膜的Si基Ge量子点红外探测器.采用气态源分子束外延(GSMBE)方法在Si(100)衬底上生长了20层的自组织Ge量子点.在此基础上,流水制作了p-i-n结构的量子点红外探测器.为了提高探测器的响应度,采用Si3N4作为增透膜以增强探测器对入射光的吸收.用传输矩阵方法模拟的结果显示,185上nm厚的Si3N4增透膜可以使探测器在1310 nm波长处具有较高的吸收率.根据此结果,用等离子体增强化学气相沉积(PECVD)方法在探测器表面淀积了185 nm的Si3N4.在室温下,测得量子点探测器在1.31μm处的响应度为8.5 mA/W,跟没有增透膜的器件相比,响应度提高了将近30倍.     

基于兰姆波谐振器和超表面的谐振式热红外探测器研究

设计了一种基于氮化铝(AlN)兰姆波谐振器和超表面的谐振式热红外探测器,基于超表面的吸收器用于对特定波长红外辐射的吸收,再利用AlN兰姆波谐振器的温度频率效应检测红外辐射。首先,对兰姆波谐振器的电极周期、电极宽度、AlN薄膜厚度和支撑轴尺寸进行优化设计,设计了电极周期分别为12μm和1.2μm的谐振器结构,其工作频率分别为365 MHz和2 544 MHz。其次,设计了方形结构超表面的等离子体吸收器,并研究分析其红外吸收机理及结构尺寸对吸收性能的影响规律。通过集成超表面红外吸收器并调节吸收结构尺寸,实现可调谐、近100%的双带吸收性能,在3μm～5μm和8μm～12μm处的吸收率均超过99.5%,谐振式热红外探测器的响应时间低于0.8 ms、热噪声等效功率低于10^-11 Hz/μW。     

非制冷红外焦平面高灵敏像元微桥设计

介绍了硅微桥结构的传热物理模型及其理论计算方法。提出一种星膜像元尺寸为360μm×360μm,具有“桌形”绝热框架支撑的微桥结构像元,用有限元分析证明其有较小的热导G,能获得很高的响应率。微桥结构在非制冷红外焦平面（UFPA）单元探测器中起着力学支撑、热隔离和电连接的作用,其品质优劣直接影响着UFPA器件的成像性能。     

一种黑硅吸收层的热电堆红外探测器设计

设计一种以黑硅这种对几乎所以可见光和部分红外光具有很高吸收率的新型材料作为表面吸收层的热电堆红外探测器,针对这一设计作出了大量关于黑硅对不同波长下的红外吸收率的研究。通过红外基本理论,结合MEMS工艺的兼容性,设计采用两种热电偶材料叠放的方式,并以氧化硅薄膜作为隔离的结构;另外,探测器采用氧化硅上制作的多晶硅作为新型衬底。在器件释放中被XeF2正面腐蚀的部分是多晶硅,这样的设计解决了硅释放的对准问题和SOI衬底陈本高的问题。这种材料可以提高探测器的性能同时减小成本。     

一种凸纹薄膜CMUT阵列的设计与实现

为提升电容式微机械超声换能器(CMUT)的输出声压,提出一种新型凸纹薄膜CMUT阵列设计与实现方法。首先结合解析法与有限元分析法设计器件;然后结合牺牲层释放工艺与电镀方法在CMUT电极上制备尺寸为3μm×2μm的镍凸纹圆环;最后对凸纹薄膜CMUT阵列进行光学、电学与声学特性测量。声学测量结果表明在塌陷模式下78%的工作点范围内,凸纹薄膜CMUT的输出声压均比常规的平膜CMUT高。当直流偏置电压为160 V时,凸纹薄膜CMUT的输出声压提升21.2%,3-dB相对带宽为54%。本研究成果为新型CMUT的设计与实现提供了有益的指导。     

GaN基倒装LED与光栅的集成器件的仿真分析

在发光二极管(LED)上制作光子光栅结构将会提高LED的光提取效率,这使得LED应用范围更广。根据时域有限差分法(FDTD)数值计算方法,利用Rsoft软件仿真设计了氮化镓(Ga N)基倒装LED和光栅的集成器件。主要改变光栅的高度、宽度,得到Λ=0. 6μm,w=0. 3μm,h=0. 3μm时,最大的出光效率89%。通过远场图分析了光束的准直性以及通过改变探测器偏转角度得到光提取效率的变化情况。     

氧化钒热敏薄膜非致冷红外探测器的等效模型

建立了氧化钒热敏薄膜微测辐射热计的PSPICE模型,结合一个具体的CMOS读出电路给出探测器的等效电路模型,分析了探测器的电学和噪声特性,根据等效模型基于微测辐射热计电阻RD和读出电路MOS沟道宽度2个设计参数对噪声等效温差(NETD)进行了优化,优化数据表明:参数RD取值为2~11 kΩ,W取值为0.1~1.0μm时,得到的NETD值为0.133 4~0.188 5 K。     

Self-supporting uncooled infrared microbolometers with low-thermalmass

A new micromachined microbolometer array structure is presented that utilizes a self-supporting semiconducting yttrium barium copper oxide (Y-Ba-Cu-O) thin film thermometer. The Y-Ba-Cu-O thermometer is held above the substrate only by the electrode arms without the need of any underlying supporting membrane. This represents a significant improvement in the state-of-the-art for microbolometers by eliminating the thermal mass associated with the supporting membrane. The reduced thermal mass permits lowering the thermal conductance to the substrate to obtain increased responsivity or having a shorter thermal time constant to allow for higher frame rate camera. The simple structure does not suffer from warping problems associated with stress imbalances in multilayer microbolometer structures that utilize a supporting membrane such as Si₃N₄. Devices were fabricated by growing Y-Ba-Cu-O films on a conventional polyimide sacrificial layer mesa. Subsequent etching of the sacrificial layer provides the air gap that thermally isolates the microbolometer. Y-Ba-Cu-O possesses a relatively high temperature coefficient of resistance of 3.1%/K at room temperature. The 400-nm-thick Y-Ba-Cu-O film exhibited absorptivity of about 30%. The responsivity and detectivity approached 10⁴ V/W and 10⁸ cm Hz^1/2/W to filtered blackbody infrared (IR) radiation covering the 2.5 to 13.5 μm band. This extrapolates to noise equivalent temperature difference (NETD) less than 100 mK. The micromachining techniques employed are post-complementary metal-oxide-semiconductor (CMOS) compatible, allowing for the fabrication of focal plane arrays for IR cameras     

3D-feed horn antenna-coupled microbolometer

In this paper, we proposed a microbolometer coupled with 3D feed horn antenna. It is a new device that enhances the performance of the microbolometer by coupling 3D horn shape antenna. We designed the optimum horn antenna size that has 20.08 dB directivity. And we designed the microbolometer as a circular shape in order to reduce the coupling loss between the horn antenna. We confirmed that the detectivity of the designed microbolometer would be improved as the noise characteristics of the microbolometer are enhanced by coupling feed horn antenna which acts as a cold shield. The detectivity of the designed 3D antenna-coupled microbolometer was improved about seven times more than that of the conventional microbolometer in state of background limited infrared performance. Fabrications of the microbolometer are carried out by a surface micromachining method. We achieved the thermally good isolated floating structure. And the 3D feed horn antenna was constructed by using a mirror-reflected parallel beam illuminator (MRPBI) system which is invented for rotating and tilted illumination. Using this method, we acquired the feed horn shape antenna mold. And we also acquired antenna plate by using PDMS injection method. Finally, to couple the antenna and the microbolometer, we proposed the PDMS injection bonding method.     

3D Optical microstructure fabrication and its bonding to micro IR detector using elastomeric polymer

This paper describes polidimethylsiloxane(PDMS) based bonding for assembly of microstructure device, an UV lithography applications for fabricating a 3-dimensional (3D) feed-horn-shaped structure mold array, and obtaining parallel light by using a mirror-reflected parallel-beam illuminator (MRPBI) system. A 3D feed-horn-shaped micro-electro-mechanical systems (MEMS) antenna has some attractive features for array applications, which can be used to improve microbolometer performance and to enhance the optical efficiency for thin film transistor-liquid crystal display (TFT-LCD) and other display devices but currently, MEMS technology has faced many difficulties in the fabrication of a 3D feed-horn-shaped MEMS antenna array itself. The purpose of this paper is to propose a new fabrication method to realize a 3D feed-horn-shaped MEMS antenna array by using a mirror-reflected parallel-beam illuminator (MRPBI) System with a very slowly rotated, inclined x-y-z stage. With a conventional UV lithography apparatus, it is very difficult to fabricate high-aspect-ratio structures (HARS) because a typical UV lithography apparatus cannot produce perfectly parallel light. From a theoretical analysis, a columnar illuminator over 6 m in height is required to achieve parallel light, but generally a laboratory height is not 6 m. Also, a novel method of lithography was tried to make a 3D structure array by exposing a planar wafer to the generated parallel light and rotating an inclined x-y-z stage at an ultra-slow rate. An optimization of the 3D structure array can be achieved by simulating a 3D feed-horn MEMS antenna. The feasibility of fabricating both a 3D feed horn MEMS antenna and assembly of detector with 3D feed-horn MEMS antenna was demonstrated. As a result, it seems possible to use a 3D feed-horn-shaped MEMS antenna to improve microbolometer performance and to fabricate several optical microstructure applications.The authors wish to acknowledge that this paper is the result of research accomplished with the financial support of the Intelligent Microsystems Center, Seoul, Korea, which is carrying out one of the 21st centurys New Frontier R&D Projects sponsored by the Korea Ministry of Science & Technology.     

一种新型可调光栅的制作方法

介绍了一种可调光栅的制作方法。首先通过紫外线光刻的方法,制作出微米尺度的光栅结构(周期8μm),然后将光栅复制在聚甲基硅氧烷(PDMS)薄膜上,形成内嵌式PDMS光栅。利用PDMS优异的弹性,将此薄膜沿着光栅栅线的方向拉伸,随着栅线的伸长,光栅常数也随之变小,周期调节极限为5μm。传统方法制作可调光栅,工艺条件苛刻,制作过程复杂,难以控制,制作成本高,周期较长。提出的制作可调光栅的方法成本低,周期短,工艺过程简单易控制,可广泛应用于微型光谱仪、扫描仪、光通信等领域。     

Spatial relationships between snow contaminant content, grain size, and surface temperature from multispectral images of Mt. Rainier, Washington (USA)

We use multispectral MODIS/ASTER Airborne Simulator (MASTER) data collected at Mt. Rainier, Washington (USA) to map spatial covariance between snowpack properties and to evaluate techniques for quantitative estimation of reflectance, grain size, and temperature. The late-August MASTER images reveal a distinct pattern of snow contaminant content, grain size, and temperature related to a recent snowfall and late-summer melting. Spatial correlation between grain size and temperature patterns suggests that rapid destructive metamorphism of the fresh snow occurred when temperatures were near 0 °C. We use 10 specific locations to evaluate hemispherical-directional reflectance factor (HDRF), grain size, and temperature retrievals. We map relative snow contaminant content using visible (0.4-0.8 μm) HDRF spectra. Atmospheric correction and topographic modeling limit the accuracy of HDRF estimates. We use MASTER-derived spectra near 1.8 and 2.2 μm to estimate optical grain size (by comparison to modeled layers of ice spheres) and physical grain size (by comparison to measured spectra with known physical grain size and by correlation to ground measurements). Estimated physical grain sizes were less than estimated optical grain sizes. Differing definitions of optical and physical grain sizes could contribute to this discrepancy. Limitations at 1.8 and 2.2 μm, including reduced discrimination between larger grain radii (>∼500 μm physical, >∼200 μm optical) and low signal-to-noise ration with atmospheric effects and decreasing solar irradiance, suggest that grain size retrieval may be improved at other wavelengths (e.g., 1.1 μm). Accounting for uncertainty in emissivity, atmospheric correction, and detector noise, we estimate systematic errors in our radiant temperatures at <1.8 °C. This study shows both strengths and limitations for coregistered visible, short-wave infrared, and thermal infrared images to estimate snowpack properties and reveal their spatial coherence.     

Comparison of some characteristics of thin‐film‐electroluminescent ZnS: Er,F planar and edge emitters

Abstract— The following main differences have been revealed in the characteristics of an edge thin‐film‐electroluminescent ZnS: Er,F emitter compared to those of a similar planar emitter: (1) the 1.535‐μm band more highly dominates over other bands in the EL spectrum; (2) the voltage (V) dependence of the intensity of this band is the strongest; (3) the 1.535‐μm band narrows with increasing voltage and its frequency. The above differences are explained, firstly, by smaller optical losses in the ZnS: Er,F film for the near‐infrared emission than for the visible one and, secondly, by an optical amplification over the 1.535‐μm band in the edge emitter.     

Wafer-level reliability characterization for wafer-level-packaged microbolometer with ultrasmall array size

For the development of a small and low-cost microbolometer, wafer-level reliability characterization techniques for vacuum-level packaged wafers are introduced. Amorphous-silicon-based microbolometer-type vacuum sensors fabricated on an 8-inch wafer are bonded with a cap wafer by using an Au–Sn eutectic solder. Membrane deflection and integrated vacuum sensor techniques are independently used to characterize the hermeticity at the wafer level. For a packaged wafer with a membrane thickness below 100 μm, it is possible to determine the hermeticity via a screening test performed using an optical detector. An integrated vacuum sensor having the same structure as a bolometer pixel shows a vacuum level below 100 mTorr. All steps from the packaging process to the fine hermeticity test are implemented at the wafer level to verify that high-volume and low-cost production of the microbolometer is possible.     

用于光刻系统仿真的多边形处理算法

为提高光刻仿真效率,通过对光刻原理进行研究,提出了2种多边形处理算法,将掩模上的多边形图案进行切分优化,将其划分成若干矩形或三角形。在Linux环境下应用C语言设计出一个完整的光刻仿真系统,设计的具体光学参数为:光源波长为193nm,数值孔径为0.3~0.8,部分相干系数可调范围为0.2~0.8,可一次性仿真1μm×1μm到10μm×10μm范围内的45 nm~0.18μm工艺的复杂版图,并通过多次实验进行验证。实验结果表明:原版图图像的边缘细节得到保留,且该算法有效地减少了光刻模拟的计算复杂度与计算时间,整体效率提升20%以上,为当前智能传感器系统芯片的制造节省了宝贵时间。