Wafer emissivity independent temperature measurements

A study on the techniques to yield wafer emissivity independent temperature measurements in rapid thermal processing has been presented. This study focuses on the Steag-AST Electronik approach to enhance wafer emissivity by using the Hotliner*. The Hotliner comprises of a heavily doped p-Si substrate sandwiched with Si₃N₄/SiO₂ from both sides. Experimental measurements on the optical properties of the Hotliner using a spectral emissometer operating in the wavelength range of 1–20 μm are presented here. Results of the simulation of the experimental data using the MIT/SEMATECH Multi-Rad model are discussed. Hotliner is a trademark of Steag-AST Electronik, patent pending.     

Modeling and simulation of emissivity of silicon-related materials and structures

A brief review of the models that have been proposed in the literature to simulate the emissivity of silicon-related materials and structures is presented. The models discussed in this paper include ray tracing, numerical, phenomenological, and semi-quantitative approaches. A semi-empirical model, known as Multi-Rad, based on the matrix method of multilayers is used to evaluate the reflectance, transmittance, and emittance for Si, SiO₂/Si, Si₃N₄/SiO₂/Si/SiO₂/Si₃N₄ (Hotliner), and separation by implantation of oxygen (SIMOX) wafers. The influence of doping concentration and dopant type as well as the effect of the angle of incidence on the radiative properties of silicon is examined. The results of these simulations lead to the following conclusions: (1) at least within the limitations of the Multi-Rad model, near the absorption edge, the radiative properties of Si are not affected significantly by the angle of incidence unless the angle is very steep; (2) at low temperatures, the emissivity of silicon shows complex structure as a function of wavelength; (3) for SiO₂/Si, changes in emissivity are dominated by substrate effects; (4) Hotliner has peak transmittance at 1.25 μm, and its emissivity is almost temperature independent; and (5) SIMOX exhibits significant changes in emissivity in the wavelength range of 1–20 μm.     

Spectral mixture analysis of simulated thermal infraredspectrometry data: An initial temperature estimate bounded TESSMA searchapproach

At sensor thermal infrared (TIR) radiation varies depending on the temperature and emissivity of surface materials and the modifying impact of atmospheric absorption and emission. TIR imaging spectrometry often involves extracting temperature, emissivity, and/or surface composition, which are useful in diverse studies ranging from climatology to land use analyses. A two-stage application of temperature emissivity separation (TES) using spectral mixture analysis (SMA) or TESSMA, was employed to characterize isothermal mixtures on a subpixel basis. This two-stage approach first uses the relationship between a virtual cold endmember fraction and surface temperature to extract initial image temperature estimates. Second, an isothermal SMA application searches the region within the maximum temperature error range of the initial estimate, selecting the best subpixel spectral mixture fit. Work presented includes characterizations of synthetically generated temperature and constituent mixture gradient test images, and a discussion of errors associated with selecting temperature search ranges 25% and 75% smaller than the initial temperature calculation error range. Results using this two-stage approach indicate improved overall temperature estimates, constituent estimates, and constituent fraction estimates using simulated TIR data     

Perspectives on emissivity measurements and modeling in silicon

A spectral emissometer operating in the wavelength range of 1–20 μm and temperature range of 30–900°C has been utilized to simultaneously measure the reflectance, transmittance and emittance of silicon. Interesting differences in the optical properties have been reported due to differences in surface morphology. Quantitative results of the effects of rough side incidence versus smooth side on the optical properties of the same silicon wafer are analyzed in this study. This analysis is based on a standard one-parameter, multiple-reflection model as extended by Vandenabeele and Maex to include effects of a roughened surface. Their modification essentially replaces the usual internal attenuation factor by an enhanced effective attenuation factor to take into account the effects of surface roughness. In the present study, it has been found that this very simple model gives a good account of the optical properties when radiation is incident on the smooth side of the wafer but fails for incidence for the roughside.     

地物目标热红外光谱发射率的野外测量方法研究

在航天红外遥感应用中,地物目标光谱发射率是卫星遥感测量地面温度的一个重要参数。野外测量的大气环境、目标背景和地物的热力学特性等因素的影响,使得野外测量地物目标表面光谱发射率变得较为复杂。重点讨论了利用傅里叶变换红外光谱仪野外测量地物目标光谱发射率的方法和程序,介绍了几种正确分离目标温度与发射率的方法。野外测量实验结果表明,按照文中所述的测量方法,测量得到的地物热红外光谱发射率具有良好的一致性,发射率测量误差小于0．02。     

激光诱导表面周期性结构对铜薄膜红外发射特性的改变

金属铜在中红外波段的发射率极低,所以铜薄膜是一种性能优异且对抗被动式中红外热探测器隐身的材料,而在铜薄膜表面使用激光诱导表面周期性结构(LIPSS)可以显著提高其在中红外波段的发射率。首先使用双温方程模型模拟LIPSS形成过程中材料软化的过程,然后使用波长为1064nm的偏振脉冲激光在融石英基底上的铜薄膜表面诱导产生周期为波长量级的LIPSS,最后基于实验产生的铜薄膜LIPSS搭建仿真模型并对其在近红外和中红外波段的发射率进行分析。模拟结果表明,铜薄膜LIPSS的产生可以显著提高其在中红外波段的发射率,该方法可以实现铜薄膜对被动式中红外热探测器的隐身。     

EPDM基红外隐身涂层耐热性及使用寿命预测研究

从发射率变化的角度建立了红外隐身涂层失效的评价标准.根据Arrhenius公式研究了涂层寿命的估算方法.采用IR-2型发射率测试仪,测试了低红外发射率EPDM/Cu涂层在不同温度下发射率的变化,得出了涂层的最高耐受温度,并预测了涂层在不同Ma数的飞机蒙皮上的使用寿命.结果表明:涂层的最高耐受温度为523 K;涂层在1 Ma和1.5 Ma的蒙皮上的寿命分别可以达到4.91×103h和3.78×104h.理论计算结果与实验结论比较符合,这表明此预测方法在实际应用中有一定的普遍性,能够比较准确地预测红外隐身涂层的使用寿命.     

单目标极小值优化法的多波长真温反演研究

在多波长温度测量系统中,光谱发射率假设为波长或温度模型来实现真温的求解。由于模型假设存在一定的不确定性,光谱发射率模型与实际光谱发射率的变化规律可能不符,会造成较大的真温反演误差。另外,光谱发射率与波长或温度之间的函数关系通用性较差,尤其是待测辐射体发生改变时,这种关系自然也就不复存在了。为了获得正确的真温,首次将优化思想引入到方法中,建立了单目标极小值优化法（Single Objective Minimization Optimization Method,SMO）完成真温反演。新方法无需建立光谱发射率和波长或温度之间的模型,降低了真温求解方法的复杂性和技术难度。与原有的光谱发射率与温度之间的模型（也称二次测量法,Second Measurement Method,SMM法）相比,在相同的初始条件下,新方法与二次测量法相比,反演速度提高了95%以上。     

低温目标光谱发射率建模及弱信号检测技术的研究

利用小波变换技术对辐射信号进行预处理和去噪，实现了辐射信号的高精度检测；进而，设计了一种组合神经网络发射率模型，依据测温仪测得的亮温可以高精度地辨识出被测目标的发射率模型，这种建模方法不需给定发射率固定的样本数据，给出具体理论推导过程。仿真结果表明，此方法是获知连续光谱发射率及真温的一种有效的方法。     

Improvements in the split-window technique for land surfacetemperature determination

Land surface temperature (LST) retrievals obtained from NOAA Advanced Very High Resolution Radiometer (AVHRR) are of considerable importance for climatic research. However, the accurate evaluation of LST from space has been severely limited because of the difficulty in separating atmospheric from surface effects as the surface cannot be modeled as a black-body radiator. With this goal in mind, a novel extension of the split-window technique is presented in which the atmospheric contribution to the radiance measured by the satellite is investigated by the ratioing of covariance and variance of the brightness temperatures measured in channels 4 and 5 of AVHRR/2. Furthermore, the contribution of emissivity is evaluated from coefficients that depend on the spectral emissivities in both thermal channels. Using a wide range of simulations from an atmospheric radiative transfer model it is shown that the proposed algorithm provides an estimate of LST, to within 0.4 K if the spectral surface emissivity is known, which is better than that given by the currently used split-window algorithms for LST determination. Also the limitations on algorithm accuracy are discussed considering different values of noise equivalent temperature. Finally the authors present the preliminary results obtained using the proposed method from AVHRR data over a semi-arid region-of Northwestern Victoria in Australia provided by CSIRO, and a mountainous region of Northeast of France acquired in the frame of Regio Klimat Projekt     

多波长辐射温度计最少波长数确定的理论依据

正确地选择多波长辐射温度计的波长数对于多波长辐射温度计的设计至关重要,它关系到经过数据处理得到的目标真温及光谱发射率是否可信。本文提出的多波长辐射湿度计最少波长数的确定准则为多波长辐射温度计在波长数选择方面提供了理论依据。     

引入无量纲模型及弯曲系数的三波段红外测温优化研究

以红外辐射基本理论为基础,将红外温度测量同被测物发射率相分离,构建未涉及发射率的红外三波段测温向量组,解决红外测温结果同发射率耦合度低的问题。进一步优化三波段向量组,提出无量纲发射率模型及适宜波段条件。通过对发射率线性函数进行优化,引入弯曲指数n,拓展发射率函数的应用范围。适宜波段条件的提出则保证了三波段测温向量组结果的精确性。对四个硫化矿样本应用三波段测温法同传统红外测温法进行实验测温对比研究,分析结果表明:三波段测温法同真实温度吻合度较常规红外测量好,且相对误差明显小于传统红外测温,验证了三波段测温法的可用性及精确性。三波段测温法在保证测量精度的同时拓宽了普通单波段红外热像仪的应用范围,保证了硫化矿自燃红外预测数值精度。     

脉冲加热材料热物性多光谱动态测量装置的研制

提出一种将多光谱测温法和积分球反射法相结合的脉冲加热技术测量材料热物性的新方法。基于积分球反射法,利用多光谱测温法获得材料在多个光谱下的辐射信息，可同时获得试样在多个光谱下的法向光谱发射率。介绍了利用该方法的脉冲加热瞬态热物性测量装置的各组成部分及其工作原理，该装置能 同时测量带状试样的比热、电阻率、全波长半球发射率及多个光谱下的法向光谱发射率。     

基于神经网络的多光谱测温方法研究

提出了基于神经网络的多波长温度计数据处理的新方法。实验结果表明,该方法可以解决绝大多数工程材料的目标真温及光谱发射率的测量问题。     

A temperature and emissivity separation algorithm for AdvancedSpaceborne Thermal Emission and Reflection Radiometer (ASTER)images

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) scanner on NASA's Earth Observing System (EOS)-AM1 satellite (launch scheduled for 1998) will collect five bands of thermal infrared (TIR) data with a noise equivalent temperature difference (NEΔT) of ⩽0.3 K to estimate surface temperatures and emissivity spectra, especially over land, where emissivities are not known in advance. Temperature/emissivity separation (TES) is difficult because there are five measurements but six unknowns. Various approaches have been used to constrain the extra degree of freedom. ASTER's TES algorithm hybridizes three established algorithms, first estimating the normalized emissivities and then calculating emissivity band ratios. An empirical relationship predicts the minimum emissivity from the spectral contrast of the ratioed values, permitting recovery of the emissivity spectrum. TES uses an iterative approach to remove reflected sky irradiance. Based on numerical simulation, TES should be able to recover temperatures within about ±1.5 K and emissivities within about ±0.015. Validation using airborne simulator images taken over playas and ponds in central Nevada demonstrates that, with proper atmospheric compensation, it is possible to meet the theoretical expectations. The main sources of uncertainty in the output temperature and emissivity images are the empirical relationship between emissivity values and spectral contrast, compensation for reflected sky irradiance, and ASTER's precision, calibration, and atmospheric compensation     

RBF网络在多光谱测温中的应用研究

介绍了一种人工神经网络在多光谱测温数据处理中的应用。利用人工神经网络,结合多种发射训练样本模型,可以自动辨识被测目标的发射率模型,从而得到目标的真温和光谱发射率。应用二次细分的方法进一步提高了测量精度,并分析了各种测量误差对测温精度的影响。仿真结果表明此方法是获知真温与发射率的一种较好的方法。     

Fluorescence and superfluorescence line narrowing and tunability ofNd3+ doped fibers

The inhomogeneous behavior of the 1.06 μm-neodymium transitions in doped optical fibers have been investigated, using the fluorescence line narrowing technique, pumping on the ⁴F_3/2 and ⁴F_5/2 sublevels at 4 K. Each observed transition has been identified. As the pump wavelength varies, the shift of the main fluorescence line is 40 nm, with the two pumping levels. We have studied the spectral behavior of the superfluorescence as a function of the pump wavelength, the temperature, and the absorbed power. The spectral evolution depends on λ_p with 19 nm-tuning range at low temperature. At 300 K, the quasihomogeneous behavior of the transition decreases the tunability to 14 nm. Based on these results, we present a simple technique permitting precise prediction of gain and spectral line shapes of superfluorescent Nd-doped fiber sources     

Estimating Broadband Emissivity of Arid Regions and Its Seasonal Variations Using Thermal Infrared Remote Sensing

Surface emissivity in the thermal infrared region is an important parameter for determining the surface radiation budget in climate, weather, and hydrological models. This paper focuses on estimating the spatial and temporal variations of the surface emissivities using thermal infrared remotely sensed data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard NASA's Terra satellite. We developed a regression approach to use the ASTER and MODIS data for estimating the broadband emissivity (BBE; 8-13.5 mum). The regressions were calibrated using a library of spectral emissivity data for terrestrial materials. We applied these regressions to ASTER and MODIS data to obtain emissivity maps for several arid regions of the Earth. In the 8-9-mum band for sparsely or nonvegetated desert areas, emissivity values between 0.66 and 0.96 have been observed, which are due to the low emissivity of quartz-rich sands at these wavelengths. As a result, the range of BBE is between 0.86 and 0.96. The seasonal variation over a two-year period and the dependence on land cover/soil type were also investigated.     

HgCdTe long-wavelength infrared photovoltaic detectors fabricated using plasma-induced junction formation technology

A long-wavelength infrared (LWIR) HgCdTe photodiode fabrication process has been developed based on reactive ion etching (RIE) plasma-induced p-to-n type conversion for junction formation. The process has been successfully applied to produce devices using both vacancy-doped and gold-doped liquid phase epitaxy (LPE)-grown p-type HgCdTe material with a cut-off wavelength of 10 μm at 77 K. The fabrication procedure is outlined and results are presented on completed devices that indicate the effect of variations in processing parameters. The fabricated devices have been characterized by measurements of the diode dark I-V characteristic over the temperature range 20–200 K, as well as by spectral responsivity measurements. Analysis of the device I-V data, variable area data, and modeling of diode dark current mechanisms indicates that gold-doped material results in higher performing devices compared to vacancy-doped material. Device performance is found to be strongly affected by trap-assisted tunneling currents and surface leakage currents at zero bias. Nonoptimum surface passivation is likely to be the major factor limiting performance at this early stage of device technology development.     

红外多谱线二维辐射温度场重建算法的研究

对于2000 K以上的温度场,采用热像仪对温度场进行检测时,由于热像仪存在饱和问题,所以采用热像仪重建温度场这种测量的方法已不再适用。利用多组光学探头通过光纤远传,实现多光谱多通道数据的测量。在无需预先假设发射率与波长之间的模型关系基础上,通过迭代算法获得表面某些点的真温。通过布置成十字测温结构的多光谱方法实现涡轮增压锅炉多点温度的测量,构建了整个高温温度场的温度分布。结果表明:该方法用来测量高炉温度场分布可行、预测误差较小,可以为高温温度场的分析诊断提供参考。