一种光谱型椭偏仪的校准方法

针对光谱型椭偏仪校准结果受测量模型影响大的问题进行研究,提出一种不受测量模型影响的校准方法,即通过校准椭偏角实现光谱型椭偏仪的校准。依据椭偏仪测量原理,通过仿真分析确定实现较大范围内椭偏角校准所需标准样片的薄膜厚度量值,并采用半导体热氧化工艺制备出性能稳定的膜厚标准样片。使用标准样片对型号为M-2000XF的光谱型椭偏仪的椭偏角进行校准,样片厚度为2,50,500 nm对应的椭偏角偏差分别在±0.6°,±1.5°,±2°以内,该偏差对薄膜厚度的影响不超过±0.5 nm。经实验表明:该方法不受椭偏仪测量模型的影响,可有效解决光谱型椭偏仪的校准问题。     

SiO2/Si膜厚标准样品校准相调制型光谱椭偏仪研究

椭圆偏振仪(或简称椭偏仪)在薄膜研究领域应用广泛.文章主要研究了相调制型光谱椭偏仪光路准直及参数优化过程,并通过硅上二氧化硅膜厚标准样品测量及数据拟合处理对光谱椭圆偏振仪进行校准.经过光路准直调整和参数优化后的椭圆偏振仪测量膜厚标准样品,拟合测量数据并将显示测量厚度值与标准样品厚度值比较,测量值在不确定范围内.     

分振幅斯托克斯参量的椭偏测厚方法

为了实现对纳米级薄膜的快速测量,运用了基于分振幅斯托克斯参量测量的椭偏测厚的方法,对该方法中的原理.计算和参量测量方法进行研究,并构建了实验系统.首先,设计了一个光路在同一平面上的分振幅斯托克斯参量测量装置,用偏振片和1/4波片组合产生已知的偏振态来定标该装置,用4个性能一致的光电探测器实现快速测量光束的斯托克斯参量.然后用实验系统测量纳米级薄膜样品的入射和反射偏振光的斯托克斯参量,求得椭偏参量ψ和Δ,再求得薄膜样品的厚度d和折射率n.讨论了斯托克斯参量测量的误差问题,最后与常用的消光法椭偏仪作了对比测量实验.测量结果与椭偏消光法比较,d和n的相关系数均大于85%,说明两仪器有很好的一致性.实验研究表明,该方法通过测量入射光和反射光的偏振态,能快速测量纳米级薄膜的参数.系统构建容易,调节方便,定标简单.     

低介电常数多孔二氧化硅薄膜的制备与研究

本文报道了一种新型纳米多孔低介电常数薄膜的制备方法.以十六烷基三甲基溴化铵(CTAB)为模板剂,正硅酸乙酯为硅源,盐酸为催化剂,采用溶胶-凝胶技术,通过提拉法制备了二氧化硅透明介孔薄膜.用红外光谱、小角XRD、原子力显微镜对样品进行了表征,并采用椭偏仪和阻抗分析仪测量薄膜的折射率和介电常数.通过调节表面活性剂浓度和老化时间等实验条件制备出了K＜2.5、机械强度好的低介电常数薄膜.     

纳米尺寸膜厚标准样片的椭偏分析

针对膜厚标准样片的高精度测量问题,基于光谱型椭偏仪测量系统,提出对膜厚标准样片逐层分析的方法。利用相应的匹配算法,对比硅上二氧化硅模厚标准样片的等效结构模型和四相结构模型,实现对薄膜样片的厚度表征和椭偏分析。其次,通过对样片进行为期12周的测量考核,完成对薄膜样片表层分子吸附机理的分析。实验结果表明:针对研制的标称值为2～1 000 nm硅上二氧化硅膜厚标准样片,中间层的厚度存在先递减后递增的趋势。其中,在标称值为50～500 nm范围内,等效结构模型与四相结构模型测量结果的绝对误差在±0.2 nm以内,因此,可以采用等效结构模型的方法开展仪器的校准工作。另外,提出通过加热实现对标准样片解吸附的方案,有效解决超薄膜样片的储存问题。     

大气压非平衡等离子体沉积氧化硅薄膜

本文搭建了一套大气压等离子体薄膜沉积系统,其装置采用喷枪方式,结合运动机构控制喷枪按特定轨迹移动镀膜。四乙氧基硅烷(TEOS)作为硅的先驱体,氮气为先驱体载气和等离子体放电气体,基底温度50℃～300℃,进行了大气压等离子体化学气相沉积氧化硅薄膜的研究。运用红外光谱(FTIR)、光学椭偏仪,扫描电镜(SEM)和纳米压痕仪对沉积的薄膜进行了表征。研究表明,薄膜中富含Si—O—Si键且有少量S—OH键;较高基底温度有利于在硅基底上得到一层平整致密的薄膜;基底温度300℃时薄膜硬度达到4.8GPa,略低于采用PECVD方法沉积的氧化硅薄膜。     

透射式外差椭偏测量及非线性误差分析

结合激光外差干涉法和透射式椭偏测量原理,研究了一种快速、高精度测量纳米厚度薄膜光学参数的方法．给出了光学系统设计和理论分析,使用两个声光调制器产生20kHz的差频,直接比较平行分量和垂直分量外差信号的幅值和相位,得到所需要的椭偏参数．光束偏振态的椭圆化及偏振分光不完全所引起的非线性误差是影响纳米薄膜测量精度的主要因素,推导出椭偏参数非线性误差的近似解析表达式,计算结果表明由此导致的膜厚测量误差可达几个nm,相对而言,激光器和反射镜等器件产生的光束椭偏化是其主要原因．     

用消光式椭圆偏振光谱测量薄膜光学参数的方法

本文主要介绍如何应用 TP—77型椭偏仪与 WDF 反射式单色仪组合,实现不同波长下的消光椭偏测量。此方法可测量薄膜厚度、折射率、吸收系数等光学参数。     

多层薄膜光学常数的椭偏法研究

研究了椭偏测量中多层薄膜拟和模型建立的过程,并对一未知多层光学薄膜进行了椭偏分析,建立了substrate/film1/EMA/film2/srough的物理结构模型.采用椭偏法,在首先确定出基底光学常数的基础上,提出了从单层、双层、三层逐次建模拟和的分析方法.研究结果表明:对于透明或弱吸收光学薄膜,采用柯西公式可以较好表征材料的色散关系.椭偏分析最终得到的未知薄膜基本结构为G(1.52)/2.0312(203.0 nm)1.4636(170.1 nm)2.079 1(170.4 nm)/A,膜系设计及分光光度计测量的透射光谱证实了这一结果.对多层膜厚度和光学常数的分析表明,椭偏法仍然是一种行之有效的薄膜光学常数测量方法.     

溅射法低温生长纳米硅薄膜及异质结电池

用射频溅射法在P型硅衬底上生长了纳米硅薄膜,衬底温度控制在100℃左右,工作气体选用H2 Ar,氢气的分压控制在31%到73%,同时改变薄膜的沉积时间.用Raman、XRD、AFM、SEM 及椭偏仪对薄膜的特性进行了测定.XRD的测试结果表明,样品中存在一种微结构,不同于用PECVD方法生长的薄膜.椭偏仪的测试结果给出这种薄膜具有宽带隙.在室温条件下对异质结薄膜电池的I-V特性进行了测量.     

Determination of film thickness and refractive index in one measurement of phase-modulated ellipsometry

Ellipsometry is often used to determine the refractive index and/or the thickness of a polymer layer on a substrate. However, simultaneous determination of these parameters from a single-wavelength single-angle measurement is not always possible. The present study determines the sensitivity of the method to errors of measurement for the case of phase modulated ellipsometry and identifies conditions for decoupling film thickness and refractive index. For a specific range of film thickness, both the thickness and the refractive index can be determined from a single measurement with high precision. This optimal range of the film thickness is determined for organic thin films, and the analysis is tested on hydrogel-like polymer films in air and in water.     

Correlation between optical path modulations and transmittance spectra of a-Si:H thin films

The optical constants of plasma-enhanced chemical-vapor-deposited amorphous silicon (a-Si:H) thin film upon a transparent substrate are determined within the UV-visible region by measurement of the transmittance spectrum. Apart from thickness irregularities, the effects of vertical film inhomogeneities (refractive-index distribution) on the spectrum are discussed. In this respect, although consideration of any possible variation in thickness of the film within the area illuminated by the probe beam is sufficient for correcting the modulation of the extrema of interference fringes, including in the model the thin transitional regions at substrate-film and film-air interfaces might be an alternative method for understanding the overall optical behavior of the spectrum.     

光反射干涉谱新方法测试薄膜厚度和光学常数

依据测量薄膜和光之间相互作用可确定薄膜特性的原理,并基于光反射干涉谱与德国最新研发薄膜分析软件SCOUT的新方法可测量已知或未知材料的多层薄膜厚度及其折射率n、消光系数k。通过实际测试证明：该方法可测试单晶硅、玻璃、ITO玻璃基底上沉积薄膜的厚度,样品基本不需要特别准备,对样品无破坏性,测试精准。理论上可以测量所有透光或半透光薄膜的厚度和光学常数,操作非常简便,适合于镀膜行业的在线检测和实时监控,且SCOUT软件在多层膜及多种材料的研发、制备等方面具有应用潜力。     

介质薄膜的透射光谱测量及其光学参数的分析

介绍介质薄膜透射光谱的测量以及基于分析薄膜透射光谱的计算薄膜光学参数的方法。对制备在玻璃基板上的二氧化钛、二氧化硅和氧化锌薄膜进行了可见光谱区的透射比测量，并用包络线方法和最优化方法对这些透明薄膜的光学参数进行了计算和分析。着重讨论了最优化方法在分析薄膜光学参数中的应用及其误差分析。此外，还对包络线方法和最优化方法进行了比较。     

OVPD und Anwendung optischer Spektroskopiemethoden zur Wachstumskontrolle. OVPD and Applications of Optical Spectroscopic Methods to Growth Control

Organic Vapor Phase Deposition (OVPD) is a new thin film growth technique which is very suitable for deposition of uniform thin films on larger substrate areas. The polarization sensitive methods, ellipsometry and Reflectance Anisotropy Spectroscopy (RAS), have huge potential for the control of the growth in the OVPD process. The capability of ellipsometry to determine the thickness and the optical constants of OVPD deposited films was demonstrated using as example an Alq₃ film. RAS showed high potential for the detection of very thin organic anisotropic films, as exemplified for an PTCDA film.     

In situ ellipsometric study of copper growth on silicon

Thin copper films are of high interest for interconnect applications. However, optical studies, such as ellipsometry, of metallic thin films are still rare as the measurements are difficult to interpret due to the lack of a transparent range and often island-like growth at very low coverages. We investigated by in situ spectroscopic ellipsometry the growth of thermally evaporated thin copper films on silicon substrates from 0.5 nm to more than 100 nm, a thickness for which bulk-like response is observed. A strong change in the optical response was observed for films thinner than 10 nm as a result of plasmonic effects. The data at each thickness was modeled by employing the effective medium approximation theory. Besides the layer thickness and the void filling fraction, giving the film density, we obtained information about the mean free path of electrons in the thin films and compared it to single crystals. Cu oxidation was studied by deliberately introducing oxygen or air in the chamber, leading to a fast and pronounced change in the optical response. The data analysis provides detailed information on film thickness and quality.     

用ECRCVD方法制备优质氮化硅钝化膜

利用电子回旋共振等离子体化学气相沉积(ECR—CVD)技术，以SiH4和N2为反应气体进行了氮化硅钝化薄膜的低温沉积技术的研究。采用原子力显微镜、傅立叶变换红外光谱和椭圆偏振光检测等技术对薄膜的表面形貌、结构、厚度和折射率等性质进行了测量。结果表明，采用ECR—CVD技术能够在较低的衬底温度条件下以较高的沉积速率制备厚度均匀的氮化硅薄膜，薄膜中H含量很低。薄膜沉积速率随微波功率和混合气体中硅烷比例的增加而增大。折射率随微波功率的增大而减小，随混合气体中硅炕比例的增大而增大。在相同气体混合比和微波功率条件下，较高衬底温度条件下制备的薄膜折射率较大。     

Instrument-invariant method of film thickness determination by means of substrate-to-film X-ray peak intensity ratioing

A simple method for the determination of thin film thickness using X-ray spectrometry is described. The ratio of the substrate X-ray peak intensity to that of the film is taken as a measure of the thickness of the film. A calibration curve, constructed using specimens of known thickness, can then be used for thockness determination. The results are independent of the incident electron beam current. The calibration curve is made instrument invariant by means of a normalization procedure and by taking into account the respective X-ray take-off angles. Normalized calibration curves are reported for 13 different elements on a silicon substrate, covering thicknesses between 2.5 and 650 nm. The method, ideally suited to thin films on solid substrates, can also be applied to films not on substrates, and in the presence of a thin organic interfacial layer between film and substrate.     

Complete optical analysis of a non-absorbing thin film on an absorbing substrate by a new method of immersion spectroscopic reflectometry

A new method for determining the thickness and the spectral dependence of the refractive index characterizing a non-absorbing thin film placed on an absorbing substrate is described in this paper. Within this method two spectral dependences of the reflectance corresponding to the system immersed into two different non- absorbing ambients are employed. The main advantage of the method is that the values of the thickness and the refractive index can be determined by means of explicit formulae. The second important advantage is the fact that non-absorbing thin films with relatively small thicknesses can be analysed. The method is applied to amorphous SiO₂ thin films placed on silicon single-crystal wafers.     

Use of artificial neural networks to predict thickness and optical constants of thin films from reflectance data

Artificial neural networks and the Levenberg–Marquardt algorithm are combined to calculate the thickness and refractive index of thin films from spectroscopic reflectometry data. Two examples will be discussed, the first is a measurement of thickness and index of transparent films on silicon, and the second is a measurement of three thicknesses and index of poly-silicon in a rough poly-silicon on oxide stack. A neural network is a set of simple, highly interconnected processing elements imitating the activity of the brain, which are capable of learning information presented to them. Reflectometry has been used by the semiconductor industry to measure thin film thickness for decades. Modeling the optical constants of a film in the visible region with a Cauchy dispersion model allows the determination of both thickness and refractive index of most transparent thin films from reflectance data. The use of an alloy interpolation model for the optical constants of poly-silicon allows the determination of thicknesses and poly optical constants. In this work artificial neural networks are used to obtain good initial estimates for thickness and dispersion model parameters, these estimates are then used as the starting point for the Levenberg–Marquardt algorithm which converges to the final solution in a few iterations. These measurement programs were implemented on a Nanometrics NanoSpec 8000XSE.