【作者】 胡春光；

【导师】 胡小唐； Peter Zeppenfeld；

【作者基本信息】 天津大学 ， 测试计量技术及仪器， 2007， 博士

【摘要】 反射差分光谱仪是一种对表面光学各向异性具有高灵敏度的新型光学测量仪器,在半导体材料表面分析与加工、金属表面研究、液晶器件检测等领域已获得成功应用。随着应用范围的不断扩展,仪器综合性能朝更高的方向发展,快速全光谱并行测量型仪器是主要发展方向之一。本论文围绕这一主题,首先对光弹调制式单通道仪器进行了多通道改造,搭建了一台双通道并行测量样机;在此基础上,提出了旋转补偿器式多通道并行、快速测量型反射差分光谱仪的概念,并完成第一台以旋转补偿器为调制技术的反射差分光谱仪。经过与光弹调制式单通道商用仪器实验结果的比对,新型仪器在保持相同测量精度的同时,将全光谱的测量时间缩短为原有的1/10,较好地将快速测量与全光谱并行测量的特点融于一体。按照工作开展的顺序,课题的研究内容和成果可归纳为以下几个方面:1.对单通道光弹调制器式仪器进行多通道改造,创新性地提出基于数据采集板与计算机虚拟技术的采集方案,实验分析了采集板性能和数据处理方法对测量精度的影响,如快速傅里叶变换和锁相放大技术,并创新性地提出两种普适公式用于校正多通道测量中光弹调制器的位相延迟随波长非线性变化造成的误差。2.首次提出旋转补偿器式反射差分光谱仪的概念,并通过建立数学模型,分析了仪器多种误差源,如器件自身缺陷、光学器件装配误差、传感器测量误差等,与测量结果间存在的数学联系,创新性地提出基于起偏器方位角的系统误差标定方法和旋转起偏器消除系统误差的在线校正方法。针对数据的采集与处理,创新性地提出基于实时读取补偿器旋转角度与最小二乘法的方案。3.开发第一台旋转补偿器式多功能反射差分光谱仪,仪器包括光学测量系统,电子控制系统以及软件等部分。在仪器控制环节提出数据同步采集机制。4.系统地测试并分析了光源、探测器、补偿器等器件自身可能存在的缺陷及其对仪器测量性能的影响,讨论了处理光谱数据的几种数学方法,并利用单通道光弹调制式商用机,对旋转补偿器式仪器的性能进行了对比性测试。5.采用旋转补偿器式仪器实际测试多种样品,进一步评价新仪器性能,同时指出存在的不足。实验结果显示,无论是相对值远小于1的微弱反射差分信号,还是接近1的强信号,旋转补偿器式仪器都能准确测量,且测量速度10倍快于单通道商用机。实验还表明,反射差分光谱仪对亚纳米量级的样品表层原子结构、纳米量级表面原子团簇以及亚微米尺度微加工结构在表面二维空间呈现的各向异性都具有极高的灵敏度。更多还原

【Abstract】 Reflectance difference spectroscopy (RDS) is a linear optical instrument which measures the difference in the normal incidence reflectivity for two mutually perpendicular orientations of the polarization vector as a function of photon energy. The technique is extremely sensitive to any kind of the in-plane optical anisotropy of matters and has been successfully applied in the studies of semiconductor surfaces, metal surfaces, and polymer surfaces. Particularly, it is widely used as a powerful tool for the real-time inline measurement in industry. According to the continuous extending of its application in different fields, the instruments can do fast full spectrum acquisition are required. This has stimulated lot of research and development efforts carried out in both industry and universities over the world. Focusing on the realization of this challenging task, in the PhD work, two systems based on different phase modulation techniques have been development. For the first system, we have set up a prototype multi-channel RD spectrometer by modifying a commercial single-channel RD spectrometer which is based on photoelastic modulator (PEM) techniques. Then, with a new concept of RDS configuration based on rotating compensation techniques established in this work, a prototype machine is developed. The testing results show that the time consumed for one full spectrum is one order of magnitude less than that for commercial one without loosing measurement precision. Therefore, the function of fast data acquisition is successfully realized. The main achievements of this PhD work are listed by time sequence in the following:1. A new scheme for multi-channel PEM based RDS was introduced based on a general high speed data acquisition board and virtual instrumentation technique on PC. And a two-channel PEM based RDS was built up as a prototype of the new kind of multi-channel instrument. The influences of acquisition board performances and two frequency domain analysis methods on measurement precision, such as FFT and Lock-in amplifier, were discussed. Two more general PEM retardation corrections for full spectrum range were promoted for calculating the exact phase retardation of PEM at every wavelength.2. The mathematic model of rotating-compensator based RDS was established by Stokes matrix. All kinds of measurement errors including systematic and statistical ones and their origins were studied in detail. Perticular attention has been given to the imperfections of optical elements, azimuth misalignments and error signals from detector. The mathematic relationships between measurement errors and these error sources were derived. Two new calibration / correction methods for system were promoted. One was based on polarizer’s azimuth and another was an on-line method based on polarizer rotation. A combination of the real time angular positions of the compensator and a least-square method was applied to data analysis.3. A prototype of rotating-compensator based RDS was built up, which composes 3 parts namely, optical probe system, electronic control system, and operation software. A method of reading simultaneously both the real time angular position of the compensator and the integrated intensity on the detector was used for data acquisition.4. The test and analysis for each component’s imperfection was conducted, especially for the light source, the compensator, and the CCD detector. Then, several mathematical methods in data analysis for improving signal to noise ratio were discussed. At last, the comparison of measurement precision between the commercial single-channel PEM based RDS and the new spectrometer was performed.5. In order to evaluate the performance of the new instrument thoroughly, some samples in addition to Si(110) were measured by both the new instrument and the commercial RDS. The results show that in the full range of RDS signal (between -1 and +1), the new spectrometer can measure the signal exactly and the measurement speed is 10 times faster than that of the commercial RDS. It also indicates that RDS is very sensitive to anisotropy of surface electronic structure, whatever it comes from subnano-scale atom structure, nano-scale cluster, and submicro-scale micro-maching structure.更多还原