Zeidler J R, Kohles R B, Bashara N M
Appl Opt. 1974 Aug 1;13(8):1938-45. doi: 10.1364/AO.13.001938.
The types of error produced by beam deviation in the optical elements of an ellipsometer are examined. It is shown that there are two types of error that may be significant-systematic errors due to a variation in the plane of incidence and in the angle of incidence at the specimen and errors due to the combined effects of beam displacement and nonuniformities in either the detector response or the optical properties of the specimen, the compensator, the polarizer, the analyzer, or the specimen cell. Analytic expressions for the variation in the plane of incidence and in the angle of incidence are given in terms of parameters that can be determined experimentally. A method by which these parameters can be measured is described. It is shown that the azimuthal variation in the angle of incidence produces fundamental errors in conventional zone averaging techniques because the values of psi and Delta are averaged at different angles of incidence in different zones. Methods of experimentally predetermining when such errors are likely to be significant are discussed, and a procedure that cancels most systematic errors due to beam deviation in each zone is described. The combined effects of beam deviation in the polarizer, the compensator, the cell windows, and the analyzer are considered in several commonly used configurations, and the configurations that minimize beam deviation errors are described.
研究了椭圆偏振仪光学元件中光束偏差产生的误差类型。结果表明，存在两种可能显著的误差类型：一种是由于样品表面入射角和入射面的变化引起的系统误差，另一种是由于光束位移以及探测器响应或样品、补偿器、偏振器、分析器或样品池光学特性不均匀性的综合影响所导致的误差。给出了以可通过实验确定的参数表示的入射角和入射面变化的解析表达式。描述了一种测量这些参数的方法。结果表明，入射角的方位角变化在传统的区域平均技术中会产生基本误差，因为在不同区域中，ψ和Δ的值是在不同入射角下进行平均的。讨论了通过实验预先确定此类误差何时可能显著的方法，并描述了一种消除每个区域中由于光束偏差引起的大多数系统误差的程序。在几种常用配置中考虑了偏振器、补偿器、样品池窗口和分析器中光束偏差的综合影响，并描述了使光束偏差误差最小化的配置。
