Interferometric measurement of functional surfaces
Interferometric measurement of functional surfaces
复制标题
功能表面的干涉测量
DOI：
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
J. Niehues
中科院分区：
文献类型：
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作者：
P. Lehmann;Weichang Xie;P. Kuehnhold;J. Niehues
随着精密制造和微技术能力的提高，对高精度工业计量系统的需求也在不断增加。特别是在测量功能表面时，面光学原理被广泛应用。此外，如果需要纳米高度分辨率，干涉仪似乎是最有前途的仪器。首先，这方面的贡献集中在传输特性的白光干涉仪与微观领域的看法。通常，显微仪器受到其有限的横向分辨率能力的影响。因此，这些仪器的传递函数通常被假设为显示线性低通特性。通过理论模拟和实验研究，对白光干涉仪的传输特性进行了研究。我们的研究结果表明，在大多数实际情况下，这些仪器表现为非线性，即输出表面轮廓不能从输入轮廓通过一个简单的线性滤波器操作。虽然白光干涉仪已经很成熟，但如果将其用于测量微观甚至亚微观结构，则存在一些进一步的限制。如果测量对象上存在边缘、陡峭的斜坡或陡峭的斜坡变化，则会出现蝙蝠翼等特征误差。此外，为了避免色散效应，需要在色差校正方面付出很大努力。否则，在从相干峰的评估获得的轮廓与从干涉信号的相位产生的轮廓之间将存在系统差异。如果从相干峰的位置获得条纹阶数，则这些可能导致2π相位跳跃。最后，如果测量的微结构显示表面斜率的不连续性，则也可能导致测量伪影。本文分析了不同的现象，并讨论了克服现有局限性的方法。
Increasing capabilities in precision manufacturing and micro technology are accompanied by increasing demands of high precision industrial metrology systems. Especially for measuring functional surfaces, areal optical principles are widely used. If, in addition, nanometer height resolution is needed interferometers seem to be the most promising instruments. First, this contribution focuses on the transfer characteristics of white-light interferometers with microscopic field of view. In general, microscopic instruments suffer from their limited lateral resolution capabilities. Hence, the transfer function of these instruments is typically assumed to show a linear low-pass characteristic. We studied the transfer characteristics of white-light interferometers by theoretical simulations and experimental investigations. Our results show that in most practical cases these instruments behave nonlinear, i.e. the output surface profile cannot be obtained from the input profile by a simple linear filter operation. Although they are well-established, there are some further limitations of white-light interferometers if they are used to measure micro or even sub-microstructures. If edges, steeper slopes or abrupt slope changes are present on a measuring object characteristic errors such as batwings occur. Furthermore, a high effort concerning the correction of chromatic aberration is necessary in order to avoid dispersion effects. Otherwise, there will be systematic discrepancies between profiles obtained from evaluation of the coherence peak and those resulting from the phase of the interference signals. These may lead to 2π phase jumps if the fringe order is obtained from the position of the coherence peak. Finally, measurement artifacts may also result if the measured micro-structure shows discontinuities of the surface slope. This contribution analyses the different phenomena and discusses approaches to overcome existing limitations.