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首页> 外文会议>Conference on Optics and Photonics for Advanced Dimensional Metrology >Optical topography measurement of steeply-sloped surfaces beyond the specular numerical aperture limit
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Optical topography measurement of steeply-sloped surfaces beyond the specular numerical aperture limit

机译：超出镜面数值孔径限制的陡坡表面的光学形貌测量

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摘要

Engineered functional surfaces often feature varying slopes on macro- and micro-scales. When surfaces are mirror-like, the highest surface slope that can be measured by a far-field 3D imaging optical surface measuring instrument is the arcsine of the numerical aperture (NA) of the objective lens, i.e. the acceptance angle of the lens. However, progress in instrument design has allowed for measurement of non-specular surfaces with slopes steeper than this "traditional" NA limit. Nonetheless, there is currently a lack of understanding about the instrument response to surfaces with steep slopes beyond this limit. It is unclear over what surface spatial frequencies we can expect to accurately report fine surface-feature details. Here we present results demonstrating the capability of a commercial coherence scanning interferometer for measuring surface topography of a roughened flat and a blazed grating with tilt angles greater than the NA slope limit. We show that the surface form, i.e. the tilted plane, can be measured correctly. But, while surface texture information that can appear useful is also obtained, tilting significantly influences the measurement accuracy of micro-scale texture, and for asymmetric gratings, can depend on the tilting direction. A simplified surface scattering model suggests that the loss of scattered power captured by the instrument and a low signal-to-noise ratio causes the reduction of measurement accuracy. However, a rigorous three-dimensional instrument model is needed for a full understanding; we will develop this in our future work.
机译：工程功能表面通常在宏观和微观尺度上具有变化的斜率。当表面是镜面状时，可以通过远场3D成像光学表面测量仪测量的最大表面倾斜度是物镜的数值孔径（NA）的反正弦值，即透镜的接受角。然而，仪器设计的进步已允许测量斜率大于此“传统” NA限值的非镜面表面。尽管如此，目前对于斜率超过此极限的表面对仪器的响应尚缺乏了解。目前尚不清楚我们可以期望精确地报告精细的表面特征细节的表面空间频率。在这里，我们提供的结果证明了商用相干扫描干涉仪能够测量倾斜角大于NA斜率极限的粗糙平面和闪耀光栅的表面形貌。我们表明可以正确地测量表面形式，即倾斜平面。但是，尽管还获得了看似有用的表面纹理信息，但倾斜会显着影响微尺度纹理的测量精度，对于非对称光栅，倾斜角度可能取决于倾斜方向。简化的表面散射模型表明，仪器捕获的散射功率的损失和低信噪比会导致测量精度降低。但是，需要一个严格的三维仪器模型才能全面了解。我们将在未来的工作中对此进行开发。

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