Numerical investigations of the potential for laser focus sensors in micrometrology
Numerical investigations of the potential for laser focus sensors in micrometrology
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激光聚焦传感器在显微测量中的潜力的数值研究
DOI：
10.1117/12.2270252
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
R. Mastylo
中科院分区：
文献类型：
--
作者：
J. Bischoff;E. Manske;R. Mastylo
激光聚焦传感器(LFS)1安装在扫描纳米定位和测量机(NPMM)上，可实现接近衍射极限的分辨率，测量面积非常大，最高可达200 x 200 mm~1。计划进一步扩展，以解决8英寸及以上的晶片尺寸。因此，它们更适合于大晶圆上的微观计量。另一方面，在最先进的半导体工业中，最小的横向特征小到几纳米，因此远远超出经典光学的分辨率极限。新技术，如强迫症或ODP3，4ak.a。因为散射测量在很大程度上帮助克服了这些限制。然而，散射法依赖于规则的图案，因此，测量必须在特殊的参考栅格或盒子上进行，而不是在管芯内。因此，在测量和实际感兴趣的结构之间存在差距，随着特征大小的缩小，这成为越来越多的问题。另一方面，近场方法也可以极大地扩展分辨率极限，但它们需要非常具有挑战性的控制来保持足够小的工作距离以保持在近场区域内。因此，从理论上研究了LFS扫描系统的可行性和局限性。基于激光聚焦传感器扫描简单地形的模拟，发现通过相邻地形特征的光学相互作用引起的邻近干涉效应，可以在一定程度上克服衍射限制。我们认为，以激光聚焦传感器光学系统的完整模型为基础，结合地形衍射，采用与OCD类似的方法，通过严格的衍射模拟来重建衍射轮廓是很有可能的。不同之处在于必须建模的信号本身。标准的OCD是基于光谱的，而LFS则利用高度扫描信号。给出了不同类型地形(密集与稀疏、规则与单一)的模拟结果，其中横向特征接近或超过了经典分辨率极限。此外，还研究了地形高度对探测能力的影响。为此，考虑了几种传感器原理和极化设置，例如双色针孔传感器和傅科刀传感器。结果表明，当测量与复杂的轮廓恢复技术和一些先验知识相结合时，即使在“经典”光学设置下，分辨率也有可能超过阿贝或瑞利极限。最后，根据文7中提出的方法，基于摄动模拟得出了测量不确定度。
Laser focus sensors (LFS)1attached to a scanning nano-positioning and measuring machine (NPMM) enable near diffraction limit resolution with very large measuring areas up to 200 x 200 mm1. Further extensions are planned to address wafer sizes of 8 inch and beyond. Thus, they are preferably suited for micro-metrology on large wafers. On the other hand, the minimum lateral features in state-of-the-art semiconductor industry are as small as a few nanometer and therefore far beyond the resolution limits of classical optics. New techniques such as OCD or ODP3,4a.k.a. as scatterometry have helped to overcome these constraints considerably. However, scatterometry relies on regular patterns and therefore, the measurements have to be performed on special reference gratings or boxes rather than in-die. Consequently, there is a gap between measurement and the actual structure of interest which becomes more and more an issues with shrinking feature sizes. On the other hand, near-field approaches would also allow to extent the resolution limit greatly5but they require very challenging controls to keep the working distance small enough to stay within the near field zone.Therefore, the feasibility and the limits of a LFS scanner system have been investigated theoretically. Based on simulations of laser focus sensor scanning across simple topographies, it was found that there is potential to overcome the diffraction limitations to some extent by means of vicinity interference effects caused by the optical interaction of adjacent topography features. We think that it might be well possible to reconstruct the diffracting profile by means of rigorous diffraction simulation based on a thorough model of the laser focus sensor optics in combination with topography diffraction6in a similar way as applied in OCD. The difference lies in the kind of signal itself which has to be modeled. While standard OCD is based on spectra, LFS utilizes height scan signals. Simulation results are presented for different types of topographies (dense vs. sparse, regular vs. single) with lateral features near and beyond the classical resolution limit. Moreover, the influence of topography height on the detectability is investigated. To this end, several sensor principles and polarization setups are considered such as a dual color pin hole sensor and a Foucault knife sensor. It is shown that resolution beyond the Abbe or Rayleigh limit is possible even with “classical” optical setups when combining measurements with sophisticated profile retrieval techniques and some a-priori knowledge. Finally, measurement uncertainties are derived based on perturbation simulations according to the method presented in7.
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DOI：
--
发表时间：
2000
期刊：
SPIE Optics + Photonics
影响因子：
--
作者：
J. Bischoff;R. Brunner
通讯作者：
R. Brunner
DOI：
--
发表时间：
1986
期刊：
影响因子：
--
作者：
H. Haferkorn
通讯作者：
H. Haferkorn
垂直扫描白光干涉仪的横向分辨率和传输特性。
影响因子：
1.9
作者：
Weichang Xie;P. Lehmann;J. Niehues
通讯作者：
J. Niehues
影响因子：
2.7
作者：
Jaeger, G.;Manske, E.;Balzer, F.
通讯作者：
Balzer, F.
使用激光聚焦传感器进行轮廓测量建模
DOI：
--
发表时间：
2011
期刊：
Optical Metrology
影响因子：
--
作者：
J. Bischoff;E. Manske;H. Baitinger
通讯作者：
H. Baitinger