To satisfy the continuous demand of ever smaller feature sizes, plasma etching technologies in microelectronics enable the fabrication of device structures in the nanometer range. To control these processes, real-time access to the structure’s dimensions is needed. We develop a special method of optical critical dimension metrology and evaluate the feasibility of reconstructing the etched dimensions from experimental reflectivity spectra of the surface, taken about every second. For a periodic 2D model structure etched into a silicon, we develop and test a fast algorithm.

To reduce the computing time, we generate a library of spectra before the etching. We demonstrate that, by replacing the numerically simulated spectra in the reconstruction algorithm by spectra interpolated from the library, it is possible to compute the geometry parameters in times less than a second. Finally, to also reduce memory size and computing time for the library, we reduce the scanning of the parameter values to a sparse grid.

为了满足越来越小的特征尺寸的持续需求，微电子学中的等离子体蚀刻技术使得能够制造纳米范围的器件结构。为了控制这些过程，需要实时访问结构的尺寸。我们开发了一种特殊的光学临界尺寸度量方法，并评估了从表面的实验反射率光谱（大约每秒一次）重建蚀刻尺寸的可行性。对于蚀刻到硅中的周期性2D模型结构，我们开发并测试了一种快速算法。

为了减少计算时间，我们在蚀刻之前生成了一个光谱库。我们证明，通过用从库中插入的光谱替换重建算法中的数值模拟光谱，可以在不到一秒的时间内计算出几何参数。最后，为了减少库的内存大小和计算时间，我们减少了将参数值扫描到稀疏网格的过程。