SU‐8 is an important, epoxy‐based, negative photoresist that can create high aspect ratio features. Spectroscopic ellipsometry (SE) is a nondestructive analytical technique that can be performed in the open air. In this study, reflection and transmission SE measurement data were combined to model the optical function of SU‐8 photoresist. The data were fit using three different models: (i) a B‐spline model, (ii) a four‐Gaussian oscillator model with an ultraviolet (UV) and an infrared (IR) pole, and (iii) a Cody–Lorentz model with three additional Gaussian oscillators. All three models successfully fit the data, where the B‐spline model showed the lowest mean squared error. In situ SE data were also collected and fitted to follow possible changes in the optical properties of the SU‐8 during its development. Time‐dependent density functional theory (TD‐DFT) modeling of a complete SU‐8 monomer is qualitatively and quantitatively consistent with the measured optical function.

中文翻译：

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SU-8光刻胶在190至1680 nm（0.740–6.50 eV）范围内的椭圆偏振光谱

SU-8是一种重要的基于环氧的负性光刻胶，可产生高深宽比的特征。椭圆偏振光谱法（SE）是一种无损分析技术，可以在露天进行。在这项研究中，反射和透射SE测量数据被组合起来以模拟SU-8光刻胶的光学功能。使用三种不同的模型对数据进行拟合：（i）B样条曲线模型；（ii）具有紫外线（UV）和红外（IR）极点的四高斯振荡器模型；以及（iii）Cody-Lorentz模型与三个额外的高斯振荡器。这三个模型都成功地拟合了数据，其中B样条模型显示出最低的均方误差。还收集并拟合了现场SE数据，以跟踪SU-8在开发过程中光学特性的可能变化。