为快速、准确地获得厚层光刻胶内部衍射光场的分布,利用角谱理论的思想,考虑入射光通过掩模后在光刻胶面的反射、透射和光刻胶曝光过程中其折射率及吸收系数在深度方向上的变化,建立了衍射光场在厚层光刻胶中传输的理论模型。为减小计算量,对快速傅里叶算法进行了改进。该方法数值计算速度快,计算结果准确,并适用于光在折射率渐变的其它介质中的传播。最后,对厚层光刻胶中光场分布进行了数值模拟;计算模拟表明,对于厚层光刻胶,其表面的反射、透射和折射率及吸收系数在深度方向变化对衍射光场分布有明显的影响。

The angular spectrum theory is introduced to analyze optical diffraction lithography in thick film photoresist, and the reflection and transmission on the interface and the variation of dielectric coefficient in depth direction in thick film inhomogeneous resist are considered. A novel lithography model is put forward to simplify the analysis of optical diffraction, and the fast Fourier transform (FFT) algorithm is converted into convolution calculation to save computation cost. Numerical calculation results show that the reflection and transmission on the interface and the variation of dielectric coefficient in depth direction have important effects on the diffractive field intensity of thick film resist.