针对现代光刻中,超大数值孔径的情况下,通过简单的傅里叶衍射理论模拟掩模的传递函数的方法不够精确,必须得考虑倾斜照明带来的阴影效应。因此本文针对交替式相移掩模,提出了一种考虑阴影效应的近似模型。重新定义了阴影比率的公式。该方法是傅里叶衍射理论的扩展,是一种依赖于入射角的函数。分别给出了交替式相移掩模空间域和空间频率域的传递函数的表达式。并对提出的近似模型的衍射效率以及干涉场光强分布进行了仿真。结果表明,衍射效率和干涉场的强度分布是随着入射角的改变而改变的,不同线宽的衍射效率也不同。并且衍射效率是关于零度入射角对称分布。

In order to improve the resolution of photolithographic system,hyper numerical aperture is needed.However,analysis of transfer function with Fourier diffraction theory will be inadequate,and shadowing effects must be considered for oblique illumination.Therefore,a new approximation model for alternating phase shift mask considering shadowing effects was proposed in this paper,and shadowing ratio was redefined.Extended Fourier diffraction theory was used,and a relation of function depended on incident angle.Expressions for alternating phase shift mask were given for both space domain and frequency domain.Diffraction efficiencies and interference fields were simulated using approximation model.The results show that diffraction efficiencies and interference fields vary with incident angles and diffraction efficiencies vary with linewidth too.Moreover,diffraction efficiencies are symmetric about the zero incident angle.