基于DILL经典曝光模型,对其分别在深度轴和时间轴上进行扩展:在深度轴上,以基尔霍夫衍射公式为基础,引入复折射率,利用光束传输法的思想计算了某曝光时刻下胶体内部的光场分布;在时间轴上,分析SU8光刻胶的特点及曝光反应过程,建立合适的光交联反应动力学模型,计算不同曝光时刻下的光场分布。通过整个曝光模型的建立,最终给出一定曝光时间后的光场分布;结果表明,在曝光阶段,胶内深层光场整体分布随时间变化不大,曝光时间对曝光阶段光场分布的影响较小,这种影响将在后烘阶段得以放大。
Dill's classical exposure model on depth axis and time axis are generalized, respectively. On the depth axis, based on the Kirchhoff diffraction equation, complex-number-refraction-index was introduced, and the diffractive illumination distribution inside the resist at one moment was calculated by using the Beam Propagation Method (BPM) . On the time axis, the characteristic of SU8 and its reaction course during exposure were analyzed, an appropriate chemical reaction kinetics model of the photocrosslinking reaction was built, and the diffractive illumination distribution at different moment was calculated. Finally, by building a kind of integrated exposure model, the diffractive illumination distribution after some exposure time was calculated. The results indicate that the illumination distribution variation with time inside the resist is not obvious and the impact of exposure time on illumination distribution is relatively low, which will be expanded during the post-exposure-bake process.