为了更精确地确定邻近效应参数,借助优化的电子散射模型,利用改进的Monte Carlo算法模拟了电子束在固体中的散射过程,得到了不同曝光条件下抗蚀剂中的能量沉积分布.利用最小二乘非线性曲线拟合法对该分布进行了双高斯拟合,得到了邻近效应参数α,β和η的值,并与实验结果进行了比较发现,最小二乘非线性曲线拟合法可以用于邻近效应参数的确定.对不同曝光条件的参数拟合显示,增加入射电子束能量,α减小,β增大,而η几乎不变;增加抗蚀剂厚度,α增大,β和η变化不明显;增大衬底材料原子序数,β减小,η增大,而α几乎不变.所得结果不但能为电子束曝光条件的优化、邻近效应的降低提供理论指导,而且还能为邻近效应校正快速地提供精确的参数.
In order to determine the proximity effect parameters more accurately, the process of the electron beam scattering in solid was simulated with the optimized model of electron beam scattering and modified Monte Carlo algorithm. It was obtained that the distribution of the energy deposition of different exposure in resist. The double Gaussian fitting of energy distribution was carried out by the method of nonlinear least-squares curve fitting, which elicited the parameters (α, β and η). The comparison between the fitting parameters and the experiment results shows that the method of nonlinear least-squares curve fitting can be used to determine the parameters of proximity effect. The parameters fitting for different exposure shows the change trend of α, β and η. The increment of electron beam energy leads to the decrease of α and increase of β, while η is almost constant. The increase of resist thickness results in the increment of α while β and η are almost invariable. The increase of substrate's atom number causes decrease of β and increment of η, while α is unchangeable. The results can not only provide theoretical guide for optimizing the exposure conditions and reducing the proximity effect in electron beam lithography, but also can quickly provide more accurate parameters for proximity effect correction.