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为有效控制成像线宽,研究了高数值孔径光学光刻中的体效应并提出一种光刻胶膜层优化方法,利用成像中的摇摆效应平衡体效应对成像线宽的影响。首先根据系统数值孔径和照明相干因子确定成像光入射角分布,相对所有入射光求出光刻胶底面单位体积吸收的能量平均值。然后用最小二乘法拟合得到能量平均值随光刻胶厚度变化的解析式并求能量平均值的导数。最后通过优化光刻胶膜层,使能量平均值的导数绝对值最小。按优化结果设计光刻胶膜层,利用商业光刻软件Prolith9.0得到成像线宽随光刻胶厚度的变化。结果表明,该方法能在3040nm的光刻胶厚度范围,有效地减小由体效应引起的成像线宽的变化。
In order to effectively control the imaging linewidth, the bulk effect in high numerical aperture optical lithography was studied and a method of optimizing the photoresist layer was proposed. The effects of the bulk effect on the imaging linewidth were balanced by the swing effect in imaging. Firstly, the angle of incidence of the imaging light is determined according to the numerical aperture of the system and the illumination coherence factor, and the energy absorbed by the bottom of the photoresist is averaged over all the incident light. Then the least square method is used to fit the analytic formula of the mean value of the energy with the thickness of the photoresist and the derivative of the mean value of the energy is obtained. Finally, by optimizing the photoresist layer, the absolute value of the derivative of the energy average is minimized. According to the result of optimization, a photoresist film was designed. Prink9.0 was used to obtain the imaging line width with the thickness of the photoresist. The results show that this method can effectively reduce the change of imaging linewidth caused by the body effect at the thickness of 3040nm.