刀口半影最小化的光刻机扫描狭缝研究

Research of scanning slit with minimal penumbra of blade's edge in lithography

扫描狭缝是步进扫描光刻机中控制曝光剂量的重要单元,而扫描狭缝产生过大的刀口半影会影响曝光性能。首先,根据步进扫描光刻机照明原理,通过分析掩模面上光强分布与扫描狭缝刀口厚度及位置的相对关系,推导出掩模面上刀口半影宽度的计算公式,同时针对数值孔径NA为0.75的光刻机照明系统模型分别对非共面和共面扫描狭缝在掩模面上的刀口半影进行仿真分析;研制了一种四刀口共面的高精度扫描狭缝装置,不仅满足步进扫描光刻机的同步性能需求,并且有效减小了X向和Y向的刀口半影;最后对所研制的扫描狭缝动态性能以及掩模面上实际刀口半影进行了测试。结果表明,当最大扫描速度达到470mm/s时,扫描刀口动态跟随误差始终在±30μm以内,同时两个方向的刀口半影均不超过0.5mm,满足90nm分辨率步进扫描光刻机的需求。

Scanning slit is an important element for controlling exposure dose in step-and-scan lithography.Too large a penumbra of the blade＇s edge in scanning slit could affect the exposure performance.Firstly,according to the illumination principle of a step-and-scan lithography,the calculation formula of the penumbra of the blade＇s edge at the reticle plane was derived by analyzing the relationship between the intensity distribution of the reticle and the thickness and location of the blades in the scanning slit.The theoretical value of the penumbra of the coplanar and noncoplanar blade＇s edges at the reticle plane was verified using the simulating light model of a 0.75 NA lithography.Secondly,a high-accuracy scanning slit apparatus with four coplanar blades wasdeveloped,which not only meets the synchronization performance requirements of the step-and-scan lithography,but also reduces the penumbra of the blade＇s edges in the Xand Y-direction.Finally,the dynamic performance of the scanning blades and the actual penumbra of the blade＇s edges at the reticle plane were also experimentally tested.The test results indicate that when the scanning speed reaches470 mm/s,the dynamic position error of the blade is within ±30μm and the penumbra of all edges does not exceed 0.5 mm and meets the requirements of the 90 nm step-and-scan lithography.