Sub-pixel alignment for direct-write electron beam lithography
Sub-pixel alignment for direct-write electron beam lithography
复制标题
DOI：
10.1016/j.mee.2004.02.019
复制
发表时间：
2004-06-01
影响因子：
2.3
通讯作者：
Liddle, JA
中科院分区：
文献类型：
--
作者：
Anderson, EH;Ha, D;Liddle, JA
我们开发了一种新颖的亚像素对齐算法，该算法基于计算对齐标记模板的自相关与模板与成像标记的互相关的拟合的残差值的 3 x 3 阵列。然后通过二阶多项式拟合残差阵列，并且根据多项式分析确定具有最小残差的位置——最佳对准位置。该方法自然地在对准标记的离散像素和模板图像之间进行插值。该方法非常稳健，可以在信噪比低至 -4 dB 的情况下有效使用。通过适当选择标记材料可以增强其性能，Au 标记的信噪比为 0.48 dB，达到两倍。使用 5 nm Cr/50 nm 获得 +/-2 nm 的对准重复性。 Au 标记具有 5 nm 像素。使用 10 nm 像素，Au/Cr 标记可实现 4.3 nm、3sigma 的精度，而 360 nm Si 形貌可通过 100 nm 抗蚀剂涂层实现 14.8 nm、3sigma 或 19.7 nm、3sigma 的重复性。该技术被用于使用两次对准曝光来制造波带片。观察到重叠值优于 5 nm。 (C) 2004 Elsevier B.V. 保留所有权利。
We have developed a novel, sub-pixel alignment algorithm based on calculating a 3 x 3 array of residual values of the fit of an auto-correlation of an alignment mark template with the cross-correlation of the template with an imaged mark. The residual array is then fit by a second order polynomial, and the location having the minimum residual - the optimum alignment location - is determined analytically from the polynomial. This method naturally interpolates between the discrete pixels of the alignment mark and template images. The method is robust and can be used effectively with signal-to-noise ratios as low as -4 dB. Its performance is enhanced by appropriate choice of mark material, with Au marks with a signal-to-noise ratio of 0.48 dB yielding a factor of two. Alignment repeatabilities of +/-2 nm were obtained using 5 nm Cr/50 nm. Au marks with a 5 nm pixel. Using a 10 nm pixel, accuracies of 4.3 nm, 3sigma were achieved with Au/Cr marks while 360 nm of Si topography yielded repeatabilities of 14.8 nm, 3sigma or 19.7 nm, 3sigma with a 100 nm resist coating. The technique was employed in the fabrication of a zone plate using two aligned exposures. Overlay values better than 5 nm were observed. (C) 2004 Elsevier B.V. All rights reserved.