接近式光刻对准中的叠栅干涉测角方法

Angular Measurement Using Moire Interferometry for Alignment of Proximity Lithography

干涉测量是众多科学与工程领域广泛采用的精密计量手段。探索了一种方便可控的基于双光栅衍射的叠栅干涉相敏测角方法,可直接用于接近式光刻过程中掩模衬底的倾斜矫正及面内角调节,便于微纳米器件及微光电子系统集成等相关应用。本方法旨在分别利用双光栅多次衍射产生的对称与相似级次,实现(m,-m)级叠栅干涉与(m,0)级叠栅干涉,产生相位与二者相对倾斜角、面内角有关的场分布。分析推导了叠栅干涉测角的基本原理,然后介绍相应的(m,-m)级与(m,0)级干涉测角方案设计。具体而言,二者均类似地根据条纹偏转及频率变化分别以离轴与同轴的方式监测倾斜及面内偏转角度。设计相应的组合光栅标记进行实验验证。实验结果及分析表明,倾斜角与面内角的调节精度分别可达10-3 rad及10-4 rad。

Interferometry is among the widely-used precise metrologies in varieties of science and engineering fields. An easy-to-control moire interferometric angular measurement method based on multi-diffraction of dual gratings is proposed, to facilitate tilt remediation and in-plane angle adjustment between mask and substrate in proximity lithography, as well as related applications in micro/nano devices and micro-optoelectronics system etc. This method aims to take advantages of symmetric and similar orders generated from dual-gratings diffractions to realize the （ m, - m ） and （ m, O） interferometry, in which fields with phase distribution associated with tilt and in- plane angle are formed. The fundmental of presented moire interferometry is derived in detail and related schemes of （ m, -m） and （ m, 0） interferometric measurement are introduced. Specifically, both schemes monitor the tilt and in-plane angle according to the fringe deflection and frequency variation in an on-axis and off-axis manner respectively. Corresponding composite gratings are designed for experimental verification. Experimental and analytical results indicate that the tilt and in-plane angle can be adjusted with an accracy below 10-a rad and 10- 4 rad, respectively.