State Key Laboratory of Optical Technologies for Microfabrication, Institute of Optics & Electronics, Chinese Academy of Sciences, Chengdu 610209, China.
Opt Lett. 2010 Sep 15;35(18):3132-4. doi: 10.1364/OL.35.003132.
We demonstrate a tilt-modulated phase imaging method to adjust the gap inconsistency for wafer-mask leveling in proximity lithography. Two gratings with close periods are etched on the mask and used as leveling marks. At the illumination of a monochromatic planar wave, the diffracted image of one grating is projected back onto the other one beside it through reflection at the wafer surface. Any wafer-mask tilts in two orthogonal sections are directly modulated into the phase distribution of the interference field and can be directly remedied according to the frequency and angle deviation of the two sets of fringes. Finally, wafer-mask leveling can be achieved at only one spot with preserved accuracy. Computational and experimental results confirm that tilts at the magnitude of 10(-3) rad can be readily resolved by this method.
我们展示了一种倾斜调制相衬成像方法，用于调整接近光刻中晶圆掩模调平的间隙不一致性。掩模上刻蚀了两个具有相近周期的光栅，并用作调平标记。在单色平面波的照射下，一个光栅的衍射图像通过在晶圆表面的反射，被投影回到旁边的另一个光栅上。两个正交方向上的任何晶圆-掩模倾斜都会直接调制到干涉场的相位分布中，并可以根据两组条纹的频率和角度偏差直接进行校正。最后，仅在一个点上就可以实现晶圆-掩模调平，且精度保持不变。计算和实验结果证实，该方法可以轻易地分辨出幅度为 10(-3) rad 的倾斜。
