Li Nianhua, Wu Wei, Chou Stephen Y
NanoStructure Laboratory, Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA.
Nano Lett. 2006 Nov;6(11):2626-9. doi: 10.1021/nl0603395.
Accurate multi-level overlay capability for nanoimprint lithography (NIL) is essential to integrated circuit manufacturing and other multilayer imprint applications. Using the "beat" grating image (Moiré fringe) generated by overlaying two sets of gratings that have slightly different periods, we obtained an alignment signal with a sensitivity better than 10 nm in nanoimprint lithography. The alignment signal is, as expected, independent of the size of the gap between the wafer and the imprint mold. We achieved a single-point overlay accuracy (error distribution) of sub-20 nm between the first and second imprinted layers by using two sets of Moiré fringes. With higher precision nanopositioning stages, better single-point alignment accuracy is expected. Furthermore, we achieved sub-150 nm alignment over an area of 1 sq in and sub-250 nm over the entire area of a 4 in wafer using simple low-resolution stages without temperature control or wafer-mold mismatch compensation. With better stages, precision temperature control, and wafer-mold mismatch compensation, we believe that much higher overlay alignment accuracy over large areas (either in a 1 sq in die or a full wafer) is feasible.
纳米压印光刻（NIL）精确的多层覆盖能力对于集成电路制造及其他多层压印应用至关重要。通过叠加两组周期略有不同的光栅所产生的“拍”光栅图像（莫尔条纹），我们在纳米压印光刻中获得了灵敏度优于10纳米的对准信号。正如预期的那样，该对准信号与晶圆和压印模具之间间隙的大小无关。通过使用两组莫尔条纹，我们在第一和第二压印层之间实现了低于20纳米的单点覆盖精度（误差分布）。使用更高精度的纳米定位台，有望实现更好的单点对准精度。此外，我们使用简单的低分辨率台，在无温度控制或晶圆 - 模具失配补偿的情况下，在1平方英寸的区域内实现了低于150纳米的对准，在4英寸晶圆的整个区域内实现了低于250纳米的对准。借助更好的台、精确的温度控制和晶圆 - 模具失配补偿，我们相信在大面积（无论是1平方英寸的芯片还是整个晶圆）上实现更高的覆盖对准精度是可行的。
