Kim Yongwoo, Jung Howon, Kim Seok, Jang Jinhee, Lee Jae Yong, Hahn Jae W
Nano Photonics Laboratory, School of Mechanical Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul, 120-749, Korea.
Opt Express. 2011 Sep 26;19(20):19296-309. doi: 10.1364/OE.19.019296.
In nanolithography using optical near-field sources to push the critical dimension below the diffraction limit, optimization of process parameters is of utmost importance. Herein we present a simple analytic model to predict photoresist profiles with a localized evanescent exposure that decays exponentially in a photoresist of finite contrast. We introduce the concept of nominal developing thickness (NDT) to determine the proper developing process that yields the best topography of the exposure profile fitting to the isointensity contour. Based on this model, we experimentally investigated the NDT and obtained exposure profiles produced by the near-field distribution of a bowtie-shaped nanoaperture. The profiles were properly fit to the calculated results obtained by the finite differential time domain method. Using the threshold exposure dose of a photoresist, we can determine the absolute intensity of the intensity distribution of the near field and analyze the difference in decay rates of the near field distributions obtained via experiment and calculation. For maximum depth of 41 nm, we estimate the uncertainties in the measurements of profile and intensity to be less than 6% and about 1%, respectively. We expect this method will be useful in detecting the absolute value of the near-field distribution produced by nano-scale devices.
在利用光学近场源将关键尺寸推至衍射极限以下的纳米光刻技术中，工艺参数的优化至关重要。在此，我们提出一个简单的解析模型，用于预测在具有有限对比度的光刻胶中，随局域倏逝曝光呈指数衰减的光刻胶轮廓。我们引入标称显影厚度（NDT）的概念，以确定能产生与等强度轮廓拟合最佳的曝光轮廓形貌的合适显影工艺。基于该模型，我们通过实验研究了NDT，并获得了由蝴蝶结形纳米孔径的近场分布产生的曝光轮廓图。这些轮廓图与通过时域有限差分法得到的计算结果拟合良好。利用光刻胶的阈值曝光剂量，我们可以确定近场强度分布的绝对强度，并分析通过实验和计算获得的近场分布衰减率的差异。对于最大深度为41nm的情况，我们估计轮廓和强度测量的不确定度分别小于6%和约1%。我们预计该方法将有助于检测纳米级器件产生的近场分布的绝对值。
