超大数值孔径光刻中的负显影模型研究

Negative tone development (NTD) has received great attentions as a patterning technology for line space and contact patterns with small pitches, due to it has higher image contrast, smaller line edge roughness and larger process window. Traditional NTD physical modelspredict the resist profilewith single paramenter optimization, its accuracy cannot meet the requirements of lithography beyond 14nm node. In order to address the above mentioned problem, this proposal aims to establish a physical model with high accuracy for NTD process. The effect of resist volume shrinkage after NTD process is firstly investigated from the perspective of theoretical analysis and experimental data. This research proposal also investigates the effect of post-development profile (critical dimension, sidewall angle, height) by modulations and working functions of pattern dimension, optical parameters (such as dose and off-center focus), process parameters (post-exposure baking time and baking temperature). The impacts of variousparameters, including pattern dimension, optical parameters, process parameters, on the resist profile are considered in the proposed NTD model. The accuracy and precision of NTD model is confirmed by the means of rigorous simulation and experimental data. In addition, the combinations of pattern dimension, optical parameters, process parameters to grantee the best resist profile after NTD process can be acquired by using the proposed NTD model and optimization algorithms. This research proposal has significant instructive value on further improvment of the accuracy of rigorous lithography simulation, source-mask optimization and optical proximity correction, as well the development of industrialized process recipe.

基于更高的图形对比度、更小的边缘粗糙度、更大的工艺窗口等优点，负显影工艺被广泛应用于小尺寸金属层和通孔层的制备中。现有负显影工艺的物理模型只能体现单个参数对光刻胶显影后形貌的影响，其精度尚不能用于负显影工艺中光刻胶形貌的准确预测。为解决这一问题，本课题以建立高精度的负显影物理模型为目标，利用理论分析和片上实验相结合的手段研究光刻胶负显影工艺中体积收缩效应，揭示图形尺寸、光学参数（曝光剂量、离焦量）、工艺参数（后烘时间和温度）对光刻胶负显影后的形貌（特征尺寸、侧壁角、高度）的调制机理，建立表征图形尺寸、光学参数、工艺参数等多个参数对光刻影响的负显影物理模型，通过开展计算机仿真实验和片上实验验证负显影模型的精度与准确性，结合负显影模型和优化算法，确定图形尺寸、光学参数、工艺参数的最佳组合。本课题的开展对进一步提高光刻仿真的精度，以及产业化工艺菜单的研制具有重要的指导意义。

负显影工艺与亮场掩模结合可以提高光刻曝光的图形对比度和工艺窗口，已被用于集成电路制造先进技术节点小尺寸金属层的制造中。针对模拟负显影工艺的光刻胶物理模型尚不完善、物理模型的校准需要多参数优化方法等问题，本课题从光学模型、光刻胶物理模型、模型校准方法、多参数优化方法与应用等方面开展研究内容，取得以下研究成果：在光学模型和光刻胶物理模型方面，课题深入研究了光刻系统光学成像的原理，以及光刻胶曝光、烘烤及显影工艺的原理，提出了基于切比雪夫谱方法和弦模型的光刻胶物理模型；在模型校准方面，课题在光刻胶物理模型基础上，以集成电路金属层的典型线条结构为研究对象，课题详细分析了光刻胶物理模型中各参数对光刻胶最终显影形貌的影响及敏感度分布，基于敏感度分布函数，课题建立了光刻胶物理模型校准流程和方法，并开发了模型校准工具，该方法和工具的适用性和有效性通过实验数据得到了验证，针对典型结构，校准后模型的预测精度可以达到90%以上；在多参数优化方法与应用方面，课题基于光刻胶显影模型校准过程中建立的优化方法，对光刻技术相关的光源参数优化、三维掩模衍射近场的快速分析、投影物镜像差分析及指标分解等优化问题进行了研究和探讨。研究结果表明，通过使用多参数优化方法，可以极大提升光刻工艺参数和投影物镜像差的优化效率。本项目研究成果可以为国产光刻工艺研发和光刻胶研发过程中的工艺参数、光刻胶参数的优化提供理论依据和参考。