[论文解读] Lithographic performance of ZEP520A and mr-PosEBR resists exposed by electron beam and extreme ultraviolet lithography

Roberto Fallica, Dimitrios Kazazis+5 more|arXiv (Cornell University)|Jan 1, 2017

Advancements in Photolithography Techniques参考文献 32被引用 25

一句话总结

本研究评估了原本专为电子束光刻（EBL）设计的ZEP520A和mr-PosEBR抗蚀剂在极紫外（EUV）光刻中的光刻性能。这两种抗蚀剂均表现出高灵敏度（最小曝光剂量 <12 mJ/cm²），可实现25 nm半节距线条/槽结构的高分辨率图案化，且线边缘粗糙度较低（<6 nm），同时保持优异的刻蚀选择性，表明成熟的EBL工艺可直接延伸至EUV光刻，实现高分辨率、大面积纳米加工，且图案质量与良率俱佳。

ABSTRACT

Pattern transfer by deep anisotropic etch is a well-established technique for fabrication of nanoscale devices and structures. For this technique to be effective, the resist material plays a key role and must have high resolution, reasonable sensitivity and high etch selectivity against the conventional silicon substrate or underlayer film. In this work, the lithographic performance of two high etch resistance materials was evaluated: ZEP520A (Nippon Zeon Co.) and mr-PosEBR (micro resist technology GmbH). Both materials are positive tone, polymer-based and non-chemically amplified resists. Two exposure techniques were used: electron beam lithography (EBL) and extreme ultraviolet (EUV) lithography. These resists were originally designed for EBL patterning, where high quality patterning at sub-100 nm resolution was previously demonstrated. In the scope of this work, we also aim to validate their extendibility to EUV for high resolution and large area patterning. To this purpose, the same EBL process conditions were employed at EUV. The figures of merit, i.e. dose to clear, dose to size, and resolution, were extracted and these results are discussed systematically. It was found that both materials are very fast at EUV (dose to clear lower than 12 mJ/cm2) and are capable of resolving dense lines/space arrays with a resolution of 25 nm half-pitch. The quality of patterns was also very good and the sidewall roughness was below 6 nm. Interestingly, the general-purpose process used for EBL can be extended straightforwardly to EUV lithography with comparable high quality and yield. Our findings open new possibilities for lithographers who wish to devise novel fabrication schemes exploiting EUV for fabrication of nanostructures by deep etch pattern transfer.

研究动机与目标

• 评估非化学放大型抗蚀剂ZEP520A和mr-PosEBR在极紫外（EUV）光刻中的可行性。
• 在相同工艺条件下，比较EBL与EUV-IL中两种抗蚀剂的光刻性能——包括灵敏度、分辨率和图案质量。
• 将最小曝光剂量、最小尺寸剂量和线边缘粗糙度（LER）作为EUV与EBL曝光的关键性能指标。
• 确定通用型EBL工艺配方是否可直接迁移至EUV光刻，实现相似的高质量图案化。
• 探索这些抗蚀剂在纳米加工中用于混合-匹配 EUV-EBL 工艺的潜力。

提出的方法

• 使用EBL（Vistec EBPG 5000 Plus）和EUV-IL（ASML TWINSCAN NXE:3300）设备，在相同工艺条件下对两种抗蚀剂进行处理。
• 采用EBL和EUV-IL在50 nm、25 nm和22 nm半节距下分别图案化密集的线条/槽阵列。
• 通过CD随剂量变化的对比曲线测量最小曝光剂量和最小尺寸剂量。
• 利用扫描电子显微镜（SEM）计量技术，对不同曝光剂量下的线条/槽阵列测量线边缘粗糙度（LER）。
• 通过归一化图像对数斜率（NILS）比较潜像质量，同时考虑EBL中的束斑步进效应和EUV-IL中的单束相干性。
• 使用PMMA作为参考抗蚀剂，用于对比灵敏度和性能表现。

实验结果

研究问题

• RQ1 原本为EBL开发的ZEP520A和mr-PosEBR抗蚀剂，能否在EUV光刻中实现与EBL相当的性能表现？
• RQ2 与EBL相比，这些抗蚀剂在EUV曝光下的灵敏度（最小曝光剂量和最小尺寸剂量）如何？
• RQ3 在高分辨率线条/槽图案中，这些抗蚀剂在EBL与EUV-IL中的线边缘粗糙度（LER）表现如何比较？
• RQ4 潜像质量（NILS）在EBL与EUV-IL中对LER的影响程度如何？
• RQ5 标准EBL工艺配方是否可直接迁移至EUV光刻，而无需优化即可实现高分辨率图案化？

主要发现

• ZEP520A和mr-PosEBR在EUV下均表现出高灵敏度，最小曝光剂量低于12 mJ/cm²，显著优于PMMA。
• 在EUV-IL下，25 nm半节距线条/槽的最小尺寸剂量分别为79.2 mJ/cm²（ZEP520A）和88.7 mJ/cm²（mr-PosEBR）。
• 实现的最小线边缘粗糙度（LER）为：ZEP520A为1.5 nm，mr-PosEBR为4 nm，均在各自对应的最小尺寸剂量下达到。
• 在EBL中，ZEP520A的LER为2 nm，低于mr-PosEBR的6 nm，表明在束斑步进条件下，ZEP520A具有更优的图案保真度。
• 对于两种抗蚀剂，EUV-IL中的LER始终低于EBL，归因于EUV中更高的NILS和更低的散粒噪声。
• 本研究证实，通用型EBL工艺配方可直接扩展至EUV-IL，实现与EBL相当的高分辨率图案化，且具有优异的良率和质量。