Effect of water vapor pressure on positive and negative tone electron-beam patterning of poly(methyl methacrylate)
Effect of water vapor pressure on positive and negative tone electron-beam patterning of poly(methyl methacrylate)
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DOI：
10.1116/6.0002118
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发表时间：
2023-01
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影响因子：
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通讯作者：
Deepak Kumar;Krishnaroop Chaudhuri;J. Brill;Jonathan T. Pham;J. Hastings
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文献类型：
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作者：
Deepak Kumar;Krishnaroop Chaudhuri;J. Brill;Jonathan T. Pham;J. Hastings
可变压力电子束光刻（VP-EBL）采用低于大气压的环境气体以减少电子束光刻期间的充电。VP-EBL先前已被证明可以消除图案失真，并在绝缘基板上图案化聚（甲基丙烯酸甲酯）（PMMA）时提供更高的分辨率。然而，水蒸气如何影响对比度和清除剂量仍然是未知的，也没有研究过水蒸气对PMMA负性行为的影响。此外，水蒸气最近已被证明会改变Teflon AF的VP-EBL过程的辐射化学。尚未对PMMA探索辐射化学的此类变化。在这项工作中，VP-EBL进行导电基板上的PMMA图案的水蒸气的影响，从电荷耗散的影响分开研究。此外，研究了正性和负性过程，以确定水蒸气对断链和交联的影响。发现PMMA的对比度随着正性和负性图案化的水蒸气压力的增加而显著改善。正性图形的清除剂量随着蒸气压的增加而适度增加，这与气体中电子散射的情况是一样的。然而，负性图案化的起始设定剂量随着压力而显著增加，揭示了曝光机制的更显著变化。X射线光电子能谱和红外透射光谱表明，水蒸气只有轻微改变暴露的PMMA的组合物。此外，电子在水蒸气中的散射产生了一个更大的清晰区域周围的负色调图案。这种效果可能是有用的，用于增加的范围内的开发区域周围的交联PMMA超出背散射电子的范围。因此，用于PMMA的VP-EBL引入了一种调整清除/起始剂量和对比度的新方法，同时允许对负色调图案周围的清除区域的大小进行额外控制。
Variable-pressure electron-beam lithography (VP-EBL) employs an ambient gas at subatmospheric pressures to reduce charging during electron-beam lithography. VP-EBL has been previously shown to eliminate pattern distortion and provide improved resolution when patterning poly(methyl methacrylate) (PMMA) on insulating substrates. However, it remains unknown how water vapor affects the contrast and clearing dose nor has the effect of water vapor on the negative-tone behavior of PMMA been studied. In addition, water vapor has recently been shown to alter the radiation chemistry of the VP-EBL process for Teflon AF. Such changes in radiation chemistry have not been explored for PMMA. In this work, VP-EBL was conducted on conductive substrates to study the effect of water vapor on PMMA patterning separately from the effects of charge dissipation. In addition, both positive and negative-tone processes were studied to determine the effect of water vapor on both chain scission and cross-linking. The contrast of PMMA was found to improve significantly with increasing water vapor pressure for both positive and negative-tone patterning. The clearing dose for positive-tone patterning increases moderately with vapor pressure as would be expected for electron scattering in a gas. However, the onset set dose for negative-tone patterning increased dramatically with pressure revealing a more significant change in the exposure mechanism. X-ray photoelectron spectra and infrared transmission spectra indicate that water vapor only slightly alters the composition of exposed PMMA. Also, electron scattering in water vapor yielded a much larger clear region around negative-tone patterns. This effect could be useful for increasing the range of the developed region around cross-linked PMMA beyond the backscattered electron range. Thus, VP-EBL for PMMA introduces a new means of tuning clearing/onset dose and contrast, while allowing additional control over the size of the cleared region around negative-tone patterns.