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.

中文翻译：

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水蒸气压力对聚（甲基丙烯酸甲酯）正负色调电子束图案化的影响

可变压力电子束光刻 (VP-EBL) 使用低于大气压的环境气体来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未知，也没有研究水蒸气对 PMMA 负色调行为的影响。此外，最近已证明水蒸气会改变特氟龙 AF 的 VP-EBL 工艺的辐射化学。尚未针对 PMMA 探索辐射化学的此类变化。在这项工作中，VP-EBL 在导电基板上进行，以研究水蒸气对 PMMA 图案化的影响，与电荷耗散的影响分开。此外，研究了正色调和负色调过程以确定水蒸气对断链和交联的影响。发现 PMMA 的对比度随着正色调和负色调图案的水蒸气压力的增加而显着提高。正如气体中电子散射所预期的那样，正色调图案化的清除剂量会随着蒸气压的增加而适度增加。然而，随着压力的增加，负性图案的起始设定剂量显着增加，这表明曝光机制发生了更显着的变化。X 射线光电子能谱和红外透射光谱表明，水蒸气只会轻微改变暴露的 PMMA 的成分。此外，水蒸气中的电子散射在负色调图案周围产生了更大的清晰区域。这种效应可用于增加交联 PMMA 周围发达区域的范围，使其超出背散射电子范围。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清除区域的大小进行额外控制。