Mechanism and dynamics of the reaction of XeF2 with fluorinated Si(100): Possible role of gas phase dissociation of a surface reaction product in plasmaless etching
Mechanism and dynamics of the reaction of XeF2 with fluorinated Si(100): Possible role of gas phase dissociation of a surface reaction product in plasmaless etching
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DOI：
10.1063/1.3118629
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发表时间：
2009-04-28
影响因子：
4.4
通讯作者：
Ceyer, S. T.
中科院分区：
文献类型：
--
作者：
Hefty, R. C.;Holt, J. R.;Ceyer, S. T.
在150K下观察到二氟化氙单原子和双原子在1ML以上的F覆盖率下与Si-Si sigma-dimer和Si(100)(2)x1的sigma-晶格键反应。在零F覆盖范围的极限下，单原子提取气相产物XEf的一个可测量部分在探测之前被充分的内部激发以解离成F和Xe原子。利用在零覆盖极限下确定的Xe原子内部能量和取向分布，将动量守恒定律、能量守恒定律和质量守恒定律应用于高覆盖下测量的F原子速度和角分布，模拟了高覆盖下Xe原子的速度和角分布及其强度。模拟结果较好地预测了Xe原子在高覆盖度下的速度和角分布，这主要是因为Xe原子的放热系数随着覆盖率的增加而保持不变。这种恒定是在随着覆盖率增加而增加的势能面的吸引力和XEF产品沿势面的动态之间权衡的适当结果。能量、动量和质量守恒分析也被用来区分XeF气相解离产生的Xe原子和双原子抽离产生的Xe原子。这一区别使得能够计算单原子和双原子抽运路径的百分比，以及由双原子抽运、非弹性散射和解吸产生的Xe原子可用的两条路径的百分比。模拟结果表明，XeF气相解离产生的F原子中，有9%~12%的F原子向表面散射。这些氟原子很可能很容易与硅反应，形成更高的氟化物，最终导致蚀刻。表面反应散射产物的气相分解是解释在无等离子体条件下XeF2对硅的独特反应能力的一种新机制。(C)2009年美国物理研究所。[DOI：10.1063/1.3118629]
Xenon difluoride is observed to react with Si-Si sigma-dimer and sigma-lattice bonds of Si(100)(2) x 1 at 150 K by single and two atom abstraction at F coverages above 1 ML. As in the limit of zero F coverage, a measurable fraction of the scattered, gas phase product of single atom abstraction, XeF, is sufficiently internally excited to dissociate into F and Xe atoms before detection. Using the XeF internal energy and orientation distributions determined in the limit of zero coverage, the laws of conservation of momentum, energy, and mass are applied to the measured F velocity and angular distributions at higher coverage to simulate the Xe atom velocity and angular distributions and their intensities at higher coverage. The simulation predicts the observed Xe atom velocity and angular distributions at high coverage reasonably well, largely because the exothermicity channeled to XeF remains approximately constant as the coverage increases. This constancy is an opportune consequence of the trade-off between the attractiveness of the potential energy surface as the coverage is increased and the dynamics of the XeF product along the potential surface. The energy, momentum, and mass conservation analysis is also used to distinguish between Xe atoms that arise from XeF gas phase dissociation and Xe atoms that are produced by two atom abstraction. This distinction enables the calculation of percentages of the single and two atom abstraction pathways, as well as the percentages of the two pathways available to the Xe atom produced by two atom abstraction, inelastic scattering, and desorption. Finally, the simulation reveals that between 9% and 12% of F atoms produced by gas phase dissociation of XeF are scattered back toward the surface. These F atoms likely react readily with Si to form the higher fluorides that ultimately lead to etching. Gas phase dissociation of the scattered product of a surface reaction is a novel mechanism to explain the unique reactivity of XeF2 to etch Si in the absence of a plasma. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3118629]