Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA.
J Chem Phys. 2010 Jul 28;133(4):044710. doi: 10.1063/1.3457159.
An atomistic, chemically realistic, kinetic Monte Carlo simulator of anisotropic Si(100) etching was developed. Surface silicon atoms were classified on the basis of their local structure, and all atoms of each class were etched with the same rate. A wide variety of morphologies, including rough, striped, and hillocked, was observed. General reactivity trends were correlated with specific morphological features. The production of long rows of unstrained dihydride species, recently observed in NH(4)F (aq) etching of Si(100), could only be explained by the rapid etching of dihydrides that are adjacent to (strained) monohydrides-so-called "alpha-dihydrides." Some etch kinetics promoted the formation of {111}-microfaceted pyramidal hillocks, similar in structure to those observed experimentally during Si(100) etching. Pyramid formation was intrinsic to the etch kinetics. In contrast with previously postulated mechanisms of pyramid formation, no masking agent (e.g., impurity, gas bubble) was required. Pyramid formation was explained in terms of the slow etch rate of the {111} sides, {110} edges, and the dihydride species that terminated the apex of the pyramid. As a result, slow etching of Si(111) surfaces was a necessary, but insufficient, criterion for microfacet formation on Si(100) surfaces.
开发了一种各向异性 Si(100)刻蚀的原子级、化学逼真、动力学蒙特卡罗模拟器。根据局部结构对表面硅原子进行分类，每个类别的所有原子都以相同的速率进行刻蚀。观察到各种形貌，包括粗糙、条纹和隆起。一般反应性趋势与特定的形态特征相关联。最近在 Si(100)的 NH(4)F(aq)刻蚀中观察到的长排未应变二氢化物物种的产生，只能通过快速刻蚀与（应变）单氢化物相邻的二氢化物来解释——所谓的“α-二氢化物”。一些刻蚀动力学促进了{111}-微面金字塔形隆起的形成，其结构类似于在 Si(100)刻蚀过程中实验观察到的那些。金字塔的形成是刻蚀动力学的固有特征。与之前提出的金字塔形成机制不同，不需要掩蔽剂（例如杂质、气泡）。根据金字塔顶点终止的{111}面、{110}边和二氢化物物种的缓慢刻蚀速率，解释了金字塔的形成。因此，Si(111)表面的缓慢刻蚀是 Si(100)表面微面形成的必要但不充分条件。
