F等离子体刻蚀Si中Lag效应的分子动力学模拟

通过分子动力学模拟的方法对感应耦合等离子体刻蚀中Lag效应的产生机理进行了研究. 研究结果表明，在刻蚀过程中普遍存在Lag效应，宽槽的刻蚀率明显比窄槽的刻蚀率要高，这是由于宽槽更有利于产物从槽中的逸出；窄槽中产物从槽中逸出的速率较低，较多的产物拥挤在窄槽中降低了入射的F等离子体入射的速度，从而降低了F等离子体到达Si表面的能量，而相同条件下，刻蚀率随能量的降低而降低；另一方面，窄槽中入射的等离子体与槽壁的距离较近，使得入射的F更容易与槽壁表面的Si的悬挂键结合沉积在槽壁表面，使刻蚀出的槽宽度变窄，进一步影响到后继粒子的入射；Lag 效应随槽宽的减小而增强，随温度的升高而减弱，随入射粒子能量的升高而增强. 关键词： 分子动力学 Lag效应 刻蚀 刻蚀率

Molecular dynamics simulation of Lag effect in fluorine plasma etching Si

We present a simulation model of fluorine plasma etching of silicon. A mechanism for lag effect in the silicon surface etched by an inductively coupled plasma is investigated using molecular dynamics simulation. The results show that the lag effect is popular in etching process and that the etching rate of wide grooves is higher than that of the narrow ones. A probable reason is that the wide groove is produced more easily than the narrow groove. And the escape rate of product in narrow groove is lower than in wide groove. This is because a lot of products huddle together in the groove, which causes the speed of incident ions to decrease, and thus the energy of ions reaching the surface is reduced. The etching rate increases with the decrease of energy under otherwise identical conditions. On the other hand, the incident F particles are more close to the sidewall, which leads to the fact that the incident F particles will be easier to deposit on the surface of the wall. Then the width of the groove becomes narrower and narrower. The subsequent incident particles will be more difficult to reach the bottom of the groove. The lag effect increases not only with the decrease of the width of the groove but also with the enhancement of energy, and it decreases with temperature rising.
Keywords： molecular dynamics Lag effect etching etching rate