Ion Energy And Angular Distributions Manipulated By Pulse Bias In Capacitively Coupled Discharge

Capacitively coupled plasma (CCP) source is one of most important equipment for etching, film deposition and surface modification in semiconductor industry. As the feature size of integrated circuits constantly shrinking, it is a big challenge to accurately control the energy and angle of ions. The device size is smaller, the ion transport situation which affected by the charging effect caused by charge accumulation and space nonuniformity is more serious. In order to keep the advantage of the capacitively coupled discharges (simple device, good uniformity and cheap) and improve the control precision of ion, we propose the method of pulse bias in capacitively coupled discharge.In Chapter2, We use a hybrid model to simulate the characteristics of a pulse sheath in capacitively coupled discharge. The hybrid model includes a fluid model which is used to simulate the characteristics of the collisional sheath, and a Monte-Carlo (MC) method by which the ion energy and ion angular distributions (IEDs and IADs) are calculated. Finally introduces the flow chart about simulation of sheath characteristic and MC method.In Chapter3, The pulse bias sheath is simulated by hybrid model in some discharge parameters. Through analyzing the spatiotemporal variations of sheath potential, ion density, ion angle and ion energy, results show that the sheath potential is influenced by radio frequency (rf) and pulse synchronously, and the pulse has more influence. The distributions of ion density and velocity in the sheath are mainly dominated by the potential distribution, pulse bias can produce a relatively flat ion current.In Chapter4, We study ion transport affected by power parameter, gas pressure and charging effect under the rectangular wave pulse bias. The results show that when we adjust the pulse duty ratio, it can change the height of ion energy peaks; when the pulse amplitude is adjusted, it can effectively change the position of ion energy peaks; the deflection angle of ion is bigger, the height of ion energy peaks is reduced and the width of ion energy peak is broaden, when gas pressure getting big; the net charge density will getting large which influence the IEDs heavily when the duty ratio of pulse increases.In Chapter5, we focus on the charging effect referred in Chapter4, and take the pulse with special voltage waveform for working. The results show that the tailored pulse waveform can effectively decrease the charging effect, and make the peaks of ion energy narrower. In addition, by adjusting the size of tailored waveform amplitude, we can effectively control the peaks’ position; we also can also effectively manipulate the peaks’ height through adjusting the proportion of tailored waveform.