A Study of the Particle Transport and Surface Reactions in Microstructures on Substrates during Plasma Processing

点击翻译按钮获取中文摘要

An understanding of the particle transport and surface reactions in microstructures on substrates are indispensable for the control of advanced plasma processing for the fabrication of sub-0.1 μm devices. We have developed an atomic scale model of the particle transport and surface reactions, to simulate the feature profile evolution for nanometer-scale control of the profile and critical dimensions during plasma etching. The model is a phenomenological one at an intermediate scale between molecular dynamics simulation and continuum models. The model takes into account the transport of ions and neutrals in microstructures, multilayer surface reactions through ion-enhanced etching, and the resulting feature profile evolution, where the transport is analyzed by a particle simulation based on successively injected single-particle trajectories with three velocity components. To incorporate an atomistic picture into the model, the substrates are taken to consist of a large number of small c … More ells or lattices in the entire computational domain of interest, and the evolving interfaces are modeled by using the cell removal method ; the substrate atoms are allocated in the respective square lattices of atomic scale. Moreover, the Monte Carlo calculation is employed for the trajectory of incident energetic ions that penetrate into substrates. The present model has a prominent feature to phenomenologically simulate the multilayer surface reaction, the surface roughness, and also the feature profile evolution during etching. The etching of planar Si substrates with chlorine chemistries was simulated for a test of validity of the present model, showing the structure of surface reaction layers, the distribution of Cl atoms therein, and the surface roughness that depend on incident neutral-to-ion flux ratio and ion energy. The etch yield as a function of neutral-to-ion flux ratio for different ion energies gave a similar tendency to the known experimental data, indicating that the present model properly reflects synergistic effects between neutral reactants and energetic ions in the ion-enhanced etching.The feature profile evolution during etching was then simulated for sub-0.1 μm line-and-space patterns of Si, taking into account also the effects of chemical etching, passivation layer formation (surface oxidation and inhibitor deposition), and surface charging. The numerical results exhibited the reactive ion etching (RIE) lag that occurs depending on neutral-to-ion flux ratio and ion energy, being compared with the experiments of etching and plasma and surface diagnostics. The degree of RIE lag was found to be more significant at higher flux ratios and higher energies, being associated with the difference in surface chlorination at the feature bottom ; in effect, for narrow pattern features of the order of sub-0.1 μm, the bottom surfaces tend to intrinsically starve for neutral reactants owing to severe effects of the geometrical shadowing. Moreover, based on these results, we developed the fabrication processes for advanced gate etch processes of new gate dielectric and electrode materials. Less