Investigation of ion transportation in high-aspect-ratio holes from fluorocarbon plasma for SiO₂ etching

We investigated the behavior of ions in deep contact holes under actual dry etching conditions by comparing results between experimental and numerical simulations. In the experiments, we directly measured the ions that penetrated a real-contact-hole-sized (0.2 μm) micro-capillary plate, which was a membrane with many throughholes fabricated on a Si wafer with a structure customized to simulate the actual electric field profiles in the contact holes. As expected, both results suggested that the ion flux and the ion energy were depressed at the bottom surface and strongly depended on the hole aspect ratio. However, we found some differences between the experiments and the calculations. We believe these were caused by variations in the experimental results and by unknown parameters in the calculation model of the ion kinetics in the deep contact holes. Quantitative analysis will be possible in the future after the results conform to each other and the unknown parameters are clarified.