Infinite selectivity in dry etching process for high-aspect-ratio hole using C7HF7 gas plasma

In the high-aspect-ratio hole etching process, there is a strong need for high selectivity of SiO2 and SiN films against the amorphous carbon mask. To meet this demand, we conducted research on the selective deposition on the top of the mask. By exclusively depositing a fluorocarbon polymer film on the mask’s top surface using a mixture of 2,3,5,6-tetrafluorobenzotrifluoride (C7HF7) and C3HF5 gas plasma, we achieved infinite selectivity. This area-selective deposition ensures the durability of the mask without clogging the hole patterns, resulting in a high-performance etching process with possible lowest mask height.