Investigation of a facile plasma-driven method for in situ cleaning of metal-based contamination

Self-cleaning of tin contaminants was realized utilizing a self-driven hydrogen plasma. Cleaning rates of 0.7–6 nm min^-1 were achieved for removal of discontinuous tin particles at different powers. The analysis of topography and cross-sectional morphology revealed that the removal of tin particles was achieved through top-down cleaning with hydrogen plasma, where the upper part of spherical tin particles was always more intensely cleaned under the synergistic effect of hydrogen atoms and ions due to the vertical incidence of ions to the substrate during the whole cleaning process. Redeposition of tin atoms caused by physical sputtering and its promotion of the chemical cleaning effect was observed for the first time. Reflectance recovery measurements during cleaning and surface analysis of the substrate after cleaning indicated that nondestructive cleaning with a reflectance loss of less than 1% can be achieved at a relatively low power of 120 W. Plasma-induced substrate damage, such as holes and valleys, reduced the reflectance of the substrate when cleaning was performed at a high power greater than 120 W, so this method should only be considered for application under conditions without substrate exposure. This study provides a comprehensive understanding of the removal of discontinuous tin particles using the in situ self-driven plasma cleaning method, and also provides meaningful guidance for the extension of this method in other potential fields of application.