Laser Cleaning of Nano- and Microcontaminants From Critical Silicon Surfaces

Sub-micrometer (0.1-1 μm) polystyrene and alumina particles were removed by single-shot pulsed laser radiation from Si wafer surfaces with or without pre-deposited thin liquid layers. Nearly complete (>90%) single-shot laser cleaning has been achieved in combinations of polystyrene and alumina particles with 2-propanol and water, respectively, while for other combinations cleaning was absent or incomplete. Optical microscopy has revealed important transient microscopic interactions between particles and Si substrates in the pre-deposited micron-thick liquid layers, resulting in some cases in strongly reduced particle-substrate coupling. Visualization results give insight into particle removal mechanisms relevant to our laser cleaning experimental conditions.