Damage Free Particle Removal from EUVL Mask Layers by High Energy Laser Shock Cleaning (LSC)

The paper deals about the method of small particle removal based on laser induced plasma (LIP) shock wave has been recently applied to clean wafers and masks in semiconductor processes. The silica particles of 50 nm removed from EUVL mask layers by high energy LSC without surface damage by controlling the gap distance. High temperature of plasma plume by the focused laser beam caused the surface damage. It is important not only to increase the laser energy to remove small particles, but also to control the gap distance to avoid the surface damage.