A substrate processing method may include forming a plasma; extracting ions from the plasma and accelerating the ions to have uniform or substantially uniform directivity using a grid system; irradiating the ions at a reflector, wherein the reflector includes a plurality of reflecting plates each having a metal plate and an insulating layer on the metal plate, wherein the reflecting plates are parallel or substantially parallel such that the insulating layers are exposed to the ions; reflecting the ions incident on the reflecting plates away from the insulating layers of the reflecting plates; colliding the ions reflected away from the insulating layers with the metal plates to convert the ions into neutral beams; and irradiating the neutral beams onto a substrate to process the substrate.