An apparatus includes a wafer stage and a particle removing assembly. The wafer stage includes a cup adjacent to a wafer chuck. The particle removing assembly is configured to remove contaminant particles from the cup. In some embodiments, the particle removing assembly comprises a flexible ejecting member that includes one or more elongated tubes, a front tip, and a cleaning tip adapter configured to attach the front tip to each of the one or more elongated tubes. The front tip includes front openings and lateral openings from which pressurized cleaning material are introduced onto an unreachable area of the cup to remove the contaminant particles from the cup.