Assessment for introduction of immersion lithography into volume manufacturing has recently started, where one of the key focus areas includes defectivity. Particularly, the possible presence of bubbles in the immersion liquid could act as a defect source. The impact of bubbles strongly depends on their size and distance from the resist. This paper shows that a thick topcoat acts as a pellicle and suppresses the printability of the bubbles. A 1.5 μm thick topcoat has been developed especially for this purpose. A model experiment has been set to validate this approach and leads to a conclusion on the printability of defects depending on their size and distance from the resist. Both simulation and results from the model experiment are shown. In addition, a new method to detect very small bubbles will be introduced.