In-situ and real-time investigation of EUV pellicle mechanical stress within EUV inner pod

EUV pellicle is easily deformed due to its structural weakness, thereby altering its transmission as well as impacting the fabrication yield. We present a novel approach via both a chromatic confocal sensor and a conductance tester to investigate the mechanical properties of pellicle within EUV inner pod during pump/vent operations. A theoretical model addressing the residual stress of pellicle is further applied to explain the intrinsic ASML pellicle deflection of 100 um during vacuum conditions (from 5 to 500 Pa). Together, the proposed approach may enable real-time examination of EUV pellicle mechanics, which should be amenable for worldwide mask cores.