EUV lithography has been implemented in high volume wafer production. Consequently, maximizing yield is of major importance. One key component to achieve optimal yield is using a pellicle to hold particles out of the focal plane and thereby minimize the printing of defects. The carbon nanotube (CNT) pellicle is a membrane consisting of a network of carbon nanotubes, which demonstrates EUV transmission up to 98%. The challenge is to balance the CNT material parameters for optimal performance in the EUV scanner: low probability for particles to pass, high durability in the scanner environment, while maintaining high transmission and low impact on imaging. While our earlier reporting on full-field CNT pellicle exposures demonstrated minimal impact on imaging, the focus of the current paper is on extended exposures on NXE:3400. In the scanner, the EUV light induces a hydrogen plasma that etches the CNTs, resulting in decreasing membrane density and increasing EUV transmission. In this work, we quantify the CNT pellicle etch rate in a real scanner environment and correlate the findings to those obtained in an offline test setup. Our exposures were performed using two different pellicles, with EUV transmission of 89% and 95%, for up to 3000 wafers. Additionally, we demonstrated the effectiveness of pellicle purification prior to mounting on the reticle, which is important to avoid contamination from the as-fabricated CNT pellicle onto the reticle surface. Current ongoing developments focus on further increasing the pellicle durability in the scanner environment. The presented results demonstrate the potential of a CNT-based pellicle at high EUV powers.
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