Carbon nanotube pellicles: imaging results of the first full-field extreme ultraviolet exposures

Extreme ultraviolet (EUV) lithography was recently implemented in high-volume wafer production. Consequently, maximizing yield is gaining importance. One key component to achieving optimal yield is using a pellicle to hold particles out of the focal plane and thereby minimizing the printing of defects. The carbon nanotube (CNT) pellicle is a membrane consisting of a network of CNTs with a demonstrated EUV transmission (EUV-T) of up to 98%. The challenge is balancing the CNT material parameters for optimal performance in the EUV scanner: low probability for particles to pass, low impact on imaging through scattered light, and high durability in the scanner environment, while maintaining high transmission. We report results of the first full-field CNT pellicle exposures on an EUV scanner. We demonstrate handling of the pellicles, without breakage, and provide a first assessment of their imaging behavior. Multiple single- and double-walled uncoated CNT pellicles with EUV-T of up to 97.7% were exposed on the EUV scanner at imec, and minimal impact on the imaging was confirmed. In these exposures, uncoated CNT pellicles that do not yet meet the specifications regarding lifetime were used. Therefore, ongoing developments focus on CNT durability in scanner environments. The presented demonstration proves the value of a CNT-based EUV pellicle solution.