CNT pellicles: Imaging results of the first full-field EUV exposures

Abstract

EUV lithography has recently been implemented in high volume wafer production. Consequently, maximizing yield is gaining 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 Nano Tube (CNT) pellicle is a membrane consisting of a network of carbon nanotubes, and demonstrated 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, low impact on imaging through scattered light, high durability in the scanner environment, while maintaining high transmission. We report results of the first full-field CNT pellicle exposures on an NXE EUV scanner. We demonstrate handling of the pellicles on the scanner, without breakage, and provides a first assessment of their imaging behavior. Multiple single- and double-walled uncoated CNT pellicles with EUV transmission up to 97.7% were exposed on the NXE scanner at imec, and minimal impact on the imaging is confirmed. In these exposures, uncoated CNT pellicles were used which will not meet the specifications regarding lifetime. Therefore, current ongoing developments focus on CNT coating and durability in scanner environment. The presented demonstration proves the value of a CNT-based EUV pellicle solution.