Multiple CNT-based pellicles were mounted on reticles and exposed in the NXE:3300 EUV scanner at imec, demonstrating the successful fabrication and scanner handling of full-field CNT-based pellicles. The tested pellicles had a single-pass EUV transmission up to 97%. The impact on imaging was found to be low and correctable based on critical dimension (CD), dose, and transmission measurements.
A pellicle is a membrane used to protect the photomask from contamination during high-volume semiconductor manufacturing and is mounted a few millimeters above the surface of the photomask so that if particles land on the pellicle, they will be too far out of focus to print. Developing an EUV pellicle is very challenging, since 13.5nm light is absorbed by most materials. In addition, stringent thermal, chemical, and mechanical requirements must be achieved. Such highly transparent pellicle is critical to enable high yield and throughput in advanced semiconductor manufacturing.
“Imec has leveraged partners in the semiconductor industry, materials companies and fundamental research to develop an innovative EUV pellicle design with potential to survive scanner powers beyond 600W,” said Emily Gallagher, principal member of technical staff at imec. “We have seen tremendous progress in carbon nanotube membrane development in the past year and, based on strong collaborations with our partners, are confident it will result in a high-performance pellicle solution in the near future.”
CNTs are one-atom-thick carbon sheets rolled into tubes. The CNTs can be single-, double- or multi-walled and can vary in diameter and in length. These engineered CNTs can be arranged in different configurations to form membranes of different densities.
Since 2015, imec has been working with selected CNT suppliers (Canatu Oy and Lintec of America, Nano-Science & Technology Center) to develop membranes that meet the EUV pellicle targets for properties like transmittance, thermal durability, permeability, and strength and to enable the imaging results reported today. Future work will focus on achieving acceptable lifetimes for high volume manufacturing of these pellicles in scanners.
