The EUV CNT pellicle: balancing material properties to optimize performance

EUV lithography wafer production has begun and consequently maximizing yield gains importance. One key component to high-yield lithography in manufacturing is using a pellicle to hold particles out of the focal plane and thereby minimize their impact on imaging. Using a pellicle simplifies manufacturing by eliminating wafer inspections that are used to indirectly monitor the presence of printable defects on the mask. The CNT-based pellicle – a membrane consisting of a network of carbon nanotubes – offers the advantage of very high EUV transmission and has demonstrated good durability at high EUV scanner power. Moreover, the microscopic properties of the network can be tuned by modifying several CNT membrane parameters, such as the individual CNT type and diameter, the degree of bundling, the density and the coating. The challenge is balancing these CNT material parameters for optimal performance in the EUV scanner: high transmission, low impact on imaging through scattered light, and low probability for particles to pass. Each of these areas will be addressed along with simulated and experimental data illustrating the value of a CNT-based EUV pellicle solution today and for the future.