Resist evaluation at 50 nm in the EUV using interferometric spatial frequency doubled imaging

摘要

By using a spatial frequency doubling method, our 10x Schwarzschild optic can print high-contrast features at 50 nm with low line-edge roughness (LER). In this paper, we also present new techniques for evaluating photoresists at EUV wavelengths using our system. One method is used to determine the ultimate resolution of a resist through linewidth vs. dose measurements. Another is to investigate line-edge roughness properties by varying the aerial image contrast of a pattern. A novel filtering method is proposed that would allow multiple contrasts to be printed in a single exposure. This is achieved by varying the duty cycle and line/space transmission levels of the object grating. Since this is a single exposure technique it would allow for more controlled contrast tests when evaluating resists.