Effects of flare in extreme ultraviolet lithography: Learning from the engineering test stand

摘要

One of the technical challenges for introducing extreme ultraviolet lithography (13.5 nm) into high volume manufacturing is flare. Flare reduces aerial image contrast and creates critical dimension (CD) variations across the die due to local chrome density dependent flare variations. Therefore, it is important to experimentally characterize flare on a full-field stepper and develop methods to mitigate and compensate for its effects. In this article, the impact of flare on depth of focus and exposure latitude are experimentally quantified using the engineering test stand. In addition, we report a marked increase in line width roughness due to high levels of flare in the optical system. A technique for the extraction of the point spread function due to scatter using density dependent CD data has been demonstrated for more accurate flare variation compensation.