Pattern printability for off-axis incident light in extreme ultraviolet lithography

Off-axis incident light produces shadowing and an imbalance in the diffracted light. Shadowing causes a change in the critical dimension (CD) and a shift in the position of patterns due to the multiple interference of the absorber and buffer layers. In addition, the imbalance in the diffracted light influences the optical proximity-effect correction (OPC) of actual patterns with a process factor k1 below 0.6. In this study, the main factors influencing OPC were investigated. These include asymmetric aberrations and optical proximity effects (OPE) in line patterns. OPC was then applied to a T-shaped pattern. It is found that the mask error factor (MEF) in low-contrast regions of a layout is an important consideration in OPC.