Reducing imaging defects in high-resolution photolithography

Photoresist defects can occur in large, seemingly noncritical features in high-resolution photolithography although it is capable of resolving features of much smaller dimensions. Both optical illumination and wafer topography may contribute to the formation of resist defects in large features. This letter examines optical simulations to uncover the specific nature of these resist defects and proposes local correction methods to improve the photolithographic process. For example, adding a back-etched phase feature in the center of a large isolated trench feature reduces the illumination-responsible resist scumming effect, and optimizing the multilayered film stack can eliminate the resist defect when printing a large contact feature on the structured wafer substrate.