Portable Conformable Mask-A Hybrid Near-Ultraviolet And Deep-Ultraviolet Patterning Technique

Abstract

Deep-UV conformable printing offers the capability of delineating submicrometer features with high aspect ratios. The profile of the resist image can easily be manipulated from overcut to vertical and undercut. However, making intimate contact between the mask and the wafer potentially induces defects. On the other hand, near-UV optical projection printing can be defect-free but cannot achieve a high aspect ratio in the photoresist image. In this paper a double layer resist system is used to combine the advantages of the two printing methods while eliminating the shortcomings. A thin AZ layer is spun on a thick PMMA layer. The AZ1350J layer is conventionally deliniated with a near-UV mask aligner. Because AZ1350J is opaque to deep-UV radiation, it acts as a built in conformable mask which can be carried with the wafer to a deep-UV blanket-exposure station to delineate the PMMA layer.