Deep-UV Liquid Immersion Mastering of High Density Optical Discs

A liquid immersion technique has been developed to increase the numerical aperture (NA) of a 257 nm optical disc mastering system from 0.9 to 1.2. The resolution enhancement was demonstrated in grooves. In 25 nm resist, 70 nm wide grooves were written with liquid immersion, compared to 100 nm wide grooves far-field. Liquid immersion was also successfully applied to mastering of read-only-memory (ROM) discs for the Blu-ray Disc system. Replicated discs with a density corresponding to 25 GB in a single layer on a 12 cm disc at a track pitch of 320 nm showed a jitter of 6.9% with limit equalizer.