Helmar Van Santen

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.

Liquid Immersion Deep-UV Optical Disc Mastering for Blu-ray Disc Read-Only Memory

The liquid immersion mastering technique has been successfully applied to the mastering of read-only memory (ROM) discs for the Blu-ray disc (BD) system. Replicated discs with a density corresponding to 25 GB in a single layer on a 12 cm disc showed a bottom jitter of less than 5%. Results concerning process latitude and disc uniformity are presented. A full-format 25 GB ROM disc containing over 2 h of high-definition video content has been mastered according to the BD target specification. The results obtained for a reduced channel bit length show the potential of liquid immersion mastering for densities beyond 31 GB per layer.

Deep-UV liquid immersion mastering of high-density optical discs

A water 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 developed system is capable of performing point exposures on a rotating disc at scanning velocities of more than 5 m/s. Gas inclusion in the immersion liquid, either from the photo-resist or through the dynamic movement of the substrate could be avoided. Furthermore, unwanted mechanical disturbances were sufficiently suppressed. Contamination of the photo-resist was avoided through careful handling of the water that was applied as immersion liquid. The resulting resolution enhancement was demonstrated in grooves. In 25 nm Novolac type resist, 70 nm wide grooves were written with liquid immersion, compared to 100 nm wide grooves at NA = 0.9. Liquid immersion was also successfully applied to write the master substrate from which a ROM disc can be made through injection molding. ROM discs for the recently launched Blu-ray Disc system have been successfully written with a density corresponding to 25 GB in a single layer of a 12 cm disc.