Morio Tomiyama

TeOX-Based Film for Heat-Mode Inorganic Photoresist Mastering

A TeOX-based inorganic photoresist was developed for mastering utilizing heat-mode recording. We discovered that the novel organic thermal isolation film markedly improved the patterning resolution of phase change mastering. We demonstrated Blu-ray Disc read only memory (ROM) mastering with a blue laser diode, using the TeOX-based photoresist and the thermal isolation film. The jitter values of a replicated disc were less than 6% at the full range of the disc. It was also proven that the mastering system is capable of recording 80 nm L/S. In addition, the mechanism of development was clarified.

Quadruple-Layer Write-Once Disk for Blue Laser Based on Te–O–Pd Recording Films

The excellent performance of a 100-GB-capacity write-once disk was demonstrated. The disk has quadruple recording layers, i.e., Layer 3, 2, 1, and 0 (from the laser-incident side of the disk) based on the 4× Blu-ray disc (BD) format. Each layer is provided with a phase-change type memory film of Te–O–Pd, whose thickness was 20 nm for Layer 0, and only 6 nm for Layers 1, 2, and 3 in order to obtain high transmissivity. Additionally, for Layers 2 and 3, a metallic reflection layer was not needed and an AlN film with high thermal conductivity was formed next to each recording film. The AlN film suppressed the heat-induced damage of thin recording films. Consequently, the high transmissivities of 64% (Layer 1), 75% (Layer 2), and 81% (Layer 3) were achieved so that a quadruple layer disk with high quality was realized. The experimental disk showed tolerance to a wide range of writing speeds from 1× (36 Mbps) to 4× (144 Mbps). Good jitter values for each layer within an available maximum laser power of 27 mW on the disk were demonstrated. The acceleration test for lifetime using the Arrhenius plots showed that this write-once disk has an estimated lifetime of more than 100 years at 30 °C and 85% relative humidity (RH).

Master Recording for High-Density Disk Using 248 nm Laser Beam Recorder

A deep ultra-violet (UV) laser beam recorder (LBR) with 248 nm wavelength was developed to realize a high-density disk. The characteristics of the LBR are the wavelength and the multifunctional design. Among the possible laser wavelengths, 248 nm is the shortest wavelength applicable with Novolac photoresist, and the LBR has both modulation and deflection functions to support various formats flexibly. It was confirmed that the LBR performance was such that a groove of even 0.26 µm track pitch could be recorded, and the shape was observed with a scanning electron microscope (SEM). The disk with a groove of 0.32 µm track pitch recorded by the LBR had a practical deviation in the tracking error signal, and the addressed disk with phase-change material and a 0.1-mm-thick cover layer showed the stable reproduction of the address and a practical jitter at the equivalent density for achieving 25 GB capacity at 120 mm in diameter, on the condition of having a pick-up head with a wavelength of 400 nm and an NA of 0.85.

Accomplishment of Blu-ray disc ROM by electron beam recording: dual layer with 50-GB capacity

A BD-ROM production-capable Electron Beam Recorder (EBR) has been developed, resulting from an optimization program conducted on a prior prototype. The key technical improvements are a comprehensive upgrade of the mechanical master driving system to reduce the track pitch deviations and the implementation of a dynamic focus system, including an axial run-out checker to obtain a uniform jitter. And the multi-pulse write strategy was adopted to control the pit shapes. The resulting masters show a typical radial track pitch variation comprised in the range ±6.6nm across the entire recorded area. The corresponding push-pull signal deviation is found to be less than 18% on the whole disc and less than 14% in one revolution. The signal jitter of dual layered BD-ROM disc less than 6.1% on layer 0, and less than 6.7% on layer 1 with large enough push-pull amplitude through the whole radius. These results are fully compliant with the requirements for the dual layered BD-ROM disc of 50GB capacity.

50 GB Read Only Memory Disc with Dual Layer Structure

We developed a 50 GB dual layer read only memory (ROM) disc made by electron beam recorder (EBR) recording. The practical recording velocity was realized by control of the recording pulse and the adjustment of the post exposure bake (PEB) condition of the chemically amplified resist. An applicable replication process of dual layer ROM disc to production was realized. The recording condition was optimized for each layer. A sufficient jitter value was obtained from each layer.