We demonstrate the capability of 100-GB density recording by electron beam mastering and readout by a near-field optical pickup with an effective NA of 2.05 and a blue LD of 405-nm wavelength. A silicon (Si) disk of 100-GB density is fabricated by an optimized Si etching process condition to form suitable pit pattern shapes for the near-field readout.
We improved the electron beam recorder with a differential pumping head for higher density discs and mass production. The beam diameters were improved by exchanging the aperture size of the objective lens and beam stability were also improved by adding a sound proof case. As for the performance of the improved electron beam recorder, we showed that a 104Gb/in<sup>2</sup> (150GB capacity/layer) density disc with EFM plus modulation codes can be fabricated. We also improved the pit shape uniformity and a margin of the process by introducing the appropriate write strategy that is simulated by the Monte Carlo simulation to the recording pulses.
Near-field mastering process with a 266 nm laser was improved in the stability for long time exposure and in the performance for ROM exposure. The exposure stability was achieved by using a chemically amplified type photoresist and by setting the air gap large. The exposure performance was achieved by reducing the aberration of the objective lens and by adjusting the focal position precisely. As a result, 100 nm narrow width was obtained in the groove structure, and good signal quality was obtained from a 25 gigabyte (GB) read only memory (ROM) disc. A full area exposure for a 25 GB ROM disc was also achieved.
We have achieved high density near field readout of a 100 GB capacity (69.5 Gbit/in<sup>2</sup>) disc by using a solid immersion lens with numerical aperture of 2.05. In order to realize the solid immersion lens wtih numerical aperture of 2.05, the solid immersion lens was made from Bi<sub>4</sub>Ge<sub>3</sub>O<sub>12</sub> mono-crystal. The refractive index of Bi<sub>4</sub>Ge<sub>3</sub>O<sub>12</sub> is 2.23 at the wavelegnth of 405 nm. A conventional optical pick-up actuator with the solid immersion lens was used for the near field optical disc system. We confirmed that the near field readout system is promising method of realizing a high density optical disc system.
We have demonstrated the capability of 100GB density recording by the electron beam mastering and readout by a near-field optical pick-up with an effective NA of 2.05 and a blue LD of 405 nm wavelength. The Si disc of 100GB density was fabricated by the optimized Si etching process condition to form suitable pit pattern shape for the near-field readout.
We describe a 0.4W average power at maximum, frequency-quintupled Q-switched Nd:YAG laser at a repetition rate of 7 kHz, which is a potential light source for next generation microlithography. Calculated results for the conversion efficiencies considering pump depletion will be discussed. Our results allow to foresee further scaling up 213 nm power up to the 1W level by increasing the fundamental power.
A new lithography technique using continuous wave (CW) 266 nm radiation from an all solid state frequency quadrupled Nd:YAG laser is described and demonstrated. This laser has proved to be a highly efficient and promising deep UV light source in fabrication of 0.25 micron design rule device. Furthermore, we obtained 0.2 micron L/S pattern with phase shift mask. Speckle free images are obtained with rotating diffuser. The performance and potential of this new laser as a light source of microlithography are discussed and compared with KrF excimer laser theoretically and experimentally.