Hiroshi Ooki

Performance of resolution enhancement technique using both multiple exposure and nonlinear resist

We have proposed a resolution enhancement lithography technique named NOLMEX. In this paper, we investigate the performance of this method by using the analytical relationship between line-and-space pattern resolution and NA, and by numerical calculation for isolated hole patterns. It is confirmed that this technique is useful for both kinds of patterns. Using the NOLMEX method, a 0.1-µ m-rule pattern can be fabricated by optical lithography.

Laser computed-tomography microscope

The computed tomography (CT) technique is implemented in an optical transmission microscope with a laser as a light source. A rotational Pechan prism is used in the illumination optics of the microscope for projecting a thick 3-D sample onto a 2-D array detector in different directions. A minicomputer is employed for 3-D reconstruction from the observed image data. Energy throughput efficiency and signal-to-noise ratio in the developed CT microscope are higher than those of our previously developed CT microscope [J. Opt. Soc. Am. A 4, 292 (1987)]. Instrumentation of this microscope is described and some experimental results are shown with biological samples.

A Novel Super-Resolution Technique for Optical Lithography : Nonlinear Multiple Exposure Method

A novel method for optical lithography using a resist with nonlinear photosensitivity and the multiple exposure technique is described. By means of this method, the diffraction-limited optical cutoff frequency is raised markedly, which cannot be realized by any of the other methods proposed previously. A brief explanation of the principle is given and computer simulations are demonstrated.

Differential interference contrast microscope with differential detection for optimizing image contrast.

A laser scanning differential interference contrast microscope using a differential detection method is proposed. This microscope permits observers to control the differential image contrast with a simple operation. Utilizing this function, the observers are capable of obtaining the optimized differential image whose contrast is most favorable for observation. A simple theoretical analysis and experimental considerations are described.

Sampled servo read only memory system using single carrier independent pit edge recording

Single carrier independent pit edge recording (SCIPER) is a high-density optical disk recording method which stores information by modulating the position of pit edges in small discrete steps. A high-density read only memory (ROM) system for computer use is one possible application of SCIPER technology. This application requires fast access times and high recording densities, and hence we are developing a SCIPER system based on a red 680 nm laser and sampled servo techniques. We chose a SCIPER format with a linear recording density of 0.24 µm/bit and a track pitch of 1.0 µm. With this format and under optimal conditions we obtained tangential and radial skew margins of ±0.75° and ±0.7°, respectively, and found that the system can tolerate clock jitter values of up to 3.4 ns rms. By employing zone constant angular velocity (CAV) we expect to realize a 3.5-inch, 1.3-Gbyte ROM drive.

Polarization Effect on Signal from Optical ROM Using Solid Immersion Lens

In a high-numerical-aperture optical head using a solid immersion lens (SIL), it is anticipated that the polarization of the diffracted beam is disturbed, this affects the signals. To study this problem, a rigorous simulator based on the three-dimensional vector diffraction theory has been developed. Polarization disturbance for various NAs has been estimated and it has been clarified that the polarization is disturbed not only in the SIL head but also in the conventional high-NA head whose disk substrate is not covered with protective glass. The influence of polarization disturbance on the readout signals has been determined and discussed for the various polarizations.

Portable phase measuring interferometer using Shack-Hartmann method

A real-time inspection is useful and effective to optimize lens aberrations of excimer-exposure sytem, which can expose patterns less than 100 nm. We have developed a portable i.e., compact and lightweight phase measuring interferometer (P-PMI), which can be attached to a stage of the exposure system during real-time monitoring the aberration of the projection lens mounted on the exposure system. Measured repeatability of the wavefront measurement is ab out 0.1 mλ and tool-to-tool difference is 0.6mλ. Measured wavefront during adjusting a projection lens agree dwell with a simulated result. LWA was successfully optimized using P-PMI data.

A novel type of laser scanning microscope: theoretical considerations

Abstract A novel type of confocal laser scanning microscope using a waveguide device is proposed and theoretical considerations are given. This microscope is capable of obtaining an image with differential interference constrast by means of mode interference in the waveguide device. The performance of this microscope was analyzed using Fourier optics and the two-dimensional beam propagation method. The outstanding feature of this microscope is its capability of obtaining information from the object about its phase and amplitude separately.

Laser Scanning Mode Interference Contrast Microscope and Its Application to Step Height Measurement

The image contrast of the laser scanning mode interference contrast (LASMIC) microscope is descrihed. Some experimental results show the high performance of the LASMIC microscope in visualizing small phase changes on the surface of the sample. Furthermore, as a new application of the LASMIC microscope, quantitative measurement of step heights using LASMIC signals is proposed. The principle of this measurement is described theoretically and its effectiveness is verified experimentally.

A Novel Super Resolution Technique for High-Density Optical Data Storage using Mode Interference in Channel Waveguides

A novel super-resolution system using a waveguide device is proposed and theoretical considerations are given. This system is capable of raising the storage density of optical discs considerably. The detected signal is calculated using scalar diffraction theory and the three-dimensional beam propagation method. The structure of the disc is substantially the same as that of conventional compact discs, which is the outstanding advantage of this method.