Toyokazu Nakamura

New ferroelectric liquid crystals with a trifluoromethyl group

Abstract New chiral dopants, possessing a trifluoromethyl group, have been synthesized. These dopants have different polar groups, located between the chiral centre and the diphenylacetylene core. The polar part is chosen from ester, methylene ether and ether linkages. Each new chiral dopant was mixed with a non-chiral liquid crystal mixture or a ferroelectric liquid crystal mixture, and their transition temperatures and electrooptic properties measured. The largest spontaneous polarization, 4·1 nC cm−2, was obtained at 25°C for the ferroelectric liquid crystal mixture in which the dopant, with a methylene ether linkage, was incorporated. Molecular orbital calculations (MNDO method) for the dopants show that the calculated dipole moments are correlated with the measured spontaneous polarization, and the calculated results explain the experimental results quite well. In addition, it has been found that the conformation of the chiral part is an important factor which affects the magnitude of spontaneous pol...

VLSI fault localization using electron beam voltage contrast image : novel image acquisition and localization method

Novel methods have been developed concerning voltage contrast image acquisition using the electron beam tester, and concerning fault searching on a VLSI chip, and have been applied to real faults of VLSI devices. The developed voltage contrast image acquisition method has been shown to have acquisition time about thousand times faster than that of the conventional stroboscopic method. The strategy used in searching is that of tracing back upstream of the fault by referring to the voltage-contrast-subtracted image. This strategy is more effective than the conventional dynamic fault imaging (DFI) method where all the images on the entire chip area and all test vectors are acquired. The results showed that the location time was five times or more shorter than using conventional location methods such as electron beam waveform measurement with the aid of a computer aided design (CAD) database.

Novel method for aligning ferroelectric liquid crystal on substrate

We have depeloped a novel method for transferring a well aligned ferroelectric liquid crystal (FLC) thin film onto a solid substrate. A free-standing FLC film has been successfully obtained on a solid substrate with this method. A homeotropic alignment in smectic phase has been confirmed with polarizing microscope and X-ray diffraction. We will report this novel method for transferring a free-standing film and discuss some applications of this film.

An in-line process monitoring method using electron beam induced substrate current

In-line process monitoring technology plays a vital role in accelerating yield ramps and quickly identifying and resolving yield excursions in the system on a chip era. We have developed an in-line process monitoring method that uses electron beam induced substrate current. It is especially suitable for deep contacts and via holes. This method makes it possible to monitor non-destructive contacts and the via-hole formation process with a hole-bottom nm-order SiO2 film thickness measurement and a hole-bottom diameter measurement. Moreover, it allows us to evaluate etching-process variation over an 8-inch wafer in less than 20 min. The results can be used for in-line device sorting as well as for decisions regarding the timing of etching machine maintenance.

Simulation of Interfacial Interaction Effects on Electro-Optic Switching in Ferroelectric Liquid Crystals

The simulation of ferroelectric liquid crystal switching dynamics revealed that director depending interfacial interaction between liquid crystal molecules and substrate surface has a pronounced effect on FLC switching processes. When the interfacial interaction is strong, switching processes have multiple steps, polarization reversal current shows multiple peaks and optical response time becomes long. Especially, if the interfacial interaction polar component is large, optical stability is decreased. This simulation enables designing ferroelectric liquid crystal switching devices with fast response and good optical bistability.