Yoshihiro Morimoto

Influence of the Grain Boundaries and Intragrain Defects on the Performance of Poly‐Si Thin Film Transistors

The influence of grain boundaries and intragrain defects on poly-Si thin-film transistors (TFTS) was investigated by examining the crystallinity of poly-Si films formed by solid phase crystallization (SPC) and excimer laser annealing (ELA), and the electrical characteristics of transistors fabricated on the poly-Si films were examined. The increase in grain size by SPC improves field effect mobility (μ Fe ) due to the increase in the emission current over the potential barrier height at the grain boundary. The decrease in intragrain defect densities by an oxide thinning process improves the threshold voltage (V h ) and subthreshold voltage swing (S). On the contrary, in spite of the small grain size of 800 A, polv-Si TFTs fabricated by ELA exhibit good characteristics with a high μ FE low V th and low S, and good uniformity. It is found that since the realization of excellent performance and good uniformity in poly-Si TFTs depends on a low trap state density at the grain boundaries and a low intragrain defect density, poly-Si films formed by ELA are well suited for the application to poly-Si TFT liquid crystal display with peripheral integrated circuits.

Influence of the Existence of an Underlying SiO2 Layer on the Lateral Solid‐Phase Epitaxy of Amorphous Silicon

The influence of the existence of an underlying SiO 2 layer on the lateral solid-phase epitaxy (L-SPE) of amorphous Si was investigated by comparing the characteristics of L-SPE with and without an underlying SiO 2 layer. For the L-SPE with an underlying SiO 2 layer which had a change from {110} to {111} facet growth, high density crystal defects, most of which were dislocations, were detected especially in the {111} facet growth region. The formation of {111} facets is caused primarily by high density dislocations incorporated by relaxation of the stress which originates from the retardation of Si atom rearrangement

Improvement in Surface Morphology and Crystal Epitaxial CaF 2 on Si (100) Through two Mbe Growth Stages

We report the first study on improvement in surface morphology and crystal quality of as—grown epitaxial CaF 2 film on a (100) Si substrate grown through two MBE growth stages without any post-growth treatment. The degree of improvement in surfacemorphology and crystal quality depends not only on the thickness of an initial thin CaF 2 film grown at the early growth stage of 550oC but also on both the subsrate temperature and thickness of a sequential grown CaF 2 film used for thesecond growth stage. Under optimum conditions, the CaF 2 films exhibited high quality with an RBS/channeling minimum yield of 4%, together with a very smooth surface morphology without any other nuclel or cracks.

Optimization of low-temperature poly-Si TFT-LCDs and a large-scale production line for large glass substrates

An update of the progress of inherently low-temperature poly-Si (LTPS) technologies, such as ELA, ion doping, and activation in conjunction with chemical vapor deposition (CVD) and pho. tolithography will be given. We will also discuss whether LTPS LCDs will be applied to a large-scale production line using a large motherglass substrate. It was found that a more-powerful excimer laser as well as photolithography with higher-resolution and a more-precise overlaid arrangement woulc enable a large-scale production line handling motherglass of 4th generation size to be constructed ir the very near future with reasonable investment and productivity costs.