Dependence of single-crystalline Si TFT characteristics on the channel position inside a location-controlled grain

To obtain high-performance thin-film transistors (TFTs), a comprehensive study of the channel position of TFTs inside a location-controlled grain was carried out. The location of the grain is precisely controlled by the μ-Czochralski process using an excimer laser. The grain was grown from a thin Si column embedded in SiO₂ (grain filter). The characteristics of the TFTs drastically improved when the channel region was not centered above the grain filter. With TFTs whose current-flow direction is parallel to the radial direction of the grain filter, an electron mobility and subthreshold swing of ∼600cm²/V·s and 0.21V/dec respectively were obtained.