Selective Single-Crystalline-Silicon Growth at the Pre-defined Active Region of a Thin Film Transistor on Glass by Using Continuous Wave Laser Irradiation

Abstract

We have developed a new silicon (Si) crystallization method that makes it possible to form single-crystalline Si in the channel regions of thin-film transistors (TFTs) on non-alkali glass without introducing thermal damage. The method includes using a frequency-doubled (2ω) diode-pumped solid-state (DPSS) Nd:YVO4 continuous-wave (CW) laser (λ=532 nm). The unique characteristics of this crystallization method are the introduction of a pre-defined thick capping-Si layer on a pre-patterned channel region and laser irradiation from the back surface through the glass substrate. We succeeded in forming 2-µm-wide and 20-µm-long single-crystalline Si in the channel region of a TFT. A high-performance n-channel TFT on a glass substrate was obtained using a 450°C fabrication process. The TFT had a field-effect mobility of 400 cm2/Vs, a subthreshold swing of 0.16 V/dec, and a threshold voltage of 0.24 V.