High Performance Thin Film Transistors (TFTs) of Polycrystalline Silicon Crystallized by the Double Laser Crystallization (DLC) Technique

Ultra-large grain poly-crystalline silicon has been formed by the double laser crystallization (DLC) method. In-situ images were captured to monitor the transient melting and solidification process in order to understand the crystallization induced by steep laser intensity gradients. SEM (scanning electron microscope) images of crystallized film after Secco etch revealed grain size up to 10μm. High performance thin film transistors (TFTs) were fabricated on the DLC-made poly-crystalline material. The highly localized crystal growth and well-defined orientation allowed precise definition of channels on large grains. The electrical performance of the fabricated devices was studied, indicating a field-effect mobility in the saturation range of undoped channel of 124 cm2/V.sec, threshold voltage of 0.2V and on-off current ratio of 1E8 for n-type devices.