METHOD OF MANUFACTURING THIN FILM TRANSISTOR HAVING LIGHTLY DOPED DRAIN REGION

摘要

A method for fabricating a thin film transistor is provided to reduce off-current by fabricating a thin film transistor having an LDD(lightly doped drain) region between a source/drain region and a channel region. An amorphous silicon layer is formed on a substrate(10). The amorphous silicon layer is crystallized to form a polysilicon layer. An insulation layer is formed on the polysilicon layer. A mask structure is formed on the insulation layer to mask a partial region of the polysilicon layer, including a gate mask and a photoresist layer that are sequentially stacked. Impurities of a first density are implanted into one and the other ends of the polysilicon layer not covered with the mask structure by an ion beam implantation method to form a source region(14S), a drain region(14D) and a channel region(14C) between the source and drain regions in the polysilicon layer. An ion beam is irradiated to the photoresist layer to shrink the photoresist layer so that one and the other ends of the gate mask are protruded. By using the shrunk photoresist layer as an etch mask, the gate mask and the insulation layer are etched by the same width as the shrunk photoresist layer to form a gate electrode(22a) and a gate insulation layer(16a). Impurities of a second density lower than the first density are implanted into one and the other ends of the channel region exposed to a gap between the gate insulation layer and the source/drain region to form an LDD region.