Method of fabricating polysilicon thin film transistor with catalyst

A method of forming a polycrystalline silicon thin film transistor, comprising

• forming a buffer layer over a substrate;
• forming an amorphous silicon layer over the buffer layer;
• applying a catalytic metal to a surface of the amorphous silicon layer;
• crystallizing the entire amorphous silicon layer having the catalytic metal thereon into a whole polycrystalline silicon layer;
• annealing the whole polycrystalline silicon layer directly on the buffer layer and having the catalytic metal thereon in an N2 gas atmosphere to stabilize the whole polycrystalline silicon layer;
• after annealing, etching a surface of the stabilized whole polycrystalline silicon layer using an etchant to remove a residual catalytic metal left on the surface of the whole polycrystalline silicon layer;
• patterning the whole polycrystalline silicon layer to form an island-shaped active layer;
• forming a gate insulation layer on a first area of the island-shaped active layer;
• forming a gate electrode on the gate insulation layer;
• applying a dopant to the island-shaped active layer using the gate electrode as a mask to form source and drain regions on respective sides of the first active area;
• forming a second insulation layer to cover the gate electrode and the source and drain regions;
• forming source and drain contact holes in the second insulation layer to expose portions of the source region and the drain region, respectively;
• and
• forming source and drain electrodes, the source electrode contacting the source region through the source contact hole, and the drain electrode contacting the drain region through the drain contact hole.