Self-aligned LDD poly-Si thin-film transistor

摘要

A method of fabricating a polysilicon thin film transistor with a self-aligned lightly doped drain (LDD) is described. At first a polysilicon-island region and a gate insulating layer are subsequently formed on a glass substrate performed by a pre-treatment. Then a metal layer and a cap layer are subsequently formed on the gate insulating layer. The cap layer and the metal layer are defined to form a gate. A heavily doped region is formed in the polysilicon island region with serving the gate as a mask. An activation step is performed on the heavily doped region and a sidewall of the metal layer. The cap layer above the metal layer and the sidewall of the metal layer performed by the activation step are removed. A lightly doped region is formed in the polysilicon-island region with serving the remaining metal layer.