Polysilicon thin film transistor and manufacturing method thereof

Abstract

The invention provides a polysilicon thin film transistor and a manufacturing method thereof. The manufacturing method comprises the steps of: providing a substrate, forming a polysilicon active layeron the substrate, sequentially forming a gate insulating layer and a polysilicon gate layer on the polysilicon active layer; performing a chemico-mechanical polishing process for removing a part of asidewall covering layer above the polysilicon gate layer; and performing a first ion implantation process to implant ions into the polysilicon gate layer; performing a second ion implantation processto implant ions into the polysilicon gate layer and polysilicon active layer on both sides of the sidewall, so as to form a source doped region and a drain doped region. Under the condition that theion implantation dose of the polysilicon gate layer is not reduced, the source-drain depletion region overlap is reduced by reducing the ion implantation doses of the source doped region and the draindoped region, thereby preventing source and drain penetration. At the same time, the ion implantation dose of the polysilicon gate layer is ensured, the threshold voltage drift of the thin film transistor is avoided, and the characteristics of the polysilicon thin film transistor are improved.

Description

technical field [0001] The invention relates to the technical field of semiconductor integrated circuits, in particular to a polysilicon thin film transistor and a manufacturing method thereof. Background technique [0002] The source and drain of the polysilicon thin film transistor are formed on the polysilicon active layer, and because of its high mobility, it is more and more used. The source and drain of the single crystal silicon thin film transistor are formed on the single crystal silicon active layer. Both single crystal silicon thin film transistors and polycrystalline silicon thin film transistors need ion implantation doping in the process of forming source and drain electrodes. Because the implanted ions diffuse more easily in polycrystalline silicon than in single crystal silicon, polycrystalline silicon thin film transistors and single crystal Compared with silicon thin film transistors, the channel length is narrower, and it is easy to cause source and drain...

AI Technical Summary

Problems solved by technology

Both single crystal silicon thin film transistors and polycrystalline silicon thin film transistors need ion implantation doping in the process of forming source and drain electrodes. Because the implanted ions diffuse more easily in polycrystalline silicon than in single crystal silicon, polycrystalline silicon thin film transistors and single crystal Compared with silicon thin film transistors, the channel length is narrower, and it is easy to cause source and drain punchthrough due to the overlapping of source and drain depletion regions, which may lead to the loss of transistor characteristics.

Images