Method of forming polysilicon gate structure in image sensor device

Abstract

A method of fabricating polysilicon gate structure in an image sensor device includes depositing a gate dielectric layer on a surface of a substrate. Then a polysilicon layer is deposited over the gate dielectric layer. Next, a protection film is deposited over the polysilicon layer. A hard mask is formed over the protection film, and the polysilicon gate structure is patterned. Following that, the hard mask is stripped off. The protection film exhibits etching selectivity against the polysilicon layer and has a thickness of between 40 and 60 angstroms. The hard mask is removed by phosphoric acid solution wet etching process.

Description

technical field [0001] Embodiments of the present invention relate to a method of forming a polysilicon gate structure in an image sensor device. Background technique [0002] The reliability of gate oxides in integrated circuits (ICs) is critical to delivering high performance IC chips. Key performance criteria in image sensor ICs include speed and packing density, among others. As is known in the art, scaling, ie, reducing device size, is the primary means to achieve increased packing density. Scaled-down device dimensions in turn mean the use of smaller channel lengths and widths. To increase the speed, the saturation drain current must be increased (I dsat ). Known channel length or gate oxide thickness (t ox ) reduction will result in I dsat increase. [0003] Although the benefits of using thin oxides are well known in the art, such oxides must exhibit adequate stability properties under normal circuit operating conditions. An additional contributor to reliabil...

AI Technical Summary

Problems solved by technology

An additional contributor to reliability problems is damage to thin gate oxides when metal conductors such as polysilicon gates that sit above the gate oxide are locally charged

Images