Method for forming metal gate

Abstract

A method for forming a metal gate comprises the steps of providing a semiconductor substrate; forming an interface material layer, a high K medium layer and a polycrystalline silicon layer on the surface of the semiconductor substrate; carrying out first nitridation processing on the surface of the polycrystalline silicon layer, and forming a nitrogen silicon compound on the surface of the polycrystalline silicon layer; forming a hard mask layer on the polycrystalline silicon layer after the first nitridation processing, wherein the hard mask layer possesses an opening for exposing the nitrogen silicon compound on the surface of the polycrystalline silicon layer; etching the polycrystalline silicon layer, the high K medium layer and the interface material layer along the opening to form an interface layer, a high K medium layer and a dummy gate; forming an interlayer medium layer on the surface of the semiconductor substrate, wherein the surface of the interlayer medium layer is parallel and level with the top surface of the dummy gate; removing the dummy gate to form a groove, and filling metal in the groove to form the metal gate. The nitrogen silicon compound can prevent an oxygen element from penetrating the polycrystalline silicon layer to react with the silicon on the surface of the semiconductor substrate to form a silicon oxide, and enables the thickness of the interface material layer not to change.

Description

technical field [0001] The invention relates to the field of semiconductor manufacturing, in particular to a method for forming a metal gate. Background technique [0002] With the continuous development of integrated circuit manufacturing technology, the feature size of MOS transistors is getting smaller and smaller. In order to reduce the parasitic capacitance of the gate of MOS transistors and improve the device speed, the gate stack of high K gate dielectric layer and metal gate structure is introduced into MOS transistors. In order to avoid the influence of the metal material of the metal gate on other structures of the transistor, the gate stack structure of the metal gate and the high-K gate dielectric layer is usually fabricated by a “gate last” process. [0003] Figure 1~Figure 4 A schematic cross-sectional structure diagram of a method for forming a metal gate using a "gate-last" process in the prior art. First please refer to figure 1 , providing a semiconduc...

AI Technical Summary

Problems solved by technology

[0007] However, the thickness of the interface material layer (or interface layer) formed in the prior art is easy to change, which affects the stability of the transistor

Images